The dwarf starburst galaxy NGC 1705: New HII region element abundances and reddening variations near the center
Abstract
NGC 1705 is a well-studied dwarf galaxy, exhibiting evidence of gas outflows driven by a very recent burst of star formation. Literature values of the nebular oxygen abundance span a range between 12+log(O/H) = 8.0 and 8.5. Here, we present new EFOSC2 spectra of 16 H II regions in NGC 1705. For the first time, [O III] λ 4363 was detected in five H II regions. The mean oxygen abundance derived directly from measured electron temperatures is 12+log(O/H) = 8.21 ± 0.05, which corresponds to 35% of the solar value. From Balmer emission flux ratios, we have observed variations in the extinction (between zero and 0.9 mag in V) on spatial scales of about 10 arcsec (250 pc) in radius from the super star cluster. One should therefore be cautious about possible spatial variations of the extinction along different lines of sight in the galaxy, and about how extinction corrections are applied to studies of resolved stellar populations. NGC 1705 has the appearance of a normal dwarf galaxy, on which is superposed a recent intense episode of star formation. There appears to be no evidence of any external trigger for the starburst.
- Publication:
-
Starbursts: From 30 Doradus to Lyman Break Galaxies
- Pub Date:
- May 2005
- Bibcode:
- 2005ASSL..329P..36L