arXiv subjects

G. Mark Voit

Publications and source records attributed to G. Mark Voit.

At least 19 recordsLinked to original sources

arXiv2026

O VI Emission in Starbursting BCGs: An HST-COS Extension of "Reigniting the FUSE"

In this extension of our "Reigniting the FUSE" series, we have obtained new far-ultraviolet spectroscopy of 3 starbursting brightest cluster galaxies with the Cosmic Origins Spectrograph (COS) aboard HST. With these new data, in combination with archival COS data of 2 additional systems, we measure star formation rates (SFRs) from the young stellar continuum and cooling rates through $10^{5.5}$ K gas with the O VI $1032,1038\,\mathring{\rm A}$ doublet ($\dot{M}_{\rm O\,VI}$). We use these measurements to increase the size of the "Reigniting the FUSE" sample, which itself contains high resolution far UV spectroscopy for 29 nearby massive elliptical galaxies from FUSE, and extend it 1 dex upwards in SFR and cooling rate. Our derived SFRs agree well with photometric GALEX$+$WISE SFRs from the literature. The new data also reinforce the previously observed trend in cooling efficiency ($\dot{M}_{\rm O\,VI}/\dot{M}_{\rm max}$; where $\dot{M}_{\rm max}$ is the X-ray luminosity-based cooling rate) versus mass, with groups cooling more efficiently than clusters by a factor of $\sim$4-5. When we isolate a sample of the most star-forming central galaxies, we find that the star formation rates, X-ray spectroscopic cooling rates, and UV spectroscopic cooling rates are all consistent with one another, on average, while retaining substantial system-to-system scatter, reflecting time-depenent multiphase condensation and cold gas reservoir evolution. The remainder of the sample, in contrast, overwhelmingly shows ratios of ${\rm SFR}/\dot{M}_{\rm O\,VI} \sim {\rm SFR}/\dot{M}_{\rm X,spec} \sim 10\%$.

astro-ph.GA↗

arXiv2026

And Then There WEre Baryons (ATWEB): The Baryon Budget of the Universe in Halos and the IGM over 13 Billion Years of Cosmic Time

Observations of the local Universe show that, except in the most massive galaxy clusters, the baryon fraction within halos falls below the cosmic mean. This deficit can be characterized using the previously established closure radius, the halocentric distance within which the enclosed baryon fraction reaches the cosmic value. Using the TNG, EAGLE and SIMBA simulations, we examine how, when, and on what scales the baryonic and dark matter distributions diverge. At z=0 less than 30% of cosmic baryons reside within galaxy-hosting halos, compared with ~45% of the dark matter, leaving over 70% of all baryons in the IGM. Building on the closure radius, we introduce three further characteristic scales: the compensation radius, closure envelope, and compensation envelope. The compensation radius marks where the enclosed total mass recovers its gravity-only value, and today it typically lies inside the closure radius in all three models. The closure and compensation envelopes are the largest median radii across halo mass. Galaxy groups provide the largest contribution per dex of halo mass to IGM enrichment with halo-associated baryons and redistribute baryons over the largest distances. They set the closure envelope, which reaches ~2-6.5 Mpc at z=0, depending on the model. The closure radius usually increases with cosmic time at fixed halo mass. Tracking individual halos, we find open baryon cycles with substantial redistribution beyond halo boundaries across all halo masses, while even the progenitors of today's most massive clusters fall below the cosmic baryon fraction. The compensation envelope grows toward low redshift, reaching ~1.5-5.5 Mpc at z=0. Across cosmic time, it coincides with the scale on which the matter power spectrum recovers its gravity-only form, establishing a direct link between the spatial extent of baryon redistribution and the impact of feedback on large-scale structure.

astro-ph.CO↗

arXiv2026

Mapping Gas Accretion and Stellar Kinematics to Sub-kiloparsec Scales in NGC 4696 with JWST/NIRSpec

