VLA-FIRST Search Output Columns

This document defines the catalog entries describing the VLA-FIRST Data Archive as delivered to STScI by the FIRST Team.

Archive Background:

The FIRST survey (Faint Images of the Radio Sky at Twenty-cm) is a high angular resolution survey of the North Galactic Cap intended to match the 10,000 deg**2 survey area of the Sloan Digital Sky Survey. Observation are made in the VLA's B configuration operating at frequencies of 1365 and 1425 MHz in the bandwidth synthesis mode. The synthesized beam has a FWHM of 5.4". Each field is observed for 3 minutes, resulting in a typical image rms of <0.15 mJy/beam.

Details of the survey design, pipeline processing algorithms, and catalog generation may be found in Becker et.al. 1995; this paper, along with further information on FIRST, is retrievable via the FIRST web page http://sundog.stsci.edu. Users interested in deriving quatitative information from the maps for scientific purposes are advised to read the FIRST paper first. Questions or comments on the FIRST survey should be addresssed to Bob Becker.

General Results Options

Most mission search results pages have the following general features/options. (Note that the sorting, paging and VOPlot options all require JAVASCRIPT to be supported and turned on, and the interactive plotting option uses HTML5 which is not supported in Internet Explorer before version 9.)

1. Clicking on the column headings at the TOP of the results table will sort the returned results based on the selected field. Clicking the column heading a second time will sort the results in descending order. As of August, 2014 sorting is now possible with RA and Dec coordinates in sexigesimal notation, and the previous bugs whereby exponents are ignored in numbers using exponential notation (e.g., 6.3E-3 is sorted as if it were 6.3), and signs were ignored in floating point numbers have both been corrected. Note however that the sort functions (like many interactive features) are written in javascript which is not always supported in older browsers. Alternatively, selecting the sort options in the initial query does not depend on javascript, and will sort the entire search result, not just the displayed rows.

2. Clicking one of the column headings at the END of the results table (or clicking the "columns help" link at the top of the page) will display help information about the search results page and the displayed columns (i.e., this page).

3. By default, results are shown with 500 entries per page, with links to additional pages if more than 500 entries were returned. The number of rows per page can be modified using the "Records per Page" form element on the search form. The total number of entries returned is set by the "Maximum Records" value from the search page.

4. One numerical column can be plotted versus another using VOPlot although see the Help page regarding issues with the latest version of Java.

5. For some missions, thumbnail images of the returned entries can be displayed by clicking the link listed just below the VOPlot link.

6. The mark column, as described below, can be used to plot spectra and download files. Plots are now interactive with added features.

Column Information

Columns:

 

Row

The row number of each record in the results of your search.

Field Name

The field name for VLA-FIRST data is in the format HHMMM+/-DD.

Data ID

The Data ID consists of the J2000 coordinates of the field center in the format HHMMM+/-DDMMM (with implied decimal points before the final M's) followed by a character that gives some idea of the epoch for observation and processing.

Clicking on the Data ID entry in the search results table will bring up a dialog box permiting download of the VLA data.

RA (J2000)

Object's Right Ascension in J2000 coordinates specified in hours, minutes, and seconds.

Dec (J2000)

Object's declination in J2000 coordinates specified in degrees, minutes, and seconds.

VLA Program ID

VLA Program ID

AIPS Image Class

AIP Image Class

Max Pixel Value

Maximum Pixel Value

Min Pixel Value

Minimum Pixel Value

Galactic Latitude

The galactic latitude for this observation.

Galactic Longitude

The galactic longitude for this observation.

Ecliptic Latitude

The ecliptic latitude for this observation.

Ecliptic Longitude

The ecliptic longitude for this observation.

Angular Separation (')

The angular separation in arcminutes between the observation and the search center (the coordinates you're searching on). This is calculated during the search, and the search results are sorted in order of increasing angular separation.

It also means that you can give a search radius like, say, 2 .. 8 to find all observations between 2 and 8 arcminutes from some position. This could be used, for example, to find the observations in the vicinity of a bright 3C radio source.