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IR20126CXO - IRAS 20126+4104 Chandra X-Ray Point Source Catalog

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Overview

This table contains results from Chandra ACIS-I and Karl G. Jansky Very Large Array 6-cm continuum observations of the IRAS 20126+4104 massive star-forming region. The authors detect 150 X-ray sources within the 17' x 17' ACIS-I field, and a total of 13 radio sources within the 9.2' primary JVLA beam at 4.9 GHz. Among these observations are the first 6-cm detections of the central sources reported by Hofner et al. (2007, A&A, 465, 197), namely, I20N1, I20S, and I20var. A new variable radio source is also reported in Section 3.2 of the reference paper, [MHA2015] VLA G78.1907+3.364. Searching the 2MASS archive, the authors identified 88 near-infrared (NIR) counterparts to the X-ray sources. Only four of the X-ray sources had 6-cm counterparts. Based on an NIR color-color analysis and on the Besancon simulation of Galactic stellar populations, the authors estimate that approximately 80 X-ray sources are associated with this massive star-forming region. They detect an increasing surface density of X-ray sources toward the massive protostar IRAS 20126+4104 and infer the presence of a cluster of at least 43 young stellar objects within a distance of 1.2 pc from this protostar.

The authors observed the IRAS 20126+4104 region with the Chandra ACIS-I instrument on 2003 March 17 for a total exposure time of 39.35 ks. C-band (6 cm) continuum observations of the massive star-forming region IRAS 20126+4104 were conducted with the VLA operated by NRAO on 2011 August 7. These X-ray and radio data are augmented by NIR and optical archival data. For the Mid-IR wavelength regions, the authors searched the Spitzer Enhanced Imaging Products Point Source catalog.


Catalog Bibcode

2015ApJS..219...41M

References

X-ray and radio observations of the massive star-forming region IRAS 20126+4104
    Montes V.A., Hofner P., Anderson C., Rosero V.
   <Astrophys. J. Suppl. Ser., 219, 41 (2015)>
   =2015ApJS..219...41M    (SIMBAD/NED BibCode)

Provenance

This table was created by the HEASARC in March 2016 based on the CDS catalog J/ApJS/219/41 files table1.dat and table5.dat.

Parameters

Source_Number
A unique identification number for each Chandra source in this catalog in order of increasing J2000.0 Right Ascension.

Original_Name
The J2000.0 position-based Chandra source designation as originally specified in the published catalog (except that the 'CXOU' prefix rather than the 'CXO' prefix has been used). These original names are deprecated because they do not conform with the IAU standard for such names, since the coordinates have been rounded rather than truncated, and the Declination part of the name is given to more precision than the CDS Dictionary of Nomenclature of Celestial Objects recommends.

Name
The corrected J2000.0 position-based Chandra source designation, using the prefix 'CXOU' for Chandra X-ray Observatory, Unregistered. These names conform with the IAU standard for such names, since the coordinates have been truncated rather than rounded, and the Declination part of the name is given to a precision of arcseconds, as the CDS Dictionary of Nomenclature of Celestial Objects recommends for Chandra sources, e.g., 'CXOU J201347.0+411541'.

RA
The Right Ascension of the X-ray source in the selected equinox. This was given in J2000.0 sexagesimal coordinates to a precision of 0.001 seconds of time in the original table.

Dec
The Declination of the X-ray source in the selected equinox. This was given in J2000.0 sexagesimal coordinates to a precision of 0.01 arcseconds in the original table.

LII
The Galactic Longitude of the X-ray source.

BII
The Galactic Latitude of the X-ray source.

Count_Rate
The observed Chandra ACIS-I count rate of the X-ray source in the 0.5-8 keV band, in counts per second. This was converted by the HEASARC from the units of ct ks-1 used in the original table.

Flux
The observed X-ray flux of the source in the 0.5-8 keV band, in erg s-1 cm-2. The details of the models used to fit the X-ray spectra of the Chandra sources and to derive fluxes are given in Section 3.1.3 of the reference paper. No reliable fits were found for 12 of the 150 sources, and for these 12 sources no fluxes are listed.

Hardness_Ratio
The hardness ratio, HR, of the X-ray source. HR is defined as (hx - sx)/(hx + sx) where hx is the count rate in the 2-8 keV energy range and sx is the count rate in the 0.5-2 keV band. Values of +/-1.00 for HR thus indicate that the source was only detected in the hard or soft energy bands, respectively. A blank value for the hardness ratio (HR) indicates that the source was only detected in the full (0.5-8 keV) energy range.

Var_Flag
The variability of the X-ray source, coded as follows:

        V = Variable;
       FL = Flaring;
  (blank) = Constant.
  

