Conference talk, Observing the Universe at millimeter wavelengths 2025

Kavli Institute for Cosmological Physics/University of Chicago, Chicago, IL, June 26, 2025

Conference talk, American Physics Society Global Summit 2025

Anaheim, CA, March 15, 2025

Seminar, Fermi National Accelerator Laboratory

Battavia, IL, January 13, 2025

Conference talk, Cosmology and galaxy astrophysics with simulations and machine learning 2024

Center for Computational Astrophysics/Flatiron Institute, New York, NY, December 12, 2024

Seminar, Kavli Institute for Cosmological Physics/University of Chicago

Chicago, IL, November 21, 2024

Webinar, Laboratoire de Physique Subatomique et Cosmologie

Grenoble, France, October 07, 2024

Junior scientist talk, CMB-S4 2023 Summer Collaboration meeting

National Center for Supercomputing Applications/University of Illinois Urbana-Champaign, Urbana, IL, August 01, 2024

Junior scientist talk, CMB-S4 2023 Summer Collaboration meeting

SLAC National Accelerator Laboratory, Menlo Park, CA, July 31, 2023

Conference talk, Observing the Universe at millimeter wavelengths 2023

Laboratoire de Physique Subatomique et Cosmologie, Grenoble, France, June 28, 2023

Conference talk, Observing the Universe at millimeter wavelengths 2023

Laboratoire de Physique Subatomique et Cosmologie, Grenoble, France, June 26, 2023

Talk, Argonne HEP Young Scientists Symposium Series

Argonne National Laboratory, Lemont, IL, March 22, 2022

Seminar, University of Michigan

Ann Arbor, Michigan, March 09, 2022

Thesis defense, Laboratoire de Physique Subatomique et Cosmologie

Grenoble, France, September 27, 2021

Conference talk, Observing the Universe at millimeter wavelengths 2021

Sapienza University, Rome, Italy, June 29, 2021

Conference talk, Observing the Universe at millimeter wavelengths 2021

Sapienza University, Rome, Italy, June 28, 2021

Talk, French national colloquim 'Action Dark Energy' 2020

Online, October 15, 2020

Seminar, Institut de Planétologie et d'Astrophysique de Grenoble

Grenoble, France, July 03, 2020

Seminar, Laboratoire de Physique Subatomique et Cosmologie

Grenoble, France, July 01, 2020

Conference talk, CosmoGold IAP 2019

Institut d'Astrophysique de Paris, Paris, France, June 25, 2019

Conference talk, Observing the Universe at millimeter wavelengths 2019

Laboratoire de Physique Subatomique et Cosmologie, Grenoble, France, June 04, 2019

Journal Articles

halox: Dark matter halo properties and large-scale structure calculations using JAX

Kéruzoré, F. (2025), arXiv e-prints, arXiv:2509.22478.

NASA ADS | arXiv | Abstract

Dark matter halos are fundamental structures in cosmology, forming the gravitational potential wells hosting galaxies and clusters of galaxies. Their properties and statistical distribution (including the halo mass function) are invaluable tools to infer the fundamental properties of the Universe. The \texttt{halox} package is a JAX-powered Python library enabling differentiable and accelerated computations of key properties of dark matter halos, and of the halo mass function. The automatic differentiation capabilities of \texttt{halox} enable its usage in gradient-based workflows, e.g. in efficient Hamiltonian Monte Carlo sampling or machine learning applications.

The picasso gas model: Painting intracluster gas on gravity-only simulations

Kéruzoré, F., Bleem, L. E., Frontiere, N., et al. (2024), The Open Journal of Astrophysics, 7, 116.

NASA ADS | arXiv | Abstract

We introduce picasso, a model designed to predict thermodynamic properties of the intracluster medium based on the properties of halos in gravity-only simulations. The predictions result from the combination of an analytical gas model, mapping gas properties to the gravitational potential, and of a machine learning model to predict the model parameters for individual halos based on their scalar properties, such as mass and concentration. Once trained, the model can be applied to make predictions for arbitrary potential distributions, allowing its use with flexible inputs such as N−body particle distributions or radial profiles. We present the model, and train it using pairs of gravity-only and hydrodynamic simulations. We show that when trained to learn the mapping from gravity-only to non-radiative hydrodynamic simulations, picasso can make remarkably accurate and precise predictions of intracluster gas thermodynamics, with percent-level bias and ~20% scatter for r/R500c∈[0.1,1]. Training the model on hydrodynamic simulations including sub-resolution physics modeling yields robust predictions as well, albeit with the introduction of a radius-dependent bias and an increase in scatter. We further show that the model can be trained to make accurate predictions from very minimal halo information, down to mass and concentration, at the cost of modestly reduced precision. picasso is made publicly available on Github (https://github.com/fkeruzore/picasso) as a Python package, which includes trained models that can be used to make predictions easily and efficiently, in a fully auto-differentiable and hardware-accelerated framework.

Optimization and Quality Assessment of Baryon Pasting for Intracluster Gas using the Borg Cube Simulation

Kéruzoré, F., Bleem, L. E., Buehlmann, M., et al. (2023), The Open Journal of Astrophysics, 6, 43.

NASA ADS | arXiv | Abstract

Synthetic datasets generated from large-volume gravity-only simulations are an important tool in the calibration of cosmological analyses. Their creation often requires accurate inference of baryonic observables from the dark matter field. We explore the effectiveness of a baryon pasting algorithm in providing precise estimations of three-dimensional gas thermodynamic properties based on gravity-only simulations. We use the Borg Cube, a pair of simulations originating from identical initial conditions, with one run evolved as a gravity-only simulation, and the other incorporating non-radiative hydrodynamics. Matching halos in both simulations enables comparisons of gas properties on an individual halo basis. This comparative analysis allows us to fit for the model parameters that yield the closest agreement between the gas properties in both runs. To capture the redshift evolution of these parameters, we perform the analysis at five distinct redshift steps, spanning from $z=0$ to $2$. We find that the investigated algorithm, utilizing information solely from the gravity-only simulation, achieves few-percent accuracy in reproducing the median intracluster gas pressure and density, albeit with a scatter of approximately 20%, for cluster-scale objects up to $z=2$. We measure the scaling relation between integrated Compton parameter and cluster mass ($Y_{500c} | M_{500c}$), and find that the imprecision of baryon pasting adds less than 5% to the intrinsic scatter measured in the hydrodynamic simulation. We provide best-fitting values and their redshift evolution, and discuss future investigations that will be undertaken to extend this work.

panco2: a Python library to measure intracluster medium pressure profiles from Sunyaev-Zeldovich observations

Kéruzoré, F., Mayet, F., Artis, E., et al. (2023), The Open Journal of Astrophysics, 6, 9.

NASA ADS | arXiv | Abstract

We present panco2, an open-source Python library designed to extract galaxy cluster pressure profiles from maps of the thermal Sunyaev-Zeldovich effect. The extraction is based on forward modeling of the total observed signal, allowing to take into account usual features of millimeter observations, such as beam smearing, data processing filtering, and point source contamination. panco2 offers a large flexibility in the inputs that can be handled and in the analysis options, enabling refined analyses and studies of systematic effects. We detail the functionalities of the code, the algorithm used to infer pressure profile measurements, and the typical data products. We present examples of running sequences, and the validation on simulated inputs. The code is available on GitHub at https://github.com/fkeruzore/panco2, and comes with an extensive technical documentation to complement this paper at https://panco2.readthedocs.io.

Exploiting NIKA2/XMM-Newton imaging synergy for intermediate-mass high-z galaxy clusters within the NIKA2 SZ large program. Observations of ACT-CL J0215.4+0030 at z ∼ 0.9

Kéruzoré, F., Mayet, F., Pratt, G. W., et al. (2020), Astronomy and Astrophysics, 644, A93.

NASA ADS | arXiv | Abstract

High-resolution mapping of the intracluster medium (ICM) up to high redshift and down to low masses is crucial to derive accurate mass estimates of the galaxy cluster and to understand the systematic effects affecting cosmological studies based on galaxy clusters. We present a spatially resolved Sunyaev-Zel'dovich (SZ)/X-ray analysis of ACT-CL J0215.4+0030, a high-redshift (z = 0.865) galaxy cluster of intermediate mass (M₅₀₀ ≃ 3.5 × 10¹⁴ M_⊙) observed as part of the ongoing NIKA2 SZ large program, which is a follow-up of a representative sample of objects at 0.5 ≤ z ≤ 0.9. In addition to the faintness and small angular size induced by its mass and redshift, the cluster is contaminated by point sources that significantly affect the SZ signal. This is therefore an interesting case study for the most challenging sources of the NIKA2 cluster sample. We present the NIKA2 observations of this cluster and the resulting data. We identified the point sources that affect the NIKA2 maps of the cluster as submillimeter galaxies with counterparts in catalogs of sources constructed by the SPIRE instrument on board the Herschel observatory. We reconstructed the ICM pressure profile by performing a joint analysis of the SZ signal and of the point-source component in the NIKA2 150 GHz map. This cluster is a very weak source that lies below the selection limit of the Planck catalog. Nonetheless, we obtained high-quality estimates of the ICM thermodynamical properties with NIKA2. We compared the pressure profile extracted from the NIKA2 map to the pressure profile obtained from X-ray data alone by deprojecting the public XMM-Newton observations of the cluster. We combined the NIKA2 pressure profile with the X-ray deprojected density to extract detailed information on the ICM. The radial distribution of its thermodynamic properties (the pressure, temperature and entropy) indicate that the cluster has a highly disturbed core. We also computed the hydrostatic mass of the cluster, which is compatible with estimations from SZ and X-ray scaling relations. We conclude that the NIKA2 SZ large program can deliver quality information on the thermodynamics of the ICM even for one of its faintest clusters after a careful treatment of the contamination by point sources.

The reduced images are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/644/A93

Towards constraining cosmological parameters with SPT-3G observations of 25% of the sky

Vitrier, A., Fichman, K., Balkenhol, L., et al. (2025), arXiv e-prints, arXiv:2510.24669.

NASA ADS | arXiv | Abstract

The South Pole Telescope (SPT), using its third-generation camera, SPT-3G, is conducting observations of the cosmic microwave background (CMB) in temperature and polarization across approximately 10 000 deg$^2$ of the sky at 95, 150, and 220 GHz. This comprehensive dataset should yield stringent constraints on cosmological parameters. In this work, we explore its potential to address the Hubble tension by forecasting constraints from temperature, polarization, and CMB lensing on Early Dark Energy (EDE) and the variation in electron mass in spatially flat and curved universes. For this purpose, we investigate first whether analyzing the distinct SPT-3G observation fields independently, as opposed to as a single, unified region, results in a loss of information relevant to cosmological parameter estimation. We develop a realistic temperature and polarization likelihood pipeline capable of analyzing these fields in these two ways, and subsequently forecast constraints on cosmological parameters. Our findings indicate that any loss of constraining power from analyzing the fields separately is primarily concentrated at low multipoles ($\ell$ < 50) and the overall impact on the relative uncertainty on standard $Λ$CDM parameters is minimal (< 3%). Our forecasts suggest that SPT-3G data should improve by more than a factor of 200 and 3000 the Figure of Merit (FoM) of the EDE and the varying electron mass models, respectively, when combined with Planck data. The likelihood pipeline developed and used in this work is made publicly available online.

Thermal Sunyaev-Zel’dovich effect at the core of CL J1226.9+3332 revealed by NOEMA

Muñoz-Echeverría, M., Macías-Pérez, J.-F., Neri, R., et al. (2025), Astronomy and Astrophysics, 702, A275.

NASA ADS | arXiv | Abstract

We present first detailed maps of the thermal Sunyaev-Zel'dovich (tSZ) effect on a z = 0.89 cluster with the NOrthern Extended Millimeter Array (NOEMA). The high sensitivity of these observations enabled the effective identification and removal of the millimetre-wave sources contaminating the tSZ signal, thus isolating the influence of the hot electron gas of the cluster on the cosmic microwave background radiation from other emissions. The tSZ observed with success by NOEMA was modelled together with previous single-dish observations (IRAM 30-metre, Green Bank Telescope, and Caltech Sub-millimeter Observatory) to obtain the first core-to-outskirts (from ∼15 to ∼1500 kpc) pressure profile reconstruction on such a high-redshift galaxy cluster. NOEMA observations with a high angular resolution have shown that the pressure profile is flat in the core of the cluster. These observations confirm the disturbed nature of CL J1226.9+3332 and map for the first time the distribution of its thermal gas at arcsecond scales in the environments of the central cluster galaxy. Our results showcase the excellent capabilities of NOEMA to complement and enhance the data provided by other millimetre-wave instruments in resolving the core of high-redshift clusters via tSZ emission.

