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Center for Astrophysics Research and Technologies Seminar Series Information

 

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Using Radio Continuum Observations to Study Why Gaseous Halos Lag

Thursday November 8, 2018
2:00 pm


 Presenter:  Tim Braun (UNM)
 Series:  Center for Astrophysics Research and Technologies Seminar Series
 Abstract:  Gaseous halos are excellent laboratories to study spiral galaxy evolution (e.g., star formation feedback and accretion events), because they are the interface between the disk of a galaxy and the surrounding intergalactic medium. Recent kinematical studies of halo gas in edge-on galaxies show an increasingly ubiquitous phenomenon: the rotation velocity of extraplanar gas lags the rotation of the disk (lagging halo) and decreases with height off of the midplane. Simple ballistic models of disk-halo gas circulation fail to predict the steepness of these lags. However, the addition of nonthermal pressures from cosmic rays and magnetic fields in the halo may reconcile the observed and modeled lag amplitudes.

In this work, we attempt to 2D/3D model the nonthermal halo radial pressure gradients in a sub-sample of twelve edge-on galaxies from the Continuum Halos in Nearby Galaxies - an EVLA Survey (CHANG-ES) sample with measured lags. We also detail a new single dish (SD) and interferometric (INT) joint deconvolution algorithm used to combine our wideband GBT and VLA CHANG-ES continuum data in order to solve the missing short-spacings problem (missing large-scale flux and total flux densities). This combination technique feathers SD and INT data within an iterative image reconstruction scheme and supports many INT imaging options including multi-term multi-frequency synthesis, multi-scale modeling, and joint mosaicing.
 Host:  Richard Rand
 Location:  Room 190, Physics & Astronomy

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