10,436 research outputs found
The Herschel Virgo Cluster Survey. III. A constraint on dust grain lifetime in early-type galaxies
Passive early-type galaxies (ETGs) provide an ideal laboratory for studying the interplay between dust formation around evolved stars and its subsequent destruction in a hot gas. Using Spitzer-IRS and Herschel data we compare the dust production rate in the envelopes
of evolved AGB stars with a constraint on the total dust mass. Early-type galaxies which appear to be truly passively evolving are not detected by Herschel. We thus derive a distance independent upper limit to the dust grain survival time in the hostile environment of ETGs of <46 ± 25 Myr for amorphous silicate grains. This implies that ETGs which are detected at far-infrared wavelengths have
acquired a cool dusty medium via interaction. Given likely time-scales for ram-pressure stripping, this also implies that only galaxies with dust in a cool (atomic) medium can release dust into the intra-cluster medium
Detecting entanglement in spatial interference
We discuss an experimentally amenable class of two-particle states of motion
giving rise to nonlocal spatial interference under position measurements. Using
the concept of modular variables, we derive a separability criterion which is
violated by these non-Gaussian states. While we focus on the free motion of
material particles, the presented results are valid for any pair of canonically
conjugate continuous variable observables and should apply to a variety of
bipartite interference phenomena.Comment: 4 pages; corresponds to published versio
Bell test for the free motion of material particles
We present a scheme to establish non-classical correlations in the motion of
two macroscopically separated massive particles without resorting to
entanglement in their internal degrees of freedom. It is based on the
dissociation of a diatomic molecule with two temporally separated Feshbach
pulses generating a motional state of two counter-propagating atoms that is
capable of violating a Bell inequality by means of correlated single particle
interferometry. We evaluate the influence of dispersion on the Bell
correlation, showing it to be important but manageable in a proposed
experimental setup. The latter employs a molecular BEC of fermionic Lithium
atoms, uses laser-guided atom interferometry, and seems to be within the reach
of present-day technology.Comment: 4 pages, 1 figure; corresponds to published versio
Model-independent determination of the gluon condensate in four-dimensional SU(3) gauge theory
We determine the non-perturbative gluon condensate of four-dimensional SU(3)
gauge theory in a model independent way. This is achieved by carefully
subtracting high order perturbation theory results from non-perturbative
lattice QCD determinations of the average plaquette. No indications of
dimension two condensates are found. The value of the gluon condensate turns
out to be of a similar size as the intrinsic ambiguity inherent to its
definition.Comment: 5 pages, 5 figures, v2: references added, conclusions improved,
contrast of figures improved, 1 typo correcte
Mid-infrared colour gradients and the colour-magnitude relation in Virgo early-type galaxies
We make use of Spitzer imaging between 4 and 16 micron and near-infrared data
at 2.2 micron to investigate the nature and distribution of the mid-infrared
emission in a sample of early-type galaxies in the Virgo cluster. These data
allow us to conclude, with some confidence, that the emission at 16 micron in
passive ETGs is stellar in origin, consistent with previous work concluding
that the excess mid-infrared emission comes from the dusty envelopes around
evolved AGB stars. There is little evidence for the mid-infrared emission of an
unresolved central component, as might arise in the presence of a dusty torus
associated with a low-luminosity AGN. We nonetheless find that the 16 micron
emission is more centrally peaked than the near-infrared emission, implying a
radial stellar population gradient. By comparing with independent evidence from
studies at optical wavelengths, we conclude that a metallicity that falls with
increasing radius is the principal driver of the observed gradient. We also
plot the mid-infrared colour-magnitude diagram and combine with similar work on
the Coma cluster to define the colour-magnitude relation for absolute K-band
magnitudes from -26 to -19. Because a correlation between mass and age would
produce a relation with a gradient in the opposite sense to that observed, we
conclude that the relation reflects the fact that passive ETGs of lower mass
also have a lower average metallicity. The colour-magnitude relation is thus
driven by metallicity effects. In contrast to what is found in Coma, we do not
find any objects with anomalously bright 16 micron emission relative to the
colour-magnitude relation. Although there is little overlap in the mass ranges
probed in the two clusters, this may suggest that observable ``rejuvenation''
episodes are limited to intermediate mass objects.Comment: 8 pages, 4 figure
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An Exploration of Spotted White Dwarfs from K2
The 21st European Workshop on White Dwarfs was held in Austin, TX from July 23rd to 27th of 2018The Kepler K2 mission has discovered a significant
population of white dwarf stars that exhibit
photometric variability due to surface inhomogeneities
likely related to magnetism. These “spotted”
white dwarfs present not only in temperature
regimes where we expect convection to dominate
white dwarf photospheres, but also where
radiation should dominate. We present an exploration
of spotted white dwarfs as a function of
various physical characteristics, including temperature,
magnetic field strength, and rotational period,
in order to better understand the origins of
these photometric variations.Astronom
Changes in Post-Marital Residence Rules in an Era of National Reform: The Urban to Rural Disjunction in Contemporary China
Alternatives to the traditional practice of patrilocal postmarital residence exist in modern day China and vary from urban to rural areas. Social and economic reforms that were instituted in postMao China had an influence on post-marital residence rules. These reforms include marriage laws, reproduction restrictions, the return to family farms, and greater access to employment. Government reforms had different impacts on urban and rural families, creating different family structures and compositions. Family customs, like post-marital residence, also diverged along rural and urban lines. In rural areas, patrilocality persists, but matrilocal marriage arrangements are increasing. In urban areas, a strong preference for neolocality is evident. There are also indications that patrilocal and matrilocal residence arrangements are becoming short-term transitions to neolocal residence. Using a collection of post-Mao literature, this paper examines the relationship between government policies and changes in urban and rural post-marital residence rules in contemporary China
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