54 research outputs found
The 6dF galaxy survey: fundamental plane data
We report the 6dFGS Fundamental Plane (6dFGSv) catalogue that is used to estimate distances and peculiar velocities for nearly 9000 early-type galaxies in the local (z < 0.055) universe. Velocity dispersions are derived by cross-correlation from 6dF V-band spectra with typical S/N of 12.9âĂ
â1 for a sample of 11 315 galaxies; the median velocity dispersion is 163âkmâsâ1 and the median measurement error is 12.9 per cent. The photometric Fundamental Plane (FP) parameters (effective radii and surface brightnesses) are determined from the JHK 2MASS images for 11 102 galaxies. Comparison of the independent J- and K-band measurements implies that the average uncertainty in XFP, the combined photometric parameter that enters the FP, is 0.013âdex (3 per cent) for each band. Visual classification of morphologies was used to select a sample of nearly 9000 early-type galaxies that form 6dFGSv. This catalogue has been used to study the effects of stellar populations on galaxy scaling relations, to investigate the variation of the FP with environment and galaxy morphology, to explore trends in stellar populations through, along and across the FP, and to map and analyse the local peculiar velocity field
The outer halos of elliptical galaxies
Recent progress is summarized on the determination of the density
distributions of stars and dark matter, stellar kinematics, and stellar
population properties, in the extended, low surface brightness halo regions of
elliptical galaxies. With integral field absorption spectroscopy and with
planetary nebulae as tracers, velocity dispersion and rotation profiles have
been followed to ~4 and ~5-8 effective radii, respectively, and in M87 to the
outer edge at ~150 kpc. The results are generally consistent with the known
dichotomy of elliptical galaxy types, but some galaxies show more complex
rotation profiles in their halos and there is a higher incidence of
misalignments, indicating triaxiality. Dynamical models have shown a range of
slopes for the total mass profiles, and that the inner dark matter densities in
ellipticals are higher than in spiral galaxies, indicating earlier assembly
redshifts. Analysis of the hot X-ray emitting gas in X-ray bright ellipticals
and comparison with dynamical mass determinations indicates that non-thermal
components to the pressure may be important in the inner ~10 kpc, and that the
properties of these systems are closely related to their group environments.
First results on the outer halo stellar population properties do not yet give a
clear picture. In the halo of one bright galaxy, lower [alpha/Fe] abundances
indicate longer star formation histories pointing towards late accretion of the
halo. This is consistent with independent evidence for on-going accretion, and
suggests a connection to the observed size evolution of elliptical galaxies
with redshift.Comment: 8 pages. Invited review to appear in the proceedings of "Galaxies and
their Masks" eds. Block, D.L., Freeman, K.C. & Puerari, I., 2010, Springer
(New York
Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy
We review HB stars in a broad astrophysical context, including both variable
and non-variable stars. A reassessment of the Oosterhoff dichotomy is
presented, which provides unprecedented detail regarding its origin and
systematics. We show that the Oosterhoff dichotomy and the distribution of
globular clusters (GCs) in the HB morphology-metallicity plane both exclude,
with high statistical significance, the possibility that the Galactic halo may
have formed from the accretion of dwarf galaxies resembling present-day Milky
Way satellites such as Fornax, Sagittarius, and the LMC. A rediscussion of the
second-parameter problem is presented. A technique is proposed to estimate the
HB types of extragalactic GCs on the basis of integrated far-UV photometry. The
relationship between the absolute V magnitude of the HB at the RR Lyrae level
and metallicity, as obtained on the basis of trigonometric parallax
measurements for the star RR Lyrae, is also revisited, giving a distance
modulus to the LMC of (m-M)_0 = 18.44+/-0.11. RR Lyrae period change rates are
studied. Finally, the conductive opacities used in evolutionary calculations of
low-mass stars are investigated. [ABRIDGED]Comment: 56 pages, 22 figures. Invited review, to appear in Astrophysics and
Space Scienc
