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CCOSMOSCAT - Chandra COSMOS (C-COSMOS) Survey X-Ray Point Source Catalog |
HEASARC Archive |
Overview
The Chandra COSMOS Survey (C-COSMOS) is a large, 1.8 Ms, Chandra program that has imaged the central 0.5 deg2 of the COSMOS field (centered at RA, Dec of 10 hours , +02 degrees) with an effective exposure of ~ 160 ks, and an outer 0.4 deg2 area with an effective exposure of ~ 80 ks. The limiting source detection depths are 1.9 x 10-16 erg cm-2 s-1 in the soft (0.5 - 2 keV) band, 7.3 x 10-16 erg cm-2 s-1 in the hard (2 - 10 keV) band, and 5.7 x 10-16 erg cm-2 s-1 in the full (0.5 - 10 keV) band. In this paper, the authors describe the strategy, design, and execution of the C-COSMOS survey, and present the catalog of 1761 point sources detected at a probability of being spurious of < 2 x 10-5 (1655 in the full, 1340 in the soft, and 1017 in the hard bands). By using a grid of 36 heavily (~ 50%) overlapping pointing positions with the ACIS-I imager, a remarkably uniform (+/-12%) exposure across the inner 0.5 deg2 field was obtained, leading to a sharply defined lower flux limit. The widely different point-spread functions obtained in each exposure at each point in the field required a novel source detection method, because of the overlapping tiling strategy, which is described in a companion paper. This method produced reliable sources down to a 7-12 counts, as verified by the resulting log N-log S curve, with sub-arcsecond positions, enabling optical and infrared identifications of virtually all sources, as reported in a second companion paper.Supporting data products for this table (including images, event files, and exposure maps) are available at the COSMOS Survey website and at IRSA. At the IRSA website, it is also possible to search a database that includes "postage stamps" of the X-ray data for each source, along with the multi-wavelength optical and infrared data, including the I-band, K-band, and Spitzer 3.6-micron (Band 1) images used in the Part III paper (Civano et al. 2012) to identify the sources.
See also the related table CCOSMOSOID for the optical and infrared identifications of the surveyed X-ray point sources.
Catalog Bibcode
2009ApJS..184..158EReferences
The Chandra COSMOS Survey.
I. Overview and Point Source Catalog
Elvis M., Civano F., Vignali C., Puccetti S., Fiore F., Cappelluti N.,
Aldcroft T.L., Fruscione A., Zamorani G., Comastri A., Brusa M., Gilli R.,
Miyaji T., Damiani F., Koekemoer A.M., Finoguenov A., Brunner H.,
Urry C.M., Silverman J., Mainieri V., Hasinger G., Griffiths R.,
Carollo M., Hao H., Guzzo L., Blain A., Calzetti D., Carilli C., Capak P.,
Ettori S., Fabbiano G., Impey C., Lilly S., Mobasher B., Rich M.,
Salvato M., Sanders D.B., Schinnerer E., Scoville N., Shopbell P.,
Taylor J.E., Taniguchi Y., Volonteri M.
<Astrophys. J. Suppl. Ser., 184, 158-171 (2009)>
=2009ApJS..184..158E
The Chandra Survey of the COSMOS Field.
II. Source Detection and Photometry
Puccetti S., Vignali C., Cappelluti N., Fiore F., Zamorani G., Aldcroft
T.L., Elvis M., Gilli R., Miyaji T., Brunner H., and 8 coauthors
<Astrophys. J. Suppl. Ser., 185, 586 (2009)>
=2009ApJS..185..586P
The Chandra COSMOS Survey.
III. Optical and Infrared Identification of X-Ray Point Sources
Civano F., Elvis M., Brusa M., Comastri A., Salvato M., Zamorani G.,
Aldcroft T., Bongiorno A., Capak P., Cappelluti N., Cisternas M., Fiore F.,
Fruscione A., Hao H., Kartaltepe J., Koekemoer A., Gilli R., Impey C.D.,
Lanzuisi G., Lusso E., Mainieri V., Miyaji T., Lilly S., Masters D.,
Puccetti S., Schawinski K., Scoville N.Z., Silverman J., Trump J., Urry M.,
Vignali C., Wright N.J.
