arXiv subjects

Antonella Fruscione

Publications and source records attributed to Antonella Fruscione.

17 recordsLinked to original sources

arXiv2026

SAOImageDS9: An Essential Tool for Astronomical Exploration

SAOImageDS9 (DS9) is an open-source, cross-platform application for the visualization and analysis of astronomical data. Developed at the Smithsonian Astrophysical Observatory, DS9 evolved from an example implementation of reusable imaging components into one of the most widely used astronomical display environments. It has remained useful because it supports many astronomical file formats and coordinate systems, can work directly with event data and image cubes, provides interactive region-based analysis, and can communicate with external tools through command-line and messaging interfaces. DS9 is used in research, mission operations, and education across a range of wavelengths and at both ground- and space-based observatories. This paper summarizes the historical development of DS9, its principal capabilities, and its impact on the astronomical community, and concludes with an appendix describing the internal architecture that has supported its long-term sustainability.

astro-ph.IM↗

arXiv2026

CIAO: Chandra's Data Analysis System for X-Ray Astronomy and Beyond

The Chandra Interactive Analysis of Observations (CIAO) software, developed by the Chandra X-ray Center, has been the data analysis package for the Chandra X-ray Observatory since its launch in 1999. Over nearly three decades, CIAO has grown from a small software suite into a widely used system for X-ray data analysis and beyond. CIAO provides tools for calibration, spectral, imaging, and timing analysis, together with high-level scripts and the \sherpa\ modeling and fitting application. Its modular design and unified data model allow users to build flexible analysis workflows while maintaining consistency with the Chandra data processing pipeline. Visualization capabilities are provided through integration with SAOImageDS9 and Python-based tools, and simulation components such as ChaRT and MARX extend the analysis environment to include detailed modeling of instrumental effects. In this paper we describe CIAO's design, evolution, and capabilities after 25 years of Chandra operations. We also describe its core architecture, scripting environment, modeling, visualization tools, simulation components, and testing infrastructure, as well as the documentation and user support system that have contributed to its widespread use. CIAO's continued development and broad adoption highlight its important role in X-ray astronomy and its usefulness in multiwavelength astrophysical research.

astro-ph.IM↗

arXiv2024

Sherpa: An Open Source Python Fitting Package

We present an overview of Sherpa, an open source Python project, and discuss its development history, broad design concepts and capabilities. Sherpa contains powerful tools for combining parametric models into complex expressions that can be fit to data using a variety of statistics and optimization methods. It is easily extensible to include user-defined models, statistics, and optimization methods. It provides a high-level User Interface for interactive data-analysis, such as within a Jupyter notebook, and it can also be used as a library component, providing fitting and modeling capabilities to an application. We include a few examples of Sherpa applications to multiwavelength astronomical data. The code is available GitHub: https://github.com/sherpa/sherpa

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arXiv2020

Metallicity and X-ray luminosity variations in NGC 922

We present a systematic study of the metallicity variations within the collisional ring galaxy NGC 922 based on long-slit optical spectroscopic observations. We find a metallicity difference between star-forming regions in the bulge and the ring, with metallicities ranging from almost solar to significantly sub-solar ($\rm{[12+\log(O/H)]\sim 8.2}$). We detect $\rm He\,_I$ emission in the bulge and the ring star-forming regions indicating ionization from massive stars associated with recent ($<10$ Myr) star-formation, in agreement with the presence of very young star-clusters in all studied regions. We find an anti-correlation between the X-ray luminosity and metallicity of the sub-galactic regions of NGC 922. The different regions have similar stellar population ages leaving metallicity as the main driver of the anti-correlation. The dependence of the X-ray emission of the different regions in NGC 922 on metallicity is in agreement with similar studies of the integrated X-ray output of galaxies and predictions from X-ray binary population models.

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arXiv2019

Temperature Profiles of Hot Gas In Early Type Galaxies

Using the data products of the Chandra Galaxy Atlas (Kim et al. 2019a), we have investigated the radial profiles of the hot gas temperature in 60 early type galaxies. Considering the characteristic temperature and radius of the peak, dip, and break (when scaled by the gas temperature and virial radius of each galaxy), we propose a universal temperature profile of the hot halo in ETGs. In this scheme, the hot gas temperature peaks at RMAX = 35 +/- 25 kpc (or ~0.04 RVIR) and declines both inward and outward. The temperature dips (or breaks) at RMIN (or RBREAK) = 3 - 5 kpc (or ~0.006 RVIR). The mean slope between RMIN (RBREAK) and RMAX is 0.3 +/- 0.1. Allowing for selection effects and observational limits, we find that the universal temperature profile can describe the temperature profiles of 72% (possibly up to 82%) of our ETG sample. The remaining ETGs (18%) with irregular or monotonically declining profiles do not fit the universal profile and require another explanation. The temperature gradient inside RMIN (RBREAK) varies widely, indicating different degrees of additional heating at small radii. Investigating the nature of the hot core (HC with a negative gradient inside RMIN), we find that HC is most clearly visible in small galaxies. Searching for potential clues associated with stellar, AGN feedback, and gravitational heating, we find that HC may be related to recent star formation. But we see no clear evidence that AGN feedback and gravitational heating play any significant role for HC.

