confetti-artifacts-in-clean.html

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    <h2 class="entry-title">
      <a href="https://keflavich.github.io/blog/confetti-artifacts-in-clean.html" rel="bookmark"
         title="Permalink to Confetti artifacts in clean">Confetti artifacts in clean</a></h2>
 
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    <abbr class="published" title="2021-10-15T10:21:00-06:00">
      2021/10/15
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    <address class="vcard author">
      By <a class="url fn" href="https://keflavich.github.io/blog/author/adam-ginsburg-adamgginsburggmailcom.html">Adam Ginsburg (Adam.G.Ginsburg@gmail.com)</a>
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  <div class="entry-content">
    <p>We have noted a “confetti” problem in some of the ALMA-IMF cube images.
It is called confetti because <em>one</em> of its manifestations is individual
bright pixels in the model image.</p>
<p>This notebook shows where confetti is - and is not a problem.</p>
<p><a class="reference external" href="https://github.com/ALMA-IMF/notebooks/blob/master/ConfettiQA.ipynb">https://github.com/ALMA-IMF/notebooks/blob/master/ConfettiQA.ipynb</a></p>
<div class="section" id="preliminaries-skip-this">
<h2>Preliminaries: skip this</h2>
<pre class="code python literal-block">
<span class="kn">from</span> <span class="nn">spectral_cube</span> <span class="kn">import</span> <span class="n">SpectralCube</span><span class="w">
</span><span class="kn">import</span> <span class="nn">warnings</span><span class="w">
</span><span class="n">warnings</span><span class="o">.</span><span class="n">simplefilter</span><span class="p">(</span><span class="s1">'ignore'</span><span class="p">)</span>
</pre>
<pre class="code python literal-block">
<span class="o">%</span><span class="n">matplotlib</span> <span class="n">inline</span><span class="w">
</span><span class="kn">import</span> <span class="nn">pylab</span> <span class="k">as</span> <span class="nn">pl</span><span class="w">
</span><span class="kn">from</span> <span class="nn">astropy.visualization</span> <span class="kn">import</span> <span class="n">simple_norm</span>
</pre>
<pre class="code python literal-block">
<span class="kn">from</span> <span class="nn">astropy</span> <span class="kn">import</span> <span class="n">units</span> <span class="k">as</span> <span class="n">u</span>
</pre>
</div>
<div class="section" id="g008-67-continuum">
<h2>G008.67 Continuum</h2>
<p>This is the G008.67 continuum image in Band 3.</p>
<p>It has “confetti” pieces in the model image, but there is no problem: no
artificial point sources are introduced.</p>
<pre class="code python literal-block">
<span class="n">contmodel</span> <span class="o">=</span> <span class="n">SpectralCube</span><span class="o">.</span><span class="n">read</span><span class="p">(</span><span class="s1">'/orange/adamginsburg/ALMA_IMF/2017.1.01355.L/imaging_results/G008.67_B3_uid___A001_X1296_X1c1_continuum_merged_12M_robust-0.5_selfcal5_finaliter.model.tt0'</span><span class="p">,</span> <span class="nb">format</span><span class="o">=</span><span class="s1">'casa_image'</span><span class="p">)</span><span class="w">
</span><span class="n">contimage</span> <span class="o">=</span> <span class="n">SpectralCube</span><span class="o">.</span><span class="n">read</span><span class="p">(</span><span class="s1">'/orange/adamginsburg/ALMA_IMF/2017.1.01355.L/imaging_results/G008.67_B3_uid___A001_X1296_X1c1_continuum_merged_12M_robust-0.5_selfcal5_finaliter.image.tt0'</span><span class="p">,</span> <span class="nb">format</span><span class="o">=</span><span class="s1">'casa_image'</span><span class="p">)</span><span class="w">
</span><span class="n">contresid</span> <span class="o">=</span> <span class="n">SpectralCube</span><span class="o">.</span><span class="n">read</span><span class="p">(</span><span class="s1">'/orange/adamginsburg/ALMA_IMF/2017.1.01355.L/imaging_results/G008.67_B3_uid___A001_X1296_X1c1_continuum_merged_12M_robust-0.5_selfcal5_finaliter.residual.tt0'</span><span class="p">,</span> <span class="nb">format</span><span class="o">=</span><span class="s1">'casa_image'</span><span class="p">)</span>
