Results from the DEEP2 Redshift Survey

1
Results from the DEEP2 Redshift Survey
Cambridge, July 2004

• Jeffrey Newman
• for the DEEP2 Team

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The DEEP2 Collaboration

• Team Members
• U.C. Berkeley M. Davis (PI), A. Coil, M. Cooper,
  B. Gerke, R. Yan, C. Conroy
• 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
• U. Hawaii N. Kaiser, G. Luppino
• LBNL J. Newman, D. Madgwick
• U. Pitt. A. Connolly JPL P. Eisenhardt
• Princeton D. Finkbeiner Keck G. Wirth
• K survey (Caltech) K. Bundy, C. Conselice, R.
  Ellis, P. Eisenhardt

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Outline

• What is the DEEP2 Redshift Survey?
• Recent news
• (Some!) results from DEEP2
• Internal kinematics of galaxies
• Kinematics of satellites around galaxies
• Groups and clusters
• Galaxy and group correlations
• Galaxy properties vs. environment
• Luminosity functions
• KA galaxies

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DEEP2 in brief

• 4 Fields 14 17 52 30 (includes Groth Survey
  Strip), 16 52 34 55, 23 30 00
  00, and 02 30 00 00
• Field dimensions 30 by 120 (15 ? 120 for
  Groth field) 20x80x1300 h-1 Mpc comoving
• Primary Redshift Range z0.7-1.4, preselected
  using BRI photometry to eliminate galaxies with
  zlt0.7
• Spectroscopy 50,000 1-hour Keck/DEIMOS slitmask
  spectra of targets to a limit of RAB24.1 cover
  6600-9200Å in each spectrum with R5000
• High resolution allows us to split the OII
  doublet and obtain kinematic information for most
  targets

Keck access 80 nights of UC time over 3 years
(July 2002-July 2005) 50 of the way done
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DEEP2 versus local surveys
SDSS
2dFGRS
LCRS
DEEP2
z0
CFASSRS
PSCZ
z1
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DEEP2 vs. previous surveys of distant galaxies
Galaxies found in large numbers well beyond z1
Note z0.7 color cut
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Our color cuts are highly successful!

• By applying a relatively simple BRI color cut,
  we have a sample that is 13 zlt0.75, vs. gt60
  with no cut.
• Only 3 of objects that we reject are at zgt0.75
  (5 are at gt0.7).
• In the Extended Groth Strip, we apply no color
  cut, enhancing multiwavelength studies and also
  making this test possible.

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Coordinated observations ofthe Extended Groth
Strip
Spitzer MIPS, IRAC
Background 2 x 2 deg from POSS
DEEP2 spectra and Caltech / JPL Ks imaging
DEEP2/CFHT B,R,I
Plus VLA (6 21 cm), SCUBA, etc.
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Observing conditions this spring have been
frustrating
The CFHT dome as seen from Gemini
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So weve had to also look elsewhere for
inspiration

• 126 Cycle 13 HST orbits allocated for a 2-color
  (VI) Advanced Camera for Surveys mosaic in EGS
  (already under way!)
• Deep Spitzer IRAC and MIPS observations in EGS
  were completed in June
• 1.4 Msec of Chandra time awarded for an ACIS
  mosaic of the full 15x2 degree DEEP2 Groth Strip
  field

