1. The Combined Array for Research in Millimeter-Wave Astronomy
Science with CARMA:
The Combined Array for Research in Millimeter-Wave Astronomy
Alberto Bolatto
Radio Astronomy Lab
UC Berkeley
Adam Leroy*
Josh Simon*
Erik Rosolowsky*
Leo Blitz
Fabian Walter
NGC 2976
CO on H

2. CARMA is the merger of the OVRO, BIMA, and SZA arrays
What is CARMA?
CARMA is the merger of the OVRO, BIMA, and SZA arrays
It is a partnership between Caltech, UC Berkeley, Illinois, Maryland, and Chicago
Caltech
Anneila Sargent
Andrew Beard
Geoff Blake
Paul Daniel
Jim Fredsti
Curt Giovanine
Dave Hawkins
Rick Hobbs
Mark Hodges
Stan Hudson
Russ Keeney
Derrick Key
James Lamb
Ron Lawrence
Steve Miller
Nick Scoville
Steve Scott
Brad Wiitala
David Woody
U.C. Berkeley
Leo Blitz
Don Backer
Alberto Bolatto
Calvin Cheng
Danning Chou
Greg Engargiola
Ed Fields
Matt Fleming
Rick Forster
Carl Heiles
David McMahon
Alessandro Navarrini
Imke de Pater
Colby Kraybill
Dick Plambeck
Doug Thornton
Lynn Urry
Harold Weaver
Jack Welch
Mel Wright
U. Illinois
Dick Crutcher
You-Hua Chu
Robert Gruendl
Leslie Looney
Kee-Tae Kim
Jason Kirk
Dave Mehringer
David Meier
Joe Mohr
Jun-ichi Nakashima
Ray Plante
Lew Snyder
Edmund Sutton
U. Maryland
Stuart Vogel
Mike A'Hearn
Andy Harris
Mukul Kundu
Lee Mundy
Glen Petitpas
Marc Pound
Eve Ostriker
Kevin Rauch
Jim Stone
Peter Teuben
Stephen White
Mark Wolfire
U. Chicago
John Carlstrom
John Cartwright
Kim Coble
Frank DiDonna
Ryan Hennessy
Ellen LaRue
Erik Leitch
Michael Loh
Clem Pryke
Ben Redall
Chris Reer
Markus Runyan
Dan Siegal
Project Manager: Douglas Bock
(Tony Beasley)

3. What is CARMA?
OVRO, BIMA, and the SZA are relocating to Cedar Flat (Inyo Mountains, altitude 2.2 km)
200 m
Central Array Area just cleared, late August
VR simulation in D-array configuration

4. Training grounds for next generations of ALMA users
The role of CARMA
Training grounds for next generations of ALMA users
First rate science: millimeter-wave interferometry facility on road to ALMA, together with IRAM’s PdBI
Simpler, flexible platform for new developments:
E.g., array receivers for wide-field interferometry and large scale surveys

5. Specifications 23 dishes: 800 m2 collecting area
6 OVRO 10 m dishes
9 BIMA 6 m dishes
8 SZA 3.5 m dishes
800 m2 collecting area
Superb image fidelity:
253 baselines
Heterogeneous array
5 configurations:
4 m to 2.2 km long baselines
10” to 0.1” angular resolution
4 mm median WV burden, 225~0.25
Atmosphere ×2 more stable than Hat Creek and OVRO:
frequent operation at 1mm and in extended arrays

6. First light correlator:
The Instrument
RF & IF system:
Laser link system: 8 GHz × 2 polarizations
fiber support for array receivers
1mm Rx: OVRO 4 GHz
BIMA upgrading to 4 GHz
3mm Rx: planned upgrade to MMICs
Currently developing dual polarization Rx
First light correlator:
Based on COBRA FPGA technology
8 × 500 MHz windows (3 LR, 5 HR)
Next generation correlator:
Full Stokes parameters
Tropospheric phase correction:
Correlation WVR under development

7. Construction is moving forward
OVRO stopped and upgrading
BIMA deconstructed and transported
First telescope pads in place
Building foundations poured
Power and fiber trenching proceeding
Operations beginning August 2005

8. Why am I excited about this?
Two words: Extragalactic Vermin HI H2
The processes that control the conversion from atomic gas to molecular gas to stars on galactic scales are not well understood
Molecular cloud properties of extragalactic GMCs are basically unknown
Without this information, baryons cannot be reliably incorporated into large scale simulations

9. The link between atomic and molecular gas
Why are GMCs only found on top of HI filaments?
Why are GMCs only found inside a certain radius, even though there is little change in N(HI)?
What is regulating the HI→H2→SF transition on galactic scales?
GMCs over color HI map in M33
Engargiola et al. (2003)

10. The link between atomic and molecular gas
Why are GMCs only found on top of HI filaments?
Why are GMCs only found inside a certain radius, even though there is little change in N(HI)?
What is regulating the HI→H2→SF transition on galactic scales?
Color GMCs over HI contours in IC10
Leroy, Walter et al. (in prep.)

11. Clue # 1
Azimuthally averaged H2 fraction is strongly correlated with local hydrostatic pressure, mostly set by stellar surface density
(Blitz & Rosolowsky 2004;
Wong & Blitz 2002)
N(H2)/N(HI) = 0.8(P/PO)0.9
(ΣHIΣ*0.5)0.9
IC10

12. (Leroy et al., submitted, poster)
Clue # 2
Very tight correlation between molecular and stellar mass in a large sample of local galaxies
(Leroy et al., submitted, poster)
Taken together, these findings suggest that the surface density of the stellar disk plays an important role in regulating the HI→H2

13. Studying GMCs in other galaxies
The challenges:
Low S/N  we only see “the tips” of the GMCs
Marginal resolution  beam deconvolution is essential
Confusion & blending  what is a cloud?
Cloud Radius
Spatial Mask
Line Profile

14. GMC properties across the Local Group
Cloud properties appear remarkably constant regardless of environment
M  RV2
V  R1/2
 ΣH2 ~ constant
 Pcl ~ ΣH22 ~ const
If Jeans instability determines cloud fragmentation,
 IMF ~ invariant
M/R2 = const

15. Bottom line
A strong observational program on nearby galaxies is crucial to understand the fundamental processes at work in the near and far universe
Taking over from
BIMA: the
first 32 antennas
of the ATA under
construction at
Hat Creek

16. Merci beaucoup