- ID:
- ivo://nasa.heasarc/ngc6530cxo
- Title:
- NGC 6530 Chandra X-Ray Point Source Catalog
- Short Name:
- NGC6530CXO
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- In a deep 60 ks Chandra ACIS-I X-ray observation of the very young (~ 1.5 - 2.0 Myr) cluster NGC 6530 on 2001 Jun 18-19, the authors have detected 884 X-ray point sources and argue that a very large fraction of them (90%-95%) must be pre-main-sequence (PMS) cluster members, mostly low-mass stars. This is a significant enlargement of the known NGC 6530 stellar population with respect to previous optical studies, including H-alpha surveys. They identify 220 X-ray sources with catalogued stars down to V = 17, while most unidentified sources have fainter counterparts. Moreover, they find an infrared counterpart in the 2MASS (CDS. No. <II/246>) Catalog for 731 X-ray sources. The optically identified cluster X-ray sources are found in a band in the H-R diagram above the main sequence, in the locus of 0.5 - 1.5 Myr PMS stars, with masses down to 0.5 - 1.5 solar masses (M_sun). The pointing direction for the Chandra observation was the NGC 6530 cluster center at RA = 18^h 04^m 24.38^s, Dec = -24^o 21' 05.8" (J2000.0). The PWDetect algorithm found 884 X-ray point sources in the ACIS-I image above a detection significance threshold chosen to ensure only 1 spurious detection on the average. The Sung et al. (2000, AJ, 120, 333; <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/AJ/120/333">CDS Cat. <J/AJ/120/333></a>) = SCB Catalog of optical objects against which the X-ray point source list was compared doed not cover the easternmost 2.25' of the ACIS FOV (RAs later than 18^h 04^m 52^s), notice, which comprises about 13% of the ACIS FOV. There are 46 detected X-ray sources (5.2% of the total) in the area not covered by the SCB Catalog. A matching distance of 4 times the X-ray error radius or 2.0" (whichever is greater) was used to identify optical counterparts to the X-ray sources, after a systematic shift between the X-ray and optical positions of -0.4" and 1.84" in RA and declination, respectively, was applied. The authors estimate that as many as 28 of their 220 optical identifications may be spurious, preferentially those in the outer parts of the FOV where the positional uncertainties are larger. There are 8792 'good' 2MASS sources in the ACIS FOV. A matching distance of 4 times the X-ray error radius or 1.5" (whichever is greater) was used to identify 2MASS counterparts to the X-ray sources, after systematic corrections of 0.3" and 1.75" in RA and declination, respectively, were applied to the 'raw' X-ray positions. There are 13 cases where there are two possible IR counterparts to a single X-ray source, and 2 cases where there are three possible IR Counterparts to a single X-ray source. (Notice that, in such cases, this table contains multiple entries, one for each counterpart, and hence there are 901 entries compared to 884 X-ray sources.) The authors conclude that the plausible number of spurious X-ray-2MASS identifications is between 30 and 50. Overall, there remain 146 X-ray sources with no optical or IR identification. This table was created by the HEASARC in December 2006 based on CDS table J/ApJ/608/781, the file table1.dat. This is a service provided by NASA HEASARC .
