154 research outputs found
Correlated states and nuclear reactions: An experimental test with low energy beams
An experimental program is described in this paper, aiming at detecting the formation of correlated coherent states (CCSs) in thin surface layers of crystals when bombarded by a very low energy proton or deuteron beam. CCSs are a generalization of ``nonclassical'' states of light, such as coherent and squeezed states, whose existence has been demonstrated long ago, giving rise to the remarkable development of quantum optics. In other fields, ranging from condensed matter physics to cosmology, such states have been intensively studied, but a clear signature of their existence is still lacking. This may be a clue to several unexplained phenomena, including the strong enhancement of nuclear fusion reaction rates in some crystal lattices, which have been reported on by several experiments and cannot be accounted for by electron screening only. Such an investigation is extremely relevant to nuclear astrophysics studies, few-body nucleon systems, and nucleon nucleon-interaction problems and, in particular, to energy-related nuclear fusion studies
A weak lensing analysis of the PLCK G100.2-30.4 cluster
We present a mass estimate of the Planck-discovered cluster PLCK G100.2-30.4,
derived from a weak lensing analysis of deep SUBARU griz images. We perform a
careful selection of the background galaxies using the multi-band imaging data,
and undertake the weak lensing analysis on the deep (1hr) r-band image. The
shape measurement is based on the KSB algorithm; we adopt the PSFex software to
model the Point Spread Function (PSF) across the field and correct for this in
the shape measurement. The weak lensing analysis is validated through extensive
image simulations. We compare the resulting weak lensing mass profile and total
mass estimate to those obtained from our re-analysis of XMM-Newton
observations, derived under the hypothesis of hydrostatic equilibrium. The
total integrated mass profiles are in remarkably good agreement, agreeing
within 1 across their common radial range. A mass is derived for the cluster from our weak lensing
analysis. Comparing this value to that obtained from our reanalysis of
XMM-Newton data, we obtain a bias factor of (1-b) = 0.8 0.1. This is
compatible within 1 with the value of (1-b) obtained by Planck
Collaboration XXIV from their calibration of the bias factor using
newly-available weak lensing reconstructed masses.Comment: 11 pages, 12 figures, accepted for publication on Astronomy &
Astrophysics; updates in affiliation
The evolving cluster cores: Putting together the pieces of the puzzle
In this work we address the issue of whether the division of clusters in cool
cores (CCs) and non-cool cores (NCCs) is due to a primordial difference or to
how clusters evolve across cosmic time. Our first goal is to establish if
spectra from the central regions of a subclass of NCCs known as cool core
remnants (CCRs) are consistent with having a small but significant amount of
short cooling time gas, thereby allowing a transformation to CC systems on a
timescale of a giga year. Our second goal is to determine if low ionization Fe
lines emitted from this residual cool gas will be detectable by the
calorimeters that will fly on board XRISM and ATHENA. We performed a spectral
analysis of CCR systems with a multi temperature model and, assuming the
different components to be in pressure equilibrium with one another, derived
entropy and cooling time distributions for the X-ray emitting gas. We find that
in most of our systems, the spectral model allows for a fraction of low
entropy, short cooling time gas with a mass that is comparable to the one in CC
systems. Moreover, simulations show that future spectrometers on board XRISM
and ATHENA will have the power to directly resolve emission lines from the low
temperature gas, thereby providing incontrovertible evidence for its presence.
Within the scenario that we have explored, the constant fraction of CCs
measured across cosmic time emerges from a dynamical equilibrium where CCs
transformed in NCCs through mergers are balanced by NCCs that revert to CCs.