</pre>
<pre class="code python literal-block">
<span class="c1"># zoom in</span><span class="w">
</span><span class="n">contslc</span> <span class="o">=</span> <span class="p">(</span><span class="mi">0</span><span class="p">,</span> <span class="nb">slice</span><span class="p">(</span><span class="mi">950</span><span class="p">,</span><span class="mi">1050</span><span class="p">),</span> <span class="nb">slice</span><span class="p">(</span><span class="mi">1900</span><span class="p">,</span><span class="mi">2050</span><span class="p">))</span>
</pre>
<pre class="code python literal-block">
<span class="n">pl</span><span class="o">.</span><span class="n">figure</span><span class="p">(</span><span class="n">figsize</span><span class="o">=</span><span class="p">(</span><span class="mi">15</span><span class="p">,</span><span class="mi">15</span><span class="p">))</span><span class="w">
</span><span class="n">pl</span><span class="o">.</span><span class="n">imshow</span><span class="p">(</span><span class="n">contmodel</span><span class="p">[</span><span class="n">contslc</span><span class="p">]</span><span class="o">.</span><span class="n">value</span><span class="p">,</span> <span class="n">norm</span><span class="o">=</span><span class="n">simple_norm</span><span class="p">(</span><span class="n">contmodel</span><span class="p">[</span><span class="n">contslc</span><span class="p">]</span><span class="o">.</span><span class="n">value</span><span class="p">,</span> <span class="n">max_percent</span><span class="o">=</span><span class="mf">99.995</span><span class="p">,</span> <span class="n">stretch</span><span class="o">=</span><span class="s1">'asinh'</span><span class="p">),</span> <span class="n">interpolation</span><span class="o">=</span><span class="s1">'none'</span><span class="p">,</span> <span class="n">origin</span><span class="o">=</span><span class="s1">'lower'</span><span class="p">)</span><span class="w">
</span><span class="n">_</span><span class="o">=</span><span class="n">pl</span><span class="o">.</span><span class="n">title</span><span class="p">(</span><span class="s2">&quot;model&quot;</span><span class="p">)</span>
</pre>
<img alt="" src="https://keflavich.github.io/blog/images/output_8_0.png" />
<pre class="code python literal-block">
<span class="n">pl</span><span class="o">.</span><span class="n">figure</span><span class="p">(</span><span class="n">figsize</span><span class="o">=</span><span class="p">(</span><span class="mi">15</span><span class="p">,</span><span class="mi">15</span><span class="p">))</span><span class="w">
</span><span class="n">im</span> <span class="o">=</span> <span class="n">contimage</span><span class="p">[</span><span class="mi">0</span><span class="p">][</span><span class="n">contslc</span><span class="p">[</span><span class="mi">1</span><span class="p">:]]</span><span class="o">.</span><span class="n">value</span><span class="w">
</span><span class="n">pl</span><span class="o">.</span><span class="n">imshow</span><span class="p">(</span><span class="n">im</span><span class="p">,</span> <span class="n">norm</span><span class="o">=</span><span class="n">simple_norm</span><span class="p">(</span><span class="n">im</span><span class="p">,</span> <span class="n">stretch</span><span class="o">=</span><span class="s1">'log'</span><span class="p">,</span> <span class="n">max_percent</span><span class="o">=</span><span class="mf">99.995</span><span class="p">),</span> <span class="n">interpolation</span><span class="o">=</span><span class="s1">'none'</span><span class="p">,</span>  <span class="n">origin</span><span class="o">=</span><span class="s1">'lower'</span><span class="p">)</span><span class="w">
</span><span class="n">_</span><span class="o">=</span><span class="n">pl</span><span class="o">.</span><span class="n">title</span><span class="p">(</span><span class="s2">&quot;image&quot;</span><span class="p">)</span>
