3,317 research outputs found
Moths and How to Rear Them. Paul Villiard. New York: Funk and Wagnalls, 1969. xiv, 242 pp. $10.00.
Excerpt: W.J.B. Crotch\u27s A Silkmoth Rearer\u27s Handbook (1956) and Wild Silk Moths of the United States by Michael Collins and Robert Weast (1961) have been standard rearers\u27 manuals for some time, but both are limited to one group of large moths, and there has been a decided need for a low-priced guide covering rearing procedures for a much wider range of Lepidoptera. For a number of reasons, Villiard\u27s book falls short of this goal
A Very Hot, High Redshift Cluster of Galaxies: More Trouble for Omega_0 = 1
We have observed the most distant (z=0.829) cluster of galaxies in the
Einstein Extended Medium Sensitivity Survey, with the ASCA and ROSAT
satellites. We find an X-ray temperature of 12.3 +3.1/-2.2 keV for this
cluster, and the ROSAT map reveals significant substructure. The high
temperature of MS1054-0321 is consistent with both its approximate velocity
dispersion, based on the redshifts of 12 cluster members we have obtained at
the Keck and the Canada-France-Hawaii telescopes, and with its weak lensing
signature. The X-ray temperature of this cluster implies a virial mass ~ 7.4 x
10^14 h^-1 solar masses, if the mean matter density in the universe equals the
critical value, or larger if Omega_0 < 1. Finding such a hot, massive cluster
in the EMSS is extremely improbable if clusters grew from Gaussian
perturbations in an Omega_0 = 1 universe. Combining the assumptions that
Omega_0 = 1 and that the intial perturbations were Gaussian with the observed
X-ray temperature function at low redshift, we show that the probability of
this cluster occurring in the volume sampled by the EMSS is less than a few
times 10^{-5}. Nor is MS1054-0321 the only hot cluster at high redshift; the
only two other EMSS clusters already observed with ASCA also have
temperatures exceeding 8 keV. Assuming again that the initial perturbations
were Gaussian and Omega_0 = 1, we find that each one is improbable at the <
10^{-2} level. These observations, along with the fact that these luminosities
and temperatures of the high- clusters all agree with the low-z L_X-T_X
relation, argue strongly that Omega_0 < 1. Otherwise, the initial perturbations
must be non-Gaussian, if these clusters' temperatures do indeed reflect their
gravitational potentials.Comment: 20 pages, 4 figures, To appear in 1 Aug 1998 ApJ (heavily revised
version of original preprint
No planet for HD 166435
The G0V star HD166435 has been observed by the fiber-fed spectrograph ELODIE
as one of the targets in the large extra-solar planet survey that we are
conducting at the Observatory of Haute-Provence. We detected coherent,
low-amplitude, radial-velocity variations with a period of 3.7987days,
suggesting a possible close-in planetary companion. Subsequently, we initiated
a series of high-precision photometric observations to search for possible
planetary transits and an additional series of CaII H and K observations to
measure the level of surface magnetic activity and to look for possible
rotational modulation. Surprisingly, we found the star to be photometrically
variable and magnetically active. A detailed study of the phase stability of
the radial-velocity signal revealed that the radial-velocity variability
remains coherent only for durations of about 30days. Analysis of the time
variation of the spectroscopic line profiles using line bisectors revealed a
correlation between radial velocity and line-bisector orientation. All of these
observations, along with a one-quarter cycle phase shift between the
photometric and the radial-velocity variationss, are well explained by the
presence of dark photospheric spots on HD166435. We conclude that the
radial-velocity variations are not due to gravitational interaction with an
orbiting planet but, instead, originate from line-profile changes stemming from
star spots on the surface of the star. The quasi-coherence of the
radial-velocity signal over more than two years, which allowed a fair fit with
a binary model, makes the stability of this star unusual among other active
stars. It suggests a stable magnetic field orientation where spots are always
generated at about the same location on the surface of the star.Comment: 9 pages, 8 figures, Accepted for publication in A&
Star Formation, Radio Sources, Cooling X-ray Gas, and Galaxy Interactions in the Brightest Cluster Galaxy in 2A0335+096
We present deep emission-line imaging taken with the SOAR Optical Imaging
Camera of the brightest cluster galaxy (BCG) in the nearby (z=0.035) X-ray
cluster 2A0335+096. We analyze long-slit optical spectroscopy, archival VLA,
Chandra X-ray, and XMM UV data. 2A0335+096 is a bright, cool-core X-ray
cluster, once known as a cooling flow. Within the highly disturbed core
revealed by Chandra X-ray observations, 2A0335+096 hosts a highly structured
optical emission-line system. The redshift of the companion is within 100 km/s
of the BCG and has certainly interacted with the BCG, and is likely bound to
it. The comparison of optical and radio images shows curved filaments in
