19,746 research outputs found
The Structural Parameters of Bulges, Bars and Discs in the Local Universe
Image decomposition of galaxies is now routinely used to estimate the
structural parameters of galactic components. In this work, I address questions
on the reliability of this technique. In particular, do bars and AGN need to be
taken into account to obtain the structural parameters of bulges and discs? And
to what extent can we trust image decomposition when the physical spatial
resolution is relatively poor? With this aim, I performed multi-component
(bar/bulge/disc/AGN) image decomposition of a sample of very nearby galaxies
and their artificially redshifted images, and verified the effects of removing
the bar and AGN components from the models. Neglecting bars can result in a
overestimation of the bulge-to-total luminosity ratio of a factor of two, even
if the resolution is low. Similar effects result when bright AGN are not
considered in the models, but only when the resolution is high. I also show
that the structural parameters of more distant galaxies can in general be
reliably retrieved, at least up to the point where the physical spatial
resolution is about 1.5 Kpc, but bulge parameters are prone to errors if its
effective radius is small compared to the seeing radius, and might suffer from
systematic effects. I briefly discuss the consequences of these results to our
knowledge of the stellar mass budget in the local universe, and finish by
showing preliminary results from a large SDSS sample on the dichotomy between
classical and pseudo-bulges.Comment: 4 pages, 3 figures; contributed talk to appear in "Formation and
Evolution of Galaxy Bulges", proceedings of the IAU Symp. 245, held in
Oxford, UK, July 2007, M. Bureau, E. Athanassoula, B. Barbuy (eds.
Ambivalent sexism and perceptions of men and women who violate gendered family roles
This study draws on ambivalent sexism theory to explore the role of benevolent and hostile gender attitudes in determining perceptions of individuals who comply with traditional gender roles or violate them. Three hundred and eleven participants were presented with a description of a male or a female target who was either a primary breadwinner or a primary caregiver. As hypothesized, hostile sexism predicted more negative perceptions of a female breadwinner, whereas benevolent sexism predicted more positive perceptions of a female caregiver. Moreover, participants who endorsed hostile attitudes toward men reacted more positively to a nontraditional male caregiver, whereas those who endorsed benevolent attitudes toward men reacted more negatively to a male caregiver. Implications regarding the nature of ambivalent gender attitudes are discussed
Size matters: the value of small populations for wintering waterbirds
Protecting systematically selected areas of land is a major step towards biodiversity conservation worldwide. Indeed, the identification and designation of protected areas more often than not forms a core component of both national and international conservation policies. In this paper we provide an overview of those Special Protection Areas and Ramsar Sites that have been classified in Great Britain as of 1998/99 for a selection of wintering waterbird species, using bird count data from the Wetland Bird Survey.
The performance of this network of sites is remarkable, particularly in comparison with published analyses of networks elsewhere in the world. Nevertheless, the current site-based approach, whilst having the great benefit of simplicity, is deliberately biased towards aggregating species at the expense of the more dispersed distribution species. To ensure that the network continues successfully to protect nationally and internationally important waterbird populations, efforts now need to concentrate on the derivation of species-specific representation targets and, in particular, the ways in which these can be incorporated into the site selection process. Although these analyses concern the performance of protected areas for waterbirds in Great Britain, the results have wide-ranging importance for conservation planning in general and the design of protected area networks
Three-Dimensional Bar Structure and Disc/Bulge Secular Evolution
Kn-band imaging of a sample of 30 edge-on spiral galaxies with a boxy or
peanut-shaped (B/PS) bulge is discussed. Galaxies with a B/PS bulge tend to
have a more complex morphology than galaxies with other bulge types,
unsharp-masked images revealing structures that trace the major orbit families
of three-dimensional bars. Their surface brightness profiles are also more
complex, typically containing 3 or more clearly separated regions, including a
shallow or flat intermediate region (Freeman Type II profiles), suggestive of
bar-driven transfer of angular momentum and radial redistribution of material.
The data also suggest abrupt variations of the discs' scaleheights, as expected
from the vertical resonances and instabilities present in barred discs but
contrary to conventional wisdom. Counter to the standard `bulge + disc' model,
we thus propose that galaxies with a B/PS bulge are composed of a thin
concentrated disc (a disc-like bulge) contained within a partially thick bar
(the B/PS bulge), itself contained within a thin outer disc. The inner disc
most likely formed through bar-driven processes while the thick bar arises from
buckling instabilities. Both are strongly coupled dynamically and are formed
mostly of the same (disc) material.Comment: 6 pages, including 1 figure. To appear in "Island Universes:
Structure and Evolution of Disk Galaxies", ed. R. de Jong (Springer:
Dordrecht
A growing disconnection from nature is evident in cultural products
Human connection with nature is widely believed to be in decline, even though empirical evidence on the magnitude and temporal pattern of the change is scarce. Studying works of popular culture in English throughout the 20th century and later, we document a cultural shift away from nature, beginning in the 1950s. Since then, references to nature have been decreasing steadily in fiction, song lyrics, and film storylines. No parallel decline is observed in references to the human-made environment. These findings are cause for concern, not only because they imply foregone benefits from engagement with nature, but also because cultural products are agents of socialization that can evoke curiosity, respect, and concern for the natural world
Boxy/peanut/X bulges, barlenses and the thick part of galactic bars: What are they and how did they form?
Bars have a complex three-dimensional shape. In particular their inner part
is vertically much thicker than the parts further out. Viewed edge-on, the
thick part of the bar is what is commonly known as a boxy-, peanut- or X- bulge
and viewed face-on it is referred to as a barlens. These components are due to
disc and bar instabilities and are composed of disc material. I review here
their formation, evolution and dynamics, using simulations, orbital structure
theory and comparisons to observations.Comment: 21 pages, 7 figures, invited review to appear in "Galactic Bulges",
E. Laurikainen, R. Peletier, D. Gadotti, (eds.), Springe
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