1,486 research outputs found
Mass loss out of close binaries. II
Liberal evolution of interacting binaries has been proposed previously by
several authors in order to meet various observed binary characteristics better
than conservative evolution does. Since Algols are eclipsing binaries the
distribution of their orbital periods is precisely known. The distribution of
their mass ratios contains however more uncertainties. We try to reproduce
these two distributions theoretically using a liberal scenario in which the
gainer star can lose mass into interstellar space as a consequence of its rapid
rotation and the energy of a hot spot. In a recent paper (Van Rensbergen et al.
2010, A&A) we calculated the liberal evolution of binaries with a B-type
primary at birth where mass transfer starts during core hydrogen burning of the
donor. In this paper we include the cases where mass transfer starts during
hydrogen shell burning and it is our aim to reproduce the observed
distributions of the system parameters of Algol-type semi-detached systems. Our
calculations reveal the amount of time that an Algol binary lives with a well
defined value of mass ratio and orbital period. We use these data to simulate
the distribution of mass ratios and orbital periods of Algols. Binaries with a
late B-type initial primary hardly lose any mass whereas those with an early B
primary evolve in a non-conservative way. Conservative binary evolution
predicts only ~ 12 % of Algols with a mass ratio q above 0.4. This value is
raised up to ~ 17 % using our scenario of liberal evolution, which is still far
below the ~ 45 % that is observed. Observed orbital periods of Algol binaries
larger than one day are faithfully reproduced by our liberal scenario. Mass
ratios are reproduced better than with conservative evolution, but the
resemblance is still poor.Comment: 11 pages, 6 figures, accepted for publication in A&A; accepted
versio
Transportation policy for campus climate action planning: Process and policy implications
This article discusses the innovative methods used to complete the transportation components of Cal Poly’s Climate Action Plan (CAP). The campus\u27s CAP was completed by a BSCRP studio during the fall and winter quarters (2015-2016AY) in collaboration with Facilities Planning and Capital Projects. Professors William Riggs and Adrienne Greve (instructors for the studio along with Chris Clark) developed the methods discussed here, and C. Kai Lord-Farmer was the graduate assistant who assisted in completing the technical analysis
Molecular Gas in the Low Metallicity, Star Forming Dwarf IC 10
We present a complete survey of CO 1->0 emission in the Local Group dwarf
irregular IC 10. The survey, conducted with the BIMA interferometer, covers the
stellar disk and a large fraction of the extended HI envelope with the
sensitivity and resolution necessary to detect individual giant molecular
clouds (GMCs) at the distance of IC 10 (950 kpc). We find 16 clouds with a
total CO luminosity of 1 x 10^6 K km s^-1 pc^2, equivalent to 4 x 10^6 Msun of
molecular gas using the Galactic CO-to-H2 conversion factor. Observations with
the ARO 12m find that BIMA may resolve out as much as 50% of the CO emission,
and we estimate the total CO luminosity as 2.2 x 10^6 K km s^-1 pc^2. We
measure the properties of 14 GMCs from high resolution OVRO data. These clouds
are very similar to Galactic GMCs in their sizes, line widths, luminosities,
and CO-to-H2 conversion factors despite the low metallicity of IC 10 (Z ~ 1/5
Zsun). Comparing the BIMA survey to the atomic gas and stellar content of IC 10
we find that most of the CO emission is coincident with high surface density
HI. IC 10 displays a much higher star formation rate per unit molecular (H2) or
total (HI+H2) gas than most galaxies. This could be a real difference or may be
an evolutionary effect - the star formation rate may have been higher in the
recent past.Comment: 21 pages, 14 figures, Accepted to Ap
Mass loss out of close binaries
In a liberal evolutionary scenario, mass can escape from a binary during eras
of fast mass transfer. We calculate the mass lost by binaries with a B-type
primary at birth where mass transfer starts during hydrogen core burning of the
donor. We simulate the distribution of mass-ratios and orbital periods for
those interacting binaries. The amount of time the binary shows Algol
characteristics within different values of mass-ratio and orbital period has
been fixed from conservative and liberal evolutionary calculations. We use
these data to simulate the distribution of mass-ratios and orbital periods of
Algols with the conservative as well as the liberal model. We compare
mass-ratios and orbital periods of Algols obtained by conservative evolution
with those obtained by our liberal model. Since binaries with a late B-type
primary evolve almost conservatively, the overall distribution of mass-ratios
will only yield a few Algols more with high mass-ratios than conservative
calculations do. Whereas the simulated distribution of orbital periods of
Algols fits the observations well, the simulated distribution of mass-ratios
produces always too few systems with large values.Comment: 6 pages, 6 figures, accepted for publication in A&A; accepted versio
Towards Quantum Repeaters with Solid-State Qubits: Spin-Photon Entanglement Generation using Self-Assembled Quantum Dots
In this chapter we review the use of spins in optically-active InAs quantum
dots as the key physical building block for constructing a quantum repeater,
with a particular focus on recent results demonstrating entanglement between a
quantum memory (electron spin qubit) and a flying qubit (polarization- or
frequency-encoded photonic qubit). This is a first step towards demonstrating
entanglement between distant quantum memories (realized with quantum dots),
which in turn is a milestone in the roadmap for building a functional quantum
repeater. We also place this experimental work in context by providing an
overview of quantum repeaters, their potential uses, and the challenges in
implementing them.Comment: 51 pages. Expanded version of a chapter to appear in "Engineering the
Atom-Photon Interaction" (Springer-Verlag, 2015; eds. A. Predojevic and M. W.
