http ://hea-www.harvard.edu/ AstroStat /slog/2008/eotw-chisq- distribution / Weaving together Astronomy+Statistics+Computer Science+Engineering+Intrumentation, far beyond the growing borders Fri, 01 Jun 2012 18:47:52 +0000 hourly 1 http ://wordpress.org/?v=3.4 http ://hea-www.harvard.edu/ AstroStat /slog/2008/eotw-chisq- distribution /comment-page-1/#comment-308 Alex Sun, 27 Jul 2008 01:52:08 +0000 http ://hea-www.harvard.edu/ ... Thanks, Aneta, very useful comment. ...

... We demonstrate through numerical simulations that model parameters estimated with our technique are essentially bias-free, even when the average number of counts per bin is 1. ... The IW technique avoids such biases by estimating through successive iterations, where for each iteration, j, , and the best-fit parameters are determined by minimization of . ... In our sample, we find that the minimum values and best-fit parameters converge after about 6 iterations. ...

The problem of solar wind data correlation for the observations onboard several spacecraft is very important for three points of view: . ... This problem is studied now in detail by systematic determination of ion flux and ion velocity data correlations by INTERBALL-1 (IKI group), WIND and IMP 8 (both - MIT group). ... Solar wind plasma correlation lengths from IMP 8, WIND and INTERBALL-1. ... Correlation of solar wind observations onboard several spacecraft: INTERBALL-1, IMP 8 and WIND data. ...

... PPTA timeline . ... List of projects . ... RedGW . ... One of the main goals of pulsar timing array projects is to limit the existence of a background of gravitational waves (GWs). Jenet et al. (2006) developed a method to determine such a limit if (and only if) the pulsar timing residuals were statistically white. In the paper we used data from six pulsars from the PPTA project to obtain a limit. The remaining pulsars were rejected because their timing residuals were not white. ...

Next: Star Formation Rate and Up: No Title Previous: Calculation of Evolutionary Tracks . To start calculations, we choose the distributions of the initial binary parameters: the mass of the primary ZAMS component, , binary mass ratio, , orbital separation a . ... whereas the mass ratio distribution is not. ... The zero assumption often made is that the mass ratio distribution has a flat shape, that is binaries with a high mass ratio occur as frequently as those with equal masses. ...

Next: The Newton--Raphson Method. Up: Fitting of Data Previous: Fitting of Data . ... In a linear problem, if the errors on the observations have a gaussian distribution, the ``Maximum Likelihood Principle'' gives you the ``best estimate'' of the parameters as the solution of the so-called ``Least Squares Minimization'' that follows: . ... A certain number of numerical methods have been developed to solve the non--linear least squares problem, four have so far been implemented in MIDAS. ...

... Fitting the observed dependence includes calculations of the polarization cross-sections averaged over particles orientation and size distribution, their normalization and the comparison of obtained dependencies with Serkowski's curve representing observational data for a chosen star. ... Variations of the polarization factors with wavelength are shown in Fig. 16 for homogeneous spheroidal particles with PF orientation. ... The distinction between prolate and oblate spheroids is also clearly seen. ...

... The package AMPLE (Adaptable Minor Planet Ephemerides) is dedicated to solving a number of problems concerning minor planets with the aid of IBM-type personal computer. ... Obtaining selection of orbital elements and/ or photometric parameters of minor planets in conformity with imposed restrictions. ... The orbital elements of all minor planets used in AMPLE for 2015 have been determined in IAA on the ground of available observations in the catalogue of observations of the Minor Planet Center. ...

... In brief: the frequency-dependent radiative transfer equation is solved for a dust under assumption of spherically-symmetric geometry for its distribution taking into account particle size distribution and quantum heating effects for the very small dust particles. ... Table: Model parameters for IRAS04296+3429. ... parameter . ... hot dust shell) . ... The best fit to the spectral energy distribution of IRAS04296 is shown by heavy solid line (see Table2 for details concerning parameters of the model...

. N OTE: . Only clusters with R<60 kpc were used to compute the spatial parameters and metallicity gradients for all subsystems except the corona. The numbers in parantheses give the number of clusters for which the corresponding parameter is known. The X O scale length of the old halo is strongly distorted by the observed asymmetry of the distribution of the corresponding clusters projected onto the XY plane ( Fig. 4А ) . discussion in the text | previous table .

