Docstoc

ps - Rencontres de Moriond

Document Sample
ps - Rencontres de Moriond Powered By Docstoc
					     ONE MILLION
      GALAXIES


Cosmography and Cosmology



          Michael S. Vogeley
          Department of Physics
          Drexel University


XXXVth Recontres de Moriond, Energy Densities in the Universe
Quantitative Large-Scale Structure: Lick Survey

                                              1 million galaxies!
                                              Lick observatory plates
                                              Counts by eye (Shane-
                                              Wirtanen), map by
                                              Seldner et al. 1977
                                              Analyses by Peebles,
                                              Groth, and Fry, et al.
                                              Angular correlation
                                              functions: 2, 3, 4-pt




                                                                        Groth & Peebles (1977)
           Michael S. Vogeley, Drexel University
              Hints of Greatness: The Shift to 3D

                                            The Photon-Counting Cowboys

                                            KOSS (1981):
                                            50 Mpc/h Void in Bootes
Kirshner et al. (1981)                      Anomalous?
                                            Truly empty?
                                            Formation mechanism?

                                            Center for Astrophysics (1982):
                                            Power-law 3D correlations
                                            Pairwise velocity dispersion
                                            Predict gravity field
                                            Comparison with N-body sim’s
                                            “Frothy…filamentary superclusters”

Davis & Peebles (1983)



                         Michael S. Vogeley, Drexel University
Voids, Walls, and Peaks: Death to CDM?



                                                 CfA slice(1986), CfA2, SSRS:
                                                 Structures as large as survey
                                                 Voids fill space
                                                 P(k) rules out SCDM
  Geller & Huchra (1988)
                                                 APM galaxy catalog (1990):
                                                 Too much large-scale power
                                                 for SCDM

                                                 BEKS pencil-beams (1990):
                                                 128 Mpc/h Peaks in 1D P(k)

                                                 Characteristic scales in LSS?
 Maddox et al. (1990)




                   Michael S. Vogeley, Drexel University
                   All-Sky: The IRAS z Surveys

IRAS 2Jy (1989), 1.2Jy (1993)
QDOT (1991), PSCz 0.6Jy (1999)

Selection of galaxies independent
of photo plates, Galactic extinction
IR-selected trace same structures
with lower density in clusters

Similar statistics, but
lower clustering amplitude
Clear evidence for biasing on
all scales

All-sky benefits:
         spherical window
         density-velocity study                               Saunders et al. (2000)




                      Michael S. Vogeley, Drexel University
           CCD-Based Surveys and the Era of Multiplexing
Shectman et al.
(1996)
                                                             Las Campanas Redshift Survey:
                                                             R-band CCD driftscan photometry
                                                             100 Fiber-fed spectrograph

                                                             Ubiquitous voids and walls
                                                             - the end of “greatness”?

                                                             Peak in the 2D power spectrum near
                                                             same scale as BEKS

                                                             Limited by geometry
                                                             What if we survey the whole sky?




                  Landy et al. (1996)


                                        Michael S. Vogeley, Drexel University
       Current Status on Large-Scale Structure

• What drives structure formation?
   – Gravity!
• Cosmological parameters?
    matter  0.2  0.4,   1  matter, h  0.7
• Components of mass-energy density?
   – Baryon fraction (?), CDM, HDM?, what else?
   – Is the cosmological “constant” constant?
• Galaxy formation: connecting mass to light
   – Gastrophysics and biasing

                Michael S. Vogeley, Drexel University
       Critical Issues for Large-Scale Structure

• Features in P(k) at peak scale
  and beyond
  – Is the peak too sharp?
  – Wiggles in the spectrum?
  – Structure on Gpc scales?                           Vogeley (1999)


• Messy details about galaxies
  – Galaxy segregation (“biasing”)
  – Galaxy evolution (purely
    local?)
  – Voids: Are they too empty?
                                                       Blanton et al. (1999)
               Michael S. Vogeley, Drexel University
           Features in the 3D Power Spectrum

                                                          Baryonic Wiggles

                                                          Eisenstein & Hu (1998)




                                                               LSS+CMB
                                                           Gawiser & Silk (1998)



Slope agreement at small scale
Linear to non-linear transition
Feature at 0.1-0.2h/Mpc
Peak at 0.03-0.04h/Mpc
Slope, ampl <0.03?

             Physics on peak scale?
               LSS vs. CMB
                  Michael S. Vogeley, Drexel University
                                        Voids and Void Galaxies
De Lapparent, Geller, & Huchra (1986)




                                                                            Cen & Ostriker (1998)


                                                           Data vs. N-body+hydro:
                                                            sim voids too empty?
                                                           Data vs. N-body+SAMs:
                                                            sim void edges not sharp?

