VLAM311P4G - VLA M 31 1.4-GHz Source Catalog

Overview

This table contains the Data Release 2 of the Point Source Catalog created from a series of previously constructed radio-continuum images of M 31 at a wavelength lambda of 20 cm (frequency nu = 1.4 GHz) from archived VLA observations. In total, the authors identify a collection of 916 unique discrete radio sources across the field of M 31. Comparing these detected sources with those listed by Gelfand et al. (2004, ApJS, 155, 89, HEASARC table VLAM31325M) at lambda = 92 cm (325 MHz), the spectral index of 98 sources has been derived. The majority (73%) of these sources exhibit a spectral index of alpha < -0.6, indicating that their emission is predominantly non-thermal in nature, which is typical for background objects and Supernova Remnants (SNRs).

This table contains the integrated flux densities for 1,131 detections of 916 unique sources detected at 1.4 GHz in 28 VLA observations. Of these 916 unique sources, 109 were detected in at least two separate images. For such sources, the authors list a group identifier, a group count, and an average flux and error. Sources were cross referenced with the Gelfand et al. (2004) catalog of sources detected at 92 cm. For matched sources, the flux density at this wavelength and the derived spectral index between 20 and 92 cm are listed.

Catalog Bibcode

2014SerAJ.189...15G

References

20cm VLA radio-continuum study of M31. Images and point source catalogues DR2:
Extraction of a supernova remnant sample.
    Galvin T.J., Filipovic M.D.
    <Serbian Astron. J., 189, 15 (2014)>
    =2014SerAJ.189...15G        (SIMBAD/NED BibCode)

Provenance

This table was created by the HEASARC in May 2015 based on CDS Catalog J/Other/Ser/189.15 file m31radio.dat.

Parameters

Name
The radio detection designation '[GF2014] VLA JHHMMSS+DDMMSS'. The prefix '[GF2014] VLA' for 'Galvin, Filipovic 2014 Very Large Array' was created by the HEASARC in the style recommended by the Dictionary of Nomenclature of Celestial Objects for J2000.0 position-based names, and is unofficial. Many sources have multiple detections (indicated by having the parameter num_sources_in_group value > 1 and a non-blank group_id value) and in some cases, because of their having different positions can have different (detection) names, as these latter are based on the truncated coordinates of the individual detection.

RA
The Right Ascension of the VLA 1.4-GHz radio detection in the selected equinox. This was given in J2000.0 equatorial coordinates to a precision of 0.01 seconds of time in the original table.

Dec
The Declination of the VLA 1.4-GHz radio detection in the selected equinox. This was given in J2000.0 equatorial coordinates to a precision of 0.01 or 0.1 arcseconds in the original table.

LII
The Galactic Longitude of the VLA 1.4-GHz radio detection.

BII
The Galactic Latitude of the VLA 1.4-GHz radio detection.

Flux_1p4_GHz
The integrated flux density of the VLA 1.4-GHz radio detection, in mJy.

VLA_Proj_Seg_Code
The VLA project and segment code for the observation in which the detection was made. VLA Project AC0308 was conducted as part of the NVSS. Its segment is listed as a number instead of a normal letter segment code.

Group_ID
The group (unique source) identifier for detections which correspond to a common source. This parameter only contains a value if a source has more than one detection, i.e., if it were found in two or more VLA observations.

Num_Sources_In_Group
The number of individual detections of a common source (or 'group' in the authors' terminology). This parameter only contains a value if a source has more than one detection, i.e., if it were found in two or more VLA observations.

Avg_Group_Flux
The average integrated flux density of the VLA 1.4-GHz radio detections for a given source (group), in mJy. This parameter only contains a value if a source has more than one detection, i.e., if it were found in two or more VLA observations.

Avg_Group_Flux_Error
The uncertainty in the average integrated flux density of the VLA 1.4-GHz radio detections for a given source (group), in mJy. This parameter only contains a value if a source has more than one detection, i.e., if it were found in two or more VLA observations.

Flux_325_MHz
The Gelfand et al. (2004, ApJS, 155, 89) 325-MHz (92-cm) integrated flux density of the matched source within 5 arcseconds of the 1.4-GHz source position, in mJy, if available.

Flux_325_MHz_Error
The uncertainty in the Gelfand et al. (2004, ApJS, 155, 89) 325-MHz (92-cm) integrated flux density of the matched source within 5 arcseconds of the 1.4-GHz source position, in mJy.

Spectral_Index
The derived spectral index alpha of the radio source between 1.4 GHz (20 cm) and 325 MHz (92 cm), where S_nu ~ nu^alpha. This was calculated using the measured flux density (flux_1p4_ghz parameter values) at 1.4 GHz for sources detected only once, or the average 1.4-GHz flux density (avg_group_flux parameter values) for sources with multiple detections, both from the present study, and the 325-MHz flux density from Gelfand et al. (2004, ApJS, 155, 89), if the latter was available.

Group_Pos_Flag
This parameter (created by the HEASARC) is relevant only for multiply detected sources (entries with non-null group_id values) for which 325-MHz counterparts were found. It is set to 1 to indicate the particular detection in a given group (source) for which the original table listed the 325-MHz counterpart information (flux, error and spectral index), else is set to 0. The HEASARC believes that the authors used the flagged 1.4-GHz detection position as the 'best' position and the center of their 5-arcsecond radius in which they searched for a corresponding 325-MHz source in the Gelfand et al. (2004) catalog.

Contact Person

Questions regarding the VLAM311P4G database table can be addressed to the HEASARC Help Desk.

Page Author: Browse Software Development Team
Last Modified: Monday, 16-Sep-2024 17:36:23 EDT