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CXOGSGSRC - Chandra ACIS GSG Point-Like X-Ray Source Catalog |
HEASARC Archive |
Overview
The Chandra archival data are a valuable resource for various studies on different X-ray astronomy topics. In this paper, the authors utilize this wealth of information and present a uniformly processed data set, which can be used to address a wide range of scientific questions. The data analysis procedures are applied to 10,029 Advanced CCD Imaging Spectrometer observations, which produces 363,530 source detections belonging to 217,828 distinct X-ray sources. This number is twice the size of the Chandra Source Catalog (Version 1.1). The catalogs in this paper provide abundant estimates of the detected X-ray source properties, including source positions, counts, colors, fluxes, luminosities, variability statistics, etc.Cross-correlation of these objects with galaxies shows that 17,828 sources are located within the D25 isophotes of 1,110 galaxies, and 7,504 sources are located between the D25 and 2*D25 isophotes of 910 galaxies. Contamination analysis with the log N-log S relation indicates that 51.3% of objects within 2*D25 isophotes are truly relevant to galaxies, and the "net" source fraction increases to 58.9%, 67.3%, and 69.1% for sources with luminosities above 1037, 1038, and 1039 erg/s, respectively. Among the possible scientific uses of this catalog mentioned in this paper, the authors discuss the possibility of studying intra-observation variability, inter-observation variability, and supersoft sources (SSSs). About 17,092 detected sources above 10 counts are classified as variable in individual observation with the Kolmogorov-Smirnov (K-S) criterion (PK-S < 0.01). There are 99,647 sources observed more than once and 11,843 sources observed 10 times or more, offering a wealth of data with which to explore their long-term variability. There are 1,638 individual objects (~2,350 detections) classified as SSSs. As a quite interesting subclass, detailed studies on X-ray spectra and optical spectroscopic follow-up are needed to categorize these SSSs and pinpoint their properties. In addition, this survey can enable a wide range of statistical studies, such as X-ray activity in different types of stars, X-ray luminosity functions in different types of galaxies, and multi-wavelength identification and classification of different X-ray populations.
The ACIS observations were downloaded from the Chandra Data Archive on 2014 December 4, yielding 10,047 ACIS observations. Eighteen observations with PI as "Calibration" or Exposure as zero were excluded. Finally, there are 10,029 ACIS observations containing 4,146 ACIS-I observations and 5,883 ACIS-S observations in our sample. The exposure times for the selected observations cover a range from 50 s to 190 ks, with a total of 221,851 ks.
This HEASARC table comprises the list of 218,789 X-ray point sources detected in the Chandra ACIS Survey and listed in the machine-readable version of Table 5 from the reference paper. This number is somewhat larger than the number of independent sources (217,828) stated in the abstract and Section 5 of the reference paper because if a source lies within 2*R25 of more than one galaxy it is listed multiple times, once for each galaxy with which it may be associated. All parameters are the same for such duplicate cases except for the entry_number, alt_name, adopted_distance, luminosity, src_nucleus_offset, norm_src_nucleus_offset and (in some cases) source_type.
Catalog Bibcode
2016ApJS..224...40WReferences
CHANDRA ACIS survey of X-ray point sources: the source catalog.
Wang S., Liu J., Qiu Y., Bai Y., Yang H., Guo J., Zhang P.
