- ID:
- ivo://nasa.heasarc/ngc4382cxo
- Title:
- NGC 4382 Chandra LMXB Catalog
- Short Name:
- NGC4382CXO
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The authors used the Chandra X-Ray Observatory ACIS-S3 to image the X-ray-faint elliptical galaxy NGC 4365 and the lenticular galaxy NGC 4382. This table presents only the NGC 4382 results; however, the results for NGC 4365 are also available in <a href="ngc4365cxo.html">a separate table</a>. NGC 4382 was observed on 2001 May 29-30 for 39749 s. The observations resolved much of the X-ray emission into 58 sources for NGC 4382, most of which are low-mass X-ray binaries (LMXBs) associated with the galaxy. Within two effective radii of NGC 4382, about 22% of the counts were resolved into sources, 33% were attributed to unresolved LMXBs, and 45% were attributed to diffuse gas. The authors defined two hardness ratios: HR21 = (M - S)/(M + S) and HR31 = (H - S)/(H + S), where S, M, and H are the total counts in the soft (0.3 - 1 keV), medium (1 - 2 keV), and hard (2 - 10 keV) bands, respectively. This table was created by the HEASARC in June 2018 based upon the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/599/218">CDS Catalog J/ApJ/599/218</a> file table2.dat. This is a service provided by NASA HEASARC .
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- ID:
- ivo://nasa.heasarc/ngc4365cxo
- Title:
- NGC 4365 Chandra LMXB Catalog
- Short Name:
- NGC4365CXO
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The authors used the Chandra X-Ray Observatory ACIS-S3 to image the X-ray-faint elliptical galaxy NGC 4365 and the lenticular galaxy NGC 4382. This table presents only the NGC 4365 results; however, the results for NGC 4382 are also available in <a href="ngc4382cxo.html">a separate table</a>. NGC 4365 was observed on 2001 June 23 with a live exposure of 40429 s. The observations resolved much of the X-ray emission into 99 sources for NGC 4365, most of which are low-mass X-ray binaries (LMXBs) associated with the galaxy. Within one effective radius of NGC 4365, about 45% of the counts were resolved into sources, 30% were attributed to unresolved LMXBs, and 25% were attributed to diffuse gas. The authors identified 18 out of the 37 X-ray sources in a central field in NGC 4365 with globular clusters. The authors defined two hardness ratios: HR21 = (M - S)/(M + S) and HR31 = (H - S)/(H + S), where S, M, and H are the total counts in the soft (0.3 - 1 keV), medium (1 - 2 keV), and hard (2 - 10 keV) bands, respectively. This table was created by the HEASARC in June 2018 based upon the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/599/218">CDS Catalog J/ApJ/599/218</a> file table1.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc6530oid
- Title:
- NGC 6530 Chandra Point Source Optical/IR Identifications Catalog
- Short Name:
- NGC6530OID
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The authors have obtained astrometry and BVI photometry, down to a V magnitude of ~22, of the very young open cluster NGC 6530, from observations taken with the Wide Field Imager (WFI) camera at the MPG/ESO 2.2m Telescope. They have positionally matched their optical catalog with the list of X-ray sources found in a Chandra-ACIS observation of this cluster (Damiani et al. 2004, ApJ, 608, 781: available in Browse both via links from this table and also as the NGC6530CXO table), finding a total of 828 stars in common, 90% of which are pre-main sequence stars in NGC 6530. The data used in this work come from the combination of optical BVI images taken with the WFI camera made on 27-28 July 2000, a 60 ks Chandra ACIS X-ray observation, and public near-infrared data from the All-Sky Catalog of Point Sources of the Two Micron All Sky Survey (2MASS, CDS Cat. <II/24>). The total number of optical sources falling in the Chandra FOV is 8956, while the Damiani et al. (2004, ApJ, 608, 781) Catalog contains 884 X-ray sources, who concluded that at least 90% of the X-ray sources are very probable cluster members. To cross-correlate the X-ray and optical catalogs, the authors used a matching distance of < 4 sigmaX, where sigmaX is the the X-ray positional error, or 1.5", whichever is smaller, after a systematic shift between the X-ray and WFI positions of 0.2" in RA and -0.26" in Dec had been