{"id":11085,"date":"2020-04-14T23:33:08","date_gmt":"2020-04-15T09:33:08","guid":{"rendered":"http:\/\/www.eaobservatory.org\/jcmt\/?p=11085"},"modified":"2020-12-29T10:55:54","modified_gmt":"2020-12-29T20:55:54","slug":"changing-the-de-biasing-in-a-pol2-vector-catalogue","status":"publish","type":"post","link":"https:\/\/www.eaobservatory.org\/jcmt\/2020\/04\/changing-the-de-biasing-in-a-pol2-vector-catalogue\/","title":{"rendered":"Changing the de-biasing in a POL2 vector catalogue"},"content":{"rendered":"<p>The new <span style=\"font-family: 'courier new', courier, monospace\">poledit<\/span> command in the <a href=\"http:\/\/starlink.eao.hawaii.edu\/devdocs\/sun223.htx\/sun223.html\">Starlink POLPACK<\/a> package (see a <a href=\"https:\/\/www.eaobservatory.org\/jcmt\/2020\/04\/adding-an-ast-mask-column-to-a-pol2-vector-catalogue\/\">previous blog post<\/a>) has an option to recalculate the PI (polarised intensity) and P (percentage polarisation) values using a specified form of de-biasing. If the existing catalogue is in file &#8220;<span style=\"font-family: 'courier new', courier, monospace\">mycat.FIT<\/span>&#8220;, you can do:<\/p>\n<p><code>% polpack<br \/>\n% poledit mycat newcat mode=debias debiastype=mas<\/code><\/p>\n<p>This will create a new file &#8220;<span style=\"font-family: 'courier new', courier, monospace\">newcat.FIT<\/span>&#8221; containing a copy of &#8220;<span style=\"font-family: 'courier new', courier, monospace\">mycat.FIT<\/span>&#8220;, but with new P and PI columns re-calculated from the existing Q, U, I and DPI values using the <a href=\"https:\/\/arxiv.org\/abs\/1407.0178\">&#8220;Modified Asymptotic&#8221; (MAS) bias estimator<\/a>\u00a0(any de-biasing used to create the original catalogue is ignored). The options for the DEBIASTYPE parameter are:<\/p>\n<ul>\n<li>&#8220;MAS&#8221;: De-bias using the modified asymptotic estimator<\/li>\n<li>&#8220;AS&#8221;: De-bias using the asymptotic estimator<\/li>\n<li>&#8220;None&#8221;: Do not include any de-biasing<\/li>\n<\/ul>\n<p>See<a href=\"https:\/\/www.eaobservatory.org\/jcmt\/2020\/04\/new-de-biasing-method-for-pol2-data\/\"> a previous blog post<\/a> for more on these types of de-biasing.<\/p>\n<p>The following plot shows the results of using the above command. The horizontal axis is PI\/DPI (polarised intensity signal to noise ratio) with no de-biasing. The vertical axis is the new PI\/DPI value created with each of the DEBIASTYPE options listed above (red is &#8220;AS&#8221;, blue is &#8220;MAS&#8221; and green is &#8220;None&#8221;)<\/p>\n<p><a href=\"http:\/\/www.eaobservatory.org\/jcmt\/wp-content\/uploads\/sites\/2\/2020\/04\/poledit-debias.png\"><img loading=\"lazy\" class=\"alignnone wp-image-11088\" src=\"http:\/\/www.eaobservatory.org\/jcmt\/wp-content\/uploads\/sites\/2\/2020\/04\/poledit-debias-300x232.png\" alt=\"\" width=\"477\" height=\"369\" srcset=\"https:\/\/www.eaobservatory.org\/jcmt\/wp-content\/uploads\/sites\/2\/2020\/04\/poledit-debias-300x232.png 300w, https:\/\/www.eaobservatory.org\/jcmt\/wp-content\/uploads\/sites\/2\/2020\/04\/poledit-debias-194x150.png 194w, https:\/\/www.eaobservatory.org\/jcmt\/wp-content\/uploads\/sites\/2\/2020\/04\/poledit-debias-150x116.png 150w, https:\/\/www.eaobservatory.org\/jcmt\/wp-content\/uploads\/sites\/2\/2020\/04\/poledit-debias.png 693w\" sizes=\"(max-width: 477px) 100vw, 477px\" \/><\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>The new poledit command in the Starlink POLPACK package (see a previous blog post) has an option to recalculate the PI (polarised intensity) and P (percentage polarisation) values using a specified form of de-biasing. If the existing catalogue is in file &#8220;mycat.FIT&#8220;, you can do: % polpack % poledit mycat\u2026 <a class=\"continue-reading-link\" href=\"https:\/\/www.eaobservatory.org\/jcmt\/2020\/04\/changing-the-de-biasing-in-a-pol2-vector-catalogue\/\">Continue reading<\/a><\/p>\n","protected":false},"author":13,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[36],"tags":[37],"_links":{"self":[{"href":"https:\/\/www.eaobservatory.org\/jcmt\/wp-json\/wp\/v2\/posts\/11085"}],"collection":[{"href":"https:\/\/www.eaobservatory.org\/jcmt\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.eaobservatory.org\/jcmt\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.eaobservatory.org\/jcmt\/wp-json\/wp\/v2\/users\/13"}],"replies":[{"embeddable":true,"href":"https:\/\/www.eaobservatory.org\/jcmt\/wp-json\/wp\/v2\/comments?post=11085"}],"version-history":[{"count":2,"href":"https:\/\/www.eaobservatory.org\/jcmt\/wp-json\/wp\/v2\/posts\/11085\/revisions"}],"predecessor-version":[{"id":11089,"href":"https:\/\/www.eaobservatory.org\/jcmt\/wp-json\/wp\/v2\/posts\/11085\/revisions\/11089"}],"wp:attachment":[{"href":"https:\/\/www.eaobservatory.org\/jcmt\/wp-json\/wp\/v2\/media?parent=11085"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.eaobservatory.org\/jcmt\/wp-json\/wp\/v2\/categories?post=11085"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.eaobservatory.org\/jcmt\/wp-json\/wp\/v2\/tags?post=11085"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}