-
J D Vieira,
D P Marrone,
S C Chapman,
C De Breuck,
Y D Hezaveh,
A Weiβ,
J E Aguirre,
K A Aird,
M Aravena,
M L N Ashby, [......],
L Shaw,
E Shirokoff,
J S Spilker,
B Stalder,
Z Staniszewski,
A A Stark,
K Story,
K Vanderlinde,
N Welikala,
R Williamson
[show abstract]
[hide abstract]
ABSTRACT: In the past decade, our understanding of galaxy evolution has been revolutionized by the discovery that luminous, dusty starburst galaxies were 1,000 times more abundant in the early Universe than at present. It has, however, been difficult to measure the complete redshift distribution of these objects, especially at the highest redshifts (z > 4). Here we report a redshift survey at a wavelength of three millimetres, targeting carbon monoxide line emission from the star-forming molecular gas in the direction of extraordinarily bright millimetre-wave-selected sources. High-resolution imaging demonstrates that these sources are strongly gravitationally lensed by foreground galaxies. We detect spectral lines in 23 out of 26 sources and multiple lines in 12 of those 23 sources, from which we obtain robust, unambiguous redshifts. At least 10 of the sources are found to lie at z > 4, indicating that the fraction of dusty starburst galaxies at high redshifts is greater than previously thought. Models of lens geometries in the sample indicate that the background objects are ultra-luminous infrared galaxies, powered by extreme bursts of star formation.
Nature 03/2013; · 36.28 Impact Factor
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Y. D. Hezaveh,
D. P. Marrone,
C. D. Fassnacht,
J. S. Spilker,
J. D. Vieira,
J. E. Aguirre,
K. A. Aird,
M. Aravena,
M. L. N. Ashby,
M. Bayliss, [......],
L. Shaw,
E. Shirokoff,
B. Stalder,
Z. Staniszewski,
A. A. Stark,
K. Story,
K. Vanderlinde,
A. Weiß,
N. Welikala,
R. Williamson
[show abstract]
[hide abstract]
ABSTRACT: We present Atacama Large Millimeter/submillimeter Array (ALMA) 860 micrometer
imaging of four high-redshift (z=2.8-5.7) dusty sources that were detected
using the South Pole Telescope (SPT) at 1.4 mm and are not seen in existing
radio to far-infrared catalogs. At 1.5 arcsec resolution, the ALMA data reveal
multiple images of each submillimeter source, separated by 1-3 arcsec,
consistent with strong lensing by intervening galaxies visible in near-IR
imaging of these sources. We describe a gravitational lens modeling procedure
that operates on the measured visibilities and incorporates
self-calibration-like antenna phase corrections as part of the model
optimization, which we use to interpret the source structure. Lens models
indicate that SPT0346-52, located at z=5.7, is one of the most luminous and
intensely star-forming sources in the universe with a lensing corrected FIR
luminosity of 3.7 X 10^13 L_sun and star formation surface density of 4200
M_sun yr^-1 kpc^-2. We find magnification factors of 5 to 22, with lens
Einstein radii of 1.1-2.0 arcsec and Einstein enclosed masses of 1.6-7.2x10^11
M_sun. These observations confirm the lensing origin of these objects, allow us
to measure the their intrinsic sizes and luminosities, and demonstrate the
important role that ALMA will play in the interpretation of lensed
submillimeter sources.
03/2013;
-
J. D. Vieira,
D. P. Marrone,
S. C. Chapman,
C. De Breuck,
Y. D. Hezaveh,
A. Weiss,
J. E. Aguirre,
K. A. Aird,
M. Aravena,
M. L. N. Ashby, [......],
K. K. Schaffer,
L. Shaw,
E. Shirokoff,
J. S. Spilker,
B. Stalder,
A. A. Stark,
K. Story,
K. Vanderlinde,
N. Welikala,
R. Williamson
[show abstract]
[hide abstract]
ABSTRACT: In the past decade, our understanding of galaxy evolution has been
revolutionized by the discovery that luminous, dusty, starburst galaxies were
1,000 times more abundant in the early Universe than at present. It has,
however, been difficult to measure the complete redshift 2 distribution of
these objects, especially at the highest redshifts (z > 4). Here we report a
redshift survey at a wavelength of three millimeters, targeting carbon monoxide
line emission from the star-forming molecular gas in the direction of
extraordinarily bright millimetrewave-selected sources. High-resolution imaging
demonstrates that these sources are strongly gravitationally lensed by
foreground galaxies. We detect spectral lines in 23 out of 26 sources and
multiple lines in 12 of those 23 sources, from which we obtain robust,
unambiguous redshifts. At least 10 of the sources are found to lie at z > 4,
indicating that the fraction of dusty starburst galaxies at high redshifts is
greater than previously thought. Models of lens geometries in the sample
indicate that the background objects are ultra-luminous infrared galaxies,
powered by extreme bursts of star formation.
