Results for "Paul E. J. Nulsen"

total 259872took 0.20s
Uniformity of foreground Galactic neutral Hydrogen over cooling flow clustersApr 02 2003Radio maps at 21 cm of foreground neutral hydrogen over three cooling flow clusters of galaxies show that the foreground gas is uniform on scales from about 1 -- 10 arcmin. Five sigma limits on fluctuations in the foreground column density for Abell 3581, ... More
The Extended Fe distribution in the intracluster medium and the implications regarding AGN HeatingFeb 08 2008Sep 17 2008We present a systematic analysis of XMM-Newton observations of 8 cool-core clusters of galaxies and determine the Fe distribution in the intracluster medium relative to the stellar distribution in the central dominant galaxy (CDG). Our analysis shows ... More
Substructure in the cold front cluster Abell 3667Nov 19 2008We present evidence for the existence of significant substructure in the cold front cluster Abell 3667 based on multi-object spectroscopy taken with the 3.9m Anglo Australian Telescope. This paper is the second in a series analyzing the relationship between ... More
Minor merger-induced cold fronts in Abell 2142 and RXJ1720.1+2638Sep 26 2011We present evidence for the existence of substructure in the "relaxed appearing" cold front clusters Abell 2142 and RXJ1720.1+2638. The detection of these substructures was made possible by comprehensive multi-object optical spectroscopy obtained with ... More
Interaction of the AGN and X-ray Emitting GasOct 07 2003The process that prevents the deposition of cooled gas in cooling flows must rely on feedback in order to maintain gas with short cooling times, while preventing the bulk of the gas from cooling to low temperatures. The primary candidate for the feedback ... More
Interaction of Cygnus A with its environmentFeb 17 2015Cygnus A, the nearest truly powerful radio galaxy, resides at the centre of a massive galaxy cluster. Chandra X-ray observations reveal its cocoon shocks, radio lobe cavities and an X-ray jet, which are discussed here. It is argued that X-ray emission ... More
The dwarf galaxy population in Abell 2218May 21 2004We present results from a deep photometric study of the rich galaxy cluster Abell 2218 (z=0.18) based on archival HST WFPC2 F606W images. These have been used to derive the luminosity function to extremely faint limits (M_{F606W}=-13.2 mag, mu_{0}=24.7 ... More
Abell 1201: The anatomy of a cold front cluster from combined optical and X-ray dataOct 25 2008We present a combined X-ray and optical analysis of the cold front cluster Abell 1201 using archival Chandra, data and multi-object spectroscopy taken with the 3.9m Anglo Australian and 6.5m Multiple Mirror Telescopes. This paper represents the first ... More
A High Fidelity Sample of Cold Front Clusters from the Chandra ArchiveSep 14 2009This paper presents a sample of "cold front" clusters selected from the Chandra archive. The clusters are selected based purely on the existence of surface brightness edges in their Chandra images which are modeled as density jumps. A combination of the ... More
Shocking Tails in the Major Merger Abell 2744Apr 04 2012We identify four rare "jellyfish" galaxies in Hubble Space Telescope imagery of the major merger cluster Abell 2744. These galaxies harbor trails of star-forming knots and filaments which have formed in-situ in gas tails stripped from the parent galaxies, ... More
A Chandra - VLA Investigation of the X-ray Cavity System and Radio Mini-Halo in the Galaxy Cluster RBS 797Apr 27 2012We present a study of the cavity system in the galaxy cluster RBS 797 based on Chandra and VLA data. RBS 797 (z = 0.35), is one of the most distant galaxy clusters in which two pronounced X-ray cavities have been discovered. The Chandra data confirm the ... More
A Chandra study of the large-scale shock and cool filaments in Hydra A: Evidence for substantial gas dredge-up by the central outburstFeb 26 2011We present the results of a Chandra study of the Hydra A galaxy cluster, where a powerful AGN outburst created a large-scale cocoon shock. We investigated possible azimuthal variations in shock strength and shape, finding indications for a weak shock ... More
XMM-Newton view of MS0735+7421: the most energetic AGN outburst in a galaxy clusterNov 08 2006We discuss the possible cosmological effects of powerful AGN outbursts in galaxy clusters by starting from the results of an XMM-Newton observation of the supercavity cluster MS0735+7421.
