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CARMA: The Combined Array for Research in
Millimeter Wave Astronomy
CARMA Web site
I. General project/facility description
- Overview of the facility/project
CARMA combines Caltech's and BIMA's (Berkeley Illinois Maryland Association)
millimeter-wave arrays on a new, higher site. It is expected that
CARMA, operating on a site with improved atmospheric transmission,
with increased collecting area, much enhanced uv coverage, and enhanced
electronics, will provide sensitivity at 1 mm that is an order of
magnitude better than the exisiting arrays. We anticipate that U
Chicago's Sunyaev Zel'dovich array (SZA) will become an integral part
of CARMA in 2007, after initially independent operation on Cedar Flat.
CARMA is currently (2005) being developed and constructed at the new site,
Cedar Flat, at 7200 ft elevation in California's Inyo Mountains, and
about 30 minutes drive from Owens Valley Radio Observatory.
The new CARMA facility will replace the older facilities, namely, the
Millimeter Array and the BIMA
Millimeter Array at Hat Creek
- Managing institution and organization
CARMA will be managed by an association of the BIMA universities
(UC Berkeley, U Illinois, U Maryland) and Caltech. The CARMA Board
of Representatives has overall authority and responsibility
for fiscal oversight, long-term policy, operation and management
of the CARMA Association. A Science Steering Committee consisting of 8
scientists from the member universities provides advice. The Project
Director coordinates the operation, oversight, and management of
CARMA, as well as implementing the policies and decisions of the
Board in consultation and coordination with the Science Steering
Under a separate Memorandum of Understanding between the
University of Chicago and Caltech, the SZA is currently being
constructed at OVRO and will eventually be integrated into CARMA.
To this end, negotiations between Caltech and Chicago are underway.
When these are completed, the University of Chicago will join
the CARMA Association and be allotted a seat on the Board,
while one of the Caltech slots on the SSC will be officially
allotted to Chicago. In practice, the SZA P.I., John Carlstrom,
already participates actively in SSC deliberations.
- Funding source(s)
Capital construction costs for CARMA are estimated at $15M,
of which NSF is contributing 1/3. The Caltech contribution
derives from private funds while that from the BIMA partners
relies on state funding
from California, Illinois and Maryland.
Discussions among the partner universities about combining the
BIMA and OVRO arrays have been underway for more than five years.
Some private/state funds were made available as early as 2000, and in
that same year NSF provided seed money to support a project manager.
Further NSF funding was assigned through a Major Research
Infrastructure (MRI) grant in 2001. The balance of the remaining
NSF capital contribution was awarded as part of the response to
the CARMA Collaborative Research Proposal submitted in 2002.
- Construction history and cost
All potential CARMA sites were on U. S. Forest Service land, and
considerable expense, time, and effort had to be devoted to the
environmental permitting process. Cedar Flat was finally awarded
in January 2004. Permission to develop the site took a few months
longer. Nevertheless, the central array site is now cleared and
25 pads for the more compact array configurations are in place,
as is associated trenching. Foundations for the three major
buidlings have been poured. The nine BIMA pedestals and reflectors
arrived on site in October/November of this year and now await
newly-designed bases. The OVRO antennas are being upgraded at
the old site since there is as yet no power at Cedar Flat. They
should be moved in March/April. Despite the delays in the
permitting process and in site development, we anticipate that
CARMA will be operating - although perhaps only on a shared
risk basis - by the end of 2005. At that time, pads with
associated fiber and power will be available for the C, D,
and E arrays. The more extended A and B arrays will become
available later in 2006.
- Operational history and cost
Routine operation of the array should be possible in a limited
number of modes in spring, 2006. Since their inception, the BIMA
and OVRO arrays have been supported by operations funding from
the NSF, supplemented by the respective states (Berkeley, Illinois,
Maryland) and by private sources (Caltech). It is anticipated
that this will be the operational model for CARMA.
II. Technical details
- Specifics of
CARMA consists of a hybrid array
combining the six 10.4-m antennas from OVRO with nine
6.1-m antennas from BIMA, operating at wavelengths from 1 to 10 mm
(in future 0.8 to 10 mm).
