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Published February 10, 2017 | Submitted + Published
Journal Article Open

ALMA Resolves the Nuclear Disks of Arp 220


We present 90 mas (37 pc) resolution ALMA imaging of Arp 220 in the CO (1-0) line and continuum at λ = 2.6 mm. The internal gas distribution and kinematics of both galactic nuclei are well resolved for the first time. In the west nucleus, the major gas and dust emission extends out to 0."2 radius (74 pc); the central resolution element shows a strong peak in the dust emission but a factor of 3 dip in the CO line emission. In this nucleus, the dust is apparently optically thick (τ_(2.6 mm) ~ 1) at λ = 2.6 mm with a dust brightness temperature of ~147 K. The column of interstellar matter at this nucleus is N_(H2) ⩾ 2 x 10^(26)cm^(−2), corresponding to ~900 gr cm^(−2). The east nucleus is more elongated with radial extent 0."3 or ~111 pc. The derived kinematics of the nuclear disks provide a good fit to the line profiles, yielding the emissivity distributions, the rotation curves, and velocity dispersions. In the west nucleus, there is evidence of a central Keplerian component requiring a central mass of 8 × 10^8 M⊙. The intrinsic widths of the emission lines are Δν(FWHM) = 250 (west) and 120 (east) km s^(−1). Given the very short dissipation timescales for turbulence (≾10^5 years), we suggest that the line widths may be due to semicoherent motions within the nuclear disks. The symmetry of the nuclear disk structures is impressive, implying the merger timescale is significantly longer than the rotation period of the disks.

Additional Information

© 2017 The American Astronomical Society. Received 2016 May 28; revised 2017 January 6; accepted 2017 January 6; published 2017 February 8. We thank the referee for a very thorough review of the manuscript and useful suggestions for clarification. We thank Zara Scoville for proofreading the manuscript. This paper makes use of the following ALMA data: https: //almascience:nrao:edu/aq/?project code = 2015:1:00113:S. ALMA is a partnership of ESO (representing its member states), NSF (USA), and NINS (Japan), together with NRC (Canada) and NSC and ASIAA (Taiwan), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO, and NAOJ. This work was done in part at the Aspen Center for Physics, which is supported by National Science Foundation grant PHY−1066293. T.A.T. is supported by NSF Grant #1516967. T.A.T. thanks the Simons Foundation and organizers Juna Kollmeier and Andrew Benson for support for the Galactic Winds: Beyond Phenomenology symposium series.

Attached Files

Published - Scoville_2017_ApJ_836_66.pdf

Submitted - 1605.09381v1.pdf


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