Different flavors of molecular megamasers trace different types of galaxies and provide information on different structural components. H2O megamaser regions may trace the inner parsec-scale surroundings of the nucleus, while the OH and H2CO megamasers emissions may trace of the inner few hundred parsecs. OH and H2CO masers trace the population of ultra-luminous FIR galaxies, which are mostly dusty nuclei powered by compact starbursts. The H2O megamasers are found among LINERs and Seyfert 2's, which are relatively "naked" and not dominated by dust and starformation. The pumping schemes for the various flavors H2O sources provide direct links to the physical environment. The strongest megamasers sources have been mapped at the highest angular resolution resulting in spectacular views of the dynamics of the nuclear regions. For H2O sources most of the emission has been recovered, while for OH sources a significant fraction of the integrated OH line emission may be missing. The molecular megamasers trace different galaxy populations with redshift. With global VLBI systems, the disks of powerful sources like NGC 4258 could be resolved out to redshifts of 0.06. The OH emission regions in Arp 220 could be resolved out to redshifts of 0.9, which is well into the redshift range of interest for galaxy evolution. The OH luminosity characteristics suggest that prominent OH galaxies may be found abundantly at higher redshifts.
Galaxies and their Constituents at the Highest Angular Resolutions
- Pub Date:
- January 2001