Two estimates of the distance to the Galactic Centre

Francis, Charles; Anderson, Erik

doi:10.1093/mnras/stu631

Cited by 56 publications

(39 citation statements)

References 75 publications

(115 reference statements)

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“…Although there are no globular clusters in the analyzed area according to the Francis & Anderson (2014) catalog, their presence in nearby regions could bias the number of RR Lyrae stars found. This possible effect on our catalog was investigated on the three closest globular clusters to our sample of RRab stars.…”

Section: Resultsmentioning

confidence: 99%

Mapping the outer bulge with RRab stars from the VVV Survey

Gran

Minniti

Saito

et al. 2016

A&A

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Context. The VISTA Variables in the Vía Láctea (VVV) is a near-IR time-domain survey of the Galactic bulge and southern plane. One of the main goals of this survey is to reveal the 3D structure of the Milky Way through their variable stars. In particular, enormous numbers of RR Lyrae stars have been discovered in the inner regions of the bulge (−8• ) by optical surveys such as OGLE and MACHO, but leaving an unexplored window of more than ∼47 sq deg (−10.0• and −10.3• b −8.0 • ) observed by the VVV Survey. Aims. Our goal is to characterize the RR Lyrae stars in the outer bulge in terms of their periods, amplitudes, Fourier coefficients, and distances in order to evaluate the 3D structure of the bulge in this area. The distance distribution of RR Lyrae stars will be compared to that of red clump stars, which is known to trace a X-shaped structure, in order to determine whether these two different stellar populations share the same Galactic distribution. Methods. A search for RR Lyrae stars was performed in more than ∼47 sq deg at low Galactic latitudes (−10.3• ). In the procedure the χ 2 value and analysis of variance (AoV) statistic methods were used to determine the variability and periodic features of the light curves, respectively. To prevent misclassifications, the analysis was performed only on the fundamental mode RR Lyrae stars (RRab) owing to similarities found in the near-IR light curve shapes of contact eclipsing binaries (W UMa) and first overtone RR Lyrae stars (RRc). On the other hand, the red clump stars of the same analyzed tiles were selected, and cuts in the color-magnitude diagram were applied and the maximum distance restricted to ∼20 kpc in order to construct a similar catalog in terms of distances and covered area compared to the RR Lyrae stars. Results. We report the detection of more than 1000 RR Lyrae ab-type stars in the VVV Survey located in the outskirts of the Galactic bulge. A few of them are possibly associated with the Sagittarius Dwarf Spheroidal Galaxy. We calculated colours, reddening, extinction, and distances of the detected RR Lyrae stars in order to determine the outer bulge 3D structure. Our main result is that, at the low galactic latitudes mapped here, the RR Lyrae stars trace a centrally concentrated spheroidal distribution. This is a noticeably different spatial distribution to the one traced by red clump stars known to follow a bar and X-shaped structure. We estimate the completeness of our sample at 80% for K s ≤ 15 mag.

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Section: Resultsmentioning

confidence: 99%

Mapping the outer bulge with RRab stars from the VVV Survey

Gran

Minniti

Saito

et al. 2016

A&A

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“…The centroid of the distance distribution of globular clusters, the basis for the famous early work by Shapley (1918), continues to be used for estimating R0 (Bica et al 2006;Francis & Anderson 2014). These studies are based on the catalogue of Harris (2010, and earlier), where individual distances are estimated from HB magnitudes and reddening.…”

Section: Secondary Estimatesmentioning

confidence: 99%

The Galaxy in Context: Structural, Kinematic, and Integrated Properties

Bland-Hawthorn¹,

Gerhard

2016

Annu. Rev. Astron. Astrophys.

1,395

846

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Our Galaxy, the Milky Way, is a benchmark for understanding disk galaxies. It is the only galaxy whose formation history can be studied using the full distribution of stars from faint dwarfs to supergiants. The oldest components provide us with unique insight into how galaxies form and evolve over billions of years. The Galaxy is a luminous (L ) barred spiral with a central box/peanut bulge, a dominant disk, and a diffuse stellar halo. Based on global properties, it falls in the sparsely populated "green valley" region of the galaxy colour-magnitude diagram. Here we review the key integrated, structural and kinematic parameters of the Galaxy, and point to uncertainties as well as directions for future progress. Galactic studies will continue to play a fundamental role far into the future because there are measurements that can only be made in the near field and much of contemporary astrophysics depends on such observations.

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“…Although the direct Galactic Center distance determinations by the Genzel and Ghez groups are arguably the most precise Galactic Center distance estimates available to date, their derivation is very sensitive to a range of modeling assumptions (e.g., Gillessen et al 2009;Francis & Anderson 2014). Two potentially important issues the underlying assumption of Keplerian motion of the S stars around Sgr A*.…”

Section: Direct Distance Determinationsmentioning

confidence: 99%

“…Francis & Anderson (2014) pointed out that the corrections for the relativistic geodetic effect (de Sitter precession) attempted by Gillessen et al (2009) are based on the assumption that this precession arises in the Schwarzschild metric, whereas one should instead adopt the Kerr metric associated with a relativistically rotating central black hole. In turn, this leads to 'frame dragging' (also known as the Lense-Thirring effect), which is predicted to affect both the S stars' orbits and the light paths into the line of sight.…”

Section: Direct Distance Determinationsmentioning

confidence: 99%

Clustering of Local Group Distances: Publication Bias or Correlated Measurements? Iv. The Galactic Center

Grijs

Bono

2016

ApJS

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Aiming at deriving a statistically well-justified Galactic Center distance, R 0 , and reducing any occurrence of publication bias, we compiled the most comprehensive and most complete database of Galactic Center distances available to date, containing 273 new or revised R 0 estimates published since records began in October 1918 until June 2016. We separate our R 0 compilation into direct and indirect distance measurements. The latter include a large body of estimates that rely on centroid determinations for a range of tracer populations as well as measurements based on kinematic observations of objects at the solar circle, combined with a mass and/or rotational model of the Milky Way. Careful assessment of the Galactic Center distances resulting from orbital modeling and statistical parallax measurements in the Galactic nucleus yields our final Galactic Center distance recommendation of R 0 = 8.3 ± 0.2 (statistical) ± 0.4 (systematic) kpc. The centroid-based distances are in good agreement with this recommendation. Neither the direct measurements nor the post-1990 centroidbased distance determinations suggest that publication bias may be important. The kinematics-based distance estimates are affected by significantly larger uncertainties, but they can be used to constrain the Galaxy's rotation velocity at the solar Galactocentric distance, Θ 0 . Our results imply that the International Astronomical Union-recommended Galactic Center distance (R IAU 0 = 8.5 kpc) needs a downward adjustment, while its Θ 0 recommendation (Θ 0 = 220 km s −1 ) requires a substantial upward revision.

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Two estimates of the distance to the Galactic Centre

Cited by 56 publications

References 75 publications

Mapping the outer bulge with RRab stars from the VVV Survey

Mapping the outer bulge with RRab stars from the VVV Survey

The Galaxy in Context: Structural, Kinematic, and Integrated Properties

Clustering of Local Group Distances: Publication Bias or Correlated Measurements? Iv. The Galactic Center

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