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BEGIN:VEVENT
DTSTART;TZID=Atlantic/Canary:20180306T123000
DTEND;TZID=Atlantic/Canary:20180306T133000
UID:iactalks-1129
X-WR-CALNAME: IAC Talks: Open Astronomy Seminars
X-ORIGINAL-URL: /iactalks/Talks/view/1129
CREATED:2018-03-06T12:30:00+00:00
X-WR-CALDESC: IAC Talks upcomming talks
SUMMARY:What is the Milky Way outer halo made of? High resolution spectrosc
 opy of distant red giants
DESCRIPTION:What is the Milky Way outer halo made of? High resolution spect
 roscopy of distant red giants\nDr. Giuseppina Battaglia\n\nIn a framework 
 where galaxies form hierarchically, extended stellar haloes are predicted 
 to be an ubiquitous feature around Milky Way-like galaxies and to consist 
 mainly of the shredded stellar component of smaller galactic systems. The 
 type of accreted stellar systems are expected to vary according to the spe
 cific accretion and merging history of a given galaxy, and so is the fract
 ion of stars formed in situ versus accreted. Analysis of the chemical prop
 erties of Milky Way halo stars out to large Galactocentric radii can provi
 de important insights into the properties of the environment in which the 
 stars that contributed to the build-up of different regions of the Milky W
 ay stellar halo formed. In this talk I will first give an overview of some
  of the main properties of the Milky Way stellar halo based on literature 
 studies. I will then present results concerning the chemical properties of
  the outer regions of the Milky Way stellar halo, based on the elemental a
 bundances of halo stars with large present-day Galactocentric distances, &
 gt;15 kpc. The data-set we acquired consists of high resolution HET/HRS, M
 agellan/MIKE and VLT/UVES spectra for 28 red giant branch stars covering a
  wide metallicity range, -3.1 ≲ [Fe/H] ≲-0.6. We show that the ratio o
 f α-elements over Fe as a function of [Fe/H] for our sample of outer
  halo stars is not dissimilar from the pattern shown by MW halo stars from
  solar neighborhood samples. On the other hand, significant differences ap
 pear at [Fe/H] ≳-1.5 when considering chemical abundance ratios such as 
 [Ba/Fe], [Na/Fe], [Ni/Fe], [Eu/Fe], [Ba/Y]. Qualitatively, this type of ch
 emical abundance trends are observed in massive dwarf galaxies, such as Sa
 gittarius and the Large Magellanic Cloud. This appears to suggest a larger
  contribution in the outer halo of stars formed in an environment with hig
 h initial star formation rate and already polluted by asymptotic giant bra
 nch stars with respect to inner halo samples. 
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