The Legacy of BIMA and the Challenge of CARMA

Jason Kirk – University of IllinoisCardiff Astro-Chemistry 2005

Outline• Interferometer Arrays• The BIMA Consortium• BIMA Details• Example Results

– The hunt for large molecules– Magnetic Field in SF regions– Subarcsecond imagining of discs– Combined LINEAR Observations

• Interlude: ATA • OVRO (6 dishes)• SZA (8 dishes)

• CARMA

• Ceder Flats

• Antenna Locations

• Relative Performance

• Imaging with CARMA

• Moving BIMA

• Summery

Interferometer Arrays (1/2)Why?● Achieve the ultra-high resolution of an unfeasibly large telescope at a

fraction of the cost

How?● Pair of telescopes (Baselines) – sample brightness distribution at a point

in Fourier space (u,v)

● Length of baseline is inversely proportional to the spatial scale sampled

● Earth rotation

● Given a “sufficient” sample of points in Fourier space their inversion will give a representation of the original brightness distribution

Interferometer Arrays (2/2)Limitations?● “Zero order spacing” / Spatial sampling● Technical Complexity● Data reduction – phase and amplitude calibration● Data rate● Different methods of inversion/cleaning/processing

Examples:● MERLIN, VLA, VLBI, SMA, IRAM, KECK

BIMA consortium

Radio Astronomy Laboratory of the University of California at Berkeley

Laboratory for Astronomical Imaging of the University of Illinois

Laboratory for Millimeter Astronomy of the University of Maryland,

Financed by the US National Science Foundation

Berkeley Illinois

Maryland Array

BIMA Details (1/2)● Ten element (45-baselines) interferometer array

located at Hat Creek, California● First light 3-element array in 1985, 9 element array in

1995, 10-elements in 1996 (“Telescope No. 3”)● Operates as 1mm (210-270 GHz ) and 3mm (70-116

GHz ) depending on weather conditions● Four standard arrays (A-D) with resolutions 0.4, 2, 6,

14 arcsec at 100 GHz● Baselines ranging from 7m to 1.3 km● 2 arcmin Field of View (Primary Beam)

BIMA Details (2/2)● 90-900 MHz IF Bandwidth● Up to 4 spectral window in each sideband (mirrored)● Window bandwidths: 6.25 / 12.5 / 25 / 100 MHz● 1024 channels split between the four windows

depending on correlator mode● Observation parameterized by customized c-shell

environment● Data reduction via the MIRIAD package● 30% of time reserved for visitor projects

Ex 1: The hunt for large molecules (1/2)Remijan, Shiao, Friedel, Meier and Snyder, 2004, ApJ, 617, 384-398

Hunting for pre-biotic molecules in high-mass star formations regions. Including Formic and Acetic Acids because they structurally resemble glycine

Interstellar Methanol

CH3OH

Formic Acid HCOOH

Acetic Acid CH3COOH

Methyl Formulate HCOOCH3

Methyl and Ethyl Cyanide

CH3CN and CH3CH2CN

Ex 1: The hunt for large molecules (2/2)Detected two new sources of formic acid towards G19.61-0.23

and W75

EX 2:Magnetic fields

Lai, Crutcher, Girart & Rao, 2002, ApJ, 566, 925

Ex 3: Subarcsecond imagining of discs

Looney, Mundy and Welch, 2000, ApJ, 529, 477

First subarcsecond continuum imaging at 2.7mm of 24 protostellar disc systems

HL Tauri

EX 4: Combined LINEAR Observations● Hogerheijde et al, 2004, AJ, 127, 2406● In “single dish mode” detected weak CN J=1-0

emission from comet C/1999/LINEAR S4 before comet break-up, no emission detected afterwards

● Observations from BIMA and OVRO were combined in software to create a virtual array. Data reduction and process challenges were met, but unfortunately the emission was just too faint

