Other
Scientific paper
Jan 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995phdt.........6t&link_type=abstract
Thesis (PH.D.)--CALIFORNIA INSTITUTE OF TECHNOLOGY, 1995.Source: Dissertation Abstracts International, Volume: 56-06, Section: B
Other
3
Galaxy Formation, Near Infrared, Redshift
Scientific paper
We present the results from two complementary surveys for young and forming ellipticals or spheroids at high redshift, one based on a narrowband imaging technique using a Fabry-Perot interferometer, and the other a serendipitous long-slit spectroscopic survey. The Fabry-Perot survey is sensitive to Ly alpha emission in four discrete redshift ranges: z = 2.80-2.98, 3.27-3.45, 4.42-4.60, and 4.75-4.89. The total area of the survey was 0.63 deg^2 , surveyed to a 1sigma limiting line flux of {~}8.5 times 10^{-17} erg cm^ {-2} {rm s}^{-1} . An area of 0.05 deg^2 was surveyed to a fainter flux limit of { ~}1.5 times 10^{-17} erg cm^{-2} {rm s}^{-1}. A total comoving volume of 110,000 Mpc^3 was surveyed to a 1sigma limiting restframe emission line luminosity of {~}2.0 times 1043 erg s^ {-1} (a Friedman cosmology with H _0 = 75 km s^{-1} Mpc^{-1} and Omega_0 = 0.2 is assumed throughout this thesis). The long-slit survey is sensitive to Ly alpha in the range of 3.1 <= z <= 5.2, with lesser areas surveyed across the entire optical passband. A total of 421 independent spectroscopic frames were searched, covering an area of 0.0042 deg^2 (14.97 arcmin ^2). 65 emission-line candidates were identified, including 30 galaxies with z_sp{~ }<1 and 2 quasars. An additional 20 objects were assigned tentative redshifts, all with z_sp{~}<1.2, and have properties consistent with the galaxies seen in the deep field redshift surveys. The remaining objects are candidate Lyalpha galaxies at high redshift, with isolated, unidentified emission lines and little or no continuum. They require further spectroscopy to check on their nature. A total comoving volume of 102,600 Mpc^3 was surveyed to a 1 sigma limiting restframe emission line luminosity of {~}2.45 times 10^ {43} erg s^{-1} . In neither case was an obvious population of primeval galaxies revealed, despite the combined surveys covering a volume of space sufficient to include ~ 200 galaxies with rm L >= L _{*} (using the local space density of massive galaxies, and assuming no density evolution). These galaxies could have been detected if they unobscured by dust and were actively forming stars at a rate of 100 M _odot yr^{ -1}. A number of candidates remain to be followed up with spectroscopic observations, and may yet prove to be the elusive PGs. The lack of detection of a population of Lyalpha-luminous objects could be due to dust quenching of the Lyalpha line, a higher redshift of formation than surveyed, short lifetime in the Lyalpha-bright phase, or even masking of the star-formation emission-line signature by an active nucleus. A study on the feasibility of conducting primeval galaxy surveys in the near infrared, based on emission -lines of (O II), (O III), and the Balmer lines, and the results of a preliminary survey based on these techniques, are also presented. It is shown that the new large-format infrared arrays will reach the necessary sensitivities over large enough areas to make such surveys practical.
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