25 research outputs found
Results from PAMELA, ATIC and FERMI : Pulsars or Dark Matter ?
It is well known that the dark matter dominates the dynamics of galaxies and
clusters of galaxies. Its constituents remain a mystery despite an assiduous
search for them over the past three decades. Recent results from the
satellite-based PAMELA experiment detect an excess in the positron fraction at
energies between 10-100 GeV in the secondary cosmic ray spectrum. Other
experiments namely ATIC, HESS and FERMI show an excess in the total electron
(\ps + \el) spectrum for energies greater 100 GeV. These excesses in the
positron fraction as well as the electron spectrum could arise in local
astrophysical processes like pulsars, or can be attributed to the annihilation
of the dark matter particles. The second possibility gives clues to the
possible candidates for the dark matter in galaxies and other astrophysical
systems. In this article, we give a report of these exciting developments.Comment: 27 Pages, extensively revised and significantly extended, to appear
in Pramana as topical revie
A review of elliptical and disc galaxy structure, and modern scaling laws
A century ago, in 1911 and 1913, Plummer and then Reynolds introduced their
models to describe the radial distribution of stars in `nebulae'. This article
reviews the progress since then, providing both an historical perspective and a
contemporary review of the stellar structure of bulges, discs and elliptical
galaxies. The quantification of galaxy nuclei, such as central mass deficits
and excess nuclear light, plus the structure of dark matter halos and cD galaxy
envelopes, are discussed. Issues pertaining to spiral galaxies including dust,
bulge-to-disc ratios, bulgeless galaxies, bars and the identification of
pseudobulges are also reviewed. An array of modern scaling relations involving
sizes, luminosities, surface brightnesses and stellar concentrations are
presented, many of which are shown to be curved. These 'redshift zero'
relations not only quantify the behavior and nature of galaxies in the Universe
today, but are the modern benchmark for evolutionary studies of galaxies,
whether based on observations, N-body-simulations or semi-analytical modelling.
For example, it is shown that some of the recently discovered compact
elliptical galaxies at 1.5 < z < 2.5 may be the bulges of modern disc galaxies.Comment: Condensed version (due to Contract) of an invited review article to
appear in "Planets, Stars and Stellar
Systems"(www.springer.com/astronomy/book/978-90-481-8818-5). 500+ references
incl. many somewhat forgotten, pioneer papers. Original submission to
Springer: 07-June-201
The stellar and sub-stellar IMF of simple and composite populations
The current knowledge on the stellar IMF is documented. It appears to become
top-heavy when the star-formation rate density surpasses about 0.1Msun/(yr
pc^3) on a pc scale and it may become increasingly bottom-heavy with increasing
metallicity and in increasingly massive early-type galaxies. It declines quite
steeply below about 0.07Msun with brown dwarfs (BDs) and very low mass stars
having their own IMF. The most massive star of mass mmax formed in an embedded
cluster with stellar mass Mecl correlates strongly with Mecl being a result of
gravitation-driven but resource-limited growth and fragmentation induced
starvation. There is no convincing evidence whatsoever that massive stars do
form in isolation. Various methods of discretising a stellar population are
introduced: optimal sampling leads to a mass distribution that perfectly
represents the exact form of the desired IMF and the mmax-to-Mecl relation,
while random sampling results in statistical variations of the shape of the
IMF. The observed mmax-to-Mecl correlation and the small spread of IMF
power-law indices together suggest that optimally sampling the IMF may be the
more realistic description of star formation than random sampling from a
universal IMF with a constant upper mass limit. Composite populations on galaxy
scales, which are formed from many pc scale star formation events, need to be
described by the integrated galactic IMF. This IGIMF varies systematically from
top-light to top-heavy in dependence of galaxy type and star formation rate,
with dramatic implications for theories of galaxy formation and evolution.Comment: 167 pages, 37 figures, 3 tables, published in Stellar Systems and
Galactic Structure, Vol.5, Springer. This revised version is consistent with
the published version and includes additional references and minor additions
to the text as well as a recomputed Table 1. ISBN 978-90-481-8817-
The Gaia-ESO Public Spectroscopic Survey: Motivation, implementation, GIRAFFE data processing, analysis, and final data products
