14,488 research outputs found
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
The Physical State of the Intergalactic Medium or Can We Measure Y?
We present an argument for a {\it lower limit} to the Compton- parameter
describing spectral distortions of the cosmic microwave background (CMB). The
absence of a detectable Gunn-Peterson signal in the spectra of high redshift
quasars demands a high ionization state of the intergalactic medium (IGM).
Given an ionizing flux at the lower end of the range indicated by the proximity
effect, an IGM representing a significant fraction of the
nucleosynthesis-predicted baryon density must be heated by sources other than
the photon flux to a temperature \go {\rm few} \times 10^5\, K. Such a gas at
the redshift of the highest observed quasars, , will produce a y\go
10^{-6}. This lower limit on rises if the Universe is open, if there is a
cosmological constant, or if one adopts an IGM with a density larger than the
prediction of standard Big Bang nucleosynthesis.Comment: Proceedings of `Unveiling the Cosmic Infrared Background', April
23-25, 1995, Maryland. Self-unpacking uuencoded, compressed tar file with two
figures include
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
A New Local Temperature Distribution Function for X-ray Clusters: Cosmological Applications
(abridged) We present a new determination of the local temperature function
of X-ray clusters. We use a new sample comprising fifty clusters for which
temperature information is now available, making it the largest complete sample
of its kind. It is therefore expected to significantly improve the estimation
of the temperature distribution function of moderately hot clusters. We find
that the resulting temperature function is higher than previous estimations,
but agrees well with the temperature distribution function inferred from the
BCS and RASS luminosity function. We have used this sample to constrain the
amplitude of the matter fluctuations on cluster's scale of
Mpc, assuming a mass-temperature relation based
on recent numerical simulations. We find for an
model. Our sample provides an ideal reference at to
use in the application of the cosmological test based on the evolution of X-ray
cluster abundance (Oukbir & Blanchard 1992, 1997). Using Henry's sample, we
find that the abundance of clusters at is significantly smaller, by
a factor larger than 2, which shows that the EMSS sample provides strong
evidence for evolution of the cluster abundance. A likelihood analysis leads to
a rather high value of the mean density parameter of the universe: (open case) and (flat case), which is
consistent with a previous, independent estimation based on the full EMSS
sample by Sadat et al.(1998). Some systematic uncertainties which could alter
this result are briefly discussed.Comment: 31 pages, 12 figures, mathches the version published in Astronomy and
Astrophysic
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