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VLAGBSSER - VLA Gould's Belt Survey Serpens Region Source Catalog

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Overview

This table contains results from a deep (~17 µJy) radio continuum observations of the Serpens molecular cloud, the Serpens south cluster, and the W40 region that were obtained using the Jansky Very Large Array (JVLA) in its A configuration. The authors detected a total of 146 sources, 29 of which are young stellar objects (YSOs), 2 of which are BV stars, and 5 more of which are associated with phenomena related to YSOs. Based on their radio variability and spectral index, the authors propose that about 16 of the remaining 110 unclassified sources are also YSOs. For approximately 65% of the known YSOs detected here as radio sources, the emission is most likely non-thermal and related to stellar coronal activity. As also recently observed in Ophiuchus, this sample of YSOs with X-ray counterparts lies below the fiducial Guedel & Benz (1993, ApJ, 405, L63) relation. In the reference paper, the authors analyze the proper motions of nine sources in the W40 region, thus allowing them to better constrain the membership of the radio sources in the region.

The Serpens molecular cloud and the Serpens South cluster were observed in the same observing sessions on three different epochs (2011 June 17, July 19, and September 12 UT), using 25 and 4 pointings, respectively, with the JVLA at 4.5 and 4.5GHz. The W40 region, on the other hand, was only observed on two epochs (2011 June 17 and July 16), using 13 pointings. The details of the observations are listed in Table 1 of the reference paper.

The authors adopted the same criteria as Dzib et al. (2013, ApJ, 775, 63) to consider a detection as firm. For new sources, i.e., those without reported counterparts in the literature, they considered 5-sigma detections, where sigma is the rms noise of the area around the source. For known sources with counterparts in the literature, on the other hand, they included 4-sigma detections. According to these criteria, they detected 94 sources in the Serpens molecular cloud, 41 in the W40 region, and 8 in the Serpens South cluster, for a total of 143 detections. Out of the 143 sources, 69 are new detections (see Section 3.2 of the reference paper).

GBS-VLA source positions were compared with source positions from X-ray, optical, near-IR, mid-IR, and radio catalogs. GBS-VLA sources were considered to have a counterpart at another wavelength when the positional coincidences were better than the combined uncertainties of the two data sets. These were about 1 arcsecond for the IR catalogs. For the X-ray and radio catalogs it depended on the instrument and its configuration. The search was done in SIMBAD and included all the major catalogs. The authors also accessed the lists with all YSOs in the c2d-GB clouds compiled by Dunham et al.(2013, AJ, 145, 94) and L.E. Allen et al. (2015, in preparation). In total, 354 c2d-GB sources lie inside the regions observed by the present survey. In order to find their radio counterparts, the authors imaged regions of 64 pixels in each dimension, centered in the c2d-GB positions, and combining accordingly with each region, the three or two epochs. For this search, they only used the field whose phase center was closest to the source. Three additional radio sources were found in Serpens South in this pursuit, increasing the number of the radio detections to 146.


Catalog Bibcode

2015ApJ...805....9O

References

The Gould's Belt Very Large Array survey.
II. The Serpens region.
    Ortiz-Leon G.N., Loinard L., Mioduszewski A.J., Dzib S.A., Rodriguez L.F.,
    Pech G., Rivera J.L., Torres R.M., Boden A.F., Hartmann L., Evans Ii N.J.,
    Briceno C., Tobin J., Kounkel M.A., Gonzalez-lopezlira R.A.
   <Astrophys. J., 805, 9 (2015)>
   =2015ApJ...805....9O    (SIMBAD/NED BibCode)

Provenance

This table was created by the HEASARC in October 2015 based on electronic versions of Tables 2, 3 and 6 from the reference paper, which were obtained from the CDS (Catalog J/ApJ/805/9 files table2.dat, table3.dat and table6.dat).

Parameters

Region_Code
This parameter contains a code indicating the field in which the source was detected, as follows:

    S   = Detected sources in the Serpens molecular cloud;
    W40 = Detected sources in the W40 region;
    Ss  = Detected sources in the Serpens South cluster.
  

Name
The radio source J2000.0 position-based designation, viz., 'GBS-VLA JHHMMSS.ss+DDMMSS.s', where the prefix reflects the fact that these sources were found as part of the Gould's Belt Very Large Array Survey.

RA
The Right Ascension of the radio source in the selected equinox. This was not given explicitly in the original table but was constructed by the HEASARC from the J2000.0 position-based source designation which was given to a precision of 0.01 seconds of time.

