SDSS-III: Massive Spectroscopic Surveys of the Distant Universe, the Milky Way Galaxy, and Extra-Solar Planetary Systems

TLDR: SDSS-III as discussed by the authors is a program of four spectroscopic surveys on three scientific themes: dark energy and cosmological parameters, the history and structure of the Milky Way, and the population of giant planets around other stars.

Abstract: Building on the legacy of the Sloan Digital Sky Survey (SDSS-I and II), SDSS-III is a program of four spectroscopic surveys on three scientific themes: dark energy and cosmological parameters, the history and structure of the Milky Way, and the population of giant planets around other stars. In keeping with SDSS tradition, SDSS-III will provide regular public releases of all its data, beginning with SDSS DR8 (which occurred in Jan 2011). This paper presents an overview of the four SDSS-III surveys. BOSS will measure redshifts of 1.5 million massive galaxies and Lya forest spectra of 150,000 quasars, using the BAO feature of large scale structure to obtain percent-level determinations of the distance scale and Hubble expansion rate at z 100 per resolution element), H-band (1.51-1.70 micron) spectra of 10^5 evolved, late-type stars, measuring separate abundances for ~15 elements per star and creating the first high-precision spectroscopic survey of all Galactic stellar populations (bulge, bar, disks, halo) with a uniform set of stellar tracers and spectral diagnostics. MARVELS will monitor radial velocities of more than 8000 FGK stars with the sensitivity and cadence (10-40 m/s, ~24 visits per star) needed to detect giant planets with periods up to two years, providing an unprecedented data set for understanding the formation and dynamical evolution of giant planet systems. (Abridged)

Figures

Figure 7. Example spectra of several classes of SEGUE-2 stars, all taken from the same spectroscopic plate. The left-hand panels show the flux-calibrated spectra for a halo blue horizontal branch (BHB) star, a main-sequence turnoff (MSTO) star, and a K giant (KG) star, identified by plate-MJD-fiber. The stellar atmospheric parameter estimates for each object are shown below the label, as determined by the SSPP. The right-hand panels show the blue portion of each spectrum after continuum normalization by the SSPP. Prominent spectral features in each spectrum are labeled. Dereddened apparent magnitudes, from top to bottom, are g0 = 16.27, 17.82, 17.31 and r0 = 16.35, 17.49, 16.67, respectively. All of these stars are much brighter than the SEGUE magnitude limit.

Figure 10. Selected sections of simulated APOGEE spectra for two giant stars with Teff = 4000 K, log g = 1.0, and [Fe/H] = −1.0 (solid line) and 0.0 (gray line) showing some of the absorption lines that will be used to measure element abundances. The vertical scale is in Fλ units (erg cm−2 s−1 Å−1), with an arbitrary normalization. The plotted regions cover only ∼15% of the full APOGEE spectral range.

Table 5 BOSS Parameter Constraint Forecasts

Figure 1. Schematic diagram of a BOSS spectrograph (one of two), with elements as labeled. The “slithead” is in fact a pseudo-slit containing 500 aligned fibers.

Figure 2. Comoving space density of BOSS galaxies from data taken in Spring 2010. The separate contributions of the LOZ cut, CMASS cut, and previously observed SDSS-I/II galaxies are shown, together with the total. The dashed curve shows our “goal” of constant density to z = 0.6 and tapering density beyond. There is a deficit near z = 0.45 at the transition between the two cuts, where obtaining accurate photometric redshifts for target selection is difficult.

Table 2 Summary of SEGUE-2

Full text

The Astronomical Journal, 142:72 (24pp), 2011 September doi:10.1088/0004-6256/142/3/72
C

