ADC/CDS Standard Document for Catalog:
/external/radio/E8002/

E/VIII/2   Atlas of Images from the FIRST Survey                  (Becker+ 1997)
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Atlas of Images from the FIRST Survey                                          
   Becker R.H., Helfland D.J., White, R.L., Gregg M.D., Laurent-Muehleisen S.A.
   <Space Telescope Science Institute and National Radio Observatory (1997)>   
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Keywords:  Imagery, Radio Survey
ADC_Keywords: radio; External catalog 

Location: http://sundog.stsci.edu/first/images.html
          ftp://gibbon.cv.nrao.edu/pub/first/
   
Description:   
  FIRST -- Faint Images of the Radio Sky at Twenty-cm -- is a project
  designed to produce the radio equivalent of the Palomar Observatory 
  Sky Survey over 10,000 square degrees of the North Galactic Cap. 
  Using the NRAO Very Large Array (VLA) in its B-configuration, we 
  acquire 3-minute snapshots covering a hexagonal grid using 2×7 3-MHz 
  frequency channels centered at 1365 and 1435 MHz. The data are edited,
  self-calibrated, mapped, and CLEANed using an automated pipeline based 
  largely on routines in the Astronomical Image Processing System (AIPS). 
  A final atlas of maps is produced by coadding the twelve images 
  adjacent to each pointing center. These maps have 1.8" pixels, a 
  typical rms of 0.15 mJy, and a resolution of 5". The noise in the 
  coadded maps varies by only 15% from the best to the worst places 
  in the maps, except in the vicinity of bright sources (> 100 mJy) 
  where sidelobes can lead to an increased noise level. At the 1 mJy 
  source detection threshold, there are ~90 sources per square degree,
   ~35% of which have resolved structure on scales from 2-30".
   
  The survey area has been chosen to coincide with that of the Sloan 
  Digital Sky Survey (SDSS); at the m(v)~24 limit of SDSS, ~50% of 
  the optical counterparts to FIRST sources will be detected.
   
  Both the images and the catalogs constructed from the FIRST observations 
  are being made available to the astronomical community as soon as 
  sufficient quality-control tests have been completed. In addition, 
  the raw visibility data are available from NRAO as soon as the 
  observations have been taken, so radio astronomers can make maps
  of particular fields of interest before our final images are available.

Description of the Atlas of Images:   
  The final images from FIRST, produced by coadding the twelve (or 
  sometimes more) single-field pointings adjacent to each pointing 
  center, have 1.8" pixels, a typical rms of 0.15 mJy, and a resolution 
  of 5". At the 1 mJy source detection threshold, there are ~90 sources 
  per square degree, ~35% of which have resolved structure on scales 
  from 2-30".
   
  Note that the images are quite large, typically 1150x1550 pixels = 7.1 
  Mbytes to cover a 34.5 arcmin x 46.5 arcmin = 0.45 square degree area 
  of the sky. A 10 pixel strip at the top of each image contains a 
  copyright notice.
   
  The most convenient access to the FIRST images is through the FIRST 
  Cutout Server, which allows an image section to be extracted from the 
  coadded image database at a user-specified position. The cutout server 
  is also linked to the FIRST Search Engine, so that the catalog can be 
  searched for sources of interest and then images can be obtained for 
  those objects.
   
  The full images are also available. The 5086 coadded images from the 
  1993 and 1994 observations are archived in the HST data archive at 
  the Space Telescope Science Institute. A notice will be posted here 
  when the additional ~4500 images from the 1995 observations are 
  available. The images may be requested by anyone who is a registered 
  HST archive user. There is now a web interface to the HST archive, making
  access to the images simpler than before.
   
  The images can also be obtained via ftp from the National Radio i
  Astronomy Observatory and may soon be available at other archival sites.
   
The FIRST survey publications:   
  White et al. (1997) describe the construction of the FIRST survey 
  catalog. An extensive set of tests have been carried out to 
  determine the accuracy of the catalog parameters. The source flux 
  density distribution dN/dS is determined, and the FIRST catalog 
  is compared with the Guide Star Catalog, the IRAS Faint Source 
  Catalog, and the ROSAT WGA catalog. Gregg et al. (1996) describe 
  spectroscopic followup observations of bright quasar candidates in 
  the FIRST catalog. Becker et al. (1994, 1995) describe the genesis 
  of the FIRST project, 
   
References:
   ``A Catalog of 1.4 GHz Radio Sources from the FIRST Survey''
   White, R. L., Becker, R. H., Helfand, D. J., & Gregg, M. D. 1997,
   Astrophysical Journal, 475, 479
   
   ``The FIRST Bright QSO Survey''
   Gregg, M. D. Becker, R. H., White, R. L., Helfand, D. J., McMahon, 
   R. G., & Hook, I. M.  1996, Astronomical Journal, 112, 407
   
   ``The FIRST Survey: Faint Images of the Radio Sky at Twenty-cm''
   Becker, R. H., White, R. L., & Helfand, D. J. 1995, Astrophysical 
   Journal, 450, 559
   
   ``The VLA's FIRST Survey''
   Becker, R. H., White, R. L., & Helfand, D. J. 1994, Astronomical 
   Data Analysis Software and Systems III, ASP Conference Series, 
   v. 61, eds. D. R. Crabtree, R. J. Hanisch, & J.  Barnes, p. 165
   
Acknowledgements:
  The information presented was based on information at the FIRST site by 
    Richard L. White, rlw@stsci.edu
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(End)          N. Paul M. Kuin          April 21, 1997