The combination of the Karl G. Jansky Very Large Array, Atacama Large Millimeter/submillimeter Array, and Hubble Space Telescope provides simultaneous insights into star-formation, cold dust, and the existing stellar populations in distant galaxies in the Hubble Ultra Deep Field. Credit: Wiphu Rujopakarn/Kavli IPMU
Wiphu Rujopakarn, Visiting Scientist
Astronomers have gotten their first look at exactly where most of
today’s stars were born. To do so, they used the National Science
Foundation’s Karl G. Jansky Very Large Array (VLA) and the Atacama Large
Millimeter/submillimeter Array (ALMA) to look at distant galaxies seen
as they were some 10 billion years ago.
At that time, the Universe was experiencing its peak rate of star formation. Most stars in the present Universe were born then.
“We knew that galaxies in that era were forming stars prolifically,
but we didn’t know what those galaxies looked like, because they are
shrouded in so much dust that almost no visible light escapes them,”
said Wiphu Rujopakam, of the Kavli Institute for the Physics and
Mathematics of the Universe at the University of Tokyo and Chulalongkorn
University in Bangkok, who was lead author on the research paper.
Radio waves, unlike visible light, can get through the dust. However,
in order to reveal the details of such distant — and faint — galaxies,
the astronomers had to make the most sensitive images ever made with the
VLA.
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.
Paper details:
Journal:
The Astrophysical Journal
Title: VLA AND ALMA IMAGING OF INTENSE GALAXY-WIDE STAR FORMATION IN z ~ 2 GALAXIES
DOI: 10.3847 / 0004 - 637 X / 833/1/12 (Published December 1, 2016)
arXiv.org: arxiv.org/abs/1607.07710
Local research contact:
Wiphu Rujopakam
Visiting Scientist
Kavli Institute for the Physics and Mathematics of the Universe
E-mail: wiphu.rujopakarn@ipmu.jp
Media contact:
John Amari
Public Relations Office
Kavli Institute for the Physics and Mathematics of the Universe
E-mail: press@ipmu.jp
Tel: 04-7136-5977
Related links:
National Radio Astronomy Observatory (NROA) press release
