Issue |
Astron. Astrophys. Suppl. Ser.
Volume 130, Number 2, June I 1998
|
|
---|---|---|
Page(s) | 285 - 298 | |
DOI | https://doi.org/10.1051/aas:1998412 | |
Published online | 15 June 1998 |
Starbursts in barred spiral galaxies*
III. Definition of a homogeneous sample of starburst nucleus galaxies
1
Observatoire Midi-Pyrénées, UMR 5572, 14 avenue E. Belin, F-31400 Toulouse, France
2
School of Physics & Astronomy, Tel-Aviv University, 69978 Tel-Aviv, Israël
3
Observatoire de Besançon, UPRES-A 6091, BP. 1615, F-25010 Besançon Cedex, France
Send offprint request to: T. Contini, contini@wise.tau.ac.il
Received:
30
September
1997
Accepted:
1
December
1997
This paper presents optical long-slit spectroscopic observations of
105 barred Markarian IRAS galaxies. These observations are used to determine
the spectral type (starburst or Seyfert) of emission-line regions in the
nucleus and along the bar of the galaxies, in order to define a
homogeneous sample of Starburst Nucleus Galaxies (SBNGs).
Our selection criteria (ultraviolet excess, far infrared emission and barred
morphology) have been very efficient for selecting star-forming galaxies,
since our sample of 221 emission-line regions includes 82% nuclear or
extranuclear starbursts. The contamination by Seyferts is low (9%). The
remaining galaxies (9%) are objects with ambiguous classification (Hii or
LINER).
The dust content and Hα luminosity increase towards the nuclei of
the galaxies. No significant variation of the electron density is found
between nuclear and bar Hii regions. However, the mean Hα luminosity
and electron density in the bar are higher than in typical disk Hii
regions.
We investigate different mechanisms for explaining the excess of nitrogen
emission observed in our starburst nuclei. There is no evidence for the
presence of a weak hidden active galactic nucleus in our starburst galaxies.
The cause of this excess is probably a selective enrichment of nitrogen in the
nuclei of the galaxies, following a succession of short and intense bursts of
star formation.
Our sample of SBNGs, located at a mean redshift of ~0.015,
has moderate Hα ( erg s-1) and far infrared (
) luminosities. The types are distributed equally among early- and
late-type giant spirals with a slight preference for Sbc/Sc types because of
their barred morphology. The majority (62%) of SBNGs are isolated with no sign
of gravitational interaction. In terms of distance, luminosity and level of
interaction, SBNGs are intermediate between Hii galaxies
and luminous infrared galaxies.
Key words: galaxies: starburst / galaxies: active / galaxies: statistics / galaxies: ISM / infrared: galaxies
© European Southern Observatory (ESO), 1998