Deciphering the Last Major Invasion of the Milky Way

By G. Gilmore, R. Wyse, J. Norris. 2002

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We present first results from a spectroscopic survey of ~2000 F/G stars 0.5-5 kpc from the Galactic plane, obtained with the Two Degree Field facility on the Anglo-Australian Telescope. These data show the mean rotation velocity of the thick disk about the Galactic center a few kiloparsecs from the plane is very different than expected, being ~100 km s-1 rather than the predicted ~180 km s-1. We propose that our sample is dominated by stars from a disrupted satellite that merged with the disk of the Milky Way some 10-12 Gyr ago. We do not find evidence for the many substantial mergers expected in hierarchical clustering theories. We find yet more evidence that the stellar halo retains kinematic substructure, indicative of minor mergers.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/9a979e33b2714854b07f6a95a40ff4c0b41a4c1e

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Citations in the corpus

Simulations of minor mergers - I. General properties of thick discs (2008, background): “Kinematically, the values of the velocity ellipsoids of our thick disks, measured at R ≈ 2.4RD , are in good agreement with the one observed at the solar radius in the Milky Way (σR,σφ,σZ)∼(65,54,38) km/s (e.g., see Layden et al. 1996; Chiba & Beers 2001; Soubiran et al. 2003; Alcobé & Cubarsi 2005”
AN ANCIENT EXTRASOLAR SYSTEM WITH FIVE SUB-EARTH-SIZE PLANETS (2015, background): “…be too low to arise from dynamical perturbations induced by the Galactic bar (Navarro et al. 2004) while coinciding with that of the debris identified by Gilmore et al. (2002) lying below and above the Galactic plane, of which the Arcturus stream could very well be the solar-neighborhood extension.”
A Spectroscopic Study of the Ancient Milky Way: F- and G-Type Stars in the Third Data Release of the Sloan Digital Sky Survey (2005, background): “Gilmore et al. (2002) argue that this is possible, as the debris from the merging satellites will end up in higher, more slowly-rotating orbits than stars newly formed, but detailed simulations are necessary.”
Observations of Thick Disks in the Hubble Space Telescope Ultra Deep Field (2006, background): “…1996; Velazquez & White 1999; Aguerri et al. 2001); (3) they arise independently of thin disks as tidally stripped debris from companion galaxies (Gilmore et al. 2002; Abadi et al. 2003; Wyse et al. 2006); (4) they arise as a first step in the cooling of the disk from a highly turbulent initial…”
The Galaxy and its stellar halo: insights on their formation from a hybrid cosmological approach (2008, background): “…properties that closely match the observed ones: our Galaxy is believed to have had a quiet merging history, with the last major merging event occurring some 10-12 Gyr ago (Gilmore et al. 2002), and it is a quite isolated galaxy with the closest cluster (Virgo) lying at a distance of about 20 Mpc.”
Lectures on Dark Matter Physics (2016, background): “2 Coulomb and Yukawa example For the Coulomb potential V (r) = ↵/r, one can obtain an analytic expression for the Sommerfeld enhancement [9, 10],”
The Emergence of the Thick Disk in a Cold Dark Matter Universe (2004, unknown): “The heating of the disk early in its violent evolution, as in scenario 2), is well supported by Galactic observations (Quillen & Garret 2001; Wyse 2000; Gilmore et al. 2002; Freeman & Bland-Hawthorn 2002; FBL).”
THE SPATIAL STRUCTURE OF MONO-ABUNDANCE SUB-POPULATIONS OF THE MILKY WAY DISK (2011, background): “…components are found to be old (Bensby et al. 2005; Yoachim & Dalcanton 2008), kinematically hot (Chiba & Beers 2000; Soubiran et al. 2003; Gilmore et al. 2002; Yoachim & Dalcanton 2005), and metal-poor (compared to the thin-disk components), as well as enhanced in α-elements (Fuhrmann…”
Stellar Abundance and Galactic Chemical Evolution through LAMOST Spectroscopic Survey (2006, methodology): “…of abundances and kinematics of stars in the various places of the thin and thick disks, such as the low-resolution spectroscopic survey of the stars situated at 0.5–5kpc from the Galactic plane (Gilmore et al. 2002) and the spectroscopic study based on SDSS survey (Allende Prieto et al. 2006).”
THICK DISKS OF EDGE-ON GALAXIES SEEN THROUGH THE SPITZER SURVEY OF STELLAR STRUCTURE IN GALAXIES (S4G): LAIR OF MISSING BARYONS? (2011, background): “The fourth possibility is that the thick disk is formed by accretion of stars from disrupted small satellite galaxies after the initial buildup of the galaxy (Statler 1988; Gilmore et al. 2002; Abadi et al. 2003; Navarro et al. 2004; Martin et al. 2004; Read et al. 2008).”
Structural Parameters of Thin and Thick Disks in Edge-on Disk Galaxies (2005, background): “Kinematically, MW thick disk stars have both larger velocity dispersions and slower net rotation than stars in the thin disk (Nissen 1995; Chiba & Beers 2000; Gilmore et al. 2002; Soubiran et al. 2003; Parker et al. 2004).”
Galactic Stellar and Substellar Initial Mass Function (2003, background): “Recent observations (Gilmore et al. 2002) have detected a substantial population of stars a few kpc above the Galactic disk with kinematic properties (rotational velocity and velocity dispersion) intermediate between the canonical thick disk and the spheroid.”
THE GENESIS OF THE MILKY WAY'S THICK DISK VIA STELLAR MIGRATION (2010, background): “Kinematically, thick disk stars have larger velocity dispersions and lag the net rotation of the disk (Nissen 1995; Chiba & Beers 2000; Gilmore et al. 2002; Soubiran et al. 2003; Parker et al. 2004; Wyse et al. 2006).”