4,204 research outputs found
A latest Cretaceous to earliest Paleogene dinoflagellate cyst zonation of Antarctica, and implications for phytoprovincialism in the high southern latitudes
The thickest uppermost Cretaceous to lowermost Paleogene (Maastrichtian to Danian) sedimentary succession in the world is exposed on southern Seymour Island (65° South) in the James Ross Basin, Antarctic Peninsula. This fossiliferous shallow marine sequence, which spans the Cretaceous–Paleogene boundary, has allowed a high-resolution analysis of well-preserved marine palynomorphs. Previous correlation of Cretaceous–Paleogene marine palynomorph assemblages in the south polar region relied on dinoflagellate cyst biozonations from New Zealand and southern Australia. The age model of the southern Seymour Island succession is refined and placed within the stratigraphical context of the mid to high southern palaeolatitudes. Quantitative palynological analysis of a new 1102 m continuous stratigraphical section comprising the uppermost Snow Hill Island Formation and the López de Bertodano Formation (Marambio Group) across southern Seymour Island was undertaken. We propose the first formal late Maastrichtian to early Danian dinoflagellate cyst zonation scheme for the Antarctic based on this exceptional succession. Two new late Maastrichtian zones, including three subzones, and one new early Danian zone are defined. The oldest beds correlate well with the late Maastrichtian of New Zealand. In a wider context, a new South Polar Province based on Maastrichtian to Danian dinoflagellate cysts is proposed, which excludes most southern South American marine palynofloras. This interpretation is supported by models of ocean currents around Antarctica and implies an unrestricted oceanic connection across Antarctica between southern South America and the Tasman Sea
Space Velocities of L- and T-type Dwarfs
(Abridged) We have obtained radial velocities of a sample of 18 ultracool
dwarfs (M6.5-T8) using high-resolution, near-infrared spectra obtained with
NIRSPEC and the Keck II telescope. We have confirmed that the radial velocity
of Gl 570 D is coincident with that of the K-type primary star Gl 570 A, thus
providing additional support for their true companionship. The presence of
planetary-mass companions around 2MASS J05591914-1404488 (T4.5V) has been
analyzed using five NIRSPEC radial velocity measurements obtained over a period
of 4.37 yr. We have computed UVW space motions for a total of 21 L and T dwarfs
within 20 pc of the Sun. This population shows UVW velocities that nicely
overlap the typical kinematics of solar to M-type stars within the same spatial
volume. However, the mean Galactic (44.2 km/s) and tangential (36.5 km/s)
velocities of the L and T dwarfs appear to be smaller than those of G to M
stars. A significant fraction (~40%) of the L and T dwarfs lies near the Hyades
moving group (0.4-2 Gyr), which contrasts with the 10-12% found for
earlier-type stellar neighbors. Additionally, the distributions of all three
UVW components (sigma_{UVW} = 30.2, 16.5, 15.8 km/s) and the distributions of
the total Galactic (sigma_{v_tot} = 19.1 km/s) and tangential (sigma_{v_t} =
17.6 km/s) velocities derived for the L and T dwarf sample are narrower than
those measured for nearby G, K, and M-type stars, but similar to the
dispersions obtained for F stars. This suggests that, in the solar
neighborhood, the L- and T-type ultracool dwarfs in our sample (including brown
dwarfs) is kinematically younger than solar-type to early M stars with likely
ages in the interval 0.5-4 Gyr.Comment: Accepted for publication in Ap
Use of a modified World Café process to discuss and set priorities for a Community of Practice supporting implementation of ReQoL a new mental health and quality of life Patient Reported Outcome Measure (PROM)
Ubv CCD Standards Near 5C1 Radio Sources at Intermediate Galactic Latitude-I
We have been doing a photometric and astrometric sample survey programme on
Schmidt plates in a few selected directions in the Galaxy with an aim to study
galactic stellar populations. In order to calibrate Schmidt plates
photometrically, it is necessary to have a number of photometric standards
which cover the entire range of magnitudes to be studied on the plates. As
Schmidt plates cover a wide area of the sky, the standards should also be
spread over the surface of the plate so as to minimise geometrical effects
present on the plate. This paper is first in a series of papers aimed at to
provide photometric standards in the selected galactic directions to be
studied. In this paper we present photometric magnitudes obtained through CCD
observation in the galactic direction (l=170deg, b=45deg) centered at
alpha(2000) = 9h 41m 20s and delta(2000) = +49deg 54' 20'' and covering an area
of 14 sq degs. B and V magnitudes have been obtained for a total of 214 stars
out of which for 73 stars U magnitudes also have been obtained. The magnitude
range covered is 11<V<21 and 0.18<B-V<1.85.Comment: Postscript file, 13 pages, 1 figure (figure available on request),
