371 research outputs found
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
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 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
VIP: An Experiment to Search for a Violation of the Pauli Exclusion Principle
The Pauli Exclusion Principle is a basic principle of Quantum Mechanics, and
its validity has never been seriously challenged. However, given its
fundamental standing, it is very important to check it as thoroughly as
possible. Here we describe the VIP (VIolation of the Pauli exclusion principle)
experiment, an improved version of the Ramberg and Snow experiment (E. Ramberg
and G. Snow, {\it Phys. Lett. B} {\bf 238}, 438 (1990)); VIP has just completed
the installation at the Gran Sasso underground laboratory, and aims to test the
Pauli Exclusion Principle for electrons with unprecedented accuracy, down to
. We report preliminary experimental
results and briefly discuss some of the implications of a possible violation.Comment: Plenary talk presented by E. Milotti at Meson 2006, Cracow, 9-13 June
200
New experimental limit on the Pauli Exclusion Principle violation by electrons
The Pauli Exclusion Principle (PEP) is one of the basic principles of modern
physics and, even if there are no compelling reasons to doubt its validity, it
is still debated today because an intuitive, elementary explanation is still
missing, and because of its unique stand among the basic symmetries of physics.
The present paper reports a new limit on the probability that PEP is violated
by electrons, in a search for a shifted K line in copper: the presence
of this line in the soft X-ray copper fluorescence would signal a transition to
a ground state already occupied by 2 electrons. The obtained value, , improves the existing limit by almost two
orders of magnitude.Comment: submitted to Phys. Lett.
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
New experimental limit on Pauli Exclusion Principle violation by electrons (the VIP experiment)
The Pauli Exclusion Principle is one of the basic principles of modern
physics and is at the very basis of our understanding of matter: thus it is
fundamental importance to test the limits of its validity. Here we present the
VIP (Violation of the Pauli Exclusion Principle) experiment, where we search
for anomalous X-rays emitted by copper atoms in a conductor: any detection of
these anomalous X-rays would mark a Pauli-forbidden transition. ] VIP is
currently taking data at the Gran Sasso underground laboratories, and its
scientific goal is to improve by at least four orders of magnitude the previous
limit on the probability of Pauli violating transitions, bringing it into the
10**-29 - 10**-30 region. First experimental results, together with future
plans, are presented.Comment: To appear in proceedings of the XLVI International Winter Meeting on
Nuclear Physics, Bormio, Italy, January 20-26, 200
The VIP Experiment
The Pauli Exclusion Principle (PEP) is a basic principle of Quantum
Mechanics, and its validity has never been seriously challenged. However, given
its importance, it is very important to check it as thoroughly as possible.
Here we describe the VIP (Violation of PEP) experiment, an improved version of
the Ramberg and Snow experiment (Ramberg and Snow, Phys. Lett. B238 (1990)
438); VIP shall be performed at the Gran Sasso underground laboratories, and
aims to test the Pauli Exclusion Principle for electrons with unprecedented
accuracy, down to Comment: 7 pages, 5 figures, PDF only, presented by Edoardo Milotti to the
conference "Quantum Theory: reconsideration of foundations-3", Vaxjo
(Sweden), June, 6-11 200
Testing the Pauli Exclusion Principle for Electrons
One of the fundamental rules of nature and a pillar in the foundation of
quantum theory and thus of modern physics is represented by the Pauli Exclusion
Principle. We know that this principle is extremely well fulfilled due to many
observations. Numerous experiments were performed to search for tiny violation
of this rule in various systems. The experiment VIP at the Gran Sasso
underground laboratory is searching for possible small violations of the Pauli
Exclusion Principle for electrons leading to forbidden X-ray transitions in
copper atoms. VIP is aiming at a test of the Pauli Exclusion Principle for
electrons with high accuracy, down to the level of 10 - 10,
thus improving the previous limit by 3-4 orders of magnitude. The experimental
method, results obtained so far and new developments within VIP2 (follow-up
experiment at Gran Sasso, in preparation) to further increase the precision by
2 orders of magnitude will be presented.Comment: Proceedings DISCRETE 2012-Third Symposium on Prospects in the Physics
of Discrete Symmetries, Lisbon, December 3-7, 201
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