Mapping luminous blue compact galaxies with VIRUS-P

Morphology, line ratios, and kinematics

¹ Leibniz-Institut für Astrophysik, An der Sternwarte 16, 14482 Potsdam, Germany
e-mail: luzma@aip.de; akelz@aip.de; mmroth@aip.de; ole@aip.de
² Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain
³ Departamento de Astrofísica, Universidad de la Laguna, 38206, La Laguna, Tenerife, Spain
e-mail: nicola.caon@iac.es; bgarcia@iac.es
⁴ Centro de Astrofísica and Faculdade de Ciências, Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal
e-mail: papaderos@astro.up.pt

Received: 14 May 2012
Accepted: 29 August 2012

Abstract

Context. Blue compact galaxies (BCG) are narrow emission-line systems that undergo a violent burst of star formation. They are compact, low-luminosity galaxies, with blue colors and low chemical abundances, which offer us a unique opportunity to investigate collective star formation and its effects on galaxy evolution in a relatively simple, dynamically unperturbed environment. Spatially resolved spectrophotometric studies of BCGs are essential for a better understanding of the role of starburst-driven feedback processes on the kinematical and chemical evolution of low-mass galaxies near and far.

Aims. We carry out an integral field spectroscopy (IFS) study of a sample of luminous BCGs, with the aim to probe the morphology, kinematics, dust extinction, and excitation mechanisms of their warm interstellar medium (ISM).

Methods. We obtained IFS data for five luminous BCGs with VIRUS-P, the prototype instrument for the Visible Integral Field Replicable Unit Spectrograph, attached to the 2.7 m Harlan J. Smith Telescope at the McDonald Observatory. VIRUS-P consists of a square array of 247 optical fibers, which covers a 109″ × 109″ field of view, with a spatial sampling of and a 0.3 filling factor. We observed in the 3550–5850 Å spectral range, with a resolution of 5 Å FWHM. From these data we built two-dimensional maps of the continuum and the most prominent emission-lines ([O ii] λ3727, Hγ, Hβ and [O iii] λ5007), and investigated the morphology of diagnostic emission-line ratios and the extinction patterns in the ISM as well as stellar and gas kinematics. Additionally, from integrated spectra we inferred total line fluxes and luminosity-weighted extinction coefficients and gas-phase metallicities.

Results. All galaxies exhibit an overall regular morphology in the stellar continuum, while their warm ISM morphology is more complex: in II Zw 33 and Mrk 314, the star-forming regions are aligned along a chain-structure; Haro 1, NGC 4670 and III Zw 102 display several salient features, such as extended gaseous filaments and bubbles. A significant intrinsic absorption by dust is present in all galaxies, the most extreme case being III Zw 102. Our data reveal a plethora of kinematical patterns, from overall regular gas and stellar rotation to complex velocity fields produced by structurally and kinematically distinct components.