2011. The American Astronomical Society. All rights reserved. Printed in the U.S.A.
SDSS-III: MASSIVE SPECTROSCOPIC SURVEYS OF THE DISTANT UNIVERSE,
THE MILKY WAY, AND EXTRA-SOLAR PLANETARY SYSTEMS
Daniel J. Eisenstein
1,2
, David H. Weinberg
3,4
, Eric Agol
5
, Hiroaki Aihara
6
, Carlos Allende Prieto
7,8
,
Scott F. Anderson
5
, James A. Arns
9
,
´
Eric Aubourg
10,11
, Stephen Bailey
12
, Eduardo Balbinot
13,14
,
Robert Barkhouser
15
, Timothy C. Beers
16
, Andreas A. Berlind
17
, Steven J. Bickerton
18
, Dmitry Bizyaev
19
,
Michael R. Blanton
20
, John J. Bochanski
21
, Adam S. Bolton
22
, Casey T. Bosman
23
, Jo Bovy
20
, W. N. Brandt
21,24
,
Ben Breslauer
25
, Howard J. Brewington
19
, J. Brinkmann
19
, Peter J. Brown
22
, Joel R. Brownstein
22
, Dan Burger
17
,
Nicolas G. Busca
10
, Heather Campbell
26
, Phillip A. Cargile
17
, William C. Carithers
12
, Joleen K. Carlberg
25
,
Michael A. Carr
18
, Liang Chang
23,27
, Yanmei Chen
28
, Cristina Chiappini
14,29,30
, Johan Comparat
31
,
Natalia Connolly
32
, Marina Cortes
12
, Rupert A. C. Croft
33
, Katia Cunha
1,34
, Luiz N. da Costa
14,35
,
James R. A. Davenport
5
, Kyle Dawson
22
, Nathan De Lee
23
, Gustavo F. Porto de Mello
14,36
, Fernando de Simoni
14,35
,
Janice Dean
25
, Saurav Dhital
17
, Anne Ealet
37
, Garrett L. Ebelke
19,38
, Edward M. Edmondson
26
, Jacob M. Eiting
39
,
Stephanie Escoffier
37
, Massimiliano Esposito
7,8
, Michael L. Evans
5
, Xiaohui Fan
1
, Bruno Femen
´
ıa Castell
´
a
7,8
,
Leticia Dutra Ferreira
14,36
, Greg Fitzgerald
40
, Scott W. Fleming
23
, Andreu Font-Ribera
41
, Eric B. Ford
23
,
Peter M. Frinchaboy
42
, Ana Elia Garc
´
ıa P
´
erez
25
, B. Scott Gaudi
3
,JianGe
23
, Luan Ghezzi
14,35
, Bruce A. Gillespie
19
,
G. Gilmore
43
,L
´
eo Girardi
14,44
, J. Richard Gott
18
, Andrew Gould
3
, Eva K. Grebel
45
, James E. Gunn
18
,
Jean-Christophe Hamilton
10
, Paul Harding
46
, David W. Harris
22
, Suzanne L. Hawley
5
, Frederick R. Hearty
25
,
Joseph F. Hennawi
47
, Jonay I. Gonz
´
alez Hern
´
andez
7
, Shirley Ho
12
, David W. Hogg
20
, Jon A. Holtzman
38
,
Klaus Honscheid
4,39
, Naohisa Inada
48
, Inese I. Ivans
22
, Linhua Jiang
1
, Peng Jiang
23,49
, Jennifer A. Johnson
3,4
,
Cathy Jordan
19
, Wendell P. Jordan
19,38
, Guinevere Kauffmann
50
, Eyal Kazin
20
, David Kirkby
51
, Mark A. Klaene
19
,
G. R. Knapp
18
, Jean-Paul Kneib
31
, C. S. Kochanek
3,4
, Lars Koesterke
52
, Juna A. Kollmeier
53
, Richard G. Kron
54,55
,
Hubert Lampeitl
26
, Dustin Lang
18
, James E. Lawler
56
, Jean-Marc Le Goff
11
, Brian L. Lee
23
, Young Sun Lee
16
,
Jarron M. Leisenring
25
, Yen-Ting Lin
6,57
, Jian Liu
23
,DanielC.Long
19
, Craig P. Loomis
18
, Sara Lucatello
44
,
Britt Lundgren
58
, Robert H. Lupton
18
,BoMa
23
, Zhibo Ma
46
, Nicholas MacDonald
5
, Claude Mack
17
,
Suvrath Mahadevan
21,59
, Marcio A. G. Maia
14,35
, Steven R. Majewski
25
, Martin Makler
14,60
, Elena Malanushenko
19
,
Viktor Malanushenko
19
, Rachel Mandelbaum
18
, Claudia Maraston
26
, Daniel Margala
51
, Paul Maseman
1,25
,
Karen L. Masters
26
, Cameron K. McBride
17
, Patrick McDonald
12,61
, Ian D. McGreer
1
, Richard G. McMahon
43
,
