DEEP2 Galaxy Redshift Survey and Post-Starburst galaxies at z~1

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DEEP2 Galaxy Redshift SurveyandPost-Starburst
galaxies at z1
Renbin Yan University of California, Berkeley
And The DEEP2 Team
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The DEEP2 Collaboration
The DEEP2 Galaxy Redshift Survey, which uses the
DEIMOS spectrograph on the Keck II telescope, is
studying both galaxy properties and large-scale
structure at z1.

• U.C. Berkeley
• M. Davis (PI)
• A. Coil
• M. Cooper
• B. Gerke
• R. Yan
• C. Conroy
• LBNL
• J. Newman
• U. Hawaii
• N. Kaiser

U.C. Santa Cruz S. Faber (Co-PI) D. Koo P.
Guhathakurta D. Phillips C. Willmer B.
Weiner R. Schiavon K. Noeske A. Metevier L.
Lin N. Konidaris G. Graves
JPL P. Eisenhardt Princeton D. Finkbeiner U.
Pitt. A. Connolly K survey (Caltech) K.
Bundy C. Conselice R. Ellis
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Comparison with Other Surveys
DEEP2 was designed to have comparable size and
density to previous generation local redshift
surveys and is gt50 times larger than previous
surveys at z0.3-1.
DEEP2 is similar to LCRS in sample size but at
z1 - with a very different geometry
20?80?1000 h-3 Mpc3 per field (LCDM)
SDSS
2dF
LCRS
DEEP2
z0 z1
CFA SSRS
PSCZ
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A Redshift Survey at z1

• Observational details
• 3 sq. degrees
• 4 fields (0.5o x lt2o)
• primary z0.75-1.4 (pre-selected using BRI
  photometry)
• gt40,000 redshifts
• 5106 h-3 Mpc3
• 80 Keck nights
• One-hour exposures
• RAB24.1
• 1200 l/mm 6500-9200 Å
• 1.0 slit FWHM? 68 km/s

• Studying Evolution
• Age of the Universe 13.7 Gyr
• z0.7 - 6.0 Gyr ago
• z1.0 - 7.5 Gyr ago
• z1.4 - 8.5 Gyr ago
• Within DEEP2 we are surveying
• 2.5 Gyr or 20 of the history
• of the Universe, and SDSS/2dF comparisons give
  3x this baseline

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Coordinated observations ofthe Extended Groth
Strip (EGS)
Spitzer MIPS, IRAC
Background 2 x 2 deg from POSS
DEEP2 spectra and Caltech / JPL Ks imaging
HST/ACS V,I (Cycle 13)
Plus VLA (6 21 cm), SCUBA, etc.
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Redshift Distribution of Data z0.7-1.4
Our color cuts are very successful! 90 of our
targets are at zgt0.75 and we miss only 3 of
high-z objects.

• Status
• Designed as a
• three-year survey
• Began summer 2002
• 80 night UC time allocation is now complete
• Finished 3 of 4 fields, 4th
• gt75 done (will complete
• in S06)

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Redshift Maps in 4 Fields z0.7-1.2
Cone diagram of 1/12 of the full DEEP2 sample
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DEEP2 sees the same color bi-modality as SDSS,
COMBO-17, etc. to z1.4
Our R-band magnitude limit corresponds to 4000Å
rest-frame at z0.7, 2800 Å at z1.4 . As
redshift increases, red galaxies of a given
luminosity fall out before blue ones.
Willmer et al. 2005
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Post-Starburst Galaxies (EA or KA)
Post-starburst galaxies show little on-going
star-formation (lack of emission lines) but
strong Balmer absorption features due to recent
star-formation (within 1 Gyr) - post-starburst
galaxies. Their spectra can be well modeled by
the combination of two components an old stellar
population and an A-star population.
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Post-starburst Mysteries

• Do all red sequence galaxies come from
  post-starbursts?
• What is the abundance at high-z Cluster vs.
  field?
• What is their origin? Merger remnant? Satellite
  harassment? Superwind? Ram-Pressure Stripping?

DEEP2 covers a large enough volume to find a
large statistical sample. EGS will add
multiwavelength SEDs and morphologies. We will be
able to shed light on these issues.
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The Selection of EA galaxies
We use H? instead of OII because OII in red
galaxies is heavily contaminated by AGN or
LINERs. (Yan et al. in prep, see poster)
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Color of Post-Starburst Galaxies
These galaxies populate the gap in the color
bi-modality and part of the red sequence - they
may provide clues as to how galaxies move onto
the red sequence. We are investigating their
morphologies and environments.
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Other recent and upcoming papers include

• Angular clustering of galaxies Coil et al.,
  2004, ApJ, 617, 765
• DEEP2 survey strategy dark energy Davis et
  al.,astro-ph/0408344
• Evolution of close-pairs/merger rates Lin et
  al., 2004, ApJ, 617, 9
• Satellite galaxy kinematics Conroy et al.,
  astro-ph/0409305
• Measuring environment in deep redshift surveys
  Cooper et al., submitted
• Luminosity function Willmer et al. Faber et
  al., submitted.
• Group correlation function Coil et al.,
  submitted.
• Void statistics in the DEEP2 sample Conroy et
  al., submitted.
• Overview of the DEEP2 sample Faber et al., in
  prep.