Cosmological Effects of Powerful AGN Outbursts in Galaxy Clusters: Insights from an XMM-Newton Observation of MS0735+7421Jan 12 2007We report on the results of an analysis of XMM-Newton observations of MS0735+7421, the galaxy cluster which hosts the most energetic AGN outburst currently known. The previous Chandra image shows twin giant X-ray cavities (~200 kpc diameter) filled with ... More
In Search of the Dark Ages -- An Experimental ChallengeApr 13 2004Most direct source detections beyond z~7 are likely to arise from wide-field narrowband surveys of Ly-a emission in the J band. For this to be true, the Ly-a emission must somehow escape from compact star-forming regions (CSR) presumably associated with ... More
Heating Hot Atmospheres with Active Galactic NucleiSep 13 2007High resolution X-ray spectroscopy of the hot gas in galaxy clusters has shown that the gas is not cooling to low temperatures at the predicted rates of hundreds to thousands of solar masses per year. X-ray images have revealed giant cavities and shock ... More
The role of cooling flows in galaxy formationJun 02 1995The present structure of galaxies is governed by the radiative dissipation of the gravitational and supernova energy injected during formation. A crucial aspect of this process is whether the gas cools as fast as it falls into the gravitational potential ... More
AGN feedback in clusters: shock and sound heatingApr 01 2013Observations support the view that feedback, in the form of radio outbursts from active nuclei in central galaxies, prevents catastrophic cooling of gas and rapid star formation in many groups and clusters of galaxies. Variations in jet power drive a ... More
Fuelling quasars with hot gasAug 25 1999We consider a model for quasar formation in which massive black holes are formed and fuelled largely by the accretion of hot gas during the process of galaxy formation. In standard hierarchical collapse models, objects about the size of normal galaxies ... More
The Dissection of Abell 2744: A Rich Cluster Growing Through Major and Minor MergersDec 06 2010New Chandra X-ray data and extensive optical spectroscopy, obtained with AAOmega on the 3.9 m Anglo-Australian Telescope, are used to study the complex merger taking place in the galaxy cluster Abell 2744. Combining our spectra with data from the literature ... More
Abell 1201: a Minor merger at second core passageMay 08 2012We present an analysis of the structures and dynamics of the merging cluster Abell~1201, which has two sloshing cold fronts around a cooling core, and an offset gas core approximately 500kpc northwest of the center. New Chandra and XMM-Newton data reveal ... More
Mechanical Feedback from Active Galactic Nuclei in Galaxies, Groups, and ClustersMar 30 2012The radiative cooling timescales at the centers of hot atmospheres surrounding elliptical galaxies, groups, and clusters are much shorter than their ages. Therefore, hot atmospheres are expected to cool and to form stars. Cold gas and star formation are ... More
What is a Cool-Core Cluster? A Detailed Analysis of the Cores of the X-ray Flux-Limited HIFLUGCS Cluster SampleNov 02 2009We use the largest complete sample of 64 galaxy clusters (HIghest X-ray FLUx Galaxy Cluster Sample) with available high-quality X-ray data from Chandra, and apply 16 cool-core diagnostics to them, some of them new. We also correlate optical properties ... More
Dark Matter Subhalos and the X-ray Morphology of the Coma ClusterFeb 08 2013Apr 12 2013Structure formation models predict that clusters of galaxies contain numerous massive subhalos. The gravity of a subhalo in a cluster compresses the surrounding intracluster gas and enhances its X-ray emission. We present a simple model, which treats ... More
Cavities and shocks in the galaxy group HCG 62 as revealed by Chandra, XMM and GMRT dataDec 15 2009Mar 16 2010We report on the results of an analysis of Chandra, XMM-Newton and new GMRT data of the X-ray bright compact group of galaxies HCG 62, which is one of the few groups known to possess clear, small X-ray cavities in the inner regions. This is part of an ... More
Evidence for a TDE origin of the radio transient Cygnus A-2Apr 12 2019In 2015, a radio transient named Cygnus A-2 was discovered in Cygnus A with the Very Large Array. Because of its radio brightness ($\nu F_{\nu} \approx 6 \times 10^{39}$ erg s$^{-1}$), this transient likely represents a secondary black hole in orbit around ... More
