249 research outputs found
CARMA observations of massive Planck-discovered cluster candidates at z>0.5 associated with WISE overdensities: strategy, observations and validation
We present 1-2 arcmin spatial resolution CARMA-8 31-GHz observations towards
19 unconfirmed Planck cluster candidates, selected to have significant galaxy
overdensities from the WISE early data release and thought to be at z>1 from
the WISE colors of the putative brightest cluster galaxy (BCG). We find a
Sunyaev-Zeldovich (SZ) detection in the CARMA-8 data towards 9 candidate
clusters, where one detection is considered tentative. For each cluster
candidate we present CARMA-8 maps, a study of their radio-source environment
and we assess the reliability of the SZ detection. The CARMA SZ detections
appear to be SZ-bright, with the mean, primary-beam-corrected peak flux density
of the decrement being -2.9mJy/beam with a standard deviation of 0.8, and are
typically offset from the Planck position by approximately 80 arcsec. Using
archival imaging data in the vicinity of the CARMA SZ centroids, we present
evidence that one cluster matches Abell 586-a known z~0.2 cluster; four
candidate clusters are likely to have 0.3<z<0.7; and, for the remaining 4, the
redshift information is inconclusive. We also argue that the sensitivity limits
resulting from the cross-correlation between Planck and WISE makes it
challenging to use our selection criterion to identify clusters at z > 1.Comment: 29 pages, MNRAS, in pres
CARMA follow-up of the northern unconfirmed PLANCK galaxy cluster candidates
We present CARMA observations of the three northern unconfirmed galaxy
clusters discovered by the PLANCK satellite. We confirm the existence of two
massive clusters (PLCKESZ G115.71+17.52 and PLCKESZ G121.11+57.01) at high
significance. For these clusters, we present refined centroid locations from
the 31 GHz CARMA data, as well as mass estimates obtained from a joint analysis
of CARMA and PLANCK data. We do not detect the third candidate, PLCKESZ
G189.84-37.24, and place an upper limit on its mass of M500 < 3.2 X 10^(14)
M_SUN at 68% confidence. Considering our data and the characteristics of the
PLANCK Early Release SZ Catalog, we conclude that this object is likely to be a
cold-core object in the plane of our Galaxy. As a result, we estimate the
purity of the ESZ Catalog to be greater than 99.5%.Comment: Accepted for publication in the Astrophysical Journal. 9 pages, 4
figures, 4 tables. arXiv admin note: text overlap with arXiv:astro-ph/061011
Application of Municipal Biosolids to Bahiagrass Pasture: Trace Metals in Harvested Forage
Municipal biosolids (sewage sludge) are the by-products of wastewater treatment plants and their production, worldwide, has steadily increased over the past years. Florida is one of the fastest growing states in the USA. Biosolids are readily and increasingly available throughout the state. Pasture fertilization has been shown to increase biomass and quality of bahiagrass (Paspalum notatum Flugge) dramatically in Florida sandy soils. Nevertheless, with low cattle prices, ranchers are forced to reduce fertilizers inputs. Biosolids contain considerable amounts of nutrients, especially nitrogen (N), phosphorus (P), sulphur (S), calcium (Ca), and micronutrients, and are inexpensive when compared with commercial fertilizers. Nevertheless, the concern remains that metals contained in these residuals accumulate in the tissues, in levels that would result be harmful to animals consuming the forage. This study investigated effects of seven rates of municipal biosolids applied to bahiagrass pasture on trace metal concentration in the forage. Iron (Fe), copper (Cu), cadmium (Cd), lead (Pb), and nickel (Ni) concentrations were determined in the tissue sampled at various dates after initial biosolids application. Metal concentrations were increased with increasing rates of biosolids, especially with the highest rate, in the first harvest date, but decreased with successive harvests. By the fourth harvest, Cd, Pb and Ni were hardly detected in forage. The increases verified in plant metal contents were not substantial enough to yield concerns regarding animal consumption, even with the higher rates of biosolids
CARMA observations of massive Planck-discovered cluster candidates at z>0.5 associated with WISE overdensities: Breaking the size-flux degeneracy
We use a Bayesian software package to analyze CARMA-8 data towards 19
unconfirmed Planck SZ-cluster candidates from Rodriguez-Gonzalvez et al.
