88 research outputs found
A Case of Spontaneous Adrenal Hemorrhage in Pregnancy
A case study looking at a 25 year old patient at 31 weeks gestation with spontaneous adrenal hemorrhage
Venusian atmospheric and Magellan properties from attitude control data
Results are presented of the study of the Venusian atmosphere, Magellan aerodynamic moment coefficients, moments of inertia, and solar moment coefficients. This investigation is based upon the use of attitude control data in the form of reaction wheel speeds from the Magellan spacecraft. As the spacecraft enters the upper atmosphere of Venus, measurable torques are experienced due to aerodynamic effects. Solar and gravity gradient effects also cause additional torques throughout the orbit. In order to maintain an inertially fixed attitude, the control system counteracts these torques by changing the angular rates of three reaction wheels. Model reaction wheel speeds are compared to observed Magellan reaction wheel speeds through a differential correction procedure. This method determines aerodynamic, atmospheric, solar pressure, and mass moment of inertia parameters. Atmospheric measurements include both base densities and scale heights. Atmospheric base density results confirm natural variability as measured by the standard orbital decay method. Potential inconsistencies in free molecular aerodynamic moment coefficients are identified. Moments of inertia are determined with a precision better than 1 percent of the largest principal moment of inertia
The observability of galaxy merger signatures in nearby gas-rich spirals
Galaxy mergers are crucial to understanding galaxy evolution, therefore we must determine their observational signatures to select them from large IFU galaxy samples such as MUSE and SAMI. We employ 24 high-resolution idealized hydrodynamical galaxy merger simulations based on the âFeedback In Realistic Environmentâ (FIRE-2) model to determine the observability of mergers to various configurations and stages using synthetic images and velocity maps. Our mergers cover a range of orbital configurations at fixed 1:2.5 stellar mass ratio for two gas rich spirals at low redshift. Morphological and kinematic asymmetries are computed for synthetic images and velocity maps spanning each interaction. We divide the interaction sequence into three: (1) the pair phase; (2) the merging phase; and (3) the post-coalescence phase. We correctly identify mergers between first pericentre passage and 500Â Myr after coalescence using kinematic asymmetry with 66Â perâcent completeness, depending upon merger phase and the field of view of the observation. We detect fewer mergers in the pair phase (40Â perâcent) and many more in the merging and post-coalescence phases (97Â perâcent). We find that merger detectability decreases with field of view, except in retrograde mergers, where centrally concentrated asymmetric kinematic features enhances their detectability. Using a cut-off derived from a combination of photometric and kinematic asymmetry, we increase these detections to 89Â perâcent overall, 79Â perâcent in pairs, and close to 100Â perâcent in the merging and post-coalescent phases. By using this combined asymmetry cut-off we mitigate some of the effects caused by smaller fields of view subtended by massively multiplexed integral field spectroscopy programmes
The Sydney-AAO Multi-object Integral field spectrograph (SAMI)
We demonstrate a novel technology that combines the power of the multi-object
spectrograph with the spatial multiplex advantage of an integral field
spectrograph (IFS). The Sydney-AAO Multi-object IFS (SAMI) is a prototype
wide-field system at the Anglo-Australian Telescope (AAT) that allows 13
imaging fibre bundles ("hexabundles") to be deployed over a 1-degree diameter
field of view. Each hexabundle comprises 61 lightly-fused multimode fibres with
reduced cladding and yields a 75 percent filling factor. Each fibre core
diameter subtends 1.6 arcseconds on the sky and each hexabundle has a field of
view of 15 arcseconds diameter. The fibres are fed to the flexible AAOmega
double-beam spectrograph, which can be used at a range of spectral resolutions
(R=lambda/delta(lambda) ~ 1700-13000) over the optical spectrum (3700-9500A).
