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OMC2P3CXO - OMC-2 and OMC-3 Chandra X-Ray Point Source Catalog

HEASARC
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Overview

The OMC-2 and OMC-3 Chandra X-Ray Point Source Catalog contains the results of the Chandra X-ray observation of Orion Molecular Clouds 2 and 3 (OMC-2 and OMC-3). A deep exposure of ~100 ks detects ~400 X-ray sources in the field of view (FOV) of the ACIS array, providing one of the largest X-ray catalogs in a star-forming region as of the date that this was published (February 2002). Coherent studies of the source detection, time variability, and energy spectra were performed. The authors classified the X-ray sources into Class I, Class II, and Class III+MS types based on the J-, H-, and K-band colors of their near-infrared counterparts, and discussed the X-ray properties (temperature, absorption, and time variability) along these evolutionary phases.

The results of the X-ray imaging analysis and a correlation with the 2MASS Catalog are given for all the detected X-ray sources. Notice that the sources '[TKT2002] I1' - '[TKT2002] I354' and '[TKT2002] S1' - '[TKT2002] S11' were detected in the total-band image (0.5 - 8.0 keV) images of the ACIS-I and the ACIS-S2 CCDs, respectively, but that source '[TKT2002] I355' - '[TKT2002] I369' and '[TKT2002] S12' - '[TKT2002] S13' were detected only in the hard-band (2.0 - 8.0 keV) images of the ACIS-I and the ACIS-S2 CCDs, and '[TKT2002] I370' - '[TKT2002] I385' were detected only in the soft-band (0.5 - 2.0 keV) image of the ACIS-I. No new source was detected in the soft band image of the ACIS-S2 CCD.


Catalog Bibcodes

2002ApJ...566..974T
2003ApJ...585..602T

References

X-ray properties of young stellar objects in OMC-2 and OMC-3 from the
Chandra X-ray observatory.
    Tsujimoto M., Koyama K., Tsuboi Y., Goto M., Kobayashi N.
   <Astrophys. J. 566, 974 (2002)>
   =2002ApJ...566..974T
Erratum: X-ray properties of young stellar objects in OMC-2 and OMC-3 from
the Chandra X-ray observatory (ApJ, 566, 974 [2002]).
    Tsujimoto M., Koyama K., Tsuboi Y., Goto M., Kobayashi N.
   <Astrophys. J. 585, 602 (2003)>
   =2003ApJ...585..602T

Provenance

This table was created by the HEASARC in January 2007 based on CDS table J/ApJ/566/974, files table1.dat and table2.dat.

Parameters

Source_Number
A running source number in order of increasing J2000 Right Ascension, with sources detected in the ACIS-I FOV indicated with an 'I' prefix and those detected in the ACIS-S (S2) FOV indicated with an 'S' prefix.

Name
The name of the X-ray source using the 'CXOU J' prefix for Chandra X-Ray Observatory unregistered sources recommended by the CDS Dictionary of Astronomical Nomenclature and the J2000 coordinates (hhmmss.ss-ddmmss.s).

Alt_Name
The alternative name for the X-ray source using the '[TKT2002]' prefix recommended by the CDS Dictionary of Astronomical Nomenclature and the X-ray source number (q.v.).

RA
The Right Ascension of the X-ray source in the selected equinox. This was given in J2000 coordinates and to a precision of 0.01 seconds of time in the original published paper and machine-readable table. The initial X-ray RAs were corrected to the 2MASS reference frame by removing a systematic offset of -0.186" in Right Ascension.

Dec
The Declination of the X-ray source in the selected equinox. This was given in J2000 coordinates and to a precision of 0.1 arseconds in the erratum to the original published paper and the corrected machine-readable table. (The values given in the erratum corrected the original published values with a systematic offset of ~1.8"). The initial X-ray Declinations were corrected to the 2MASS reference frame by removing a systematic offset of +0.200" in Declination.

LII
The Galactic Longitude of the X-ray source.

BII
The Galactic Latitude of the X-ray source.

Counts
The X-ray photon counts for the X-ray source in the 0.5 - 8.0 keV energy band.