Capturing the 3D Motion of an Infalling Galaxy via Fluid DynamicsNov 14 2016The Fornax Cluster is the nearest galaxy cluster in the southern sky. NGC 1404 is a bright elliptical galaxy falling through the intracluster medium of the Fornax Cluster. The sharp leading edge of NGC 1404 forms a classical "cold front" that separates ... More
Deep Chandra observations of NGC 1404: cluster plasma physics revealed by an infalling early-type galaxyDec 02 2016Dec 23 2016The intracluster medium (ICM), as a magnetized and highly ionized fluid, provides an ideal laboratory to study plasma physics under extreme conditions that cannot yet be achieved on Earth. NGC 1404 is a bright elliptical galaxy that is being gas stripped ... More
A Merger Shock in Abell 2034Nov 21 2013We present a $250\,$ks Chandra observation of the cluster merger A2034 with the aim of understanding the nature of a sharp edge previously characterized as a cold front. The new data reveal that the edge is coherent over a larger opening angle and is ... More
Pahs, Ionized Gas, and Molecular Hydrogen in Brightest Cluster Galaxies of Cool Core Clusters of GalaxiesMar 08 2011We present measurements of 5-25 {\mu}m emission features of brightest cluster galaxies (BCGs) with strong optical emission lines in a sample of 9 cool-core clusters of galaxies observed with the Infrared Spectrograph on board the Spitzer Space Telescope. ... More
A physical model for the hard X-ray backgroundAug 01 2000We combine a semi-analytic galaxy formation model (Nulsen and Fabian 1997) with a prescription for the obscured growth of massive black holes (Nulsen and Fabian 2000; Fabian 1999), to reproduce the hard X-ray background (XRB), the local 2-10keV AGN luminosity ... More
Capturing the 3D Motion of an Infalling Galaxy via Fluid DynamicsNov 14 2016Dec 04 2016The Fornax Cluster is the nearest galaxy cluster in the southern sky. NGC 1404 is a bright elliptical galaxy falling through the intracluster medium of the Fornax Cluster. The sharp leading edge of NGC 1404 forms a classical "cold front" that separates ... More
Deep Chandra observations of NGC~1404: cluster plasma physics revealed by an infalling early-type galaxyDec 02 2016The intracluster medium (ICM), as a magnetized and highly ionized fluid, provides an ideal laboratory to study plasma physics under extreme conditions that cannot yet be achieved on Earth. NGC~1404 is a bright elliptical galaxy that is being gas stripped ... More
Capturing the 3D Motion of an Infalling Galaxy via Fluid DynamicsNov 14 2016Dec 23 2016The Fornax Cluster is the nearest galaxy cluster in the southern sky. NGC 1404 is a bright elliptical galaxy falling through the intracluster medium of the Fornax Cluster. The sharp leading edge of NGC 1404 forms a classical "cold front" that separates ... More
Radio AGN in galaxy clusters: heating hot atmospheres and driving supermassive black hole growth over cosmic timeJun 29 2012Dec 01 2012We estimate the average radio-AGN (mechanical) power deposited into the hot atmospheres of galaxy clusters over more than three quarters of the age of the Universe. Our sample was drawn from eight major X-ray cluster surveys, and includes 685 clusters ... More
The Recent Growth History of the Fornax Cluster Derived from Simultaneous Sloshing and Gas Stripping: Simulating the Infall of NGC 1404Sep 06 2018We derive the recent growth history of the Fornax Cluster, in particular the recent infall of the giant elliptical galaxy NGC 1404. We show, using a simple cluster minor merger simulation tailored to Fornax and NGC 1404, that a second or more likely third ... More
Detection of Superluminal Motion in the X-Ray Jet of M87May 10 2019Jun 12 2019Chandra HRC observations are investigated for evidence of proper motion and brightness changes in the X-ray jet of the nearby radio galaxy M87. Using images spanning 5 yr, proper motion is measured in the X-ray knot HST-1, with a superluminal apparent ... More
Buoyant AGN bubbles in the quasi-isothermal potential of NGC 1399Aug 28 2017Oct 08 2017The Fornax Cluster is a low-mass cool-core galaxy cluster. We present a deep {\sl Chandra} study of NGC 1399, the central dominant elliptical galaxy of Fornax. The cluster center harbors two symmetric X-ray cavities coincident with a pair of radio lobes ... More
