A First Look at Birthplaces of Most Current Stars

The new observations, using the VLA and ALMA, have answered longstanding questions about just what mechanisms were responsible for the bulk of star formation in those galaxies. They found that intense star formation in the galaxies they studied most frequently occured throughout the galaxies, as opposed to much smaller regions in present-day galaxies with similar high star-formation rates.

The astronomers used the VLA and ALMA to study galaxies in the Hubble Ultra Deep Field, a small area of sky observed since 2003 with NASA’s Hubble Space Telescope (HST). The HST made very long exposures of the area to detect galaxies in the far-distant Universe, and numerous observing programs with other telescopes have followed up on the HST work.

“We used the VLA and ALMA to see deeply into these galaxies, beyond the dust that obscured their innards from Hubble,” said Kristina Nyland, of the National Radio Astronomy Observatory (NRAO). “The VLA showed us where star formation was occurring, and ALMA revealed the cold gas that is the fuel for star formation,” she added.

“In this study, we made the most sensitive image ever made with the VLA,” said Preshanth Jagannathan, also of NRAO. “If you took your cellphone, which transmits a weak radio signal, and put it at more than twice the distance to Pluto, near the outer edge of the solar system, its signal would be roughly as strong as what we detected from these galaxies,” he added.

The study of the galaxies was done by an international team of astronomers. Others involved include James Dunlop of the University of Edinburgh and Rob Ivison of the University of Edinburgh and the European Southern Observatory. The researchers reported their findings in the Dec. 1 issue of the Astrophysical Journal.

ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada), NSC and ASIAA (Taiwan), and KASI (Republic of South Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.