Olga Mena Requejo
62
, Brice M
´
enard
15,63
, Jordi Miralda-Escud
´
e
64,65
, Heather L. Morrison
46
, Fergal Mullally
18,66
,
Demitri Muna
20
, Hitoshi Murayama
6
, Adam D. Myers
67
, Tracy Naugle
19
, Angelo Fausti Neto
13,14
,
Duy Cuong Nguyen
23
, Robert C. Nichol
26
, David L. Nidever
25
, Robert W. O’Connell
25
, Ricardo L. C. Ogando
14,35
,
Matthew D. Olmstead
22
, Daniel J. Oravetz
19
, Nikhil Padmanabhan
58
, Martin Paegert
17
,
Nathalie Palanque-Delabrouille
11
, Kaike Pan
19
, Parul Pandey
22
, John K. Parejko
58
, Isabelle P
ˆ
aris
68
,
Paulo Pellegrini
14
, Joshua Pepper
17
, Will J. Percival
26
, Patrick Petitjean
68
, Robert Pfaffenberger
38
, Janine Pforr
26
,
Stefanie Phleps
69
, Christophe Pichon
68
, Matthew M. Pieri
3,70
, Francisco Prada
71
, Adrian M. Price-Whelan
20
,
M. Jordan Raddick
15
, Beatriz H. F. Ramos
35,14
,I.NeillReid
72
, Celine Reyle
73
, James Rich
11
, Gordon T. Richards
74
,
George H. Rieke
1
, Marcia J. Rieke
1
, Hans-Walter Rix
47
, Annie C. Robin
73
, Helio J. Rocha-Pinto
14,36
,
Constance M. Rockosi
75
, Natalie A. Roe
12
, Emmanuel Rollinde
68
, Ashley J. Ross
26
, Nicholas P. Ross
12
,
Bruno Rossetto
14,36
, Ariel G. S
´
anchez
69
, Basilio Santiago
13,14
, Conor Sayres
5
, Ricardo Schiavon
76
,
David J. Schlegel
12
, Katharine J. Schlesinger
3
, Sarah J. Schmidt
5
, Donald P. Schneider
21,59
, Kris Sellgren
3
,
Alaina Shelden
19
, Erin Sheldon
61
, Matthew Shetrone
77
, Yiping Shu
22
, John D. Silverman
6
, Jennifer Simmerer
22
,
Audrey E. Simmons
19
, Thirupathi Sivarani
23,78
, M. F. Skrutskie
25
,An
ˇ
ze Slosar
61
, Stephen Smee
15
, Verne V. Smith
34
,
Stephanie A. Snedden
19
, Keivan G. Stassun
17,79
, Oliver Steele
26
, Matthias Steinmetz
29
, Mark H. Stockett
56
,
Todd Stollberg
40
, Michael A. Strauss
18
, Alexander S. Szalay
15
, Masayuki Tanaka
6
, Aniruddha R. Thakar
15
,
Daniel Thomas
26
, Jeremy L. Tinker
20
, Benjamin M. Tofflemire
5
, Rita Tojeiro
26
, Christy A. Tremonti
28
,
Mariana Vargas Maga
˜
na
10
, Licia Verde
64,65
, Nicole P. Vogt
38
, David A. Wake
58
, Xiaoke Wan
23
,JiWang
23
,
Benjamin A. Weaver
20
, Martin White
80
, Simon D. M. White
50
,JohnC.Wilson
25
,JohnP.Wisniewski
5
,
W. Michael Wood-Vasey
81
, Brian Yanny
54
, Naoki Yasuda
6
, Christophe Y
`
eche
11
, Donald G. York
55,82
,
Erick Young
1,83
, Gail Zasowski
25
, Idit Zehavi
46
, and Bo Zhao
23
1
Steward Observatory, Tucson, AZ 85721, USA
2
Harvard College Observatory, Cambridge, MA 02138, USA
3
Department of Astronomy, Ohio State University, Columbus, OH 43210, USA
4
Center for Cosmology and Astro-Particle Physics, Ohio State University, Columbus, OH 43210, USA
5
Department of Astronomy, University of Washington, Seattle, WA 98195, USA
6
Institute for the Physics and Mathematics of the Universe, The University of Tokyo, Kashiwa 277-8583, Japan
7
Instituto de Astrof
´
ısica de Canarias, E38205 La Laguna, Tenerife, Spain
8
Departamento de Astrof
´
ısica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
9
Kaiser Optical Systems, Ann Arbor, MI 48103, USA
10
Astroparticule et Cosmologie (APC), Universit
´
e Paris-Diderot, 75205 Paris Cedex 13, France
1