We present the first spectroscopic results obtained with SAMI for a sample of
galaxies at z~0.05. We discuss the prospects of implementing hexabundles at a
much higher multiplex over wider fields of view in order to carry out
spatially--resolved spectroscopic surveys of 10^4 to 10^5 galaxies.Comment: 24 pages, 16 figures. Accepted by MNRA
The WiggleZ Dark Energy Survey: Star-formation in UV-luminous galaxies from their luminosity functions
We present the ultraviolet (UV) luminosity function of galaxies from the
GALEX Medium Imaging Survey with measured spectroscopic redshifts from the
first data release of the WiggleZ Dark Energy Survey. This sample selects
galaxies with high star formation rates: at 0.6 < z < 0.9 the median star
formation rate is at the upper 95th percentile of optically-selected (r<22.5)
galaxies and the sample contains about 50 per cent of all NUV < 22.8, 0.6 < z <
0.9 starburst galaxies within the volume sampled.
The most luminous galaxies in our sample (-21.0>M_NUV>-22.5) evolve very
rapidly with a number density declining as (1+z)^{5\pm 1} from redshift z = 0.9
to z = 0.6. These starburst galaxies (M_NUV<-21 is approximately a star
formation rate of 30 \msuny) contribute about 1 per cent of cosmic star
formation over the redshift range z=0.6 to z=0.9. The star formation rate
density of these very luminous galaxies evolves rapidly, as (1+z)^{4\pm 1}.
Such a rapid evolution implies the majority of star formation in these large
galaxies must have occurred before z = 0.9.
We measure the UV luminosity function in 0.05 redshift intervals spanning
0.1<z<0.9, and provide analytic fits to the results. At all redshifts greater
than z=0.55 we find that the bright end of the luminosity function is not well
described by a pure Schechter function due to an excess of very luminous
(M_NUV<-22) galaxies. These luminosity functions can be used to create a radial
selection function for the WiggleZ survey or test models of galaxy formation
and evolution. Here we test the AGN feedback model in Scannapieco et al.
(2005), and find that this AGN feedback model requires AGN feedback efficiency
to vary with one or more of the following: stellar mass, star formation rate
and redshift.Comment: 27 pages; 13 pages without appendices. 22 figures; 11 figures in the
main tex
The WiggleZ Dark Energy Survey: improved distance measurements to z = 1 with reconstruction of the baryonic acoustic feature
We present significant improvements in cosmic distance measurements from the WiggleZ Dark Energy Survey, achieved by applying the reconstruction of the baryonic acoustic feature technique. We show using both data and simulations that the reconstruction technique can often be effective despite patchiness of the survey, significant edge effects and shot-noise. We investigate three redshift bins in the redshift range 0.2 < z < 1, and in all three find improvement after reconstruction in the detection of the baryonic acoustic feature and its usage as a standard ruler. We measure model-independent distance measures DV(rsfid/rs) of 1716 ± 83, 2221 ± 101, 2516 ± 86 Mpc (68 perâcent CL) at effective redshifts z = 0.44, 0.6, 0.73, respectively, where DV is the volume-averaged distance, and rs is the sound horizon at the end of the baryon drag epoch. These significantly improved 4.8, 4.5 and 3.4 per cent accuracy measurements are equivalent to those expected from surveys with up to 2.5 times the volume of WiggleZ without reconstruction applied. These measurements are fully consistent with cosmologies allowed by the analyses of the Planck Collaboration and the Sloan Digital Sky Survey. We provide the DV(rsfid/rs) posterior probability distributions and their covariances. When combining these measurements with temperature fluctuations measurements of Planck, the polarization of Wilkinson Microwave Anisotropy Probe 9, and the 6dF Galaxy Survey baryonic acoustic feature, we do not detect deviations from a flat Î cold dark matter (ÎCDM) model. Assuming this model, we constrain the current expansion rate to Hâ = 67.15 ± 0.98 km sâ»ÂčMpcâ»Âč. Allowing the equation of state of dark energy to vary, we obtain wDE = â1.080 ± 0.135. When assuming a curved ÎCDM model we obtain a curvature value of ΩK = â0.0043 ± 0.0047
Catalogs of Hot White Dwarfs in the Milky Way from GALEX's Ultraviolet Sky Surveys. Constraining Stellar Evolution
We present comprehensive catalogs of hot star candidates in the Milky Way,
selected from GALEX far-UV (FUV, 1344-1786 AA) and near-UV (NUV, 1771-2831 AA)
imaging. The FUV and NUV photometry allows us to extract the hottest stellar
objects, in particular hot white dwarfs (WD), which are elusive at other
wavelengths because of their high temperatures and faint optical luminosities.
