1,897 research outputs found
Pop III GRBs: an estimative of the event rate for future surveys
We discuss the theoretical event rate of gamma-ray bursts (GRBs) from the
collapse of massive primordial stars. We construct a theoretical model to
calculate the rate and detectability of these GRBs taking into account all
important feedback and recent results from numerical simulations of pristine
gas. We expect to observe a maximum of N 0.2 GRBs per year
integrated over at z > 6 with \textit{Swift} and N 10 GRBs per year
integrated over at z > 6 with EXIST.Comment: 6 pages, 2 figures, published in Proceedings of the Gamma-Ray Bursts
2012 Conference (GRB 2012
AMADA-Analysis of Multidimensional Astronomical Datasets
We present AMADA, an interactive web application to analyse multidimensional
datasets. The user uploads a simple ASCII file and AMADA performs a number of
exploratory analysis together with contemporary visualizations diagnostics. The
package performs a hierarchical clustering in the parameter space, and the user
can choose among linear, monotonic or non-linear correlation analysis. AMADA
provides a number of clustering visualization diagnostics such as heatmaps,
dendrograms, chord diagrams, and graphs. In addition, AMADA has the option to
run a standard or robust principal components analysis, displaying the results
as polar bar plots. The code is written in R and the web interface was created
using the Shiny framework. AMADA source-code is freely available at
https://goo.gl/KeSPue, and the shiny-app at http://goo.gl/UTnU7I.Comment: Accepted for publication in Astronomy & Computin
Random Primordial Magnetic Fields and the Gas Content of Dark Matter Halos
We recently predicted the existence of random primordial magnetic fields
(RPMF) in the form of randomly oriented cells with dipole-like structure with a
cell size and an average magnetic field . Here we investigate models
for primordial magnetic field with a similar web-like structure, and other
geometries, differing perhaps in and . The effect of RPMF on the
formation of the first galaxies is investigated. The filtering mass, , is
the halo mass below which baryon accretion is severely depressed. We show that
these RPMF could influence the formation of galaxies by altering the filtering
mass and the baryon gas fraction of a halo, . The effect is particularly
strong in small galaxies. We find, for example, for a comoving B_0=0.1\muG,
and a reionization epoch that starts at and ends at , for
at , the becomes severely depressed for
M<10^7\msun, whereas for the becomes severely depressed only
for much smaller masses, M<10^5\msun. We suggest that the observation of
and at high redshifts can give information on the intensity and
structure of primordial magnetic fields.Comment: 7 pages, 10 figures, accepted for publication in MNRAS (several
improvements after suggestions of the referee
SCONCE: A cosmic web finder for spherical and conic geometries
The latticework structure known as the cosmic web provides a valuable insight
into the assembly history of large-scale structures. Despite the variety of
methods to identify the cosmic web structures, they mostly rely on the
assumption that galaxies are embedded in a Euclidean geometric space. Here we
present a novel cosmic web identifier called SCONCE (Spherical and CONic Cosmic
wEb finder) that inherently considers the 2D (RA,DEC) spherical or the 3D
(RA,DEC,) conic geometry. The proposed algorithms in SCONCE generalize the
well-known subspace constrained mean shift (SCMS) method and primarily address
the predominant filament detection problem. They are intrinsic to the
spherical/conic geometry and invariant to data rotations. We further test the
efficacy of our method with an artificial cross-shaped filament example and
apply it to the SDSS galaxy catalogue, revealing that the 2D spherical version
of our algorithms is robust even in regions of high declination. Finally, using
N-body simulations from Illustris, we show that the 3D conic version of our
algorithms is more robust in detecting filaments than the standard SCMS method
under the redshift distortions caused by the peculiar velocities of halos. Our
cosmic web finder is packaged in python as SCONCE-SCMS and has been made
publicly available.Comment: 20 pages, 9 figures, 2 table
Origin of Intense Magnetic Fields Near Black Holes Due to Non-Minimal Gravitational-Electromagnetic Coupling
The origin of magnetic fields in astrophysical objects is a challenging
problem in astrophysics. Throughout the years, many scientists have suggested
that non-minimal gravitational-electromagnetic coupling (NMGEC) could be the
origin of the ubiquitous astrophysical magnetic fields. We investigate the
possible origin of intense magnetic fields by NMGEC near
rotating neutron stars and black holes, connected with magnetars, quasars, and
gamma-ray bursts. Whereas these intense magnetic fields are difficult to
explain astrophysically, we find that they are easily explained by NMGEC.Comment: 7 pages, accepted for publication in Phys. Lett.
