1,712 research outputs found
A Merger Scenario for the Dynamics of Abell 665
We present new redshift measurements for 55 galaxies in the vicinity of the
rich galaxy cluster Abell 665. When combined with results from the literature,
we have good velocity measurements for a sample of 77 confirmed cluster members
from which we derive the cluster's redshift z=0.1829 +/- 0.0005 and
line-of-sight velocity dispersion of 1390 +/- 120 km/s. Our analysis of the
kinematical and spatial data for the subset of galaxies located within the
central 750 kpc reveals only subtle evidence for substructure and
non-Gaussianity in the velocity distribution. We find that the brightest
cluster member is not moving significantly relative to the other galaxies near
the center of the cluster. On the other hand, our deep ROSAT high resolution
image of A665 shows strong evidence for isophotal twisting and centroid
variation, thereby confirming previous suggestions of significant substructure
in the hot X-ray--emitting intracluster gas. In light of this evident
substructure, we have compared the optical velocity data with N-body
simulations of head-on cluster mergers. We find that a merger of two similar
mass subclusters (mass ratios of 1:1 or 1:2) seen close to the time of
core-crossing produces velocity distributions that are consistent with that
observed.Comment: 30 pages and 7 figures. Accepted by the Astrophysical Journal Full
resoultion figures 1 and 3 available in postscript at
http://www.physics.rutgers.edu/~percy/A665paper.htm
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Kepler-4B: A Hot Neptune-Like Planet of A G0 Star Near Main-Sequence Turnoff
Early time-series photometry from NASA's Kepler spacecraft has revealed a planet transiting the star we term Kepler-4, at R.A. = 19(h)02(m)27.(s)68, delta = +50 degrees 08'08 '' 7. The planet has an orbital period of 3.213 days and shows transits with a relative depth of 0.87 x 10(-3) and a duration of about 3.95 hr. Radial velocity (RV) measurements from the Keck High Resolution Echelle Spectrometer show a reflex Doppler signal of 9.3(-1.9)(+1.1) m s(-1), consistent with a low-eccentricity orbit with the phase expected from the transits. Various tests show no evidence for any companion star near enough to affect the light curve or the RVs for this system. From a transit-based estimate of the host star's mean density, combined with analysis of high-resolution spectra, we infer that the host star is near turnoff from the main sequence, with estimated mass and radius of 1.223(-0.091)(+0.053) M(circle dot) and 1.487(-0.084)(+0.071) R(circle dot).We estimate the planet mass and radius to be {M(P), R(P)} = {24.5 +/- 3.8 M(circle plus), 3.99 +/- 0.21 R(circle plus)}. The planet's density is near 1.9 g cm(-3); it is thus slightly denser and more massive than Neptune, but about the same size.W. M. Keck FoundationNASA's Science Mission DirectorateAstronom
Using digital and hand printing techniques to compensate for loss: re-establishing colour and texture in historic textiles
Conservators use a range of 'gap filling' techniques to improve the structural stability and presentation of objects. Textile conservators often use fabric supports to provide reinforcement for weak areas of a textile and to provide a visual infill in missing areas. The most common technique is to use dyed fabrics of a single colour but while a plain dyed support provides good reinforcement, it can be visually obtrusive when used with patterned or textured textiles. Two recent postgraduate dissertation projects at the Textile Conservation Centre (TCC) have experimented with hand printing and digital imaging techniques to alter the appearance of support fabrics so that they are less visually obtrusive and blend well with the colour and texture of the textile being supported. Case studies demonstrate the successful use of these techniques on a painted hessian rocking horse and a knitted glove from an archaeological context
Architecture of Kepler's Multi-transiting Systems: II. New investigations with twice as many candidates
We report on the orbital architectures of Kepler systems having multiple
planet candidates identified in the analysis of data from the first six
quarters of Kepler data and reported by Batalha et al. (2013). These data show
899 transiting planet candidates in 365 multiple-planet systems and provide a
powerful means to study the statistical properties of planetary systems. Using
a generic mass-radius relationship, we find that only two pairs of planets in
these candidate systems (out of 761 pairs total) appear to be on Hill-unstable
orbits, indicating ~96% of the candidate planetary systems are correctly
interpreted as true systems. We find that planet pairs show little statistical
preference to be near mean-motion resonances. We identify an asymmetry in the
distribution of period ratios near first-order resonances (e.g., 2:1, 3:2),
with an excess of planet pairs lying wide of resonance and relatively few lying
narrow of resonance. Finally, based upon the transit duration ratios of
adjacent planets in each system, we find that the interior planet tends to have
a smaller transit impact parameter than the exterior planet does. This finding
suggests that the mode of the mutual inclinations of planetary orbital planes
is in the range 1.0-2.2 degrees, for the packed systems of small planets probed