- New capabilities anticipated/planned in next 5-10 years
Discussions among the partners about desirable capability improvements
are now (Jan 2005) underway. Increased sensitivity and resolution are the
driving requirements with a concomittant enhancement of correlator
power. It will also be important to exploit the unique capabilities
of the 23-element heterogeneous array. Dual polarization capability,
on the fly mapping, dedicated single dish capability, and the
addition of 1 mm receivers to the SZA complement, are also being considered.
III. User profile
- % of "open skies" time
Caltech and BIMA have always made a significant fraction of the
observing time on their arrays available to
the community at large. CARMA will continue this practice. As a
result of discussions between NSF and the university partners,
it is expected that approximately one third of the time will be "open
- Institutional affiliations of users
Over the years, colleagues from numerous institutions across the
United States, as well as an international subset, have made good
use of the BIMA and OVRO arrays. We anticipate that CARMA users will
come from these same groups but also expect that the enhanced
capabilities may attract a broader community. For example, the
discovery of the so-called "sub-millimeter galaxies" was already
bringing in OVRO proposals from optical astronomers.
- Student access, involvement,
Time allocation on both the BIMA and OVRO arrays relied on peer
review and scientific merit. We expect to apply the same standards
to CARMA proposal evaluation. That said, we emphasize that student
theses and post-doctoral research are very important to the
university partners. We regard it as of prime importance that
students in particular are assigned sufficient observing time for
approved thesis projects. As part of the educational process,
students and postdocs at the partner universities have always
taken a large measure of the responsibility for day-to-day array
operations and we expect that to continue. Over the years, we
have also provided thesis observing time for students from
universities other than the original CARMA partners and expect
to continue that practice, assuming that there is appropriate
support from their advisors.
IV. Science Overview
- Current forefront scientific programs
- Major discoveries (through 1999)
CARMA's promise has its foundation in the scientific discoveries
with the BIMA and OVRO arrays over the years. Interferometric imaging at millimeter
wavelengths has opened up a many new research areas of star formation
and galaxy evolution, especially when coupled with infrared observations
from IRAS, the Kuiper Airborne Observatory, and optical observations
from HST and ground based telescopes. In fact, these highlights
represent a summation of the major discoveries from "all years" .
Every 3-year proposal from Caltech and BIMA to NSF has included major
breakthroughs. Suffice it to say that the
justification for ALMA (at that time called the Millimeter Wave Array)
provided in the "Bahcall Report" - the decade survey for the 1990's
presented, and relied heavily on, early OVRO and BIMA array
- Science highlights of last 5
These results from OVRO/BIMA:
- First measurement of the dark matter distribution at the
centers of dwarf galaxies at 100 pc resolution.
- Continuum detection of the new class of high-redshift sub-millimeter galaxies.
- Large surveys of molecular gas in the disks and nuclei of
normal, active and starbust galaxies at 100-300 pc resolution
- Imaging of the Sunyaev-Zel'dovich Effect and a determination
of Ho and Ω
- Detection of arcminute-scale Cosmic Microwave Background
- First complete survey of Giant Molecular Clouds (GMCs) in a
spiral galaxy (M33).
- Discovery of a short-lived, intermediate stage of disk
formation in protostars.
- Imaging of ring-arcs in the dust distribution around Vega.
- Evidence for an HL Tau companion at the edge of the 0.2 arcsec
- Measurement of polarization of thermal molecular lines of
- Detection of prebiotic molecules in hot molecular cores in
the Galactic disk.
- Imaging the weather on Titan.
- Main future science questions to be
At the high altitude site, the most immediate improvement will be the
ability to observe routinely at short wavelengths (1 mm). The
enhancements in sensitivity, image fidelity, and bandwidth over
what is possible at either existing array will make a whole new
range of science available. A few possible projects include:
- Wide area surveys of faint objects, such as high-redshift
sub-millimeter galaxies which probe early galaxy evolution.
- By probing large numbers of protostellar disks over a
wide range of ages and environments, we will
dramatically increase our understanding of how planetary systems evolve.
