1,911 research outputs found
Beyond capitalism and liberal democracy: on the relevance of GDH Cole’s sociological critique and alternative
This article argues for a return to the social thought of the often ignored early 20th-century English thinker GDH Cole. The authors contend that Cole combined a sociological critique of capitalism and liberal democracy with a well-developed alternative in his work on guild socialism bearing particular relevance to advanced capitalist societies. Both of these, with their focus on the limitations on ‘free communal service’ in associations and the inability of capitalism to yield emancipation in either production or consumption, are relevant to social theorists looking to understand, critique and contribute to the subversion of neoliberalism. Therefore, the authors suggest that Cole’s associational sociology, and the invitation it provides to think of formations beyond capitalism and liberal democracy, is a timely and valuable resource which should be returned to
HR 266=ADS 784: an Early Type Spectroscopic, Speckle Astrometric Multiple System
The detection and nature of a \u27speckle astrometric\u27 system are reported with attention given to alternative interpretations of the system components. The HR 226 = ADS 784 system is described as a short-period binary (with a period of 4.241148 +/- 0.000008 d) orbiting an unseen companion (with a period of 1769 +/- 10 d), and the triple\u27s visual orbit is 83.10 +/- 0.20 yr. The elements of the various orbits taken from spectroscopic data are employed to develop the model scenarios. The masses and spectral types of the components are developed and used to calculate the inclinations of the short-, intermediate-, and long-period orbits. The computations show that the inclinations are similar and can be interpreted as three coplanar orbits; however, this conclusion suggests that the unseen companion\u27s absorption features should be detectable. Since the absorption features are not detectable it is concluded that the unseen companion is either a pair of late-type lower-mass stars or one rapidly rotating star
Close Pairs as Proxies for Galaxy Cluster Mergers
Galaxy cluster merger statistics are an important component in understanding
the formation of large-scale structure. Unfortunately, it is difficult to study
merger properties and evolution directly because the identification of cluster
mergers in observations is problematic. We use large N-body simulations to
study the statistical properties of massive halo mergers, specifically
investigating the utility of close halo pairs as proxies for mergers. We
examine the relationship between pairs and mergers for a wide range of merger
timescales, halo masses, and redshifts (0<z<1). We also quantify the utility of
pairs in measuring merger bias. While pairs at very small separations will
reliably merge, these constitute a small fraction of the total merger
population. Thus, pairs do not provide a reliable direct proxy to the total
merger population. We do find an intriguing universality in the relation
between close pairs and mergers, which in principle could allow for an estimate
of the statistical merger rate from the pair fraction within a scaled
separation, but including the effects of redshift space distortions strongly
degrades this relation. We find similar behavior for galaxy-mass halos, making
our results applicable to field galaxy mergers at high redshift. We investigate
how the halo merger rate can be statistically described by the halo mass
function via the merger kernel (coagulation), finding an interesting
environmental dependence of merging: halos within the mass resolution of our
simulations merge less efficiently in overdense environments. Specifically,
halo pairs with separations less than a few Mpc/h are more likely to merge in
underdense environments; at larger separations, pairs are more likely to merge
in overdense environments.Comment: 12 pages, 9 figures; Accepted for publication in ApJ. Significant
additions to text and two figures changed. Added new findings on the
universality of pair mergers and added analysis of the effect of FoF linking
length on halo merger
Effects of correlation between merging steps on the global halo formation
The excursion set theory of halo formation is modified by adopting the
fractional Brownian motion, to account for possible correlation between merging
steps. We worked out analytically the conditional mass function, halo merging
rate and formation time distribution in the spherical collapse model. We also
developed an approximation for the ellipsoidal collapse model and applied it to
the calculation of the conditional mass function and the halo formation time
distribution. For models in which the steps are positively correlated, the halo
merger rate is enhanced when the accreted mass is less than , while
for the negatively correlated case this rate is reduced. Compared with the
standard model in which the steps are uncorrelated, the models with positively
correlated steps produce more aged population in small mass halos and more
younger population in large mass halos, while for the models with negatively
correlated steps the opposite is true. An examination of simulation results
shows that a weakly positive correlation between successive merging steps
appears to fit best. We have also found a systematic effect in the measured
mass function due to the finite volume of simulations. In future work, this
will be included in the halo model to accurately predict the three point
