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

Published online by Cambridge University Press:  14 August 2015

R. Guzman
Affiliation:
UCO/Lick Observatory, Board of Astronomy and Astrophysics University of California, Santa Cruz, USA
A.C. Phillips
Affiliation:
UCO/Lick Observatory, Board of Astronomy and Astrophysics University of California, Santa Cruz, USA
J. Gallego
Affiliation:
UCO/Lick Observatory, Board of Astronomy and Astrophysics University of California, Santa Cruz, USA

Abstract

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We study the global properties of 51 compact field galaxies with redshifts z ~ 0.2 - 1.3 and apparent magnitudes I814 < 23.74 in the flanking fields of the Hubble Deep Field. All these galaxies have angular half-light radii re < 0.5 arcsec. Keck spectra covering ~4000-9000 Å, combined with HST І814 images and Keck V-band images, were used to derive redshifts, V606 - I814 colors, absolute blue magnitudes (MB), linear half-light radii (Re), blue average surface brightnesses within Re (SBe), velocity widths (σ), virial masses (M), mass-to-light ratios (M/L), excitations (O[III]/Hβ), and star formation rates (SFR). The results of this study can be summarized as follows:

  1. (i): Only 12% of the 51 compact galaxies have absorption-line dominated spectra, while 88% show strong, narrow emission lines, similar to the so-called CNELGs (e.g., Koo, this volume).

  2. (ii): Despite being very luminous (i.e., LB ~ L*; see figure la), compact emission-line galaxies are low-mass stellar sytems (i.e., M ≤ 1010 Mʘ, typically; see figure lb).

  3. (iii): Roughly 60% of the compact emission-line galaxies have colors, sizes, surface brightnesses, luminosities, velocity widths, excitations, star formation rates, and mass-to-light ratios characteristic of young, star-forming HII galaxies (see figures 1 and 2). The remaining 40% form a more heterogeneous class of evolved starbursts, similar to local disk starburst galaxies.

  4. (iv): Without additional star formation, galaxy evolution models predict that HII-like distant compacts will fade to resemble today’s spheroidal galaxies such as NGC 205 (Koo, this volume).

Type
II. Joint Discussions
Copyright
Copyright © Kluwer 1998

References

Guzmán, R., Gallego, J., Koo, D.C., et al. 1997, ApJ, to appear in NovemberGoogle Scholar
Phillips, A.C., Guzmán, R., Gallego, J., et al. 1997, ApJ, to appear in NovemberGoogle Scholar