Avaliação da qualidade de vida, da dor nas costas, da funcionalidade e de alteraçÔes da coluna vertebral de estudantes de fisioterapia
O objetivo deste estudo foi avaliar a qualidade de vida, dor nas costas, funcionalidade e as alteraçÔes da coluna vertebral de estudantes de fisioterapia. Participaram 42 universitĂĄrios, sendo avaliada a coluna vertebral por meio do arcĂŽmetro, a dor nas costas por meio de um questionĂĄrio multidimensional de dor, a qualidade de vida por meio do questionĂĄrio SF-36 e funcionalidade a partir do Roland-Morris. Foi realizada estatĂstica descritiva e teste qui-quadrado (α=0,05). Os resultados demonstraram: prevalĂȘncia de alteraçÔes nas curvaturas da coluna vertebral de 38,1%; (n=16); alta prevalĂȘncia de dor nas costas (69%; n=29); baixa prevalĂȘncia de comprometimento da funcionalidade (3,4%; n=1); que nĂŁo hĂĄ associação entre as alteraçÔes nas curvaturas da coluna vertebral e funcionalidade e dor nas costas; e que os escores dos domĂnios do SF-36 foram maiores que 45, exceto o domĂnio "dor", cujo escore aproximado foi de 35. Conclui-se que quanto menor os nĂveis de intensidade da dor melhor o nĂvel de qualidade de vida
IBD risk loci are enriched in multigenic regulatory modules encompassing putative causative genes.
GWAS have identified >200 risk loci for Inflammatory Bowel Disease (IBD). The majority of disease associations are known to be driven by regulatory variants. To identify the putative causative genes that are perturbed by these variants, we generate a large transcriptome data set (nine disease-relevant cell types) and identify 23,650 cis-eQTL. We show that these are determined by âŒ9720 regulatory modules, of which âŒ3000 operate in multiple tissues and âŒ970 on multiple genes. We identify regulatory modules that drive the disease association for 63 of the 200 risk loci, and show that these are enriched in multigenic modules. Based on these analyses, we resequence 45 of the corresponding 100 candidate genes in 6600 Crohn disease (CD) cases and 5500 controls, and show with burden tests that they include likely causative genes. Our analyses indicate that â„10-fold larger sample sizes will be required to demonstrate the causality of individual genes using this approach
Data from: Consequences of a nectar yeast for pollinator preference and performance
Pollinators utilize floral resources that vary in colour, scent and reward quality. Variation in such traits, including nectar rewards, in addition to cues associated with their quality, can influence pollinator foraging decisions with consequences for pollinator reproductive success. Nectar is commonly subject to colonization by micro-organisms capable of affecting a suite of traits important for pollinator attraction and fitness; yet, links between microbial presence and changes in pollinator preference and performance remain few.
Here, we evaluated the effects of a nectar-inhabiting micro-organism on pollinator foraging behaviour and reproduction using the common eastern bumblebee Bombus impatiens and the cosmopolitan nectar yeast Metschnikowia reukaufii. Using a combination of choice and no-choice behavioural and feeding assays, we manipulated the presence and viability of M. reukaufii in nectar and assessed bumblebee foraging and reproductive responses.
Bombus impatiens workers responded positively to the presence of yeasts. Foragers trained to associate yeast presence with flower colour visited a significantly greater proportion of flowers inoculated with yeast when subject to a colour discrimination test. Moreover, foragers naĂŻve to nectar yeasts incorporated more yeast-inoculated flowers into initial foraging bouts when presented with a novel floral array. In addition, bees spent significantly longer foraging on yeast-inoculated flowers compared to yeast-free flowers. However, when we manipulated yeast presence and viability in microcolonies of queenless workers, we found no effect of yeast on components of bumblebee reproduction, such as initiation of egg laying and number of eggs laid. This lack of an effect of yeast persisted even under conditions of pollen limitation.
Taken together, these results suggest that nectar yeasts can enhance floral signalling and alter pollinator foraging behaviour at individual flowers, though they may not directly affect pollinator performance. Thus, nectar yeasts may play a significant role in mediating pollinator foraging behaviour, with consequences for plant fitness and evolution of floral traits
- âŠ