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VLAGBSOPH - VLA Gould's Belt Survey Ophiuchus Complex Source Catalog

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Overview

This table contains results from large-scale (~2000 arcmin2), deep (~20 microJy), high-resolution (~1") radio observations of the Ophiuchus star-forming complex obtained with the Karl G. Jansky Very Large Array (JVLA) at wavelengths of 4 and 6 cm (frequencies of 7.5 and 4.5 GHz). In total, 189 sources were detected, 56 of them associated with known young stellar objects (YSOs), and 4 with known extragalactic objects; the other 129 remain unclassified, but most of them are most probably background quasars. The vast majority of the young stars detected at radio wavelengths have spectral types K or M, although four objects of A/F/B types and two brown dwarf candidates are also detected. At least half of these young stars are non-thermal (gyrosynchrotron) sources, with active coronae characterized by high levels of variability, negative spectral indices, and (in some cases) significant circular polarization. As expected, there is a clear tendency for the fraction of non-thermal sources to increase from the younger (Class 0/I or flat spectrum) to the more evolved (Class III or weak-line T Tauri) stars. The young stars detected both in X-rays and at radio wavelengths broadly follow a Gudel-Benz relation, but with a different normalization than the most radio-active types of stars. Finally, the authors detected a ~70 mJy compact extragalactic source near the center of the Ophiuchus core, which should be used as gain calibrator for any future radio observations of this region.

The observations were obtained with the JVLA of the National Radio Astronomy Observatory (NRAO). Two frequency sub-bands, each 1-GHz wide, and centered at 4.5 and 7.5 GHz, respectively, were recorded simultaneously. The observations were obtained on three different epochs (2011 February 17/19, April 3/4, and May 4/6) typically separated from one another by a month. The angular resolution of the observations is of the order of 1 arcsecond.

To identify sources in their observations, the authors used the images corresponding to the concatenation of the three epochs, which provided the highest sensitivity. The criteria used to consider a detection as firm were: (1) sources with reported counterparts and a flux larger than four times the rms noise of the area, or (2) sources with a flux larger than five times the rms noise of the area and without reported counterparts.

The authors searched the literature for previous radio detections, and for counterparts at X-ray, optical, near-infrared, and mid-infrared wavelengths. The search was done in SIMBAD, and accessed all the major catalogs (listed explicitly in the footnote of Table 3 in the reference paper). Note that the Spitzer c2d catalog includes cross-references to other major catalogs which were taken into account in their counterpart search. The authors considered a radio source associated with a counterpart at another wavelengths if the separation between the two was below the combined uncertainties of the two data sets. This was about 1.5 arcseconds for the optical and infrared catalogs, but could be significantly larger for some of the radio catalogs (for instance, the NVSS has a positional uncertainty of about 5 arcseconds). The authors found that only 76 of the sources detected here had previously been reported at radio wavelengths (matches are listed in the radio_name parameter in such cases), while the other 113 are new radio detections. On the other hand, they found a total of 100 counterparts at other wavelengths. Note that there are a significant number of sources that were previously known at radio wavelengths and have known counterparts at other frequencies. As a consequence, the number of sources that were previously known (at any frequency) is 134, while 55 of the sources in this sample are reported here for the first time. The authors argue that most of these 55 objects are likely background sources. They note, however, that 18 of the 129 unclassified objects (55 identified here for the first time and 74 previously known at radio wavelengths) are compact, have a positive spectral index, or exhibit high variability. Since these latter two properties are not expected of quasars (which are certainly variable, but usually not strongly on such short timescale), but would be natural characteristics of young stars, the authors argue that a small population of YSOs might be present among the unclassified sources. This population could account for, at most, 15% of the unclassified sources, and possibly significantly less.