</pre>
<img alt="" src="https://keflavich.github.io/blog/images/output_9_0.png" />
<pre class="code python literal-block">
<span class="n">pl</span><span class="o">.</span><span class="n">figure</span><span class="p">(</span><span class="n">figsize</span><span class="o">=</span><span class="p">(</span><span class="mi">15</span><span class="p">,</span><span class="mi">15</span><span class="p">))</span><span class="w">
</span><span class="n">im</span> <span class="o">=</span> <span class="n">contresid</span><span class="p">[</span><span class="mi">0</span><span class="p">][</span><span class="n">contslc</span><span class="p">[</span><span class="mi">1</span><span class="p">:]]</span><span class="o">.</span><span class="n">value</span><span class="w">
</span><span class="n">pl</span><span class="o">.</span><span class="n">imshow</span><span class="p">(</span><span class="n">im</span><span class="p">,</span> <span class="n">norm</span><span class="o">=</span><span class="n">simple_norm</span><span class="p">(</span><span class="n">im</span><span class="p">,</span> <span class="n">stretch</span><span class="o">=</span><span class="s1">'linear'</span><span class="p">),</span> <span class="n">interpolation</span><span class="o">=</span><span class="s1">'none'</span><span class="p">,</span>  <span class="n">origin</span><span class="o">=</span><span class="s1">'lower'</span><span class="p">)</span><span class="w">
</span><span class="n">_</span><span class="o">=</span><span class="n">pl</span><span class="o">.</span><span class="n">title</span><span class="p">(</span><span class="s2">&quot;Residual&quot;</span><span class="p">)</span>
</pre>
<img alt="" src="https://keflavich.github.io/blog/images/output_10_0.png" />
<div class="section" id="g008-67-cube">
<h3>G008.67 Cube</h3>
<p>The G008.67 cube <em>does</em> have a problem!</p>
<pre class="code python literal-block">
<span class="n">cube</span> <span class="o">=</span> <span class="n">SpectralCube</span><span class="o">.</span><span class="n">read</span><span class="p">(</span><span class="s1">'/orange/adamginsburg/ALMA_IMF/2017.1.01355.L/imaging_results/G008.67_B3_spw0_12M_n2hp.image'</span><span class="p">,</span> <span class="nb">format</span><span class="o">=</span><span class="s1">'casa_image'</span><span class="p">)</span><span class="o">.</span><span class="n">with_spectral_unit</span><span class="p">(</span><span class="n">u</span><span class="o">.</span><span class="n">km</span><span class="o">/</span><span class="n">u</span><span class="o">.</span><span class="n">s</span><span class="p">,</span> <span class="n">velocity_convention</span><span class="o">=</span><span class="s1">'radio'</span><span class="p">)</span><span class="w">
</span><span class="n">resid</span> <span class="o">=</span> <span class="n">SpectralCube</span><span class="o">.</span><span class="n">read</span><span class="p">(</span><span class="s1">'/orange/adamginsburg/ALMA_IMF/2017.1.01355.L/imaging_results/G008.67_B3_spw0_12M_n2hp.residual'</span><span class="p">,</span> <span class="nb">format</span><span class="o">=</span><span class="s1">'casa_image'</span><span class="p">)</span><span class="o">.</span><span class="n">with_spectral_unit</span><span class="p">(</span><span class="n">u</span><span class="o">.</span><span class="n">km</span><span class="o">/</span><span class="n">u</span><span class="o">.</span><span class="n">s</span><span class="p">,</span> <span class="n">velocity_convention</span><span class="o">=</span><span class="s1">'radio'</span><span class="p">)</span><span class="w">
</span><span class="n">model</span> <span class="o">=</span> <span class="n">SpectralCube</span><span class="o">.</span><span class="n">read</span><span class="p">(</span><span class="s1">'/orange/adamginsburg/ALMA_IMF/2017.1.01355.L/imaging_results/G008.67_B3_spw0_12M_n2hp.model'</span><span class="p">,</span> <span class="nb">format</span><span class="o">=</span><span class="s1">'casa_image'</span><span class="p">)</span><span class="o">.</span><span class="n">with_spectral_unit</span><span class="p">(</span><span class="n">u</span><span class="o">.</span><span class="n">km</span><span class="o">/</span><span class="n">u</span><span class="o">.</span><span class="n">s</span><span class="p">,</span> <span class="n">velocity_convention</span><span class="o">=</span><span class="s1">'radio'</span><span class="p">)</span>