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- ID:
- ivo://nasa.heasarc/ngc2362cxo
- Title:
- NGC 2362 Chandra X-Ray Point Source Catalog
- Short Name:
- NGC2362CXO
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains the results of an observation of the young cluster NGC 2362 in X-rays with Chandra ACIS-I in which 387 point X-ray sources, most of which are shown to be cluster members, were detected using PWDetect, a wavelet-based source detection algorithm, with a detection threshold chosen to ensure no more than one spurious detection in the entire ACIS FOV. The table lists all of the detected X-ray sources and their basic X-ray properties, as well as their proposed identifications with optical stars, using data from Moitinho et al. (2001ApJ...563L..73M; UBVRI photometry) and Dahm (2005, <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/AJ/130/1805">CDS Cat. <J/AJ/130/1805></a>; H-alpha data), as well as newer photometric data from Moitinho et al. (2005, in 'Cores to Clusters' [A&SSL, 324], 167). A matching position of less than 4 times the X-ray positional uncertainty of the X-ray source from PWDetect was used. Also included in the table is a classification of the optically-identified X-ray sources, based on their positions in the HR Diagram, which helps to separate rather clearly the cluster members from interloping field objects. This table was created by the HEASARC in March 2007 based on CDS table J/A+A/460/133 files table2.dat and table3.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc6231cx2
- Title:
- NGC 6231 Chandra X-Ray Point Source Catalog 2
- Short Name:
- NGC6231CX2
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- NGC 6231 is a young cluster (age ~2-7 Myr) dominating the Sco OB1 association (distance ~1.59 kpc) with ~100 O and B stars and a large pre-main-sequence stellar population. The authors combine a reanalysis of archival Chandra X-ray data with multi-epoch near-infrared (NIR) photometry from the VISTA Variables in the Via Lactea (VVV) survey and published optical catalogs to obtain a catalog of 2148 probable cluster members. This catalog is 70% larger than previous censuses of probable cluster members in NGC 6231. It includes many low-mass stars detected in the NIR but not in the optical and some B stars without previously noted X-ray counterparts. In addition, the authors identify 295 NIR variables, about half of which are expected to be pre-main-sequence stars. With the more complete sample, they estimate a total population in the Chandra field of 5700-7500 cluster members down to 0.08 M<sub>sun</sub> (assuming a universal initial mass function) with a completeness limit at 0.5 M<sub>sun</sub>. A decrease in stellar X-ray luminosities is noted relative to other younger clusters. However, within the cluster, there is little variation in the distribution of X-ray luminosities for ages less than 5 Myr. The X-ray spectral hardness for B stars may be useful for distinguishing between early-B stars with X-rays generated in stellar winds and B-star systems with X-rays from a pre-main-sequence companion (>35% of B stars). A small fraction of catalog members have unusually high X-ray median energies or reddened NIR colors, which might be explained by absorption from thick or edge-on disks or being background field stars. This work makes use of some basic cluster properties available from the literature. Summaries of older studies are provided by Sana et al. (2006, J/A+A/454/1047), available in <a href="/W3Browse/xmm-newton/ngc6231xmm.html">NGC6231XMM</a>, and Reipurth (2008hsf2.book.....R). Expanded catalogs of cluster members have been provided by Sung et al. (2013, J/AJ/145/37) and Damiani et al. 2016, J/A+A/596/A82 (DMS2016), available at <a href="/W3Browse/chandra/ngc6231cxo.html">NGC6231CXO</a>. Chandra X-ray observations were made using the imaging array on the Advanced CCD Imaging Spectrometer (ACIS-I; Garmire et al. 2003SPIE.4851...28G). This instrument is an array of four CCD detectors that subtends 17'x17'. The target was observed in 2005 July (Sequence 200307; PI: S. Murray) in two observations (ObsID 5372 and 6291), and the data were retrieved from the Chandra Data Archive. The NIR ZYJHK<sub>s</sub> data were obtained from the VVV survey (Minniti et al. 2010NewA...15..433M; Saito et al. 2012, Cat. II/337). VVV is a multi-epoch NIR survey that covers both the Galactic bulge and an adjacent Galactic disk region and was carried out using the 4.1 m VISTA telescope on Cerro Paranal. The VVV data were taken with the VISTA Infrared CAMera (VIRCAM; Dalton et al. 2006SPIE.6269E..0XD), a 4x4 array of Raytheon VIRGO 2048x2048 20 micron pixel detectors with a pixel scale of 0.34". In addition to the VVV photometry, public optical or infrared catalogs are available from surveys and publications. We have included VPHAS+ photometry (Drew et al. 2014, J/MNRAS/440/2036), UBVRI (Johnson-Cousins system) and H-alpha photometry from Sung et al. (2013, J/AJ/145/37), and Spitzer/IRAC photometry from the GLIMPSE survey (Benjamin et al. 2003, Cat. II/293). This table was created by the HEASARC in October 2020 based upon the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/AJ/154/87">CDS Catalog J/AJ/154/87</a> file table1.dat, table3.dat, and table5.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc1333cxo
