Chandra's First Decade of Discovery

Galaxies

Star-Formation History and Young X-ray Binary Populations: The Case of the Small Magellanic Cloud

Vallia Antoniou, Harvard-Smithsonian Center for Astrophysics
Andreas Zezas (Harvard-Smithsonian Center for Astrophysics), D. Hatzidimitriou (University of Crete, Greece), V. Kalogera (Department of Physics and Astronomy, Northwestern University)

Using Chandra, XMM-Newton and optical photometric and spectroscopic catalogs we study the young (<100 Myr) X-ray binary populations of the Small Magellanic Cloud, which at ~60 kpc is our second nearest star-forming galaxy. In particular, we investigate the importance of Be/X-ray binaries as a dominant component of young X-ray binary populations, based on a study of the connection between X-ray source populations and their parent stellar populations. We find that a significant number of Be/X-ray binaries and/or pulsars are connected with a burst of star formation ~25-60 Myr ago, while regions with weak star-formation rate at ~42 Myr, such as the SMC Wing, are deficient in Be/X-ray binaries. We argue that the very strong similarity between the age of maximum occurence of Be stars and the age of the parent populations of X-ray binaries in the Small Magellanic Cloud indicates that the Be phenomenon plays a significant role in the number of X-ray binary populations in this age range. Finally, based on the spatial correlation between the star-formation activity and the X-ray binaries, we set a limit on their kick velocity of ~15-20 km/s, while there is strong indication for velocities of even a factor of two lower, and we estimate a Be/X-ray binary production rate of ~1 system per 10-6 M⊙/yr.

Galactic wind in the bulge of Andromeda Galaxy

Akos Bogdan, Max Planck Institut für Astrophysik
Marat Gilfanov (Max Planck Institut für Astrophysik, Garching; Space Research Institute, Moscow)

We investigate the unresolved X-ray emission originating from the bulge of M31. We show that a part of this emission is due to a large number of faint sources - mainly accreting white dwarfs and active binaries, associated with the old stellar population, similar to the Galactic ridge X-ray emission of the Milky Way. We also detect soft X-ray emission from ionized gas. It has a temperature of 3-4 million K and its mass is about few million solar masses. The gas distribution is extended along the minor axis of the galaxy suggesting that it may be outflowing in the direction perpendicular to the disk of M31 at the rate of ~0.1 solar masses per year. The mass and energy budget of this galactic wind is maintained by the mass loss from evolved stars and by the energy input from type Ia Supernovae. Based on the detailed study of the unresolved emission from M31, it becomes possible to put constraints on the progenitors of classical nova outbursts. The comparison between the gravitational energy, - released by accreting white dwarfs - and the observed X-ray luminosity, reveals the nature of the classical nova progenitors.

Infant Ellipticals: The Evolution of Young Merger-Remnants

Nicola Brassington, Harvard-Smithsonian CfA
Pepi Fabbiano (Harvard-Smithsonian CfA)

Studies of elliptical galaxies have revealed an intriguing population of young merger-remnant galaxies, which are found to be X-ray faint when compared to mature ellipticals. Here I will present the properties of two post-mergers (1-2 Gyr since coalescence) that have recently been observed with Chandra and I will discuss how these observations have allowed us to probe an important gap in the evolution of elliptical galaxies. From these observations we can place constraints on the growth of post-merger X-ray luminosity per unit mass, investigate the point source population and observe how the diffuse emission evolves through the regeneration of hot gas haloes. Further, I will also compare these observed X-ray haloes with hydrodynamical simulations of decoupled hot gas within elliptical galaxies.

