256 research outputs found
Simulating the Hot X-ray Emitting Gas in Elliptical Galaxies
We study the chemo-dynamical evolution of elliptical galaxies and their hot
X-ray emitting gas using high-resolution cosmological simulations. Our Tree
N-body/SPH code includes a self-consistent treatment of radiative cooling, star
formation, supernovae feedback, and chemical enrichment. We present a series of
LCDM cosmological simulations which trace the spatial and temporal evolution of
heavy element abundance patterns in both the stellar and gas components of
galaxies. X-ray spectra of the hot gas are constructed via the use of the
vmekal plasma model, and analysed using XSPEC with the XMM EPN response
function. Simulation end-products are quantitatively compared with the
observational data in both the X-ray and optical regime. We find that radiative
cooling is important to interpret the observed X-ray luminosity, temperature,
and metallicity of the interstellar medium of elliptical galaxies. However,
this cooled gas also leads to excessive star formation at low redshift, and
therefore results in underlying galactic stellar populations which are too blue
with respect to observations.Comment: 6 pages, 3 figures, to appear in the proceedings of "The IGM/Galaxy
Connection - The Distribution of Baryons at z=0", ed. M. Putman & J.
Rosenberg; High resolution version is available at
http://astronomy.swin.edu.au/staff/dkawata/research/papers.htm
The nature of the variable millimetreâselected AGN in the brightest cluster galaxy of Abell 851
We present the detection of a bright 3âmm continuum source in the brightest cluster galaxy (BCG) in Abell 0851 (z = 0.411) with the NOrthern Extended Millimeter Array (NOEMA). When this detection is compared to other multifrequency observations across 21cmâ 100ÎŒm, including new Arcminute Microkelvin Imager 15âGHz observations, we find evidence for a relatively flat, variable core source associated with the BCG. The radio power and amplitude of variability observed in this galaxy is consistent with the cores in lower redshift BCGs in X-rayâselected clusters, and the flat mmâcm spectrum is suggestive of the BCG being a low-luminosity active galactic nucleus archetype. The discovery of this system could provide a basis for a long-term study of the role of low-luminosity radio mode âregulatoryâ feedback in massive clusters
Driving massive molecular gas flows in central cluster galaxies with AGN feedback
We present an analysis of new and archival ALMA observations of molecular gas in 12 central cluster galaxies. We examine emerging trends in molecular filament morphology and gas velocities to understand their origins. Molecular gas masses in these systems span 109ââ1011Mââ , far more than most gas-rich galaxies. ALMA images reveal a distribution of morphologies from filamentary to disc-dominated structures. Circumnuclear discs on kiloparsec scales appear rare. In most systems, half to nearly all of the molecular gas lies in filamentary structures with masses of a few Ă108--10Mâ that extend radially several to several tens of kpc. In nearly all cases the molecular gas velocities lie far below stellar velocity dispersions, indicating youth, transience, or both. Filament bulk velocities lie far below the galaxyâs escape and free-fall speeds indicating they are bound and being decelerated. Most extended molecular filaments surround or lie beneath radio bubbles inflated by the central active galactic nuclei (AGNs). Smooth velocity gradients found along the filaments are consistent with gas flowing along streamlines surrounding these bubbles. Evidence suggests most of the molecular clouds formed from low entropy X-ray gas that became thermally unstable and cooled when lifted by the buoyant bubbles. Uplifted gas will stall and fall back to the galaxy in a circulating flow. The distribution in morphologies from filament to disc-dominated sources therefore implies slowly evolving molecular structures driven by the episodic activity of the AGNs
Revealing the velocity structure of the filamentary nebula in NGC 1275 in its entirety
We have produced for the first time a detailed velocity map of the giant filamentary nebula surrounding NGC 1275, the Perseus clusterâs brightest galaxy, and revealed a previously unknown rich velocity structure across the entire nebula. These new observations were obtained with the optical imaging Fourier transform spectrometer SITELLE at CFHT. With its wide field of view (ââŒ11 arcminâĂâ11 arcmin), SITELLE is the only integral field unit spectroscopy instrument able to cover the 80 kpcâ Ă â55 kpc (â3.8 arcminâĂâ2.6 arcmin) large nebula in NGC 1275. Our analysis of these observations shows a smooth radial gradient of the [NâII]λ6583/H α line ratio, suggesting a change in the ionization mechanism and source across the nebula. The velocity map shows no visible general trend or rotation, indicating that filaments are not falling uniformly onto the galaxy, nor being uniformly pulled out from it. Comparison between the physical properties of the filaments and Hitomi measurements of the X-ray gas dynamics in Perseus is also explored
