Sloan Digital Sky Survey

Experimental Astrophysics Group

Fermilab

Sloan Digital Sky Survey (E885)

Goal:Conduct fundamental research in

cosmology, particularly formation and evolution of galaxies and large

scale structureApproach:

Digital map of ¼ of sky in 5 bandsSpectra of 1 million galaxies,

100,000 quasarsResources:

2.5 m telescope in New MexicoLarge CCD camera640 fiber spectrograph15 partner institutions

Operations:2000-2005

Participating InstitutionsUniversity of Chicago

Fermi National Accelerator LaboratoryInstitute for Advanced Study

Japan Participation GroupJohns Hopkins UniversityKorean Scientist Group

Los Alamos National LaboratoryMax Planck Institute for Astronomy, HeidelbergMax Planck Institute for Astrophysics, Garching

New Mexico State UniversityUniversity of Pittsburgh

University of Portsmouth, UK Princeton University US Naval Observatory

University of Washington

FNAL in SDSS

Role:Data acquisitionData processingSurvey PlanningData distributionSupport telescope and instrument

systemsScience:

Large-scale structureWeak lensing and strong lensingGalaxy clusters Milky Way halo structure/Dark MatterDark energyGalaxy evolutionQSO luminosity functionsSupernovaeNear Earth Asteroids

Participants:EAGTAGPPDCD (outside EAG)

SDSS-I operations through June, 2005

SDSS-II to continue operations foranother 3 years (fill the gap and finish spectroscopy).

Percent Complete

78% as of Aug 6, 2003

48% as of Aug 6, 2003

IMAGING

SPECTROSCOPY

Baseline:8452 sq. deg.

Baseline:1696 tiles

Status(July 2005)(North survey only)

Square degrees at baselineas of July 1, 2005

74% as of July 1, 2005

Eisenstein et al. 2005 ApJ in press

Detection of the 'Baryon Acoustic Peak' in the clustering ofGalaxies on Large Scaleswith SDSS:

Demonstrates:

1. There is some'thing' whichbehaveslike dark matter(not all baryons)at redshift 1000(just like at z=0).

2. There arebaryons whichinteract withphoton plasmaand evolvegravitationally.

Baryonsto Total Matter(Dark + Light) ratio

0.200.1850.170 (all dark matter)

3.Ratio ofthese two'types ofmatter',light and dark,is determined.

4. Combinedwith CMBresults:Curvature ~0,i.e. we livein aEuclidean'Flat Universe'.

“Key Project”goal of SDSS

''Result of the week''

PHYSICS

The on-line database gets a million queries a month

SDSS-II (2005-2008)● Legacy Survey

– Fill the gap in the North Galactic Cap: ~few hundred sq. deg. imaging and ~500 spectroscopic plates

– Unique, high photometric precision, homogeneous legacy data set for future science

– Filled volume to improve large-scale structure studies● SEGUE

– Imaging and spectroscopy into the Milky Way: 3500 sq. deg. imaging and 400 spectroscopic plates

– Goals to study the structure and evolution of our galaxy and to probe the dark matter halo of the Milky Way

● Supernova Survey

– 200 Type Ia supernovae with high-quality light curves, in the redshift gap z=0.05-0.35, to probe dark energy

Sample LEGACY rich cluster field

The SEGUE experiment combines accurate low-latitude stellar photometry with radial velocities and chemical abundance

information from spectroscopy to answer questions about the global structure of the Milky Way, including its DARK MATTER halo.