Detection of Superluminal Motion in the X-ray Jet of M87May 10 2019Chandra HRC observations are investigated for evidence of proper motion and brightness changes in the X-ray jet of the nearby radio galaxy M87. Using images spanning 5 years, proper motion is measured in the X-ray knot HST-1, with a superluminal apparent ... More
AGN Driven Weather and Multiphase Gas in the Core of the NGC 5044 Galaxy GroupOct 04 2010A deep Chandra observation of the X-ray bright group, NGC 5044, shows that the central region of this group has been strongly perturbed by repeated AGN outbursts. These recent AGN outbursts have produced many small X-ray cavities, cool filaments and cold ... More
Gas sloshing regulates and records the evolution of the Fornax ClusterNov 05 2017We present results of a joint {\sl Chandra} and {\sl XMM-Newton} analysis of the Fornax Cluster, the nearest galaxy cluster in the southern sky. Signatures of merger-induced gas sloshing can be seen in the X-ray image. We identify four sloshing cold fronts ... More
Are Radio AGN Powered by Accretion or Black Hole Spin?Jul 07 2010Nov 22 2010We compare accretion and black hole spin as potential energy sources for outbursts from AGN in brightest cluster galaxies (BCGs). Based on our adopted spin model, we find that the distribution of AGN power estimated from X-ray cavities is consistent with ... More
Model-independent X-ray mass determinationsAug 13 2010A new method is introduced for making X-ray mass determinations of spherical clusters of galaxies. Treating the distribution of gravitating matter as piecewise constant and the cluster atmosphere as piecewise isothermal, X-ray spectra of a hydrostatic ... More
Exploring the unusually high black hole-to-bulge mass ratios in NGC4342 and NGC4291: the asynchronous growth of bulges and black holesMar 07 2012Jun 06 2012We study two nearby, early-type galaxies, NGC4342 and NGC4291, that host unusually massive black holes relative to their low stellar mass. The observed black hole-to-bulge mass ratios of NGC4342 and NGC4291 are ~6.9% and ~1.9%, respectively, which significantly ... More
A 1D fluid model of the Centaurus A jetDec 11 2018Feb 25 2019We implement a steady, one-dimensional flow model for the X-ray jet of Centaurus A in which entrainment of stellar mass loss is the primary cause of dissipation. Using over 260 ks of new and archival Chandra/ACIS data, we have constrained the temperature, ... More
The Regulation of Cooling and Star Formation in Luminous Galaxies by AGN Feedback and the Cooling-Time/Entropy Threshold for the Onset of Star FormationFeb 13 2008Jun 11 2008Using broadband optical imaging and Chandra X-ray data for a sample of 46 cluster central dominant galaxies (CDGs), we investigate the connection between star formation, the intracluster medium (ICM), and the central active galactic nucleus (AGN). We ... More
A 1D fluid model of the Centaurus A jetDec 11 2018Jan 31 2019We implement a steady, one-dimensional flow model for the X-ray jet of Centaurus A in which entrainment of stellar mass loss is the primary cause of dissipation. Using over 260 ks of new and archival Chandra/ACIS data, we have constrained the temperature, ... More
Gas Sloshing and Radio Galaxy Dynamics in the Core of the 3C449 GroupOct 29 2012We present results from a 140 ks Chandra/ACIS-S observation of the hot gas around the canonical FR I radio galaxy 3C 449. An earlier, shorter 30 ks Chandra observation of the group gas showed an unusual entropy distribution and a surface brightness edge ... More
Kelvin-Helmholtz instabilities at the sloshing cold fronts in the Virgo cluster as a measure for the effective ICM viscosityNov 20 2012Sloshing cold fronts (CFs) arise from minor merger triggered gas sloshing. Their detailed structure depends on the properties of the intra-cluster medium (ICM): hydrodynamical simulations predict the CFs to be distorted by Kelvin-Helmholtz instabilities ... More
Deep Chandra Observations of Abell 2199: the Interplay between Merger-Induced Gas Motions and Nuclear Outbursts in a Cool Core ClusterJul 30 2013We present new Chandra observations of Abell 2199 that show evidence of gas sloshing due to a minor merger, as well as impacts of the radio source, 3C 338, hosted by the central galaxy, NGC 6166, on the intracluster gas. The new data are consistent with ... More
