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Science with CARMA: The Combined Array for Research in Millimeter-Wave Astronomy Alberto Bolatto Radio Astronomy Lab UC Berkeley Adam Leroy* Josh Simon*

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Presentation on theme: "Science with CARMA: The Combined Array for Research in Millimeter-Wave Astronomy Alberto Bolatto Radio Astronomy Lab UC Berkeley Adam Leroy* Josh Simon*"— Presentation transcript:

1 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 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 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 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. 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) VR simulation in D-array configuration 200 m Central Array Area just cleared, late August

4 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 IRAMs PdBI Simpler, flexible platform for new developments: –E.g., array receivers for wide-field interferometry and large scale surveys

5 Specifications 23 dishes: –6 OVRO 10 m dishes –9 BIMA 6 m dishes –8 SZA 3.5 m dishes 800 m 2 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 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? 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 Two words: Extragalactic Vermin HIHI H2H2

9 The link between atomic and molecular gas Why are GMCs only found on top of H I filaments? Why are GMCs only found inside a certain radius, even though there is little change in N(H I )? What is regulating the H I H 2 SF transition on galactic scales? GMCs over color H I map in M33 Engargiola et al. (2003)

10 The link between atomic and molecular gas Why are GMCs only found on top of H I filaments? Why are GMCs only found inside a certain radius, even though there is little change in N(H I )? What is regulating the H I H 2 SF transition on galactic scales? Color GMCs over H I contours in IC10 Leroy, Walter et al. (in prep.)

11 Clue # 1 Azimuthally averaged H 2 fraction is strongly correlated with local hydrostatic pressure, mostly set by stellar surface density (Blitz & Rosolowsky 2004; Wong & Blitz 2002) N(H 2 )/N(H I ) = 0.8(P/P O ) 0.9 (Σ HI Σ * 0.5 ) 0.9 N(H 2 )/N(H I ) = 0.8(P/P O ) 0.9 (Σ HI Σ * 0.5 ) 0.9 IC10

12 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 H I H 2

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 M/R 2 = const Cloud properties appear remarkably constant regardless of environment M RV 2 V R 1/2 Σ H2 ~ constant P cl ~ Σ H2 2 ~ const If Jeans instability determines cloud fragmentation, IMF ~ invariant

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


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