86 research outputs found
Planet geometric center tracker, volume 1 Final report, Oct. 1964 - Jul. 1967
Tracker for locating geometric centers of Mars, Venus, or Jupite
Redshifts and Velocity Dispersions of Galaxy Clusters in the Horologium-Reticulum Supercluster
We present 118 new optical redshifts for galaxies in 12 clusters in the
Horologium-Reticulum supercluster (HRS) of galaxies. For 76 galaxies, the data
were obtained with the Dual Beam Spectrograph on the 2.3m telescope of the
Australian National University at Siding Spring Observatory. After combining 42
previously unpublished redshifts with our new sample, we determine mean
redshifts and velocity dispersions for 13 clusters, in which previous
observational data were sparse. In six of the 13 clusters, the newly determined
mean redshifts differ by more than 750 km/s from the published values. In the
case of three clusters, A3047, A3109, and A3120, the redshift data indicate the
presence of multiple components along the line of sight. The new cluster
redshifts, when combined with other reliable mean redshifts for clusters in the
HRS, are found to be distinctly bi-modal. Furthermore, the two redshift
components are consistent with the bi-modal redshift distribution found for the
inter-cluster galaxies in the HRS by Fleenor et al. (2005).Comment: 13 pages, 3 figures, Accepted to A
XO-3b: A Massive Planet in an Eccentric Orbit Transiting an F5V Star
We report the discovery of a massive (Mpsini = 13.02 +/- 0.64 Mjup; total
mass 13.25 +/- 0.64 Mjup), large (1.95 +/- 0.16 Rjup) planet in a transiting,
eccentric orbit (e = 0.260 +/- 0.017) around a 10th magnitude F5V star in the
constellation Camelopardalis. We designate the planet XO-3b, and the star XO-3,
also known as GSC 03727-01064. The orbital period of XO-3b is 3.1915426 +/-
0.00014 days. XO-3 lacks a trigonometric distance; we estimate its distance to
be 260 +/- 23 pc. The radius of XO-3 is 2.13 +/- 0.21 Rsun, its mass is 1.41
+/- 0.08 Msun, its vsini = 18.54 +/- 0.17 km/s, and its metallicity is [Fe/H] =
-0.177 +/- 0.027. This system is unusual for a number of reasons. XO-3b is one
of the most massive planets discovered around any star for which the orbital
period is less than 10 days. The mass is near the deuterium burning limit of 13
Mjup, which is a proposed boundary between planets and brown dwarfs. Although
Burrows et al. (2001) propose that formation in a disk or formation in the
interstellar medium in a manner similar to stars is a more logical way to
differentiate planets and brown dwarfs, our current observations are not
adequate to address this distinction. XO-3b is also unusual in that its
eccentricity is large given its relatively short orbital period. Both the
planetary radius and the inclination are functions of the spectroscopically
determined stellar radius. Analysis of the transit light curve of XO-3b
suggests that the spectroscopically derived parameters may be over estimated.
Though relatively noisy, the light curves favor a smaller radius in order to
better match the steepness of the ingress and egress. The light curve fits
imply a planetary radius of 1.25 +/- 0.15 Rjup, which would correspond to a
mass of 12.03 +/- 0.46 Mjup.Comment: 26 pages, 10 figures. Accepted by ApJ. Current version has several
small corrections as a result of a bug in the fitting softwar
XO-2b: Transiting Hot Jupiter in a Metal-rich Common Proper Motion Binary
We report on a V=11.2 early K dwarf, XO-2 (GSC 03413-00005), that hosts a
Rp=0.98+0.03/-0.01 Rjup, Mp=0.57+/-0.06 Mjup transiting extrasolar planet,
XO-2b, with an orbital period of 2.615857+/-0.000005 days. XO-2 has high
metallicity, [Fe/H]=0.45+/-0.02, high proper motion, mu_tot=157 mas/yr, and has
a common proper motion stellar companion with 31" separation. The two stars are
nearly identical twins, with very similar spectra and apparent magnitudes. Due
to the high metallicity, these early K dwarf stars have a mass and radius close
to solar, Ms=0.98+/-0.02 Msolar and Rs=0.97+0.02/-0.01 Rsolar. The high proper
motion of XO-2 results from an eccentric orbit (Galactic pericenter, Rper<4
kpc) well confined to the Galactic disk (Zmax~100 pc). In addition, the phase
space position of XO-2 is near the Hercules dynamical stream, which points to
an origin of XO-2 in the metal-rich, inner Thin Disk and subsequent dynamical
scattering into the solar neighborhood. We describe an efficient Markov Chain
Monte Carlo algorithm for calculating the Bayesian posterior probability of the
system parameters from a transit light curve.Comment: 14 pages, 10 Figures, Accepted in ApJ. Negligible changes to XO-2
system properties. Removed Chi^2 light curve analysis section, and simplified
MCMC light curve analysis discussio
Luminous superclusters: remnants from inflation
We derive the luminosity and multiplicity functions of superclusters compiled
for the 2dF Galaxy Redshift Survey, the Sloan Digital Sky Survey (Data Release
4), and for three samples of simulated superclusters. We find for all
supercluster samples Density Field (DF) clusters, which represent high-density
peaks of the class of Abell clusters, and use median luminosities/masses of
richness class 1 DF-clusters to calculate relative luminosity/mass functions.
