185 research outputs found
Trusted CI Experiences in Cybersecurity and Service to Open Science
This article describes experiences and lessons learned from the Trusted CI
project, funded by the US National Science Foundation to serve the community as
the NSF Cybersecurity Center of Excellence. Trusted CI is an effort to address
cybersecurity for the open science community through a single organization that
provides leadership, training, consulting, and knowledge to that community. The
article describes the experiences and lessons learned of Trusted CI regarding
both cybersecurity for open science and managing the process of providing
centralized services to a broad and diverse community.Comment: 8 pages, PEARC '19: Practice and Experience in Advanced Research
Computing, July 28-August 1, 2019, Chicago, IL, US
The Report of the California State Polytechnic University Pomona SFS Engagement
The Report of the California State Polytechnic University Pomona SFS EngagementNSF Grant #1547272NSF Grant #1504526Ope
Probing the single-particle character of rotational states in F using a short-lived isomeric beam
A beam containing a substantial component of both the ,
ns isomeric state of F and its , 109.77-min ground
state has been utilized to study members of the ground-state rotational band in
F through the neutron transfer reaction , in inverse kinematics.
The resulting spectroscopic strengths confirm the single-particle nature of the
13/2 band-terminating state. The agreement between shell-model
calculations, using an interaction constructed within the shell, and our
experimental results reinforces the idea of a single-particle/collective
duality in the descriptions of the structure of atomic nuclei
Trusted CI SLATE Engagement
Final report of the Trusted CI SLATE Engagement.NSF #1547272NSF #1724821Ope
The Report of the 2019 NSF Cybersecurity Summit for Large Facilities and Cyberinfrastructure
The Report of the 2019 NSF Cybersecurity Summit for Large Facilities and CyberinfrastructureNSF #1547272Ope
MaGICC discs: matching observed galaxy relationships over a wide stellar mass range
We use the same physical model to simulate four galaxies that match the relation between stellar and total mass, over a mass range that includes the vast majority of disc galaxies. The resultant galaxies, part of the Making Galaxies in a Cosmological Context (MaGICC) program, also match observed relations between luminosity, rotation velocity, size, colour, star formation rate, HI mass, baryonic mass, and metallicity. Radiation from massive stars and supernova energy regulate star formation and drive outflows, balancing the complex interplay between cooling gas, star formation, large scale outflows, and recycling of gas in a manner which correctly scales with the mass of the galaxy. Outflows also play a key role in simulating galaxies with exponential surface brightness profiles, flat rotation curves and dark matter cores. Our study implies that large scale outflows are the primary driver of the dependence of disc galaxy properties on mass. We show that the amount of outflows invoked in our model is required to meet the constraints provided by observations of OVI absorption lines in the circum-galactic-media of local galaxies
The Impact of Cooling and Feedback on Disc Galaxies
We present detailed, analytical models for the formation of disc galaxies to
investigate the impact that cooling and feedback have on their structural
properties. In particular, we investigate which observables extracted directly
from the models are best suited as virial mass estimators, and to what extent
they allow the recovery of the model input parameters regarding the feedback
and cooling efficiencies. Contrary to naive expectations, the luminosities and
circular velocities of disc galaxies are extremely poor indicators of total
virial mass. Instead, we show that the product of disc scale length and
rotation velocity squared yields a much more robust estimate. We show that
feedback can cause a narrow correlation between galaxy mass fraction and halo
spin parameter, similar to that found recently by van den Bosch, Burkert and
Swaters from an analysis of dwarf galaxy rotation curves. Finally we
investigate the impact that cooling and feedback have on the colors,
metallicities, star formation histories and Tully-Fisher relation of disc
galaxies.Comment: 20 pages, 12 figures. To be published in MNRA
The dependence of dark matter profiles on the stellar-to-halo mass ratio: a prediction for cusps versus cores
We use a suite of 31 simulated galaxies drawn from the MaGICC project to investigate the effects of baryonic feedback on the density profiles of dark matter haloes. The sample covers a wide mass range: 9.4×109 <Mhalo/M� <7.8×1011, hosting galaxies with stellarmasses in the range 5.0×105 <M∗/M� < 8.3×1010, i.e. from dwarf to L∗. The galaxies are simulated with blastwave supernova feedback and, for some of them, an additional source of energy from massive stars is included. Within this feedback scheme we vary several parameters, such as the initial mass function, the density threshold for star formation, and energy from supernovae and massive stars. The main result is a clear dependence of the inner slope of the dark matter density profile, α in ρ ∝ rα, on the stellar-to-halo mass ratio, M∗/Mhalo. This relation is independent of the particular choice of parameters within our stellar feedback scheme, allowing a prediction for cusp versus core formation. When M∗/Mhalo is low, �0.01 per cent, energy from stellar feedback is insufficient to significantly alter the inner dark matter density, and the galaxy retains a cuspy profile. At higher stellar-to-halo mass ratios, feedback drives the expansion of the dark matter and generates cored profiles. The flattest profiles form where M∗/Mhalo ∼ 0.5 per cent. Above this ratio, stars formed in the central regions deepen the gravitational potential enough to oppose the supernova-driven expansion process, resulting in cuspier profiles. Combining the dependence of α on M∗/Mhalo with the empirical abundance matching relation between M∗ and Mhalo provides a prediction for how α varies as a function of stellar mass. Further, using the Tully–Fisher relation allows a prediction for the dependence of the dark matter inner slope on the observed rotation velocity of galaxies. The most cored galaxies are expected to have Vrot ∼ 50 km s−1, with α decreasing for more massive disc galaxies: spirals with Vrot ∼ 150 km s−1 have central slopes α ≤−0.8, approaching again the Navarro–Frenk–White profile. This novel prediction for the dependence of α on disc galaxy mass can be tested using observational data sets and can be applied to theoretical modelling of mass profiles and populations of disc galaxies
The Formation of a Disk Galaxy within a Growing Dark Halo
We present a dynamical model for the formation and evolution of a massive
disk galaxy, within a growing dark halo whose mass evolves according to
cosmological simulations of structure formation. The galactic evolution is
simulated with a new 3D chemo-dynamical code, including dark matter, stars and
a multi-phase ISM. The simulations start at redshift z=4.85 with a small dark
halo in a LCDM universe and we follow the evolution until the present epoch.
The energy release by massive stars and SNe prevents a rapid collapse of the
baryonic matter and delays the maximum star formation until z=1. The galaxy
forms radially from inside-out and vertically from halo to disk. The first
galactic component that forms is the halo, followed by the bulge, the disk-halo
transition region, and the disk. At z=1, a bar begins to form which later turns
into a triaxial bulge. There is a pronounced deficiency of low-metallicity disk
stars due to pre-enrichment of the disk ISM with metal-rich gas from the bulge
and inner disk (G-dwarf problem). The mean rotation and the distribution of
orbital eccentricities for all stars as a function of metallicity are not very
different from those observed in the solar neighbourhood, showing that
homogeneous collapse models are oversimplified. The approach presented here
provides a detailed description of the formation and evolution of an isolated
disk galaxy in a LCDM universe, yielding new information about the kinematical
and chemical history of the stars and the ISM, but also about the evolution of
the luminosity, the colours and the morphology of disk galaxies.Comment: 23 pages, LaTeX, 18 figures, A&A accepted, a high resolution version
of the paper can be found at http://www.astro.unibas.ch/leute/ms.shtm
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