We present JWST/NIRSpec IFU spectroscopy of the central $618\times618$ pc$^2$ ($\sim3''\times3''$) of NGC 4696, the BCG in the Centaurus cluster. Leveraging the $\sim0.1''$ ($20.6$ pc) pixel size of JWST, we resolve a compact circumnuclear rotating disk (radius of $\sim120$ pc) traced by Pa$α$ and H$_2$ 1$-$0 S(1) emission, which allows a reassessment of the AGN position based on the kinematic centre of this disk. A central Pa$α$ velocity dispersion reaching $σ\sim449$ km s$^{-1}$ implies a SMBH mass of $\sim10^9$ M$_\odot$, corresponding to a sphere of influence of $r_\mathrm{inf}\sim60$ pc, resolved by our observations. Position-velocity diagrams reveal an increase from $\sim-200$ to $\sim600$ km s$^{-1}$ on scales of $\sim150$ pc (a gradient of $4.7$ km s$^{-1}$ pc$^{-1}$) and an accretion rate of $\sim18$ M$_\odot$ yr$^{-1}$ feeding the CND. The Pa$α$ emission shows a double-component in the core, with a high-dispersion redshifted component reaching $σ\sim600$ km s$^{-1}$. In contrast, MUSE H$α$ observations covering the $\sim10$ kpc-scale filamentary structure recover only weak velocity gradients ($\lesssim150$ km s$^{-1}$) within $\sim300\times300$ pc$^2$ and do not resolve the disk due to larger PSFs and pixel sizes. ALMA CO(2-1) data reveal only compact molecular clumps within a $\sim410\times410$ pc$^2$ region, with no extended counterpart to the structures traced by Pa$α$ and H$_2$ 1$-$0 S(1). Stellar kinematics show a smooth velocity field and broad dispersion profile, clearly decoupled from both the multiphase gas and the hot ICM probed by XRISM. These results provide a direct, spatially resolved view of gas dynamics within the inner few hundred parsecs, demonstrating the power of JWST/NIRSpec to probe SMBH feeding.

astro-ph.GA↗

arXiv2026

Reigniting the FUSE II: O VI Emission in Massive Elliptical Galaxies

This is the second paper in a series where we examine archival far-ultraviolet spectroscopy of 29 massive elliptical galaxies from the Far Ultraviolet Spectroscopic Explorer (FUSE) with modern methods. In the first paper, we performed SED modeling with aperture-matched photometry and analyzed the young and old stellar populations in these galaxies. In this paper, we report extinction-corrected O VI $λλ$1032,1038 $\mathring{\rm A}$ fluxes and upper limits for each galaxy, which we use to infer the rate at which gas is cooling through $10^{5.5}$ K via multiphase condensation of the galaxy's CGM ($\dot{M}_{\rm O\,VI}$) under the assumption of steady radiative cooling. By considering both Galactic and intrinsic extinction, we overwhelmingly find $\dot{M}_{\rm O\,VI}$ to be larger than values found previously in the literature by a median of $\sim 80\%$. Additionally, we quantify correlations between $\dot{M}_{\rm O\,VI}$ and star formation rates, classical luminosity-based X-ray cooling rates, and X-ray spectroscopic cooling rates. The results suggest that the efficiency of cooling from the $\gtrsim 10^7$ K circumgalactic medium evolves with host mass, being suppressed by a factor of $\sim 4$-$5$ more at the cluster scale than it is at the group and elliptical scales. In contrast, under the steady cooling assumption, cooling from $10^{5.5}$ K to the molecular phase appears to be suppressed by an order of magnitude, independent of mass, requiring turbulent mixing layers, thermal conduction, multiphase recycling, a bottom-heavy initial mass function, or some other additional physics to explain.

astro-ph.GA↗

arXiv2026

High-spectral-resolution Observations of the [S II] Emission-line Doublet in the Filamentary Nebula Surrounding NGC 1275

