1. Searching for circumnuclear molecular torus in Seyfert galaxy NGC 4945
Outline:
Motivations
Observations--SMA
Results
Summary

2. Motivation
Search for circumnuclear molecular torus in Seyfert galaxies.
Measure physical properties.
Replenishment of the torus.
Probe gravitational potential.

3. Matsushita et al. (2004, ApJL, in press)
Motivation
Search for circumnuclear molecular torus in Seyfert galaxies.
Measure physical properties.
Replenishment of the torus.
Probe gravitational potential.
Optical image of M51
12CO(1-0) NMA
12CO(2-1)
SMA
12CO(3-2)
SMA
810 pc
Sawada-Satoh et al.
Matsushita et al. (2004, ApJL, in press)
Sakamoto et al.
(1999, ApJS, 124, 403)

4. Sample selection NGC 4945: Seyfert 2
Distance ~ 3.9 Mpc (1” = 19 pc), one of closest Seyfert galaxies.
DEC = - 490, only accessible mm/sub-m interferometer is SMA.

5. Observation--SMA Observe on: 5.24.2004
Compact configuration N-S elongation (7 x 6m ants)
FWHM primary beam: 55” = 1.1 kpc
Synthesized beam: 5.1” x 2.8” (100 x 60 pc)
Wide bandwidth of SMA (4 GHz), observe 12CO, 13CO, C18O and continuum together.
Detection limit ~ 106 Mסּ.
55”

6. Intensity maps Velocity maps
Results(1)
Intensity maps Velocity maps
12CO
12CO
100 pc
100 pc
13CO
13CO
100 pc
100 pc
C18O
C18O
100 pc
100 pc

7. Results(2)—P-V diagram
Solid body rotation with gradient = 1160 kms-1 kpc-1, ( tracing rising part of rotation curve).
Molecular gas ring coinciding with starburst ring.
Dynamical mass within 380 pc = 3 x 109 Mסּ
10”, 200 pc
Pα emission shows a ring like structure with 10” in diameter
Marconi et al. 2000

8. continuum emission Flux density Log [Jy] DEC SMA RA continuum map
Synchrotron Radiation
SMA
RA continuum map
SED of NGC Log [Hz]
SED rules out synchrotron emission.
Size continuum ~ 300 pc, same as C18O.
Continuum likely from dust.

9. continuum emission DEC RA continuum map C18O intensity map
SED rules out synchrotron emission.
Size continuum ~ 300 pc, similar as C18O.
Continuum likely from dust.

10. Discussion Central gas concentration
- Rotating disk within 380 pc  molecular torus? central disk?
- Molecular gas mass from 12CO, 13CO and C18O = 108 – 109 Mסּ
- Molecular gas Mass derived from dust = 7 x 108 Mסּ(gas/dust=100)
- Enclosed mass within 380 pc = 3 x 109 Mסּ
- MBH < 106 (From H2O megamaser Greenhill et al. 1996)  enclosed
mass dominated by stars.
- Non-circular motion from 380 – 900 pc  need to model kinematics
The molecular gas could be ring, or torus. We need higher resolution observation.

11. Summary & Future work Two possiblilities
- Circumnuclear molecular torus size 380 pc
with mass dominated by stars.
- Molecular gas (disk) settled into central
gravitational potential.
Image at higher angualr resolution.
Higher CO transitions.

13. Starburst activity
Pα emission shows a ring like structure with 10” in diameter
100 pc
Bright IRAS source (at 100 μm) with 75% emission concentrated at central 12” x 9” region.
Moderate star formation rate: ~0.4Mסּ/yr (from infrared luminosity)
Starburst ring in Pα, inner 100 pc and 200 pc outside.
Conical structure in optical.
100 pc
True color RGB image shows a conical structure originated from the central 100 pc region
Moorwood et al. 1996, Marconi et al. 2000