included. This resulted in a number of multiple identifications, among which 4 turned into unique identifications when a reduced distance of 1.5" was used. This finally resulted in 721 single, 44 double, and 3 triple identifications in the optical catalog; in addition, one X-ray source has 4 optical identifications, and another has 6 optical identifications. The total number of X-ray sources with WFI counterparts is therefore 770; of them, only 15 X-ray identified stars come from the Sung et al. (2000, AJ, 120, 333) Catalog and are not in the WFI Catalog. The total number of optical sources with an X-ray counterpart is 828. The agreement between X-ray and WFI optical positions is excellent in most cases, with offsets below 1". This database table was created by the HEASARC in February 2007, based on CDS table J/A+A/430/941/table5.dat This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc1332cxo
- Title:
- NGC 1332 Chandra X-Ray Compact Source Catalog
- Short Name:
- NGC1332CXO
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- Chandra ACIS-S3 (Advanced CCD Imaging Spectrometer) observations of the nearby S0 galaxy NGC 1332 resolve much of the X-ray emission into 73 point sources, of which 37 lie within the D<sub>25</sub> isophote. The remaining galaxy emission comprises hot, diffuse gas and unresolved sources and is discussed in two companion papers. The point-source X-ray luminosity function (XLF) shows the characteristic break seen in other early-type galaxies at ~2 x 10<sup>38</sup> ergs s<sup>-1</sup>. After applying corrections for detection incompleteness at low luminosities due to source confusion and contamination from diffuse galactic emission, the break vanishes and the data are well described as a single power law. This result casts further doubt on there being a "universal" XLF break in early-type galaxies, marking the division between neutron star and black hole systems. The logarithmic slope of the differential XLF (dN/dL), beta = 2.7 +/- 0.5, is marginally (~2.5 sigma) steeper than has been found for analogous completeness-corrected fits of other early-type galaxies but closely matches the behavior seen at high luminosities in these systems. Two of the sources within D<sub>25</sub> are ultraluminous X-ray sources (ULXs), although neither have LX > 2 x 10<sup>39</sup> ergs s<sup>-1</sup>. The absence of very luminous ULXs in early-type galaxies suggests a break in the XLF slope at ~1-2 x 10<sup>39</sup> ergs s<sup>-1</sup>, although the data were not of sufficient quality to constrain such a feature in NGC 1332. The sources have a spatial distribution consistent with the optical light and display a range of characteristics that are consistent with an LMXB population. The general spectral characteristics of the individual sources, as well as the composite source spectra, are in good agreement with observations of other early-type galaxies, although a small number of highly absorbed sources are seen. Two sources have very soft spectra, two show strong variability, indicating compact binary nature, and one source shows evidence of an extended radial profile. The authors do not detect a central source in NGC 1332, but find a faint (L<sub>X</sub> = 2 +/- 1 x 10<sup>38</sup> ergs s<sup>-1</sup>) point source coincident with the center of the companion dwarf galaxy NGC 1331. The region of sky containing NGC 1332 was observed with the ACIS instrument aboard Chandra between 2002 September 19 10:39 and September 20 02:59 UTC for a nominal ~60 ksec exposure.. This table contains the 73 bona fide X-ray compact sources detected in this observation, excluding one source centered within 1" of the galaxy centroid that is actually the central part of the diffuse galactic emission, one source within the D<sub>25</sub> isophote of the neighboring galaxy NGC 1331, and one source with no photons within the 0.5-7.0 keV band which is likely to be spurious. The spatial extent of 72 of the 73 sources is consistent with the instrumental PSF. One source (number 14) is clearly more extended than the PSF. This table was created by the HEASARC in May 2018 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/612/848">CDS Catalog J/ApJ/612/848</a> file table1.dat, the list of detected X-ray sources in the Chandra observation of NGC 1332. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc1068cxo