03/2013;
-
A. Weiss,
C. De Breuck,
D. P. Marrone,
J. D. Vieira,
J. E. Aguirre,
K. A. Aird,
M. Aravena,
M. L. N. Ashby,
M. Bayliss,
B. A. Benson, [......],
K. K. Schaffer,
E. Shirokoff,
J. S. Spilker,
B. Stalder,
Z. Staniszewski,
A. A. Stark,
K. Story,
K. Vanderlinde,
N. Welikala,
R. Williamson
[show abstract]
[hide abstract]
ABSTRACT: Using the Atacama Large Millimeter/submillimeter Array (ALMA), we have
conducted a blind redshift survey in the 3 mm atmospheric transmission window
for 26 strongly lensd dusty star-forming galaxies (DSFGs) selected with the
South Pole Telescope (SPT). The sources were selected to have S_1.4mm>20 mJy
and a dust-like spectrum and, to remove low-z sources, not have bright radio
(S_843MHz<6mJy) or far-infrared counterparts (S_100um<1 Jy, S_60um<200mJy). We
robustly detect 44 line features in our survey, which we identify as redshifted
emission lines of 12CO, 13CO, [CI], H2O, and H2O+. We find one or more spectral
features in 23 sources yielding a ~90% detection rate for this survey; in 12 of
these sources we detect multiple lines, while in 11 sources we detect only a
single line. For the sources with only one detected line, we break the redshift
degeneracy with additional spectroscopic observations if available, or infer
the most likely line identification based on photometric data. This yields
secure redshifts for ~70% of the sample. The three sources with no lines
detected are tentatively placed in the redshift desert between 1.7<z<2.0. The
resulting mean redshift of our sample is =3.5. This finding is in contrast
to the redshift distribution of radio-identified DSFGs, which have a
significantly lower mean redshift of =2.3 and for which only 10-15% of the
population is expected to be at z>3. We discuss the effect of gravitational
lensing on the redshift distribution and compare our measured redshift
distribution to that of models in the literature.
03/2013;
-
Z. Hou,
C. L. Reichardt,
K. T. Story,
B. Follin,
R. Keisler,
K. A. Aird,
B. A. Benson,
L. E. Bleem,
J. E. Carlstrom,
C. L. Chang, [......],
L. Shaw,
E. Shirokoff,
H. G. Spieler,
Z. Staniszewski,
A. A. Stark,
A. van Engelen,
K. Vanderlinde,
J. D. Vieira,
R. Williamson,
O. Zahn
[show abstract]
[hide abstract]
ABSTRACT: We explore extensions to the standard LCDM cosmological model using new
measurements of the cosmic microwave background (CMB) from the South Pole
Telescope (SPT). Adding SPT measurements to WMAP7 significantly improves
constraints on possible extensions to the LCDM model; the addition of
low-redshift measurements of H0 and BAO leads to further improvements. Before
combining these datasets, we check for consistency in the LCDM model between
measurements of the CMB (SPT+WMAP7), H0 and BAO, and find evidence for some
tension between the datasets. Within the CMB data alone, we find only weak
support for physics beyond the LCDM model due to a slight trend of decreasing
power at smaller angular scales, relative to the prediction of the LCDM model.
