The GBT as a MM Telescope ALMA Science Workshop ALMA Science Workshop May 2004 May 2004 Brian Mason (NRAO-GB) Brian Mason (NRAO-GB)
Dec 14, 2015
The GBT as a MM Telescope
ALMA Science WorkshopALMA Science WorkshopMay 2004May 2004Brian Mason (NRAO-GB)Brian Mason (NRAO-GB)
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)
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)
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
GBT + ACS: 4 Ghz
Wideband Analog Spectrometer-25 Ghz; auto/cross correlation
Very stringent requirements on stability & flatness
• GBT currently operational through 52 Ghz• Near Future: prototype operation up to 94
Ghz• Fall/Winter 2005/2006: Regular 3mm
operation• Stay tuned...
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
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
• Point source photometry ~ D^4• Point source discovery ~ Nfeed D^2• Extended source mapping~ Nfeed
• + simultaneous high resolution & zero spacing
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
• kHz phase switching
• Simultaneous detection of
– 4 frequency channels
– 2 polarizations
– 2 beams BIMA
CBI
ACBAR
Caltech Continuum Backend Caltech/NRAO