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<!-- DOI: 10.1051/0004-6361/200809876 -->

<h2 class="sec">Online Material</h2>



<h2 class="sec"><a name="SECTION00080000000000000000"></a><A NAME="sect:ap1"></A>
Appendix A: Full description of the extended halo removal
</h2>

<p>
In this Appendix we give a detailed description of the whole procedure followed to remove the objects with extended halos.

<p>
This is the  outline of the whole  process, while the single steps are explained in some detail thereafter:
<DL COMPACT>
<DT>1.
<DD>A background map is computed using the original images.
<p>
<DT>2.
<DD>The extended objects   (galaxies and stars) to  be removed are selected interactively.

<p>
<DT>3.
<DD><A NAME="point1"></A> For each selected object, the following steps are performed:
  <DL COMPACT>
<DT>(a)
<DD>The objects projected onto it are masked<A NAME="tex2html32"
 HREF="#foot1046"><sup><IMG  ALIGN="BOTTOM" BORDER="1" ALT="[*]" SRC="/icons/foot_motif.png"></sup></A> with an interactive procedure.<A NAME="mask"></A>
<p>
<DT>(b)
<DD>Its isophotes are fitted with the IRAF task <TT>ellipse</TT>.

<p>
<DT>(c)
<DD>The resulting elliptical isophotes are then used as the input of the task <TT>bmodel</TT> to construct a model of the extended  object.

<p>
<DT>(d)
<DD>The model is subtracted from the original image.

<p>
<DT>(e)
<DD>In the case of galaxies, when the subtraction leaves residuals due to   the structure of  the galaxy,  these are removed manually with <TT>imedit</TT>.
  </DL><DT>4.
<DD>After  removing all the  selected  objects from the  initial image a new
  background map is calculated.

<p>
<DT>5.
<DD>A mask of the remaining objects  is constructed with <TT>SExtractor</TT>. This
  mask  is  then  used   in  a   second  iteration  to   improve   the
  interactively-made   masks (point&nbsp;(<a href="/articles/aa/full_html/2009/15/aa09876-08/aa09876-08.html#mask">3a</a>))   applied  during  the
  isophote fitting procedure.

<p>
<DT>6.
<DD>At  this   point, the      procedure can   be  repeated    from
  point&nbsp;(<a href="/articles/aa/full_html/2009/15/aa09876-08/aa09876-08.html#point1">3</a>) until the subtraction is satisfactory.
</DL>The   process is iterative   and could be  repeated   as many times as necessary but we found  that one iteration was  enough to reach a good photometric quality.

<p>

<div class="inset-old">
<table>
<tr><td><!-- init Label --><A NAME="fig:VGalModel">&#160;</A><!-- end Label--><A NAME="1047"></A><A NAME="figure802"
 HREF="img95.png"><IMG
 WIDTH="101" HEIGHT="96" SRC="Timg95.png"
 ALT="\begin{figure}
\par\includegraphics[width=8.8cm,clip]{9876f16}
\end{figure}"></A><!-- HTML Figure number: 9 --></td>
<td class="img-txt"><span class="bold">Figure A.1:</span><p>
<I> Upper panel</I>: fraction of galaxies that were modeled. <I> Lower panel</I>: total number of galaxies that were modeled.</p></td>
</tr><tr><td colspan="2"><a href="http://dexter.edpsciences.org/applet.php?pdf_id=9&DOI=10.1051/0004-6361/200809876" target="DEXTER">Open with DEXTER</a></td></tr>

</table></div>
<p>
Now we explain in more detail all the steps of the procedure:
<DL>
<DT><STRONG><B>First  background computation</B>:</STRONG>
<DD>due to
the variations found from chip to chip and to avoid the influence of
  the interchip regions  (which <TT>SExtractor</TT> treats as  if they were part of
  the actual image) the images were split into their original chips.

