334 research outputs found
The Atacama Cosmology Telescope: Sunyaev-Zel'dovich Selected Galaxy Clusters at 148 GHz from Three Seasons of Data
[Abridged] We present a catalog of 68 galaxy clusters, of which 19 are new
discoveries, detected via the Sunyaev-Zel'dovich effect (SZ) at 148 GHz in the
Atacama Cosmology Telescope (ACT) survey of 504 square degrees on the celestial
equator. A subsample of 48 clusters within the 270 square degree region
overlapping SDSS Stripe 82 is estimated to be 90% complete for M_500c > 4.5e14
Msun and 0.15 < z < 0.8. While matched filters are used to detect the clusters,
the sample is studied further through a "Profile Based Amplitude Analysis"
using a single filter at a fixed \theta_500 = 5.9' angular scale. This new
approach takes advantage of the "Universal Pressure Profile" (UPP) to fix the
relationship between the cluster characteristic size (R_500) and the integrated
Compton parameter (Y_500). The UPP scalings are found to be nearly identical to
an adiabatic model, while a model incorporating non-thermal pressure better
matches dynamical mass measurements and masses from the South Pole Telescope. A
high signal to noise ratio subsample of 15 ACT clusters is used to obtain
cosmological constraints. We first confirm that constraints from SZ data are
limited by uncertainty in the scaling relation parameters rather than sample
size or measurement uncertainty. We next add in seven clusters from the ACT
Southern survey, including their dynamical mass measurements based on galaxy
velocity dispersions. In combination with WMAP7 these data simultaneously
constrain the scaling relation and cosmological parameters, yielding \sigma_8 =
0.829 \pm 0.024 and \Omega_m = 0.292 \pm 0.025. The results include
marginalization over a 15% bias in dynamical mass relative to the true halo
mass. In an extension to LCDM that incorporates non-zero neutrino mass density,
we combine our data with WMAP7+BAO+Hubble constant measurements to constrain
\Sigma m_\nu < 0.29 eV (95% C. L.).Comment: 32 pages, 21 figures To appear in J. Cosmology and Astroparticle
Physic
The Atacama Cosmology Telescope: Dusty Star-Forming Galaxies and Active Galactic Nuclei in the Southern Survey
We present a catalog of 191 extragalactic sources detected by the Atacama
Cosmology Telescope (ACT) at 148 GHz and/or 218 GHz in the 2008 Southern
survey. Flux densities span 14-1700 mJy, and we use source spectral indices
derived using ACT-only data to divide our sources into two sub-populations: 167
radio galaxies powered by central active galactic nuclei (AGN), and 24 dusty
star-forming galaxies (DSFGs). We cross-identify 97% of our sources (166 of the
AGN and 19 of the DSFGs) with those in currently available catalogs. When
combined with flux densities from the Australian Telescope 20 GHz survey and
follow-up observations with the Australia Telescope Compact Array, the
synchrotron-dominated population is seen to exhibit a steepening of the slope
of the spectral energy distribution from 20 to 148 GHz, with the trend
continuing to 218 GHz. The ACT dust-dominated source population has a median
spectral index of 3.7+0.62-0.86, and includes both local galaxies and sources
with redshifts as great as 5.6. Dusty sources with no counterpart in existing
catalogs likely belong to a recently discovered subpopulation of DSFGs lensed
by foreground galaxies or galaxy groups.Comment: 13 pages, 8 figures, 4 table
The Atacama Cosmology Telescope: The polarization-sensitive ACTPol instrument
The Atacama Cosmology Telescope (ACT) is designed to make high angular
resolution measurements of anisotropies in the Cosmic Microwave Background
(CMB) at millimeter wavelengths. We describe ACTPol, an upgraded receiver for
ACT, which uses feedhorn-coupled, polarization-sensitive detector arrays, a 3
degree field of view, 100 mK cryogenics with continuous cooling, and meta
material anti-reflection coatings. ACTPol comprises three arrays with separate
cryogenic optics: two arrays at a central frequency of 148 GHz and one array
operating simultaneously at both 97 GHz and 148 GHz. The combined instrument
sensitivity, angular resolution, and sky coverage are optimized for measuring
angular power spectra, clusters via the thermal Sunyaev-Zel'dovich and kinetic
Sunyaev-Zel'dovich signals, and CMB lensing due to large scale structure. The
receiver was commissioned with its first 148 GHz array in 2013, observed with
both 148 GHz arrays in 2014, and has recently completed its first full season
of operations with the full suite of three arrays. This paper provides an
overview of the design and initial performance of the receiver and related
systems
The Atacama Cosmology Telescope: Two-Season ACTPol Lensing Power Spectrum
We report a measurement of the power spectrum of cosmic microwave background
(CMB) lensing from two seasons of Atacama Cosmology Telescope Polarimeter
(ACTPol) CMB data. The CMB lensing power spectrum is extracted from both
temperature and polarization data using quadratic estimators. We obtain results
that are consistent with the expectation from the best-fit Planck LCDM model
over a range of multipoles L=80-2100, with an amplitude of lensing A_lens =
1.06 +/- 0.15 (stat.) +/- 0.06 (sys.) relative to Planck. Our measurement of
the CMB lensing power spectrum gives sigma_8 Omega_m^0.25 = 0.643 +/- 0.054;
including baryon acoustic oscillation scale data, we constrain the amplitude of
