A Deep New CCD/Objective-Prism Survey for Emission-Line Galaxies

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Session 35 -- Digitizing the Sky Part I
Oral presentation, Tuesday, 31, 1994, 8:30-12:30

[35.06] A Deep New CCD/Objective-Prism Survey for Emission-Line Galaxies

J.J. Salzer (Wesleyan U.), V. Lipovetsky, A. Kniazev (SAO), T.A. Boroson (NOAO), T.X. Thuan (U. Virginia), Y. Izotov (Ukrainian Acad. Sci.), J.W. Moody (BYU)

\vskip -0.06in We describe our new digital objective-prism survey for extragalactic emission-line objects. Our international collaborative effort initiated observations in March 1994 on the 0.61-m Burrell Schmidt telescope located at KPNO. The technique we employ combines the benefits of a traditional photographic objective-prism survey with the advantages of using a CCD detector. We will select emission-line galaxy candidates primarily by their [O III]$\lambda$5007 and/or H$\beta$ lines, similar to familiar line-selected samples such as the UM, Case, and Second Byurakan surveys. However, we expect to be sensitive to galaxies with continuum magnitudes as faint as B = 20 -- 21, much deeper than any existing surveys. In addition to providing much higher QE and larger dynamic range compared to photographic plates, CCDs have the added advantages for our survey of delivering digitized spectra which will allow for automated object selection, as well as providing the ability to determine the selection characteristics and completeness limits of the sample directly from the survey data. The field of view of our CCD is 1.1$^\circ$ square, and the prism employed delivers 19 \AA /pixel at 5000 \AA. The spectral range covered (4800 -- 5500 \AA ) is restricted by a special filter developed for this project that excludes the strong night-sky line at 5577 \AA. This arrangement greatly reduces the sky background while still providing coverage out to z = 0.10 for the strong [O III]$\lambda$5007 line and to z = 0.14 for H$\beta$. Our initial pilot project covers 100 square degrees and overlaps the CfA Century Redshift Survey in the north Galactic cap. We anticipate extending the survey to cover large areas of both Galactic caps in the future. Examples of objects discovered in our initial semester of observations will be presented, along with an assessment of the depth and reliabilty of the survey technique. Our scientific goals for this survey include a more accurate determination of the luminosity function and spatial distribution of AGN and actively star-forming galaxies.

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