Observations of the Hubble Deep Field South with the Infrared Space Observatory - I. Observations, data reduction and mid-infrared source counts

摘要

We present results from a deep mid-infrared survey of the Hubble Deep FieldSouth (HDF-S) region performed at 7 and 15 micron with the CAM instrument onboard the Infrared Space Observatory (ISO). The final map in each band wasconstructed by the coaddition of four independent rasters, registered usingbright sources securely detected in all rasters, with the absolute astrometrybeing defined by a radio source detected at both 7 and 15 micron. We soughtdetections of bright sources in a circular region of radius 2.5 arcmin at thecentre of each map, in a manner that simulations indicated would produce highlyreliable and complete source catalogues using simple selection criteria.Merging source lists in the two bands yielded a catalogue of 35 distinctsources, which we calibrated photometrically using photospheric models oflate-type stars detected in our data. We present extragalactic source countresults in both bands, and discuss the constraints they impose on models ofgalaxy evolution models, given the volume of space sampled by this galaxypopulation.