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CARGM31CXO - Carina Nebula Gum 31 Chandra X-Ray Point Source Catalog

HEASARC
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Overview

Gum 31 is a prominent, but still rather poorly studied, HII region around the stellar cluster NGC 3324 at the northwestern periphery of the Carina nebula complex. The aim of the authors aim was to reveal and characterize the young stellar population in Gum 31. An X-ray survey is the only efficient way to identify young stars in this region, which has extremely high galactic field-star contamination, that can avoid the strong biases of infrared-excess-selected samples of disk-bearing young stars.

The authors used the Chandra observatory to perform a deep (70 ks) X-ray observation of the Gum 31 region and detected 679 X-ray point sources. This extends and complements the X-ray survey of the central Carina nebula regions performed in the Chandra Carina Complex Project (CCCP, available in the HEASARC database system as the CARINACXO table). Using deep near-infrared images from their recent VISTA survey of the Carina nebula complex, their comprehensive Spitzer point-source catalog, and optical archive data, the authors identify counterparts for 75% of these X-ray sources.

The aimpoint of the ACIS-I observation was set to be RA(J2000) = 10h 37m 36.6s, Dec(J2000) = -58o 41' 18". This position is close to the center of the H II region, and allows both the stellar cluster NGC 3324 and the cluster G286.38-0.26 to be in the inner parts of the field-of-view, where the point-spread function is still very good. The pointing roll angle (i.e., the orientation of the detector with respect to the celestial north direction) was 138.35o. The ACIS field-of-view is just wide enough to cover the full spatial extent of the optically bright Gum 31 H II region and some parts of the surrounding dust shell (see Fig. 1 of the reference paper). The ACIS-I field of view is 17' x 17', which corresponds to 11.3 p x 11.3 pc at the Gum 31 distance of 2.3 kpc). The total net exposure time of the observation was 68,909s (19.14 h). The details of the source detection procedures are described in Section 21. of the reference paper. The final X-ray catalog contains 679 individual point sources. The number of extracted counts ranges from 3 for the faintest sources, up to 920 for the strongest source, while the median value is 11 counts.

This table contains the basic X-ray properties and near- and mid-infrared photometry of the X-ray sources detected in the Gum 31 field. The details of the IR matching to the X-ray sources are given in Sections 4.1, 4.2 and 4.3 of the reference paper.


Catalog Bibcode

2014A&A...564A.120P

References

Chandra X-ray observation of the HII region Gum 31 in the Carina nebula complex.
    Preibisch T., Mehlhorn M., Townsley L., Broos P., Ratzka T.
    <Astron. Astrophys. 564, A120 (2014)>
    =2014A&A...564A.120P        (SIMBAD/NED BibCode)

Provenance

This table was created by the HEASARC in May 2014 based on CDS Catalog J/A+A/564/A120 files table1.dat and table3.dat.

Parameters

Source_Number
A uniquely identifying source number for the Chandra Gum 31 region X-ray source. sorted by in order of increasing RA (J2000.0).

Name
The source designation registered with the CDS Dictionary of Nomenclature of Celestial Objects, using the prefix of 'CXOPMTB' for 'Chandra X-ray Observatory Preibisch, Mehlhorn, Townsley, Broos' and the J2000.0 equatorial coordinates truncated to 0.01 seconds of time in RA and to 0.1 arcseconds in Dec, e.g., 'CXOPMTB J103624.0-584017.1'.

RA
The Right Ascension Right Ascension of the X-ray source in the selected equinox. This was given in J2000 decimal degree coordinates to an accuracy of 10-6 degrees (0.0036 arcseconds) in the original reference.

Dec
The Declination Right Ascension of the X-ray source in the selected equinox. This was given in J2000 decimal degree coordinates to an accuracy of 10-6 degrees (0.0036 arcseconds) in the original reference.

LII
The Galactic Longitude of the X-ray source.

BII
The Galactic Latitude of the X-ray source.

Error_Radius
The estimated standard deviation of the random component of the position error, sqrt({sigma}x2+{sigma}y2), in arcseconds. The single-axis position errors, {sigma}x and {sigma}y, are estimated from the single-axis standard deviations of the PSF inside the extraction region and the number of counts extracted.

Off_Axis
The off-axis angle of the X=ray source from the pointing direction, in arcminutes.

FB_Counts
The net total-band (0.5-8 keV) total counts in the X-ray source.

FB_Counts_Error
The 1-sigma error in the net total-band (0.5-8 keV) total counts in the X-ray source.

FB_Bck_Counts
The number of background counts expected in the source extraction region for the X-ray source in the total band.

HB_Counts
The net hard-band (2-8 keV) total counts in the X-ray source.

