823 research outputs found
Imaging Simulations of the Sunyaev-Zel'dovich Effect for ALMA
We present imaging simulations of the Sunyaev-Zel'dovich effect of galaxy
clusters for the Atacama Large Millimeter/submillimeter Array (ALMA) including
the Atacama Compact Array (ACA). In its most compact configuration at 90GHz,
ALMA will resolve the intracluster medium with an effective angular resolution
of 5 arcsec. It will provide a unique probe of shock fronts and relativistic
electrons produced during cluster mergers at high redshifts, that are hard to
spatially resolve by current and near-future X-ray detectors. Quality of image
reconstruction is poor with the 12m array alone but improved significantly by
adding ACA; expected sensitivity of the 12m array based on the thermal noise is
not valid for the Sunyaev-Zel'dovich effect mapping unless accompanied by an
ACA observation of at least equal duration. The observations above 100 GHz will
become excessively time-consuming owing to the narrower beam size and the
higher system temperature. On the other hand, significant improvement of the
observing efficiency is expected once Band 1 is implemented in the future.Comment: 16 pages, 12 figures. Accepted for publication in PASJ. Note added in
proof is include
Systematic Errors in the Hubble Constant Measurement from the Sunyaev-Zel'dovich effect
The Hubble constant estimated from the combined analysis of the
Sunyaev-Zel'dovich effect and X-ray observations of galaxy clusters is
systematically lower than those from other methods by 10-15 percent. We examine
the origin of the systematic underestimate using an analytic model of the
intracluster medium (ICM), and compare the prediction with idealistic triaxial
models and with clusters extracted from cosmological hydrodynamical
simulations. We identify three important sources for the systematic errors;
density and temperature inhomogeneities in the ICM, departures from
isothermality, and asphericity. In particular, the combination of the first two
leads to the systematic underestimate of the ICM spectroscopic temperature
relative to its emission-weighed one. We find that these three systematics well
reproduce both the observed bias and the intrinsic dispersions of the Hubble
constant estimated from the Sunyaev-Zel'dovich effect.Comment: 26 pages, 7 figures, accepted for publication in ApJ, Minor change
Locating the Warm-Hot Intergalactic Medium in the Simulated Local Universe
We present an analysis of mock spectral observation of warm-hot intergalactic
medium (WHIM) using a constrained simulation of the local universe. The
simulated map of oxygen emission lines from local WHIM reproduces well the
observed structures traced by galaxies in the real local universe. We further
attempt to perform mock observations of outer parts of simulated Coma cluster
and A3627 adopting the expected performance of DIOS (Diffuse Intergalactic
Oxygen Surveyor), which is proposed as a dedicated soft X-ray mission to search
for cosmic missing baryons. We find that WHIMs surrounding nearby clusters are
detectable with a typical exposure time of a day, and thus constitute realistic
and promising targets for DIOS. We also find that an X-ray emitting clump in
front of Coma cluster, recently reported in the XMM-Newton observation, has a
counterpart in the simulated local universe, and its observed spectrum can be
well reproduced in the simulated local universe if the gas temperature is set
to the observationally estimated value.Comment: 25 pages, 3 tables, 16 figures. Accepted for publication in PASJ.
High resolution PS/PDF files are available at
http://www-utap.phys.s.u-tokyo.ac.jp/~kohji/research/x-ray/index.htm
The Sunyaev-Zel'dovich Effect at Five Arc-seconds: RXJ1347.5-1145 Imaged by ALMA
We present the first image of the thermal Sunyaev-Zel'dovich effect (SZE)
obtained by the Atacama Large Millimeter/submillimeter Array (ALMA). Combining
7-m and 12-m arrays in Band 3, we create an SZE map toward a galaxy cluster
RXJ1347.5-1145 with 5 arc-second resolution (corresponding to the physical size
of 20 kpc/h), the highest angular and physical spatial resolutions achieved to
date for imaging the SZE, while retaining extended signals out to 40
arc-seconds. The 1-sigma statistical sensitivity of the image is 0.017 mJy/beam
or 0.12 mK_CMB at the 5 arc-second full width at half maximum. The SZE image
shows a good agreement with an electron pressure map reconstructed
independently from the X-ray data and offers a new probe of the small-scale
structure of the intracluster medium. Our results demonstrate that ALMA is a
powerful instrument for imaging the SZE in compact galaxy clusters with
unprecedented angular resolution and sensitivity. As the first report on the
detection of the SZE by ALMA, we present detailed analysis procedures including
corrections for the missing flux, to provide guiding methods for analyzing and
interpreting future SZE images by ALMA.Comment: 20 pages, 13 figures. Accepted for publication in PAS
Submillimeter detection of the Sunyaev -- Zel'dovich effect toward the most luminous X-ray cluster at z=0.45
We report on the detection of the Sunyaev -- Zel'dovich (SZ) signals toward
the most luminous X-ray cluster RXJ1347-1145 at Nobeyama Radio Observatory (21
and 43 GHz) and at James Clerk Maxwell Telescope (350 GHz). In particular the
latter is the first successful detection of the SZ temperature increment in the
submillimeter band which resolved the profile of a cluster of galaxies. Both
the observed spectral dependence and the radial profile of the SZ signals are
fully consistent with those expected from the X-ray observation of the cluster.