<p>
After  that, an initial background  estimation was computed for each
  chip     using   <TT>SExtractor</TT>      with    <TT>BACK_SIZE=256</TT>     and
  <TT>BACK_FILTERSIZE=3</TT> as input parameter values. To reduce the
  influence of  bright  pixels,   those  with intensities   above   an
  established threshold  were  replaced by  the  mode of the  pixel
  intensity of   the same chip,  which   can  be considered  as a first
  estimation of the  background  level.  The  threshold  was  set manually
  before starting the process seeking to not remove the bright part of
  the background.

<p>
Once the background was obtained for each chip, the single
  background images were mosaiced to construct a global background
  map. This background map was then subtracted from the original
  image.

<p>
<DT><STRONG><B>Selection of the objects to be removed</B>:</STRONG>
<DD>the selection
  of the objects to be modeled and removed was done in a subjective
  way but following several guidelines.  First, the BCG was always
  modeled. Elliptical galaxies<A NAME="tex2html33"
 HREF="#foot814"><sup><IMG  ALIGN="BOTTOM" BORDER="1" ALT="[*]" SRC="/icons/foot_motif.png"></sup></A>  highly blended and/or
  surrounded by small objects were also modeled.  The selection of the
  stars to be modeled was more field-dependent.  As the amount of work
  needed increased substantially with the number of objects to be
  modeled, in those fields with a high density of stars only the
  brightest stars were modeled.  Sometimes, a star was modeled to
  avoid the contamination from a close bright galaxy.

<p>
Figure&nbsp;<a href="/articles/aa/full_html/2009/15/aa09876-08/aa09876-08.html#fig:VGalModel">A.1</a> shows the distribution in <I>V</I> of the galaxies
  that have been processed in this way. Up to <IMG
 ALIGN="MIDDLE" BORDER="0"
 SRC="img96.png"
 ALT="$V\sim 14$">
most of the
  galaxies have been modeled.

<p>
<DT><STRONG><B>Fitting  and   modeling</B>:</STRONG>
<DD>to   reduce  the  computation
  time, the process of isophote fitting, modeling and model
  subtraction was done on small images of the selected objects
  extracted from the background-subtracted global image.

<p>
The isophote fitting was  done using the IRAF task <TT>ellipse</TT>. 
  However,   before that, all   the  projected objects and problematic
  regions (e.g.  interchip  regions) were  masked.   Due to the  large
  number of objects that should be masked and  taking advantage of the
  iterative  process, this  first step  was  enough to make a
  rough mask. Below we will show how the improvement is achieved.

<p>
A few differences were introduced when dealing with stars or
  galaxies.  For stars the ellipticity was fixed to zero and the
  fitting did not reach the innermost region (usually saturated and,
  therefore, not suitable for fitting isophotes).  Also, the center
  of the isophotes was not fixed because quite often the reflections of
  the stars were off-center with respect to the&nbsp;central regions.  For
  galaxies no restrictions were imposed.

<p>
The output of <TT>ellipse</TT> was used as the input of the task
  <TT>bmodel</TT> which allows us to construct a two dimensional model
  of the object.  This model was subtracted from the original image
  (i.e.&nbsp;before the first background subtraction).

<p>
This step was done for all selected objects.

<p>
<DT><STRONG><B>Second background estimation and object mask</B>:</STRONG>
<DD>the outcome of the
  previous step was an image similar to the original one, in which
  large objects have been removed. This allowed us to obtain an
  improved background map, a&nbsp;better background subtracted image and a
  better detection of the small objects. In fact, using <TT>SExtractor</TT> with
  the background-subtracted images after removing  the models, it
  was possible to get a careful mask of all objects (except, of
  course, from those that were removed from the image).  This new
  mask would serve to refine the previous (manually-done) one.

<p>
<DT><STRONG><B>Second fit and modeling</B>:</STRONG>
<DD>the fitting process done in
  the first iteration was repeated using a refined mask for each
  object. This helped to get a better fit and, as a result, a better
  model.

