14,710 research outputs found
Gas stripping in galaxy groups - the case of the starburst spiral NGC 2276
Ram pressure stripping of galactic gas is generally assumed to be inefficient
in galaxy groups due to the relatively low density of the intragroup medium and
the small velocity dispersions of groups. To test this assumption, we obtained
Chandra X-ray data of the starbursting spiral NGC 2276 in the NGC 2300 group of
galaxies, a candidate for a strong galaxy interaction with hot intragroup gas.
The data reveal a shock-like feature along the western edge of the galaxy and a
low-surface-brightness tail extending to the east, similar to the morphology
seen in other wavebands. Spatially resolved spectroscopy shows that the data
are consistent with intragroup gas being pressurized at the leading western
edge of NGC 2276 due to the galaxy moving supersonically through the intragroup
medium at a velocity ~850 km/s. Detailed modelling of the gravitational
potential of NGC 2276 shows that the resulting ram-pressure could significantly
affect the morphology of the outer gas disc but is probably insufficient to
strip large amounts of cold gas from the disc. We estimate the mass loss rates
due to turbulent viscous stripping and starburst outflows being swept back by
ram pressure, showing that both mechanisms could plausibly explain the presence
of the X-ray tail. Comparison to existing HI measurements shows that most of
the gas escaping the galaxy is in a hot phase. With a total mass loss rate of
roughly 5 M_Sun/yr, the galaxy could be losing its entire present HI supply
within a Gyr. This demonstrates that the removal of galactic gas through
interactions with a hot intragroup medium can occur rapidly enough to transform
the morphology of galaxies in groups. Implications of this for galaxy evolution
in groups and clusters are briefly discussed.Comment: 16 pages, 8 figures, accepted for publication in MNRA
3D simulations of self-propelled, reconstructed jellyfish using vortex methods
We present simulations of the vortex dynamics associated with the
self-propelled motion of jellyfish. The geometry is obtained from image
segmentation of video recordings from live jellyfish. The numerical simulations
are performed using three-dimensional viscous, vortex particle methods with
Brinkman penalization to impose the kinematics of the jellyfish motion. We
study two types of strokes recorded in the experiment1. The first type (stroke
A) produces two vortex rings during the stroke: one outside the bell during the
power stroke and one inside the bell during the recovery stroke. The second
type (stroke B) produces three vortex rings: one ring during the power stroke
and two vortex rings during the recovery stroke. Both strokes propel the
jellyfish, with stroke B producing the highest velocity. The speed of the
jellyfish scales with the square root of the Reynolds number. The simulations
are visualized in a fluid dynamics video.Comment: 1 page, 1 figur
Study of high voltage solar array configurations with integrated power control electronics
Solar array electrical configurations for voltage regulatio
Coupling of shells in a carbon nanotube quantum dot
We systematically study the coupling of longitudinal modes (shells) in a
carbon nanotube quantum dot. Inelastic cotunneling spectroscopy is used to
probe the excitation spectrum in parallel, perpendicular and rotating magnetic
fields. The data is compared to a theoretical model including coupling between
shells, induced by atomically sharp disorder in the nanotube. The calculated
excitation spectra show good correspondence with experimental data.Comment: 8 pages, 4 figure
Meteorological application of Apollo photography Final report
Development of meteorological information and parameters based on cloud photographs taken during Apollo 9 fligh
A note on Kerr/CFT and free fields
The near-horizon geometry of the extremal four-dimensional Kerr black hole
and certain generalizations thereof has an SL(2,R) x U(1) isometry group.
Excitations around this geometry can be controlled by imposing appropriate
boundary conditions. For certain boundary conditions, the U(1) isometry is
enhanced to a Virasoro algebra. Here, we propose a free-field construction of
this Virasoro algebra.Comment: 10 pages, v2: comments and references adde
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