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.

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

The MAMBO 1.2 mm imaging survey of the COSMOS field

Environment of submillimeter galaxies

Conclusions & Prospects

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 de

nsity (arbitrary units)

Wavelength (m)

Starburst and QSOs in the early Universe

SCUBA

MAMBO

Hubble Deep Field North

SCUBA map

Hubble Deep Field North

Optical image

Submillimeter blank-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

Scoville et al. (2007)

• Total area of 2 square degs.

• Deep exposures:

I~26.5 (mag), (1.4 GHz) ~ 7 Jy

• 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)

The COSMOS field

The COSMOS field

MAMBO imaging of COSMOS

MAMBO = Max-Planck Millimeter Bolometer array on the IRAM 30 m telescope in Granada, Spain

An area of 20’x20’ mapped to an rms noise level of 1 mJy per 11’’ beam

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)

Optical coverage

Spitzer – shallow coverage

MAMBO imaging of COSMOS

Detected:

15 sources >4significance, 11 of which have radio counterparts

10 sources 3 – 4 significance based on a radio identification

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.

Environment of submillimeter galaxies

What is the ‘fate’ of sub-mm galaxies?

Will they end up in the most 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).

• 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? )

Environment of submillimeter 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)

Study the environment of MAMBO galaxies

Starburst QSO QSO in dense environment

Starburst/QSO transition scenario

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)

Environment of submillimeter galaxies

• 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)

Efficient method to select galaxies at redshifts 1.5-2.5 : BzK color-color criterion (Daddi et al. 2004)

Figure. BzK color-color criterion.

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

Consistency check

Reliability of our maps

Both maps trace mostly the same structures, supporting the reliability of our map.

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.

Results

• Some MAMBO galaxies are located in regions with enhanced density of low-z galaxies

• Consistent with lensing by foreground galaxies

Figure. Distribution of densities at the position of MAMBO galaxies (filled) compared with the field (open).

Four MAMBO galaxies are located in overdense environments at high-z.

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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.

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( -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%

Photometric redshifts

Further evidence:

Photometric redshifts for galaxies within 20” from the MAMBO galaxy position.

K-band selected

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

More evidence

Plateau de Bureau Interferometer in its D-configuration

Higher resolution of ~3”

Better sensitivity

Tentative detection (3) 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.

Conclusions & Prospects

• MAMBO survey of the COSMOS field.

• We studied the density of high-redshift BzK 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)