Furthermore, CCs and NCCs should not be viewed as distinct sub classes, but as
``states" between which clusters can move.Comment: To appear in Astronomy & Astrophysic
A newly identified galaxy group thanks to tidal streams of intragroup light
In the accretion-driven growth scenario, part of the intracluster light is
formed in the group environment. We report the serendipitous discovery of a
group of galaxies with signs of diffuse light in the foreground of the known
galaxy cluster MACS J0329-0211 at z=0.45. Our investigation began with the
detection of diffuse light streams around a pair of bright galaxies in the
southeastern region of a Suprime-Cam image of the galaxy cluster MACS
J0329-0211. Our analysis is based on the extended CLASH-VLT redshift catalog
and on new spectroscopic data obtained ad hoc with the Italian Telescopio
Nazionale Galileo. We use the density reconstruction method to analyze the
redshift distribution of the galaxies in the region around the galaxy pair. We
also use available photometric and X-ray data to better characterize the
properties of the group. Thanks to the large amount of redshift data collected
in this region, we have been able to discover the existence of a group of
galaxies, here called GrG J0330-0218, which is associated with the pair of
galaxies. These are the two brightest group galaxies (BGG1 and BGG2). We
extracted 41 group members from the redshift catalog and estimate a mean
redshift z=0.1537 and a line-of-sight velocity dispersion sigmav=370 km/s. In
the phase-space diagram, the distribution of the galaxies of GrG J0330-0218
follows the characteristic trumpet-shaped pattern, which is related to the
escape velocity of galaxy clusters, suggesting that the group is a virialized
structure. Under this assumption, the mass of the group is M200 about 6E13
Msun. We also measured a mass-to-light ratio of 130 Msun/Lsun and a luminosity
fraction of diffuse light of about 20% within 0.5 R200. We conjecture that
galaxy pairs that are surrounded by diffuse light, probably due to tidal
interactions, can serve as signposts for groups.Comment: Astronomy & Astrophysics accepted, 13 pages, 10 figure
Mapping the hot gas temperature in galaxy clusters using X-ray and Sunyaev-Zel'dovich imaging
We propose a method to map the temperature distribution of the hot gas in galaxy clusters that uses resolved images of the thermal Sunyaev-Zelâdovich (tSZ) effect in combination with X-ray data. Application to images from the New IRAM KIDs Array (NIKA) and XMM-Newton allows us to measure and determine the spatial distribution of the gas temperature in the merging cluster MACS J0717.5+3745, at z = 0.55. Despite the complexity of the target object, we find a good morphological agreement between the temperature maps derived from X-ray spectroscopy only â using XMM-Newton (TXMM) and Chandra (TCXO) â and the new gas-mass-weighted tSZ+X-ray imaging method (TSZX). We correlate the temperatures from tSZ+X-ray imaging and those from X-ray spectroscopy alone and find that TSZX is higher than TXMM and lower than TCXO by ~ 10% in both cases. Our results are limited by uncertainties in the geometry of the cluster gas, contamination from kinetic SZ (~10%), and the absolute calibration of the tSZ map (7%). Investigation using a larger sample of clusters would help minimise these effects
X-ray characterisation of the massive galaxy clusterClG-J104803.7+313843 at z=0.76 with XMM-Newton
We present the characterisation of the massive cluster ClG-J
at performed using a serendipitous XMM-Newton observation. High
redshift and massive objects represent an ideal laboratory to benchmark our
understanding of how cluster form and assembly formation driven mainly by
gravity.Leveraging the high throughput of XMM-Newton we were firstly able to
determine the redshift of the object, shedding light on ambiguous photometric
redshift associations. We investigated the morphology of this cluster which
shows signs of merging activities in the outskirts and a flat core. We also
measured the radial density profile up to . With these quantities in
hand, we were able to determine the mass, , using the YX proxy. This quantity improves previous
measurement of the mass of this object by a factor of . The
characterisation of one cluster at such mass and redshift regime is fundamental
as these objects are intrinsically rare, the number of objects discovered so
far being less than . Our study highlights the importance of using
X-ray observations in combination with ancillary multi-wavelength data to
improve our understanding of high-z and massive clustersComment: Submitted to A&
A radio bubble shredded by gas sloshing?