The Astronomical Journal, 142:72 (24pp), 2011 September Eisenstein et al.
11
CEA, Centre de Saclay, Irfu/SPP, F-91191 Gif-sur-Yvette, France
12
Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
13
Instituto de F
´
ısica, UFRGS, Porto Alegre, RS 91501-970, Brazil
14
Laborat
´
orio Interinstitucional de e-Astronomia-LIneA, Rio de Janeiro, RJ 20921-400, Brazil
15
Center for Astrophysical Sciences, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA
16
Department of Physics & Astronomy and JINA: Joint Institute for Nuclear Astrophysics, Michigan State University, E. Lansing, MI 48824, USA
17
Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, USA
18
Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, USA
19
Apache Point Observatory, Sunspot, NM 88349, USA
20
Center for Cosmology and Particle Physics, New York University, New York, NY 10003, USA
21
Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802, USA
22
Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112, USA
23
Department of Astronomy, University of Florida, Bryant Space Science Center, Gainesville, FL 32611-2055, USA
24
Institute for Gravitation and the Cosmos, The Pennsylvania State University, University Park, PA 16802, USA
25
Department of Astronomy, University of Virginia, Charlottesville, VA 22904-4325, USA
26
Institute of Cosmology and Gravitation (ICG), University of Portsmouth, Portsmouth, PO1 3FX, UK
27
Yunnan Astronomical Observatory, Chinese Academy of Sciences, Yunnan, China
28
Department of Astronomy, University of Wisconsin–Madison, Madison, WI 53706-1582, USA
29
Leibniz-Institut fuer Astrophysik Potsdam (AIP), 14482 Potsdam, Germany
30
3-Istituto Nazionale di Astrofisica-OATrieste, Via G. B. Tiepolo 11 34143, Italy
31
Laboratoire d’Astrophysique de Marseille, CNRS-Universit
´
e de Provence, 13388 Marseille Cedex 13, France
32
Department of Physics, Hamilton College, Clinton, NY 13323, USA
33
Bruce and Astrid McWilliams Center for Cosmology, Carnegie Mellon University, Pittsburgh, PA 15213, USA
34
National Optical Astronomy Observatory, Tucson, AZ 85719, USA
35
Observat
´
orio Nacional, Rio de Janeiro, RJ 20921-400, Brazil
36
Observat
´
orio do Valongo, Universidade Federal do Rio de Janeiro, Ladeira do Pedro Ant
ˆ
onio 43, 20080-090 Rio de Janeiro, Brazil
37
Centre de Physique des Particules de Marseille, Aix-Marseille Universit
´
eCNRS/IN2P3, Marseille, France
38
Department of Astronomy, MSC 4500, New Mexico State University, Las Cruces, NM 88003, USA
39
Department of Physics, Ohio State University, Columbus, OH 43210, USA
40
New England Optical Systems, Marlborough, MA 01752, USA
41
Institut de Ci
´
encies de l’Espai (CSIC-IEEC), 08193 Bellaterra, Barcelona, Spain
42
Department of Physics & Astronomy, Texas Christian University, Fort Worth, TX 76129, USA
43
Institute of Astronomy, University of Cambridge, Cambridge, CB3 0HA, UK
44
Osservatorio Astronomico di Padova-INAF, Vicolo dell’Osservatorio 5, I-35122 Padova, Italy
45
Astronomisches Rechen-Institut, Zentrum f
¨
ur Astronomie der Universit
¨
at Heidelberg, 69120 Heidelberg, Germany
46
Department of Astronomy, Case Western Reserve University, Cleveland, OH 44106, USA
47
Max-Planck-Institut f
¨
ur Astronomie, K
¨
onigstuhl 17, D-69117 Heidelberg, Germany
48
Research Center for the Early Universe, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan
49
Key Laboratory for Research in Galaxies and Cosmology, The University of Science and Technology of China,
Chinese Academy of Sciences, Hefei, Anhui 230026, China
50
Max-Planck-Institut f
¨
ur Astrophysik, D-85748 Garching, Germany
51
Department of Physics and Astronomy, University of California, Irvine, CA 92697, USA
52
Texas Advanced Computer Center, University of Texas, Austin, TX 78758-4497, USA
53
Observatories of the Carnegie Institution of Washington, Pasadena, CA 91101, USA
54
Fermi National Accelerator Laboratory, Batavia, IL 60510, USA
55
Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637, USA
56
Department of Physics, University of Wisconsin, Madison, WI 53706, USA
57
Institute of Astronomy and Astrophysics, Academia Sinica, Taipei 10617, Taiwan
58
Yale Center for Astronomy and Astrophysics, Yale University, New Haven, CT 06520, USA
59
Center for Exoplanets and Habitable Worlds, Pennsylvania State University, University Park, PA 16802, USA
60
ICRA-Centro Brasileiro de Pesquisas F
´
ısicas, Urca, Rio de Janeiro, RJ 22290-180, Brazil
61
Bldg 510 Brookhaven National Laboratory, Physics Department, Upton, NY 11973, USA
62
Instituto de Fisica Corpuscular IFIC/CSIC, Universidad de Valencia, Valencia, Spain
63
CITA, University of Toronto, Toronto, Ontario M5S 3H8, Canada
64
Instituci
´
o Catalana de Recerca i Estudis Avan¸cats, Barcelona, Spain
65
Institut de Ci
`
encies del Cosmos, Universitat de Barcelona/IEEC, Barcelona 08028, Spain
66
SETI Institute/NASA Ames Research Center, Moffett Field, CA 94035, USA
67
Department of Astronomy, University of Illinois, Urbana, IL 61801, USA
68
Institut d’Astrophysique de Paris, Universit
´
e Paris 6, UMR7095-CNRS, F-75014 Paris, France
69
Max Planck Institute for Extraterrestrial Physics, 85748 Garching, Germany
70
CASA, University of Colorado, Boulder, CO 80309, USA
71
Instituto de Astrofisica de Andalucia (CSIC), E-18008 Granada, Spain
72
Space Telescope Science Institute, Baltimore, MD 21218, USA
73
Institut Utinam, Observatoire de Besan¸con, Universit
´
e de Franche-Comt
´
e, BP1615, F-25010 Besan¸con Cedex, France
74
Department of Physics, Drexel University, Philadelphia, PA 19104, USA
75
UCO/Lick Observatory, University of California, Santa Cruz, Santa Cruz, CA 95064, USA
76
Gemini Observatory, Hilo, HI 96720, USA
77
University of Texas at Austin, McDonald Observatory, Fort Davis, TX 79734, USA
78
Indian Institute of Astrophysics, II Block, Koramangala, Bangalore 560 034, India
79
Department of Physics, Fisk University, Nashville, TN, USA
80
Physics Department, University of California, Berkeley, CA 94720, USA
81
Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260, USA
82
Enrico Fermi Institute, University of Chicago, Chicago, IL 60637, USA
83
SOFIA Science Center/USRA, NASA Ames Research Center, MS 211-3, Moffett Field, CA 94035, USA
Received 2011 January 10; accepted 2011 June 23; published 2011 August 9
2

