Bibcode
Monreal-Ibero, A.; Vílchez, J. M.; Walsh, J. R.; Muñoz-Tuñón, C.
Bibliographical reference
Astronomy and Astrophysics, Volume 517, id.A27
Advertised on:
7
2010
Journal
Citations
68
Refereed citations
62
Description
Context. Starbursts are one of the main contributors to the chemical
enrichment of the interstellar medium. However, mechanisms governing the
interaction between the recent star formation and the surrounding gas
are not fully understood. Because of their a priori simplicity, the
subgroup of H II galaxies constitute an ideal sample to study these
mechanisms. Aims: A detailed 2D study of the central region of
NGC 5253 has been performed to characterize the stellar and ionized gas
structure as well as the extinction distribution, physical properties
and kinematics of the ionized gas in the central ~210 pc × 130 pc.
Methods: We utilized optical integral field spectroscopy (IFS)
data obtained with FLAMES. Results: A detailed extinction map for
the ionized gas in NGC 5253 shows that the largest extinction is
associated with the prominent Giant H II region. There is an offset of
~0.5 arcsec between the peak of the optical continuum and the extinction
peak in agreement with findings in the infrared. We found that stars
suffer less extinction than gas by a factor of ~0.33. The [S
ii]λ6717/[S ii]λ6731 map shows an electron density
(Ne) gradient declining from the peak of emission in Hα
(790 cm-3) outwards, while the argon line ratio traces areas
with Ne ~ 4200-6200 cm-3. The area polluted with
extra nitrogen, as deduced from the excess [N ii]λ6584/Hα,
extends up to distances of 3.3 farcsec (~60 pc) from the maximum
pollution, which is offset by ~1.5 arcsec from the peak of continuum
emission. Wolf-Rayet features are distributed in an irregular pattern
over a larger area (~100 pc × 100 pc) and associated with young
stellar clusters. We measured He+ abundances over most of the
field of view and values of He++/H+ ⪉ 0.0005
in localized areas which do not coincide, in general, with the areas
presenting W-R emission or extra nitrogen. The line profiles are
complex. Up to three emission components were needed to reproduce them.
One of them, associated with the giant H II region, presents supersonic
widths and [N ii]λ6584 and [S ii]λλ6717,6731
emission lines shifted up to 40 km s-1 with respect to
Hα. Similarly, one of the narrow components presents offsets in
the [N ii]λ6584 line of ⪉20 km s-1. This is the
first time that maps with such velocity offsets for a starburst galaxy
have been presented. The observables in the giant H II region fit with a
scenario where the two super stellar clusters (SSCs) produce an outflow
that encounters the previously quiescent gas. The south-west part of the
FLAMES IFU field is consistent with a more evolved stage where the star
clusters have already cleared out their local environment.
Based on observations collected at the European Organisation for
Astronomical Research in the Southern Hemisphere, Chile (ESO Programme
078.B-0043).
Related projects
Starbursts in Galaxies GEFE
Starsbursts play a key role in the cosmic evolution of galaxies, and thus in the star formation (SF) history of the universe, the production of metals, and the feedback coupling galaxies with the cosmic web. Extreme SF conditions prevail early on during the formation of the first stars and galaxies, therefore, the starburst phenomenon constitutes a
Casiana
Muñoz Tuñón