This trend could be due to a logarithmic scale dependence of the power-law
index of the primordial power spectrum, nrun. Alternatively, the trend could
arise either from adjustments at small or large scales. The power at small
scales is sensitive to the damping scale which is influenced by both the helium
abundance, Yp and the effective number of neutrino species, Neff. The power at
large scales is affected by the ISW effect which is sensitive to the sum of
neutrino masses, mnu. These extensions have similar observational consequences
and are partially degenerate when considered simultaneously. These degeneracies
can weaken or enhance the apparent deviation of any single extension from the
LCDM model. Of the 6 one-parameter model extensions considered, we find the CMB
data to have the largest statistical preference for running within [-0.046,
-0.003] at 95% confidence...[abridged]
12/2012;
-
K. T. Story,
C. L. Reichardt,
Z. Hou,
R. Keisler,
K. A. Aird,
B. A. Benson,
L. E. Bleem,
J. E. Carlstrom,
C. L. Chang,
H-M. Cho, [......],
L. Shaw,
E. Shirokoff,
H. G. Spieler,
Z. Staniszewski,
A. A. Stark,
A. van Engelen,
K. Vanderlinde,
J. D. Vieira,
R. Williamson,
O. Zahn
[show abstract]
[hide abstract]
ABSTRACT: We present a measurement of the cosmic microwave background (CMB) temperature
power spectrum using data from the recently completed South Pole Telescope
Sunyaev-Zel'dovich (SPT-SZ) survey. This measurement is made from observations
of 2540 deg^2 of sky with arcminute resolution at 150 GHz, and improves upon
previous measurements using the SPT by tripling the sky area. We report CMB
temperature anisotropy power over the multipole range 650<\ell<3000. We fit the
SPT bandpowers, combined with the results from the seven-year Wilkinson
Microwave Anisotropy Probe (WMAP7) data release, with a six-parameter LCDM
cosmological model and find that the two datasets are consistent and well fit
by the model. Adding SPT measurements significantly improves LCDM parameter
constraints, and in particular tightens the constraint on the angular sound
horizon \theta_s by a factor of 2.7. The impact of gravitational lensing on the
CMB power spectrum is detected with 8.1 \sigma, the most significant detection
to date. The inferred amplitude of the lensing spectrum is consistent with the
LCDM prediction. This sensitivity of the SPT+WMAP7 data to lensing by
large-scale structure at low redshifts allows us to constrain the mean
curvature of the observable universe with CMB data alone to be
\Omega_K=-0.003+0.014-0.018. Using the SPT+WMAP7 data, we measure the spectral
index of scalar fluctuations to be ns=0.9623+/-0.0097 in the LCDM model, a 3.9
\sigma preference for a scale-dependent spectrum with ns<1. The SPT measurement
of the CMB damping tail helps break the degeneracy that exists between the
tensor-to-scalar ratio r and ns in large-scale CMB measurements, leading to an
upper limit of r<0.18 (95% C.L.) in the LCDM+r model. Adding low-redshift
measurements of the Hubble constant ($H_0$) and the baryon acoustic oscillation
(BAO) feature ...[abridged]
10/2012;
-
J. T. Sayre,
P. Ade,
K. A. Aird,
J. E. Austermann,
J. A. Beall,
D. Becker,
B. A. Benson,
L. E. Bleem,
J. Britton,
J. E. Carlstrom, [......],
E. Shirokoff,
K. Story,
C. Tucker,
K. Vanderlinde,
J. D. Vieira,
G. Wang,
R. Williamson,
V. Yefremenko,
K. W. Yoon,
E. Young
[show abstract]
[hide abstract]
ABSTRACT: The SPTpol camera is a two-color, polarization-sensitive bolometer receiver,
and was installed on the 10 meter South Pole Telescope in January 2012. SPTpol
is designed to study the faint polarization signals in the Cosmic Microwave
Background, with two primary scientific goals. One is to constrain the
tensor-to-scalar ratio of perturbations in the primordial plasma, and thus
constrain the space of permissible inflationary models. The other is to measure
the weak lensing effect of large-scale structure on CMB polarization, which can
be used to constrain the sum of neutrino masses as well as other growth-related
parameters. The SPTpol focal plane consists of seven 84-element monolithic
arrays of 150 GHz pixels (588 total) and 180 individual 90 GHz single-pixel
modules. In this paper we present the design and characterization of the 90 GHz
modules.
10/2012;
-
K. Story,
E. Leitch,
P. Ade,
K. A. Aird,
J. E. Austermann,
J. A. Beall,
D. Becker,
A. N. Bender,
B. A. Benson,
L. E. Bleem, [......],
G. Smecher,
B. Stalder,
C. Tucker,
K. Vanderlinde,
J. D. Vieira,
G. Wang,
R. Williamson,
V. Yefremenko,
K. W. Yoon,
E. Young
[show abstract]
[hide abstract]
ABSTRACT: We present the software system used to control and operate the South Pole
Telescope. The South Pole Telescope is a 10-meter millimeter-wavelength
telescope designed to measure anisotropies in the cosmic microwave background
(CMB) at arcminute angular resolution. In the austral summer of 2011/12, the
SPT was equipped with a new polarization-sensitive camera, which consists of
1536 transition-edge sensor bolometers. The bolometers are read out using 36
independent digital frequency multiplexing (\dfmux) readout boards, each with
its own embedded processors. These autonomous boards control and read out data
from the focal plane with on-board software and firmware. An overall control
software system running on a separate control computer controls the \dfmux
boards, the cryostat and all other aspects of telescope operation. This control
software collects and monitors data in real-time, and stores the data to disk
for transfer to the United States for analysis.
