Dust in active nuclei II. Powder or gravel?

被引:192
作者
Maiolino, R [1 ]
Marconi, A [1 ]
Oliva, E [1 ]
机构
[1] Osservatorio Astrofis Arcetri, I-50125 Florence, Italy
关键词
galaxies : Seyfert; galaxies : nuclei; galaxies : ISM; dust; extinction;
D O I
10.1051/0004-6361:20000012
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
In a companion paper, Maiolino et al. (2001) presented various observational evidences for "anomalous" dust properties in the circumnuclear region of AGNs and, in particular, the reduced EB-V/N-H and A(V)/N-H ratios, the absence of the silicate absorption feature in mid-IR spectra of Sy2s and the absence of the carbon dip in UV spectra of reddened Sy1s. In this paper we discuss various explanations for these facts. The observational constraints favor a scenario where coagulation, catalyzed by the high densities in the circumnuclear region, yields to the formation of large grains. The resulting extinction curve is featureless, flatter than Galactic and the EB-V/N-H and A(V)/N-H ratios are significantly reduced. These results should warn about an inappropriate use of the standard Galactic extinction curve and A(V)/N-H ratio when dealing with the extreme gas conditions typical of the circumnuclear clouds of AGNs. We also investigated alternative scenarios for the observed anomalous properties of dust in AGNs. Some of these scenarios might explain some of the observed properties for a few objects, but they generally fail to account for all of the observational constraints obtained for the large sample of AGNs studied in these works.
引用
收藏
页码:37 / 48
页数:12
相关论文
共 69 条
[1]   Polarized broad-line emission from low-luminosity active galactic nuclei [J].
Barth, AJ ;
Filippenko, AV ;
Moran, EC .
ASTROPHYSICAL JOURNAL, 1999, 525 (02) :673-684
[2]   THE ORIGIN OF THE OPTICAL POLARIZATIONS OF SEYFERT-1 GALAXIES [J].
BERRIMAN, G .
ASTROPHYSICAL JOURNAL, 1989, 345 (02) :713-729
[3]  
BRINDLE C, 1990, MON NOT R ASTRON SOC, V244, P577
[4]   THE RELATIONSHIP BETWEEN INFRARED, OPTICAL, AND ULTRAVIOLET EXTINCTION [J].
CARDELLI, JA ;
CLAYTON, GC ;
MATHIS, JS .
ASTROPHYSICAL JOURNAL, 1989, 345 (01) :245-256
[5]   INTERSTELLAR DUST IN RHO OPHIUCHI DARK CLOUD [J].
CARRASCO, L ;
STROM, SE ;
STROM, KM .
ASTROPHYSICAL JOURNAL, 1973, 182 (01) :95-109
[6]  
Clavel J, 2000, ASTRON ASTROPHYS, V357, P839
[7]   STEPS TOWARD DETERMINATION OF THE SIZE AND STRUCTURE OF THE BROAD-LINE REGION IN ACTIVE GALACTIC NUCLEI .1. AN 8 MONTH CAMPAIGN OF MONITORING NGC-5548 WITH IUE [J].
CLAVEL, J ;
REICHERT, GA ;
ALLOIN, D ;
CRENSHAW, DM ;
KRISS, G ;
KROLIK, JH ;
MALKAN, MA ;
NETZER, H ;
PETERSON, BM ;
WAMSTEKER, W ;
ALTAMORE, A ;
BARIBAUD, T ;
BARR, P ;
BECK, S ;
BINETTE, L ;
BROMAGE, GE ;
BROSCH, N ;
DIAZ, AI ;
FILIPPENKO, AV ;
FRICKE, K ;
GASKELL, CM ;
GIOMMI, P ;
GLASS, IS ;
GONDHALEKAR, P ;
HACKNEY, RL ;
HALPERN, JP ;
HUTTER, DJ ;
JORSATER, S ;
KINNEY, AL ;
KOLLATSCHNY, W ;
KORATKAR, A ;
KORISTA, KT ;
LAOR, A ;
LASOTA, JP ;
LEIBOWITZ, E ;
MAOZ, D ;
MARTIN, PG ;
MAZEH, T ;
MEURS, EJA ;
NAIR, AD ;
OBRIEN, P ;
PELAT, D ;
PEREZ, E ;
PEROLA, GC ;
PTAK, RL ;
RODRIGUEZPASCUAL, P ;
ROSENBLATT, EI ;
SADUN, AC ;
SANTOSLLEO, M ;
SHAW, RA .
ASTROPHYSICAL JOURNAL, 1991, 366 (01) :64-81
[8]   The profiles of polarized broad Hα lines in radio galaxies [J].
Corbett, EA ;
Robinson, A ;
Axon, DJ ;
Young, S ;
Hough, JH .
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 1998, 296 (03) :721-738
[9]  
Dietrich M, 2000, ASTRON ASTROPHYS, V354, P17
[10]   OPTICAL-PROPERTIES OF INTERSTELLAR GRAPHITE AND SILICATE GRAINS [J].
DRAINE, BT ;
LEE, HM .
ASTROPHYSICAL JOURNAL, 1984, 285 (01) :89-108