The Evolution of X-ray Clusters of Galaxies
Considerable progress has been made over the last decade in the study of the
evolutionary trends of the population of galaxy clusters in the Universe. In
this review we focus on observations in the X-ray band. X-ray surveys with the
ROSAT satellite, supplemented by follow-up studies with ASCA and Beppo-SAX,
have allowed an assessment of the evolution of the space density of clusters
out to z~1, and the evolution of the physical properties of the intra-cluster
medium out to z~0.5. With the advent of Chandra and Newton-XMM, and their
unprecedented sensitivity and angular resolution, these studies have been
extended beyond redshift unity and have revealed the complexity of the
thermodynamical structure of clusters. The properties of the intra-cluster gas
are significantly affected by non-gravitational processes including star
formation and Active Galactic Nucleus (AGN) activity. Convincing evidence has
emerged for modest evolution of both the bulk of the X-ray cluster population
and their thermodynamical properties since redshift unity. Such an
observational scenario is consistent with hierarchical models of structure
formation in a flat low density universe with Omega_m=0.3 and sigma_8=0.7-0.8
for the normalization of the power spectrum. Basic methodologies for
construction of X-ray-selected cluster samples are reviewed and implications of
cluster evolution for cosmological models are discussed.Comment: 40 pages, 15 figures. Full resolution figures can be downloaded from
http://www.eso.org/~prosati/ARAA
Recommended from our members
The mass distribution of the unusual merging cluster Abell 2146 from strong lensing
Abell 2146 consists of two galaxy clusters that have recently collided close to the plane of the sky, and it is unique in showing two large shocks on images. With an early stage merger, shortly after first core passage, one would expect the cluster galaxies and the dark matter to be leading the X-ray emitting plasma. In this regard, the cluster Abell 2146-A is very unusual in that the X-ray cool core appears to lead, rather than lag, the brightest cluster galaxy (BCG) in their trajectories. Here we present a strong-lensing analysis of multiple-image systems identified on images. In particular, we focus on the distribution of mass in Abell 2146-A in order to determine the centroid of the dark matter halo. We use object colours and morphologies to identify multiple-image systems; very conservatively, four of these systems are used as constraints on a lens mass model. We find that the centroid of the dark matter halo, constrained using the strongly lensed features, is coincident with the BCG, with an offset of â2 kpc between the centres of the dark matter halo and the BCG. Thus from the strong-lensing model, the X-ray cool core also leads the centroid of the dark matter in Abell 2146-A, with an offset of â30 kpc.JEC acknowledges support from The University of Texas at Dallas, and NASA through a Fellowship of the Texas Space Grant Consortium. Based on observations made with the NASA/ESA HST, obtained through programme 12871 through the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. Additional funding supporting JEC, LJK, and DIC came from a grant from the Space Telescope Science Institute under the same programme 12871. Additional funding supporting JEC and LJK came from a grant from the National Science Foundation, number 1517954. This work was supported in part by World Premier International Research Center Initiative (WPI Initiative), MEXT, Japan, and JSPS KAKENHI Grant Number 26800093 and 15H05892
The Hot and Energetic Universe: AGN feedback in galaxy clusters and groups
Mechanical feedback via Active Galactic Nuclei (AGN) jets in the centres of
galaxy groups and clusters is a crucial ingredient in current models of galaxy
formation and cluster evolution. Jet feedback is believed to regulate gas
cooling and thus star formation in the most massive galaxies, but a robust
physical understanding of this feedback mode is currently lacking. The large
collecting area, excellent spectral resolution and high spatial resolution of
Athena+ will provide the breakthrough diagnostic ability necessary to develop
this understanding, via: (1) the first kinematic measurements on relevant
spatial scales of the hot gas in galaxy, group and cluster haloes as it absorbs
the impact of AGN jets, and (2) vastly improved ability to map thermodynamic
conditions on scales well-matched to the jets, lobes and gas disturbances
produced by them. Athena+ will therefore determine for the first time how jet
energy is dissipated and distributed in group and cluster gas, and how a
feedback loop operates in group/cluster cores to regulate gas cooling and AGN
fuelling. Athena+ will also establish firmly the cumulative impact of powerful