- Title:
- NGC 1068 Chandra X-Ray Compact Source Catalog
- Short Name:
- NGC1068CXO
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains some of the results from a study of the compact X-ray source population in the Seyfert 2 galaxy NGC 1068, imaged with a 50-ks Chandra observation. The authors find a total of 84 compact sources on the ACIS-S3 chip, of which 66 are located within the 25.0 B-mag/arcsec<sup>2</sup> isophote of the galactic disk of NGC 1068. In the reference paper, the spectra of the 21 X-ray sources with at least 50 counts were modeled with both multicolor disk blackbody and power-law models. The power-law model provides the better description of the spectrum for 18 of these sources. For fainter sources, the spectral index was estimated from the hardness ratio. Five sources have 0.4-8 keV intrinsic luminosities greater than 10<sup>39</sup> ergs s<sup>-1</sup>, assuming that their emission is isotropic and that they are associated with NGC 1068. The authors refer to these sources as intermediate-luminosity X-ray objects (IXOs). If these five sources are X-ray binaries accreting with luminosities that are both sub-Eddington and isotropic, then the implied source masses are >~7 solar masses, and so they are inferred to be black holes. Most of the spectrally modeled sources have spectral shapes similar to Galactic black hole candidates. However, the brightest compact source in NGC 1068 has a spectrum that is much harder than that found in Galactic black hole candidates and other IXOs. The brightest source also shows large amplitude variability on both short-term and long-term timescales, with the count rate possibly decreasing by a factor of 2 in ~2 ks during this Chandra observation, and the source flux decreasing by a factor of 5 between this observation and the grating observations taken just over 9 months later. The ratio of the number of sources with luminosities greater than 2.1 x 10<sup>38</sup> ergs s<sup>-1</sup> in the 0.4-8 keV band to the rate of massive (>5 solar masses) star formation is the same, to within a factor of 2, for NGC 1068, the Antennae, NGC 5194 (the main galaxy in M51), and the Circinus galaxy. This suggests that the rate of production of X-ray binaries per massive star is approximately the same for galaxies with currently active star formation, including "starbursts." The authors were concerned with the study of the discrete X-ray source population in NGC 1068, imaged within the 8.4 arcmin x 8.4 arcmin (35.3 kpc x 35.3 kpc) field of view of the ACIS S3 chip. Images were extracted from the reprocessed level 2 events file in soft (0.4-1.5 keV), hard (1.5-5.0 keV) and full (0.4-5.0 keV) energy bands. The authors used the CIAO program wavdetect to search the images in the three energy bands for discrete sources of X-ray emission. They analyzed the images using wavelet scales in the range from 1 pixel (0.492 arcsec) to 16 pixels (7.87 arcsec), separated by a factor of sqrt(2). The wavelet source detection threshold was set to 10<sup>-6</sup>, which gives approximately one false source for the whole S3 chip. The total number of sources detected by wavdetect in the soft, hard, and full energy band images was 115, 67, and 138, respectively. Each of these sources was examined carefully by eye, and only those 84 sources that appear compact to the eye are included in this source list. This table was created by the HEASARC in August 2015 based on the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/591/138">CDS Catalog J/ApJ/591/138</a> file table1.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc4649cxo
- Title:
- NGC 4649 Chandra X-Ray Discrete Source Catalog
- Short Name:
- NGC4649CXO