We analyze new high-spectral resolution SITELLE observations (R = $λ/Δλ$ = 7000) of the filamentary nebula surrounding NGC 1275, central galaxy of the Perseus cluster. We present here analysis of the \sii$\lambda6716$ and \sii$\lambda6731$ emission line doublet, using its ratio to determine the electron density of the optically emitting filaments. We compare these measurements with electron densities derived from deep Chandra X-ray observations of the intra-cluster medium (ICM) to determine if any correlations in density can be found. We report the detection of a clear dichotomy between the outer filaments, displaying on average lower \sii\text{ }emission line ratio of $\sim 1.1$ and the inner filaments displaying higher ratios of $\sim 1.3$. These results indicate that most of the gaseous filaments lie close to the low-density threshold for the density measurement of $\sim 10^2\text{ cm}^{-3}$. Using radial profiles, we find that the inner filaments have a roughly constant density, whereas the ICM density decreases with radius. In the outer filaments, we observe hints of local connections between the densities of the ICM and optical filaments, but no clear correlation seems to be observed overall. We also combined these density measurements with cold molecular CO gas observations to derive a relationship between temperature, density and pressure for the multiphase environment surrounding NGC 1275. Finally, we investigated potential models to explain the observed density measurements and explored similar studies of filamentary nebula around other central galaxies of cool-core galaxy clusters.

astro-ph.GA↗

arXiv2026

Introducing sapphire: Towards Hybrid Physics-Informed, Data-Driven Modeling of Galaxy Formation

Semi-analytic models (SAMs) have been treating galaxy populations as dynamical systems for $\gtrsim50$ years, but their evolution equations remain poorly constrained. We introduce sapphire, a modular, automatically differentiable, GPU-accelerated SAM written in JAX. For the first time, we compute exact Jacobian and Hessian matrices of a galaxy formation SAM, using the Pandya et al. (2023) nonlinear differential equation system as an example. These allow efficient, interpretable local and global sensitivity analyses, which reveal that supernova energy loading is the key astrophysical parameter. We use gradient descent and Hamiltonian Monte Carlo (HMC) to perform comprehensive mock parameter recovery tests. These indicate that the $z=0$ stellar-to-halo-mass relation alone does not contain enough information to infer many astrophysical parameters. Using observations of star-forming galaxies from the MaNGA survey and the Behroozi et al. (2019) empirical model as one baseline, we derive multiple posteriors assuming different combinations of data, including $z=0$ interstellar medium gas fractions and metallicities. The inferred physical parameters suggest that galaxies self-regulate their star formation primarily through preventative rather than ejective feedback, though this remains uncertain due to the lack of satellite galaxies, black holes and multi-phase galactic atmosphere physics. Both Fisher and HMC forecasts demonstrate the potential of sapphire to enable precision inference for galaxy formation and cosmology in a hybrid physics-informed, data-driven way, but more work is needed to expand its library of models and methods. We make sapphire publicly available at https://github.com/virajpandya/sapphire.

astro-ph.GA↗

arXiv2026

JWST reveals how black holes are fed: kiloparsec-scale multiphase filaments feed sub-kiloparsec circumnuclear disks

The Centaurus cluster is one of the most important archetypes of radio-mode AGN feedback, with its central galaxy, NGC 4696, launching powerful jets that inflate X-ray cavities and regulate cooling and star formation. NGC 4696 lies within a spectacular multiphase nebula of filaments extending over tens of kiloparsecs and spanning six decades in temperature, from hot (10^8 K) X-ray-emitting plasma to cold molecular gas. Owing to its proximity, Hubble Space Telescope H_alpha imaging reveals a striking S-shaped ionized-gas swirl within the black hole's sphere of influence - the first such structure identified in a cluster core. Here we present the first JWST observations of NGC 4696 with NIRSpec, probing the inner 618 pc * 618 pc at 10 pc resolution. These data reveal that the ionized swirl is a rotating, multiphase circumnuclear disk (CND) physically and kinematically connected to the larger-scale filamentary network. This provides the long-sought missing link between kiloparsec-scale cooling flows and black hole accretion on <100 pc scales. Strikingly, the observed morphology and kinematics are reproduced by tailored magnetohydrodynamic simulations, in which filamentary gas condenses from the hot atmosphere, loses angular momentum, and feeds a rotating CND that mediates accretion onto the black hole. A similar structure in NGC 1275, the Perseus cluster's central galaxy, together with our results on NGC 4696 - two prototypical radio-mode AGN feedback systems - points to a common mechanism: multiphase filaments transport gas from cluster scales down to the vicinity of the black hole via a CND, closing the AGN feedback loop and establishing a physically grounded framework for self-regulated galaxy evolution.

