Giuseppina Fabbiano - Academia.edu (original) (raw)

Papers by Giuseppina Fabbiano

arXiv (Cornell University), Jun 10, 2010

There are already hundreds of terabytes of astronomical data in the public domain, and soon the a... more There are already hundreds of terabytes of astronomical data in the public domain, and soon the astronomical community will generate tens of petabytes of new data. There is an enormous science potential to be unleashed by the ability to find relevant datasets, access them, analyze them quantitatively, compare them with theoretical models, and ultimately understand their astrophysical implications. The VAO will enable researchers to (1) analyze data obtained with different instruments over the entire observable spectrum; (2) connect large data sets with high performance computational resources to aid analysis, detect, quantify and visualize hidden patterns, and (3) gain understanding of astrophysical phenomena with the aid of state-of-the art models. The VAO-SC strongly supports these goals. However, we acknowledge that substantial work is needed to achieve them fully. In particular, the VAO needs to move fast from the 'infrastructure building emphasis' of the NVO phase to be a fully scienceenabling organization.

The Astrophysical Journal, 2017

We present results of a joint Chandra/XMM-Newton analysis of the early-type galaxies NGC 4649 and... more We present results of a joint Chandra/XMM-Newton analysis of the early-type galaxies NGC 4649 and NGC 5846 aimed at investigating differences between mass profiles derived from X-ray data and those from optical data, to probe the state of the hot interstellar medium (ISM) in these galaxies. If the hot ISM is at a given radius in hydrostatic equilibrium (HE), the X-ray data can be used to measure the total enclosed mass of the galaxy. Differences from optically derived mass distributions therefore yield information about departures from HE in the hot halos. The X-ray mass profiles in different angular sectors of NGC 4649 are generally smooth with no significant azimuthal asymmetries within 12 kpc. Extrapolation of these profiles beyond this scale yields results consistent with the optical estimate. However, in the central region (r 3 < kpc) the X-ray data underpredict the enclosed mass, when compared with the optical mass profiles. Consistent with previous results, we estimate a nonthermal pressure component accounting for 30% of the gas pressure, likely linked to nuclear activity. In NGC 5846 the X-ray mass profiles show significant azimuthal asymmetries, especially in the NE direction. Comparison with optical mass profiles in this direction suggests significant departures from HE, consistent with bulk gas compression and decompression due to sloshing on ∼15 kpc scales; this effect disappears in the NW direction, where the emission is smooth and extended. In this sector we find consistent X-ray and optical mass profiles, suggesting that the hot halo is not responding to strong nongravitational forces.

The Astrophysical Journal, 2003

We have analyzed a 90 ksec long observation of the bright nucleus of M33 made with Chandra /ACIS.... more We have analyzed a 90 ksec long observation of the bright nucleus of M33 made with Chandra /ACIS. We detected low-amplitude (∼ 10%) highly significant variability on timescales of ∼ 5000 sec. We also find associated spectral variability. The two main spectral components (a power-law with Γ ∼ 2 and a multicolor disk-MCD-with kT∼ 0.9 − 1.2 keV) vary in relative flux. The MCD temperature also increases with increasing MCD flux. The pattern of variability is reminiscent of (but not identical to) galactic black hole binaries. A ∼ 15 M ⊙ accreting black hole may explain this source.

Chandra observations show the importance of the X-ray band for studying the evolution of galaxies... more Chandra observations show the importance of the X-ray band for studying the evolution of galaxies. Binary X-ray sources are an easily detectable tracer of the stellar population. Chandra studies of these populations are giving us insights into the nature and formation of these binaries, and provide the basis for diagnostics of galaxy evolution. With Chandra and XMM-Newton we can explore relatively poorly known aspects of the black hole population of the universe: ultra-luminous X-ray sources, that may be connected with the 'missing' intermediate mass black holes predicted by hierarchical galaxy and black hole formation scenarios; and quiescent supermassive nuclear black holes and their surroundings, as a way of understanding the full range of the AGN phenomenon. Finally, the X-ray band provides the only way to explore hot plasmas in galaxies; recent observations are revealing the importance of these plasmas as vehicles of both chemical enrichment and energy.

Proceedings of the International Astronomical Union, 2009

This talks reviews the history of the discovery of the hot ISM in elliptical galaxies, and the en... more This talks reviews the history of the discovery of the hot ISM in elliptical galaxies, and the ensuing debate on the suitability of X-ray observations of these galaxies for mass measurements. How much of the X-ray emission is truly from a hot ISM, and is this ISM in hydrostatic equilibrium? While the debate went on, a deeper understanding on the evolution of the halos was generated. High resolutionChandraobservations are providing an answer.

Observational Evidence of Activity in Galaxies, 1987

Seyferts from 0.3 to 100 microns have been examined. We focus on the modifying effects of dust, b... more Seyferts from 0.3 to 100 microns have been examined. We focus on the modifying effects of dust, both in terms of absorption and re-radiation. After allowance is made for dust and the presence of extranuclear contributions to the IRAS fluxes, there remains a ubiquitous underlying distribution which we believe to be non-thermal. There is evidence that the thermal infrared components corresponding to hot and warm dust may be associated with the broad and narrow emission line regions.

