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Cited by 215Stellar, planetary, and galactic studiesGalaxies: Formation, Evolution, PhenomenaAstrophysical Phenomena and Observations

ON THE SHOULDERS OF GIANTS: PROPERTIES OF THE STELLAR HALO AND THE MILKY WAY MASS DISTRIBUTION

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Kafle, Prajwal Raj, Sharma, Sanjib, Lewis, Geraint F., Bland-Hawthorn, Joss·2014·The Astrophysical Journal
DOI 10.1088/0004-637x/794/1/59
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Abstract

Halo stars orbit within the potential of the Milky Way, and hence their kinematics can be used to understand the underlying mass distribution. However, the inferred mass distribution depends sensitively on assumptions made on the density and the velocity anisotropy profiles of the tracer population. Also, there is a degeneracy between the parameters of the halo and those of the disk or bulge. Most previous attempts that use halo stars have made arbitrary assumptions about these. In this paper, we decompose the Galaxy into three major components—a bulge, a Miyamoto–Nagai disk, and a Navarro–Frenk–White dark matter halo – and then model the kinematic data of the halo blue horizontal branch and K-giant stars from the Sloan Extension for Galactic Understanding and Exploration. Additionally, we use the gas terminal velocity curve and the Sgr A* proper motion. With the distance of the Sun from the center of the Galaxy R ☉ = 8.5 kpc, our kinematic analysis reveals that the density of the stellar halo has a break at and an exponential cutoff in the outer parts starting at . Also, we find that the tracer velocity anisotropy is radially biased with β s = 0.4 ± 0.2 in the outer halo. We measure halo virial mass M vir to be , concentration c to be , disk mass to be , disk scale length to be , and bulge mass to be . The halo mass is found to be small, and this has important consequences. The giant stars reveal that the outermost halo stars have low velocity dispersion, but interestingly this suggests a truncation of the stellar halo density rather than a small overall mass of the Galaxy. Our estimates of local escape velocity and dark matter density ( GeV cm −3 ) are in good agreement with recent estimates. Some of the above estimates, in particular M vir , are dependent on the adopted value of R ☉ and also on the choice of the outer power-law index of the tracer number density.

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Crossref · 10.1088/0004-637x/794/1/59

Cites

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  • The break in the halo density profile also manifests itself in a change in the shape of the velocity ellipsoid of halo stars around this distance.

    “This break also manifests itself in a change in the shape of the velocity ellipsoid of halo stars around this distance, as reported by Kafle et al. (2014).”

    From Streams, Substructures, and the Early History of the Milky Way (2020) · cites this paper as Kafle et al. (2014)

    Section 4.2 reports a change in velocity anisotropy near 17 kpc, and Section 5.5 places the BHB density-profile break at about 17 kpc. But the paper does not establish that the density break causes the change in the velocity ellipsoid’s shape; Section 4.1 instead links the density break to a drop in radial velocity dispersion. No page numbers are available in our copy. (LLM, conf=0.82)

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  • This potentially explains why mass estimates based on fitting the rotation curve are systematically lower than determinations based on other methods.

    “This potentially explains why mass estimates based on fitting the rotation curve (e.g. Bovy et al. 2012; Kafle et al. 2014) are systematically lower than determinations based on other methods”

    From The milky way total mass profile as inferred from Gaia DR2 (2020) · cites this paper as Kafle et al. 2014

    In Results and Discussion (page unavailable), the paper constructs a best-fit rotation curve and compares it with terminal-velocity data. Its concluding discussion (page unavailable) says its mass estimate is lower than previously measured estimates. It does not establish that rotation-curve-fitting estimates are systematically lower than estimates from other methods, and its mass fit also uses stellar-halo data. (LLM, conf=0.82)

    Experimental — accuracy not yet measured

  • Most studies that assume an NFW profile for the Galactic halo argue that the halo has a very high concentration, typically ∼14 or higher.

    “Such studies argue that the Galactic halo has a very high concentration, typically ∼ 14 or higher”

    From The milky way total mass profile as inferred from Gaia DR2 (2020) · cites this paper as Kafle et al. 2014

    Section 5.3 reports an NFW-model halo concentration of 21.1, supporting this paper as one example of an estimate above 14. It does not establish that most NFW-based studies find concentrations of approximately 14 or higher; the same section says it is difficult to judge whether its estimate is typical. (LLM, conf=0.86)

    Experimental — accuracy not yet measured

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Cites

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Research works printed but not linked: 7

  1. Binney, J., & Merrifield, M. (ed.) 1998, Galactic Astronomy (Princeton, NJ: Princeton Univ. Press)
  2. Binney, J., & Tremaine, S. 2008, Galactic Dynamics (2nd ed.; Princeton, NJ: Princeton Univ. Press)
  3. Gillessen, S., Eisenhauer, F., Fritz, T. K., et al. 2013, in IAU Symp. 289, Advancing the Physics of Cosmic Distances, ed. R. de Grijs (Cambridge: Cambridge Univ. Press), 29
  4. Nikiforov, I. 2004, in ASP Conf. Ser. 316, Order and Chaos in Stellar and Planetary Systems, ed. G. G. Byrd, K. V. Kholshevnikov, A. A. Myllri, I. I. Nikiforov, & V. V. Orlov (San Francisco, CA: ASP), 199
  5. Planck Collaboration, Ade, P. A. R., Aghanim, N., et al. 2013, arXiv:1303.5076 · arXiv
  6. Reid, M. J. 1993, ARA&A, 31, 345 · DOI
  7. Sofue, Y. 2013, in Planets, Stars, and Stellar Systems, Vol. 5: Galactic Structure and Stellar Populations, ed. T. D. Oswalt & G. Gilmore (Berlin: Springer), 985

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Authors
Kafle, P. R., Sharma, S., Lewis, G. F., & Bland-Hawthorn, J.
Affiliations
The University of Sydney (AU)
Corresponding author
Kafle, Prajwal Raj
ORCID
Venue
The Astrophysical Journal
Publisher
American Astronomical Society
Published
2014-09-24
Volume
794
Issue
1
Pages
59
ISSN
  • 0004-637X (ISSN-L)
  • 1538-4357
DOI
10.1088/0004-637x/794/1/59
OpenAlex
W2066628301
Cited by
215
References
124
Citations by year
2026: 3 · 2025: 13 · 2024: 18 · 2023: 14 · 2022: 13 · 2021: 14 · 2020: 25 · 2019: 21 · 2018: 19 · 2017: 22 · 2016: 23 · 2015: 29 · 2014: 1
FWCI
13.48
Type
journal article
Language
en
Open access
Licence
Locations
  • The Astrophysical Journal (publishedVersion)
  • arXiv (Cornell University) (submittedVersion)
  • UWA Profiles and Research Repository (UWA) (submittedVersion)
  • arXiv (Cornell University)
Topics
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Stellar, planetary, and galactic studies
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Galaxies: Formation, Evolution, Phenomena
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Astrophysical Phenomena and Observations
Keywords
Milky Way mass distribution, stellar halo, halo kinematics, velocity anisotropy, halo density profiles, virial mass, dark matter density, blue horizontal branch stars, K giant stars, Navarro-Frenk-White halo, bulge mass, escape velocity

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