<p>
The main difference with respect to the first iteration is that
  after the subtraction of the model from the galaxies, sometimes some
  residuals remained in the central regions.  In such cases, these
  were manually edited using the IRAF task <TT>imedit</TT>.  When
  editing the images only clearly spurious residuals were replaced by
  pixels simulating the background signal adding a Gaussian noise
  whose sigma was computed from surrounding regions.  This has no
  effect on an object's photometry since the photometry of large
  galaxies is done with another image, avoiding the spurious detection
  of the residuals.

<p>
<DT><STRONG><B>Construction of the  final images</B>:</STRONG>
<DD>in most fields, only
  two iterations were enough to achieve a satisfactory result. After
  modeling all the selected extended objects and subtracting them from
  the initial image,  the background was recomputed again and finally
  subtracted from the model-subtracted image.  The output of this
  procedure was a background-subtracted image without the extended
  modeled objects. 

<p>
The final step was to produce the complementary image containing only
 the modeled galaxies.  To  be consistent in   the photometry of   the
 extended galaxies we do not use the models. We constructed a new image
 containing the original pixels (background subtracted) of the removed
 galaxies. However,  to minimize the effect  of the projected objects,
 the intensities of   the pixels in which  these   fell were  in  fact
 replaced by the  intensities of the  models in the same pixels. In
 practice, this  was  done constructing  a   new mask of the   objects
 contained in  the background-subtracted  image without large  objects
 using <TT>SExtractor</TT>.  Then, the    final image was computed following   these
 criteria for its pixels:
  <UL>
<LI>If the  pixel did not belong to  an  object (value  in the mask
    equal  to  zero)  then the  background-subtracted image  value was
    kept that corresponded to the original pixel of the galaxy.

<p>
<LI>If  the pixel indeed belonged to  an object (value in the mask
    greater than zero)  then the value in the  model was taken instead
    of the value in the original image.

<p>
<LI>If the pixel fell in an interchip region then the value from
    the model was used if available. In this way, we were able to
    improve the photometry of large galaxies with large regions lost
    in the interchip regions.
  </UL>Of course, for construction, the image of the large galaxies also lacks the bright stars.
</DL>This procedure  was done in  both bands (<I>V</I>,<I>B</I>) removing,  of course, the same objects.

<p>
<div class="inset-old">
<table>
<tr><td><!-- init Label --><A NAME="fig:StarsRealSim">&#160;</A><!-- end Label--><A NAME="1048"></A><A NAME="figure828"
 HREF="img97.png"><IMG
 WIDTH="97" HEIGHT="92" SRC="Timg97.png"
 ALT="\begin{figure}
\par\includegraphics[width=8.5cm,clip]{9876f17}
\end{figure}"></A><!-- HTML Figure number: 10 --></td>
<td class="img-txt"><span class="bold">Figure A.2:</span><p>
Comparison of the real counts (continuous line) with that
coming from the simulations. Long dashes line: input distribution of the simulated stars taken from Besan&#231;on models. Dotted line: simulated stars classified as stars. Long-short dashed line: simulated stars detected.</p></td>
</tr><tr><td colspan="2"><a href="http://dexter.edpsciences.org/applet.php?pdf_id=10&DOI=10.1051/0004-6361/200809876" target="DEXTER">Open with DEXTER</a></td></tr>

</table></div>
<p>

<h2 class="sec"><a name="SECTION00090000000000000000"></a><A NAME="appendix2"></A>
Appendix B: Image simulations
</h2>

<p>
One of the methods most commonly used to check the reliability of a procedure of star/galaxy classification is to test the procedure using images in which synthetic objects have been added. Of course, this method relies upon the idea that the artificial objects are similar enough (from the point of view of the classifying program) to the real objects so that one can extrapolate the results obtained from the simulations (from which the input and the output are known) to the
real objects.

