Understanding hydrogen recombination line observations with ALMA and EVLA

Thomas Peters (1,2,3), Steven N. Longmore (4) and Cornelis P. Dullemond (1) ((1) Zentrum für Astronomie der Universität Heidelberg, Institut für Theoretische Astrophysik, Albert-Ueberle-Str. 2, D-69120 Heidelberg, Germany; (2) Fellow of the Baden-Württemberg Stiftung; (3) Institut für Theoretische Physik, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland; (4) European Southern Observatory, Karl-Schwarzschild-Str. 2, D-85748 Garching bei München, Germany)

Hydrogen recombination lines are one of the major diagnostics of H II region physical properties and kinematics. In the near future, the Expanded Very Large Array (EVLA) and the Atacama Large Millimeter Array (ALMA) will allow observers to study recombination lines in the radio and sub-mm regime in unprecedented detail. In this paper, we study the properties of recombination lines, in particular at ALMA wavelengths. We find that such lines will lie in almost every wideband ALMA setup and that the line emission will be equally detectable in all bands. Furthermore, we present our implementation of hydrogen recombination lines in the adaptive-mesh radiative transfer code RADMC-3D. We particularly emphasize the importance of non-LTE (local thermodynamical equilibrium) modeling since non-LTE effects can drastically affect the line shapes and produce asymmetric line profiles from radially symmetric H II regions. We demonstrate how these non-LTE effects can be used as a probe of systematic motions (infall & outflow) in the gas. We use RADMC-3D to produce synthetic observations of model H II regions and study the necessary conditions for observing such asymmetric line profiles with ALMA and EVLA.

Complete preprint ==> http://arxiv.org/abs/1206.7041

This entry was posted in Atomic data applications and tagged , , , , , . Bookmark the permalink.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s