Bibcode
Cairós, L. M.; Caon, N.; Zurita, C.; Kehrig, C.; Weilbacher, P.; Roth, M.
Referencia bibliográfica
Astronomy and Astrophysics, Volume 507, Issue 3, 2009, pp.1291-1301
Fecha de publicación:
12
2009
Revista
Número de citas
32
Número de citas referidas
31
Descripción
Aims: By means of optical integral field spectroscopy observations, we
aim to differentiate and characterize the starburst component in the
blue compact dwarf (BCD) galaxy Mrk 1418. In particular we propose to
study the stellar and ionized gas morphology, to investigate the
ionization mechanism(s) acting in the interstellar medium, and to derive
the physical parameters and abundances of the ionized gas.
Methods: Integral field spectroscopy observations of Mrk 1418 were
carried out with the Potsdam multi-aperture spectrophotometer (PMAS) at
the 3.5 m telescope at Calar Alto Observatory. The central 16
arcsec×16 arcsec (1.14 × 1.14 kpc2 at the
distance of Mrk 1418) were mapped with a spatial sampling of 1 arcsec;
we took data in the 3590-6996 Å spectral range, with a linear
dispersion of 3.2 Å per pixel. The seeing was about 1farcs5. From
these data we built maps of the most prominent emission lines, namely [O
ii], Hβ, [O iii], Hα, [N ii], and [S ii], as well as of
several continuum bands, plus maps of the main line ratios: [O
iii]/Hβ, [N ii]/Hα, [S ii]/Hα, and Hα/Hβ,
and derived the physical parameters and gaseous metal abundances of the
different star-forming regions detected in the field of view.
Results: Mrk 1418 shows a distorted morphology both in the continuum and
in the ionized gas maps; the current star- formation episode is taking
place in five knots, distributed around the nucleus of the galaxy. The
interstellar medium surrounding these knots is photo-ionized by stars,
with no clear evidence for other excitation mechanisms. The galaxy
displays an inhomogeneous dust distribution, with the high
Hα/Hβ ratio in the central areas indicating a large amount of
dust. The oxygen abundances derived for the individual star-forming
knots are very similar, suggesting that the ionized interstellar medium
is chemically homogeneous in O/H over spatial scales of hundreds of
parsecs. This abundance (Z ≈ 0.4 Z&sun; from the empirical
calibrations) places Mrk 1418 among the high metallicity BCD group. Conclusions: These findings show the advantages of IFS when
investigating the properties of such complex objects as BCDs, with an
asymmetric star-forming component. Only a bidimensional mapping of their
central regions allows approaching such questions as the star formation
processes in BCDs, the star-forming history of the individual starburst
knots, or the abundance gradients.
Based on observations obtained at the German-Spanish Astronomical
Center, Calar Alto, operated by the Max-Planck-Institut fur Astronomie
Heidelberg jointly with the Spanish National Commission for Astronomy.
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