Hardness_Ratio
The hardness ratio of the X-ray souurce, HR, defined as HR = (H-S)/(H+S), where H and S are the photon counts in the hard band (2.0 - 8.0 keV) and in the soft band (0.5 - 2.0 keV), respectively.

JH_Color
The (J-H) color of the nearest 2MASS counterpart to the X-ray source, in the CIT color system derived from 2MASS J, H, and K_s_ band photometry (see Carpenter, 2001AJ....121.2851C, for more details). A matching radius of 3" was used to find the nearest CXO-2MASS pairs.

HK_Color
The (H-K) color of the nearest 2MASS counterpart to the X-ray source, in the CIT color system derived from 2MASS J, H, and K_s_ band photometry (see Carpenter, 2001AJ....121.2851C, for more details). A matching radius of 3" was used to find the nearest CXO-2MASS pairs.

Variable_Flag
The results of timing and spectroscopic analyses are listed for all of the 123 "bright2" sources. A "bright2" source is a source for which (i) more than 200 counts were accumulated and (ii) the number of source counts was three or more times the background counts in the photon accumulation region. X-ray lightcurves (without background subtraction) were made for all detected sources and chi-squared fits then made on the assumption that the X-ray flux was constant. This flag parameter is set to 'd' to indicate sources which are time-variable using a significance criterion of 0.01.

Upper_Probability
The results of timing and spectroscopic analyses are listed for all of the 123 "bright2" sources. A "bright2" source is a source for which (i) more than 200 counts were accumulated and (ii) the number of source counts was >= 3 times the background counts in the photon accumulation region. The best-fit parameters from the thin-thermal plasma model fitting are tabulated regardless of whether or not the fit was formally accepted or rejected. The upper probability for the spectral fit is defined as the integral from alpha to infinity of the function [Chi_nu^2^(x) dx], where the Chi_nu^2 value and the degree of freedom of the fit are alpha and nu, respectively. Fits with the upper probability larger than 0.01 are "accepted" while those less than or equal to 0.01 are "rejected". Even the "best-fit" parameters of rejected fittings represent values of some physical meaning or approximated values. The authors thus use these values in the same way as the accepted ones.

NH
The hydrogen column density n_H derived from the spectral fit, in H atoms per square cm.

NH_Lower
The lower (1-sigma confidence level) limit to n_H, in H atoms per square cm.

NH_Upper
The upper (1-sigma confidence level) limit to n_H, in H atoms per square cm.

Te_Plasma
The best-fit value of the plasma temperature kT found from the spectral fit to the X-ray source, and given in keV. The best-fit values of the temperature were searched for in the range of less than 20 keV.

Te_Plasma_Lower
The lower (1-sigma confidence level) limit to kT, in keV.

Te_Plasma_Upper
The upper (1-sigma confidence level) limit to kT, in keV.

Metallicity
The best-fit value of the plasma metallicity Z relative to the solar photospheric value found from the spectral fit to the X-ray source. The best fit values of metallicity were searched for in the range of less than 5 times the solar photopspheric value.

Metallicity_Lower
The lower (1-sigma confidence level) limit to Z, in multiples of the solar photospheric value.

Metallicity_Upper
The upper (1-sigma confidence level) limit to Z, in multiples of the solar photospheric value.

Lx
The X-ray luminosity L_x of the source, in units of erg/s, in the 0.5 to 8.0 keV band and corrected for absorption.

Lx_Lower
The lower (1-sigma confidence level) limit to L_x, in erg/s.

Lx_Upper
The upper (1-sigma confidence level) limit to L_x, in erg/s.

Broad_Class
A classification of the source based on the J-, H-, K_s-band magnitudes of its 2MASS Counterpart using the following schema, which is based on the standard characterization of pre-main sequence stars into types 0 and I (protostars), II (pre-main sequence stars with disks) and III (ones lacking disks):

      I       = class I source
      II      = class II source
      III+MS  = class III source and/or main-sequence star
      others  = source which are not in one of these groups
      no data = source can not be classified due to lack of a NIR counterpart
  

Contact Person

Questions regarding the OMC2P3CXO database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 30-Jan-2007