astro-ph.GA↗

arXiv2025

The Case for Hot-Mode Accretion in Abell 2029

Radiative cooling and AGN heating are thought to form a feedback loop that regulates the evolution of low redshift cool-core galaxy clusters. Numerical simulations suggest that formation of multiphase gas in the cluster core imposes a floor on the ratio of cooling time ($t_{\rm cool}$) to free-fall time ($t_{\rm ff}$) at $\min ( t_{\rm cool} / t_{\rm ff} ) \approx 10$. Observations of galaxy clusters show evidence for such a floor, and usually the cluster cores with $\min ( t_{\rm cool} / t_{\rm ff} ) \lesssim 30$ contain abundant multiphase gas. However, there are important outliers. One of them is Abell 2029, a massive galaxy cluster ($M_{200} \gtrsim 10^{15}$ M$_\odot$) with $\min( t_{\rm cool}/t_{\rm ff}) \sim 20$, but little apparent multiphase gas. In this paper, we present high resolution 3D hydrodynamic AMR simulations of a cluster similar to A2029 and study how it evolves over a period of 1-2 Gyr. Those simulations suggest that Abell 2029 self-regulates without producing multiphase gas because the mass of its central black hole ($\sim 5\times 10^{10} \, M_\odot$) is great enough for Bondi accretion of hot ambient gas to produce enough feedback energy to compensate for radiative cooling.

astro-ph.GA↗

arXiv2025

Constraining star formation in M87 using deep HST UV data

We analyzed the deepest Hubble Space Telescope (HST) F275W ultraviolet (UV) imaging of M87 to obtain the most robust constraints on its star formation rate (SFR) and star formation history (SFH). After removing the galaxy continuum and globular clusters, we detected an excess of UV point sources near the center. By comparing their colors to young stellar source (YSS) colors generated by stochastically simulated star formation (SF) for various SFRs and SFHs, we ruled out their origin as a UV-upturn population and identified them as YSS. We found an extremely low SFR of $\sim 2\times10^{-5}$ M$_\odot$ yr$^{-1}$ in M87, with evidence of a weak starburst $\sim$125 Myr ago that formed $\sim 1000$ M$_\odot$ of stars. Unlike other cool-core clusters where SF is stronger and directly linked to cooling gas, we found no spatial correlation between YSS and H$α$ filaments. Comparing SF activity with M87's AGN outburst history suggests that recent AGN feedback events ($\lesssim$12 Myr ago) neither triggered nor were associated with any detectable SF, however, earlier outbursts may have triggered weak starbursts. We detected UV filaments co-spatial with H$α$ filaments with similar lengths and widths, though they are obscured by dust near the center. These filaments are likely powered by metal-line emission from collisional ionization, suggesting ongoing low-level precipitation of the intracluster medium. Our results indicate that AGN feedback has quenched SF significantly in M87 for at least 200 Myr, even though some precipitation persists. Additionally, we identified a hotspot created by the counterjet, with the spectral index also constrained.

astro-ph.GA↗

arXiv2025

Introducing the Descriptive Parametric Model: Gaseous Profiles for Galaxies, Groups, and Clusters