Suppression of small baryonic structures due to a primordial magnetic field
We investigate the impact of the existence of a primordial magnetic field on
the filter mass, characterizing the minimum baryonic mass that can form in dark
matter (DM) haloes. For masses below the filter mass, the baryon content of DM
haloes are severely depressed. The filter mass is the mass when the baryon to
DM mass ratio in a halo is equal to half the baryon to DM ratio of the
Universe. The filter mass has previously been used in semianalytic calculations
of galaxy formation, without taking into account the possible existence of a
primordial magnetic field. We examine here its effect on the filter mass. For
homogeneous comoving primordial magnetic fields of or 2 nG and a
reionization epoch that starts at a redshift and is completed at
, the filter mass is increased at redshift 8, for example, by factors
4.1 and 19.8, respectively. The dependence of the filter mass on the parameters
describing the reionization epoch is investigated. Our results are particularly
important for the formation of low mass galaxies in the presence of a
homogeneous primordial magnetic field. For example, for B_0\sim 1\nG and a
reionization epoch of and , our results indicate that
galaxies of total mass M\sim5 \times 10^8\msun need to form at redshifts
, and galaxies of total mass M\sim10^8\msun at redshifts
.Comment: 5 pages, 3 figures, accepted for publication in MNRA
Origin of G Magnetic Fields in the Central Engine of Gamma Ray Bursts
Various authors have suggested that the gamma-ray burst (GRB) central engine
is a rapidly rotating, strongly magnetized, G) compact
object. The strong magnetic field can accelerate and collimate the relativistic
flow and the rotation of the compact object can be the energy source of the
GRB. The major problem in this scenario is the difficulty of finding an
astrophysical mechanism for obtaining such intense fields. Whereas, in
principle, a neutron star could maintain such strong fields, it is difficult to
justify a scenario for their creation. If the compact object is a black hole,
the problem is more difficult since, according to general relativity it has "no
hair" (i.e., no magnetic field). Schuster, Blackett, Pauli, and others have
suggested that a rotating neutral body can create a magnetic field by
non-minimal gravitational-electromagnetic coupling (NMGEC). The
Schuster-Blackett form of NMGEC was obtained from the Mikhail and Wanas's
tetrad theory of gravitation (MW). We call the general theory NMGEC-MW.
We investigate here the possible origin of the intense magnetic fields G in GRBs by NMGEC-MW. Whereas these fields are difficult to
explain astrophysically, we find that they are easily explained by NMGEC-MW. It
not only explains the origin of the G fields when the
compact object is a neutron star, but also when it is a black hole.Comment: 9 pages, accepted for publication in JCA
Borderline personality disorder and bias in the recognition of facial expressions of emotion: a pathway to understand the psychopathology
Background The identification of facial emotions is a key skill as it promotes rapid and accurate recognition of emotions and enables better communication and greater social adaptation. More recent studies have suggested that impaired social interactions may be related to deficits in social cognition and therefore in the recognition of facial expressions, contributing to social disturbance among individuals with borderline personality disorder (BPD). Objective To present the results of an empirical study assessing the recognition of facial emotion expressions in women with BPD, having as reference a group of healthy women from the general population. Methods The subjects (40 female with BPD and 40 controls) were assessed with a dynamic task on a computer screen for recognition of facial expressions of emotion. Results The BPD group had a lower accuracy in perceiving emotions of fear and surprise and slowness in recognising happiness. Logistic regression analyses also identified an association between BPD and higher sensitivity in the recognition of anger. Discussion Women with BPD made more mistakes in the recognition of negative emotions, which can bias the behaviour and regulation of affective states, favouring in turn the emergence of some typical symptoms associated with BPD
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