arXiv subjects

Valeria Olivares

Publications and source records attributed to Valeria Olivares.

At least 19 recordsLinked to original sources

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.

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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.

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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.

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arXiv2026

BlackHoleWeather -- Spin-coupled chaotic cold accretion across the meso-scale: Morphology and thermodynamics

Supermassive black hole (SMBH) spin is a key but poorly constrained ingredient of the feeding-feedback loop. Chaotic cold accretion (CCA) of cold gas clouds delivers rapidly varying three-dimensional torques that drive spin evolution and jet-axis reorientation, and in turn spin regulates jet power. We introduce a time-dependent SMBH spin model linking resolved multiphase feeding at meso scales to unresolved relativistic angular-momentum transfer at the innermost stable circular orbit (ISCO). We perform GPU-accelerated hydrodynamical simulations of a group atmosphere with jet feedback and SMBH spin evolution, resolving multiphase inflow and angular-momentum direction below parsec scales. We compare fixed-axis, direct, and hybrid prescriptions, with the latter preserving the resolved torque direction while filtering its magnitude through a Kerr ISCO closure. We then apply the hybrid model to low- and high-turbulence group setups. The cold-gas reservoir is nearly independent of whether the jet is fixed, spin-coupled, or rapidly reorienting. The spin prescription instead controls the inner feeding-feedback coupling, modulating central accretion, jet efficiency, and feedback geometry. The hybrid model is bracketed by analytic limits, whereas the direct model overestimates spin variability and jet-axis wandering, showing that an ISCO closure is required. Low-spin SMBHs are easier to reorient because a misaligned torque acts on a smaller angular-momentum reservoir. The decisive quantity is the coherence of the delivered angular momentum: the low-turbulence run preserves longer feeding bridges and faster spin evolution, whereas stronger turbulence fragments the inflow and enhances torque cancellation. In CCA, turbulence regulates whether the cold reservoir remains connected, how the angular momentum reaches the SMBH, where the next jet points, and how feedback is imprinted onto the halo.

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arXiv2026

BlackHoleWeather -- Jet-regulated chaotic cold accretion across the meso scale: Morphology and thermodynamics

How mechanical AGN feedback couples to multiphase condensation across scales remains a problem in galaxy groups and clusters. It is unclear how jets reshape the chaotic cold accretion (CCA) cycle and regulate black-hole fueling. BlackHoleWeather aims to build a unified description of the AGN baryon cycle across horizon, galactic, and group scales. Here we focus on how weather states shape the morphology and thermodynamics of jet-regulated CCA. We perform two hydrodynamical simulations of a turbulent, radiatively cooling galaxy-group atmosphere with self-regulated AGN feedback. The runs are initialized in two turbulence regimes and evolved with a kinetic mass-loaded jet. The jet prevents cooling via heating, but anisotropically reorganizes condensation through compression, entrainment, and turbulent mixing. In the stronger-turbulence case, condensation starts later but becomes extended, filamentary, and mixed, with a broader hot-warm-cold bridge, a porous cocoon, and burst-dominated fueling. This run evolves toward a cloud-dominated state with inefficient central accretion. In the weaker-turbulence case, condensation starts earlier and remains coherent and centrally confined, yielding a regular cocoon, a longer-lived inner cold reservoir with sustained fueling. In both runs, condensation is suppressed inside the jet channel and survives in the surrounding atmosphere and along the jet-ambient interface. Once condensation begins, SMBH fueling becomes super-Bondi. These results extend CCA from a pure cooling + turbulence problem to a jet-regulated weather process. Ambient turbulence acts as a control parameter, producing an extended stormy phase, a centrally retained rainy cycle, and, in the high-turbulence case, a later cloudy state with inefficient central fueling. The meso scale emerges as the layer linking halo thermodynamics to SMBH feeding within the broader BlackHoleWeather framework.

