The Environment of MAMBO Galaxies

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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
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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

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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)
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Starburst and QSOs in the early Universe
Hubble Deep Field North SCUBA map
Hubble Deep Field North Optical image
SCUBA
MAMBO
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 z2
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The COSMOS field
The COSMOS field

• Total area of 2 square degs.
• Deep exposures
• I26.5 (mag), s (1.4 GHz) 7 mJy
• Sensitive census of galaxies, their evolution
  and density growth up to z1.5 (a third the age
  of the Universe, 4.3 Gyr after the Big Bang)

Scoville et al. (2007)
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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 20x20 mapped to an rms noise level
of 1 mJy per 11 beam
Optical coverage
Spitzer shallow coverage
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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 gt4s significance, 11 of
which have radio counterparts 10 sources 3s 4s
significance based on a radio identification
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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).
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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)

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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 lt 1.4)

Figure. BzK color-color criterion.
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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
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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.
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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

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6
3
1
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.
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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 (20x20).
Answer Very unlikely. For COSBO-1, P(20)
10.4 For COSBO-3, P(20) lt 1e-3 For COSBO-6,
P(20) 0.25 For COSBO-16, P(20) 2.5
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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
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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.
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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)