From 1cfa265bc7a007f4b0ed228bf7acffaaf7672e8e Mon Sep 17 00:00:00 2001
From: Jürgen Knödlseder <jurgen.knodlseder@irap.omp.eu>
Date: Fri, 16 Oct 2015 22:30:15 +0200
Subject: [PATCH] Add the shell width bias as a known issue.

---
 doc/source/issues.rst | 26 +++++++++++++++++++-------
 1 file changed, 19 insertions(+), 7 deletions(-)

diff --git a/doc/source/issues.rst b/doc/source/issues.rst
index d56c6b6..fe2f1fb 100644
--- a/doc/source/issues.rst
+++ b/doc/source/issues.rst
@@ -5,22 +5,23 @@ Known issues
 
 Below you will find a list of known issues.
 
-- :ref:`Broken power law has unreliable errors <issues_bplaw>`
-- :ref:`Errors become unreliable when fitting the pivot energy <issues_pivot>`
-- :ref:`Binned analysis is biased when using coarse binning <issues_binned>`
+- :ref:`Broken power law has unreliable errors <issue_bplaw>`
+- :ref:`Errors become unreliable when fitting the pivot energy <issue_pivot>`
+- :ref:`Binned analysis is biased when using coarse binning <issue_binned>`
+- :ref:`Shell model is biased when width is comparable to angular resolution <issue_shell>`
 
 
-.. _issues_bplaw:
+.. _issue_bplaw:
 
 .. topic:: Broken power law has unreliable errors
 
    The broken power law spectral model has unreliable errors, specifically
    for the prefactor and the break value. Errors are in general too large,
-   and this is related to the fact that the law's gradient is discontinous
+   and this is related to the fact that the law's gradient is discontinuous
    in energy. There is not very much we can do about it, it's inherent in
    the law.
 
-.. _issues_pivot:
+.. _issue_pivot:
 
 .. topic:: Errors become unreliable when fitting the pivot energy
 
@@ -34,7 +35,7 @@ Below you will find a list of known issues.
    parameters of the model to assure non-degeneracy of the free
    parameters.
 
-.. _issues_binned:
+.. _issue_binned:
 
 .. topic:: Binned analysis is biased when using coarse binning
 
@@ -45,3 +46,14 @@ Below you will find a list of known issues.
    per pixel for the spatial binning and 10 bins per decade for the
    spectral binning. If the binning is too coarse, the spectral parameters 
    that are fitted will be biased.
+
+.. _issue_shell:
+
+.. topic:: Shell model is biased when width is comparable to angular resolution
+
+   When the width of the shell model becomes comparable to or smaller
+   than the angular resolution, the shell width tends to be overestimated
+   while the shell radius tends to be underestimated.
+   The fitted shell width and radius should thus not be overinterpreted
+   when the width is close to the angular resolution of CTA.
+
--
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