- Title:
- NGC 1333 Chandra X-Ray Point Source Catalog
- Short Name:
- NGC1333CXO
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- NGC 1333, a highly active star formation region within the Perseus molecular cloud complex, has been observed on 2000 July 12.96 - 13.48 with the ACIS-I detector on board the Chandra X-Ray Observatory. The aim point of the array was 3 29 06.1, +31 19 38 (J2000,0 RA and Dec), the satellite roll angle was 95.7 degrees, and the effective exposure time after removing time intervals contaminated by background flaring was 37.8 ks. In this image with a sensitivity limit in luminosity of ~10<sup>28</sup> erg/s for X-ray sources at the 318 pc distance of NGC 1333, 127 X-ray sources were detected, most with sub-arcsecond positional accuracy. While 32 of these sources appear to be foreground stars and extragalactic background objects, 95 X-ray sources are identified with known cluster members. The X-ray luminosity function of the discovered young stellar object (YSO) population spans a range of log L<sub>X</sub> ~= 28.0 - 31.5 erg s<sup>-1</sup> in the 0.5 - 8 keV band, and the absorption column densities range from log N<sub>H</sub> ~=20 to 23 cm<sup>-2</sup>. Most of the sources have plasma temperatures between 0.6 and 3 keV, but a few sources show higher temperatures up to ~7 keV. Comparison with K-band source counts indicates that all of the known cluster members with K < 12 and about half of the members with K > 12 were detected. (K ~= 11, the peak of the K-band luminosity function, corresponds to 0.2 - 0.4 M_solar stars for a cluster age of ~1 Myr). Seven of the 20 known YSOs in NGC 1333 which are producing jets or molecular outflows were detected, as well as one deeply embedded object without outflows. No evident difference in X-ray emission of young stars with and without outflows is found. This present table contains X-ray, optical and near-infrared information on the 109 X-ray sources that were detected above a source significance threshold of 1 x 10<sup>-6</sup> in any of 3 energy bands: soft: 0.5 - 2.0 keV, hard: 2.0 - 8.0 keV, or full: 0.5 - 8.0 keV, excluding 8 sources that were deemed to be spurious on visual examination of the images. The faintest on-axis source emerging from the wavelet detection procedure has 5 extracted counts, corresponding to a source of log L<sub>X</sub> ~ 28.0 in the total (0.5 - 8.0 keV) band for a source with negligible interstellar absorption (A<sub>V</sub> ~ 1) and a typical source spectrum of a kT ~ 1 keV thermal plasma. This limit increases to 28.6 (29.3) if the absorption is increased to A<sub>V</sub> ~ 5 (10). The sensitivity decreases by a factor of 4 at the edge of the field compared to the central regions. 80 of the significant 109 sources (73%) have counterparts in a non-X-ray band. This table does not include 18 tentative X-ray sources listed in Table 3 of the reference paper that were found by the authors by searching for concentrations of photons spatially coincident with known sources from near-IR, mm/sub-mm, and radio catalogs of this region which did not reach the detection significance given above. Most of these tentative sources are believed to be real sources. This table was created by the HEASARC in March 2007 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/575/354">CDS catalog J/ApJ/575/354</a> files table1.dat and table2.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc2024cxo
- Title:
- NGC 2024 Chandra X-Ray Point Source Catalog
- Short Name:
- NGC2024CXO
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The NGC 2024 Chandra X-Ray Point Source Catalog contains the results of a sensitive 76 ks Chandra observation of the young stellar cluster in NGC 2024, lying at a distance of ~415 pc in the Orion B giant molecular cloud. Previous infrared observations have shown that this remarkable cluster contains several hundred embedded young stars, most of which are still surrounded by circumstellar disks. Thus, it presents a rare opportunity to study X-ray activity in a large sample of optically invisible protostars and classical T Tauri stars (CTTSs) undergoing accretion. Chandra detected 283 X-ray sources, of which 248 were identified with counterparts at other wavelengths, mostly in the near-infrared. Astrometric registration of Chandra images against the Two Micron All Sky Survey (2MASS) resulted in positional offsets of ~0.25" near field center, yielding high confidence identifications of infrared counterparts. The Chandra detections are characterized by hard, heavily absorbed spectra and specular variability. Spectral analysis of more than 100 of the brightest X-ray sources yields a mean V-band extinction of ~10.5 magnitudes and typical plasma energies <kT> ~ 3 keV. Chandra detected all but one of a sample of 27 classical T Tauri stars (CTTSs) identified from previous near- and mid-infrared photometry, and their X-ray and bolometric luminosities are correlated. IRS 2b, which is thought to be a massive embedded late O or early B star that may be the ionizing source of NGC 2024, is detected as an X-ray source. Seven millimeter-bright cores (FIR 1-7) in NGC 2024 that may be protostellar were not detected, with the possible exception of faint emission near the unusual core FIR 4. This table was created by the HEASARC in January 2007 based on CDS table J/ApJ/598/375/table1.