The Disturbed 17 keV Cluster Associated with the Radio Galaxy 3C 438Jun 27 2007We present results from a {\em Chandra} observation of the cluster gas associated with the FR II radio galaxy 3C 438. This radio galaxy is embedded within a massive cluster with gas temperature $\sim$17 keV and bolometric luminosity of 6$\times10^{45}$ ... More
Variability and Proper Motion of X-ray Knots in the Jet of Centaurus AJan 02 2019Jan 22 2019We report results from Chandra observations analyzed for evidence of variability and proper motion in the X-ray jet of Centaurus A. Using data spanning 15 years, collective proper motion of $11.3\pm3.3$ mas yr$^{-1}$, or $0.68\pm0.20c$, is detected for ... More
Chandra and XMM-Newton Observations of the Bimodal Planck SZ-detected Cluster PLCKG345.40-39.34 (A3716) with High and Low Entropy Subcluster CoresFeb 17 2015We present results from Chandra, XMM-Newton, and ROSAT observations of the Planck SZ-detected cluster A3716 (PLCKG345.40-39.34 - G345). We show that G345 is, in fact, two subclusters separated on the sky by 400 kpc. We measure the subclusters' gas temperatures ... More
Chandra observations of NGC4342, an optically faint, X-ray gas-rich early-type galaxyMar 07 2012Jun 06 2012Chandra X-ray observations of NGC4342, a low stellar mass (M_K=-22.79 mag) early-type galaxy, show luminous, diffuse X-ray emission originating from hot gas with temperature of kT~0.6 keV. The observed 0.5-2 keV band luminosity of the diffuse X-ray emission ... More
The complex X-ray morphology of NGC 7618: A major group-group merger in the local Universe?Jan 17 2006We present results from a short {\em Chandra}/ACIS-S observation of NGC 7618, the dominant central galaxy of a nearby ($z$=0.017309, d=74.1 Mpc) group. We detect a sharp surface brightness discontinuity 14.4 kpc N of the nucleus subtending an angle of ... More
On the soft X-ray spectrum of cooling flowsOct 25 2000Strong evidence for cooling flows has been found in low resolution X-ray imaging and spectra of many clusters of galaxies. However high resolution X-ray spectra of several clusters from the Reflection Grating Spectrometer (RGS) on XMM-Newton now show ... More
Baryons at the Edge of the X-ray Brightest Galaxy ClusterFeb 11 2011Studies of the diffuse X-ray emitting gas in galaxy clusters have provided powerful constraints on cosmological parameters and insights into plasma astrophysics. However, measurements of the faint cluster outskirts have become possible only recently. ... More
The Growth of Black Holes and Bulges at the Cores of Cooling FlowsDec 11 2006Central cluster galaxies (cDs) in cooling flows are growing rapidly through gas accretion and star formation. At the same time, AGN outbursts fueled by accretion onto supermassive black holes are generating X-ray cavity systems and driving outflows that ... More
The soft X-ray background: evidence for widespread disruption of the gas halos of galaxy groupsOct 06 1999Almost all of the extragalactic X-ray background (XRB) at 0.25 keV can be accounted for by radio-quiet quasars, allowing us to derive an upper limit of 4 \bgunit\ for the remaining background at 0.25 keV. However, the XRB from the gas halos of groups ... More
Average Heating Rate of Hot Atmospheres in Distant Clusters by Radio AGN: Evidence for Continuous AGN HeatingJul 14 2011Aug 16 2011We examine atmospheric heating by radio active galactic nuclei (AGN) in distant X-ray clusters by cross correlating clusters selected from the 400 Square Degree (400SD) X-ray Cluster survey with radio sources in the NRAO VLA Sky Survey. Roughly 30% of ... More
Luminosity segregation in three clusters of galaxies (A119, 2443, 2218)Oct 05 2005We use deep wide-field V-band imaging obtained with the Wide Field Camera at the prime focus of the Issac Newton Telescope to study the spatial and luminosity distribution of galaxies in three low redshift (0.04<z<0.2) clusters: Abell 119, Abell 2443 ... More
X-ray Supercavities in the Hydra A Cluster and the Outburst History of the Central Galaxy's Active NucleusDec 04 2006A 227 ksec Chandra Observatory X-ray image of the hot plasma in the Hydra A cluster has revealed an extensive cavity system. The system was created by a continuous outflow or a series of bursts from the nucleus of the central galaxy over the past 200-500 ... More
The Detectability of AGN Cavities in Cooling-Flow ClustersSep 02 2009Sep 04 2009Chandra X-ray Observatory has revealed X-ray cavities in many nearby cooling flow clusters. The cavities trace feedback from the central active galactic nulceus (AGN) on the intracluster medium (ICM), an important ingredient in stabilizing cooling flows ... More
