ALMA Observations of Warm Molecular Gas and Cold Dust in NGC 34

May 2014 • 2014ApJ...787...48X

Authors • Xu, C. K. • Cao, C. • Lu, N. • Gao, Y. • van der Werf, P. • Evans, A. S. • Mazzarella, J. M. • Chu, J. • Haan, S. • Diaz-Santos, T. • Meijerink, R. • Zhao, Y. -H. • Appleton, P. • Armus, L. • Charmandaris, V. • Lord, S. • Murphy, E. J. • Sanders, D. B. • Schulz, B. • Stierwalt, S.

Abstract • We present Atacama Large Millimeter Array (ALMA) Cycle-0 observations of the CO (6-5) line emission (rest-frame frequency = 691.473 GHz) and of the 435 μm dust continuum emission in the nuclear region of NGC 34, a local luminous infrared galaxy at a distance of 84 Mpc (1'' = 407 pc) which contains a Seyfert 2 active galactic nucleus (AGN) and a nuclear starburst. The CO emission is well resolved by the ALMA beam (0.''26 × 0.''23), with an integrated flux of f CO(6-5) = 1004 (± 151) Jy km s-1. Both the morphology and kinematics of the CO (6-5) emission are rather regular, consistent with a compact rotating disk with a size of 200 pc. A significant emission feature is detected on the redshifted wing of the line profile at the frequency of the H13CN (8-7) line, with an integrated flux of 17.7 ± 2.1(random) ± 2.7(systematic) Jy km s-1. However, it cannot be ruled out that the feature is due to an outflow of warm dense gas with a mean velocity of 400 km s-1. The continuum is resolved into an elongated configuration, and the observed flux corresponds to a dust mass of M dust = 106.97 ± 0.13 M . An unresolved central core (radius ~= 50 pc) contributes 28% of the continuum flux and 19% of the CO (6-5) flux, consistent with insignificant contributions of the AGN to both emissions. Both the CO (6-5) and continuum spatial distributions suggest a very high gas column density (gsim 104 M pc-2) in the nuclear region at radius <~ 100 pc.

The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.


IPAC Authors


Phil Appleton

Senior Scientist


Lee Armus

Senior Scientist

Joe Mazzarella

Senior Scientist