The JCMT in the ALMA EraSurveying the Sub-millimetre Sky

(Canada / Netherlands / Great Britain)

Doug Johnstone

NRC/HIA

A New Suite of Instruments

• Faster bolometer array (SCUBA2)– Continuum mapping at multiple wavelengths

• Ancillary devices (polarimeter, FTS)– Magnetic fields, line- and SED-fitting

• Heterodyne Receiver Array (HARP-B)– 16 receivers @350 GHz (CO 3-2 etc)

• Submillimetre array (eSMA)

SCUBA2The Future of Sub-Millimetre Mapping

• >100 times faster than present instruments

• Survey large regions of the sky quickly– Square degrees per hour

• Survey to the point-source confusion limit– Allow for ‘complete’ source counts

• Finding chart for ALMA– Beam size 15", centroid to a few arcseconds

SCUBA2 Key Features

• A large 7x7 arcminute field-of-view– Fully sampled - Nyquist at 850m

• Sensitivity governed by the sky background

• Simultaneous imaging at 850m & 450m

• No chopping required – Greater sensitivity to

large-scale structure

~8 arcmin (~100mm)

Focal plane layout

Estimated performance

Parameter 450m SCUBA SCUBA-2

850m SCUBA SCUBA-2

Per-pixel NEFD(mJy/Hz)

400 75 90 32

Point-source NEFD(mJy/Hz)

400 107 90 22

Point source fluxExtraction speed

1 10 1 12

Large area mappingspeed

1 810 1 980

Large-scale surveys

Herschel/SPIRE(350m)25 arcsec : 16 arcmin2

(simulation by Hughes & Gaztanaga)

Compact ALMA(450m)0.01 arcsec : 0.02 arcmin2

JCMT/SCUBA(850m)14 arcsec : 5 arcmin2

(HDF image from Hughes et al. 1998)

JCMT/SCUBA-2(450m)7 arcsec resolution : 64 arcmin2 field-of-view(simulation by Governato et al.)

SCUBA-2 will map large areas of sky at least 10 times faster than ALMA to the same S/N...

Deep extragalactic surveys

SCUBA-2 field-of-view

Hubble Deep Field

Deep imaging? It would take SCUBA-2 ~50 hours to map 1 deg2 area of sky to the confusion limit (0.5 mJy) at 850m

A 50-hrobservationwith SCUBA

Wide-field Galactic surveys

All sky survey? It would take SCUBA-2 ~500 hours to map the entire Mauna Kea sky to the depth of the SCUBA Galactic Centre image

~15 shifts (or 120 hrs) of telescope time

SCUBA-2 could map the entire area shown left in just a couple of hours to the same S/N...

Full moon

Galactic Plane

SCUBA Galactic Centre Survey

Ophiuchus – JCMT 2003

In 2003 observed 4 sq. degrees to 40 mJy/bm as part of the COMPLETE Project.

Took 40 hours!

Largest SCUBA map to dateExpect 100’s of new compact sources

Found only 2!

Ancillary Instruments

• Polarimeter– Measure polarized emission and orientation

• Importance of magnetic fields (especially in regions of star formation)

• Study the properties of dust

• Fourier Transform Spectrometer– Moderate-resolution spectrum

• Quickly obtain strong emission lines (e.g. CO)

• Hot core diagnostics

– Low-resolution spectrum• SED shape - temperature and dust emissivity

Polarimetry of the Orion Ridge

When and How?

• SCUBA2 on the telescope by end of 2005– Full functionality in 2006

• Legacy Surveys being determined NOW!– Likely 50% of telescope time– Still time to forward ideas to JCMT members

• Tri-Partate agreement for JCMT expires 2009– Future of the JCMT beyond 2009 open to ideas– There will still be a great deal of sky to map!

• Partenership Opportunities

SCUBA-2 Website: http://www.roe.ac.uk/ukatc/projects/scubatwo

Canadian SCUBA-2

Consortium