ALMA’s view of the outflow associated with the Herbig-Haro object HH 46/47
Wide-field view of the star-forming region around the Herbig-Haro object HH 46/47
The Herbig-Haro object HH 46/47 in the constellation of Vela
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Astronomers using the Atacama Large
Millimeter/submillimeter Array (ALMA) have obtained a vivid close-up
view of material streaming away from a newborn star. By looking at the
glow coming from carbon monoxide molecules in an object called
Herbig-Haro 46/47 they have discovered that its jets are even more
energetic than previously thought. The very detailed new images have
also revealed a previously unknown jet pointing in a totally different
direction.
Young stars are violent objects that eject material at speeds as high
as one million kilometres per hour. When this material crashes into the
surrounding gas it glows, creating a Herbig-Haro object [1].
A spectacular example is named Herbig-Haro 46/47 and is situated about
1400 light-years from Earth in the southern constellation of Vela (The
Sails). This object was the target of a study using ALMA during the
Early Science phase, whilst the telescope was still under construction
and well before the array was completed.
The new images reveal fine detail in two jets, one coming towards
Earth and one moving away. The receding jet was almost invisible in
earlier pictures made in visible light, due to obscuration by the dust
clouds surrounding the new-born star. ALMA has not only provided much
sharper images than earlier facilities but also allowed astronomers to
measure how fast the glowing material is moving through space.
These new observations of Herbig-Haro 46/47 revealed that some of the
ejected material had velocities much higher than had been measured
before. This means the outflowing gas carries much more energy and
momentum than previously thought.
The team leader and first author of the new study, Héctor Arce (Yale University, USA) explains that "ALMA's
exquisite sensitivity allows the detection of previously unseen
features in this source, like this very fast outflow. It also seems to
be a textbook example of a simple model where the molecular outflow is
generated by a wide-angle wind from the young star."
The observations were obtained in just five hours of ALMA observation
time – even though ALMA was still under construction at the time –
similar quality observations with other telescopes would have taken ten
times longer.
"The detail in the Herbig-Haro 46/47 images is stunning. Perhaps
more stunning is the fact that, for these types of observations, we
really are still in the early days. In the future ALMA will provide even
better images than this in a fraction of the time," adds Stuartt Corder (Joint ALMA Observatory, Chile), a co-author on the new paper.
Diego Mardones (Universidad de Chile), another co-author, emphasises that "this
system is similar to most isolated low mass stars during their
formation and birth. But it is also unusual because the outflow impacts
the cloud directly on one side of the young star and escapes out of the
cloud on the other. This makes it an excellent system for studying the
impact of the stellar winds on the parent cloud from which the young
star is formed."
The sharpness and sensitivity achieved by these ALMA observations
also allowed the team to discover an unsuspected outflow component that
seems to be coming from a lower mass companion to the young star. This
secondary outflow is seen almost at right angles to the principal object
and is apparently carving its own hole out of the surrounding cloud.
Arce concludes that "ALMA has made it possible to detect features
in the observed outflow much more clearly than previous studies. This
shows that there will certainly be many surprises and fascinating
discoveries to be made with the full array. ALMA will certainly
revolutionise the field of star formation!"
Notes
[1] The astronomers George Herbig and
Guillermo Haro were not the first to see one of the objects that now
bear their names, but they were the first to study the spectra of these
strange objects in detail. They realised that they were not just clumps
of gas and dust that reflected light, or glowed under the influence of
the ultraviolet light from young stars, but were a new class of objects
associated with shocks created by material ejected at high speeds in
star formation regions.
More information
The Atacama Large Millimeter/submillimeter
Array (ALMA), an international astronomy facility, is a partnership of
Europe, North America and East Asia in cooperation with the Republic of
Chile. ALMA is funded in Europe by the European Southern Observatory
(ESO), in North America by the U.S. National Science Foundation (NSF) in
cooperation with the National Research Council of Canada (NRC) and the
National Science Council of Taiwan (NSC) and in East Asia by the
National Institutes of Natural Sciences (NINS) of Japan in cooperation
with the Academia Sinica (AS) in Taiwan. ALMA construction and
operations are led on behalf of Europe by ESO, on behalf of North
America by the National Radio Astronomy Observatory (NRAO), which is
managed by Associated Universities, Inc. (AUI) and on behalf of East
Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint
ALMA Observatory (JAO) provides the unified leadership and management
of the construction, commissioning and operation of ALMA.
This research was presented in a paper entitled "ALMA Observations of
the HH 46/47 Molecular Outflow" by Héctor Arce et al, to appear in the
Astrophysical Journal.
The team is composed of Héctor G. Arce (Yale University, New Haven,
USA), Diego Mardones (Universidad de Chile, Santiago, Chile), Stuartt A.
Corder (Joint ALMA Observatory, Santiago, Chile), Guido Garay
(Universidad de Chile), Alberto Noriega-Crespo (Infrared Processing and
Analysis Center, California Institute of Technology, Pasadena, USA) and
Alejandro C. Raga (Instituto de Ciencias Nucleares, Mexico).
ESO is the foremost intergovernmental astronomy organisation in
Europe and the world's most productive ground-based astronomical
observatory by far. It is supported by 15 countries: Austria, Belgium,
Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy,
the Netherlands, Portugal, Spain, Sweden, Switzerland and the United
Kingdom. ESO carries out an ambitious programme focused on the design,
construction and operation of powerful ground-based observing facilities
enabling astronomers to make important scientific discoveries. ESO also
plays a leading role in promoting and organising cooperation in
astronomical research. ESO operates three unique world-class observing
sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO
operates the Very Large Telescope, the world's most advanced
visible-light astronomical observatory and two survey telescopes. VISTA
works in the infrared and is the world's largest survey telescope and
the VLT Survey Telescope is the largest telescope designed to
exclusively survey the skies in visible light. ESO is the European
partner of a revolutionary astronomical telescope ALMA, the largest
astronomical project in existence. ESO is currently planning the
39-metre European Extremely Large optical/near-infrared Telescope, the
E-ELT, which will become "the world's biggest eye on the sky".
Links
Contacts
Héctor ArceYale University
New Haven, USA
Tel: +1 203 432 3018
Email: hector.arce@yale.edu
Diego Mardones
Universidad de Chile
Santiago, Chile
Tel: + 56 2 977 1143
Email: dmardone@das.uchile.cl
Stuartt Corder
Joint ALMA Observatory
Santiago, Chile
Email: scorder@alma.cl
Lars Lindberg Christensen
Head, ESO education and Public Outreach Department
Garching bei München, Germany
Cell: +49 173 38 72 621
Email: lars@eso.org