Thermal SZ effect at the core of CL J1226.9+3332 revealed by NOEMA

Muñoz-Echeverría, M., Macías-Pérez, J.-F., Neri, R., et al. (2025), arXiv e-prints, arXiv:2509.14048.

NASA ADS | arXiv | Abstract

We present first detailed maps of the thermal Sunyaev-Zel'dovich (tSZ) effect on a $z = 0.89$ cluster with the NOrthern Extended Millimeter Array (NOEMA). The high sensitivity of these observations enabled the effective identification and removal of the millimetre-wave sources contaminating the tSZ signal, thus isolating the influence of the cluster's hot electron gas on the cosmic microwave background radiation from other emissions. The tSZ observed with success by NOEMA is modelled together with previous single dish (IRAM 30-metre, Green Bank Telescope, and Caltech Sub-millimeter Observatory) observations to obtain the first core to outskirts (from $\sim$ 15 to $\sim$ 1500 kpc) pressure profile reconstruction on such a high redshift galaxy cluster. High angular resolution NOEMA observations have shown that the pressure profile is flat in the core of the cluster. These observations confirm the disturbed nature of CL J1226.9+3332 and map for the first time the distribution of its thermal gas at arcsecond scales, in the environments of the central cluster galaxy. Our results showcase NOEMA's excellent capabilities to complement and enhance the data provided by other millimetre-wave instruments in resolving the core of high-redshift clusters via tSZ emission.

Detection of Millimeter-Wavelength Flares from Two Accreting White Dwarf Systems in the SPT-3G Galactic Plane Survey

Wan, Y., Vieira, J. D., Chichura, P. M., et al. (2025), arXiv e-prints, arXiv:2509.08962.

NASA ADS | arXiv | Abstract

Blind discoveries of millimeter-wave (mm-wave) transient events in non-targeted surveys, as opposed to follow-up or pointed observations, have only become possible in the past decade using cosmic microwave background surveys. Here we present the first results from the SPT-3G Galactic Plane Survey -- the first dedicated high-sensitivity, wide-field, time-domain, mm-wave survey of the Galactic Plane, conducted with the South Pole Telescope (SPT) using the SPT-3G camera. The survey field covers approximately 100 $\text{deg}^2$ near the Galactic center. In 2023 and 2024, this survey consists of roughly 1,500 individual 20-minute observations in three bands centered at 95, 150, and 220 GHz, with plans for more observations in the coming years. We report the detection of two transient events exceeding a 5$σ$ threshold in both the 95 and 150 GHz bands in the first two years of SPT-3G Galactic Plane Survey data. Both events are unpolarized and exhibit durations of approximately one day, with peak flux densities at 150 GHz of at least 50 mJy. The peak isotropic luminosities at 150 GHz are on the order of $10^{31}~\text{erg}~\text{s}^{-1}$. Both events are associated with previously identified accreting white dwarfs. Magnetic reconnection in the accretion disk is a likely explanation for the observed millimeter flares. In the future, we plan to expand the transient search in the Galactic Plane by lowering the detection threshold, enabling single-band detections, analyzing lightcurves on a range of timescales, and including additional data from future observations.

Continuum, CO, and water vapour maps of the Orion Nebula: First millimetre spectral imaging with CONCERTO

Désert, F.-X., Macías-Pérez, J. F., Beelen, A., et al. (2025), Astronomy and Astrophysics, 701, A210.

NASA ADS | arXiv | Abstract

Context. The millimetre spectrum of Galactic regions and galaxies is rich in continuum and molecular lines. This diversity is mostly explored using either broad-band photometry or high-resolution heterodyne spectroscopy. Aims. We aim to map the millimetre continuum emission of Galactic regions with an intermediate spectral resolution between broadband photometry and heterodyne spectroscopy, enabling us to rapidly cover large sky areas with spectroscopy. Methods. We report observations of the Orion Nebula with the CONCERTO instrument, which was installed at the APEX telescope focal plane from 2021 to 2023. Results. We find that the spectrum of Orion is dominated by dust emission with an emissivity index ranging between 1.3 and 2.0, along with strong CO(2-1) and H₂O lines, which are naturally separated from the continuum due to the CONCERTO spectral capabilities. Many regions also show strong free-free emission at lower frequencies. Conclusions. We demonstrate the spectral capabilities of CONCERTO at intermediate spectral resolution, with a frequency coverage from 130 to 310 GHz. A sensitivity of 200 mK is achieved in one second, for one beam and a 6 GHz frequency width, over an 18 arcmin diameter field of view, which is within a factor of three of the expectations. We show that we can spectrally disentangle the continuum from the CO line emission, but the line is not resolved at a resolution of ~8000 km s^–1. The slope of the millimetre continuum is line-free mapped for the first time in Orion.

NIKA2 Cosmological Legacy Survey: Blind detection of galaxy clusters in the COSMOS field via the Sunyaev-Zel’dovich effect

Chérouvrier, D., Macías-Pérez, J. F., Désert, F. X., et al. (2025), Astronomy and Astrophysics, 700, A30.

NASA ADS | arXiv | Abstract

Clusters of galaxies, formed in the latest stages of structure formation, are unique cosmological probes. With the advent of large CMB surveys like those from the Planck satellite, the ACT and SPT telescopes, we now have access to a large number of galaxy clusters detected at millimeter wavelengths via the thermal Sunyaev-Zel'dovich (tSZ) effect. Nevertheless, it is interesting to complement them with high-angular-resolution (tens of arcseconds) observations to target the lowest-mass and highest-redshift clusters. This is the case of observations with the NIKA2 camera, which is installed on the IRAM 30-m telescope in Pico Veleta, Spain. We used the existing 150 GHz (2 mm) data from the NIKA2 Cosmological Legacy Survey (N2CLS) Large Program to blindly search for galaxy clusters in the well-known COSMOS field, across a 877 arcmin² region centered on (RA, Dec)_J2000 = (10h00m28.81s, +02d17m30.44s). We first developed a dedicated data reduction pipeline to construct NIKA2 maps at 2 mm. We then used a matched-filter algorithm to extract cluster candidates assuming a universal pressure profile to model the expected cluster tSZ signal. We computed the purity and completeness of the sample by applying the previous algorithm to simulated maps of the sky signal in the COSMOS field, including tSZ contribution, point sources and instrumental noise. We find a total of 16 cluster candidates at S/N > 4, from which eight have either an optical or X-ray cluster (or group of galaxies) counterpart. This is the first blind detection of clusters of galaxies at mm wavelengths at 18″ angular resolution. For candidates with available redshift estimates, we derived their mass by modeling the cluster tSZ signal with a universal pressure profile via a MCMC analysis. From this analysis, we confirm that NIKA2 and the IRAM 30-m telescope should be sensitive to low-mass clusters at intermediate and high redshift, complementing current and planned large tSZ-based cluster surveys.

SPT-3G D1: Axion Early Dark Energy with CMB experiments and DESI

Khalife, A. R., Balkenhol, L., Camphuis, E., et al. (2025), arXiv e-prints, arXiv:2507.23355.

NASA ADS | arXiv | Abstract

We present the most up-to-date constraints on axion early dark energy (AEDE) from cosmic microwave background (CMB) and baryon acoustic oscillation (BAO) measurements. In particular, we assess the impact of data from ground-based CMB experiments, the South Pole Telescope (SPT) and the Atacama Cosmology Telescope (ACT) -- both with and without $Planck$ -- on constraints on AEDE. We also highlight the impact that BAO information from the Dark Energy Spectroscopic Instrument (DESI) has on these constraints. From CMB data alone, we do not find statistically significant evidence for the presence of AEDE, and we find only moderate reduction in the Hubble tension. From the latest SPT data alone, we find the maximal fractional contribution of AEDE to the cosmic energy budget is $f_{\rm EDE}\,<\,0.12$ at $95\,$% confidence level (CL), and the Hubble tension between the SPT and SH0ES results is reduced to the $2.3\,σ$ level. When combining the latest SPT, ACT, and $Planck$ datasets, we find $f_{\rm EDE}\,<\,0.091$ at $95\,$% CL and the Hubble tension at the $3.3\, σ$ level. In contrast, adding DESI data to the CMB datasets results in mild preference for AEDE and, in some cases, non-negligible reduction in the Hubble tension. From SPT+DESI, we find $f_{\rm EDE}\,=\,0.081^{+0.037}_{-0.052}$ at $68\,$% CL, and the Hubble tension reduces to $1.5\,σ$. From the combination of DESI with all three CMB experiments, we get $f_{\rm EDE}\,=\, 0.071^{+0.035}_{-0.038}$ at $68\,$% CL and a weak preference for AEDE over $Λ$CDM. This data combination, in turn, reduces the Hubble tension to $2.3\, σ$. We highlight that this shift in parameters when adding the DESI dataset is a manifestation of the discrepancy currently present between DESI and CMB experiments in the concordance model $Λ$CDM.

The NIKA2 cosmological legacy survey at 2 mm: catalogs, colors, redshift distributions, and implications for deep surveys

Béthermin, M., Lagache, G., Carvajal-Bohorquez, C., et al. (2025), arXiv e-prints, arXiv:2506.22046.

NASA ADS | arXiv | Abstract

Millimeter galaxy surveys are particularly effective in detecting dusty star-forming galaxies at high redshift. While such observations are typically conducted at ~1mm, studies suggest that 2mm may be better suited for selecting sources at even higher redshifts. We use the unprecedented 2mm data from the N2CLS, together with the SIDES simulation, to study and interpret the statistical properties of 2mm-selected galaxies. We use the N2CLS robust sample at 2mm, which contains 25 sources in the deep GOODS-N field and 90 sources in the wide COSMOS. The sources are matched with the N2CLS 1.2mm sources, the ancillary 850um sources, and redshift catalogs to study the colors and redshift distributions. We also produce end-to-end simulations based on SIDES and the observed N2CLS detector timelines to interpret the data. We find a mean S2/S1.2 color of 0.215$\pm$0.006 with a standard deviation of 0.056$\pm$0.004. We measure a mean redshift of $3.6\pm0.3$ in GOODS-N, which is marginally higher than expectations from SIDES ($3.0\pm0.2$) because of an overdensity at $z\sim5.2$, and $3.0\pm0.2$ in COSMOS, which agrees with the $3.2\pm0.2$ predicted by SIDES. We also show that the observed S2/S1.2 colors exhibit a weak dependence with redshift but a large dispersion, which limits its efficiency to select high-z sources. Finally, we studied the nine 2mm sources not detected at 1.2mm, and found that two of them are radiogalaxies, one is a z~2 galaxy, and the remaining six are compatible with the expected number of spurious detections. The N2CLS survey shows no evidence for any exotic 2mm-only galaxy population. Using SIDES, we show that 2mm samples have a higher mean redshift compared to 1.2mm because they miss z~2 dusty galaxies. Finally, we compare the N2CLS with the ex-MORA survey and show that N2CLS is more efficient than interferometric observations to build samples of high-z dusty galaxies.

SPT-3G D1: CMB temperature and polarization power spectra and cosmology from 2019 and 2020 observations of the SPT-3G Main field

Camphuis, E., Quan, W., Balkenhol, L., et al. (2025), arXiv e-prints, arXiv:2506.20707.

NASA ADS | arXiv | Abstract

We present measurements of the temperature and E-mode polarization angular power spectra of the cosmic microwave background (CMB) from observations of 4% of the sky with SPT-3G, the current camera on the South Pole Telescope (SPT). The maps used in this analysis are the deepest used in a CMB TT/TE/EE analysis to date. The maps and resulting power spectra have been validated through blind and unblind tests. The measurements of the lensed EE and TE spectra are the most precise to date at l=1800-4000 and l=2200-4000, respectively. Combining our TT/TE/EE spectra with previously published SPT-3G CMB lensing results, we find parameters for the standard LCDM model consistent with Planck and ACT-DR6 with comparable constraining power. We report a Hubble constant of $H_0=66.66\pm0.60$ km/s/Mpc from SPT-3G alone, 6.2 sigma away from local measurements from SH0ES. For the first time, combined ground-based (SPT+ACT) CMB primary and lensing data have reached Planck's constraining power on some parameters, a milestone for CMB cosmology. The combination of these three CMB experiments yields the tightest CMB constraints to date, with $H_0=67.24\pm0.35$ km/s/Mpc, and the amplitude of clustering $σ_8=0.8137\pm0.0038$. CMB data alone show no evidence for physics beyond LCDM; however, we observe a 2.8 sigma difference in LCDM between CMB and baryon acoustic oscillation (BAO) results from DESI-DR2, which is relaxed in extended models. The combination of CMB and BAO yields 2-3 sigma shifts from LCDM in the curvature of the universe, the amplitude of CMB lensing, or the dark energy equation of state. It also drives mild preferences for models that address the Hubble tension through modified recombination or variations in the electron mass in a non-flat universe. This work highlights the growing power of ground-based CMB experiments and lays a foundation for further cosmological analyses with SPT-3G.