Great Observatories
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Coordinated observations of the Extended Groth
Strip, updated
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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Spitzer/IRAC imaging in EGS
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HST/ACS imaging in EGS
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For some objects, we obtain spatially-resolved
kinematics - i.e., rotation curves
Cooper et al. 2005
Four 2-d spectra showing resolved, tilted OII
emission, and derived circular velocity Vc(r).
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Synergies in the Extended Groth Strip
The combination of data available in the EGS will
make a wide variety of new projects possible
e.g. Spitzer/IRAC will allow us to measure
stellar masses of DEEP2 galaxies, GALEX
Spitzer/MIPS will measure star formation rates,
etc. The only way to identify these galaxies
morphologies is via HST we have applied for time
in the new cycle.
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For most of the others, we can measure integrated
linewidths
Fit lines to 1- D extracted spectrum. Kinematic
measurement even when spatially unresolved
Altogether we measure linewidths for 80 of all
blue galaxies
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DEEP2 Tully-Fisher relation Season 1
Based on 3200 galaxies with zgt 0.65 Some
evidence for evolution in slope zero point from
z0.4 need HST imaging to check inclination
effects and throw out irregular/merging objects.
Weiner et al. 2004
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Velocity dispersions of satellite galaxies
We can explore the potential wells of isolated
galaxies to larger radii using the relative
velocities of their faint neighbors (cf. Zaritsky
1993, Prada et al. 2003). Measure halo velocity
dispersion of 140?20 km/s, or an NFW halo mass
of 5.5 ? 2 ?1012 Msun. Matches SDSS for same
mags. rel. to L (5.4?1). Provides a test for
galaxy-halo assignment in simulations,etc.
NFW fit
Conroy et al. 2004
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Galaxy Groups and Clusters in DEEP2
redpairs blueNgt2 size?log (?) ? log (halo
mass)
We have used Voronoi-based methods optimized with
mock DEEP2 catalogs to identify clusters and
groups of galaxies (cf. Marinoni et al. 2002, Yan
et al. 2003).
Gerke et al. 2004
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Kinematics in Groups

• In those tests, groups are found reliably down
  to velocity dispersion ?400 km/s . Observed
  abundances of groups as a function of ?, z can
  constrain dark energy models, much like
  abundances as a function of X-ray TX /LX .

DEEP2 measurements (points with error bars) and
LCDM mock catalogs (line blue shaded region)
agree very well!
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Two-point correlations x(rp,p)
entire redshift range
two redshift sub-samples
line-of-sight separation
lt1 pointing, 5 of final sample!
transverse separation
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Projected correlation function
Summing x(rp,p) along line-of-sight yields
wp(rp) can recover the real-space correlation
fctn. if assume x(r) (r0/r)g Redder/absorption-do
minated galaxies exhibit much stronger
correlations, as also is seen at lower redshifts.
The difference in clustering strength is
significant even with r0/g covariance. The DEEP2
sample as a whole is not strongly biased compared
to the dark matter (assuming LCDM) r0 3.5
0.8 CHIMP g 1.65 /- 0.1 b 1 0.2
Coil et al. 2004, in press (astro-ph/0305586)
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Now looking at group correlations
Group-group correlation function
Galaxy-galaxy correlation fit
Coil et al. 2004b
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Galaxy properties and environment

• Spectroscopic redshifts allow us to determine
  the environments galaxies reside in e.g. by
  dividing into cluster vs. field populations or
  using continuous measures like projected
  Nth-nearest neighbor distance.

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Galaxy properties and environment

• Trends from z0 studies persist at z1 redder
  galaxies are found in denser environments.
• (note ?3 is the projected 3rd-nearest-neighbor
  distance over a 1000 km/s redshift interval,
  turned into surface density)

Gerke et al. 2004
Cooper et al. 2005
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Little trend with luminosity

• As seen by Hogg et al. (2002) at z0, any trends
  as a function of luminosity are much weaker,
  except at the brightest magnitudes where DEEP2
  has too little volume for robust results.

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Strong trend with OII EW

• OII equivalent widths correlate with
  environment as strongly as rest-frame color. In
  EGS, we can compare and cross-calibrate multiple
  SFR indicators (OII flux, UV continuum, MIPS
  mid-IR flux, etc.) for integrated studies of SFR
  vs. environment.

Cooper et al. 2005
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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. 2004
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DEEP2 and COMBO-17 agree well on Luminosity
functions to z 1.2

• Red galaxies M brightens by about 1.6 mag to
  z 1, but number density is lower.
• Blue galaxies M brightens by about 0.8 mag to
  z 1, number density is constant.