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc2808cxo
- Title:
- NGC 2808 Chandra X-Ray Point Source Catalog
- Short Name:
- NGC2808CXO
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains the sources detected in a Chandra X-ray observation of the Galactic globular cluster NGC 2808, as well as the corresponding XMM-Newton data for those sources which have XMM-Newton X-ray counterparts. Using new Chandra X-ray observations and existing XMM-Newton X-ray and Hubble Space Telescope far-ultraviolet observations, the authors aim to detect and identify the faint X-ray sources belonging to NGC 2808 in order to understand their role in the evolution of globular clusters. The authors classify the X-ray sources associated with the cluster by analysing their colors and variability. Previous observations with XMM-Newton and far-ultraviolet observations with Hubble are re-investigated to help identify the Chandra sources associated with the cluster. The authors compare their results to population synthesis models and observations of other Galactic globular clusters. NGC 2808 was observed with the Chandra X-ray Observatory Advanced CCD Imaging Spectrometer-Imager (ACIS-I) on 2007 June 19-21 (28 months after the XMM-Newton observation referred to the reference paper) for two distinct exposures of 46 and 11 kiloseconds. The authors detect 113 sources, of which 16 fall inside the half-mass radius of NGC 2808 and are concentrated towards the cluster core. This table was created by the HEASARC in February 2009 based on the electronic version of Table 1 from the paper which was obtained from the CDS (their catalog J/A+A/490/641 file table1.dat). This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc1399cxo
- Title:
- NGC 1399 Chandra X-Ray Source Catalog
- Short Name:
- NGC1399CXO
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains results from a wide-field study of the globular cluster (GC)/low-mass X-ray binary (LMXB) connection in the giant elliptical NGC 1399. The large field of view of the Advanced Camera for Surveys/WFC, combined with the high resolution of the Hubble Space Telescope and Chandra, allow the authors to constrain the LMXB formation scenarios in elliptical galaxies. They confirm that NGC 1399 has the highest LMXB fraction in GCs of all nearby elliptical galaxies studied so far, even though the exact value depends on galactocentric distance due to the interplay of a differential GC versus galaxy light distribution and the GC color dependence. In fact, LMXBs are preferentially hosted by bright, red GCs out to > 5 R<sub>eff</sub> of the galaxy light. The finding that GCs hosting LMXBs follow the radial distribution of their parent GC population argues against the hypothesis that the external dynamical influence of the galaxy affects the LMXB formation in GCs. On the other hand, field-LMXBs closely match the host galaxy light, thus indicating that they are originally formed in situ and not inside GCs. The authors measure GC structural parameters, finding that the LMXB formation likelihood is influenced independently by mass, metallicity, and GC structural parameters. In particular, the GC central density plays a major role in predicting which GCs host accreting binaries. Finally, this analysis shows that LMXBs in GCs are marginally brighter than those in the field, and in particular the only color-confirmed GC with L<sub>X</sub> > 10<sup>39</sup> erg/s shows no variability, which may indicate a superposition of multiple LMXBs in these systems. The optical data were taken with the ACS on board the HST (GO-10129), in the F606W filter. A detailed description of the HST data and source catalogs are given in Puzia T.H. et al. 2011, in preparation. The X-ray data were retrieved from the Chandra public archive (CXC). The authors selected observations 319 (ACIS-S; 2000 Jan 18) and 1472 (ACIS-I; 2003 May 26). This table contains the list of 230 X-ray sources detected in the overlap region common to Chandra ACIS-I, Chandra ACIS-S and HST ACS observation (see Fig 1 of the reference paper). Details of the X-ray source detection methodology are given in Section 2.2 of the reference paper. This table was created by the HEASARC in January 2013 based on the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/736/90">CDS Catalog J/ApJ/736/90</a> file table3.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc2516xmm
