- ID:
- ivo://CDS.VizieR/J/ApJ/888/118
- Title:
- Chandra and IR study toward IRAS 16562-3959
- Short Name:
- J/ApJ/888/118
- Date:
- 17 Jan 2022 11:46:14
- Publisher:
- CDS
- Description:
- We present the results from Chandra X-ray observations, and near- and mid-infrared analysis, using VISTA/VVV and Spitzer/GLIMPSE catalogs, of the high-mass star-forming region IRAS 16562-3959, which contains a candidate for a high-mass protostar. We detected 249 X-ray sources within the ACIS-I field of view. The majority of the X-ray sources have low count rates (<0.638cts/ks) and hard X-ray spectra. The search for YSOs in the region using VISTA/VVV and Spitzer/GLIMPSE catalogs resulted in a total of 636 YSOs, with 74 Class I and 562 Class II YSOs. The search for near- and mid-infrared counterparts of the X-ray sources led to a total of 165 VISTA/VVV counterparts, and a total of 151 Spitzer/GLIMPSE counterparts. The infrared analysis of the X-ray counterparts allowed us to identify an extra 91 Class III YSOs associated with the region. We conclude that a total of 727 YSOs are associated with the region, with 74 Class I, 562 Class II, and 91 Class III YSOs. We also found that the region is composed of 16 subclusters. In the vicinity of the high-mass protostar, the stellar distribution has a core-halo structure. The subcluster containing the high-mass protostar is the densest and the youngest in the region, and the high-mass protostar is located at its center. The YSOs in this cluster appear to be substantially older than the high-mass protostar.
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- ID:
- ivo://CDS.VizieR/J/A+A/464/211
- Title:
- Chandra and near-IR obs. of Cyg OB2
- Short Name:
- J/A+A/464/211
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The aim of this work is to identify the so far unknown low mass stellar population of the ~2Myr old Cygnus OB2 star forming region, and to investigate the X-ray and near-IR stellar properties of its members. We analyzed a 97.7ks Chandra ACIS-I observation pointed at the core of the Cygnus OB2 region. Sources were detected using the PWDETECT code and were positionally correlated with optical and near- IR catalogs from the literature. Source events were extracted with the Acis E XTRACT package. X-ray variability was characterized through the Kolmogorov-Smirnov test and spectra were fitted using absorbed thermal plasma models. We detected 1003 X-ray sources. Of these, 775 have near-IR counterparts and are expected to be almost all associated with Cygnus OB2 members.
- ID:
- ivo://CDS.VizieR/II/253A
- Title:
- Chandra Deep Field South: multi-colour data
- Short Name:
- II/253A
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Table 3 contains the object catalogue of the COMBO-17 CDFS field. The observations were carried out with the Wide Field Imager (WFI) at the MPG/ESO 2.2-m telescope on La Silla, Chile, between October 1999 and January 2001 in four independent observing runs. The field measures 31.5'x30', is centered on RA=03:32:25, DE=-27:48:50 and contains the Chandra Deep Field South. The table contains 63501 objects found on the deep R-band image cdfs_r.fit by SExtractor with S/N>3. The 5-{sigma} magnitude limit for point sources is Rmag=26.0. Morphological information from the SExtractor measurement is included. Multiple observations in different observing runs of six different filters allow the identification of variable objects. The table contains positions, flags and flux measurements in UBVRI and 12 optical medium-band filters. In addition, we include multi-colour classification, photometric redshifts, luminosity distances and a number of absolute restframe magnitudes in different filters (Johnson, Sloan, Bessell). cdfs_u.fit, cdfs_b.fit, cdfs_v.fit, cdfs_r.fit and cdfs_i.fit are coadded sumframes in UBVRI of the CDFS field. These sumframes are stacked from flat-fielded and cosmic-corrected individual images by applying only full pixel shifts. Therefore, the coordinate frames differ slightly between the images. The coordinates in Table 3 refer to image cdfs_r.fit. The images in BVRI are obtained from observations carried out in observing run D (Oct 1999, see also Note (11) in the byte-by-byte description of table3.dat) while the U-band image is obtained from observing run G (Jan 2001). The exposure times are 14400s (U), 5000s (B), 8400s (V), 15000s (R) and 7550s (I). The intensity levels are given in units of photons hitting the detector (already corrected for the gain of the CCD). The data included here supersede the table2.dat of the COMBO-17 published in 2001 (J/A+A/377/442)
- ID:
- ivo://CDS.VizieR/J/ApJS/155/271
- Title:
- Chandra Deep Field-South: Optical spectroscopy
- Short Name:
- J/ApJS/155/271
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of our spectroscopic follow-up program of the X-ray sources detected in the 942ks exposure of the Chandra Deep Field-South (CDFS). A total of 288 possible counterparts were observed at the VLT with the FORS1/FORS2 spectrographs for 251 of the 349 Chandra sources (including three additional faint X-ray sources). Spectra and R-band images are shown for all the observed sources and R-K colors are given for most of them. Spectroscopic redshifts were obtained for 168 X-ray sources, of which 137 have both reliable optical identification and redshift estimate (including 16 external identifications). The R<24 observed sample comprises 161 X-ray objects (181 optical counterparts), and 126 of them have unambiguous spectroscopic identification.
