Spectroscopic CCD surveys for quasars at large redshift. III. The Palomar Transit Grism Survey catalog

Donald P. Schneider, Maarten Schmidt, James E. Gunn

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This paper reports the initial results of the Palomar Transit Grism Survey (PTGS). The PTGS was designed to produce a sample of z>2.7 quasars that were identified by well-defined selection criteria. The survey consists of six narrow (≈8.5′ wide) strips of sky; the total effective area is 61.47 sq deg. Low-resolution slitless spectra, covering the wavelength range from 4400 to 7500 Å, were obtained for approximately 600 000 objects. The wavelength- and flux-calibrated spectra were searched for emission lines with an automatic software algorithm. A total to 1655 emission features in the grism data satisfied our signal-to-noise ratio and equivalent width selection criteria; subsequent slit spectroscopy of the candidates confirmed the existence of 1052 lines (928 different objects). Six groups of emission lines were detected in the survey: Lyman α+N V, C IV, C III], Mg II, Hβ+[O III], and Hα+[S II]. More than two-thirds of the candidates are low-redshift (z<0.45) emission-line galaxies; ninety objects are high-redshift quasars (z>2.7) detected via their Lyman α+N V emission lines. The survey contains three previously unknown quasars brighter than 17th magnitude; all three have redshifts of ≈1.3. In this paper we present the observational properties of the survey, the algorithms used to select the emission-line candidates, and the catalog of emission-line objects.

Original languageEnglish (US)
Pages (from-to)1245-1269
Number of pages25
JournalAstronomical Journal
Issue number4
StatePublished - Apr 1994

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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