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The authors performed a Chandra X-ray observation of the X-ray bright E2 elliptical galaxy NGC 4649 (M 60). In addition to bright diffuse emission, they resolved 165 discrete sources, most of which are presumably low-mass X-ray binaries (LMXBs). As found in previous studies, the luminosity function of the resolved sources is well-fitted by a broken power law. In NGC 4697 and NGC 1553, the break luminosity was comparable to the Eddington luminosity of a 1.4 solar mass neutron star. One possible interpretation of this result is that those sources with luminosities above the break are accreting black holes and those below are mainly accreting neutron stars. The total X-ray spectrum of the resolved sources is well fitted by a hard power law. NGC 4649 was observed on 2000 April 20 on the ACIS-S3 CCD operated at a temperature of -120 C and with a frame time of 3.2 s. In addition to the S3 chip, the ACIS chips I2, I3, S1, S2, and S4 were also turned on for the duration of the observation. Although a number of serendipitous sources were seen on the other chips, the analysis of NGC 4649 in this paper was based on data from the S3 chip alone. The total exposure for the S3 chip was 36,780 s. The discrete X-ray source population on the ACIS S3 image was determined using a wavelet detection algorithm in the 0.3 - 10.0 keV band, and they were confirmed with a local cell detection method. The authors used the CIAO, WAVDETECT, and CELLDETECT programs. The high spatial resolution of Chandra implies that the sensitivity to point sources is not affected very strongly by the background. Thus, the source detection was done using the entire exposure of 36,780 s, including periods with background flares. The wavelet source detection significance threshold was set at 10<sup>-6</sup>, which implies that less than 1 false source (due to a statistical fluctuation in the background) would be detected in the entire S3 image. This significance threshold approximately corresponds to requiring that the source flux be determined to better than 3 sigma. This table was created by the HEASARC in April 2007 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/600/729">CDS catalog J/ApJ/600/729</a> file table1.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc1600cxo
- Title:
- NGC 1600 Chandra X-Ray Discrete Source Catalog
- Short Name:
- NGC1600CXO
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The authors observed the X-ray-bright E3 galaxy NGC 1600 and nearby members of the NGC 1600 group with the Chandra X-Ray Observatory ACIS-S3 to study their X-ray properties. NGC 1600 is the brightest member of the NGC 1600 group; NGC 1601 (1.6 arcminutes away) and NGC 1603 (2.5 arcminutes away) are the two nearest galaxies, both of which are non-interacting members. The authors adopted the 2MASS Point Source Catalog position of J2000.0 RA = 04<sup>h</sup> 31<sup>m</sup> 39.87<sup>s</sup>, Dec = -05<sup>o</sup> 05' 10.5" as the location of the center of the NGC 1600 galaxy. Unresolved emission dominates the Chandra observation; however, some of the emission is resolved into 71 sources, most of which are low-mass X-ray binaries associated with NGC 1600. Twenty-one of the sources have L<sub>X</sub> > 2 x 10<sup>39</sup> ergs/s (0.3-10.0 keV; assuming they are at the distance of NGC 1600 of 59.98 Mpc), marking them as ultraluminous X-ray point source (ULX) candidates. NGC 1600 may have the largest number of ULX candidates in an early-type galaxy to date; however, cosmic variance in the number of background active galactic nuclei cannot be ruled out. The spectrum and luminosity function (LF) of the resolved sources are more consistent with sources found in other early-type galaxies than with sources found in star-forming regions of galaxies. The source LF and the spectrum of the unresolved emission both indicate that there are a large number of unresolved point sources. The authors propose that these sources are associated with globular clusters (GCs) and that NGC 1600 has a large GC specific frequency. Observations of the GC population in NGC 1600 would be very useful for testing this prediction. NGC 1600 was observed in two intervals on 2002 September 18-19 (ObsID 4283) and 2002 September 20 (ObsID 4371) with live exposures of 26,783 and 26,752 s, respectively. The first observation showed clear evidence of a major background "flare" in the first 20% of the observation. The second observation had some small fluctuations greater than 20% from the mean rate. After these were filtered, observations 4283 and 4371 had flare-free exposure times of 21,562 and 23,616 s, respectively. This table lists all 71 discrete sources detected by wavdetect over the 0.3-6 keV energy range in the combination of the two observations. The first 3 sources (source numbers 1, 2 and 3) are clearly extended according