<Astrophys. J. Suppl. Ser., 224, 40-40 (2016)>
=2016ApJS..224...40W (SIMBAD/NED BibCode)
Provenance
This table was created by the HEASARC in March 2017 primarily based on CDS Catalog J/ApJS/224/40/ file table5.dat, the catalog of X-ray point sources in the Chandra ACIS Survey. The positional information for these sources was taken from CDS Catalog J/ApJS/224/40/ file table3.dat, the list of separation detections for these X-ray sources, using the first listed detection in each case.Sources with Negative Distances in Original Table
There were 49 sources in the original table which had negative adopted distances of -0.20 Mpc, the significance of which is unclear. The HEASARC has reset these distances to 0.20 Mpc in all cases. The sources in question are listed below:|name |alt_name |ra |dec |error_radius|src_nucleus_offset|distance|lx |flux |max_significance| |CXOGSG J024055.0+593130| |02 40 55.05|+59 31 30.0| 4.14| | -0.2000|2.890e+35|6.02e-14| 4.972| |CXOGSG J024056.8+593303| |02 40 56.90|+59 33 03.3| 2.38| | -0.2000|5.230e+35|1.09e-13| 9.890| |CXOGSG J024107.3+593327| |02 41 07.30|+59 33 27.3| 3.25| | -0.2000|1.220e+35|2.55e-14| 3.083| |CXOGSG J024110.0+593515| |02 41 09.99|+59 35 15.5| 1.37| | -0.2000|4.150e+35|6.57e-14| 11.051| |CXOGSG J024117.5+593319| |02 41 17.52|+59 33 19.4| 3.16| | -0.2000|6.860e+34|1.43e-14| 2.565| |CXOGSG J024120.1+593314| |02 41 20.16|+59 33 14.7| 2.82| | -0.2000|8.350e+34|1.74e-14| 2.845| |CXOGSG J024122.3+592917| |02 41 22.37|+59 29 17.8| 3.61| | -0.2000|2.440e+35|4.36e-14| 4.800| |CXOGSG J024125.0+593451| |02 41 25.01|+59 34 51.1| 1.61| | -0.2000|1.230e+35|2.57e-14| 4.472| |CXOGSG J024126.7+593454| |02 41 26.73|+59 34 54.0| 1.11| | -0.2000|2.450e+35|3.98e-14| 7.620| |CXOGSG J024131.0+593630| |02 41 31.05|+59 36 30.5| 1.00| | -0.2000|3.900e+36|7.90e-13| 113.898| |CXOGSG J024131.3+593339| |02 41 31.36|+59 33 39.3| 1.86| | -0.2000|8.500e+34|1.77e-14| 3.433| |CXOGSG J024138.3+593008| |02 41 38.39|+59 30 08.6| 4.66| | -0.2000|5.140e+34|1.07e-14| 1.847| |CXOGSG J024139.3+593715| |02 41 39.31|+59 37 15.2| 1.00| | -0.2000|1.300e+36|2.45e-13| 46.069| |CXOGSG J024142.0+593511| |02 41 41.99|+59 35 11.2| 1.00| | -0.2000|3.010e+35|5.81e-14| 12.574| |CXOGSG J024142.1+593527| |02 41 42.13|+59 35 27.8| 1.00| | -0.2000|2.250e+35|4.44e-14| 9.648| |CXOGSG J024144.8+593734| |02 41 44.88|+59 37 34.8| 1.00| | -0.2000|9.650e+35|1.52e-13| 28.522| |CXOGSG J024145.9+593457| |02 41 45.95|+59 34 57.1| 1.00| | -0.2000|3.820e+35|7.96e-14| 15.674| |CXOGSG J024148.0+593003| |02 41 47.95|+59 30 03.7| 3.25| | -0.2000|9.360e+34|1.66e-14| 3.194| |CXOGSG J024149.2+593343| |02 41 49.28|+59 33 44.0| 1.10| | -0.2000|1.060e+35|2.20e-14| 4.776| |CXOGSG J024149.3+593511| |02 41 49.36|+59 35 11.3| 1.00| | -0.2000|1.800e+35|2.78e-14| 8.133| |CXOGSG J024151.8+593608|PGC 10217 X3|02 41 51.90|+59 36 08.4| 1.00| 0.346| -0.2000|6.290e+34|1.10e-14| 2.975| |CXOGSG J024154.1+593735| |02 41 54.15|+59 37 35.5| 1.00| | -0.2000|1.500e+35|3.13e-14| 4.032| |CXOGSG J024154.7+593749| |02 41 54.74|+59 37 49.9| 1.02| | -0.2000|5.950e+34|1.24e-14| 2.482| |CXOGSG J024154.7+593406| |02 41 54.78|+59 34 06.6| 1.00| | -0.2000|2.870e+35|5.52e-14| 12.592| |CXOGSG