The distance to the Galactic center determined by OB stars

Branham, Richard L.

doi:10.1007/s10509-014-2005-9

Cited by 14 publications

(16 citation statements)

References 31 publications

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“…9.1.1; Reid et al 2014) or even the distance to the center of the MW (e.g. Gillessen et al 2009;Sofue et al 2011;Branham 2014) are difficult to measure; the area within which a reasonably robust analysis can be made is only between the end of the central bar and the Sun's Galactocentric radius, R 0 (Dehnen & Binney 1998); and the parameters of arbitrary models for the DM geometry must be fit, e.g. using a Navarrow-Frenck-White (1997) or Einasto (1965) profile plus assumptions about the halo's oblateness.…”

Section: Introductionmentioning

confidence: 99%

The difficulty of measuring the local dark matter density

Hessman

2015

A&A

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The analysis of the vertical velocity dispersion of disc stars in the local Milky Way is the most direct astronomical means of estimating the local dark matter density, ρ DM . Current estimates for ρ DM based on the mid-plane dynamic density use a local baryonic correction that ignores the non-local effects of spiral structure and significantly underestimates the amount of dynamically relevant gas now known to be present in the ISM; the additional gas plus the remaining uncertainties make it practically impossible to measure ρ DM from mid-plane kinematics alone. The sampling of inhomogeneous tracer populations with different scale-heights and scale-lengths results in a systematic increase in the observed dispersion gradients and changes in the nominal density distributions that, if not properly considered, can be misinterpreted as a sign of more dark matter. If the disc gravity is modelled locally using an infinite disc, the local variation in the vertical gravity due to the globally exponential disc components results in an underestimation of the baryonic contribution by as much as ∼40%. Given only the assumptions of stationarity, an axially and vertically symmetric disc, doubly exponential tracer and mass-component density profiles, a phenomenologically justified model for the cross-dispersion component σ Rz , and a realistic model for g z (z), it is possible to solve the full vertical Jeans equation analytically for the vertical dispersion σ z (z) and hence test the robustness of previous attempts at measuring ρ DM . When the model parameters for σ Rz are estimated from SEGUE G dwarf star data, it is still not possible to explain the difference in behaviour seen in the simple thick-and thin-disc datasets reported by Buedenbender et al. (2014, MNRAS, submitted). Rather than being a fundamental problem with the kinematical model, this effect appears to be a further sign of the difficulty of defining and handling kinematically homogeneous tracer populations.

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Section: Introductionmentioning

confidence: 99%

The difficulty of measuring the local dark matter density

Hessman

2015

A&A

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“…The uncertainties, where available, are the statistical uncertainties only; no explicit references to systematic uncertainties were found. However, one can of course gain insight into the latter by examining the different values provided by a number of authors for different assumptions made (e.g., Lynden-Bell & Lin 1977;Einasto et al 1979;Jackson 1985;Caldwell & Coulson 1988;Merrifield 1992;Miyamoto & Zhu 1998;Feast et al 1998;Zhu 2000;Shen & Zhu 2007;Xue et al 2008;Yuan et al 2008;Reid et al 2009a,b;Bovy et al 2009;Bobylev 2013;Zhu & Shen 2013;Branham 2014;Bobylev & Bajkova 2015).…”

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confidence: 99%

Clustering of Local Group Distances: Publication Bias or Correlated Measurements? V. Galactic Rotation Constants

Grijs

Bono

2017

ApJS

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As part of on an extensive data mining effort, we have compiled a database of 162 Galactic rotation speed measurements at R 0 (the solar Galactocentric distance), Θ 0 . Published between 1927 and 2017 June, this represents the most comprehensive set of Θ 0 values since the 1985 meta analysis that led to the last revision of the International Astronomical Union's recommended Galactic rotation constants. Although we do not find any compelling evidence of the presence of 'publication bias' in recent decades, we find clear differences among the Θ 0 values and the Θ 0 /R 0 ratios resulting from the use of different tracer populations. Specifically, young tracers (including OB and supergiant stars, masers, Cepheid variables, Hii regions, and young open clusters), as well as kinematic measurements of Sgr A* near the Galactic Center, imply a significantly larger Galactic rotation speed at the solar circle and a higher Θ 0 /R 0 ratio (i.e., Θ 0 = 247 ± 3 km s −1 and Θ 0 /R 0 = 29.81 ± 0.32 km s −1 kpc −1 ; statistical uncertainties only) than any of the tracers dominating the Galaxy's mass budget (i.e., field stars and the Hi/CO distributions). Using the latter as most representative of the bulk of the Galaxy's matter distribution, we arrive at an updated set of Galactic rotation constants, Θ 0 = 225 ± 3 (statistical) ± 10 (systematic) km s −1 , R 0 = 8.3 ± 0.2 (statistical) ± 0.4 (systematic) kpc, and Θ 0 /R 0 = 27.12 ± 0.39 (statistical) ± 1.78 (systematic) km s −1 kpc −1 .

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“…Finally, note the paper by Branham (2014), who analyzed the three-dimensional kinematics of more than 6000 OB stars within r < 3 kpc of the Sun. He used a method based on the generalized Oort formulas, with two more terms having been added to Eqs.…”

Section: Following the Recommendations Of Reid Et Al (2014)mentioning

confidence: 99%

Analysis of galactic rotation from masers based on a nonlinear oort model

Бобылев

Bajkova

2014

Astron. Lett.

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Based on data on Galactic masers with measured trigonometric parallaxes, we have tested a nonlinear model of Galactic rotation using generalized Oort formulas. This model is shown to yield pretty good results up to heliocentric distances of 3-4 kpc. The main feature of the method is the possibility of estimating the solar Galactocentric distance R 0 . This distance has been found by analyzing ≈60 masers to be R 0 = 8.3 ± 0.4 kpc. Our study of the threedimensional kinematics of more than 100 masers based on the Ogorodnikov-Milne model has shown that significant nonlinearities are present only in the xy plane (rotation around the Galactic z axis) due to the peculiarities of the Galactic rotation curve. No significant linear dependences have been found in the xz and yz planes. We show the presence of a wave in the velocities w as a function of coordinate x or distance R with a wavelength of 3 kpc and an amplitude of 10 km s −1 . The wave is particularly prominent in the Local and Perseus arms.

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The distance to the Galactic center determined by OB stars

Cited by 14 publications

References 31 publications

The difficulty of measuring the local dark matter density

The difficulty of measuring the local dark matter density

Clustering of Local Group Distances: Publication Bias or Correlated Measurements? V. Galactic Rotation Constants

Analysis of galactic rotation from masers based on a nonlinear oort model

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