ISO Status Report - November 2005
ISO continues to have a significant presence in the refereed literature, with 1264 papers published until August 2005 (~130 per year in the Active Archive Phase). Recent highlights include:
- The identification in a sample of 32 protostars of calcite as most likely carrier of dust features seen in half of the sample at 90-110 micron with the LWS spectrometer.
The result, published in A&A by Chiavassa et al., indicates that calcite seems to be formed relatively easily around protostars, despite the observation that on Earth it needs aqueous solutions. This raises the question of whether conditions simulating liquid water are common around forming stars and what creates them. In 2002, Kemper et al. had reported calcite in a planetary nebula, NGC 6302, also based on ISO data.
- The discovery of Polycyclic Aromatic Hydrocarbons (PAHs) in the halo of NGC 5907, one of the largest edge-on systems in the sky.
NGC 5907 has been an important target in searches for faint stellar halos since it has no appreciable bulge and was originally thought to be isolated. The ISO data show that most of the MIR emission is dominated by PAHs and it is likely that emission from very small grains contribute only negligible. The flux ratios are typical of galaxies with low star formation rates or quiescent regions within galaxies (e.g. M 83) and a very high PAH/continuum ratio is observed. A significant new discovery is the presence of PAHs in the halo of the galaxy. In the narrow bands that isolate single PAH features, the emission shows structure similar to high latitude features seen in other galaxies in other tracers (Irwin et al, A&A, accepted).