The Sloan Digital Sky Survey Huan Lin Experimental Astrophysics Group Fermilab
Beamline Calorimeter Massive Spectrometer Sloan Digital Sky Survey (E885) Goal: Conduct fundamental research in cosmology, particularly formation & evolution of galaxies and large scale structure Approach: Digital map of ¼ of sky in 5 bands Spectra of 1 million galaxies, 100,000 quasars Resources: 2.5 m telescope in New Mexico Large CCD camera 640 fiber spectrograph 13 partner institutions
Fermi National Accelerator Laboratory Princeton University University of Chicago Institute for Advanced Study Japanese Promotion Group US Naval Observatory University of Washington Johns Hopkins University Max Planck Institute for Astronomy, Heidelberg Max Planck Institute, Garching New Mexico State University Los Alamos National Laboratory University of Pittsburgh Partner Institutions
Funding Agencies • Alfred P. Sloan Foundation • Participating Institutions • NASA • NSF • DOE • Japanese Monbukagakusho • Max Planck Society
FNAL in SDSS Role: Data acquisition Data processing Survey Planning Data distribution Support telescope and instrument systems Science: Galaxy correlation functions Weak lensing Galaxy clusters Milky Way halo structure Galaxy evolution QSO luminosity functions Near Earth Asteroids Of 103 refereed papers, 17 have current or former FNAL scientist or student supervised by FNAL as lead author Participants EAG TAG PPD Comp. Comm. Fab. (CD)
Apache Point Observatory, New Mexico
The Mosaic Camera 2.5 degree wide field of view 30 photometric CCDs (each 2048 x 2048 pixels) 6 columns of 5 filters (ugriz)
Survey Layout Mosaic camera scans along great circles on the sky North Galactic Hemisphere South Galactic Hemisphere
Two interleaved scans (run 259, 273) taken on successive nights, Nov 1998 Color coding: g r i (3 images taken in succession over 8 minutes)
U. of Washington Plug plate designs Fermilab Plug plates Data Tapes Apache Point Obs.
3. Identify Galaxies, Quasars
4. Design Plates 3 deg diameter 7 sq deg area
Tiling Survey tile centers and target assignments to tiles are optimized Sampling Rates: >92% all targets >99% non-colliding Blanton et al. 2003, AJ, 125, 2276
Plugging the fibers 592 science targets 16 calibration stars 32 skies 640 fibers
5. Spectroscopy Wavelength Spectra of 100 objects out of 640 Total
Imaging Sky Coverage 74% as of May 30, 2003 6255/8452 square degrees Spectroscopy Sky Coverage 47% as of May 27, 2003 794/1688 tiles
Status of data collection (May 2003) • Imaging • 6255 sq deg “unique” imaging in hand • 22 terabytes processed through pipelines (including reprocessing) • Spectroscopy • 794 “unique” tiles • 139 additional special purpose plates • ~50,000 Quasars • ~300,000 Galaxies • (bigger than 2dF survey)
Access & Distribution of SDSS Data • I. Early Data Release (EDR) • June 2001 • Commissioning data + first survey quality data • 460 sq deg. + 24,000 spectra • II. Data Release 1 (DR1β) • April 2003 • 2099 sq. deg. + 150,000 spectra • 3 Terabytes total
Data Access Mechanisms • http://www.sdss.org/dr1/ • Data Archive Server • Footprint • Finding Chart • Image Query Server • Spectro Query Server • rsync or http access to flatfiles • Volume: 1 square degree = 1 Gbyte.
Large Scale Structure: Galaxy Power Spectrum
Evolution of large scale structure with redshift in a variety of N-body simulations The clustering of galaxies observed today evolved from the initial quantum fluctuations in the early universe.
