VLAGBSTAU - VLA Gould's Belt Survey Taurus-Auriga Complex Source Catalog

Overview

This table contains results from a multi-epoch radio study of the Taurus-Auriga complex made with the Karl G. Jansky Very Large Array (JVLA) at frequencies of 4.5 GHz and 7.5 GHz. A total of 610 sources were detected, 59 of which are related to young stellar objects (YSOs) and 18 to field stars. The properties of 56% of the young stars are compatible with non-thermal radio emission. The authors also show that the radio emission of more evolved YSOs tends to be more non-thermal in origin and, in general, that their radio properties are compatible with those found in other star-forming regions. By comparing their results with previously reported X-ray observations, the authors noticed that YSOs in Taurus-Auriga follow a Guedel-Benz relation with a scaling factor, kappa, of 0.03, as they previously suggested for other regions of star formation. In general, YSOs in Taurus-Auriga and in all the previous studied regions seem to follow this relation with a dispersion of ~1 dex. Finally, the authors propose that most of the remaining sources are related with extragalactic objects but provide a list of 46 unidentified radio sources whose radio properties are compatible with a YSO nature (identified in this implementation of their catalog by values for the parameter radio_yso_flag of 'Y').

The observations were obtained with the JVLA of the National Radio Astronomy Observatory (NRAO) in its B and BnA configuration. 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 in three different time periods (February 25/26/28 to March 6, April 12/17/20/25, and April 30 to May 1/5/14/22, all in 2011) typically separated from one another by a month: see Table 1 of the reference paper for more details. For their study, the authors observed 127 different target fields distributed across the cloud complex (Figure 1 of the reference paper). The fields were chosen to cover previously known YSOs. In 33 of those fields, the authors could observe more than one YSO target, while in the remaining 94 fields, only one YSO was targeted. In most cases, the infrared evolutionary class (i.e., Classes I, II, or III) or T Tauri evolutionary status (classical or weak line) of the targeted sources was known from the literature.

The final images covered circular areas of 8.8 and 14.3 arcminutes in diameter, for the 7.5 and 4.5 GHz sub-bands, respectively, and were corrected for the effects of the position-dependent primary beam response. The noise levels reached for each individual observation was about ~40 µJy and ~30 µJy, at 4.5 GHz and7.5 GHz, respectively. The visibilities of the three, or two, observations obtained for each field were concatenated to produce a new image with a lower noise level (of about ~25 µJy at 4.5 GHz and ~18 µJy at 7.5 GHz). The angular resolution of ~1 arcsecond (see the synthesized beam sizes in Table 1 of the reference paper) allows an uncertainty in position of ~0.1 arcseconds or better.

In the observed area, there are a total of 196 known YSOs.The first step was the identification of radio sources in the observed fields. The authors follow the procedure and criteria presented by Dzib et al. (2013, ApJ, 775, 63) who consider a detection as firm if the sources have a flux larger than 4 times the noise level and there is a counterpart known at another wavelength, else they require a flux which is 5 times the noise level. The identification was done using the images corresponding to the concatenation of the observed epochs, which provides the highest sensitivity. From this, a total of 609 sources were detected. Of these sources, 215 were only detected in the 4.5 GHz sub-band, while six were only detected in the 7.5 GHz sub-band. The remaining 388 sources were detected in both sub-bands.

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 using SIMBAD, and accessed all the major catalogs. They considered a radio source to be associated with a counterpart at another wavelength if the separation between the two was below the combined uncertainties of the two data sets. This was about 1.0 arcsecond 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). They found that only 120 of the sources detected here had previously been reported at radio wavelengths, while the other 491 are new radio detections. On the other hand, the authors found a total of 270 counterparts at other wavelengths. In the literature, 18 are classified as field stars, 49 as extragalactic, 1 is classified as either a star or an extragalactic source in different surveys, 49 are classified as YSOs, 11 are classified as either YSO and extragalactic, and the remaining 143 sources are unclassified. Note that 56 sources were previously known at radio wavelengths but do not have known counterparts at other frequencies. As a consequence, the number of sources that were previously known (at any frequency) is 327, while 284 of the sources in this sample are reported here for the first time.

