- ID:
- ivo://CDS.VizieR/J/ApJ/876/53
- Title:
- Chandra X-ray point sources in the Fornax cluster
- Short Name:
- J/ApJ/876/53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Based on archival Chandra observations with a total exposure of 1.3Ms, we study X-ray point sources in the Fornax cluster of galaxies, with the primary aim of searching for intracluster X-ray source populations. We detect 1177 point sources out to a projected radius of ~30' (~180kpc) from the cluster center and down to a limiting 0.5-8keV luminosity of ~3x10^37^erg/s. We construct the source surface density profile, after excluding sources associated with foreground stars, known globular clusters, ultra-compact dwarfs, and galactic nuclei. From this profile we statistically identify ~183 excess sources that are not associated with the bulk stellar content of the individual member galaxies of Fornax, nor with the cosmic X-ray background. Taking into account Poisson error and cosmic variance, the cumulative significance of this excess is at the >~2{sigma} level (with a maximum of 3.6{sigma}) outside three effective radii of the central giant elliptical, NGC 1399. The luminosity function of the excess sources is found to be significantly steeper than that of the GC-hosting sources (presumably low-mass X-ray binaries (LMXBs)), disfavoring the possibility that unidentified GCs are primarily responsible for the excess. We show that a large fraction of the excess can be related to the extended stellar halo of NGC 1399 and/or the diffuse intracluster light, thus providing strong evidence for the presence of intracluster X-ray sources in Fornax, the second unambiguous case for a galaxy cluster after Virgo. Other possible origins of the excess, including supernova-kicked LMXBs and stripped nucleated dwarf galaxies are discussed.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/758/15
- Title:
- Chandra X-ray point sources of NGC 300
- Short Name:
- J/ApJ/758/15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the source catalog of a new Chandra ACIS-I observation of NGC 300 obtained as part of the Chandra Local Volume Survey. Our 63ks exposure covers ~88% of the D_25_ isophote (R{approx}6.3kpc) and yields a catalog of 95 X-ray point sources detected at high significance to a limiting unabsorbed 0.35-8 keV luminosity of ~10^36^erg/s. Sources were cross-correlated with a previous XMM-Newton catalog, and we find 75 "X-ray transient candidate" sources that were detected by one observatory, but not the other. We derive an X-ray scale length of 1.7+/-0.2kpc and a recent star formation rate of 0.12M_{sun}_/yr in excellent agreement with optical observations. Deep, multi-color imaging from the Hubble Space Telescope, covering ~32% of our Chandra field, was used to search for optical counterparts to the X-ray sources, and we have developed a new source classification scheme to determine which sources are likely X-ray binaries, supernova remnants, and background active galactic nucleus candidates. Finally, we present the X-ray luminosity functions (XLFs) at different X-ray energies, and we find the total NGC 300 X-ray point-source population to be consistent with other late-type galaxies hosting young stellar populations (<~50Myr). We find that XLF of sources associated with older stellar populations has a steeper slope than the XLF of X-ray sources coinciding with young stellar populations, consistent with theoretical predictions.
- ID:
- ivo://CDS.VizieR/J/ApJ/635/214
- Title:
- Chandra X-ray sources and NIR identifications
- Short Name:
- J/ApJ/635/214
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the Chandra Advanced CCD Imaging Spectrometer Imaging array (ACIS-I), we have carried out a deep hard X-ray observation of the Galactic plane region at (l,b)~(28.5{deg}, 0.0{deg}), where no discrete X-ray source had been reported previously. We have detected 274 new point X-ray sources (4{sigma} confidence), as well as strong Galactic diffuse emission within two partially overlapping ACIS-I fields (~250arcmin^2^ in total). The point-source sensitivity was 3x10^-15^ergs/s/cm^2^ in the hard X-ray band (2-10keV) and 2x10^-16^ergs/s/cm^2^ in the soft band (0.5-2keV). The sum of all the detected point-source fluxes accounts for only 10% of the total X-ray flux in the field of view. Following up the Chandra observation, we have performed a near-infrared (NIR) survey with SofI at ESO/NTT. Almost all the soft X-ray sources have been identified in the NIR, and their spectral types are consistent with main-sequence stars, suggesting that most of them are nearby X-ray-active stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/669/765
- Title:
- Chandra X-ray sources in LALA Cetus field
- Short Name:
- J/ApJ/669/765
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The 174ks Chandra Advanced CCD Imaging Spectrometer exposure of the Large Area Lyman Alpha Survey (LALA) Cetus field is the second of the two deep Chandra images on LALA fields. In this paper we present the Chandra X-ray sources detected in the Cetus field, along with an analysis of X-ray source counts, stacked X-ray spectrum, and optical identifications. A total of 188 X-ray sources were detected: 174 in the 0.5-7.0keV band, 154 in the 0.5-2.0keV band, and 113 in the 2.0-7.0keV band. The X-ray source counts were derived and compared with LALA field (172ks exposure).
