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The Environment of MAMBO Galaxies in the COSMOS field

The Environment of MAMBO Galaxies in the COSMOS field. Manuel Aravena F. Bertoldi , C. Carilli , E. Schinnerer , H. J. McCracken, K. M. Menten , M. Salvato. NRAO postdoc symposium. Socorro 2009. Outline. Introduction From starburst to QSOs Starburst galaxies in the early Universe

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The Environment of MAMBO Galaxies in the COSMOS field

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  1. The Environment of MAMBO Galaxies in the COSMOS field Manuel Aravena F. Bertoldi, C. Carilli, E. Schinnerer, H. J. McCracken, K. M. Menten, M. Salvato NRAO postdoc symposium. Socorro 2009

  2. Outline • Introduction • From starburst to QSOs • Starburst galaxies in the early Universe • The MAMBO 1.2 mm imaging survey of the COSMOS field • Environment of submillimeter galaxies • Conclusions & Prospects

  3. Introduction: Evolutionary sequence What is the relation between typical ULIRGs and optically bright QSOs? • Observations (e.g. Sanders et al. 1988) and Simulations (Gerritsen 1997). Morphology Spectral Energy Distribution (SED) Flux density (arbitrary units) Wavelength (mm)

  4. Starburst and QSOs in the early Universe Hubble Deep Field North SCUBA map Hubble Deep Field North Optical image SCUBA MAMBO Submillimeterblank-field surveys discovered a population of dusty high-redshift galaxies in which a significant fraction of the stars in the Universe were created. Submillimeter galaxies (SMGs): Mstar ~ 1011 Msun , L ~ 1013-14 Lsun, at z~2

  5. The COSMOS field The COSMOS field • Total area of 2 square degs. • Deep exposures: • I~26.5 (mag), s (1.4 GHz) ~ 7 mJy • Sensitive census of galaxies, their evolution and density growth up to z=1.5 (a third the age of the Universe, 4.3 Gyr after the Big Bang) Scoville et al. (2007)

  6. MAMBO imaging of COSMOS MAMBO = Max-Planck Millimeter Bolometer array on the IRAM 30 m telescope in Granada, Spain AzTEC 1.1 mm survey (Scott et al. 2008) Bolocam 1.1 mm survey (Aguirre et al., in prep.) MAMBO 1.2 mm survey (Bertoldi, et al. 2007) An area of 20’x20’ mapped to an rms noise level of 1 mJy per 11’’ beam Optical coverage Spitzer – shallow coverage

  7. MAMBO imaging of COSMOS Figure. MAMBO 1.2 mm final map. Detected sources are marked with a circle and their respective ID number. Figure. MAMBO 1.2 mm rms noise map. Detected: 15 sources >4s significance, 11 of which have radio counterparts 10 sources 3s – 4s significance based on a radio identification

  8. Environment of submillimeter galaxies What is the ‘fate’ of sub-mm galaxies? Will they end up in the most dense environments ? • Small survey areas and low-density of sources (Blain et al. 2002) • The largest surveys cover ~ 30’ x 30’ • Little is known about their relation with environment (isolated?, in dense environments? ) Massive radio galaxies are typically found in very dense environments up to redshift of ~ 4. Figure. Galaxy cluster. X-rays (blue). Optical view taken with the HST. Radio (red).

  9. Environment of submillimeter galaxies Starburst/QSO transition scenario Starburst QSO QSO in dense environment If sub-mm galaxies evolve into elliptical galaxies in dense environments, they would show signs of clustering in the epoch they were most abundant (redshift ~ 1.5-2.5) Study the environment of MAMBO galaxies • To date, few studies has been done to investigate the high-redshift environment of SMGs • It is possible to study the local environment of sub-mm galaxies at high-redshift. • Need to select objects at redshift similar to that of MAMBO galaxies (redshift ~ 1.5-2.5)

  10. Environment of submillimeter galaxies Efficient method to select galaxies at redshifts 1.5-2.5 : BzK color-color criterion (Daddi et al. 2004) • New deep K-band imaging of COSMOS • (McCracken et al., submitted) • K-band selected catalogue • Use BzK criterion to split the sample into: • sBzK + pBzK(redshift ~1.4-2.5) • nBzK(redshift <~ 1.4) Figure.BzK color-color criterion.

  11. Projected density maps of low- and high-redshift BzK galaxies • Densities computed using the 7th nearest neighbour estimator (Dressler, 1980): , where d7 is the distance to the 7th nearest neighbour. Density map of low-redshift BzK galaxies Density map of high-redshift BzK galaxies

  12. Consistency check Figure. Background: Density map computed from the K-band selected catalog. Red contours: Density map computed by Scoville et al. (2007) from the COSMOS I-band catalog. Reliability of our maps Both maps trace mostly the same structures, supporting the reliability of our map.

  13. Results Figure. Distribution of densities at the position of MAMBO galaxies (filled) compared with the field (open). • Some MAMBO galaxies are located in regions with enhanced density of low-z galaxies • Consistent with lensing by foreground galaxies 16 6 3 1 Four MAMBO galaxies are located in overdense environments at high-z.

  14. Environment of submillimeter galaxies Figure. BzK true color image of the fields of the four MAMBO galaxies embedded in the most overdense regions of high-redshift galaxies.

  15. How likely is that the association of MAMBO galaxies with these overdensities is produced by chance? Poisson probability of chance association that a significant density peak is found by chance within a distance d from a millimeter source (Downes et al., 1983) : P(d) ~ 1 – exp( -p d2 n ), where n number density of peaks in the area of the COSMOS MAMBO field (~20’x20’). Answer: Very unlikely. For COSBO-1, P(20”) = 10.4%For COSBO-3, P(20”) < 1e-3% For COSBO-6, P(20”) = 0.25%For COSBO-16, P(20”) = 2.5%

  16. Photometric redshifts K-band selected Further evidence: Photometric redshifts for galaxies within 20” from the MAMBO galaxy position. • Figure. Histograms represent the redshift distribution for : • High-redshift BzK galaxies (dark-gray ) • All galaxies (light-gray) • MAMBO galaxies (black entry) Peaks in redshift distribution. Most galaxies at high redshift

  17. More evidence Plateau de Bureau Interferometer in its D-configuration Higher resolution of ~3” Better sensitivity Tentative detection (3s) of 2 continuum sources with the PdBI at 1.3 mm toward COSBO-6 Integrated 1.3 mm flux over the whole area is 3.7 +\- 0.3 mJy, consistent with the MAMBO 1.2 mm flux of 5.2+\- 1.0 mJy. The flux derived for the central source is consistent with its radio emission, assuming it has a starburst-like SED.

  18. Conclusions & Prospects • MAMBO survey of the COSMOS field. • We studied the density of high-redshiftBzK galaxies around MAMBO galaxies. • Four MAMBO sources appear to be located in strong overdensities of red galaxies at high-redshift. • Photometric redshifts and millimeter continuum imaging support these results. • Spectroscopy with the Keck telescope will be crucial to confirm groups around SMGs • Millimeter imaging of the MAMBO sources to locate possible multiple sources • Similar studies in other deep fields for statistical analyses (e.g. CDF-S)

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