VLAGBSORI - VLA Gould's Belt Survey Orion Complex Source Catalog

Overview

This table contains results from a high-sensitivity (60 µJy), large-scale (2.26 deg²) survey obtained with the Karl G. Jansky Very Large Array (JVLA) as part of the Gould's Belt Survey (GBS) program. The authors detected 374 and 354 sources at 4.5 and 7.5 GHz, respectively. Of these, 148 are associated with previously known young stellar objects (YSOs). Another 86 sources previously unclassified at either optical or infrared wavelengths exhibit radio properties that are consistent with those of young stars. The overall properties of these sources at radio wavelengths such as their variability and radio to X-ray luminosity relation are consistent with previous results from the GBS. These detections provide target lists for follow-up Very Long Baseline Array radio observations to determine their distances, as YSOs are located in regions of high nebulosity and extinction, making it difficult to measure their optical parallaxes.

The observations were obtained with the JVLA of the National Radio Astronomy Observatory (NRAO) in its A configuration. The observations of the 210 fields in the Orion Molecular Clouds A and B were obtained in three different epochs (2011 June 25 to July 4, July 23 to 30, and August 25 to 29, as described in Table 1 of the reference paper) typically separated from one another by a month. The 210 individual fields have been split into 7 maps, with 30 fields being observed per map, as follows: 12 in the lambda Ori region, 3 in L1622, 27 are shared between NGC 2068 and NGC 2071, 14 are shared between NGC 2023 and NGC 2024, 11 in the sigma Ori region, 109 in the Orion Nebula Cluster (ONC), 16 in L1641-N, 8 in L1641-C, and 10 in L1641-S (see Figures 1 to 7 in the reference paper). Two frequency sub-bands, each 1-GHz wide, and centered at 4.5 and 7.5 GHz, respectively, were recorded simultaneously. The authors achieved a nearly uniform rms noise of 60 µJy beam^-1 at both frequencies in all the regions. The only exception to this is in the Trapezium region due to nebular emission; there the noise was 200 µJy beam^-1 after excluding baselines smaller than 150 kilo-lambda during imaging to remove extended emission.

Sources were identified through a visual inspection of the individual fields at 4.5 GHz during the cleaning and imaging process since an automated source identification was deemed to be not sufficiently advanced and produced results that were too unreliable. In particularly clustered regions such as the Trapezium and NGC 2024, in addition to standard imaging, data from all three epochs were combined into a single image for source identification purposes only to improve statistical significance of each detection. The authors detected a combined total of 374 sources among the three epochs for all of the regions. All sources but one had fluxes greater than five times the rms noise in at least one epoch. The remaining source, 'GBS-VLA J053518.67-052033.1', was detected at two epochs with maximum detection probability of 4.9 sigma in a single epoch data. It is found in the Trapezium region, and has known counterparts in other wavelength regimes.

The authors cross-referenced their catalog of sources with previous major radio, infrared, optical and X-ray surveys of the regions published in the literature. They have generally considered sources in these surveys to be counterparts if they had positional coincidences less than 1 arcsecond, but have allowed for larger offsets if the combined uncertainty between the databases was large. Of 374 detected sources, 261 have been previously found at another wavelength region, while 113 are new detections. 146 sources have been detected in X-rays, 94 at optical wavelengths, 218 at infrared, and 63 in previous radio surveys. Of the previously identified sources, 1 is extragalactic, while the other 148 as young stellar objects (YSOs). Of the YSOs, 106 have been placed on the standard class system based on the IRAC color-color classification of Allen et al. (2004, ApJS, 154, 363). There are 11 Class 0/I, 26 Class II, and 70 Class III type stars. A total of 225 sources are either new detections or, to the authors' knowledge, have not been previously classified in the literature. Of these remaining objects, they have identified 86 as exhibiting variability or high levels of circular polarization. While the authors cannot exclude the possibility that any of them are extragalactic in nature, quasars are not expected to vary as strongly on timescales of few weeks to few months, and exhibit very weak circular polarization, so these sources (listed in Table 5 of the reference paper) are likely YSO candidates. Using the same criteria of variability and circular polarization would identify only 107 of the 148 previously-known YSOs; thus we cannot tell which of the remaining 139 unidentified sources are YSOs or extragalactic objects.

Catalog Bibcode

2014ApJ...790...49K

References

The Gould's Belt Very Large Array Survey.
III. The Orion Region.
    Kounkel M., Hartmann L., Loinard L., Mioduszewski A.J.,  Dzib S.A.,
    Ortiz-Leon G.N., Rodriguez L.F., Pech G., Rivera J.L., Torres R.M.,
    Boden A.F.,  Evans II N.J., Briceno C., Tobin J.
   <Astrophys. J., 790, 49 (2014)>
   =2014ApJ...790...49K

Provenance

This table was created by the HEASARC in July 2015 based on electronic versions of Tables 2 and 4 from the reference paper, which were obtained from the ApJ web site.