PSF_Fraction
The fraction of the PSF (at 1.497 keV) which is enclosed within the source extraction region. A reduced PSF fraction (significantly below 90%) may indicate that the source is in a crowded region.

Significance
The photometric significance of the X-ray source. This is computed as the net source counts divided by the upper error in the net counts.

Log_Prob_No_Src_Limit
This parameter is set to '<' if the corresponding parameter value, log_prob_no_src, is an upper limit.

Log_Prob_No_Src
The logarithm of the probability P_B_that the extracted counts in the total band from the source region are from the background. Some sources have PB values above the 1% threshold that defines the catalog because the local background estimates can rise during the final extraction iteration after sources are removed from the catalog.

Anomalies_Flag
This parameter flags X-ray source anomalies as follows:

     G = fractional time that source was on a detector (FRACEXPO from mkarf)
          is <0.9
     p = source piled up
     s = source on readout streak
     a = photometry and spectrum contain >10% afterglow events
  

Ks_Var_Statistic
A variability characterization Pconst of the X-ray source counts in the total band based on the one-sided Kolmogorov-Smirnov (K-S) statistic. In this sample, 42 sources show significant X-ray variability (probability of being constant Pconst < 0.005) and an additional 48 sources are classified as possibly variable (0.005 < Pconst < 0.05). The variability codes are as follows:

     a = no evidence for variability (0.05 < Pconst)
     b = possibly variable (0.005 <Pconst <0.05)
     c = definitely variable (Pconst <0.005)
       = no value is reported for sources with fewer than four counts or for
          sources in chip gaps or on field edges
  

Median_Energy
The background-corrected median photon energy in the total band for the X-ray source, in keV.

IR_Name
The IAU-type designation of the corresponding VISTA or 2MASS counterpart to the X-ray source. For VISTA sources, the HEASARC uses the (unregistered) prefix of 'VISTA'. In both cases, the source is described using the J2000.0 equatorial coordinates truncated to 0.01 seconds of time and to 0.1 arcseconds.

Jmag
The near-infrared J-band magnitude of the corresponding VISTA or 2MASS counterpart to the X-ray source.

Hmag
The near-infrared H-band magnitude of the corresponding VISTA or 2MASS counterpart to the X-ray source.

Ks_Mag
The near-infrared Ks-band magnitude of the corresponding VISTA or 2MASS counterpart to the X-ray source.

Jmag_SNR
The signal-to-noise ratio of the J-band flux measurement.

Hmag_SNR
The signal-to-noise ratio of the H-band flux measurement.

Ks_Mag_SNR
The signal-to-noise ratio of the K_s-band flux measurement.

IR_Flag
This flag parameter is set to 1 if the near-IR photometry is derived from the VISTA data, 2 if the near-IR photometry is from the 2MASS point source catalog, or to 0 if no near-IR counterpart is known.

Spitzer_Name
The IAU-type designation of the corresponding Spitzer mid-IR counterpart to the X-ray source. The HEASARC has created this designation using the prefix of '[OPR2014] SST' for 'Ohlendorf, Preibisch, Roccatagliata et al. 2014 (AJ, submitted) Spitzer Space Telescope', and the J2000.0 equatorial coordinates truncated to 0.01 seconds of time and to 0.1 arcseconds.

IRAC_3p6_um_Mag
The Spitzer IRAC 3.6-micron band magnitude of the mid-IR counterpart to the X-ray source.

IRAC_4p5_um_Mag
The Spitzer IRAC 4.5-micron band magnitude of the mid-IR counterpart to the X-ray source.

IRAC_5p8_um_Mag
The Spitzer IRAC 5.8-micron band magnitude of the mid-IR counterpart to the X-ray source.

IRAC_8p0_um_Mag
The Spitzer IRAC 8.0-micron band magnitude of the mid-IR counterpart to the X-ray source.

IRAC_3p6_um_Mag_SNR
The signal-to-noise ratio of the Spitzer IRAC 3.6-um band flux measurement of the mid-IR counterpart to the X-ray source.

IRAC_4p5_um_Mag_SNR
The signal-to-noise ratio of the Spitzer IRAC 4.5-um band flux measurement of the mid-IR counterpart to the X-ray source.

IRAC_5p8_um_Mag_SNR
The signal-to-noise ratio of the Spitzer IRAC 5.8-um band flux measurement of the mid-IR counterpart to the X-ray source.

IRAC_8p0_um_Mag_SNR
The signal-to-noise ratio of the Spitzer IRAC 8.0-um band flux measurement of the mid-IR counterpart to the X-ray source.


Contact Person

Questions regarding the CARGM31CXO database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 28-May-2014