by these observations.Comment: Accepted to Ap
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Channelling optics for high quality imaging of sensory hair
A long distance microscope (LDM) is extended by a lens and aperture array. This newly formed channelling LDM is superior in high quality, high-speed imaging of large field of views (FOV). It allows imaging the same FOV like a conventional LDM, but at improved magnification. The optical design is evaluated by calculations with the ray tracing code ZEMAX. High-speed imaging of a 2 × 2 mm(2) FOV is realized at 3.000 frames per second and 1 μm per pixel image resolution. In combination with flow sensitive hair the optics forms a wall shear stress sensor. The optics images the direct vicinity of twenty-one flow sensitive hair distributed in a quadratic array. The hair consists of identical micro-pillars that are 20 μm in diameter, 390 μm in length and made from polydimethylsiloxane (PDMS). Sensor validation is conducted in the transition region of a wall jet in air. The wall shear stress is calculated from optically measured micro-pillar tip deflections. 2D wall shear stress distributions are obtained with currently highest spatiotemporal resolution. The footprint of coherent vortical structures far away from the wall is recovered in the Fourier spectrum of wall shear stress fluctuations. High energetic patterns of 2D wall shear stress distributions are identified by proper orthogonal decomposition (POD)
Encodings of Range Maximum-Sum Segment Queries and Applications
Given an array A containing arbitrary (positive and negative) numbers, we
consider the problem of supporting range maximum-sum segment queries on A:
i.e., given an arbitrary range [i,j], return the subrange [i' ,j' ] \subseteq
[i,j] such that the sum of the numbers in A[i'..j'] is maximized. Chen and Chao
[Disc. App. Math. 2007] presented a data structure for this problem that
occupies {\Theta}(n) words, can be constructed in {\Theta}(n) time, and
supports queries in {\Theta}(1) time. Our first result is that if only the
indices [i',j'] are desired (rather than the maximum sum achieved in that
subrange), then it is possible to reduce the space to {\Theta}(n) bits,
regardless the numbers stored in A, while retaining the same construction and
query time. We also improve the best known space lower bound for any data
structure that supports range maximum-sum segment queries from n bits to
1.89113n - {\Theta}(lg n) bits, for sufficiently large values of n. Finally, we
provide a new application of this data structure which simplifies a previously
known linear time algorithm for finding k-covers: i.e., given an array A of n
numbers and a number k, find k disjoint subranges [i_1 ,j_1 ],...,[i_k ,j_k ],
such that the total sum of all the numbers in the subranges is maximized.Comment: 19 pages + 2 page appendix, 4 figures. A shortened version of this
paper will appear in CPM 201
Discovery of the Transiting Planet Kepler-5B
We present 44 days of high duty cycle, ultra precise photometry of the 13th magnitude star Kepler-5 (KIC 8191672, T(eff) = 6300 K, log g = 4.1), which exhibits periodic transits with a depth of 0.7%. Detailed modeling of the transit is consistent with a planetary companion with an orbital period of 3.548460 +/- 0.000032 days and a radius of 1.431(-0.052)(+0.041) R(J). Follow-up radial velocity measurements with the Keck HIRES spectrograph on nine separate nights demonstrate that the planet is more than twice as massive as Jupiter with a mass of 2.114(-0.059)(+0.056) M(J) and a mean density of 0.894 +/- 0.079 g cm(-3).NASA's Science Mission DirectorateAstronom
Kepler-7b: A Transiting Planet with Unusually Low Density
We report the discovery and confirmation of Kepler-7b, a transiting planet
with unusually low density. The mass is less than half that of Jupiter, Mp =
0.43 Mj, but the radius is fifty percent larger, Rp = 1.48 Rj. The resulting
density, 0.17 g/cc, is the second lowest reported so far for an extrasolar
planet. The orbital period is fairly long, P = 4.886 days, and the host star is
not much hotter than the Sun, Teff = 6000 K. However, it is more massive and
considerably larger than the sun, Mstar = 1.35 Msun and Rstar = 1.84 Rsun, and
must be near the end of its life on the Main Sequence.Comment: 19 pages, 3 figure
Kepler-47: A Transiting Circumbinary Multi-Planet System
We report the detection of Kepler-47, a system consisting of two planets
orbiting around an eclipsing pair of stars. The inner and outer planets have
radii 3.0 and 4.6 times that of the Earth, respectively. The binary star
consists of a Sun-like star and a companion roughly one-third its size,
orbiting each other every 7.45 days. With an orbital period of 49.5 days,
eighteen transits of the inner planet have been observed, allowing a detailed
characterization of its orbit and those of the stars. The outer planet's
orbital period is 303.2 days, and although the planet is not Earth-like, it
resides within the classical "habitable zone", where liquid water could exist
on an Earth-like planet. With its two known planets, Kepler-47 establishes that
close binary stars can host complete planetary systems.Comment: To appear on Science Express August 28, 11 pages, 3 figures, one
table (main text), 56 pages, 28 figures, 10 table
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