First semesters data is now public
http//deep.berkeley.edu/DR1
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Poster AGN Origin of O II in Red Galaxies---
Implications for post-starburst galaxy studies

• Conclusions
• 1) Galaxies display bimodality in O II/Ha
  ratios, which corresponds to the bimodality in
  rest-frame colors.
• 2) Line-emitting red galaxies have line ratios
  following those of AGN or LINERs.
• 3) Post-starburst galaxies identified in the SDSS
  dataset using Ha often exhibit significant O II
  EW their position in O II-Ha plot suggest they
  might be AGN or LINERs.
• 4) O II emission in LINERs can be as strong as
  in star-forming galaxies. Locally, it is only a
  proxy for SFR in blue galaxies.
• 5) post-starburst samples defined using O II
  will be very incomplete, especially if AGN rates
  and intensity were higher in the past. We
  recommend using H? as an alternative for high
  redshift.

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Thank You
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Pre-selection of high-z targets with using colors

• Plotted are the colors of some galaxies with
  known redshifts in our fields those at low
  redshift are plotted as blue, those at high
  redshift as red. We use a simple color cut
  defined by three line segments to select galaxies
  at zgt0.75.
• We do not apply these color cuts in the EGS!

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DEEP2 slitmask spectroscopy
l
position
Using custom-milled slitmasks with DEIMOS we are
obtaining spectra of 150 targets at a time. A
total of 400 slitmasks will be required for the
survey we can tilt slits up to 30 degrees to
obtain rotation curves.
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Surveys of distant galaxies can constrain both
cosmology and galaxy evolution

• The evolution of large-scale structure is
  strongly dependent on the underlying cosmology.
• By comparing the universe at high redshift to
  what is seen by large local surveys such as SDSS,
  one can perform many unique cosmological tests
  and simultaneously study galaxy formation and
  evolution.

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Scientific Goals of the DEEP2 Galaxy Redshift
Survey

1. Characterize the properties of galaxies (colors,
   sizes, linewidths, luminosities, etc.) at z1 for
   comparison to z0
2. Study the clustering statistics (2- and 3-pt.
   correlations) of galaxies as a function of their
   properties, illuminating the nature of the galaxy
   bias
3. Determine N(s,z) of groups and clusters at high
   redshift, providing constraints on ?m and w
4. Measure the small-scale thermal motions of
   galaxies at z1, providing a mass scale for halo
   models (measuring ?m and bias, in the paradigm
   when DEEP2 was designed)

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DEEP2 has been made possible by DEIMOS, a new
instrument on Keck II
DEIMOS (PI Faber) and Keck provide a unique
combination of wide-field multiplexing (up to 160
slitlets over a 16x4 field), high resolution
(R5000), spectral range (2600 Å at highest
resolution), and collecting area.
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And HST ACS VI imaging finished last month!
Currently reduced mosaic
0.2 of the upcoming EGS dataset
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Finding groups in DEEP2

• We find groups using the locations of galaxies in
  redshift space - no photometric information is
  used, just the overdensity in the 3d galaxy
  distribution.

In particular, we are using the Voronoi-Delaunay
Method of Marinoni et al. (2002), which has been
optimized for use at high z and performs well.
(For our purposes, clusters are just especially
massive groups.)
Group in early DEEP2 data
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First DEEP2 Group Catalog
We currently have group catalogs for 3 fields
Gerke et al. 2005, astro-ph/0410721
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Galaxy Properties and Environment

• We measure galaxy environments using
  projected 3rd-nearest neighbor distance, shown to
  be near-optimal in Cooper et al. 2005
  (submitted). There are strong trends of galaxy
  density with restframe color and OII equivalent
  width (a proxy for star formation rate) the
  color trend can explain the OII one.

log density
blue color red
OII equivalent width (SFR)
Cooper et al. 2005
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Color vs. Equivalent Width of OII
Red galaxies have low OII equivalent width,
while blue galaxies span a wide range. It
appears that the scatter in this relation is most
likely not due to environment. We are currently
matching the DEEP2 colors and magnitudes to SDSS
to look for evolution in environmental dependence
between z1 and z0.
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Environment over the CMD
SDSS, z0.1
DEEP2, 0.75ltzlt1.05
redder
brighter

• Trends from z0 studies persist at z1 e.g.
  redder or brighter galaxies are preferentially
  found in dense environments.

Cooper et al. 2005