</pre>
<pre class="code python literal-block">
<span class="n">xslc</span> <span class="o">=</span> <span class="nb">slice</span><span class="p">(</span><span class="mi">1620</span><span class="p">,</span><span class="mi">1654</span><span class="p">)</span><span class="w">
</span><span class="n">yslc</span> <span class="o">=</span> <span class="nb">slice</span><span class="p">(</span><span class="mi">709</span><span class="p">,</span><span class="mi">743</span><span class="p">)</span><span class="w">
</span><span class="n">cubeslice</span> <span class="o">=</span> <span class="p">(</span><span class="nb">slice</span><span class="p">(</span><span class="kc">None</span><span class="p">),</span> <span class="n">yslc</span><span class="p">,</span> <span class="n">xslc</span><span class="p">)</span><span class="w">
</span><span class="n">cube1slice</span> <span class="o">=</span> <span class="p">(</span><span class="mi">98</span><span class="p">,</span> <span class="n">yslc</span><span class="p">,</span> <span class="n">xslc</span><span class="p">)</span>
</pre>
</div>
</div>
<div class="section" id="confetti-a-false-point-source">
<h2>Confetti: a false (?) point source</h2>
<p>In the image below, we see a new source introduced in the 35.140 km/s
panel.</p>
<p>There is no comparable source in either of the adjacent panels!</p>
<p>That means either there is a genuinely pointlike source with linewidth
much narrower than 0.77 km/s, or this source is fake.</p>
<pre class="code python literal-block">
<span class="n">specpix</span> <span class="o">=</span> <span class="n">np</span><span class="o">.</span><span class="n">arange</span><span class="p">(</span><span class="mi">94</span><span class="p">,</span><span class="mi">94</span><span class="o">+</span><span class="mi">9</span><span class="p">)</span><span class="w">
</span><span class="n">panels</span> <span class="o">=</span> <span class="n">cube</span><span class="p">[</span><span class="n">cubeslice</span><span class="p">]</span><span class="o">.</span><span class="n">plot_channel_maps</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="n">specpix</span><span class="p">,</span> <span class="n">fig_smallest_dim_inches</span><span class="o">=</span><span class="mi">15</span><span class="p">,</span> <span class="n">norm</span><span class="o">=</span><span class="n">simple_norm</span><span class="p">(</span><span class="n">cube</span><span class="p">[</span><span class="n">cube1slice</span><span class="p">]</span><span class="o">.</span><span class="n">value</span><span class="p">))</span>
</pre>
<img alt="" src="https://keflavich.github.io/blog/images/output_15_0.png" />
<p>It is caused by one hot (bright) pixel surrounded by many faint pixels</p>
<pre class="code python literal-block">
<span class="n">panels</span> <span class="o">=</span> <span class="n">model</span><span class="p">[</span><span class="n">cubeslice</span><span class="p">]</span><span class="o">.</span><span class="n">plot_channel_maps</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="n">specpix</span><span class="p">,</span> <span class="n">fig_smallest_dim_inches</span><span class="o">=</span><span class="mi">15</span><span class="p">,</span> <span class="n">norm</span><span class="o">=</span><span class="n">simple_norm</span><span class="p">(</span><span class="n">model</span><span class="p">[</span><span class="n">cube1slice</span><span class="p">]</span><span class="o">.</span><span class="n">value</span><span class="p">,</span> <span class="n">stretch</span><span class="o">=</span><span class="s1">'log'</span><span class="p">,</span> <span class="n">max_percent</span><span class="o">=</span><span class="mf">99.93</span><span class="p">))</span>