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arXiv2019

Chandra Early-Type Galaxy Atlas

The hot ISM in early type galaxies (ETGs) plays a crucial role in understanding their formation and evolution. The structural features of the hot gas identified by Chandra observations point to key evolutionary mechanisms, (e.g., AGN and stellar feedback, merging history). In our Chandra Galaxy Atlas (CGA) project, taking full advantage of the Chandra capabilities, we systematically analyzed the archival Chandra data of 70 ETGs and produced uniform data products for the hot gas properties. The primary data products are spatially resolved 2D spectral maps of the hot gas from individual galaxies. We emphasize that new features can be identified in the spectral maps which are not readily visible in the surface brightness maps. The high-level images can be viewed at the dedicated CGA website, and the CGA data products can be downloaded to compare with data at other wavelengths and to perform further analyses. Utilizing our data products, we address a few focused science topics.

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arXiv2018

The X-Ray Luminosity Function of Ultra Luminous X-Ray Sources in Collisional Ring Galaxies

Ring galaxies are fascinating laboratories: a catastrophic impact between two galaxies (one not much smaller than the other) has produced fireworks especially in the larger one, when hit roughly perpendicularly to the plane. We analyze the point sources, produced by the starburst episode following the impact, in the rings of seven galaxies and determine their X-ray luminosity function (XLF). In total we detect 63 sources, of which 50 have luminosity L$_X \geq 10^{39}$ erg s$^{-1}$, classifying them as ultra luminous X-ray sources (ULXs). We find that the total XLF is not significantly different from XLFs derived for other kinds of galaxies, with a tendency of having a larger fraction of high X-ray luminosity objects. Both the total number of ULXs and the number of ULXs per unit star formation rate are found in the upper envelope of the more normal galaxies distribution. Further analysis would be needed to address the issue of the nature of the compact component in the binary system.

astro-ph.HE↗

arXiv2018

Disturbed Fossil Group Galaxy NGC 1132

We have analyzed the Chandra archival data of NGC 1132, a well-known fossil group, i.e. a system expected to be old and relaxed long after the giant elliptical galaxy assembly. Instead, the Chandra data reveal that the hot gas morphology is disturbed and asymmetrical, with a cold front following a possible bow shock. We discuss possible origins of the disturbed hot halo, including sloshing by a nearby object, merger, ram pressure by external hotter gas and nuclear outburst. We consider that the first two mechanisms are likely explanations for the disturbed hot halo, with a slight preference for a minor merger with a low impact parameter because of the match with simulations and previous optical observations. In this case, NGC 1132 may be a rare example of unusual late mergers seen in recent simulations. Regardless of the origin of the disturbed hot halo, the paradigm of the fossil system needs to be reconsidered.

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arXiv2017

Constraining the Physical State of the Hot Gas Halos in NGC 4649 and NGC 5846

We present results of a joint \textit{Chandra}/\textit{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 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 non-thermal 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 $\sim 15$ 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 non-gravitational forces.

astro-ph.GA↗

arXiv2014

The Chandra Cygnus OB2 Legacy Survey: Design and X-ray Point Source Catalog

The Cygnus OB2 association is the largest concentration of young and massive stars within 2 kpc of the Sun, including an estimated 65 O-type stars and hundreds of OB stars. The Chandra Cygnus OB2 Legacy Survey is a large imaging program undertaken with the Advanced CCD Imaging Spectrometer onboard the Chandra X-ray Observatory. The survey has imaged the central 0.5 deg^2 of the Cyg OB2 association with an effective exposure of 120ks and an outer 0.35 deg^2 area with an exposure of 60ks. Here we describe the survey design and observations, the data reduction and source detection, and present a catalog of 8,000 X-ray point sources. The survey design employs a grid of 36 heavily (~50%) overlapping pointings, a method that overcomes Chandra's low off-axis sensitivity and produces a highly uniform exposure over the inner 0.5 deg^2. The full X-ray catalog is described here and is made available online.

