The GBT as a MM Telescope

ALMA Science WorkshopALMA Science WorkshopMay 2004May 2004Brian Mason (NRAO-GB)Brian Mason (NRAO-GB)

PTCS Team: Richard PrestageKim ConstantikesDana 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

•

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

Technologiessuitable for a muchlarger bolometerarray

UPenn; NASA/GSFC; NRAO; NIST; Cardiff

Testi & Sargent (1998)

OVRO50h 1 mJy/Bm

5’ x 5’

Penn Array8 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’’

RX J2228+2037

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 ReceiversKa: 26 – 40 GhzW: 68 - 92 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

•

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

Technologiessuitable for a muchlarger bolometerarray

UPenn; NASA/GSFC; NRAO; NIST; Cardiff

Blank

GBT Instrumentation

• LIST PAST/FUTURE• SHOW PICTURE OF FREQ

COVERAGE

GBT Instrumentation

• LIST PAST/FUTURE• SHOW PICTURE OF FREQ

COVERAGE

Mapping with Single Dishes

GBT can address cluster gas properties and evolution

Z=0

Z=5Z=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

3K

1K

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