Multi-wavelength study of a new sample of blue compact dwarf galaxies^*

IV. Optical multi-pupil spectroscopy of 18 objects

¹ Byurakan Astrophysical Observatory and Isaac Newton Institute of Chile, Armenian Branch, 378443 Byurakan, Armenia
² Observatoire Astronomique de Marseille-Provence and Laboratoire d'Astrophysique de Marseille, 2 Place Le Verrier, 13248 Marseille Cedex 04, France
³ Institut d'Astrophysique de Paris, 98bis Boulevard Arago, 75014 Paris, France
⁴ Special Astrophysical Observatory, Nizhnij Arkhyz, Karachai-Circassian Republic 357147, Russia

Corresponding author: D. Kunth, kunth@iap.fr

Received: 18 January 2001
Accepted: 24 May 2002

Abstract

We present the multi-pupil integral field spectroscopy of 18 Blue Compact Dwarf Galaxies performed at the 6 m telescope of the SAO (Russia). We produce an atlas of the Hα, [OIII], [SII] emission–line intensity distributions, the excitation parameter ([OIII]/Hβ ratio), the continuum maps in blue and red and the velocity fields as derived from the 2D spectra. We provide detailed individual descriptions of the objects with a table of their spectroscopic properties. From the atlas and the velocity maps, we have classified the sample according to the following scheme: – Nine objects show spatially coincident distributions with respect to their emission lines, excitation parameter and the continuum. In this case, these galaxies are repeating star-formation sequences at the same spatial location. Mrk 1416 also belongs to this class of BCDG but has a secondary site of star formation. – Eight objects in which the distributions in emission lines brightness, excitation parameter and in continuum strength differ from each other at various degrees. These objects are galaxies with several sites of star formation of various ages and spatial locations. They can be ideal templates for testing the models of star formation. – From the 2-D [SII] emission–line distribution we find a superbubble structure in one object and possibly in 2 others. – Ten objects show an overall quite regular radial velocity gradient. On the other hand, in 8 objects, the kinematical major axis of this regular velocity field does not align with the photometric major axis, suggesting dynamical disturbances, gas/star decoupling and/or instabilities. – Six objects have irregular velocity fields, implying that the rotation of a gaseous disk is not their dominant dynamical . – SBS 1723+565B is not a dwarf galaxy but a giant irregular galaxy or an interacting system experiencing a high star formation rate.