We develop and present the Descriptive Parametric Model (DPM), a tool for generating profiles of gaseous halos (pressure, electron density, and metallicity) as functions of radius, halo mass, and redshift. The model assumes single-phase, spherically symmetric, volume-filling warm/hot gas. The DPM framework enables mock observations of the circumgalactic medium (CGM), group halos, and clusters across a number of wavebands including X-ray, sub-millimeter/millimeter, radio, and ultraviolet (UV). We introduce three model families calibrated to reproduce cluster profiles while having different extrapolations to the CGM -- (i) self-similar halos, (ii) a reduced gas model for lower halo masses, and (iii) a model with shallower radial slopes at lower masses. We demonstrate how our z=0.0-0.6 models perform when applied to stacked and individual X-ray emission profiles, measurements of the thermal and kinetic Sunyaev-Zel'dovich Effect, electron dispersion measures from fast radio bursts, O VI absorption, and UV-derived pressures. Our investigation supports models that remove baryons from halos more effectively and have shallower profiles at lower halo mass. We discuss biases and systematics when modelling observables using consistent hot gaseous halo models for all wavebands explored. We release the DPMhalo code to encourage the use of our framework and new formulations in future investigations. Included with the DPMhalo distribution is a set of recent observations that allow the reproduction of most plots in this paper.

astro-ph.GA↗

arXiv2025

Precipitation plausible: magnetized thermal instability in the intracluster medium

Observations of galaxy-cluster cores reveal that AGN feedback is strongly associated with both a short central cooling time ($t_{\rm c} \lesssim 10^9 \, {\rm yr}$) and accumulations of cold gas ($\lesssim 10^4 \, {\rm K}$). Also, the central ratio of cooling time to freefall time is rarely observed to drop below $t_{\rm c}/t_{\rm ff} \approx 10$, and large accumulations of cold gas are rarely observed in environments with $t_{\rm c} / t_{\rm ff} \gtrsim 30$. Here we show that the critical range -- $10 \lesssim t_{\rm c}/t_{\rm ff} \lesssim 30$ -- plausibly results from magnetized thermal instability. We present numerical simulations of magnetized stratified atmospheres with an initially uniform magnetic field. Thermal instability in an otherwise static atmosphere with $t_{\rm c}/t_{\rm ff} \approx 10$ progresses to nonlinear amplitudes, causing cooler gas to accumulate, as long as the background ratio of thermal pressure to magnetic pressure is $β\lesssim 100$. And in atmospheres with $t_{\rm c}/t_{\rm ff} \approx 20$, cooler gas accumulates for $β\lesssim 10$. Magnetized atmospheres are therefore much more likely to precipitate than unmagnetized atmospheres with otherwise identical properties. We hypothesize that AGN feedback triggered by accumulations of cold gas prevents $t_{\rm c}/t_{\rm ff}$ from dropping much below 10, because cold gas inevitably precipitates out of magnetized galactic atmospheres with lower ratios, causing $t_{\rm c}/t_{\rm ff}$ to rise.

astro-ph.GA↗

arXiv2025

A Practical Guide to Hosting a Virtual Conference

Virtual meetings have long been the outcast of scientific interaction. For many of us, the COVID-19 pandemic has only strengthened that sentiment as countless Zoom meetings have left us bored and exhausted. But remote conferences do not have to be negative experiences. If well designed, they have some distinct advantages over conventional in-person meetings, including universal access, longevity of content, as well as minimal costs and carbon footprint. This article details our experiences as organizers of a successful fully virtual scientific conference, the KITP program "Fundamentals of Gaseous Halos" hosted over 8 weeks in winter 2021. Herein, we provide detailed recommendations on planning and optimization of remote meetings, with application to traditional in-person events as well. We hope these suggestions will assist organizers of future virtual conferences and workshops.

cs.CY↗

arXiv2025

Mapping the Filamentary Nebula of NGC 1275 with Multiwavelength SITELLE Observations