<p>
We followed this method using the tasks of the IRAF's package <TT>artdata</TT>.  We made catalogs of galaxies and stars to build the artificial images that were added to the real images.  In this way
we could test also the effects of the variations of the background and other real conditions that are difficult or impossible to simulate. The effects of crowding coming from adding more objects to real images were measured to produce less than&nbsp;<IMG
 ALIGN="MIDDLE" BORDER="0"
 SRC="img67.png"
 ALT="$10\%$">
of the lost objects in the most crowded image.  Then we proceeded with these images as with the real ones.  The resulting parameters from <TT>SExtractor</TT> were compared between real and synthetic objects, showing that they were at first sight quite
similar, giving us confidence that the extrapolation from simulations to real objects could be done. However, the comparison of the final counts from the real and the simulated objects made us distrust the simulations, especially that of the faint stars.  The reason for this conclusion is illustrated in  Fig.&nbsp;<a href="/articles/aa/full_html/2009/15/aa09876-08/aa09876-08.html#fig:StarsRealSim">A.2</a>. This figure shows the star counts from the original catalogs of WINGS (continuous line) and from the simulations.  For simulated stars three lines have been plotted.  The long dashed one represents the input catalog and the numbers are taken from the models of the Galaxy from Besan&#231;on.  The long-short dashed line represents the counts of detected simulated stars.  Finally, the dotted line shows the counts of the simulated stars classified as stars, which should be the counts to be compared with the data from WINGS' stars catalog (continuous
line).  From this figure it can be seen that, at the faintest magnitudes, it was easier for <TT>SExtractor</TT> to distinguish a real star than a simulated one, violating the initial premise that simulated objects are similar to real ones.

<p>
In the  construction  of the simulated  stars we  took bright  but not saturated stars to have  a well sampled   point spread function  (PSF) even  at the  wings.   So, one   expects simulated stars to   be more concentrated  than real ones and then  easier to be classified as stars by <TT>SExtractor</TT>, which is the opposite of what was  found.  The doubts became greater when  simulations were done  using two different PSFs, one for bright stars computed  from a bright start and  another  one for faint
stars computed from a fainter star. In this case, the fraction of faint simulated stars identified as stars by  <TT>SExtractor</TT>  increased.   Therefore, the simulations  turn out to be too dependent on the&nbsp;input.

<p>
As this seemed to be a problem of the  <TT>mkobjects</TT> task we tried with the <TT>addstars</TT>  feature of the <TT>daophot</TT> package to create  the  synthetic stars. Since this   is a package  made to study stars we expected a better treatment of the simulations.  However, the
results were similar.

<p>
The   origin of  the  difficulties   is  not  clear. Probably, small variations of  the  local conditions where  objects  are added produce large effects in faint simulated objects.

<p>
All  these  results convinced  us  not  to  use   the results  of  the simulations to  measure       the reliability  of      our star/galaxy classification   at faint magnitudes.  However,    we did not find such problematic       behavior         at         bright       magnitudes. Figure&nbsp;<a href="/articles/aa/full_html/2009/15/aa09876-08/aa09876-08.html#fig:StarsRealSim">A.2</a>  shows that the  problems of  detection of simulated stars (before any classification as galaxy or star) start above <IMG
 ALIGN="MIDDLE" BORDER="0"
 SRC="img51.png"
 ALT="$V\sim 22$">
when       the      detection     rate     drops     (see Fig.&nbsp;<a href="/articles/aa/full_html/2009/15/aa09876-08/aa09876-08.html#fig:completeness">5</a>). For   these reason  we decided  to still
rely on the simulations  to estimate the   photometric errors and  the detection rates since, unfortunately, there is no better procedure to estimate such quantities.

<p>

<h2 class="sec"><a name="SECTION000100000000000000000"></a><A NAME="sec:appendix3"></A>
Appendix C: Comparison with WFPC2@HST image
</h2>