to the authors. The authors expect 11 +/- 2 foreground/background sources to be present based on the source counts in Brandt et al. (2000, AJ, 119, 2349) and Mushotzky et al. (2000, Nature, 404, 459). The authors determined the observed X-ray hardness ratios for the sources, using the same techniques that they have used previously. They define three hardness ratios as H21 = (M-S)/(M+S), H31 = (H-S)/(H+S), and H32 = (H-M)/(H+M), where S,M, and H are the total counts in the soft (0.3-1 keV), medium (1-2 keV) and hard (2-6 keV) respectively. From their previous definitions, they have reduced the hard band from 2-10 to 2-6 keV: since the 6-10 keV range is dominated by background photons for most sources, this should increase the S/N of the hardness ratio techniques. The hardness ratios measure observed counts, which are affected by Galactic absorption and quantum efficiency (QE) degradation in the Chandra ACIS detectors. In order to compare with other galaxies, it is useful to correct the hardness ratios for these two soft X-ray absorption effects. Therefore, the authors have calculated the intrinsic hardness ratios, denoted by a superscript 0, using a correction factor in each band appropriate to the best-fit spectrum of the resolved sources, and these are what are quoted in this table. This table was created by the HEASARC in May 2018 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/617/262/">CDS Catalog J/ApJ/617/262/</a> file table1.dat, the list of detected discrete X-ray sources in the Chandra observation of the NGC 1600 group. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc1893cxo
- Title:
- NGC 1893 Chandra X-Ray Point Source Catalog
- Short Name:
- NGC1893CXO
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The outer Galaxy, where the environmental conditions are different from the solar neighbourhood, is a laboratory in which it is possible to investigate the dependence of the star formation process on the environmental parameters. The authors investigate the X-ray properties of NGC 1893, a young cluster (~ 1 - 2 Myr) in the outer part of the Galaxy (galactic radius >= 11 kpc), where they expect differences in the disk evolution and in the mass distribution of the stars, so as to explore the X-ray emission of its members and compare it with that of young stars in star forming regions near to the Sun. The authors analyze 5 deep Chandra ACIS-I observations with a total exposure time of 450 ks. Source events of the 1021 X-ray sources have been extracted with the IDL-based routine ACIS-Extract. Using spectral fitting and quantile analysis of X-ray spectra, they derive X-ray luminosities and compare the respective properties of Class II and Class III members. They also evaluate the variability of sources using the Kolmogorov-Smirnov test and identify flares in the lightcurves. The X-ray luminosity of NGC 1893 X-ray members is in the range 10<sup>29.5</sup> - 10<sup>31.5</sup> erg s<sup>-1</sup>. Diskless stars are brighter in X-rays than disk-bearing stars, given the same bolometric luminosity. The authors find that 34% of the 1021 lightcurves appear variable and that they show 0.16 flares per source, on the average. Comparing their results with those relative to the Orion Nebula Cluster, they find that, after accounting for observational biases, the X-ray properties of NGC 1893 and the Orion stars are very similar. The authors conclude that the X-ray properties of stars in NGC 1893 are not affected by the environment and that the stellar population in the outer Galaxy may have the same coronal properties as nearby star-forming regions. The X-ray luminosity properties and the X-ray luminosity function appear to be universal and can therefore be used for estimating distances and for determining stellar properties. This table was created by the HEASARC in March 2012 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/539/A74">CDS Catalog J/A+A/539/A74</a> file catalog.dat, the catalog of 1021 X-ray sources detected towards NGC 1893. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc404cxo
- Title:
- NGC 404 Chandra X-Ray Point Source Catalog
- Short Name:
- NGC404CXO
