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/deg2 (Puget et al. 1996) 44 Jy/deg2 (Fixsen et al. 1998)

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

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

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

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

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

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

Local SMG Analog: Arp 220 nearest ULIRG (75 Mpc), LIR=1012.2 Lsun Sakamoto et al., in prep Scoville et al. 1998 HST/NICMOS 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

SMA site on Mauna Kea

Arp 220 CO Excitation: J=6-5 W E Matsushita et al., in prep 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?)

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

The AzTEC/COSMOS Survey 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

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

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

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 AzTEC 1100mm SMA IRAC 3.6mm ACS 814nm

Postage Stamps Younger et al. 2007

SMA/AzTEC Astrometry

SMA/AzTEC Photometry

Radio/Submm Flux Ratios higher z than radio selected sources

IRAC 3.6m Counterparts higher z than radio selected sources

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

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

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

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