radio galaxies on the evolution of baryons from the epoch of group/cluster
formation to the present day
Quasar feedback survey: molecular gas affected by central outflows and by âŒ10-kpc radio lobes reveal dual feedback effects in \u27radio quiet\u27 quasars
\ua9 The Author(s) 2023. Published by Oxford University Press on behalf of Royal Astronomical Society. We present a study of molecular gas, traced via CO (3â2) from Atacama Large Millimeter/submillimeter Array data, of four z < 0.2, âradio quietâ, type 2 quasars (Lbol ⌠1045.3â1046.2 erg sâ1; L1.4 GHz ⌠1023.7â1024.3 WHzâ1). Targets were selected to have extended radio lobes (â„ 10 kpc), and compact, moderate-power jets (1â10 kpc; Pjet ⌠1043.2â1043.7 erg sâ1). All targets show evidence of central molecular outflows, or injected turbulence, within the gas discs (traced via high-velocity wing components in CO emission-line profiles). The inferred velocities (Vout = 250â440 km sâ1) and spatial scales (0.6â1.6 kpc), are consistent with those of other samples of luminous low-redshift active galactic nuclei. In two targets, we observe extended molecular gas structures beyond the central discs, containing 9â53 per cent of the total molecular gas mass. These structures tend to be elongated, extending from the core, and wrap-around (or along) the radio lobes. Their properties are similar to the molecular gas filaments observed around radio lobes of, mostly âradio loudâ, brightest cluster galaxies. They have the following: projected distances of 5â13 kpc; bulk velocities of 100â340 km sâ1; velocity dispersion of 30â130 km sâ1; inferred mass outflow rates of 4â20 Mâ yrâ1; and estimated kinetic powers of 1040.3â1041.7 erg sâ1. Our observations are consistent with simulations that suggest moderate-power jets can have a direct (but modest) impact on molecular gas on small scales, through direct jetâcloud interactions. Then, on larger scales, jet-cocoons can push gas aside. Both processes could contribute to the long-term regulation of star formation
The quasar feedback survey: discovering hidden Radio-AGN and their connection to the host galaxy ionized gas
We present the first results from the Quasar Feedback Survey, a sample of 42 z 1042.1 ergs sâ1) with moderate radio luminosities (i.e. L1.4GHz > 1023.4 W Hzâ1; median L1.4GHz = 5.9 Ă 1023 W Hzâ1). Using high spatial resolution (âŒ0.3â1 arcsec), 1.5â6 GHz radio images from the Very Large Array, we find that 67 perâcent of the sample have spatially extended radio features on âŒ1â60 kpc scales. The radio sizes and morphologies suggest that these may be lower radio luminosity versions of compact, radio-loud AGNs. By combining the radio-to-infrared excess parameter, spectral index, radio morphology, and brightness temperature, we find radio emission in at least 57 perâcent of the sample that is associated with AGN-related processes (e.g. jets, quasar-driven winds, or coronal emission). This is despite only 9.5â21 perâcent being classified as radio-loud using traditional criteria. The origin of the radio emission in the remainder of the sample is unclear. We find that both the established anticorrelation between radio size and the width of the [O III] line, and the known trend for the most [O III] luminous AGNs to be associated with spatially extended radio emission, also hold for our sample of moderate radio luminosity quasars. These observations add to the growing evidence of a connection between the radio emission and ionized gas in quasar host galaxies. This work lays the foundation for deeper investigations into the drivers and impact of feedback in this unique sample
The Hot and Energetic Universe: AGN feedback in galaxy clusters and groups
Mechanical feedback via Active Galactic Nuclei (AGN) jets in the centres of galaxy groups and clusters is a crucial ingredient in current models of galaxy formation and cluster evolution. Jet feedback is believed to regulate gas cooling and thus star formation in the most massive galaxies, but a robust physical understanding of this feedback mode is currently lacking. The large collecting area, excellent spectral resolution and high spatial resolution of Athena+ will provide the breakthrough diagnostic ability necessary to develop this understanding, via: (1) the first kinematic measurements on relevant spatial scales of the hot gas in galaxy, group and cluster haloes as it absorbs the impact of AGN jets, and (2) vastly improved ability to map thermodynamic conditions on scales well-matched to the jets, lobes and gas disturbances produced by them. Athena+ will therefore determine for the first time how jet energy is dissipated and distributed in group and cluster gas, and how a feedback loop operates in group/cluster cores to regulate gas cooling and AGN fuelling. Athena+ will also establish firmly the cumulative impact of powerful radio galaxies on the evolution of baryons from the epoch of group/cluster formation to the present day
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