Active Galactic Nuclei, 1989

Two types of active nuclei have been observed in normal spiral galaxies in X-rays with the Einste... more Two types of active nuclei have been observed in normal spiral galaxies in X-rays with the Einstein Observatory: low-activity AGN, and starburst regions. The prototype of the first kind is the nucleus of M81 (Elvis and Van Speybroeck 1982; Fabbiano 1988a), trat similar nuclei might also be those of M33 and NGC 1313. Soft X-ray spectra of these nuclei suggest relatively steep soft X-ray components (Trinchieri, Fabbiano and Peres 1988; Fabbiano and Trinchieri 1987; Fabbiano 1988a), reminiscent of those observed in QSOs by Bechtold et al (1987) and Wilkes and Elvis (1987). In M81, in particular, this soft component might supply enough photons to explain the optical line spectrum. If this soft X-ray component originates from an accretion disk surrounding a central black hole, the mass of the latter is likely to be smaller than 10 4 "" 5 solar masses. Plumes of extended X-ray emission have been found associated with the starburst nuclei of NGC 253 and M82 (Fabbiano and Trinchieri 1984; Watson, Stanger and Griffiths 1984), suggesting nuclear gaseous outflows. Subsequent optical work by many authors has confirmed this view (e.g. Heckman, Annus and Miley 1987). A recent work on lowresolution X-ray images of these two galaxies suggest that this gaseous component extends at a significant distance from the galactic disks (Fabbiano 1988b). In M82, in particular, there is evidence of a gaseous halo, not bound to the system, extending as far as 9' from the nucleus along the minor axis. Very recently, a systematic analysis of X-ray images of spiral galaxies has revealed another such nucleus, in the edge-on galaxy NGC 3628. Follow up CCD imaging and optical spectroscopy by Heckman and Keel is confirming the presence of a nuclear outflow.

Astronomy & Astrophysics, 2000

We have measured the spectral properties of five galaxies of low to intermediate Lx/Lb ratios wit... more We have measured the spectral properties of five galaxies of low to intermediate Lx/Lb ratios with BeppoSAX and ASCA. A hard component (kT ~ 4-10 keV) is observed in all galaxies. In NGC 1553 the BeppoSAX data show that this component is extended, and suggest an origin for the emission in the evolved stellar population. In NGC 3115, a point-like

We present a wide field study of the Globular Clusters/Low Mass X-ray Binaries connection in the ... more We present a wide field study of the Globular Clusters/Low Mass X-ray Binaries connection in the cD elliptical NGC1399, combining HST/ACS and Chandra high resolution data. We find evidence that LMXB formation likelihood is influenced by GCs structural parameters, in addition to the well known effects of mass and metallicity, independently from galactocentric distance.

Observatory Operations: Strategies, Processes, and Systems, 2006

The calibration database implemented for the Chandra X-ray Observatory is the most detailed and e... more The calibration database implemented for the Chandra X-ray Observatory is the most detailed and extensive CalDB of its kind to date. Built according to the NASA High Energy Astrophysics Science Archive Research Center (HEASARC) CalDB prescription, the Chandra CalDB provides indexed, selectable calibration data for detector responses, mirror effective areas, grating efficiencies, instrument geometries, default source aim points, CCD characteristics, and quantum efficiencies, among many others. The combined index comprises approximately 500 entries. A standard FTOOLS parametric interface allows users and tools to access the index. Unique dataset selection requires certain input calibration parameters such as mission, instrument, detector, UTC date and time, and certain ranged parameter values. The goals of the HEASARC CalDB design are (1) to separate software upgrades from calibration upgrades, (2) to allow multi-mission use of analysis software (for missions with a compliant CalDB) and (3) to facilitate the use of multiple software packages for the same data. While we have been able to meet the multivariate needs of Chandra with the current CalDB implementation from HEASARC, certain requirements and desirable enhancements have been identified that raise the prospect of a developmental rewrite of the CalDB system. The explicit goal is to meet Chandra's specific needs better, but such upgrades may also provide significant advantages to CalDB planning for future missions. In particular we believe we will introduce important features aiding in the development of mission-independent analysis software. We report our current plans and progress.

Observatory Operations: Strategies, Processes, and Systems II, 2008

The Chandra Source Catalog, presently being developed by the Chandra X-ray Center, will be the de... more The Chandra Source Catalog, presently being developed by the Chandra X-ray Center, will be the definitive catalog of all X-ray sources detected by the Chandra X-ray Observatory. The catalog interface will provide users with a simple mechanism to perform advanced queries on the data content of the archival holdings on a source-by-source basis for X-ray sources matching user-specified search criteria, and is intended to satisfy the needs of a broad-based group of scientists, including those who may be less familiar with astronomical data analysis in the X-ray regime. For each detected X-ray source, the catalog will record commonly tabulated quantities that can be queried, including source position, dimensions, multi-band fluxes, hardness ratios, and variability statistics, derived from all of the observations that include the source within the field of view. However, in addition to these traditional catalog elements, for each X-ray source the catalog will include an extensive set of file-based data products that can be manipulated interactively by the catalog user, including source images, event lists, light curves, and spectra from each observation in which a source is detected. In this paper, we emphasize the design and development of the Chandra Source Catalog. We describe the evaluation process used to plan the data content of the catalog, and the selection of the tabular properties and file-based data products to be provided to the user. We discuss our approach for managing catalog updates derived from either additional data from new observations or from improvements to calibrations and/or analysis algorithms.

X-ray astronomy is the prime available window on astrophysical compact objects: black holes, neut... more X-ray astronomy is the prime available window on astrophysical compact objects: black holes, neutron stars and white dwarfs. New observational opportunities have led to an explosion of knowledge in this field. This book provides a comprehensive overview of the astrophysics of compact objects that emit X-rays. Sixteen chapters written by the foremost experts in the field cover the observations and the astrophysical interpretation of these objects. Topics covered include binary systems, gamma ray burst sources, anomalous X-ray pulsars, super-soft sources, and enigmatic fast X-ray transients. Further chapters are dedicated to isolated neutron stars and the X-ray source populations of globular clusters. The properties of X-ray binaries are discussed in depth in chapters on quasi-periodic oscillations and related aperiodic X-ray variability, X-ray bursts, black holes, and relativistic jets. This is a valuable reference for both graduate students and active researchers.

