ALMA OBSERVATIONS OF WARM DENSE GAS IN NGC?1614—BREAKING OF THE STAR FORMATION LAW IN THE CENTRAL KILOPARSEC*

摘要

We present ALMA Cycle-0 observations of the CO (6-5) line emission and of the 435 μm dust continuum emission in the central kiloparsec of NGC?1614, a local luminous infrared galaxy at a distance of 67.8?Mpc (). The CO emission is well resolved by the ALMA beam (026 × 020) into a circumnuclear 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 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 ΣSFR ~ 100 M ☉ yr–1 kpc–2 and . 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 active galactic nucleus in NGC?1614. Comparisons with radio continuum emission show a strong deviation from an expected local correlation between ΣGas and ΣSFR, indicating a breakdown of the Kennicutt-Schmidt law on the linear scale of ~100?pc.