astro-ph.SR↗

arXiv2009

The Chandra COSMOS Survey, I: Overview and Point Source Catalog

The Chandra COSMOS Survey (C-COSMOS) is a large, 1.8 Ms, Chandra} program that has imaged the central 0.5 sq.deg of the COSMOS field (centered at 10h, +02deg) with an effective exposure of ~160ksec, and an outer 0.4sq.deg. area with an effective exposure of ~80ksec. The limiting source detection depths are 1.9e-16 erg cm(-2) s(-1) in the Soft (0.5-2 keV) band, 7.3e(-16) erg cm^-2 s^-1 in the Hard (2-10 keV) band, and 5.7e(-16) erg cm(-2) s(-1) in the Full (0.5-10 keV) band. Here we describe the strategy, design and execution of the C-COSMOS survey, and present the catalog of 1761 point sources detected at a probability of being spurious of <2e(-5) (1655 in the Full, 1340 in the Soft, and 1017 in the Hard bands). By using a grid of 36 heavily (~50%) overlapping pointing positions with the ACIS-I imager, a remarkably uniform (to 12%) exposure across the inner 0.5 sq.deg field was obtained, leading to a sharply defined lower flux limit. The widely different PSFs obtained in each exposure at each point in the field required a novel source detection method, because of the overlapping tiling strategy, which is described in a companion paper. (Puccetti et al. Paper II). This method produced reliable sources down to a 7-12 counts, as verified by the resulting logN-logS curve, with sub-arcsecond positions, enabling optical and infrared identifications of virtually all sources, as reported in a second companion paper (Civano et al. Paper III). The full catalog is described here in detail, and is available on-line.

astro-ph.CO↗

arXiv2005

Chandra Detection of the First X-ray Forest along the Line of Sight To Mkn 421

We present the first >=3.5 sigma (conservative) or >=5.8 sigma (sum of lines significance) detection of two Warm-Hot Intergalactic Medium (WHIM) filaments at z>0, which we find along the line of sight to the blazar Mkn 421. These systems are detected through highly ionized resonant metal absorption in high quality Chandra-ACIS and -HRC Low Energy Transmission Grating (LETG) spectra of Mkn 421, obtained following our two Target of Opportunity requests during two outburst phases. The two intervening WHIM systems that we detect, have OVII and NVII columns of N(OVII)=(1.0 +/- 0.3) x 1e15 cm-2} N(NVII)=(0.8 +/- 0.4) x 1e15 cm-2, and N(OVII)=(0.7 +/- 0.3) x 1e15 cm-2, N(NVII)=(1.4 +/- 0.5) x 1e15 cm-2 respectively. From the detected number of WHIM filaments along this line of sight we can estimate the number of OVII filaments per unit redshift with columns larger than 7e14 cm-2, dP(OVII)/dz(N(OVII)>=7e14) = 67^{+88}_{-43}, consistent, within the large 1-sigma errors, with the hydrodynamical simulation predictions of dP(OVII)/dz(N(OVII)>=7e14) = 30. Finally, we measure a cosmological mass density of X-ray WHIM filaments Omega_b = 0.027^{+0.038}_{-0.019} x 10^{[O/H]_{-1}}, consistent with both model predictions and the estimated number of 'missing' baryons at low redshift.

astro-ph↗

arXiv2005

X-ray Luminosity and Absorption Column Fluctuations in the H2O Maser Galaxy NGC 4258 from Weeks to Years

We report monitoring of the 0.3-10 keV spectrum of NGC4258 with XMM over 1.5 years.We als o report reprocessing of an overlapping series of archival Chandra observations. By including earlier ASCA and SAX observations, we present a new, nine-year time series of models fit to the X-ray spectrum of NGC4258. Over the nine years, the photoelectric absorbing column (~10^23 cm^-2) did not vary detectably, except for a ~40% drop between two ASCA epochs separated by 3 years and a ~60% rise between two XMM epochs separated by just 5 months. In contrast, factor of 2-3 changes are seen in absorbed flux on the timescale of years. These are uncorrelated with changes in absorbing column and indicative of central engine variability. The most rapid change in luminosity (5-10 keV) that we detect is ~30% over 19 days. The warped disk, a known source of H2O maser emission in NGC4258, is believed to cross the line of sight to the central engine. We propose that the variations in absorbing column arise from inhomogeneities sweeping across the line of sight in the rotating disk at the radius where the disk crosses the line of sight. We estimate that the inhomogeneities are ~10^15 cm in size at the crossing radius of 0.29 pc, slightly smaller than the expected scale height of the disk. This result thus provides strong evidence that the warped accretion disk is the absorber. This is the first direct confirmation that obscuration in type-2 AGN may, in some cases, arise in thin, warped accretion disks, rather than in geometrically thick tori. We do not detect Fe Kalpha line emission in any of our XMM spectra. We do not observe evidence of absorption lines in the XMM or reprocessed Chandra data.