paper accepted for publication in the Bulletin of Astronomical Society of
Indi
GYES, a multifibre spectrograph for the CFHT
We have chosen the name of GYES, one of the mythological giants with one
hundred arms, offspring of Gaia and Uranus, for our instrument study of a
multifibre spectrograph for the prime focus of the Canada-France-Hawaii
Telescope. Such an instrument could provide an excellent ground-based
complement for the Gaia mission and a northern complement to the HERMES project
on the AAT. The CFHT is well known for providing a stable prime focus
environment, with a large field of view, which has hosted several imaging
instruments, but has never hosted a multifibre spectrograph. Building upon the
experience gained at GEPI with FLAMES-Giraffe and X-Shooter, we are
investigating the feasibility of a high multiplex spectrograph (about 500
fibres) over a field of view 1 degree in diameter. We are investigating an
instrument with resolution in the range 15000 to 30000, which should provide
accurate chemical abundances for stars down to 16th magnitude and radial
velocities, accurate to 1 km/s for fainter stars. The study is led by
GEPI-Observatoire de Paris with a contribution from Oxford for the study of the
positioner. The financing for the study comes from INSU CSAA and Observatoire
de Paris. The conceptual study will be delivered to CFHT for review by October
1st 2010.Comment: Contributed talk at the Gaia ELSA conference 2010, S\`evres 7-11 June
2010, to be published on the EAS Series, Editors: C. Turon, F. Arenou & F.
Meynadie
Simulation of Stellar Objects in SDSS Color Space
We present a simulation of the spatial, luminosity and spectral distributions
of four types of stellar objects. We simulate: (1) Galactic stars, based on a
Galactic structure model, a stellar population synthesis model, stellar
isochrones, and stellar spectral libraries; (2) white dwarfs, based on model
atmospheres, the observed luminosity function, mass distribution, and Galactic
distribution of white dwarfs; (3) quasars, based on their observed luminosity
function and its evolution, and models of emission and absorption spectra of
quasars; and (4) compact emission line galaxies, based on the observed
distribution of their spectral properties and sizes. The results are presented
in the color system of the Sloan Digital Sky Survey (SDSS), with realistic
photometric error and Galactic extinction. The simulated colors of stars and
quasars are compared with observations in the SDSS system and show good
agreement. The stellar simulation can be used as a tool to analyze star counts
and constrain models of Galactic structure, as well as to identify stars with
unusual colors. The simulation can also be used to establish the quasar target
selection algorithm for the SDSS.Comment: 52 pages, 22 figures, to appear in AJ; simulated catalogs available
at http://www.astro.princeton.edu/~fan/sdss_simu.htm
Early Results from APOKASC
Asteroseismology and spectroscopy provide complementary constraints on the
fundamental and chemical properties of stars. I describe the first results from
APOKASC, a collaboration between the Kepler asteroseismic science consortium
(KASC) and the SDSS-III APOGEE survey. These include (1) the first test of
asteroseismic scaling relationships in the metal-poor regime using halo and
thick disk stars identified in the APOKASC sample; and (2) the calibration of
spectroscopic parameters using precise asteroseismic measurements of surface
gravity. I also highlight future research avenues that are made possible by
this unique sample of thousands of well-characterized red giant stars.Comment: Proc. of the workshop "Asteroseismology of stellar populations in the
Milky Way" (Sesto, 22-26 July 2013), Astrophysics and Space Science
Proceedings, (eds. A. Miglio, L. Girardi, P. Eggenberger, J. Montalban
Fertilization Management to Improve Stockpiled Tall Fescue in the Fall
In 2019 and 2021, a tall fescue fertility study was conducted at the K-State Experiment Station near Columbus, KS. The purpose of the study was to determine the effect of summer fertilization on forage quality and quantity in stockpiled fescue. If a producer can stockpile high-quality forage for late fall and early winter grazing, protein supplementation may not be necessary for fall calving cows
Impact of Fertility and Mowing on Crabgrass Quantity and Quality for Hay Production in Southeast Kansas
A crabgrass variety trial comparing Quick-N-Big and Mojo crabgrasses was conducted in 2021 at the K-State Experiment Station outside of Columbus, KS. The trial evaluated forage quantity and quality under different fertilization and harvest management practices
Bermudagrass Under Different Fertility and Harvest Management Practices
A second year of a bermudagrass fertility study was conducted at the K-State Research and Experiment Station outside of Columbus, KS, in 2021. The purpose of the study was to simulate forage producers’ practices of managing bermudagrass and determine how each practice affected forage production and quality
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