The Nature of Compact Galaxies at Z ~ 0.2-1.3: Implications for Galaxy Evolution and the Star Formation History of the Universe

Guzman, R.; Phillips, A. C.; Gallego, J.; Koo, D. C.; Lowenthal, J. D.
Bibliographical reference

Galaxy Scaling Relations: Origins, Evolution and Applications, proceedings from the ESO Workshop held November, 1996, edited by Luiz Nicolaci da Costa and Alvio Renzini (Springer-Verlag), p. 226.

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1997
Number of authors
5
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0
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0
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0
Description
We study the global scaling-laws of 51 compact field galaxies with redshifts z = 0.2-1.3 and apparent magnitudes I<23.74 in the flanking fields of the Hubble Deep Field. Roughly 60% of the 45 compact emission-line galaxies have sizes, surface brightnesses, luminosities, velocity widths, excitations, star formation rates (SFR), and mass-to-light ratios characteristic of young star-forming HII galaxies. The remaining 40% form a more heterogeneous class of evolved starbursts, similar to local disk starburst galaxies. Without additional star formation, HII-like distant compacts will most likely fade to resemble today's spheroidal galaxies such as NGC 205. Our sample implies a lower limit for the global comoving SFR density of 0.004 M/yr/Mpc^3 at z = 0.55, and 0.008 M/yr/Mpc^3 at z = 0.85. These values, when compared to a similar sample of local galaxies, support a history of the universe in which the SFR density declines by a factor 10 from z = 1 to today. From the comparison with the SFR densities derived from previous data sets, we conclude that compact emission-line galaxies, though only 20% of the general field population, may contribute as much as 45% to the global SFR of the universe at 0.4 < z < 1.