Sample: 205,443 galaxies2417 sq degmean redshift z = 0.1 Shown: 66976 galaxies within 5° of equatorial plane, color coded by absolute magnitude Tegmark et al. 2003
Calculate 3D galaxy power spectrum by expanding galaxy distribution in pseudo-Karhunen-Loève eigenmodes, accounting for complicated survey geometry Example angular modes on sky Example modes in equatorial plane Tegmark et al. 2003
Real-space power spectrum of L* SDSS galaxies Relative Clustering Bias 3D Galaxy Power Spectrum WMAP fit flat, ΩΛ=0.73 (Spergel et al. 2003) Tegmark et al. 2003 Wavenumber
SDSS P(k) fit:Ωm = 0.291 ± 0.023 L* galaxy σ8 = 0.93 ± 0.02 fixed: h = 0.72, baryon fraction Ωb/Ωm = 0.17, spectral index ns=1 Power Spectrum Tegmark et al. 2003 Wavenumber
Mass (Solar) Temperature O B A F G K M L T 50000 K 20000 K 10000 K 7500 K 5500 K 3500 K 2000 K 1200 K 900 K 20 10 5 2 1 0.7 0.4 0.1 0.05 u g r i z
m-M = 5log d(pc) + 5 M = +4.2 (g' band) magnitude distance 0.1 < g'-r' < 0.3 (Color selection) 17 3.6 18 5.7 19 9.1 20 14.4 21 22.9 22 36.3 23 57.5 (kpc) As the Milky Way disk has a radius of about 10 kpc, F stars of this mag are well suited to explore structure.
Monoceros Structure Sagittarius South Stream New Structure? Sagittarius North stream F stars along Celestial Equator
Rings around the Galaxy (Yanny & Newberg)
No precession in Spherical potential q=1.0 unreachable in same orbit In flattened potential, can hit points above and below the plane on side of the Galaxy. q=0.7
Summary • SDSS status: 74% complete imaging, 47% spectroscopy (May 2003) • Public Data Release 1 (beta) now available • http://www.sdss.org/dr1 • Science • Today discussed the galaxy power spectrum and galactic structure • Many, many other topics, e.g. quasars, galaxy clusters, lensing, luminosity functions, rare stars, GRB counterparts, asteroids, … • http://www.sdss.org/publications
The Supernova Acceleration Probe (SNAP) Huan Lin Experimental Astrophysics Group Fermilab
Energy budget of Universe Dark Matter: 30% Dark Energy: 65%
Current SN Results (from A. Kim) • Two groups, the Supernova Cosmology Project and the Hi-Z Team, find evidence for an accelerating Universe.
SNAP Science Goals and Project Design (from S. Perlmutter) • Large 2 meter class telescope, large field of view (0.7 sq degree) • Dedicated space-based mission • Visible to near-infrared camera • Space-based to avoid absorption in earth’s atmosphere • Detailed spectrum at maximum light to characterize supernovae • Observing program of repeated images in visible to near-infrared • Discover large numbers of supernovae (2000) • Look back 3 - 10 billion years (z=0.5 - 1.7, light is redshifted up to 1.7 um) • Measure each supernova in detail (light curve, spectrum)
SPACECRAFT CONFIGURATION Secondary Mirror Hexapod and “Lampshade” Light Baffle Door Assembly Main Baffle Assembly Secondary Metering Structure Primary Solar Array Primary Mirror Optical Bench Solar Array, ‘Dark-Side’ Instrument Metering Structure Instrument Radiator Tertiary Mirror Fold-Flat Mirror Instrument Bay Spacecraft Shutter
(from A. Kim) SNAP Telescope • 2-m primary aperture, 3-mirror anastigmatic design. • Provides a wide-field flat focal plane.
(from A. Kim) Instrumentation: Imager • A large solid-angle camera (0.7 square degrees) provides multiplexed supernova discovery and followup. • Covers wavelength region of interest, 0.35- 1.7 microns. • Fixed filter mosaic on top of the imager sensors. • 3 NIR bandpasses. • 6 visible bandpasses. • Coalesce all sensors at one focal plane. • 36 2k x 2k HgCdTe NIR sensors covering 0.9-1.7 μm. • 36 3.5k x 3.5k CCDs covering 0.35-1.0 μm. CCDs Guider HgCdTe Spectrograph Spectr. port rin=6.0 mrad; rout=13.0 mrad rin=129.120 mm; rout=283.564 mm
Detailed Imaging and Spectral Data for SNAP Supernovae (from S. Perlmutter) At every moment in the explosion event, each individual supernova is “sending” us a rich stream of information about its internal physical state. Lightcurve & Peak Brightness Images Redshift & SN Properties Spectra
Simulated SNAP data (from S. Perlmutter) Each SNAP point represents ~50-supernova bin Relative Magnitude Difference Redshift