59 research outputs found
The FENIKS Survey: Spectroscopic Confirmation of Massive Quiescent Galaxies at z ~ 3-5
The measured ages of massive, quiescent galaxies at imply that
massive galaxies quench as early as . While the number of
spectroscopic confirmations of quiescent galaxies at has increased over
the years, there are only a handful at . We report spectroscopic
redshifts of one secure () and two tentative (, )
massive () quiescent galaxies with 11 hours of
Keck/MOSFIRE -band observations. Our candidates were selected from the
FENIKS survey, which uses deep Gemini/Flamingos-2 imaging optimized
for increased sensitivity to the characteristic red colors of galaxies at with strong Balmer/4000 \AA\ breaks. The rest-frame and
colors of 3/4 quiescent candidates are consistent with Gyr old stellar
populations. This places these galaxies as the oldest objects at these
redshifts, and challenges the notion that quiescent galaxies at are all
recently-quenched, "post-starburst'' galaxies. Our spectroscopy shows that the
other quiescent-galaxy candidate is a broad-line AGN () with strong,
redshifted +[O III] emission with a velocity offset km/s,
indicative of a powerful outflow. The star-formation history of our highest
redshift candidate suggests that its progenitor was already in place by , reaching 10 by . These observations
reveal the limit of what is possible with deep near-infrared photometry and
targeted spectroscopy from the ground and demonstrate that secure spectroscopic
confirmation of quiescent galaxies at is only feasible with JWST.Comment: 20 pages, 11 figures, submitted to Ap
The K2-HERMES Survey: Age and Metallicity of the Thick Disc
Asteroseismology is a promising tool to study Galactic structure and
evolution because it can probe the ages of stars. Earlier attempts comparing
seismic data from the {\it Kepler} satellite with predictions from Galaxy
models found that the models predicted more low-mass stars compared to the
observed distribution of masses. It was unclear if the mismatch was due to
inaccuracies in the Galactic models, or the unknown aspects of the selection
function of the stars. Using new data from the K2 mission, which has a
well-defined selection function, we find that an old metal-poor thick disc, as
used in previous Galactic models, is incompatible with the asteroseismic
information. We show that spectroscopic measurements of [Fe/H] and
[/Fe] elemental abundances from the GALAH survey indicate a mean
metallicity of for the thick disc. Here is the
effective solar-scaled metallicity, which is a function of [Fe/H] and
[/Fe]. With the revised disc metallicities, for the first time, the
theoretically predicted distribution of seismic masses show excellent agreement
with the observed distribution of masses. This provides an indirect
verification of the asteroseismic mass scaling relation is good to within five
percent. Using an importance-sampling framework that takes the selection
function into account, we fit a population synthesis model of the Galaxy to the
observed seismic and spectroscopic data. Assuming the asteroseismic scaling
relations are correct, we estimate the mean age of the thick disc to be about
10 Gyr, in agreement with the traditional idea of an old -enhanced
thick disc.Comment: 21 pages, submitted to MNRA
Rapidly Progressive Cardiac Manifestation of Behçet's Disease Involving Conduction System and Aortic Valve
Cardiac conduction system impairment is a rare clinical manifestation of Behçet's disease. We report a patient who showed 1st degree atrioventricular block at first presentation, and showed aggravated finding of 3rd degree atrioventricular block on five months later. His cardiac manifestation finally developed to acute severe aortic regurgitation on six months later from his first cardiac manifestation. We observed this rapid progression during 6 months and successfully improved symptom and disease severity of the patient with treatment targeting Behçet's disease
Fundamental relations for the velocity dispersion of stars in the Milky Way
We explore the fundamental relations governing the radial and vertical velocity dispersions of stars in the Milky Way, from combined studies of complementary surveys including GALAH, LAMOST, APOGEE, the NASA Kepler and K2 missions, and Gaia DR2. We find that different stellar samples, even though they target different tracer populations and employ a variety of age estimation techniques, follow the same set of fundamental relations. We provide the clearest evidence to date that, in addition to the well-known dependence on stellar age, the velocity dispersions of stars depend on orbital angular momentum Lz, metallicity and height above the plane |z|, and are well described by a multiplicatively separable functional form. The dispersions have a power-law dependence on age with exponents of 0.441±0.007 and 0.251±0.006 for σz and σR respectively, and the power law is valid even for the oldest stars. For the solar neighborhood stars, the apparent break in the power law for older stars, as seen in previous studies, is due to the anti-correlation of Lz with age. The dispersions decrease with increasing Lz until we reach the Sun's orbital angular momentum, after which σz increases (implying flaring in the outer disc) while σR flattens. For a given age, the dispersions increase with decreasing metallicity, suggesting that the dispersions increase with birth radius. The dispersions also increase linearly with |z|. The same set of relations that work in the solar neighborhood also work for stars between 3 < R/kpc < 20. Finally, the high-[α/Fe] stars follow the same relations as the low-[α/Fe] stars
The thermochemistry of the lead-oxygen-sulphur system
Thesis (Ph.D.) -- University of Adelaide, Dept. of Mining, Metallurgical and Chemical Engineering, 196
Rhetoric vs practice : a re-examination of the 1916 Arab Revolt's advisers
The First World War's 1916 Arab Revolt has become, in the West, a renowned episode in part because of the presence of one dominating character: T.E. Lawrence. However, "Lawrence of Arabia" is only the most prominent of the many Western agents sent to advise the Revolt. The narratives of these advisers have come to dominate the most Westerners popular conception of the Arab uprising. Most scholars have portrayed the British advisers to the Arab Revolt as "pro-Arab." The aim of this thesis is to challenge that portrayal through a careful analysis of the writings (published and unpublished) and actions of the four advisers: T.E. Lawrence, Sir Ronald Storrs, Major Sir Hubert Young, Lt Col. Sir Percy Joyce.I argue for a more subtle, complex, heterogeneous version of the advisers Pro-Arab approach. By examining the advisers' published accounts and the available archival resources the contrast between the rhetoric surrounding their legends and the actual practice of their war experiences will be laid bare. The goal of the thesis is to use primary sources to demonstrate, in various areas of their relationships with Arabs, a discourse of superiority versus inferiority. This work has consequently attempted to present a less altruistic agenda emerging from the advisers' wartime conduct. In its place I have demonstrated numerous instances where they coerced and enforced their own interpretation of Arab desires and even an "Arab" identity onto the Revolt itself and furthermore, cemented these interpretations into Western popular culture
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