<p>
To check the completeness estimations done with simulations we performed a comparison using data from the Hubble Space Telescope. We downloaded the images of the BCG of A1795 taken with the WFPC2 from the HST archive<A NAME="tex2html35"
 HREF="#foot844"><sup><IMG  ALIGN="BOTTOM" BORDER="1" ALT="[*]" SRC="/icons/foot_motif.png"></sup></A>. We chose the <I>F555W</I>&nbsp;filter which was the one that best matches the <I>V</I>&nbsp;band images that we used to construct our catalogs.  From the mosaic of the WFPC2 we removed the PC&nbsp;chip in which the BCG was located since this produced problems for <TT>SExtractor</TT> and we were interested in knowing the completeness at faint magnitudes. After that, <TT>SExtractor</TT> was run on the image and the resulting catalog was matched and compared with the WINGS&nbsp;catalog. We performed the matching against the global WINGS&nbsp;catalogs, i.e. including stars, galaxies and objects of unknown classification. Figure&nbsp;<a href="/articles/aa/full_html/2009/15/aa09876-08/aa09876-08.html#fig:hst_comp">C.1</a> (upper panel) shows the completeness computed for the A1795&nbsp;field using the simulations (continuous line) and the completeness compared with the HST&nbsp;data.  We also include  the errors in the computation of these data since the area is quite small and therefore the number of detected objects (lower panel) is also quite&nbsp;low.

<p>
<div class="inset-old">
<table>
<tr><td><!-- init Label --><A NAME="fig:hst_comp">&#160;</A><!-- end Label--><A NAME="1051"></A><A NAME="figure848"
 HREF="img98.png"><IMG
 WIDTH="101" HEIGHT="98" SRC="Timg98.png"
 ALT="\begin{figure}
\par\includegraphics[width=8.8cm,clip]{9876f18}
\end{figure}"></A><!-- HTML Figure number: 11 --></td>
<td class="img-txt"><span class="bold">Figure C.1:</span><p>
Comparison of the completeness of the WINGS&nbsp;catalog of the field of A1795. <I> Upper panel</I>: the continuous line shows the completeness computed from simulations while the dots with the error bars show the completeness when comparing from HST&nbsp;data. The error bars are constructing using <IMG
 ALIGN="MIDDLE" BORDER="0"
 SRC="img12.png"
 ALT="$1\sigma $">&nbsp;Poisson errors. <I> Lower panel</I>: number of objects detected in the HST&nbsp;image. Since the area is quite small the total numbers are also small producing the large uncertainties in the computation of the completeness.</p></td>
</tr><tr><td colspan="2"><a href="http://dexter.edpsciences.org/applet.php?pdf_id=11&DOI=10.1051/0004-6361/200809876" target="DEXTER">Open with DEXTER</a></td></tr>

</table></div>
<p>
Although the HST image is much sharper than our ground-based image, it is not much deeper and it also shows problems of completeness in the range of comparison (lower panel of Fig.&nbsp;<a href="/articles/aa/full_html/2009/15/aa09876-08/aa09876-08.html#fig:hst_comp">C.1</a>). This and other issues in the matching procedure (such as pairs of objects that are not resolved in the WINGS&nbsp;image) introduce uncertainties in the comparison so this should be considered as a complementary check to the completeness computed using the simulations. 

<p>

<h2 class="sec"><a name="SECTION000110000000000000000"></a><A NAME="sec:AddInfo"></A>
Appendix D: Additional information
</h2>

<p>
In addition to the data of the single objects found in each field we include several tables containing information about observational features and peculiarities of either the single clusters or the fields on which they are projected.

<p>
Position, redshift, Abell richness, Bautz-Morgan type, X-ray luminosity and galactic extinction of the whole WINGS sample can be found in Table&nbsp;5 of Paper&nbsp;I.

