EDP Sciences
Free access
Volume 421, Number 2, July II 2004
Page(s) 539 - 554
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20035847

A&A 421, 539-554 (2004)
DOI: 10.1051/0004-6361:20035847

Deep VLT spectroscopy of the blue compact dwarf galaxies Tol 1214-277 and Tol 65

Y. I. Izotov1, P. Papaderos2, N. G. Guseva1, K. J. Fricke2 and T. X. Thuan3

1  Main Astronomical Observatory, Ukrainian National Academy of Sciences, 27 Zabolotnoho str., Kyiv 03680, Ukraine
2  Universitäts - Sternwarte, Geismarlandstraße 11, 37083 Göttingen, Germany
3  Astronomy Department, University of Virginia, Charlottesville, VA 22903, USA

(Received 11 December 2003 / Accepted 29 March 2004)

We present VLT spectroscopic observations with different spectral resolutions and different slit orientations of the two metal-deficient blue compact dwarf (BCD) galaxies Tol 1214-277 and Tol 65. The oxygen abundances in the brightest H II regions of Tol 1214-277 and Tol 65 are found to be $12 + {\rm log~O/H} = 7.55 \pm 0.01$ and $7.54 \pm 0.01$, or $Z_\odot$/24. The nitrogen-to-oxygen abundance ratios in the two galaxies are log N/O = - $1.64 \pm 0.03$ and - $1.60 \pm 0.02$ and lie in the narrow range found for other most metal-deficient BCDs. The helium mass fraction derived in several H II regions in both galaxies is consistent with a high primordial helium mass fraction, $Y_{\rm p}\sim 0.244$. We confirm the detection of the high-ionization forbidden emission line [Fe V] $\lambda$4227 in the spectrum of Tol 1214-277.

Additionally, weak [Ne IV] $\lambda$4725, [Fe VI] $\lambda$5146, $\lambda$5177, and [Fe VII] $\lambda$5721, $\lambda$6087 emission lines are detected in the high-resolution spectrum of Tol 1214-277. The detection of these lines implies the presence of hard radiation with photon energy in the range ~4-8 Ryd. Emission lines are detected in the spectra of eight galaxies in the fields of Tol 1214-277 and Tol 65. Seven of these galaxies are background objects, while one galaxy has a redshift close to that of Tol 1214-277. Situated at a projected distance of ~14.5 kpc from Tol 1214-277, this galaxy is probably a companion of the BCD.

Key words: galaxies: starburst -- galaxies: abundances -- galaxies: individual: Tol 1214-277 -- galaxies: individual: Tol 65

Offprint request: Y. I. Izotov, izotov@mao.kiev.ua

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