The SCUBA-2 Cosmology
Legacy Survey
Jim Geach on behalf of the S2CLS
consortium
What is the SCUBA-2
Cosmology Legacy Survey?
Largest of the JCMT Legacy Surveys: 65% of all SCUBA-2 time
to be spent on JLS, over half this is spent on CLS
CLS (high redshift)
1778 hours
50.9%
GBS (local star formation)
412 hours
11.8%
SASSy (‘all/ambitious’ sky survey)
480 hours
13.8%
NGLS (nearby galaxies)
100 hours
2.9%
JPS (Galactic plane)
450 hours
12.9%
SONS (stars)
270 hours
7.7%
3490 hours
291 nights
What is the SCUBA-2
Cosmology Legacy Survey?
Simple two tier strategy covering well-known fields:
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Wide survey at 850um in grade 2-3 conditions
Target area 10 deg2 (probably get 50% of this)
Uniform coverage to 1sigma=1.2mJy.
PONG mapping. ~80% complete
• Deep survey at 450um + 850um in grade 1 conditions
• Target area 0.25 deg2
• Uniform coverage 1sigma=1.2mJy @ 450um,
confusion limited at 850um.
• DAISY mapping. ~50% complete
Science drivers
• Comprehensive survey of SMGs detected at 850um (N~104) over
several ~degree scale fields
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measure clustering / halo properties
constrain bright-end counts
reliably probe properties of fainter SMGs (3-5mJy)
AGN/starburst connection, transition objects
‘very’ high-z science (IR luminosity density at z>5, rare objects)
cross-correlation studies
‘Keyhole’ confusion limited survey at 450+850um
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properties of 450um-selected SMGs below HSO confusion limit
resolving CIB at 450um (closer to peak)
probing very faint end of counts (P(D) analyses)
joint stellar/dust/gas morphologies (CANDELS overlap, ALMA)
Targets
Including deep CANDELS
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COSMOS (2 deg)
UKIDSS-UDS/SXDF (1 deg)
GOODS-N
Extended Groth Strip / AEGIS
Other wide fields
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Akari-NEP
Lockman Hole Owen
SSA22
SSA22
Akari-NEP
COSMOS
EGS
Lockman Hole
UDS
1 degree
Average cost of an SMG: £400*
*don’t quote me on this
Legacy value: priceless
S2CLS is a ‘factory’ for
detecting dusty
starbursts at z>1
Pinpoint
counterparts
with ~few asec
accuracy
Excellent ancillary data
(e.g. CANDELS) probing
stellar emission,
redshifts, morphologies
ALMA offers HST-matched
resolution: directly
compare dust and gas to
stellar emission on subgalactic scales
4
0
1
2
3
2
Area (deg )
5
6
Cumulative area
0
1
2
3
4
5
1s (mJy)
~3 deg2 at rms<2mJy…
improvement over SHADES by order of magnitude
Why are we doing this?
Dole+06
Why are we doing this?
Dole+06
Why are we doing this?
Observed 850um flux density
ULIRG
LIRG
Bethermin+11
JEG+Papadopoulos 12
At z>2, bulk of IR luminosity density
is emitted by ULIRGs: epoch of
formation of most massive galaxies
today
Negative k-correction at 850um
provides uniform luminosity
selection at fixed flux limit out to
z~10! Huge volume column.
Early science highlights
and prospects
Cycle 1 ALMA follow-up of CLS sources
at sub-arcsec resolution
First measurement of 450um number counts
JEG+ 2013
SCUBA-2
Recover ~50% with
MIPS stack
Herschel
Directly resolve
~15% of CIB @
450um
JEG+ 2013
Average sub-mm flux of Lyman Break
Galaxies
Coppin, JEG+ 2014 arXiv:1407.6712
Stacked LBGs in SXDF at z=3,
4, 5 (850um)
Typical S850 ~ 0.2 - 1 mJy
Cross-correlating galaxies with CLS
Smith, JEG+ 2014 in prep
Rare objects: Lyman-alpha Blobs
JEG+ 2014
SCUBA-2
SAURON/FORS
Next steps…
Clear need to complete COSMOS field – tremendous
legacy value in this field (including HSC UD). Would
require at least another winter (probably two) to reach
full CLS depth.
Complete the deep 450+850 mapping of CANDELS
fields – progress has been severely hampered by poor
weather. Complement to HSC UD.
Obvious continuation of CLS would be wider area –
mapping of all HSC deep fields to ~30 deg2? Time
investment would be ~1000s hours for useful depths.