Lyman Alpha emission from ULIRGs at z=0.15

Abstract

Most of high redshift star formation occurs in IR-bright galaxies. Cosmic average star formation peaks around redshift of 2. One of the main tracer of these galaxies is the Lyman-alpha line. Ly-alpha photons are highly susceptible to dust absorption. However, surprising results of recent studies have found that a large fraction of IR- bright galaxies also have \lya\ in emission. In the present work we attempt to understand the origin of this \lya\ emission using high resolution imaging results from Hubble Space Telescope. Interpretation of \lya\ observations is extremely complex as these photons traverse through a large portion of ISM before being able to escape. Resolved imaging in \lya\ can help us trace the path of \lya\ photons through ISM and conclude the constituents of ISM. This has motivated studies of nearby analog of high redshift galaxies. Only HST provides the UV access and resolution to do this. Several studies of UV-selected galaxies have been carried using HST. UV-selected galaxies are only a small fraction of galaxies at high-z. So far, no study has ever imaged the IR-bright systems in \lya\ . We image 5 local ultra luminous infrared galaxies (ULIRGs) on a spatial scales of just 140 pc in \lya\ . Preliminary results show that 3 out of 5 ULIRGs in our sample have \lya\ in emission globally.