TwoMASS_Name
The 2MASS near-infrared (NIR) source designation of the counterpart to the X-ray source using the form that the CDS Dictionary of Nomenclature of Celestial Objects recommends, viz., '2MASS JHHMMSSss+DDMMSSs'. The authors used the 2MASS All-Sky Point Source Catalog to find the NIR counterparts. A matching radius of 1 arcsecond was chosen for X-ray sources with off-axis positions of <= 3 arcminutes and was enlarged to 2" for sources with off-axis positions of > 3' because of the off-axis Chandra PSF degradation. With these criteria, the authors found a total of 88 counterparts for the 150 X-ray sources (59%). Most (90%) of the NIR counterparts have high-quality photometry in the JHKs bands.

TwoMASS_Flag
A non-blank value of this flag indicates the presence of a note concerning the 2MASS counterpart, as follows:

    a = Theses sources have in the 2MASS band one or two filter detections with
        quality flag U. This means that the source is not detected in this band or
        it is detected but not resolved in a consistent fashion with other bands.
        The 2MASS data for those sources are not used for the cluster analysis.
    b = The majority of the 2MASS counterparts have a quality flag A (high-quality
        photometry) in the three bands, except for nine of them. The photometric
        quality flags listed for those nine sources, respectively, for the J, H,
        and Ks bands: source 15 AAC, source 21 AAB, source 36 AAB, source 41 AAE,
        source 55 BAA, source 61 BAC, source 67 AAB, source 78 BAA,
        source 111 AEA.
    c = Spectral type OB star. Identifiers: HD 228515, ALS 11001, CSI+41-20127 1,
        GSC 03155-00985, LS III +41 6, 2MASS J20142661+4112101, TYC 3155-985-1.
    e = Spectral type B star. Identifiers: TYC 3155-859-1, ALS 11003,
        CSI+41-20128 2, GSC 03155-00859, LS III +41 7, 2MASS J20143205+4112498.
    f = Spectral type F8 star. Identifiers: HD 228527, AG+41 1862, BD+40 4073,
        GSC 03155-00817, 2MASS J20143246+4114537, PPM 59547, SAO 49350,
        TYC 3155-817-1.
    g = Spectral type K5 star. Identifiers: HD 228590, BD+40 4078,
        GSC 03159-00721, 2MASS J20151437+4115318, TYC 3159-721-1.
  

Spitzer_Name
The Spitzer Space Telescope (SST) mid-infrared source designation of the counterpart to the X-ray source using the form that the CDS Dictionary of Nomenclature of Celestial Objects recommends for unregistered SST sources, viz., 'SSTU JHHMMSS.ss+DDMMSS.s'. In the original paper, the authors used a prefix of 'SSTSLP' for the SST sources. For the Mid-IR wavelength regions, the authors searched the Spitzer Enhanced Imaging Products Point Source catalog. Using the same procedure as for the 2MASS catalog (q.v.), they found a total of 19 counterparts for the X-ray sources within the entire ACIS field. Qiu et al. (2008, ApJ, 685, 1005) have reported Spitzer IRAC and MIPS observations of a 5' x 5' area of the IRAS 20126+4104 core. The present authors found that only three of their sources have X-ray counterparts: these are also included here.

Spitzer_Flag
A non-blank value of this flag indicates the presence of a note concerning the SST counterpart, as follows:

    d = Same Spitzer counterparts found as in Qiu et al. (2008, ApJ, 685, 1005).
  

VLA_Name
The JVLA radio source designation of the 6-cm counterpart to the X-ray source using the prefix '[MHA2015] VLA' for 'Montes, Hofner, Anderson 2015 Very Large Array' created by the HEASARC in the style based on the CDS Dictionary of Nomenclature of Celestial Objects recommendations for such sources, and the Galactic coordinates of the source, e.g., '[MHA2015] VLA GLL.llll+B.bbbb'. The authors compared the VLA sources detected in their observation of this region with the ACIS sources in order to find the radio counterparts of the X-ray sources. They found that only four of the ACIS sources have radio counterparts. All the radio counterparts have position differences smaller than 1.0 arcsecond. Their 6-cm flux densities are listed in Table 4 of the original paper.

USNOB1_Name
The USNO-B1 Source designation of the optical counterpart to the X-ray source. The optical counterparts of the ACIS sources were found using the USNO-B1.0 catalog. Applying the same selection criteria as for 2MASS and Spitzer, viz., a matching radius of 1 arcsecond for X-ray sources with off-axis positions of <= 3 arcminutes and a larger one of 2" for sources with off-axis positions of > 3', the authors found that 80 of the ACIS sources (53%) have optical counterparts.

Jmag
The 2MASS J-band magnitude of the NIR counterpart to the X-ray source.

Hmag
The 2MASS H-band magnitude of the NIR counterpart to the X-ray source.

Ks_Mag
The 2MASS Ks-band magnitude of the NIR counterpart to the X-ray source.


Contact Person

Questions regarding the IR20126CXO database table can be addressed to the HEASARC User Hotline.
Page Author: Browse Software Development Team
Last Modified: Wednesday, 16-Mar-2016 15:23:45 EDT