The Stormy Weather in the NGC 5044 Group of Galaxies as Revealed by Chandra

Laurence David, SAO
C. Jones (SAO), W. Forman (SAO), P.E.J. Nulsen (SA)

A Chandra observation of the X-ray bright group NGC 5044 shows that the central X-ray emitting gas has been strongly perturbed by recent AGN outbursts and by motion of the central galaxy relative to the group gas. The NGC 5044 group hosts many small radio quiet cavities with a nearly isotropic distribution, cool filaments, a semi-circular cold front and a two-armed spiral shaped feature of cool gas. A 610 MHz GMRT observation reveals the presence of extended emission with a “torus-shaped” morphology. The largest X-ray filament appears to thread the radio torus, suggesting that the lower entropy gas within the filament is being uplifted from the center of the group. The 235 MHz radio emission is much more extended than the 610 MHz emission, with little overlap between the two frequencies. One component of the 235 MHz emission passes through the largest X-ray cavity and is then deflected just behind the cold front. A second detached radio lobe is also detected beyond the cold front. All of the smaller X-ray cavities in the center of NGC 5044 are undetected in the GMRT observations. Since the smaller bubbles are probably no longer momentum driven by the central AGN, their motion will be affected by the group weather as they buoyantly rise outward. Hence, most of the enthalpy within the smaller bubbles will likely be deposited near the group center and isotropized by the group weather. Interior to the cold front there are several clouds of high abundance gas which probably arise from uplifted SNeIa enriched material. Beyond the cold front, there are several arc-like streams of metal enriched gas which may be the disrupted remains of the high abundance clouds which are only exposed to the group weather once they have been uplifted beyond the cold front.

Chandra Observations of Soft Sources in Galaxies: New insights into binary evolution, Type Ia progenitors, and intermediate-mass black holes

Rosanne Di Stefano, CfA
Frank Primini, Brandon Patel, Jifeng Liu (CfA), Jochen Greiner (MPE), Albert Kong (Taiwan); Roberto Soria (China)

At the time Chandra was launched, we knew of only two dozen super soft x-ray sources (SSSs). Furthermore, the natures of most had not yet been understood. Chandra observations of more than 300 galaxies has discovered >1000 SSSs and established the statistics of the class while at the same time identifying its most extreme and intriguing members. We have discovered slightly harder sources, quasisoft x-ray sources (QSSs), and also much more luminous soft sources than any known in our Galaxy or in the Magellanic Clouds, with L in the range 1040-1041 erg/s. Beyond the numbers, these observations have taught us a great deal about binary evolution, nuclear burning on white dwarfs and the progenitors of Type Ia supernovae, and models for intermediate-mass black holes. We review the revolution in our understanding of these sources made possible by the first decade of Chandra.

Supernova Remnants in the ChASeM33 X-ray Observations of M33

Richard Edgar, SAO
Knox S. Long (STScI), William P. Blair (JHU), Frank Winkler (Middlebury) and the ChASeM33 team

M33 contains many emission nebulae identified as supernova remnants(SNRs) based on the high [S II]:H alpha ratios characteristic of shocked gas. Using Chandra data from the ChASeM33 survey with a 0.35-2 keV sensitivity of about 2 x 1034 ergs s-1, we have detected more than 70 of these nebulae, yielding confirmation of their SNR identifications, and providing the largest homogeneous sample of remnants detected at optical, radio, and X-ray wavelengths in any galaxy, including the Milky Way. A spectral analysis of the six X-ray brightest SNRs reveals that two, G98-31 and G98-35, have spectra that appear to be dominated by ejecta from a core-collapse explosion. In general, the X-ray detected SNRs have soft X-ray spectra compared to the vast majority of sources detected along the line of sight to M33. We found no new extended X-ray sources likely to be SNRs. It is unlikely that there remain to be discovered any other thermally dominated X-ray SNR with luminosities of above 4 x 1035 ergs s-1 in the portions of M33 covered by the ChASeM33 survey. There are no close analogues of Cas A or the Crab Nebula in M33, but we have found an X-ray source with a power law spectrum coincident with a small-diameter radio source that may be the first pulsar-wind nebula recognized in the galaxy. This work was supported by NASA grant NAS G06-7073A and NASA contract NAS8-03060.