The filamentary nebula encompassing the central galaxy of the Perseus Cluster, NGC 1275, is a complex structure extending dozens of kiloparsecs from NGC 1275. Decades of previous works have focused on establishing the primary formation and ionization mechanisms in different filaments. These studies have pointed to a lack of star formation in the majority of the filaments, the importance of magnetic fields and turbulence in several regions, and the role of interactions between the intercluster medium (ICM) and the cool gas in the filaments, as well as the role of interaction between the central radio source, 3C84, and the filaments. In this paper, we present multi-filter observations of the entire filamentary system that cover the optical bandpass, using the SITELLE instrument at the Canada-France-Hawai'i Telescope. Here, we use the data analysis software, \href{https://crhea93.github.io/LUCI/index.html}{\texttt{LUCI}}, to produce flux maps of the prominent emission lines present in the filters: \oii{}$λ$3726/3729, \oiii{}$λ$5007, H$β$, \nii{}$λ$6548, \nii{}$λ$6583, and H$α$. We use these maps to produce BPT and WHAN diagrams to study the ionization mechanisms at play in each distinct region of the filamentary nebula. First, we confirm the absence of \oiii{}$λ$5007 in the extended filaments, although we detect this line in the central core, revealing a compact region where photoionization by the AGN might affect local conditions. Our findings corroborate previous claims that the ionization in the extended filaments could be caused by the cooling ICM via collisional excitation and/or mixing. Moreover, they support the conclusion that magnetic fields play an important role in the formation and continued existence of the filaments.

astro-ph.GA↗

arXiv2024

Precipitation possible: turbulence-driven thermal instability with constrained entropy profiles

Precipitation of cold gas due to thermal instability in both galaxy clusters and the circumgalactic medium may regulate AGN feedback. We investigate thermal instability in idealized simulations of the circumgalactic medium with a parameter study of over 600 three-dimensional hydrodynamic simulations of stratified turbulence with cooling, each evolved for 10 Gyr. The entropy profiles are maintained in a steady state via an idealized `thermostat' process, consistent with galaxy cluster entropy profiles. In the presence of external turbulent driving, we find cold gas precipitates, with a strong dependence whether the turbulent driving mechanism is solenoidal, compressive, or purely vertical. In the purely-vertical turbulent driving regime, we find that significant cold gas may form when the cooling time to free-fall time $t_{\rm cool} / t_{\text{ff}} \lesssim 5$. Our simulations with a ratio of $t_{\rm cool} / t_{\text{ff}} \sim 10$ do not precipitate under any circumstances, perhaps because the thermostat mechanism we use maintains a significant non-zero entropy gradient.

astro-ph.GA↗

arXiv2024

A New Superbubble Finding Algorithm: Description and Testing

We present a new algorithm for identifying superbubbles in HI column density maps of both observed and simulated galaxies that has only a single adjustable parameter. The algorithm includes an automated galaxy-background separation step to focus the analysis on the galactic disk. To test the algorithm, we compare the superbubbles it finds in a simulated galactic disk with the ones it finds in 21cm observations of a similar galactic disk. The sizes and radial distribution of those superbubbles are indeed qualitatively similar. However, superbubbles in the simulated galactic disk have lower central HI column densities. The HI superbubbles in the simulated disk are spatially associated with pockets of hot gas. We conclude that the algorithm is a promising method for systematically identifying and characterizing superbubbles using only HI column density maps that will enable standardized tests of stellar feedback models used in galaxy simulations.

astro-ph.GA↗

arXiv2024

X-ray Cool Core Remnants Heated by Strong Radio AGN Feedback

Strong AGN heating provides an alternative means for the disruption of cluster cool cores (CCs) to cluster mergers. In this work we present a systematic Chandra study of a sample of 108 nearby ($z<0.1$) galaxy clusters, to investigate the effect of AGN heating on CCs. About 40% of clusters with small offsets between the BCG and the X-ray centre ($\le50$ kpc) have small CCs. For comparison, 14 of 17 clusters with large offsets have small CCs, which suggests that mergers or sloshing can be efficient in reducing the CC size. Relaxed, small CC clusters generally have weak radio AGNs ($P_{1.4\rm GHz}<10^{23}$ W Hz$^{-1}$), and they show a lack of systems hosting a radio AGN with intermediate radio power ($2\times10^{23}<P_{1.4\rm GHz}<2\times10^{24}$ W Hz$^{-1}$). We found that the strongest circumnuclear ($<1$ kpc) X-ray emission only exists in clusters with strong radio AGN. The duty cycle of relaxed, small CC clusters is less than half of that for large CC clusters. It suggests that the radio activity of BCGs is affected by the properties of the surrounding gas beyond the central $\sim10$ kpc, and strong radio AGNs in small X-ray CCs fade more rapidly than those embedded in large X-ray CCs. A scenario is also presented for the transition of large CCs and coronae due to radio AGN feedback. We also present a detailed analysis of galaxy cluster 3C 129.1 as an example of a CC remnant possibly disrupted by radio AGN.

