115 research outputs found
"Crossing Brooklyn Ferry": The Shaping Imagination
Presents a brief reading of "Crossing Brooklyn Ferry" that shows how Whiman\u27s "fascination for panoramas, dioramas, and dime museums" informs the effects achieved in the poem
Crossing Brooklyn Ferry : The Shaping Imagination
Presents a brief reading of Crossing Brooklyn Ferry that shows how Whiman\u27s fascination for panoramas, dioramas, and dime museums informs the effects achieved in the poem
Modeling the Laser Interferometer Space Antenna Optics
The Laser Interferometer Space Antenna (LISA), shown below, will detect gravitational waves produced by objects such as binary black holes or objects falling into black holes (extreme mass ratio inspirals) over a frequency range of l0(exp -4) to 0.1 Hz. Within the conceptual frame work of Newtonian physics, a gravitational wave produces a strain, (Delta)l/l, with magnitudes of the order of Earth based gravitational wave detectors, such as the Laser Interferometer Gravitational-Wave Observatory (LIGO) project, use Michelson interferometers with arm lengths l = 4 km to detect these strains. Earth induced seismic noise limits ground-based instruments detecting gravitational waves with frequencies lower than approx. 1 Hz
Polarization Considerations for the Laser Interferometer Space Antenna
A polarization ray trace model of the Laser Interferometer Space Antenna s (LISA) optical path is being created. The model will be able to assess the effects of various polarizing elements and the optical coatings on the required, very long path length, picometer level dynamic interferometry. The computational steps are described. This should eliminate any ambiguities associated with polarization ray tracing of interferometers and provide a basis for determining the computer model s limitations and serve as a clearly defined starting point for future work
Radio Mode Outbursts in Giant Elliptical Galaxies
Outbursts from active galactic nuclei (AGN) affect the hot atmospheres of
isolated giant elliptical galaxies (gE's), as well as those in groups and
clusters of galaxies. Chandra observations of a sample of nearby gE's show that
the average power of AGN outbursts is sufficient to stop their hot atmospheres
from cooling and forming stars, consistent with radio mode feedback models. The
outbursts are intermittent, with duty cycles that increases with size.Comment: 4 pages, 3 figures, to appear in proceedings of "The Monster's Fiery
Breath", Eds. Sebastian Heinz & Eric Wilcots (AIP conference series
All Curled Up: A Numerical Investigation of Shock-Bubble Interactions and the Role of Vortices in Heating Galaxy Clusters
Jets from active galactic nuclei in the centers of galaxy clusters inflate
cavities of low density relativistic plasma and drive shock and sound waves
into the intracluster medium. When these waves overrun previously inflated
cavities, they form a differentially rotating vortex through the
Richtmyer-Meshkov instability. The dissipation of energy captured in the vortex
can contribute to the feedback of energy into the atmospheres of cool core
clusters. Using a series of hydrodynamic simulations we investigate the
efficiency of this process: we calculate the kinetic energy in the vortex by
decomposing the velocity field into its irrotational and solenoidal parts.
Compared to the two-dimensional case, the 3-dimensional Richtmyer-Meshkov
instability is about a factor of 2 more efficient. The energy in the vortex
field for weak shocks is E_vortex ~ rho_ICM v_shock^2 V_bubble (with dependence
on the geometry, density contrast, and shock width). For strong shocks, the
vortex becomes dynamically unstable, quickly dissipating its energy via a
turbulent cascade. We derive a number of diagnostics for observations and
laboratory experiments of shock-bubble interactions, like the shock-vortex
standoff distance, which can be used to derive lower limits on the Mach number.
The differential rotation of the vortex field leads to viscous dissipation,
which is sufficiently efficient to react to cluster cooling and to dissipate
the vortex energy within the cooling radius of the cluster for a reasonable
range of vortex parameters. For sufficiently large filling factors (of order a
few percent or larger), this process could thus contribute significantly to AGN
feedback in galaxy clusters.Comment: 16 pages, 24 figure
Supermassive Black Hole Feedback
Understanding the processes that drive galaxy formation and shape the
observed properties of galaxies is one of the most interesting and challenging
frontier problems of modern astrophysics. We now know that the evolution of
galaxies is critically shaped by the energy injection from accreting
supermassive black holes (SMBHs). However, it is unclear how exactly the
physics of this feedback process affects galaxy formation and evolution. In
particular, a major challenge is unraveling how the energy released near the
SMBHs is distributed over nine orders of magnitude in distance throughout
galaxies and their immediate environments. The best place to study the impact
of SMBH feedback is in the hot atmospheres of massive galaxies, groups, and
galaxy clusters, which host the most massive black holes in the Universe, and
where we can directly image the impact of black holes on their surroundings. We
identify critical questions and potential measurements that will likely
transform our understanding of the physics of SMBH feedback and how it shapes
galaxies, through detailed measurements of (i) the thermodynamic and velocity
fluctuations in the intracluster medium (ICM) as well as (ii) the composition
of the bubbles inflated by SMBHs in the centers of galaxy clusters, and their
influence on the cluster gas and galaxy growth, using the next generation of
high spectral and spatial resolution X-ray and microwave telescopes.Comment: 10 pages, submitted to the Astro2020 decada
Mary Celestino : The Forces of Nature
McNamara describes the places on Pelee Island represented in Celestino's exhibition, focusing on how her paintings bear witness to the human destruction of nature. Hall compares Celestino's Magic Realist works to European and early Canadian symbolist landscape painting. Statements by Celestino and Nataley Nagy. Biographical notes. 37 bibl. ref
- …