Catalog Bibcode

2015ApJ...801...91D

References

The Gould's Belt Very Large Array Survey.
I. The Taurus-Auriga complex.
    Dzib S.A., Loinard L., Rodriguez L.F., Mioduszewski A.J., Ortiz-Leon G.N.,
    Kounkel M.A., Pech G., Rivera J.L., Torres R.M., Boden A.F., Hartmann L.,
    Evans II N.J., Briceno C., Tobin J.
   <Astrophys. J., 801, 91 (2015)>
   =2015ApJ...801...91D

Provenance

This table was created by the HEASARC in July 2015 based on electronic versions of Tables 1, 4 and 5 from the reference paper, which were obtained from the ApJ web site.

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. The HEASARC notes that the values of this parameter in the machine-readable version of Table 2 on the ApJ web site from which this parameter was populated differ from those in the printed version of this table (which lists only the first ten entries in order of increasing RA). The HEASARC thus cautions that the values of this parameter in the present database table should be considered suspect.

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. The HEASARC notes that the values of this parameter in the machine-readable version of Table 2 on the ApJ web site from which this parameter was populated differ from those in the printed version of this table (which lists only the first ten entries in order of increasing RA). The HEASARC thus cautions that the values of this parameter in the present database table should be considered suspect.

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 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.

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_~ nu^alpha, 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 'E' to indicate that the source is extended. Radio spectral indices and variabilities 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 prefixes refer to the following references:

     XEST = Guedel et al. (2007, A&A, 468, 353);
      1RXS = Voges et al. (1999, A&A, 349, 389);
        RX = Neuhaeuser et al. (1995, A&A, 297, 391);
   BFR2003 = Bally et al. (2003, ApJ, 584, 843).

Spitzer_Match_Flag
This flag parameter is set to 'Y' to indicate that there is a matching Spitzer Space Telescope (SST) source in Padgett et al. (2007, BAAS, 39, 780).

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).

Radio_Match_Flag
This flag parameter is set to the name of the radio catalog or reference, if there is a previous radio detection, or to the common name of the source, e.g., DG Tau, T Tau, Haro 6-10, or TMC-2A 1. The remaining values refer to the following references:

      NVSS = Condon et al. (1998, AJ, 115, 1693);
        BW = Becker & White (1985, ApJ, 297, 649);
       SBS = Skinner et al. (1993, ApJS, 87, 217);
      OFMM = O'Neal et al. (1990, AJ, 100, 1610);
     LRDRG = Loinard et al. (2007, ApJ, 671, 546);
       RAR = Rodriguez et al. (1995, ApJL, 454, L149);
        CB = Cohen & Bieging (1986, AJ, 92, 1396);
     ARC92 = Anglada et al. (1992, ApJ, 395, 494);
      RRAB = Reipurth et al. (2004, AJ, 127, 1736);
       B96 = Bontemps (1996, PhD Thesis, Univ. Paris XI);
   GRL2000 = Giovanardi et al. (2000, ApJ, 538, 728);
      RR98 = Rodriguez & Reipurth (1998, RMxAA, 34, 13).

Source_Type
The object type ('YSO', 'YSO?' or 'E' for extragalactic) for the radio source counterpart. In the literature, 18 of the 610 sources are classified as field stars, 49 as extragalactic, 1 is classified as either a star or an extragalactic source in different surveys, 49 are classified as YSOs, 11 are classified as either YSO and extragalactic, and the remaining 143 sources are unclassified. In their sample of 530 possible background sources, 50 are either highly variable (3 times the sigma(Var.) level) or have a flat or positive spectral index value (within the range given by alpha +/- sigma(alpha)). Four of these were previously known to be extragalactic sources. The remaining 46 sources are listed in Table 5 of the reference paper and are indicated in this HEASARC table by their having a value of 'Y' for the radio_yso_flag parameter. From the arguments presented in their paper, the authors expect about 24 extragalactic sources with these characteristics. Thus, about half of the 48 sources are most certainly extragalactic, while the nature of the other half is unclear. They might be previously unidentified YSOs, but (given the inherent uncertainties on the radio properties of different classes of active galactic nuclei) they could also be extragalactic background sources.

Radio_Yso_Flag
This HEASARC-created parameter is set to 'Y' if the source is one of the 46 newly detected sources (listed in Table 5 of the reference paper) which the authors suspected to be possible (~50% probability) YSOs, based solely on their radio properties; otherwise, it is set to 'N'.

Contact Person

Questions regarding the VLAGBSTAU database table can be addressed to the HEASARC Help Desk.

Page Author: Browse Software Development Team
Last Modified: Monday, 16-Sep-2024 17:36:20 EDT