DEEP2 Galaxy Redshift Survey
and
Post-Starburst galaxies at z~1
Renbin Yan
University of California, Berkeley
And
The DEEP2 Team
Lijiang - August, 2005
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 z=1.
U.C. Berkeley
U.C. Santa Cruz
JPL
M. Davis (PI)
A. Coil
M. Cooper
B. Gerke
R. Yan
C. Conroy
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
P. Eisenhardt
LBNL
J. Newman
U. Hawaii
N. Kaiser
Princeton
D. Finkbeiner
U. Pitt.
A. Connolly
K survey (Caltech)
K. Bundy
C. Conselice
R. Ellis
Comparison with Other Surveys
DEEP2 was designed to have comparable size and density to
previous generation local redshift surveys and is
>50 times larger than previous surveys at z~0.3-1.
DEEP2 is similar
to LCRS in sample
size but at z=1 with a very
different
geometry:
1.00E+06
Number of Galaxies
SDSS
2dF
1.00E+05
LCRS
DEEP2
1.00E+04
1.00E+03
1.00E+05
CFA+
SSRS
z~0
z~1
PSCZ
1.00E+06
1.00E+07
Volume (h -3 Mpc3)
1.00E+08
~20801000 h-3
Mpc3 per field
(LCDM)
Lijiang - August, 2005
A Redshift Survey at z=1:
Studying Evolution:
•Age of the Universe = 13.7 Gyr
• z=0.7 - ~6.0 Gyr ago
• z=1.0 - ~7.5 Gyr ago
• z=1.4 - ~8.5 Gyr ago
Observational details:
• 3 sq. degrees
• 4 fields (0.5o x <2o)
• primary z~0.75-1.4 (preselected using BRI photometry)
• >40,000 redshifts
• ~5·106 h-3 Mpc3
Within DEEP2 we are surveying
• 80 Keck nights
2.5 Gyr or ~20% of the history
• One-hour exposures
of the Universe, and SDSS/2dF
comparisons give ~3x this baseline • RAB=24.1
• 1200 l/mm: ~6500-9200 Å
• 1.0” slit: FWHM 68 km/s
Lijiang - August, 2005
Coordinated observations of
the Extended Groth Strip (EGS)
Background: 2 x 2 deg
from POSS
Spitzer MIPS, IRAC
DEEP2 spectra
and Caltech / JPL
Ks imaging
HST/ACS
V,I (Cycle 13)
DEEP2/CFHT
B,R,I
GALEX NUV+FUV
Chandra & XMM:
Past coverage
Awarded (1.4Ms)
Plus VLA (6 & 21
cm), SCUBA, etc….
Lijiang - August, 2005
Redshift Distribution of Data: z~0.7-1.4
Our color cuts are very
successful! ~90% of our
targets are at z>0.75 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
>75% done (will complete
in S06)
Lijiang - August, 2005
Redshift Maps in 4 Fields: z=0.7-1.2
Cone diagram of 1/12 of the full DEEP2 sample
Lijiang - August, 2005
DEEP2 sees the same color bi-modality as
SDSS, COMBO-17, etc. to z~1.4
Our R-band magnitude limit corresponds to ~4000Å rest-frame at
z=0.7, ~2800 Å at z=1.4 . As redshift increases, red galaxies of a
given luminosity fall out before blue ones.
Willmer et al. 2005
Lijiang - August, 2005
Post-Starburst Galaxies (E+A or K+A)
Post-starburst galaxies
show little on-going starformation (lack of
emission lines) but strong
Balmer absorption
features due to recent starformation (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.
Lijiang - August, 2005
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.
Lijiang - August, 2005
The Selection of E+A 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)
Lijiang - August, 2005
Color of Post-Starburst Galaxies
These galaxies populate
the ‘gap’ in the color bimodality 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.
Lijiang - August, 2005
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 semester’s data is now public:
http://deep.berkeley.edu/DR1
Lijiang - August, 2005
Poster: AGN Origin of [O II] in Red Galaxies
--- Implications for post-starburst galaxy studies
Conclusions
1) Galaxies display bimodality in [O II]/Hα 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 Hα
often exhibit significant [O II] EW; their position in [O II]-Hα 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.
Lijiang - August, 2005
Thank You
Lijiang - August, 2005
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
z>0.75.
•We do not apply these
color cuts in the EGS!
Lijiang - August, 2005
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.
Lijiang - August, 2005
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.
Lijiang - August, 2005
Scientific Goals of the
DEEP2 Galaxy Redshift Survey
1. Characterize the properties of galaxies (colors, sizes,
linewidths, luminosities, etc.) at z~1 for comparison to z~0
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 z~1,
providing a mass scale for halo models (measuring m and bias,
in the paradigm when DEEP2 was designed)
Lijiang - August, 2005
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
16’x4’ field), high
resolution (R~5000),
spectral range
(~2600 Å at highest
resolution), and
collecting area.
Lijiang - August, 2005
And HST ACS VI imaging finished last
month!
Currently reduced mosaic
0.2% of the upcoming EGS dataset
Lijiang - August, 2005
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.
position
l
Group in early DEEP2 data
In particular, we are
using the VoronoiDelaunay 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.)
Lijiang - August, 2005
First DEEP2 Group Catalog
We currently have group catalogs for 3 fields
Gerke et al. 2005, astro-ph/0410721
Lijiang - August, 2005
Galaxy Properties and Environment
log density
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.
color red
Cooper et al. 2005
blue
[OII] equivalent width (SFR)
Lijiang - August, 2005
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 z=1 and z=0.
Lijiang - August, 2005
Environment over the CMD
SDSS, z~0.1
DEEP2, 0.75<z<1.05
redder
brighter
Trends from z~0 studies persist at z~1: e.g. redder or brighter
galaxies are preferentially found in dense environments.
Cooper et al. 2005
Lijiang - August, 2005