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arXiv2026

BlackHoleWeather -- Chaotic cold accretion across the meso-scale: Variability and kinematics

Accretion onto supermassive black holes (SMBHs) in realistic halos is time-variable, governed by turbulence, cooling, and multiphase condensation. In chaotic cold accretion (CCA), clouds and filaments condense out of the hot gas and feed the SMBH stochastically. We investigate how turbulence regulates the variability, radial transport, and kinematics of CCA, focusing on the meso-scale connecting halo rain to inner inflow. We analyse 3D hydrodynamic simulations with a GPU-accelerated code, including cooling and driven subsonic turbulence in a stratified galaxy group, resolving scales from kpc to sub-pc and probing two turbulent weather regimes. In both regimes, SMBH accretion proceeds through CCA, remains super-Bondi, and varies by up to $\sim 2$ dex. The runs diverge mainly at meso-scales: strong stirring sustains fragmented feeding and clear inflow enhancement at 0.1-1 kpc, whereas weaker turbulence yields a smoother central cascade. Yet innermost feeding rates remain similar, implying SMBH accretion is not directly supply-limited by macro-scale weather. Accretion rate distributions peak at low Eddington ratios, indicating maintenance-mode state. Accretion rate power spectra follow a broken power law, with pink noise on long/intermediate timescales and a steeper red-noise tail at high frequencies, consistent with parsec-scale collisional damping. CCA modes are captured by two complementary diagnostics: the $\mathcal{C}$-ratio ($\equiv t_{\rm cool}/t_{\rm eddy}$) $\approx 1$ identifies soft X-ray gas as the gateway of condensation, while the k-plot (line broadening vs. shift) shows that the weather distinction is strongest on meso-scales, where the stormy regime produces broader, overlapping multiphase kinematics than the rainy regime. The meso-scale bridges halo rain and micro-scale CCA feeding, regulating spatial transport, kinematic imprint, and temporal coherence of SMBH growth.

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arXiv2026

BlackHoleWeather -- Chaotic cold accretion across the meso-scale: Morphology and thermodynamics

Supermassive black holes (SMBHs) self-regulate galaxies, groups, and clusters, yet the pathway transporting gas from halo scales to sub-pc radii remains debated. In hot stratified atmospheres, subsonic turbulence can trigger nonlinear thermal instability and a multiphase condensation cascade, producing chaotic time-variable BH `weather'. A key missing link is how the meso-scale connects halo rain to nuclear inflow. We study turbulence-driven condensation and chaotic cold accretion (CCA) in a group-scale halo, quantifying how the stirring level shapes multiphase morphology, thermodynamics, and SMBH feeding. We ran 3D hydrodynamic hyper-zoom simulations with a GPU-accelerated code, including cooling and driven subsonic turbulence in a hot intragroup halo. Two endpoint runs bracket weak and strong stirring, capturing distinct BH weather states. In both regimes the atmosphere becomes thermally unstable and develops a multiphase medium spanning 8-10 dex in temperature and density. Strong stirring delays cold gas accretion and sustains an extended filament-rich rain pattern to kpc radii (`stormy' CCA), with broader thermodynamic distributions beyond the nucleus. Weak stirring triggers earlier condensation but yields a more compact rain, with most cold gas confined within 100 pc (`rainy' CCA). At micro-scales the inflow is partly mediated by a clumpy rotating torus. Despite large differences in condensed cold mass, the BH accretion rate is recurrently boosted by up to 100x above the hot-mode Bondi baseline and varies weakly between the weather regimes, indicating that feeding is regulated primarily by how efficiently multiphase structures couple to the central inflow. Modest turbulence changes are sufficient to shift the same hot halo between stormy (extended) and rainy (centralized) BH weather, providing a quantitative multiscale baseline for interpreting multiphase CCA and SMBH feeding.

