ALMA surveyed the Hubble Ultra Deep Field, uncovering new details of the star-forming history of the universe. This close-up image reveals one such galaxy (orange), rich in carbon monoxide, showing it is primed for star formation. The blue features are galaxies imaged by Hubble. Credit: B. Saxton (NRAO/AUI/NSF); ALMA (ESO/NAOJ/NRAO); NASA/ESA Hubble
ALMA surveyed the Hubble Ultra Deep Field, uncovering new details of the star-forming history of the universe. This animated GIF reveals one such galaxy (orange), rich in carbon monoxide, showing it is primed for star formation. The blue features are galaxies imaged by Hubble. Credit: B. Saxton (NRAO/AUI/NSF); ALMA (ESO/NAOJ/NRAO); NASA/ESA Hubble
A trove of galaxies, rich in dust and cold gas (indicating star-forming potential) was imaged by ALMA (orange) in the Hubble Ultra Deep Field. Credit: B. Saxton (NRAO/AUI/NSF); ALMA (ESO/NAOJ/NRAO); NASA/ESA Hubble
Animated GIF showing a trove of galaxies, rich in dust and cold gas (indicating star-forming potential) that was imaged by ALMA (orange) in the Hubble Ultra Deep Field. Credit: B. Saxton (NRAO/AUI/NSF); ALMA (ESO/NAOJ/NRAO); NASA/ESA Hubble
Looking
back through cosmic time in the Hubble Ultra Deep Field, ALMA traced
the presence of carbon monoxide gas. This enabled astronomers to create a
3-D image of the star-forming potential of the cosmos. Credit: R.
Decarli (MPIA); ALMA (ESO/NAOJ/NRAO)
Videos
Animation revealing ALMA's exploration of the Hubble Ultra Deep Field. The new ALMA observations, which are significantly deeper and sharper than previous surveys at millimeter wavelengths, reveal a population of galaxies that is not clearly evident in any other deep surveys of the sky and trace the previously unknown abundance of star-forming gas at different points in time. The ALMA data (orange) is supperimposed on the Hubble data. Credit: B. Saxton (NRAO/AUI/NSF); ALMA (ESO/NAOJ/NRAO); NASA/ESA Hubble. Music: Mark Mercury
Interview with astronomer Fabian Walter explaining recent ALMA observations of the Hubble Ultra Deep Field. Credit: B. Saxton & J. Hellerman (NRAO/AUI/NSF); ALMA (ESO/NAOJ/NRAO); NASA/ESA Hubble
Uncovers Insights into 'Golden Age' of Galaxy Formation
An international team of astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) has explored the same distant corner of the universe first revealed in the iconic image of the Hubble Ultra Deep Field (HUDF).
The
new ALMA observations, which are significantly deeper and sharper than
previous surveys at millimeter wavelengths, trace the previously unknown
abundance of star-forming gas at different points in time, providing
new insights into the "Golden Age" of galaxy formation approximately 10
billion years ago.
The researchers presented their findings
today at the Half a Decade of ALMA conference in Palm Springs,
California. The results also are accepted for publication in a series of
seven scientific papers appearing in the Astrophysical Journal.
Just
like the pioneering deep-field observations with the NASA/ESA Hubble
Space Telescope, scientists using ALMA surveyed a seemingly unremarkable
section of the cosmos in a so-called "blind search." This type of
observation probes a specific region of space to see what can be
discovered serendipitously rather than homing in on a predetermined
target, like an individual galaxy or star-forming nebula.
"We
conducted the first fully blind, three-dimensional search for cool gas
in the early universe," said Chris Carilli, an astronomer with the
National Radio Astronomy Observatory (NRAO) in Socorro, New Mexico, and
member of the research team. "Through this, we discovered a population
of galaxies that is not clearly evident in any other deep surveys of the
sky."
Unlike Hubble, which studies visible and infrared light
from bright cosmic objects like stars and galaxies, ALMA studies the
faint millimeter-wavelength light emitted by cold gas and dust, the raw
material of star formation. ALMA's ability to see a completely different
portion of the electromagnetic spectrum allows astronomers to study a
different class of astronomical objects, such as massive star-forming
clouds and protoplanetary disks, as well as objects that are too faint
to observe in visible light.
