Sunyaev–Zel'dovich Array

<h2 id="experiment">Experiment</h2>
<p>The SZA has been used for multi-wavelength observations of over 100 galaxy clusters, both on its own and as a part of the <a href="/facts/Combined_Array_for_Research_in_Millimeter-wave_Astronomy/bTz78Bqx">Combined Array for Research in Millimeter-wave Astronomy</a> (CARMA), which was decommissioned after 3 April 2015.<a class="footnote-ref" id="fnref:1" href="#fn:1"><sup>1</sup></a> From 2005 to 2007, SZA undertook a deep 31 GHz (<a href="/facts/Gigahertz/6Wshj5qm">Gigahertz</a>) survey of several patches of sky.
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<h2 id="instrument">Instrument</h2>
<p>The SZA is not a single telescope, but an array of 8 telescopes operating together as an <a href="/facts/Interferometer/X3E1SsQT">interferometer</a>. An interferometer does not detect light in quite the same way as an ordinary telescope, by measuring the total power collected by a single dish; instead, it looks at differences between the light falling on pairs of telescopes. Like water waves, light waves can interfere with each other, producing a complex pattern of intensity enhancements where the waves constructively interfere, and nulls where they destructively interfere.
</p><p>As light from a source washes over the array, an interferometer detects this <a href="/facts/Interference_pattern/lI5f78I4">interference pattern</a> — hence the name. The source's structure on the sky can then be inferred from the interference pattern in much the same way that one might infer the size and shape of a stone thrown into a pond from the pattern of ripples left in its wake.
</p><p>The native resolution of an interferometer depends not on the size of the individual telescopes (as with a traditional single telescope), but on their separation. Pairs of telescopes with large separations provide sensitivity to small-scale structure, while short spacings are sensitive to large-scale structure on the sky. The 8 SZA telescopes are small enough to be placed very close together, which provides maximum sensitivity to the (large-scale) SZ signal from clusters.  When the SZA was combined with the other telescopes in the CARMA array, which had longer separations and were sensitive to finer angular scales, it formed a complete picture of galaxy clusters at very high resolution.
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<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>"CARMA public pages". www.mmarray.org. Retrieved 27 May 2020. Observations finished on April 3, 2015, and the Observatory was shut down. Decommissioning is complete. The equipment has been removed from all the buildings. Antenna removal started on June 16, 2015 <a href="https://www.mmarray.org/" target="_blank">https://www.mmarray.org/</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
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Sunyaev–Zel'dovich Array open-in-new

Sunyaev–Zel'dovich Array