<Astrophys. J. Suppl. Ser., 201, 30 (2012)>
=2012ApJS..201...30C
Provenance
This table was created by the HEASARC in November 2009 based on an electronic version of the C-COSMOS Catalog which was obtained from the Astrophysical Journal web site.Parameters
Name
The Chandra source name, following the standard IAU position-based
convention with the prefix "CXOC" for "Chandra X-ray Observatory COSMOS"
survey and the J2000.0 source coordinates.
Source_Number
The Chandra source number. Source numbers are in order of
detection: first those detected in the full band with detml >= 10.8, followed
by those detected in the soft band only and by those detected in the hard band
only.
Alt_Name
An alternative designation for the Chandra source using the
'ECV2009' prefix for Elvis, Civano, Vignali (2009) and the source number,
in the style (expected to be) recommended by the Dictionary of Nomenclature
of Celestial Objects.
RA
The Right Ascension of the Chandra source in the selected equinox. This
was given in J2000.0 coordinates to a precision of 1 microdegree (3.6 mas).
Dec
The Declination of the Chandra source in the selected equinox. This was
given in J2000.0 coordinates to a precision of 1 microdegree (3.6 mas).
LII
The Galactic Longitude of the Chandra source.
BII
The Galactic Latitude of the Chandra source.
Error_Radius
The Chandra source positional error pos_err = sqrt[sigma(RA)2
+ sigma(Dec)2], in arcseconds, computed using the following equation
Pos_error = PSF_radius/sqrt(S), where S is the number of net source counts,
after the subtraction of the background, in a circular region of radius
corresponding to the 50% encircled energy in the field where the source is
at the lowest off-axis angle (Paper II, Puccetti et al. 2009, ApJS, submitted).
Count_Rate
The count rate CR in the full energy band (0.5 - 7 keV), in
ct/s. These are effective count rates that would apply if the source had been
observed at the aim point in every pointing, i.e., computed by dividing the
best fit counts for the source by the effective exposure time at the position
of the source (the effective exposure time includes corrections for vignetting,
dither, bad pixels and spatially dependent quantum efficiency).
Count_Rate_Error
The error in the count rate in the full energy band
(0.5 - 7 keV), in ct/s. The count rate error E(CR) at 68% confidence level was
computed using the equation E(CR) == sqrt[C_(s,90%) + (1+a)B_90%]/0.9T,
where C_s are the source counts estimated by EMLdetect, corrected to an area
including 90% of the PSF, B are the background counts evaluated from the
background rate (counts pixel-1) estimated by EMLdetect multiplied for
an area of radius R_w, which is the mean of the radii, corresponding to
90% enclosed counts fraction (ECF) of each observation, weighted by the
observation exposure relative to the total exposure, and T is the vignetting
corrected exposure time at the position of the source from the exposure maps.
The authors use a value of a = 0.5, to allow for uncertainties in the
background, which is computed through the EMLdetect procedure:
see Paper II, Puccetti et al. (2009, ApJS, submitted) for more details.
Flux
The full-band 0.5 - 10 keV flux of the Chandra source, in
erg cm-2 s-1, computed converting count rates CR to fluxes F using the
following formula: F = CR/(CF*1011), where CF is the energy conversion
factor 0.742 counts erg-1 cm2) appropriate for a power-law spectrum with
spectral index Gamma = 1.4 and Galactic column density NH = 2.7 x 1020
cm-2. For sources not detected in this band, a 90% upper limit is reported
(see Paper II for details). Notice that the energy ranges used for the
full-band count rates and fluxes are different (0.5 - 7.0 keV versus 0.5 -
10.0 keV, respectively), as discussed in Section 2 of the reference paper.
Flux_Error
The error in the full-band 0.5 - 10 keV flux of the Chandra
source, in erg cm-2 s-1, computed from the count rate error in the
same way that the flux is computed from the count rate.
SNR
The full-band signal-to-noise ratio of the Chandra source.
Exposure
The full-band exposure time derived from the exposure map, in
seconds (converted by the HEASARC from the ks units given in the original
table).
