Issue |
A&A
Volume 463, Number 2, February IV 2007
|
|
---|---|---|
Page(s) | 481 - 492 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361:20054146 | |
Published online | 23 November 2006 |
Galactic star formation rates gauged by stellar end-products
1
INAF/Osservatorio Astronomico di Trieste, via G.B. Tiepolo 11, 34143 Trieste, Italy e-mail: persic@oats.inaf.it
2
School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel
3
CASS, University of California, San Diego, La Jolla, CA 92093, USA
Received:
5
September
2005
Accepted:
12
October
2006
Young galactic X-ray point sources (XPs) closely trace the ongoing star
formation in galaxies. From measured XP number counts we extract the
collective 2-10 keV luminosity of young XPs, , which we
use to gauge the current star formation rate (SFR) in galaxies. We find
that, for a sample of local star-forming galaxies (i.e., normal spirals
and mild starbursts),
correlates linearly with the SFR
over three decades in luminosity. A separate, high-SFR sample of starburst
ULIRGs can be used to check the calibration of the relation. Using their
(presumably SF-related) total 2-10 keV luminosities we find that these
sources satisfy the SFR–
relation, as defined by the
weaker sample, and extend it to span
decades in luminosity.
The SFR–
relation is also likely to hold for distant
(
) Hubble Deep Field North galaxies, especially so if
these high-SFR objects are similar to the (more nearby) ULIRGs. It is
argued that the SFR–
relation provides the most adequate
X-ray estimator of instantaneous SFR by the phenomena characterizing
massive stars from their birth (FIR emission from placental dust clouds)
through their death as compact remnants (emitting X-rays by accreting
from a close donor). For local, low/intermediate-SFR galaxies, the
simultaneous existence of a correlation of the instantaneous SFR with
the total 2-10 keV luminosity, Lx, which traces the SFR integrated
over the last
yr, suggests that during such epoch the SF in
these galaxies has been proceeding at a relatively constant rate.
Key words: galaxies: starburst / infrared: galaxies / radio continuum: galaxies / X-rays: binaries / X-rays: galaxies
© ESO, 2007
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