10/2012;
-
J. W. Henning,
P. Ade,
K. A. Aird,
J. E. Austermann,
J. A. Beall,
D. Becker,
B. A. Benson,
L. E. Bleem,
J. Britton,
J. E. Carlstrom, [......],
E. Shirokoff,
K. Story,
C. Tucker,
K. Vanderlinde,
J. D. Vieira,
G. Wang,
R. Williamson,
V. Yefremenko,
K. W. Yoon,
E. Young
[show abstract]
[hide abstract]
ABSTRACT: The SPTpol camera is a dichroic polarimetric receiver at 90 and 150 GHz.
Deployed in January 2012 on the South Pole Telescope (SPT), SPTpol is looking
for faint polarization signals in the Cosmic Microwave Background (CMB). The
camera consists of 180 individual Transition Edge Sensor (TES) polarimeters at
90 GHz and seven 84-polarimeter camera modules (a total of 588 polarimeters) at
150 GHz. We present the design, dark characterization, and in-lab optical
properties of the 150 GHz camera modules. The modules consist of
photolithographed arrays of TES polarimeters coupled to silicon platelet arrays
of corrugated feedhorns, both of which are fabricated at NIST-Boulder. In
addition to mounting hardware and RF shielding, each module also contains a set
of passive readout electronics for digital frequency-domain multiplexing. A
single module, therefore, is fully functional as a miniature focal plane and
can be tested independently. Across the modules tested before deployment, the
detectors average a critical temperature of 478 mK, normal resistance R_N of
1.2 Ohm, unloaded saturation power of 22.5 pW, (detector-only) optical
efficiency of ~ 90%, and have electrothermal time constants < 1 ms in
transition.
10/2012;
-
J. E. Austermann,
K. A. Aird,
J. A. Beall,
D. Becker,
A. Bender,
B. A. Benson,
L. E. Bleem,
J. Britton,
J. E. Carlstrom,
C. L. Chang, [......],
E. Shirokoff,
A. A. Stark,
K. Story,
K. Vanderlinde,
J. D. Vieira,
G. Wang,
R. Williamson,
V. Yefremenko,
K. W. Yoon,
O. Zahn
[show abstract]
[hide abstract]
ABSTRACT: SPTpol is a dual-frequency polarization-sensitive camera that was deployed on
the 10-meter South Pole Telescope in January 2012. SPTpol will measure the
polarization anisotropy of the cosmic microwave background (CMB) on angular
scales spanning an arcminute to several degrees. The polarization sensitivity
of SPTpol will enable a detection of the CMB "B-mode" polarization from the
detection of the gravitational lensing of the CMB by large scale structure, and
a detection or improved upper limit on a primordial signal due to inflationary
gravity waves. The two measurements can be used to constrain the sum of the
neutrino masses and the energy scale of inflation. These science goals can be
achieved through the polarization sensitivity of the SPTpol camera and careful
control of systematics. The SPTpol camera consists of 768 pixels, each
containing two transition-edge sensor (TES) bolometers coupled to orthogonal
polarizations, and a total of 1536 bolometers. The pixels are sensitive to
light in one of two frequency bands centered at 90 and 150 GHz, with 180 pixels
at 90 GHz and 588 pixels at 150 GHz. The SPTpol design has several features
designed to control polarization systematics, including: single-moded feedhorns
with low cross-polarization, bolometer pairs well-matched to difference
atmospheric signals, an improved ground shield design based on far-sidelobe
measurements of the SPT, and a small beam to reduce temperature to polarization
leakage. We present an overview of the SPTpol instrument design, project
status, and science projections.
