Reconsidering the Galactic coordinate system
Abstract
Initially defined by the IAU in 1958, the Galactic coordinate system was thereafter transformed in 1984 from the B1950.0 FK4based system to the J2000.0 FK5based system. In 1994, the IAU recommended that the dynamical reference system FK5 be replaced by the ICRS, which is a kinematical nonrotating 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 noninertiality 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 microarcsecond level.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 February 2011
 DOI:
 10.1051/00046361/201014961
 arXiv:
 arXiv:1010.3773
 Bibcode:
 2011A&A...526A..16L
 Keywords:

 astrometry;
 Galaxy: general;
 reference systems;
 Astrophysics  Astrophysics of Galaxies
 EPrint:
 10 pages, 3 figures, accepted for publication in A&