Intense Star Formation within Resolved Compact Regions in a Galaxy at z=2.3

TL;DR

This study uses gravitational lensing and high-resolution sub-mm imaging to resolve and analyze intense star-forming regions in a galaxy at z=2.3, revealing that early Universe star formation occurs in extremely luminous, dense regions similar in physics to local molecular cloud cores.

Contribution

The paper demonstrates the use of gravitational lensing combined with high-resolution imaging to resolve star-forming regions at ~100 parsecs in a high-redshift galaxy, revealing their properties and similarities to local star formation.

Findings

Star-forming regions are ~100 parsecs in size.

Luminosity densities are comparable to local dense molecular cloud cores.

Star formation physics at z~2 resembles that in local galaxies.

Abstract

Massive galaxies in the early Universe have been shown to be forming stars at surprisingly high rates. Prominent examples are dust-obscured galaxies which are luminous when observed at sub-millimeter (sub-mm) wavelengths and which may be forming stars at rates upto 1,000Mo/yr. These intense bursts of star formation are believed to be driven by mergers between gas rich galaxies. However, probing the properties of individual star-forming regions within these galaxies is beyond the spatial resolution and sensitivity of even the largest telescopes at present. Here, we report observations of the sub-mm galaxy SMMJ2135-0102 at redshift z=2.3259 which has been gravitationally magnified by a factor of 32 by a massive foreground galaxy cluster lens. This cosmic magnification, when combined with high-resolution sub-mm imaging, resolves the star-forming regions at a linear scale of just ~100 parsecs. We find that the luminosity densities of these star-forming regions are comparable to the dense cores of giant molecular clouds in the local Universe, but they are ~100x larger and 10^7 times more luminous. Although vigorously star-forming, the underlying physics of the star formation processes at z~2 appears to be similar to that seen in local galaxies even though the energetics are unlike anything found in the present-day Universe.