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Legacy surveys with SCUBA2 - to coldly go where no man has gone before…

Legacy surveys with SCUBA2 - to coldly go where no man has gone before…. Obergurgl March 2007. SCUBA surveys. Many teams, many surveys Blank field surveys (confusion-limited) Gravitationally lensed surveys Few 100 SMGs detected Small field  slow buildup of samples. SHADES. 8 mJy.

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Legacy surveys with SCUBA2 - to coldly go where no man has gone before…

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  1. Legacy surveys with SCUBA2 -to coldly go where no man has gone before… Obergurgl March 2007

  2. SCUBA surveys • Many teams, many surveys • Blank field surveys (confusion-limited) • Gravitationally lensed surveys • Few 100 SMGs detected • Small field  slow buildup of samples SCUBA-2 Legacy Surveys

  3. SHADES 8 mJy A survey of SCUBA surveys HDF SCUBA-2 Legacy Surveys

  4. 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

  5. SCUBA-2 type surveys 1 deg2 field, will be mapped to confusion limit in 23 hours by SCUBA-2 at 850 m SCUBA-2 field-of-view (from Gastañaga et al.) SCUBA-2 Legacy Surveys

  6. 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

  7. 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

  8. 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

  9. JCMT Legacy Surveys • Cosmology Legacy Survey (most highly rated): 490 hours band 1 (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 (2nd highly rated) – SCUBA-2 and HARP • Galactic Plane survey – SCUBA-2 and HARP • Spectral line survey – HARP only SCUBA-2 Legacy Surveys

  10. Debris disk survey 850m Fomalhaut at 450m Beam size • 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 ? Size of Pluto’s orbit Holland et al. (2001) SCUBA-2 Legacy Surveys

  11. 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. SCUBA-2 Legacy Surveys

  12. SFR implied by SMG’s The IMF problem(s) in SMGs Integral under green curve would exceed local stellar mass estimates for normal IMF. SCUBA-2 Legacy Surveys

  13. SCUBA-2 Galactic plane survey SCUBA Galactic Centre Survey M8 ≈15 shifts (or 120 hrs) of telescope time M16 SCUBA-2 Galactic PLANE Survey SCUBA-2 Legacy Surveys

  14. SCUBA Galactic centre survey 450m SCUBA FOV SCUBA-2 FOV 850m (Pierce-Price et al.) SCUBA-2 Legacy Surveys

  15. IRAS 100 m: Gould’s Belt SCUBA-2 Legacy Surveys

  16. 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

  17. 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 deg2) at 850 m, deep survey at 450 m (0.5 deg2) • 5-year program: large survey (50 deg2) at 850 m, deep survey at 450 m (1.3 deg2) • 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

  18. Survey properties • 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 we resolve only ≈20% of background. • Bright sources are typically 20 mJy  limited dynamic range in flux • Wide 850 m survey of only 1 layer (from Andrew Blain) SCUBA-2 Legacy Surveys

  19. Survey depths and widths (2-yr plan) • Wide 850m survey: 20 deg2 to 1 = 0.7 mJy. Comparable to a Schmidt plate to the depth of the SCUBA-HDF-N map. Expected to yield several 103 sources at >10, several 104 at >3. • Deep 450m survey: 0.5 deg2 to 1 = 0.5 mJy (expected confusion limit). • Intended area of SHADES, to average over sufficient cosmic volume. • Expected to yield several 102 sources at >10, several 103 at >3. • Deep 850m survey: 0.5 deg2 to 1 = 0.15 mJy (ignoring confusion). • In parallel with 450 m map, which will be used for deconvolution. SCUBA-2 Legacy Surveys

  20. 850 m survey: 450 m survey: Survey fields Field selection (partly) driven by complementary data of the required depth; e.g., KAB=25 SCUBA-2 Legacy Surveys

  21. 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

  22. Clustering and evolution • Clustering signal even without any redshift information • Photo-z’s  clustering as function of z • Assign halo masses to SMGs • Same at all redshifts? SCUBA-2 Legacy Surveys

  23. 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 Js—Ks > 2.3, which brings the Balmer break between Js and Ks for z > 2 • 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

  24. Stacking DRGs DRGs, EROs DRGs: S850 = 1.11  0.28 mJy ≈20% of background (Knudsen et al., 2005) random positions SCUBA-2 Legacy Surveys

  25. 1mm1mm1nm Microwave Background IR/Optical Background X-Ray Background Stars+BlackHoles AGN Big Bang Cosmic backgrounds (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 SCUBA-2 Legacy Surveys

  26. 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1011L galaxies Out to z=1: full census of >21011L 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

  27. Elbaz diagram SCUBA (450m) SCUBA-2 Legacy Surveys

  28. Deep 850m source counts • Currently from gravitationally lensing cluster fields small survey volumes, affected by cosmic variance • Deconvolved deep 850m map large enough to average out cosmic variance • Several 103 sources expected at >10 down to 1.5 mJy (resolves ≈ 40% of 850 m background) 10 (Knudsen, Van der Werf & Kneib, 2007) SCUBA-2 Legacy Surveys

  29. 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, since the data are going to be taken by many different persons (often not even member of the cosmology survey team). • 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

  30. 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? SCUBA-2 Legacy Surveys

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