Journal article
The Lyman alpha reference sample VI. Lyman alpha escape from the edge-on disk galaxy Mrk 1486
Astronomy and astrophysics (Berlin), Vol.587, p.A77
03/01/2016
DOI: 10.1051/0004-6361/201526876
Abstract
Context. Recent numerical simulations suggest that the strength of the Lyman alpha (Ly alpha) line of star-forming disk galaxies strongly depends on the inclination at which they are observed: from edge-on to face-on, we expect to see a change from a strongly attenuated Ly alpha line to a strong Ly alpha emission line.
Aims. We aim to understand how a strong Ly alpha emission line is able to escape from the low-redshift highly inclined (edge-on) disk galaxy Mrk 1486 (z similar to 0.0338). To our knowledge, this work is the first observational study of Ly alpha transport inside an edge-on disk galaxy.
Methods. Using a large set of HST imaging and spectroscopic data, we investigated the interstellar medium (ISM) structure and the dominant source of Ly alpha radiation inside Mrk 1486. Moreover, using a 3D Monte Carlo Ly alpha radiation transfer code, we studied the radiative transfer of Ly alpha and UV continuum photons inside a 3D geometry of neutral hydrogen (HI) and dust that models the ISM structure at the galaxy center. Our numerical simulations predicted the Ly alpha line profile that we then compared to the one observed in the HST/COS spectrum of Mrk 1486.
Results. While a pronounced Ly alpha absorption line emerges from the disk of Mrk 1486, very extended Ly alpha structures are observed at large radii from the galaxy center: a large Ly alpha-halo and two very bright Ly alpha regions located slightly above and below the disk plane. The analysis of IFU H alpha spectroscopic data of Mrk 1486 indicates the presence of two bipolar outflowing halos of HI gas at the same location as these two bright Ly alpha regions. Comparing different diagnostic diagrams (such as [OIII](5007)/H beta versus [OI](6300)/H alpha) to photo-and shock-ionization models, we find that the Ly alpha production of Mrk 1486 is dominated by photoionization inside the galaxy disk. From this perspective, our numerical simulations succeed in reproducing the strength and shape of the observed Ly alpha emission line of Mrk 1486 by assuming a scenario in which the Ly alpha photons are produced inside the galaxy disk, travel along the outflowing halos, and scatter on cool HI materials toward the observer.
Conclusions. Extended bipolar galactic winds are frequently observed from star-forming disk galaxies. Given the advantage Ly alpha photons take of such outflowing HI materials to easily escape from Mrk 1486, this mechanism may explain the origin of strong Ly alpha emission lines frequently observed from highly inclined galaxies at high-redshift. This therefore challenges the robustness of the expected viewing-angle effect on the Ly alpha properties of star-forming disk galaxies.
Details
- Title: Subtitle
- The Lyman alpha reference sample VI. Lyman alpha escape from the edge-on disk galaxy Mrk 1486
- Creators
- Florent Duval - The University of TokyoGoran Ostlin - Stockholm UniversityMatthew Hayes - Stockholm UniversityErik Zackrisson - Uppsala UniversityAnne Verhamme - University of GenevaIvana Orlitova - Czech Academy of Sciences, Astronomical InstituteAngela Adamo - Stockholm UniversityLucia Guaita - Astronomical Observatory of RomeJens Melinder - Stockholm UniversityJohn M. Cannon - Macalester CollegePeter Laursen - University of CopenhagenThoger Rivera-Thorsen - Stockholm UniversityE. Christian Herenz - Leibniz Institute for Astrophysics PotsdamPieter Gruyters - Stockholm UniversityJ. Miguel Mas-Hesse - Instituto Nacional de Técnica AeroespacialDaniel Kunth - Institut d'Astrophysique de ParisAndreas Sandberg - Stockholm UniversityDaniel Schaerer - Research Institute in Astrophysics and PlanetologyTore Mansson - Stockholm University
- Resource Type
- Journal article
- Publication Details
- Astronomy and astrophysics (Berlin), Vol.587, p.A77
- Publisher
- Edp Sciences S A
- DOI
- 10.1051/0004-6361/201526876
- ISSN
- 0004-6361
- eISSN
- 1432-0746
- Number of pages
- 24
- Grant note
- Swedish National Space Board (SNSB); Swedish National Space Agency (SNSA) GACR 14-20666P / Czech Science Foundation; Grant Agency of the Czech Republic Japan Society for the Promotion of Science (JSPS) fund; Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT); Japan Society for the Promotion of Science Centre National d'Etudes Spatiales (CNES); Centre National D'etudes Spatiales EGGS-278202 / ERC-StG grant; European Research Council (ERC) 2011-5349 / Swedish Research Council Swedish Research Council (Vetenskapsradet); Swedish Research Council
- Language
- English
- Date published
- 03/01/2016
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984627227002771
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