Oxygen abundance distributions in six late-type galaxies based on SALT spectra of HII regions

Spectra of 34 H II regions in the late-type galaxies NGC1087, NGC2967, NGC3023, NGC4030, NGC4123, and NGC4517A were observed with the South African Large Telescope (SALT). In all 34 H II regions, oxygen abundances were determined through the "counterpart" method (C method). Additionally, in two H II regions in which the auroral lines were detected oxygen abundances were measured through the classic Te method. We also estimated the abundances in our H II regions using the O3N2 and N2 calibrations and compared those with the C-based abundances. With these data we examined the radial abundance distributions in the disks of our target galaxies. We derived surface-brightness profiles and other characteristics of the disks (the surface brightness at the disk center and the disk scale length) in three photometric bands for each galaxy using publicly available photometric imaging data. The radial distributions of the oxygen abundances predicted by the relation between abundance and disk surface brightness in the W1 band obtained for spiral galaxies in our previous study are close to the radial distributions of the oxygen abundances determined from the analysis of the emission line spectra for four galaxies where this relation is applicable. Hence, when the surface-brightness profile of a late-type galaxy is known, this parametric relation can be used to estimate the likely present-day oxygen abundance in its disk.Comment: 15 pages, 11 figures; Accepted for publication in Astronomy & Astrophysic

Two extremely metal-poor emission-line galaxies in the Sloan Digital Sky Survey

We present spectroscopic observations with the 3.6m ESO telescope of two emission-line galaxies, J2104-0035 and J0113+0052, selected from the Data Release 4 (DR4) of the Sloan Digital Sky Survey (SDSS). From our data we determine the oxygen abundance of these systems to be respectively 12+logO/H = 7.26+/-0.03 and 7.17+/-0.09, making them the two most metal-deficient galaxies found thus far in the SDSS and placing them among the five most metal-deficient emission-line galaxies ever discovered. Their oxygen abundances are close to those of the two most metal-deficient emission-line galaxies known, SBS0335-052W with 12+logO/H = 7.12+/-0.03 and I Zw 18 with 12+logO/H = 7.17+/-0.01.Comment: 5 pages, 3 figures. Accepted for publication in Astronomy and Astrophysic

The metallicities of UM151, UM408 and A1228+12 revisited

We present the results of new spectrophotometry and heavy element abundance determinations for 3 dwarf galaxies UM151, UM408 and A1228+12 (RMB132). These galaxies have been claimed in the literature to have very low metallicities, corresponding to log(O/H)+12 < 7.65, that are in the metallicity range of some candidate local young galaxies. We present higher S/N data for these three galaxies. UM151 and UM408 have significantly larger metallicities: log(O/H)+12 = 8.5 and 7.93, respectively. For A1228+12 our new log(O/H)+12 = 7.73 is close to that recalculated from earlier data (7.68). Thus, the rederived metallicities allow us to remove these objects from the list of galaxies with Z < 1/20 Z_Sun.Comment: LaTeX, 8 pages with 3 Postscript figures, A&A in pres

The Hamburg/SAO survey for emission-line galaxies. VI. The sixth list of 126 galaxies

We present the sixth list with results of the Hamburg/SAO Survey for Emission-Line Galaxies. The final list resulted from follow-up spectroscopy conducted with the 4.5m MMT telescope in 1996, and with 2.2m CAHA and 6m SAO telescopes in 2000 to 2003. The data of this snap-shot spectroscopy survey confirmed 134 emission-line objects out of 182 observed candidates and allowed their quantitative spectral classification and redshift determination. We classify 73 emission-line objects as definite or probable blue compact or HII galaxies (BCG), 8 as QSOs, 4 as Seyfert 1 and 2 galaxies. 30 low-excitation objects were classified as definite or probable starburst nuclei (SBN), 3 as dwarf amorphous nuclei starburst galaxies (DANS) and 2 as LINERs. Due to the low signal-to-noise ratio we could not classify 14 ELGs (NON). For another 9 galaxies we did not detect any significant emission lines. For 98 emission-line galaxies, the redshifts and/or line intensities are determined for the first time. For the remaining 28 previously-known ELGs we give either improved data the line intensities or some independent measurements. The detection rate of ELGs is ~70%. This paper completes the classification of strong-lined ELGs found in the zone of the Hamburg/SAO survey. Together with previously known BCG/HII galaxies in this zone, this sample of ~500 objects is the largest to date in a well bound region.Comment: 18 pages, including 8 tables and 1 figure. Plots of the spectra of 126 ELGs are in a separate 13-page Appendix. Accepted for publication in Astron.Astrophys. Full paper with full-resolution figures is available at http://www.eso.org/~akniaze