Astronomy and Astrophysics – Astronomy
Scientific paper
May 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010mnras.404..811c&link_type=abstract
Monthly Notices of the Royal Astronomical Society, Volume 404, Issue 2, pp. 811-829.
Astronomy and Astrophysics
Astronomy
2
Galaxies: Individual: Ngc4900, Galaxies: Spiral, Galaxies: Stellar Content
Scientific paper
We present Optically Adaptive System for Imaging Spectroscopy (OASIS) observations obtained at the Canada-France-Hawaii Telescope for the SB(rs)c galaxy NGC4900. About 800 spectra in the wavelength range 4700-5500 and 6270-7000Å have been collected with a spatial resolution of ~50pc. This galaxy is part of a sample to study the stellar populations and their history in the central region of galaxies. In this paper, we present our iterative technique developed to describe consistently the different stellar components seen through emission and absorption lines. In NGC4900, we find many young bursts of star formation distributed along the galaxy large-scale bar on each side of the nucleus. They represent nearly 40 per cent of the actual stellar mass in the field of view. The age for these bursts ranges from 5.5 to 8Myr with a metallicity near and above 2Zsolar. The extinction map gives E(B - V) values from 0.19 +/- 0.01 near the youngest bursts to 0.62 +/- 0.06 in a dusty internal bar perpendicular to the large-scale bar. The Mg2 and FeI absorption lines indicate the superposition of a background stellar population with an age between 100Myr and 3Gyr, and a subsolar metallicity on average. We propose that all these episodes of star formation are the consequence of a secular evolution. In this scenario, the galactic large-scale bar plays an important role with respect to the recent bursts and the dusty nuclear bar observed. The iterative technique allows us to improve the determination of the stellar population parameters, mainly an older age is obtained for the old component and more reliable stellar population masses are found. A composite/transition type activity in the galaxy nucleus is also revealed with this technique.
Cantin Simon
Mollá Mercedes
Pellerin Anne
Robert Carmelle
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