Bibcode
Perez-Fournon, I.; Hatziminaoglou, E.; Cassata, P.; Rodighiero, G.; Franceschini, A.; Hernan-Caballero, A.; Lonsdale, C.; SWIRE Team
Bibliographical reference
American Astronomical Society Meeting 207, #63.46; Bulletin of the American Astronomical Society, Vol. 37, p.1254
Advertised on:
12
2005
Citations
0
Refereed citations
0
Description
We present the results of a morphological analysis of a small subset of
the SWIRE galaxy population. Our analysis is based on public ACS data
taken inside the SWIRE N1 field. We distinguish two very general classes
of galaxies, bulge- and disc-dominated galaxies, the first class being
referred to with the general term 'spheroids' and the second containing
everything from spirals to irregulars and pairs. Even though the
requirement for 3.6- and/or 4.5-micron detections favours the selection
of early-type galaxies, the observations show that the large majority
(close to 80 per cent) of the 3.6- and 4.5-micron galaxy population,
even at these moderately faint fluxes, is dominated by spiral and
irregular galaxies or mergers, already suggesting that elliptical
galaxies assemble late. We then limit our sample to objects with IRAC
fluxes brighter than 10 microJy, estimated ˜ 90 per cent
completeness limit of the SWIRE catalogs, and compare the observed
counts to model predictions. The observed 3.6- and 4.5-micron early-type
counts are in very good agreement with the estimations of the
hierarchical scenario, showing however a deficit toward the faint end,
possibly reflecting some incompleteness that is already introduced at
this flux level. The monolithic predictions imply steeper counts and
fail in reproducing the observations.