Tuesday, May 14, 2013

McClure-Griffiths, N. M.; et al.;Atomic Hydrogen in a Galactic Center Outflow

Atomic Hydrogen in a Galactic Center Outflow
[arXiv:1304.7538v1, pdf, First author, second, third, fourth]
This is part of the results from a survey where the authors found several cool, T < 4000 K, H I clouds in a definite pattern around the Galactic Center. The distribution and kinematics of the cloud implied that they were created from a starburst located at the center of the galaxy that has been affecting the galaxy for the past ∼ 2 × 106 years.

They did this by calculating the local standard of rest (LSR) velocities for the cloud centers and then using a simulation that calculated the effect on clouds with a random distribution of velocities and comparing to their observations they determined that the observed clouds did not have kinematics similar to galactic rotation but have a distribution that implies ballistic motion away from the galactic center (see figure below).

They also give a bound on the velocity of the stellar winds that can create this type of distribution  "The [Kolmogorov-Smirnov] test implies that wind velocities greater than 270 km s−1 and less than 150 km s−1 are not consistent with the observed cloud velocities."

They conclude that these clouds are the remnants of a superbubble which was created by a starburst at the center of the Milky Way. They also mention survivability and life spans of the clouds. They provide some bounds to the life spans. They also rely heavily on the simulations of Jackie Cooper to reach some conclusions about the environment of the wind and clouds.

No comments:

Post a Comment