We show that the fraction of very luminous (massive) superclusters in real
samples is more than tenfolds greater than in simulated samples. Superclusters
are generated by large-scale density perturbations which evolve very slowly.
The absence of very luminous superclusters in simulations can be explained
either by non-proper treatment of large-scale perturbations, or by some yet
unknown processes in the very early Universe.Comment: 6 pages, 3 Figures, submitted for Astronomy and Astrophysic
Superclusters of galaxies from the 2dF redshift survey. I. The catalogue
We use the 2dF Galaxy Redshift Survey data to compile catalogues of
superclusters for the Northern and Southern regions of the 2dFGRS, altogether
543 superclusters at redshifts 0.009 < z < 0.2. We analyse methods of compiling
supercluster catalogues and use results of the Millennium Simulation to
investigate possible selection effects and errors. We find that the most
effective method is the density field method using smoothing with an
Epanechnikov kernel of radius 8 Mpc/h. We derive positions of the highest
luminosity density peaks and find the most luminous cluster in the vicinity of
the peak, this cluster is considered as the main cluster and its brightest
galaxy the main galaxy of the supercluster. In catalogues we give equatorial
coordinates and distances of superclusters as determined by positions of their
main clusters. We also calculate the expected total luminosities of the
superclusters.Comment: 16 pages, 11 figures, submitted for Astronomy and Astrophysics.
High-resolution pdf file and supplementary data can be found at
http://www.aai.ee/~maret/2dfscl.htm
Superclusters of galaxies from the 2dF redshift survey. II. Comparison with simulations
We investigate properties of superclusters of galaxies found on the basis of
the 2dF Galaxy Redshift Survey, and compare them with properties of
superclusters from the Millennium Simulation. We study the dependence of
various characteristics of superclusters on their distance from the observer,
on their total luminosity, and on their multiplicity. The multiplicity is
defined by the number of Density Field (DF) clusters in superclusters. Using
the multiplicity we divide superclusters into four richness classes: poor,
medium, rich and extremely rich. We show that superclusters are asymmetrical
and have multi-branching filamentary structure, with the degree of asymmetry
and filamentarity being higher for the more luminous and richer superclusters.
The comparison of real superclusters with Millennium superclusters shows that
most properties of simulated superclusters agree very well with real data, the
main differences being in the luminosity and multiplicity distributions.Comment: 15 pages, 13 Figures, submitted for Astronomy and Astrophysic
The richest superclusters. I. Morphology
We study the morphology of the richest superclusters from the catalogues of
superclusters of galaxies in the 2dF Galaxy Redshift Survey and compare the
morphology of real superclusters with model superclusters in the Millennium
Simulation. We use Minkowski functionals and shapefinders to quantify the
morphology of superclusters: their sizes, shapes, and clumpiness. We generate
empirical models of simple geometry to understand which morphologies correspond
to the supercluster shapefinders. We show that rich superclusters have
elongated, filamentary shapes with high-density clumps in their core regions.
The clumpiness of superclusters is determined using the fourth Minkowski
functional . In the - shapefinder plane the morphology of
superclusters is described by a curve which is characteristic to
multi-branching filaments. We also find that the differences between the fourth
Minkowski functional for the bright and faint galaxies in observed
superclusters are larger than in simulated superclusters.Comment: 14 pages, 8 figures, submitted to Astronomy and Astrophysic
2nd Annual Computer & Technology Law Institute
Materials from the 2nd Annual Computer & Technology Law Institute held by UK/CLE in March 2000
High Levels of Serum Prolactin Protect Against Diabetic Retinopathy by Increasing Ocular Vasoinhibins
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