The Astrophysical Journal, 2011

This paper is the third in a series in which we present deep Chandra ACIS-S imaging spectroscopy ... more This paper is the third in a series in which we present deep Chandra ACIS-S imaging spectroscopy of the Seyfert 1 galaxy NGC 4151, devoted to study its complex circumnuclear X-ray emission. Emission features in the soft X-ray spectrum of the bright extended emission (L 0.3-2 keV ∼ 10 40 erg s −1) at r > 130 pc (2) are consistent with blended brighter O vii, O viii, and Ne ix lines seen in the Chandra HETGS and XMM-Newton RGS spectra below 2 keV. We construct emission line images of these features and find good morphological correlations with the narrowline region clouds mapped in [O iii] λ5007. Self-consistent photoionization models provide good descriptions of the spectra of the large-scale emission, as well as resolved structures, supporting the dominant role of nuclear photoionization, although displacement of optical and X-ray features implies a more complex medium. Collisionally ionized emission is estimated to be 12% of the extended emission. Presence of both low-and high-ionization spectral components and extended emission in the X-ray image perpendicular to the bicone indicates leakage of nuclear ionization, likely filtered through warm absorbers, instead of being blocked by a continuous obscuring torus. The ratios of [O iii]/soft X-ray flux are approximately constant (∼15) for the 1.5 kpc radius spanned by these measurements, indicating similar relative contributions from the low-and high-ionization gas phases at different radial distances from the nucleus. If the [O iii] and X-ray emission arise from a single photoionized medium, this further implies an outflow with a wind-like density profile. Using spatially resolved X-ray features, we estimate that the mass outflow rate in NGC 4151 is ∼2 M yr −1 at 130 pc and the kinematic power of the ionized outflow is 1.7 × 10 41 erg s −1 , approximately 0.3% of the bolometric luminosity of the active nucleus in NGC 4151.

The Astrophysical Journal, 2003

Chandra observations of the supermassive black hole in the nucleus of IC 1459 show a weak (L X =8... more Chandra observations of the supermassive black hole in the nucleus of IC 1459 show a weak (L X =8×10 40 erg s −1 , 0.3-8 keV), unabsorbed nuclear X-ray source, with a slope Γ = 1.88±0.09, and no strong Fe-K line at 6.4 keV (EW<382 eV). This describes a normal AGN X-ray spectrum, but lies at 3×10 −7 below the Eddington limit. The SED of the IC 1459 nucleus is extremely radio loud compared to normal radio-loud quasars. The nucleus is surrounded by hot ISM (kT∼0.5-0.6 keV) with an average density of 0.3 cm −3 , within the central ∼180 pc radius, which is comparable to the gravitational capture radius, r A ∼140 pc. We estimate that for a standard AGN efficiency of 10%, the Bondi accretion would correspond to a luminosity of ∼6×10 44 erg s −1 , nearly four orders of magnitude higher than L X. ADAF solutions can explain the X-ray spectrum, but not the high radio/X-ray ratio. A jet model fits the radio-100µm and X-ray spectra well. The total power in this jet is ∼10% of L Bondi , implying that accretion close to the Bondi rate is needed.

The Astrophysical Journal, 2003

A high angular resolution study of the nucleus of the FR I galaxy IC4296 using Chandra ACIS-S and... more A high angular resolution study of the nucleus of the FR I galaxy IC4296 using Chandra ACIS-S and VLBA observations is presented, with the aim of studying the nature of the accretion process. Pointlike and hard X-ray emission is found, well described by a moderately absorbed power law of Γ = 1.48 +0.42 −0.34 ; no iron fluorescence line from cold material is detected. The 0.3-10 keV luminosity is 2.4 × 10 41 erg s −1 , that is ∼ 400 times lower than the accretion luminosity resulting from the estimated Bondi mass accretion rate and a radiative efficiency of 10%. On the parsec scale a jet and a counter-jet extend out from a central unresolved "core" in the 8.4 GHz image. Their orientation is in good agreement with that of the large scale jets and their bulk speed is relativistic. The parsec scale spectrum is convex over 2-22 GHz. The observed nuclear luminosity is not likely to be reconciled with the accretion luminosity by assuming that Compton thick material surrounds the nucleus. Low radiative efficiency accretion flow models (ADAF and its variants) cannot account for the observed emission and spectral shape of the nucleus in the radio band. The power in the jets accounts for a sizable fraction (10%) of the accretion luminosity; therefore the mass accretion rate needs not to be much different from the estimate obtained using

