A substantial population of high-redshift, early-type galaxies is detected in very deep UBVRIJHK images. Four elliptical profile galaxies are identified in the redshift range 1 < z < 2, with very red spectral energy distributions implying ages of greater than or similar to 2 Gyr for standard passive evolution. We also find later type IR-luminous galaxies at similarly high redshift (10 objects with z > 1, H < 25), with weak UV emission implying single-burst ages of greater than or similar to 1 Gyr. The number and luminosity densities of these galaxies are comparable to the local E/S0-Sbc populations for Omega(m) > 0.2, suggesting that the major fraction of luminous Hubble sequence galaxies has evolved little since z similar to 2. A highly complete photometric redshift distribution is constructed to H = 25 (69 galaxies) that shows a broad spread of redshift, peaking at z similar to 1.5, in reasonable agreement with some analyses of the Hubble Deep Field. Four "dropout" galaxies are detected at z approximate to 3.8 and are compact in the IR, similar to 0.5 kpc h(-1) at rest frame 3500 Angstrom. No example of a blue IR-luminous elliptical galaxy is found, thus restricting the star formation epoch of elliptical galaxies to z greater than or equal to 5-10 for a standard initial mass function and modest extinction.
Detection of evolved high-redshift galaxies in deep NICMOS VLT images
ROSATI, Piero
1999
Abstract
A substantial population of high-redshift, early-type galaxies is detected in very deep UBVRIJHK images. Four elliptical profile galaxies are identified in the redshift range 1 < z < 2, with very red spectral energy distributions implying ages of greater than or similar to 2 Gyr for standard passive evolution. We also find later type IR-luminous galaxies at similarly high redshift (10 objects with z > 1, H < 25), with weak UV emission implying single-burst ages of greater than or similar to 1 Gyr. The number and luminosity densities of these galaxies are comparable to the local E/S0-Sbc populations for Omega(m) > 0.2, suggesting that the major fraction of luminous Hubble sequence galaxies has evolved little since z similar to 2. A highly complete photometric redshift distribution is constructed to H = 25 (69 galaxies) that shows a broad spread of redshift, peaking at z similar to 1.5, in reasonable agreement with some analyses of the Hubble Deep Field. Four "dropout" galaxies are detected at z approximate to 3.8 and are compact in the IR, similar to 0.5 kpc h(-1) at rest frame 3500 Angstrom. No example of a blue IR-luminous elliptical galaxy is found, thus restricting the star formation epoch of elliptical galaxies to z greater than or equal to 5-10 for a standard initial mass function and modest extinction.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