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Chandra Acis Survey of M33 (ChASeM33): The unequal siblings NGC604 and IC131

Terrance Gaetz, SAO
R. Tuellmann (CfA), P. P. Plucinsky (CfA), T. J. Gaetz (CfA), K. S. Long (STSci), W. P. Blair (JHU), F. Haberl (MPE, Germany), K. D. Kuntz (JHU/GSFC), T. G. Pannuti (Morehead State University, KY), W. Pietsch (MPE, Germany), B. Williams (University of Washington, WA), P. F. Winkler (Middlebury College, VT)

We present results from the first detailed analysis of the diffuse X-ray emission in NGC604 and IC131. These regions are the only X-ray bright giant HII regions in M33 and were observed as part of ChASeM33. The main bubbles in NGC604 are filled with a hot thermal plasma of kT=0.5keV. The X-ray gas mass and unabsorbed X-ray luminosity in the western part of NGC604 are consistent with stellar mass-loss from ~200 OB-stars and agree well with predictions from the standard bubble model. In the eastern part of NGC604 mass loss from young stars alone cannot account for the X-ray luminosity and another mechanism, such as off-center SNRs, is required to produce the additional luminosity. The X-ray spectrum of the extended emission in IC131 can be equally well fitted by an absorbed powerlaw (Γ=2.2) or an absorbed thermal plasma model (kT=4.3keV). Both models predict that more than 40% of the luminosity is emitted above 2keV. Compared to other HII regions, IC131 is extreme regarding its large extent of the X-ray emission (~200pc), the lack of O stars, its high electron temperature (assuming thermal emission), and large fraction of hard X-rays. A thermal plasma of 4keV poses serious challenges to theoretical models, as it is unclear how such high electron temperatures can be obtained. In case the gas is non-thermal, it remains to be understood if the same mechanisms which create non-thermal X-rays or accelerate CRs in SNRs are applicable to these much larger scales. In both cases appropriate theoretical models are needed. Clearly, NGC604 and IC131 seem to be in completely different evolutionary stages. All O-type stars in IC131 seemed to have turned into SNe, whereas the western part of NGC604 awaits its first SNe to occur. Support for this work was provided by NASA through Chandra Award Number G06-7073A.

Energy injection in AWM4: a cool corona, a strong radio source, and missing X-ray cavities

Simona Giacintucci, Harvard-Smithsonian Center for Astrophysics
E. O'Sullivan (CfA), J. Vrtilek (CfA), L. David (CfA), S. Raychaudhury (University of Birmingham), P. Mazzotta (University of Rome; CfA), T.Venturi (INAF-IRA)

We will present the results of the combined X-ray/radio analysis of the group/poor cluster of galaxies AWM4, using a new 80 ksec Chandra observation and low frequency GMRT radio data, taken as part of a larger project of an in-depth study of the AGN feedback in the group environment. Previous XMM-Newton observations showed AWM4 to be isothermal, with its powerful central radio galaxy the most likely source of heating. However, with only small lobes detected at 1.4GHz and with no indications of cavities or shocks associated with the AGN, the question of the coupling between jets and intra-group gas remained unresolved. Deep, low frequency GMRT radio observations have revealed the full extent of the radio jets and lobes and allowed us to determine their age, orientation, energy and physical parameters. Our new Chandra data reveals the small-scale galactic corona fueling the AGN and explains why this long, energetic outburst has not quenched cooling in the core. While some weak X-ray features associated with the jets and lobes are detected, we do not detect the clear cavities seen in many other similar systems, bringing us back to the question of the nature of the interaction between the jets and the IGM. We discuss possible interpretations, including entrainment or mixing of thermal gas into the jets and lobes, contributions from non-thermal emission, and dynamical motions of the BCG within the group. AWM4 provides a strong example of the benefits of a combined X-ray/multi-band radio approach to the study of AGN feedback, and emphasizes the power of Chandra's superb spatial resolution to search for the small-scale features which are key to our understanding of the mechanisms of this process.