The combined analysis of 21GHz and 350GHz data reproduces the temperature and
core-radius of the cluster determined with the ROSAT and ASCA satellites when
we adopt the slope of the density profile from the X-ray observations.
Therefore our present data provide the strongest and most convincing case for
the detection of the submillimeter SZ signal from the cluster, as well as in
the Rayleigh -- Jeans regime. We also discuss briefly the cosmological
implications of the present results.Comment: 11 pages, The Astrophysical Journal (Letters), in pres
DIOS: the Diffuse Intergalactic Oxygen Surveyor
We present our proposal for a small X-ray mission DIOS (Diffuse Intergalactic
Oxygen Surveyor), consisting of a 4-stage X-ray telescope and an array of TES
microcalorimeters, cooled with mechanical coolers, with a total weight of about
400 kg. The mission will perform survey observations of warm-hot intergalactic
medium using OVII and OVIII emission lines, with the energy coverage up to 1.5
keV. The wide field of view of about 50' diameter, superior energy resolution
close to 2 eV FWHM, and very low background will together enable us a wide
range of science for diffuse X-ray sources. We briefly describe the design of
the satellite, performance of the subsystems and the expected results.Comment: 9 pages, 11 figures, a proceedings of SPIE "Astronomical Telescopes
and Instrumentation" 200
Numerical Evolution of General Relativistic Voids
In this paper, we study the evolution of a relativistic, superhorizon-sized
void embedded in a Friedmann-Robertson-Walker universe. We numerically solve
the spherically symmetric general relativistic equations in comoving,
synchronous coordinates. Initially, the fluid inside the void is taken to be
homogeneous and nonexpanding. In a radiation- dominated universe, we find that
radiation diffuses into the void at approximately the speed of light as a
strong shock---the void collapses. We also find the surprising result that the
cosmic collapse time (the -crossing time) is much smaller than
previously thought, because it depends not only on the radius of the void, but
also on the ratio of the temperature inside the void to that outside. If the
ratio of the initial void radius to the outside Hubble radius is less than the
ratio of the outside temperature to that inside, then the collapse occurs in
less than the outside Hubble time. Thus, superhorizon-sized relativistic void
may thermalize and homogenize relatively quickly. These new simulations revise
the current picture of superhorizon-sized void evolution after first-order
inflation.Comment: 37 pages plus 12 figures (upon request-- [email protected])
LaTeX, FNAL-PUB-93/005-
Spatial correlation functions and the pairwise peculiar velocity dispersion of galaxies in the PSCz survey: implications for the galaxy biasing in cold dark matter models
We report on the measurement of the two-point correlation function, and the
pairwise peculiar velocity of galaxies in the IRAS PSCz survey. We compute
these statistics first in redshift space, and then obtain the projected
functions which have simple relations to the real-space correlation functions
on the basis of the method developed earlier in analyzing the Las Campanas
Redshift Survey (LCRS) by Jing, Mo, & B\"orner (1998). We find that the real
space two-point correlation function can be fitted to a power law with and r_0=3.70 \mpc. The pairwise peculiar
velocity dispersion is close to 400 \kms at r_p=3\mpc
and decreases to about 150 \kms at r_p \approx 0.2 \mpc. These values are
significantly lower than those obtained from the LCRS. In order to understand
the implications of those measurements on the galaxy biasing, we construct mock
samples for a low density spatially-flat cold dark matter model (, , , ) using a set of
high-resolution N-body simulations. Applying a stronger cluster-underweight
biasing () than for the LCRS (), we are
able to reproduce these observational data, except for the strong decrease of
the pairwise peculiar velocity at small separations. This is qualitatively
ascribed to the different morphological mixture of galaxies in the two
catalogues. Disk-dominated galaxy samples drawn from the theoretically
constructed GIF catalog yield results rather similar to our mock samples with
the simple cluster-underweight biasing.Comment: accepted for publication in ApJ; 24 pages with 9 figure
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