1,129 research outputs found
In the eye of the beholder: owner preferences for variations in cats' appearances with specific focus on skull morphology
Changes in the popularity of cat breeds are largely driven by human perceptions of, and selection for, phenotypic traits including skull morphology. The popularity of breeds with altered skull shapes appears to be increasing, and owner preferences are an important part of this dynamic. This study sought to establish how and why a range of phenotypic attributes, including skull shape, affect preferences shown by cat owners. Two questionnaires were distributed on-line to cat owners who were asked to rate preferences for pictures of cats on a 0â10 scale. Veterinarian consensus established the skull types of the cats pictured (i.e., level of brachycephaly (BC) or dolichocephaly (DC)). Preferences were then explored relative to cat skull type, coat and eye color, and coat length. Generalized estimating equations identified relationships between physical characteristics and respondent ratings. Further sub-analyses explored effects of respondents' occupation, location and previous cat ownership on rating scores. Overall, cats with extreme changes in skull morphology (both BC and DC) were significantly less preferred than mesocephalic cats. Green eyes, ginger coat color and medium length coat were most preferred. Current owners of a BC or DC pure bred cat showed significantly greater preference for cats with similar features and significantly lower preference for the opposite extreme. Respondents from Asia were significantly more likely to prefer both BC and DC cats as compared to respondents from other locations. Finally, those in an animal care profession, as compared to other professions, provided a significantly lower preference rating for BC cats but not for DC cats. This work, despite the acknowledged limitations, provides preliminary evidence that preferences for cat breeds, and their associated skull morphologies, are driven by both cultural and experiential parameters. This information may allow for better targeting of educational materials concerning cat breeds
Resolved stellar mass maps of galaxies. I: method and implications for global mass estimates
(Abridged) We introduce a novel technique to construct spatially resolved
maps of stellar mass surface density in galaxies based on optical and near IR
imaging. We use optical/NIR colour(s) to infer effective stellar mass-to-light
ratios (M/L) at each pixel, which are then multiplied by the surface brightness
to obtain the local stellar surface mass density. We build look-up tables to
express M/L as a function of colour(s) by marginalizing over a Monte Carlo
library of 50,000 stellar population synthesis (SPS) models by Charlot &
Bruzual (2007), which include a revised prescription for the TP-AGB stellar
evolutionary phase, with a wide range of dust exinctions. In order to extract
reliable flux and colour information at any position in the galaxy, we perform
a median adaptive smoothing of the images that preserves the highest possible
spatial resolution. As the most practical and robust, and hence fiducial
method, we express the M/L in the H band as a function of (g-i) and (i-H).
Stellar mass maps computed in this way have a typical accuracy of 30 per cent
or less at any given pixel, determined from the scatter in the models. We
compare maps obtained with our fiducial method with those derived using other
combinations of bandpasses and the old BC03 TP-AGB prescription. Finally, we
compare total stellar mass estimates obtained by integrating resolved mass maps
with those obtained with unresolved photometry. In galaxies with evident dust
lanes, unresolved estimates may miss up to 40 per cent of the total stellar
mass because dusty regions are strongly under-represented in the luminous
fluxes.Comment: Accepted for publication on MNRAS on Aug 10th 2009. 21 pages, 14
figures (see http://www.mpia.de/homes/zibetti/mass_maps_I.pdf for full
resolution). One appendix added and minor changes done wrt to original
submissio
On the Nature of the EIS Candidate Clusters: Confirmation of z<0.6 candidates
We use public V-band imaging data from the wide-angle surveys conducted by
the ESO Imaging Survey project (EIS) to further investigate the nature of the
EIS galaxy cluster candidates. These were originally identified by applying a
matched-filter algorithm which used positional and photometric data of the
galaxy sample extracted from the I-band survey images. In this paper, we apply
the same technique to the galaxy sample extracted from V-band data and compare
the new cluster detections with the original ones. We find that ~75% of the
low-redshift cluster candidates (z<0.6) are detected in both passbands and
their estimated redshifts show good agreement with the scatter in the redshift
differences being consistent with the estimated errors of the method. For the
``robust'' I-band detections the matching frequency approaches ~85%. We also
use the available (V-I) color to search for the red sequence of early-type