The Astronomical Journal, 142:72 (24pp), 2011 September Eisenstein et al.
ABSTRACT
Building on the legacy of the Sloan Digital Sky Survey (SDSS-I and II), SDSS-III is a program of four spectroscopic
surveys on three scientific themes: dark energy and cosmological parameters, the history and structure of the Milky
Way, and the population of giant planets around other stars. In keeping with SDSS tradition, SDSS-III will provide
regular public releases of all its data, beginning with SDSS Data Release 8 (DR8), which was made public in 2011
January and includes SDSS-I and SDSS-II images and spectra reprocessed with the latest pipelines and calibrations
produced for the SDSS-III investigations. This paper presents an overview of the four surveys that comprise
SDSS-III. The Baryon Oscillation Spectroscopic Survey will measure redshifts of 1.5 million massive galaxies and
Lyα forest spectra of 150,000 quasars, using the baryon acoustic oscillation feature of large-scale structure to obtain
percent-level determinations of the distance scale and Hubble expansion rate at z<0.7 and at z ≈ 2.5. SEGUE-
2, an already completed SDSS-III survey that is the continuation of the SDSS-II Sloan Extension for Galactic
Understanding and Exploration (SEGUE), measured medium-resolution (R = λ/Δλ ≈ 1800) optical spectra of
118,000 stars in a variety of target categories, probing chemical evolution, stellar kinematics and substructure, and
the mass profile of the dark matter halo from the solar neighborhood to distances of 100 kpc. APOGEE, the Apache
Point Observatory Galactic Evolution Experiment, will obtain high-resolution (R ≈ 30,000), high signal-to-noise
ratio (S/N  100 per resolution element), H-band (1.51 μm <λ<1.70 μm) spectra of 10
5
evolved, late-type
stars, measuring separate abundances for ∼15 elements per star and creating the first high-precision spectroscopic
survey of all Galactic stellar populations (bulge, bar, disks, halo) with a uniform set of stellar tracers and spectral
diagnostics. The Multi-object APO Radial Velocity Exoplanet Large-area Survey (MARVELS) will monitor radial
velocities of more than 8000 FGK stars with the sensitivity and cadence (10–40 m s
−1
, ∼24 visits per star) needed
to detect giant planets with periods up to two years, providing an unprecedented data set for understanding the
formation and dynamical evolution of giant planet systems. As of 2011 January, SDSS-III has obtained spectra of
more than 240,000 galaxies, 29,000 z  2.2 quasars, and 140,000 stars, including 74,000 velocity measurements
of 2580 stars for MARVELS.
Key words: cosmology: observations – Galaxy: evolution – planets and satellites: detection – surveys
Online-only material: color figure
1. INTRODUCTION
The Sloan Digital Sky Survey (SDSS; York et al. 2000)
and the Legacy Survey of SDSS-II performed deep imaging
of 8400 deg
2
of high Galactic latitude sky in five optical
bands, repeat imaging of an equatorial stripe in the southern
Galactic cap (SGC, roughly 25 epochs on 300 deg
2
), and
spectroscopy of more than 900,000 galaxies, 100,000 quasars,
and 200,000 stars (Abazajian et al. 2009). In addition to
completing the original SDSS goals, SDSS-II (which operated
from 2005–2008) executed a supernova survey in the southern
equatorial stripe (Frieman et al. 2008a), discovering more than
500 spectroscopically confirmed Type Ia supernovae in the
redshift range 0.1 <z<0.4, and it also performed an imaging
and spectroscopic survey of the Galaxy, known as SEGUE (the
Sloan Extension for Galactic Understanding and Exploration;
Yanny et al. 2009), with 3200 deg
2
of additional imaging and
spectra of 240,000 stars selected in a variety of target categories.
These surveys were accomplished using a dedicated 2.5 m
telescope
84
with a wide field of view (7 deg
2
,3
◦
diameter; Gunn
et al. 2006), a large mosaic CCD camera (Gunn et al. 1998),
a pair of double spectrographs, each fed by 320 optical fibers
plugged into custom-drilled aluminum plates, and an extensive
network of data reduction and calibration pipelines and data
archiving systems. The resulting data sets have supported an
enormous range of investigations, making the SDSS one of the
most influential astronomical projects of recent decades (Madrid
& Macchetto 2006, 2009).
The achievements of SDSS-I and II and the exceptional power
of the SDSS facilities for wide-field spectroscopy together
84
The Sloan Foundation 2.5 m Telescope at Apache Point Observatory
(APO), in Sunspot, NM, USA.
inspired SDSS-III, a six-year program begun in 2008 July and
consisting of four large spectroscopic surveys on three scientific
themes: dark energy and cosmological parameters, the history
and structure of the Milky Way, and the population of giant
planets around other stars. This paper provides an overview of
the four SDSS-III surveys, each of which will be described in
greater depth by one or more future publications covering survey
strategy, instrumentation, and data reduction software.
The Baryon Oscillation Spectroscopic Survey (BOSS) is the
primary dark-time survey of SDSS-III. It aims to determine
the expansion history of the universe with high precision by
using the baryon acoustic oscillation (BAO) feature in large-
scale structure as a standard ruler for measuring cosmological
distances (Eisenstein & Hu 1998; Blake & Glazebrook 2003;
Seo & Eisenstein 2003). More specifically, the BOSS redshift
survey of 1.5 million massive galaxies aims to measure the
distance–redshift relation d
A
(z) and the Hubble parameter H(z)
with percent-level precision out to z = 0.7, using the well-
established techniques that led to the first detections of the BAO
feature (Cole et al. 2005; Eisenstein et al. 2005). Pioneering a
new method of BAO measurement, BOSS will devote 20% of
its fibers to obtaining Lyα forest absorption spectra of 150,000
distant quasars, achieving the first precision measurements of
cosmic expansion at high redshift (z ≈ 2.5) and serving as a
pathfinder for future surveys employing this technique. BOSS is
also performing spectroscopic surveys of approximately 75,000
ancillary science targets in a variety of categories. To enable
BOSS to cover 10,000 deg
2
, the SDSS imaging camera was
used at the start of SDSS-III to survey an additional 2500 deg
2
of high-latitude sky in the SGC; this imaging was completed in
2010 January. Because BOSS was designed to observe targets
1–2 mag fainter than the original SDSS spectroscopic targets,
substantial upgrades to the SDSS spectrographs were required.
3