AGN Heating in Fossil Galaxy Groups - A Joint Chandra and GMRT Study.

Nazirah Jetha, NSSTC/UAH
Habib Khosroshahi (IPM/University of Birmingham, UK) Chandreyee Sengupta (NCRA, Pune, India), Somak Raychaudhuary (University of Birmingham, UK), Halime Miraghaee (IPM),

We present a sample of fossil galaxy groups with pre-existing Chandra and/or XMM-Newton X-ray observations and new low frequency GMRT data. Fossil galaxy groups are ideal laboratories for studying feedback mechanisms and how energy injection affects the IGM, since due to the lack of recent merging activity, we expect the IGM to be relatively pristine and affected only by any AGN activity that has occurred in the group. Our Chandra X-ray observations reveal features resembling AGN-inflated bubbles, whilst our GMRT radio data show evidence of extended emission from the central AGN that may be filling the bubble. This has enabled us to estimate the work done by the central AGN, place limits on the rates of energy injection and discuss the nature of the plasma filling the bubble.

The X-ray source population of IC 10

Roy Kilgard, Wesleyan University
Ben Placek (Alfred University), Andrea Prestwich (SAO)

The Local Group dwarf galaxy IC 10 is the nearest starburst to the Milky Way. Its proximity and low metallicity make it an ideal candidate for the study of high-mass X-ray binaries in quiescence. IC 10 presents an unique case for studying a complete sample of such objects, something made difficult in the Milky Way by absorption in the Galactic disc and in other galaxies by their distances.We present results from a set of Chandra/ACIS-S imaging observations of IC 10, including spectra, lightcurves, X-ray colors, and X-ray luminosity functions. The XLF is steeper than for the more luminous HMXBs observed in other galaxies, thus implying that the “universal” luminosity function for HMXBs does not extend below 1e36 erg/s. We also present initial results from a search for optical counterparts to the X-ray sources using archival HST/ACS observations. Approximately 10% of the sources have strong optical counterpart candidates, all of which appear to be high-mass stars.

An X-ray Study of the Nearby Massive Early-Type Galaxy NGC 4472

Ralph Kraft, SAO
W. R. Forman (SAO), C. Jones (SAO), P. E. J. Nulsen (SAO), M. J. Hardcastle (Hertfordshire), D. A. Evans (MIT/Kavli Institute), S. Raychaudhury (Birmingham), G. Sivakoff (Virginia), C. Sarazin (Virginia), S. S. Murray (SAO)

We present results from a deep archival XMM-Newton observation of the nearby massive early-type galaxy NGC 4472. This galaxy is in the early stages of merging with the Virgo cluster (1.35 Mpc from M87), and is the most optically luminous galaxy in the local Universe. Our earlier Chandra observations (Biller et al. 2004) showed a complex morphology in the X-ray emitting gas including cavities associated with twin radio lobes, a surface brightness discontinuity presumable due to an interaction with the Virgo cluster gas, and a filamentary arm similar to structures seen in M87. The deep XMM-Newton observation clearly demonstrates the existence of a ram pressure stripped tail anti-coincident to M87 and a surface brightness discontinuity, presumably the contact discontinuity between two moving fluids, between the core of NGC 4472 and the Virgo cluster gas. A temperature map of the NGC 4472 gas shows complex temperature variations in the core, perhaps indicative of non-azimuthally symmetric gas motions induced by the merger. Such motions have been predicted in various hydrodynamic simulations of galaxy/cluster mergers (Heinz et al. 2003). We also detect four filaments of cold gas in the temperature map extending roughly 25 kpc from the nucleus, one of which is coincident with the feature seen in the short Chandra observation. We discuss the implications of these results in terms of our understanding of group/cluster merger dynamics.

