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VLAONCCAT - VLA Orion Nebula Cluster Compact Source Catalog

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Overview

This table contains a deep centimeter-wavelength catalog of the Orion Nebula Cluster (ONC), based on a 30-hr single-pointing observation with the Karl G. Jansky Very Large Array (JVLA) in its high-resolution A configuration using two 1-GHz bands centered on 4.7 and 7.3 GHz. A total of 556 compact sources were detected in a map with a nominal rms noise of 3 µJy/beam, limited by complex source structure and the primary beam response. Compared to previous catalogs, these detections increase the sample of known compact radio sources in the ONC by more than a factor of seven. The new data show complex emission on a wide range of spatial scales. Following a preliminary correction for the wideband primary-beam response, the authors determine radio spectral indices for 170 sources whose index uncertainties are less than +/-0.5. They compare the radio to the X-ray and near-infrared point-source populations, noting similarities and differences.

The observations were carried out with the JVLA of the National Radio Astronomy Observatory on 2012 September 30 and October 2-5 under the auspices of the project code SD630. Data were taken using the VLA's C-band (4-8 GHz) receivers in full polarization mode, with two 1-GHz basebands centered at 4.736 and 7.336 GHz to provide a good baseline for source spectral index determination. Apart from the first epoch, the field was simultaneously observed with the Chandra X-Ray Observatory. Mostly of interest for variability information, these data will be presented as part of a follow-up paper.


Catalog Bibcode

2016ApJ...822...93F

References

The population of compact radio sources in the Orion Nebula Cluster.
    Forbrich J., Rivilla V.M., Menten K.M., Reid M.J., Chandler C.J., Rau U.,
    Bhatnagar S., Wolk S.J., Meingast S.
   <Astrophys. J., 822, 93-93 (2016)>
   =2016ApJ...822...93F    (SIMBAD/NED BibCode)

Provenance

This table was created by the HEASARC in September 2016 based on CDS Catalog J/ApJ/822/93 file table1.dat (the compact source catalog).

Parameters

Source_Number
A running radio source number in order of increasing J2000.0 Right Ascension.

Name
The name of the radio source using the '[FRM2016] VLA' prefix (for Forbrich, Rivilla, Menten 2016 Very Large Array source) and the J2000.0 coordinates of the source in the (higher precision than standard to avoid duplicate names) J2000.0 equatorial coordinates-based name format ('HHMMSS.ss+DDMMSS.s'), e.g., '[FRM2016] VLA J053447.99-052054.1'. These names were created by the HEASARC in the style recommended by the Dictionary of Nomenclature of Celestial Objects. In the reference paper, the prefixes were not used.

Off_Axis
The angular distance of the radio source from the phase center of the JVLA observation, in arcminutes.

RA
The Right Ascension of the radio source centroid in the selected equinox. This was given in J2000.0 sexagesimal coordinates to a precision of 10-5 seconds of time in the original table.

RA_Error
The positional uncertainty in the Right Ascension of the radio source as estimated by JMFIT, in seconds of time. The 556 sources have median position errors, as estimated by JMFIT, of 6 mas in RA and 7 mas in Dec, with maximum errors of 0.1 arcseconds. These errors simply reflect the S/N ratio, and since not all of the sources are true point sources, this error reflects both the fit and potentially also source structure. The authors estimate an overall absolute astrometric accuracy of 20-30 mas.

Dec
The Declination of the radio source centroid in the selected equinox. This was given in J2000.0 sexagesimal coordinates to a precision of 10-4 arcseconds in the original table.

Dec_Error
The positional uncertainty in the Declination of the radio source as estimated by JMFIT, in arcseconds. The 556 sources have median position errors, as estimated by JMFIT, of 6 mas in RA and 7 mas in Dec, with maximum errors of 0.1 arcseconds. These errors simply reflect the S/N ratio, and since not all of the sources are true point sources, this error reflects both the fit and potentially also source structure. The authors estimate an overall absolute astrometric accuracy of 20-30 mas.

LII
The Galactic Longitude of the radio source.

BII
The Galactic Latitude of the radio source.

Flux_6p1_GHz
The peak flux density of the radio source, corrected for primary-beam attenuation using the CASA task widebandpbcor, in mJy, estimated using the AIPS JMFIT task and a Gaussian fit to the source. The authors enforced a consistent signal-to-noise cutoff of S/N > 5 in the concatenated data, where the task mainly used the global rms to calculate S/N. Given the spatial complexity of the radio emission, there is no generally useful cutoff criterion in the local S/N, but 98% of these sources have a local S/N > 3.

Flux_6p1_GHz_Error
The uncertainty in the peak flux density of the radio source, in mJy, estimated using the AIPS JMFIT task and a Gaussian fit to the source

Spectral_Index
The radio spectral index (Alpha) of the source between the two 1-GHz basebands centered at 4.736 and 7.336 GHz which were selected for this study, and corrected for the primary-beam response. As discussed in the text of the reference paper, this is given only for the 157 sources for which the associated errors determined from the multi-frequency synthesis images were <= 0.5 and JMFIT peak fluxes could be determined.

Spectral_Index_Error
The uncertainty in the radio spectral index (Alpha) of the source.

Source_Flags
This parameter contains information on previous radio identifications within 0.5 arcseconds of the position of the radio source, as follows:

        K: Kounkel et al. (2014, ApJ, 790, 49);
        Z: Zapata et al. (2004, AJ, 127, 2252;
    GMR N: Garay et al. (1987, ApJ, 314, 535) and subsequent publications,
           where N = A, B, etc., is the specific source designation.
  

Coup_Source_Number
The corresponding X-ray source number, if one lies within 0.5 arcseconds of the radio source position, taken from COUP (Getman et al. 2005, ApJS, 160, 319).

Log_Lx
The logarithm of the total, absorption-corrected X-ray (0.5-8.0 keV) luminosity of the COUP counterpart, in erg s-1, from Getman et al. (2005, ApJS, 160, 319).

Vision_NIR_ID
The J2000.0 positional part of the corresponding VISION near-infrared source identification, if one lies within 0.5 arcseconds of the radio source position, taken from Meingast et al. (2016, A&A, 587, A153).


Contact Person

Questions regarding the VLAONCCAT database table can be addressed to the HEASARC User Hotline.
Page Author: Browse Software Development Team
Last Modified: Friday, 09-Dec-2016 13:32:40 EST