We present the deep UBVRI observations of the HDF-S NICMOS field obtained as part of the Science Verification of the VLT Unit 1 telescope. The images have been used to construct object catalogs and to obtain photometric redshifts. The effective field of view is similar or equal to 70 x 70 arcsec(2), and the formal 5 sigma limiting magnitudes (in a 2 FWHM aperture) are 26.3, 27.8, 27.5, 26.9, 25.2 in the U, B, V, R and I bands, respectively. Thanks to the sub-arcsecond image quality, relatively long exposure time, and large collecting area of the VLT, this is the deepest set of multicolor images ever obtained from a,groundbased telescope. Galaxy counts have been derived independently in each band, and show no significant departures from previous data from wider areas. A multicolor photometric catalog of all the galaxies selected in the R band has also been obtained and used to derive photometric redshifts for all galaxies with R less than or equal to 26.5, using also the J,H and K magnitudes from the NICMOS deep observations. A significant fraction (similar or equal to 28%)of the galaxies is placed at z greater than or equal to 2. Among them, six robust candidates are found at z greater than or equal to 2.5.
The VLT observations of the HDF-S NICMOS field: photometric catalog and high redshift galaxy candidates
ROSATI, Piero;
1999
Abstract
We present the deep UBVRI observations of the HDF-S NICMOS field obtained as part of the Science Verification of the VLT Unit 1 telescope. The images have been used to construct object catalogs and to obtain photometric redshifts. The effective field of view is similar or equal to 70 x 70 arcsec(2), and the formal 5 sigma limiting magnitudes (in a 2 FWHM aperture) are 26.3, 27.8, 27.5, 26.9, 25.2 in the U, B, V, R and I bands, respectively. Thanks to the sub-arcsecond image quality, relatively long exposure time, and large collecting area of the VLT, this is the deepest set of multicolor images ever obtained from a,groundbased telescope. Galaxy counts have been derived independently in each band, and show no significant departures from previous data from wider areas. A multicolor photometric catalog of all the galaxies selected in the R band has also been obtained and used to derive photometric redshifts for all galaxies with R less than or equal to 26.5, using also the J,H and K magnitudes from the NICMOS deep observations. A significant fraction (similar or equal to 28%)of the galaxies is placed at z greater than or equal to 2. Among them, six robust candidates are found at z greater than or equal to 2.5.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