The Astrophysical Journal, 2006

We present a systematic study of the low mass X-ray binary (LMXB) populations of 6 elliptical gal... more We present a systematic study of the low mass X-ray binary (LMXB) populations of 6 elliptical galaxies, aimed at investigating the detected LMXB − globular cluster (GC) connection. We utilize Chandra archival data to identify 665 X-ray point sources and HST archival data supplemented by ground observations to identify 6173 GCs. Applying rigorous X-ray and optical photometry and conservative matching criteria, we associate 209 LMXBs with red GC (RGC) and 76 LMXBs with blue GCs (BGC), while we find no optical GC counterpart for 258 LMXBs. This is the largest GC−LMXB sample studied so far. We confirm previous reports suggesting that the fraction of GCs associated with LMXBs is ∼ 3 times larger in RGCs than in BGCs, indicating that metallicity is a primary factor in the GC−LMXB formation. While as already known, the brighter (and bigger) GCs have a higher probability to host LMXBs, we find that this optical luminosity (or mass) dependency is stronger in RGCs than in BGCs. We also find that GCs located near the galaxy center have a higher probability to harbor LMXBs compared to those in the outskirts. The radial distributions of GC−LMXBs (for both RGC and BGC) are steeper than those of the whole optical GC sample, but consistent with those of the optical halo light, suggesting that there must be another parameter (in addition to metallicity) governing LMXB formation in GCs. This second parameter must depend on the galacto-centric distance. One possibility is a galacto-centric distance dependent encounter rate. We find no statistically significant difference in the X-ray properties (shape of X-ray luminosity function, L X /L V distribution, X-ray spectra) among RGC−LMXBs, BGC−LMXBs and field−LMXBs. The similarity of the X-ray spectra of BGC−LMXBs and RGC−LMXBs is inconsistent with the irradiationinduced stellar wind model prediction of more absorbed X-ray spectra in

The Astrophysical Journal, 2011

We have studied the X-ray emission within the inner ∼150 pc radius of NGC 4151 by constructing hi... more We have studied the X-ray emission within the inner ∼150 pc radius of NGC 4151 by constructing high spatial resolution emission line images of blended OVII, OVIII, and NeIX. These maps show extended structures that are spatially correlated with the radio outflow and optical [OIII] emission. We find strong evidence for jet-gas cloud interaction, including morphological correspondences with regions of X-ray enhancement, peaks of near-infrared [FeII] emission, and optical clouds. In these regions, moreover, we find evidence of elevated NeIX/OVII ratios; the X-ray emission of these regions also exceeds that expected from nuclear photoionization. Spectral fitting reveals the presence of a collisionally ionized component. The thermal energy of the hot gas suggests that 0.1% of the estimated jet power is deposited into the host interstellar medium through interaction between the radio jet and the dense medium of the circum-nuclear region. We find possible pressure equilibrium between the collisionally ionized hot gas and the photoionized line-emitting cool clouds. We also obtain constraints on the extended iron and silicon fluorescent emission. Both lines are spatially unresolved. The upper limit on the contribution of an extended emission region to the Fe Kα emission is 5% of the total, in disagreement with a previous claim that 65% of the Fe Kα emission originates in the extended narrow line region.

The Astrophysical Journal, 2011

We report on the imaging analysis of ∼200 ks sub-arcsecond resolution Chandra Advanced CCD Imagin... more We report on the imaging analysis of ∼200 ks sub-arcsecond resolution Chandra Advanced CCD Imaging Spectrometer (ACIS-S) observations of the nearby Seyfert 1 galaxy NGC 4151. Bright, structured soft X-ray emission is observed to extend from 30 pc to 1.3 kpc in the southwest from the nucleus, much farther than seen in earlier X-ray studies. The terminus of the northeastern X-ray emission is spatially coincident with a CO gas lane, where the outflow likely encounters dense gas in the host galactic disk. X-ray emission is also detected outside the boundaries of the ionization cone, which indicates that the gas there is not completely shielded from the nuclear continuum, as would be the case for a molecular torus collimating the bicone. In the central r < 200 pc region, the subpixel processing of the ACIS data recovers the morphological details on scales of <30 pc (<0. 5) first discovered in Chandra High Resolution Camera images. The X-ray emission is more absorbed toward the boundaries of the ionization cone, as well as perpendicular to the bicone along the direction of a putative torus in NGC 4151. The innermost region where X-ray emission shows the highest hardness ratio is spatially coincident with the nearinfrared-resolved H 2 emission and dusty spirals we find in an Hubble Space Telescope V − H color image. The agreement between the observed H 2 line flux and the value predicted from X-ray-irradiated molecular cloud models supports photo-excitation by X-rays from the active nucleus as the origin of the H 2 line, although contribution from UV fluorescence or collisional excitation cannot be ruled out with current data. The discrepancy between the mass of cold molecular gas inferred from recent CO and near-infrared H 2 observations may be explained by the anomalous CO abundance in this X-ray-dominated region. The total H 2 mass derived from the X-ray observation agrees with the recent measurement by Storchi-Bergmann et al.

The Astronomical Journal, 1998

We present optical and archival X-ray data on the disturbed-morphology radio elliptical galaxy NG... more We present optical and archival X-ray data on the disturbed-morphology radio elliptical galaxy NGC 1316 (Fornax A), which displays numerous low surface brightness shells, loops, and tails. An extended (81A ] 27A, or 9 kpc ] 3 kpc) emission-line region (EELR) at a projected distance of 35 kpc from the nucleus has been discovered in an approximately 90 kpc ] 35 kpc, 3.0 ] 109 tidal tail. The position L B_ and extreme size of the EELR suggest that it is related to the merger process. We suggest that the ionization mechanism of the EELR is shock excitation and that the gas is a remnant from the merger progenitor. X-ray emission is detected near two tidal tails. Hot, D5 ] 106 K, gas is probably the predominant gas component in the tidal-tail interstellar medium. However, based on the current tidaltail (cold ] warm ] hot) gas mass, a large fraction of the progenitor gas may already reside in the nucleus of NGC 1316. The numerous and varied tidal-tail system suggests that a disk-disk or disk-E merger could have taken place º1 Gyr ago, while a low-mass, gas-rich galaxy would have started to merge D0.5 Gyr ago.

