Transcript Legacy surveys with SCUBA2
Legacy surveys with SCUBA2 to coldly go where no man has gone before… Paul van der Werf Sterrewacht Leiden
Obergurgl March 2007
SCUBA surveys
Many teams, many surveys Blank field surveys (confusion limited) Gravitationally lensed surveys Few 100 SMGs detected Small field samples slow buildup of SCUBA-2 Legacy Surveys 2
A survey of SCUBA surveys
HDF SHADES 8 mJy
SCUBA-2 Legacy Surveys 3
From SCUBA to SCUBA-2
Field of view 8’ 8’: 10 SCUBA SCUBA-2 brings rectangular array imaging to submm astronomy 8 arrays of 40 32 TES detectors – 4 arrays at 850 m, 4 at 450 m Fully sampled imaging at 850 m Per pixel NEP 50 (220) mJy/√Hz at 850 (450) m SCUBA-2 Legacy Surveys 4
SCUBA-2 type surveys
1 deg 2 field, will be mapped to confusion limit in 23 hours by SCUBA-2 at 850 m SCUBA-2 field-of-view SCUBA-2 Legacy Surveys (from Gastañaga et al.) 5
Outline
JCMT Legacy Survey process SCUBA-2 Legacy Surveys SCUBA-2 Cosmology Legacy Survey 850 m survey science 450 m survey science SCUBA-2 Legacy Surveys 6
Legacy survey process
Concept of legacy surveys proposed to JCMT board Legacy surveys can use both SCUBA-2 and HARP (16-pixel 350 GHz receiver) Call for proposals by the board – resulted in oversubscription of all assumed (usable) JCMT time in 2007-2009 time by factor 5.5
International workshop in Leiden led to coordinated proposals Each proposal evaluated by a number of referees from outside the JCMT community Process overseen by the JCMT Survey Steering Group, which made a recommendation to the JCMT board, which was adopted SCUBA-2 Legacy Surveys 7
Outcome of the process
Two sets of surveys: 2-year surveys and 5-year surveys Two-year plan approved; 5-year plan approved in principle, but new call for surveys after 2 years During this period, 55% of the available time on JCMT will go to the Legacy Surveys Surveys are overseen by the JCMT Survey Oversight Committee, which advises the JCMT board; teams will report every six months and must demonstrate progress, keeping up with the data stream, ability to produce a uniform dataset, etc.
Data initially proprietary, but obligation to release reduced data SCUBA-2 Legacy Surveys 8
JCMT Legacy Surveys
Cosmology Legacy Survey 490 hours band 1 (most highly rated): (this is 90% of the expected available band 1 time!) and 630 hours band 2/3 SCUBA-2 All-Sky Survey (SASSy): 500 hours band 4 to 150 mJy depth (all-sky in 5 years) – see Stephen Serjeant for details Debris disks – complete set of nearby stars Nearby galaxies survey – SCUBA-2 and HARP Gould’s Belt survey (2 nd highly rated) – SCUBA-2 and HARP Galactic Plane survey – SCUBA-2 and HARP Spectral line survey – HARP only SCUBA-2 Legacy Surveys 9
Debris disk survey
850 m ?
Fomalhaut at 450 m Beam size Holland et al. (2001) Size of Pluto’s orbit Few hundred nearby stars, mapped to the confusion limit at 850 m Will likely produce very nice target set for adaptive optics observations of SMGs SCUBA-2 Legacy Surveys 10
Star formation
Our lack of detailed understanding of star formation is a major stumbling block: while we know a lot about low-mass star formation, very little is known about the formation of high-mass stars (rare and short-lived); yet these power the SMGs.
there is no good theory for the origin of the IMF and whether or not there should be a “universal” IMF; yet this central to estimated of SFR, stellar mass etc.
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The IMF problem(s) in SMGs
SFR implied by SMG’s SCUBA-2 Legacy Surveys Integral under green curve would exceed local stellar mass estimates for normal IMF.
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SCUBA-2 Galactic plane survey
M16 SCUBA-2 Legacy Surveys M8
SCUBA Galactic Centre Survey ≈15 shifts (or 120 hrs) of telescope time SCUBA-2 Galactic PLANE Survey
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SCUBA Galactic centre survey
450 m SCUBA FOV SCUBA-2 FOV 850 m (Pierce-Price et al.) 14 SCUBA-2 Legacy Surveys
SCUBA-2 Legacy Surveys
IRAS 100
m: Gould’s Belt
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Star formation surveys
Galactic plane survey will reveal systematically reveal the progenitors of massive star formation (IR dark clouds and similar very dense structures) anatomy of the Milky Way at 850 m – important reference point for extragalactic studies Gould’s Belt survey – comprehensive survey of low-mass star formation These surveys could only be implemented as a result of the Legacy Survey process. SCUBA-2 Legacy Surveys 16
SCUBA-2 Cosmology Legacy Survey
4 PIs: Jim Dunlop, Mark Halpern, Ian Smail, Paul van der Werf; + ≈ 100 co-I’s 2-year program: large survey (20 deg 2 ) at 850 m, deep survey at 450 m (0.5 deg 2 ) 5-year program: large survey (50 deg 2 ) at 850 m, deep survey at 450 m (1.3 deg 2 ) Time allocation for the 2-year program: 41 nights band 1 weather, 61 nights band 2/3 SCUBA-2 field-of-view SCUBA-2 Legacy Surveys 17
Survey properties
(from Andrew Blain) SCUBA-2 Legacy Surveys Survey volumes are always very long in the radial direction.