Catalog Bibcode

2013ApJ...775...63D

References

The Gould's Belt Very Large Array Survey.
I. The Ophiuchus complex.
    Dzib S.A., Loinard L., Mioduszewski A.J., Rodriguez L.F., Ortiz-Leon G.N.,
    Pech G., Rivera J.L., Torres R.M., Boden A.F., Hartmann L., Evans II N.J.,
    Briceno C., Tobin J.
   <Astrophys. J., 775, 63 (2013)>
   =2013ApJ...775...63D

Provenance

This table was created by the HEASARC in July 2015 based on electronic versions of Tables 1, 3 and 5 from the reference paper, which were obtained from the CDS (Catalog J/ApJ/775/63 files table1.dat, table3.dat and table5.dat).

HEASARC Implementation

While ingesting this table, the HEASARC discovered that 4 of the radio sources had different names in Table 5 from the reference paper than were used in Tables 1 and 3 from the same source (see below). In all 4 cases, the HEASARC retained the names used in Tables 1 and 3 in its version.
    Name in Tables 1 and 3        Name in Table 5

GBS-VLA J162719.50-244140.3   GBS-VLA J162719.50-244140.4
GBS-VLA J162721.81-244335.9   GBS-VLA J162721.81-244336.0
GBS-VLA J162724.19-242929.8   GBS-VLA J162724.19-242929.6
GBS-VLA J162739.42-243915.8   GBS-VLA J162739.41-243915.8

Parameters

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.

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.

Flux_4p5_GHz_Error
The 4.5-GHz flux density uncertainty that results from the statistical noise in the images, in mJy.

Flux_4p5_GHz_Syserr
The 4.5-GHz flux density systematic uncertainty of 5% that results from possible errors in the absolute flux calibration, in mJy.

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 three epochs. 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_Flag
This flag parameter is set to 'a' if the source was not detected at three times the noise level at this frequency in the individual epochs, but was detected in the image of the concatenated epochs.

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

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.

Flux_7p5_GHz_Error
The 7.5-GHz flux density uncertainty that results from the statistical noise in the images, in mJy.

Flux_7p5_GHz_Syserr
The 7.5-GHz flux density systematic uncertainty of 5% that results from possible errors in the absolute flux calibration, in mJy.

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 three epochs. 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_Flag
This flag parameter is set to 'a' if the source was not detected at three times the noise level at this frequency in the individual epochs, but was detected in the image of the concatenated epochs.

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

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).

Spectral_Index_Error
The uncertainty in the radio spectral index, alpha.

Extent_Flag
This flag parameter is set to 'Ex' to indicate that the source is extended. Radio spectral indices are not given for extended sources.

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:

    ROXRA    = Grosso et al. (2000, A&A, 359, 113;
    A and BF = Imanishi et al. (2003, J, PASJ, 55, 653: '[INT2003] AA-NN'
                                                       in Simbad);
    DROXO    = Pillitteri et al. (2010, A&A, 519, A34);
    ROX      = Montmerle et al. (1983, ApJ, 269, 182);
    ROXs     = Bouvier & Appenzeller (1992, A&AS, 92, 481);
    1RXS     = Voges et al. (1999, CDS Cat. IX/10);
    RX       = Martin et al. (1998, MNRAS, 300, 733: '[MMG98] RX JHHMM.m+DDMMa'
                                                       in Simbad).
  

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).

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 Cutri et al. (2012, CDS Cat. II/311).

IR_Flag
This flag parameter is set to 'a' to indicate that there is 2MASS and SST data for the source 'GBS-VLA J162722.96-242236.6' in Marsh et al. (2010, ApJ, 719, 550: '[MPK2010b] NNNNN' in Simbad).

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

    ROC and ROS = Andre et al. (1987, AJ, 93, 1182);
    GDS         = Gagne et al. (2004, ApJ, 613, 393);
    NVSS        = Condon et al. (1998, CDS Cat. VIII/65);
    LFAM        = Leous et al. (1991ApJ, 379, 683);
    SFAM        = Stine et al. (1988AJ, 96, 1394).
  