Radio Properties of Cavities in the ICM: Imprints of AGN ActivityDec 14 2006We present new, high resolution radio images of sources associated with cD galaxies and X-ray cavity systems located in cluster cores. The cavity properties derived from archival Chandra observations give reliable estimates of the total jet power and ... More
X-ray Cavities and Cooling FlowsNov 12 2003Recent data have radically altered the X-ray perspective on cooling flow clusters. X-ray spectra show that very little of the hot intracluster medium is cooler than about 1 keV, despite having short cooling times. In an increasing number of cooling flow ... More
New Perspectives on Cooling Flows and Cluster Radio SourcesDec 14 2000We discuss new results from the Chandra X-ray Observatory and XMM-Newton on cluster cooling flows, emphasizing early results from our Chandra programs. We find cooling rates reduced by factors of 5-10 compared to those from earlier missions. Nevertheless, ... More
Chandra Observations of Nuclear Outflows in the Elliptical Galaxy NGC4552 in the Virgo ClusterApr 19 2006We use a 54.4 ks Chandra observation to study nuclear outflow activity in NGC4552 (M89), an elliptical galaxy in the Virgo Cluster. Chandra images in the 0.5-2 keV band show two ring-like features ~1.7 kpc in diameter in the core of NGC4552, as reported ... More
A Systematic Study of Radio-Induced X-ray Cavities in Clusters, Groups, and GalaxiesFeb 13 2004Apr 30 2004We present an analysis of sixteen galaxy clusters, one group and one galaxy drawn from the Chandra X-ray Observatory's data archive. These systems possess prominent X-ray surface brightness depressions associated with cavities or bubbles that were created ... More
ASCA and ROSAT observations of nearby cluster cooling flowsOct 11 1999Oct 20 2000We present a detailed analysis of the X-ray properties of the cooling flows in a sample of nearby, X-ray bright clusters of galaxies using high-quality ASCA spectra and ROSAT X-ray images. We demonstrate the need for multiphase models to consistently ... More
The cluster-scale AGN outburst in Hydra AAug 17 2004Deep Chandra observations of the Hydra A Cluster reveal a feature in the X-ray surface brightness that surrounds the 330 MHz radio lobes of the AGN at the cluster center. Surface brightness profiles of this feature and its close association with the radio ... More
A 70 kpc X-ray tail in the cluster A3627Nov 17 2005Dec 20 2005We present the discovery of a 70 kpc X-ray tail behind the small late-type galaxy ESO137-001 in the nearby, hot (T=6.5 keV) merging cluster A3627, from both Chandra and XMM observations. The tail has a length-to-width ratio of ~ 10. It is luminous (L_{0.5-2 ... More
Radiative Efficiency and Content of Extragalactic Radio Sources: Toward a Universal Scaling Relation Between Jet Power and Radio PowerJun 11 2008We present an analysis of the energetics and particle content of the lobes of 24 radio galaxies at the cores of cooling clusters. The radio lobes in these systems have created visible cavities in the surrounding hot, X-ray-emitting gas, which allow direct ... More
The effect of supernova heating on cluster properties and constraints on galaxy formation modelsOct 01 1998Models of galaxy formation should be able to predict the properties of clusters of galaxies, in particular their gas fractions, metallicities, X-ray luminosity-temperature relation, temperature function and mass-deposition-rate function. Fitting these ... More
Chandra Observations of Gas Stripping in the Elliptical Galaxy NGC 4552 in the Virgo ClusterAug 26 2005Apr 20 2006We use a 54.4 ks Chandra observation to study ram-pressure stripping in NGC4552 (M89), an elliptical galaxy in the Virgo Cluster. Chandra images in the 0.5-2 keV band show a sharp leading edge in the surface brightness 3.1 kpc north of the galaxy center, ... More
The Feedback-Regulated Growth of Black Holes and Bulges through Gas Accretion and Starbursts in Cluster Central Dominant GalaxiesMay 12 2006Jul 20 2006We present an analysis of the growth of black holes through accretion and bulges through star formation in 33 galaxies at the centers of cooling flows. Most of these systems show evidence of cavities in the intracluster medium (ICM) inflated by radio ... More
