High-z Early-Type Galaxies
The formation and the evolution of early-type galaxies (ETGs, elliptical, bulge-dominated and passive galaxies), is one of the most important topic in observational cosmology. At least 70% of the baryonic mass in the local universe is locked into stars in the ETGs. For this reason, the understanding of their build-up and growth is fundamental to trace the assembly of the baryonic mass and of galaxies in the Universe. Most of the studies based on samples of ETGs at z<1 agree with considering completed their build-up at z~0.8. However, how and when the ETGs assembled their mass is still unclear and poorly constrained pushing at higher z the redshift of interest.
The study of the population of ETGs at z>1 is the main subject of a research activity jointly carried out at OAB by Marcella Longhetti and Paolo Saracco. The research program carried out since 2002 is focused on the following items:
Spectroscopic search for high-mass ETGs at z>1 - TESIS, the TNG EROs Spectroscopic Identification Survey, aimed at collecting low-res (R~50) near-IR spectra over 14000 AA of a sample of bright (K<18.5, Vega) Extremely Red Objects (EROs) selected from the MUNICS fields among which to detect ETGs. We identified 10 ETGs at 1.2<z<1.7 [1, 2, 3, 4]. Here, you can get the spectra of the 10 ETGs from TESIS.
Morphology, Kormendy relation and size evolution from the TESIS z>1 ETGs - HST-NICMOS observations of the 10 ETGs have been obtained with the NIC2 camera (0.075 arcsec/pixel) in the F160W band during cicle 14. The morphology and the Kormendy relation have been studied [5]. Here you can get the HST-NIC2 images of the 10 ETGs.
Scaling relations (Kormendy, Size-Luminosity/Mass relation) of 1<z<2 ETGs - We constructed a sample of 32 ETGs at 1<z<2 with spectroscopic confirmation of their redshift and spectral type and covered by HST-NICMOS observations in the F160W filter to study the properties of the population of ETGs in this redshift range [6, 7]. Here you can find the multiwavelength catalog and the NICMOS images.
Estimating the stellar mass and the age of ETGs - We used extensive simulations to quantify the uncertanties and the dependence on different models and on model parameters in estimating the stellar mass of galaxies and the age of their stellar population. The attention has been focused first on early-type galaxies. Here you can find the calibrated relations to derive k-corrections and stellar masses for z>1 ETGs in a model independent way [8].
Related papers:
[1]"Massive z~1.3 evolved galaxies revealed", Saracco P., Longhetti M., Severgnini P., et al. 2003, A&A 398, 127
[2]"The density of very massive evolved galaxies to z~1.7", Saracco P., Longhetti M., Severgnini P., et al. 2005, MNRAS, 357, L40
[3]"Looking of obscured QSO in the X-ray emitting ERO population", Severgnini P., Della Ceca R., Braito V., et al. 2005, A&A, 431, 87
[4]"Dating the stellar population in massive early-type galaxies at z~1.5", Longhetti M., Saracco P., Severgnini P., et al., 2005, MNRAS, 361, 897
[5]"The Kormendy relation of massive elliptical galaxies at z~1.5: evidence of size evolution", Longhetti M., Saracco P., Severgnini P., et al. 2007, MNRAS, 374, 614
[6]"The evolution of the morphological scale of early-type galaxies since z~2", Saracco P., Longhetti M., Andreon S., Mignano A. 2007, Il Nuovo Cimento, 122 B, 9
[7]"The population of early-type galaxies at 1<z<2 - New clues on their formation and evolution", Saracco P., Longhetti M., Andreon S. 2009, MNRAS, 392, 718
[8]"Stellar mass estimates in early-type galaxies: procedure, uncertainties and models dependence", Longhetti M., Saracco P. 2008, MNRAS, in press, (arXiv:0811.4041)