We generated catalogs of UV sources from two GALEX's surveys: AIS (All-Sky
Imaging Survey, depth ABmag~19.9/20.8 in FUV/NUV) and MIS (Medium-depth Imaging
Survey, depth ~22.6/22.7mag). The two catalogs (from GALEX fifth data release)
contain 65.3/12.6 million (AIS/MIS) unique UV sources with error(NUV)<0.5mag,
over 21,435/1,579 square degrees. We also constructed subcatalogs of the UV
sources with matched optical photometry from SDSS (7th data release): these
contain 0.6/0.9million (AIS/MIS) sources with errors <0.3mag in both FUV and
NUV, excluding sources with multiple optical counterparts, over an area of
7,325/1,103 square degrees. All catalogs are available online. We then selected
28,319(AIS)/9,028(MIS) matched sources with FUV-NUV<-0.13; this color cut
corresponds to stellar Teff hotter than ~18,000 K. An additional color cut of
NUV-r>0.1 isolates binaries with largely differing Teff's, and some intruding
QSOs. Available spectroscopy for a subsample indicates that hot-star candidates
with NUV-r<0.1 have negligible contamination by non-stellar objects. We discuss
the distribution of sources in the catalogs, and the effects of error and color
cuts on the samples. The density of hot-star candidates increases from high to
low Galactic latitudes, but drops on the MW plane due to dust extinction. Our
hot-star counts at all latitudes are better matched by Milky Way models
computed with an initial-final mass relation that favours lower final masses.
(ABRIDGED)Comment: To appear in MNRAS. Better printed in colou
Integrated photonic building blocks for next-generation astronomical instrumentation I: the multimode waveguide
We report on the fabrication and characterization of composite multimode
waveguide structures that consist of a stack of single-mode waveguides
fabricated by ultrafast laser inscription. We explore 2 types of composite
structures; those that consist of overlapping single-mode waveguides which
offer the maximum effective index contrast and non overlapped structures which
support multiple modes via strong evanescent coupling. We demonstrate that both
types of waveguides have negligible propagation losses (to within experimental
uncertainty) for light injected with focal ratios >8, which corresponds to the
cutoff of the waveguides. We also show that right below cutoff, there is a
narrow region where the injected focal ratio is preserved (to within
experimental uncertainty) at the output. Finally, we outline the major
application of these highly efficient waveguides; in a device that is used to
reformat the light in the focal plane of a telescope to a slit, in order to
feed a diffraction-limited spectrograph.Comment: 15 pages, 11 figures, accepted to Optics Expres
The SLUGGS Survey: stellar kinematics, kinemetry and trends at large radii in 25 early-type galaxies
Due to longer dynamical time-scales, the outskirts of early-type galaxies retain the footprint of their formation and assembly. Under the popular two-phase galaxy formation scenario, an initial in situ phase of star formation is followed by minor merging and accretion of ex situ stars leading to the expectation of observable transitions in the kinematics and stellar populations on large scales. However, observing the faint galactic outskirts is challenging, often leaving the transition unexplored. The large-scale, spatially resolved stellar kinematic data from the SAGES Legacy Unifying Galaxies and GlobularS (SLUGGS) survey are ideal for detecting kinematic transitions. We present kinematic maps out to 2.6 effective radii on average, kinemetry profiles, measurement of kinematic twists and misalignments, and the average outer intrinsic shape of 25 SLUGGS galaxies. We find good overall agreement in the kinematic maps and kinemetry radial profiles with literature. We are able to confirm significant radial modulations in rotational versus pressure support of galaxies with radius so that the central and outer rotational properties may be quite different. We also test the suggestion that galaxies may be more triaxial in their outskirts and find that while fast rotating galaxies were already shown to be axisymmetric in their inner regions, we are unable to rule out triaxiality in their outskirts.We compare our derived outer kinematic information to model predictions from a two-phase galaxy formation scenario. We find that the theoretical range of local outer angular momentum agrees well with our observations, but that radial modulations are much smaller than predicted
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