3. Observations and data reduction of the K band mosaic
We are in the process of mapping the central 2 of the Nuclear Bulge and selected areas further out in the H and K band ( 1.65 and 2.2 µm) using the IRAC 2B camera with the ESO-MPG 2.2m telescope on La Silla, Chile. The IRAC 2B camera uses a NICMOS3 chip with 2562 pixels. The pixel scale can be changed between and using lenses A to E, respectively (Lidman et al. 1996). For the chosen lens B we have a pixel scale of . This produces images of size . The image shown here in Fig. 1a and b is part of a K band mosaic which - when finished - will cover an area of size . An observing technique has been selected which allows us to recover an extended background emission using a nearby dark cloud as reference point (see also Table 2). 494 images were used to construct the K band mosaic image of the central shown in Fig. 1a and discussed in this paper (see Appendix A and B for a more detailed discussion of observing and data processing techniques. Appendix C deals specifically with problems associated with K band source counts). Since IRS 7, one of the strongest individual sources in all of our NIR images, is variable on time-scales of months (we measured Jy in 1995 and Jy in 1996) we used the IR star SA 109-71 as flux density calibrator. In the UKIRT Faint Standard Star List this star is designated FS 28 with flux densities mJy and mJy.
The 1.2 mm bolometer observations were made using the 7- through 37-channel bolometer arrays developed by E. Kreysa and coworkers of the MPIfR (Kreysa et al., 1996) with the IRAM 30m-MRT. Uranus and Mars were used as flux density calibrators. Extinction caused by the atmosphere was measured using SKYDIPS. The observing and reduction procedures will be detailed in a forthcoming paper. In Fig. 1b the surface brightness of the dust emission is overlaid as a contour map on the K band mosaic shown in Fig. 1a.
© European Southern Observatory (ESO) 1999
Online publication: August 13, 199