J/ApJ/653/127 9.7um silicate features in AGNs (Shi+, 2006)
9.7µm silicate features in active galactic nuclei:
new insights into unification models.
Shi Y., Rieke G.H., Hines D.C., Gorjian V., Werner M.W., Cleary K.,
Low F.J., Smith P.S., Bouwman J.
<Astrophys. J., 653, 127-136 (2006)>
=2006ApJ...653..127S 2006ApJ...653..127S
ADC_Keywords: Active gal. nuclei ; Abundances
Keywords: galaxies: active - galaxies: nuclei
Abstract:
We describe observations of 9.7um silicate features in 97 AGNs,
exhibiting a wide range of AGN types and of X-ray extinction toward
the central nuclei. We find that the strength of the silicate feature
correlates with the HI column density estimated from fitting the
X-ray data, such that low HI columns correspond to silicate emission,
while high columns correspond to silicate absorption. The behavior is
generally consistent with unification models in which the large
diversity in AGN properties is caused by viewing-angle-dependent
obscuration of the nucleus. Radio-loud AGNs and radio-quiet quasars
follow roughly the correlation between HI columns and the strength of
the silicate feature defined by Seyfert galaxies. The agreement among
AGN types suggests a high-level unification with similar
characteristics for the structure of the obscuring material. We
demonstrate the implications for unification models qualitatively with
a conceptual disk model. The model includes an inner accretion disk
(<0.1pc in radius), a middle disk (0.110pc in radius) with a dense
diffuse component and with embedded denser clouds, and an outer clumpy
disk (10-300pc in radius).
Description:
Our sample (see table 1) includes a variety of types of AGNs:
radio-loud quasars, FR II radio galaxies, Seyfert 1 and Seyfert 2
galaxies, broad absorption-line quasars (BALQs), low-ionization
nuclear emission-line region (LINER) galaxies, and non-BAL radio-quiet
quasars, including optically selected Palomar-Green (PG) quasars and
IR quasars selected by the Two Micron All Sky Survey (2MASS),
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 83 97 Source Characteristics
refs.dat 42 25 References
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 23 A23 --- Name Source name
25- 29 F5.3 --- z Redshift
31- 35 A5 --- Type AGN type (1)
37- 41 F5.2 --- Str Silicate feature strength (2)
43- 46 F4.2 --- E_Str ? Upper uncertainty limit in Str
48- 51 F4.2 --- e_Str ? Lower uncertainty limit in Str
53 I1 --- r_Str Reference on Str, in refs.dat file
55 A1 --- l_NH Limit flag on NH
57- 64 F8.3 10+22/cm2 NH ? Intrinsic H I column density
66- 72 F7.3 10+22/cm2 E_NH ? Upper uncertainty limit in NH
74- 80 F7.3 10+22/cm2 e_NH ? Lower uncertainty limit in NH
82- 83 I2 --- r_NH ? Reference on NH, in refs.dat file
--------------------------------------------------------------------------------
Note (1): AGN type as follows:
PG = PG quasar
RLQ = radio-loud quasar
Sy1 = Seyfert 1 galaxies
Sy2 = Seyfert 2 galaxies
BALQ = broad absorption-line quasar
FRII = FR II radio galaxies
LINER = low-ionization nuclear emission-line region
2MQ = 2MASS quasar
Note (2): The strength of the 9.7um silicate feature is defined as
(Ff-Fc)/Fc , where Ff and Fc and are the observed flux density and
underlying continuum flux density, respectively, at the peak (for
emission) or the minimum (for absorption) of the silicate feature.
The feature strength in this definition is a direct measure of the
optical depth for the silicate absorption.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: refs.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Ref Reference number
4- 22 A19 --- BibCode BibCode
24- 42 A19 --- Aut Author's name
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 31-Jul-2008