Mapping the properties of blue compact dwarf galaxies: integral field spectroscopy with PMAS^*

¹ Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany e-mail: [luzma;ckehrig;mmroth;pweilbacher]@aip.de
² Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain and Departamento de Astrofísica, Universidad de la Laguna, 38205, La Laguna, Tenerife, Spain e-mail: [nicola.caon;czurita]@iac.es

Received: 6 January 2010
Accepted: 29 March 2010

Abstract

Context. Blue compact dwarf (BCD) galaxies are low-luminosity, low-metal content dwarf systems undergoing violent bursts of star formation. They present a unique opportunity to probe galaxy formation and evolution and to investigate the process of star formation in a relatively simple scenario. Spectrophotometric studies of BCDs are essential to disentangle and characterize their stellar populations.

Aims. We perform integral field spectroscopy of a sample of BCDs with the aim of analyzing their morphology, the spatial distribution of some of their physical properties (excitation, extinction, and electron density) and their relationship with the distribution and evolutionary state of the stellar populations.

Methods. Integral field spectroscopy observations of the sample galaxies were carried out with the Potsdam Multi-Aperture Spectrophotometer (PMAS) at the 3.5 m telescope at Calar Alto Observatory. An area × in size was mapped with a spatial sampling of × . We obtained data in the 3590–6996 Å spectral range, with a linear dispersion of 3.2 Å  per pixel. From these data we built two-dimensional maps of the flux of the most prominent emission lines, of two continuum bands, of the most relevant line ratios, and of the gas velocity field. Integrated spectra of the most prominent star-forming regions and of whole objects within the FOV were used to derive their physical parameters and the gas metal abundances.

Results. Six galaxies display the same morphology both in emission line and in continuum maps; only in two objects, Mrk 32 and Tololo 1434+032, the distributions of the ionized gas and of the stars differ considerably. In general the different excitation maps for a same object display the same pattern and trace the star-forming regions, as expected for objects ionized by hot stars; only the outer regions of Mrk 32, I Zw 123 and I Zw 159 display higher []/Hα values, suggestive of shocks. Six galaxies display an inhomogeneous dust distribution. Regarding the kinematics, Mrk 750, Mrk 206 and I Zw 159 display a clear rotation pattern, while in Mrk 32, Mrk 475 and I Zw 123 the velocity fields are flat.