A deeper submm survey does not probe a larger volume, but fainter galaxies at all redshifts .
JCMT/SCUBA-2 confusion limit at 850 m is 0.8 mJy; to 3 resolve only ≈20% we of background.
Bright sources are typically 20 mJy limited dynamic range in flux Wide 850 m survey of only 1 layer 18
Survey depths and widths (2-yr plan)
Wide 850 m survey: 20 deg Comparable to a Schmidt plate to the depth of the SCUBA-HDF-N map.
Expected to yield several 10 3 2 to 1 = 0.7 mJy sources at >10 .
, several 10 4 at >3 .
Deep 450 m survey: 0.5 deg Expected to yield several 10 2 2 to 1 = 0.5 mJy Intended area of SHADES, to average over sufficient cosmic volume.
sources at >10 (expected confusion limit).
, several 10 3 at >3 .
Deep 850 m survey: 0.5 deg 2 to 1 = 0.15 mJy (ignoring confusion).
In parallel with 450 m map, which will be used for deconvolution.
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Survey fields
850 m survey:
field RA
XMM-LSS ECDFS Cosmos Lockman Bootes EGS ELAIS-N1 Akari-NEP 2 3 10 10 14 14 16 18
area
[deg 2 ] 5 3 2 4 2 1 2 1 SCUBA-2 Legacy Surveys 450 m survey:
field RA
UDS ECDFS Cosmos GOODS-N Akari-NEP SA22 2 3 10 12 18 22 Field selection (partly) driven by complementary data of the required depth ; e.g., K AB =25
area
[deg 2 ] <0.25
<0.25
<0.25
0.05
0.02
0.02
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Science case 850
m survey
Clustering of SMGs Relation with other populations through massive source stacking Extreme objects (>30 mJy) – how many? what are they?
10 detections: easier identification, better photo-z Properties of host galaxies – stellar masses, K—z diagram, growing AGN?
New tests for semi-analytical models Rich source of follow-up by e.g., ALMA SCUBA-2 Legacy Surveys 21
Clustering and evolution
Clustering signal even without any redshift information Photo-z’s function of z clustering as Assign halo masses to SMGs Same at all redshifts?
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Relations between source populations
Availability of very deep data from e.g., UDS and IRAC allows recovery of submm signal from a selected population. E.g.: Lyman Break Galaxies have no detectable submm emission even after massive source stacking, but Distant Red Galaxies (DRGs) do!
Defined by J s —K s for z > 2 > 2.3, which brings the Balmer break between J s and K s DRGs: massive galaxies with high SFRs; source density 3 arcmin –2 for K<22.5 is comparable to SMGs with >0.8 mJy at 850 m (as estimated from lensing surveys).
1 unlensed DRG detected directly with SCUBA (5 mJy). SCUBA-2 Legacy Surveys 23
Stacking DRGs
DRGs, EROs
S
850 DRGs: = 1.11 0.28 mJy ≈20% of background (Knudsen et al., 2005) random positions SCUBA-2 Legacy Surveys 24
Cosmic backgrounds
1mm 1
m 1nm Microwave Background IR/Optical Background
(Puget et al. 1996, Hauser et al. 1998 Fixsen et al. 1998)
IRBG peaks at ≈200
m.
At 850
m, 30
lower At 450
m, only 3
lower X-Ray Background Big Bang Stars+BlackHoles AGN
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Science case 450
m survey
Probe the IR/submm background close to its spectral peak Resolve ≈ 75% of the 450 m background: new territory!
Out to z=3: full census of ULIRGs in survey volume Out to z=2: full census of >3 10 11
L
galaxies Out to z=1: full census of >2 10 11
L
galaxies Connection to other populations without stacking Deconvolve confusion-limited 850 m map Evolution of IR/submm luminosity function, obscured star formation history SCUBA-2 Legacy Surveys 26
Elbaz diagram
SCUBA (450
m)
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Deep 850
m source counts
10 Currently from gravitationally lensing cluster fields small survey volumes, affected by cosmic variance Deconvolved deep 850 variance m map large enough to average out cosmic Several 10 3 sources expected at >10 down to 1.5 mJy (resolves ≈ 40% of 850 m background) (Knudsen, Van der Werf & Kneib, 2007) SCUBA-2 Legacy Surveys 28
Practical challenges at 450
m
Even in excellent weather observing at 450 m is challenging.
Special care needed in calibration – monitor conditions and take beammaps several times per night Need to establish a rigorous observing protocol cosmology survey team).
, since the data are going to be taken by many different persons (often not even member of the Surface accuracy of JCMT dish <22 m is needed; this needs to be monitored and maintained .
Crucial requirement for 450 m survey depth and uniformity SCUBA-2 Legacy Surveys 29
Conclusions and outlook
850 m survey will produce statistically accurate results, and robust samples for easier follow-up.
Clustering is a key application The 450 m survey is unique in probing lower SFRs Deep complementary data is essential Follow-up is crucial: deep radio, near-IR deployable IFUs, redshift machines using CO Numbers are still “low” a next-generation instrument?
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