Overdense fireworks in GOODS-N: Unveiling a record number of massive dusty star forming galaxies at z$\sim$5.2 with the N2CLS

Lagache, G., Xiao, M., Beelen, A., et al. (2025), arXiv e-prints, arXiv:2506.15322.

NASA ADS | arXiv | Abstract

As part of the N2CLS Survey, we have identified a remarkable overdensity of ten bright dusty star-forming galaxies at z$\sim$5.2 in the GOODS-N field. Three of these galaxies, N2GN_1_01, 06, and 23 (known as GN10, HDF850.1, and S3, respectively), had previously been spectroscopically confirmed as members of the exceptional large-scale structure at z$\sim$5.1-5.3, which is notably elongated along the line of sight, spanning 30 cMpc. We present the spectroscopic confirmation of N2GN_1_13 at z$_{\rm spec}$=5.182, a massive dusty star-forming galaxy identified through targeted NOEMA observations, and N2GN_1_61 at z$_{\rm spec}$=5.201, revealed using JWST/FRESCO data. In addition to these five spectroscopically confirmed members, we identify five further candidates with photometric redshifts consistent with the overdense structure. These galaxies are massive (with a median stellar mass of 10$^{11}$ M$_{\odot}$) and highly obscured (with a median A$_V$ of 2.9), caught in a short-lived yet extreme starburst phase at z$\sim$5.2. Their high SFRs (with a median of 680 M$_{\odot}$ yr$^{-1}$), efficient baryon to stellar mass conversion ($ε_{\star}>$20%), substantial gas reservoir and dust content, suggest rapid evolution and imminent quenching. Six of these galaxies reside in overdense filaments, while the remaining four may trace new distinct structures which will have to be spectroscopically confirmed. These few dusty galaxies dominate the star formation within the overdensity, contributing more than the numerous H$_α$ emitters, and surpassing the cosmic average star formation rate density for this epoch. Their properties suggest an accelerated evolution that current models and simulations have difficulty reproducing.

Exploiting high-resolution NIKA2 data to study the intracluster medium and dynamical state of ACT-CL J0240.0+0116

Paliwal, A., De Petris, M., Ferragamo, A., et al. (2025), Astronomy and Astrophysics, 698, A2.

NASA ADS | arXiv | Abstract

It is crucial to have a detailed understanding of the intracluster medium (ICM) to infer precise cluster physics, such as the cluster's dynamical state, in order to carry out cluster-based cosmological studies. This knowledge limits the accuracy and precision of mass estimation, which is a key parameter for such studies. In this paper, we conduct an in-depth analysis of cluster ACT-CL J0240.0+0116 using a multi-wavelength approach, with a primary focus on high angular resolution Sunyaev-Zeldovich (SZ) thermal component observations obtained under the New IRAM KIDs Array 2 (NIKA2) Sunyaev-Zeldovich Large Programme (LPSZ). We created composite images using NIKA2, X-ray, and optical galaxy number density maps. The results reveal distinct signs of disturbance within the cluster, with distributions of gas and member galaxies that do not overlap. We also found suggestions for an inflow of matter onto the cluster from the south-west direction. We classified the cluster as disturbed, using morphological indicators derived from its SZ, X-ray, and optical image. The SZ signal in the cluster is also contaminated by a strong central point source. We adopted different approaches to handling this contaminant and found that the estimates of our pressure and hydrostatic mass profiles are robust to the point source mitigation model. The hydrostatic mass of the cluster is estimated at 4.25_‑0.45^+0.50 × 10¹⁴ M_⊙ in the case where the point source was masked. These values are consistent with the mass estimated using only X-ray data and with the values from previous SZ studies of the Atacama Cosmology Telescope (ACT) survey, with improved precision on the mass estimate. Our findings strongly suggest that ACT-CL J0240.0+0116 is a disturbed cluster system, and the detailed observations and derived values serve as a compelling case study for the capabilities of the LPSZ in mapping the cluster ICM with high precision.

Millimeter-wave observations of Euclid Deep Field South using the South Pole Telescope: A data release of temperature maps and catalogs

Archipley, M., Hryciuk, A., Bleem, L. E., et al. (2025), arXiv e-prints, arXiv:2506.00298.

NASA ADS | arXiv | Abstract

Context. The South Pole Telescope third-generation camera (SPT-3G) has observed over 10,000 square degrees of sky at 95, 150, and 220 GHz (3.3, 2.0, 1.4 mm, respectively) overlapping the ongoing 14,000 square-degree Euclid Wide Survey. The Euclid collaboration recently released Euclid Deep Field observations in the first quick data release (Q1). Aims. With the goal of releasing complementary millimeter-wave data and encouraging legacy science, we performed dedicated observations of a 57-square-degree field overlapping the Euclid Deep Field South (EDF-S). Methods. The observing time totaled 20 days and we reached noise depths of 4.3, 3.8, and 13.2 $μ$K-arcmin at 95, 150, and 220 GHz, respectively. Results. In this work we present the temperature maps and two catalogs constructed from these data. The emissive source catalog contains 601 objects (334 inside EDF-S) with 54% synchrotron-dominated sources and 46% thermal dust emission-dominated sources. The 5$σ$ detection thresholds are 1.7, 2.0, and 6.5 mJy in the three bands. The cluster catalog contains 217 cluster candidates (121 inside EDF-S) with median mass $M_{500c}=2.12 \times 10^{14} M_{\odot}/h_{70}$ and median redshift $z$ = 0.70, corresponding to an order-of-magnitude improvement in cluster density over previous tSZ-selected catalogs in this region (3.81 clusters per square degree). Conclusions. The overlap between SPT and Euclid data will enable a range of multiwavelength studies of the aforementioned source populations. This work serves as the first step towards joint projects between SPT and Euclid and provides a rich dataset containing information on galaxies, clusters, and their environments.

Constraints on Inflationary Gravitational Waves with Two Years of SPT-3G Data

Zebrowski, J. A., Reichardt, C. L., Anderson, A. J., et al. (2025), arXiv e-prints, arXiv:2505.02827.

NASA ADS | arXiv | Abstract

We present a measurement of the $B$-mode polarization power spectrum of the cosmic microwave background anisotropies at 32 $\le$ $\ell$ $<$ 502 for three bands centered at 95, 150, and 220 GHz using data from the SPT-3G receiver on the South Pole Telescope. This work uses SPT-3G observations from the 2019 and 2020 winter observing seasons of a $\sim$1500 deg$^2$ patch of sky that directly overlaps with fields observed with the BICEP/Keck family of telescopes, and covers part of the proposed Simons Observatory and CMB-S4 deep fields. Employing new techniques for mitigating polarized atmospheric noise, the SPT-3G data demonstrates a white noise level of 9.3 (6.7) $μ$K-arcmin at $\ell \sim 500$ for the 95 GHz (150 GHz) data, with a $1/\ell$ noise knee at $\ell$=128 (182). We fit the observed six auto- and cross-frequency $B$-mode power spectra to a model including lensed $Λ$CDM $B$-modes and a combination of Galactic and extragalactic foregrounds. This work characterizes foregrounds in the vicinity of the BICEP/Keck survey area, finding foreground power consistent with that reported by the BICEP/Keck collaboration within the same region, and a factor of $\sim$ 3 higher power over the full SPT-3G survey area. Using SPT-3G data over the BICEP/Keck survey area, we place a 95% upper limit on the tensor-to-scalar ratio of $r < 0.25$ and find the statistical uncertainty on $r$ to be $σ(r) = 0.067$.

Detection of Thermal Emission at Millimeter Wavelengths from Low-Earth Orbit Satellites

Foster, A., Chokshi, A., Anderson, A. J., et al. (2025), The Open Journal of Astrophysics, 8, 51.

NASA ADS | arXiv | Abstract

The detection of satellite thermal emission at millimeter wavelengths is presented using data from the 3rd-Generation receiver on the South Pole Telescope (SPT-3G). This represents the first reported detection of thermal emission from artificial satellites at millimeter wavelengths. Satellite thermal emission is shown to be detectable at high signal-to-noise on timescales as short as a few tens of milliseconds. An algorithm for downloading orbital information and tracking known satellites given observer constraints and time-ordered observatory pointing is described. Consequences for cosmological surveys and short-duration transient searches are discussed, revealing that the integrated thermal emission from all large satellites does not contribute significantly to the SPT-3G survey intensity map. Measured satellite positions are found to be discrepant from their two-line element (TLE) derived ephemerides up to several arcminutes which may present a difficulty in cross-checking or masking satellites from short-duration transient searches.

Constraints on Nonthermal Pressure at Galaxy Cluster Outskirts from a Joint SPT and XMM-Newton Analysis

Sarkar, A., McDonald, M., Bleem, L., et al. (2025), The Astrophysical Journal, 984, L63.

NASA ADS | arXiv | Abstract

We present joint South Pole Telescope and XMM-Newton observations of eight massive galaxy clusters (0.8–2 × 10¹⁵ M_⊙) spanning a redshift range of 0.16–0.35. Employing a novel Sunyaev–Zel'dovich + X-ray fitting technique, we effectively constrain the thermodynamic properties of these clusters out to the virial radius. The resulting best-fit electron density, deprojected temperature, and deprojected pressure profiles are in good agreement with previous observations of massive clusters. For the majority of the cluster sample (five out of eight clusters), the entropy profiles exhibit a self-similar behavior near the virial radius. We further derive hydrostatic mass, gas mass, and gas fraction profiles for all clusters up to the virial radius. Comparing the enclosed gas fraction profiles with the universal gas fraction profile, we obtain nonthermal pressure fraction profiles for our cluster sample at >0.5R₅₀₀, demonstrating a steeper increase between R₅₀₀ and R₂₀₀ that is consistent with the hydrodynamical simulations. Our analysis yields nonthermal pressure fraction ranges of 8%–28% (median: 15% ± 11%) at R₅₀₀ and 21%–35% (median: 27% ± 12%) at R₂₀₀. Notably, weak-lensing mass measurements are available for only four clusters in our sample, and our recovered total cluster masses, after accounting for nonthermal pressure, are consistent with these measurements.

Unified and consistent structure growth measurements from joint ACT, SPT and \textit{Planck} CMB lensing

Qu, F. J., Ge, F., Kimmy Wu, W. L., et al. (2025), arXiv e-prints, arXiv:2504.20038.

NASA ADS | arXiv | Abstract

We present the tightest cosmic microwave background (CMB) lensing constraints to date on the growth of structure by combining CMB lensing measurements from the Atacama Cosmology Telescope (ACT), the South Pole Telescope (SPT) and \textit{Planck}. Each of these surveys individually provides lensing measurements with similarly high statistical power, achieving signal-to-noise ratios of approximately 40. The combined lensing bandpowers represent the most precise CMB lensing power spectrum measurement to date with a signal-to-noise ratio of 61 and an amplitude of $A_\mathrm{lens}^\mathrm{recon} = 1.025 \pm 0.017$ with respect to the theory prediction from the best-fit CMB \textit{Planck}-ACT cosmology. The bandpowers from all three lensing datasets, analyzed jointly, yield a $1.6\%$ measurement of the parameter combination $S_8^\mathrm{CMBL} \equiv σ_8\,(Ω_m/0.3)^{0.25} = 0.825^{+0.015}_{-0.013}$. Including Dark Energy Spectroscopic Instrument (DESI) Baryon Acoustic Oscillation (BAO) data improves the constraint on the amplitude of matter fluctuations to $σ_8 = 0.829 \pm 0.009$ (a $1.1\%$ determination). When combining with uncalibrated supernovae from \texttt{Pantheon+}, we present a $4\%$ sound-horizon-independent estimate of $H_0=66.4\pm2.5\,\mathrm{km\,s^{-1}\,Mpc^{-1}} $. The joint lensing constraints on structure growth and present-day Hubble rate are fully consistent with a $Λ$CDM model fit to the primary CMB data from \textit{Planck} and ACT. While the precise upper limit is sensitive to the choice of data and underlying model assumptions, when varying the neutrino mass sum within the $Λ\mathrm{CDM}$ cosmological model, the combination of primary CMB, BAO and CMB lensing drives the probable upper limit for the mass sum towards lower values, comparable to the minimum mass prior required by neutrino oscillation experiments.