Bell et al. 2004, Willmer et al. 2004
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Some galaxies are neitherred and dead nor blue
and forming stars
It remains unclear exactly how galaxies evolve
towards the red sequence. Some clues may come
from KA galaxies, transitional objects that
have no ongoing star formation (measured from
emission line strengths), but still contain
young, A-star like stellar populations. DEEP2
will find hundreds of them.
Thin Black DEIMOS spectrum (minus
continuum) Blue A-star component fit Red K-star
component fit Green Emission-line fit Thick
Black combined fit
Yan et al. 2004
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Conclusions

• The DEEP2 Redshift Survey is more than halfway
  done. We have gt25,000 high-resolution spectra,
  most of them for galaxies with zgt0.7.
• The Extended Groth Strip will be a unique
  Northern field for its combination of deep
  multiwavelength data over a wide area (compare to
  CDF-S/GEMS in the South). We intend to produce a
  public archive combining all datasets - more
  observations there are very welcome!
• There is more going on (especially on galaxy
  properties and evolution) than I could talk about
  in so little time.

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Update on Marc Davis...

• Marc suffered a stroke one year ago his
  recovery and rehabilitation is ongoing, but he is
  back at work every day, and is now going to some
  conferences, giving talks, etc.
• Hes at the workshop in Aspen now

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CFHT BRI photometry is quite effective for
selecting objects with zgt0.7

• Plotted at right are the trajectories galaxies
  observed at z0 would take in our color-color
  space as a function of redshift. Diamonds are
  plotted every 0.2 in z the transition from zlt0.7
  to zgt0.7 is marked by the change from dotted to
  solid lines.
• A simple curve (nearly parallel to the
  reddening vector) can be used to distinguish
  low-redshift from high-redshift objects. If we
  do not apply such a color cut, half the galaxies
  we observe would be at zlt0.7 (and our sample
  would be much more dilute as a result).

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Advantages of a high-dispersion survey
Blue curve fraction of sky flux in a 100 Å
window coming from sky lines (as opposed to
continuum) Red curve fraction of pixels in that
same window that are on sky lines, for a 1200
l/mm grating. Most pixels have low background
effective OH suppression
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Advantages of a high-dispersion survey
The high resolution used for DEEP2 observations
yields well-resolved linewidths for all objects,
and rotation curves as a free byproduct for
thousands. Shown are four 2d spectra exhibiting
resolved OII emission and the derived circular
velocity Vc(r).
36
Coordinated observations ofthe Extended Groth
Strip
MIPS, IRAC (Deep)
Background 2 x 2 deg from POSS
MIPS, IRAC (Med)
DEEP2/DEIMOS Spectra
DEEP2/CFHT B,R,I
WFPC2/Groth V,I
SCUBA
In this field, we will
XMM Chandra
- apply no zgt0.7 color cut
- survey half the area, but with
twice the mask density of other fields
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What to remember about the DEEP2 sample

• 1) In all fields but EGS, zlt0.7 galaxies are
  excluded by our preselection effectively. We
  will need to investigate what types of objects we
  miss in more detail (mostly just mag. errors?).
• 2) The sample is magnitude-limited in CFHT RAB.
  This corresponds to restframe 4000 Å at z0.7,
  2800 Å by z1.4 .
• 3) Even the brightest galaxies with red
  rest-frame U-B will go past the magnitude limit
  at zgt1.1-1.2 .
• 4) We observe only 70 of possible targets due
  to slitmask-making constraints (spectra cannot be
  allowed to overlap on the detector). Even with
  adaptive tiling, 3 slitlets, etc., we do worse
  than this in dense regions.

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Testing our BRI color selection

• We now have thousands of redshifts in the
  Extended Groth strip, for which we attempt to
  observe targets regardless of their color. This
  allows us to test the impact of our target
  selection (which was tuned based on 300 zs) on
  the survey.

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What is left to be done after WMAP?