- We will measure GMCs in Local Group galaxies to
a resolution of about 2 pc, and resolve GMCs in a wide variety of
more distant galaxies.
- With the SZA as part of CARMA, we will refine measurements
of the cosmological constant.
- Synergies with other major forefront
The accessibilty of routine, high resolution 1 mm imaging will be important
for complimentarity with space missions such as HST and Spitzer,
and ground-based facilities such as SMA, LST, Keck and Gemini.
During the years it will take to construct
ALMA, CARMA will play a pathfinder role for mm-wave science,
instrumentation, and imaging techniques. Once ALMA comes on-line,
CARMA will serve as a test bed for potential ALMA upgrade
technologies. The continuing success of ALMA will depend on a steady
influx of inspired, capable, and experienced young people, many of
who will come from the CARMA group.
- Unique contributions
CARMA provides the US university-based, northern hemisphere, hybrid
configuration complement to ALMA, as noted distinctly in the 2000 AASC
- CARMA will be the first heterogeneous millimeter array, combining
antennas of different sizes into a single powerful imaging instrument.
This novel design combines the small antennas' view of large regions
of the sky with the large antennas' sensitivity to very faint objects,
allowing precise imaging of the Universe over a wide range of
V. Education/Outreach activities
- Visitor facility
Both OVRO and Hat Creek Observatory (HCO) play important roles in
education and outreach in the local community, giving tours, holding
open houses, visiting local schools, writing newspaper articles,
working with local educators at the K-12 and college level, mentoring
local high school students, etc.
On behalf of CARMA, Caltech is discussing joining a planned
interagency visitor center for the Owens Valley. This would include
displays highlighting the contribution of astronomy to science,
technology and education. Being part of this center would provide
a high-visibility focus for the array. A CARMA brochure suitable
for the visitor center already exists.
- Student programs
University facilities provide an ideal environment for graduate
students and postdoctoral fellows to acquire hands-on observing
experience and instrument development skills while making
exciting scientific discoveries. The most notable achievements
at BIMA and OVRO have usually involved young researchers.
During the past three years, at least 18 Ph.D. theses were based
in large part on array observations. CARMA will build on these
successes. More than a dozen professorial faculty are committed
to the project, and the enhanced capabilities of the new array
will attract high-quality students and postdocs. The latter will,
as now, be awarded most of the observing time and be responsible
for the bulk of the observing with the array. The experience so
gained -- especially in trouble-shooting and other
forms of advanced problem-solving -- is unique, and carries
over to other endeavors.
As part of formal training, the BIMA summer school is held
annually at Hat Creek Radio Observatory (HCRO: the BIMA array site).
This provides intensive hands-on training in mm-wave radio astronomy
concepts, equipment and techniques. During the past three years, 45
people have attended, coming from 11 institutions: ASIAA (Taiwan),
NAIC, CfA, Fed. U. Brazil, U. Illinois, U. Maryland, U. New Mexico,
U. Chicago, U. Wisconsin, Shasta College and UC Berkeley. The summer
school is always filled to capacity, and we plan to continue it.
- Other (as apply)
Members of BIMA and OVRO are active in Virtual Observatory (VO)
initiatives, and we expect broader VO involvement through CARMA.
The BIMA data archive and the Astrophysical Data Image Library (ADIL),
developed and maintained by the BIMA Illinois group, are the foundation upon
which the CARMA archive will be built, and already has many of the
characteristics desired for the VO. Not only will the CARMA archive
be the repository for raw data from the telescopes, it will also
function as a digital library to support multi-wavelength science
and archival research. Images from CARMA projects will become
accessible via the archive to scientists from all disciplines and
to the general public.
VI. Documentation/website URLs
URL of EPO website
- URL of facility website
Already BIMA, OVRO, and CARMA maintain active
web sites for use by the community (see http:www.mmarray.org for links).
URL(s) of any brief overviews of project/facility
URL(s) of miscellaneous documentation
This page created and maintained for the RMSPG by
Last modified: Tue Mar 1 16:10:38 EST 2005after review
by Anneila Sargent.