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arXiv2026

BlackHoleWeather -- Spin-coupled chaotic cold accretion across the meso scale: Variability and kinematics

Supermassive black hole (SMBH) spin records the vector history of accretion. In chaotic cold accretion (CCA), this history is set by clouds and filaments whose torques can add coherently, cancel, or reverse before reaching the horizon-scale closure. We test whether halo stirring regulates SMBH spin by changing the radial continuity and torque coherence of the meso-scale accretion bridge. We focus on spin evolution, jet-axis reorientation, accretion variability, and CCA kinematics. We analyse four 3D hydrodynamical simulations in a 100-kpc box, reaching sub-pc resolution, including SMBH spin-coupled jet feedback. All runs use the Hybrid SMBH spin model validated in a companion paper. Two simulations maintain continuous driven solenoidal turbulence, while two matched controls let the same initial turbulent field decay. The main effect of persistent stirring is to disrupt mass and angular-momentum continuity across the meso-scale bridge. Although all runs develop comparable macro-scale inflow, in the driven-turbulence suite, gas struggles to reach pc scales, and the radial accretion rate drops by 2-3 orders of magnitude. Torque delivery in this case is fragmented and cancellation-dominated. The interrupted-turbulence suite, on the other hand, preserves a connected gas channel to the sink, while sustaining higher torque coherence. Driven runs therefore settle to slow effective jet-axis drift, whereas interrupted runs maintain reorientation rates higher by about two orders of magnitude and can briefly reach a few degrees during coherent retrograde episodes. The same split appears in power spectra and k-plots: connected rain enhances low-frequency accretion power and produces narrower, phase-ordered kinematics, while stirring steepens high-frequency damping and broadens the gas velocity loci for all phases.

astro-ph.GA↗

arXiv2026

BlackHoleWeather -- Jet-regulated chaotic cold accretion across the meso scale: Variability and kinematics

Chaotic cold accretion (CCA) predicts that supermassive black holes are fed by multiphase clouds condensing from turbulent hot atmospheres. In jet-regulated systems cold gas must also remain dynamically connected to the central accretion region. We investigate how a self-regulated kinetic jet modifies the kinematics, radial transport, and variability of CCA across the meso-scale of a typical galaxy-group atmosphere. The runs differ only in turbulent driving strength. We measure accretion histories, Eddington ratios, power spectra, phase-separated mass fluxes, projected k-plots, and cooling-to-eddy-time (C-ratio) profiles. Both runs become CCA-fed once precipitation begins, with accretion rising from Bondi-like to strongly super-Bondi values while remaining mostly low-Eddington and mechanically dominated. The strongly stirred run develops an early stormy phase with extended condensation, bursty feeding, and strong inflow/outflow variability, but later enters a cloudy phase in which cold and warm gas persist at meso- and inner macro-scales while sink coupling weakens. The calmer run maintains a compact rainy state with a longer-lived central reservoir. Accretion-rate spectra show flicker-like low-frequency slopes and red-noise tails; in the cloudy phase, the normalization drops and the low-frequency slope flattens. Phase-separated fluxes show fountain-like recycling in the strongly stirred run, but inner-kpc recycling in the calmer run. The jet excavates a hot channel where sustained condensation is suppressed, while C~1 is reached mostly outside the cone and near the jet-ambient interface. Jet-regulated CCA is controlled by meso-scale transport, not only by cold-gas production. Within the BlackHoleWeather framework, combined k-plot and C-ratio diagnostics are crucial to distinguish cold gas that is merely present from cold gas dynamically linked to SMBH feeding.

astro-ph.HE↗

arXiv2026

AGN Feedback and the Development of Dusty Multiphase Gas in X-ray Emitting Elliptical Galaxies

This paper investigates the physical and kinematic properties of dust-rich regions in a small sample of group-centered elliptical galaxies, emphasizing their connection with the hot X-ray emitting gas and detailed dust grain characteristics. Comprehensive multi-wavelength data, including H-alpha and CO emission detected by MUSE and ALMA, demonstrate the presence of dust clouds embedded within complex, hot X-ray atmospheres shaped by AGN feedback. X-ray images show bubbles and cavities surrounded by bright rims. We find that dust regions containing molecular gas traced by CO are preferentially located at the rims of these X-ray cavities, suggesting that AGN-driven outflows enhance the condensation of cold, dusty gas at these compressive interfaces. Kinematic measurements indicate that molecular and ionized gas phases are dynamically and spatially linked, supporting the framework of a multiphase medium arising from the top-down condensation rain in the hot plasma and related chaotic cold accretion. Crucially, spatial variations in the total-to-selective extinction ratio Rv show that regions where dust, CO, and H-alpha emission coincide exhibit notably smaller Rv values, implying steeper extinction curves and the predominance of smaller or less evolved dust grains within these mixed-phase environments. This contrasts with larger Rv values found elsewhere in the dust clouds, suggesting grain growth or survival mechanisms within shielded cold gas.

