RINGS AND RADIAL WAVES IN THE DISK OF THE MILKY WAY

By Yan Xu, Heidi Jo Newberg, J. Carlin, Chao Liu, Licai Deng, Jing Li, R. Schonrich, Brian Yanny. 2015

166 citations recorded by the source corpus.

We show that in the anticenter region, between Galactic longitudes of 110° < l < 229°, there is an oscillating asymmetry in the main-sequence star counts on either side of the Galactic plane using data from the Sloan Digital Sky Survey. This asymmetry oscillates from more stars in the north at distances of about 2 kpc from the Sun to more stars in the south at 4–6 kpc from the Sun to more stars in the north at distances of 8–10 kpc from the Sun. We also see evidence that there are more stars in the south at distances of 12–16 kpc from the Sun. The three more distant asymmetries form roughly concentric rings around the Galactic center, opening in the direction of the Milky Way’s spiral arms. The northern ring, 9 kpc from the Sun, is easily identified with the previously discovered Monoceros Ring. Parts of the southern ring at 14 kpc from the Sun (which we call the TriAnd Ring) have previously been identified as related to the Monoceros Ring, and others have been called the Triangulum Andromeda Overdensity. The two nearer oscillations are approximated by a toy model in which the disk plane is offset by the order of 100 pc up and then down at different radii. We also show that the disk is not azimuthally symmetric around the Galactic anticenter and that there could be a correspondence between our observed oscillations and the spiral structure of the Galaxy. Our observations suggest that the TriAnd and Monoceros Rings (which extend to at least 25 kpc from the Galactic center) are primarily the result of disk oscillations.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/10bf68dad0f7efdb5d1fe5159d7a6090c2782b52

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In Astronomy and Astrophysics

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Citations in the corpus

• The Galaxy in Context: Structural, Kinematic, and Integrated Properties (2016, background): “The nature of this stream is unknown (cf. Xu et al. 2015): Unlike the Canis Major overdensity, which may be related to the warp, the ring appears to have its own identity after correcting for the warp (Momany et al. 2006) and may even rotate slightly faster than the disk (Ivezić et al. 2008).”
• The GALAH survey and Gaia DR2: dissecting the stellar disc’s phase space by age, action, chemistry, and location (2018, background): “There is only a finite number of kinematic plumes in the zVz plane because the corrugations have a long wavelength of order several kiloparsecs, as observed in the Galaxy (Xu et al. 2015) and in external galaxies (Matthews & Uson 2008b), and expected from theory (Masset & Tagger 1997).”
• Red Clump Stars from LAMOST II: the outer disc of the Milky Way (2017, background): “Furthermore, Xu et al. (2015) discovered that star counts in the north and south of the Galactic midplane of the outer disc are not symmetric but rather display wave-like oscillations.”
• Target Selection for the SDSS-IV APOGEE-2 Survey (2017, background): “TriAnd’s nature as either a satellite remnant or disk substructure, and/or the superposition of multiple structures, remains unresolved (e.g., Martin et al. 2007; Chou et al. 2011; Xu et al. 2015; Price-Whelan et al. 2015).”
• The influence of Sagittarius and the Large Magellanic Cloud on the stellar disc of the Milky Way Galaxy (2017, methodology): “Signs of oscillations in the direction of Triangulum and Andromeda (Martin, Ibata & Irwin 2007) have also been mapped by Xu et al. (2015) as well as in A13 (Li et al. 2017).”