Large-scale mass distribution behind the Galactic plane

Abstract

We map the 1200 km/s smoothed mass-density distribution in the Galactic zone of avoidance (ZOA), within 6000 km/s of the Local Group, using POTENT reconstruction from peculiar velocities of galaxies. The interpolation into the ZOA is based on the assumed gravitational nature of the velocity field implying a potential flow. The main dynamical features at a distance r about 4000 km/s are (1) the peak of the Great Attractor connecting Centaurus and Pavo at l = 330 deg, (2) a moderate bridge connecting Perseus-Pisces and Cepheus at l = 140 deg, and (3) an extension of a large void from the southern Galactic hemisphere into the ZOA near the direction of Puppis, l about 220-270 deg. We find a strong correlation between the mass density and the IRAS and optical galaxy density at b = +/- 20 deg, which indicates that the main dynamical features in the ZOA should also be seen in galaxy surveys throughout the Galactic plane. The gravitational acceleration at the Local Group, based on the mass distribution out to about 6000 km/s, is strongly affected by the mass distribution in the ZOA. (Author)