- ID:
- ivo://CDS.VizieR/J/A+A/377/442
- Title:
- Chandra Deep Field South: R-band photometry
- Short Name:
- J/A+A/377/442
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Table2 is based on an object list that was created by applying SExtractor software to an R-band image coadded from 36 frames with 15070s total exposure time taken in October 1999 using the Wide Field Imager at the MPG/ESO 2.2-m telescope on La Silla, Chile. The field measures 31.5'x30', is centered on 03:32:25-27:48:50 and contains the Chandra Deep Field South. The average PSF is on the order of 0.75". The catalog contains 63501 objects found by SExtractor with S/N>3. It has not been cleaned for spurious detection of false objects arising from scattered light or diffraction spikes of extremely bright stars. Using this object list aperture magnitudes 'Bmag', 'Vmag' and 'Rmag' were measured on B-, V- and R-band images taken in October 1999. These are listed with its errors. Additionally an aperture magnitude 'R2mag' with its error is included that is taken from R-band imaging from February 2000 with an exposure time of 8440s taken in 21 frames, yielding a total exposure time in the R-band of 23510s=6.5h. The 10-sigma magnitude limits for point sources are Bmag=24.9, Vmag=24.6, Rmag=25.1 and R2mag=24.8. The aperture magnitudes were calculated by counting the flux in an aperture with a Gaussian weighting function of 1.3" width. The flux is scaled to the total flux expected for stars.
- ID:
- ivo://CDS.VizieR/J/ApJS/228/2
- Title:
- Chandra Deep Field-South survey: 7Ms sources
- Short Name:
- J/ApJS/228/2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present X-ray source catalogs for the ~7Ms exposure of the Chandra Deep Field-South (CDF-S), which covers a total area of 484.2arcmin^2^. Utilizing wavdetect for initial source detection and ACIS Extract for photometric extraction and significance assessment, we create a main source catalog containing 1008 sources that are detected in up to three X-ray bands: 0.5-7.0keV, 0.5-2.0keV, and 2-7keV. A supplementary source catalog is also provided, including 47 lower-significance sources that have bright (K_s_<=23) near-infrared counterparts. We identify multiwavelength counterparts for 992 (98.4%) of the main-catalog sources, and we collect redshifts for 986 of these sources, including 653 spectroscopic redshifts and 333 photometric redshifts. Based on the X-ray and multiwavelength properties, we identify 711 active galactic nuclei (AGNs) from the main-catalog sources. Compared to the previous ~4Ms CDF-S catalogs, 291 of the main-catalog sources are new detections. We have achieved unprecedented X-ray sensitivity with average flux limits over the central ~1arcmin^2^ region of ~1.9x10^-17^, 6.4x10^-18^, and 2.7x10^-17^erg/cm^2^/s in the three X-ray bands, respectively. We provide cumulative number-count measurements observing, for the first time, that normal galaxies start to dominate the X-ray source population at the faintest 0.5-2.0keV flux levels. The highest X-ray source density reaches ~50500deg^-2^, and 47%+/-4% of these sources are AGNs (~23900deg^-2^).
