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1. Probing Hot Gas Components of the Circumgalactic Medium in Cosmological Simulations with the Thermal Sunyaev–Zel’dovich Effect

   https://doi.org/10.3847/1538-4357/ac4750  

   Kim, Junhan; Golwala, Sunil; Bartlett, James G.; Amodeo, Stefania; Battaglia, Nicholas; Benson, Andrew J.; Hill, J. Colin; Hopkins, Philip F.; Hummels, Cameron B.; Moser, Emily; et al (February 2022, The Astrophysical Journal)

   Abstract The thermal Sunyaev–Zel’dovich (tSZ) effect is a powerful tool with the potential for constraining directly the properties of the hot gas that dominates dark matter halos because it measures pressure and thus thermal energy density. Studying this hot component of the circumgalactic medium (CGM) is important because it is strongly impacted by star formation and active galactic nucleus (AGN) activity in galaxies, participating in the feedback loop that regulates star and black hole mass growth in galaxies. We study the tSZ effect across a wide halo-mass range using three cosmological hydrodynamical simulations: Illustris-TNG, EAGLE, and FIRE-2. Specifically, we present the scaling relation between the tSZ signal and halo mass and the (mass-weighted) radial profiles of gas density, temperature, and pressure for all three simulations. The analysis includes comparisons to Planck tSZ observations and to the thermal pressure profile inferred from the Atacama Cosmology Telescope (ACT) measurements. We compare these tSZ data to simulations to interpret the measurements in terms of feedback and accretion processes in the CGM. We also identify as-yet unobserved potential signatures of these processes that may be visible in future measurements, which will have the capability of measuring tSZ signals to even lower masses. We also perform internal comparisons between runs with different physical assumptions. We conclude (1) there is strong evidence for the impact of feedback at R 500 , but that this impact decreases by 5 R 500 , and (2) the thermodynamic profiles of the CGM are highly dependent on the implemented model, such as cosmic-ray or AGN feedback prescriptions. 

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2. Constraining cosmic ray transport models using circumgalactic medium properties and observables

   https://doi.org/10.1093/mnras/staf1984  

   Lu, Yue Samuel; Kereš, Dušan; Hopkins, Philip F; Ponnada, Sam B; Faucher-Giguère, Claude-André; Hummels, Cameron B (December 2025, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT Cosmic rays (CRs) are a pivotal non-thermal component of galaxy formation and evolution. However, the intricacies of CR physics, particularly how they propagate in the circumgalactic medium (CGM), remain largely unconstrained. In this work, we study CGM properties in FIRE-2 (Feedback In Realistic Environments) simulations of the same Milky Way (MW)–mass halo at $z=0$ with different CR transport models that produce similar diffuse $$\sim$$ GeV $$\gamma$$-ray emission, as an attempt to further constrain CR transport models. We study the gas morphology and thermal properties, and generate synthetic observations of rest-frame UV ion absorption columns and X-ray emission. CRs lower galaxy masses and star formation rates (SFRs) while supporting more cool CGM gas, which boosts the H i and O vi column densities in the CGM, bringing simulations more in line with observations, but there can be large differences between CR transport models and resolution levels. X-ray emission within and close to galaxies is consistent with thermal (free–free and metal-line) emission plus X-ray binaries, while more extended ($$\sim 100\,$$ kpc) CGM emission is potentially dominated by inverse Compton scattering (ICS), motivating future work on the spatially resolved X-ray profiles. Although comparisons with observations are sensitive to sample selection and mimicking the details of observations, and our analysis did not result in strong constraints on CR models, the differences between simulations are significant and could be used as a framework for future studies. 

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3. The Circumgalactic Medium from the CAMELS Simulations: Forecasting Constraints on Feedback Processes from Future Sunyaev–Zeldovich Observations

   Moser, E; Battaglia, N; Nagai, D; Lau, E; Machado_Poletti_valle, Luis_Fernando; Villaescuas-Navarro, F; Amodeo, S; Angles-Alcazar, D; Bryan, GL; Dave, R; et al (July 2022, Astrophysical journal)

