The Lyman Alpha Reference Sample. Iii. Properties of the Neutral Ism From GBT and Vla Observations

Abstract

We present new H I imaging and spectroscopy of the 14 UV-selected starforming galaxies in the Lyman Alpha Reference Sample (LARS), aimed for a detailed study of the processes governing the production, propagation, and escape of Lyα photons. New H I spectroscopy, obtained with the 100m Green Bank Telescope (GBT), robustly detects the H I spectral line in 11 of the 14 observed LARS galaxies (although the profiles of two of the galaxies are likely confused by other sources within the GBT beam); the three highest redshift galaxies are not detected at our current sensitivity limits. The GBT profiles are used to derive fundamental H I line properties of the LARS galaxies. We also present new pilot H I spectral line imaging of 5 of the LARS galaxies obtained with the Karl G. Jansky Very Large Array (VLA). This imaging localizes the H I gas and provides a measurement of the total H I mass in each galaxy. In one system, LARS 03 (UGC 8335 or Arp 238), VLA observations reveal an enormous tidal structure that extends over 160 kpc from the main interacting systems and that contains >10 9 M of H I. We compare various H I properties with global Lyα quantities derived from HST measurements. The measurements of the Lyα escape fraction are coupled with the new direct measurements of H I mass and significantly disturbed H I velocities. Our robustly detected sample reveals that both total H I mass and linewidth are tentatively correlated with key Lyα tracers. Further, on global scales, these data support a complex coupling between Lyα propagation and the H I properties of the surrounding medium.

The stellar mass, star formation rate and dark matter halo properties of LAEs at z ∼ 2

“…Galaxies with a low Mgas likely have a low HI column density, thus making it easier for Lyα photons to escape because of a reduced number of resonant scatterings. Indeed, Pardy et al (2014) have found a tentative anticorrelation of HI gas mass with the Lyα escape fraction and the Lyα equivalent width using 14 local galaxies (Lyα Reference Sample; Hayes et al 2013;Östlin et al 2014).…”

Statistical properties of diffuse Lyα haloes around star-forming galaxies atz∼ 2

“…Deep optical and near-infrared spectra for gas dynamics and line diagnostics indicate that the ISM of LAEs have a low NH i, ISM (e.g. Hashimoto et al 2013;Nakajima et al 2013;Chonis et al 2013;Shibuya et al 2014a,b;Song et al 2014;Pardy et al 2014). So far, there are no conclusive observational tests including our results that rule out this first scenario.…”

The Lyα Reference Sample. VIII. Characterizing Lyα Scattering in Nearby Galaxies

“…Figure 14. Characteristic scattering distance vs. the H I column density for the LARS galaxies for which these data exist (Pardy et al 2014). The Spearman correlation coefficient is r = 0.67 with a probability of a correlation arising by chance of p = 0.22.…”

“…We explored this relationship using data for the LARS galaxies from the Very Large Array (VLA; Pardy et al 2014). At present, data are published for only five galaxies in the sample: LARS02, LARS03, LARS04, LARS08, and LARS09.…”

“…One of the best samples in which to study resolved Lyα is the Lyman Alpha Reference Sample (LARS; Hayes et al 2013Hayes et al , 2014Östlin et al 2014;Pardy et al 2014;Rivera-Thorsen et al 2015;Duval et al 2016;Herenz et al 2016). The LARS sample comprises 14 nearby ( < < z 0.02 0.2) Lyα-emitting and/or absorbing galaxies with extensive Hubble Space Telescope (HST) broadband and narrowband imaging, supplemented by observations from numerous other telescopes.…”