1991 Fiscal Year Final Research Report Summary
Evolution of Galaxies and Observational Cosmology
| Project/Area Number |
02640207
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Astronomy
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| Research Institution | National Astronomical Observatory |
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Principal Investigator |
YOSHII Yuzuru National Astronomical Observatory, Celestial Mechanics & Ephemerides, Associate Professor, 位置天文・天体力学研究系, 助教授 (00158388)
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| Project Period (FY) |
1990 – 1991
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| Keywords | Galaxy Evolution / Cosmology / Cosmological Constant |
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| Research Abstract |
Cosmological predictions of number count and redshift distribution of faint galaxies are made by incorporating detection and selection effects in the theoretical framework. It is shown that the detection rate for galaxies at given apparent magnitude strongly depends on the detection criterion and magnitude measurement algorithm, and that a large number of faint galaxies with high redshifts should remain undetected in recent galaxy surveys. By using a current model of galaxy luminosity evolution with the assumption that galaxies do not evolve in number or cliameter, the predictions are compared directly with the uncorrected B_JR_FIK-band galaxy count data reaching B_J = 27mag or the equivalent depth and also with the Durham redshift distribution to B_J = 23mag. It is concluded that a flat and low-density OMEGA_O - 0.1 universe with non-zero cosmological constant can account for all the data but a flat and high-density OMEGA_O = 1 universe shows a marked discrepancy with all the data. The hypothesis of galaxy evolution in number and/or diameter is tested against the faint observations. Contrary to usual expectations, a number evolution driven by galaxy mergers cannot reconcile the observed high count at B_J = 27mag and the high densityOMEGA_O = 1 universe because many high-redshift premergers should not be counted according to the criterion adopted in the recent surveys. The central surface brightness versus apparent magnitude relation is found to be sensitive solely to a change of intrinsic size of galaxies so that it is used as a probe of their diameter evolution. Comparison between the predicted and observed relations indicates that the bulk of galaxies have undergone very little diameter evolution over a considerable fraction of their age.
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