Using Lyman-α to detect galaxies that leak Lyman continuum

By A. Verhamme, I. Orlitová, D. Schaerer, M. Hayes. 2014

210 citations recorded by the source corpus.

Aims. We propose to infer the output of the ionising continuum-leaking properties of galaxies based upon their Ly line profiles. Methods. We carried out Ly radiation transfer calculations in two models of Hii regions. These models are porous to ionising continuum escape: 1) we define Lyman-continuum (LyC) optically thin star clusters, in which massive stars produce enough ionising photons to keep the surrounding interstellar medium transparent to the ionising continuum, in other words, almost totally ionised, and 2) we define riddled ionisation-bounded media that are surrounded by neutral interstellar medium, but have holes, which results in a covering fraction lower than unity. Results. The Ly spectra that emerge from these configurations have distinctive features: 1) a classical asymmetric redshifted profile in the first case, but with a small shift of the profile maximum compared to the systemic redshift (vpeak 150 km s 1 ); 2) a main peak at the systemic redshift in the second case (vpeak = 0), with a non-zero Ly flux bluewards of the systemic redshift as a consequence. If in a galaxy that leaks ionising photons the Ly component that emerges from the leaking star cluster(s) is assumed to dominate the total Ly spectrum, the Ly shape may be used as a pre-selection tool for detecting LyC-leaking galaxies in objects with high spectral resolution Ly spectra (R 4000). Our predictions are corroborated by examination of a sample of ten local starbursts with high-resolution HST/COS Ly spectra that are known in the literature as LyC leakers or leaking candidates. Conclusions. Observations of Ly profiles at high resolution are expected to show definite signatures revealing the escape of Lymancontinuum photons from star-forming galaxies.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/fe428c0ee24f5888e7c1ec18843ce6f9329ce1a9

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In Astronomy and Astrophysics

1. Naveen A. Reddy
2. C. Steidel
3. A. Shapley
4. D. Erb
5. M. Pettini
6. R. Dav'e
7. G. Rudie
8. P. Hopkins

In Instrumentation

1. Naveen A. Reddy
2. C. Steidel
3. A. Shapley
4. D. Erb
5. M. Pettini
6. G. Rudie
7. M. Bogosavljević
8. R. Trainor

Citations in the corpus

• Lyα Emitting Galaxies as a Probe of Reionisation (2014, background): “These same paths enable Lyα photons to escape close to line centre (Behrens et al. 2014; Verhamme et al. 2014).”
• The Keck Lyman Continuum Spectroscopic Survey (KLCS): The Emergent Ionizing Spectrum of Galaxies at z ∼ 3 (2018, methodology): “…relationship between the kinematics and escape of Lyα emission and the leakage of significant LyC emission have varied depending on the physical model assumed for the structure and kinematics of the ISM (e.g., Yajima et al. 2014; Verhamme et al. 2015; Dijkstra et al. 2016; Verhamme et al. 2017).”
• Lyα EMISSION FROM GREEN PEAS: THE ROLE OF CIRCUMGALACTIC GAS DENSITY, COVERING, AND KINEMATICS (2015, background): “Remarkably, even the low end of this range leads to high Lyα optical depth at line center, even if it is optically thin to hydrogen-ionizing Lyman continuum (LyC) photons (τLyα > 10 2 –103; Verhamme et al. 2006, 2015).”