Ionized Gas Kinematics at High Resolution. II: Discovery of a Double Infrared Cluster in II Zw 40

Abstract

The nearby dwarf galaxy II Zw 40 hosts an intense starburst. At the center of the starburst is a bright compact radio and infrared source, thought to be a giant dense HII region containing ~14,000 O stars. Radio continuum images suggest that the compact source is actually a collection of several smaller emission regions. We accordingly use the kinematics of the ionized gas to probe the structure of the radio-infrared emission region. With TEXES on the NASA-IRTF we measured the 10.5um [SIV] emission line with effective spectral resolutions, including thermal broadening, of ~25 and ~3 km/s and spatial resolution ~1". The line profile shows two distinct, spatially coextensive, emission features. The stronger feature is at galactic velocity and has FWHM 47 km/s. The second feature is ~44km/s redward of the first and has FWHM 32 km/s. We argue that these are two giant embedded clusters, and estimate their masses to be ~3x10^5Mo and ~1.5x10^5 Mo. The velocity shift is unexpectedly large for such a small spatial offset. We suggest that it may arise in a previously undetected kinematic feature remaining from the violent merger that formed the galaxy.

8 pages, 4 figures, Accepted to ApJ

References in corpus (5)

• Integral field near-infrared spectroscopy of II Zw 40
• Elemental Abundances of Blue Compact Dwarfs from mid-IR Spectroscopy with Spitzer
• [Ne II] Observations of Gas Motions in Compact and Ultracompact H II Regions
• Brackett Lines from the Super Star Cluster Nebulae in He 2-10
• [S IV] in the NGC 5253 Supernebula: Ionized Gas Kinematics at High Resolution

Cited by in corpus (6)

• Physical Properties of II Zw 40's Super Star Cluster and Nebula: New Insights and Puzzles from UV Spectroscopy
• ALMA Reveals Potential Localized Dust Enrichment from Massive Star Clusters in II Zw 40
• The Youngest Globular Clusters
• Ionized Gas Kinematics at High Resolution V: [NeII], Multiple Clusters, High Efficiency Star Formation and Blue Flows in He 2-10
• Ionized Gas Kinematics at High Resolution IV: Star Formation and a Rotating Core in the Medusa (NGC 4194)
• Observing the influence of the youngest super star clusters in NGC 1569: Keck Brackett $\alpha$ spectroscopy