• Standard paradigm contains
• Dark matter ?m 0.27-0.07
• Dark energy 70
• Spectral index ns 0.99-0.04
• Equation of state parameter for DE wlt-0.8
• Unfinished business
• What is the meaning of such a mixture?
• Formation history of galaxies and clusters
• Better constraints, possible evolution of w

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Survey strategy imaging

• We have obtained deep CFHT 12k imaging in three
  bands (BRI) to allow photometric pre-selection of
  targets with zgt0.7 otherwise, the majority of
  objects observed would be at lower z. The
  imaging is complete and fully reduced.

A 200? ? 200? BRI image from one of our fields
Photo-z preselection of targets
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Slitmask spectroscopy
Using custom-milled slitmasks with DEIMOS we are
obtaining spectra of 120 targets at a time. A
total of 480 slitmasks will be required for the
survey we can tilt slits up to 30 degrees to
obtain rotation curves.
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Scientific Goals of the DEEP2 Redshift Survey

• 1) Characterize the properties of galaxies
  (colors, sizes, linewidths, luminosities, etc.)
  at z1 for comparison to z0 samples
• 2) Study the clustering statistics (2- and
  3-point correlations) of galaxies as a function
  of their properties, illuminating the nature of
  the galaxy bias
• 3) Measure the small-scale thermal motions of
  galaxies at z1, providing a measure of ?m and
  galaxy bias
• 4) Determine the apparent velocity functions of
  galaxies and clusters at high redshift, providing
  constraints on fundamental cosmological
  parameters such as wP/?DE

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First spectroscopy of DEEP2 masks

• Each slitmask has 120 objects over an 8k x8k
  array. The average slit length is 5 with a gap
  of 0.5 between slits. We tilt slits up to 30
  degrees to trace the long axis of a galaxy.

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DEIMOS reduced data
Right A small percentage of one mask an OII
playground!
Left We will obtain thousands of well-resolved
rotation curves
Below Analysis of a tilted slitlet reduced data
above, raw data below. We routinely achieve
Poisson-limited sky subtraction in most cases.
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A fully automated reduction pipeline
SDSS spectral pipeline code by Schlegel et al.
allowed us to rapidly develop a full 2d and 1d
spectral reduction pipeline that is completely
automated
A few percent of one DEEP2 mask, rectified,
flat-fielded, CR cleaned, wavelength-rectified,
and sky subtracted. Note the resolved OII
doublets. Shown is a small group of galaxies
with velocity dispersion ? ? 250 km/s at z?1.
Note the clean residuals of sky lines!
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Status of the DEEP2 Survey

• DEIMOS commissioning began June 2002 under clear
  skies and was extremely successful.
• DEEP2 observing campaign began in July 2002. At
  the end of 3 semesters of the 6 planned, we have
  completed 48 of the survey slitmasks (plus 8
  masks for KTRS)!
• Observations complete mid 2005 (we hope)
• Analysis complete late 2006

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Early results and current work include

• Spectroscopic classification of galaxies at z1
  (Madgwick et al., accepted)
• The dependence of clustering (?) on galaxy
  properties
• (Coil et al., submitted)
• Mock catalogs for DEEP2 (Yan et al., submitted
  Yan et al., in prep)
• Detection and membership determination for
  clusters and groups of galaxies (Gerke et al., in
  prep)
• Satellite galaxy dynamics (Conroy et al., in
  prep)
• Luminosity function evolution (Willmer et al., in
  prep)

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Early results and current work include

• Resolved kinematics of galaxies (Cooper et al.,
  in prep)
• The dependence of galaxy properties on
  environment (Cooper/Gerke/Madgwick et al., in
  prep)
• Unresolved kinematics of galaxies linewidths
  (Weiner et al., in prep)
• Stellar populations in red galaxies (Schiavon et
  al., in prep)
• Angular correlations in the DEEP2 photometric
  sample (Coil et al., in prep)
• OII emission in red galaxies (Konidaris et al.,
  in prep)

And many more to come!!!
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Principal Component Analysis (PCA)
PCA allows us to define a minimum set of
eigenspectra that span most of the variance in
our sample. The most influential component
primarily quantifies the strength of OII 3727.