Cosmology from CMB lensing and delensed EE power spectra using 2019–2020 SPT-3G polarization data

Ge, F., Millea, M., Camphuis, E., et al. (2025), Physical Review D, 111, 083534.

NASA ADS | arXiv | Abstract

From CMB polarization data alone, we reconstruct the CMB lensing power spectrum, comparable in overall constraining power to previous temperature-based reconstructions, and an unlensed E-mode power spectrum, with clear detections of the third through the tenth acoustic peaks. The observations, taken in 2019 and 2020 with the South Pole Telescope (SPT) and the SPT-3G camera, cover 1500 deg2 at 95, 150, and 220 GHz with arcminute resolution and roughly 4.9 μK-arcmin coadded noise in polarization. The power spectrum estimates, together with systematic parameter estimates and a joint covariance matrix, follow from a Bayesian analysis using the marginal unbiased score expansion (MUSE) method. The E-mode spectrum at ℓ>2000 and lensing spectrum at L>350 are the most precise to date. Assuming the ΛCDM model, and using only these SPT data and priors on τ and absolute calibration from Planck, we find H0=66.81±0.81 km/s/Mpc, comparable in precision to the Planck determination and in 5.4σ tension with the most precise H0 inference derived via the distance ladder. We also find S8≡σ8(Ωm/0.3)0.5=0.850±0.017, providing further independent evidence of a slight tension with low-redshift structure probes. The ΛCDM model provides a good simultaneous fit to the combined Planck, ACT, and SPT data, and thus passes a powerful test. Combining these CMB datasets with BAO observations, we explore extensions to the ΛCDM model. We find that the effective number of neutrino species, spatial curvature, and primordial helium fraction are consistent with standard model values, and that the 95% confidence upper limit on the neutrino mass sum is 0.075 eV, close to the minimum sum expected from observations of solar and atmospheric neutrino oscillations. The SPT data are consistent with the somewhat weak (<3σ) preference for excess lensing power seen in Planck and ACT data relative to predictions of the ΛCDM model given the combined Planck, ACT, and BAO datasets. We also detect at greater than 3σ the influence of nonlinear evolution in the CMB lensing power spectrum and discuss it in the context of the S8 tension. Forthcoming SPT-3G analyses will feature deeper and wider observations in temperature and polarization, providing even tighter constraints and more powerful tests of the ΛCDM model.

A panchromatic view of N2CLS GOODS-N: The evolution of the dust cosmic density since z ∼ 7

Berta, S., Lagache, G., Beelen, A., et al. (2025), Astronomy and Astrophysics, 696, A193.

NASA ADS | arXiv | Abstract

To understand early star formation, it is essential to determine the dust mass budget of high-redshift galaxies. Sub-millimeter rest-frame emission, dominated by cold dust, is an unbiased tracer of dust mass. The New IRAM KID Arrays 2 (NIKA2) conducted a deep blank field survey at 1.2 and 2.0 mm in the GOODS-N field as part of the NIKA2 Cosmological Legacy Survey (N2CLS), detecting 65 sources with S/N ≥ 4.2. Thanks to a dedicated interferometric program with NOEMA and other high-angular resolution data, we identified the multi-wavelength counterparts of these sources and resolved them into 71 individual galaxies. We built detailed spectral energy distributions (SEDs) and assigned a redshift to 68 of them over the range 0.6 < z < 7.2. We fit these SEDs using modified blackbody and Draine & Li (2007, ApJ, 657, 810) models and the panchromatic approaches MAGPHYS, CIGALE, and SED3FIT, thus deriving their dust mass (M_dust), infrared luminosity (L_IR), and stellar mass (M_⋆). Eight galaxies require an active galactic nucleus torus component, and another six require an unextinguished young stellar population. A significant fraction of our galaxies are classified as starbursts based on their position on the M_⋆ versus star formation rate plane or their depletion timescales. We computed the dust mass function in three redshift bins (1.6 < z ≤ 2.4, 2.4 < z ≤ 4.2 and 4.2 < z ≤ 7.2) and determined the Schechter function that best describes it. The dust cosmic density, ρ_dust, increases by at least an order of magnitude from z ∼ 7 to z ∼ 1.5, as predicted by theoretical works. At lower redshifts, the evolution flattens. Nonetheless, significant differences exist between results obtained with different selections and methods. The superb GOODS-N data set enabled a systematic investigation into the dust properties of distant galaxies. N2CLS holds promise for combining these deep field findings with the wide COSMOS field into a self-consistent analysis of dust in galaxies both near and far.

The SPT-Deep Cluster Catalog: Sunyaev-Zel’dovich Selected Clusters from Combined SPT-3G and SPTpol Measurements over 100 Square Degrees

Kornoelje, K., Bleem, L. E., Rykoff, E. S., et al. (2025), arXiv e-prints, arXiv:2503.17271.

NASA ADS | arXiv | Abstract

We present a catalog of 500 galaxy cluster candidates in the SPT-Deep field: a 100 deg$^2$ field that combines data from the SPT-3G and SPTpol surveys to reach noise levels of 3.0, 2.2, and 9.0 $\mu$K-arcmin at 95, 150, and 220 GHz, respectively. This is comparable to noise levels expected for the wide field survey of CMB-S4, a next-generation CMB experiment. Candidates are selected via the thermal Sunyaev-Zel'dovich (SZ) effect with a minimum significance of $\xi = 4.0$, resulting in a catalog of purity $\sim 89 \%$. Optical data from the Dark Energy Survey and infrared data from the Spitzer Space Telescope are used to confirm 442 cluster candidates. The clusters span $0.12 < z \lesssim 1.8$ and $1.0 \times 10^{14} M_{\odot}/h_{70} < M_{500c} < 8.7 \times 10^{14} M_{\odot}/h_{70}$. The sample's median redshift is 0.74 and the median mass is $1.7 \times 10^{14} M_{\odot}/h_{70}$; these are the lowest median mass and highest median redshift of any SZ-selected sample to date. We assess the effect of infrared emission from cluster member galaxies on cluster selection by performing a joint fit to the infrared dust and tSZ signals by combining measurements from SPT and overlapping submillimeter data from Herschel/SPIRE. We find that at high redshift ($z>1)$, the tSZ signal is reduced by $17.4^{+3.1}_{-2.9} \%$ ($3.7^{+0.7}_{-0.7}\%$) at 150 GHz (95 GHz) due to dust contamination. We repeat our cluster finding method on dust-nulled SPT maps and find the resulting catalog is consistent with the nominal SPT-Deep catalog, demonstrating dust contamination does not significantly impact the SPT-Deep selection function; we attribute this lack of bias to the inclusion of the SPT 220 GHz band.

Multiprobe cosmology from the abundance of SPT clusters and DES galaxy clustering and weak lensing

Bocquet, S., Grandis, S., Krause, E., et al. (2025), Physical Review D, 111, 063533.

NASA ADS | arXiv | Abstract

Cosmic shear, galaxy clustering, and the abundance of massive halos each probe the large-scale structure of the Universe in complementary ways. We present cosmological constraints from the joint analysis of the three probes, building on the latest analyses of the lensing-informed abundance of clusters identified by the South Pole Telescope (SPT) and of the auto- and cross-correlation of galaxy position and weak lensing measurements (3×2pt) in the Dark Energy Survey (DES). We consider the cosmological correlation between the different tracers and we account for the systematic uncertainties that are shared between the large-scale lensing correlation functions and the small-scale lensing-based cluster mass calibration. Marginalized over the remaining Λ cold dark matter (ΛCDM) parameters (including the sum of neutrino masses) and 52 astrophysical modeling parameters, we measure Ωm=0.300±0.017 and σ8=0.797±0.026. Compared to constraints from Planck primary cosmic microwave background (CMB) anisotropies, our constraints are only 15% wider with a probability to exceed of 0.22 (1.2σ) for the two-parameter difference. We further obtain S8≡σ8(Ωm/0.3)0.5=0.796±0.013 which is lower than the Planck measurement at the 1.6σ level. The combined SPT cluster, DES 3×2pt, and Planck datasets mildly prefer a nonzero positive neutrino mass, with a 95% upper limit ∑mν<0.25 eV on the sum of neutrino masses. Assuming a wCDM model, we constrain the dark energy equation of state parameter w=-1.15-0.17+0.23 and when combining with Planck primary CMB anisotropies, we recover w=-1.20-0.09+0.15, a 1.7σ difference with a cosmological constant. The precision of our results highlights the benefits of multiwavelength multiprobe cosmology and our analysis paves the way for upcoming joint analyses of next-generation datasets.

Measurement and Modeling of Polarized Atmosphere at the South Pole with SPT-3G

Coerver, A., Zebrowski, J. A., Takakura, S., et al. (2025), The Astrophysical Journal, 982, 15.

NASA ADS | arXiv | Abstract

We present the detection and characterization of fluctuations in linearly polarized emission from the atmosphere above the South Pole. These measurements make use of data from the SPT-3G receiver on the South Pole Telescope in three frequency bands centered at 95, 150, and 220 GHz. We use the cross-correlation between detectors to produce an unbiased estimate of the power in Stokes I, Q, and U parameters on large angular scales. Our results are consistent with the polarized signal being produced by the combination of Rayleigh scattering of thermal radiation from the ground and thermal emission from a population of horizontally aligned ice crystals with an anisotropic distribution described by Kolmogorov turbulence. The measured spatial scaling, frequency scaling, and elevation dependence of the polarized emission are explained by this model. Polarized atmospheric emission has the potential to significantly impact observations on the large angular scales being targeted by searches for inflationary B-mode CMB polarization. We present the distribution of measured angular power spectrum amplitudes in Stokes Q and I for 4 yr of Austral winter observations, which can be used to simulate the impact of atmospheric polarization and intensity fluctuations at the South Pole on a specified experiment and observation strategy. We present a mitigation strategy that involves both downweighting significantly contaminated observations and subtracting a polarized atmospheric signal from the 150 GHz band maps. In observations with the SPT-3G instrument, the polarized atmospheric signal is a well-understood and subdominant contribution to the measured noise after implementing the mitigation strategies described here.

Pointing Accuracy Improvements for the South Pole Telescope with Machine Learning

Chichura, P. M., Rahlin, A., Anderson, A. J., et al. (2025), Journal of Astronomical Instrumentation, 14, 2550001.

NASA ADS | arXiv | Abstract

In this paper, we present improvements to the pointing accuracy of the South Pole Telescope (SPT) using machine learning. The ability of the SPT to point accurately at the sky is limited by its structural imperfections, which are impacted by the extreme weather at the South Pole. Pointing accuracy is particularly important during SPT participation in observing campaigns with the Event Horizon Telescope (EHT), which requires stricter accuracy than typical observations with the SPT. We compile a training dataset of historical observations of astronomical sources made with the SPT-3G and EHT receivers on the SPT. We train two XGBoost models to learn a mapping from current weather conditions to two telescope drive control arguments — one which corrects for errors in azimuth and the other for errors in elevation. Our trained models achieve root mean squared errors on withheld test data of 2.′′14 in cross-elevation and 3.′′57 in elevation, well below our goal of 5′′ along each axis. We deploy our models on the telescope control system and perform further in situ test observations during the EHT observing campaign in April 2024. Our models result in significantly improved pointing accuracy: for sources within the range of input variables where the models are best trained, average combined pointing error improved 33%, from 15.′′9 to 10.′′6. These improvements, while significant, fall shy of our ultimate goal, but they serve as a proof of concept for the development of future models. Planned upgrades to the EHT receiver on the SPT will necessitate even stricter pointing accuracy which will be achievable with our methods.

Interpreting millimeter emission from IMEGIN galaxies NGC 2146 and NGC 2976

Ejlali, G., Tabatabaei, F. S., Roussel, H., et al. (2025), Astronomy and Astrophysics, 693, A88.

