2,314 research outputs found
The MASSIVE Survey - VII. The Relationship of Angular Momentum, Stellar Mass and Environment of Early-Type Galaxies
We analyse the environmental properties of 370 local early-type galaxies
(ETGs) in the MASSIVE and ATLAS3D surveys, two complementary volume-limited
integral-field spectroscopic (IFS) galaxy surveys spanning absolute -band
magnitude , or stellar mass . We find these galaxies to reside in a diverse range of
environments measured by four methods: group membership (whether a galaxy is a
brightest group/cluster galaxy, satellite, or isolated), halo mass, large-scale
mass density (measured over a few Mpc), and local mass density (measured within
the th neighbour). The spatially resolved IFS stellar kinematics provide
robust measurements of the spin parameter and enable us to examine
the relationship among , , and galaxy environment. We find a
strong correlation between and , where the average
decreases from to below 0.1 with increasing mass, and the fraction
of slow rotators increases from % to 90%. We show for
the first time that at fixed , there are almost no trends between galaxy
spin and environment; the apparent kinematic morphology-density relation for
ETGs is therefore primarily driven by and is accounted for by the joint
correlations between and spin, and between and environment. A
possible exception is that the increased at high local density
is slightly more than expected based only on these joint correlations. Our
results suggest that the physical processes responsible for building up the
present-day stellar masses of massive galaxies are also very efficient at
reducing their spin, in any environment.Comment: Accepted to MNRA
The MASSIVE Survey XIII -- Spatially Resolved Stellar Kinematics in the Central 1 kpc of 20 Massive Elliptical Galaxies with the GMOS-North Integral-Field Spectrograph
We use observations from the GEMINI-N/GMOS integral-field spectrograph (IFS)
to obtain spatially resolved stellar kinematics of the central kpc of
20 early-type galaxies (ETGs) with stellar masses greater than in the MASSIVE survey. Together with observations from the wide-field
Mitchell IFS at McDonald Observatory in our earlier work, we obtain
unprecedentedly detailed kinematic maps of local massive ETGs, covering a scale
of kpc. The high () signal-to-noise of the GMOS spectra
enable us to obtain two-dimensional maps of the line-of-sight velocity,
velocity dispersion , as well as the skewness and kurtosis
of the stellar velocity distributions. All but one galaxy in the sample have
profiles that increase towards the center, whereas the slope of
at one effective radius () can be of either sign. The is
generally positive, with 14 of the 20 galaxies having positive within the
GMOS aperture and 18 having positive within . The positive
and rising towards small radii are indicative of a central black
hole and velocity anisotropy. We demonstrate the constraining power of the data
on the mass distributions in ETGs by applying Jeans anisotropic modeling (JAM)
to NGC~1453, the most regular fast rotator in the sample. Despite the
limitations of JAM, we obtain a clear minimum in black hole mass,
stellar mass-to-light ratio, velocity anisotropy parameters, and the circular
velocity of the dark matter halo.Comment: Accepted to Ap
Identification of key residues that confer Rhodobacter sphaeroides LPS activity at horse TLR4/MD-2.
The molecular determinants underpinning how hexaacylated lipid A and tetraacylated precursor lipid IVa activate Toll-like receptor 4 (TLR4) are well understood, but how activation is induced by other lipid A species is less clear. Species specificity studies have clarified how TLR4/MD-2 recognises different lipid A structures, for example tetraacylated lipid IVa requires direct electrostatic interactions for agonism. In this study, we examine how pentaacylated lipopolysaccharide from Rhodobacter sphaeroides (RSLPS) antagonises human TLR4/MD-2 and activates the horse receptor complex using a computational approach and cross-species mutagenesis. At a functional level, we show that RSLPS is a partial agonist at horse TLR4/MD-2 with greater efficacy than lipid IVa. These data suggest the importance of the additional acyl chain in RSLPS signalling. Based on docking analysis, we propose a model for positioning of the RSLPS lipid A moiety (RSLA) within the MD-2 cavity at the TLR4 dimer interface, which allows activity at the horse receptor complex. As for lipid IVa, RSLPS agonism requires species-specific contacts with MD-2 and TLR4, but the R2 chain of RSLA protrudes from the MD-2 pocket to contact the TLR4 dimer in the vicinity of proline 442. Our model explains why RSLPS is only partially dependent on horse TLR4 residue R385, unlike lipid IVa. Mutagenesis of proline 442 into a serine residue, as found in human TLR4, uncovers the importance of this site in RSLPS signalling; horse TLR4 R385G/P442S double mutation completely abolishes RSLPS activity without its counterpart, human TLR4 G384R/S441P, being able to restore it. Our data highlight the importance of subtle changes in ligand positioning, and suggest that TLR4 and MD-2 residues that may not participate directly in ligand binding can determine the signalling outcome of a given ligand. This indicates a cooperative binding mechanism within the receptor complex, which is becoming increasingly important in TLR signalling.This work was supported by a project grant from the Horserace Betting Levy Board to CEB and a Horserace Betting Levy Board Veterinary Research
