Issue |
A&A
Volume 450, Number 1, April IV 2006
|
|
---|---|---|
Page(s) | 15 - 23 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361:20054045 | |
Published online | 03 April 2006 |
Circumnuclear star-forming activities along the Hubble sequence
Department of Astronomy, Nanjing University, Nanjing 210093, PR China e-mail: shileiastro@yahoo.com; qsgu@nju.edu.cn
Received:
13
August
2005
Accepted:
5
December
2005
In order to study circumnuclear star-forming
activity along the Hubble sequence, we cross-correlated the
Sloan Digital Sky Survey Data Release 2 (SDSS DR2) with the
Third Reference Catalog of Bright Galaxies (RC3) to derive a
large sample of 1015 galaxies with both morphological and
spectral information. Among these, 385 sources are classified
as star-forming galaxies, and the SDSS fibre covered the
circumnuclear regions (0.2-2.0 kpc). By using the spectral
synthesis method to remove the contribution from the underlying
old stellar population, we measured the emission lines fluxes
accurately, which are then used to estimate the star-formation
rates(SFRs). Our main findings are: (1) early-type spirals
show much higher Hα luminosities, and hence higher SFRs,
and also suffer more extinctions than late-type ones. The
equivalent widths (EWs) of Hα emission lines show
a similar trend; however, the very late types (Sdm ~ Irr) do
have large fractions of high EWs; (2) we confirm that
shows a strong correlation with the strengths of
metallic absorption lines (such as CN band, G band, and Mg Ib).
Both these lines and the Balmer absorption lines show
interesting variations between Sbc and Sd type galaxies; (3) the
bar structure tightly relates to the enhanced star formation
activity, an effect that is even more significant in the
early-type spirals. But we should note that the bar structure
is not a necessary or sufficient condition for galaxies to
harbor circumnuclear star formations.
Key words: Galaxy: general / galaxies: stellar content / galaxies: statistics
© ESO, 2006
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