Dec
The Declination of the radio source in the selected equinox. This was not given explicitly in the original table but was constructed by the HEASARC from the J2000.0 position-based source designation which was given to a precision of 0.1 arcseconds.

LII
The Galactic Longitude of the radio source.

BII
The Galactic Latitude of the radio source.

Source_Flag
This parameter can contain a value of 'P' indicating that the source is without reported counterparts and was detected with an integrated flux <5 sigma, but with a peak flux >= 5 sigma.

New_Detection_Flag
This parameter contains a flag indicating whether or not the radio source is a 'new' detection, as follows:

    Y = Source without reported counterparts at any frequency;
    N = Source with known counterpart.
  

Flux_4p5_GHz_Limit
This limit parameter is set to '<' if the corresponding flux density is an upper limit rather than a detection.

Flux_4p5_GHz
The 4.5-GHz flux density of the radio source, in mJy. The flux densities are measured in the combined epoch images.

Flux_4p5_GHz_Error
The uncertainty in the 4.5-GHz flux density of the radio source, in mJy. The quoted flux errors comprise the statistical error provided by IMFIT, the 5% absolute flux uncertainty, and the uncertainty induced by the pointing error of the VLA primary beam, added in quadrature.

Var_4p5_GHz_Limit
This limit parameter is set to '>' if the corresponding flux density variability percentage is a lower limit rather than an actual value.

Var_4p5_GHz
The variability of the source flux density at 4.5 GHz, in percent. The estimate of the level of variability of the sources was measured by comparing the source fluxes measured at the two (for the W40 field) or three epochs (for the Serpens fields). Specifically, the authors calculated, for each source and at each frequency, the difference between the highest and lowest measured fluxes, and normalized this by dividing it by the maximum flux.

Var_4p5_GHz_Error
The uncertainty in the variability of the source flux density at 4.5 GHz, in percent.

Var_4p5_GHz_Flag
This flag parameter contains the following two non-blank coded values concerning the variability of the source flux density at 4.5 GHz,:

    A = Source not detected at three times the noise level in individual epochs,
        but detected on the image of the concatenated epochs;
    e = Extended, and therefore not studied for variability.
  

Flux_7p5_GHz_Limit
This limit parameter is set to '<' if the corresponding flux density is an upper limit rather than a detection.

Flux_7p5_GHz
The 7.5-GHz flux density of the radio source, in mJy. The flux densities are measured in the combined epoch images.

Flux_7p5_GHz_Error
The uncertainty in the 7.5-GHz flux density of the radio source, in mJy. The quoted flux errors comprise the statistical error provided by IMFIT, the 5% absolute flux uncertainty, and the uncertainty induced by the pointing error of the VLA primary beam, added in quadrature.

Var_7p5_GHz_Limit
This limit parameter is set to '>' if the corresponding flux density variability percentage is a lower limit rather than an actual value.

Var_7p5_GHz
The variability of the source flux density at 7.5 GHz, in percent. The estimate of the level of variability of the sources was measured by comparing the source fluxes measured at the two (for the W40 field) or three epochs (for the Serpens fields). Specifically, the authors calculated, for each source and at each frequency, the difference between the highest and lowest measured fluxes, and normalized this by dividing it by the maximum flux.

Var_7p5_GHz_Error
The uncertainty in the variability of the source flux density at 7.5 GHz, in percent.

Var_7p5_GHz_Flag
This flag parameter contains the following two non-blank coded values concerning the variability of the source flux density at 7.5 GHz,:

    A = Source not detected at three times the noise level in individual epochs,
        but detected on the image of the concatenated epochs;
    e = Extended, and therefore not studied for variability.
  

Spectral_Index_Limit
This limit parameter is set to '<' if the corresponding spectral index is an upper limit rather than an actual value, and to '>' if the corresponding flux density variability percentage is a lower limit rather than an actual value.

Spectral_Index
The radio spectral index, alpha, where the flux density as a function of frequency, nu, S_nu_~ nualpha, from the flux densities measured in each sub-band (at 4.5 and 7.5 GHz), where alpha = log(S4.5/S7.5)/log(4.5GHz/7.5GHz). See Section 3.3 of the reference paper for more details.

Spectral_Index_Error
The uncertainty in the radio spectral index, alpha.

YSO_Candidate_Flag
This flag parameter was added by CDS based on the presence or absence of the radio source in Table 5 of the reference paper Sources listed in Table 5 have parameter values of 'c' indicating that the authors consider them to be YSO candidates based just on their radio properties, while sources not listed in Table 5 have blank values of this parameter

Alt_Name
An alternative name for the source if it has a previously known counterpart.

