Mon. Not. R. Astron. Soc., 429, 2351-2360 (2013/March-1)
Outside-in stellar formation in the spiral galaxy M33?
ROBLES-VALDEZ F., CARIGI L. and PEIMBERT M.
Abstract (from CDS):
We present and discuss results from chemical evolution models for M33. For our models we adopt a galactic formation with an inside-out scenario. The models are built to reproduce three observational constraints of the M33 disc: the radial distributions of the total baryonic mass, the gas mass, and the O/H abundance. From observations, we find that the total baryonic mass profile in M33 has a double exponential behaviour, decreasing exponentially for r ≤ 6kpc, and increasing lightly for r > 6kpc due to the increase of the gas mass surface density. To adopt a concordant set of stellar and Hii region O/H values, we had to correct the latter for the effect of temperature variations and O dust depletion. Our best model shows a good agreement with the observed radial distributions of: the star formation rate (SFR), the stellar mass, C/H, N/H, Ne/H, Mg/H, Si/H, P/H, S/H, Ar/H, Fe/H and Z. According to our model, the star formation efficiency is constant in time and space for r ≤ 6kpc, but the SFR efficiency decreases with time and galactocentric distance for r > 6kpc. The reduction of the SFR efficiency occurs earlier at higher r. While the galaxy follows the inside-out formation scenario for all r, the stars follow the inside-out scenario only up to r = 6kpc, but for r > 6kpc the stars follow an outside-in formation. The stellar formation histories inferred for each r imply that the average age of the stars for r > 6 increases with r.
© 2012 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society (2012)
galaxy: abundances - galaxy: evolution - galaxies: individual: M33
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