NASA ADS | arXiv | Abstract

The millimeter continuum emission from galaxies provides important information about cold dust, its distribution, its heating, and its role in the interstellar medium (ISM). This emission also carries an unknown portion of the free-free and synchrotron radiation. The IRAM 30 m Guaranteed Time Large Project, Interpreting Millimeter Emission of Galaxies with IRAM and NIKA2 (IMEGIN) provides a unique opportunity to study the origin of the millimeter emission at angular resolutions of < 18″ in a sample of nearby galaxies. As a pilot study, we present millimeter observations of two IMEGIN galaxies, NGC 2146 (starburst) and NGC 2976 (peculiar dwarf) at 1.15 mm and 2 mm. Combined with the data taken with the Spitzer, Herschel, Planck, WSRT, and the 100 m Effelsberg telescopes, we modeled the infrared-to-radio Spectral Energy Distribution (SED) of these galaxies, both globally and at resolved scales, using a Bayesian approach to (1) dissect different components of the millimeter emission, (2) investigate the physical properties of dust, and (3) explore the correlations between millimeter emission, gas, and star formation rate (SFR). We find that cold dust is responsible for most of the 1.15 mm emission in both galaxies and at 2 mm in NGC 2976. The free-free emission emits more importantly in NGC 2146 at 2 mm. The cold dust emissivity index is flatter in the dwarf galaxy (β = 1.3 ± 0.1) compared to the starburst galaxy (β = 1.7 ± 0.1). Mapping the dust-to-gas ratio, we find that it changes between 0.004 and 0.01 with a mean of 0.006 ± 0.001 in the dwarf galaxy. In addition, there is no global balance between the formation and dissociation of H₂ in this galaxy. We find tight correlations between the millimeter emission and both the SFR and molecular gas mass in both galaxies.

SPT clusters with DES and HST weak lensing. II. Cosmological constraints from the abundance of massive halos

Bocquet, S., Grandis, S., Bleem, L. E., et al. (2024), Physical Review D, 110, 083510.

NASA ADS | arXiv | Abstract

We present cosmological constraints from the abundance of galaxy clusters selected via the thermal Sunyaev-Zel'dovich (SZ) effect in South Pole Telescope (SPT) data with a simultaneous mass calibration using weak gravitational lensing data from the Dark Energy Survey (DES) and the Hubble Space Telescope (HST). The cluster sample is constructed from the combined SPT-SZ, SPTpol ECS, and SPTpol 500d surveys, and comprises 1,005 confirmed clusters in the redshift range 0.25–1.78 over a total sky area of 5200 deg2. We use DES Year 3 weak-lensing data for 688 clusters with redshifts z<0.95 and HST weak-lensing data for 39 clusters with 0.6<z<1.7. The weak-lensing measurements enable robust mass measurements of sample clusters and allow us to empirically constrain the SZ observable-mass relation without having to make strong assumptions about, e.g., the hydrodynamical state of the clusters. For a flat ΛCDM cosmology, and marginalizing over the sum of massive neutrinos, we measure Ωm=0.286±0.032, σ8=0.817±0.026, and the parameter combination σ8(Ωm/0.3)0.25=0.805±0.016. Our measurement of S8≡σ8Ωm/0.3=0.795±0.029 and the constraint from Planck CMB anisotropies (2018 TT, TE, EE+lowE) differ by 1.1σ. In combination with that Planck dataset, we place a 95% upper limit on the sum of neutrino masses ∑mν<0.18 eV. When additionally allowing the dark energy equation of state parameter w to vary, we obtain w=-1.45±0.31 from our cluster-based analysis. In combination with Planck data, we measure w=-1.34-0.15+0.22, or a 2.2σ difference with a cosmological constant. We use the cluster abundance to measure σ8 in five redshift bins between 0.25 and 1.8, and we find the results to be consistent with structure growth as predicted by the ΛCDM model fit to Planck primary CMB data.

SPT clusters with DES and HST weak lensing. I. Cluster lensing and Bayesian population modeling of multiwavelength cluster datasets

Bocquet, S., Grandis, S., Bleem, L. E., et al. (2024), Physical Review D, 110, 083509.

NASA ADS | arXiv | Abstract

We present a Bayesian population modeling method to analyze the abundance of galaxy clusters identified by the South Pole Telescope (SPT) with a simultaneous mass calibration using weak gravitational lensing data from the Dark Energy Survey (DES) and the Hubble Space Telescope (HST). We discuss and validate the modeling choices with a particular focus on a robust, weak-lensing-based mass calibration using DES data. For the DES Year 3 data, we report a systematic uncertainty in weak-lensing mass calibration that increases from 1% at z=0.25 to 10% at z=0.95, to which we add 2% in quadrature to account for uncertainties in the impact of baryonic effects. We implement an analysis pipeline that joins the cluster abundance likelihood with a multiobservable likelihood for the Sunyaev-Zel'dovich effect, optical richness, and weak-lensing measurements for each individual cluster. We validate that our analysis pipeline can recover unbiased cosmological constraints by analyzing mocks that closely resemble the cluster sample extracted from the SPT-SZ, SPTpol ECS, and SPTpol 500d surveys and the DES Year 3 and HST-39 weak-lensing datasets. This work represents a crucial prerequisite for the subsequent cosmological analysis of the real dataset.

First Constraints on the Epoch of Reionization Using the Non-Gaussianity of the Kinematic Sunyaev-Zel’dovich Effect from the South Pole Telescope and Herschel-SPIRE Observations

Raghunathan, S., Ade, P. A. R., Anderson, A. J., et al. (2024), Physical Review Letters, 133, 121004.

NASA ADS | arXiv | Abstract

We report results from an analysis aimed at detecting the trispectrum of the kinematic Sunyaev-Zel'dovich (kSZ) effect by combining data from the South Pole Telescope (SPT) and Herschel-SPIRE experiments over a 100 deg2 field. The SPT observations combine data from the previous and current surveys, namely SPTpol and SPT-3G, to achieve depths of 4.5, 3, and 16 μK-arcmin in bands centered at 95, 150, and 220 GHz. For SPIRE, we include data from the 600 and 857 GHz bands. We reconstruct the velocity-induced large-scale correlation of the small-scale kSZ signal with a quadratic estimator that uses two cosmic microwave background (CMB) temperature maps, constructed by optimally combining data from all the frequency bands. We reject the null hypothesis of a zero trispectrum at 10.3σ level. However, the measured trispectrum contains contributions from both the kSZ and other undesired components, such as CMB lensing and astrophysical foregrounds, with kSZ being sub-dominant. We use the AGORA simulations to estimate the expected signal from CMB lensing and astrophysical foregrounds. After accounting for the contributions from CMB lensing and foreground signals, we do not detect an excess kSZ-only trispectrum and use this nondetection to set constraints on reionization. By applying a prior based on observations of the Gunn-Peterson trough, we obtain an upper limit on the duration of reionization of Δzre,50<4.5 (95% confidence level). We find these constraints are fairly robust to foregrounds assumptions. This trispectrum measurement is independent of, but consistent with, Planck's optical depth measurement. This result is the first constraint on the epoch of reionization using the non-Gaussian nature of the kSZ signal.

Testing the ΛCDM Cosmological Model with Forthcoming Measurements of the Cosmic Microwave Background with SPT-3G

Prabhu, K., Raghunathan, S., Millea, M., et al. (2024), The Astrophysical Journal, 973, 4.

NASA ADS | arXiv | Abstract

We forecast constraints on cosmological parameters enabled by three surveys conducted with SPT-3G, the third-generation camera on the South Pole Telescope. The surveys cover separate regions of 1500, 2650, and 6000 deg² to different depths, in total observing 25% of the sky. These regions will be measured to white noise levels of roughly 2.5, 9, and 12μK -armin, respectively, in cosmic microwave background (CMB) temperature units at 150 GHz by the end of 2024. The survey also includes measurements at 95 and 220 GHz, which have noise levels a factor of ∼1.2 and 3.5 times higher than 150 GHz, respectively, with each band having a polarization noise level ∼2 times higher than the temperature noise. We use a novel approach to obtain the covariance matrices for jointly and optimally estimated gravitational lensing potential band powers and unlensed CMB temperature and polarization band powers. We demonstrate the ability to test the ΛCDM model via the consistency of cosmological parameters constrained independently from SPT-3G and Planck data, and consider the improvement in constraints on ΛCDM extension parameters from a joint analysis of SPT-3G and Planck data. The ΛCDM cosmological parameters are typically constrained with uncertainties up to ∼2 times smaller with SPT-3G data, compared to Planck, with the two data sets measuring significantly different angular scales and polarization levels, providing additional tests of the standard cosmological model.

Flaring Stars in a Nontargeted Millimeter-wave Survey with SPT-3G

Tandoi, C., Guns, S., Foster, A., et al. (2024), The Astrophysical Journal, 972, 6.

NASA ADS | arXiv | Abstract

We present a flare star catalog from 4 yr of nontargeted millimeter-wave survey data from the South Pole Telescope (SPT). The data were taken with the SPT-3G camera and cover a 1500 deg² region of the sky from 20^h40^m0^s to 3^h20^m0^s in right ascension and from ‑42° to ‑70° in declination. This region was observed on a nearly daily cadence from 2019 to 2022 and chosen to avoid the plane of the galaxy. A short-duration transient search of this survey yields 111 flaring events from 66 stars, increasing the number of both flaring events and detected flare stars by an order of magnitude from the previous SPT-3G data release. We provide cross-matching to Gaia DR3, as well as matches to X-ray point sources found in the second ROSAT all-sky survey. We have detected flaring stars across the main sequence, from early-type A stars to M dwarfs, as well as a large population of evolved stars. These stars are mostly nearby, spanning 10–1000 pc in distance. Most of the flare spectral indices are constant or gently rising as a function of frequency at 95/150/220 GHz. The timescale of these events can range from minutes to hours, and the peak ν L _ν luminosities range from 10²⁷ to 10³¹ erg s^‑1 in the SPT-3G frequency bands.

SPT-SZ MCMF: an extension of the SPT-SZ catalogue over the DES region

Klein, M., Mohr, J. J., Bocquet, S., et al. (2024), Monthly Notices of the Royal Astronomical Society, 531, 3973.

NASA ADS | arXiv | Abstract

We present an extension to a Sunyaev-Zel'dovich Effect (SZE) selected cluster catalogue based on observations from the South Pole Telescope (SPT); this catalogue extends to lower signal to noise than the previous SPT-SZ catalogue and therefore includes lower mass clusters. Optically derived redshifts, centres, richnesses, and morphological parameters together with catalogue contamination and completeness statistics are extracted using the multicomponent matched filter (MCMF) algorithm applied to the S/N > 4 SPT-SZ candidate list and the Dark Energy Survey (DES) photometric galaxy catalogue. The main catalogue contains 811 sources above S/N = 4, has 91 per cent purity, and is 95 per cent complete with respect to the original SZE selection. It contains in total 50 per cent more clusters and twice as many clusters above z = 0.8 in comparison to the original SPT-SZ sample. The MCMF algorithm allows us to define subsamples of the desired purity with traceable impact on catalogue completeness. As an example, we provide two subsamples with S/N > 4.25 and S/N > 4.5 for which the sample contamination and cleaning-induced incompleteness are both as low as the expected Poisson noise for samples of their size. The subsample with S/N > 4.5 has 98 per cent purity and 96 per cent completeness and is part of our new combined SPT cluster and DES weak-lensing cosmological analysis. We measure the number of false detections in the SPT-SZ candidate list as function of S/N, finding that it follows that expected from assuming Gaussian noise, but with a lower amplitude compared to previous estimates from simulations.

Mass calibration of DES Year-3 clusters via SPT-3G CMB cluster lensing

Ansarinejad, B., Raghunathan, S., Abbott, T. M. C., et al. (2024), Journal of Cosmology and Astroparticle Physics, 2024, 024.

