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Science-Technology

Published on August 29, 2007

Author: Breezy

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Target Selection for the DEEP2 Redshift Survey:  Target Selection for the DEEP2 Redshift Survey Jeffrey Newman for the DEEP2 Team Atlanta, Jan. 2003 The DEEP2 Collaboration:  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 Scientific Goals of the DEEP2 Redshift Survey:  Scientific Goals of the DEEP2 Redshift Survey 1) Characterize the properties of galaxies (colors, sizes, linewidths, luminosities, etc.) at z~1 for comparison to z~0 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 z~1, 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 w=P/ρDE DEEP2 in brief:  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: z=0.7-1.4, preselected using BRI photometry to eliminate galaxies with zandlt;0.7 (otherwise would make up 60% of the sample) Spectroscopy: ~60,000 1-hour, R~5000 DEIMOS slitmask spectra of targets to a limit of RAB=24.1 High resolution allows us to split the O[II] doublet and obtain kinematic information for a large fraction of targets Keck access: 80 nights of UC time over 3 years andgt;45% of the way done!!! Comparison between DEEP2 and local surveys:  Comparison between DEEP2 and local surveys CFA+SSRS PSCZ LCRS DEEP2 2dFGRS SDSS z~0 z~1 DEEP2 vs. previous surveys of distant galaxies :  DEEP2 vs. previous surveys of distant galaxies Galaxies found in large numbers well beyond z = 1 Testing our BRI color selection:  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 z’s) on the survey. Our cuts are highly successful!:  Our cuts are highly successful! By applying a relatively simple BRI color cut, we have a sample that is 13% zandlt;0.75, vs. andgt;60% with no cut; whereas only 3% of objects that were rejected are at zandgt;0.75 (5% andgt;0.7). What to remember about the DEEP2 sample::  What to remember about the DEEP2 sample: 1) In all fields but EGS, zandlt;0.7 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 z=0.7, 2800 Å by z=1.4 . 3) Even the brightest galaxies with red rest-frame U-B will go past the magnitude limit at zandgt;~1.1-1.2 . 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. DEEP2 Color-magnitude diagrams vs redshift:  DEEP2 Color-magnitude diagrams vs redshift 1.0-1.2 0.8-1.0 andlt; 1.2 0.65-0.8 Weiner et al. 2003, Willmer et al. 2003 Faint red galaxies are missing; seen also in local samples Update on Marc Davis...:  Update on Marc Davis... Marc suffered a stroke in late June; his recovery and rehabilitation is ongoing, and will continue through much of this year. He is now visiting campus most afternoons, attending team meetings, reading email, etc. His participation increases every week, but the top priority for now remains rehab. Redshift Distribution of Current Data:  Redshift Distribution of Current Data We are currently measuring redshifts for ~80% of targets in one hour of spectroscopy. Many DEEP2 failures are at zandgt;1.5 . Color cut is working very well! CFHT BRI photometry is quite effective for selecting objects with z>0.7:  CFHT BRI photometry is quite effective for selecting objects with zandgt;0.7 Plotted at right are the trajectories galaxies observed at z=0 would take in our color-color space as a function of redshift. Diamonds are plotted every 0.2 in z; the transition from zandlt;0.7 to zandgt;0.7 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 zandlt;0.7 (and our sample would be much more dilute as a result). Advantages of a high-dispersion survey:  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 Advantages of a high-dispersion survey:  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). Coordinated observations ofthe Extended Groth Strip:  Coordinated observations of the Extended Groth Strip MIPS, IRAC (Deep) MIPS, IRAC (Med) DEEP2/DEIMOS Spectra DEEP2/CFHT B,R,I WFPC2/Groth V,I SCUBA XMM andamp; Chandra Background: 2 x 2 deg from POSS In this field, we will: - apply no zandgt;0.7 color cut - survey half the area, but with twice the mask density of other fields DEEP2 has been made possible by DEIMOS, a new instrument on Keck II:  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. We are assembling detailed portraits of the local Universe – but how did it reach its current state?:  We are assembling detailed portraits of the local Universe – but how did it reach its current state? The DEEP2 Faint Galaxy Redshift Survey has been designed to answer these questions by studying both galaxies and large-scale structure at z~1 in detail for comparison to the present-day Universe. In this way, we can see cosmic evolution in action. Redshift Surveys have been vital to our understanding of the Universe:  Redshift Surveys have been vital to our understanding of the Universe The original CfA Survey (~2,000 redshifts, 25/clear night) revealed the filamentary nature of the galaxy distribution, motivating some of the first numerical simulations of LSS Surveys more than 100 times as large have been completed since (e.g. 2dFGRS) or are underway (SDSS). These new surveys provide strong constraints on statistics of the local (z andlt; 0.2) galaxy distribution, of great interest for testing cosmological models Large surveys also allow measurements of the distributions of galaxy properties (e.g. luminosity function, velocity function, stellar mass function), in addition to correlations amongst properties of individual objects DEEP2 in Summary:  DEEP2 in Summary 3.5 sq. degrees in 4 fields surveyed 60,000 targets, selected based on BRI photometry to have zandgt;0.7 andgt;50,000 redshifts ~6·106 h-3 Mpc3 One-hour exposures RAB  24.1 mag R~5000 slitmask spectra: linewidths for  70%, spatially-resolved kinematics in andgt;20% Keck access: 80 nights of UC time over 3 years Observing season: April-October Surveys of distant galaxies can constrain both galaxy formation and cosmology...:  Surveys of distant galaxies can constrain both galaxy formation and cosmology... The evolution of