1998/01/19 by Frank J. Masci, Masci, Frank J.
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics (astro-ph) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9801181
PhD thesis: 270 pages, 70 figures - everything, including style files are included in one single file. Latex file is thesis.tex
arxiv created 1998/01/19 · openalex publication_date 1998/01/19 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
A majority of quasar surveys have been based on criteria which assume strong\nblue continua or a UV-excess. Any amount of dust along the line-of-sight is\nexpected to drastically extinguish the optical/UV flux leading to a selection\nbias. Radio surveys however should suffer no bias against extinction by dust.\nRecently, a large complete sample of radio-selected quasars has become\navailable (the `Parkes sample'). A majority of these sources exhibit\noptical--to--near-infrared continua that are exceedingly `red', very unlike\nthose of quasars selected optically. The purpose of this thesis, broadly\nspeaking, is to explore the problem of incompleteness in optical quasar surveys\ndue to obscuration by dust, and to interpret the relatively `red' continua\nobserved in the Parkes quasar sample. The first part of this thesis explores\nthe observational consequences of an intervening (foreground) cosmological dust\ncomponent, such as that located in galaxies and clusters. The second part\nexamines the continuum properties of Parkes-quasars in the framework of a\nnumber of absorption and emission mechanisms to assess the importance of\nextinction by dust. It is found that spectroscopic and photometric data for the\n``reddest'' quasars (with B-K>5) is best explained by the dust model, rather\nthan ``purely'' by an intrinsic emission property.\n