Browse
this table...

VLAECDFS1P4 - VLA Extended-Chandra Deep Field-South 1.4-GHz Source Catalog

HEASARC
Archive

Overview

Deep radio observations at 1.4 GHz for the Extended Chandra Deep Field South were performed in 2007 June through September and presented in a first data release (Miller et al. 2008, ApJS, 179, 114). The survey was made using six separate pointings of the Very Large Array with over 40 hr of observation per pointing. In the current study, the authors improve on the data reduction to produce a second data release (DR2) mosaic image. This DR2 image covers an area of about a third of a square degree, reaches a best rms sensitivity of 6 microJy (uJy), and has a typical sensitivity of 7.4 uJy per 2.8" by 1.6" beam. The authors also present a more comprehensive catalog, including sources down to peak flux densities of five or more times the local rms noise, along with information on source sizes and relevant pointing data. In their paper, they discuss in some detail the consideration of whether sources are resolved under the complication of a radio image created as a mosaic of separate pointings, each suffering some degree of bandwidth smearing, and the accurate evaluation of the flux densities of such sources. Finally, the radio morphologies and optical/near-IR counterpart identifications are used to identify 17 likely multiple-component sources so as to arrive at a catalog of 883 radio sources (and also 49 individual components of the 17 multi-component sources), which is roughly double the number of sources contained in the first data release.

In order to cover the full E-CDF-S area at near-uniform sensitivity, the authors pointed the VLA at six separate coordinate locations arranged in a hexagonal grid around the adopted center of the CDF-S, viz. RA, Dec (J2000) 03h 32m 28.00s, -27o 48' 30.0". The observations were spread over many days on account of the low declination of the field and typically amounted to 5 hr of time per calendar date. The details of the individual pointings are:

    Pointing ID    R.A. (J2000)   DE. (J2000)   rms sensitivity for final
                                                 image

    ECDFS    1     03:33:22.25    -27:48:30.0    10.5 uJy
    ECDFS    2     03:32:55.12    -27:38:03.0     9.4 uJy
    ECDFS    3     03:32:00.88    -27:38:03.0     9.7 uJy
    ECDFS    4     03:31:33.75    -27:48:30.0     9.5 uJy
    ECDFS    5     03:32:00.88    -27:58:57.0    10.0 uJy
    ECDFS    6     03:32:55.12    -27:58:57.0     9.3 uJy
The images corresponding to the six individual pointings were combined to form the final mosaic image (shown in Figure 1 of the reference paper).

This HEASARC table contains the catalog of 883 radio sources (Table 3 in the reference paper) and also the catalog of 49 individual components of the 17 multi-component sources (Table 4 in the reference paper), so that there are a total of 932 entries in the present table. To allow users to easily distinguish these types of entry, the HEASARC created a parameter type_flag which is set to 'S' for the 883 source entries and to 'C' for the 49 component entries. The HEASARC created names for the sources following the standard CDS and IAU recommendations for position-based names and using the prefix of '[MBF2013]' for Miller, Bonzini, Fomalont (2013), the first 3 authors and the date of publication of the reference paper. For the components, we have used the names based on the positions of the parent sources and the suffixes 'A', 'B', etc, in order of increasing J2000.0 RA. Thus, for the multi-component source [MBF2013] J033115.0-275518 which has 3 components, there are 4 entries in this table, one for the entire source, and one for each component, e.g.:

Name                        | type_flag   |    RA (J2000.0)    Dec (J2000.0)

[MBF2013] J033115.0-275518  |    S        |    03 31 15.04  |   -27 55 18.8
[MBF2013] J033115.0-275518 A|    C        |    03 31 13.99  |   -27 55 19.9
[MBF2013] J033115.0-275518 B|    C        |    03 31 15.06  |   -27 55 18.9
[MBF2013] J033115.0-275518 C|    C        |    03 31 17.05  |   -27 55 15.2
The 17 sources thought to consist of multiple components associated with a single host object are each listed with a single aggregate integrated flux density. Gaussian fits to the individual components associated with these sources are separately listed for their components

Catalog Bibcode

2013ApJS..205...13M

References

The Very Large Array 1.4 GHz survey of the Extended Chandra Deep Field South:
second data release.
    Miller N.A., Bonzini M., Fomalont E.B., Kellermann K.I., Mainieri V.,
    Padovani P., Rosati P., Tozzi P., Vattakunnel S.
   <Astrophys. J. Suppl. Ser., 205, 13 (2013)>
   =2013ApJS..205...13M    (SIMBAD/NED BibCode)

Provenance

This table was created by the HEASARC in May 2013 based on CDS Catalog J/ApJS/205/13 files table3.dat and table4.dat.

Parameters

Type_Flag
To allow users to easily distinguish the type of entry, the HEASARC created this parameter, which is set to 'S' for the 883 source entries listed in Table 3 of the reference paper and to 'C' for the 49 component entries listed in Table 4 of the reference paper.

