Starburst in the Ultraluminous Galaxy Arp 220: Constraints from Observations of Radio Recombination Lines and Continuum

Abstract

We report the first detection at multiple radio wavelengths (13, 6, and 3.6 cm) of 18 compact sources within both nuclei of the Ultra Luminous Infra-Red Galaxy (ULIRG) Arp 220. In just over half of the sources we find that the observed spectra are consistent with the standard model of powerful Type IIn supernovae interacting with their pre-explosion stellar wind. The rate of appearance of new radio sources ascribed to these supernova events suggests that a large fraction of core-collapse supernovae in Arp 220 are highly luminous, possibly implying a radically different stellar initial mass function (IMF) or stellar evolution compared to galactic disks. A second group of sources, consisting of the brightest and longest monitored sources at 18 cm, do not easily fit the radio supernova model. We propose that these are young supernova remnants that have just begun interacting with their surrounding dense ISM. 8th European VLBI Network Symposium

Very Large Array Observations of the H92α Line from NGC 5253 and Henize 2‐10: Ionized Gas around Super Star Clusters

“…The commonly occurring relatively high density of D104 cm~3 for the compact ionized gas in the starburst regions in He 2-10 and NGC 5253 and also in other starburst galaxies (Gilbert et al 2000 ;Zhao et al 1997 ;Anantharamaiah et al 2000 ; TBH00 ; KJ99) is striking. One model that may be able to explain these commonly occurring high densities is that of Jog & Das (1992.…”

“…derive a threeÈdensity component model of the ionized gas in Arp 220 based on line and continuum data from 1.4 to 230 GHz (Anantharamaiah et al 2000).…”

“…Vol. 557 RRL data is essential and models have to be constructed to explain the data with a minimum number of di †erent density components (as was done in the case of Arp 220 by Anantharamaiah et al 2000). 4.…”

“…The aim is to model the density structure, kinematics, and geometry of the ionized gas in these regions and to determine an extinction-independent star formation rate. An example of such a study of Arp 220 has been presented by Anantharamaiah et al (2000).…”

Estimating sizes of faint, distant galaxies in the submillimetre regime

“…E.g. in Arp 220 with a similar SFR (Anantharamaiah et al 2000), the majority of the star formation occurs inside 1 kpc of the centre (Scoville, Yun & Bryant 1997), resulting in an average SFR of approximately 70 M yr −1 kpc −2 (Anantharamaiah et al 2000). We can also compare this to SMGs, e.g.…”