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains a comprehensive X-ray point-source catalog of NGC 404, the closest face-on (inclination angle of 11 degrees) S0 galaxy to the Milky Way, which was obtained as part of the Chandra Local Volume Survey (CLVS) and originally published in Binder et al. (2013). A new 97-ks Chandra ACIS-S observation of NGC 404 was combined with archival observations for a total exposure of ~123 ks. This survey yields 74 highly significant X-ray point sources and is sensitive to a limiting unabsorbed luminosity of ~6 x 10<sup>35</sup> erg/s in the 0.35-8 keV band. To constrain the nature of each X-ray source, cross-correlations with multi-wavelength data were generated. The authors searched overlapping Hubble Space Telescope (HST) observations for optical counterparts to their X-ray detections, but found only two X-ray sources with candidate optical counterparts. They found 21 likely low-mass X-ray binaries (LMXBs), although this number is a lower limit due to the difficulties in separating LMXBs from background active galactic nuclei (AGN). The X-ray luminosity functions (XLFs) in both the soft and hard energy bands are presented in the 2013 reference paper. The XLFs in the soft band (0.5-2 keV) and the hard band (2-8 keV) have a limiting luminosity at the 90% completeness limit of 10<sup>35</sup> erg/s and 10<sup>36</sup> erg/s, respectively, significantly lower than previous X-ray studies of NGC 404. The authors find the XLFs to be consistent with those of other X-ray populations dominated by LMXBs. However, the number of luminous (>10<sup>37</sup> erg/s) X-ray sources per unit stellar mass in NGC 404 is lower than is observed for other galaxies. The relative lack of luminous XRBs may be due to a population of LMXBs with main-sequence companions formed during an epoch of elevated star formation ~0.5 Gyr ago. NGC 404 was observed during Chandra X-Ray Observatory Cycle 12 on 2010 October 21-22 for 97 ks using the ACIS-S array (Obs. ID 12339). The authors additionally utilized archival observations: NGC 404 was observed on 1999 December 19 (Obs. ID 870) for ~24 ks and on 2000 August 30 (Obs. ID 384) for ~2 ks, both using the ACIS-S array. The authors created images in the following energy bands (keV): 0.35-8.0, 0.35-1.0, 1.0-2.0, 2.0-8.0 with bin sizes of 1, 2, 3, and 4. The iterative source detection strategy that was used is described in Section 2.3 of Binder et al. (2012, ApJ, 758, 15). ACIS-Extract (AE) was run a final time on the source list that was produces after an initial run of wavdetect followed by several iterations of AE, and the Poisson probability of not being a source (pns) value was computed in each of the following nine energy bands: 0.5 - 8.0, 0.5 - 2.0, 2.0 - 8.0, 0.5 - 1.0, 1.0 - 2.0, 2.0 - 4.0, 4.0 - 8.0, 0.35 - 1.0 or 0.35 - 8.0 keV. To be included in the final NGC 404 catalog, a source was required to have a pns value less than 4 x 10<sup>-6</sup> in any of the nine energy bands. The final CLVS source catalog for NGC 404 contains 74 sources. Given the survey size of these NGC 404 observations, there are expected to be ~1.6 false sources included in this NGC 404 final source catalog. Three HST fields were used to search for optical counterparts for each of the X-ray sources. One field (labeled "DEEP") was taken as part of the Advanced Camera for Surveys (ACS) Nearby Galaxy Survey Treasury (ANGST, GO-10915; Dalcanton et al. 2009, ApJS, 183, 67), while the other two shallower fields (labeled "NE" and "SW") were obtained as part of GO-11986. Details of the HST data acquisition and data reduction are provided in Williams et al. (2010, ApJ, 716, 71). This table was created by the HEASARC in September 2015 primarily based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/763/128">CDS Catalog J/ApJ/763/128</a> files table3.dat, table4.dat, table5.dat, table6.dat, table10.dat, table12.dat and table13.dat (Binder et al. 2013) which contain the properties of the 74 Chandra point sources found in this study.and of their multi-wavelength counterparts. As noted above, the HEASARC has added an extra parameter b4_flux which was taken from the machine-readable version of Table 5 of Binder et al. (2015). This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc6357cxo
- Title:
- NGC 6357 Chandra X-Ray Point Source Catalog
- Short Name:
- NGC6357CXO
