2,044 research outputs found
Measuring cluster masses with CMB lensing: a statistical approach
We present a method for measuring the masses of galaxy clusters using the
imprint of their gravitational lensing signal on the cosmic microwave
background (CMB) temperature anisotropies. The method first reconstructs the
projected gravitational potential with a quadratic estimator and then applies a
matched filter to extract cluster mass. The approach is well-suited for
statistical analyses that bin clusters according to other mass proxies. We find
that current experiments, such as Planck, the South Pole Telescope and the
Atacama Cosmology Telescope, can practically implement such a statistical
methodology, and that future experiments will reach sensitivities sufficient
for individual measurements of massive systems. As illustration, we use
simulations of Planck observations to demonstrate that it is possible to
constrain the mass scale of a set of 62 massive clusters with prior information
from X-ray observations, similar to the published Planck ESZ-XMM sample. We
examine the effect of the thermal (tSZ) and kinetic (kSZ) Sunyaev-Zeldovich
(SZ) signals, finding that the impact of the kSZ remains small in this context.
The stronger tSZ signal, however, must be actively removed from the CMB maps by
component separation techniques prior to reconstruction of the gravitational
potential. Our study of two such methods highlights the importance of broad
frequency coverage for this purpose. A companion paper presents application to
the Planck data on the ESZ-XMM sample.Comment: 9 pages, 5 figures, version accepted for publication in A&
Point Source Confusion in SZ Cluster Surveys
We examine the effect of point source confusion on cluster detection in
Sunyaev-Zel'dovich (SZ) surveys. A filter matched to the spatial and spectral
characteristics of the SZ signal optimally extracts clusters from the
astrophysical backgrounds. We calculate the expected confusion (point source
and primary cosmic microwave background [CMB]) noise through this filter and
quantify its effect on the detection threshold for both single and multiple
frequency surveys. Extrapolating current radio counts, we estimate that
confusion from sources below 100 microJy limits single-frequency surveys to
1-sigma detection thresholds of Y 3.10^{-6} arcmin^2 at 30 GHz and Y 10^{-5}
arcmin^2 at 15 GHz (for unresolved clusters in a 2 arcmin beam); these numbers
are highly uncertain, and an extrapolation with flatter counts leads to much
lower confusion limits. Bolometer surveys must contend with an important
population of infrared point sources. We find that a three-band matched filter
with 1 arcminute resolution (in each band) efficiently reduces confusion, but
does not eliminate it: residual point source and CMB fluctuations contribute
significantly the total filter noise. In this light, we find that a 3-band
filter with a low-frequency channel (e.g, 90+150+220 GHz) extracts clusters
more effectively than one with a high frequency channel (e.g, 150+220+300 GHz).Comment: Accepted for publication in Astronomy & Astrophysics; Updated grant
information in acknowledgement
The Planck SZ Cluster Catalog: Expected X-ray Properties
Surveys based on the Sunyaev-Zel'dovich (SZ) effect provide a fresh view of
the galaxy cluster population, one that is complementary to X-ray surveys. To
better understand the relation between these two kinds of survey, we construct
an empirical cluster model using scaling relations constrained by current X-ray
and SZ data. We apply our model to predict the X-ray properties of the Planck
SZ Cluster Catalog (PCC) and compare them to existing X-ray cluster catalogs.
We find that Planck should significantly extend the depth of the previous
all-sky cluster survey, performed in the early 1990s by the ROSAT satellite,
and should be particularly effective at finding hot, massive clusters (T > 6
keV) out to redshift unity. These are rare objects, and our findings suggest
that Planck could increase the observational sample at z > 0.6 by an order of
magnitude. This would open the way for detailed studies of massive clusters out
to these higher redshifts. Specifically, we find that the majority of
newly-detected Planck clusters should have X-ray fluxes 10^{-13} ergs/s/cm^2 <
f_X[0.5-2 keV] < 10^{-12} ergs/s/cm^2, i.e., distributed over the decade in
flux just below the ROSAT All Sky Survey limit. This is sufficiently bright for
extensive X-ray follow-up campaigns. Once Planck finds these objects,
XMM-Newton and \textit{Chandra} could measure temperatures to 10% for a sample
of ~ 100 clusters in the range 0.5 < z < 1, a valuable increase in the number
of massive clusters studied over this range.Comment: 8 pages, 7 figures submitted to A&A; accepted 29 May 201
An SZ/X-ray galaxy cluster model and the X-ray follow-up of the Planck clusters
Sunyaev-Zel'dovich (SZ) cluster surveys will become an important cosmological
tool over next few years, and it will be essential to relate these new surveys
to cluster surveys in other wavebands. We present an empirical model of cluster
SZ and X-ray observables constructed to address this question and to motivate,
dimension and guide X-ray follow-up of SZ surveys. As an example application of
the model, we discuss potential XMM-Newton follow-up of Planck clusters.Comment: 4 pages, 5 figures. To appear in the proceedings of the XXXXIIIrd