NASA ADS | arXiv | Abstract

We measure the stacked lensing signal in the direction of galaxy clusters in the Dark Energy Survey Year 3 (DES Y3) redMaPPer sample, using cosmic microwave background (CMB) temperature data from SPT-3G, the third-generation CMB camera on the South Pole Telescope (SPT). Here, we estimate the lensing signal using temperature maps constructed from the initial 2 years of data from the SPT-3G 'Main' survey, covering 1500 deg² of the Southern sky. We then use this lensing signal as a proxy for the mean cluster mass of the DES sample. The thermal Sunyaev-Zel'dovich (tSZ) signal, which can contaminate the lensing signal if not addressed, is isolated and removed from the data before obtaining the mass measurement. In this work, we employ three versions of the redMaPPer catalogue: a Flux-Limited sample containing 8865 clusters, a Volume-Limited sample with 5391 clusters, and a Volume&Redshift-Limited sample with 4450 clusters. For the three samples, we detect the CMB lensing signal at a significance of 12.4σ, 10.5σ and 10.2σ and find the mean cluster masses to be M _200m = 1.66±0.13 [stat.]± 0.03 [sys.], 1.97±0.18 [stat.]± 0.05 [sys.], and 2.11±0.20 [stat.]± 0.05 [sys.]×10¹⁴ M_⊙, respectively. This is a factor of ∼ 2 improvement relative to the precision of measurements with previous generations of SPT surveys and the most constraining cluster mass measurements using CMB cluster lensing to date. Overall, we find no significant tensions between our results and masses given by redMaPPer mass-richness scaling relations of previous works, which were calibrated using CMB cluster lensing, optical weak lensing, and velocity dispersion measurements from various combinations of DES, SDSS and Planck data. We then divide our sample into 3 redshift and 3 richness bins, finding no significant discrepancies with optical weak-lensing calibrated masses in these bins. We forecast a 5.7% constraint on the mean cluster mass of the DES Y3 sample with the complete SPT-3G surveys when using both temperature and polarization data and including an additional ∼ 1400 deg² of observations from the 'Extended' SPT-3G survey.

Reducing Model Error Using Optimised Galaxy Selection: Weak Lensing Cluster Mass Estimation

Rau, M. M., Kéruzoré, F., Ramachandra, N., & Bleem, L. (2024), arXiv e-prints, arXiv:2406.11950.

NASA ADS | arXiv | Abstract

Galaxy clusters are one of the most powerful probes to study extensions of General Relativity and the Standard Cosmological Model. Upcoming surveys like the Vera Rubin Observatory's Legacy Survey of Space and Time are expected to revolutionise the field, by enabling the analysis of cluster samples of unprecedented size and quality. To reach this era of high-precision cluster cosmology, the mitigation of sources of systematic error is crucial. A particularly important challenge is bias in cluster mass measurements induced by inaccurate photometric redshift estimates of source galaxies. This work proposes a method to optimise the source sample selection in cluster weak lensing analyses drawn from wide-field survey lensing catalogs to reduce the bias on reconstructed cluster masses. We use a combinatorial optimisation scheme and methods from variational inference to select galaxies in latent space to produce a probabilistic galaxy source sample catalog for highly accurate cluster mass estimation. We show that our method reduces the critical surface mass density $\Sigma_{\rm crit}$ modelling bias on the 60-70% level, while maintaining up to 90% of galaxies. We highlight that our methodology has applications beyond cluster mass estimation as an approach to jointly combine galaxy selection and model inference under sources of systematics.

The XXL Survey. LI. Pressure profile and Y_SZ − M scaling relation in three low-mass galaxy clusters at z ∼ 1 observed with NIKA2

Adam, R., Ricci, M., Eckert, D., et al. (2024), Astronomy and Astrophysics, 684, A18.

NASA ADS | arXiv | Abstract

Context. The thermodynamical properties of the intracluster medium (ICM) are driven by scale-free gravitational collapse, but they also reflect the rich astrophysical processes at play in galaxy clusters. At low masses (∼10¹⁴ M_⊙) and high redshift (z ≳ 1), these properties remain poorly constrained, observationally speaking, due to the difficulty in obtaining resolved and sensitive data.
Aims: We aim to investigate the inner structure of the ICM as seen through the Sunyaev-Zel'dovich (SZ) effect in this regime of mass and redshift. We focused on the thermal pressure profile and the scaling relation between SZ flux and mass, namely the Y_SZ − M scaling relation.
Methods: The three galaxy clusters XLSSC 072 (z = 1.002), XLSSC 100 (z = 0.915), and XLSSC 102 (z = 0.969), with M₅₀₀ ∼ 2 × 10¹⁴ M_⊙, were selected from the XXL X-ray survey and observed with the NIKA2 millimeter camera to image their SZ signal. XMM-Newton X-ray data were used as a complement to the NIKA2 data to derive masses based on the Y_X − M relation and the hydrostatic equilibrium.
Results: The SZ images of the three clusters, along with the X-ray and optical data, indicate dynamical activity related to merging events. The pressure profile is consistent with that expected for morphologically disturbed systems, with a relatively flat core and a shallow outer slope. Despite significant disturbances in the ICM, the three high-redshift low-mass clusters follow the Y_SZ − M relation expected from standard evolution remarkably well.
Conclusions: These results indicate that the dominant physics that drives cluster evolution is already in place by z ∼ 1, at least for systems with masses above M₅₀₀ ∼ 10¹⁴ M_⊙.

The FITS file of the published NIKA2 maps are available at the CDS via anonymous ftp to cdsarc.cds.unistra.fr (ftp://130.79.128.5) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/684/A18.

Faint mm NIKA2 dusty star-forming galaxies: Finding the high-redshift population

Bing, L.-J., Beelen, A., Lagache, G., et al. (2024), Astronomy and Astrophysics, 683, A232.

NASA ADS | arXiv | Abstract


Aims: High-redshift dusty star-forming galaxies (DSFGs) are proposed to be the progenitors of massive quiescent galaxies arising at cosmic noon, providing a crucial insight into the formation, assembly, and early quenching of massive galaxies in the early Universe. However, their high redshift combined with high dust obscuration adds significant difficulties to their redshift measurement, which is mandatory for detailed studies of their physical properties. Blind mm spectral scans are the most unbiased way in prinicple for obtaining accurate spectroscopic redshifts for these sources, but identifying faint molecular and atomic lines within limited telescope time for faint DSFGs is also difficult with these scans.
Methods: We developed a new framework to constrain the source redshift. The method jointly accounts for the detection and/or nondetection of spectral lines and the prior information from the photometric redshift and total infrared luminosity from spectral energy distribution analysis. The method uses the estimated total infrared luminosity to predict the line fluxes at given redshifts and generates model spectra. The redshift-dependent spectral models were then compared with the observed spectra to determine the redshift.
Results: We applied this joint redshift analysis method to four high-z dusty star-forming galaxy candidates selected from the NIKA2 observations of the HLSJ091828.6+514223 (HLS) field that were further observed by NOEMA with blind spectral scans. These sources only have Herschel SPIRE photometry as ancillary data. They were selected because SPIRE counterparts are faint or entirely lacking and thus favor to select the highest-redshift candidates. The method finds a spectroscopic redshift of 4 in the five NOEMA-counterpart detected sources, with z > 3. Based on these measurements, we derived the CO and [CI] lines and mm continuum fluxes from the NOEMA data and studied the properties of their interstellar medium and star formation. We find cold dust temperatures in some of the HLS sources compared to the general population of submm galaxies, which might be related to the bias introduced by the SPIRE-dropout selection. All sources except for one have a short gas-depletion time of a few hundred million years, which is typical of high-z submm galaxies. The only exception shows a longer gas-depletion time of up to a few billion years. This is comparable to the gas-depletion times of main-sequence galaxies at the same redshift. Furthermore, we identify a possible overdensity of dusty star-forming galaxies at z = 5.2 that is traced by two sources in our sample, as well as a lensed galaxy HLSJ091828.6+514223.
Conclusions: We demonstrate that our method when applied to mm-selected DSFGs is able to determine the redshift accurately. This accuracy with only multiple emission lines with a low signal-to-noise ratio shows promising potential for the blind redshift search in large samples of high-z DSFGs, even in the absence of optical to near infrared photometric redshifts.

Galaxy Clusters Discovered via the Thermal Sunyaev-Zel’dovich Effect in the 500-square-degree SPTpol Survey

Bleem, L. E., Klein, M., Abbot, T. M. C., et al. (2024), The Open Journal of Astrophysics, 7, 13.

NASA ADS | arXiv | Abstract

We present a catalog of 689 galaxy cluster candidates detected at significance $\xi>4$ via their thermal Sunyaev-Zel'dovich (SZ) effect signature in 95 and 150 GHz data from the 500-square-degree SPTpol survey. We use optical and infrared data from the Dark Energy Camera and the Wide-field Infrared Survey Explorer (WISE) and \spitzer \ satellites, to confirm 544 of these candidates as clusters with $\sim94\%$ purity. The sample has an approximately redshift-independent mass threshold at redshift $z>0.25$ and spans $1.5 \times 10^{14} < M_{500c} < 9.1 \times 10^{14}$ $M_\odot/h_{70}$ \ and $0.03<z\lesssim1.6$ in mass and redshift, respectively; 21\% of the confirmed clusters are at $z>1$. We use external radio data from the Sydney University Molonglo Sky Survey (SUMSS) to estimate contamination to the SZ signal from synchrotron sources. The contamination reduces the recovered $\xi$ by a median value of 0.032, or $\sim0.8\%$ of the $\xi=4$ threshold value, and $\sim7\%$ of candidates have a predicted contamination greater than $\Delta \xi = 1$. With the exception of a small number of systems $(<1\%)$, an analysis of clusters detected in single-frequency 95 and 150 GHz data shows no significant contamination of the SZ signal by emission from dusty or synchrotron sources. This cluster sample will be a key component in upcoming astrophysical and cosmological analyses of clusters. The SPTpol millimeter-wave maps and associated data products used to produce this sample are available at https://pole.uchicago.edu/public/data/sptpol_500d_clusters/index.html, and the NASA LAMBDA website. An interactive sky server with the SPTpol maps and Dark Energy Survey data release 2 images is also available at NCSA https://skyviewer.ncsa.illinois.edu.

The hydrostatic-to-lensing mass bias from resolved X-ray and optical-IR data

Muñoz-Echeverría, M., Macías-Pérez, J. F., Pratt, G. W., et al. (2024), Astronomy and Astrophysics, 682, A147.

NASA ADS | arXiv | Abstract

An accurate reconstruction of galaxy cluster masses is key to use this population of objects as a cosmological probe. In this work we present a study on the hydrostatic-to-lensing mass scaling relation for a sample of 53 clusters whose masses were reconstructed homogeneously in a redshift range between z = 0.05 and 1.07. The M₅₀₀ mass for each cluster was indeed inferred from the mass profiles extracted from the X-ray and lensing data, without using a priori observable-mass scaling relations. We assessed the systematic dispersion of the masses estimated with our reference analyses with respect to other published mass estimates. Accounting for this systematic scatter does not change our main results, but enables the propagation of the uncertainties related to the mass reconstruction method or used dataset. Our analysis gives a hydrostatic-to-lensing mass bias of (1−b) = 0.739_−0.070^+0.075 and no evidence of evolution with redshift. These results are robust against possible subsample differences.

Measurement of gravitational lensing of the cosmic microwave background using SPT-3G 2018 data

Pan, Z., Bianchini, F., Wu, W. L. K., et al. (2023), Physical Review D, 108, 122005.

NASA ADS | arXiv | Abstract

We present a measurement of gravitational lensing over 1500 deg² of the Southern sky using SPT-3G temperature data at 95 GHz and 150 GHz taken in 2018. The lensing amplitude relative to a fiducial Planck 2018 Lambda cold dark matter (Λ CDM ) cosmology is found to be 1.020 ±0.060 , excluding instrumental and astrophysical systematic uncertainties. We conduct extensive systematic and null tests to check the robustness of the lensing measurements, and report a minimum-variance combined lensing power spectrum over angular multipoles of 50 <L <2000 , which we use to constrain cosmological models. When analyzed alone and jointly with primary cosmic microwave background (CMB) spectra within the Λ CDM model, our lensing amplitude measurements are consistent with measurements from SPT-SZ, SPTpol, ACT, and Planck. Incorporating loose priors on the baryon density and other parameters including uncertainties on a foreground bias template, we obtain a 1 σ constraint on σ₈Ω_m^0.25=0.595 ±0.026 using the SPT-3G 2018 lensing data alone, where σ₈ is a common measure of the amplitude of structure today and Ω_m is the matter density parameter. Combining SPT-3G 2018 lensing measurements with baryon acoustic oscillation (BAO) data, we derive parameter constraints of σ₈=0.810 ±0.033 , S₈≡σ₈(Ω_m/0.3 )^0.5=0.836 ±0.039 , and Hubble constant H₀=68.8_-1.6^+1.3 km s^-1 Mpc^-1 . Our preferred S₈ value is higher by 1.6 to 1.8 σ compared to cosmic shear measurements from DES-Y3, HSC-Y3, and KiDS-1000 at lower redshift and smaller scales. We combine our lensing data with CMB anisotropy measurements from both SPT-3G and Planck to constrain extensions of Λ CDM . Using CMB anisotropy and lensing measurements from SPT-3G only, we provide independent constraints on the spatial curvature of Ω_K=0.01 4_-0.026^+0.023 (95% C.L.) and the dark energy density of Ω_Λ=0.72 2_-0.026^+0.031 (68% C.L.). When combining SPT-3G lensing data with SPT-3G CMB anisotropy and BAO data, we find an upper limit on the sum of the neutrino masses of ∑m_ν<0.30 eV (95% C.L.). Due to the different combination of angular scales and sky area, this lensing analysis provides an independent check on lensing measurements by ACT and Planck.