10/2012;
-
E. M. George,
P. Ade,
K. A. Aird,
J. E. Austermann,
J. A. Beall,
D. Becker,
A. Bender,
B. A. Benson,
L. E. Bleem,
J. Britton, [......],
E. Shirokoff,
K. Story,
C. Tucker,
K. Vanderlinde,
J. D. Vieira,
G. Wang,
R. Williamson,
V. Yefremenko,
K. W. Yoon,
E. Young
[show abstract]
[hide abstract]
ABSTRACT: In January 2012, the 10m South Pole Telescope (SPT) was equipped with a
polarization-sensitive camera, SPTpol, in order to measure the polarization
anisotropy of the cosmic microwave background (CMB). Measurements of the
polarization of the CMB at small angular scales (~several arcminutes) can
detect the gravitational lensing of the CMB by large scale structure and
constrain the sum of the neutrino masses. At large angular scales (~few
degrees) CMB measurements can constrain the energy scale of Inflation. SPTpol
is a two-color mm-wave camera that consists of 180 polarimeters at 90 GHz and
588 polarimeters at 150 GHz, with each polarimeter consisting of a dual
transition edge sensor (TES) bolometers. The full complement of 150 GHz
detectors consists of 7 arrays of 84 ortho-mode transducers (OMTs) that are
stripline coupled to two TES detectors per OMT, developed by the TRUCE
collaboration and fabricated at NIST. Each 90 GHz pixel consists of two
antenna-coupled absorbers coupled to two TES detectors, developed with Argonne
National Labs. The 1536 total detectors are read out with digital
frequency-domain multiplexing (DfMUX). The SPTpol deployment represents the
first on-sky tests of both of these detector technologies, and is one of the
first deployed instruments using DfMUX readout technology. We present the
details of the design, commissioning, deployment, on-sky optical
characterization and detector performance of the complete SPTpol focal plane.
10/2012;
-
D. R. Semler,
R. Šuhada,
K. A. Aird,
M. L. N. Ashby,
M. Bautz,
M. Bayliss,
G. Bazin,
S. Bocquet,
B. A. Benson,
L. E. Bleem, [......],
A. A. Stark,
K. Story,
C. W. Stubbs,
A. van Engelen,
K. Vanderlinde,
J. D. Vieira,
A. Vikhlinin,
R. Williamson,
O. Zahn,
A. Zenteno
[show abstract]
[hide abstract]
ABSTRACT: We report the first investigation of cool-core properties of galaxy clusters
selected via their Sunyaev--Zel'dovich (SZ) effect. We use 13 galaxy clusters
uniformly selected from 178 deg^2 observed with the South Pole Telescope (SPT)
and followed up by the Chandra X-ray Observatory. They form an approximately
mass-limited sample (> 3 x 10^14 M_sun h^-1_70) spanning redshifts 0.3 < z <
1.1. Using previously published X-ray-selected cluster samples, we compare two
proxies of cool-core strength: surface brightness concentration (cSB) and
cuspiness ({\alpha}). We find that cSB is better constrained. We measure cSB
for the SPT sample and find several new z > 0.5 cool-core clusters, including
two strong cool cores. This rules out the hypothesis that there are no z > 0.5
clusters that qualify as strong cool cores at the 5.4{\sigma} level. The
fraction of strong cool-core clusters in the SPT sample in this redshift regime
is between 7% and 56% (95% confidence). Although the SPT selection function is
significantly different from the X-ray samples, the high-z cSB distribution for
the SPT sample is statistically consistent with that of X-ray-selected samples
at both low and high redshifts. The cool-core strength is inversely correlated
with the offset between the brightest cluster galaxy and the X-ray centroid,
providing evidence that the dynamical state affects the cool-core strength of
the cluster. Larger SZ-selected samples will be crucial in understanding the
evolution of cluster cool cores over cosmic time.
08/2012;
-
M McDonald,
M Bayliss,
B A Benson,
R J Foley,
J Ruel,
P Sullivan,
S Veilleux,
K A Aird,
M L N Ashby,
M Bautz, [......],
K Story,
C W Stubbs,
R Suhada,
A van Engelen,
K Vanderlinde,
J D Vieira,
A Vikhlinin,
R Williamson,
O Zahn,
A Zenteno
[show abstract]
[hide abstract]
ABSTRACT: In the cores of some clusters of galaxies the hot intracluster plasma is dense enough that it should cool radiatively in the cluster's lifetime, leading to continuous 'cooling flows' of gas sinking towards the cluster centre, yet no such cooling flow has been observed. The low observed star-formation rates and cool gas masses for these 'cool-core' clusters suggest that much of the cooling must be offset by feedback to prevent the formation of a runaway cooling flow. Here we report X-ray, optical and infrared observations of the galaxy cluster SPT-CLJ2344-4243 (ref. 11) at redshift z = 0.596. These observations reveal an exceptionally luminous (8.2 × 10(45) erg s(-1)) galaxy cluster that hosts an extremely strong cooling flow (around 3,820 solar masses a year). Further, the central galaxy in this cluster appears to be experiencing a massive starburst (formation of around 740 solar masses a year), which suggests that the feedback source responsible for preventing runaway cooling in nearby cool-core clusters may not yet be fully established in SPT-CLJ2344-4243. This large star-formation rate implies that a significant fraction of the stars in the central galaxy of this cluster may form through accretion of the intracluster medium, rather than (as is currently thought) assembling entirely via mergers.