Name
The source designation created by the HEASARC following the standard CDS and IAU recommendations for position-based names and using the prefix of '[MBF2013]' for Miller, Bonzini, Fomalont (2013), the first 3 authors and the date of publication of the reference paper. For the components, we have used the names based on the positions of the parent sources and the suffixes 'A', 'B', etc, in order of increasing J2000.0 RA. See the Overview for an example of the naming convention.

RA
The Right Ascension of the radio source or component in the selected equinox. This was given in J2000.0 coordinates to a precision of 0.01 seconds of time in the original table. In most cases, the listed position is that of the center of the Gaussian that best fits the data. The typical position errors for strong, unresolved sources observed with the VLA at 1.4 GHz are 0.1", and position errors attributed to the Gaussian fitting in the presence of noise are on the order of the beam size divided by twice the S/N (Condon 1997, PASP, 109,166). Thus, the position error in RA for a 5-sigma point source would be sqrt (0.12 + [1.6/(2 * 5)]2) ~ 0.2". For some resolved sources, the radio emission is poorly fit by a Gaussian and the source is evaluated using an irregularly shaped aperture that covers the apparent emission (the AIPS task tvstat). These sources are flagged by a source_flags value of 'a', and their positions are usually just the location of the maximum emission within the aperture.

Dec
The Declination of the radio source or component in the selected equinox. This was given in J2000.0 coordinates to a precision of 0.1 arcseconds in the original table. In most cases, the listed position is that of the center of the Gaussian that best fits the data. The typical position errors for strong, unresolved sources observed with the VLA at 1.4 GHz are 0.1", and position errors attributed to the Gaussian fitting in the presence of noise are on the order of the beam size divided by twice the S/N (Condon 1997, PASP, 109,166). Thus, the position error in Dec for a 5-sigma point source would be sqrt (0.12 + [2.8/(2 * 5)]2) ~ 0.3". For some resolved sources, the radio emission is poorly fit by a Gaussian and the source is evaluated using an irregularly shaped aperture that covers the apparent emission (the AIPS task tvstat). These sources are flagged by a source_flags value of 'a', and their positions are usually just the location of the maximum emission within the aperture.

LII
The Galactic Longitude of the radio source or component.

BII
The Galactic Latitude of the radio source or component.

SNR_1p4_GHz
The signal-to-noise ratio (S/N) of the 1.4-GHz radio source or component, i.e., the ratio of the fitted peak flux density (flux_1p4_ghz) to the local rms noise (flux_1p4_ghz_error).

Flux_1p4_GHz
The peak flux density of the 1.4-GHz radio source or component, in mJy/beam. This was given in units of uJy/beam in the original table.

Flux_1p4_GHz_Error
The local rms noise, in mJy/beam. This is evaluated using the rms map and thus represents the local noise within a 135" diameter circle around the source position. This was given in units of uJy/beam in the original table.

Int_Flux_1p4_GHz
The integrated flux density of the 1.4-GHz radio source or component, in mJy. This was given in units of uJy in the original table. These values represent the Gaussian fit to the source unless otherwise noted. For the extended sources poorly fit by a Gaussian, the total flux density within the irregularly shaped aperture is indicated.

Int_Flux_1p4_GHz_Error
The error in the integrated flux density of the 1.4-GHz radio source or component, in mJy. This was given in units of uJy in the original table. These values represent the Gaussian fit to the source unless otherwise noted. For the extended sources poorly fit by a Gaussian, this error is just the square root of the number of beams covering the aperture used times the local rms noise.

Mosaic_Major_Axis
The major axis of the 1.4-GHz radio source or component as taken from from the mosaic image, in arcseconds. This represents the fitted source size including convolution with the 2.8" by 1.6" beam. In addition, this parameter includes the differing contributions of bandwidth smearing from each of the pointings contributing to the mosaic image at the position of the source.

Mosaic_Minor_Axis
Th minor axis of the 1.4-GHz radio source or component as taken from from the mosaic image, in arcseconds. This represents the fitted source size including convolution with the 2.8" by 1.6" beam. In addition, this parameter includes the differing contributions of bandwidth smearing from each of the pointings contributing to the mosaic image at the position of the source.

Mosaic_Position_Angle
The position angle of the 1.4-GHz radio source or component as taken from from the mosaic image, in degrees east from North, where the 2.8" by 1.6" beam has a PA of 0 degrees. In addition, this parameter includes the differing contributions of bandwidth smearing from each of the pointings contributing to the mosaic image at the position of the source.

Best_Pointing_ID
The index number of the individual pointing which has the lowest rms noise at the position of the source or component. The pointings are numbered 1 to 6, starting due east of the center of the mosaic and progressing clockwise (see Table 1 of the reference paper for the full details on the individual pointings).

