ISO Status Report - February 2005
Science Highlights
ISO continues to have a significant presence in the refereed literature, with 1188 papers published to date. Recent highlights include:
- Spectroscopy of polycyclic aromatic hydrocarbons and very small grains in photo-dissociation regions
Spectral maps of photodissociation regions in two bright molecular clouds (NGC 7023 and rho-Ophiuchi SR3), obtained with ISOCAM CVF aboard ISO have been presented. Three different spectra and their associated spatial distribution are extracted from the analysis. Close to the centre of the star, very small and hot grains are seen, interpreted to be clusters of Polycyclic Aromatic Hydrocarbons (PAHs), while further away from the star these are disintegrated into free-flying PAHs by the UV radiation present in the boundary between the star and the molecular cloud. This is traced by the variation of the 7.7 um peak in the spectrum to 7.8 micron when going from the outside to the centre. The paper is based on Highly Processed Data Products retrieved from the ISO Data Archive (Rapacioli et al., A&A, 2005).
- A population of extreme mid-to-near-infrared sources: Obscured AGN and dusty starbursts
A sample of mid-infrared detected sources from the European Large Area ISO Survey (ELAIS) regions is presented, characterised by strong mid-IR radiation with faint near-IR and optical counterparts (extreme mid-to-near-IR objects or EMNOs). These are argued to most likely be obscured AGNs, based on SED shapes and X-ray data. Very strong dusty starbursts at z>1 may also have high mid-to-near-IR flux ratios, but using the MIR/NIR and FIR/MIR ratios these may be separated. Most of these appear to be ULIRGs, half are also extremely red objects (ERO). This simple broad band selection method makes EMNOs a useful window into high-redshift obscured nuclear activity and its sought after relation to star-formation, in a similar way that EROs have been used to define samples of high-redshift early type galaxies (Johansson et al., A&A, 2004).