Texas A&M, May 2007 The Growth of LSS in a Dark Energy Dominated Universe Marc Davis UC Berkeley

The DEEP2 Collaboration U.C. Berkeley M. Davis (PI) D. Croton M. Cooper B. Gerke R. Yan U.C. Santa Cruz S. Faber (Co-PI) D. Koo P. Guhathakurta U.C. Santa Cruz D. Phillips S. Kassin K. Noeske A. Metevier L. Lin N. Konidaris G. Graves J. Harker Other Institutions J. Newman (LBNL) A. Coil (Arizona) C. Willmer (Arizona) B. Weiner (Arizona) R. Schiavon (UVA) C. Conroy (Princeton) N. Kaiser (Hawaii ) D. Finkbeiner (Harvard) A. Connolly (Pitt.) The DEEP2 Galaxy Redshift Survey used the DEIMOS spectrograph at the Keck II telescope to study both galaxy properties and large-scale structure at z~1.

Texas A&M, May 2007 DEEP2 has been made possible by DEIMOS, a new instrument on Keck II DEIMOS: PI: Faber wide-field multiplexing (up to 160 slitlets over a 16’x4’ field) high resolution (R~5000) spectral range (~2600 Å at highest resolution) CCD array of 8k x 8k

Texas A&M, May 2007 DEEP2 pre-selects high-z galaxies using observed colors

DEEP2 mask selection Targeted galaxies are enclosed with white curves Solid slits are objects selected on a given mask. dotted and dashed lines are galaxies from neighboring masks.

Texas A&M, May 2007 DEEP2 slitmask spectroscopy Using custom-milled slitmasks with DEIMOS we obtained spectra of ~150 targets at a time. A total of 400 slitmasks was required for the survey; we tilted slits up to 30 degrees to obtain rotation curves. position

Texas A&M, May 2007 AEGIS: the All-wavelength Extended Groth Strip International Survey Spitzer MIPS, IRAC DEEP2 spectra and Caltech/JPL K s imaging HST/ACS V,I (Cycle 13) DEEP2/CFHT B,R,I GALEX NUV+FUV Chandra & XMM: XMM Chandra (1.6Ms) Plus VLA (6 & 21 cm), SCUBA, etc….

Texas A&M, May 2007 X-ray analysis - detection and photometry P.Nandra et al. Each square has integration time of 200 ksec Source selection and photometry by own method –Elliptical shaped PSFs All data will be released in August, Ms

Texas A&M, May 2007 Comparison with Other Surveys z~0 z~1 DEEP2 SDSS 2dF CFA+ SSRS LCRS PSCZ DEEP2 -- comparable in size and density to previous generation local redshift surveys >50 times larger than previous surveys at z~ DEEP2 is similar to LCRS in sample size but at z=1 - with a very different geometry: ~20  80  1000 h -3 Mpc 3 per field (LCDM)

Texas A&M, May 2007 A Redshift Survey at z=1: 3 sq. degrees 4 fields (0.5 o x <2 o ) 80 Keck nights, one-hour exposures to R AB =24.1 primarily z~ ( pre-selected using BRI photometry ) 46,585 unique redshifts, error ~30 km/s ~5·10 6 h -3 Mpc l/mm: ~ Å 1.0” slit: FWHM  68 km/s z= spans lookback time ~ 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

Texas A&M, May 2007 Redshift Distribution of DEEP2 Survey

Texas A&M, May 2007 DEEP2 Status Update DEEP2 began observations in July Observations are now >95% finished, with >49k spectra in hand and 3 of 4 fields completed. Follow-up observations have begun. First season’s data is already public: Next data release (DR2) includes ~75% of the data and has also been released!

Texas A&M, May 2007 Redshift Maps in 4 Fields: z= Cone diagram of 1/12 of the full DEEP2 sample

Texas A&M, May 2007 Galaxy groups in DEEP2, z position Overdensities identified in redshift space. Use the VDM algorithm of Marinoni et al. (2002). Group in early DEEP2 data s~250 km/sec

Texas A&M, May 2007 DEEP2 Group Catalog Gerke et al. 2005, astro-ph/ Shown are groups for 3 fields --length of ellipse proportional to velocity dispersion Groups with  >350 km/s

Looking for DEEP2 groups in the X-ray 200 ks Chandra observation in the Extended Groth Strip (1/8 of total coverage), with positions of 7 DEEP2 groups superimposed (2 300 km/s) T. Fang et al, 2006, in press

Texas A&M, May 2007 Real Groups/Mock Groups x-r redshift plot y-r redshift plot X-y projected on sky galaxies shown in 3 projections Real or Mock???

Why search for groups in DEEP2? Apparent abundance of groups: dN( ,z)/dzd  Provides a useful test of dark energy eq. of state (Newman et al, 2002) differences in the volume element varies by 3x between w=0 and w=-1 For groups of modest-mass, the evolution of dispersion is 2nd order Heavy black curve is  T =.3 DEIMOS took ~7 years to build; at time of designing science expt.  T was still undetermined, and DE was not discussed.

Size of the Universe versus w

Abundance versus Redshift Simulated Data!!

Measured dispersion with galaxies compared to reality -- tremendous scatter!

Texas A&M, May 2007 Dispersion with galaxies

Texas A&M, May 2007 Constraints expected on parameters w,  8,  m

DEEP2 Cluster Counts DEEP2 survey counted ~300 groups Velocity dispersion measured in each case Counts of N( , z) is a strong test of w B. Gerke will have results out “soon”

Texas A&M, May 2007 DEEP2 observations are >96% done DR2 has occurred in January: AEGIS ApJL special issue Way too many new results to cover in one talk! Conclusions on DEEP2

Texas A&M, May 2007 We are beginning to measure w… Gerke et al Constraints of 314 groups Plot does not use redshift information Furthermore, we are still checking systematics!!

Texas A&M, May 2007 Velocity bias and N(  ) A degenerate parameter is the “velocity bias”, b v. (factor by which the velocity dispersion of galaxies in a cluster differs from the dark matter dispersion. Some simulations currently favor b v =1.1, others 0.9.) Degeneracy between: b v ~1.1  M ~0.4  8 ~1 w ~-1.25.

Dependence on systematics Systematic errors predominantly affect the constraints in the w direction, which is primarily driven by DEEP2 group abundances. SDSS groups can still provide strong constraints in the  m direction (assuming  8 is known), as there errors are small enough that the shape of the velocity function is providing significant constraints.

What if we had 20x as much area? Future baryonic- oscillation surveys could be used to make this same measurement if they are densely sampled. A 60 square degree survey could yield tight constraints on w - IF systematics are well- constrained.

Texas A&M, May 2007 By combining area with depth, AEGIS allows us to study rare objects in detail… B. Gerke, JN et al. 2006, AEGIS ApJL, Accepted

Texas A&M, May 2007 Like a spectroscopically identified, dual AGN at z=0.7 HH [OIII] 4959 [OIII] 5007 / z position

Texas A&M, May 2007 HST reveals a fairly-normal early-type host

Texas A&M, May 2007 AEGIS gives its SED over 9 decades in