(2015), that are associated with significant overdensities in WISE. We used two
cluster parameterizations, one based on a (fixed shape) generalized-NFW
pressure profile and another based on a beta-gas-density profile (with varying
shape parameters) to obtain parameter estimates for the nine CARMA-8
SZ-detected clusters. We find our sample is comprised of massive,
Y_{500}=0.0010 \pm 0.0015 arcmin^2, relatively compact, theta_{500}= 3.9 \pm
2.0 arcmin systems. Results from the beta model show that our cluster
candidates exhibit a heterogeneous set of brightness-temperature profiles.
Comparison of Planck and CARMA-8 measurements showed good agreement in Y_{500}
and an absence of obvious biases. We estimated the total cluster mass M_{500}
as a function of z for one of the systems; at the preferred photometric
redshift of 0.5, the derived mass, M_{500} \approx 0.8 \pm 0.2 \times 10^{15}
Msun. Spectroscopic Keck/MOSFIRE data confirmed a galaxy member of one of our
cluster candidates to be at z=0.565. Applying a Planck prior in Y_{500} to the
CARMA-8 results reduces uncertainties for both parameters by a factor >4,
relative to the independent Planck or CARMA-8 measurements. We here demonstrate
a powerful technique to find massive clusters at intermediate z \gtrsim 0.5
redshifts using a cross-correlation between Planck and WISE data, with
high-resolution follow-up with CARMA-8. We also use the combined capabilities
of Planck and CARMA-8 to obtain a dramatic reduction by a factor of several, in
parameter uncertainties.Comment: 26 pages, 8 figures, appearing in MNRAS (responded to referee report
Joint analysis of X-ray and Sunyaev Zel'dovich observations of galaxy clusters using an analytic model of the intra-cluster medium
We perform a joint analysis of X-ray and Sunyaev Zel'dovich (SZ) effect data
using an analytic model that describes the gas properties of galaxy clusters.
The joint analysis allows the measurement of the cluster gas mass fraction
profile and Hubble constant independent of cosmological parameters. Weak
cosmological priors are used to calculate the overdensity radius within which
the gas mass fractions are reported. Such an analysis can provide direct
constraints on the evolution of the cluster gas mass fraction with redshift. We
validate the model and the joint analysis on high signal-to-noise data from the
Chandra X-ray Observatory and the Sunyaev-Zel'dovich Array for two clusters,
Abell 2631 and Abell 2204.Comment: ApJ in pres
CARMA Measurements of the Sunyaev-Zel'dovich Effect in RXJ1347.5-1145
We demonstrate the Sunyaev-Zel'dovich (SZ) effect imaging capabilities of the
Combined Array for Research in Millimeter-wave Astronomy (CARMA) by presenting
an SZ map of the galaxy cluster RXJ1347.5-1145. By combining data from multiple
CARMA bands and configurations, we are able to capture the structure of this
cluster over a wide range of angular scales, from its bulk properties to its
core morphology. We find that roughly 9% of this cluster's thermal energy is
associated with sub-arcminute-scale structure imparted by a merger,
illustrating the value of high-resolution SZ measurements for pursuing cluster
astrophysics and for understanding the scatter in SZ scaling relations. We also
find that the cluster's SZ signal is lower in amplitude than suggested by a
spherically-symmetric model derived from X-ray data, consistent with
compression along the line of sight relative to the plane of the sky. Finally,
we discuss the impact of upgrades currently in progress that will further
enhance CARMA's power as an SZ imaging instrument.Comment: 8 pages, 6 figure
Galaxy Clusters at z>=1: Gas Constraints from the Sunyaev-Zel'dovich Array
We present gas constraints from Sunyaev-Zel'dovich (SZ) effect measurements
in a sample of eleven X-ray and infrared (IR) selected galaxy clusters at z
>=1, using data from the Sunyaev-Zel'dovich Array (SZA). The cylindrically
integrated Compton-y parameter, Y , is calculated by fitting the data to a
two-parameter gas pressure profile. Where possible, we also determine the
temperature of the hot intra-cluster plasma from Chandra and XMM-Newton data,
and constrain the gas mass within the same aperture (r_2500 ) as Y . The SZ
effect is detected in the clusters for which the X-ray data indicate gas masses
above ~ 10^13 Msun, including XMMU J2235-2557 at redshift z = 1.39, which to
date is one of the most distant clusters detected using the SZ effect. None of
the IR-selected targets are detected by the SZA measurements, indicating low
gas masses for these objects. For these and the four other undetected clusters,