J024154.9+593615|PGC 10217 X2|02 41 55.03|+59 36 15.3| 1.00| 0.090| -0.2000|1.680e+35|3.50e-14| 6.506| |CXOGSG J024157.7+593714| |02 41 57.72|+59 37 14.4| 1.00| | -0.2000|7.340e+34|1.53e-14| 2.530| |CXOGSG J024158.1+593708| |02 41 58.10|+59 37 08.9| 1.00| | -0.2000|1.330e+35|2.77e-14| 4.542| |CXOGSG J024200.4+593526| |02 42 00.45|+59 35 26.4| 1.00| | -0.2000|1.250e+35|2.07e-14| 2.526| |CXOGSG J024201.3+593606|PGC 10217 X1|02 42 01.34|+59 36 06.5| 1.00| 0.855| -0.2000|2.560e+35|5.33e-14| 2.028| |CXOGSG J024202.0+593646| |02 42 02.01|+59 36 47.0| 1.00| | -0.2000|2.100e+35|4.38e-14| 2.110| |CXOGSG J024202.2+593843| |02 42 02.22|+59 38 43.1| 1.00| | -0.2000|7.730e+35|1.45e-13| 23.011| |CXOGSG J024203.0+593300| |02 42 03.03|+59 33 00.9| 1.00| | -0.2000|3.050e+35|4.36e-14| 10.616| |CXOGSG J024206.2+593341| |02 42 06.18|+59 33 41.3| 1.44| | -0.2000|7.820e+34|1.42e-14| 3.004| |CXOGSG J024208.4+593642| |02 42 08.47|+59 36 42.6| 1.10| | -0.2000|7.150e+34|1.49e-14| 2.498| |CXOGSG J024209.4+593607| |02 42 09.46|+59 36 07.9| 1.15| | -0.2000|5.470e+34|1.14e-14| 2.519| |CXOGSG J024211.3+593419| |02 42 11.35|+59 34 20.0| 1.00| | -0.2000|1.650e+35|2.86e-14| 7.417| |CXOGSG J024211.7+593149| |02 42 11.75|+59 31 49.4| 1.34| | -0.2000|2.850e+35|4.65e-14| 7.841| |CXOGSG J024211.8+593114| |02 42 11.90|+59 31 14.8| 2.77| | -0.2000|9.500e+34|1.98e-14| 2.743| |CXOGSG J024216.2+593857| |02 42 16.26|+59 38 57.8| 1.54| | -0.2000|1.050e+35|2.19e-14| 3.098| |CXOGSG J024225.9+594432| |02 42 26.00|+59 44 32.7| 4.50| | -0.2000|2.770e+35|5.77e-14| 4.083| |CXOGSG J024227.9+593058| |02 42 27.99|+59 30 58.6| 2.07| | -0.2000|3.130e+35|4.97e-14| 6.067| |CXOGSG J024231.3+593245| |02 42 31.40|+59 32 45.9| 3.07| | -0.2000|8.020e+34|1.67e-14| 2.659| |CXOGSG J024235.0+593508| |02 42 34.98|+59 35 08.6| 1.71| | -0.2000|1.540e+35|2.57e-14| 5.388| |CXOGSG J024238.0+593600| |02 42 38.08|+59 36 00.4| 1.96| | -0.2000|1.430e+35|2.98e-14| 4.665| |CXOGSG J024241.7+594043| |02 42 41.90|+59 40 43.6| 2.67| | -0.2000|2.450e+35|5.02e-14| 4.768| |CXOGSG J024243.9+593036| |02 42 43.97|+59 30 36.5| 5.31| | -0.2000|1.160e+35|2.42e-14| 2.950| |CXOGSG J024253.1+594056| |02 42 53.17|+59 40 56.6| 4.17| | -0.2000|1.760e+35|3.66e-14| 4.240| |CXOGSG J024300.8+593339| |02 43 00.88|+59 33 39.4| 4.43| | -0.2000|1.830e+35|3.81e-14| 3.849| |CXOGSG J024304.1+593520| |02 43 04.12|+59 35 20.2| 4.40| | -0.2000|2.010e+35|4.19e-14| 3.832|
Parameters
Entry_Number
This parameter contains a HEASARC-created unique sequential identification
number for each entry in the catalog.
Group_Number
The group number to which the X-ray source belongs. Each source record in the
catalog was constructed by combining source detections from multiple
observations, which required matching the source detections from all of the
observations that included the same region of the sky. A first step was to
divide the 10,029 ACIS observations into 4,683 groups based on the proximity
of the pointings. The observations in the same group with overlapping fields
of view were hence studied together. There are 1,145 groups with two or more
Chandra ACIS observations, including seven groups (group 1, 2, 5, 7, 11, 13,
and 28) with more than 100 observations.