Training Scholarship to KLI. This work was also supported by a Wellcome Trust program grant to NJG and CEB. CEB is a BBSRC Research Development Fellow.This is the final version of the article. It first appeared from PLOS at http://dx.doi.org/10.1371/journal.pone.0098776
The MASSIVE Survey - V. Spatially-Resolved Stellar Angular Momentum, Velocity Dispersion, and Higher Moments of the 41 Most Massive Local Early-Type Galaxies
We present spatially-resolved two-dimensional stellar kinematics for the 41
most massive early-type galaxies (MK ~ 10^11.8
Msun) of the volume-limited (D < 108 Mpc) MASSIVE survey. For each galaxy, we
obtain high-quality spectra in the wavelength range of 3650 to 5850 A from the
246-fiber Mitchell integral-field spectrograph (IFS) at McDonald Observatory,
covering a 107" x 107" field of view (often reaching 2 to 3 effective radii).
We measure the 2-D spatial distribution of each galaxy's angular momentum
(lambda and fast or slow rotator status), velocity dispersion (sigma), and
higher-order non-Gaussian velocity features (Gauss-Hermite moments h3 to h6).
Our sample contains a high fraction (~80% ) of slow and non-rotators with
lambda <~ 0.2. When combined with the lower-mass ETGs in the ATLAS3D survey, we
find the fraction of slow-rotators to increase dramatically with galaxy mass,
reaching ~50% at MK ~ -25.5 mag and ~90% at MK <~ -26 mag. All of our fast
rotators show a clear anti-correlation between h3 and V/sigma, and the slope of
the anti-correlation is steeper in more round galaxies. The radial profiles of
sigma show a clear luminosity and environmental dependence: the 12 most
luminous galaxies in our sample (MK <~ -26 mag) are all brightest cluster/group
galaxies (except NGC 4874) and all have rising or nearly flat sigma profiles,
whereas five of the seven "isolated" galaxies are all fainter than MK = -25.8
mag and have falling sigma. All of our galaxies have positive average h4; the
most luminous galaxies have average h4 ~ 0.05 while less luminous galaxies have
a range of values between 0 and 0.05. Most of our galaxies show positive radial
gradients in h4, and those galaxies also tend to have rising sigma profiles. We
discuss the implications for the relationship among dynamical mass, sigma, h4,
and velocity anisotropy for these massive galaxies.Comment: 32 pages, 14 figures, 16 appendix figures. Accepted to MNRA
Automated white matter hyperintensity segmentation using Bayesian Model Selection: assessment and correlations with cognitive change
Accurate, automated white matter hyperintensity (WMH) segmentations are needed for large-scale studies to understand contributions of WMH to neurological diseases. We evaluated Bayesian Model Selection (BaMoS), a hierarchical fully-unsupervised model selection framework for WMH segmentation. We compared BaMoS segmentations to semi-automated segmentations, and assessed whether they predicted longitudinal cognitive change in control, early Mild Cognitive Impairment (EMCI), late Mild Cognitive Impairment (LMCI), subjective/significant memory concern (SMC) and Alzheimer’s (AD) participants. Data were downloaded from the Alzheimer’s disease Neuroimaging Initiative (ADNI). Magnetic resonance images from 30 control and 30 AD participants were selected to incorporate multiple scanners, and were semi-automatically segmented by 4 raters and BaMoS. Segmentations were assessed using volume correlation, Dice score, and other spatial metrics. Linear mixed-effect models were fitted to 180 control, 107 SMC, 320 EMCI, 171 LMCI and 151 AD participants separately in each group, with the outcomes being cognitive change (e.g. mini-mental state examination; MMSE), and BaMoS WMH, age, sex, race and education used as predictors. There was a high level of agreement between BaMoS’ WMH segmentation volumes and a consensus of rater segmentations, with a median Dice score of 0.74 and correlation coefficient of 0.96. BaMoS WMH predicted cognitive change in: control, EMCI, and SMC groups using MMSE; LMCI using clinical dementia rating scale; and EMCI using Alzheimer’s disease assessment scale-cognitive subscale (p < 0.05, all tests). BaMoS compares well to semi-automated segmentation, is robust to different WMH loads and scanners, and can generate volumes which predict decline. BaMoS can be applicable to further large-scale studies
Impaired self awareness after traumatic brain injury: inter-rater reliability and factor structure of the dysexecutive questionnairre (DEX) in patients, significant others and clinicians
Aims: This study sought to address two questions: (1) what is the inter-rater reliability
of the Dysexecutive Questionnaire (DEX) when completed by patients, their significant
others, and clinicians; and (2) does the factor structure of the DEX vary for these three
groups?