arXiv (Cornell University), Jun 10, 2010

There are already hundreds of terabytes of astronomical data in the public domain, and soon the a... more There are already hundreds of terabytes of astronomical data in the public domain, and soon the astronomical community will generate tens of petabytes of new data. There is an enormous science potential to be unleashed by the ability to find relevant datasets, access them, analyze them quantitatively, compare them with theoretical models, and ultimately understand their astrophysical implications. The VAO will enable researchers to (1) analyze data obtained with different instruments over the entire observable spectrum; (2) connect large data sets with high performance computational resources to aid analysis, detect, quantify and visualize hidden patterns, and (3) gain understanding of astrophysical phenomena with the aid of state-of-the art models. The VAO-SC strongly supports these goals. However, we acknowledge that substantial work is needed to achieve them fully. In particular, the VAO needs to move fast from the 'infrastructure building emphasis' of the NVO phase to be a fully scienceenabling organization.

The Astrophysical Journal, 2017

We present results of a joint Chandra/XMM-Newton analysis of the early-type galaxies NGC 4649 and... more We present results of a joint Chandra/XMM-Newton analysis of the early-type galaxies NGC 4649 and NGC 5846 aimed at investigating differences between mass profiles derived from X-ray data and those from optical data, to probe the state of the hot interstellar medium (ISM) in these galaxies. If the hot ISM is at a given radius in hydrostatic equilibrium (HE), the X-ray data can be used to measure the total enclosed mass of the galaxy. Differences from optically derived mass distributions therefore yield information about departures from HE in the hot halos. The X-ray mass profiles in different angular sectors of NGC 4649 are generally smooth with no significant azimuthal asymmetries within 12 kpc. Extrapolation of these profiles beyond this scale yields results consistent with the optical estimate. However, in the central region (r 3 < kpc) the X-ray data underpredict the enclosed mass, when compared with the optical mass profiles. Consistent with previous results, we estimate a nonthermal pressure component accounting for 30% of the gas pressure, likely linked to nuclear activity. In NGC 5846 the X-ray mass profiles show significant azimuthal asymmetries, especially in the NE direction. Comparison with optical mass profiles in this direction suggests significant departures from HE, consistent with bulk gas compression and decompression due to sloshing on ∼15 kpc scales; this effect disappears in the NW direction, where the emission is smooth and extended. In this sector we find consistent X-ray and optical mass profiles, suggesting that the hot halo is not responding to strong nongravitational forces.

The Astrophysical Journal, 2003

We have analyzed a 90 ksec long observation of the bright nucleus of M33 made with Chandra /ACIS.... more We have analyzed a 90 ksec long observation of the bright nucleus of M33 made with Chandra /ACIS. We detected low-amplitude (∼ 10%) highly significant variability on timescales of ∼ 5000 sec. We also find associated spectral variability. The two main spectral components (a power-law with Γ ∼ 2 and a multicolor disk-MCD-with kT∼ 0.9 − 1.2 keV) vary in relative flux. The MCD temperature also increases with increasing MCD flux. The pattern of variability is reminiscent of (but not identical to) galactic black hole binaries. A ∼ 15 M ⊙ accreting black hole may explain this source.

Chandra observations show the importance of the X-ray band for studying the evolution of galaxies... more Chandra observations show the importance of the X-ray band for studying the evolution of galaxies. Binary X-ray sources are an easily detectable tracer of the stellar population. Chandra studies of these populations are giving us insights into the nature and formation of these binaries, and provide the basis for diagnostics of galaxy evolution. With Chandra and XMM-Newton we can explore relatively poorly known aspects of the black hole population of the universe: ultra-luminous X-ray sources, that may be connected with the 'missing' intermediate mass black holes predicted by hierarchical galaxy and black hole formation scenarios; and quiescent supermassive nuclear black holes and their surroundings, as a way of understanding the full range of the AGN phenomenon. Finally, the X-ray band provides the only way to explore hot plasmas in galaxies; recent observations are revealing the importance of these plasmas as vehicles of both chemical enrichment and energy.

Proceedings of the International Astronomical Union, 2009

This talks reviews the history of the discovery of the hot ISM in elliptical galaxies, and the en... more This talks reviews the history of the discovery of the hot ISM in elliptical galaxies, and the ensuing debate on the suitability of X-ray observations of these galaxies for mass measurements. How much of the X-ray emission is truly from a hot ISM, and is this ISM in hydrostatic equilibrium? While the debate went on, a deeper understanding on the evolution of the halos was generated. High resolutionChandraobservations are providing an answer.

Observational Evidence of Activity in Galaxies, 1987

Seyferts from 0.3 to 100 microns have been examined. We focus on the modifying effects of dust, b... more Seyferts from 0.3 to 100 microns have been examined. We focus on the modifying effects of dust, both in terms of absorption and re-radiation. After allowance is made for dust and the presence of extranuclear contributions to the IRAS fluxes, there remains a ubiquitous underlying distribution which we believe to be non-thermal. There is evidence that the thermal infrared components corresponding to hot and warm dust may be associated with the broad and narrow emission line regions.

