Tuesday, April 23, 2013

A Dust-Obscured Massive Maximum-Starburst Galaxy in the Early Universe

Astronomers of the Herschel Multi-tiered Extragalactic Survey (HerMES) project announce in the journal Nature the discovery of an unusually massive, maximum-starburst galaxy at a redshift of 6.34, or when the Universe was only 880 million years old. Because current theories of galaxy formation and evolution predict smaller galaxies with slower rates of star production in the early Universe, the detection of such a galaxy is challenging. 
HerMES is the largest project that has being carried out using ESA's Herschel Space Observatory, and other telescopes around the world have made an important contribution,including the William Herschel Telescope (WHT). The extreme galaxy reported here was first detected in the early images obtained using Herschel's SPIRE instrument, the so-called HerMES First Look Survey field (HFLS), showing very unsual red colours in the three bands observed at 250, 350 and 500 microns.

Observations followed using ACAM and LIRIS instruments at the WHT as part of IAC-DDT and ITP programmes (principal investigator: Pérez-Fournon, IAC). These data reveal a faint object close to the position obtained at millimeter interferometric wavelengths. Further analysis from deeper observations using GTC, Keck and Spitzer observatories showed that there are two galaxies appearing very close together.
The field around HFLS3 in the optical (left, GTC OSIRIS), near-IR (top right, WHT LIRIS Ks) and near-IR adaptive optics (bottom right, Keck NIRC2 Ks). In the optical only the foreground G1B galaxy at redshift 2.092 is visible but in the near-IR HFLS3 galaxy at redshift 6.337 is also detected (its rest-frame light lies in UV/optical wavelength range) [ JPEG ]. 
One of these galaxies, or HFLS3, contains 100 billion solar masses of highly-excited, chemically evolved interstellar medium (ISM) which constitutes at least 40% of its baryonic mass. HFLS3 is converting the ISM into stars at 2000 times faster than does our Milky Way galaxy. This is among the highest rates observed at any epoch and thus HFLS3 is a maximum starburst galaxy.

More information

Research reference:

  • D.A. Riechers et al. 2013, "A dust-obscured massive maximum-starburst galaxy at a redshift of 6.34", Nature, 496, 329. Paper.
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