</pre>
<img alt="" src="https://keflavich.github.io/blog/images/output_17_0.png" />
<p>There is no sign of it in the residual - it is apparently canceled out
between positive and negative components added to the model</p>
<pre class="code python literal-block">
<span class="n">panels</span> <span class="o">=</span> <span class="n">resid</span><span class="p">[</span><span class="n">cubeslice</span><span class="p">]</span><span class="o">.</span><span class="n">plot_channel_maps</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="n">specpix</span><span class="p">,</span> <span class="n">fig_smallest_dim_inches</span><span class="o">=</span><span class="mi">15</span><span class="p">)</span>
</pre>
<img alt="" src="https://keflavich.github.io/blog/images/output_19_0.png" />
<p>The manifestation in the spectra is a very sharp peak at just one pixel.</p>
<pre class="code python literal-block">
<span class="n">pl</span><span class="o">.</span><span class="n">figure</span><span class="p">(</span><span class="n">figsize</span><span class="o">=</span><span class="p">(</span><span class="mi">14</span><span class="p">,</span><span class="mi">6</span><span class="p">))</span><span class="w">
</span><span class="n">xx</span><span class="p">,</span><span class="n">yy</span><span class="o">=</span><span class="mi">1638</span><span class="p">,</span><span class="mi">725</span><span class="w">
</span><span class="n">cube</span><span class="p">[:,</span><span class="n">yy</span><span class="p">,</span><span class="n">xx</span><span class="p">]</span><span class="o">.</span><span class="n">quicklook</span><span class="p">()</span><span class="w">
</span><span class="n">resid</span><span class="p">[:,</span><span class="n">yy</span><span class="p">,</span><span class="n">xx</span><span class="p">]</span><span class="o">.</span><span class="n">quicklook</span><span class="p">()</span><span class="w">
</span><span class="n">modspec</span> <span class="o">=</span> <span class="n">model</span><span class="p">[:,</span><span class="n">yy</span><span class="p">,</span><span class="n">xx</span><span class="p">]</span><span class="w">
</span><span class="n">pl</span><span class="o">.</span><span class="n">plot</span><span class="p">(</span><span class="n">cube</span><span class="o">.</span><span class="n">spectral_axis</span><span class="p">,</span> <span class="n">modspec</span><span class="o">*</span><span class="n">cube</span><span class="o">.</span><span class="n">pixels_per_beam</span><span class="p">,</span> <span class="n">label</span><span class="o">=</span><span class="s1">'model'</span><span class="p">)</span>
</pre>
<img alt="" src="https://keflavich.github.io/blog/images/output_21_1.png" />
<p>Pixels to either side look fine</p>
<pre class="code python literal-block">
<span class="n">pl</span><span class="o">.</span><span class="n">figure</span><span class="p">(</span><span class="n">figsize</span><span class="o">=</span><span class="p">(</span><span class="mi">14</span><span class="p">,</span><span class="mi">14</span><span class="p">))</span><span class="w">
</span><span class="n">ii</span> <span class="o">=</span> <span class="mi">1</span><span class="w">
</span><span class="k">for</span> <span class="n">dx</span> <span class="ow">in</span> <span class="p">(</span><span class="o">-</span><span class="mi">1</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">):</span><span class="w">
</span>    <span class="k">for</span> <span class="n">dy</span> <span class="ow">in</span> <span class="p">(</span><span class="o">-</span><span class="mi">1</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">):</span><span class="w">
</span>        <span class="n">ax</span> <span class="o">=</span> <span class="n">pl</span><span class="o">.</span><span class="n">subplot</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span> <span class="mi">3</span><span class="p">,</span> <span class="n">ii</span><span class="p">)</span><span class="w">