The Astronomical Journal, 142:72 (24pp), 2011 September Eisenstein et al.
The upgraded spectrographs were commissioned in Fall 2009.
As of early 2011 January, BOSS had obtained 240,000 galaxy
spectra and 29,000 high-redshift (z  2.2) quasar spectra.
From 2008 July to 2009 July, SDSS-III undertook a spectro-
scopic survey of 118,000 stars in a variety of target categories,
using the original SDSS spectrographs. This survey, called
SEGUE-2, is similar in design to the SEGUE-1 spectroscopic
survey of SDSS-II, but it used the results of SEGUE-1 to re-
fine its target selection algorithms.
85
While SEGUE-1 included
both deep and shallow spectroscopic pointings, SEGUE-2
obtained only deep pointings to better sample the outer halo,
which is the primary reason SEGUE-2 observed fewer stars
than SEGUE. Together, the SEGUE-1 and SEGUE-2 surveys
comprise 358,000 stars observed along a grid of sightlines to-
taling 2500 deg
2
, with spectral resolution R ≡ λ/Δλ ≈ 1800
spanning 3800 Å <λ<9200 Å (where Δλ is the FWHM
of the line-spread function). Typical parameter measurement
errors are 5–10 km s
−1
in radial velocity (RV), 100–200 K in
T
eff
, and 0.21 dex in [Fe/H], depending on signal-to-noise ratio
(S/N) and stellar type (see Section 3). These data allow unique
constraints on the stellar populations and assembly history of
the outer Galaxy and on the mass profile of the Galaxy’s dark
matter halo. SEGUE-2 observations are now complete.
SDSS-III also includes two bright-time surveys, generally
performed when the moon is above the horizon and the lunar
phase is more than 70 deg from new moon. The first of these is
the Multi-object APO Radial Velocity Exoplanet Large-area
Survey (MARVELS), which uses fiber-fed, dispersed fixed-
delay interferometer (DFDI) spectrographs (Erskine & Ge 2000;
Ge 2002;Geetal.2002;vanEykenetal.2010) to monitor
stellar RVs and detect the periodic perturbations caused by
orbiting giant planets. MARVELS aims to monitor 8400 F,
G, and K stars in the magnitude range V = 8–12, observing
each star ∼24 times over a 2–4 year interval to a typical
photon-limited velocity precision per observation of 8 m s
−1
at V = 9, 17 m s
−1
at V = 10, and 27 m s
−1
at V = 11,
with the goal of achieving total errors within a factor of 1.3
of the photon noise. These observations will provide a large
and well characterized statistical sample of giant planets in the
period regime needed to understand the mechanisms of orbital
migration and planet–planet scattering, as well as rare systems
that would escape detection in smaller surveys. MARVELS
began operations in Fall 2008 with a 60 fiber instrument, which
we hope to supplement with a second 60 fiber instrument for the
second half of the survey. As of 2011 January, it has obtained
more than 74,000 RV measurements of 2580 stars.
The Apache Point Observatory Galactic Evolution Exper-
iment (APOGEE) will undertake an H-band (1.51–1.70 μm)
spectroscopic survey of 10
5
evolved late-type stars spanning the
Galactic disk, bulge, and halo, with a typical limiting (Vega-
based) magnitude of H ≈ 12.5 per field. Near-IR spectroscopy
can be carried out even in regions of high dust extinction, which
will allow APOGEE to survey uniform populations of giant/
supergiant tracer stars in all regions of the Galaxy. APOGEE
spectra will have resolution R ≈ 30,000, roughly 15 times that
of SEGUE-2, and will achieve an S/N  100 per resolution ele-
ment for most stars. These spectra will enable detailed chemical
fingerprinting of each individual program star, typically with
0.1 dex measurement precision for ∼15 chemical elements that
85
We will henceforth use the retrospective term “SEGUE-1” to refer to the
SEGUE survey conducted in SDSS-II, and we will use “SEGUE” to refer to
the two surveys generically or collectively.
trace different nucleosynthetic pathways and thus different pop-
ulations of progenitor stars. Once APOGEE begins operations,
MARVELS and APOGEE will usually observe simultaneously,
sharing the focal plane with fibers directed to the two instru-
ments, although this will not be practical in all fields. APOGEE
will use a 300 fiber, cryogenic spectrograph that is now (2011
May) being commissioned at APO.
SDSS-III will continue the SDSS tradition of releasing all
data to the astronomical community and the public, including
calibrated images and spectra and catalogs of objects with
measured parameters, accompanied by powerful database tools
that allow efficient exploration of the data and scientific analysis
(Abazajian et al. 2009). These public data releases will be
numbered consecutively with those of SDSS-I and II; the first
is Data Release 8 (DR8; Aihara et al. 2011), which occurred
in 2011 January, simultaneously with the submission of this
paper. To enable homogeneous analyses that span SDSS-I, II,
and III, DR8 includes essentially all SDSS-I/II imaging and
spectra, processed with the latest data pipelines and calibrations.
DR8 also includes all the new imaging data obtained for
BOSS and all SEGUE-2 data. DR9, currently scheduled for
Summer 2012, will include BOSS spectra obtained through
2011 July, new SEGUE stellar parameter determinations that
incorporate ongoing pipeline and calibration improvements,
and MARVELS RV measurements obtained through 2010
December. DR10, currently scheduled for 2013 July, will
include BOSS and APOGEE spectra obtained through 2012
July. All data releases are cumulative. The final data release,
currently scheduled for 2014 December, will include all BOSS
and APOGEE spectra and all MARVELS RV measurements.
The four subsequent sections describe the individual surveys
in greater detail. We provide a short overview of the technical
and scientific organization of SDSS-III in Section 6 and some
brief concluding remarks in Section 7.
2. BOSS
According to general relativity (hereafter GR), the gravity
of dark matter, baryonic matter, and radiation should slow the
expansion of the universe over time. Astronomers attempting
to measure this deceleration using high-redshift Type Ia su-
pernovae found instead that cosmic expansion is accelerating
(Riess et al. 1998; Perlmutter et al. 1999), a startling discovery
that had been anticipated by indirect arguments (e.g., Peebles
1984; Efstathiou et al. 1990;Kofmanetal.1993; Krauss &
Turner 1995; Ostriker & Steinhardt 1995; Liddle et al. 1996)
and has since been buttressed by more extensive supernova sur-
veys and by several independent lines of evidence (see, e.g.,
Frieman et al. 2008b for a recent review). Cosmic acceleration
is widely viewed as one of the most profound phenomenological
puzzles in contemporary fundamental physics. The two highest
level questions in the field are the following.
1. Is cosmic acceleration caused by a breakdown of GR
on cosmological scales, or is it caused by a new en-
ergy component with negative pressure (“dark energy”)
within GR?
2. If the acceleration is caused by “dark energy,” is its energy
density constant in space and time and thus consistent
with quantum vacuum energy (Zel’dovich 1968) or does
its energy density evolve in time and/or vary in space?
For observational cosmology, the clearest path forward is to
measure the history of cosmic expansion and the growth of
dark matter clustering over a wide range of redshifts with the
4

