Baryonic content of the warm-hot intergalactic medium at low redshift
Abstract
We present the morphological analysis based on HST-NICMOS observations in the F160W filter of a sample of 30 early-type galaxies spectroscopically confirmed at 1.2<z<2. We derive the effective radius R_e and the mean surface brightness mu_e of galaxies in the rest-frame R-band. We find that early-types at z~1.5 are characterized by a surface brightness (SB) much higher then their local counterparts with comparable R_e. In particular, we find that the mean SB of these early-types should get fainter by ~2.5 mag from z~1.5 to z=0 to match the SB of the local early-types with comparable R_e. This evolution exceeds by a factor two the luminosity evolution expected for early-types in this redshift range and more than a factor three the one derived from the observed luminosity function of galaxies. Consequently, an evolution of the effective radius R_e from the epoch of their formation towards z=0 has to be invoked and the hypothesis of fixed size rejected.
- Publication:
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Nuovo Cimento B Serie
- Pub Date:
- September 2007
- DOI:
- 10.1393/ncb/i2008-10478-9
- arXiv:
- arXiv:0801.2269
- Bibcode:
- 2007NCimB.122.1307S
- Keywords:
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- Astrophysics
- E-Print:
- 4 pages, 2 figures. To appear in the proceedings of `A Century of Cosmology', S. Servolo, August 2007, to be published in Il Nuovo Cimento