Methods: We obtained DEX ratings for 113 patients with an acquired brain injury from
two brain injury services in the UK and two services in Ireland. We gathered data from
two groups of raters—”significant others” (DEX-SO) such as partners and close family
members and “clinicians” (DEX-C), who were psychologists or rehabilitation physicians
working closely with the patient and who were able to provide an opinion about the
patient’s level of everyday executive functioning. Intra-class correlation coefficients and
their 95% confidence intervals were calculated between each of the three groups (self,
significant other, clinician). Principal axis factor (PAF) analyses were also conducted for
each of the three groups.
Results: The factor analysis revealed a consistent one-factor model for each of the
three groups of raters. However, the inter-rater reliability analyses showed a low level of
agreement between the self-ratings and the ratings of the two groups of independent
raters. We also found low agreement between the significant others and the clinicians.
Conclusion: Although there was a consistent finding of a single factor solution for each
of the three groups, the low level of agreement between significant others and clinicians
raises a question about the reliability of the DEX.</p
Impaired self awareness after traumatic brain injury: inter-rater reliability and factor structure of the dysexecutive questionnairre (DEX) in patients, significant others and clinicians
Aims: This study sought to address two questions: (1) what is the inter-rater reliability
of the Dysexecutive Questionnaire (DEX) when completed by patients, their significant
others, and clinicians; and (2) does the factor structure of the DEX vary for these three
groups?
Methods: We obtained DEX ratings for 113 patients with an acquired brain injury from
two brain injury services in the UK and two services in Ireland. We gathered data from
two groups of raters—”significant others” (DEX-SO) such as partners and close family
members and “clinicians” (DEX-C), who were psychologists or rehabilitation physicians
working closely with the patient and who were able to provide an opinion about the
patient’s level of everyday executive functioning. Intra-class correlation coefficients and
their 95% confidence intervals were calculated between each of the three groups (self,
significant other, clinician). Principal axis factor (PAF) analyses were also conducted for
each of the three groups.
Results: The factor analysis revealed a consistent one-factor model for each of the
three groups of raters. However, the inter-rater reliability analyses showed a low level of
agreement between the self-ratings and the ratings of the two groups of independent
raters. We also found low agreement between the significant others and the clinicians.
Conclusion: Although there was a consistent finding of a single factor solution for each
of the three groups, the low level of agreement between significant others and clinicians
raises a question about the reliability of the DEX.</p
The Lick AGN Monitoring Project: Reverberation Mapping of Optical Hydrogen and Helium Recombination Lines
We have recently completed a 64-night spectroscopic monitoring campaign at
the Lick Observatory 3-m Shane telescope with the aim of measuring the masses
of the black holes in 12 nearby (z < 0.05) Seyfert 1 galaxies with expected
masses in the range ~10^6-10^7M_sun and also the well-studied nearby active
galactic nucleus (AGN) NGC 5548. Nine of the objects in the sample (including
NGC 5548) showed optical variability of sufficient strength during the
monitoring campaign to allow for a time lag to be measured between the
continuum fluctuations and the response to these fluctuations in the broad
Hbeta emission, which we have previously reported. We present here the light
curves for the Halpha, Hgamma, HeII 4686, and HeI 5876 emission lines and the
time lags for the emission-line responses relative to changes in the continuum
flux. Combining each emission-line time lag with the measured width of the line
in the variable part of the spectrum, we determine a virial mass of the central
supermassive black hole from several independent emission lines. We find that
the masses are generally consistent within the uncertainties. The time-lag
response as a function of velocity across the Balmer line profiles is examined
for six of the AGNs. Finally we compare several trends seen in the dataset
against the predictions from photoionization calculations as presented by
Korista & Goad. We confirm several of their predictions, including an increase
in responsivity and a decrease in the mean time lag as the excitation and
ionization level for the species increases. Further confirmation of
photoionization predictions for broad-line gas behavior will require additional
monitoring programs for these AGNs while they are in different luminosity
states. [abridged]Comment: 37 pages, 18 figures and 15 tables, accepted for publication in the
Astrophysical Journa
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