ALMA Observations of Warm Dense Gas in NGC 1614 — Breaking of Star Formation Law in the Central kpc

Creators: Xu, C. K.; Cao, C.; Lu, N.; Gao, Y.; Díaz-Santos, T.; Herrero-Illana, R.; Meijerink, R.; Privon, G.; Zhao, Y.-H.; Evans, A. S.; König, S.; Mazzarella, J. M.; Aalto, S.; Appleton, P.; Armus, L.; Charmandaris, V.; Chu, J.; Haan, S.; Inami, H.; Murphy, E. J.; Sanders, D. B.; Schulz, B.; van der Werf, P.

Abstract

We present ALMA Cycle-0 observations of the CO (6-5) line emission and of the 435 μm dust continuum emission in the central kpc of NGC 1614, a local luminous infrared galaxy (LIRG) at a distance of 67.8 Mpc (1" = 329 pc). The CO emission is well resolved by the ALMA beam (0."26×0."20) into a circum-nuclear ring, with an integrated flux of f_(CO (6-5)) = 898 (±153) Jy km s^(-1), which is 63(±12)% of the total CO (6-5) flux measured by Herschel. The molecular ring, located between 100 pc < r < 350 pc from the nucleus, looks clumpy and includes seven unresolved (or marginally resolved) knots with median velocity dispersion of ∼ 40 km s^(-1). These knots are associated with strong star formation regions with Σ_(SFR) ∼ 100 M_⊙ yr^(-1) kpc^(-2) and Σ_(Gas) ∼ 10^4 M_⊙ pc^(-2). The non-detections of the nucleus in both the CO (6-5) line emission and the 435 μm continuum rule out, with relatively high confidence, a Compton-thick AGN in NGC 1614. Comparisons with radio continuum emission show a strong deviation from an expected local correlation between Σ_(Gas) and Σ_(SFR), indicating a breakdown of the Kennicutt-Schmidt law on the linear scale of ∼100 pc.

Additional Information

© 2015 The American Astronomical Society. Received 2014 September 2; accepted 2014 November 4; published 2015 January 12. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. We thank Adam Leroy and Tony Remijan from NAASC for their help with data reduction. We thank an anonymous referee for constructive comments. Y.G. is partially supported by NSFC-11173059, NSFC-11390373, and CASXDB09000000. Y.Z. thanks the NSF of Jiangsu Province for partial support under grant BK2011888. V.C. acknowledges partial support from the EU FP7 grant PIRSES-GA-2012- 316788. This paper makes use of the following ALMA data: ADS/JAO.ALMA#2011.0.00182.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 research has made extensive use of the NASA/ IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

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