we quote upper limits on Y and Mgas_SZ , with the latter derived from scaling
relations calibrated with lower redshift clusters. We compare the constraints
on Y and X-ray derived gas mass Mgas_X-ray to self-similar scaling relations
between these observables determined from observations of lower redshift
clusters, finding consistency given the measurement error.Comment: 6 pages, 2 figures, submitted on ApJ
Foreground Predictions for the Cosmic Microwave Background Power Spectrum from Measurements of Faint Inverted Radio Sources at 5 GHz
We present measurements of a population of matched radio sources at 1.4 and 5
GHz down to a flux limit of 1.5 mJy in 7 sq. degs. of the NOAO Deep Field
South. We find a significant fraction of sources with inverted spectral indices
that all have 1.4 GHz fluxes less than 10 mJy, and are therefore too faint to
have been detected and included in previous radio source count models that are
matched at multiple frequencies. Combined with the matched source population at
1.4 and 5 GHz in 1 sq. deg. in the ATESP survey, we update models for the 5 GHz
differential number counts and distributions of spectral indices in 5 GHz flux
bins that can be used to estimate the unresolved point source contribution to
the cosmic microwave background temperature anisotropies. We find a shallower
logarithmic slope in the 5 GHz differential counts than in previously published
models for fluxes < 100 mJy as well as larger fractions of inverted spectral
indices at these fluxes. Because the Planck flux limit for resolved sources is
larger than 100 mJy in all channels, our modified number counts yield at most a
10% change in the predicted Poisson contribution to the Planck temperature
power spectrum. For a flux cut of 5 mJy with the South Pole Telescope and a
flux cut of 20 mJy with the Atacama Cosmology Telescope we predict a ~30% and
~10% increase, respectively, in the radio source Poisson power in the lowest
frequency channels of each experiment relative to that predicted by previous
models.Comment: 14 pages, 9 figures, includes ApJ proof correction
Comparison of Hectospec Virial Masses with SZE Measurements
We present the first comparison of virial masses of galaxy clusters with
their Sunyaev-Zel'dovich Effect (SZE) signals. We study 15 clusters from the
Hectospec Cluster Survey (HeCS) with MMT/Hectospec spectroscopy and published
SZE signals. We measure virial masses of these clusters from an average of 90
member redshifts inside the radius . The virial masses of the clusters
are strongly correlated with their SZE signals (at the 99% confidence level
using a Spearman rank-sum test). This correlation suggests that can be
used as a measure of virial mass. Simulations predict a powerlaw scaling of
with 1.6. Observationally, we
find =1.110.16, significantly shallower (given the formal
uncertainty) than the theoretical prediction. However, the selection function
of our sample is unknown and a bias against less massive clusters cannot be
excluded (such a selection bias could artificially flatten the slope).
Moreover, our sample indicates that the relation between velocity dispersion
(or virial mass estimate) and SZE signal has significant intrinsic scatter,
comparable to the range of our current sample. More detailed studies of scaling
relations are therefore needed to derive a robust determination of the relation
between cluster mass and SZE.Comment: 6 pages, 2 figures, accepted to ApJ Letters, minor revisions,
shortened titl
Discovery of a Dissociative Galaxy Cluster Merger with Large Physical Separation
We present DLSCL J0916.2+2951 (z=0.53), a newly discovered major cluster
merger in which the collisional cluster gas has become dissociated from the
collisionless galaxies and dark matter. We identified the cluster using optical
and weak lensing observations as part of the Deep Lens Survey. Our follow-up
observations with Keck, Subaru, Hubble Space Telescope, and Chandra show that
the cluster is a dissociative merger and constrain the dark matter
self-interaction cross-section {\sigma}_{DM}m_{DM}^{-1}\leq7 cm^2g^{-1}. The
system is observed at least 0.7\pm0.2 Gyr since first pass-through, thus
providing a picture of cluster mergers 2-5 times further progressed than
similar systems observed to date. This improved temporal leverage has
implications for our understanding of merging clusters and their impact on
galaxy evolution.Comment: Accepted ApJ Letters. [v2] changes: 1 new figure (2b), figure 3 made
color, and minor improvements to the text. 6 pages, 4 figures, 1 tabl
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