Active Galactic Nuclei, 1989

Two types of active nuclei have been observed in normal spiral galaxies in X-rays with the Einste... more Two types of active nuclei have been observed in normal spiral galaxies in X-rays with the Einstein Observatory: low-activity AGN, and starburst regions. The prototype of the first kind is the nucleus of M81 (Elvis and Van Speybroeck 1982; Fabbiano 1988a), trat similar nuclei might also be those of M33 and NGC 1313. Soft X-ray spectra of these nuclei suggest relatively steep soft X-ray components (Trinchieri, Fabbiano and Peres 1988; Fabbiano and Trinchieri 1987; Fabbiano 1988a), reminiscent of those observed in QSOs by Bechtold et al (1987) and Wilkes and Elvis (1987). In M81, in particular, this soft component might supply enough photons to explain the optical line spectrum. If this soft X-ray component originates from an accretion disk surrounding a central black hole, the mass of the latter is likely to be smaller than 10 4 "" 5 solar masses. Plumes of extended X-ray emission have been found associated with the starburst nuclei of NGC 253 and M82 (Fabbiano and Trinchieri 1984; Watson, Stanger and Griffiths 1984), suggesting nuclear gaseous outflows. Subsequent optical work by many authors has confirmed this view (e.g. Heckman, Annus and Miley 1987). A recent work on lowresolution X-ray images of these two galaxies suggest that this gaseous component extends at a significant distance from the galactic disks (Fabbiano 1988b). In M82, in particular, there is evidence of a gaseous halo, not bound to the system, extending as far as 9' from the nucleus along the minor axis. Very recently, a systematic analysis of X-ray images of spiral galaxies has revealed another such nucleus, in the edge-on galaxy NGC 3628. Follow up CCD imaging and optical spectroscopy by Heckman and Keel is confirming the presence of a nuclear outflow.

Astronomy & Astrophysics, 2000

We have measured the spectral properties of five galaxies of low to intermediate Lx/Lb ratios wit... more We have measured the spectral properties of five galaxies of low to intermediate Lx/Lb ratios with BeppoSAX and ASCA. A hard component (kT ~ 4-10 keV) is observed in all galaxies. In NGC 1553 the BeppoSAX data show that this component is extended, and suggest an origin for the emission in the evolved stellar population. In NGC 3115, a point-like

We present a wide field study of the Globular Clusters/Low Mass X-ray Binaries connection in the ... more We present a wide field study of the Globular Clusters/Low Mass X-ray Binaries connection in the cD elliptical NGC1399, combining HST/ACS and Chandra high resolution data. We find evidence that LMXB formation likelihood is influenced by GCs structural parameters, in addition to the well known effects of mass and metallicity, independently from galactocentric distance.

Observatory Operations: Strategies, Processes, and Systems, 2006

The calibration database implemented for the Chandra X-ray Observatory is the most detailed and e... more The calibration database implemented for the Chandra X-ray Observatory is the most detailed and extensive CalDB of its kind to date. Built according to the NASA High Energy Astrophysics Science Archive Research Center (HEASARC) CalDB prescription, the Chandra CalDB provides indexed, selectable calibration data for detector responses, mirror effective areas, grating efficiencies, instrument geometries, default source aim points, CCD characteristics, and quantum efficiencies, among many others. The combined index comprises approximately 500 entries. A standard FTOOLS parametric interface allows users and tools to access the index. Unique dataset selection requires certain input calibration parameters such as mission, instrument, detector, UTC date and time, and certain ranged parameter values. The goals of the HEASARC CalDB design are (1) to separate software upgrades from calibration upgrades, (2) to allow multi-mission use of analysis software (for missions with a compliant CalDB) and (3) to facilitate the use of multiple software packages for the same data. While we have been able to meet the multivariate needs of Chandra with the current CalDB implementation from HEASARC, certain requirements and desirable enhancements have been identified that raise the prospect of a developmental rewrite of the CalDB system. The explicit goal is to meet Chandra's specific needs better, but such upgrades may also provide significant advantages to CalDB planning for future missions. In particular we believe we will introduce important features aiding in the development of mission-independent analysis software. We report our current plans and progress.

Observatory Operations: Strategies, Processes, and Systems II, 2008

The Chandra Source Catalog, presently being developed by the Chandra X-ray Center, will be the de... more The Chandra Source Catalog, presently being developed by the Chandra X-ray Center, will be the definitive catalog of all X-ray sources detected by the Chandra X-ray Observatory. The catalog interface will provide users with a simple mechanism to perform advanced queries on the data content of the archival holdings on a source-by-source basis for X-ray sources matching user-specified search criteria, and is intended to satisfy the needs of a broad-based group of scientists, including those who may be less familiar with astronomical data analysis in the X-ray regime. For each detected X-ray source, the catalog will record commonly tabulated quantities that can be queried, including source position, dimensions, multi-band fluxes, hardness ratios, and variability statistics, derived from all of the observations that include the source within the field of view. However, in addition to these traditional catalog elements, for each X-ray source the catalog will include an extensive set of file-based data products that can be manipulated interactively by the catalog user, including source images, event lists, light curves, and spectra from each observation in which a source is detected. In this paper, we emphasize the design and development of the Chandra Source Catalog. We describe the evaluation process used to plan the data content of the catalog, and the selection of the tabular properties and file-based data products to be provided to the user. We discuss our approach for managing catalog updates derived from either additional data from new observations or from improvements to calibrations and/or analysis algorithms.

X-ray astronomy is the prime available window on astrophysical compact objects: black holes, neut... more X-ray astronomy is the prime available window on astrophysical compact objects: black holes, neutron stars and white dwarfs. New observational opportunities have led to an explosion of knowledge in this field. This book provides a comprehensive overview of the astrophysics of compact objects that emit X-rays. Sixteen chapters written by the foremost experts in the field cover the observations and the astrophysical interpretation of these objects. Topics covered include binary systems, gamma ray burst sources, anomalous X-ray pulsars, super-soft sources, and enigmatic fast X-ray transients. Further chapters are dedicated to isolated neutron stars and the X-ray source populations of globular clusters. The properties of X-ray binaries are discussed in depth in chapters on quasi-periodic oscillations and related aperiodic X-ray variability, X-ray bursts, black holes, and relativistic jets. This is a valuable reference for both graduate students and active researchers.

