The Imprint of Cosmic Ray Driven Outflows on Lyman-α Spectra
Abstract
Recent magnetohydrodynamic simulations of the star-forming interstellar medium (ISM) with parsec-scale resolution indicate that relativistic cosmic rays (CRs) support the launching of galactic outflows on scales of a few kpc. If these fundamental constituents of the ISM are injected at the sites of supernova (SN) explosions, the outflows are smoother, colder, and denser than the highly structured, hot-phase driven outflows forming, e.g., by thermal SN energy injection alone. In this Letter we present computations of resonant Lyman-α(Lyα) radiation transfer through snapshots of a suite of stratified disk simulations from the SILCC project. For a range of thermal, radiative, and kinetic feedback models only simulations including non-thermal CRs produce Lyα spectra with enhanced red peaks and strong absorption at line center—similar to observed systems. The absence of CR feedback leads to spectra incompatible with observations. We attribute this to the smoother neutral gas distribution of CR supported outflows within a few kpc from the disk midplane.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 2018
- DOI:
- 10.3847/2041-8213/aad286
- arXiv:
- arXiv:1805.12251
- Bibcode:
- 2018ApJ...862L...7G
- Keywords:
-
- cosmic rays;
- galaxies: formation;
- galaxies: ISM;
- line: formation;
- radiative transfer;
- scattering;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 6 pages, 4 figures