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SUMMARY:The effect of cosmic rays in the evolution of a Milky Way-like gal
 axy and its circum-galactic medium - Francisco Rodríguez Montero (Oxford)
DTSTART:20230519T103000Z
DTEND:20230519T113000Z
UID:TALK200962@talks.cam.ac.uk
CONTACT:Sandro Tacchella
DESCRIPTION:Despite the many successes of cosmological galaxy formation an
 d evolution simulations\, they commonly implement baryonic feedback in a p
 henomenological manner by calibrating "boosting" parameters\, which somewh
 at diminishes their predictive power and restricts their usefulness to int
 erpret observational data. An alternative approach is to improve the model
 ling of feedback processes from first principles\, by self-consistently in
 cluding components which have by-and-large been overlooked\, like radiatio
 n\, magnetic fields and cosmic rays (CRs). We study the influence of CRs i
 njected by supernovae (SN) in the interstellar medium (ISM) and their impa
 ct on the launching of outflows in a cosmological zoom simulation of a Mil
 ky Way-like galaxy. We find that\, in the same way as artificially boostin
 g SN feedback does\, including CRs decreases the stellar mass by 1 dex at 
 high redshift and about a factor 4 at lower redshift as compared to pure h
 ydrodynamical and magneto-hydrodynamical simulations\, bringing our galaxy
  in better agreement with abundance-matching models. This significant supp
 ression of star formation originates from a combination of the ability of 
 CRs to deplete cold\, high-density\, star-forming ISM gas and a higher pro
 portion of SN energy being injected in low-density gas. Consistent with pr
 evious results in the literature\, we also find enhanced\, multi-phase out
 flows\, with warm ionised gas dominating the mass budget\, a large contrib
 ution of warm neutral and cold gas at high redshift\, and all outflow phas
 es experiencing further acceleration by CR pressure outside of the galaxy.
  CRs also largely alter the thermodynamical state of the circum-galactic m
 edium\, making it colder and denser and slowing down the filamentary inflo
 w of pristine gas provided by the cosmic web. Overall\, CRs drastically ch
 ange the evolution of our Milky Way-like galaxy\, particularly at high red
 shift\, pointing to their potentially fundamental role in shaping galaxy f
 ormation.
LOCATION:Ryle seminar room + online
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