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The Lyman continuum escape and ISM properties in Tololo 1247-232-new insights from HST and VLA
Stockholm Univ, AlbaNova Univ Ctr, Dept Astron, Oskar Klein Ctr, SE-10691 Stockholm, Sweden..
Stockholm Univ, AlbaNova Univ Ctr, Dept Astron, Oskar Klein Ctr, SE-10691 Stockholm, Sweden..
Stockholm Univ, AlbaNova Univ Ctr, Dept Astron, Oskar Klein Ctr, SE-10691 Stockholm, Sweden..
Stockholm Univ, AlbaNova Univ Ctr, Dept Astron, Oskar Klein Ctr, SE-10691 Stockholm, Sweden..
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2017 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 469, no 3, p. 3252-3269Article in journal (Refereed) Published
Abstract [en]

Low- and intermediate-mass galaxies are widely discussed as cause of reionization at redshift z similar to 10-6. However, observational proof of galaxies that are leaking ionizing radiation (Lyman continuum; LyC) is a currently ongoing challenge and the list of LyC emitting candidates is still short. Tololo 1247-232 is among those very few galaxies with recently reported leakage. We performed intermediate resolution ultraviolet spectroscopy with the Cosmic Origins Spectrograph onboard the Hubble Space Telescope and confirm ionizing radiation emerging from Tololo 1247-232. Adopting an improved data reduction procedure, we find that LyC escapes from the central stellar clusters, with an escape fraction of 1.5 +/- 0.5 per cent only, i.e. the lowest value reported for the galaxy so far. We further make use of far-ultraviolet absorption lines of Si II and Si IV as a probe of the neutral and ionized interstellar medium ( ISM). We find that most of the ISM gas is ionized, likely facilitating LyC escape from density bounded regions. Neutral gas covering as a function of line-of-sight velocity is derived using the apparent optical depth method. The ISM is found to be sufficiently clumpy, supporting the direct escape of LyC photons. We further report on broad-band UV and optical continuum imaging as well as narrow-band imaging of Lya, Ha and H beta. Using stellar population synthesis, an Lya escape fraction of 8 per cent was derived. We also performed Very Large Array 21cm imaging. The hydrogen hyperfine transition was not detected, but a deep upper limit atomic gas mass of less than or similar to 10(9) M-circle dot could be derived. The upper limit gas fraction defined as M-HI/M-* is only 20 per cent. Evidence is found that the HI gas halo is relatively small compared to the Lyman Alpha Reference Sample (Hayes et al. 2013, 2014; Ostlin et al. 2014).

Place, publisher, year, edition, pages
2017. Vol. 469, no 3, p. 3252-3269
Keyword [en]
galaxies: evolution, galaxies: individual: Tololo 1247-232, galaxies: ISM, galaxies: starburst, radio continuum: galaxies, ultraviolet: galaxies
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:uu:diva-333511DOI: 10.1093/mnras/stx951ISI: 000406836200051OAI: oai:DiVA.org:uu-333511DiVA, id: diva2:1162977
Funder
Swedish Research CouncilSwedish National Space Board
Available from: 2017-12-05 Created: 2017-12-05 Last updated: 2017-12-05Bibliographically approved

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