The AstroStat Slog » LF http://hea-www.harvard.edu/AstroStat/slog Weaving together Astronomy+Statistics+Computer Science+Engineering+Intrumentation, far beyond the growing borders Fri, 09 Sep 2011 17:05:33 +0000 en-US hourly 1 http://wordpress.org/?v=3.4 my first AAS. V. measurement error and EM http://hea-www.harvard.edu/AstroStat/slog/2008/first-aas-measurement-error-and-em/ http://hea-www.harvard.edu/AstroStat/slog/2008/first-aas-measurement-error-and-em/#comments Fri, 20 Jun 2008 03:46:05 +0000 hlee http://hea-www.harvard.edu/AstroStat/slog/?p=336 While discussing different view points on the term, clustering, one of the conversers led me to his colleague’s poster. This poster (I don’t remember its title and abstract) was my favorite from all posters in the meeting.

He rewrote the EM algorithm to include measurement errors in redshifts. Indexed parameters associated with different redshifts and corresponding standard deviations (measurement errors, treated as nuisance parameters) were included in the likelihood function that corrected bias and manifested bimodality in the LFs clearly at the different evolutionary stages.

I encouraged him to talk statisticians to characterize and to generalize his measurement error included likelihoods, and to optimize his EM algorithm. Because of approximations in algebra and the many parameters from measurement errors from redshifts, some assumptions and constraints were imposed intensively and I thought a collaboration with statisticians suits to get around constraints and to generalize his measurement error included likelihood.

]]> http://hea-www.harvard.edu/AstroStat/slog/2008/first-aas-measurement-error-and-em/feed/ 1 [ArXiv] 2nd week, June 2008 http://hea-www.harvard.edu/AstroStat/slog/2008/arxiv-2nd-week-june-2008/ http://hea-www.harvard.edu/AstroStat/slog/2008/arxiv-2nd-week-june-2008/#comments Mon, 16 Jun 2008 14:47:42 +0000 hlee http://hea-www.harvard.edu/AstroStat/slog/?p=335 As Prof. Speed said, PCA is prevalent in astronomy, particularly this week. Furthermore, a paper explicitly discusses R, a popular statistics package.

  • [astro-ph:0806.1140] N.Bonhomme, H.M.Courtois, R.B.Tully
        Derivation of Distances with the Tully-Fisher Relation: The Antlia Cluster
    (Tully Fisher relation is well known and one of many occasions statistics could help. On the contrary, astronomical biases as well as measurement errors hinder from the collaboration).
  • [astro-ph:0806.1222] S. Dye
        Star formation histories from multi-band photometry: A new approach (Bayesian evidence)
  • [astro-ph:0806.1232] M. Cara and M. Lister
        Avoiding spurious breaks in binned luminosity functions
    (I think that binning is not always necessary and overdosed, while there are alternatives.)
  • [astro-ph:0806.1326] J.C. Ramirez Velez, A. Lopez Ariste and M. Semel
        Strength distribution of solar magnetic fields in photospheric quiet Sun regions (PCA was utilized)
  • [astro-ph:0806.1487] M.D.Schneider et al.
        Simulations and cosmological inference: A statistical model for power spectra means and covariances
    (They used R and its package Latin hypercube samples, lhs.)
  • [astro-ph:0806.1558] Ivan L. Andronov et al.
        Idling Magnetic White Dwarf in the Synchronizing Polar BY Cam. The Noah-2 Project (PCA is applied)
  • [astro-ph:0806.1880] R. G. Arendt et al.
        Comparison of 3.6 – 8.0 Micron Spitzer/IRAC Galactic Center Survey Point Sources with Chandra X-Ray Point Sources in the Central 40×40 Parsecs (K-S test)
]]> http://hea-www.harvard.edu/AstroStat/slog/2008/arxiv-2nd-week-june-2008/feed/ 0 [ArXiv] 3rd week, May 2008 http://hea-www.harvard.edu/AstroStat/slog/2008/arxiv-3rd-week-may-2008/ http://hea-www.harvard.edu/AstroStat/slog/2008/arxiv-3rd-week-may-2008/#comments Mon, 26 May 2008 18:59:38 +0000 hlee http://hea-www.harvard.edu/AstroStat/slog/?p=316 Not many this week, but there’s a great read.

