Singly Peaked Asymmetric Lyα from Starburst Galaxies

We present results of Monte Carlo calculations for the Lyα line transfer in an expanding dusty supershell, surrounding Lyα sources in a starburst galaxy. The Lyα photons escape the system by a number of backscatterings, which results in a series of emission peaks redward of the systemic redshift, in contrary to observed singly peaked asymmetric profiles. We find that in order to form a singly peaked asymmetric Lyα emission, dust should be distributed in the ionized bubble, as well as within the supershell of neutral hydrogen. We also find that the overall escape probability of Lyα photons is determined by H I column density, Doppler width, and expansion velocity of the supershell, as well. The kinematic information of the expanding supershell is preserved in the profile of Lyα emission even when the supershell is dusty. Our results are potentially useful to fit the P Cygni-type Lyα line profiles from starburst galaxies, either nearby galaxies or high-z Lyman break galaxies.

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