Astronomy and Astrophysics – Astrophysics – Cosmology and Extragalactic Astrophysics
Scientific paper
2010-03-27
Astronomy and Astrophysics
Astrophysics
Cosmology and Extragalactic Astrophysics
accepted in Astronomy & Astrophysics. 21 pages, 22 figures
Scientific paper
ABRIDGED: A detailed 2D study of the central region of NGC5253 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 ~210pc x 130pc. We utilized optical integral field spectroscopy (IFS) data obtained with FLAMES. A detailed extinction map for the ionized gas in NGC5253 shows that the largest extinction is associated with the prominent Giant HII region. There is an offset of ~0.5" 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 [SII]l6717/[SII]l6731 map shows an electron density (N_e) gradient declining from the peak of emission in Ha (790cm^-3) outwards, while the argon line ratio traces areas with $N_e~4200 - 6200cm^(-3). The area polluted with extra nitrogen, as deduced from the excess [NII]/Ha, extends up to distances of 3.3" (~60pc) from the maximum pollution, which is offset by ~1.5" from the peak of continuum emission. Wolf-Rayet features are distributed in an irregular pattern over a larger area (~100pc x 100pc) 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 HII region, presents supersonic widths and [NII] and [SII] emission lines shifted up to 40km/s with respect to Ha. Similarly, one of the narrow components presents offsets in the [NII] line of <~20km/s. This is the first time that maps with such velocity offsets for a starburst galaxy have been presented.
Monreal-Ibero Ana
Munoz-Tunon Casiana
Vilchez José M.
Walsh Jonathan R.
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