Best_Flux_1p4_GHz_Error
The rms noise at the position of the source or component in the best pointing, in units of mJy/beam. This was given in units of uJy/beam in the original table.

Best_Major_Axis_Lower
The 1-sigma lower limit, i.e, the nominal value minus 1 sigma, to the major axis size of the source or component in the best pointing, in arcseconds. Since these values are based on Gaussian fitting to the source in the best pointing, i.e., the single pointing with the lowest rms, they have accounted for bandwidth smearing and have been deconvolved to remove the synthesized beam.

Best_Major_Axis_Upper
The 1-sigma upper limit, i.e, the nominal value plus 1 sigma, to the major axis size of the source or component in the best pointing, in arcseconds. Since these values are based on Gaussian fitting to the source in the best pointing, i.e., the single pointing with the lowest rms, they have accounted for bandwidth smearing and have been deconvolved to remove the synthesized beam.

Best_Minor_Axis_Lower
The 1-sigma lower limit, i.e, the nominal value minus 1 sigma, to the minor axis size of the source or component in the best pointing, in arcseconds. Since these values are based on Gaussian fitting to the source in the best pointing, i.e., the single pointing with the lowest rms, they have accounted for bandwidth smearing and have been deconvolved to remove the synthesized beam.

Best_Minor_Axis_Upper
The 1-sigma upper limit, i.e, the nominal value plus 1 sigma, to the minor axis size of the source or component in the best pointing, in arcseconds. Since these values are based on Gaussian fitting to the source in the best pointing, i.e., the single pointing with the lowest rms, they have accounted for bandwidth smearing and have been deconvolved to remove the synthesized beam.

Best_Position_Angle
The nominal value of the position angle of the source or component in the best pointing, in degrees. Since these values are based on Gaussian fitting to the source in the best pointing, i.e., the single pointing with the lowest rms, they have accounted for bandwidth smearing and have been deconvolved to remove the synthesized beam.

Extended_Flag
If the source were found to be extended using the "envelope" method (see Section 3.2 of the reference paper), this Boolean flag parameter is set to 1. Sources that were unresolved under this test have a value of 0.

Flux_Choice_Flag
This flag indicates the prescription for the recommended flux density measurement to use for the source (see Section 3.4 of the reference paper). If the value is set to 'P', the flux density is better represented by the peak flux density, whereas if it is set to 'I', the integrated flux density is recommended.

Contrib_Pointing_IDs
This is a listing of the pointings (delineated in Table 1 of the reference paper) that contribute to the mosaic image at the position of the source. Thus, if the source position falls within the 33% power point of the primary beam (about 20') associated with an individual pointing, that pointing is noted here. This information allows users to inspect the images associated with the individual pointings to further assess source morphology and characteristics.

K_Source_ID
For sources that were identified in Kellermann et al. (2008, ApJS, 179, 71), this parameter contains the associated identification number of the radio source or component taken from that study.

K_Int_Flux_1p4_GHz
For sources that were identified in Kellermann et al. (2008, ApJS, 179, 71), this parameter contains the integrated flux density of the radio source or component, in mJy, taken from that study. This was given in units of uJy in the original table.

K_Int_Flux_1p4_GHz_Error
For sources that were identified in Kellermann et al. (2008, ApJS, 179, 71), this parameter contains the error in the integrated flux density of the radio source or component, in mJy, taken from that study. This was given in units of uJy in the original table.

K_Angular_Size_Limit
This parameter is set to '<' if the associated parameter value is an upper limit rather than an actual value.

K_Angular_Size
For sources that were identified in Kellermann et al. (2008, ApJS, 179, 71), this parameter contains the deconvolved size of the radio source or component, in arcseconds, taken from that study.

Source_Flags
This parameter contains flag(s) [a-g] indicating notes on the source, such as extended source morphologies and other source fitting details, as follows:

      a = Extended source evaluated with aperture photometry and AIPS
          task TVSTAT. Indicated position and peak flux density are
          the maximum within the aperture, and size is based on attempt
          at fitting source with single Gaussian.
      b = Multiple component source.
      c = Pointing 5 (03:32:00.88 -27:58:57.0, J2000) used for source fit
      d = Pointing 4 (03:31:33.75 -27:48:30.0, J2000) used for source fit
      e = Pointing 2 (03:32:55.12 -27:38:03.0, J2000) used for source fit
      f = Source has strong core plus more diffuse extended emission. The
          indicated source size is that of the extended emission based on a
          two-component Gaussian fit.
      g = Pointing 1 (03:33:22.25 -27:48:30.0, J2000) used for source fit
  

Multiple_Source_Number
The 17 sources which have multiple components (entries with source_flags = 'a') have been given unique identification numbers N from 1 to 17. They are also illustrated in the reference paper: to easily find the appropriate figure, just add 5 to the multiple_source_number value: thus, N = 1 is shown in Fig. 6.


Contact Person

Questions regarding the VLAECDFS1P4 database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 24-May-2013