Non-Gravitational Heating in the Hierarchical Formation of X-ray ClustersJul 08 1999Jul 11 2000The strong deviation in the properties of X-ray clusters from simple scaling laws highlights the importance of non-gravitational heating and cooling processes in the evolution of proto-cluster gas. We investigate this from two directions: by finding the ... More
Metal transport by gas sloshing in M87Feb 02 2010We present the results of an XMM-Newton mosaic covering the central ~200 kpc of the nearby Virgo cluster. We focus on a strong surface brightness discontinuity in the outskirts of the brightest cluster galaxy, M87. Using both XMM-Newton and Suzaku, we ... More
AGN Feedback in the Compact Group of Galaxies HCG 62 - as revealed by Chandra, XMM and GMRT dataSep 17 2009As a part of an ongoing study of a sample of galaxy groups showing evidence for AGN/hot gas interaction, we report on the preliminary results of an analysis of new XMM and GMRT data of the X-ray bright compact group HCG 62. This is one of the few groups ... More
Irregular sloshing cold fronts in the nearby merging groups NGC 7618 and UGC 12491: evidence for Kelvin-Helmholtz instabilitiesJun 11 2012We present results from two \sim30 ks Chandra observations of the hot atmospheres of the merging galaxy groups centered around NGC 7618 and UGC 12491. Our images show the presence of arc-like sloshing cold fronts wrapped around each group center and \sim100 ... More
The large-scale shock in the cluster of galaxies Hydra AOct 01 2008Jan 09 2009We analyzed a deep XMM-Newton observation of the cluster of galaxies Hydra A, focusing on the large-scale shock discovered as a surface brightness discontinuity in Chandra images. The shock front can be seen both in the pressure map and in temperature ... More
Gas Sloshing and Bubbles in the Galaxy Group NGC 5098Apr 03 2009Jul 06 2009We present results from Chandra observations of the galaxy pair and associated galaxy group NGC 5098, and find evidence for both gas sloshing and AGN heating. The X-ray brightness images show diffuse emission with a spiral structure, centered on NGC 5098a, ... More
Spectacular X-ray tails, intracluster star formation and ULXs in A3627Oct 05 2009Dec 02 2009We present the discovery of spectacular double X-ray tails associated with ESO137-001 and a possibly heated X-ray tail associated with ESO137-002, both late-type galaxies in the closest rich cluster Abell 3627. A deep Chandra observation of ESO137-001 ... More
The Cocoon Shocks of Cygnus A: Pressures and Their Implications for the Jets and LobesFeb 27 2018We use 2.0 Msec of Chandra observations to investigate the cocoon shocks of Cygnus A and some implications for its lobes and jet. Measured shock Mach numbers vary in the range 1.18-1.66 around the cocoon. We estimate a total outburst energy of $\simeq ... More
Jet Interactions with the Hot Halos of Clusters and GalaxiesAug 03 2007Aug 29 2007X-ray observations of cavities and shock fronts produced by jets streaming through hot halos have significantly advanced our understanding of the energetics and dynamics of extragalactic radio sources. Radio sources at the centers of clusters have dynamical ... More
A Powerful AGN Outburst in RBS 797Mar 03 2011Utilizing $\sim 50$ ks of Chandra X-ray Observatory imaging, we present an analysis of the intracluster medium (ICM) and cavity system in the galaxy cluster RBS 797. In addition to the two previously known cavities in the cluster core, the new and deeper ... More
An Energetic AGN Outburst Powered by a Rapidly Spinning Supermassive Black Hole or an Accreting Ultramassive Black HoleNov 18 2008Mar 19 2009Powering the 10^62 erg nuclear outburst in the MS0735.6+7421 cluster central galaxy by accretion implies that its supermassive black hole (SMBH) grew by ~6x10^8 solar masses over the past 100 Myr. We place upper limits on the amount of cold gas and star ... More
The powerful outburst in Hercules AApr 15 2005The radio source Hercules A resides at the center of a cooling flow cluster of galaxies at redshift z = 0.154. A Chandra X-ray image reveals a shock front in the intracluster medium (ICM) surrounding the radio source, about 160 kpc from the active galactic ... More
Interaction of Radio Lobes with the Hot Intracluster Medium: Driving Convective Outflow in Hydra AOct 24 2001The radio lobes of Hydra A lie within cavities surrounded by a rim of enhanced X-ray emission in the intracluster gas. Although the bright rim appears cooler than the surrounding gas, existing Chandra data do not exclude the possibility that the rim is ... More