The Gaia-ESO Public Spectroscopic Survey is an ambitious project designed to
obtain astrophysical parameters and elemental abundances for 100,000 stars,
including large representative samples of the stellar populations in the
Galaxy, and a well-defined sample of 60 (plus 20 archive) open clusters. We
provide internally consistent results calibrated on benchmark stars and star
clusters, extending across a very wide range of abundances and ages. This
provides a legacy data set of intrinsic value, and equally a large wide-ranging
dataset that is of value for homogenisation of other and future stellar surveys
and Gaia's astrophysical parameters. This article provides an overview of the
survey methodology, the scientific aims, and the implementation, including a
description of the data processing for the GIRAFFE spectra. A companion paper
(arXiv:2206.02901) introduces the survey results. Gaia-ESO aspires to quantify
both random and systematic contributions to measurement uncertainties. Thus all
available spectroscopic analysis techniques are utilised, each spectrum being
analysed by up to several different analysis pipelines, with considerable
effort being made to homogenise and calibrate the resulting parameters. We
describe here the sequence of activities up to delivery of processed data
products to the ESO Science Archive Facility for open use. The Gaia-ESO Survey
obtained 202,000 spectra of 115,000 stars using 340 allocated VLT nights
between December 2011 and January 2018 from GIRAFFE and UVES. The full
consistently reduced final data set of spectra was released through the ESO
Science Archive Facility in late 2020, with the full astrophysical parameters
sets following in 2022
Defining Terms Used for Animals Working in Support Roles for People with Support Needs
This is the final version. Available on open access from MDPI via the DOI in this recordData Availability Statement:
De-identified qualitative data can be made available by contacting the lead author.The nomenclature used to describe animals working in roles supporting people can be confusing. The same term may be used to describe different roles, or two terms may mean the same thing. This confusion is evident among researchers, practitioners, and end users. Because certain animal roles are provided with legal protections and/or government-funding support in some jurisdictions, it is necessary to clearly define the existing terms to avoid confusion. The aim of this paper is to provide operationalized definitions for nine terms, which would be useful in many world regions: "assistance animal", "companion animal", "educational/school support animal", "emotional support animal", "facility animal", "service animal", "skilled companion animal", "therapy animal", and "visiting/visitation animal". At the International Society for Anthrozoology (ISAZ) conferences in 2018 and 2020, over 100 delegates participated in workshops to define these terms, many of whom co-authored this paper. Through an iterative process, we have defined the nine terms and explained how they differ from each other. We recommend phasing out two terms (i.e., "skilled companion animal" and "service animal") due to overlap with other terms that could potentially exacerbate confusion. The implications for several regions of the world are discussed
Against Dedicated Methods:Relational Expertise in Participatory Design with People with Dementia
This chapter narrates the search for ways to involve people with dementia in the design process based on insights from three projects, several workshops and an educational module involving people with dementia and their network of caregivers and family. This six year-trajectory was part of a Ph.D. project and started ambitiously with the endeavor to find a dedicated method for involvement, inspired by those developed to involve children or people with aphasia. The aim was to develop a set of design guidelines for (successfully) involving people with dementia in the design process. It became clear that using a set of guidelines as a universal, dedicated, or passe-partout way of working for every person with dementia, would not work. We argue that the foundations for a more suitable individualized approach lie in the build-up of a personal relationship between the person with dementia and the designer. Based on such a personal relationship, ways to facilitate involvement of a person with dementia can be defined and design decisions can be collaboratively taken. Person-Centered Care is seen as a guide in the build-up of the relational expertise that a designer needs in order to collaborate with a person with dementia and that enables designers to value and articulate shared decision making