... Default . ... The descriptions below focus on the meaning of each filename parameter, leaving the exact details of the inferred default value to be explained in the algorithm section. evlist . ... file . The response matrix file (OGIP-compliant format). ... If a spectrum file is not provided ( withspectrum =no) this parameter specifies the INDEX number of a source in the source description list (parameter srclist ), and thereby the incidence angle and selection regions for the response matrix. ...

Next: Solution Up: Simultaneous Phase Retrieval and Previous: Data Model . Following Snyder, Hammoud, and White (1993), we simplify the noise model by defining the modified data . ... In this case, the modified data are approximately equal in distribution to a Poisson process whose mean function is . Therefore, the pseudo-log-likelihood takes the form . ... An explicit, closed form solution to this problem is not known. ...

... The Radon transform (also known as the Hough transform) is formulated as a family of line integrals through a two-dimensional function. ... The Radon transform provides us with a simple means of computing the FF plane of the autochirplet transform, by using the Wigner distribution, and arriving at a transform space that tells us basically the same information as the chirplet FF-plane, except that we benefit from the greater resolution of the Wigner distribution. ...

Some peculiarities of orbits of observed comets. ... Icarus, 2005 Simulation and reality Distribution of anti-perihelia of short-period comets with e 0.9 ( ecliptic coordinates ) Distribution of anti-perihelia of short-period comets with e 0.9 ( ecliptic coordinates ) Distribution of anti-perihelia of long-period comets with 0.9 e 1 ( ecliptic coordinates ) ­ ...

Next: The Evolution of Stars Up: NICMOS Science Previous: A Coronagraphic Search for . ... The NICMOS Parallel program . ... The Stellar Population . ... NICMOS Camera 3 is being used in parallel mode to observe galactic fields at both high and low galactic latitudes. ... Most of the fields are at high galactic latitude; as Figure 1 shows, only 8 pointings are within |b| = 10 o , i.e. the galactic disk. Figure 1: NICMOS parallel fields distribution in galactic latitude. ... Figure 6 ). ...

Statistics for Astronomy IV: Maximum Likelihood B. Nikolic b.nikolic@mrao.cam.ac.uk Astrophysics Group, Cavendish Laboratory, University of Cambridge http://www.mrao.cam.ac.uk/~bn204/lecture/astrostats.html 3 November 2008 Goals for this Lecture Maximum Likelihood Example Recap Alternatives to ML How to find the Maximum Likelihood Errors estimation in Maximum Likelihood Monte Carlo simulation Problems Outline ... or equivalently the log-likelihood log L( ). ...

In this chapter we will consider an example of visual expert system written on the Actor Prolog language. ... There are a lot of methods of oil field bed stimulation that increase output of the oil production: thermal, physical-chemical, gas, microbiological, and others. ... Fig. ... The Top-Most diagram consists of three blocks: the "Describe parameters of hydrocarbon field" block, the "Check adaptability of existed methods of oil production" block, and the "Display solution" block. ... Gas methods. ...

... The sample of the Local Volume galaxies (distance smaller than 10 Mpc) gives a unique opportunity to study the properties of galaxies including the weakest objects: the absolute magnitude M B -10 and the virial mass M vir 10 9 M x263C;. ... Luminosity function of the Local Volume galaxies. ... The luminosity functions for galaxies are presented: red dashed line - from the 2dFGRS survey (Norberg et al. 2002); blue dash-dotted line - from the SDSS survey (Blanton et al. ...

... Subject and Problems of Stellar Astronomy. ... Plane of Galaxy, Methods of Its Location Determination. ... Stars Distances. ... Other Methods of Stars Distances Determination. ... Tangential Velocities, Their Determination by Self-Motions. ... Determination of Solar Apex and Spatial Velocity by Radial and Spatial Velocities of Stars. ... Features of Orientation and Parameters of Peculiar Stellar Velocities Ellipsoid. ... General and Selective Light Absorption in Galaxy. ... Darc Clouds in Galaxy. ...

Hideyuki Saio Simon Jeffery are exploring models for the evolution of stars formed by the merger of two white dwarfs. The attached movie provides a simulation of the major events involved in the merger process. ... An initial binary system consists of two white dwarfs of masses M 1 and M 2 (given) with an orbital period ( P ). ... We adopt a simple expression for the white dwarf radius as a function of mass (in solar units): . ... The merged star evolution is simulated by a quadratic expansion . ...