Astronomy and Astrophysics, volume 476, 151-175 (2007/12-2)
The contribution of very massive high-redshift SWIRE galaxies to the stellar mass function.
BERTA S., LONSDALE C.J., POLLETTA M., SAVAGE R.S., FRANCESCHINI A., BUTTERY H., CIMATTI A., DIAS J., FERUGLIO C., FIORE F., HELD E.V., LA FRANCA F., MAIOLINO R., MARCONI A., MATUTE I., OLIVER S.J., RICCIARDELLI E., RUBELE S., SACCHI N., SHUPE D. and SURACE J.
Abstract (from CDS):
In the last couple of years a population of very massive (M*>1011M☉), high-redshift (z≥2) galaxies has been identified, but its role in galaxy evolution has not yet been fully understood. It is necessary to perform a systematic study of high-redshift massive galaxies, in order to determine the shape of the very massive tail of the stellar mass function and determine the epoch of their assembly. We selected high-z massive galaxies at 5.8µm, in the SWIRE ELAIS-S1 field (1deg2). Galaxies with the 1.6µm stellar peak redshifted into the IRAC bands (z≃1-3, called ``IR-peakers'') were identified. Stellar masses were derived by means of spectro-photometric fitting and used to compute the stellar mass function (MF) at z=1-2 and 2-3. A parametric fit to the MF was performed, based on a Bayesian formalism, and the stellar mass density of massive galaxies above z=2 determined. We present the first systematic study of the very-massive tail of the galaxy stellar mass function at high redshift. A total of 326 sources were selected. The majority of these galaxies have stellar masses in excess of 1011M☉ and lie at z>1.5. The availability of mid-IR data turned out to be a valuable tool to constrain the contribution of young stars to galaxy SEDs, and thus their M*/L ratio. The influence of near-IR data and of the chosen stellar library on the SED fitting are also discussed. The z=2-3 stellar mass function between 1011 and ∼1012M☉ is probed with unprecedented detail. A significant evolution is found not only for galaxies with M∼1011M☉, but also in the highest mass bins considered. The comoving number density of these galaxies was lower by more than a factor of 10 at z=2-3, with respect to the local estimate. SWIRE 5.8µm peakers more massive than 1.6x1011M☉ provide 30-50% of the total stellar mass density in galaxies at z=2-3.
galaxies: evolution - galaxies: luminosity function, mass function - galaxies high-redshift - galaxies: fundamental parameters - galaxies: statistics - infrared: galaxies
VizieR on-line data:
<Available at CDS (J/A+A/476/151): table.dat>
Table: ESIS NNNNNN N=326 among (Nos 69900-264125).
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