SLOAN DIGITALSKY SURVEY

Scot J. KleinmanSDSS, APO, NMSU

Outline

I. Description of SDSS survey

II. Data Products

III. Data Release 1 and How to Get at it!

Sloan Digital Sky Survey

Goals:1. Image ¼ of sky in 5 bands to r=23 mag2. Obtain redshifts of 1 million galaxies to r=183. Obtain redshift of 100,000 quasars to r=19

4. Approximately 100,000,000 photometric objects!

Technique:1. Construct a 2.5 m telescope, CCD array

imager, 640 fiber spectrograph at ApachePoint, New Mexico

2. Operate for 5 years 3. Find a way to pay the bills!

Science Goals

1. Measure large scale structure of galaxies ina volume of 0.2% of the visible universe

2. Measure large scale distribution of quasarsin a volume 100% of the visible universe

3. Measure structure and kinematics of stars inthe Milky Way Galaxy

4. Conduct additional leading-edge science projects

Partner InstitutionsFermi National Accelerator LaboratoryPrinceton UniversityUniversity of ChicagoInstitute for Advanced StudyJapanese Promotion GroupUS Naval ObservatoryUniversity of WashingtonJohns Hopkins UniversityMax Planck Institute for Astronomy, HeidelbergMax Planck Institute, GarchingNew Mexico State UniversityLos Alamos National LaboratoryUniversity of Pittsburgh

Funding Agencies

● Alfred P. Sloan Foundation● Participating Institutions● NASA● NSF● DOE● Japanese Monbukagakusho● Max Planck Society

Project Schedule and Cost

● Project Timeline– 1988: Project conceived– 1990: Construction activities started – April 2000: Observing operations began– June 2005: Observing phase complete– July 2006: Last data release– 2005- 2007 Extension?

● Project Cost– Construction costs: $55M– Operations cost: $28M (current forecast)– Total project cost: $83M (current forecast)

● Telescope:

– 2.5m f/5 Richey-Chretien alt-az– ~3 deg FOV with almost no distortion– Apache Pt. Observatory, NM, ~2800m

● Imaging:

– Drift-scans with 54s integrations per chip– u=22.0, g=22.2, r=22.2, i=21.3, z=20.5– ~0.4'' per pixel in a 2.5 deg field– Median PSF ~1.4'' in R– Photometric Calibration good to ~2-3%– Astrometry: good to <0.1'' rms per coordinate

How the SDSS Works

● Spectroscopy– 2 640-fiber-fed dual-

channel spectrographs using pre-drilled plugplates

– Red: ~3800-6150 Ang; Blue: ~5800-9200 Ang

– 3'' fibers

– Resolution ~1900 (1850-2200) 69km/s pixels

– Exposures: typically 45min or enough to get a S/N=4 for g=20.2 and i=19.9

How the SDSS Works

Survey Coverage

~6000 sq. deg currently scanned

2.5-m Telescope

Apache PointObs.

Fermilab

Data Tapes

Plug plate designs

Plug plates

U. of Washington

The Mosaic Camera

SDSS Filters

Images● fpC*.fit files are ``corrected frames''

● fpAtlas*.fit files are ``postage stamp'' object cutouts with sky subracted.

● These are flat-fielded, bias-subtracted frames with bright stars removed. Sky is NOT subtracted, but available in FITS SKY keyword in fpC*.fit files.

● An object is specified by Run, Rerun, CamCol, Field, and ID

● Details and links at: http://www.sdss.org/dr1/products/images/index.html

● You'll need something to tell you the 5 magic parameters for the field/object you want ...

Photometry● tsObj*.fit files are binary fits files: one object per row

● Again, you need the 5 magic parameters

● 2 ``Sky versions'': Target and Best

● Many different magnitudes: Petrosian, de Vaucouleurs, Exponential, Model, PSF, Fiber

● Bright, resolved: Petrosian; Unresolved: PSF; Unresolved colors: Model. Small bug in u magnitudes for RED objects

● Galactic extinction supplied, but not applied

● Many QA flags --- MUST be checked

● Also: coordinates, proper motion, targeting info., ROSAT/FIRST matches, ...

● Details at: http://www.sdss.org/dr1/products/catalog/

Spectra● spPlate*.fits: all calibrated spectra per plate

● spSpec*.fits: single calibrated spectrum. Includes fits, and all measured parameters (lines and synthetic u, g, and r magnitudes)

● Many QA flags ...

● Classified as: Unknown, Star, Galaxy, QSO, High-z QSO, Sky, Late-type Star (M+), or Emission Line Galaxy

● Need three magic parameters: Plate, MJD, FiberID

● All wavelengths are VACUUM WAVELENGTHS

● Details at: http://www.sdss.org/dr1/products/spectra/index.html

http://das.sdss.org/DR1-cgi-bin/DAS

http://das.sdss.org/DR1-cgi-bin/IQS

http://das.sdss.org/DR1-cgi-bin/SQS

SQLhttp://skyserver.pha.jhu.edu/dr1/en/tools/search/sql.asp

SQL

SQL

SQL

Spectro Cross-ID Query to get photometric and other informationfor a list of objects identified by plate, MJD, and fiberID.

