![]() | Annu. Rev. Astron. Astrophys. 1991. 29:
581-625 Copyright © 1991 by Annual Reviews. All rights reserved |
9.2 NGC 1068
NGC 1068 is the nearest galaxy with both a Seyfert
II active nucleus
and a high rate of star formation in its inner disk. Half of the total
luminosity (2 x 1011 L) originates from an extended disk of young
stars at radii < 1.5 kpc
(Telesco & Harper
1980);
the remainder arises
in a source < 0.5" in size, centered on the Seyfert nucleus. This
galaxy has been the focus of numerous molecular line studies (see
Table 1), with the highest resolution
corresponding to 260 pc.
In Figure 14, the integrated CO emission at
2.9" resolution is shown superposed on a U-band optical image
(Planesas et al 1991).
Two spiral
arms of molecular gas are seen encircling the nucleus at a radius of
approximately 1.5 kpc, with many distinct emission complexes of size
up to 500 pc and masses up to 7 x 108 M. The arms, containing a total
H2 mass of 5 x 109 M
, originate at the outer ends
of a stellar bar
seen in the near infrared
(Scoville et al 1988,
Thronson et al 1989c).
The kinematics of the molecular ring can be fit by circular
rotation if the position angle of the major axis is 90° or by rotation
plus expansion if the major axis position angle is taken as 40°
(Planesas et al 1991).
![]() |
Figure 14. Map of the integrated CO
emission in NGC 1068 overlaid on a
U-band image of the inner region of the galaxy
(Planesas et al 1991).
The major features seen in CO are the inner spiral arms (~ 5 x
109 M |
In Figure 14, an emission peak may also be seen
coincident with the
Seyfert nucleus. Although approximately half of this emission is radio
continuum from the central non-thermal source, the remainder is
probably CO emission. The total mass of H2 in the nuclear
source at a
radii < 130 pc is approximately 8 x 107 M. The dust associated with
this gas may be responsible for obscuring the direct line of sight to
the Seyfert I nucleus hypothesized on the basis of optical
spectropolarimetry
(Antonucci & Miller
1985).