- ID:
- ivo://CDS.VizieR/J/MNRAS/400/299
- Title:
- Chandra deep protocluster survey
- Short Name:
- J/MNRAS/400/299
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present X-ray point-source catalogues for a deep ~400ks Chandra ACIS-I (Advanced CCD Imaging Spectrometer) exposure of the SSA22 field. The observations are centred on a z=3.09 protocluster, which is populated by Lyman break galaxies (LBGs), Ly{alpha} emitters (LAEs) and extended Ly{alpha}-emitting blobs (LABs). The survey reaches ultimate (3 count) sensitivity limits of ~5.7x10^-17^ and ~3.0x10^-16^erg/cm^2^/s for the 0.5-2 and 2-8keV bands, respectively (corresponding to L_2-10keV_~5.7x10^42^erg/s and L_10-30keV_~2.0x10^43^erg/s at z=3.09, respectively, for an assumed photon index of {GAMMA}=1.4). These limits make SSA22 the fourth deepest extragalactic Chandra survey yet conducted, and the only one focused on a known high-redshift structure. In total, we detect 297 X-ray point sources and identify one obvious bright extended X-ray source over a ~330arcmin^2^ region. In addition to our X-ray catalogues, we provide all available optical spectroscopic redshifts and near-infrared and mid-infrared photometry available for our sources.
- ID:
- ivo://CDS.VizieR/J/MNRAS/458/4530
- Title:
- Chandra Galactic Bulge Survey
- Short Name:
- J/MNRAS/458/4530
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As part of the Chandra Galactic Bulge Survey (GBS), we present a catalogue of optical sources in the GBS footprint. This consists of two regions centered at Galactic latitude b=1.5{deg} above and below the Galactic Centre, spanning (lxb)=(6{deg}x1{deg}). The catalogue consists of 2 or more epochs of observations for each line of sight in r', i' and H{alpha} filters. The catalogue is complete down to r'=20.2 and i'=19.2mag; the mean 5{sigma} depth is r'=22.5 and i'=21.1mag. The mean root-mean-square residuals of the astrometric solutions is 0.04-arcsec. We cross-correlate this optical catalogue with the 1640 unique X-ray sources detected in Chandra observations of the GBS area, and nd candidate optical counterparts to 1480 X-ray sources. We use a false alarm probability analysis to estimate the contamination by interlopers, and expect ~10 0 per cent of optical counterparts to be chance alignments. To determine the most likely counterpart for each X-ray source, we compute the likelihood ratio for all optical sources within the 4{sigma} X-ray error circle. This analysis yields 1480 potential counterparts (~90 per cent of the sample). 584 counterparts have saturated photometry (r'<=17, i'<=16), indicating these objects are likely foreground sources and the real counterparts. 171 candidate counterparts are detected only in the i' -band. These sources are good qLMXB and CV candidates as they are X-ray bright and likely located in the Bulge.
- ID:
- ivo://CDS.VizieR/J/ApJ/763/128
- Title:
- Chandra Local Volume Survey: NGC 404 sources
- Short Name:
- J/ApJ/763/128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comprehensive X-ray point-source catalog of NGC 404 obtained as part of the Chandra Local Volume Survey. A new 97ks Chandra ACIS-S observation of NGC 404 was combined with archival observations for a total exposure of ~123ks. Our survey yields 74 highly significant X-ray point sources and is sensitive to a limiting unabsorbed luminosity of ~6x10^35^erg/s in the 0.35-8keV band. To constrain the nature of each X-ray source, cross-correlations with multi-wavelength data were generated. We searched overlapping Hubble Space Telescope observations for optical counterparts to our X-ray detections, but find only two X-ray sources with candidate optical counterparts. We find 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. The X-ray luminosity functions (XLFs) in both the soft and hard energy bands are presented. The XLFs in the soft band (0.5-2keV) and the hard band (2-8keV) have a limiting luminosity at the 90% completeness limit of 10^35^erg/s and 10^36^erg/s, respectively, significantly lower than previous X-ray studies of NGC 404. We find the XLFs to be consistent with those of other X-ray populations dominated by LMXBs. However, the number of luminous (>10^37^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 ~0.5Gyr ago.
- ID:
- ivo://CDS.VizieR/J/AJ/137/3210
- Title:
- Chandra observations of h Persei
- Short Name:
- J/AJ/137/3210
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe Chandra/ACIS-I observations of the massive ~13-14Myr-old cluster, h Persei, part of the famous Double Cluster (h and {chi} Per) in Perseus. Combining the list of Chandra-detected sources with new optical/IR photometry and optical spectroscopy reveals ~165 X-ray bright stars with V<~23. Roughly 142 have optical magnitudes and colors consistent with cluster membership.