Counts
The aperture photometry counts in the full band (0.5 - 7 keV) as
derived from event data for each individual Obs_id and CCD where a source
lands. Notice that this will not necessarily be equal to the product of the
count rate and the exposure time. Circular extraction regions corresponding
to the 90% ECF for that observation are centered on the source R.A. and Dec.
The individual photometry values are then merged to produce a single set of
values accounting for the ECF for each Obs_ID, given the different extraction
regions needed.
Counts_Error
The error in the full-band (0.5 - 7 keV) aperture photometry
net counts.
AP_Exposure
The exposure time in the full-band (0.5 - 7 keV) from the same
region used to generate the aperture photometry, in seconds (converted by the
HEASARC from the ks units given in the original table).
SB_Count_Rate
The count rate CR in the soft energy band (0.5 - 2 keV), in
ct/s. These are effective count rates that would apply if the source had been
observed at the aim point in every pointing, i.e., computed by dividing the
best fit counts for the source by the effective exposure time at the position
of the source (the effective exposure time includes corrections for vignetting,
dither, bad pixels and spatially dependent quantum efficiency).
SB_Count_Rate_Error
The error in the count rate in the soft energy band
(0.5 - 2 keV), in ct/s. The count rate error E(CR) at 68% confidence level was
computed using the equation E(CR) == sqrt[C_(s,90%) + (1+a)B_90%]/0.9T,
where C_s are the source counts estimated by EMLdetect, corrected to an area
including 90% of the PSF, B are the background counts evaluated from the
background rate (counts pixel-1) estimated by EMLdetect multiplied for
an area of radius R_w, which is the mean of the radii, corresponding to
90% enclosed counts fraction (ECF) of each observation, weighted by the
observation exposure relative to the total exposure, and T is the vignetting
corrected exposure time at the position of the source from the exposure maps.
The authors use a value of a = 0.5, to allow for uncertainties in the
background, which is computed through the EMLdetect procedure:
see Paper II, Puccetti et al. (2009, ApJS, submitted) for more details.
SB_Flux
The soft-band 0.5 - 2 keV flux of the Chandra source, in
erg cm-2 s-1, computed converting count rates CR to fluxes F using the
following formula: F = CR/(CF*1011), where CF is the energy conversion
factor 1.837 counts erg-1 cm2) appropriate for a power-law spectrum with
spectral index Gamma = 1.4 and Galactic column density NH = 2.7 x 1020
cm-2. For sources not detected in this band, a 90% upper limit is reported
(see Paper II for details).
SB_Flux_Error
The error in the soft-band 0.5 - 2 keV flux of the Chandra
source, in erg cm-2 s-1, computed from the count rate error in the
same way that the flux is computed from the count rate.
SB_SNR
The soft-band signal-to-noise ratio of the Chandra source.
SB_Exposure
The soft-band exposure time derived from the exposure map, in
seconds (converted by the HEASARC from the ks units given in the original
table).
SB_Counts
The aperture photometry counts in the soft band (0.5 - 2 keV) as
derived from event data for each individual Obs_id and CCD where a source
lands. Notice that this will not necessarily be equal to the product of the
count rate and the exposure time. Circular extraction regions corresponding
to the 90% ECF for that observation are centered on the source R.A. and Dec.
The individual photometry values are then merged to produce a single set of
values accounting for the ECF for each Obs_ID, given the different extraction
regions needed.
SB_Counts_Error
The error in the soft-band (0.5 - 2 keV) aperture
photometry net counts.
SB_AP_Exposure
The exposure time in the soft-band (0.5 - 2 keV) from the
same region used to generate the aperture photometry, in seconds (converted by
the HEASARC from the ks units given in the original table).
HB_Count_Rate
The count rate CR in the hard energy band (2 - 7 keV), in
ct/s. These are effective count rates that would apply if the source had been
observed at the aim point in every pointing, i.e., computed by dividing the
best fit counts for the source by the effective exposure time at the position
of the source (the effective exposure time includes corrections for vignetting,
dither, bad pixels and spatially dependent quantum efficiency).
