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Дата изменения: Wed Oct 7 22:26:50 1998
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Поисковые слова: ultraviolet
BIB-VERSION:: AST-PP-v1.0
ID:: epreps.stsci//prep1192
ENTRY:: March 9, 1998
TITLE:: Far Ultraviolet Spectra of Starburst Galaxies: Stellar Population and the Kinematics of the Interstellar Medium
SUBTITLE::
AUTHOR:: Delgado, Rosa M. González (1)
AUTHOR:: Leitherer, Claus (1)
AUTHOR:: Heckman, Timothy (2) (3)
AUTHOR:: Lowenthal, James D. (4)
AUTHOR:: Ferguson, Henry C. (1)
AUTHOR:: Robert, Carmelle (5)
AFFIL:: (1) Space Telescope Science Institute 3700 San Martin Drive Baltimore, MD 21218 USA
AFFIL:: (2) Department of Physics & Astronomy, The Johns Hopkins University Baltimore, MD 21218
AFFIL:: (3) Adjunct Astronomer at ST ScI
AFFIL:: (4) University of California, Lick Observatory, Santa Cruz, CA 95064
AFFIL:: (5) Université Laval, Departement de Physique, Ste-Foy, PQ, G1K 7P1, Canada and Observatoire du Mont Mégantic
DATE:: November 1997
JOURNAL:: To appear in: The Astrophysical Journal
SUBMITTED:: 13 June 1997
ACCEPTED:: 11 October 1997
OTHER_ACCESS::
COPYRIGHT:: Copyright 1997 The Association of Universities for Research in Astronomy, Inc. All Rights Reserved.
LANGUAGE:: English
ABSTRACT::

The far ultraviolet spectra of the four starburst galaxies NGC 6090,
Mrk 66, Mrk 1267, and IRAS 0833+6517 were observed with HUT
during the Astro-2 mission. Additional data were obtained for
IRAS 0833+6517 with the HST+GHRS. We analyse the observations in terms
of the stellar content and the kinematics of the interstellar medium, and
we discuss the implications of these results for the interpretation of the
ultraviolet spectra of high-redshift galaxies.


Evolutionary synthesis models are used to constrain the star formation
history from the absolute ultraviolet flux and from the stellar components of
the absorption lines SiIV and CIV, and from the far ultraviolet lines
OVI+L+CII. The
spectral energy distributions from these models are used as input to the
photoionization code CLOUDY to predict [OIII]/H and the column densities of the cool component
of the ionized gas (SiII and CII) associated with the HII region. The results
indicate continuous star formation during about 9 Myr or, alternatively,
bursts with an age between 3 and 6 Myr, and a mass consistent with that from
the H flux. Evidence for significant
dilution by a field star population is found in all galaxies, except
NGC 6090.


Most of the interstellar absorption lines are saturated. Their equivalent
widths indicate a large velocity dispersion in the gas. Other evidence for
large scale-motions of the interstellar gas comes from blueshifts of
several hundred km s-1 with respect to the
systemic velocity in the interstellar lines of NGC 6090, Mrk 66,
and IRAS 0833+6517. These outflows are most likely driven by the
starburst.


L was detected in emission in three
of the galaxies (NGC 6090, Mrk 66, and IRAS 0833+6517). The
dereddened ratio L/H in IRAS 0833+6517 is
close to the recombination value, indicating that extinction is more important
than multiple resonant scattering effects. However, the GHRS spectrum of
IRAS 0833+6517 clearly shows that the emision profile of
L is asymmetric, with the blue
wing being absorbed by neutral gas. This indicates that the velocity
structure of the neutral gas and the scattering by HI atoms can
play an important role in the escape of the
L photons as well.

END:: epreps.stsci//prep1192