Observing Plan

Distant Clusters

The observations will be conducted using EMMI red-arm in short integrations in shift-and-stare mode, to ensure excellent flat-fields. The expected magnitude limit for point sources in the coadded images on the NTT with a seeing of 0.7 arcsec is V~23.7 and I~22.8 at 5-sigma. Six repeated scans will be carried out in 2 contiguous, partly overlapping strips. The repeated scans will allow to reach one magnitude fainter (V~24.7 and I~23.8 for point sources) and will ease the identification and removal of cosmic rays. In order to estimate the expected completeness for high-z galaxies, drift-scan data was simulated by degrading deeper images to the NTT integrations time. The number of galaxies in each magnitude bin of the original and the degraded images was then compared. Based on these simulations, the completeness limit of high-z galaxies is expected to be better than 80% down to V~24.5. These observations will require about 192 hours.

Quasars

Using EMMI-red arm, scans will be carry out in the passbands BB (EMMI- red arm blue band) (3 scans) and Gunn-z (single scans) over the same region observed in V and I to search for distant clusters, as described above. This multicolor data will be used to select high redshift (z>3) quasars. The expected limiting magnitudes are B~24.5, V~24.7, I~23.8 and z~22.3. This part of the survey will require about 64 hours.

High Redshift Galaxies

The preferred configuration for the survey is based on the new NTT direct camera SUSI2, which employs a mosaic of two highly efficient 4096 x 2048 CCDs. We propose to observe 2x5 SUSI2 fields (each 5'x5') in the four bands U, G, r Gunn and I, for a total field of 0.07 square degrees. The exposure times per field to reach 5 sigma detections to the magnitude limits quoted in the scientific goals are estimated to be 9000, 3600, 2400, and 3600 seconds, respectively. The observations will be gathered in the form of short, dithered exposures. The infrared K and J observations will be done with SOFI at the same telescope focus (10 fields in K with an integration time of 3 hrs/field and a single field in J for 24 hrs, including overhead). About 128 hours are needed to carry out the program including the calibration and the read-out overtime. The advantages of the proposed instrument configuration are the availability of an efficient U band (very useful to discriminate between low and high redshift candidates), the superior image quality of the NTT direct focus (both in terms of image angular size and homogeneity of the PSF over the field of view) and the good match with the large field infrared facility SOFI at the same telescope focus. These are major plus with respect to other large field surveys that are planned for 1997-98 using CCD mosaics typically at the prime focus of 4m class telescopes.

Details of differents parts of the ESO Imaging Survey

Science Goal		Area (sq. deg.)		Scans		Filters		Hours		mlim(5-sigma)
Distant clusters		30		6 X 2		V		96		24.5
Idem		30		6 X 2		I		96		23.5
Quasars		30		3 X 2		B		48		24.5 (point source)
Idem		30		2		Gunn-z		16		22.3 (point source)
Idem		30		2		V		----		24.8 (point source)
Idem		30		2		I		----		23.8 (point source)
High-z galaxies		0.07		pointed		UGrIJK		128		26, K=21.5, J=24.0
Total		----		----		----		384		----