correlation function estimated from simulations.Comment: 8 pages, submitted to MNRA
The Clustering of Massive Halos
The clustering properties of dark matter halos are a firm prediction of
modern theories of structure formation. We use two large volume,
high-resolution N-body simulations to study how the correlation function of
massive dark matter halos depends upon their mass and formation history. We
find that halos with the lowest concentrations are presently more clustered
than those of higher concentration, the size of the effect increasing with halo
mass; this agrees with trends found in studies of lower mass halos. The
clustering dependence on other characterizations of the full mass accretion
history appears weaker than the effect with concentration. Using the integrated
correlation function, marked correlation functions, and a power-law fit to the
correlation function, we find evidence that halos which have recently undergone
a major merger or a large mass gain have slightly enhanced clustering relative
to a randomly chosen population with the same mass distribution.Comment: 10 pages, 8 figures; text improved, references and one figure added;
accepted for publication in Ap
Metallicities and Radial Velocities of Five Open Clusters Including a New Candidate Member of the Monoceros Stream
Near infrared spectra of 133 red giant stars from ten Galactic open clusters
and two Galactic globular clusters spanning 2.2 dex in metallicity and 11 Gyr
in age are presented. We combine this sample with ten clusters from Cole and
collaborators to investigate the Ca II triplet line strengths and their
relation to cluster metallicity and position along the red giant branch. We
show that characterizing the stellar surface gravity using Ks band photometry
(relative to the horizontal branch) taken from the Two Micron All-Sky Survey
allows for metallicity measurements at least as precise as those derived using
V or I band data. This has the great advantage that uniform photometry and
reliable astrometry is available for a large number of clusters. Using Ks band
photometry also reduces the effect of differential reddening within a given
cluster. We find no significant evidence for age or metallicity effects to the
linear Ca II triplet - metallicity relationship over the small range in
magnitudes studied when homogeneous reference metallicities are used. We derive
the first spectroscopic metallicity and new radial velocity estimates for five
open clusters: Berkeley 81, Berkeley 99, IC 1311, King 2, and NGC 7044. King 2
has an anomalous radial velocity compared with the local disk population. We
discuss the possibility that it is part of the Monoceros tidal stream.Comment: 35 pages, 14 figures, 9 tables. Accepted for publication in MNRA
Radial Velocity and Metallicity of the Globular Cluster IC4499 Obtained with AAOmega
We present radial velocity and metallicity measurements for the far-southern
Galactic globular cluster IC4499. We selected several hundred target red giant
stars in and around the cluster from the 2MASS point source catalog, and
obtained spectra at the near-infrared calcium triplet using the AAOmega
spectrograph. Observations of giants in globular clusters M4, M22, and M68 were
taken to provide radial velocity and metallicity comparison objects. Based on
velocity data we conclude that 43 of our targets are cluster members, by far
the largest sample of IC4499 giants spectroscopically studied. We determine the
mean heliocentric radial velocity of the cluster to be 31.5 plus or minus 0.4
km/s, and find the most likely central velocity dispersion to be 2.5 plus or
minus 0.5 km/s. This leads to a dynamical mass estimate for the cluster of 93
plus or minus 37 thousand solar masses. We are sensitive to cluster rotation
down to an amplitude of about 1 km/s, but no evidence for cluster rotation is
seen. The cluster metallicity is found to be [Fe/H] = -1.52 plus or minus 0.12
on the Carretta-Gratton scale. The radial velocity of the cluster, previously
highly uncertain, is consistent with membership in the Monoceros tidal stream,
but also with a halo origin. The horizontal branch morphology of the cluster is
slightly redder than average for its metallicity, but it is likely not
unusually young compared to other clusters of the halo. The new constraints on
the cluster kinematics and metallicity may give insight into its extremely high
specific frequency of RR Lyrae stars.Comment: Accepted to MNRAS, 13 pages, 9 figure
On the Luminosity Dependence of the Galaxy Pairwise Velocity Dispersion
(Abridged) We make predictions for the pairwise velocity dispersion (PVD) of
galaxies with models that are constrained to match the projected correlation
function and luminosity function of galaxies in the Two-Degree Field Galaxy
Redshift Survey (2dFGRS). We use these data to constrain the halo occupation
distribution (HOD), then calculate the PVD by populating the halos of a high
resolution N-body simulation. We examine the luminosity and scale dependence of
the predicted PVD. At r3 Mpc/h, we find that the PVD decreases
with increasing galaxy luminosity. This result is mostly driven by the fraction
of satellite galaxies f_sat, which is well-constrained by the correlation
function. We find f_sat~25% for galaxies fainter than L_star, while for
brighter galaxies the satellite fraction rapidly declines, creating the
decrease in the PVD with luminosity. At r=1 Mpc/h, the PVD has no dependence on
luminosity because satellite galaxies dominate the statistics for all objects.
