Science with CARMA:Science with CARMA:The Combined Array for Research

in Millimeter-Wave Astronomy

Alberto Alberto BolattoBolatto

Radio Astronomy LabRadio Astronomy LabUC BerkeleyUC Berkeley

Adam Leroy*Adam Leroy*Josh Simon*Josh Simon*Erik Rosolowsky*Erik Rosolowsky*Leo BlitzLeo BlitzFabian WalterFabian Walter

NGC 2976CO on H

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. BerkeleyLeo Blitz Don Backer Alberto Bolatto Calvin Cheng Danning Chou Greg Engargiola Ed Fields Matt FlemingRick Forster Carl HeilesDavid McMahonAlessandro Navarrini Imke de PaterColby Kraybill Dick Plambeck Doug Thornton Lynn Urry Harold Weaver Jack Welch Mel Wright

CaltechAnneila 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. IllinoisDick Crutcher You-Hua ChuRobert GruendlLeslie LooneyKee-Tae KimJason KirkDave MehringerDavid MeierJoe MohrJun-ichi NakashimaRay PlanteLew SnyderEdmund Sutton

U. MarylandStuart Vogel Mike A'Hearn Andy Harris Mukul Kundu Lee Mundy Glen Petitpas Marc Pound Eve Ostriker Kevin Rauch Jim Stone Peter Teuben Stephen WhiteMark Wolfire

U. ChicagoJohn CarlstromJohn CartwrightKim CobleFrank DiDonnaRyan HennessyEllen LaRueErik LeitchMichael LohClem PrykeBen RedallChris ReerMarkus RunyanDan Siegal

Project Manager: Douglas Bock (Tony Beasley)

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

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

Specifications• 23 dishes:

– 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

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

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

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

HI H2

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 M33Engargiola et al. (2003)

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 IC10Leroy, Walter et al. (in prep.)

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

N(H2)/N(HI) = 0.8(P/PO)0.9

(ΣHIΣ*0.5)0.9

IC10

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

Taken together, these findings suggest that the surface density of the stellar disk plays an important role in regulating the HI→H2

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

GMC properties across the Local Group

M/R2 = const

• 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

Bottom line

A strong observational program on nearby galaxies is crucial to understand the

fundamental processes at work in the near and far universe

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

Merci beaucoupMerci beaucoup