The Physical Scale of the Far-Infrared Emission in the Most Luminous Submillimeter Galaxies

TL;DR

This study uses high-resolution submillimeter imaging to measure the physical sizes of two luminous high-redshift galaxies, suggesting they may be Eddington-limited starbursts with implications for star formation models.

Contribution

First high-resolution submillimeter images of these galaxies, providing size estimates and evidence for Eddington-limited starburst activity at high redshift.

Findings

Angular sizes of 0.6-1.0 arcsec for GN20 and 0.3-0.4 arcsec for AzTEC1

Physical starburst regions of 1.5-8 kpc in size

Preliminary evidence of Eddington-limited star formation in these galaxies

Abstract

We present high resolution submillimeter interferometric imaging of two of the brightest high-redshift submillimeter galaxies known: GN20 and AzTEC1 at 0.8 and 0.3 arcsec resolution respectively. Our data - the highest resolution submillimeter imaging of high redshift sources accomplished to date - was collected in three different array configurations: compact, extended, and very extended. We derive angular sizes of 0.6 and 1.0 arcsec for GN20 and 0.3 and 0.4 arcsec for AzTEC1 from modeling their visibility functions as a Gaussian and elliptical disk respectively. Because both sources are B-band dropouts, they likely lie within a relatively narrow redshift window around z~4, which indicates their angular extent corresponds to physical scales of 4-8 and 1.5-3 kpc respectively for the starburst region. By way of a series of simple assumptions, we find preliminary evidence that these hyperluminous starbursts - with star formation rates >1000 $M_\odot$ yr$^{-1}$ - are radiating at or close to their Eddington limit. Should future high resolution observations indicate that these two objects are typical of a population of high redshift Eddington-limited starbursts, this could have important consequences for models of star formation and feedback in extreme environments.