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Source regions of banded chorus
Pickett, J. S.; Inan, U. S.; Bell, T. F. +1 more
ELF/VLF chorus emissions are very intense electromagnetic plasma waves that are naturally and spontaneously excited near the magnetic equatorial plane outside the plasmasphere during periods of magnetic disturbance. These emissions are believed to play an important role in the acceleration of 10 to 100 keV radiation belt electrons to MeV energies …
Global Twist of Sunspot Magnetic Fields Obtained from High-Resolution Vector Magnetograms
Tiwari, Sanjiv Kumar; Venkatakrishnan, P.; Sankarasubramanian, K.
The presence of fine structures in sunspot vector magnetic fields has been confirmed from Hinode as well as other earlier observations. We studied 43 sunspots based on the data sets taken from ASP/DLSP, Hinode (SOT/SP), and SVM (USO). In this Letter, (1) we introduce the concept of signed shear angle (SSA) for sunspots and establish its importance…
Imaging the Circumnuclear Region of NGC 1365 with Chandra
Elvis, M.; Fabbiano, G.; Howell, J. H. +4 more
We present the first Chandra/ACIS imaging study of the circumnuclear region of the nearby Seyfert galaxy NGC 1365. The X-ray emission is resolved into pointlike sources and complex, extended emission. The X-ray morphology of the extended emission shows a biconical soft X-ray-emission region extending ~5 kpc in projection from the nucleus, coincide…
Titan's hydrodynamically escaping atmosphere: Escape rates and the structure of the exobase region
Strobel, Darrell F.
In Strobel [Strobel, D.F., 2008. Icarus, 193, 588-594] a mass loss rate from Titan's upper atmosphere, ∼4.5×10 amus, was calculated for a single constituent, N 2 atmosphere by hydrodynamic escape as a high density, slow outward expansion driven principally by solar UV heating due to CH 4 absorption. It was estimated, but not …
The possible role of vortex shedding in the excitation of kink-mode oscillations in the solar corona
Nakariakov, V. M.; Aschwanden, M. J.; van Doorsselaere, T.
We propose a model for the excitation of horizontally polarised transverse (kink) magnetoacoustic oscillations of solar coronal loops by upflows associated with coronal mass ejections. If the magnetic field in the plasma that is dragged in the vertical direction by the flow is parallel to the loop, the phenomenon of vortex shedding causes the appe…
A robust morphological classification of high-redshift galaxies using support vector machines on seeing limited images. II. Quantifying morphological k-correction in the COSMOS field at 1 < z < 2: Ks band vs. I band
Rouan, D.; Sanders, D. B.; Salvato, M. +10 more
Context: Morphology is the most accessible tracer of galaxies physical structure, but its interpretation in the framework of galaxy evolution still remains problematic. Its quantification at high redshift requires deep high-angular resolution imaging, which is why space data (HST) are usually employed. At z > 1, the HST visible cameras however …
An Extended Dust Disk in a Spiral Galaxy: An Occulting Galaxy Pair in the ACS Nearby Galaxy Survey Treasury
Dalcanton, J. J.; Holwerda, B. W.; Keel, W. C. +2 more
We present an analysis of an occulting galaxy pair, serendipitously discovered in the ACS Nearby Galaxy Survey Treasury observations of NGC 253 taken with the Hubble Space Telescope's (HST) Advanced Camera for Surveys in F475W, F606W, and F814W (SDSS - g, broad V, and I). The foreground disk system (at z <= 0.06) shows a dusty disk much more ex…
The Mid-Infrared Continua of Seyfert Galaxies
Kraemer, S. B.; Crenshaw, D. M.; Richards, Gordon T. +1 more
An analysis of archival mid-infrared (mid-IR) spectra of Seyfert galaxies from the Spitzer Space Telescope observations is presented. We characterize the nature of the mid-IR active nuclear continuum by subtracting a template starburst spectrum from the Seyfert spectra. The long wavelength part of the spectrum contains a strong contribution from t…
An HST/ACS investigation of the spatial and chemical structure and sub-structure of NGC 891, a Milky Way analogue
Ibata, Rodrigo; Mouhcine, Mustapha; Rejkuba, Marina
We present a structural analysis of NGC 891, an edge-on galaxy that has long been considered to be an analogue of the Milky Way. Using star-counts derived from deep Hubble Space Telescope/Advanced Camera for Surveys (HST/ACS) images, we detect the presence of a thick disc component in this galaxy with vertical scaleheight hZ = 1.44 +/- …
M31* and its circumnuclear environment
Wakker, Bart P.; Wang, Q. Daniel; Li, Zhiyuan
We present a multiwavelength investigation of the circumnuclear environment of the Andromeda galaxy (M31), utilizing archival Chandra, FUSE, GALEX, HST and Spitzer data as well as ground-based observations. Based on the Chandra/ACIS data, we tightly constrain the X-ray luminosity of M31*, the central supermassive black hole (SMBH) of the galaxy, t…