The stratification of ISM properties in the edge-on galaxy NGC 891 revealed by NIKA2

Katsioli, S., Xilouris, E. M., Kramer, C., et al. (2023), Astronomy and Astrophysics, 679, A7.

NASA ADS | arXiv | Abstract

Context. As the millimeter wavelength range remains a largely unexplored spectral region for galaxies, the IMEGIN large program aims to map the millimeter continuum emission of 22 nearby galaxies at 1.15 and 2 mm.
Aims: Using the high-resolution maps produced by the NIKA2 camera, we explore the existence of very cold dust and take possible contamination by free-free and synchrotron emission into account. We study the IR-to-radio emission coming from different regions along the galactic plane and at large vertical distances.
Methods: New observations of NGC 891, using the NIKA2 camera on the IRAM 30 m telescope, along with a suite of observations at other wavelengths were used to perform a multiwavelength study of the spectral energy distribution in the interstellar medium in this galaxy. This analysis was performed globally and locally, using the advanced hierarchical Bayesian fitting code, HerBIE, coupled with the THEMIS dust model.
Results: Our dust modeling is able to reproduce the near-IR to millimeter emission of NGC 891, with the exception of an excess at a level of 25% obtained by the NIKA2 observations in the outermost parts of the disk. The radio continuum and thermal dust emission are distributed differently in the disk and galaxy halo. Different dusty environments are also revealed by a multiwavelength investigation of the emission features. Our detailed decomposition at millimeter and centimeter wavelengths shows that emission at 1 mm is purely originated by dust. Radio components become progressively important with increasing wavelengths. Finally, we find that emission arising from small dust grains accounts for ∼9.5% of the total dust mass, reaching up to 20% at large galactic latitudes. Shock waves in the outflows that shatter the dust grains might explain this higher fraction of small grains in the halo.
Conclusions: NIKA2 observations have proven essential for a complete characterization of the interstellar medium in NGC 891. They have been critical to separate the dust, free-free, and synchrotron emission in the various emitting regions within the galaxy.

NIKA2 Cosmological Legacy Survey. Survey description and galaxy number counts

Bing, L., Béthermin, M., Lagache, G., et al. (2023), Astronomy and Astrophysics, 677, A66.

NASA ADS | arXiv | Abstract

Context. Finding and characterizing the heavily obscured galaxies with extreme star formation up to very high redshift is key for constraining the formation of the most massive galaxies in the early Universe. It has been shown that these obscured galaxies are major contributors to the accumulation of stellar mass to z ~ 4. At higher redshift, and despite recent progress, the contribution of dust-obscured galaxies remains poorly known.
Aims: Deep surveys in the millimeter domain are necessary in order to probe the dust-obscured galaxies at high redshift. We conducted a large observing program at 1.2 and 2 mm with the NIKA2 camera installed on the IRAM 30m telescope. This NIKA2 Cosmological Legacy Survey (N2CLS) covers two emblematic fields: GOODS-N and COSMOS. We introduce the N2CLS survey and present new 1.2 and 2 mm number counts measurements based on the tiered N2CLS observations (from October 2017 to May 2021) covering 1169 arcmin².
Methods: After a careful data reduction and source extraction, we develop an end-to-end simulation that combines an input sky model with the instrument noise and data reduction pipeline artifacts. This simulation is used to compute the sample purity, flux boosting, pipeline transfer function, completeness, and effective area of the survey (taking into account the non-homogeneous sky coverage). For the input sky model, we used the 117 square degree SIDES simulations, which include galaxy clustering. Our formalism allows us to correct the source number counts to obtain galaxy number counts, the difference between the two being due to resolution effects caused by the blending of several galaxies inside the large beam of single-dish instruments.
Results: The N2CLS-May2021 survey is already the deepest and largest ever made at 1.2 and 2 mm. It reaches an average 1σ- noise level of 0.17 and 0.048 mJy on GOODS-N over 159 arcmin², and 0.46 and 0.14 mJy on COSMOS over 1010 arcmin², at 1.2 and 2 mm, respectively. For a purity threshold of 80%, we detect 120 and 67 sources in GOODS-N and 195 and 76 sources in COSMOS at 1.2 and 2 mm, respectively. At 1.2 mm, the number counts measurement probes consistently 1.5 orders of magnitude in flux density, covering the full flux density range from previous single-dish surveys and going a factor of 2 deeper into the sub-mJy regime. Our measurement connects the bright single-dish to the deep interferometric number counts. At 2 mm, our measurement matches the depth of the deepest interferometric number counts and extends a factor of 2 above the brightest constraints. After correcting for resolution effects, our results reconcile the single-dish and interferometric number counts, which can be further accurately compared with model predictions.
Conclusions: While the observation in GOODS-N have already reached the target depth, we expect the final N2CLS survey to be 1.5 times deeper for COSMOS. Thanks to its volume-complete flux selection, the final N2CLS sample will be an ideal reference for conducting a full characterization of dust-obscured galaxies at high redshift.

Multi-probe analysis of the galaxy cluster CL J1226.9+3332. Hydrostatic mass and hydrostatic-to-lensing bias

Muñoz-Echeverría, M., Macías-Pérez, J. F., Pratt, G. W., et al. (2023), Astronomy and Astrophysics, 671, A28.

NASA ADS | arXiv | Abstract

The precise estimation of the mass of galaxy clusters is a major issue for cosmology. Large galaxy cluster surveys rely on scaling laws that relate cluster observables to their masses. From the high-resolution observations of ∼45 galaxy clusters with the NIKA2 and XMM-Newton instruments, the NIKA2 Sunyaev-Zel'dovich Large Program should provide an accurate scaling relation between the thermal Sunyaev-Zel'dovich effect and the hydrostatic mass. In this paper we present an exhaustive analysis of the hydrostatic mass of the well-known galaxy cluster CL J1226.9+3332, the highest-redshift cluster in the NIKA2 Sunyaev-Zel'dovich Large Program at z = 0.89. We combined the NIKA2 observations with thermal Sunyaev-Zel'dovich data from the NIKA, Bolocam, and MUSTANG instruments and XMM-Newton X-ray observations, and tested the impact of the systematic effects on the mass reconstruction. We conclude that slight differences in the shape of the mass profile can be crucial when defining the integrated mass at R₅₀₀, which demonstrates the importance of the modelling in the mass determination. We prove the robustness of our hydrostatic mass estimates by showing the agreement with all the results found in the literature. Another key factor for cosmology is the bias of the masses estimated assuming the hydrostatic equilibrium hypothesis. Based on the lensing convergence maps from the Cluster Lensing And Supernova survey with Hubble (CLASH) data, we obtain the lensing mass estimate for CL J1226.9+3332. From this we are able to measure the hydrostatic-to-lensing mass bias for this cluster, which spans from 1 − b_HSE/lens ∼ 0.7 to 1, presenting the impact of data sets and mass reconstruction models on the bias.

Candidate cosmic filament in the GJ526 field, mapped with the NIKA2 camera

Lestrade, J.-F., Désert, F.-X., Lagache, G., et al. (2022), Astronomy and Astrophysics, 667, A23.

NASA ADS | arXiv | Abstract

Distinctive large-scale structures have been identified in the spatial distribution of optical galaxies up to redshift z ∼ 1. In the more distant universe, the relationship between the dust-obscured population of star-forming galaxies observed at millimetre wavelengths and the network of cosmic filaments of dark matter apparent in all cosmological hydrodynamical simulations is still under study. Using the NIKA2 dual-band millimetre camera, we mapped a field of ∼90 arcmin² in the direction of the star GJ526 simultaneously in its 1.15-mm and 2.0-mm continuum wavebands to investigate the nature of the quasi-alignment of five sources found ten years earlier with the MAMBO camera at 1.2 mm. We find that these sources are not clumps of a circumstellar debris disc around this star as initially hypothesized. Rather, they must be dust-obscured star-forming galaxies, or sub-millimetre galaxies (SMGs), in the distant background. The new NIKA2 map at 1.15 mm reveals a total of seven SMGs distributed in projection on the sky along a filament-like structure crossing the whole observed field. Furthermore, we show that the NIKA2 and supplemental Herschel photometric data are compatible with a model of the spectral energy distributions (SEDs) of these sources when a common redshift of 2.5 and typical values of the dust parameters for SMGs are adopted. Hence, we speculate that these SMGs might be located in a filament of the distant `cosmic web'. The length of this candidate cosmic filament crossing the whole map is at least 4 cMpc (comoving), and the separations between sources are between 0.25 cMpc and 1.25 cMpc at this redshift, in line with expectations from cosmological simulations. Nonetheless, further observations to determine the precise spectroscopic redshifts of these sources are required to definitively support this hypothesis of SMGs embedded in a cosmic filament of dark matter.

The Cluster HEritage project with XMM-Newton: Mass Assembly and Thermodynamics at the Endpoint of structure formation. I. Programme overview

CHEX-MATE Collaboration, Arnaud, M., Ettori, S., et al. (2021), Astronomy and Astrophysics, 650, A104.

NASA ADS | arXiv | Abstract

The Cluster HEritage project with XMM-Newton - Mass Assembly and Thermodynamics at the Endpoint of structure formation (CHEX-MATE) is a three-mega-second Multi-Year Heritage Programme to obtain X-ray observations of a minimally-biased, signal-to-noise-limited sample of 118 galaxy clusters detected by Planck through the Sunyaev-Zeldovich effect. The programme, described in detail in this paper, aims to study the ultimate products of structure formation in time and mass. It is composed of a census of the most recent objects to have formed (Tier-1: 0.05 < z < 0.2; 2 × 10¹⁴ M_⊙ < M₅₀₀ < 9 × 10¹⁴ M_⊙), together with a sample of the highest mass objects in the Universe (Tier-2: z < 0.6; M₅₀₀ > 7.25 × 10¹⁴ M_⊙). The programme will yield an accurate vision of the statistical properties of the underlying population, measure how the gas properties are shaped by collapse into the dark matter halo, uncover the provenance of non-gravitational heating, and resolve the major uncertainties in mass determination that limit the use of clusters for cosmological parameter estimation. We will acquire X-ray exposures of uniform depth, designed to obtain individual mass measurements accurate to 15 − 20% under the hydrostatic assumption. We present the project motivations, describe the programme definition, and detail the ongoing multi-wavelength observational (lensing, SZ, radio) and theoretical effort that is being deployed in support of the project.

Exploring the hydrostatic mass bias in MUSIC clusters: application to the NIKA2 mock sample

Gianfagna, G., De Petris, M., Yepes, G., et al. (2021), Monthly Notices of the Royal Astronomical Society, 502, 5115.

NASA ADS | arXiv | Abstract

Clusters of galaxies are useful tools to constrain cosmological parameters, only if their masses can be correctly inferred from observations. In particular, X-ray and Sunyaev-Zeldovich (SZ) effect observations can be used to derive masses within the framework of the hydrostatic equilibrium. Therefore, it is crucial to have a good control of the possible mass biases that can be introduced when this hypothesis is not valid. In this work, we analysed a set of 260 synthetic clusters from the MUSIC simulation project at redshifts 0 ≤ z ≤ 0.82. We estimate the hydrostatic mass of the MUSIC clusters from X-ray only (temperature and density) and from X-ray and SZ (density and pressure). Then, we compare them with the true 3D dynamical mass. The biases are of the order of 20 per cent. We find that using the temperature instead of the pressure leads to a smaller bias, although the two values are compatible within 1σ. Non-thermal contributions to the total pressure support, arising from bulk motion and turbulence of the gas, are also computed and show that they are sufficient to account for this bias. We also present a study of the correlation between the mass bias and the dynamical state of the clusters. A clear correlation is shown between the relaxation state of the clusters and the bias factor. We applied the same analysis on a subsample of 32 objects, already selected for supporting the NIKA2 SZ Large Program.

