Lyman Imaging of High-Redshift Galaxies.III.New Observations of Four QSO Fields

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view Abstract Citations (247) References (38) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Lyman Imaging of High-Redshift Galaxies.III.New Observations of Four QSO Fields Steidel, Charles C. ; Pettini, Max ; Hamilton, Donald Abstract We present the results of deep Lyman limit imaging in four new fields as part of a continuing search for galaxies at 3.0 < z< 3.5. The technique uses a custom broadband filter set (U_n_GR) designed to isolate objects having Lyman continuum breaks superposed on otherwise flat-spectrum ultraviolet continua. The observations are specifically aimed at detecting known galaxies producing optically thick QSO metal line absorption systems, but are equally sensitive to more generally distributed objects at the redshifts of interest. We have identified a plausible candidate for the QSO absorber in one out of the four new fields surveyed; in the other three the absorbing galaxy must be either fainter than R = 25.5 or closer than ~1 arcsec to the QSO sight line (or both). Together with previously published results of the survey, we have now detected in two out of six cases objects with the expected properties of star-forming galaxies at z ~> 3 within 3 arcsec of the QSO sight lines; the two candidate absorbers have similar luminosities, M_B_ ~ 22 (q_0_ = 0.5, H_0_ = 50 km s^-1^ Mpc^-1^), and impact parameters, R ~ 10h^-1^ kpc. We find the average surface density of robust Lyman break objects to be ~0.5 galaxies per square arcminute to a magnitude limit R = 25.0. A simple, "no evolution" model based on the properties of normal galaxies at z <~ 1 predicts a density of Lyman break objects only a few times larger than observed. We conclude that there is a substantial population of star-forming galaxies, of relatively normal luminosity, already in place at z = 3-3.5. If normal galaxies experienced a period of very high star formation early on in their history, it must have occurred prior to z = 3.5. It is possible that the observed surface density of z > 3 objects is biased by the presence of a luminous QSO in the redshift range of interest; the surveyed fields are too small to examine the possibility of a spatial association of the z > 3 candidates with the QSOs. We suggest a number of future observations that would resolve this question and clarify the nature of the putative "normal" galaxy population beyond z ~ 3. Publication: The Astronomical Journal Pub Date: December 1995 DOI: 10.1086/117709 arXiv: arXiv:astro-ph/9509089 Bibcode: 1995AJ....110.2519S Keywords: COSMOLOGY: THEORY; COSMOLOGY: OBSERVATIONS; GALAXIES: EVOLUTION; Astrophysics E-Print: 35 pages, uuencoded, compressed postscript. 15 Figures available on ftp://astro.caltech.edu/users/ccs/llg_figures.tar.Z, or request preprints from ccs@astro.caltech.edu. To appear in The Astronomical Journal, 1995 December full text sources arXiv | ADS | data products NED (344) SIMBAD (5)