The Position of the Galactic Centre (Paper V)

Oort, J. H.; Rougoor, G. W.

doi:10.1093/mnras/121.2.171

Cited by 14 publications

(5 citation statements)

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“…The Galactic Center, as we understand it today, was first identified through the discovery of Sgr A by radio astronomers (Piddington & Minnett 1951). Based on its unique radio emission properties and its precise coincidence with the dynamical center of the rotating inner HI disk (Oort & Rougoor 1960), the IAU officially adopted Sgr A as the center of the Galaxy, making its position the zero of longitude and latitude in a new system of Galactic coordinates (Blaauw et al 1959). Later Balick & Brown (1974) discovered the unresolved source Sgr A * , now known to be at the location of the Milky Way's supermassive black hole, at (lc, bc) = (−0.056 • , −0.046 • ) (Reid & Brunthaler 2004).…”

Section: Locationmentioning

confidence: 99%

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

Bland-Hawthorn¹,

Gerhard

2016

Annu. Rev. Astron. Astrophys.

1,390

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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Section: Locationmentioning

confidence: 99%

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

Bland-Hawthorn¹,

Gerhard

2016

Annu. Rev. Astron. Astrophys.

1,390

846

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“…The Sun is effectively defined to be in the plane even though it is thought to be some 10-20 pc above the HI principal plane (Zhu 2009). The revision and reconstruction of the galactic coordinate system was presented in a series of five papers (Blaauw et al 1960;Blaauw 1960;Oort & Rougoor 1960). The system was defined by three principal values:…”

Section: Iau1958 Galactic Coordinate Systemmentioning

confidence: 99%

Reconsidering the Galactic coordinate system

Liu

Zhu

Zhang

2010

A&A

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Initially defined by the IAU in 1958, the Galactic coordinate system was thereafter transformed in 1984 from the B1950.0 FK4-based system to the J2000.0 FK5-based system. In 1994, the IAU recommended that the dynamical reference system FK5 be replaced by the ICRS, which is a kinematical non-rotating system defined by a set of remote radio sources. However the definition of the Galactic coordinate system was not updated at that time. We consider that the present Galactic coordinates may be problematic because of the unrigorous transformation method from the FK4 to the FK5 and of the non-inertiality of the FK5 system with respect to the ICRS. This has led to some confusion when applying of the Galactic coordinates. We tried to find the transformation matrix in the framework of the ICRS after carefully investigating the definition of the Galactic coordinate system and transformation procedures, but we could not find a satisfactory Galactic coordinate system that is connected steadily to the ICRS. To avoid unnecessary misunderstandings, we suggest reconsidering the definition of the Galactic coordinate system which should be directly connected with the ICRS for highly precise observations at the micro-arcsecond level.

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“…Paper V (Oort & Rougoor 1960) presented further arguments based on optical and radio data for positing Sgr A to mark the dynamical centre of the Galaxy. Based on Blaauw's (1960) argument that the H i plane was a superior means of defining the Galactic plane and NGP (abandoning van Tulder's optical-based methodology), and employing the H i plane defined by to define the Galactic plane, and defining the radio source Sgr A as the logical choice of origin Oort & Rougoor 1960), the commission proposed the IAU GCS to have NGP at α IAU P = 12 h 49 m , δ IAU P = +27 • .4 with position angle θ IAU P = 123 • (all B1950; Blaauw et al 1960). The position angle θ is that of the "the new galactic pole of the great circle passing through Sagittarius A" (Blaauw et al 1960).…”

Section: Introductionmentioning

confidence: 99%

Revised geometric estimates of the North Galactic Pole and the Sun's height above the Galactic mid-plane

Karim

Mamajek

2016

Mon. Not. R. Astron. Soc.

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Astronomers are entering an era of µas-level astrometry utilizing the 5-decade-old IAU Galactic coordinate system that was only originally defined to ∼0 • .1 accuracy, and where the dynamical centre of the Galaxy (Sgr A*) is located ∼0 • .07 from the origin. We calculate new independent estimates of the North Galactic Pole (NGP) using recent catalogues of Galactic disc tracer objects such as embedded and open clusters, infrared bubbles, dark clouds, and young massive stars. Using these catalogues, we provide two new estimates of the NGP. Solution 1 is an "unconstrained" NGP determined by the galactic tracer sources, which does not take into account the location of Sgr A*, and which lies 90 • .120 ± 0 • .029 from Sgr A*, and Solution 2 is a "constrained" NGP which lies exactly 90 • from Sgr A*. The "unconstrained" NGP has ICRS position: α N GP = 192 • .729 ± 0 • .035, δ N GP = 27 • .084 ± 0 • .023 and θ = 122 • .928 ± 0 • .016. The "constrained" NGP which lies exactly 90 • away from Sgr A* has ICRS position: α N GP = 192 • .728 ± 0 • .010, δ N GP = 26 • .863 ± 0 • .019 and θ = 122 • .928 ± 0 • .016. The difference between the solutions is likely due to the Sun lying above the Galactic midplane. Considering the angular separation between Sgr A* and our unconstrained NGP, and if one adopts the recent estimate of the Galactocentric distance for the Sun of R 0 = 8.2 ± 0.1 kpc, then we estimate that the Sun lies z 17 ± 5 pc above the Galactic midplane. Our value of z is consistent with the true median of 55 previous estimates published over the past century of the Sun's height above the Galactic mid-plane (z 17 ± 2 pc).

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The Position of the Galactic Centre (Paper V)

Cited by 14 publications

References 0 publications

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

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

Reconsidering the Galactic coordinate system

Revised geometric estimates of the North Galactic Pole and the Sun's height above the Galactic mid-plane

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