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591 high velocity stars in the Galactic halo selected from LAMOST DR7 and Gaia DR2 | | Yin-Bi Li
; A-Li Luo
; You-Jun Lu
; Xue-Sen Zhang
; Jiao Li
; Rui Wang
; Fang Zuo
; Maosheng Xiang
; Yuan-Sen Ting
; T.Marchetti
; Shuo Li
; You-Fen Wang
; Shuo Zhang
; Kohei Hattori
; Yong-Heng Zhao
; Hua-Wei Zhang
; Gang Zhao
; | | Date: |
20 Nov 2020 | | Abstract: | In this paper, we report 591 high velocity star candidates (HiVelSCs)
selected from over 10 million spectra of the data release seven (DR7) of the
Large Sky Area Multi-object Fiber Spectroscopic Telescope and the second Gaia
data release, with three-dimensional velocities in the Galactic rest-frame
larger than 445 km/s. We show that at least 43 HiVelSCs are unbound to the
Galaxy with escape probabilities larger than 50%, and this number decreases to
eight if the possible parallax zero-point error is corrected. Most of these
HiVelSCs are metal-poor and slightly alpha-enhanced inner halo stars. Only 14%
of them have [Fe/H] > -1, which may be the metal-rich "in situ" stars in halo
formed in the initial collapse of the Milky Way or metal-rich stars formed in
the disk or bulge but kinematically heated. The low ratio of 14% implies that
the bulk of stellar halo was formed from the accretion and tidal disruption of
satellite galaxies. In addition, HiVelSCs on the retrograde orbits have a
slightly lower metallicities on average compared with these on the prograde
orbits, meanwhile metal-poor HiVelSCs with [Fe/H] < -1 have an even faster mean
retrograde velocity compared with metal-rich HiVelSCs. To investigate the
origins of HiVelSCs, we perform orbit integrations and divide them into four
types, i.e., hypervelocity stars, hyper-runaway stars, runaway stars and fast
halo stars. A catalog for these 591 HiVelSCs, including radial velocities,
atmospheric parameters, Gaia astrometric parameters, spatial positions, and
velocities, etc., is available at
this http URL. | | Source: | arXiv, 2011.10206 | | Services: | Forum | Review | PDF | Favorites | |
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