   It is important to understand the cycle of baryons through the circumgalactic medium (CGM) in the context of galaxy formation and evolution. In this study, we forecast constraints on the feedback processes heating the CGM with current and future Sunyaev–Zeldovich (SZ) observations. To constrain these processes, we use a suite of cosmological simulations, the Cosmology and Astrophysics with MachinE Learning Simulations (CAMELS). CAMELS varies four different feedback parameters of two previously existing hydrodynamical simulations, IllustrisTNG and SIMBA. We capture the dependences of SZ radial profiles on these feedback parameters with an emulator, calculate their derivatives, and forecast future constraints on these feedback parameters from upcoming experiments. We find that for a galaxy sample similar to what would be obtained with the Dark Energy Spectroscopic Instrument at the Simons Observatory, all four feedback parameters can be constrained (some within the 10% level), indicating that future observations will be able to further restrict the parameter space for these subgrid models. Given the modeled galaxy sample and forecasted errors in this work, we find that the inner SZ profiles contribute more to the constraining power than the outer profiles. Finally, we find that, despite the wide range of parameter variation in active galactic feedback in the CAMELS simulation suite, we cannot reproduce the thermal SZ signal of galaxies selected by the Baryon Oscillation Spectroscopic Survey as measured by the Atacama Cosmology Telescope. 

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4. The Circumgalactic Medium from the CAMELS Simulations: Forecasting Constraints on Feedback Processes from Future Sunyaev–Zeldovich Observations

   https://doi.org/10.3847/1538-4357/ac70c6  

   Moser, Emily; Battaglia, Nicholas; Nagai, Daisuke; Lau, Erwin; Machado Poletti Valle, Luis Fernando; Villaescusa-Navarro, Francisco; Amodeo, Stefania; Anglés-Alcázar, Daniel; Bryan, Greg L.; Dave, Romeel; et al (July 2022, The Astrophysical Journal)

   Abstract It is important to understand the cycle of baryons through the circumgalactic medium (CGM) in the context of galaxy formation and evolution. In this study, we forecast constraints on the feedback processes heating the CGM with current and future Sunyaev–Zeldovich (SZ) observations. To constrain these processes, we use a suite of cosmological simulations, the Cosmology and Astrophysics with MachinE Learning Simulations (CAMELS). CAMELS varies four different feedback parameters of two previously existing hydrodynamical simulations, IllustrisTNG and SIMBA. We capture the dependences of SZ radial profiles on these feedback parameters with an emulator, calculate their derivatives, and forecast future constraints on these feedback parameters from upcoming experiments. We find that for a galaxy sample similar to what would be obtained with the Dark Energy Spectroscopic Instrument at the Simons Observatory, all four feedback parameters can be constrained (some within the 10% level), indicating that future observations will be able to further restrict the parameter space for these subgrid models. Given the modeled galaxy sample and forecasted errors in this work, we find that the inner SZ profiles contribute more to the constraining power than the outer profiles. Finally, we find that, despite the wide range of parameter variation in active galactic feedback in the CAMELS simulation suite, we cannot reproduce the thermal SZ signal of galaxies selected by the Baryon Oscillation Spectroscopic Survey as measured by the Atacama Cosmology Telescope. 

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5. The mass and galaxy distribution around SZ-selected clusters

   https://doi.org/10.1093/mnras/stab2505  

   Shin, T; Jain, B; Adhikari, S; Baxter, E J; Chang, C; Pandey, S; Salcedo, A; Weinberg, D H; Amsellem, A; Battaglia, N; et al (September 2021, Monthly Notices of the Royal Astronomical Society)

   null (Ed.)

   ABSTRACT We present measurements of the radial profiles of the mass and galaxy number density around Sunyaev–Zel’dovich (SZ)-selected clusters using both weak lensing and galaxy counts. The clusters are selected from the Atacama Cosmology Telescope Data Release 5 and the galaxies from the Dark Energy Survey Year 3 data set. With signal-to-noise ratio of 62 (45) for galaxy (weak lensing) profiles over scales of about 0.2–20 h−1 Mpc, these are the highest precision measurements for SZ-selected clusters to date. Because SZ selection closely approximates mass selection, these measurements enable several tests of theoretical models of the mass and light distribution around clusters. Our main findings are: (1) The splashback feature is detected at a consistent location in both the mass and galaxy profiles and its location is consistent with predictions of cold dark matter N-body simulations. (2) The full mass profile is also consistent with the simulations. (3) The shapes of the galaxy and lensing profiles are remarkably similar for our sample over the entire range of scales, from well inside the cluster halo to the quasilinear regime. We measure the dependence of the profile shapes on the galaxy sample, redshift, and cluster mass. We extend the Diemer & Kravtsov model for the cluster profiles to the linear regime using perturbation theory and show that it provides a good match to the measured profiles. We also compare the measured profiles to predictions of the standard halo model and simulations that include hydrodynamics. Applications of these results to cluster mass estimation, cosmology, and astrophysics are discussed. 

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