The new ALMA observations were
specifically tailored to detect galaxies that are rich in carbon
monoxide (CO), a tracer molecule that identifies regions rich in
molecular gas and primed for star formation. Even though these molecular
gas reservoirs give rise to star formation in galaxies, they are
invisible to Hubble. ALMA can therefore reveal the "missing half" of the
galaxy formation and evolution process.
"These newly detected
carbon-monoxide rich galaxies represent a substantial contribution to
the star-formation history of the universe," said Roberto Decarli, an
astronomer with the Max Planck Institute for Astronomy (MPIA) in
Heidelberg, Germany, and member of the research team. "With ALMA we have
opened a pathway for studying the early formation and assembly of
galaxies in the Hubble Ultra Deep Field."
The new ALMA
observations of the HUDF include two distinct, yet complementary types
of data: continuum observations, which reveal dust emission and star
formation, and a spectral line survey, which looks at the cold molecular
gas fueling star formation. The line survey is particularly valuable
because it includes information about the degree to which light from
distant objects has been redshifted by the expansion of the universe.
Greater redshift means that an object is further away and seen farther
back in time.
With the most recent observations, astronomers
were able to create a three-dimensional map of star-forming gas as it
evolves over cosmic time, from the present to about two billion years
after the Big Bang.
"The new ALMA results imply a rapidly rising
gas content in galaxies with increasing look-back time," said Manuel
Aravena, an astronomer with the Diego Portales University in Santiago,
Chile, and member of the research team. "This increasing gas content is
likely the root cause for the remarkable increase in star formation
rates during the peak epoch of galaxy formation, some 10 billion years
ago."
Astronomers specifically selected the area of study in the
HUDF, a region of space in the constellation Fornax, so ground-based
telescopes in the Southern Hemisphere, like ALMA, could probe the region
as well, expanding our knowledge of the very distant universe.
The
current ALMA observations, which required approximately 40 hours of
observing time, cover an area of the sky that is one arcminute on each
side, about one sixth of the total HUDF. An approved future 150-hour
observing campaign dubbed ASPECS – the ALMA Spectroscopic Survey in the
Hubble UDF -- will cover a much larger area and further illuminate the
star-forming potential history of the universe.
"By
supplementing our understanding of this missing star-forming material,
the forthcoming large spectroscopic survey will complete our view of the
well-known galaxies in the iconic Hubble Ultra Deep Field," said Fabian
Walter, also with the MPIA and member of the research team.
More Information
The following papers are accepted for publication in the Astrophysical Journal [http://apj.aas.org].
More Information
The following papers are accepted for publication in the Astrophysical Journal [http://apj.aas.org].
"ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: Search for [CII] line and dust emission in 6< z < 8 galaxies," M. Aravena et al. [Preprint: https://arxiv.org/pdf/1607.06772v2.pdf].
"ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: implications for spectral line intensity mapping at millimeter wavelengths and CMB spectral distortions," C.L. Carilli et al. [Preprint: http://arxiv.org/pdf/1607.06773v3.pdf].
"ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: Molecular gas reservoirs in high-redshift galaxies," R. Decarli et al. [Preprint: https://arxiv.org/pdf/1607.06771v2.pdf].
"ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: CO luminosity functions and the evolution of the cosmic density of molecular gas," R. Decarli et al. [Preprint: https://arxiv.org/pdf/1607.06770v2.pdf].
"ALMA spectroscopic survey in the Hubble Ultra Deep Field: Continuum number counts, resolved 1.2-mm extragalactic background, and properties of the faintest dusty star forming galaxies," M. Aravena et al. [Preprint:https://arxiv.org/pdf/1607.06769v2.pdf].
"ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: The Infrared Excess of UV-selected z=2-10 galaxies as a function of UV-continuum Slope and Stellar Mass," R. Bouwens et al. [Preprint: https://arxiv.org/pdf/1606.05280v4.pdf].
"ALMA spectroscopic survey in the Hubble Ultra Deep Field: Continuum number counts, resolved 1.2-mm extragalactic background, and properties of the faintest dusty star forming galaxies," M. Aravena et al. [Preprint:https://arxiv.org/pdf/1607.06769v2.pdf].
"ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: Survey description," F. Walter et al. [Preprint: https://arxiv.org/abs/1607.06768].
"ALMA Spectroscopic Survey in the Hubble Ultra Deep Field: The Infrared Excess of UV-selected z=2-10 galaxies as a function of UV-continuum Slope and Stellar Mass," R. Bouwens et al. [Preprint: https://arxiv.org/pdf/1606.05280v4.pdf].