                                                           Galaxy evolution at   0.8
            Diaferio et al. (1999)
                                                           Need color, spectra, low SB, mag range
                                        Michael S. Vogeley, Drexel University
           Desiderata for New Galaxy Surveys
  Observational Systematics                Measured Galaxy Properties
               Photometry
• Large area                         • Multi-wavelength
• Consistent, accurate               • Surface-brightness
  calibration
• Galactic extinction
            Spectroscopy
• Large depth                        • Resolve features
• Complete sampling                  • Wavelength range
• Careful target selection


                  Michael S. Vogeley, Drexel University
                    A Survey of Surveys




Colless (1999)
                                                         Vogeley (1999)



                 Michael S. Vogeley, Drexel University
                                 Volume and Number Surveyed

                1.00E+09
                                                                                     SDSS
                                                                                    photo-z

                1.00E+08




                1.00E+07
                                                          SDSS
No of objects




                                                          main
                                                                                                  SDSS
                1.00E+06                                                                         abs line
                                                                             SDSS
                                                                              red

                1.00E+05           CfA+
                                   SSRS                  2dF        2dFR


                                                          LCRS
                1.00E+04
                                                       QDOT
                                        SAPM


                1.00E+03
                      1.00E+04   1.00E+05   1.00E+06     1.00E+07    1.00E+08   1.00E+09      1.00E+10      1.00E+11

                                                          Volume in M pc 3



                                     Michael S. Vogeley, Drexel University
       www.sdss.org

Michael S. Vogeley, Drexel University
                    Features of the SDSS

Unique 2.5m telescope, located at Apache Point, NM
          3 degree diameter field of view
Two surveys in one:
          Photometric survey in 5 bands
          Spectroscopic redshift survey
CCD Mosaic Camera
          30 CCDs 2K x 2K (imaging)
          22 CCDs 2K x 400 (astrometry)
Two double spectrographs
          2 x 320 fibers (3 arcsec diameter)
          resolution  / =2000
          Spectral coverage from 3900Å to 9200Å
Automated data reduction
          Over 70 man-years of development effort
          (Fermilab + collaboration scientists)
Very high data volume
          40 TB of raw data
          About 1 TB of catalog data
          Data made available to the public



                  Michael S. Vogeley, Drexel University
                 SDSS: The Photometric Survey

Northern Galactic Cap
drift-scan imaging of 10,000 square degrees
5 broad-band filters
pixel size is 0.4 arcsec
        > 800 billion pixels x 5 filters
20 TB raw imaging data  pipeline
         100,000,000 galaxies
         50,000,000 stars

Southern Galactic Cap
multiple scans (> 30 times) of one stripe
another 20 TB of raw imaging data
        detect fainter, variable, and
          moving objects
Continuous data rate of 8 Mbytes/sec


                     Michael S. Vogeley, Drexel University
       The First Stripes: 600 sq.deg. done, 9400 to go!

Camera:
  5 color imaging of 600 square degrees
  Multiple scans across the same fields
  Photometric limits as expected
  PSF variations taken out in software




                        Michael S. Vogeley, Drexel University
             SDSS: The Spectroscopic Survey

Spectroscopic targets:
        1 million galaxies (main + BRG)
        100,000 quasars
        100,000 stars
        selected objects from other catalogs
Two high-throughput spectrographs
        spectral range 3900-9200 Å
        640 spectra simultaneously
        resolution  / =2000
Automated reduction of spectra
        redshift
        spectral features
        classification


         The result: A redshift map to z=0.2 and beyond

                   Michael S. Vogeley, Drexel University
         Status Report on SDSS Spectroscopy




                                 12 plug-plate fields




                                    Both spectrographs fully operational
r’=18
galaxy
                                    >7,000 test spectra at survey spec.
z=0.19

                                    Measured throughput: 15%, 20%
                                    Redshift completeness: 98%



              Michael S. Vogeley, Drexel University
          Discovery of the Highest-Redshift Quasars


Eight of the ten highest redshift
quasars have been found in the
      first SDSS test data




                     Michael S. Vogeley, Drexel University
  Finding Rare Objects

                             Distant QSO’s are outliers
                                in color-color space




         The SDSS analysis pipeline automatically
          discovers candidate objects for
         spectroscopic followup


Michael S. Vogeley, Drexel University
               SDSS Commissioning-Data Science

High-z quasars                                 Galaxy-galaxy lensing detected in 1/44 of SDSS
Methane, L dwarfs
Structure of Galactic halo with RR Lyrae
Galaxy-galaxy weak lensing

Magnification bias from lensing
Clusters of galaxies, X-ray sources
Compact groups of galaxies and correlations
Angular correlations of galaxies
IR, FIRST sources
Quasar-galaxy cross-correlations                                 Fischer et al. (1999)
Carbon stars
QSO absorption line systems




                     Michael S. Vogeley, Drexel University
   SDSS 2.5m Observation Schedule

May 1998 - March 1999
        First light imaging - equatorial only
        Camera and software commissioning
April 1999
        Telescope pointing model
        Great circle scan tests
        Spectrograph flexure tests
May 1999
        Spectrograph testing
        Great circle driftscan imaging
June 1999
        First astronomical spectroscopy
Fall 1999
        Spectroscopic commissioning
        Target selection tests
March 2000
        Survey proper begins
        Michael S. Vogeley, Drexel University
     Outlook: A Golden Age for Structure Formation*

         Independent probes of structure out to 1Gpc
          High-resolution power spectra
          Sampling the same wavelength scales at z=0, 1000

         Multi-variate distribution of galaxies
          Photometric, spectroscopic properties
          Evolution of populations
          Segregation and “biasing”

         Multi-wavelength data bases
          Integration of X-ray, UV, Optical, IR, Radio surveys
          On-line digital data access
          Data mining methods

* “You fool, there were no good old days. You’ve simply romanticized
the agony of freezing all night in the prime-focus cage.” - F. Zwicky (perhaps)


                           Michael S. Vogeley, Drexel University

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:0
posted:12/3/2011
language:English
pages:24