The effects of biconical outflows on lyα escape from green peas

Cody Carr, Claudia Scarlata, Alaina Henry, Nino Panagia

Research output: Contribution to journalArticlepeer-review

Abstract

We analyze the spectra of 10 Green Pea galaxies, previously studied by Henry et al., using a semi-analytical line transfer model to interpret emission and absorption features observed in UV galactic spectra. We focus our analysis on various ionization states of silicon, associated with the cool (∼104 K) and warm (∼105 K) gas. By analyzing low-ionization lines, we study the relationships between the distribution and kinematics of the outflowing H I gas and the observed Lyα escape fraction, fescLya, as well as the Lyα emission peak separation, Δpeak. We find that outflow geometries that leave a portion of the source uncovered along the line of sight create the best conditions for Lyα escape and have narrow peak separations, while geometries that block the observer's view of the source create the worst conditions for Lyα escape and have large peak separations. To isolate the effects of outflow kinematics, we restrict our testing set to galaxies with spherical outflows and find that fescLya and the Lyα luminosity both increase with the extent of the galactic winds. A simple estimate suggests that the collisional excitation of neutral hydrogen by free electrons in the cool gas of the winds can account for the Lyα luminosity observed in these objects. Finally, we speculate on the relationship between outflows and the escape of ionizing radiation from the circumgalactic medium.

Original languageEnglish (US)
Article number104
JournalAstrophysical Journal
Volume906
Issue number2
DOIs
StatePublished - Jan 10 2021

Bibliographical note

Funding Information:
We acknowledge Simon Gazagnes for graciously providing stellar continuum fits for a number of our galaxies. We acknowledge the anonymous referee for a careful reading of the manuscript and providing valuable suggestions that expanded the scope of this work. Support for program number HST-GO-15626 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555.

Publisher Copyright:
© 2021. The American Astronomical Society. All rights reserved.

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