Madgwick et al. 2003 astro-ph/0305587
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PCA for classification
The strength of the first PCA eigenvalue alone
provides an effective means for determining
spectral types of galaxies, as seen in the
stacked spectra of galaxies split according to
this value.
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Galaxy colors can also be used for
classification...
PCA allows us to classify galaxies based upon
their spectra however, we can also use our BRI
photometry, along with redshift, to derive
rest-frame broadband colors. Like at z0, the
distinction between early and late types is
readily apparent.
Weiner et al. 2003, Willmer et al. 2003
52
Clustering in DEEP2 First Redshift Maps
Projected maps of two DEEP2 pointings (of 13
total). Red early-type (from PCA).
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2-point correlation function x(r)
x(r) measures the excess probability above random
of finding a galaxy in a volume dV at a distance
of r from a randomly chosen galaxy dPn dV
(1x(r) ) where n is the mean number density of
galaxies. x(r) measures the clustering in the
galaxy distribution. x(r) is known to follow a
power-law prescription locally x(r) (r0/r)g
with r05 Mpc/h and g1.8. r0 scale where the
probability of finding a galaxy pair is 2x
random In the DEEP2 survey we measure galaxy
clustering as a function of redshift, color,
spectral type and luminosity!
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DEEP2 Faint Galaxy Redshift Survey

• Details, Scientific Goals of DEEP2
• Highlights of DEIMOS spectrograph
• Survey Status and Data Pipeline
• Science Topics in Progress

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Dependence of galaxy properties on environment
The Voronoi volume of a galaxy is the amount of
space that is closer to that galaxy than any
other it provides a parameter-free measure of
the inverse number density of galaxies about any
object (cf. Marinoni et al. 2002). High z
resolution is required.
We can use this measure to study how galaxy
properties such as LF, color, spectral type, and
linewidth vary with environment in the DEEP2
sample (and compare with local surveys). For
instance, PCA emission-line galaxies are
preferentially found in low-density regions
Voronoi partition in 2 dimensions
Gerke et al., Cooper et al., in prep
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Galaxy Groups and Clusters in DEEP2
Voronoi-based methods can also be used to
identify clusters and groups of galaxies
(Marinoni et al. 2002). We are currently
optimizing such techniques with mock catalogs,
and have begun producing DEEP2 group
catalogs. This will allow both the study of
group property distributions and of group vs.
field galaxies.
redabsorption-dominated
redpairs blueNgt2 size?log (?) ? log (halo
mass)
Gerke et al. 2004, in prep
57
DEEP2 and other Surveys

• DEEP2 fields are magnets for panchromatic study
  of galaxies, groups and clusters
• Comparison of groups found to Sunyaev-Zeldovich
  field survey maps
• Comparison to X-ray maps (Chandra proposal
  submitted)
• Comparison to weak-lensing mass maps
• Deep SIRTF imaging in 7 IR bands, as well as
  GALEX imaging in the UV.
• HST/ACS imaging, eventually
• Integrated picture of galaxies and clusters to
  z1.5 should allow us to test for the sorts of
  systematic effects that may already dwarf
  statistical uncertainties.

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DEEP2 Conclusions

• DEIMOS observations began last July 5!
• DEEP2, in combination with local surveys (e.g.
  2dF, SDSS), will provide a variety of constraints
  
• Galaxy formation and evolution
• Galaxy clustering
• Measurements of cosmological parameters
• All spectra and results to be made public in
  timely fashion

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Using DEEP2 for Cosmological TestsComoving
volume vs Redshift
Green different equation of state values wP/?
for ?m0.3 Volume varies by a factor of 3 at
Z1!! Not a small effect.
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Update on Marc Davis...

• Marc suffered a stroke in late June his recovery
  and rehabilitation is ongoing, at his home.
• He is now visiting campus, attending team
  meetings, reading email, etc. His participation
  increases every week, but the top priority for
  now remains rehab.