Mathematics – Logic
Scientific paper
Dec 1997
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997hst..prop.7526f&link_type=abstract
HST Proposal ID #7526
Mathematics
Logic
Hst Proposal Id #7526 Agn/Quasars
Scientific paper
FeII emission is observed from a wide variety of astronomical objects, including protostellar disks, novae, supernovae, and quasars, but it has been notoriously hard to interpret because of the great complexity of the Fe^+ energy level structure. We are in the middle of a long term program to fully simulate the physical conditions within FeII-emitting gas and then predict the resulting spectrum. This involves the adaptation and encapsulation of vast amounts of atomic data, and its incorporation into the photoionization code Cloudy. Our approved Cycle 6 archive proposal used HST observations of the sharp lined strong FeII-emitting stars RR Tel and Eta Carinae, and the Seyfert galaxy I Zw 1, to validate the completeness and predictions of the model atom. Here we request archival HST observations of 56 low-redshift quasars to extend our Cycle 6 work to the family of AGN. Our long term goal is to deduce iron abundances from FeII emission in high redshift quasars. It is doubtful that the range of FeII equivalent widths is due to abundances alone; cloud properties must also contribute to line visibility. The HST observations will be used together with optical data and extensive grids of photoionization calculations to understand what controls the visibility of FeII emission, and to quantify what it says about iron abundances. When complete this will result in a chronometer measuring the redshift when the universe passed through an age of 1 Gyr, thus constraining several cosmological parameters.
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