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 turned on.):

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. Note that a bug currently exists whereby exponents are ignored in numbers using exponential notation (e.g., 6.3E-3 is sorted as if it were 6.3). Since most tables don't include exponential numbers this is not felt to be a major problem.
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).
By default, results are shown with 50 entries per page, with links to additional pages if more than 50 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. (Note that when the total number of returned rows is a multiple of 50, an extra page is displayed with no entries.)
One numerical column can be plotted versus another using VOPlot.
For some missions, thumbnail images of the reurned entries can be displayed by clicking the link listed just below the VOPlot link.
The mark column, as described below, can be used to plot spectra and download files.

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

AIP Image Class

Maximum 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.