</span>        <span class="n">ii</span> <span class="o">+=</span><span class="mi">1</span><span class="w">
</span>        <span class="n">cube</span><span class="p">[:,</span><span class="n">yy</span><span class="o">+</span><span class="n">dy</span><span class="p">,</span><span class="n">xx</span><span class="o">+</span><span class="n">dx</span><span class="p">]</span><span class="o">.</span><span class="n">quicklook</span><span class="p">()</span><span class="w">
</span>        <span class="n">resid</span><span class="p">[:,</span><span class="n">yy</span><span class="o">+</span><span class="n">dy</span><span class="p">,</span><span class="n">xx</span><span class="o">+</span><span class="n">dx</span><span class="p">]</span><span class="o">.</span><span class="n">quicklook</span><span class="p">()</span><span class="w">
</span>        <span class="n">modspec</span> <span class="o">=</span> <span class="n">model</span><span class="p">[:,</span><span class="n">yy</span><span class="o">+</span><span class="n">dy</span><span class="p">,</span><span class="n">xx</span><span class="o">+</span><span class="n">dx</span><span class="p">]</span><span class="w">
</span>        <span class="n">ax</span><span class="o">.</span><span class="n">plot</span><span class="p">(</span><span class="n">cube</span><span class="o">.</span><span class="n">spectral_axis</span><span class="p">,</span> <span class="n">modspec</span><span class="o">*</span><span class="n">cube</span><span class="o">.</span><span class="n">pixels_per_beam</span><span class="p">,</span> <span class="n">label</span><span class="o">=</span><span class="s1">'model'</span><span class="p">)</span><span class="w">
</span>        <span class="n">ax</span><span class="o">.</span><span class="n">set_title</span><span class="p">(</span><span class="sa">f</span><span class="s2">&quot;dx=</span><span class="si">{</span><span class="n">dx</span><span class="si">}</span><span class="s2"> dy=</span><span class="si">{</span><span class="n">dy</span><span class="si">}</span><span class="s2">&quot;</span><span class="p">)</span>
</pre>
<img alt="" src="https://keflavich.github.io/blog/images/output_23_0.png" />
<div class="section" id="when-is-confetti-not-a-problem">
<h3>When is confetti <em>not</em> a problem?</h3>
<p>Here is an example you might think is “confetti”, but is a <em>real</em> source</p>
<pre class="code python literal-block">
<span class="n">xc</span><span class="p">,</span> <span class="n">yc</span> <span class="o">=</span> <span class="mi">1812</span><span class="p">,</span> <span class="mi">905</span><span class="w">
</span><span class="n">xslc</span> <span class="o">=</span> <span class="nb">slice</span><span class="p">(</span><span class="n">xc</span><span class="o">-</span><span class="mi">12</span><span class="p">,</span><span class="n">xc</span><span class="o">+</span><span class="mi">12</span><span class="p">)</span><span class="w">
</span><span class="n">yslc</span> <span class="o">=</span> <span class="nb">slice</span><span class="p">(</span><span class="n">yc</span><span class="o">-</span><span class="mi">12</span><span class="p">,</span><span class="n">yc</span><span class="o">+</span><span class="mi">12</span><span class="p">)</span><span class="w">
</span><span class="n">cubeslice</span> <span class="o">=</span> <span class="p">(</span><span class="nb">slice</span><span class="p">(</span><span class="mi">94</span><span class="p">,</span><span class="mi">94</span><span class="o">+</span><span class="mi">9</span><span class="p">),</span> <span class="n">yslc</span><span class="p">,</span> <span class="n">xslc</span><span class="p">)</span><span class="w">
</span><span class="n">cube1slice</span> <span class="o">=</span> <span class="p">(</span><span class="mi">94</span><span class="p">,</span> <span class="n">yslc</span><span class="p">,</span> <span class="n">xslc</span><span class="p">)</span>
</pre>
<pre class="code python literal-block">
<span class="n">specpix</span> <span class="o">=</span> <span class="n">np</span><span class="o">.</span><span class="n">arange</span><span class="p">(</span><span class="mi">9</span><span class="p">)</span><span class="w">
