Classifying X‐Ray Sources in External Galaxies from X‐Ray Colors

Prestwich, Andrea; Irwin, Jimmy A.; Kilgard, R. E.; Krauss, M. I.; Zezas, A.; Primini, F. A.; Kaaret, Philip; Boroson, Bram

doi:10.1086/377366

Cited by 97 publications

(161 citation statements)

References 28 publications

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“…Hardness-ratio diagrams are a straightforward way to classify sources in general, especially for sources that do not have sufficient number of counts to allow spectral fitting (Kim et al 1992;Prestwich et al 2003). From the counts extracted from the three different bands mentioned in x 2 we construct two colors, a soft color and a hard color.…”

Section: Point Source Colorsmentioning

confidence: 99%

“…The results for the different observations are shown in Figure 2. Following Prestwich et al (2003), we consider here only sources with more than 20 detected counts in the full band to somewhat reduce statistical errors on the colors. The errors on the counts are computed with the Gehrels approximation (Gehrels 1986); errors on the colors are computed using standard error propagation.…”

Section: Point Source Colorsmentioning

confidence: 99%

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The X‐Ray Binary Population in M33. I. Source List and Luminosity Function

Grimm¹,

McDowell²,

Zezas³

et al. 2005

ASTROPHYS J SUPPL S

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In this paper we present the source list for three Chandra observations of the Local Group galaxy M33. The observations are centered on the nucleus and on the star-forming region NGC 604. We detect a total of 261 sources in an area of $0.2 deg 2 down to a flux limit of 3 ; 10 À16 ergs s À1 cm À2 , which corresponds to a luminosity of $2 ; 10 34 ergs s À1 at a distance of 840 kpc. From the source list we construct the luminosity functions of sources observed in M33. If we take into account background contamination, the luminosity functions are consistent with those of other star-forming galaxies. In addition, the combination of X-ray color analysis and the existence of ''blue'' optical counterparts strongly indicates that the X-ray point-source population in M33 consists of young objects. Above 3 ; 10 35 ergs s À1 there are few X-ray sources in the locus of the X-ray hardness ratio diagram that is generally populated by low-mass X-ray binaries.

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Section: Point Source Colorsmentioning

confidence: 99%

Section: Point Source Colorsmentioning

confidence: 99%

The X‐Ray Binary Population in M33. I. Source List and Luminosity Function

Grimm¹,

McDowell²,

Zezas³

et al. 2005

ASTROPHYS J SUPPL S

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show abstract

“…Hardness ratios can provide information about the X-ray properties of faint sources, for which the spectral fitting is not possible (see e.g. Prestwich et al 2003). The hardness ratios calculated for each source are listed in Table B.1.…”

Section: Spectral Analysis and Hardness Ratios Of Point Sourcesmentioning

confidence: 99%

XMM-Newtonobservation of the interacting galaxies NGC 1512 and NGC 1510

Ducci¹,

Kavanagh²,

Sasaki³

et al. 2014

A&A

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Context. The galaxy NGC 1512 is interacting with the smaller galaxy NGC 1510 and shows a peculiar morphology, characterised by two extended arms immersed in an HI disc whose size is about four times larger than the optical diameter of NGC 1512. Aims. For the first time we performed a deep X-ray observation of the galaxies NGC 1512 and NGC 1510 with XMM-Newton to gain information on the population of X-ray sources and diffuse emission in a system of interacting galaxies. Methods. We identified and classified the sources detected in the XMM-Newton field of view by means of spectral analysis, hardnessratios calculated with a Bayesian method, X-ray variability, and cross-correlations with catalogues in optical, infrared, and radio wavelengths. We also made use of archival Swift (X-ray) and Australia Telescope Compact Array (radio) data to better constrain the nature of the sources detected with XMM-Newton. Results. We detected 106 sources in the energy range of 0.2−12 keV, out of which 15 are located within the D 25 regions of NGC 1512 and NGC 1510 and at least six sources coincide with the extended arms. We identified and classified six background objects and six foreground stars. We discussed the nature of a source within the D 25 ellipse of NGC 1512, whose properties indicate a quasi-stellar object or an intermediate ultra-luminous X-ray source. Taking into account the contribution of low-mass X-ray binaries and active galactic nuclei, the number of high-mass X-ray binaries detected within the D 25 region of NGC 1512 is consistent with the star formation rate obtained in previous works based on radio, infrared optical, and UV wavelengths. We detected diffuse X-ray emission from the interior region of NGC 1512 with a plasma temperature of kT = 0.68 (0.31−0.87) keV and a 0.3-10 keV X-ray luminosity of 1.3 × 10 38 erg s −1 , after correcting for unresolved discrete sources.

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“…following the convention used in Ramsay & Wu (2006) in studying the Sagittarius and Carina dwarf galaxies and first introduced by Prestwich et al (2003) and Soria & Wu (2003) S, M, and H correspond to the count rates in 0.3-1 keV, 1-4 keV, and 4−10 keV energy bands.…”

Section: X-ray Colors and X-ray-to-nir Flux Ratiosmentioning

confidence: 99%

AnXMM-Newtonsearch for X-ray sources in the Fornax dwarf galaxy

Nucita

Manni

Paolis

et al. 2013

A&A

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We report the results of a deep archive XMM-Newton observation of the Fornax spheroidal galaxy that we analyzed with the aim of fully characterizing the X-ray source population (in most of the cases likely to be background active galactic nuclei) detected towards the target. A cross correlation with the available databases allowed us to find a source that may be associated with a variable star belonging to the galaxy. We also searched for X-ray sources in the vicinity of the Fornax globular clusters GC 3 and GC 4 and found two sources probably associated with the respective clusters. The deep X-ray observation was also suitable for the search of the intermediate-mass black hole (of mass 10 4 M ) expected to be hosted in the center of the galaxy. In the case of Fornax, this search is extremely difficult since the galaxy centroid of gravity is poorly constrained because of the large asymmetry observed in the optical surface brightness. Since we cannot firmly establish the existence of an X-ray counterpart of the putative black hole, we put constraints only on the accretion parameters. In particular, we found that the corresponding upper limit on the accretion efficiency, with respect to the Eddington luminosity, is as low as a few 10 −5 .

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Classifying X‐Ray Sources in External Galaxies from X‐Ray Colors

Cited by 97 publications

References 28 publications

The X‐Ray Binary Population in M33. I. Source List and Luminosity Function

The X‐Ray Binary Population in M33. I. Source List and Luminosity Function

XMM-Newtonobservation of the interacting galaxies NGC 1512 and NGC 1510

AnXMM-Newtonsearch for X-ray sources in the Fornax dwarf galaxy

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