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<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Catalogs - DS9 </title>
</head>
<!--THIS FILE IS CREATED AUTOMATICALLY - DO NOT EDIT MANUALLY-->
<body><div class="mainbar">
<a name="maintext"></a><div align="center"><h1>Catalogs</h1></div>
<p>
Return to the <a href="../index.html">DS9 Users Manual</a></p>
<hr size="5" noshade>
<div>
<h2>Synopsis</h2>
<p>
DS9 provides full support for loading, displaying,
filtering, and saving catalogs. DS9 allows you to overlay
symbols from multiple catalogs on the current image and to
create expressions to style the source symbols based on
catalog properties.
</p>
<p>
If you encounter any problems, please email ds9help [at] cfa.harvard.edu.
</p>
</div>
<hr size="5" noshade>
<h2><a name="toc">Contents</a></h2>
<ul>
<li><strong><a href="index.html#display">Displaying a Catalog</a></strong></li>
<li><strong><a href="index.html#select">Selecting Sources with the Cursor</a></strong></li>
<li><strong><a href="index.html#display2">Displaying Multiple Catalogs</a></strong></li>
<li><strong><a href="index.html#clear">Clearing Catalog Sources</a></strong></li>
<li><strong><a href="index.html#filter">Sorting and Filtering</a></strong></li>
<li><strong><a href="index.html#symbol">Specifying Symbols with Conditional Expressions</a></strong></li>
<li><strong><a href="index.html#save">Saving the Sources: Catalog Files and Region Files</a></strong></li>
<li><strong><a href="index.html#cite">Citing a Catalog in Publication</a></strong></li>
<li><strong><a href="index.html#history">History</a></strong></li>
<li>
<strong>Images</strong><ul>
<li><a href="#2masssrc">Figure 1: 2MASS Sources for the Antennae Galaxies</a></li>
<li><a href="#2masscat">Figure 2: Catalog Tool of 2MASS Sources</a></li>
<li><a href="#cscsrc">Figure 3: CSC and 2MASS Sources for the Antennae Galaxies</a></li>
<li><a href="#2masssort">Figure 4: 2MASS Sources Sorted by Decreasing Jmag</a></li>
<li><a href="#jmag14">Figure 5: Filtering 2MASS Sources: Jmag<14</a></li>
<li><a href="#jmagrange">Figure 6: Filtering 2MASS Sources: Jmag<14 or Jmag>16.5</a></li>
<li><a href="#editjmag14">Figure 7: Symbol Editing: Jmag<14 Rule</a></li>
<li><a href="#editjmag14ds9">Figure 8: Symbol Editing: Jmag<14 Sources Displayed</a></li>
<li><a href="#editjmagrange">Figure 9: Symbol Editing: Jmag>16.5 Sources Added</a></li>
<li><a href="#addlabels">Figure 10: Symbol Editing: Rule to Add a Label</a></li>
<li><a href="#addlabelsds9">Figure 11: Symbol Editing: Jmag Labels Displayed</a></li>
</ul>
</li>
</ul>
<hr>
<div class="sectionlist">
<div class="section">
<h2><a name="display">Displaying a Catalog</a></h2>
<p>
This thread uses an optical image of the Antennae Galaxies
(NGC 4038/NGC 4039) from the Digital Sky Survey (DSS). It
was retrieved via the "Analysis → Image Servers" menu
in ds9.
</p>
<p>
A number of the most popular catalogs are listed by
wavelength in the "Analysis → Catalogs" menu. More
options can be accessed via the "Search for Catalogs" option
in that menu.
</p>
<p>
First we overlay sources from 2MASS by choosing
"Analysis → Catalogs → Infrared → 2MASS
point sources". The source matches are displayed on the
ds9 display (<a href="#2masssrc">Figure 1</a>) and listed in a
"Catalog Tool" window (<a href="#2masscat">Figure 2</a>).
</p>
<div class="figure">
<div class="caption"><h3><a name="2masssrc">Figure 1: 2MASS Sources for the Antennae Galaxies</a></h3></div>
<div><img alt="[The sources are displayed in green on the optical image.]" src="2masssrc.png"></div>
</div>
<p>
A set area centered on the field of view is used for the
first catalog search. The center and size of the search
area may be adjusted in the Catalog Tool by setting the
RA, Dec, height, and width fields. The "Coordinate" and
"Size" menus may be used to set the units for those values
(degrees/sexagesimal and degrees/arcmin/arcsec,
respectively). After changing the values, click the
"Retrieve" button to update the Catalog Tool.
</p>
<div class="figure">
<div class="caption"><h3><a name="2masscat">Figure 2: Catalog Tool of 2MASS Sources</a></h3></div>
<div><img alt="[199 sources were returned for this field.]" src="2masscat.png"></div>
</div>
<p>
Note that ds9 attempts to select the correct (RA,Dec)
columns from the catalog data file in order to display the
sources. In some cases, the user will have to explicitly
set the column names by using the drop-down menus in the
Catalog Tool. In this example, ds9 correctly chose "_RAJ2000" and
"_DEJ2000".
