A Study of Active Galactic Nuclei in Low Surface Brightness Galaxies with Sloan Digital Sky Survey Spectroscopy

Active galactic nuclei (AGN) in low surface brightness galaxies (LSBGs) have received little attention in previous studies. In this paper, we present detailed spectral analysis of 194 LSBGs from the Impey et al. (1996) APM LSBG sample which have been observed spectroscopically by the Sloan Digital Sky Survey Data Release 5 (SDSS DR5). Our elaborate spectral analysis enables us to carry out, for the first time, reliable spectral classification of nuclear activities in LSBGs based on the standard emission line diagnostic diagrams in a rigorous way. Star-forming galaxies are common, as found in about 52% LSBGs. We find, contrary to some of the previous claims, that the fraction of galaxies containing an AGN is significantly lower than that found in nearby normal galaxies of high surface brightness. This is qualitatively in line with the finding of Impey et al. (2001). This result holds true even within each morphological type from Sa to Sc. LSBGs having larger central stellar velocity dispersions, or larger physical sizes, tend to have a higher chance to harbor an AGN. For three AGNs with broad emission lines, the black hole masses estimated from the emission lines are broadly consistent with the well known M-$\sigma_\ast$ relation established for normal galaxies and AGNs.Comment: 5 tables and 14 figure

I Peptide isosteric replacement preparation using zinc-mediated chain extension-aldol reactions II Formal synthesis of (+)-Brefeldin A III Zinc-mediated chain extension reactions with substituted carbenoids

A series of amino acid derived alpha-substituted-gamma-keto amides and esters have been prepared by zinc-mediated chain extension and tandem chain extension aldol reactions with various aldehydes and ketones. An efficient diastereoselective synthetic route has been developed to approach a proposed inhibitor for HCMV (Human Cytomegalovirus) protease using this zinc-mediated tandem chain extension-aldol reaction as the key step. An asymmetric formal synthesis of (+)-Brefeldin A has been developed in which the zinc-mediated ring expansion/oxidation/elimination method constitutes a key step. Preparation of beta-alkyl-gamma-keto esters through a chain extension reaction using substituted carbenoids has also been accomplished.*