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Evidence for a Population of high redshift Submm Galaxies

Evidence for a Population of high redshift Submm Galaxies. David J. Wilner. arXiv:0708.1020. Submillimeter Galaxies “COSMOS” AzTEC observations SMA follow-up, evidence for z>3 Concluding remarks. Extragalactic Background Light. COBE: CIRB ~ COB 850  m: 31 Jy/deg 2

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Evidence for a Population of high redshift Submm Galaxies

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  1. Evidence for a Population of high redshift Submm Galaxies David J. Wilner

  2. arXiv:0708.1020 • Submillimeter Galaxies • “COSMOS” AzTEC observations • SMA follow-up, evidence for z>3 • Concluding remarks

  3. Extragalactic Background Light COBE: CIRB ~ COB 850 m: 31 Jy/deg2 (Puget et al. 1996) 44 Jy/deg2 (Fixsen et al. 1998)

  4. Discrete Dusty Sources? • upper limits, BIMA Wilner and Wright 1997 • redshifted steep mm SED counteracts inverse square law dimming

  5. Discrete Dusty Sources? • first detections, JCMT/SCUBA at 850 mHughes et al. 1998 • ~ 2 - 10 mJy ~ 1012.3 -13 LSun for z > 1, ULIRGs • counterparts?

  6. Star Formation History ~80% SF is obscured Hughes et al. (1998)

  7. Blank Field Surveys • now a few hundred submm sources • SCUBA confusion limited at ~ 2 mJy • ~ 3000 sources per deg2 > 2 mJy • 20 to 30% of 850 m EBL resolved (~10 Jy) Coppin et al. 2006

  8. Counterpart Identification • not easy • HDF850.1 still controversial (!) • FIR-Radio correlation • VLA detection, <1” position • enables optical follow-up • biased against high-z Downes et al. 1999

  9. Redshift Distribution • Chapman et al. 2005 • ~70 sources (18 Keck nights) • <z> = 2.2

  10. HST/NICMOS Scoville et al. 1998 Local SMG Analog: Arp 220 • nearest ULIRG (75 Mpc), LIR=1012.2 Lsun • important template for high-z objects • advanced merger of two rotating nuclei, resolved in CO J=3-2 and 860 m continuum emission at size scales < 100 pc Sakamoto et al., in prep

  11. SMA site on Mauna Kea

  12. Arp 220 CO Excitation: J=6-5 W E • resolve CO J=6-5 and 435 m dust continuum emission • morphology very similar to low J CO lines • excitation: east nuc.~50 K (starburst), west nuc. ~100 K (AGN?) Matsushita et al., in prep

  13. Submillimeter Galaxies • Approximately half of luminous cosmic energy density is reprocessed by dust • A fraction has been resolved into discrete sources dominated by ultraluminous infrared/submm galaxies • Multiwavelength studies show these galaxies are massive and have very high star formation rates, 102-103 MSun per year • Progress has been hampered by faintness at optical wavelengths and by the poor angular resolution of today’s submm cameras

  14. COSMOS Observations • HST(ACS), Spitzer (IRAC, MIPS), VLA, Chandra, … • AzTEC bolometer on JCMT, Dec 2006 • 1.1 mm wavelength • 18 arcsec beam • 0.15 deg2 surveyed • 44 detections >3.5(all <8) The AzTEC/COSMOS Survey Scott et al. 2007

  15. High Resolution Follow-up • SMA 0.89 mm wavelength, Jan-Mar 2007 • flux limited sample of 7 AzTEC sources (1 per night) • 2 arcsec beam; ~0.2 arcsec astrometry

  16. good weather on Mauna Kea (at least some of the time)

  17. AzTEC 1100mm SMA IRAC 3.6mm ACS 814nm Overview of SMA Results • all 7 targets detected • single point sources • high significance (6 to 14) • all 7 targets have IRAC 3.6 m counterparts • Only 2 or 3 have ACS optical counterparts • 5 radio-dim sources • high submm/radio • low 3.6 m fluxes • no 24 m detections

  18. Postage Stamps Younger et al. 2007

  19. SMA/AzTEC Astrometry

  20. SMA/AzTEC Photometry

  21. Radio/Submm Flux Ratios • higher z than radio selected sources

  22. IRAC 3.6m Counterparts • higher z than radio selected sources

  23. Another: GOODS 850.5 Wang, Cowie et al. 2007 z~6?

  24. Another: LH850.02 Younger et al., in prep

  25. What’s Next? • Ground-based optical spectrum of AzTEC1? • Deeper mid-infrared observations with Spitzer • Proposal accepted to image detected radio-quiet sources with IRAC, MIPS, and IRS to get better handle on the redshift • Deep near-ir with HST/NICMOS for phot-z • Proposal accepted for HDF850.5, not for COSMOS sources • Blind search for redshifted CO with GBT or LMT or CARMA or IRAM PdBI… or ALMA • When technically feasible • Expand the high-z SMG sample, Resolve sizes • SMA follow-up of more sources underway, CARMA submitted

  26. Concluding Remarks • From AzTEC/ SMA data, evidence for a population of SMGs that peak earlier in cosmic time, likely z>3 • Brightest SMGs may be the most distant (why?) • L ~ few x 1013 LSun suggest star formation rates of ~ few x 1000 MSun per year (!) • Radio dim, submm bright sources: ~4 Jy/deg2 of CIRB • if z ~ 4 to (7), then SFRD ~ 0.04 Solar masses/yr/Mpc3 = 2 to 3x SFRD derived from optical surveys for z~4 • Substantial fraction of high-z star formation obscured

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