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VLAHDF20CM - VLA Hubble Deep Field 20-cm Source Catalog

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Overview

The authors have conducted a deep radio survey with the Very Large Array (VLA) at 1.4 GHz of a region containing the Hubble Deep Field (HDF). This survey overlaps previous observations at 8.5 GHz allowing them to investigate the radio spectral properties of microJansky sources to flux densities greater than 40 microJy (uJy) at 1.4 GHz and greater than 8 uJy at 8.5 GHz. A total of 371 sources have been catalogued at 1.4 GHz as part of a complete sample within 20 arcminutes of the HDF. The differential source count for this region is only marginally sub-Euclidean and is given by n(S) = (8.3 +/- 0.4) S^(-2.4 +/- 0.1) sr-1 Jy-1. Above about 100 uJy the radio source count is systematically lower in the HDF as compared to other fields. The authors conclude that there is clustering in this radio sample on size scales of 1 to 40 arcminutes. The 1.4 GHz-selected sample shows that the radio spectral indices are preferentially steep (mean spectral index of 0.85) and that the sources are moderately extended with average angular size Theta = 1.8". Optical identification with disk-type systems at z ~ 0.1 - 1 suggests that synchrotron emission, produced by supernovae remnants, is powering the radio emission in the majority of sources.

In 1996 November, the authors observed a field centered on the Hubble Deep Field (RA, Dec (J2000.0) = (12h 36m 49.4s, 62o 12' 58.00") for a total of 50 hours at 20 cm in the A configuration of the VLA. They reached an rms noise level near the center of the field of 7.5 uJy. They adopted 40 uJy as the formal completeness limit over the entire 1 degree field in their untapered naturally weighted 2 arcseconds image. The authors identified 314 sources within 20 arcminutes of the field center (20% power contour). They found 57 additional sources within this same region (presumably resolved at 2" resolution) in lower resolution (3.5 and 6") tapered images above completeness levels of 50 uJy at 3.5" resolution and 75 uJy at 6" resolution, making a grand total of 371 radio sources detected at 1.4 GHz within 20 arcminutes of the phase center of the field.


Catalog Bibcode

2000ApJ...533..611R

References

The nature of radio emission from distant galaxies: the 1.4 GHz observations.
    Richards E.A.
   <Astrophys. J. 533, 611 (2000)>
   =2000ApJ...533..611R

Provenance

This table was created by the HEASARC in June 2012 based on CDS Catalog J/ApJ/533/611 file table2.dat.

Parameters

Name
The source designation as given in the CDS Dictionary of Nomenclature of celestial Objects, viz., '[R2000] JHHMMSS.sss+DDMMSS.ss', where the prefix stands for Richards (200) and the J2000.0 coordinates of the source form the numerical part.

RA
The Right Ascension of the radio source in the selected equinox. This was given in J2000.0 coordinates to a precision of 0.001 seconds of time in the original table.

Dec
The Declination of the radio source in the selected equinox. This was given in J2000.0 coordinates to a precision of 0.01 arcseconds in the original table.

LII
The Galactic Longitude of the radio source.

BII
The Galactic Latitude of the radio source.

RA_Error
The 1-sigma uncertainty in the Right Ascension of the radio source, in seconds of time.

Dec_Error
The 1-sigma uncertainty in the Declination of the radio source, in arcseconds.

Flux_20_cm
The integrated sky flux density of the radio source at 1.4 GHz, in milliJanskies (mJy), after correction for the instrumental gain (see Section 3.2 of the reference paper for motre details). The original units for this parameter in the reference paper were uJy. The HEASARC converted them to mJy to conform to its standard unit for radio flux densities.

Flux_20_cm_Error
The 1-sigma uncertainty in the integrated sky flux density of the radio source at 1.4 GHz, in milliJanskies (mJy). The original units for this parameter in the reference paper were uJy. The HEASARC converted them to mJy to conform to its standard unit for radio flux densities.

Major_Axis_Limit
This parameter is set to '<' if the corresponding deconvolved best-fit Gaussian major axis is an upper limit.

Major_Axis
The deconvolved (FWHM) major axis of the best Gaussian fit to the major axis of the radio source, in arcseconds.

SNR_20_cm
The Signal-to-Noise (S/N) ratio of the detection calculated from Sp/sigma, where Sp is the peak flux density as measured in either the 2", 3.5" or 6" image and sigma equals the rms noise in that image.


Contact Person

Questions regarding the VLAHDF20CM database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 27-Jun-2012