- ID:
- ivo://CDS.VizieR/J/ApJ/561/189
- Title:
- Chandra X-ray sources in M101
- Short Name:
- J/ApJ/561/189
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A deep (98.2ks) Chandra Cycle 1 observation has revealed a wealth of discrete X-ray sources as well as diffuse emission in the nearby face-on spiral galaxy M101. From this rich data set we have created a catalog of the 110 sources from the S3 chip detected with a significance of greater than 3{sigma}. This detection threshold corresponds to a flux of ~10^-16^ergs/cm^2^/s and a luminosity of ~10^36^ergs/s for a distance to M101 of 7.2Mpc. The sources display a distinct correlation with the spiral arms of M101 and include a variety of X-ray binaries, supersoft sources, supernova remnants, and other objects of which only ~27 are likely to be background sources.
- ID:
- ivo://CDS.VizieR/J/ApJ/657/286
- Title:
- Chandra X-ray sources in M30 (NGC 7099)
- Short Name:
- J/ApJ/657/286
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the detection of six discrete, low-luminosity (LX<10^33^erg/s) X-ray sources, located within 12" of the center of the collapsed-core globular cluster M30 (NGC 7099), and a total of 13 sources within the half-mass radius, from a 50ks Chandra ACIS-S exposure.
- ID:
- ivo://CDS.VizieR/J/ApJ/598/969
- Title:
- Chandra X-ray sources in NGC 3556
- Short Name:
- J/ApJ/598/969
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a 60ks Chandra ACIS-S observation of the isolated edge-on spiral galaxy NGC 3556, together with a multiwavelength analysis of various discrete X-ray sources and diffuse X-ray features.
- ID:
- ivo://CDS.VizieR/J/A+A/460/133
- Title:
- Chandra X-ray sources in NGC 2362
- Short Name:
- J/A+A/460/133
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We observed the young cluster NGC 2362 in X-rays with Chandra ACIS-I, and detected 387 point X-ray sources, most of which are shown to be cluster members. We report here the list of all detected X-ray sources and their basic X-ray properties, and report separately their identifications with optical stars, using data from Moitinho et al. (2001ApJ...563L..73M; UBVRI photometry) and Dahm (2005, Cat. <J/AJ/130/1805>; H{alpha} data). We include in the second table a classification of optically-identified X-ray sources, based on position in the HR diagram, which helps to separate rather clearly cluster members from field objects.
- ID:
- ivo://CDS.VizieR/J/ApJ/697/224
- Title:
- Chandra X-ray sources in {omega} Cen
- Short Name:
- J/ApJ/697/224
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze a ~70ks Chandra Advanced CCD Imaging Spectrometer exposure of the globular cluster {omega} Cen (NGC 5139). The ~17'x17' field of view fully encompasses three core radii and almost twice the half-mass radius. We detect 180 sources to a limiting flux of ~4.3x10^-16^erg/cm^2^/s (L_x_=1.2x10^30^erg/s at 4.9kpc). After accounting for the number of active galactic nuclei and possible foreground stars, we estimate that 45-70 of the sources are cluster members. Four of the X-ray sources have previously been identified as compact accreting binaries in the cluster - three cataclysmic variables (CVs) and one quiescent neutron star. Correlating the Chandra positions with known variable stars yields eight matches, of which five are probable cluster members that are likely to be binary stars with active coronae. Extrapolating these optical identifications to the remaining unidentified X-ray source population, we estimate that 20-35 of the sources are CVs and a similar number are active binaries. This likely represents most of the CVs in the cluster, but only a small fraction of all the active binaries.
- ID:
- ivo://CDS.VizieR/J/ApJ/582/382
- Title:
- Chandra X-ray sources in Orion Nebula Cluster
- Short Name:
- J/ApJ/582/382
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this first of two companion papers on the Orion Nebula Cluster (ONC), we present our analysis of a 63ks Chandra HRC-I observation that yielded 742 X-ray detections within the 30'x30' field of view. To facilitate our interpretation of the X-ray image, here we collect a multiwavelength catalog of nearly 2900 known objects in the region by combining 17 different catalogs from the recent literature. We define two reference groups: an infrared sample, containing all objects detected in the K band, and an optical sample comprising low-extinction, well-characterized ONC members. We show for both samples that field object contamination is generally low. Our X-ray sources are primarily low-mass ONC members. The detection rate for optical sample stars increases monotonically with stellar mass from zero at the brown dwarf limit to ~100% for the most massive stars but shows a pronounced dip between 2 and 10M_{sun}_. We determine L_X_ and L_X_/L_bol_ or all stars in our optical sample and utilize this information in our companion paper to study correlations between X-ray activity and other stellar parameters.