astro-ph.GA↗

arXiv2024

High-Spectral Resolution Observations of the Optical Filamentary Nebula in NGC 1275

We present new high-spectral resolution observations (R = $λ/Δλ$ = 7000) of the filamentary nebula surrounding NGC 1275, the central galaxy of the Perseus cluster. These observations have been obtained with SITELLE, an imaging Fourier transform spectrometer installed on the Canada-France-Hawai Telescope (CFHT) with a field of view of $11\text{ arcmin }\times 11 \text{ arcmin}$ encapsulating the entire filamentary structure of ionised gas despite its large size of $80 \text{ kpc}\times50 \text{ kpc}$. Here, we present renewed flux, velocity and velocity dispersion maps that show in great detail the kinematics of the optical nebula at \sii$\lambda6716$, \sii$\lambda6731$, \nii$\lambda6584$, H$α$(6563Å), and \nii$\lambda6548$. These maps reveal the existence of a bright flattened disk-shaped structure in the core extending to r $\sim 10$ kpc and dominated by a chaotic velocity field. This structure is located in the wake of X-ray cavities and characterised by a high mean velocity dispersion of $134$ km/s. The disk-shaped structure is surrounded by an extended array of filaments spread out to $r\sim 50$ kpc that are 10 times fainter in flux, remarkably quiescent and has a uniform mean velocity dispersion of $44$ km/s. This stability is puzzling given that the cluster core exhibits several energetic phenomena. Based on these results, we argue that there are two mechanisms to form multiphase gas in clusters of galaxies: a first triggered in the wake of X-ray cavities leading to more turbulent multiphase gas and a second, distinct mechanism, that is gentle and leads to large-scale multiphase gas spread throughout the core.

astro-ph.GA↗

arXiv2023

The SPT-Chandra BCG Spectroscopic Survey I: Evolution of the Entropy Threshold for Cooling and Feedback in Galaxy Clusters Over the Last 10 Gyr

We present a multi-wavelength study of the brightest cluster galaxies (BCGs) in a sample of the 95 most massive galaxy clusters selected from South Pole Telescope (SPT) Sunyaev-Zeldovich (SZ) survey. Our sample spans a redshift range of 0.3 < z < 1.7, and is complete with optical spectroscopy from various ground-based observatories, as well as ground and space-based imaging from optical, X-ray and radio wavebands. At z~0, previous studies have shown a strong correlation between the presence of a low-entropy cool core and the presence of star-formation and a radio-loud AGN in the central BCG. We show for the first time that a central entropy threshold for star formation persists out to z~1. The central entropy (measured in this work at a radius of 10 kpc) below which clusters harbor star-forming BCGs is found to be as low as $K_\mathrm{10 ~ kpc} = 35 \pm 4$ keV cm$^2$ at z < 0.15 and as high as $K_\mathrm{10 ~ kpc} = 52 \pm 11$ keV cm$^2$ at z~1. We find only marginal (~1$σ$) evidence for evolution in this threshold. In contrast, we do not find a similar high-z analog for an entropy threshold for feedback, but instead measure a strong evolution in the fraction of radio-loud BCGs in high-entropy cores as a function of redshift. This could imply that the cooling-feedback loop was not as tight in the past, or that some other fuel source like mergers are fueling the radio sources more often with increasing redshift, making the radio luminosity an increasingly unreliable proxy for radio jet power. We also find that our SZ-based sample is missing a small (~4%) population of the most luminous radio sources ($νL_ν > 10^{42}$ erg/s), likely due to radio contamination suppressing the SZ signal with which these clusters are detected.

astro-ph.GA↗