Nature 08/2012; 488(7411):349-52. · 36.28 Impact Factor
-
M. McDonald,
M. Bayliss,
B. A. Benson,
R. J. Foley,
J. Ruel,
P. Sullivan,
S. Veilleux,
K. A. Aird,
M. L. N. Ashby,
M. Bautz, [......],
K. Story,
C. W. Stubbs,
R. Suhada,
A. van Engelen,
K. Vanderlinde,
J. D. Vieira,
A. Vikhlinin,
R. Williamson,
O. Zahn,
A. Zenteno
[show abstract]
[hide abstract]
ABSTRACT: In the cores of some galaxy clusters the hot intracluster plasma is dense
enough that it should cool radiatively in the cluster's lifetime, leading to
continuous "cooling flows" of gas sinking towards the cluster center, yet no
such cooling flow has been observed. The low observed star formation rates and
cool gas masses for these "cool core" clusters suggest that much of the cooling
must be offset by astrophysical feedback to prevent the formation of a runaway
cooling flow. Here we report X-ray, optical, and infrared observations of the
galaxy cluster SPT-CLJ2344-4243 at z = 0.596. These observations reveal an
exceptionally luminous (L_2-10 keV = 8.2 x 10^45 erg/s) galaxy cluster which
hosts an extremely strong cooling flow (dM/dt = 3820 +/- 530 Msun/yr). Further,
the central galaxy in this cluster appears to be experiencing a massive
starburst (740 +/- 160 Msun/yr), which suggests that the feedback source
responsible for preventing runaway cooling in nearby cool core clusters may not
yet be fully established in SPT-CLJ2344-4243. This large star formation rate
implies that a significant fraction of the stars in the central galaxy of this
cluster may form via accretion of the intracluster medium, rather than the
current picture of central galaxies assembling entirely via mergers.
08/2012;
-
J. Song,
A. Zenteno,
B. Stalder, S. Desai,
L. E. Bleem,
K. A. Aird,
R. Armstrong,
M. L. N. Ashby,
M. Bayliss,
G. Bazin, [......],
S. A. Stanford,
Z. Staniszewski,
A. A. Stark,
K. Story,
C. W. Stubbs,
A. van Engelen,
K. Vanderlinde,
J. D. Vieira,
R. Williamson,
O. Zahn
[show abstract]
[hide abstract]
ABSTRACT: We present the results of the ground- and space-based optical and
near-infrared (NIR) follow-up of 224 galaxy cluster candidates detected with
the Sunyaev-Zel'dovich (SZ) effect in the 720 deg^2 of the South Pole Telescope
(SPT) survey completed in the 2008 and 2009 observing seasons. We use the
optical/NIR data to establish whether each candidate is associated with an
overdensity of galaxies and to estimate the cluster redshift. Most photometric
redshifts are derived through a combination of three different cluster redshift
estimators using red-sequence galaxies, resulting in an accuracy of \Delta
z/(1+z)=0.017, determined through comparison with a subsample of 57 clusters
for which we have spectroscopic redshifts. We successfully measure redshifts
for 158 systems and present redshift lower limits for the remaining candidates.
The redshift distribution of the confirmed clusters extends to z=1.35 with a
median of z_{med}=0.57. Approximately 18% of the sample with measured redshifts
lies at z>0.8. We estimate a lower limit to the purity of this SPT SZ-selected
sample by assuming that all unconfirmed clusters are noise fluctuations in the
SPT data. We show that the cumulative purity at detection significance \xi>5
(\xi>4.5) is >= 95 (>= 70%). We present the red brightest cluster galaxy (rBCG)
positions for the sample and examine the offsets between the SPT candidate
position and the rBCG. The radial distribution of offsets is similar to that
seen in X-ray-selected cluster samples, providing no evidence that SZ-selected
cluster samples include a different fraction of recent mergers than
X-ray-selected cluster samples.