</span><span class="n">panels</span> <span class="o">=</span> <span class="n">cube</span><span class="p">[</span><span class="n">cubeslice</span><span class="p">]</span><span class="o">.</span><span class="n">plot_channel_maps</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="n">specpix</span><span class="p">,</span> <span class="n">fig_smallest_dim_inches</span><span class="o">=</span><span class="mi">15</span><span class="p">,</span> <span class="n">norm</span><span class="o">=</span><span class="n">simple_norm</span><span class="p">(</span><span class="n">cube</span><span class="p">[</span><span class="n">cube1slice</span><span class="p">]</span><span class="o">.</span><span class="n">value</span><span class="p">,</span> <span class="n">min_cut</span><span class="o">=</span><span class="n">cube</span><span class="p">[</span><span class="n">cubeslice</span><span class="p">]</span><span class="o">.</span><span class="n">min</span><span class="p">()</span><span class="o">.</span><span class="n">value</span><span class="p">,</span> <span class="n">max_cut</span><span class="o">=</span><span class="n">cube</span><span class="p">[</span><span class="n">cubeslice</span><span class="p">]</span><span class="o">.</span><span class="n">max</span><span class="p">()</span><span class="o">.</span><span class="n">value</span><span class="p">,</span> <span class="n">stretch</span><span class="o">=</span><span class="s1">'linear'</span><span class="p">))</span>
</pre>
<img alt="" src="https://keflavich.github.io/blog/images/output_26_0.png" />
<pre class="code python literal-block">
<span class="n">panels</span> <span class="o">=</span> <span class="n">model</span><span class="p">[</span><span class="n">cubeslice</span><span class="p">]</span><span class="o">.</span><span class="n">plot_channel_maps</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="n">specpix</span><span class="p">,</span> <span class="n">fig_smallest_dim_inches</span><span class="o">=</span><span class="mi">15</span><span class="p">,</span> <span class="n">norm</span><span class="o">=</span><span class="n">simple_norm</span><span class="p">(</span><span class="n">model</span><span class="p">[</span><span class="n">cube1slice</span><span class="p">]</span><span class="o">.</span><span class="n">value</span><span class="p">,</span> <span class="n">stretch</span><span class="o">=</span><span class="s1">'asinh'</span><span class="p">,</span> <span class="n">max_percent</span><span class="o">=</span><span class="mf">99.9</span><span class="p">,</span> <span class="n">min_cut</span><span class="o">=</span><span class="n">model</span><span class="p">[</span><span class="n">cubeslice</span><span class="p">]</span><span class="o">.</span><span class="n">min</span><span class="p">()</span><span class="o">.</span><span class="n">value</span><span class="p">,</span> <span class="n">max_cut</span><span class="o">=</span><span class="n">model</span><span class="p">[</span><span class="n">cubeslice</span><span class="p">]</span><span class="o">.</span><span class="n">max</span><span class="p">()</span><span class="o">.</span><span class="n">value</span><span class="p">,</span> <span class="p">))</span>
</pre>
<img alt="" src="https://keflavich.github.io/blog/images/output_27_0.png" />
<pre class="code python literal-block">
<span class="n">panels</span> <span class="o">=</span> <span class="n">resid</span><span class="p">[</span><span class="n">cubeslice</span><span class="p">]</span><span class="o">.</span><span class="n">plot_channel_maps</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="n">specpix</span><span class="p">,</span> <span class="n">fig_smallest_dim_inches</span><span class="o">=</span><span class="mi">15</span><span class="p">)</span>
</pre>
<img alt="" src="https://keflavich.github.io/blog/images/output_28_0.png" />
<pre class="code python literal-block">