The Astrophysical Journal, 2011

This paper is the third in a series in which we present deep Chandra ACIS-S imaging spectroscopy ... more This paper is the third in a series in which we present deep Chandra ACIS-S imaging spectroscopy of the Seyfert 1 galaxy NGC 4151, devoted to study its complex circumnuclear X-ray emission. Emission features in the soft X-ray spectrum of the bright extended emission (L 0.3-2 keV ∼ 10 40 erg s −1) at r > 130 pc (2) are consistent with blended brighter O vii, O viii, and Ne ix lines seen in the Chandra HETGS and XMM-Newton RGS spectra below 2 keV. We construct emission line images of these features and find good morphological correlations with the narrowline region clouds mapped in [O iii] λ5007. Self-consistent photoionization models provide good descriptions of the spectra of the large-scale emission, as well as resolved structures, supporting the dominant role of nuclear photoionization, although displacement of optical and X-ray features implies a more complex medium. Collisionally ionized emission is estimated to be 12% of the extended emission. Presence of both low-and high-ionization spectral components and extended emission in the X-ray image perpendicular to the bicone indicates leakage of nuclear ionization, likely filtered through warm absorbers, instead of being blocked by a continuous obscuring torus. The ratios of [O iii]/soft X-ray flux are approximately constant (∼15) for the 1.5 kpc radius spanned by these measurements, indicating similar relative contributions from the low-and high-ionization gas phases at different radial distances from the nucleus. If the [O iii] and X-ray emission arise from a single photoionized medium, this further implies an outflow with a wind-like density profile. Using spatially resolved X-ray features, we estimate that the mass outflow rate in NGC 4151 is ∼2 M yr −1 at 130 pc and the kinematic power of the ionized outflow is 1.7 × 10 41 erg s −1 , approximately 0.3% of the bolometric luminosity of the active nucleus in NGC 4151.

The Astrophysical Journal, 2003

Chandra observations of the supermassive black hole in the nucleus of IC 1459 show a weak (L X =8... more Chandra observations of the supermassive black hole in the nucleus of IC 1459 show a weak (L X =8×10 40 erg s −1 , 0.3-8 keV), unabsorbed nuclear X-ray source, with a slope Γ = 1.88±0.09, and no strong Fe-K line at 6.4 keV (EW<382 eV). This describes a normal AGN X-ray spectrum, but lies at 3×10 −7 below the Eddington limit. The SED of the IC 1459 nucleus is extremely radio loud compared to normal radio-loud quasars. The nucleus is surrounded by hot ISM (kT∼0.5-0.6 keV) with an average density of 0.3 cm −3 , within the central ∼180 pc radius, which is comparable to the gravitational capture radius, r A ∼140 pc. We estimate that for a standard AGN efficiency of 10%, the Bondi accretion would correspond to a luminosity of ∼6×10 44 erg s −1 , nearly four orders of magnitude higher than L X. ADAF solutions can explain the X-ray spectrum, but not the high radio/X-ray ratio. A jet model fits the radio-100µm and X-ray spectra well. The total power in this jet is ∼10% of L Bondi , implying that accretion close to the Bondi rate is needed.

The Astrophysical Journal, 2003

A high angular resolution study of the nucleus of the FR I galaxy IC4296 using Chandra ACIS-S and... more A high angular resolution study of the nucleus of the FR I galaxy IC4296 using Chandra ACIS-S and VLBA observations is presented, with the aim of studying the nature of the accretion process. Pointlike and hard X-ray emission is found, well described by a moderately absorbed power law of Γ = 1.48 +0.42 −0.34 ; no iron fluorescence line from cold material is detected. The 0.3-10 keV luminosity is 2.4 × 10 41 erg s −1 , that is ∼ 400 times lower than the accretion luminosity resulting from the estimated Bondi mass accretion rate and a radiative efficiency of 10%. On the parsec scale a jet and a counter-jet extend out from a central unresolved "core" in the 8.4 GHz image. Their orientation is in good agreement with that of the large scale jets and their bulk speed is relativistic. The parsec scale spectrum is convex over 2-22 GHz. The observed nuclear luminosity is not likely to be reconciled with the accretion luminosity by assuming that Compton thick material surrounds the nucleus. Low radiative efficiency accretion flow models (ADAF and its variants) cannot account for the observed emission and spectral shape of the nucleus in the radio band. The power in the jets accounts for a sizable fraction (10%) of the accretion luminosity; therefore the mass accretion rate needs not to be much different from the estimate obtained using