  • [stat.ME:0805.2756] Fionn Murtagh
    The Remarkable Simplicity of Very High Dimensional Data: Application of Model-Based Clustering

  • [astro-ph:0805.2945] Martin, de Jong, & Rix
    A comprehensive Maximum Likelihood analysis of the structural properties of faint Milky Way satellites

  • [astro-ph:0805.2946] Kelly, Fan, & Vestergaard
    A Flexible Method of Estimating Luminosity Functions [my subjective comment is added at the bottom]

  • [stat.ME:0805.3220] Bayarri, Berger, Datta
    Objective Bayes testing of Poisson versus inflated Poisson models (will it be of use when one is dealing with many zero background counts, underpopulated above zero background counts, and underpopulated source counts?)

[Comment] You must read it. It can serve as a very good Bayesian tutorial for astronomers. I think there’s a typo, nothing major, plus/minus sign in the likelihood, though. Tom Loredo kindly has informed through his extensive slog comments about Schechter function and this paper made me appreciate the gamma distribution more. Schechter function and the gamma density function share the same equation although the objective of their use does not have much to be shared (Forgive my Bayesian ignorance in the extensive usage of gamma distribution except the fact it’s a conjugate of Poisson or exponential distribution).

FYI, there was another recent arxiv paper on zero-inflation [stat.ME:0805.2258] by Bhattacharya, Clarke, & Datta
A Bayesian test for excess zeros in a zero-inflated power series distribution

]]> http://hea-www.harvard.edu/AstroStat/slog/2008/arxiv-3rd-week-may-2008/feed/ 0 [ArXiv] 4th week, Apr. 2008 http://hea-www.harvard.edu/AstroStat/slog/2008/arxiv-4th-week-apr-2008/ http://hea-www.harvard.edu/AstroStat/slog/2008/arxiv-4th-week-apr-2008/#comments Sun, 27 Apr 2008 15:29:48 +0000 hlee http://hea-www.harvard.edu/AstroStat/slog/?p=276 The last paper in the list discusses MCMC for time series analysis, applied to sunspot data. There are six additional papers about statistics and data analysis from the week.

  • [astro-ph:0804.2904]M. Cruz et al.
    The CMB cold spot: texture, cluster or void?

  • [astro-ph:0804.2917] Z. Zhu, M. Sereno
    Testing the DGP model with gravitational lensing statistics

  • [astro-ph:0804.3390] Valkenburg, Krauss, & Hamann
    Effects of Prior Assumptions on Bayesian Estimates of Inflation Parameters, and the expected Gravitational Waves Signal from Inflation

  • [astro-ph:0804.3413] N.Ball et al.
    Robust Machine Learning Applied to Astronomical Datasets III: Probabilistic Photometric Redshifts for Galaxies and Quasars in the SDSS and GALEX (Another related publication [astro-ph:0804.3417])

  • [astro-ph:0804.3471] M. Cirasuolo et al.
    A new measurement of the evolving near-infrared galaxy luminosity function out to z~4: a continuing challenge to theoretical models of galaxy formation

  • [astro-ph:0804.3475] A.D. Mackey et al.
    Multiple stellar populations in three rich Large Magellanic Cloud star clusters

  • [stat.ME:0804.3853] C. R\”over , R. Meyer, N. Christensen
    Modelling coloured noise (MCMC & sunspot data)
]]> http://hea-www.harvard.edu/AstroStat/slog/2008/arxiv-4th-week-apr-2008/feed/ 0 [ArXiv] 2nd week, Mar. 2008 http://hea-www.harvard.edu/AstroStat/slog/2008/arxiv-2nd-week-mar-2007/ http://hea-www.harvard.edu/AstroStat/slog/2008/arxiv-2nd-week-mar-2007/#comments Fri, 14 Mar 2008 19:44:34 +0000 hlee http://hea-www.harvard.edu/AstroStat/slog/2008/arxiv-2nd-week-mar-2007/ Warning! The list is long this week but diverse. Some are of CHASC’s obvious interest.