Rencontres de Morion
redMaPPer III: A Detailed Comparison of the Planck 2013 and SDSS DR8 RedMaPPer Cluster Catalogs
We compare the Planck Sunyaev-Zeldovich (SZ) cluster sample (PSZ1) to the
Sloan Digital Sky Survey (SDSS) redMaPPer catalog, finding that all Planck
clusters within the redMaPPer mask and within the redshift range probed by
redMaPPer are contained in the redMaPPer cluster catalog. These common clusters
define a tight scaling relation in the richness-SZ mass (--)
plane, with an intrinsic scatter in richness of . The corresponding intrinsic scatter in true cluster halo mass
at fixed richness is . The regularity of this scaling relation is
used to identify failures in both the redMaPPer and Planck cluster catalogs. Of
the 245 galaxy clusters in common, we identify three failures in redMaPPer and
36 failures in the PSZ1. Of these, at least 12 are due to clusters whose
optical counterpart was correctly identified in the PSZ1, but where the quoted
redshift for the optical counterpart in the external data base used in the PSZ1
was incorrect. The failure rates for redMaPPer and the PSZ1 are and
respectively, or 9.8% in the PSZ1 after subtracting the external data
base errors. We have further identified 5 PSZ1 sources that suffer from
projection effects (multiple rich systems along the line-of-sight of the SZ
detection) and 17 new high redshift () cluster candidates of
varying degrees of confidence. Should all of the high-redshift cluster
candidates identified here be confirmed, we will have tripled the number of
high redshift Planck clusters in the SDSS region. Our results highlight the
power of multi-wavelength observations to identify and characterize systematic
errors in galaxy cluster data sets, and clearly establish photometric data both
as a robust cluster finding method, and as an important part of defining clean
galaxy cluster samples.Comment: comments welcom
Ambipolar charge injection and transport in a single pentacene monolayer island
Electrons and holes are locally injected in a single pentacene monolayer
island. The two-dimensional distribution and concentration of the injected
carriers are measured by electrical force microscopy. In crystalline monolayer
islands, both carriers are delocalized over the whole island. On disordered
monolayer, carriers stay localized at their injection point. These results
provide insight into the electronic properties, at the nanometer scale, of
organic monolayers governing performances of organic transistors and molecular
devices.Comment: To be published in Nano Letter
Quasar Host Environments: The view from Planck
We measure the far-infrared emission of the general quasar (QSO) population
using Planck observations of the Baryon Oscillation Spectroscopic Survey QSO
sample. By applying multi-component matched multi-filters to the seven highest
Planck frequencies, we extract the amplitudes of dust, synchrotron and thermal
Sunyaev-Zeldovich (SZ) signals for nearly 300,000 QSOs over the redshift range
. We bin these individually low signal-to-noise measurements to obtain
the mean emission properties of the QSO population as a function of redshift.
The emission is dominated by dust at all redshifts, with a peak at ,
the same location as the peak in the general cosmic star formation rate.
Restricting analysis to radio-loud QSOs, we find synchrotron emission with a
monochromatic luminosity at (rest-frame) rising from
to between
and 3. The radio-quiet subsample does not show any synchrotron emission,
but we detect thermal SZ between and 4; no significant SZ emission is
seen at lower redshifts. Depending on the supposed mass for the halos hosting
the QSOs, this may or may not leave room for heating of the halo gas by
feedback from the QSO.Comment: 14 pages, 11 figures, accepted by A&
Joint measurement of the galaxy cluster pressure profile with Planck and SPT-SZ
We measured the average Compton profile of 461 clusters detected jointly by
the South Pole Telescope (SPT) and Planck. The number of clusters included in
this analysis is about one order of magnitude larger than in previous analyses.
We propose an innovative method developed in Fourier space to combine optimally
the Planck and SPT-SZ data, allowing us to perform a clean deconvolution of the
point spread and transfer functions while simultaneously rescaling by the
characteristic radial scale with respect to the critical density.
The method additionally corrects for the selection bias of SPT clusters in the
SPT-SZ data. We undertake a generalised Navarro-Frenk-White (NFW) fit to the
profile with only one parameter fixed, allowing us to constrain the other four
parameters with excellent precision. The best-fitting profile is in good
agreement with the Universal Pressure Profile based on REXCESS in the inner
region and with the Planck Intermediate Paper V profile based on Planck and the
XMM archive in the outer region. We investigate trends with redshift and mass,
finding no indication of redshift evolution but detecting a significant
difference in the pressure profile of the low vs. high mass subsamples, in the
sense that the low mass subsample has a profile that is more centrally-peaked
than that of the high mass subsample. [abridged]Comment: 15 pages, 12 figures, submitted to A&
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