Diffuse X-ray Emission from Late-Type Spiral Disks

K. D. Kuntz, JHU

It has long been known that the X-ray emission in late-type spiral disks is dominated by star-formation. Astrophysical consideration leads one to believe that the X-ray emission must be dominated by supernovae, as massive star winds are orders of magnitude weaker. However, direct observation of nearby galaxies show that the bulk of diffuse X-ray emission is not due to identifiable supernova remnants. Is the diffuse emission due to correlated supernovae forming rather amorphous bubbles, is it due to gas than has expanded into the halo, or is it due to highly distributed supernova that quickly lose their identity? To address this issue I have done a more careful analysis of the M101 (and M33) VLP data to 1) place stronger limits on the contributions to the diffuse emission from stars, binaries, and SNR 2) place limits on the amount of emission not correlated with star-formation. The X-ray emission has a strong non-linear global correlation with the FUV suggesting that the X-ray emission is due to the current supernova rate, but more local correlations show that this may not be the case.

Diffuse X-ray emission from M81

Zhiyuan Li, Harvard-Smithsonian Center for Astrophysics
Christine Jones (CfA), Ralph Kraft (CfA), Bill Forman (CfA), Daniel Q. Wang (UMass)

The study of hot gas in relatively gas-poor galaxies has only been promising with Chandra, thanks to its superb angular resolution and sensitivity. We present an X-ray study of the nearby early-type spiral galaxy M81, using archival Chandra observations with over 200 ks exposure. The proximity of M81 allows us to effectively resolve the bulk of X-ray binaries and thus to map the truly diffuse X-ray emission for the first time. We characterize the content, morphology, and physical state of the hot gas to explore its origin and fate, as well as its possible relation to the nuclear activity and other phases of the ISM.

A Large X-Ray Sample of Fossil Groups

Eric Miller, MIT Kavli Institute
Renato Dupke (National Observatory of Brazil and U. Michigan), Eli Rykoff (UCSB), Claudia Mendes de Oliveira (U. São Paulo)

Fossil groups are systems dominated by a single, giant elliptical galaxy, yet their X-ray emission indicates a much deeper, cluster-scale gravitational potential. They are thought to be old, undisturbed galaxy groups in which the large galaxies have merged via dynamical friction. However, there are indications (typical lack of large cool cores, star formation enrichment) that these systems may be younger or more active than previously thought. These results are complicated by the small number of fossil groups with deep X-ray data; to address this, we have constructed a sample of 15 fossil groups from the maxBCG optical cluster survey. Here we present Chandra snapshot observations of this first large, X-ray sample of optically identified fossil groups. For each group, we determine the X-ray luminosity and temperature, which span a range typical of large ellipticals to rich groups of galaxies. We describe plans for a deep X-ray follow-up program that will allow us to measure detailed density, temperature, and abundance profiles, and thus constrain the formation mechanism of these peculiar but numerous systems.

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Building the Hot Intergalactic Medium in Galaxy Groups - a Combined Chandra X-ray/GMRT Low-Frequency Radio Study.

Ewan O'Sullivan, Smithsonian Astrophysical Observatory
S.Giacintucci (SAO), J.M. Vrtilek (SAO), L.P. David (SAO), S. Raychaudhury (University of Birmingham, UK)

Galaxies play an important part in the development of the hot intergalactic medium in groups and clusters, heating and enriching the IGM through a variety of mechanisms. The combination of deep, high-resolution X-ray observations with multi-band, low-frequency radio data provides a powerful tool for the examination of shocks, star-formation and AGN activity, and the role of these processes in the formation and evolution of the hot IGM. As part of an ongoing study of the IGM in groups, we present results from Chandra and GMRT observations of Stephan's Quintet, a spiral-dominated system which appears to be in the process of building up a hot gaseous halo. Shock heating caused by the collision of a high-velocity intruder galaxy with tidally stripped HI produces a bright ridge of radio and X-ray emission, and the total mass of hot gas observed in the group is roughly equal to the deficit in HI compared to predictions, suggesting that most of the hot IGM is shock heated HI rather than accreted primordial material. With the combined observations we are able to separate the contributions of star-formation, shock emission and X-ray binaries within the ridge, and show that the star formation rate is comparable to the gas cooling rate in the ridge. We also examine the temperature structure of the hot gas, and place limits on the dynamics of the galaxy interaction and the energy of the shock. This system, along with other examples from our sample, demonstrates the worth of groups as a laboratory for studying galaxy and IGM evolution, and the benefits to be gained from a combined X-ray/radio approach.