</p>
<hr>
</div>
<div class="section">
<h2><a name="select">Selecting Sources with the Cursor</a></h2>
<p>
From the "Edit" menu in ds9, choose the "Catalog" cursor
type. Clicking on a source in the ds9 display highlights
the corresponding row in the Catalog Tool. Multiple sources may be
selected by holding down the SHIFT key while clicking them.
</p>
<p>
Similarly, highlighting a row in the Catalog Tool will blink the
source region in ds9. If the "Pan to" option in the Catalog Tool
"Preferences" menu is checked, the ds9 display also centers
on the chosen source. Mutiple rows may be selected by
holding down the SHIFT or CTRL key while selecting them.
</p>
<hr>
</div>
<div class="section">
<h2><a name="display2">Displaying Multiple Catalogs</a></h2>
<p>
More than one catalog can be displayed in the same frame.
By default, the sources are displayed as green circle
points. The color and shape can be changed in the "Symbol"
menu of the Catalog Tool to distinguish between the different catalogs.
</p>
<p>
In <a href="#cscsrc">Figure 3</a>, the Chandra Source Catalog has been
added to the display (Analysis → Catalogs → High
Energy → Chandra Source). The symbols for the CSC
sources are set to red diamonds.
</p>
<div class="figure">
<div class="caption"><h3><a name="cscsrc">Figure 3: CSC and 2MASS Sources for the Antennae Galaxies</a></h3></div>
<div><img alt="[The 2MASS sources are displayed as green circles and the CSC sources are displayed as red diamonds on the optical image.]" src="cscsrc.png"></div>
</div>
<p>
To toggle the display of each catalog, use the "Show
Regions" option in the Catalog Tool "Preferences" menu.
</p>
<hr>
</div>
<div class="section">
<h2><a name="clear">Clearing Catalog Sources</a></h2>
<p>
Simply closing the Catalog Tool will not remove the sources from the
display. It is necessary to choose "Clear" from the
corresponding Catalog Tool.
</p>
<p>
To remove <em>all</em> the sources from the display, use
"Analysis → Catalogs → Clear All".
</p>
<p>
For the rest of this thread, only the 2MASS sources will be
used.
</p>
<hr>
</div>
<div class="section">
<h2><a name="filter">Sorting and Filtering</a></h2>
<p>
The source listing is sorted on position by default. A
different column for sorting may be selected from the "Sort"
menu in the Catalog Tool. Related checkboxes determine whether the
results are listed in increasing or decreasing order.
The Catalog Tool in <a href="#2masssort">Figure 4</a> is sorted on the
"Jmag" column in decreasing order.
</p>
<div class="figure">
<div class="caption"><h3><a name="2masssort">Figure 4: 2MASS Sources Sorted by Decreasing Jmag</a></h3></div>
<div><img alt="[The sources are sorted on the Jmag column in decreasing order.]" src="2masssort.png"></div>
</div>
<p>
The "Filter" field in the Catalog Tool is used to filter out
specific rows from the source matches. A filter is
conditional expression that is evaluated for each row of the
catalog. The column name must be referenced with a dollar
sign in the expression, e.g. "$_RAJ2000".
</p>
<p>
To select the sources with low Jmag values, the filter
"$Jmag<14" is used. Click the "Filter" button to update
the Catalog Tool and the ds9 display. The results are shown in
<a href="#jmag14">Figure 5</a>.
</p>
<div class="figure">
<div class="caption"><h3><a name="jmag14">Figure 5: Filtering 2MASS Sources: Jmag<14</a></h3></div>
<div><img alt="[33 sources are included in the filter.]" src="jmag14.png"></div>
</div>
<p>
TCL expression syntax can be used to construct more complex
filters. The filter "$Jmag<14 || $Jmag>16.5" uses the
logical "OR" syntax ("||") to select any source with Jmag
less than 14 or greater than 16.5, as shown in
<a href="#jmagrange">Figure 6</a>.
</p>
<div class="figure">
<div class="caption"><h3><a name="jmagrange">Figure 6: Filtering 2MASS Sources: Jmag<14 or Jmag>16.5</a></h3></div>
<div><img alt="[70 sources are included in the filter.]" src="jmagrange.png"></div>
</div>
<p>
The uniformity of the symbols doesn't distinguish between
the low-Jmag sources and the high-Jmag sources. The
advanced symbol editing in the next section improves on this
display.
</p>
<p>
Before continuing the thread, clear the filter in the
Catalog Tool so that all the sources are displayed.
</p>
<hr>
</div>
<div class="section">
<h2><a name="symbol">Specifying Symbols with Conditional Expressions</a></h2>
<p>
The advanced symbol editing in the Catalog Tool allows you to
specify the shape, size, color, and text of each symbol
based on catalog column values.
</p>
<p>
Open the "Symbol Editor" from the "Symbol →
Advanced..." menu in the Catalog Tool. A conditional statement,
written in the TCL expression syntax, is entered in the "If"
field. The styles that should be applied are set by the
other fields (shape, color, text, etc.).