The Astronomical Journal, 142:72 (24pp), 2011 September Eisenstein et al.
highest achievable precision, searching for deviations from the
model based on GR and a cosmological constant. Supernova
surveys measure the distance–redshift relation using “standard-
ized candles” whose luminosities are calibrated by objects in
the local Hubble flow. BOSS, on the other hand, employs a
“standard ruler,” the BAO feature imprinted on matter cluster-
ing by sound waves that propagate through the baryon-photon
fluid in the pre-recombination universe (Peebles & Yu 1970;
Sunyaev & Zel’dovich 1970; Eisenstein & Hu 1998; Meiksin
et al. 1999). The BAO scale can be computed, in absolute
units, using straightforward physics and cosmological parame-
ters that are well constrained by cosmic microwave background
measurements. BAO are predicted to appear as a bump in the
matter correlation function at a comoving scale corresponding
to the sound horizon (r = 153.2 ± 1.7Mpc;Larsonetal.
2011) or as a damped series of oscillations in the matter power
spectrum (see Eisenstein et al. 2007b for a comparison of the
Fourier- and configuration-space pictures). When measured in
the three-dimensional clustering of matter tracers at redshift z,
the transverse BAO scale constrains the angular diameter dis-
tance d
A
(z) and the line-of-sight scale constrains the Hubble
parameter H (z).
The first clear detections of BAO came in 2005 from anal-
yses of the 2dF Galaxy Redshift Survey (Cole et al. 2005)
and of the luminous red galaxy (LRG) sample (Eisenstein
et al. 2001) of the SDSS (Eisenstein et al. 2005). The final
SDSS-I/II BAO measurements determine the distance to z ≈
0.275 with an uncertainty of 2.7% (Kazin et al. 2010; Percival
et al. 2010; improved from the 5% of Eisenstein et al. 2005).
Because of the leverage provided by this absolute distance mea-
surement, BAO measurements contribute substantially to the
overall cosmological constraints derived from SDSS galaxy
clustering (see Reid et al. 2010).
BOSS consists of two spectroscopic surveys, executed si-
multaneously over an area of 10,000 deg
2
. The first targets
1.5 million galaxies, selected in color–magnitude space to be
high-luminosity systems at large distances. The selection cri-
teria, described further below, produce a roughly constant co-
moving space density n  3 × 10
−4
h
3
Mpc
−3
to z = 0.6,
with a slight peak at z  0.55, then a declining space density to
z  0.8. Relative to the SDSS-I/II LRG survey, which contained
10
5
galaxies out to z = 0.45, the higher space density and higher
limiting redshift of BOSS yield an effective volume (weighted
by S/N at the BAO scale) seven times larger.
86
The second
BOSS survey targets 1.5 × 10
5
quasars, selected from roughly
4 × 10
5
targets (see below), in the redshift range 2.2  z  4,
where Lyα forest absorption in the SDSS spectral range can be
used as a tracer of high-redshift structure.
87
The high density
and large number of targets will allow BOSS to provide the
first “three-dimensional” measurements of large-scale structure
in the Lyα forest, on a sparsely sampled grid of sightlines that
collectively probe an enormous comoving volume. The possi-
bility of measuring BAO in the Lyα forest was discussed by
White (2003), and Fisher matrix forecasts were presented by
McDonald & Eisenstein (2007), whose formalism was used to
motivate and design the BOSS quasar survey. While no previous
survey has measured enough quasar spectra to reveal the BAO
