29 research outputs found
Dynamical evolution of thin dispersion-dominated planetesimal disks
We study the dynamics of a vertically thin, dispersion-dominated disk of
planetesimals with eccentricities and inclinations (normalized in Hill
units) satisfying , . This situation may be typical
for e.g. a population of protoplanetary cores in the end of the oligarchic
phase of planet formation. In this regime of orbital parameters planetesimal
scattering has an anisotropic character and strongly differs from scattering in
thick () disks. We derive analytical expressions for the planetesimal
scattering coefficients and compare them with numerical calculations. We find
significant discrepancies in the inclination scattering coefficients obtained
by the two approaches and ascribe this difference to the effects not accounted
for in the analytical calculation: multiple scattering events (temporary
captures, which may be relevant for the production of distant planetary
satellites outside the Hill sphere) and distant interaction of planetesimals
prior to their close encounter. Our calculations show that the inclination of a
thin, dispersion-dominated planetesimal disk grows exponentially on a very
short time scale implying that (1) such disks must be very short-lived and (2)
planetesimal accretion in this dynamical phase is insignificant. Our results
are also applicable to the dynamics of shear-dominated disks switching to the
dispersion-dominated regime.Comment: 16 pages, 12 figures, submitted to A
Astro2020 Project White Paper: The Cosmic Accelerometer
We propose an experiment, the Cosmic Accelerometer, designed to yield
velocity precision of cm/s with measurement stability over years to
decades. The first-phase Cosmic Accelerometer, which is at the scale of the
Astro2020 Small programs, will be ideal for precision radial velocity
measurements of terrestrial exoplanets in the Habitable Zone of Sun-like stars.
At the same time, this experiment will serve as the technical pathfinder and
facility core for a second-phase larger facility at the Medium scale, which can
provide a significant detection of cosmological redshift drift on a 6-year
timescale. This larger facility will naturally provide further detection/study
of Earth twin planet systems as part of its external calibration process. This
experiment is fundamentally enabled by a novel low-cost telescope technology
called PolyOculus, which harnesses recent advances in commercial off the shelf
equipment (telescopes, CCD cameras, and control computers) combined with a
novel optical architecture to produce telescope collecting areas equivalent to
standard telescopes with large mirror diameters. Combining a PolyOculus array
with an actively-stabilized high-precision radial velocity spectrograph
provides a unique facility with novel calibration features to achieve the
performance requirements for the Cosmic Accelerometer
Astrobites as a Community-led Model for Education, Science Communication, and Accessibility in Astrophysics
Support for early career astronomers who are just beginning to explore
astronomy research is imperative to increase retention of diverse practitioners
in the field. Since 2010, Astrobites has played an instrumental role in
engaging members of the community -- particularly undergraduate and graduate
students -- in research. In this white paper, the Astrobites collaboration
outlines our multi-faceted online education platform that both eases the
transition into astronomy research and promotes inclusive professional
development opportunities. We additionally offer recommendations for how the
astronomy community can reduce barriers to entry to astronomy research in the
coming decade
GTC Follow-up Observations of Very Metal-Poor Star Candidates from DESI
The observations from the Dark Energy Spectroscopic Instrument (DESI) will
significantly increase the numbers of known extremely metal-poor stars by a
factor of ~ 10, improving the sample statistics to study the early chemical
evolution of the Milky Way and the nature of the first stars. In this paper we
report high signal-to-noise follow-up observations of 9 metal-poor stars
identified during the DESI commissioning with the Optical System for Imaging
and low-Intermediate-Resolution Integrated Spectroscopy (OSIRIS) instrument on
the 10.4m Gran Telescopio Canarias (GTC). The analysis of the data using a
well-vetted methodology confirms the quality of the DESI spectra and the
performance of the pipelines developed for the data reduction and analysis of
DESI data.Comment: 13 pages, 4 figures, to be submitted to ApJ, data available from
https://doi.org/10.5281/zenodo.802084
Recommended from our members
Astro2020 APC White Paper: The MegaMapper: a z > 2 spectroscopic instrument for the study of Inflation and Dark Energy
MegaMapper is a proposed ground-based experiment to measure Inflation
parameters and Dark Energy from galaxy redshifts at
A Spectroscopic Road Map for Cosmic Frontier: DESI, DESI-II, Stage-5
In this white paper, we present an experimental road map for spectroscopic
experiments beyond DESI. DESI will be a transformative cosmological survey in
the 2020s, mapping 40 million galaxies and quasars and capturing a significant
fraction of the available linear modes up to z=1.2. DESI-II will pilot
observations of galaxies both at much higher densities and extending to higher
redshifts. A Stage-5 experiment would build out those high-density and
high-redshift observations, mapping hundreds of millions of stars and galaxies
in three dimensions, to address the problems of inflation, dark energy, light
relativistic species, and dark matter. These spectroscopic data will also
complement the next generation of weak lensing, line intensity mapping and CMB
experiments and allow them to reach their full potential.Comment: Contribution to Snowmass 202
GTC follow-up observations of very metal-poor star candidates from DESI
The observations from the Dark Energy Spectroscopic Instrument (DESI) will significantly increase the numbers of known extremely metal-poor stars by a factor of ∼10, improving the sample statistics to study the early chemical evolution of the Milky Way and the nature of the first stars. In this paper we report follow-up observations with high signal-to-noise ratio of nine metal-poor stars identified during the DESI commissioning with the Optical System for Imaging and Low-Resolution Integrated Spectroscopy (OSIRIS) instrument on the 10.4 m Gran Telescopio Canarias. The analysis of the data using a well-vetted methodology confirms the quality of the DESI spectra and the performance of the pipelines developed for the data reduction and analysis of DESI data