density fluctuations to be sigma_8 = 0.831 +/- 0.053. We also update
constraints on the neutrino mass sum. We verify our lensing measurement with a
number of null tests and systematic checks, finding no evidence of significant
systematic errors. This measurement relies on a small fraction of the ACTPol
data already taken; more precise lensing results can therefore be expected from
the full ACTPol dataset.Comment: 17 pages, 11 figures, to be submitted to Physical Review
Differential gene expression in tilapia Oreochromis niloticus (L., 1758) under feeding stress
Feeding stress or suboptimal feeding in fish can have a direct impact on their energy metabolism and feed use efficiency, and thus on productivity. That impact can be quantified objectively by comparing the expression of genes between fish fed ad libitum and fish fed suboptimally. Moreover, some of the genes expressed in animals fed suboptimally can also be used as candidate genes to identify feeding stress in general. To identify some of those genes, a group of 60 tilapia Oreochromis niloticus (L., 1758) was divided into two batches (fed ad libitum or suboptimally for 22 days) with two replicates. For this purpose, we carried out differential display analysis in brain tissue samples using 36 combinations of 3 polyT anchoring primers and 12 random primers. An average of 25 bands was produced per primer pair, with 31 bands expressed differentially which were excised from the gels, sequenced, and annotated with information available on public databases. Some sequences matched genes with different binding activities, regulation of transcription, and those playing a role in synapses. One of the most interesting findings was the ALOX5 gene, which plays a role in the production of lukotrienes, important mediators in inflammatory processes. The identification of genes corresponding to those bands will provide more information about mechanisms that play a role in stressful situations produced by suboptimal feeding, as well as other causes.El estrés alimentario o subalimentación de los peces afecta directamente al metabolismo energético, a la eficacia de utilización del alimento y, por tanto, a su productividad. Este efecto se puede cuantificar de forma objetiva mediante comparaciones de expresión génica con respecto a aquellos peces que han sido alimentados a saciedad. Además, algunos de los genes expresados por los peces subalimentados pueden usarse como genes candidatos para identificar estrés alimentario en general. Para identificar estos genes se dividió un grupo de 60 tilapias Oreochromis niloticus (L., 1758) en dos tratamientos (alimentado ad líbitum o con alimentación subóptima, durante 22 días) con dos réplicas. Se utilizó la técnica de differential display en muestras de cerebro con 36 combinaciones resultado de tres cebadores polyT de anclaje y 12 cebadores aleatorios. Se expresaron una media de 25 bandas por pareja de cebadores y un total de 31 bandas expresadas diferencialmente, se extrajeron, secuenciaron y anotaron con la ayuda de la información disponible en bases de datos públicas. Algunas secuencias coinciden con genes cuya función es de unión a diferentes proteínas y de regulación de la transcripción, y juegan un papel importante en la sinapsis. Es destacable el gen ALOX5, que interviene en la producción de leucotrienos, importantes mediadores de procesos inflamatorios. La identificación de los genes que corresponden a estas bandas aportará conocimiento sobre los mecanismos que intervienen en situaciones de estrés, tanto producidas por una alimentación subóptima como por otras causas.Instituto Español de Oceanografí
On the Redshift Distribution and Physical Properties of ACT-Selected DSFGs
We present multi-wavelength detections of nine candidate gravitationally-lensed dusty starforming galaxies (DSFGs) selected at 218 GHz (1.4 mm) from the ACT equatorial survey. Among the brightest ACT sources, these represent the subset of the total ACT sample lying in Herschel SPIRE fields, and all nine of the 218 GHz detections were found to have bright Herschel counterparts. By fitting their spectral energy distributions (SEDs) with a modified blackbody model with power-law temperature distribution, we find the sample has a median redshift of 4.1 (+ 1.1, -10) (68 percent confidence interval), as expected for 218 GHz selection and an apparent total infrared luminosity of log 10(uL(sub IR)/solar luminosity) = 13.86(+0.33, -0.30), which suggests that they are either strongly lensed sources or unresolved collections of unlensed DSFGs. The effective apparent diameter of the sample is square root of mu d = 4.2 (+ 1.7, -1.0) kpc, further evidence of strong lensing of multiplicity, since the typical diameter of dusty star-forming galaxies is 1.0-2.5 kpc. We emphasize that the effective apparent diameter derives from SED modeling without the assumption of opticaly thin dust (as opposed to image morphology). We find that the sources have substantial optical depth (tau = (4.2+, -1.9) of dust around the peak in the modified blackbody spectrum (lambda obs is less than 500 micrometers), a result that is robust to model choice
The Atacama Cosmology Telescope: Extragalactic Point Sources in the Southern Surveys at 150, 220 and 280 GHz observed between 2008-2010
We present a multi-frequency, multi-epoch catalog of extragalactic sources.