BIMA Summer School• Yearly summer school in

interferometer array operation run by the BIMA consortium

• Array totally given over to teaching for a week

• Open to undergrads, postgrad, and postdocs

• Now ended, keep an eye out for CARMA Summer Schools

Interlude: ATA● Allen Telescope Array● Will replace BIMA at Hat Creek● 350 6.1-meter dishes● Press coverage driven by Paul Allen’s contribution to

SETI, but will include a strong traditional science operation

● A number of different theoretical array configurations were considered, but it was found that a random spread across the Hat Creek site was as good as any deliberate shaped array

OVRO● Owens Valley Radio Observatory operated by Caltech

University● Six 10.4-meter diameter dishes● Maximum baselines of 200 north-south and east-west● Comparable spectrographic and correlator capabilities

of BIMA

SZA• Sunyaev-Zeldovich Array • Eight close packed 3.5m

telescopes• PI: John Carlstrom• First untargeted SZE

survey hunting for galaxy clusters (over 12-square degrees)

• Initially set up at OVRO• Will move to join

CARMA after a few years

CARMA● Combined Array for Research in Millimeter-wave

Astronomy (CARMA)● Two potential arrays:

– CARMA-15 : BIMA + OVRO– CARMA-23 : BIMA + OVRO + SZA

● New higher site – reduction of atmospheric effects gives a doubling of effective surface area

● SZA will be placed 30m to the side of the CARMA-15 array 0,0 position

Ceder Flats / Environmental Report

Antenna Locations• 5 planned arrays

– A - ~2km– B – 1km– C – 350m– D – 150m– E – 65m

• 25 pads at initial roll out• BIMA telescopes moved

already• OVAO telescopes move in

March• SZA moves around ‘07• NSF site visit Aug ‘05 –

planned prototype array using OVRO correlator

Figure from Wright, 2004, BIMA Memo #101

CARMA-23 UV Coverage

Dec = +30 (right), –30 (above)

Overview of (Sub)MM Arrays

226 m2 2 GHz/SB 230, 345, 100-200 K(488 m2 w/ 0.8 MHz ch. 650 GHz 200-400 KJCMT,CSO) DSB SIS >2000 K (650)

1060 m2 4 GHz/SB 115, 150, 230 100 to 2 MHz ch 345 GHz DSB 300 K (07+ 8 line) DP SIS (05/06)

>5655 m2 8 GHz/SB 115, 230, 345, 60 to 120 K(>50 12m) >1024 ch. 650 GHz DP at 3/1.3mm SSB/DSB (bsl)

764 m2 4 GHz/SB 115, 230 GHz(841 m2 SIS DSBw/SZA) 3mm MMIC

4205m, 500m

2560m 408m

5000m 10km

2225m >2km

Array Collecting Area Correlator Receivers Tsys

Relative performance of CARMA

Imaging with CARMASample simulation of Saturn using C and D arrays + the SZA (Helfer, 2004, CARMA Memo #20)

Moving BIMA (1/3)

Moving BIMA (2/3)

Moving BIMA (3/3)

Summary● BIMA was a ten-element interferometer at Hat Creek,

CA operating at 1mm and 3mm● Relocation of BIMA dishes to a new higher site and

integration with OVRO and SZA antenna to create CARMA

● BIMA has moved, OVRO will soon move, work has begun on site utilities and antenna platforms

● First science on new site planned by year’s end, full involvement of SZA by 2007

Further Information...

BIMA Definition Paper: Welsh et al., 1996, PASP 108, 93

BIMA Homepage: http://bima.astro.umd.edu/OVRO Homepage: http://www.ovro.caltech.edu/SZA Homepage: http://astro.uchicago.edu/sza/CARMA Homepage: http://www.mmarray.org/

Miscellaneous photographs are from the BIMA and CARMA websites.

The CARMA simulation video (in AVI and MPEG formats) that was shown with the original version of this talk can be found online at http://www.mmarray.org/images/sims/sims.html.