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

We present ALMA Cycle-0 observations of the CO (6-5) line emission and of the 435 mu m dust continuum emission in the central kiloparsec of NGC 1614, a local luminous infrared galaxy at a distance of 67.8 Mpc (1 " = 329 pc). The CO emission is well resolved by the ALMA beam (0." 26x0." 20) into a circumnuclear ring, with an integrated flux of f(C O(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 similar to 40 km s(-1). These knots are associated with strong star formation regions with Sigma(SFR) similar to 100M(circle dot) yr(-1) kpc(-2) and Sigma(Gas) similar to 10(4) M-circle dot pc(-2). The nondetections of the nucleus in both the CO (6-5) line emission and the 435 mu m continuum rule out, with relatively high confidence, a Compton-thick active galactic nucleus in NGC 1614. Comparisons with radio continuum emission show a strong deviation from an expected local correlation between Sigma(Gas) and Sigma(SFR), indicating a breakdown of the Kennicutt-Schmidt law on the linear scale of similar to 100 pc.