HB_Count_Rate_Error
The error in the count rate in the hard energy band
(2 - 7 keV), in ct/s. The count rate error E(CR) at 68% confidence level was
computed using the equation E(CR) == sqrt[C_(s,90%) + (1+a)B_90%]/0.9T,
where C_s are the source counts estimated by EMLdetect, corrected to an area
including 90% of the PSF, B are the background counts evaluated from the
background rate (counts pixel-1) estimated by EMLdetect multiplied for
an area of radius R_w, which is the mean of the radii, corresponding to
90% enclosed counts fraction (ECF) of each observation, weighted by the
observation exposure relative to the total exposure, and T is the vignetting
corrected exposure time at the position of the source from the exposure maps.
The authors use a value of a = 0.5, to allow for uncertainties in the
background, which is computed through the EMLdetect procedure:
see Paper II, Puccetti et al. (2009, ApJS, submitted) for more details.
HB_Flux
The hard-band 2 - 10 keV flux of the Chandra source, in
erg cm-2 s-1, computed converting count rates CR to fluxes F using the
following formula: F = CR/(CF*1011), where CF is the energy conversion
factor 0.381 counts erg-1 cm2) appropriate for a power-law spectrum with
spectral index Gamma = 1.4 and Galactic column density NH = 2.7 x 1020
cm-2. For sources not detected in this band, a 90% upper limit is reported
(see Paper II for details). Notice that the energy ranges used for the
hard-band count rates and fluxes are different (2 - 7 keV versus 2 - 10 keV,
respectively), as discussed in Section 2 of the reference paper.
HB_Flux_Error
The error in the hard-band 2 - 10 keV flux of the Chandra
source, in erg cm-2 s-1, computed from the count rate error in the
same way that the flux is computed from the count rate.
HB_SNR
The hard-band signal-to-noise ratio of the Chandra source.
HB_Exposure
The hard-band exposure time derived from the exposure map, in
seconds (converted by the HEASARC from the ks units given in the original
table).
HB_Counts
The aperture photometry counts in the hard band (2 - 7 keV) as
derived from event data for each individual Obs_id and CCD where a source
lands. Notice that this will not necessarily be equal to the product of the
count rate and the exposure time. Circular extraction regions corresponding
to the 90% ECF for that observation are centered on the source R.A. and Dec.
The individual photometry values are then merged to produce a single set of
values accounting for the ECF for each Obs_ID, given the different extraction
regions needed.
HB_Counts_Error
The error in the hard-band (2 - 7 keV) aperture photometry
net counts.
HB_AP_Exposure
The exposure time in the hard-band (2 - 7 keV) from the same
region used to generate the aperture photometry, in seconds (converted by the
HEASARC from the ks units given in the original table).
Hardness_Ratio
The hardness ratio of the Chandra source computed as follows:
HR = (H-S)/(H+S), where H are the counts in the hard band and S the counts in
the soft band. The hardness ratio was calculated starting with the EMLdetect
rate values. Pseudo-source and background count values were generated using
the net count rate, background rate (per pixel), and a 3 arcsecond source
aperture and 5 - 20 arcsecond aperture for background areas. The aperture
photometry was unsuitable for this purpose because the individual extraction
apertures do not have the constant background/source area ratios required by
the assumptions used in the Bayesian estimation of hardness ratio (BEHR)
code.
Hardness_Ratio_Neg_Err
The 90% upper error in the hardness ratio of the
Chandra source (calculated by the HEASARC from the 90% upper limit to the
hardness ratio given in the original table). The upper and lower limits were
calculated using the Bayesian estimation of hardness ratio code (BEHR; Park
et al. 2006, ApJ, 652, 610).
Hardness_Ratio_Pos_Err
The 90% lower error in the hardness ratio of the
Chandra source (calculated by the HEASARC from the 90% lower limit to the
hardness ratio given in the original table). The upper and lower limits were
calculated using the Bayesian estimation of hardness ratio code (BEHR; Park
et al. 2006, ApJ, 652, 610).
Contact Person
Questions regarding the CCOSMOSCAT database table can be addressed to the HEASARC Help Desk.Page Author: Browse Software Development Team
Last Modified: Monday, 16-Sep-2024 17:25:18 EDT
- HEASARC Director: Dr. Andy Ptak
- NASA Official: Dr. Andy Ptak
- Web Curator: J.D. Myers
- Last Modified: 16-Sep-2024