</p>
<p>
First, define a rule that sets the sources with
Jmag<14 to be red boxcircle points. The completed form
is shown in <a href="#editjmag14">Figure 7</a>. After clicking the
"Apply" button, the ds9 display is updated (<a href="#editjmag14ds9">Figure 8</a>).
</p>
<div class="figure">
<div class="caption"><h3><a name="editjmag14">Figure 7: Symbol Editing: Jmag<14 Rule</a></h3></div>
<div><img alt="[The fields are set to display sources with Jmag<14 as red boxpoints.]" src="editjmag14.png"></div>
</div>
<div class="figure">
<div class="caption"><h3><a name="editjmag14ds9">Figure 8: Symbol Editing: Jmag<14 Sources Displayed</a></h3></div>
<div><img alt="[The sources with Jmag<14 are displayed as red boxpoints.]" src="editjmag14ds9.png"></div>
</div>
<p>
The "Add" button in the Symbol Editor is used to create a
new, empty form. The second rule is defined such that
sources with Jmag>16.5 will be cyan diamonds.
After clicking the "Apply" button again, the ds9 display is
as shown in <a href="#editjmagrange">Figure 9</a>.
</p>
<div class="figure">
<div class="caption"><h3><a name="editjmagrange">Figure 9: Symbol Editing: Jmag>16.5 Sources Added</a></h3></div>
<div><img alt="[The sources with Jmag>16.5 are displayed as cyan diamonds.]" src="editjmagrange.png"></div>
</div>
<p>
To edit an existing rule, highlight the rule in the Symbol
Editor and adjust the parameters. In
<a href="#addlabels">Figure 10</a>, both rules have been updated
so that the Text field is set to "$Jmag". This
<a href="#addlabelsds9">displays the Jmag column value
next to the symbol (Figure 11)</a>.
</p>
<div class="figure">
<div class="caption"><h3><a name="addlabels">Figure 10: Symbol Editing: Rule to Add a Label</a></h3></div>
<div><img alt="[The fields are set to label each source with its Jmag column value.]" src="addlabels.png"></div>
</div>
<div class="figure">
<div class="caption"><h3><a name="addlabelsds9">Figure 11: Symbol Editing: Jmag Labels Displayed</a></h3></div>
<div><img alt="[Each source is labeled with its Jmag column value.]" src="addlabelsds9.png"></div>
</div>
<p>
The ds9 Reference Manual
has <a href="../../ref/catalog.html">further examples of
symbol expressions</a>.
</p>
<p>
The set of rules may be saved from the "File" menu in the
Symbol Editor. The output for these rules looks like:
</p>
<div class="screen"><pre style="background: #cccccc; white-space: pre; border: none; padding: 0.5em; overflow: auto; border: thin solid black;">
condition shape color text size size2 units angle
--------- ----- ----- ---- ---- ----- ----- -----
$Jmag<14 boxcircle point red $Jmag physical
$Jmag>16.5 diamond point cyan $Jmag physical
</pre></div>
<p>
The file can be loaded into a later ds9 session by opening
the Symbol Editor and using the "File → Load" menu
item. Note that the column names in the symbol rules may
have to be updated in order to use them with a different
catalog.
</p>
<hr>
</div>
<div class="section">
<h2><a name="save">Saving the Sources: Catalog Files and Region Files</a></h2>
<p><strong>Saving a Catalog File</strong></p>
<p>
The contents of the Catalog Tool may be saved from the "File →
Save" menu. If any filters are applied, the filtered output
is saved in the catalog file.
</p>
<p>
ds9 supports three catalog formats: VOTable, Starbase, and
tab-separated file. If the catalog file will be loaded
back into ds9 in the future, any of the three formats may be
chosen.
</p>
<p><strong>Saving the Sources in a Region File</strong></p>
<p>
The sources may also be converted to a ds9 region file for
use in data analysis, e.g. spectra extraction or calculating
sources counts.
</p>
<p>
Select "Copy to Regions" from the Catalog Tool "File" menu. Once
the sources are converted to regions, individual ones may be
selected and edited or deleted, if desired. Save the
regions from the "Region → Save Regions..." menu.
</p>
<hr>
</div>
<div class="section">
<h2><a name="cite">Citing a Catalog in Publication</a></h2>
<p>
If you wish to use the source information in a publication,
refer to the "Acknowledgment" item under the "File" menu in
the Catalog Tool. For instance, the 2MASS acknowledgment reads:
</p>
<div class="screen"><pre style="background: #cccccc; white-space: pre; border: none; padding: 0.5em; overflow: auto; border: thin solid black;">
Acknowledgments for CDS
This research has made use of the VizieR catalogue access tool, CDS,
Strasbourg, France. VizieR is a joint effort of CDS (Centre de Données
astronomiques de Strasbourg) and ESA-ESRIN (Information Systems Division).
</pre></div>
</div>
</div>
<hr size="5" noshade>
<h2><a name="history">History</a></h2>
<table class="history">
<tr>
<td class="historydate">08 Jan 2010</td>
<td>
Original version
</td>
</tr>
</table>
<hr size="5" noshade>
<p>
Return to the <a href="../index.html">DS9 Users Manual</a></p>
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