Arp 220: A Post-Starburst Galaxy With Little Star Formation Outside of It's Nuclear Disks

Understand

The ultra-luminous infrared galaxy Arp2 20 is a late-stage merger with several tidal structures in the outskirts and two very compact, dusty nuclei that show evidence for extreme star formation and host at least one AGN.

• New and archival high-resolution images taken by the Hubble Space Telescope provide a state-of-the-art view of the structures, dust, and stellar clusters in Arp 220.
• We find that ~90% of the Halpha emission arises from a shock-ionized bubble emanating from the AGN in the western nucleus, while the nuclear disks dominate the Pbeta emission.
• Four very young (~3-6 Myr) but lower mass (< 10^4 Msun) clusters are detected in Halpha within a few arcsec of the nuclei, but produce less than 1% of the line emission.