SEGUE(v.): To proceed to what follows without pause

8 kpc

KV

G

MSTO/F

BHB/BS

K IIISEGUE uses stellar probes of increasingabsolute brightness to probeincreasing distances in the disk, thick disk and Milky Way halo.

d < 1 kpc

d < 6 kpc

d < 15 kpc

d < 50 kpc

d < 100 kpc

Other spectroscopic surveys will not probe as deep,for instance, Blue Horizontal Branch Stars (BHBs) from a survey with V< 12 are from a volume within 1.5 kpc of the sun.

r = 1.5kpc

Streams and outer halo stars

Inner and outer halo stars

8 kpc

KV

G

F

A

K IIISEGUE uses stellar probes of increasingabsolute brightness to probeincreasing distances in the disk, thick disk and Milky Way halo.

d < 1 kpc

d < 6 kpc

d < 15 kpc

d < 50 kpc

d < 100 kpc

r = 1.5kpc

Streams and outer halo stars

Inner and outer halo stars

8 kpc

KV

G

K III

d < 1 kpc

d < 6 kpc

d < 15 kpc

d < 50 kpc

d < 100 kpc

r = 1.5kpc

Inner and outer halo stars

thin, thickdisk stars

Dark Matter dominatesdynamics out here.

0.0 0.2 0.4 0.6 0.8 1.0 1.2

14

15

16

17

18

19

20

21

22

23

g mag

g-r color

Multiple faint blueturnoffs(T.O.s) ina color-magnitude'Hess' diagramfor stars towards(l,b) = (130, -26) degindicates the presenceof likely tidal debrisin the halo of theMilky Way.

Thin+Thick disk T.O.

Distanttidal streams?or halo?

MStars

SEGUE will obtain images of stars at a wide rangeof Galactic latitudes and longitudes to probe disk andhalo structure, as well as mapping diffuse streamsof stars moving coherently through the halo of dark matter.

Resolving Galactic structural components with SEGUE stellar photometry

SDSS/SEGUEphotometricprecision of2% or bettercan distinguishhalo, disk andstreamcomponents.

[Fe/H] = -1.70 log g = 4.20 Teff = 6426

[Fe/H] = -3.59 log g = 4.20 Teff = 6416

[Fe/H] = -3.08 log g = 4.13 Teff = 6475

[Fe/H] = -2.69 log g = 3.63 Teff = 6457

[Fe/H] = -2.20 log g = 3.88 Teff = 6450

Searching for the most metal poor stars with SEGUE

CaII K

A

B

C

D

E

Metal poor stars are remnants of the earliest star formation in the Milky Way and itsbuilding blocks. The SEGUE project willsearch for metal-poor stars as part of its focus on the evolutionary history ofthe Galaxy. We show heretest SEGUE spectra of 5 stars near the main-sequence turnoff color of old stellar populations, arranged inorder of decreasing [Fe/H]. The stars are all at approximately thesame effective temperature (6450K) and surface gravity (log g = 4),so changes in the spectra are dominated by the change in metalabundance. The clear decrease in the strength of CaII K at lowermetallicities is one feature SEGUE will use to identify these rareand interesting objects from the imaging data and target them forspectroscopy. We will allocate 40,000 fibers to obtain spectra ofcandidate metal-poor stars over the course of the survey.

SDSS Supernova Survey● Science Goals

– Probe dark energy in redshift regime less sensitive to evolution than deeper surveys: sigma(w) ~ 0.1-0.15

– Study SN Ia systematics (critical for SN cosmology) with high photometric accuracy

● Program

– Repeat scans of equatorial stripe 82 for three 3-month runs (Sep-Nov, 2005-7) as weather permits

– Frame subtraction in multiple bands for SN selection– Follow-up spectroscopy for SN typing, redshifts, and k-

corrections– Obtain ~200 high-quality, densely sampled SN Ia ugriz

light curves in the redshift desert z=0.05-0.35

SDSS SN83: Type Ia at redshift z=0.05

Follow-up spectrum from APO 3.5mSDSS 2.5m imaging

The SDSS COADD: repeated scans of the same piece of sky summed.

One Scan Nine Scans summedH. LinJ. AnnisH. Lampeitl

Data Distribution

● Data Release 3 to public in Oct 2004

– www.sdss.org

– 5300 sq. deg. of sky

– 20 terabytes downloaded by public so far (includes DR1+2+3) from servers based at FNAL.

– Science publications:

● 55/yr SDSS collab● 50/yr by public

●Data release 4●Went public in July 2005

– 6700 sq. deg (+30%)