Open AccessExtinction due to amorphous carbon grains in red quasars from the Sloan Digital Sky Survey
Author(s) -
Czerny B.,
Li J.,
Loska Z.,
Szczerba R.
Publication year - 2004
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2004.07590.x
Subject(s) - physics , astrophysics , quasar , extinction (optical mineralogy) , interstellar medium , amorphous carbon , sky , cosmic dust , carbon fibers , grain size , astronomy , galaxy , composite number , optics , composite material , materials science , raman spectroscopy
We construct a quasar extinction curve based on the blue and red composite quasar spectra of Richards et al. prepared from the Sloan Digital Sky Survey. This extinction curve does not show any traces of the 2200‐Å feature characteristic of the interstellar medium, and this indicates that graphite grains are likely to be absent close to quasar nuclei. The extinction is best modelled by an AC sample of amorphous carbon grains, assuming a standard distribution of grain sizes ( p = 3.5) but slightly larger minimum grain size ( a min = 0.016 μm) and lower maximum grain size ( a min = 0.12 μm) than the respective canonical values for the interstellar medium. The dust composition is thus similar to that of the dust in carbon reach asymptotic giant branch stars. Since graphite grains form from amorphous carbon exposed to strong ultraviolet irradiation, the results indicate that the dust forms either surprisingly far from the active nucleus or in a wind that leaves the nucleus quickly enough to avoid crystallization into graphite.