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Early Results from the DEEP2 Redshift Survey Benjamin Weiner (UCO/Lick Observatory) and the DEEP collaboration
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DEEP 2 Survey Team UC Berkeley: M. Davis, J. Newman, A. Coil, D. Madgwick, M. Cooper, B. Gerke, R. Yan, C. Conroy UC Santa Cruz: S. Faber, D. Koo, P. Guhathakurta, A. Phillips, C. Willmer, R. Schiavon, N. Konidaris Caltech: C. Steidel, R. Ellis, T.Treu, C. Conselice Others: N. Kaiser, G. Wirth, A. Connolly, D. Finkbeiner, G. Luppino, P. Eisenhardt
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DEEP : two redshift surveys Deep Extragalactic Evolutionary Probe DEEP 1: redshift survey in fields with deep HST WFPC2 imaging Keck/LRIS, 625 galaxy redshifts in Groth Strip DEEP 2: large scale survey targeting galaxy properties and clustering at z ~ 1 Keck/DEIMOS, goal 50,000 galaxy redshifts
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DEEP 2 : a redshift survey at z ~ 1 1 Hour Survey: 1 hour exposures 4 fields, 3.5 square degrees magnitude limit R(AB) < 24.1 65,000 targets, 50,000 galaxy redshifts most at 0.7<z<1.5 90 Keck nights over 3 years 3 Hour Survey: deeper exposures red (elliptical) galaxies probable z>1.5 galaxies - redshift failures from 1HS
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Redshift surveys: background Las Campanas Redshift Survey (Shectman et al 1996) Surveys probe distribution of galaxies Also provide samples to study galaxy properties
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DEEP2 compared to low- z surveys
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Studying galaxies at z=1 Universe half its current age, Galaxies are younger but still recognizable Spectral features accessible to optical telescopes HST IR/optical imaging corresponds to restframe red/blue from HST WFPC2 Groth Strip
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DEEP2 target selection Galaxies selected from CFHT 12K imaging, R(AB)<24.1 4 fields, each 0.5 x 2.0 deg (Groth Strip 0.25 x 2.0 deg) Color- cut selection in 3 fields selects z>0.7 galaxies; in Groth Strip we take everything. 2- pass and 4- pass mask coverage 200” x 200” from BRI CFHT images
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DEEP2 spectroscopy DEIMOS with 1200- line grating. 6500- 9200 A, covers [O II] 3727 doublet at 0.7<z<1.5 Distinctive feature: high resolution 1.0” slit, resolution 1.5 A FWHM, [O II] well resolved 60 km/sec FW at z=1, dispersion = 25 km/sec Can measure internal kinematics: rotation/dispersion, galaxy masses
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DEIMOS spectrograph at Keck II Nasmyth focus
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Inside DEIMOS
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Spectra from DEIMOS: lots of slits! One-half of one mask. Each has 120- 150 slits, average 5” long
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Reduced data through pipeline cleaned, combined, sky subtracted Pipeline developed from SDSS code (of Schlegel, Finkbeiner, Burles) by UC Berkeley group galaxy group, ~ 250 km/sec, at z~1
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Redshift measurement and verification Find candidate redshifts by automated chi-sq fit to a set of templates Need to be checked by humans: GUI shows 1- D and 2- D data
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Progress so far Instrument working well, pipeline in operation Both in use by other Keck users 190/480 masks observed, 40% complete 8,200 galaxy redshifts checked and in catalog
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Redshift, color and magnitude 2700 galaxies in Groth Strip Large scale structure walls Color bimodality - red/blue
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Photo- z color cut Redshifts from Groth Strip verify color cut works cleanly
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Redshift success and failure Most of failures are faint blue galaxies Most of these are presumably high z, z > 1.5
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Space distribution z=0.4 z=1.3
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Galaxy restframe color and luminosity Blue/red separation No faint red Brighter blue galaxies at high z Lose red galaxies to mag cutoff Extended Groth Strip
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Galaxy restframe color and luminosity All fields: lots more galaxies at z>0.7 All fields (8000 galaxies)
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Blue luminosity function Simplistic 1/Vmax on EGS data Evolution in blue galaxies at bright end? Real calculations forthcoming (Christopher Willmer et al)
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Red galaxies are the ones with bulges DEEP 1 galaxies with HST imaging (fits by L. Simard) Blue galaxies: mostly exponential Red galaxies: more concentrated
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Red bulges are bright at z < 1 DEEP 1 galaxies with HST imaging (fits by L. Simard) Blue galaxies: starforming, disky Red galaxies: brighter bulges
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COMBO- 17 photometric survey Large area, 17 filters, photo- z Color evolution in red sequence Mass buildup in red galaxies? Bell et al. 2003
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Color bimodality and evolution? L model Z model Which is consistent with color and luminosity evolution?
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Galaxy correlation functions Alison Coil et al. 2003 submitted Clustering measure quantified Red galaxies more clustered Starforming galaxies less clustered
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Rotation curves Michael Cooper (UC Berkeley)
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Integrated emission linewidths Fit lines to 1- D extracted spectrum Kinematic measurement even when spatially unresolved
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Linewidth- magnitude relation 3200 galaxies, z > 0.65 0.65<z<0.8: slope same as low- z, ZP offset Higher redshifts: zeropoint offset increases slope flattens Bright galaxies with low dispersions
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Color- magnitude relation At high z, bright galaxies had low dispersions relative to low z TF rel Yet bright galaxies are still redder - not pure starbursts Note selection limit in high z bin
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Color- linewidth residual Pretty flat but for highest z bin Redder objects are brighter, and/or have lower dispersion than predicted from TF
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[O II] line strength relations Equivalent width Absolute strength Both increase with redshift
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[O II] luminosity function Simple 1/Vmax weighting Signature of evolution at bright end
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Velocity function (baby steps) Like a luminosity function but counts number of objects of given dispersion Simple 1/Vmax weighting Suggestion of evolution at high mass end - fewer high dispersion galaxies at high redshift?
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Where we're going Catching up to current data, and more data coming including Palomar K-band photometry More studies of galaxy properties and environment Galaxy groups Cosmological models and tests - counting halos, groups Confronting galaxy evolution models Extended Groth Strip - SIRTF, Galex, X- ray and radio data
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