Searching for circumnuclear molecular torus in Seyfert galaxy NGC 4945

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. 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. 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 Synchrotron Radiation SMA RA continuum map SED of NGC 4945 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 109Mסּ - 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. 100 pc Pα emission shows a ring like structure with 10” in diameter Starburst activity • 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