Name
The IAU-style J2000.0 position-based source designation for the the Chandra
X-ray source, viz., 'CXOGSG JHHMMSS.s+DDMMSS', registered with the Dictionary
of Nomenclature of Celestial Objects, where the 'GSG' part of the prefix
indicates that the source was named by the Galaxy Structure Group of the
National Astronomical Observatories, Chinese Academy of Sciences.
Alt_Name
The galaxy source name given by the authors to the X-ray source, e.g., 'NGC
224 X610'. In each galaxy, the X-ray sources are numbered sequentially based
on their maximum detection significance. The criterion for associating a
source with a galaxy is that it lies within 2*R25 of the center of the
galaxy, where the R25 is the elliptical radius of the D25 isophote along
the great arc connecting the galaxy center and the source. Generally, a
source is regarded as being associated with a galaxy if it is located within
the D25 isophote, but here a source with separation s in the range R25 <
s < 2*R25 is also considered to belong to the galaxy to avoid missing any
galactic sources. All of the galaxy information (e.g., coordinates, R25,
distance) come from the Third Reference Catalog of Galaxies (RC3).
Cross-correlation of these sources with galaxy isophotes yields 17,828
sources within the D25 isophotes of 1,110 galaxies, and 7,504 sources
between the D25 and 2*D25 isophotes of 910 galaxies. Note that the
authors have made no attempt herein to exclude contaminating foreground stars
or background QSOs or AGN. See Section 5 of the reference paper for their
estimate of the expected contamination rate.
Source_Flag
Sources marked with 'M' are projected within the 2*R25 domains of two or
more galaxies that have overlapping domains. This implies that such a source
will have multiple entries, one for each galaxy with which it is potentially
associated (see Overview above for more details).
RA
The Right Ascension of the X-ray source in the selected equinox. This was
given in J2000.0 coordinates to a precision of 10-5 degrees (0.036
arcseconds) in the original tables.
Dec
The Declination of the X-ray source in the selected equinox. This was given
in J2000.0 coordinates to a precision of 10-5 degrees (0.036 arcseconds) in
the original tables.
LII
The Galactic Longitude of the X-ray source.
BII
The Galactic Latitude of the X-ray source.
Error_Radius
The statistical positional error of the X-ray source, in arcseconds,
calculated using the scheme of Kim et al. (2007, ApJS, 169, 401). See Section
2.2 of the reference paper for more details.
Src_Nucleus_Offset
For sources which are projected within 2*R25 of a galaxy, the angular
offset of the source from the nucleus, in arcminutes.
Norm_Src_Nucleus_Offset
For sources which are projected within 2*R25 of a galaxy, the angular
offset of the source from the nucleus, in units of the galaxy's elliptical
radius R25.
Adopted_Distance
The distance adopted to the X-ray source, in Mpc. If the source is projected
within 2*R25 of the nucleus of a galaxy, this is the distance to the galaxy
in RC3. If the distance of the host galaxy is unknown, or if an X-ray source
is not associated with a galaxy, then the distance for the source is assumed
to be 1 Mpc. There were 49 sources in the original table which had negative
adopted distances of -0.20 Mpc, the significance of which is unclear. The
HEASARC has reset these distances to 0.20 Mpc in all such cases (see the list
of these sources in the Sources_with_Negative_Distances_in_Original_Table
section above.
Num_Observed_To_Detected
The number of times that the source was observed/detected. Thus, '2/1' means
that the source was observed twice and detected once.
Lx
The inferred X-ray luminosity LX of the source in the 0.3-8.0 keV energy
range, in erg s-1, assuming the quoted adopted distance and X-ray flux. For
sources with multiple detections, the maximum flux is used, and hence in such
cases this will be the maximum luminosity.
Flux
The flux of the X-ray source FX in the 0.3-8.0 keV energy range, in erg
s-1 cm-2, averaged over all of its detections. The source flux is
calculated for each source from its count rate, which is computed from the
source count and the exposure time and corrected by a vignetting factor. The
vignetting factor is derived from the exposure map as the ratio between the
local and the maximum map value. However, no vignetting information could be
obtained for seven observations (Chandra ObsIDs 750, 1105, 1194, 1195, 10644,
10655, and 13095) because they were performed using ACIS sub-arrays and the
aimpoint is not on the used chip, meaning the maximum map value can not be
obtained. The authors computed the energy conversion factor (ECF) between the
count rate and flux with XSPEC using the response matrix file (RMF) of the
chip center, assuming Galactic absorption and a power-law spectrum with a
photon index Gamma = 1.7, which is generally adopted for Chandra sources.
