The Reddening Curve for Active Galactic Nuclei
Abstract
We present reddening curves derived from the broad emission lines and continua of large samples of both radio-loud and predominantly radio-quiet AGNs. From these curves we determine the parameter R = A(V)/E(B-V). The curves differ substantially from the standard galactic extinction curve. The value of R is significantly greater than in the local interstellar medium. We confirm that the 2175 extinction hump is extremely weak. Our most interesting finding is that the UV extinction curves are very flat, especially for radio-loud AGNs. Our reddening curves resolve the long-standing conflict between the significant reddenings implied by the optical spectra of AGNs and almost zero reddening implied by the ultra-violet spectra. Although our reddening curve differs from the standard galactic curve, the form of the AGN reddening curves can be readily explained by standard silicate-plus-carbonaceous grain models. The models imply that there is a relative lack of small grains, especially of the small carbonaceous grains that provide the 2175 feature in our local interstellar medium.
- Publication:
-
American Astronomical Society Meeting Abstracts #200
- Pub Date:
- June 2002
- Bibcode:
- 2002AAS...200.9704G