The Astrophysical Journal, 2006

We present a systematic study of the low mass X-ray binary (LMXB) populations of 6 elliptical gal... more We present a systematic study of the low mass X-ray binary (LMXB) populations of 6 elliptical galaxies, aimed at investigating the detected LMXB − globular cluster (GC) connection. We utilize Chandra archival data to identify 665 X-ray point sources and HST archival data supplemented by ground observations to identify 6173 GCs. Applying rigorous X-ray and optical photometry and conservative matching criteria, we associate 209 LMXBs with red GC (RGC) and 76 LMXBs with blue GCs (BGC), while we find no optical GC counterpart for 258 LMXBs. This is the largest GC−LMXB sample studied so far. We confirm previous reports suggesting that the fraction of GCs associated with LMXBs is ∼ 3 times larger in RGCs than in BGCs, indicating that metallicity is a primary factor in the GC−LMXB formation. While as already known, the brighter (and bigger) GCs have a higher probability to host LMXBs, we find that this optical luminosity (or mass) dependency is stronger in RGCs than in BGCs. We also find that GCs located near the galaxy center have a higher probability to harbor LMXBs compared to those in the outskirts. The radial distributions of GC−LMXBs (for both RGC and BGC) are steeper than those of the whole optical GC sample, but consistent with those of the optical halo light, suggesting that there must be another parameter (in addition to metallicity) governing LMXB formation in GCs. This second parameter must depend on the galacto-centric distance. One possibility is a galacto-centric distance dependent encounter rate. We find no statistically significant difference in the X-ray properties (shape of X-ray luminosity function, L X /L V distribution, X-ray spectra) among RGC−LMXBs, BGC−LMXBs and field−LMXBs. The similarity of the X-ray spectra of BGC−LMXBs and RGC−LMXBs is inconsistent with the irradiationinduced stellar wind model prediction of more absorbed X-ray spectra in

The Astrophysical Journal, 2011

We have studied the X-ray emission within the inner ∼150 pc radius of NGC 4151 by constructing hi... more We have studied the X-ray emission within the inner ∼150 pc radius of NGC 4151 by constructing high spatial resolution emission line images of blended OVII, OVIII, and NeIX. These maps show extended structures that are spatially correlated with the radio outflow and optical [OIII] emission. We find strong evidence for jet-gas cloud interaction, including morphological correspondences with regions of X-ray enhancement, peaks of near-infrared [FeII] emission, and optical clouds. In these regions, moreover, we find evidence of elevated NeIX/OVII ratios; the X-ray emission of these regions also exceeds that expected from nuclear photoionization. Spectral fitting reveals the presence of a collisionally ionized component. The thermal energy of the hot gas suggests that 0.1% of the estimated jet power is deposited into the host interstellar medium through interaction between the radio jet and the dense medium of the circum-nuclear region. We find possible pressure equilibrium between the collisionally ionized hot gas and the photoionized line-emitting cool clouds. We also obtain constraints on the extended iron and silicon fluorescent emission. Both lines are spatially unresolved. The upper limit on the contribution of an extended emission region to the Fe Kα emission is 5% of the total, in disagreement with a previous claim that 65% of the Fe Kα emission originates in the extended narrow line region.

The Astrophysical Journal, 2011

We report on the imaging analysis of ∼200 ks sub-arcsecond resolution Chandra Advanced CCD Imagin... more We report on the imaging analysis of ∼200 ks sub-arcsecond resolution Chandra Advanced CCD Imaging Spectrometer (ACIS-S) observations of the nearby Seyfert 1 galaxy NGC 4151. Bright, structured soft X-ray emission is observed to extend from 30 pc to 1.3 kpc in the southwest from the nucleus, much farther than seen in earlier X-ray studies. The terminus of the northeastern X-ray emission is spatially coincident with a CO gas lane, where the outflow likely encounters dense gas in the host galactic disk. X-ray emission is also detected outside the boundaries of the ionization cone, which indicates that the gas there is not completely shielded from the nuclear continuum, as would be the case for a molecular torus collimating the bicone. In the central r < 200 pc region, the subpixel processing of the ACIS data recovers the morphological details on scales of <30 pc (<0. 5) first discovered in Chandra High Resolution Camera images. The X-ray emission is more absorbed toward the boundaries of the ionization cone, as well as perpendicular to the bicone along the direction of a putative torus in NGC 4151. The innermost region where X-ray emission shows the highest hardness ratio is spatially coincident with the nearinfrared-resolved H 2 emission and dusty spirals we find in an Hubble Space Telescope V − H color image. The agreement between the observed H 2 line flux and the value predicted from X-ray-irradiated molecular cloud models supports photo-excitation by X-rays from the active nucleus as the origin of the H 2 line, although contribution from UV fluorescence or collisional excitation cannot be ruled out with current data. The discrepancy between the mass of cold molecular gas inferred from recent CO and near-infrared H 2 observations may be explained by the anomalous CO abundance in this X-ray-dominated region. The total H 2 mass derived from the X-ray observation agrees with the recent measurement by Storchi-Bergmann et al.

The Astronomical Journal, 1998

We present optical and archival X-ray data on the disturbed-morphology radio elliptical galaxy NG... more We present optical and archival X-ray data on the disturbed-morphology radio elliptical galaxy NGC 1316 (Fornax A), which displays numerous low surface brightness shells, loops, and tails. An extended (81A ] 27A, or 9 kpc ] 3 kpc) emission-line region (EELR) at a projected distance of 35 kpc from the nucleus has been discovered in an approximately 90 kpc ] 35 kpc, 3.0 ] 109 tidal tail. The position L B_ and extreme size of the EELR suggest that it is related to the merger process. We suggest that the ionization mechanism of the EELR is shock excitation and that the gas is a remnant from the merger progenitor. X-ray emission is detected near two tidal tails. Hot, D5 ] 106 K, gas is probably the predominant gas component in the tidal-tail interstellar medium. However, based on the current tidaltail (cold ] warm ] hot) gas mass, a large fraction of the progenitor gas may already reside in the nucleus of NGC 1316. The numerous and varied tidal-tail system suggests that a disk-disk or disk-E merger could have taken place º1 Gyr ago, while a low-mass, gas-rich galaxy would have started to merge D0.5 Gyr ago.