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arXiv2026

The Rise of Ionized Gas Filaments in Early-Type Galaxies

Multiphase filamentary nebulae are ubiquitous in the brightest cluster galaxies (BCGs) of cool-core clusters, providing insight into baryon cycling and the feeding and feedback of supermassive black holes. However, BCGs account for less than 1% of all early-type galaxies (ETGs). To broaden our understanding of how multiphase filamentary nebulae form in ETGs and connect to the greater picture of galaxy evolution, it is crucial to explore ETGs that are outside of the dense centers of galaxy clusters or groups. We present VLT-MUSE IFU observations of 126 nearby non-central ETGs, detecting warm ionized gas in 62 of them. 35/62 host rotating gas disks with the majority of them morphologically and kinematically aligned with their stellar components, suggesting stellar mass loss may dominate their warm-gas origin. The remaining 27 host filamentary nebulae, often decoupled from the stellar components, resembling those observed in BCGs. These filamentary sources display unique emission line properties that cannot be fully explained by photoionization from post-asymptotic giant branch stars, active galactic nuclei, or fast gas shocks alone. For the twelve filamentary sources that have Chandra data, their soft X-ray emission exceeds or is consistent with (within uncertainties) unresolved low-mass X-ray binary emission, indicating that filamentary systems generally host an appreciable hot gas reservoir. We suggest that cooling-related processes, e.g., self-irradiation associated with the cooling hot gas, may contribute to the powering of warm gas line emission, similar to cool-core clusters, though the detailed mechanisms and physical conditions may differ. As a case study, we investigate NGC 4374, a non-central ETG with extensive Chandra observations, and find that its warm filaments are over-pressured compared to the hot filaments - opposite to what is observed in cool-core clusters.

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arXiv2025

Observations of AGN-driven feedback: dynamics and ionization of the filaments in M87

We present a comprehensive kinematic and ionization analysis of the warm ionized filaments ($10^4$ K) in M87, the central galaxy of the Virgo cluster, using new integral field spectroscopy from MEGARA (GTC) and SITELLE (CFHT). MEGARA targets the southeastern (SE) filaments (3 kpc from the nucleus), coincident with the only known molecular gas clump, and the far eastern (FE) filament (15 kpc), spatially isolated within an old radio lobe. SITELLE fully maps the filaments, offering the first complete views of their kinematics and excitation. Combined with archival ALMA, MUSE and Chandra data, these observations offer a multi-phase view of gas dynamics. The filaments display complex motions inconsistent with simple rotation. Velocity structure functions (VSFs) of the warm and cold gas in the central and SE filaments show consistent steep slopes (2/3) and flattening on small scales of a few hundred parsecs, possibly suggesting energy injection from Type Ia supernovae, though interpretation is method-limited. The FE filament shows a lower VSF amplitude, suggesting less active driving. ALMA CO emission is co-spatial and kinematically aligned with the ionized gas, the latter showing broader velocity dispersions. Ionization diagnostics indicate AGN-related processes (e.g., shocks) dominate, with higher-energy excitation near the radio lobes and lower-energy fossil feedback signatures in the FE filament. Finally, the filaments follow the same strong H$α$-X-ray surface brightness correlation seen in other clusters, supporting local thermal coupling between phases. However, the FE filament deviates from this trend, possibly due to uplift from past AGN outbursts or limitations in the analysis method.