Flux_Max_Min
The FmaxX/FminX ratio of the source over all of its detections. This
is an extreme variability indicator, with FmaxX as the maximum 0.3-8.0 8
keV flux of all detections, and FminX as the minimum flux of all
detections or upper limits. The ratio is set to unity without any quoted
errors if FmaxX equals FminX.
Flux_Max_Min_Pos_Err
The lower uncertainty in the FmaxX/FminX ratio of the source over all
of its detections.
Flux_Max_Min_Neg_Err
The upper uncertainty in the FmaxX/FminX ratio of the source over all
of its detections.
Max_Significance
The maximum detection significance for the X-ray source. The CIAO wavelet
detection algorithm called wavdetect was run on each on-axis chip with scales
of 1, 2, 4, and 8 arcsecond pixels in the 0.3-8.0 keV band, with one
normalized background created simultaneously. The significance threshold was
set to 10-6, which is equivalent to one possibly spurious pixel in one CCD.
Max_Counts
The maximum background-corrected photon counts found for the X-ray source
among its individual detections. The methodology for computing the photon
counts for the sources is discussed in Section 2.3 of the reference paper.
Sqhd_Phase_Stats
The statistics for the X-ray spectral characterization of the various
detections of the X-ray source, using the so-called SSS/QSS/Hard/Dim
classification of the X-ray source. Many galaxies house a significant
population of very soft X-ray sources, including super-soft sources (SSSs)
and quasi-soft sources (QSSs), the nature of which sources is still in
question. Di Stefano & Kong (2003, ApJ, 592, 884) employed strict hardness
ratio (HR) criteria to identify SSSs using three energy bins to define HRs:
soft (0.1-1.1 keV), medium (1.1-2.0 keV) and hard (2-7 keV). In this paper,
the photon counts were calculated using the same energy bands, and the
hierarchical classification scheme (Di Stefano & Kong 2003, astro-ph 0311374)
was used to classify whether a source is SSS, QSS, hard, or dim (i.e., less
than 10 counts). In total, about 0.6%, 6.6%, 71.3%, and 21.5% of all detected
sources are classified as SSS, QSS, hard, and dim, respectively. Thus, for
example, 's1' means the source had a hardness ratio like an SSS in one
observation, 'q2' means the HR was like a QSS in two observations, 'h3' means
the spectrum was hard in three observations, and 'd4' means it was too dim
(below 10 counts) to characterize in four observations. To summarize:
sN = number (N) of observations in SSS phase;
qN = number (N) of observations in QSS phase;
hN = number (N) of observations in hard phase;
dN = number (N) of observations in dim (< 10 counts) phase.
Obs_Var_Stats
The statistics for variability of the X-ray source during individual
observations using the K-S criterion. For example, 'v:2' means the source was
regarded as variable, (i.e., PK-S < 0.01, counts > 10), in 2 observations.
Source_Type
The authors' classification of the source using the scheme shown below:
ULX = Ultraluminous X-ray sources with observed LX (0.3-8 keV) in excess
of 2*1039 erg/s;
EULX = Maximum LX >= 1040 erg/s;
1ULX = ULX inside D25 isophotes;
1EULX = EULX inside D25 isophotes;
2ULX = ULX between D25 and 2*D25 isophotes, without nuclear
sources excluded;
2EULX = EULX between D25 and 2*D25 isophotes, without nuclear
sources excluded;
ULS = Ultraluminous supersoft sources with at least one SSS phase in
which LX (0.3-8 keV) exceeds 2*1038 erg/s
(Liu 2011, ApJS, 192, 10).
Contact Person
Questions regarding the CXOGSGSRC database table can be addressed to the HEASARC Help Desk.Page Author: Browse Software Development Team
Last Modified: Monday, 16-Sep-2024 17:26:29 EDT
- HEASARC Director: Dr. Andy Ptak
- NASA Official: Dr. Andy Ptak
- Web Curator: J.D. Myers
- Last Modified: 16-Sep-2024