355 research outputs found
CLEAR II: Evidence for Early Formation of the Most Compact Quiescent Galaxies at High Redshift
The origin of the correlations between mass, morphology, quenched fraction,
and formation history in galaxies is difficult to define, primarily due to the
uncertainties in galaxy star-formation histories. Star-formation histories are
better constrained for higher redshift galaxies, observed closer to their
formation and quenching epochs. Here we use "non-parametric" star-formation
histories and a nested sampling method to derive constraints on the formation
and quenching timescales of quiescent galaxies at . We model deep
HST grism spectroscopy and photometry from the CLEAR (CANDELS Lyman
Emission at Reionization) survey. The galaxy formation redshifts,
(defined as the point where they had formed 50\% of their stellar mass) range
from (shortly prior to the observed epoch) up to . \editone{We find that early formation redshifts are correlated with high
stellar-mass surface densities, 10.25, where is the stellar mass within 1~pkpc (proper kpc).
Quiescent galaxies with the highest stellar-mass surface density, , } show a \textit{minimum} formation
redshift: all such objects in our sample have . Quiescent
galaxies with lower surface density, $\log \Sigma_1 / (M_\odot\
\mathrm{kpc}^{-2}) = 9.5 - 10.25z_{50}
\simeq 1.5 - 8\log\Sigma_1/(M_\odot\ \mathrm{kpc}^{-2})>10.25$ uniquely identifies galaxies
that formed in the first few Gyr after the Big Bang, and we discuss the
implications this has for galaxy formation models.Comment: 13 pages, 7 figures, accepted for publication in ApJ. Includes an
interactive online appendix (https://vince-ec.github.io/appendix/appendix
Debris disks as signposts of terrestrial planet formation. II Dependence of exoplanet architectures on giant planet and disk properties
We present models for the formation of terrestrial planets, and the
collisional evolution of debris disks, in planetary systems that contain
multiple unstable gas giants. We previously showed that the dynamics of the
giant planets introduces a correlation between the presence of terrestrial
planets and debris disks. Here we present new simulations that show that this
connection is qualitatively robust to changes in: the mass distribution of the
giant planets, the width and mass distribution of the outer planetesimal disk,
and the presence of gas in the disk. We discuss how variations in these
parameters affect the evolution. Systems with equal-mass giant planets undergo
the most violent instabilities, and these destroy both terrestrial planets and
the outer planetesimal disks that produce debris disks. In contrast, systems
with low-mass giant planets efficiently produce both terrestrial planets and
debris disks. A large fraction of systems with low-mass outermost giant planets
have stable gaps between these planets that are frequently populated by
planetesimals. Planetesimal belts between outer giant planets may affect debris
disk SEDs. If Earth-mass seeds are present in outer planetesimal disks, the
disks radially spread to colder temperatures. We argue that this may explain
the very low frequency of > 1 Gyr-old solar-type stars with observed 24 micron
excesses. Among the (limited) set of configurations explored, the best
candidates for hosting terrestrial planets at ~1 AU are stars older than 0.1-1
Gyr with bright debris disks at 70 micron but with no currently-known giant
planets. These systems combine evidence for rocky building blocks, with giant
planet properties least likely to undergo destructive dynamical evolution. We
predict an anti-correlation between debris disks and eccentric giant planets,
and a positive correlation between debris disks and terrestrial planets.Comment: Astronomy and Astrophysics, in press. Movies from simulations are at
http://www.obs.u-bordeaux1.fr/e3arths/raymond/movies_debris.htm
Cenozoic oil-shale deposits in southeastern-central Queensland: palynostratigraphic age determinations and correlations for the Biloela Formation (Biloela Basin) in GSQ Monto 5
Fossil pollen and spores recovered from core chips of the Biloela Formation between 41.5 and 219.0m in GSQ Monto 5:
Confirm that freshwater, lacustrine sediments infilling the inland Biloela Basin c. 110km southwest of Gladstone are a correlative of the oil-shale-rich Rundle Formation in the Narrows Graben near Gladstone on the central Queensland coast.