We report on the detection of diffuse radio emission with peculiar morphology
in the central region of the galaxy cluster Abell 2657. The most striking
feature identified in our 144 MHz LOFAR image is a bifurcated radio arc that
extends for a projected size of 150-200 kpc. From the analysis of XMM-Newton
data, we find clear evidence of gas sloshing in the cluster and a possible dip
in X-ray surface brightness between the two radio arcs which deserves
confirmation. Interestingly, the synchrotron emission of the bifurcated radio
arc is stretched along the sloshing spiral. We compare our observational
results with numerical simulations of non-thermal components interacting with
gas motions. We suggest that the detected emission may trace a radio bubble
shredded by gas sloshing, where relativistic electrons and magnetic fields are
expected to be stretched and stirred as a consequence of tangential flows
induced by the spiralling gas motion. Lastly, we report on the presence of two
thin (6-7 kpc in width) and parallel strands of radio emission embedded in the
outer arc that are morphologically similar to the emerging population of
non-thermal filaments observed in galaxy clusters, radio galaxies, and the
Galactic centre. While this work further demonstrates the complex interplay
between thermal and non-thermal components in the intracluster medium,
follow-up observations in radio and X-rays are required to firmly determine the
origin of the features observed in Abell 2657.Comment: 12 pages, 9 figures, 1 table. Accepted for publication in MNRA
Iron in x-cop: Tracing enrichment in cluster outskirts with high accuracy abundance profiles
We present the first metal abundance profiles for a representative sample of massive clusters. Our measurements extend to R500 and are corrected for a systematic error plaguing previous outskirt estimates. Our profiles flatten out at large radii, admittedly not a new result, however the radial range and representative nature of our sample extends its import well beyond previous findings. We find no evidence of segregation between cool-core and non-cool-core systems beyond 3c0.3\ue2 R500, implying that, as was found for thermodynamic properties, the physical state of the core does not affect global cluster properties. Our mean abundance within R500 shows a very modest scatter, < 15%, suggesting the enrichment process must be quite similar in all these massive systems. This is a new finding and has significant implications for feedback processes. Together with results from the thermodynamic properties presented in a previous X-COP paper, it affords a coherent picture in which feedback effects do not vary significantly from one system to another. By combining intra-cluster medium with stellar measurements we have found the amount of Fe diffused in the intra-cluster medium to be about ten times higher than that locked in stars. Although our estimates suggest, with some strength, that the measured iron mass in clusters is well in excess of the predicted one, systematic errors prevent us from making a definitive statement. Further advancements will only be possible when systematic uncertainties, principally those associated with stellar masses, both within and beyond R500, can be reduced
High-resolution tSZ cartography of clusters of galaxies with NIKA at the IRAM 30-m telescope
The thermal Sunyaev-Zeldovich effect (tSZ) is a powerful probe to study
clusters of galaxies and is complementary with respect to X-ray, lensing or
optical observations. Previous arcmin resolution tSZ observations ({\it e.g.}
SPT, ACT and Planck) only enabled detailed studies of the intra-cluster medium
morphology for low redshift clusters (). Thus, the development of
precision cosmology with clusters requires high angular resolution observations
to extend the understanding of galaxy cluster towards high redshift. NIKA2 is a
wide-field (6.5 arcmin field of view) dual-band camera, operated at and containing KID (Kinetic Inductance Detectors), designed to
observe the millimeter sky at 150 and 260 GHz, with an angular resolution of 18
and 12 arcsec respectively. The NIKA2 camera has been installed on the IRAM
30-m telescope (Pico Veleta, Spain) in September 2015. The NIKA2 tSZ
observation program will allow us to observe a large sample of clusters (50) at
redshift ranging between 0.5 and 1. As a pathfinder for NIKA2, several clusters
of galaxies have been observed at the IRAM 30-m telescope with the NIKA
prototype to cover the various configurations and observation conditions
expected for NIKA2.Comment: Proceedings of the 28th Texas Symposium on Relativistic Astrophysics,
Geneva, Switzerland, December 13-18, 201
High angular resolution Sunyaev-Zel'dovich observations of MACS J1423.8+2404 with NIKA: Multiwavelength analysis
The prototype of the NIKA2 camera, NIKA, is an instrument operating at the
IRAM 30-m telescope, which can observe simultaneously at 150 and 260GHz. One of
the main goals of NIKA2 is to measure the pressure distribution in galaxy
clusters at high resolution using the thermal SZ (tSZ) effect. Such
observations have already proved to be an excellent probe of cluster pressure
distributions even at high redshifts. However, an important fraction of
clusters host submm and/or radio point sources, which can significantly affect
the reconstructed signal. Here we report on <20" resolution observations at 150
and 260GHz of the cluster MACSJ1424, which hosts both radio and submm point
sources. We examine the morphology of the tSZ signal and compare it to other
datasets. The NIKA data are combined with Herschel satellite data to study the
SED of the submm point source contaminants. We then perform a joint
reconstruction of the intracluster medium (ICM) electronic pressure and density
by combining NIKA, Planck, XMM-Newton, and Chandra data, focusing on the impact
of the radio and submm sources on the reconstructed pressure profile. We find
that large-scale pressure distribution is unaffected by the point sources
because of the resolved nature of the NIKA observations. The reconstructed
pressure in the inner region is slightly higher when the contribution of point
sources are removed. We show that it is not possible to set strong constraints
on the central pressure distribution without accurately removing these
contaminants. The comparison with X-ray only data shows good agreement for the
pressure, temperature, and entropy profiles, which all indicate that MACSJ1424
is a dynamically relaxed cool core system. The present observations illustrate
the possibility of measuring these quantities with a relatively small
integration time, even at high redshift and without X-ray spectroscopy.Comment: 15 pages, 17 figures, submitted to A&
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