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Centro de Astrofísica da Universidade do Porto

New light in star-forming dwarf galaxies: The PMAS integral field view of the blue compact dwarf galaxy Mrk 409

L. M. Cairós, N. Caon, P. Papaderos, C. Kehrig, P. Weilbacher, M. M. Roth, C. Zurita

Abstract
We present an integral field spectroscopic study of the central 2 × 2 kpc2 of the blue compact dwarf galaxy Mrk 409, observed with the Potsdam MultiAperture Spectrophotometer (PMAS). This study focuses on the morphology, two-dimensional chemical abundance pattern, excitation properties, and kinematics of the ionized interstellar medium in the starburst component. We also investigate the nature of the extended ring of ionized gas emission surrounding the bright nuclear starburst region of Mrk 409. PMAS spectra of selected regions along the ring, interpreted with evolutionary and population synthesis models, indicate that their ionized emission is mainly due to a young stellar population with a total mass of ∼1.5 × 106M, which started forming almost coevally ∼10 Myr ago. This stellar component is likely confined to the collisional interface of a spherically expanding, starburst-driven super-bubble with denser, swept-up ambient gas, ∼600 pc away from the central starburst nucleus. The spectroscopic properties of the latter imply a large extinction (C > 0.9), and the presence of an additional non-thermal ionization source, most likely a low-luminosity active galactic nucleus. Mrk 409 shows a relatively large oxygen abundance (12 + log(O/H) ∼ 8.4) and no chemical abundance gradients out to R ∼ 600 pc. The ionized gas kinematics displays an overall regular rotation on a northwest–southeast axis, with a maximum velocity of 60 km s-1; the total mass inside the star-forming ring is about 1.4 × 109M.

Keywords
galaxies: dwarf - galaxies: evolution - galaxies: individual (Mrk 409) - galaxies: starburst - galaxies: stellar content

Notes
Based on observations obtained at the German–Spanish Astronomical Center, Calar Alto, operated by the Max-Planck-Institut für Astronomie Heidelberg jointly with the Spanish National Commission for Astronomy.

The Astrophysical Journal
Volume 707, Page 1676
December 2009

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