Preprint typeset using LATEX style emulateapj v. 5/2/11 THE LYMAN-ALPHA REFERENCE SAMPLE: I. SURVEY OUTLINE AND FIRST RESULTS FOR MARKARIAN 259

The Lyman-alpha reference sample (LARS) is a substantial program with the Hubble Space Tele-scope (HST) that provides a sample of local universe laboratory galaxies in which to study the detailed astrophysics of the visibility and strength of the Lyman-alpha (Lyα) line of neutral hydrogen. Lyα is the dominant spectral line in use for characterizing high redshift (z) galaxies. This article presents an overview of the survey, its selection function and HST imaging observations. The sample was selected from the combined GALEX+SDSS catalogue at z = 0.028−0.19, in order to allow Lyα to be captured with combinations of long pass filters in the Solar Blind Channel (SBC) of the Advanced Camera for Surveys (ACS) on board HST. In addition, LARS utilises Hα and Hβ narrow, and u, b, i broad-band imaging with ACS and the Wide Field Camera 3 (WFC3). In order to study galaxies in which large numbers of Lyα photons are produced (whether or not they escape) we demanded an Hα equivalent width W(Hα) ≥ 100Å. The final sample of 14 galaxies covers far UV (FUV, λ ∼ 1500 Å) luminosities that overlaps with those of high-z Lyα emitters and Lyman Break Galaxies (LBGs), making LARS a valid comparison sample. We present the reduction steps used to obtain the Lyα images, including our LARS eXtraction software (LaXs) which utilises pixel-by-pixel spectral synthesis fitting of th