07/2012;
-
M A Dobbs,
M Lueker,
K A Aird,
A N Bender,
B A Benson,
L E Bleem,
J E Carlstrom,
C L Chang,
H-M Cho,
J Clarke, [......],
D Schwan,
E Shirokoff,
H G Spieler,
Z Staniszewski,
A A Stark,
K Vanderlinde,
J D Vieira,
C Vu,
B Westbrook,
R Williamson
[show abstract]
[hide abstract]
ABSTRACT: A technological milestone for experiments employing transition edge sensor bolometers operating at sub-Kelvin temperature is the deployment of detector arrays with 100s-1000s of bolometers. One key technology for such arrays is readout multiplexing: the ability to read out many sensors simultaneously on the same set of wires. This paper describes a frequency-domain multiplexed readout system which has been developed for and deployed on the APEX-SZ and South Pole Telescope millimeter wavelength receivers. In this system, the detector array is divided into modules of seven detectors, and each bolometer within the module is biased with a unique ∼MHz sinusoidal carrier such that the individual bolometer signals are well separated in frequency space. The currents from all bolometers in a module are summed together and pre-amplified with superconducting quantum interference devices operating at 4 K. Room temperature electronics demodulate the carriers to recover the bolometer signals, which are digitized separately and stored to disk. This readout system contributes little noise relative to the detectors themselves, is remarkably insensitive to unwanted microphonic excitations, and provides a technology pathway to multiplexing larger numbers of sensors.
The Review of scientific instruments 07/2012; 83(7):073113. · 1.52 Impact Factor
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B. Stalder,
J. Ruel,
R. Suhada,
M. Brodwin,
K. A. Aird,
K. Andersson,
R. Armstrong,
M. L. N. Ashby,
M. Bautz,
M. Bayliss, [......],
A. A. Stark,
K. Story,
C. W. Stubbs,
A. van Engelen,
K. Vanderlinde,
J. D. Vieira,
A. Vikhlinin,
R. Williamson,
O. Zahn,
A. Zenteno
[show abstract]
[hide abstract]
ABSTRACT: The galaxy cluster SPT-CL J0205-5829 currently has the highest
spectroscopically-confirmed redshift, z=1.322, in the South Pole Telescope
Sunyaev-Zel'dovich (SPT-SZ) survey. XMM-Newton observations measure a
core-excluded temperature of Tx=8.7keV producing a mass estimate that is
consistent with the Sunyaev-Zel'dovich derived mass. The combined SZ and X-ray
mass estimate of M500=(4.9+/-0.8)e14 h_{70}^{-1} Msun makes it the most massive
known SZ-selected galaxy cluster at z>1.2 and the second most massive at z>1.
Using optical and infrared observations, we find that the brightest galaxies in
SPT-CL J0205-5829 are already well evolved by the time the universe was <5 Gyr
old, with stellar population ages >3 Gyr, and low rates of star formation
(<0.5Msun/yr). We find that, despite the high redshift and mass, the existence
of SPT-CL J0205-5829 is not surprising given a flat LambdaCDM cosmology with
Gaussian initial perturbations. The a priori chance of finding a cluster of
similar rarity (or rarer) in a survey the size of the 2500 deg^2 SPT-SZ survey
is 69%.
05/2012;
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F. W. High,
H. Hoekstra,
N. Leethochawalit,
T. de Haan,
L. Abramson,
K. A. Aird,
R. Armstrong,
M. L. N. Ashby,
M. Bautz,
M. Bayliss, [......],
C. W. Stubbs,
R. Suhada,
S. Tokarz,
A. van Engelen,
K. Vanderlinde,
J. D. Vieira,
A. Vikhlinin,
R. Williamson,
O. Zahn,
A. Zenteno
[show abstract]
[hide abstract]
ABSTRACT: We use weak gravitational lensing to measure the masses of five galaxy
clusters selected from the South Pole Telescope (SPT) survey, with the primary
goal of comparing these with the SPT Sunyaev--Zel'dovich (SZ) and X-ray based
mass estimates. The clusters span redshifts 0.28 < z < 0.43 and have masses
M_500 > 2 x 10^14 h^-1 M_sun, and three of the five clusters were discovered by
the SPT survey. We observed the clusters in the g'r'i' passbands with the
Megacam imager on the Magellan Clay 6.5m telescope. We measure a mean ratio of
weak lensing (WL) aperture masses to inferred aperture masses from the SZ data,
both within an aperture of R_500,SZ derived from the SZ mass, of 1.04 +/- 0.18.