astro-ph↗

arXiv2000

Four Years of Extreme Ultraviolet Observations of Markarian 421. I: Spectral Analysis

We analyzed the ~950 ks of spectroscopic data accumulated by the Extreme Ultraviolet Explorer (EUVE) satellite between 1994 and 1997 for the BL Lacertae object Markarian 421. The EUV spectrum is well detected in the 70-110 A (112-177 eV) range and can be fitted by a power law model plus an absorption feature in the ~71-75 A range. Previous studies of EUV absorption features in MRK 421 and in the other EUV bright BL Lac object, PKS2155-304, explain this absorption feature as a superposition of Doppler-smeared absorption lines (mainly L- and M-shell transitions of Mg and Ne) originating in high-velocity gas clouds ionized by the beamed continuum of the associated relativistic jet. We show that, for example, Fe IX L could also be a possibility consistent with the marginal detection of oxygen absorption lines in the X-ray range. However physical models are highly sensitive to the assumptions on the photoionizing continuum and the surrounding gas.

astro-ph↗

arXiv2000

Four Years of Extreme Ultraviolet Observations of Markarian 421: II. Temporal Analysis

The Extreme Ultraviolet Explorer (EUVE) satellite accumulated ~one million seconds of public data between 1994 and 1997 for the BL Lacertae object Markarian 421. This is the second of two papers in which we present the results of spectral and temporal analysis of this EUVE data set. We analyze in the present paper the imaging data by means of power spectrum and structure function techniques, while the spectral analysis is presented in a companion paper. We find for MRK 421 a power spectrum with slope -2.14 +- 0.28 with a break at ~3 days. This is the first time that a break in the power spectrum of a BL Lacertae object has been found. We also find evidence of non-stationarity for MRK 421 EUV emission

astro-ph↗

arXiv1998

Mrk421: EUVE observations from 1994 to 1997

We present spectral and timing analysis of all the data collected by the Extreme Ultraviolet Explorer for the BL Lac object Mrk 421 from 1994 to 1997. During these years Mrk 421 has been observed by EUVE 4 times with the DS/Spectrograph and 2 times with the imaging telescopes for a total of ~1.4 millions seconds. The total EUVE light curve seems to be smoothly varying on the long time-scale while on a shorter time-scale there is evidence of an EUVE flare correlated to the 1995 TeV flare. We analysed the three spectral data set in an homogenous way using the proper off-axis calibrations and checked for the existence of absorption features around ~70 A (Kartje et al.,97,ApJ,474,630). We also show the first power spectrum analysis of the Mrk 421 EUVE lightcurves and a comparison with the predictions by theoretical models (e.g. Celotti et al.,1991,ApJ,377,403).

astro-ph↗

arXiv1996

A deep ROSAT Survey X: X-ray Luminous Narrow Emission Line Galaxies

X-ray luminous narrow emision-line galaxies (NELG) have been previously identified and proposed as an important class of extragalactic X-ray sources, with a potentially significant contribution to the total extragalactic X-ray flux at energies below $\sim$ 10 keV. In order to investigate and clarify this possibility, we have used a sample of NELG found in 5 deep ROSAT fields and similar samples belonging to the Cambridge-Cambridge ROSAT Serendipity Survey and to the {\it Einstein} Observatory Extended Medium Sensitivity Survey sample. The principal results of this investigation are as follows: a) for a given optical luminosity, the typical X-ray luminosity of NELGs is about one or two orders of magnitude higher than that of normal galaxies; b) the ratio of the surface density of NELGs compared with BLAGN increases from about 0.04 at fx >= 6 x 10^{-13} erg cm^{-2} s^{-1} to about 0.1 at fx >= 10^{-14} erg cm^{-2} s^{-1}, suggesting that the surface density of NL galaxies might be very close to that of BLAGN at fx ~ 10^{-15} erg cm^{-2} s^{-1}; c) we find that these objects are described by a cosmological evolution rate similar to that of soft X-ray selected BLAGN; d) the de-evolved (z=0) XLF of NELGs in the luminosity range 10^{41} - 5 x 10^{43} erg s^{-1} is steeper than the BLAGN (z=0) XLF in the same luminosity interval. Their spatial density is significantly lower than the spatial density of X-ray selected BLAGN at Lx(z=0) ~ 5 x 10^{43} erg s^{-1}, but this difference decreases at lower luminosities such that at Lx(z=0) < 10^{42} erg s^{-1} the spatial density of NELGs is very close to that of BLAGN. The implications of these results for the contribution of this class of objects to the cosmic X-ray background are discussed.

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