- Title:
- NGC 2516 Cluster XMM-Newton X-Ray Point Source Catalog
- Short Name:
- NGC2516XMM
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains the results from a deep X-ray survey of the young (~ 140 Myr), rich open cluster NGC 2516 obtained with the EPIC camera on board the XMM-Newton satellite. By combining the data from six observations, a high sensitivity, greater than a factor of 5 with respect to recent Chandra observations, has been achieved. Kaplan-Meier estimators of the cumulative X-ray luminosity distribution, statistically corrected for non-member contaminants, were built by the authors and compared to those of the nearly coeval Pleiades cluster. 431 X-ray sources were detected, and 234 of them have as optical counterparts cluster stars spanning the entire NGC 2516 main sequence. On the basis of X-ray emission and optical photometry, 20 new candidate members of the cluster have been identified; at the same time there are 49 X-ray sources without known optical or infrared counterpart. The X-ray luminosities of cluster stars span the range log L<sub>x</sub> (erg s<sup>-1</sup>) = 28.4 - 30.8. The representative coronal temperatures span the 0.3 - 0.6 keV (3.5 - 8 MK) range for the cool component and 1.0 - 2.0 keV (12 - 23 MK) for the hot one; similar values were found in other young open clusters like the Pleiades, IC 2391, and Blanco 1. While no significant differences were found in their X-ray spectra, NGC 2516 solar-type stars are definitely less luminous in X-rays than their nearly coeval Pleiades counterparts. The comparison with a previous ROSAT survey reveals the lack of variability amplitudes larger than a factor of 2 in solar-type cluster stars in a ~ 11 yr time scale, and thus activity cycles like in the Sun are probably absent or have a different period and amplitude in young stars. NGC 2516 has been observed several times with XMM-Newton during the first two years of satellite operations for calibration purposes. The observations used in this analysis span a period of 19 months with exposure times between 10 and 20 ks. All of these observations have been performed with the thick filter. In the combined EPIC datasets the authors detected 431 X-ray sources with a significance level greater than 5.0 sigma, which should lead statistically to at most one spurious source in the field of view. This table was created by the HEASARC in May 2007 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/450/993">CDS catalog J/A+A/450/993</a> files tablea1.dat and tableb1.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc1512xmm
- Title:
- NGC 1512/NGC 1510 XMM-Newton X-Ray Point Source Catalog
- Short Name:
- NGC1512XMM
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- The galaxy NGC 1512 is interacting with the smaller galaxy NGC 1510 and shows a peculiar morphology, characterized by two extended arms immersed in an HI disc whose size is about four times larger than the optical diameter of NGC 1512. The authors have performed the first 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 this system of interacting galaxies. They have identified and classified the sources detected in the XMM-Newton field of view by means of spectral analysis, hardness-ratios calculated with a Bayesian method, X-ray variability, and cross-correlations with catalogs in optical, infrared, and radio wavelengths. They 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. They detected 106 sources in the energy range of 0.2 - 12 keV, out of which 15 are located within the D<sub>25</sub> regions of NGC 1512 and NGC 1510 and at least six sources coincide with the extended arms. They identified and classified six background objects and six foreground stars. In the reference paper, they discuss the nature of a source within the D<sub>25</sub> 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<sub>25</sub> region of NGC 1512 is consistent with the star formation rate obtained in previous works based on radio, infrared optical, and UV wavelengths. The authors 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 1.3E+38erg/s, after correcting for unresolved discrete sources. The galaxy pair NGC 1512/1510 was observed with XMM-Newton (ObsID: 0693160101) between 2012 June 16 (20:31 UTC) and 2012 June 17 (16:24 UTC) in a single, 63-ks exposure observation. The data analysis was performed through the XMM-Newton Science Analysis System (SAS) software (version 12.0.1). The observation was largely contaminated by high background due to proton flares. After rejecting time intervals affected by high background, the net good exposure time was reduced to 26.0 ks for PN, 39.8 ks for the MOS1 and 34.8 ks for the MOS2. For each instrument, the data were divided into five energy bands: <pre> B<sub>1</sub> : 0.2 - 0.5 keV B<sub>2</sub> : 0.5 - 1.0 keV B<sub>3</sub> : 