  • [astro-ph:0803.0997] V. Smolcic et.al.
       A new method to separate star forming from AGN galaxies at intermediate redshift: The submillijansky radio population in the VLA-COSMOS survey
  • [astro-ph:0803.1048] T.A. Carroll and M. Kopf
       Zeeman-Tomography of the Solar Photosphere — 3-Dimensional Surface Structures Retrieved from Hinode Observations
  • [astro-ph:0803.1066] M. Beasley et.al.
       A 2dF spectroscopic study of globular clusters in NGC 5128: Probing the formation history of the nearest giant Elliptical
  • [astro-ph:0803.1098] Z. Lorenzo
       A new luminosity function for galaxies as given by the mass-luminosity relationship
  • [astro-ph:0803.1199] D. Coe et.al.
       LensPerfect: Gravitational Lens Massmap Reconstructions Yielding Exact Reproduction of All Multiple Images (could it be related to GREAT08 Challenge?)
  • [astro-ph:0803.1213] H.Y.Wang et.al.
       Reconstructing the cosmic density field with the distribution of dark matter halos
  • [astro-ph:0803.1420] E. Lantz et.al.
       Multi-imaging and Bayesian estimation for photon counting with EMCCD’s
  • [astro-ph:0803.1491] Wu, Rozo, & Wechsler
       The Effect of Halo Assembly Bias on Self Calibration in Galaxy Cluster Surveys
  • [astro-ph:0803.1616] P. Mukherjee et.al.
       Planck priors for dark energy surveys (some CHASCians would like to check!)
  • [astro-ph:0803.1738] P. Mukherjee and A. R. Liddle
       Planck and reionization history: a model selection view
  • [astro-ph:0803.1814] J. Cardoso et.al.
       Component separation with flexible models. Application to the separation of astrophysical emissions
  • [astro-ph:0803.1851] A. R. Marble et.al.
        The Flux Auto- and Cross-Correlation of the Lyman-alpha Forest. I. Spectroscopy of QSO Pairs with Arcminute Separations and Similar Redshifts
  • [astro-ph:0803.1857] R. Marble et.al.
        The Flux Auto- and Cross-Correlation of the Lyman-alpha Forest. II. Modelling Anisotropies with Cosmological Hydrodynamic Simulations
]]> http://hea-www.harvard.edu/AstroStat/slog/2008/arxiv-2nd-week-mar-2007/feed/ 0 [ArXiv] NGC 6397 Deep ACS Imaging, Aug. 29, 2007 http://hea-www.harvard.edu/AstroStat/slog/2007/arxiv-ngc-6397-deep-acs-imaging/ http://hea-www.harvard.edu/AstroStat/slog/2007/arxiv-ngc-6397-deep-acs-imaging/#comments Wed, 05 Sep 2007 06:26:20 +0000 hlee http://hea-www.harvard.edu/AstroStat/slog/2007/arxiv-ngc-6397-deep-acs-imaging/ From arxiv/astro-ph:0708.4030v1
Deep ACS Imaging in the Globular Cluster NGC 6397: The Cluster Color Magnitude Diagram and Luminosity Function by H.B. Richer et.al

This paper presented an observational study of a globular cluster, named NGC 6397, enhanced and more informative compared to previous observations in a sense that 1) a truncation in the white dwarf cooling sequence occurs at 28 magnitude, 2) the cluster main sequence seems to terminate approximately at the hydrogen-burning limit predicted by two independent stellar evolution models, and 3) luminosity functions (LFs) or mass functions (MFs) are well defined. Nothing statistical, but the idea of defining color magnitude diagrams (CMDs) and LFs described in the paper, will assist developing suitable statistics on CMD and LF fitting problems in addition to the improved measurements (ACS imaging) of stars in NGC 6397.

Instead of adding details of data properties and calibration process including the instrument characteristics, I like to add a few things for statisticians: First, ACS stands for Advance Camera of Surveys and its information can be found at this link. Second, NGC is an abbreviation of New General Catalogue, one of astronomers’ cataloging systems (click for its wiki). Third, CMDs and LFs are results of data processing, described in the paper, but can be considered as scatter plots and kernel density plots (histograms) to be analyzed for inferencing physical parameters. This data processing, or calibration requires multi-level transformations, which cause error propagation. Finally, the chi-square method is incorporated to fit LFs and MFs. Among numerous fitting methods, in astronomy, only the chi-square is ubiquitously used (link to a discussion on the chi-square). Could we develop more robust statistics for fitting astronomical (empirical) functions?

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