large-scale structure depends strongly on the underlying cosmology. By comparing the universe at high redshift to what is seen locally, many unique cosmological tests can be performed; while simultaneously the evolution of galaxies may be studied! What is left to be done after WMAP?:  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: wandlt;-0.8 Unfinished business: What is the meaning of such a mixture? Formation history of galaxies and clusters Better constraints, possible evolution of w Survey strategy: imaging:  Survey strategy: imaging We have obtained deep CFHT 12k imaging in three bands (BRI) to allow photometric pre-selection of targets with zandgt;0.7; 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 Slitmask spectroscopy:  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. Masks tiled across a 42’x28’ CFHT pointing:  Masks tiled across a 42’x28’ CFHT pointing Multipass target selection:  Multipass target selection On a given mask, we cannot allow spectra from different objects to overlap - so tend to undersample dense regions (like clusters!) To ameliorate this, we overlap successive masks on the sky with an adaptive tiling, giving galaxies excluded by neighbors extra chances to be observed in secondary passes In the figure to right, the first-pass region of each mask is drawn, and the objects are color-coded by mask. Most objects on each mask are in its primary region, but a few may be found outside. ~70% of all selected objects observed Slide27:  Slit masks are curved to match the focal plane and imaged onto an array of 8 2k4k MIT-LL CCDs Readout time for full array (150 MB!) is 40 seconds (16 amplifier mode) DEIMOS slit masks and detector First spectroscopy of DEEP2 masks:  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. DEIMOS reduced data:  Below: Analysis of a tilted slitlet; reduced data above, raw data below. We routinely achieve Poisson-limited sky subtraction in most cases. DEIMOS reduced data Left: We will obtain thousands of well-resolved rotation curves Right: A small percentage of one mask: an [OII] playground! A fully automated reduction pipeline :  A fully automated reduction pipeline 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! 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 Status of the DEEP2 Survey:  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 Early results and current work include::  Early results and current work include: Spectroscopic classification of galaxies at z~1 (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) Early results and current work include::  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) O[II] emission in red galaxies (Konidaris et al., in prep) And many more to come!!! Principal Component Analysis (PCA):  Principal Component Analysis (PCA) Madgwick et al. 2003 – astro-ph/0305587 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 O[II] 3727. PCA for classification:  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. Galaxy colors can also be used for classification...:  Galaxy colors can also be used for classification... Weiner et al. 2003, Willmer et al. 2003 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 z~0, the distinction between early and late types is readily apparent. Clustering in DEEP2: First Redshift Maps:  Clustering in DEEP2: First Redshift Maps Projected maps of two DEEP2 pointings (of 13 total). Red = early-type (from PCA). 2-point correlation function: x(r):  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: dP=n dV (1+x(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 r0~5 Mpc/h and g~1.8. 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! DEEP2 Faint Galaxy Redshift Survey:  DEEP2 Faint Galaxy Redshift Survey Details, Scientific Goals of DEEP2 Highlights of DEIMOS spectrograph Survey Status and Data Pipeline Science Topics in Progress Dependence of galaxy properties on environment:  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: Gerke et al., Cooper et al., in prep Voronoi partition in 2 dimensions Galaxy Groups and Clusters in DEEP2:  Galaxy Groups and Clusters in DEEP2 Gerke et al. 2004, in prep red=pairs; blue=Nandgt;2; sizelog ()  log (halo mass) 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. red=absorption-dominated Luminosity Function evolution:  Luminosity Function evolution DEEP2 luminosity function measurements are well underway. Good agreement with COMBO-17 in range of overlap; also LF as a function of color, spectral type, etc. Willmer et al. 2003 Luminosity-linewidth relations:  Luminosity-linewidth relations Weiner et al. 2004 Since we can measure both luminosities and linewidths of DEEP2 galaxies, we can also explore the relationship between the two and compare to lower-z samples. Preliminary results suggest the T-F relation becomes brighter at higher redshift, in agreement with previous work (but with much larger samples). Velocity dispersions of satellite galaxies:  Velocity dispersions of satellite galaxies Conroy et al. 2004 We can explore the potential wells of galaxies at larger radii by examining the relative velocities of faint neighbors of bright galaxies (ala Prada et al. 2003). Preliminary tests on the data are promising, and we are testing our ability to reject interlopers with the mock catalogs of Yan et al. (2003). We should have a sample of hundreds of satellites by the end of DEEP2. DEEP2 and other Surveys:  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 z~1.5 should allow us to test for the sorts of systematic effects that may already dwarf statistical uncertainties. DEEP2 Conclusions:  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 Using DEEP2 for Cosmological Tests:Comoving volume vs Redshift:  Using DEEP2 for Cosmological Tests: Comoving volume vs Redshift Green: different equation of state values w=P/ρ for m=0.3 Volume varies by a factor of 3 at Z=1!! Not a small effect. Update on Marc Davis...:  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.

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