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 m Hughes et al. 1998
~ mJy ~ 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. 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= 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

11. SMA site on Mauna Kea

12. 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?)

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, MSun per year
Progress has been hampered by faintness at optical wavelengths and by the poor angular resolution of today’s submm cameras

14. 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

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. 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

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 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/Mpc = 2 to 3x SFRD derived from optical surveys for z~4
Substantial fraction of high-z star formation obscured