The catalog is based on 150, 220 and 280 GHz observations carried out in 2008,
2009 and 2010 using the Millimeter Bolometric Array Camera on the Atacama
Cosmology Telescope. We also present and release 280 GHz maps from 2008 and
2010. The catalog contains 695 sources, found in a sky area of
square degrees. It is obtained by cross-matching sources found in 11
sub-catalogs, one for each season and frequency band. Also include are co-added
data from and square degrees using 2 and 3 years of
overlapping observations. We divide the sources into two populations,
synchrotron and dusty emitters, based on their spectral behavior in the 150-220
GHz frequency range. We find 374 synchrotron sources and 321 dusty source
candidates. Cross-matching with catalogs from radio to X-ray results in 264
synchrotron sources (71%) and 89 dusty sources (28%) with counterparts,
suggesting that 232 dusty candidates are not in existing catalogs. We study the
variability and number counts of each population. In the case of synchrotron
sources, we find year-to-year variability up to 60%, with a mean value around
35%. As expected, we find no evidence of dusty source variability. Our number
counts generally agree with previous measurements and models, except for dusty
sources at 280 GHz where some models overestimate our results. We also
characterize the spectral energy distribution of a dusty star-forming galaxy,
ACT-S J065207-551605, using our data and higher frequency observations.Comment: 24 pages, 16 figures, for associated data products see
https://lambda.gsfc.nasa.gov/product/act/act_prod_table.htm
ACTPol: On-Sky Performance and Characterization
ACTPol is the polarization-sensitive receiver on the Atacama Cosmology Telescope. ACTPol enables sensitive millimeter wavelength measurements of the temperature and polarization anisotropies of the Cosmic Microwave Background (CMB) at arcminute angular scales. These measurements are designed to explore the process of cosmic structure formation, constrain or determine the sum of the neutrino masses, probe dark energy, and provide a foundation for a host of other cosmological tests. We present an overview of the first season of ACTPol observations focusing on the optimization and calibration of the first detector array as well as detailing the on-sky performance
The optical design of the six-meter CCAT-prime and Simons Observatory telescopes
A common optical design for a coma-corrected, 6-meter aperture,
crossed-Dragone telescope has been adopted for the CCAT-prime telescope of CCAT
Observatory, Inc., and for the Large Aperture Telescope of the Simons
Observatory. Both are to be built in the high altitude Atacama Desert in Chile
for submillimeter and millimeter wavelength observations, respectively. The
design delivers a high throughput, relatively flat focal plane, with a field of
view 7.8 degrees in diameter for 3 mm wavelengths, and the ability to
illuminate >100k diffraction-limited beams for < 1 mm wavelengths. The optics
consist of offset reflecting primary and secondary surfaces arranged in such a
way as to satisfy the Mizuguchi-Dragone criterion, suppressing first-order
astigmatism and maintaining high polarization purity. The surface shapes are
perturbed from their standard conic forms in order to correct coma aberrations.
We discuss the optical design, performance, and tolerancing sensitivity. More
information about CCAT-prime can be found at ccatobservatory.org and about
Simons Observatory at simonsobservatory.org.Comment: Event: SPIE Astronomical Telescopes + Instrumentation, 2018, Austin,
Texas, USA; Proceedings Volume 10700, Ground-based and Airborne Telescopes
VII; 1070041 (2018
The Atacama Cosmology Telescope: Detection or Sunyaev-Zel'Dovich Decrement in Groups and Clusters Associated with Luminous Red Galaxies
We present a detection of the Sunyaev-Zel'dovich (SZ) decrement associated with the Luminous Red Galaxy (LRG) sample of the Sloan Digital Sky Survey. The SZ data come from 148 GHz maps of the equatorial region made by the Atacama Cosmology Telescope (ACT). The LRG sample is divided by luminosity into four bins, and estimates for the central Sunyaev-Zel'dovich temperature decrement are calculated through a stacking process. We detect and account for a bias of the SZ signal due to weak radio sources. We use numerical simulations to relate the observed decrement to Y(sub 200) and clustering properties to relate the galaxy luminosity bins to mass. We also use a relation between BCG luminosity and cluster mass based on stacked gravitational lensing measurements to estimate the characteristic halo masses. The masses are found to be in the range approx.10(exp 13) - 10(exp 14)/h Stellar Mass, a lower range than has been previously probed
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