J and Ks Images Available for General Use

J(1.25 µm) and Ks(2.16 µm) science verification images of a 5x5 arcmin region centred on RA ~ 12h:05m:26s and Dec ~ -07o:43':27'' (J2000) were obtained in March 1998 during the commissioning of SOFI at the NTT telescope on La Silla (Moorwood, Cubyand Lidman, 1998, The Messenger, 91,9). This region contains thesmaller field observed with the SUSI CCD camera (D'Odorico, 1997, The Messenger, 90,1) and for which visible images have already been madeavailable on the Web (NDF web pages.

These particular observations were made with the aim of measuring anddemonstrating the limiting performance of both SOFI and its imaging pipeline by delivering a scientifically useful product. Although less timewas available than expected, due to bad weather, we believe the resultingimages go as deep or deeper than any obtained over a comparable area andare of potential scientific value for a variety of purposes. One reason for choosing the NTT Deep Field for example was to enable the determination of photometric redshifts, by combining the SOFI/SUSI data, as a means of finding high z galaxies for spectroscopic follow-up with ISAAC during the1st period of VLT observations. This is of interest to both validate the technique of photometric redshifts at z > 1 and determine physical properties such as star formation rates, mass etc. The large number ofgalaxies detected could also constitute an important sample for the statistical analysis of number counts, correlation functions etc. Other uses and surprises are certainly expected.

The deep infrared images made available here have been reconstructed by P. Saracco from jittered observations totalling 4.3 hours and 10.4hours in J and Ks respectively and cover an area of ~ arcmin2 - taking into account the edge losses due to jittering. After co-adding the 128 (J) and 624 (Ks) frames the average FWHM of point sources in both images is about 0.75 arcsec. The limiting magnitudes at three sigmas from the background within an aperture of diameter 1.5 arcsec (2 FWHM) are Jlim=24.66 and Kslim=22.87 which correspond to a limiting surface brightness SBJ=25.1 mag/arcsec2 and SBKs=23.3 mag/arcsec2.

The J and Ks images are shown here in GIF format (north is up, east is to the left). Ifused in publications, credit should be givento the European Southern Observatory and reference made to the articleby A. Moorwood, J. G. Cuby and C. Lidman, 1998, The Messenger, 91,9)for the description of SOFI.

The following sections describe the observations and data reduction steps followed to construct the final images.