Mitchell
AzTEC Millimetre Survey of the COSMOS Field - II. Source Count Overdensity and Correlations with Large-Scale Structure
We report an over-density of bright sub-millimetre galaxies (SMGs) in the
0.15 sq. deg. AzTEC/COSMOS survey and a spatial correlation between the SMGs
and the optical-IR galaxy density at z <~ 1.1. This portion of the COSMOS field
shows a ~ 3-sigma over-density of robust SMG detections when compared to a
background, or "blankfield", population model that is consistent with SMG
surveys of fields with no extragalactic bias. The SMG over-density is most
significant in the number of very bright detections (14 sources with measured
fluxes S(1.1mm) > 6 mJy), which is entirely incompatible with sample variance
within our adopted blank-field number densities and infers an over-density
significance of >> 4. We find that the over-density and spatial correlation to
optical-IR galaxy density are most consistent with lensing of a background SMG
population by foreground mass structures along the line of sight, rather than
physical association of the SMGs with the z <~ 1.1 galaxies/clusters. The SMG
positions are only weakly correlated with weak-lensing maps, suggesting that
the dominant sources of correlation are individual galaxies and the more
tenuous structures in the region and not the massive and compact clusters.
These results highlight the important roles cosmic variance and large-scale
structure can play in the study of SMGs.Comment: 12 pages, 11 figures, 2 tables, accepted for publication in MNRA
Deep 1.1 mm-wavelength imaging of the GOODS-S field by AzTEC/ASTE - I. Source catalogue and number counts
[Abridged] We present the first results from a 1.1 mm confusion-limited map
of the GOODS-S field taken with AzTEC on the ASTE telescope. We imaged a 270
sq. arcmin field to a 1\sigma depth of 0.48 - 0.73 mJy/beam, making this one of
the deepest blank-field surveys at mm-wavelengths ever achieved. Although our
GOODS-S map is extremely confused, we demonstrate that our source
identification and number counts analyses are robust, and the techniques
discussed in this paper are relevant for other deeply confused surveys. We find
a total of 41 dusty starburst galaxies with S/N >= 3.5 within this uniformly
covered region, where only two are expected to be false detections. We derive
the 1.1mm number counts from this field using both a "P(d)" analysis and a
semi-Bayesian technique, and find that both methods give consistent results.
Our data are well-fit by a Schechter function model with (S', N(3mJy), \alpha)
= (1.30+0.19 mJy, 160+27 (mJy/deg^2)^(-1), -2.0). Given the depth of this
survey, we put the first tight constraints on the 1.1 mm number counts at
S(1.1mm) = 0.5 mJy, and we find evidence that the faint-end of the number
counts at S(850\mu m) < 2.0 mJy from various SCUBA surveys towards lensing
clusters are biased high. In contrast to the 870 \mu m survey of this field
with the LABOCA camera, we find no apparent under-density of sources compared
to previous surveys at 1.1 mm. Additionally, we find a significant number of
SMGs not identified in the LABOCA catalogue. We find that in contrast to
observations at wavelengths < 500 \mu m, MIPS 24 \mu m sources do not resolve
the total energy density in the cosmic infrared background at 1.1 mm,
demonstrating that a population of z > 3 dust-obscured galaxies that are
unaccounted for at these shorter wavelengths potentially contribute to a large
fraction (~2/3) of the infrared background at 1.1 mm.Comment: 21 pages, 9 figures. Accepted to MNRAS
Detection of an ultra-bright submillimeter galaxy in the Subaru/XMM-Newton Deep Field using AzTEC/ASTE
We report the detection of an extremely bright (37 mJy at 1100 m
and 91 mJy at 880 m) submillimeter galaxy (SMG),
AzTEC-ASTE-SXDF1100.001 (hereafter referred to as SXDF1100.001 or Orochi),
discovered in 1100 m observations of the Subaru/XMM-Newton Deep Field
using AzTEC on ASTE. Subsequent CARMA 1300 m and SMA 880 m
observations successfully pinpoint the location of Orochi and suggest that it
has two components, one extended (FWHM of 4) and one
compact (unresolved). Z-Spec on CSO has also been used to obtain a wide band
spectrum from 190 to 308 GHz, although no significant emission/absorption lines
are found. The derived upper limit to the line-to-continuum flux ratio is
0.1--0.3 (2 ) across the Z-Spec band.
