Comments on: Eddington versus Malmquist http://hea-www.harvard.edu/AstroStat/slog/2008/eddington-versus-malmquist/ 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 By: hlee http://hea-www.harvard.edu/AstroStat/slog/2008/eddington-versus-malmquist/comment-page-1/#comment-178 hlee Fri, 28 Mar 2008 04:38:48 +0000 http://hea-www.harvard.edu/AstroStat/slog/2008/eddington-versus-malmquist/#comment-178 That SAO is the SAO that I know of. :) Smithsonian Astrophysical Observatory That SAO is the SAO that I know of. :) Smithsonian Astrophysical Observatory

]]>
By: vlk http://hea-www.harvard.edu/AstroStat/slog/2008/eddington-versus-malmquist/comment-page-1/#comment-177 vlk Fri, 28 Mar 2008 02:01:14 +0000 http://hea-www.harvard.edu/AstroStat/slog/2008/eddington-versus-malmquist/#comment-177 The Eddington bias, as formulated by the man himself, applies at all intensities. Removing it is essentially the same as deconvolving with the Poisson (or Gaussian) distribution. It is prominent and unignorable for faint sources near the detection limit. Just to clarify, the Malmquist bias is not cosmological. (The SAO star catalog is at http://webviz.u-strasbg.fr/viz-bin/VizieR?-source=I/131A ) To make it work like data augmentation, your model will have to extend to the largest distance that your brightest conceivable source could be seen at. At which point your code will become extremely inefficient. The Eddington bias, as formulated by the man himself, applies at all intensities. Removing it is essentially the same as deconvolving with the Poisson (or Gaussian) distribution. It is prominent and unignorable for faint sources near the detection limit.

Just to clarify, the Malmquist bias is not cosmological. (The SAO star catalog is at http://webviz.u-strasbg.fr/viz-bin/VizieR?-source=I/131A ) To make it work like data augmentation, your model will have to extend to the largest distance that your brightest conceivable source could be seen at. At which point your code will become extremely inefficient.

]]>
By: hlee http://hea-www.harvard.edu/AstroStat/slog/2008/eddington-versus-malmquist/comment-page-1/#comment-176 hlee Thu, 27 Mar 2008 17:09:49 +0000 http://hea-www.harvard.edu/AstroStat/slog/2008/eddington-versus-malmquist/#comment-176 Malmquist bias sounds equivalent to missing data model: upon knowing a cosmological model (IMF or some mass distribution?), roughly one knows the proportion of observables, although I understand that the imf or some relevant indicators of the material universe are linked to the complexity of this bias. Eddington bias seems not just a missing problem but combined with missing and random censoring. If the magnitude of a star is small, there's no bias. If the magnitude of a star is big, then it could be not be observed (missing) but when it is observed it is the limit of observable magnitudes (or below the limit in magnitudes), not the true magnitude of the star (censoring). [Note that stars of smaller magnitudes are brighter than larger magnitudes and the same magnitude stars (in absolute magnitude) can be observed or not observed depending on their distances - Malmquist bias] By the way, what is the SAO catalog? Malmquist bias sounds equivalent to missing data model: upon knowing a cosmological model (IMF or some mass distribution?), roughly one knows the proportion of observables, although I understand that the imf or some relevant indicators of the material universe are linked to the complexity of this bias.

Eddington bias seems not just a missing problem but combined with missing and random censoring. If the magnitude of a star is small, there’s no bias. If the magnitude of a star is big, then it could be not be observed (missing) but when it is observed it is the limit of observable magnitudes (or below the limit in magnitudes), not the true magnitude of the star (censoring).

[Note that stars of smaller magnitudes are brighter than larger magnitudes and the same magnitude stars (in absolute magnitude) can be observed or not observed depending on their distances - Malmquist bias]

By the way, what is the SAO catalog?

]]>