Insight Into The Formation Of The Milky Way Through Cold Halo Substructure. I. The Echos Of Milky Way Formation

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dc.contributor.utaustinauthorPrieto, Carlos Allendeen_US
dc.creatorSchlaufman, Kevin C.en_US
dc.creatorRockosi, Constance M.en_US
dc.creatorPrieto, Carlos Allendeen_US
dc.creatorBeers, Timothy C.en_US
dc.creatorBizyaev, Dmitryen_US
dc.creatorBrewington, Howarden_US
dc.creatorLee, Young Sunen_US
dc.creatorMalanushenko, Viktoren_US
dc.creatorMalanushenko, Elenaen_US
dc.creatorOravetz, Danen_US
dc.creatorPan, Kaikeen_US
dc.creatorSimmons, Audreyen_US
dc.creatorSnedden, Stephanieen_US
dc.creatorYanny, Brianen_US
dc.date.accessioned2016-04-28T19:36:55Z
dc.date.available2016-04-28T19:36:55Z
dc.date.issued2009-10en
dc.description.abstractWe identify 10-seven for the first time-elements of cold halo substructure (ECHOS) in the volume within 17.5 kpc of the Sun in the inner halo of the Milky Way. Our result is based on the observed spatial and radial velocity distribution of metal-poor main-sequence turnoff (MPMSTO) stars in 137 Sloan Extension for Galactic Understanding and Exploration lines of sight. We point out that the observed radial velocity distribution is consistent with a smooth stellar component of the Milky Way's inner halo overall, but disagrees significantly at the radial velocities that correspond to our detections. We show that all of our detections are statistically significant and that we expect no false positives. These ECHOS represent the observable stellar debris of ancient merger events in the stellar accretion history of the Milky Way, and we use our detections and completeness estimates to infer a formal upper limit of 0.34(-0.02)(+0.02) on the fraction of the MPMSTO population in the inner halo that belong to ECHOS. Our detections and completeness calculations also suggest that there is a significant population of low fractional overdensity ECHOS in the inner halo, and we predict that 1/3 of the inner halo (by volume) harbors ECHOS with MPMSTO star number densities n approximate to 15 kpc(-3). In addition, we estimate that there are of order 10(3) ECHOS in the entire inner halo. ECHOS are likely older than known surface brightness substructure, so our detections provide us with a direct measure of the accretion history of the Milky Way in a region and time interval that has yet to be fully explored. In concert with previous studies, our result suggests that the level of merger activity has been roughly constant over the past few Gyr and that there has been no accretion of single stellar systems more massive than a few percent of a Milky Way mass in that interval.en_US
dc.description.departmentAstronomyen_US
dc.description.sponsorshipen_US
dc.identifierdoi:10.15781/T2TJ9F
dc.identifier.Filename2009_10_formationmilkyway.pdfen_US
dc.identifier.citationSchlaufman, Kevin C., Constance M. Rockosi, Carlos Allende Prieto, Timothy C. Beers, Dmitry Bizyaev, Howard Brewington, Young Sun Lee et al. "Insight into the formation of the Milky Way through cold halo substructure. I. The ECHOS of Milky Way formation." The Astrophysical Journal, Vol. 703, No. 2 (Oct., 2009): 2177.en_US
dc.identifier.doi10.1088/0004-637x/703/2/2177en_US
dc.identifier.issn0004-637Xen_US
dc.identifier.urihttp://hdl.handle.net/2152/34913
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: formationen_US
dc.subjectgalaxy: haloen_US
dc.subjectgalaxy: kinematics and dynamicsen_US
dc.subjectdigital sky surveyen_US
dc.subjecthorizontal-branch starsen_US
dc.subjectsurvey commissioning dataen_US
dc.subjectsagittarius dwarf galaxyen_US
dc.subjectmetal-poor starsen_US
dc.subjectglobular-cluster palomar-5en_US
dc.subjectmedium-resolution spectraen_US
dc.subjectsurvey photometric systemen_US
dc.subjectvelocityen_US
dc.subjectexperiment raveen_US
dc.subjectdark-matter universeen_US
dc.subjectastronomy & astrophysicsen_US
dc.titleInsight Into The Formation Of The Milky Way Through Cold Halo Substructure. I. The Echos Of Milky Way Formationen_US
dc.typeReviewen_US

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