We measure a mean ratio of spherical WL masses evaluated at R_500,SZ to
spherical SZ masses of 1.07 +/- 0.18, and a mean ratio of spherical WL masses
evaluated at R_500,WL to spherical SZ masses of 1.10 +/- 0.24. We explore
potential sources of systematic error in the mass comparisons and conclude that
all are subdominant to the statistical uncertainty, with dominant terms being
cluster concentration uncertainty and N-body simulation calibration bias.
Expanding the sample of SPT clusters with WL observations has the potential to
significantly improve the SPT cluster mass calibration and the resulting
cosmological constraints from the SPT cluster survey. These are the first WL
detections using Megacam on the Magellan Clay telescope.
05/2012;
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C. L. Reichardt,
B. Stalder,
L. E. Bleem,
T. E. Montroy,
K. A. Aird,
K. Andersson,
R. Armstrong,
M. L. N. Ashby,
M. Bautz,
M. Bayliss, [......],
K. Story,
C. W. Stubbs,
R. Suhada,
A. van Engelen,
K. Vanderlinde,
J. D. Vieira,
A. Vikhlinin,
R. Williamson,
O. Zahn,
A. Zenteno
[show abstract]
[hide abstract]
ABSTRACT: We present a catalog of 224 galaxy cluster candidates, selected through their
Sunyaev-Zel'dovich (SZ) effect signature in the first 720 deg2 of the South
Pole Telescope (SPT) survey. This area was mapped with the SPT in the 2008 and
2009 austral winters to a depth of 18 uK-arcmin at 150 GHz; 550 deg2 of it was
also mapped to 44 uK-arcmin at 95 GHz. Based on optical imaging of all
candidates and near-infrared imaging of the majority of candidates, we have
found optical and/or infrared counterparts for 158 clusters. Of these, 135 were
first identified as clusters in SPT data, including 117 new discoveries
reported in this work. This catalog triples the number of confirmed galaxy
clusters discovered through the SZ effect. We report photometrically derived
(and in some cases spectroscopic) redshifts for confirmed clusters and redshift
lower limits for the remaining candidates. The catalog extends to high redshift
with a median redshift of z = 0.55 and maximum redshift of z = 1.37. Based on
simulations, we expect the catalog to be nearly 100% complete above M500 ~ 5e14
Msun h_{70}^-1 at z > 0.6. There are 121 candidates detected at signal-to-noise
greater than five, at which the catalog purity is measured to be 95%. From this
high-purity subsample, we exclude the z < 0.3 clusters and use the remaining
100 candidates to improve cosmological constraints following the method
presented by Benson et al., 2011. Adding the cluster data to CMB+BAO+H0 data
leads to a preference for non-zero neutrino masses while only slightly reducing
the upper limit on the sum of neutrino masses to sum mnu < 0.38 eV (95% CL).
For a spatially flat wCDM cosmological model, the addition of this catalog to
the CMB+BAO+H0+SNe results yields sigma8=0.807+-0.027 and w = -1.010+-0.058,
improving the constraints on these parameters by a factor of 1.4 and 1.3,
respectively. [abbrev]
03/2012;
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L. E. Bleem,
A. van Engelen,
G. P. Holder,
K. A. Aird,
R. Armstrong,
M. L. N. Ashby,
M. R. Becker,
B. A. Benson,
T. Biesiadzinski,
M. Brodwin, [......],
Z. Staniszewski,
A. A. Stark,
D. Stern,
K. Story,
A. Vallinotto,
K. Vanderlinde,
J. D. Vieira,
R. H. Wechsler,
R. Williamson,
O. Zahn
[show abstract]
[hide abstract]
ABSTRACT: We compare cosmic microwave background lensing convergence maps derived from
South Pole Telescope (SPT) data with galaxy survey data from the Blanco
Cosmology Survey, the Wide-field Infrared Survey Explorer, and a new large
Spitzer/IRAC field designed to overlap with the SPT survey. Using optical and
infrared catalogs covering between 17 and 68 square degrees of sky, we detect
correlation between the SPT convergence maps and each of the galaxy density
maps at >4 sigma, with zero cross-correlation robustly ruled out in all cases.
The amplitude and shape of the cross-power spectra are in good agreement with
theoretical expectations and the measured galaxy bias is consistent with
previous work. The detections reported here utilize a small fraction of the
full 2500 square degree SPT survey data and serve as both a proof of principle
of the technique and an illustration of the potential of this emerging
cosmological probe.
03/2012;