Source_Type
The object type ('YSO', 'YSO?' or 'E' for extragalactic) for the radio source counterpart. Based on their optical/infrared characteristics, 2 of the 100 sources with counterparts are classified in the literature as extragalactic sources, while 55 are classified as YSOs. One additional object ('GBS-VLA J162626.31-242430.3', also known as VLA 1623B) is associated with the well-known Class 0 source VLA 1623, but it is still debated whether it is an outflow knot feature, or a protostellar object (see the discussion by Ward-Thompson et al. 2011, MNRAS, 415, 2812; and Section 5.1 of the reference paper). The remaining 42 radio sources with known counterparts at other wavelengths are, to the authors' knowledge, not classified in the literature. On the other hand, two sources ('GBS-VLA J162615.67-243421.2' and 'GBS-VLA J162626.03-244923.7') have been classified in the literature as extragalactic, on the basis of their radio properties alone.

Knot_Flag
This flag is set to 'c' for the source 'GBS-VLA J162626.31-242430.3', also known as VLA 1623B, to indicate that, as discussed in the text, it may be either a young star or an outflow knot feature.

Spect_Type
The MK spectral type of the radio source stellar counterpart, or 'BD?' for possible brown dwarf. This parameter is populated only for those radio sources for which the counterparts are YSOs.

SED_Classification
The spectral energy distribution (SED) classification of the IR counterpart to the radio source, 'WTTS' for weak-lined T Tauri star, or 'FS' for 'Faint Spectrum'. This parameter is populated only for those radio sources for which the counterparts are YSOs.

Var_Flag
This flag parameter encapsulates the radio variability characteristics of the radio source, as follows:

    Y  = when the source variability is higher than 50% in at least one
         frequency;
    N  = when the source variability is lower than 50% in at least one
         frequency.
  
This parameter is populated only for those radio sources for which the counterparts are YSOs.

CP_Flag
This flag parameter encapsulates the circular polarization characteristics of the radio source, as follows (sources in the outer fields for which the polarization could not be assessed are left blank):

    Y  = circular polarization was detected (information is given in Table 2
         of the reference paper);
    N  = circular polarization was not detected.
  
This parameter is populated only for those radio sources for which the counterparts are YSOs.

Spectral_Index_Flag
This flag parameter encapsulates the radio spectral index (alpha) of the radio source, as follows:

     P = positive: spectral index higher than 0.2;
     F = flat: spectral index between -0.2 and +0.2;
     N = negative: spectral index lower than -0.2.
  
This parameter is populated only for those radio sources for which the counterparts are YSOs.

Xray_Flag
This flag parameter encapsulates whether ('Y') or not ('N') the radio source has an X-ray counterpart. This parameter is populated only for those radio sources for which the counterparts are YSOs.

Ref_Codes
Reference codes for previous papers discussing the source. This information is given only for those radio sources for which the counterparts are YSOs. The key to the codes is as follows:

     1 = Wilking et al. (2005, AJ, 130, 1733);
     2 = Gagne et al. (2004, ApJ, 613, 393);
     3 = Murillo & Lai (2013, ApJ, 764, L15);
     4 = Andre et al. (1993, ApJ, 406, 122);
     5 = Alves de Oliveira et al. (2010, A&A, 515, A75);
     6 = Marsh et al. (2010, ApJ, 719, 550);
     7 = Pillitteri et al. (2010, A&A, 519, A34);
     8 = McClure et al. (2010, ApJS, 188, 75);
     9 = Cieza et al. (2007, ApJ, 667, 308);
    10 = Wilking et al. (2001, ApJ, 551, 357);
    11 = Martin et al. 1998, MNRAS, 300, 733);
    12 = Wahhaj et al. (2010, ApJ, 724, 835);
    13 = Bouvier & Appenzeller (1992, A&AS, 92, 481);
    14 = Torres et al. (2006, A&A, 460, 695).
  

Contact Person

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

Page Author: Browse Software Development Team
Last Modified: 17-Jul-2015