SIMBAD references

2020ApJ...891...39Y - Astrophys. J., 891, 39-39 (2020/March-1)

Dynamical relics of the ancient galactic halo.

YUAN Z., MYEONG G.C., BEERS T.C., EVANS N.W., LEE Y.S., BANERJEE P., GUDIN D., HATTORI K., LI H., MATSUNO T., PLACCO V.M., SMITH M.C., WHITTEN D.D. and ZHAO G.

Abstract (from CDS):

We search for dynamical substructures in the LAMOST DR3 very metal-poor (VMP) star catalog. After cross-matching with Gaia DR2, there are ∼3300 VMP stars with available high-quality astrometric information that have halo-like kinematics. We apply a method based on the self-organizing map STARGO to find groups clustered in the 4D space of orbital energy and angular momentum. We identify 57 dynamically tagged groups (DTGs), which we label DTG-1 to DTG-57. Most of them belong to existing massive substructures in the nearby halo, such as the Gaia Sausage or Sequoia. The stream identified by Helmi et al. is recovered, but the two disjointed portions of the substructure appear to have distinct dynamical properties. The very retrograde substructure Rg5 found previously by Myeong et al. is also retrieved. We report six new DTGs with highly retrograde orbits, two with very prograde orbits, and 12 with polar orbits. By mapping other data sets (APOGEE halo stars, and catalogs of r-process-enhanced and carbon-enhanced metal-poor [CEMP] stars) onto the trained neuron map, we can associate stars with detailed chemical abundances with the DTGs and look for associations with chemically peculiar stars. The highly eccentric Gaia Sausage groups contain representatives of both debris from the satellite itself (which is α-poor) and the Splashed Disk, sent up into eccentric halo orbits from the encounter (and which is α-rich). The new prograde substructures also appear to be associated with the Splashed Disk. The DTGs belonging to the Gaia Sausage host two relatively metal-rich r-II stars and six CEMP stars in different subclasses, consistent with the idea that the Gaia Sausage progenitor is a massive dwarf galaxy. Rg5 is dynamically associated with two highly r-process-enhanced stars with [Fe/H] ∼ -3. This finding indicates that its progenitor might be an ultrafaint dwarf galaxy that has experienced r-process enrichment from neutron star mergers.

Abstract Copyright: © 2020. The American Astronomical Society. All rights reserved.

Journal keyword(s): Milky Way stellar halo - Milky Way formation - R-process

VizieR on-line data: <Available at CDS (J/ApJ/891/39): table5.dat>

Nomenclature: Table 1: [YMB2020] DTG-NN (Nos 1-57).

Status at CDS : All or part of tables of objects could be ingested in SIMBAD with priority 2.

CDS comments: Table 1: groups DTG-NN are not in SIMBAD as well as New Rg, New Pg et New Polar substructures, Rg5 and Cand14.

Simbad objects: 30

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