Recent measurements of the PVD in Fourier space using the "dispersion model"
have reported a strong decline in PVD with increasing luminosity at k=1 h/Mpc.
We test this method with our HOD models, finding that there is no consistent
comparison between the PVD at a given k and the true dispersion at a given
value of r. This results in a luminosity dependence in k-space that is stronger
than in configuration space. The luminosity dependence of the HOD results in
Fourier space are consistent with those measured at k=1 h/Mpc; thus the recent
measurements of the PVD are fully explainable in the context of halo occupation
models. The normalization of the PVD is lower than predicted by our fiducial
model, and reproducing it requires a lower value of Omega_m (~0.2 instead of
0.3), a lower value of sigma_8 (~0.7 instead of 0.9), or strong velocity bias.Comment: 15 emulateapj pages, 8 figures, submitted to Ap
Architecturally diverse proteins converge on an analogous mechanism to inactivate Uracil-DNA glycosylase
Uracil-DNA glycosylase (UDG) compromises the replication strategies of diverse viruses from unrelated lineages. Virally encoded proteins therefore exist to limit, inhibit or target UDG activity for proteolysis. Viral proteins targeting UDG, such as the bacteriophage proteins ugi, and p56, and the HIV-1 protein Vpr, share no sequence similarity, and are not structurally homologous. Such diversity has hindered identification of known or expected UDG-inhibitory activities in other genomes. The structural basis for UDG inhibition by ugi is well characterized; yet, paradoxically, the structure of the unbound p56 protein is enigmatically unrevealing of its mechanism. To resolve this conundrum, we determined the structure of a p56 dimer bound to UDG. A helix from one of the subunits of p56 occupies the UDG DNA-binding cleft, whereas the dimer interface forms a hydrophobic box to trap a mechanistically important UDG residue. Surprisingly, these p56 inhibitory elements are unexpectedly analogous to features used by ugi despite profound architectural disparity. Contacts from B-DNA to UDG are mimicked by residues of the p56 helix, echoing the role of ugi’s inhibitory beta strand. Using mutagenesis, we propose that DNA mimicry by p56 is a targeting and specificity mechanism supporting tight inhibition via hydrophobic sequestration
AAOmega spectroscopy of 29 351 stars in fields centered on ten Galactic globular clusters
Galactic globular clusters have been pivotal in our understanding of many
astrophysical phenomena. Here we publish the extracted stellar parameters from
a recent large spectroscopic survey of ten globular clusters. A brief review of
the project is also presented. Stellar parameters have been extracted from
individual stellar spectra using both a modified version of the Radial Velocity
Experiment (RAVE) pipeline and a pipeline based on the parameter estimation
method of RAVE. We publish here all parameters extracted from both pipelines.
We calibrate the metallicity and convert this to [Fe/H] for each star and,
furthermore, we compare the velocities and velocity dispersions of the Galactic
stars in each field to the Besan\c{c}on Galaxy model. We find that the model
does not correspond well with the data, indicating that the model is probably
of little use for comparisons with pencil beam survey data such as this.Comment: 6 pages, 5 figures, 4 tables. Accepted for publication in A&A. Data
described in tables will be available on CDS (at
http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/530/A31) once publishe
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