246 research outputs found
Extreme Ultraviolet Emission in the Fornax Cluster of Galaxies
We present studies of the Extreme Ultraviolet (EUV) emission in the Fornax
cluster of galaxies; a relatively nearby well-studied cluster with X-ray
emitting cluster gas and a very large radio source. We examine both the
large-scale (~size of the X-ray emitting cluster gas), and the small-scale
(<arcmin) emission.
We find that this cluster has large-scale diffuse EUV emission. However, at
the sensitivity level of the existing EUVE data, this emission is due entirely
to the low energy tail of the X-ray emitting gas. We have also examined
small-scale structures in raw EUVE images of this cluster. We find that
small-scale irregularities are present in all raw Deep Survey images as a
result of small-scale detector effects. These effects can be removed by
appropriate flat-fielding. After flat-fielding, the Fornax cluster still shows
a few significant regions of small-scale EUV enhancement. We find that these
are emission from stars and galaxies in the field. We find that at existing
levels of sensitivity, there is no excess EUV emission in the cluster on either
large or small scales.Comment: 6 pages, 3 eps figures, aastex5, Accepted to ApJ
A 1.1 to 1.9 GHz SETI Survey of the Kepler Field: I. A Search for Narrow-band Emission from Select Targets
We present a targeted search for narrow-band (< 5 Hz) drifting sinusoidal
radio emission from 86 stars in the Kepler field hosting confirmed or candidate
exoplanets. Radio emission less than 5 Hz in spectral extent is currently known
to only arise from artificial sources. The stars searched were chosen based on
the properties of their putative exoplanets, including stars hosting candidates
with 380 K > T_eq > 230 K, stars with 5 or more detected candidates or stars
with a super-Earth (R_p 50 day orbit. Baseband voltage data
across the entire band between 1.1 and 1.9 GHz were recorded at the Robert C.
Byrd Green Bank Telescope between Feb--Apr 2011 and subsequently searched
offline. No signals of extraterrestrial origin were found. We estimate that
fewer than ~1% of transiting exoplanet systems host technological civilizations
that are radio loud in narrow-band emission between 1-2 GHz at an equivalent
isotropically radiated power (EIRP) of ~1.5 x 10^21 erg s^-1, approximately
eight times the peak EIRP of the Arecibo Planetary Radar, and we limit the the
number of 1-2 GHz narrow-band-radio-loud Kardashev type II civilizations in the
Milky Way to be < 10^-6 M_solar^-1. Here we describe our observations, data
reduction procedures and results.Comment: Accepted to the Astrophysical Journa
Far-Ultraviolet Cooling Features of the Antlia Supernova Remnant
We present far-ultraviolet observations of the Antlia supernova remnant
obtained with Far-ultraviolet IMaging Spectrograph (FIMS, also called SPEAR).
The strongest lines observed are C IV 1548,1551 and C III 977. The C IV
emission of this mixed-morphology supernova remnant shows a clumpy
distribution, and the line intensity is nearly constant with radius. The C III
977 line, though too weak to be mapped over the whole remnant, is shown to vary
radially. The line intensity peaks at about half the radius, and drops at the
edge of the remnant. Both the clumpy distribution of C IV and the rise in the C
IV to C III ratio towards the edge suggest that central emission is from
evaporating cloudlets rather than thermal conduction in a more uniform, dense
medium.Comment: 9 pages, 4 figures, will be published in ApJ December 1, 2007, v670n2
issue. see http://astro.snu.ac.kr/~jhshinn/ms.pd
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