Characterizing Transition Temperature Gas In The Galactic Corona

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dc.contributor.utaustinauthorShapiro, Paul R.en_US
dc.creatorWakker, Bart P.en_US
dc.creatorSavage, Blair D.en_US
dc.creatorFox, Andrew J.en_US
dc.creatorBenjamin, Robert A.en_US
dc.creatorShapiro, Paul R.en_US
dc.date.accessioned2016-04-28T19:42:34Z
dc.date.available2016-04-28T19:42:34Z
dc.date.issued2012-04en
dc.description.abstractWe present a study of the properties of the transition temperature (T similar to 10(5) K) gas in the Milky Way corona, based on the measurements of O VI, N V, C IV, Si IV, and Fe III absorption lines seen in the far-ultraviolet spectra of 58 sight lines to extragalactic targets, obtained with the Far-Ultraviolet Spectroscopic Explorer and the Space Telescope Imaging Spectrograph. In many sight lines the Galactic absorption profiles show multiple components, which are analyzed separately. We find that the highly ionized atoms are distributed irregularly in a layer with a scale height of about 3 kpc, which rotates along with the gas in the disk, without an obvious gradient in the rotation velocity away from the Galactic plane. Within this layer the gas has randomly oriented velocities with a dispersion of 40-60 km s(-1). On average the integrated column densities are log N(O VI) = 14.3, log N(N V) = 13.5, log N(C IV) = 14.2, log N(Si IV) = 13.6, and log N(Fe III) = 14.2, with a dispersion of just 0.2 dex in each case. In sight lines around the Galactic center and Galactic north pole, all column densities are enhanced by a factor similar to 2, while at intermediate latitudes in the southern sky there is a deficit in N(O VI) of about a factor of two, but no deficit for the other ions. We compare the column densities and ionic ratios to a series of theoretical predictions: collisional ionization equilibrium, shock ionization, conductive interfaces, turbulent mixing, thick disk supernovae, static non-equilibrium ionization (NIE) radiative cooling, and an NIE radiative cooling model in which the gas flows through the cooling zone. None of these models can fully reproduce the data, but it is clear that NIE radiative cooling is important in generating the transition temperature gas.en_US
dc.description.departmentAstronomyen_US
dc.description.sponsorshipNASA NAS5-26555, NAS5-32985, NNX10A170Gen_US
dc.identifierdoi:10.15781/T2QJ9H
dc.identifier.Filename2012_04_galacticcorona.pdfen_US
dc.identifier.citationWakker, Bart P., Blair D. Savage, Andrew J. Fox, Robert A. Benjamin, and Paul R. Shapiro. "Characterizing transition temperature gas in the galactic corona." The Astrophysical Journal, Vol. 749, No. 2 (Apr., 2012): 157.en_US
dc.identifier.doi10.1088/0004-637x/749/2/157en_US
dc.identifier.issn0004-637Xen_US
dc.identifier.urihttp://hdl.handle.net/2152/35146
dc.language.isoEnglishen_US
dc.relation.ispartofen_US
dc.relation.ispartofserialAstrophysical Journalen_US
dc.rightsAdministrative deposit of works to Texas ScholarWorks: This works author(s) is or was a University faculty member, student or staff member; this article is already available through open access or the publisher allows a PDF version of the article to be freely posted online. The library makes the deposit as a matter of fair use (for scholarly, educational, and research purposes), and to preserve the work and further secure public access to the works of the University.en_US
dc.rights.restrictionOpenen_US
dc.subjectgalaxy: haloen_US
dc.subjectism: cloudsen_US
dc.subjectism: generalen_US
dc.subjectultraviolet: ismen_US
dc.subjectultraviolet-spectroscopic-exploreren_US
dc.subjecthigh-velocity cloudsen_US
dc.subjecthighlyen_US
dc.subjectionized-gasen_US
dc.subjectlocal interstellar-mediumen_US
dc.subjectturbulent mixing layersen_US
dc.subjecto-vien_US
dc.subjectabsorptionen_US
dc.subjectfield unit observationsen_US
dc.subjectlyman-alpha systemsen_US
dc.subjectovien_US
dc.subjectabsorptionen_US
dc.subjectmilky-wayen_US
dc.subjectastronomy & astrophysicsen_US
dc.titleCharacterizing Transition Temperature Gas In The Galactic Coronaen_US
dc.typeArticleen_US

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