jay-gallagher-lessons-from-comparisons-between-the-nuclear-region-of-the-milky-way-and-those-in-nearby-spirals.html

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      <a href="https://keflavich.github.io/blog/jay-gallagher-lessons-from-comparisons-between-the-nuclear-region-of-the-milky-way-and-those-in-nearby-spirals.html" rel="bookmark"
         title="Permalink to Jay Gallagher: Lessons from Comparisons between the Nuclear Region of the Milky Way and Those in Nearby Spirals">Jay Gallagher: Lessons from Comparisons between the Nuclear Region of the Milky Way and Those in Nearby Spirals</a></h2>
 
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  <footer class="post-info">
    <abbr class="published" title="2013-09-30T14:40:00-06:00">
      2013/09/30
    </abbr>
    <address class="vcard author">
      By <a class="url fn" href="https://keflavich.github.io/blog/author/adam-ginsburg.html">Adam Ginsburg</a>
    </address>
  </footer><!-- /.post-info -->
  <div class="entry-content">
    <img alt="" src="https://keflavich.github.io/blog/iau303/images/gallagher.jpg" style="width: 800px;" />
<p>Investigation to understand assumptions made in extragalactic obs</p>
<blockquote>
<ul class="simple">
<li>MW single example - what is unique, what general?</li>
<li>SNR / CR interaction model works in M82 &amp; NGC 253, not in MW</li>
<li>MW SFR?  Is it right?</li>
<li>lots of nearby SAB moderately-barred spirals moderately analogous to MW</li>
<li>Maffei 2
+ 5x10^7 msun mol gas in rotating core</li>
<li>NGC 253
+ 10^8 msun molecular gas</li>
<li>MW
+ 3-4x10^7</li>
</ul>
</blockquote>
<p>Similar molecular and stellar content</p>
<dl class="docutils">
<dt>Major differences</dt>
<dd><ul class="first last simple">
<li>MW: SFR 0.01 Msun/yr [my comment: this seems low?]</li>
<li>IC 342 &amp; Maffei 2: 1 Msun/yr</li>
<li>NGC 253, M82: 3-8 msun/yr
+ nuclei don't follow CO vs SFR</li>
<li>NGC 253: huge wind (almost naked eye)
+ 10-100x MW CMZ thermal pressure</li>
<li>Gamma rays: MW overluminous at low energies?</li>
</ul>
</dd>
</dl>
<p>Statement: &quot;No correlation.  Extragalactic relation totally fails&quot; on a plot with 5 data points...</p>
<blockquote>
<ul class="simple">
<li>not tied to CO</li>
<li>Must be a large range in SF efficiency</li>
<li>SFR not correlated with nuclear stellar mass</li>
<li>MW in SFR low-state</li>
</ul>
</blockquote>
<dl class="docutils">
<dt>Episodic SF</dt>
<dd><ul class="first last simple">
<li>Physical state varies
+ Chemical transition?
+ driven by chemistry rather than mass?</li>
<li>SF bimodal?  Need larger sample</li>
<li>Unexpected SMBH impacts?</li>
</ul>
</dd>
</dl>
<p>Advertisement: AJ - interested in improving figure distribution.  <a class="reference external" href="mailto:aj&#64;astro.wisc.edu">aj&#64;astro.wisc.edu</a></p>
<div class="section" id="questions">
<h2>Questions</h2>
<blockquote>
<ul class="simple">
<li>Q: Comment - SF adequate to explain energetics seen</li>
<li>Q Longmore: Idea for what's stopping SF in our own galaxy.  Rate limiting factor is that gas is not self-gravitating.</li>
<li>A: turbulent, yeah.</li>
<li>Q Mitch: Positive feedback.  SF starts, gets intensified.  Squeezed by external pressures.</li>
<li>A: Agree</li>
<li>Q: SFR density of mol gas.</li>
<li>A: Cloud production mechanism is different (rather than SF &quot;relation&quot; breaking down)</li>
<li>Q: Large range in star formation.  Is wind/outflow to SFR more constant?</li>
<li>A: would like to know.  Outflows not well-measured.</li>
<li>Q: Constant at what value?</li>
<li>A: Outflow/SFR constant</li>
<li>Q Farhad: Dense gas in other galaxies?</li>
<li>A: Not known yet.  Need to know dense gas fractions</li>
<li>Q Farhad:  Need to know fraction of <em>dense</em> gas.</li>
<li>A: Bigger debate in N253</li>
</ul>
</blockquote>
</div>

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