Chemical enrichment in the cluster of galaxies Hydra ASep 15 2008Nov 14 2008We analyzed global properties, radial profiles and 2D maps of the metal abundances and temperature in the cool core cluster of galaxies Hydra A using a deep XMM-Newton exposure. The best fit among the available spectral models is provided by a Gaussian ... More
A relationship between AGN jet power and radio powerJun 29 2010Using Chandra X-ray and VLA radio data, we investigate the scaling relationship between jet power, P_jet, and synchrotron luminosity, P_rad. We expand the sample presented in Birzan et al. (2008) to lower radio power by incorporating measurements for ... More
Isotropic AGN Heating with Small Radio Quiet Bubbles in the NGC 5044 GroupMay 05 2009Aug 14 2009(abridged) A Chandra observation of the X-ray bright group NGC 5044 shows that the X-ray emitting gas has been strongly perturbed by recent outbursts from the central AGN and also by motion of the central dominant galaxy relative to the group gas. The ... More
Origins of molecular clouds in early-type galaxiesOct 26 2018We analyze $Chandra$ observations of the hot atmospheres of 40 early spiral and elliptical galaxies. Using new temperature, density, cooling time, and mass profiles, we explore relationships between their hot atmospheres and cold molecular gas. Molecular ... More
A Relationship Between Halo Mass, Cooling, AGN Heating, and the Coevolution of Massive Black HolesOct 23 2015Oct 11 2016We derive X-ray mass, luminosity, and temperature profiles for 45 galaxy clusters to explore relationships between halo mass, AGN feedback, and central cooling time. We find that radio--mechanical feedback power (referred to here as "AGN power") in central ... More
Reflections of AGN Outbursts in the Gaseous Atmosphere of M87Dec 22 2003Jan 11 2004We combined deep Chandra, ROSAT HRI, and XMM-Newton observations of M87 to study the impact of AGN outbursts on its gaseous atmosphere. Many X-ray features appear to be a direct result of repetitive AGN outbursts. In particular, the X-ray cavities around ... More
Chandra Observations of NGC 4636 - An Elliptical Galaxy in TurmoilAug 07 2001Chandra images show symmetric, 8 kpc long, arm-like features in the X-ray halo surrounding NGC 4636. The leading edges of these features are sharp and are accompanied by temperature increases of ~30%. These properties, along with their scale and symmetry, ... More
A High Resolution Study of the Hydra A Cluster with Chandra: Comparison of the Core Mass Distribution with Theoretical Predictions and Evidence for Feedback in the Cooling FlowOct 11 2000May 02 2001The cooling flow cluster Hydra A was observed during the orbital activation and calibration phase of the Chandra Observatory. While the X-ray image of the cluster exhibits complex structure in the central region as reported in McNamara $etal$, the large ... More
Conduction and the Star-Formation Threshold in Brightest Cluster GalaxiesJun 03 2008Current models of galaxy evolution suggest that feedback from active galactic nuclei is needed to explain the high-luminosity cutoff in the galaxy luminosity function. Exactly how an AGN outflow couples with the ambient medium and suppresses star formation ... More
Revealing a Highly-Dynamic Cluster Core in Abell 1664 with ChandraOct 01 2018We present new, deep (245 ks) Chandra observations of the galaxy cluster Abell 1664 ($z = 0.1283$). These images reveal rich structure, including elongation and accompanying compressions of the X-ray isophotes in the NE-SW direction, suggesting that the ... More
Chandra Observation of 3C288 - Reheating the Cool Core of a 3 keV Cluster from a Nuclear Outburst at z = 0.246Sep 07 2010We present results from a 42 ks Chandra/ACIS-S observation of the transitional FRI/FRII radio galaxy 3C288 at z = 0.246. We detect $\sim$3 keV gas extending to a radius of $\sim$0.5 Mpc with a 0.5-2.0 keV luminosity of 6.6 $\times$ 10$^{43}$ ergs s$^{-1}$, ... More
Astro2020 Science White Paper: A Unification of the Micro and Macro Physics in the Intracluster Medium of Nearby ClustersApr 14 2019Clusters of galaxies are the most massive virialized structures in the Universe. The microphysical properties of the intracluster plasma can affect dynamical processes over an enormous range: from the feedback of active galactic nuclei to shock acceleration ... More