Based on the analysis of the derived spectral energy distribution from
optical to radio wavelengths of possible counterparts near the SMA/CARMA peak
position, we suggest that Orochi is a lensed, optically dark SMG lying at behind a foreground, optically visible (but red) galaxy at . The deduced apparent (i.e., no correction for magnification) infrared
luminosity () and star formation rate (SFR) are
and 11000 yr, respectively, assuming that the
is dominated by star formation. These values suggest that Orochi
will consume its gas reservoir within a short time scale (
yr), which is indeed comparable to those in extreme starbursts like the centres
of local ULIRGs.Comment: 18 pages, 13 figure
Frontal traumatic brain injury in rats causes long-lasting impairments in impulse control that are differentially sensitive to pharmacotherapeutics and associated with chronic neuroinflammation.
Traumatic brain injury (TBI) affects millions yearly, and is increasingly associated with chronic neuropsychiatric symptoms. We assessed the long-term effects of different bilateral frontal controlled cortical impact injury severities (mild, moderate, severe) on the five-choice serial reaction time task, a paradigm with relatively independent measurements of attention, motor impulsivity and motivation. Moderately- and severely-injured animals exhibited impairments across all cognitive domains that were still evident 14 weeks post-injury, while mild-injured animals only demonstrated persistent deficits in impulse control. However, recovery of function varied considerably between subjects such that some showed no impairment (“TBI-resilient”), some demonstrated initial deficits that recovered (“TBI-vulnerable”) and some never recovered (“chronically-impaired”). Three clinically-relevant treatments for impulsecontrol or TBI, amphetamine, atomoxetine, and amantadine, were assessed for efficacy in treating injury-induced deficits. Susceptibility to TBI affected the response to pharmacological challenge with amphetamine. Whereas sham and TBI-resilient animals showed characteristic impairments in impulse control at higher doses, amphetamine had the opposite effect in chronically-impaired rats, improving task performance. In contrast, atomoxetine and amantadine reduced premature responding but increased omissions, suggesting psychomotor slowing. Analysis of brain tissue revealed that generalized neuroinflammation was associated with impulsivity even when accounting for the degree of brain damage. This is one of the first studies to characterize psychiatric-like symptoms in experimental TBI. Our data highlight the importance of testing pharmacotherapies in TBI models in order to predict efficacy, and suggest that neuroinflammation may represent a treatment target for impulse control problems following injury
The redshift distribution of dusty star forming galaxies from the SPT survey
We use the Atacama Large Millimeter/submillimeter Array (ALMA) in Cycle 1 to
determine spectroscopic redshifts of high-redshift dusty star-forming galaxies
(DSFGs) selected by their 1.4mm continuum emission in the South Pole Telescope
(SPT) survey. We present ALMA 3mm spectral scans between 84-114GHz for 15
galaxies and targeted ALMA 1mm observations for an additional eight sources.
Our observations yield 30 new line detections from CO, [CI] , [NII] , H_2O and
NH_3. We further present APEX [CII] and CO mid-J observations for seven sources
for which only a single line was detected in spectral-scan data from ALMA Cycle
0 or Cycle 1. We combine the new observations with previously published and new
mm/submm line and photometric data of the SPT-selected DSFGs to study their
redshift distribution. The combined data yield 39 spectroscopic redshifts from
molecular lines, a success rate of >85%. Our sample represents the largest data
set of its kind today and has the highest spectroscopic completeness among all
redshift surveys of high-z DSFGs. The median of the redshift distribution is
z=3.9+/-0.4, and the highest-redshift source in our sample is at z=5.8. We
discuss how the selection of our sources affects the redshift distribution,
focusing on source brightness, selection wavelength, and strong gravitational
lensing. We correct for the effect of gravitational lensing and find the
redshift distribution for 1.4mm-selected sources with a median redshift of
z=3.1+/-0.3. Comparing to redshift distributions selected at shorter
wavelengths from the literature, we show that selection wavelength affects the
shape of the redshift distribution
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