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Mapping the Galactic Halo. VIII. Quantifying Substructure

Starkenburg, Else; Helmi, Amina; Morrison, Heather; Harding, Paul; van Woerden, Hugo; Mateo, Mario; Olszewski, Edward W; Sivarani, T; Norris, John; Freeman, Kenneth; Shectman, Stephen; Dohm-Palmer, Robbie C; Frey, Lucy

Description

We have measured the amount of kinematic substructure in the Galactic halo using the final data set from the Spaghetti project, a pencil-beam high-latitude sky survey. Our sample contains 101 photometrically selected and spectroscopically confirmed giants with accurate distance, radial velocity, and metallicity information. We have developed a new clustering estimator: the "4distance" measure, which when applied to our data set leads to the identification of one group and seven pairs of clumped...[Show more]

dc.contributor.authorStarkenburg, Else
dc.contributor.authorHelmi, Amina
dc.contributor.authorMorrison, Heather
dc.contributor.authorHarding, Paul
dc.contributor.authorvan Woerden, Hugo
dc.contributor.authorMateo, Mario
dc.contributor.authorOlszewski, Edward W
dc.contributor.authorSivarani, T
dc.contributor.authorNorris, John
dc.contributor.authorFreeman, Kenneth
dc.contributor.authorShectman, Stephen
dc.contributor.authorDohm-Palmer, Robbie C
dc.contributor.authorFrey, Lucy
dc.date.accessioned2015-12-07T22:48:47Z
dc.identifier.issn0004-637X
dc.identifier.urihttp://hdl.handle.net/1885/26493
dc.description.abstractWe have measured the amount of kinematic substructure in the Galactic halo using the final data set from the Spaghetti project, a pencil-beam high-latitude sky survey. Our sample contains 101 photometrically selected and spectroscopically confirmed giants with accurate distance, radial velocity, and metallicity information. We have developed a new clustering estimator: the "4distance" measure, which when applied to our data set leads to the identification of one group and seven pairs of clumped stars. The group, with six members, can confidently be matched to tidal debris of the Sagittarius dwarf galaxy. Two pairs match the properties of known Virgo structures. Using models of the disruption of Sagittarius in Galactic potentials with different degrees of dark halo flattening, we show that this favors a spherical or prolate halo shape, as demonstrated by Newberg et al. using the Sloan Digital Sky Survey data. One additional pair can be linked to older Sagittarius debris. We find that 20% of the stars in the Spaghetti data set are in substructures. From comparison with random data sets, we derive a very conservative lower limit of 10% to the amount of substructure in the halo. However, comparison to numerical simulations shows that our results are also consistent with a halo entirely built up from disrupted satellites, provided that the dominating features are relatively broad due to early merging or relatively heavy progenitor satellites.
dc.publisherIOP Publishing
dc.sourceAstrophysical Journal, The
dc.subjectKeywords: Galaxy: evolution; Galaxy: formation; Galaxy: halo; Galaxy: kinematics and dynamics
dc.titleMapping the Galactic Halo. VIII. Quantifying Substructure
dc.typeJournal article
local.description.notesImported from ARIES
local.identifier.citationvolume698
dc.date.issued2009
local.identifier.absfor020104 - Galactic Astronomy
local.identifier.ariespublicationu3356449xPUB45
local.type.statusPublished Version
local.contributor.affiliationStarkenburg, Else, University of Groningen
local.contributor.affiliationHelmi, Amina, University of Groningen
local.contributor.affiliationMorrison, Heather, Case Western Reserve University
local.contributor.affiliationHarding, Paul, Case Western Reserve University
local.contributor.affiliationvan Woerden, Hugo, University of Groningen
local.contributor.affiliationMateo, Mario, University of Michigan
local.contributor.affiliationOlszewski, Edward W, University of Arizona
local.contributor.affiliationSivarani, T, Michigan State University
local.contributor.affiliationNorris, John, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationFreeman, Kenneth, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationShectman, Stephen, Observatories of the Carnegie Institution of Washington
local.contributor.affiliationDohm-Palmer, Robbie C, University of Michigan
local.contributor.affiliationFrey, Lucy, Case Western Reserve University
local.description.embargo2037-12-31
local.bibliographicCitation.issue1
local.bibliographicCitation.startpage567
local.bibliographicCitation.lastpage579
local.identifier.doi10.1088/0004-637X/698/1/567
dc.date.updated2016-02-24T09:55:04Z
local.identifier.scopusID2-s2.0-66649085223
local.identifier.thomsonID000266373700047
CollectionsANU Research Publications

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