<span class="n">pl</span><span class="o">.</span><span class="n">figure</span><span class="p">(</span><span class="n">figsize</span><span class="o">=</span><span class="p">(</span><span class="mi">14</span><span class="p">,</span><span class="mi">14</span><span class="p">))</span><span class="w">
</span><span class="n">ii</span> <span class="o">=</span> <span class="mi">1</span><span class="w">
</span><span class="k">for</span> <span class="n">dx</span> <span class="ow">in</span> <span class="p">(</span><span class="o">-</span><span class="mi">1</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">):</span><span class="w">
</span>    <span class="k">for</span> <span class="n">dy</span> <span class="ow">in</span> <span class="p">(</span><span class="o">-</span><span class="mi">1</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">1</span><span class="p">):</span><span class="w">
</span>        <span class="n">ax</span> <span class="o">=</span> <span class="n">pl</span><span class="o">.</span><span class="n">subplot</span><span class="p">(</span><span class="mi">3</span><span class="p">,</span> <span class="mi">3</span><span class="p">,</span> <span class="n">ii</span><span class="p">)</span><span class="w">
</span>        <span class="n">ii</span> <span class="o">+=</span><span class="mi">1</span><span class="w">
</span>        <span class="n">cube</span><span class="p">[:,</span><span class="n">yc</span><span class="o">+</span><span class="n">dy</span><span class="p">,</span><span class="n">xc</span><span class="o">+</span><span class="n">dx</span><span class="p">]</span><span class="o">.</span><span class="n">quicklook</span><span class="p">()</span><span class="w">
</span>        <span class="n">resid</span><span class="p">[:,</span><span class="n">yc</span><span class="o">+</span><span class="n">dy</span><span class="p">,</span><span class="n">xc</span><span class="o">+</span><span class="n">dx</span><span class="p">]</span><span class="o">.</span><span class="n">quicklook</span><span class="p">()</span><span class="w">
</span>        <span class="n">modspec</span> <span class="o">=</span> <span class="n">model</span><span class="p">[:,</span><span class="n">yc</span><span class="o">+</span><span class="n">dy</span><span class="p">,</span><span class="n">xc</span><span class="o">+</span><span class="n">dx</span><span class="p">]</span><span class="w">
</span>        <span class="n">ax</span><span class="o">.</span><span class="n">plot</span><span class="p">(</span><span class="n">cube</span><span class="o">.</span><span class="n">spectral_axis</span><span class="p">,</span> <span class="n">modspec</span><span class="o">*</span><span class="n">cube</span><span class="o">.</span><span class="n">pixels_per_beam</span><span class="p">,</span> <span class="n">label</span><span class="o">=</span><span class="s1">'model'</span><span class="p">)</span><span class="w">
</span>        <span class="n">ax</span><span class="o">.</span><span class="n">set_title</span><span class="p">(</span><span class="sa">f</span><span class="s2">&quot;dx=</span><span class="si">{</span><span class="n">dx</span><span class="si">}</span><span class="s2"> dy=</span><span class="si">{</span><span class="n">dy</span><span class="si">}</span><span class="s2">&quot;</span><span class="p">)</span>
</pre>
<img alt="" src="https://keflavich.github.io/blog/images/output_29_0.png" />
</div>
<div class="section" id="conclusion">
<h3>Conclusion</h3>
<p>“Confetti” is a problem, but it is not trivial to find in the model data
alone. It exhibits no features in the residual.</p>
<p>Key features to look out for are:</p>
<ul class="simple">
<li>Narrow-line features (single channel)</li>
<li>Extremely bright pointlike peaks in the model (note that this is
<em>not</em> independent evidence of a problem! All point sources occupy
single pixels in the model image by definition!)</li>
<li>Bright pointlike peaks sitting on top of slightly extended negative
backgrounds in the model (this is how the model is “canceled out” in
the residual)</li>
</ul>
</div>
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