Provide, within the resolution achieved by using palynostratigraphic-dating criteria, the first known evidence that the upper part of the Biloela Formation is Late Eocene–Early Oligocene. At present, the strongest evidence that the section is Late Eocene is the close similarity of the microflora to Late Eocene assemblages in the offshore Gippsland Basin in southeastern Australia.
An Early (earliest?) Oligocene age is equally probable if age-range data from the Murray Basin, southeastern Australia, are used. Differences in the age range of fossil species shared with southeastern Australia emphasise caution is needed when using zonation schemata developed for the continental margin Gippsland Basin and/or epicontinental Murray Basin to date Cenozoic deposits in central QueenslandThis report was commisioned by Queensland Department of Natural Resources and Mine
Factors Associated with Neutralizing Antibody Response in Piglets Experimentally Infected with Porcine Reproductive and Respiratory Virus
Host genetic differences and other factors associated with neutralizing antibody (NAb) response were examined in 464 Large White-Landrace piglets that were experimentally challenged with porcine reproductive and respiratory virus (PRRSv) isolate NVSL-97-7895. Serum samples and viremia data were collected on piglets periodically for 42 days post infection (dpi). NAb response was defined as the inverse of the highest 1:2 serial dilution of serum without cytopathic effects. Heritability and other factors associated with NAb response were estimated using an animal model in ASReml. These analyses identified two aspects of viremia that were associated with NAb response: viral load (area under the curve from 0-21 dpi) and virus rebound (a two Log increase in viremia after the virus had started to clear). These results also suggested that NAb response may be lowly heritable and provided the groundwork for further characterization of NAb response
Fossil leaves of Banksia, Banksieae and pretenders: resolving the fossil genus Banksieaephyllum
Influence of charged walls and defects on DC resistivity and dielectric relaxation in Cu-Cl boracite
Rebuttal from Raymond Reynolds, Callum Osler, Linda Tersteeg and Ian Loram.
This work was supported by BBSRC grant BB/I00579X/
A mechanical time-of-flight neutron diffractometer
A mechanical time-of-flight (TOF) neutron diffractometer has been constructed and a system of data analysis developed for the study of noncrystalline substances through radial density functions. Measurements to wave vector transfer Qmax > 25 A-1 are readily made; a resolution [Delta]Q/Qr[approximate]2[pi]/Qmax[approximate]0.25 A. These can be partially corrected for termination errors to provide a spatial resolution [Delta]r<0.15 A.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22421/1/0000871.pd
CLEAR: The Gas-Phase Metallicity Gradients of Star-Forming Galaxies at 0.6 < z < 2.6
We report on the gas-phase metallicity gradients of a sample of 264
star-forming galaxies at 0.6 < z < 2.6, measured through deep near-infrared
Hubble Space Telescope slitless spectroscopy. The observations include 12-orbit
depth Hubble/WFC3 G102 grism spectra taken as a part of the CANDELS Lya
Emission at Reionization (CLEAR) survey, and archival WFC3 G102+G141 grism
spectra overlapping the CLEAR footprint. The majority of galaxies (84%) in this
sample are consistent with a zero or slightly positive metallicity gradient
across the full mass range probed (8.5 < log M_*/M_sun < 10.5). We measure the
intrinsic population scatter of the metallicity gradients, and show that it
increases with decreasing stellar mass---consistent with previous reports in
the literature, but confirmed here with a much larger sample. To understand the
physical mechanisms governing this scatter, we search for correlations between
the observed gradient and various stellar population properties at fixed mass.
However, we find no evidence for a correlation with the galaxy properties we
consider---including star-formation rates, sizes, star-formation rate surface
densities, and star-formation rates per gravitational potential energy. We use
the observed weakness of these correlations to provide material constraints for
predicted intrinsic correlations from theoretical models.Comment: 19 pages, 10 figures (v2: typo fixed in Figure 10 label); submitted
to Ap
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