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

Atomic Hydrogen in a Galactic Center Outflow

by: N. M. McClure-Griffiths, J. A. Green, A. S. Hill, F. J. Lockman,

J. M. Dickey, B. M. Gaensler, A. J. Green

[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.

Melioli,C. et al.; Evolution of M82-like starburst winds revisited: 3D radiative cooling hydrodynamical simulations

Evolution of M82-like starburst winds revisited: 3D radiative cooling hydrodynamical simulations

by: C. Melioli, E. M. de Gouveia Dal Pino, F. Geraissate

[arXiv:1301.5005, pdf, first author, second, third]

This is an interesting paper because it is closely related to work done by Cooper et al. (first paper 2008, second paper 2009) that I have been looking at for some time. The paper deals with simulations done using a hydro AMR that has radiative cooling and some species tracking. It is more work on superbubbles and AGNs. They specifically use M82 as a test case.

The authors are from Brazil (Sao Paulo), and the code is named YGUAZU, which is a Paraguayan spelling of Iguazú (sort of appropriate for a hydro code since it means "Big Water"). Other than some basics (they use a Van Leer integrator) they only provide references and no explanation. Also interesting is the fact that they cite Strickland & Stevens (2000) in their explanation of how they set their initial conditions, but they don't use the notation of Strickland and Stevens. They use the notation of Jackie Cooper (2009) (she did work with Strickland and Stevens and used their code and set up). But these guys don't cite here even though they have copied her equations exactly.

Their energy injection centers around super stellar clusters (SSCs) "with an average size of ∼ 5.7 pc and mass (of stars) between 10⁴ and 10⁶ M_⊙(Melo et al. 2005)." They look at metals and how much gas escapes the galaxy and how much metals produced by supernovas escapes the galaxies. They conclude that most of the gas mass stays in the galaxy even with a superbubble blow out. Also most of the metals stay in the galaxy but some get transported out in the galactic winds that form due to the supernovas (the SN's pump out metal rich winds).