@@ -258,6 +258,42 @@ ellipticities greater than unity, SExtractor avoids dichotomies of
position angle when the ellipticity is very low. The Sérsic index is
allowed values between 1 and 10.
.. _spread_model_def:
Star-Galaxy separation
----------------------
The :param:`SPREAD_MODEL` estimator has been developed as a star/galaxy classifier for the DESDM pipeline :cite:`2012SPIE_8451E_0DM`, and has also been used in other surveys :cite:`2012ApJ_757_83D,2013AA_554A_101B`.
:param:`SPREAD_MODEL` indicates which of the best fitting local PSF model resampled at the current position :math:`\tilde{\boldsymbol{\phi}}` (representing a point source) or a slightly ``fuzzier'' resampled model :math:`\tilde{\boldsymbol{G}}` (representing a galaxy) matches best the image data.
:math:`\tilde{\boldsymbol{G}}` is obtained by convolving the local PSF model with a circular exponential model with scalelength = 1/16 |FWHM|, and resampling the result at the current position on the pixel grid. :param:`SPREAD_MODEL` is normalized to allow comparing sources with different PSFs throughout the field:
where :math:`\boldsymbol{p}` is the image vector centered on the source.
:math:`{\bf W}` is a weight matrix constant along the diagonal except for bad pixels where the weight is 0.
By construction, :param:`SPREAD_MODEL` is close to zero for point sources, positive for extended sources (galaxies), and negative for detections smaller than the PSF, such as cosmic ray hits.
.. note::
The definition of :param:`SPREAD_MODEL` above differs from the one given in previous papers, which was incorrect, although in practice both estimators give very similar results.
The |RMS| error on :param:`SPREAD_MODEL` is estimated by propagating the uncertainties on individual pixel values:
adsnote={Provided by the SAO/NASA Astrophysics Data System}
}
@ARTICLE{Broyden1965ACo,
AUTHOR="C. Broyden",
TITLE="A Class of Methods for Solving Nonlinear Simultaneous Equations",
@@ -50,6 +68,24 @@
adsnote={Provided by the SAO/NASA Astrophysics Data System}
}
@ARTICLE{2012ApJ_757_83D,
author={{Desai}, S. and {Armstrong}, R. and {Mohr}, J.~J. and {Semler}, D.~R. and {Liu}, J. and {Bertin}, E. and {Allam}, S.~S. and {Barkhouse}, W.~A. and {Bazin}, G. and {Buckley-Geer}, E.~J. and {Cooper}, M.~C. and {Hansen}, S.~M. and {High}, F.~W. and {Lin}, H. and {Lin}, Y.-T. and {Ngeow}, C.-C. and {Rest}, A. and {Song}, J. and {Tucker}, D. and {Zenteno}, A.},
title="{The Blanco Cosmology Survey: Data Acquisition, Processing, Calibration, Quality Diagnostics, and Data Release}",
journal={ApJ},
archivePrefix="arXiv",
eprint={1204.1210},
primaryClass="astro-ph.CO",
keywords={cosmology: observations, galaxies: clusters: general, methods: data analysis, surveys, techniques: image processing},
adsnote={Provided by the SAO/NASA Astrophysics Data System}
}
@ARTICLE{duchon1979,
author={{Duchon}, C.~E.},
title="{Lanczos Filtering in One and Two Dimensions}",
@@ -250,6 +286,24 @@ booktitle = {Astronomical Data Analysis Software and Systems (ADASS) XIII},
adsnote={Provided by the SAO/NASA Astrophysics Data System}
}
@INPROCEEDINGS{2012SPIE_8451E_0DM,
author={{Mohr}, J.~J. and {Armstrong}, R. and {Bertin}, E. and {Daues}, G. and {Desai}, S. and {Gower}, M. and {Gruendl}, R. and {Hanlon}, W. and {Kuropatkin}, N. and {Lin}, H. and {Marriner}, J. and {Petravic}, D. and {Sevilla}, I. and {Swanson}, M. and {Tomashek}, T. and {Tucker}, D. and {Yanny}, B.},
title="{The Dark Energy Survey data processing and calibration system}",
booktitle={Software and Cyberinfrastructure for Astronomy II},
