THE LYMAN ALPHA REFERENCE SAMPLE. II.<i>HUBBLE SPACE TELESCOPE</i>IMAGING RESULTS, INTEGRATED PROPERTIES, AND TRENDS

Abstract

We report upon new results regarding the Lya output of galaxies, derived from\nthe Lyman alpha Reference Sample (LARS), focusing on Hubble Space Telescope\nimaging. For 14 galaxies we present intensity images in Lya, Halpha, and UV,\nand maps of Halpha/Hbeta, Lya equivalent width (EW), and Lya/Halpha. We present\nLya and UV light profiles and show they are well-fitted by S\\'ersic profiles,\nbut Lya profiles show indices systematically lower than those of the UV (n\napprox 1-2 instead of &gt;~4). This reveals a general lack of the central\nconcentration in Lya that is ubiquitous in the UV. Photometric growth curves\nincrease more slowly for Lya than the FUV, showing that small apertures may\nunderestimate the EW. For most galaxies, however, flux and EW curves flatten by\nradii ~10 kpc, suggesting that if placed at high-z, only a few of our galaxies\nwould suffer from large flux losses. We compute global properties of the sample\nin large apertures, and show total luminosities to be independent of all other\nquantities. Normalized Lya throughput, however, shows significant correlations:\nescape is found to be higher in galaxies of lower star formation rate, dust\ncontent, mass, and several quantities that suggest harder ionizing continuum\nand lower metallicity. Eight galaxies could be selected as high-z Lya emitters,\nbased upon their luminosity and EW. We discuss the results in the context of\nhigh-z Lya and UV samples. A few galaxies have EWs above 50 AA, and one shows\nf_escLya of 80%; such objects have not previously been reported at low-z.\n