J/A+A/562/A134 Tracers of the Milky Way mass (Bratek+, 2014)
A lower bound on the Milky Way mass from general phase-space distribution
function model.
Bratek L., Sikora S., Jalocha J., Kutschera M.
<Astron. Astrophys. 562, A134 (2014)>
=2014A&A...562A.134B 2014A&A...562A.134B
ADC_Keywords: Milky Way ; Stars, masses
Keywords: techniques: radial velocities - Galaxy: halo -
Galaxy: kinematics and dynamics - Galaxy: fundamental parameters -
methods: numerical
Abstract:
We model the phase-space distribution of the kinematic tracers using
general, smooth distribution functions to derive a conservative lower
bound on the total mass within ≈150-200kpc. By approximating the
potential as Keplerian, the phase-space distribution can be simplified
to that of a smooth distribution of energies and eccentricities. Our
approach naturally allows for calculating moments of the distribution
function, such as the radial profile of the orbital anisotropy. We
systematically construct a family of phase-space functions with the
resulting radial velocity dispersion overlapping with the one obtained
using data on radial motions of distant kinematic tracers, while
making no assumptions about the density of the tracers and the
velocity anisotropy parameter β regarded as a function of the
radial variable. While there is no apparent upper bound for the Milky
Way mass, at least as long as only the radial motions are concerned,
we find a sharp lower bound for the mass that is small. In particular,
a mass value of 2.4x1011M☉, obtained in the past for lower and
intermediate radii, is still consistent with the dispersion profile at
larger radii. Compared with much greater mass values in the
literature, this result shows that determining the Milky Way mass is
strongly model-dependent. We expect a similar reduction of mass
estimates in models assuming more realistic mass profiles.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 51 3965 Radial velocity tracers with the largest
r*vt2/2G and samples SI and SII used in the text
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- Name Object name (2)
23 A1 --- SName Short name used in the paper for 5 objects
27- 34 E8.4 10+11Msun Mass Mass observable r*vr2/2G (1)
38- 44 F7.3 kpc Dist Approximate Galactocentric distance (1)
47 A1 --- SI [±] Included (+) or excluded (-) in SI sample
51 A1 --- SII [±] Included (+) or excluded (-) in SII sample
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Note (1): The numerical values were calculated in the Galactocentric coordinate
system, assuming the LSR at V0=240km/s, R0=8.5kpc, and the peculiar
Sun velocity in the LSR as U=11.1km/s, V=12.24km/s, W=7.25km/s.
Note (2):
* Stars named 85-TARGNN and 88-TARGNN are from Deason et al.,
2012MNRAS.425.2840D 2012MNRAS.425.2840D.
* Stars named xDhompalmerNN are from DOHM-PALMER et al.,
2001ApJ...555L..37D 2001ApJ...555L..37D, table2.
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Acknowledgements:
Lukasz Bratek, Lukasz.Bratek(at)ifj.edu.pl
(End) Patricia Vannier [CDS] 16-Dec-2013