East

North

1. IMAGING SURVEY

Survey Layout

North Galactic Hemisphere South Galactic Hemisphere

2. Process Data

3. Identify Galaxies, Quasars

Target Selection Criteria● Main Galaxies r' < 17.77

– 90 Galaxies/sq deg

– median z = 0.1

– 6% lost due to 55 arcsec close nieghbor limit

● Red Galaxies

– Photometric redshifts with “intrinsic” magnitude cut

– Complete to z=0.38; additional bright galaxies to z=0.5

– 12 galaxies/sq deg

● QSOs

– Complex color cuts

– i' < 19 (z < 3)

– i' < 20 (z > 3)

– 65% efficiency, 90% complete

– 13 targets/sq deg

4. Design Plates

Fiber Cartridges (9 total)

Plugging the fibers

Fibers come in bundles of 20.

Markings on plate help limit fiber reach.

5. Spectroscopy

SKY COVERAGE

DATA PRODUCTS

Redshift Catalog 1 GB parameters of 106 objectsAtlas Images 1500 GB 5 color cutouts of >108 objects Spectra 60 GB in a one-dimensional formDerived Catalogs 20 GB clusters QSO absorption lines4x4 Pixel All-Sky Map 60 GB heavily compressedCorrected Frames 15 TB

SDSS Data Products

Status of data collection (Apr 2003)● Imaging

– 5514 sq deg “unique” imaging in hand● (8158 raw, includes repeat imaging in south)

– 22 terabytes processed through pipelines (including reprocessing)

● Spectroscopy– 743 “Unique” tiles– 139 additional special purpose plates– ~50,000 Quasars– ~300,000 Galaxies– (bigger than 2df survey)

Science with the SDSS

● 31 papers submitted by collaboration in past year (2002-2003).

● 20 papers submitted by noncollaboration based on publicly released data (EDR)

Galaxy Properties(Blanton, McKay, ...)

Weak LensingMcKay, Fischer, Sheldon, et al.

Foreground Galaxy

Background galaxy (sheared)

Weak Lensing Calibration of M/L

Large Scale Structure andGalaxy Clusters

(Annis, Kim, Dodelson, van den Berk, Zehavi, ...)

Spatial 2-point Correlation Function(Zehavi et al. 2003)

Power Spectrum(Tegmark et al 2003)

The maxBcg Algorithm●

Perform step for all galaxies

●

Build a 3-d map

●

Locate maxima

●

Strengths

–

Works to high z

–

Very good photo-z

●

Weaknesses

–

Strong assumptions built in

Photometric Redshifts

The maxBcg Algorithm●

Photometric redshift for each cluster good to 0.015

●

Mass estimates from total galaxy light

●

Plot shows all clusters from a wedge 90o wide and 3o high, out to redshifts of 0.7

maxBcg Calibration from weak lensing

The Cluster Finding Renaissance

●

maxBcg (Annis et al)

–

Search for BCG and E/SO ridge

●

Hybrid Matched Filter (Kim et al)

–

Matched filter on luminosity function and radial profile

●

Cut and Enhance (Goto et al)

–

Color cuts, gaussian cloud, image processing

●

Voronoi Tessalation (Kim et al)

–

Color cuts, then tessalation

●

C4 (Miller et al)

–

Near neighbors in color-color space

●

SRC: SDSS-RASS Catalog (Annis et al)

–

E/S0 overdensities at RASS faint source position

●

FOG: The finger of god catalog (Annis et al)

–

Velocity space search for fingers of gods.

SCIENCE WITH SDSS

Quasars(Fan, Strauss, vanden Berk, Richards, Schneider, Becker,...

How to view color-color diagrams

z=6.28 Quasar (r', i', z')

Optical Depth vs. Redshift

Rare Stars(Strauss, Knapp, Harris, ...)

Cool White Dwarf

Flux deficit in red

Gamma Ray Burst Counterpart

(Lee, vanden Berk, ...)

GRB 010222 afterglow

Debris in the Milky Way Halo(Yanny, Newberg, Ivesic, ...)

Sagittarius color-mag diagram

Ghost of Sagittarius

Rings around the Galaxy(Yanny & Newberg)

Palomar 5 Globular Cluster

Palomar 5 Orbit

Palomar 5 Tidal Tails(M. Odenkirchen et al.)

Near Earth Objects in SDSSSteve Kent, Tom Quinn, Gil Holder, Mark Schaffer,

Alex Szalay, Jim Gray

Run 1140Camcol 4Field 122

Run 2138Camcol 2Field 52

Coding: g' r' i'

Distribution on Sky

Cumulative Distribution vs. Elongation from Opposition

SDSS Colors of NEOs

Results

DistanceD = 0.06 to 0.14 AU

Absolute MagH ~ 22-25 (32 to 160 m diameter)

Simulations vs. ObservationsMagnitude Distribution: OKProper Motion Distribution: OKSky Distribution: OK

Earth Collision Rate

Access & Distribution ofSDSS Data

● I. Early Data Release (EDR)– June 2001– Commissioning data + first survey quality data– 460 sq deg. + 24,000 spectra

● II. Data Release 1 (DR1-Beta)– 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.

Conclusions● SDSS is largest digital imaging survey and largest

spectroscopic survey to date● Approximately 60% complete with 5 yr survey.● Actively exploring a 2 yr extension to fill in gap

and conduct additional surveys● Over 100 papers by collaboration and non-

collaboration● Data archive will be a unique resource for many

years. Cross-matching SDSS and other surveys (2MASS, Galex, FIRST, ROSAT, UKIDSS) will further expand reach and is a motivation for National Virtual Observatory project