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EVIDENCE FOR A POPULATION OF HIGH REDSHIFT SUBMILLIMETER GALAXIES

This study presents evidence for a population of high redshift submillimeter galaxies using observations from the AzTEC camera, SMA interferometric observations, and follow-up observations with HST, SPITZER, and VLA. The results suggest that these galaxies are massive, young objects with high star formation rates, and their properties can provide insights into galaxy formation and dust production models.

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EVIDENCE FOR A POPULATION OF HIGH REDSHIFT SUBMILLIMETER GALAXIES

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

  2. P. Yamaguchi 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)

  3. Coppin et al. (2006) 20-30% of FIRB Resolved

  4. ~80% SF is obscured Hughes et al. (1998)

  5. 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.

  6. SMG COUNTERPART IDENTIFICATION 1100mm • Radio continuum • IRAC counterpart • Probability of association • N/MIR colors • Redshifted PAH emission 3.6mm

  7. 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)

  8. AzTEC 1100mm SMA 890mm IRAC 3.6mm ACS 814nm OVERVIEW OF RESULTS • We detect all seven targets at high significance (>6s) • 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

  9. 890mm 20cm 24mm 3.6mm 0.8mm AzTEC1 AzTEC2 AzTEC3 AzTEC4 AzTEC5 AzTEC6 AzTEC7

  10. ASTROMETRY OF SMA/AzTEC SOURCES

  11. PHOTOMETRY OF SMA/AzTEC SOURCES

  12. RADIO/SMM FLUX RATIOS Consistent with higher average/median redshift

  13. IRAC COUNTERPARTS Consistent with higher average/median redshift

  14. CONCLUSIONS • From AzTEC and SMA observations, evidence for a population of SMGs that peak earlier in cosmic time (z > 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]

  15. HIGH-Z SMGs IN OTHER SAMPLES - SHADES • We need bright high-significance targets targets (F850m > 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 > 3 years of observations with SCUBA • Final map has rms ~ 2 mJy • Massive multiwavelength followup (VLA, Subaru, Spitzer, Keck, XMM, Chandra, …)

  16. THE SHADES SURVEY Image Credit: J. Dunlop

  17. 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 (>6s) with the SMA • Compact, single point source singles out one radio counterpart Younger, Dunlop, Peck, Ivison et al. [in prep.]

  18. MULTIWAVELENGTH COUNTERPARTS R-band 3.6m 24m 20cm SMA 890mmPOSITION

  19. SEEMS TO BE PART OF SAME POPULATION

  20. SEEMS TO BE PART OF SAME POPULATION

  21. 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

  22. 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

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