{"id":4202,"date":"2016-09-07T15:09:06","date_gmt":"2016-09-07T15:09:06","guid":{"rendered":"http:\/\/www.particlebites.com\/?p=4202"},"modified":"2017-02-19T02:06:44","modified_gmt":"2017-02-19T02:06:44","slug":"dragonfly-44-a-potential-dark-matter-galaxy","status":"publish","type":"post","link":"https:\/\/www.particlebites.com\/?p=4202","title":{"rendered":"Dragonfly 44: A potential Dark Matter Galaxy"},"content":{"rendered":"
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Title<\/strong>: A High Stellar Velocity Dispersion and ~100 Globular Clusters for the Ultra Diffuse Galaxy Dragonfly 44<\/p>\n

Publication<\/strong>:\u00a0ApJ<\/span>, v828, Number 1<\/a>, arXiv:\u00a0<\/span>1606.06291<\/a><\/p>\n<\/div>\n

The title of this paper sounds like some standard astrophysics analyses; but, dig a little deeper and you’ll find – what I think – is an incredibly interesting, surprising and unexpected observation.<\/p>\n

<\/a>
The Coma Cluster: NASA, ESA, and the Hubble Heritage Team (STScI\/AURA)<\/figcaption><\/figure>\n

Last year, using the WM Keck Observatory and the Gemini North Telescope in Manuakea, Hawaii, the Dragonfly Telephoto Array observed\u00a0the Coma cluster (a large cluster of galaxies in the constellation Coma – I’ve included a Hubble Image to the left). The team identified a population of large, very low surface brightness (ie: not a lot of stars), spheroidal galaxies around an Ultra Diffuse Galaxy (UDG) called Dragonfly 44 (shown below). They determined that Dragonfly 44 has so few stars that gravity\u00a0could not hold it\u00a0together – so some other matter had to be involved – namely DARK MATTER (my favorite kind of unknown matter).<\/p>\n

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\"The<\/a>
The ultra-diffuse galaxy Dragonfly 44. The galaxy consists almost entirely of dark matter. It is surrounded by faint, compact sources. Image credit: Pieter van Dokkum \/ Roberto Abraham \/ Gemini Observatory \/ SDSS \/ AURA<\/figcaption><\/figure>\n

The team\u00a0used the DEIMOS instrument installed on Keck II to measure the velocities of stars for 33.5 hours over a period of six nights so they could determine the galaxy\u2019s mass. Observations of Dragonfly 44’s\u00a0rotational speed suggest that it has a mass of about one trillion solar masses,\u00a0about the same\u00a0as the\u00a0Milky Way. However, the galaxy emits only 1% of the light emitted by the Milky Way. In other words, the Milky Way has more than a hundred times more stars than Dragonfly 44. I’ve also included the Mass-to-Light ratio plot vs. the dynamical mass. This illustrates how unique Dragonfly 44 is compared to other dark matter dominated galaxies like dwarf spheroidal galaxies.<\/p>\n

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\"MLratio\"<\/a>
Relation between dynamical mass-to-light ratio and dynamical mass. Open symbols are dispersion-dominated objects from Zaritsky, Gonzalez, & Zabludoff (2006) and Wolf et al. (2010). The UDGs VCC 1287 (Beasley et al. 2016) and Dragonfly 44 fall outside of the band defined by the other galaxies, having a very high M\/L ratio for their mass.<\/figcaption><\/figure>\n

What is particularly\u00a0exciting is that we don’t understand how galaxies like this form.<\/p>\n

Their\u00a0research indicates that these UDGs could be failed galaxies, with\u00a0the sizes, dark matter content, and globular cluster systems of much more luminous objects. But we’ll need to discover more to fully understand them.<\/p>\n

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Further reading<\/strong> (works by the same authors)
\nForty-Seven Milky Way-Sized, Extremely Diffuse Galaxies in the Coma Cluster,arXiv:\u00a01410.8141<\/a>
\nSpectroscopic Confirmation of the Existence of Large, Diffuse Galaxies in the Coma Cluster:\u00a0arXiv:\u00a01504.03320<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

Title: A High Stellar Velocity Dispersion and ~100 Globular Clusters for the Ultra Diffuse Galaxy Dragonfly 44 Publication:\u00a0ApJ, v828, Number 1, arXiv:\u00a01606.06291 The title of this paper sounds like some standard astrophysics analyses; but, dig a little deeper and you’ll find – what I think – is an incredibly interesting, surprising and unexpected observation. Last … <\/p>\n

Continue reading “Dragonfly 44: A potential Dark Matter Galaxy”<\/span><\/a><\/p>\n","protected":false},"author":5,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[56,63,38,1],"tags":[],"class_list":["post-4202","post","type-post","status-publish","format-standard","hentry","category-astroparticle","category-cosmology","category-dark-matter","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/www.particlebites.com\/index.php?rest_route=\/wp\/v2\/posts\/4202","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.particlebites.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.particlebites.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.particlebites.com\/index.php?rest_route=\/wp\/v2\/users\/5"}],"replies":[{"embeddable":true,"href":"https:\/\/www.particlebites.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=4202"}],"version-history":[{"count":10,"href":"https:\/\/www.particlebites.com\/index.php?rest_route=\/wp\/v2\/posts\/4202\/revisions"}],"predecessor-version":[{"id":4692,"href":"https:\/\/www.particlebites.com\/index.php?rest_route=\/wp\/v2\/posts\/4202\/revisions\/4692"}],"wp:attachment":[{"href":"https:\/\/www.particlebites.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=4202"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.particlebites.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=4202"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.particlebites.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=4202"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}