HEASARC Implementation

The HEASARC has added a parameter radio_yso_flag which is set to 'Y' for the 86 newly detected sources (listed in Table 5 of the reference paper) which the authors suspected to be YSOs based just on their radio properties, else is set to 'N'.

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.

Max_Flux_4p5_GHz
The highest detected 4.5-GHz flux density of the radio source, in mJy, between the three observing epochs.

Max_Flux_4p5_GHz_Error
The 4.5-GHz flux density uncertainty that results from the statistical noise in the images as calculated by JMFIT, in mJy.

Max_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, indicating the lack of a detection at one of the epochs, and that the variability is calculated with the flux values of the remaining two epochs.

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 lack of a quoted variability corresponding to a quoted flux indicates that there is only a single epoch detection.

Var_4p5_GHz_Error
The uncertainty in the variability of the source flux density at 4.5 GHz, in percent. These errors include the statistical and absolute uncertainty (and, for objects far from the phase center of the primary beam, the uncertainty from the pointing error of the JVLA primary beam).

Max_Flux_7p5_GHz
The highest detected 7.5-GHz flux density of the radio source, in mJy, between the three observing epochs.

Max_Flux_7p5_GHz_Error
The 7.5-GHz flux density uncertainty that results from the statistical noise in the images as calculated by JMFIT, in mJy.

Max_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, indicating the lack of a detection at one of the epochs, and that the variability is calculated with the flux values of the remaining two epochs.

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 lack of a quoted variability corresponding to a quoted flux indicates that there is only a single epoch detection.

Var_7p5_GHz_Error
The uncertainty in the variability of the source flux density at 7.5 GHz, in percent. These errors include the statistical and absolute uncertainty (and, for objects far from the phase center of the primary beam, the uncertainty from the pointing error of the JVLA primary beam).

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.

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%, or there is no
           detection at one or more epoch with the source located in the inner
           half of the beam, in at least one frequency;
      N  = otherwise.

Source_Type
The object type ('YSO', 'Galaxy') for the radio source counterpart. The YSO class ('I', 'II' or 'III') is listed in parentheses, if known.

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:

      OX = Franciosini & Sacco (2011 A&A, 530, A150);
    3XMM = XMM-Newton Survey Science Centre (2013, XMM-Newton Serendipitous
           Source Catalog, 3XMM Version) [full name not given];
     SSM = Skinner et al. (2009, ApJ, 701, 710);
     SGB = Skinner et al. (2003, ApJ, 598, 375);
     CCS = Caballero et al. (2010, A&A, 521, A45);
     RRS = Ramirez et al. (2004, AJ, 128, 787);
     TKT = Tsujimoto et al. (2002, ApJ, 566, 974);
    COUP = Getman et al. (2005, ApJS, 160, 319);
    SOXS = Pillitteri et al. (2013, ApJ, 773, 80).

Optical_Name
The name of the optical counterpart to the radio source, if one exists. The optical designations come from the following references:

     BSM = Bayo et al. (2011, A&A, 536, A63);
     TYC = Perryman & ESA (1997, Hipparcos ans Tycho Catalogs);
   UCAC4 = Zacharias et al. (2013, AJ, 145, 44) [full name not given];
     H97 = Hillenbrand (1997, AJ, 113, 1733);
     DRS = Da Rio et al. (2009, ApJS, 183, 261);
     HHA = Hsu et al. (2012, ApJ, 752, 59).

IR_Name
The name of the infrared counterpart to the radio source, if one exists. The IR designations come from the following references:

     HMC = Hernandez et al. (2010, ApJ, 722, 1226);
      2M = Cutri et al. (2003, 2MASS Catalog) [full name not given];
     MGM = Megeath et al. (2012, AJ, 144, 192) [full name not given];
     PBZ = Pena Ramirez et al. (2012, ApJ, 754, 30);
     HHM = Hernandez et al. (2007, ApJ, 662, 1067);
     MAD = Bouy et al. (2009, A&A, 493, 931);
    ISOY = Morales-Calderon et al. (2011, ApJ, 733, 50) [full name not given];
     TKK = Tsujimoto et al. (2003, AJ, 125, 1537).

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

   NVSS = Condon et al. (1998, AJ, 115, 1693) [full name not given];
    G99 = Gibb (1999, MNRAS, 304, 1);
    RRA = Reipurth et al. (2004, AJ, 127, 1736);
     RR = Rodriguez & Reipurth (1994, A&A, 281, 882);
    RRC = Reipurth et al. (1999, AJ, 118, 983);
    GMR = Garay et al. (1987, ApJ, 314, 535);
    AVE = Anglada et al. (1998, AJ, 116, 2953);
    ARC = Avila et al. (2001, RMxAA, 37, 201).

Radio_Yso_Flag
This HEASARC-created parameter is set to 'Y' if the source is one of the 86 newly detected sources (listed in Table 5 of the reference paper) which the authors suspected to be YSOs based just on their radio properties; otherwise, it is set to 'N'.

Contact Person

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

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