The GBT as a MM Telescope ALMA Science Workshop May 2004 Brian Mason (NRAO-GB)

PTCS Team: Richard Prestage Kim Constantikes Dana Balser et al.

Current Performance Blind ptg : 5'' –(2.5mm focus) Offset ptg (90 min): < 3'' –(1.5mm focus) Tracking (30min): 1'' Q-band Efficiency: 40-45% (All pointing numbers are 1 sigma 2D RMSs)

(Lockman et al.)

The Penn Array Initial Bandpass: 86 – 94 GHz 8x8 array of TES bolometers A fully sampled (0.5fL) focal plane 8’’ beam, 4’’ beam spacing SQUID Mulxiplexed Cooled by Pulse Tube Cooler + closed-cycle He7 Fridge Technologies suitable for a much larger bolometer array UPenn; NASA/GSFC; NRAO; NIST; Cardiff

Testi & Sargent (1998) OVRO 50h  1 mJy/Bm 5’ x 5’ Penn Array 8 min  0.1 mJy/Bm 80x80+GBT 5 sec  0.1 mJy/Bm (snapshot)

Z=0 Z=5 Z=10 5 Hours: 3’x3’ to 10 uJy RMS

SZE 100 kpc at z>1  20’’ Pointecoateau etal RX J Z=0.686 Z=0.421 LaRoque et al. (2003) Penn Array  5 hours 80x80+GBT  3 minutes

(SHARC-II 350 um; figure courtesy of Dominic Benford)

Ka & W Band Receivers Ka: 26 – 40 Ghz W: Ghz

GBT + ACS: 4 Ghz Wideband Analog Spectrometer -25 Ghz; auto/cross correlation Very stringent requirements on stability & flatness

Wideband Spectroscopy

GBT currently operational through 52 Ghz Near Future: prototype operation up to 94 Ghz Fall/Winter 2005/2006: Regular 3mm operation Stay tuned...

(extra material)

(Thilker et al. 2004)

Mapping Speeds Point Source Mapping Speed ~ D^2 Nfeed Extended Source Mapping Speed ~ Nfeed 1 Hour: 200 deg^2 to 0.6 mJy 1 Hour: 6 deg^2 to 1 mJy 10 Min: 5’x5’ to 10 uJy RMS 5 Hours: 3’x3’ to 10 uJy RMS Penn Array 80x80+GBT

Dealing with Systematics +Use atmosphere to “flat-field” pixel gains (Dowell & Hildebrand)

BU/FCRAO GRS (Simon et al 2001)

The Penn Array Initial Bandpass: 86 – 94 GHz 8x8 array of TES bolometers A fully sampled (0.5fL) focal plane 8’’ beam, 4’’ beam spacing SQUID Mulxiplexed Cooled by Pulse Tube Cooler + closed-cycle He7 Fridge Technologies suitable for a much larger bolometer array UPenn; NASA/GSFC; NRAO; NIST; Cardiff

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GBT Instrumentation LIST PAST/FUTURE SHOW PICTURE OF FREQ COVERAGE

GBT Instrumentation LIST PAST/FUTURE SHOW PICTURE OF FREQ COVERAGE

Mapping with Single Dishes

 Will allow detailed SZE imaging at 5” resolution. Needed to address cluster gas properties and evolution CARMA with SZA u-v coverage dramatically improved imaging OVROSZACARMA + SZA GBT FWHM at 1 cm GBT can address cluster gas properties and evolution

Z=0 Z=5 Z=10 SED: T=58 K, beta=1.35 (Yun & Carilli 2002) 10 minutes: 5’x5’ to 10 uJy RMS

Point source photometry ~ D^4 Point source discovery ~ Nfeed D^2 Extended source mapping~ Nfeed + simultaneous high resolution & zero spacing

BIMA CBI Bond et al submitted

Spectral Lines Recombination lines HCN; HCO; DCO SiO masers Redshifted CO – optically obscured galaxies; “redshift desert” (1.5 < z < 2) Chapan et al. (2003; Nature) figure from Andrew Blain

NASA/GSFC

40 K 3K 250mK To focal plane 4 He 3 He 3K 1K Charcoal Closed-Cycle 7He Fridge

The GBT

kHz phase switching Simultaneous detection of –4 frequency channels –2 polarizations –2 beams BIMA CBI ACBAR Caltech Continuum Backend Caltech/NRAO

Current Pointing Performance Blind Pointing: (1 point/focus) Offset Pointing: (90 min) Continuous Tracking: (30 min) Benign Conditions: (1) Exclude 10:00  18:00 (2) Wind < 2.5 m/s