1.0 - 2.0 keV B<sub>4</sub> : 2.0 - 4.5 keV B<sub>5</sub> : 4.5 - 12.0 keV </pre> For the PN, data were filtered to include only single events (PATTERN = 0) in the energy band B__1, and single and double events (PATTERN <= 4) for the other energy bands. The authors excluded the energy range 7.2 - 9.2 keV to reduce the background produced by strong fluorescence lines in the outer detector area. For the MOS, single to quadruple events (PATTERN <= 12) were selected. The source detection procedure is described in Section 2.1 of the reference paper. In the final step, the authors adopted a minimum likelihood of L = 6. They removed false detections (artifacts on the detectors or diffuse emission structures) by visual inspection. They detected 106 total point sources in the NGC 1512/1510 field of view. This table was created by the HEASARC in July 2014 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/566/A115">CDS Catalog J/A+A/566/A115</a> files tableb1.dat and tableb2.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc6357oid
- Title:
- NGC 6357/Pismis 24 Chandra Point Source Optical/IR Identifications Catalog
- Short Name:
- NGC6357OID
- Date:
- 18 Apr 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- Circumstellar disks are expected to evolve quickly in massive young clusters harboring many OB-type stars. Two processes have been proposed to drive the disk evolution in such cruel environments: (1) gravitational interaction between circumstellar disks and nearby passing stars (stellar encounters), and (2) photoevaporation by UV photons from massive stars. The relative importance of both mechanisms is not well understood. Studies of massive young star clusters can provide observational constraints on the processes of driving disk evolution. The authors investigate the properties of young stars and their disks in the NGC 6357 complex, concentrating on the most massive star cluster within the complex: Pismis 24. They use infrared data from the 2MASS and Spitzer GLIMPSE surveys, complemented with their own deep Spitzer imaging of the central regions of Pismis 24, in combination with X-ray data to search for young stellar objects (YSOs) in the NGC 6357 complex. The infrared data constrain the disk presence and are complemented by optical photometric and spectroscopic observations, obtained with VLT/VIMOS, that constrain the properties of the central stars. For those stars with reliable spectral types, they combine spectra and photometry to estimate the masses and ages. For cluster members without reliable spectral types, they obtain the mass and age probability distributions from R and I-band photometry, assuming these stars have the same extinction distribution as those in the "spectroscopic" sample. The authors compare the disk properties in the Pismis 24 cluster with those in other clusters/star-forming regions employing infrared color-color diagrams. The authors discover two new young clusters in the NGC 6357 complex. They give a revised distance estimate for Pismis 24 of 1.7 +/- 0.2 kpc. They also find that the massive star Pis 24-18 is a binary system, with the secondary being the main X-ray source of the pair. The authors provide photometry in 9 bands between 0.55 and 8 micron (µm) for the members of the Pismis 24 cluster. They derive the cluster mass function and find that up to the completeness limit at low masses it agrees well with the initial mass function of the Trapezium cluster. They derive a median age of 1 Myr for the Pismis 24 cluster members. The R-band observations were performed on 2008 April 1 and 6, and the I-band observations were done on 2008 May 1, both using the VIMOS instrument on the VLT. The near-IR photometry in the J, H and K<sub>s</sub> bands were taken from the 2MASS. The mid-IR photometry at 3.6, 4.5, 5.8 and 8.0 um were obtained withe the Spitzer IRAC camera, both from the GLIMPSE I survey and from deep observations of the central Pismis 24 region carried out by the authors on 2006 September 29. The X-ray observations were made by the Chandra ACIS-I instrument and previously published by Wang et al. (2007, ApJS, 168, 100: the HEASARC NGC6357CXO table). The X-ray sources were matched to sources detected in the VIMOS R and I bands based on positional coincidence, using a 1.5 arcseconds tolerance. The accuracy of the optical and X-ray positions was 0.6 and 1.0 arcseconds, respectively. Given the high space density of sources in the central regions of Pismis 24, there may be a substantial number (up to 1/6 of the sources) of "false positives", according to the authors. This table contains the list of 643 optical/IR counterparts to the Chandra X-ray sources found by Wang et al. (2007) which were identified by the present authors: for 136 of the 779 X-ray sources, no counterparts were found. 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/A119">CDS Catalog J/A+A/539/A119</a> files table1.dat and table3.dat. This is a service provided by NASA HEASARC .