feature in the Lyα forest, analytic estimates and numerical sim-
86
The SDSS main galaxy sample (Strauss et al. 2002) contains over 700,000
galaxies, but it has a median redshift of 0.1 and therefore a much smaller
effective volume for power spectrum measurements on these scales.
87
SDSS-I/II obtained spectra of 106,000 quasars, but only 17,600 were at
z  2.2 (Schneider et al. 2010).
Tab le 1
Summary of BOSS
Duration: Fall 2009–Summer 2014, dark time
Area: 10,000 deg
2
Spectra: 1000 fibers per plate
3600 Å <λ<10000 Å
R = λ/Δλ = 1300–3000
(S/N)
2
≈ 22 pixel
−1
at i
fib
= 21 (averaged over 7000–8500 Å)
≈ 10 pixel
−1
at g
fib
= 22 (averaged over 4000–5500 Å)
Targets: 1.5 × 10
6
massive galaxies, z<0.7, i<19.9
1.5 ×10
5
quasars, z  2.2, g<22.0
selected from 4 ×10
5
candidates
75,000 ancillary science targets, many categories
Measurement goals:
galaxies: d
A
(z)to1.2%atz = 0.35 and 1.2% at z = 0.6
H (z)to2.2%atz = 0.35 and 2.0% at z = 0.6
Lyα forest: d
A
(z)to4.5%atz = 2.5
H (z)to2.6%atz = 2.5
Dilation factor to 1.8% at z = 2.5
Notes. BOSS imaging data were obtained in Fall 2008 and Fall
2009. BOSS spectroscopy uses both dark and gray time (lunar phase
70–100 deg) when the NGC is observable. Galaxy target number
includes 215,000 galaxies observed by SDSS-I/II. Measurement
goals for galaxies are 1.2 times the projected 1σ errors, allowing
some margin over idealized forecasts. Measurement goals for the
Lyα forest are equal to the 1σ forecast, but this is necessarily more
uncertain because of the novelty of the technique. The “dilation
factor” is a common factor scaling d
A
(z)andH
−1
(z)atz = 2.5.
ulations indicate that it should be clearly detectable in the BOSS
quasar survey (McDonald & Eisenstein 2007; Slosar et al. 2009;
Norman et al. 2009; White et al. 2010). The characteristics of
BOSS are summarized in Table 1.
Our forecasts, which are described in Appendix A, indicate
that BAO measurements with the BOSS galaxy survey should
yield determinations of d
A
(z) and H (z) with 1σ precision of
1.0% and 1.8%, respectively, at z = 0.35 (bin width 0.2 <
z<0.5), and with precision of 1.0% and 1.7%, respectively,
at z = 0.6(0.5 <z<0.7). The errors at the two redshifts
are essentially uncorrelated, while the errors on d
A
(z) and H (z)
at a given redshift are anti-correlated (Seo & Eisenstein 2003).
BAO are weakly affected by the effects of nonlinear structure
formation, galaxy bias, and redshift-space distortions. The
primary consequence is a damping of oscillations in the power
spectrum on small scales, which can be well approximated by a
Gaussian smoothing (Bharadwaj 1996; Crocce & Scoccimarro
2006, 2008; Eisenstein et al. 2007b; Matsubara 2008a, 2008b;
Seo et al. 2010; Orban & Weinberg 2011). Our forecasts
assume that density field reconstruction (Eisenstein et al. 2007a)
can remove 50% of the nonlinear Lagrangian displacement
of mass elements from their initial comoving locations (e.g.,
Padmanabhan et al. 2009; Noh et al. 2009), thereby sharpening
the BAO feature and improving recovery of the original signal.
Forecasts with no reconstruction would be worse by factors
of 1.6–2, while with perfect reconstruction (not achievable
in practice) they would improve by factors of 1.3–1.5. The
uncertainty in BOSS BAO measurements is dominated by
cosmic variance out to z = 0.6; at these redshifts, a much higher
density of targets (eliminating shot noise) would decrease the
errors by about a factor of 1.4, while covering the remaining
3π steradians of the sky would reduce the errors by a factor
5