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Title: Exploring Halo Substructure with Giant Stars. XV. Discovery of a Connection between the Monoceros Ring and the Triangulum–Andromeda Overdensity?

Thanks to modern sky surveys, over twenty stellar streams and overdensity structures have been discovered in the halo of the Milky Way. Here, in this paper, we present an analysis of spectroscopic observations of individual stars from one such structure, "A13", first identified as an overdensity using the M giant catalog from the Two Micron All-Sky Survey. Our spectroscopic observations show that stars identified with A13 have a velocity dispersion of $$\lesssim$$ 40 $$\mathrm{km~s^{-1}}$$, implying that it is a genuine coherent structure rather than a chance super-position of random halo stars. From its position on the sky, distance ($$\sim$$15 kpc heliocentric), and kinematical properties, A13 is likely to be an extension of another low Galactic latitude substructure -- the Galactic Anticenter Stellar Structure (also known as the Monoceros Ring) -- towards smaller Galactic longitude and farther distance. Furthermore, the kinematics of A13 also connect it with another structure in the southern Galactic hemisphere -- the Triangulum-Andromeda overdensity. Finally, we discuss these three connected structures within the context of a previously proposed scenario that one or all of these features originate from the disk of the Milky Way.
Authors:
 [1] ;  [2] ;  [3] ; ORCiD logo [4] ; ORCiD logo [5] ; ORCiD logo [6] ;  [7] ; ORCiD logo [8] ; ORCiD logo [9] ;  [5] ; ORCiD logo [10] ; ORCiD logo [11]
  1. Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Texas A & M Univ., College Station, TX (United States). Department of Physics & Astronomy; George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, College Station, TX (United States)
  2. City University of New York, LaGuardia Community College, Long Island City, NY (United States). Department of Natural Sciences
  3. Columbia Univ., New York, NY (United States). Department of Astronomy
  4. Texas A & M Univ., College Station, TX (United States). Department of Physics & Astronomy; George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, College Station, TX (United States)
  5. Univ. of Virginia, Charlottesville, VA (United States). Department of Astronomy
  6. Princeton Univ., NJ (United States). Department of Astrophysical Sciences
  7. Univ. of Virginia, Charlottesville, VA (United States). Department of Astronomy; Universidad de La Serena (Chile). Departamento de Fisica y Astronomia, Facultad de Ciencias
  8. The Carnegie Observatories, Pasadena, CA (United States)
  9. Universite Cote d Azur, OCA, CNRS, Lagrange (France)
  10. Univ. of Sydney, NSW (Australia). Sydney Institute for Astronomy, School of Physics
  11. Max Planck Institute for Astronomy, Heidelberg (Germany)
Publication Date:
Report Number(s):
arXiv:1703.05384; FERMILAB-PUB-17-389-AE
Journal ID: ISSN 1538-4357; 1624631
Grant/Contract Number:
AC02-07CH11359
Type:
Accepted Manuscript
Journal Name:
The Astrophysical Journal (Online)
Additional Journal Information:
Journal Name: The Astrophysical Journal (Online); Journal Volume: 844; Journal Issue: 1; Journal ID: ISSN 1538-4357
Publisher:
Institute of Physics (IOP)
Research Org:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; galaxies: interactions; Galaxy: disk; Galaxy: formation; Galaxy: halo; Galaxy: structure
OSTI Identifier:
1395476

Li, Ting S., Sheffield, Allyson A., Johnston, Kathryn V., Marshall, Jennifer L., Majewski, Steven R., Price-Whelan, Adrian M., Damke, Guillermo J., Beaton, Rachael L., Bernard, Edouard J., Richardson, Whitney, Sharma, Sanjib, and Sesar, Branimir. Exploring Halo Substructure with Giant Stars. XV. Discovery of a Connection between the Monoceros Ring and the Triangulum–Andromeda Overdensity?. United States: N. p., Web. doi:10.3847/1538-4357/aa7a0d.
Li, Ting S., Sheffield, Allyson A., Johnston, Kathryn V., Marshall, Jennifer L., Majewski, Steven R., Price-Whelan, Adrian M., Damke, Guillermo J., Beaton, Rachael L., Bernard, Edouard J., Richardson, Whitney, Sharma, Sanjib, & Sesar, Branimir. Exploring Halo Substructure with Giant Stars. XV. Discovery of a Connection between the Monoceros Ring and the Triangulum–Andromeda Overdensity?. United States. doi:10.3847/1538-4357/aa7a0d.
Li, Ting S., Sheffield, Allyson A., Johnston, Kathryn V., Marshall, Jennifer L., Majewski, Steven R., Price-Whelan, Adrian M., Damke, Guillermo J., Beaton, Rachael L., Bernard, Edouard J., Richardson, Whitney, Sharma, Sanjib, and Sesar, Branimir. 2017. "Exploring Halo Substructure with Giant Stars. XV. Discovery of a Connection between the Monoceros Ring and the Triangulum–Andromeda Overdensity?". United States. doi:10.3847/1538-4357/aa7a0d. https://www.osti.gov/servlets/purl/1395476.
@article{osti_1395476,
title = {Exploring Halo Substructure with Giant Stars. XV. Discovery of a Connection between the Monoceros Ring and the Triangulum–Andromeda Overdensity?},
author = {Li, Ting S. and Sheffield, Allyson A. and Johnston, Kathryn V. and Marshall, Jennifer L. and Majewski, Steven R. and Price-Whelan, Adrian M. and Damke, Guillermo J. and Beaton, Rachael L. and Bernard, Edouard J. and Richardson, Whitney and Sharma, Sanjib and Sesar, Branimir},
abstractNote = {Thanks to modern sky surveys, over twenty stellar streams and overdensity structures have been discovered in the halo of the Milky Way. Here, in this paper, we present an analysis of spectroscopic observations of individual stars from one such structure, "A13", first identified as an overdensity using the M giant catalog from the Two Micron All-Sky Survey. Our spectroscopic observations show that stars identified with A13 have a velocity dispersion of $\lesssim$ 40 $\mathrm{km~s^{-1}}$, implying that it is a genuine coherent structure rather than a chance super-position of random halo stars. From its position on the sky, distance ($\sim$15 kpc heliocentric), and kinematical properties, A13 is likely to be an extension of another low Galactic latitude substructure -- the Galactic Anticenter Stellar Structure (also known as the Monoceros Ring) -- towards smaller Galactic longitude and farther distance. Furthermore, the kinematics of A13 also connect it with another structure in the southern Galactic hemisphere -- the Triangulum-Andromeda overdensity. Finally, we discuss these three connected structures within the context of a previously proposed scenario that one or all of these features originate from the disk of the Milky Way.},
doi = {10.3847/1538-4357/aa7a0d},
journal = {The Astrophysical Journal (Online)},
number = 1,
volume = 844,
place = {United States},
year = {2017},
month = {7}
}