2019ApJ...885..102L -
Astrophys. J., 885, 102-102 (2019/November-2)
Chemical cartography. II. The assembly history of the galactic stellar halo traced by carbon-enhanced metal-poor stars.
LEE Y.S., BEERS T.C. and KIM Y.K.
Abstract (from CDS):
We present an analysis of the kinematic properties of stellar populations in the Galactic halo, making use of over 100,000 main-sequence turnoff (MSTO) stars observed in the Sloan Digital Sky Survey. After dividing the Galactic halo into an inner-halo region (IHR) and outer-halo region (OHR), based on the spatial variation of carbon-to-iron ratios in the sample, we find that stars in the OHR exhibit a clear retrograde motion of -49 ± 4 km s–1 and a more spherical distribution of stellar orbits, while stars in the IHR have zero net rotation (-3 ± 1 km s–1) with a much more radially biased distribution of stellar orbits. Furthermore, we classify the carbon-enhanced metal-poor (CEMP) stars among the MSTO sample in each halo component into CEMP-no and CEMP-s subclasses, based on their absolute carbon abundances, A(C), and examine the spatial distributions and kinematics associated with each subclass. The CEMP-no stars are the majority subclass of CEMP stars in the OHR (∼65%), and the minority subclass in the IHR (∼44%), similar to the results of several previous analyses. The CEMP-no stars in each halo region exhibit slightly higher counterrotation than the CEMP-s stars, but within statistical errors. The CEMP-no stars also show a more spherical distribution of orbits than the CEMP-s stars in each halo region. These distinct characteristics provide strong evidence that numerous low-mass satellite galaxies (similar to the ultra-faint dwarf galaxies) have donated stars to the OHR, while more massive dwarf galaxies provided the dominant contribution to the IHR.
Abstract Copyright:
© 2019. The American Astronomical Society. All rights reserved.
Journal keyword(s):
Galaxy: halo - methods: data analysis - stars: abundances - stars: carbon - stars: kinematics and dynamics
Simbad objects:
3
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