{"id":19040,"date":"2016-08-03T20:00:19","date_gmt":"2016-08-04T06:00:19","guid":{"rendered":"http:\/\/darkerview.com\/wordpress\/?p=19040"},"modified":"2016-08-03T19:12:51","modified_gmt":"2016-08-04T05:12:51","slug":"ucla-astronomers-use-keck-observatory-to-look-back-12-billion-years-and-measure-oxygen","status":"publish","type":"post","link":"https:\/\/darkerview.com\/wordpress\/?p=19040","title":{"rendered":"UCLA Astronomers Use Keck Observatory to Look Back 12 Billion Years and Measure Oxygen"},"content":{"rendered":"

W. M. Keck Observatory press release<\/a>…<\/p>\n

UCLA astronomers have used the W. M. Keck Observatory on Maunakea, Hawaii to make the first accurate measurement of the abundance of oxygen in a distant galaxy. Oxygen, the third-most abundant chemical element in the Universe, is created inside stars and released into interstellar gas when stars die. Quantifying the amount of oxygen is key to understanding how matter cycles in and out of galaxies. This research is published online in the Astrophysical Journal Letters.<\/p>\n

\"COSMOS-1908\"<\/a>
Galaxy COSMOS-1908 is in the center of this Hubble Space Telescope image, indicated by the arrow. Nearly everything in the image is a galaxy.
Credit: Ryan Sandres and the CANDELS Team<\/figcaption><\/figure>\u201cThis is by far the most distant galaxy for which the oxygen abundance has actually been measured,\u201d said Alice Shapley, a UCLA professor of astronomy, and co-author of the study. \u201cWe\u2019re looking back in time at this galaxy as it appeared 12 billion years ago.\u201d<\/p>\n

Knowing the abundance of oxygen in the galaxy called COSMOS-1908 is an important stepping stone toward allowing astronomers to better understand the population of faint, distant galaxies observed when the Universe was only a few billion years old, Shapley said.<\/p>\n

COSMOS-1908 contains approximately one billion stars. In contrast, the Milky Way contains approximately 100 billion stars. Furthermore, COSMOS-1908 contains approximately only 20 percent the abundance of oxygen that is observed in the Sun.<\/p>\n

Typically, astronomers rely on extremely indirect and imprecise techniques for estimating oxygen abundance for the vast majority of distant galaxies. But in this case, UCLA researchers used a direct measurement, said Ryan Sanders, astronomy graduate student and the study\u2019s lead author.<\/p>\n

\u201cClose galaxies are much brighter, and we have a very good method of determining the amount of oxygen in nearby galaxies,\u201d Sanders said.<\/p>\n

In faint, distant galaxies, the task is dramatically more difficult, but COSMOS-1908 was one case for which Sanders was able to apply the \u201crobust\u201d method commonly applied to nearby galaxies. \u201cWe hope this will be the first of many,\u201d he said.<\/p>\n

Shapley said that prior to Sanders\u2019 discovery, researchers didn\u2019t know if they could measure how much oxygen there was in these distant galaxies.<\/p>\n

\u201cRyan\u2019s discovery shows we can measure the oxygen and compare these observations with models of how galaxies form and what their history of star formation is,\u201d Shapley said.<\/p>\n

The researchers used an extremely advanced and sophisticated instrument called MOSFIRE (Multi-Object Spectrometer for Infra-Red Exploration) installed on the Keck I telescope at the Keck Observatory.<\/p>\n

This five-ton instrument was designed to study the most distant, faintest galaxies, said UCLA physics and astronomy professor Ian McLean, co-project leader on MOSFIRE and director of UCLA\u2019s Infrared Laboratory for Astrophysics. McLean and co-principal investigator Chuck Steidel from the California Institute of Technology built the instrument with colleagues colleagues from UCLA, Caltech, UC Santa Cruz and industrial sub-contractors.<\/p>\n

The amount of oxygen in a galaxy is determined primarily by three factors: how much oxygen comes from large stars that end their lives violently in supernova explosions \u2014 a ubiquitous phenomenon in the early Universe, when the rate of stellar births was dramatically higher than the rate in the Universe today; how much of that oxygen gets ejected from the galaxy by so-called \u201csuper winds,\u201d which propel oxygen and other interstellar gases out of galaxies at hundreds of thousands of miles per hour; and how much pristine gas enters the galaxy from the intergalactic medium, which doesn\u2019t contain much oxygen.<\/p>\n

\u201cIf we can measure how much oxygen is in a galaxy, it will tell us about all these processes,\u201d said Shapley, who, along with Sanders, is interested in learning how galaxies form and evolve, why galaxies have different structures, and how galaxies exchange material with their intergalactic environments.<\/p>\n

Shapley expects the measurements of oxygen will reveal that super winds are very important in how galaxies evolved. \u201cMeasuring the oxygen content of galaxies over cosmic time is one of the key methods we have for understanding how galaxies grow, as well as how they spew out gas into the intergalactic medium,\u201d she said.<\/p>\n

Keck Observatory\u2019s MOSFIRE collects visible-light photons from objects billions of light years away whose wavelengths have been stretched or \u201credshifted\u201d to the infrared by the expansion of the Universe. Due to the finite speed of light, MOSFIRE is providing a view of these galaxies as they existed billions of years ago, when the light first started traveling to Earth. MOSFIRE is a type of instrument known as a \u201cspectrograph,\u201d which spreads the light from astronomical objects out into a spectrum of separate wavelengths (colors), indicating the specific amount of energy emitted at each wavelength. Spectrographs enable astronomers to determine the chemical contents of galaxies, because different chemical elements \u2014 such as oxygen, carbon, iron or hydrogen \u2014 each provide a unique spectral fingerprint, emitting light at specific wavelengths.<\/p>\n

To characterize the chemical contents of COSMOS-1908, Sanders analyzed a particular wavelength in the MOSFIRE spectrum of this galaxy that is sensitive to the amount of oxygen. \u201cIt\u2019s an amazing instrument, which made Ryan\u2019s measurement possible,\u201d Shapley said.<\/p>\n

Data for COSMOS-1908 were collected as part of the MOSFIRE Deep Evolution Field (MOSDEF) survey, a large Keck Observatory project that Shapley and Sanders have carried out in collaboration with astronomers at UC Berkeley, UC Riverside and UCSD. Between 2012 and 2016, the MOSDEF survey was allocated roughly 50 nights of MOSFIRE time on the Keck I telescope to study distant galaxies forming in the early Universe.<\/p>\n","protected":false},"excerpt":{"rendered":"

W. M. Keck Observatory press release… UCLA astronomers have used the W. M. Keck Observatory on Maunakea, Hawaii to make the first accurate measurement of the abundance of oxygen in a distant galaxy. Oxygen, the third-most abundant chemical element in the Universe, is created inside stars and released into interstellar gas when stars die. Quantifying … Continue reading “UCLA Astronomers Use Keck Observatory to Look Back 12 Billion Years and Measure Oxygen”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[9],"tags":[141,50,2267],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/darkerview.com\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/19040"}],"collection":[{"href":"https:\/\/darkerview.com\/wordpress\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/darkerview.com\/wordpress\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/darkerview.com\/wordpress\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/darkerview.com\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=19040"}],"version-history":[{"count":4,"href":"https:\/\/darkerview.com\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/19040\/revisions"}],"predecessor-version":[{"id":19045,"href":"https:\/\/darkerview.com\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/19040\/revisions\/19045"}],"wp:attachment":[{"href":"https:\/\/darkerview.com\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=19040"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/darkerview.com\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=19040"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/darkerview.com\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=19040"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}