Stellar population in bulges of spiral galaxies

Details Stellar population in bulges of spiral galaxies Stellar population in bulges of spiral galaxies

Jun 2006

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006rmxac..26r.194m&link_type=abstract

XI IAU Regional Latin American Meeting of Astronomy (Eds. L. Infante & M. Rubio) Revista Mexicana de Astronomía y Astrofísica (S

Astronomy and Astrophysics

Astronomy

Scientific paper

Even if great progress has been done in tracing and modeling the galaxy spheroids formation and evolution, this topic still defied a general accepted explanation. Currently, the favorite models to explain the formation and evolution for galaxies are hierarchical merging and monolithic collapse. A way to discriminate between the above scenarios is to observe very deep in our nearby universe, to understand what kind of signature the stellar population has inherited from the galaxy formation mechanism. In order to investigate this aspect we presented an extensive project aimed at studying the stellar population of bulges in spiral galaxies to understand their chemical properties and whether these properties differ from those of elliptical galaxies. To achieve these goals, we observed a sample of disk galaxies in field and in cluster. We measured the main Lick indices (H_{β}, Mg_2, , MgFe) and the principal kinematical parameters (velocity, velocity dispersion h_3 and h_4) as function of the galactocentric radius, in order to determine the age, metallicity and alpha-enhancement for all the sample galaxies. We do not find clear gradient in the α/Fe profiles. The constant and supersolar ( α/Fe = 0.3) values of the α-enhancement ratio along radius suggests that the formation of the bulk of the stars in spiral bulges occurred with the same short (less than 1 Gyr) timescale as found in elliptical and S0 galaxies. Therefore the α/Fe radial profiles, disfavor strong inside-out or outside-in scenarios and are in conflict with the pure monolithic collapse, where a positive gradient in the α-enhancement is expected. On the other hand the globally α/Fe enhanced stellar population is not expected in the hierarchical merging scenario where the star formation is triggered by the merger event and could give higher central values of α/Fe which decrease outwards.

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