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State-Changing Soft X-Ray Sources in M31: White Dwarfs? Neutron Stars? or Black Holes?

Brandon Patel, Rutgers University, CFA
Rosanne Di Stefano (CFA), Thomas Nelson (University of Maryland at Baltimore), Frank Primini (CFA), Jifeng Liu (CFA), Marina Orio (INAF Padova and UW Madison)

Our Galaxy and the Magellanic Clouds contain ~18 well studied supersoft x-ray sources (SSSs). None of these sources has ever been observed in a harder state. Two SSSs in M31 have, however, been observed in quasisoft and/or hard states. We have used Chandra, XMM-Newton, and Swift to document these changes. We present the results and discuss possible models for the sources.

Chandra ACIS Survey of M33 (ChASeM33): An Overview of the Survey and the Point Source Catalog

Paul Plucinsky, SAO
R. Tuellmann (SA0), T. J. Gaetz (SAO), K.S. Long (STScI), K. Kuntz (JHU), B. Williams (Washington), R.P. Kirshner (Harvard), P. Challis (Harvard), M. Sasaki (Tuebingen), W. Pietsch (MPE), F. Haberl (MPE), W.P. Blair (JHU), D. Helfand (Columbia), P.F. Winkler (Middlebury), R.J. Edgar (SAO), and the ChASeM33 team

We present an overview of the Chandra ACIS Survey of M33 (ChASeM33): A Deep Survey of the Nearest Face-on Spiral Galaxy. The 1.4 Ms survey covers the galaxy out to a radius of approximately 18 arcmin (~ 4kpc). These data provide the most complete, detailed look at a spiral galaxy in X-rays. The source catalog from this survey includes 668 sources to a limiting luminosity of ~2.5 e34 ergs/s (0.35-8.0 keV). We discuss some of the analysis challenges posed by this survey and the techniques we have adopted to address these challenges. In an attempt to classify these sources, we have constructed hardness ratios for all the sources and have fit the spectra of sources with more than 100 counts. We have used these spectral results to identify sources with hard spectra typical of X-ray binaries (XRBs) or active galactic nuclei (AGNs) and soft spectra typical of foreground stars or supernova remnants (SNRs). Based on these X-ray spectra, we have identified two “ejecta-dominated” SNRs in M33 and, by including the variability data, two new eclipsing XRBs. We will also present examples of cross-correlations of the X-ray sources with previous X-ray catalogs. A spectroscopic follow-up study of the X-ray sources with optical counterparts is currently being carried out at the MMT Observatory, with spectra of 77 of the brightest counterparts acquired. We will present detailed spectral fits to some of the brightest sources. Finally, we will present a luminosity function of the point sources in this catalog. This work was supported by NASA grant NAS G06-7073A and NASA contract NAS8-03060.

Normal/Starburst Galaxies in Deep and Wide-Area X-ray Surveys

Andrew Ptak, JHU

We are studying the X-ray emission of galaxies (without AGN) locally through wide-area surveys (mostly from serendipitous data) and pointed observations of well-defined samples, and at z>0 in the Chandra Deep Fields. Our emphasis is currently on the integrated emission of the galaxies. Current results show that relation between X-ray emission and star-formation rate is probably not a simple linear correlation. The X-ray emission from late-type galaxies evolves significantly more strongly than that of early-type galaxies, which is expected given that the X-ray emission of late-type galaxies is usually dominated by recent star formation. Examples will be shown of where these results help to constrain the assessment of whether of the soft X-ray spectrum from AGN or potential AGN is dominated by starburst or AGN emission. The prospects of future very wide X-ray surveys from both current and future X-ray satellites will also be discussed.