GASTON: Galactic Star Formation with NIKA2 - evidence for the mass growth of star-forming clumps

Rigby, A. J., Peretto, N., Adam, R., et al. (2021), Monthly Notices of the Royal Astronomical Society, 502, 4576.

NASA ADS | arXiv | Abstract

Determining the mechanism by which high-mass stars are formed is essential for our understanding of the energy budget and chemical evolution of galaxies. By using the New IRAM KIDs Array 2 (NIKA2) camera on the Institut de Radio Astronomie Millimétrique (IRAM) 30-m telescope, we have conducted high-sensitivity and large-scale mapping of a fraction of the Galactic plane (GP) in order to search for signatures of the transition between the high- and low-mass star-forming modes. Here, we present the first results from the Galactic Star Formation with NIKA2 (GASTON) project, a Large Programme at the IRAM 30-m telescope that is mapping ≈2 deg² of the inner GP, centred on ℓ = 23${_{.}^{\circ}}$9, b = 0${_{.}^{\circ}}$05, as well as targets in Taurus and Ophiuchus in 1.15- and 2.00-mm continuum wavebands. In this paper, we present the first of the GASTON GP data taken, and present initial science results. We conduct an extraction of structures from the 1.15-mm maps using a dendrogram analysis and, by comparison to the compact source catalogues from Herschel survey data, we identify a population of 321 previously undetected clumps. Approximately 80 per cent of these new clumps are 70-μm-quiet, and may be considered as starless candidates. We find that this new population of clumps are less massive and cooler, on average, than clumps that have already been identified. Further, by classifying the full sample of clumps based upon their infrared-bright fraction - an indicator of evolutionary stage - we find evidence for clump mass growth, supporting models of clump-fed high-mass star formation.

The XXL Survey. XLIV. Sunyaev-Zel’dovich mapping of a low-mass cluster at z ∼ 1: a multi-wavelength approach

Ricci, M., Adam, R., Eckert, D., et al. (2020), Astronomy and Astrophysics, 642, A126.

NASA ADS | arXiv | Abstract

High-mass clusters at low redshifts have been intensively studied at various wavelengths. However, while more distant objects at lower masses constitute the bulk population of future surveys, their physical state remain poorly explored to date. In this paper, we present resolved observations of the Sunyaev-Zel'dovich (SZ) effect, obtained with the NIKA2 camera, towards the cluster of galaxies XLSSC 102, a relatively low-mass system (M₅₀₀ ∼ 2 × 10¹⁴ M_⊙) at z = 0.97 detected from the XXL survey. We combine NIKA2 SZ data, XMM-Newton X-ray data, and Megacam optical data to explore, respectively, the spatial distribution of the gas electron pressure, the gas density, and the galaxies themselves. We find significant offsets between the X-ray peak, the SZ peak, the brightest cluster galaxy, and the peak of galaxy density. Additionally, the galaxy distribution and the gas present elongated morphologies. This is interpreted as the sign of a recent major merging event, which induced a local boost of the gas pressure towards the north of XLSSC 102 and stripped the gas out of the galaxy group. The NIKA2 data are also combined with XXL data to construct the thermodynamic profiles of XLSSC 102, obtaining relatively tight constraints up to about ∼r₅₀₀, and revealing properties that are typical of disturbed systems. We also explore the impact of the cluster centre definition and the implication of local pressure substructure on the recovered profiles. Finally, we derive the global properties of XLSSC 102 and compare them to those of high-mass-and-low-redshift systems, finding no strong evidence for non-standard evolution. We also use scaling relations to obtain alternative mass estimates from our profiles. The variation between these different mass estimates reflects the difficulty to accurately measure the mass of low-mass clusters at z ∼ 1, especially with low signal-to-noise ratio data and for a disturbed system. However, it also highlights the strength of resolved SZ observations alone and in combination with survey-like X-ray data. This is promising for the study of high redshift clusters from the combination of eROSITA and high resolution SZ instruments and will complement the new generation of optical surveys from facilities such as LSST and Euclid.

Based on observations carried out under project number 179-17 and 094-18, with the NIKA2 camera at the IRAM 30 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).

Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA.

Calibration and performance of the NIKA2 camera at the IRAM 30-m Telescope

Perotto, L., Ponthieu, N., Macías-Pérez, J. F., et al. (2020), Astronomy and Astrophysics, 637, A71.

NASA ADS | arXiv | Abstract

Context. NIKA2 is a dual-band millimetre continuum camera of 2 900 kinetic inductance detectors, operating at 150 and 260 GHz, installed at the IRAM 30-m telescope in Spain. Open to the scientific community since October 2017, NIKA2 will provide key observations for the next decade to address a wide range of open questions in astrophysics and cosmology.
Aims: Our aim is to present the calibration method and the performance assessment of NIKA2 after one year of observation.
Methods: We used a large data set acquired between January 2017 and February 2018 including observations of primary and secondary calibrators and faint sources that span the whole range of observing elevations and atmospheric conditions encountered by the IRAM 30-m telescope. This allowed us to test the stability of the performance parameters against time evolution and observing conditions. We describe a standard calibration method, referred to as the "Baseline" method, to translate raw data into flux density measurements. This includes the determination of the detector positions in the sky, the selection of the detectors, the measurement of the beam pattern, the estimation of the atmospheric opacity, the calibration of absolute flux density scale, the flat fielding, and the photometry. We assessed the robustness of the performance results using the Baseline method against systematic effects by comparing results using alternative methods.
Results: We report an instantaneous field of view of 6.5' in diameter, filled with an average fraction of 84%, and 90% of valid detectors at 150 and 260 GHz, respectively. The beam pattern is characterised by a FWHM of 17.6″ ± 0.1″ and 11.1″ ± 0.2″, and a main-beam efficiency of 47%±3%, and 64%±3% at 150 and 260 GHz, respectively. The point-source rms calibration uncertainties are about 3% at 150 GHz and 6% at 260 GHz. This demonstrates the accuracy of the methods that we deployed to correct for atmospheric attenuation. The absolute calibration uncertainties are of 5%, and the systematic calibration uncertainties evaluated at the IRAM 30-m reference Winter observing conditions are below 1% in both channels. The noise equivalent flux density at 150 and 260 GHz are of 9 ± 1 mJy s^1/2 and 30 ± 3 mJy s^1/2. This state-of-the-art performance confers NIKA2 with mapping speeds of 1388 ± 174 and 111 ± 11 arcmin² mJy^-2 h^-1 at 150 and 260 GHz.
Conclusions: With these unique capabilities of fast dual-band mapping at high (better that 18″) angular resolution, NIKA2 is providing an unprecedented view of the millimetre Universe.

Unveiling the Merger Dynamics of the Most Massive MaDCoWS Cluster at z = 1.2 from a Multiwavelength Mapping of Its Intracluster Medium Properties

Ruppin, F., McDonald, M., Brodwin, M., et al. (2020), The Astrophysical Journal, 893, 74.

NASA ADS | arXiv | Abstract

The characterization of the Intracluster Medium (ICM) properties of high-redshift galaxy clusters is fundamental to our understanding of large-scale structure formation processes. We present the results of a multiwavelength analysis of the very massive cluster MOO J1142+1527 at a redshift z = 1.2 discovered as part of the Massive and Distant Clusters of WISE Survey. This analysis is based on high angular resolution Chandra X-ray and NIKA2 Sunyaev-Zel'dovich (SZ) data. The cluster thermodynamic radial profiles have been obtained with unprecedented precision at this redshift and up to 0.7R₅₀₀, thanks to the combination of high-resolution X-ray and SZ data. The comparison between the galaxy distribution mapped in infrared by Spitzer and the morphological properties of the ICM derived from the combined analysis of the Chandra and NIKA2 data leads us to the conclusion that the cluster is an ongoing merger. We have estimated a systematic uncertainty on the cluster total mass that characterizes both the impact of the observed deviations from spherical symmetry and of the core dynamics on the mass profile. We further combine the X-ray and SZ data at the pixel level to obtain maps of the temperature and entropy distributions. We find a relatively low-entropy core at the position of the X-ray peak and high-temperature regions located on its south and west sides. This work demonstrates that the addition of spatially resolved SZ observations to low signal-to-noise X-ray data brings a high information gain on the characterization of the evolution of ICM thermodynamic properties at z > 1.

Conference Proceedings

Forecasting the Y₅₀₀ - M₅₀₀ scaling relation from the NIKA2 SZ Large Program

Kéruzoré, F., Artis, E., Macías-Pérez, J.-F., et al. (2022), mm Universe @ NIKA2 - Observing the mm Universe with the NIKA2 Camera, 257, 00025.

NASA ADS | arXiv | Abstract

One of the key elements needed to perform the cosmological exploitation of a cluster survey is the relation between the survey observable and the cluster masses. Among these observables, the integrated Compton parameter Y is a measurable quantity in Sunyaev-Zeldovich (SZ) surveys, which tightly correlates with cluster mass. The calibration of the relation between the Compton parameter Y₅₀₀ and the mass M₅₀₀ enclosed within radius R₅₀₀ is one of the scientific goals of the NIKA2 SZ Large Program (LPSZ). We present an ongoing study to forecast the constraining power of this program, using mock simulated datasets that mimic the large program sample, selection function, and typical uncertainties on Y₅₀₀ and M₅₀₀. We use a Bayesian hierarchical modelling that enables taking into account a large panel of systematic effects. Our results show that the LPSZ can yield unbiased estimates of the scaling relation parameters for realistic input parameter values. The relative uncertainties on these parameters is ~ 10% for the intercept and slope of the scaling relation, and ~ 34% for its intrinsic scatter, foreshadowing precise estimates to be delivered by the LPSZ.

PANCO2: A new software to measure pressure profiles from resolved thermal SZ observations

Kéruzoré, F., Artis, E., Macías-Pérez, J.-F., et al. (2022), mm Universe @ NIKA2 - Observing the mm Universe with the NIKA2 Camera, 257, 00024.

NASA ADS | arXiv | Abstract

We have developed a new software to perform the measurement of galaxy cluster pressure profiles from high angular resolution thermal SZ observations. The code allows the user to take into account various features of millimeter observations, such as point spread function (PSF) convolution, pipeline filtering, correlated residual noise, and point source contamination, in a forward modeling approach. A major advantage of this software is its performance, enabling the extraction of the pressure profile and associated confidence intervals via MCMC sampling in times as short as a few minutes. We present the code and its validation on various realistic synthetic maps, of ideal spherical clusters, as well as of realistic, hydrodynamically simulated objects. We plan to publicly release the software in the coming months.

A low-mass galaxy cluster as a test-case study for the NIKA2 SZ Large Program

Kéruzoré, F., Adam, R., Ade, P., et al. (2020), mm Universe @ NIKA2 - Observing the mm Universe with the NIKA2 Camera, 228, 00012.

NASA ADS | arXiv | Abstract

High-resolution mapping of the hot gas in galaxy clusters is a key tool for cluster-based cosmological analyses. Taking advantage of the NIKA2 millimeter camera operated at the IRAM 30-m telescope, the NIKA2 SZ Large Program seeks to get a high-resolution follow-up of 45 galaxy clusters covering a wide mass range at high redshift in order to re-calibrate some of the tools needed for the cosmological exploitation of SZ surveys. We present the second cluster analysis of this program, targeting one of the faintest sources of the sample in order to tackle the difficulties in data reduction for such faint, low-SNR clusters. In this study, the main challenge is the precise estimation of the contamination by sub-millimetric point sources, which greatly affects the tSZ map of the cluster. We account for this contamination by performing a joint fit of the SZ signal and of the flux density of the compact sources. A prior knowledge of these fluxes is given by the adjustment of the SED of each source using data from both NIKA2 and the Herschel satellite. The first results are very promising and demonstrate the possibility to estimate thermodynamic properties with NIKA2, even in a compact cluster heavily contaminated by point sources.

Plus 37 conference proceedings as a co-author – see the dedicated Publications page for the complete list.

PhD Thesis

Cosmologie à partir des observations Sunyaev-Zeldovich d’amas de galaxies avec NIKA2

F. Kéruzoré (2021), PhD thesis, Université Grenoble Alpes (in French)

link | Abstract