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arXiv2025

The relationship between warm and hot gas-phase metallicity in massive elliptical galaxies and the influence of AGN feedback

Warm ionized gas is ubiquitous at the centers of X-ray bright elliptical galaxies. While it is believed to play a key role in the feeding and feedback processes of supermassive black holes, its origins remain under debate. Existing studies have primarily focused on the morphology and kinematics of warm ionized gas. This work aims to provide a new perspective on warm (10,000 K) ionized gas and its connection to X-ray-emitting hot gas (>10^6 K) by measuring and comparing their metallicities. We conducted a joint analysis of 13 massive elliptical galaxies using MUSE/VLT and Chandra observations. Emission-line ratios were measured for the warm ionized gas using MUSE observation, and used to infer the ionization mechanisms and derive metallicities of the warm ionized gas using HII, and LIN(E)R calibrations. We also computed the warm phase metallicity using X-ray/EUV, and pAGB stars models. For two sources at higher redshift, direct Te method was also used to measure warm gas metallicities. Our observations reveal that most sources exhibit composite ionization, with contributions from both star formation and LINER-like emission. A positive linear correlation was found between the gas-phase metallicities of the warm and hot phases, ranging from 0.3 to 1.5 Zsun, and suggest the intimate connection between the two gas phases, likely driven by gas cooling and/or mixing. In some sources the warm gas metallicity shows a central drop. A similar radial trend has been reported for the hot gas metallicity in some galaxy clusters. The ionization mechanisms of cooling flow elliptical galaxies are diverse, suggesting multiple channels for powering the warm ionized gas. The large variation in the warm gas metallicity further suggests that cold gas mass derived under the assumption of solar metallicity for the CO-to-H2 conversion factor needs to be revised by approximately an order of magnitude.

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arXiv2025

Direct observation of the X-ray counterpart of the Hα filaments and of the sloshing spiral in the Perseus galaxy cluster

Deep Chandra observations of the Perseus galaxy cluster have allowed for the discovery of X-ray counterparts to the Hα filamentary structures and of a sloshing spiral. However, both components are extremely faint, and their study is largely hindered by the volume-filling hot intracluster medium (ICM). Using the Poisson General Morphological Component Analysis (pGMCA) algorithm, a blind source separation method adapted for Poissonian statistics, we were able to extract detailed, clean morphological maps of these components. We then introduced a template fitting method to investigate their spectral characteristics. We report the first direct observation of about 1.35 keV low-energy emission from the sloshing spiral, and produce the most detailed and unpolluted map of the X-rays filaments thus far obtained.

astro-ph.HE↗

arXiv2025

JVLA and VLBA study of the merging cool core CHIPS 1911+4455 at z~0.5: radio emission from an infant AGN and from a rapidly star-forming BCG

Recent studies of galaxy clusters found peculiar cases at the boundary between non-cool core and cool core systems. While unusual, these objects can help us understand the evolution of the most massive clusters. We investigated the role of active galactic nucleus (AGN) feedback in the starburst brightest cluster galaxy (BCG) of the merging cool core cluster CHIPS 1911+4455 (z = 0.485). We conducted new multifrequency (0.3 - 5 GHz) Very Long Baseline Array (VLBA) and Jansky Very Large Array (JVLA) observations of CHIPS 1911+4455 across a wide range of scales (0.01 to 20 kpc). Our analysis reveals that the AGN in the BCG has recently awakened, showing a compact core with symmetric, ~30 pc long jets in VLBA data. The onset of the AGN may be linked to the enhanced cooling of the hot gas found in a previous study. At larger scales (10 kpc), faint radio whiskers extending to the south show a striking alignment with star-forming knots and are thus interpreted as synchrotron-emitting regions associated with the starburst BCG. The implied radio star formation rate of 100 - 155 M$_{\odot}$/yr agrees with the optical/infrared one (140 - 190 M$_{\odot}$/yr). Our JVLA and VLBA radio study, informed by previous X-ray/optical/millimeter works, indicates that CHIPS 1911+4455 represents a transitional phase in cluster evolution, where the AGN in the central galaxy has just begun to respond to copious hot gas cooling.

