EVIDENCE FOR A POPULATION OF HIGH REDSHIFT SUBMILLIMETER GALAXIES

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EVIDENCE FOR A POPULATION OF HIGH REDSHIFT
SUBMILLIMETER GALAXIES
Joshua D. Younger Harvard/CfA

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• J. D. Younger, G. G. Fazio, J. Huang (CfA)
• M. S. Yun, G. Wilson, T. Perera, K. Scott, J.
  Austermann (U Mass)
• M. L. N. Ashby, M. A. Gurwell, K. Lai, A. B.
  Peck, G. Petitpas, D. Wilner (CfA)
• D. Iono, K. Kohno, R. Kawabe (NAOJ)
• D. Hughes, I. Aretzaga (INAOE),
• J. Lowenthal (Smith)
• T. Webb (McGill),
• A. Martinez-Sansigre, E. Schinnerer, V. Smolcic
  (MPIA)
• S. Kim (Sejong Univ)

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Coppin et al. (2006)
20-30 of FIRB Resolved
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80 SF is obscured
Hughes et al. (1998)
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INTRODUCTION

• Millimeter and submillimeter (submm) observations
  are critical to our understanding of galaxy birth
  and evolution in the early Universe.
• Studies of the diffuse far-IR and millimeter
  cosmic background radiation have shown this
  radiation is due to discrete sources dominated by
  luminous and ultraluminous infrared/submm
  galaxies at high redshift
• Multiwavelength studies of these galaxies have
  shown that they are massive, young objects in the
  process of formation, with very high star
  formation rates.
• However progress in understanding these galaxies
  has been hampered by their faintness at optical
  wavelengths and the poor angular resolution ( 14
  arcsec) of submm cameras.
• SMA and Spitzer Space Telescope (infrared)
  observations of these galaxies can provide new
  insight into the true nature of these sources.

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SMG COUNTERPART IDENTIFICATION
1100mm

• Radio continuum
• IRAC counterpart
• Probability of association
• N/MIR colors
• Redshifted PAH emission

3.6mm
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OBSERVATIONS

• AzTEC camera observations (1.1 mm wavelength
  18 arcsec resolution) on the JCMT of the COSMOS
  field (0.15 deg2) detected 44 submm galaxies
  (SMGs) above 3.5?.
• SMA interferometric observations (890 ?m
  wavelength 2 arcsec resolution) of the seven
  brightest AzTEC sources detected all seven SMGs
  and pinpointed their location to 0.2 arcsec.
• Follow-up observations by HST (ACS), SPITZER
  (IRAC and MIPS), and Very Large Array (VLA)
  revealed the detailed properties of these sources.

The AzTEC/COSMOS Survey (Scott et al. 2007)
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OVERVIEW OF RESULTS

• We detect all seven targets at high significance
  (gt6s)
• All seven SMA sources have IRAC 3.6mm
  counterparts
• Only a fraction (two/three) have optical
  counterparts
• For the five radio-dim sources, the submm,
  infrared and optical properties of these
  counterparts suggest higher redshift.
• Higher submm/radio fluxes
• Systematically low IRAC fluxes
• No MIPS detection at 24 ?m

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890mm
20cm
24mm
3.6mm
0.8mm
AzTEC1
AzTEC2
AzTEC3
AzTEC4
AzTEC5
AzTEC6
AzTEC7
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ASTROMETRY OF SMA/AzTEC SOURCES
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PHOTOMETRY OF SMA/AzTEC SOURCES
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RADIO/SMM FLUX RATIOS
Consistent with higher average/median redshift
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IRAC COUNTERPARTS
Consistent with higher average/median redshift
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CONCLUSIONS

• From AzTEC and SMA observations, evidence for a
  population of SMGs that peak earlier in cosmic
  time (z gt 3)
• Constraints on galaxy formation and dust
  production models.
• From SMA imaging, brightest SMGs are single
  compact point-sources
• Constraints on the physical mechanism driving far
  infrared emission and star formation

Highlights the power of SMA to localize SMGs with
sufficient accuracy for follow-up observations
with HST and Spitzer Space Telescope.
Younger, Fazio, et al. (2007) astro-ph/0708.1020
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HIGH-Z SMGs IN OTHER SAMPLES - SHADES

• We need bright high-significance targets targets
  (F850m gt 10 mJy or so)
• wide areas
• uniform coverage
• SHADES is a complete, unbiased large-area submm
  survey
• 800 arcmin2 850mm map of two fields (LH, SXDF)
• Represents gt 3 years of observations with SCUBA
• Final map has rms 2 mJy
• Massive multiwavelength followup (VLA, Subaru,
  Spitzer, Keck, XMM, Chandra, )

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THE SHADES SURVEY
Image Credit J. Dunlop
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THE TARGET LH850.02

• Brightest 850/1100mm source in the LH
• Two likely radio counterparts, one bright
  proximate MIPS source
• We detected LH850.02 at high significance (gt6s)
  with the SMA
• Compact, single point source singles out one
  radio counterpart

Younger, Dunlop, Peck, Ivison et al. in prep.
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MULTIWAVELENGTH COUNTERPARTS
R-band
3.6?m
24?m
20cm
SMA 890mmPOSITION
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SEEMS TO BE PART OF SAME POPULATION
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SEEMS TO BE PART OF SAME POPULATION
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CONCLUSIONS

• (from a sample of 1)
• Clean illustration of problems with SMG
  counterpart identification
• Similar high-z SMG is also the brightest 850?m
  source in a wide-area blank field survey
• High-z nature of sources likely related
  correlated more closely with brightness/luminosity
  than the wavelength in which they were selected
• Brightest SMGs may be the most distant

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WHAT TO DO NEXT?

• SMGs in a biased environment MS0451 AzTEC
  sources (observing now)
• Further followup of AzTEC/COSMOS, (accepted for
  winter 09)
• Higher-resolution follow-up (accepted for winter
  09)
• CARMA observations of AzTEC/COSMOS sources
  (submitted)
• CSO photometry at 350 mm (submitted)
• SCUBA-2 Survey (both 450 and 850mm)
• Herschel Survey at 100-500mm