H-alpha emission surrounding the resolved radio source. The velocity structure
of the emission-line bar between the BCG nucleus and the companion galaxy
provides strong evidence for an interaction between the two in the last ~50
Myrs. The age of the radio source is similar to the interaction time, so this
interaction may have provoked an episode of radio activity. We estimate a star
formation rate of >7 solar mass/yr based on the Halpha and archival UV data, a
rate similar to, but somewhat lower than, the revised X-ray cooling rate of
10-30 solar masses/year estimated from XMM spectra by Peterson & workers. The
Halpha nebula is limited to a region of high X-ray surface brightness and cool
X-ray temperature. The detailed structures of H-alpha and X-ray gas differ. The
peak of the X-ray emission is not the peak of H-alpha emission, nor does it lie
in the BCG. The estimated age of the radio lobes and their interaction with the
optical emission-line gas, the estimated timescale for depletion and
accumulation of cold gas, and the dynamical time in the system are all similar,
suggesting a common trigger mechanism.Comment: Accepted AJ, July 2007 publication. Vol 134, p. 14-2
H-alpha tail, intracluster HII regions and star-formation: ESO137-001 in Abell 3627
We present the discovery of a 40 kpc H-alpha tail and at least 29
emission-line objects downstream of a star-forming galaxy ESO 137-001 in the
rich, nearby cluster A3627. The galaxy is known to possess a dramatic 70 kpc
X-ray tail. The detected H-alpha tail coincides positionally with the X-ray
tail. The H-alpha emission in the galaxy is sharply truncated on the front and
the sides near the nucleus, indicating significant ram pressure stripping. ESO
137-001 is thus the first cluster late-type galaxy known unambiguously with
both an X-ray tail and an H-alpha tail. The emission-line objects are all
distributed downstream of the galaxy, with projected distance up to 39 kpc from
the galaxy. From the analysis on the H-alpha_{off} frame and the estimate of
the background emission-line objects, we conclude that it is very likely all 29
emission-line objects are HII regions in A3627. The high surface number density
and luminosities of these HII regions (up to 10^40 ergs/s) dwarf the previously
known examples of isolated HII regions in clusters. We suggest that star
formation may proceed in the stripped ISM, in both the galactic halo and
intracluster space. The total mass of formed stars in the stripped ISM of ESO
137-001 may approach several times 10^7 solar masses. Therefore, stripping of
the ISM not only contributes to the ICM, but also adds to the intracluster
stellar light through subsequent star formation. The data also imply that ESO
137-001 is in an active stage of transformation, accompanied by the build-up of
a central bulge and depletion of the ISM.Comment: 16 pages, 1 table, 6 figures (4 in color), emulateapj5.sty, to appear
in ApJ, December 10, 2007, v671, n1. Spectroscopic data added; minor revision
and conclusions unchanged. Please read the paper with the full-resolution
figures at http://www.pa.msu.edu/~sunm/eso137_001_Ha_v1.3.ps.g
Chandra detection of the intracluster medium around 3C294 at z=1.786
We present a Chandra observation of the powerful radio galaxy 3C294 showing
clear evidence for a surrounding intracluster medium. At a redshift of 1.786
this is the most distant cluster of galaxies yet detected in X-rays. The radio
core is detected as a point source, which has a spectrum consistent with a
heavily-absorbed power law implying an intrinsic 2-10 keV luminosity of ~10^45
erg/s. A small excess of emission is associated with the southern radio
hotspots. The soft, diffuse emission from the intracluster medium is centred on
the radio source. It has an hour-glass shape in the N-S direction, extending to
radii of at least 100 kpc, well beyond the radio source. The X-ray spectrum of
this extended component is fit by a thermal model with temperature ~5 keV, or
by gas cooling from above 7 keV at rates of ~400-700 Msolar/yr. The rest-frame
0.3-10 keV luminosity of the cluster is ~4.5x10^44 erg/s. The existence of such
a cluster is consistent with a low density universe.Comment: 5 pages, 6 figures, accepted by MNRA
Coupling and induced depinning of magnetic domain walls in adjacent spin valve nanotracks
The magnetostatic interaction between magnetic domain walls (DWs) in adjacent
nanotracks has been shown to produce strong inter-DW coupling and mutual
pinning. In this paper, we have used electrical measurements of adjacent
spin-valve nanotracks to follow the positions of interacting DWs. We show that
the magnetostatic interaction between DWs causes not only mutual pinning, as
observed till now, but that a travelling DW can also induce the depinning of
DWs in near-by tracks. These effects may have great implications for some
proposed high density magnetic devices (e.g. racetrack memory, DW logic
circuits, or DW-based MRAM).Comment: The following article has been accepted by the Journal of Applied
Physic
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