Xray_Name
The name of the X-ray counterpart to the radio source, if one exists. The X-ray designations come from the following references:

   [GFM2007] NN  from Giardino et al. (2007, A&A, 463, 275);
   [KGF2010] NNN from Kuhn et al. (2010, ApJ, 725, 2485).
  

Spitzer_Match_Flag
This flag parameter is set to 'Y' to indicate that there is a matching Spitzer Space Telescope (SST) source in Evans et al. (2009, ApJS, 181, 321) or the c2d-GB clouds catalog (Dunham et al. (2013, AJ, 145, 94).

TwoMASS_Match_Flag
This flag parameter is set to 'Y' to indicate that there is a matching 2MASS source in Cutri et al. (2003, CDS Cat. II/246).

WISE_Match_Flag
This flag parameter is set to 'Y' to indicate that there is a matching WISE source in Wright et al. (2010, AJ, 140, 1868) or Cutri et al. (2012, CDS Cat. II/311).

Radio_Name
The name of the previous detection of the radio source, if one exists. The previous radio designations come from the following references:

        [ETC2005] NN   = Eiroa et al. (2005, AJ, 130, 643);
                 NVSS  = Condon et al. (1998, CDS Cat. VIII/65);
             [DCE2008] = AMI-Consortium et al. (2012, MNRAS, 420, 1019);
  [RRR2010] W40-VLA NN = Rodriguez et al. (2010, AJ, 140, 968).
  

Object_Type
A classification of the sources which was taken from the literature and is based on the IR and X-ray properties of the sources. A total of 29 of the 77 sources with counterparts are firmly classified as YSOs, while HD170634 (GBS-VLA J183024.87+011323.5) and W 40 IRS 5 (GBS-VLA J183114.82-020350.1) are typed as B7V and B1V stars, respectively. Two additional sources (GBS-VLA J183127.30-020504.5 and J183127.45-020512.0) are considered YSO candidates (Rodriguez et al. 2010, AJ, 140, 968). Three other sources have been associated with phenomena related to YSOs. Rodriguez et al. (2010) suggest that GBS-VLA J183128.67-020522.2 could correspond to a shock front from a thermal jet (possibly powered by GBS-VLA J183128.65-020529.8) interacting with the ambient interstellar medium. The sources GBS-VLA J183127.64-020513.5 and J183127.67-020519.7 have been considered as ultracompact H II (UCH II) region candidates, centered around young massive stars. However, Shuping et al. (2012, AJ, 144, 116) argue that this classification is unlikely, as the size of the unresolved radio sources at a distance of 500 pc would be less than 100 AU, much smaller than a typical UCH II region.

Spect_Type
The spectral type of the YSO counterpart to the radio source.

SED_Classification
The SED classification for the YSO counterpart to the radio source, taken from the literature as specified in the ref_sed_classification parameter value.

SED_Classification_Flag
This flag parameter is set to 'd' for the source GBS-VLA J183127.65-020509.7. This source has a mass of ~4 solar masses and no Ks band excess, thus the authors consider it to be an HAeBe candidate.

Variability_Flag
This flag parameter indicates whether or not the source is highly variable (or extended), as follows:

    Y = flux variability >~50% at a 3-sigma level in at least one frequency'
    N = variability is <50% at both frequencies;
    E = Extended.
  

Spectral_Index_Flag
This flag parameter indicates whether or not the radio spectral index is significantly positive, flat or significantly negative, as follows (where alpha is the radio spectral index):

    P = alpha higher than 0.2;
    F = flat alpha; between -0.2 and +0.2;
    N = alpha lower than -0.2.
  

Xray_Match_Flag
This flag parameter indicates whether ('Y') or not ('N') an X-ray flux has been reported for the counterpart to the radio source in the literature.

Ref_SED_Classification
The reference for the quoted SED classification, as follows:

    1 = Giardino et al. (2007, A&A, 463, 275);
    2 = Enoch et al. (2009, ApJ, 692, 973);
    3 = Kuhn et al. (2010, ApJ, 725, 2485);
    4 = Shuping et al. (2012, AJ, 144, 116);
    5 = Winston et al. (2010, AJ, 140, 266);
    6 = Preibisch (1999, A&A, 345, 583);
    7 = c2d-GB cloud catalog (Dunham et al. 2013, AJ, 145, 94).
  

Class
The HEASARC Browse object classification based on the value of the sed_classification parameter.


Contact Person

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

Page Author: Browse Software Development Team
Last Modified: 26-Oct-2015