Luminosity Functions and Point Source Properties from Multiple Chandra Observations of M81

Paul Sell, University of Wisconsin-Madison
David Pooley (University of Wisconsin-Madison), Andreas Zezas (Harvard-Smithsonian Center for Astrophysics and University of Crete, Greece), Jeroen Homan (MIT Kavli Institute for Astrophysics and Space Research), Walter Lewin (MIT Kavli Institute for Astrophysics and Space Research), Sebastian Heinz (University of Wisconsin-Madison)

We present an analysis of 15 Chandra observations of the nearby spiral galaxy M81 taken over the course of six weeks in May-July 2005. Each observation reaches a sensitivity of less than 10^37 erg/s. With these observations and one previous deeper Chandra observation, we detect hundreds of point sources and analyze their spectral and variability properties on timescales of days, months, and years. We conduct variability analyses of the X-ray luminosity functions of the total population as well as the bulge and disk populations of point sources separately. We find that, despite significant variability of individual sources, the X-ray luminosity function is fairly stable.

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Transient X-ray Binaries in Early-Type Galaxies

Gregory Sivakoff, University of Virginia
Centaurus A Very Large Project Team

In the Milky Way, soft X-ray transients are a class of low-mass X-ray binaries that are dominated by binaries whose compact object is a black hole. Although the X-ray binary populations in early-type galaxies appear to be dominated by more persistent sources, multi-epoch observations of nearby early-type galaxies in Chandra's first decade are finally beginning to reveal their transient X-ray binary population. In particular, the combination of proximity to Centaurus A, deep exposures from the Centaurus A Very Large Project, and more recent follow-up observations has allowed us to discover 9 X-ray binaries in Centaurus A that are clearly transient and may harbor black holes. We compare the behavior of transient X-ray binaries found in Centaurus A to that discovered by variability studies in three other early-type galaxies, NGC 1023, NGC 4365, and NGC 4697, as well as their Galactic brethren.

A “Pandora box” of Galaxies

Anna Wolter, INAF-OABrera
Antonella Fruscione (SAO), Nina Bonaventura (SAO)

We present XMM-Newton observations of three high X-ray luminosity “normal” galaxies:MS1204.1+2826 (NGC4104), MS1143.6+2040 (NGC3884) and MS1309.1+3208. These objects are part of a flux limited sample of 8 high X-ray luminosity galaxies from the Einstein Medium Sensitivity Survey. In addition to these three objects, three others in the sample have already been observed by XMM-Newton and Chandra. We will present the details of our new observations and analysis and compare the properties of these objects with the rest of the sample and with the high Xray luminosity normal galaxies in the deep surveys. The observations were done with the aim of confirming that high X-ray luminosity normal galaxies discovered in deep XMM-Newton and Chandra survey and classified as new classes of exotic objects were already present in earlier and much brighter samples, and that this “unusual” populations appearing at low X-ray fluxes are actually the low-flux counterparts of the nearby and X-ray bright “galaxies” that have been known for two decades. The data we will present are confirming this view.

Chandra Observations of Galaxies Correlated with Ultra-High Energy Cosmic Rays

Ingyin Zaw, New York University
William Terrano (University of Washington), Glennys Farrar (New York University)

Correlations have been observed between the highest energy cosmic rays observed by the Pierre Auger collaboration, and galaxies in the Veron-Cetty Veron catalog of Quasars and AGN. Optical observations indicate that only 14 of the 21 correlated VCV galaxies are AGN. Furthermore, an independent correlation study with luminous infrared galaxies (LIRGs) also shows significant correlations. This opens the exciting possibility of multiple source types, e.g., AGN and systems associated with star formation such as GRBs or magnetars. However, many LIRGs also harbor AGN. We report on the Chandra observations of the galaxies which are correlated with UHECRs but have not been previously classified as AGN and the implications of these detections on the possible sources of UHECRs.