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This contains some of the results from the first high spatial resolution X-ray study of the massive star-forming region NGC 6357, which were obtained in a 38 ks Chandra/ACIS observation. Inside the brightest constituent of this large H II region complex is the massive open cluster Pismis 24. It contains two of the brightest and bluest stars known, yet remains poorly studied; only a handful of optically bright stellar members have been identified. The authors have investigated the cluster extent and initial mass function and detected ~800 X-ray sources with a limiting sensitivity of ~ 10<sup>30</sup> erg s<sup>-1</sup>: this provides the first reliable probe of the rich intermediate-mass and low-mass population of this massive cluster, increasing the number of known members from optical studies by a factor of ~ 50. The high-luminosity end (log L[2-8 keV] >= 30.3 erg s<sup>-1</sup>) of the observed X-ray luminosity function in NGC 6357 is clearly consistent with a power-law relation as seen in the Orion Nebula Cluster and Cepheus B, yielding the first estimate of NGC 6357's total cluster population, a few times the known Orion population. The long-standing L<sub>X</sub> ~ 10<sup>-7</sup> L<sub>bol</sub> correlation for O stars is confirmed. Twenty-four candidate O stars and one possible new obscured massive YSO or Wolf-Rayet star are presented. Many cluster members are estimated to be intermediate-mass stars from available infrared photometry (assuming an age of ~ 1 Myr), but only a few exhibit K-band excess. The authors report the first detection of X-ray emission from an evaporating gaseous globule at the tip of a molecular pillar; this source is likely a B0-B2 protostar. NGC 6357 was observed on 2004 July 9 with the Imaging Array of the Advanced CCD Imaging Spectrometer (ACIS-I) on board Chandra. Four front-illuminated (FI) CCDs form the ACIS-I, which covers a field of view (FOV) of ~ 17 by 17 arcminutes. The observation was made in the standard Timed Exposure, Very Faint mode, with 3.2 s integration time and 5 pixel by 5 pixel event islands. The total exposure time was 38 ks and the satellite roll angle was 289 degrees. The aim point was centered on the O3 If star Pis 24-1, the heart of the OB association Pismis 24. The Chandra observation ID is 4477. Data reduction started with filtering the Level 1 event list processed by the Chandra X-ray Center pipeline to recover an improved Level 2 event list. To improve absolute astrometry, X-ray positions of ACIS-I sources were obtained by running the wavdetect wavelet-based source detection algorithm within the Chandra Interactive Analysis of Observations (CIAO) package on the original Level 2 event list, using only the central 8 by 8 arcminutes of the field. The resulting X-ray sources were matched to the 2MASS point source catalog. The authors calculated the position offsets between 277 X-ray sources and their NIR counterparts and applied an offset of +0.02" in right ascension (R.A.) and -0.33" in declination to the X-ray coordinates. From an initial list of 910 potential X-ray sources, the authors rejected sources with a P<sub>B</sub> > 1% likelihood of being a background fluctuation. The trimmed source list includes 779 sources, with full-band (0.5 - 8.0 keV) net (background-subtracted) counts ranging from 1.7 to 1837 counts. The 779 valid sources were purposely divided by the authors into two lists: the 665 sources with P<sub>B</sub> < 0.1% make up the primary source list of highly reliable sources (Table 1 in the reference paper; sources with source_type = 'M' in this table), and the remaining 114 sources with P<sub>B</sub> >= 0.1% likelihood of being spurious background fluctuations were listed as tentative sources in Table 2 of the reference paper (source_type = 'T' in this table). The authors believe that most of these tentative sources are likely real detections. This table was created by the HEASARC in October 2007 based on the merger of the electronic versions of Tables 1 (Main Source Catalog) and 2 (Tentative Sources which were obtained from the ApJ website. To help distinguish from which original table entries in this Browse table come from, the HEASARC has created a parameter called source_type which is set to 'M' for sources from Table 1 and to 'T' for sources from Table 2. This is a service provided by NASA HEASARC .