galaxies observed in rich clusters over a broad range of redshifts. This is
done by searching for a simultaneous overdensity in the three-dimensional
color-projected distance space. We find significant overdensities for ~75% of
the ``robust'' candidates with z_I<0.6. We find good agreement between the
characteristic color associated to the detected "red sequence" and that
predicted by passive evolution galaxy models for ellipticals at the redshift
estimated by the matched-filter. The results presented in this paper show the
usefulness of color data, even of two-band data, to both tentatively confirm
cluster candidates and to select possible cluster members for spectroscopic
observations. Based on the present results, we estimate that ~150 EIS clusters
with z_I<0.6 are real, making it one of the largest samples of galaxy clusters
in this redshift range currently available in the southern hemisphere.Comment: 11 pages, 10 figures, accepted for publication in A&
Velocity distributions in clusters of galaxies
We employ a high-resolution dissipationless N-body simulation of a galaxy
cluster to investigate the impact of subhalo selection on the resulting
velocity distributions. Applying a lower limit on the present bound mass of
subhalos leads to high subhalo velocity dispersions compared to the diffuse
dark matter (positive velocity bias) and to a considerable deviation from a
Gaussian velocity distribution (kurtosis -0.6). However, if subhalos are
required to exceed a minimal mass before accretion onto the host, the velocity
bias becomes negligible and the velocity distribution is close to Gaussian
(kurtosis -0.15). Recently it has been shown that the latter criterion results
in subhalo samples that agree well with the observed number-density profiles of
galaxies in clusters. Therefore we argue that the velocity distributions of
galaxies in clusters are essentially un-biased. The comparison of the galaxy
velocity distribution and the sound speed, derived from scaling relations of
X-ray observations, results in an average Mach number of 1.24. Altogether 65%
of the galaxies move supersonically and 8% have Mach numbers larger than 2 with
respect to the intra cluster gas.Comment: 5 pages, 3 figures, Accepted for publication in MNRAS(Letters
The response of perennial and temporary headwater stream invertebrate communities to hydrological extremes
The headwaters of karst rivers experience considerable hydrological variability, including spates and streambed drying. Extreme summer flooding on the River Lathkill (Derbyshire, UK) provided the opportunity to examine the invertebrate community response to unseasonal spate flows, flow recession and, at temporary sites, streambed drying. Invertebrates were sampled at sites with differing flow permanence regimes during and after the spates. Following streambed drying at temporary sites, dewatered surface sediments were investigated as a refugium for aquatic invertebrates. Experimental rehydration of these dewatered sediments was conducted to promote development of desiccation-tolerant life stages. At perennial sites, spate flows reduced invertebrate abundance and diversity, whilst at temporary sites, flow reactivation facilitated rapid colonisation of the surface channel by a limited number of invertebrate taxa. Following streambed drying, 38 taxa were recorded from the dewatered and rehydrated sediments, with Oligochaeta being the most abundant taxon and Chironomidae (Diptera) the most diverse. Experimental rehydration of dewatered sediments revealed the presence of additional taxa, including Stenophylax sp. (Trichoptera: Limnephilidae) and Nemoura sp. (Plecoptera: Nemouridae). The influence of flow permanence on invertebrate community composition was apparent despite the aseasonal high-magnitude flood events
Multi-object spectroscopy of low-redshift EIS clusters IV. Reliability of matched-filter results at z~0.3-0.4
abridged) In this paper we present new redshifts for 747 galaxies in 23 ESO
Imaging Survey (EIS) cluster fields. We use the "gap"-technique to search for
significant overdensities in redshift space for identifying groups/clusters of
galaxies. In this way we spectroscopically confirm systems in 10 of the 23
cluster candidate fields with a matched-filter estimated redshift z_MF=0.3-0.4
and with spectroscopic redshifts in the range from z=0.158 to z=0.534. We find
that the systems identified in the present paper span a broad range of
one-dimensional velocity dispersion (175-497 km/s) and richness
(12L*<=L<=65L*). Both undersampling and contamination by substructures
contribute to the uncertainty of these measurements. From the analysis of the
colours of the galaxy populations we find that ~60% of the spectroscopically
confirmed systems have a "significant" red sequence with a colour matching
passive stellar evolution models. With this paper we complete our spectroscopic
survey of the fields of 58 EIS cluster candidates with estimated redshifts
z<=0.4. We have measured a total of 1954 galaxy redshifts in the range z=0.0065
