  (Abridged) Low-luminosity, active star-forming blue compact galaxies (BCGs)
are excellent laboratories for investigating the process of star formation on
galactic scales and probing the interplay between massive stars and the
surrounding interstellar (or intergalactic) medium. We investigated the
morphology, structure, and stellar content of the Blue Compact Galaxy Mrk 900,
combining optical integral field observations obtained with VIMOS at the VLT
and deep broad-band photometry taken at the 2.5 m NOT telescope. From the
integral field data, we built continuum, emission, and diagnostic line ratio
maps and produced velocity and velocity dispersion maps. We also generated the
integrated spectrum of the major HII regions and the nuclear area to determine
reliable physical parameters and oxygen abundances. The broad-band data,
tracing the galaxy up to radius 4 kpc, allowed us to investigate the properties
of the low surface brightness underlying stellar host. We disentangle two
different stellar components in Mrk 900: a young population, which resolves
into individual stellar clusters with ages ~5.5-6.6 Myr and extends about 1 kpc
along the galaxy minor axis, is placed on top of a rather red and regular
shaped underlying stellar host, several Gyr old. We find evidence of a
substantial amount of dust and an inhomogeneous extinction pattern, with a dust
lane crossing the central starburst. Mrk 900 displays overall rotation,
although distorted in the central, starburst regions; the dispersion velocity
map is highly inhomogeneous, with values increasing up to 60 kms$^{-1}$ at the
periphery of the SF regions, where we also find hints of the presence of
shocks. Our observational results point to an interaction or merger with a
low-mass object or infalling gas as plausible trigger mechanisms for the
present starburst event.

Astrophysics of Galaxies