astro-ph.GA↗

arXiv2025

H$α$-X-ray Surface Brightness Correlation for Filaments in Cooling Flow Clusters

Massive galaxies in cooling flow clusters display clear evidence of feedback from Active Galactic Nuclei (AGN). Joint X-ray and radio observations have shown that AGN radio jets push aside the surrounding hot gas and form cavities in the hot intracluster medium (ICM). These systems host complex, kiloparsec-scale, multiphase filamentary structures, from warm ionized (10,000 K) to cold molecular ($<$100 K). These striking clumpy filaments are believed to be a natural outcome of thermally unstable cooling from the hot ICM, likely triggered by feedback processes while contributing to feeding the AGN via Chaotic Cold Accretion (CCA). However, the detailed constraints on the formation mechanism of the filaments are still uncertain, and the connection between the different gas phases has to be fully unveiled. By leveraging a sample of seven X-ray bright cooling-flow clusters, we have discovered a tight positive correlation between the X-ray surface brightness and the H$α$ surface brightness of the filaments over two orders of magnitude, as also found in stripped tails.

astro-ph.GA↗

arXiv2024

A hot core in the group-dominant elliptical galaxy NGC 777

NGC 777 provides an example of a phenomenon observed in some group-central ellipticals, in which the temperature profile shows a central peak, despite the short central cooling time of the intra-group medium. We use deep Chandra X-ray observations of the galaxy, supported by uGMRT 400 MHz radio imaging, to investigate the origin of this hot core. We confirm the centrally-peaked temperature profile and find that entropy and cooling time both monotonically decline to low values (2.62 [+0.19, -0.18] keV cm$^2$ and 71.3 [+12.8, -13.1] Myr) in the central ~700 pc. Faint diffuse radio emission surrounds the nuclear point source, with no clear jets or lobes but extending to ~10 kpc on a northwest-southeast axis. This alignment and extent agree well with a previously identified filamentary H$α$+[NII] nebula. While cavities are not firmly detected, we see X-ray surface brightness decrements on the same axis at 10-20 kpc radius which are consistent with the intra-group medium having been pushed aside by expanding radio lobes. Any such outburst must have occurred long enough ago for lobe emission to have faded below detectability. Cavities on this scale would be capable of balancing radiative cooling for at least ~240 Myr. We consider possible causes of the centrally peaked temperature profile, including gravitational heating of gas as the halo relaxes after a period of AGN jet activity, and heating by particles leaking from the remnant relativistic plasma of the old radio jets.

astro-ph.GA↗

arXiv2023

The formation channels of multiphase gas in nearby early-type galaxies

The processes responsible for the assembly of cold and warm gas in early-type galaxies (ETGs) are not well-understood. We report on the multiwavelength properties of 15 non-central, nearby ($z \leq$ 0.00889) ETGs primarily through Multi-Unit Spectroscopic Explorer (MUSE) and Chandra X-ray observations, to address the origin of their multiphase gas. The MUSE data reveals 8/15 sources contain warm ionized gas traced by the H$α$ emission line. The morphology of this gas is found to be filamentary in 3/8 sources: NGC 1266, NGC 4374, and NGC 4684 which is similar to that observed in many group and cluster-centered galaxies. All H$α$ filamentary sources have X-ray luminosities exceeding the expected emission from the stellar population, suggesting the presence of diffuse hot gas which likely cooled to form the cooler phases. The morphology of the remaining 5/8 sources are rotating gas disks, not as commonly observed in higher mass systems. Chandra X-ray observations (when available) of the ETGs with rotating H$α$ disks indicate that they are nearly void of hot gas. A mixture of stellar mass loss and external accretion was likely the dominant channel for the cool gas in NGC 4526 and NGC 4710. These ETGs show full kinematic alignment between their stars and gas, and are fast rotators. The H$α$ features within NGC 4191 (clumpy, potentially star-forming ring), NGC 4643 and NGC 5507 (extended structures) along with loosely overlapping stellar and gas populations allow us to attribute external accretion to be the primary formation channel of the cool gas in these systems.

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