to z=0.6706. Of the 58 systems we confirm 42 (~75%) with redshifts between
z=0.095 and z=0.534.Comment: Accepted for publication in A&A, 19 pages, 11 figure
Toward High-Precision Measures of Large-Scale Structure
I review some results of estimation of the power spectrum of density
fluctuations from galaxy redshift surveys and discuss advances that may be
possible with the Sloan Digital Sky Survey. I then examine the realities of
power spectrum estimation in the presence of Galactic extinction, photometric
errors, galaxy evolution, clustering evolution, and uncertainty about the
background cosmology.Comment: 24 pages, including 11 postscript figures. Uses crckapb.sty (included
in submission). To appear in ``Ringberg Workshop on Large-Scale Structure,''
ed D. Hamilton (Kluwer, Amsterdam), p. 39
Motivation of owners to purchase pedigree cats, with specific focus on the acquisition of brachycephalic cats
Background: Cats are globally popular pets and pedigree cats are increasingly prevalent, with brachycephalic breeds being the most registered breeds. How owners decide upon and acquire their cats is poorly understood. Moreover, there are growing concerns about the health and welfare of brachycephalic (BC) dogs and recent studies are raising the awareness of health and welfare problems in BC cats. Methods: An online survey investigated ownersâ motivations, perceptions and behaviours prior to, during and following acquisition of non-pedigree (NP), extreme brachycephalic pedigree (BC; i.e., Persian and Exotic Shorthair) and mild to non-BC pedigree (P) cats. Results: The survey received 1367 valid responses (NP n = 882, P n = 400, BC n = 85 (6.2%)). There were marked differences between NP, P and BC ownersâ perception of their catsâ health and welfare, reason(s) for acquisition and its process. Owners of NP were less influenced by appearance, behaviour and other features than P or BC owners. In contrast, P and BC owners were highly influenced by appearance, with P owners also placing greater importance on good breed health than BC owners. BC owners were less likely to recommend their breeds to prospective cat owners, apparently concerned by high maintenance requirements. Conclusion: Further research is needed to determine how decision-making is constructed and how it may be improved, especially in respect of welfare outcomes for extreme BC cats given the increased weighting given to appearance over health
The clustering of massive galaxies at z~0.5 from the first semester of BOSS data
We calculate the real- and redshift-space clustering of massive galaxies at
z~0.5 using the first semester of data by the Baryon Oscillation Spectroscopic
Survey (BOSS). We study the correlation functions of a sample of 44,000 massive
galaxies in the redshift range 0.4<z<0.7. We present a halo-occupation
distribution modeling of the clustering results and discuss the implications
for the manner in which massive galaxies at z~0.5 occupy dark matter halos. The
majority of our galaxies are central galaxies living in halos of mass
10^{13}Msun/h, but 10% are satellites living in halos 10 times more massive.
These results are broadly in agreement with earlier investigations of massive
galaxies at z~0.5. The inferred large-scale bias (b~2) and relatively high
number density (nbar=3e-4 h^3 Mpc^{-3}) imply that BOSS galaxies are excellent
tracers of large-scale structure, suggesting BOSS will enable a wide range of
investigations on the distance scale, the growth of large-scale structure,
massive galaxy evolution and other topics.Comment: 11 pages, 12 figures, matches version accepted by Ap
A direct image of the obscuring disk surrounding an active galactic nucleus
Active galactic nuclei (AGN) are generally accepted to be powered by the
release of gravitational energy in a compact accretion disk surrounding a
massive black hole. Such disks are also necessary to collimate powerful radio
jets seen in some AGN. The unifying classification schemes for AGN further
propose that differences in their appearance can be attributed to the opacity
of the accreting material, which may obstruct our view of the central region of
some systems. The popular model for the obscuring medium is a parsec-scale disk
of dense molecular gas, although evidence for such disks has been mostly
indirect, as their angular size is much smaller than the resolution of
conventional telescopes. Here we report the first direct images of a pc-scale
disk of ionised gas within the nucleus of NGC 1068, the archetype of obscured
AGN. The disk is viewed nearly edge-on, and individual clouds within the
ionised disk are opaque to high-energy radiation, consistent with the unifying
classification scheme. In projection, the disk and AGN axes align, from which
we infer that the ionised gas disk traces the outer regions of the long-sought
inner accretion disk.Comment: 14 pages, LaTeX, PSfig, to appear in Nature. also available at
http://hethp.mpe-garching.mpg.de/Preprint
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