<p>
In Table&nbsp;<a href="/articles/aa/full_html/2009/15/aa09876-08/aa09876-08.html#tab:UsefulData">D.1</a> we  summarize  the conversion  factors used for  this work from  CCD related  units (pixels) to  angular unit (arcsecs) and from these to linear units (kpc) at  the redshift of the target   cluster using a  cosmological   model with parameters <I>H</I><SUB>0</SUB>=75&nbsp;km&nbsp;s<sup>-1</sup>&nbsp;Mpc<sup>-1</sup>, 
<!-- MATH: $\Omega_{\rm M}=0.3$ -->
<IMG
 ALIGN="MIDDLE" BORDER="0"
 SRC="img99.png"
 ALT="$\Omega_{\rm M}=0.3$">
and  
<!-- MATH: $\Omega_\Lambda=0.7$ -->
<IMG
 ALIGN="MIDDLE" BORDER="0"
 SRC="img100.png"
 ALT="$\Omega_\Lambda=0.7$">.
We have also included the effective total area of each image which is the real area used to make the catalogs which is slightly smaller than the total field of view   (for WFC@INT images, the effective area is <IMG
 ALIGN="BOTTOM" BORDER="0"
 SRC="img15.png"
 ALT="$\sim$"><IMG
 ALIGN="MIDDLE" BORDER="0"
 SRC="img82.png"
 ALT="$90\%$">
of the total field  of  view while  for WFI@ESO  this  value  is <IMG
 ALIGN="BOTTOM" BORDER="0"
 SRC="img15.png"
 ALT="$\sim$"><IMG
 ALIGN="MIDDLE" BORDER="0"
 SRC="img101.png"
 ALT="$95\%$">). We report the angular sizes of the  apertures of <I>R</I>=2&nbsp;kpc, 5&nbsp;kpc and 10&nbsp;kpc used to construct our catalogs.

<p>
In Table&nbsp;<a href="/articles/aa/full_html/2009/15/aa09876-08/aa09876-08.html#tab:Detection">D.2</a> we list the detection limits in surface brightness, or surface brightness thresholds, (
<!-- MATH: $\mu_V({\rm Threshold})$ -->
<IMG
 ALIGN="MIDDLE" BORDER="0"
 SRC="img102.png"
 ALT="$\mu_V({\rm Threshold})$">)
as well as the <I>V</I>&nbsp;band magnitude at which the detection rate goes down to <IMG
 ALIGN="MIDDLE" BORDER="0"
 SRC="img82.png"
 ALT="$90\%$">,
<IMG
 ALIGN="MIDDLE" BORDER="0"
 SRC="img86.png"
 ALT="$75\%$">
and&nbsp;<IMG
 ALIGN="MIDDLE" BORDER="0"
 SRC="img84.png"
 ALT="$50\%$">.
These last values are average values
obtained from the simulations.

<p>
Table&nbsp;<a href="/articles/aa/full_html/2009/15/aa09876-08/aa09876-08.html#tab:BCG">D.3</a> reports the positions of the brightest cluster galaxies.  In most cases we preferred the coordinates of the peak of the emission instead of the coordinates of the barycenter because the latter are more affected by irregularities in the outer isophotes.

<p>
Finally, Table&nbsp;<a href="/articles/aa/full_html/2009/15/aa09876-08/aa09876-08.html#tab:Notes">D.4</a> lists comments or issues about the clusters and the fields which we find interesting or useful when working with our catalogs.

<p>
<A NAME="tab:UsefulData"></A><p class="inset-old"><a href="/articles/aa/full_html/2009/15/aa09876-08/tableD.1.html"><span class="bold">Table D.1:</span></a>&#160;&#160;
Useful parameters of the WINGS' clusters sample.</p>
<p>
<A NAME="tab:Detection"></A><p class="inset-old"><a href="/articles/aa/full_html/2009/15/aa09876-08/tableD.2.html"><span class="bold">Table D.2:</span></a>&#160;&#160;
Completeness limits and surface brightness detection limits.</p>
<p>
<A NAME="tab:BCG"></A><p class="inset-old"><a href="/articles/aa/full_html/2009/15/aa09876-08/tableD.3.html"><span class="bold">Table D.3:</span></a>&#160;&#160;
Coordinates of the emission peak of the brightest cluster  galaxies.</p>
<p>
<A NAME="tab:Notes"></A><p class="inset-old"><a href="/articles/aa/full_html/2009/15/aa09876-08/tableD.4.html"><span class="bold">Table D.4:</span></a>&#160;&#160;
Remarks about the individual fields.</p>
<p>
<br>

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