Galactic winds driven by cosmic ray streaming

By M. Uhlig, C. Pfrommer, M. Sharma, B. Nath, Torsten A. Ensslin, V. S. M. Garching, Mpids Goettingen, Hits Heidelberg, Rri Bangalore, Zauari Heidelberg. 2012

178 citations recorded by the source corpus.

Galactic winds are observed in many spiral galaxies with sizes from dwarfs up to the Milky Way, and they sometimes carry a mass in excess of that of newly formed stars by up to a factor of 10. Multiple driving processes of such winds have been proposed, including thermal pressure due to supernova heating, ultraviolet radiation pressure on dust grains or cosmic ray (CR) pressure. We here study wind formation due to CR physics using a numerical model that accounts for CR acceleration by supernovae, CR thermalization by Coulomb and hadronic interactions, and advective CR transport. In addition, we introduce a novel implementation of CR streaming relative to the rest frame of the gas. Streaming CRs excite Alfven waves on which they scatter, thereby limiting the CRs’ effective bulk velocity. We find that CR streaming drives powerful and sustained winds in galaxies with virial masses . In dwarf galaxies () the winds reach a mass loading factor of ∼5, expel ∼60 per cent of the initial baryonic mass contained inside the halo’s virial radius and suppress the star formation rate by a factor of ∼5. In dwarfs, the winds are spherically symmetric while in larger galaxies the outflows transition to biconical morphologies that are aligned with the disc’s angular momentum axis. We show that damping of Alfven waves excited by streaming CRs provides a means of heating the outflows to temperatures that scale with the square of the escape speed, . In larger haloes (), CR streaming is able to drive fountain flows that excite turbulence, providing another means of heating the halo gas. For halo masses , we predict an observable level of Hα and X-ray emission from the heated halo gas. We conclude that CR-driven winds should be crucial in suppressing and regulating the first epoch of galaxy formation, expelling a large fraction of baryons, and – by extension – aid in shaping the faint end of the galaxy luminosity function. They should then also be responsible for much of the metal enrichment of the intergalactic medium.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/c802a94d4081829990e527d9914e7ebe5e2cfb70

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Citations in the corpus

Towards a more realistic population of bright spiral galaxies in cosmological simulations (2013, background): “Apart from supernovae, AGN (e.g. Springel et al. 2005) and cosmic rays (Uhlig et al. 2012) have been considered as possible sources of feedback.”
DEVELOPMENT OF THE MODEL OF GALACTIC INTERSTELLAR EMISSION FOR STANDARD POINT-SOURCE ANALYSIS OF FERMI LARGE AREA TELESCOPE DATA (2016, background): “Uhlig et al. (2012) note that CR-driven winds could also suppress the star formation rate by a significant factor.”
How Stellar Feedback Simultaneously Regulates Star Formation and Drives Outflows (2015, background): “Then, other sources ofacceleration, such as supernovae from runaway OB stars (e.g.Li et al. 2015) or cosmic rays (Uhlig et al. 2012; Booth et al. 2013; Hanasz et al. 2013; Salem & Bryan 2014; Salem et al. 2014; Girichidis et al. 2016), may provide the remaining momentum deposition necessary to…”
Cosmic ray driven outflows in global galaxy disc models (2013, methodology): “…for less obvious processes, including radiation pressure (e.g. Murray, Quataert & Thompson 2005; Nath & Silk 2009; Murray, Ménard & Thompson 2011) and the ISM’s relativistic plasma component – i.e. cosmic rays (CRs; Boulares & Cox 1990; Breitschwerdt, McKenzie & Voelk 1993; Uhlig et al. 2012).”
Theoretical Challenges in Galaxy Formation (2016, background): “This is treated approximately either by streaming (Uhlig et al. 2012) or by isotropic diffusion with a typical diffusion coefficient (Booth et al. 2013, Enßlin et al. 2007, Jubelgas et al. 2008, Salem & Bryan 2014).”
SIMULATIONS OF DISK GALAXIES WITH COSMIC RAY DRIVEN GALACTIC WINDS (2013, background): “…Accelerator Laboratory, Batavia, IL 60510 USA effects of CRs have been considered in the context of galaxy formation (e.g. Jubelgas et al. 2008; Uhlig et al. 2012; Wadepuhl & Springel 2011; Salem & Bryan 2013) and galaxy cluster (Enßlin et al. 2007; Sijacki et al. 2008; Guo & Oh 2008a)…”
Cusp-core transformations in dwarf galaxies: observational predictions (2012, background): “…unresolved turbulence, magnetic field amplification and cosmic ray propagation and radiative losses in the framework of galaxy formation is at its infancy, although some recent progresses have been reported (Hanasz et al. 2006; Jubelgas et al. 2008; Scannapieco & Brüggen 2010; Uhlig et al. 2012).”
The Nine Lives of Cosmic Rays in Galaxies (2015, methodology): “A Galactic wind driven by CR streaming was studied by Uhlig et al. (2012).”
The formation of disc galaxies in high-resolution moving-mesh cosmological simulations (2013, background): “Other studies pointed out that additional feedback channels such as cosmic rays (e.g. Uhlig et al. 2012), or stellar evolutionary processes in the form of mass return (Leitner & Kravtsov 2011) need to be considered.”