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We present a detailed analysis of the ionization and thermal structure of the intergalactic medium (IGM) around a high-redshift QSO using a large suite of cosmological, multi-frequency radiative transfer (RT) simulations, exploring the…

Cosmology and Nongalactic Astrophysics · Physics 2017-04-18 Koki Kakiichi , Luca Graziani , Benedetta Ciardi , Avery Meiksin , Michele Compostella , Marius B. Eide , Saleem Zaroubi

We present semi-analytical models of galactic outflows in high redshift galaxies driven by both hot thermal gas and non-thermal cosmic rays. Thermal pressure alone may not sustain a large scale outflow in low mass galaxies (i.e $M\sim…

Astrophysics of Galaxies · Physics 2018-02-21 Saumyadip Samui , Kandaswamy Subramanian , Raghunathan Srianand

Cosmic rays (CRs) are a pivotal non-thermal component of galaxy formation and evolution. However, the intricacies of CR physics, particularly how they propagate in the circumgalactic medium (CGM), remain largely unconstrained. In this work,…

The circumgalactic medium (CGM) plays a critical role in galaxy evolution, influencing gas flows, feedback processes, and galactic dynamics. Observations show a substantial cold gas reservoir in the CGM, but the mechanisms driving its…

Astrophysics of Galaxies · Physics 2025-06-11 Matthias Weber , Timon Thomas , Christoph Pfrommer , Ruediger Pakmor

One of the most outstanding problems in the gravitational collapse scenario of early structure formation is the cooling of primordial gas to allow for small mass objects to form. As the neutral primordial gas is a poor radiator at…

Astrophysics · Physics 2009-11-13 Jens Jasche , Benedetta Ciardi , Torsten A. Ensslin

During the epoch of reionization a large number of photons were produced with frequencies below the hydrogen Lyman limit. After redshifting into the closest resonance, these photons underwent multiple scatterings with atoms. We examine the…

Astrophysics · Physics 2008-11-26 Leonid Chuzhoy , Paul R. Shapiro

Recent work has both illuminated and mystified our attempts to understand cosmic rays (CRs) in starburst galaxies. I discuss my new research exploring how CRs interact with the ISM in starbursts. Molecular clouds provide targets for CR…

High Energy Astrophysical Phenomena · Physics 2015-06-17 Brian C. Lacki

Cosmic rays (CRs) may be used to infer properties of intervening cosmic magnetic fields. Conversely, understanding the effects of magnetic fields on the propagation of high-energy CRs is crucial to elucidate their origin. In the present…

High Energy Astrophysical Phenomena · Physics 2018-11-08 R. Alves Batista , E. M. de Gouveia Dal Pino , K. Dolag , S. Hussain

The circumgalactic medium (CGM) contains information on the cumulative effect of galactic outflows over time, generally thought to be caused by feedback from star formation and active galactic nuclei. Observations of such outflows via…

Lyman-alpha photons from the first radiating sources in the Universe play a pivotal role in 21-cm radio detections of Cosmic Dawn and the Epoch of Reionization. Comments are provided on the effect of the hyperfine structure of hydrogen on…

Cosmology and Nongalactic Astrophysics · Physics 2021-06-01 A. Meiksin

Upcoming observations of the 21-cm signal from the Epoch of Reionization will soon provide the first direct detection of this era. This signal is influenced by many astrophysical effects, including long range X-ray heating of the…

Cosmology and Nongalactic Astrophysics · Physics 2017-05-03 Hannah E. Ross , Keri L. Dixon , Ilian T. Iliev , Garrelt Mellema

Cosmic rays (CRs) are the primary driver of ionization in star forming molecular clouds (MCs). Despite their potential impacts on gas dynamics and chemistry, no simulations of star cluster formation following the creation of individual…

Astrophysics of Galaxies · Physics 2024-07-26 Margot Fitz Axen , Stella Offner , Phillip F. Hopkins , Mark R. Krumholz , Michael Y. Grudic

One of the key physical processes that helps prevent strong cooling flows in galaxy clusters is the continued energy input from the central active galactic nucleus (AGN) of the cluster. However, it remains unclear how this energy is…

We investigate the dynamical interaction between cosmic rays (CRs) and the multiphase interstellar medium (ISM) using numerical magnetohydrodynamic (MHD) simulations with a two-moment CR solver and TIGRESS simulations of star-forming…

Astrophysics of Galaxies · Physics 2024-01-10 Lucia Armillotta , Eve C. Ostriker , Chang-Goo Kim , Yan-Fei Jiang

Large reservoirs of cold (~ 10^4 K) gas exist out to and beyond the virial radius in the circumgalactic medium (CGM) of all types of galaxies. Photoionization modeling suggests that cold CGM gas has significantly lower densities than…

We use hydrodynamical simulations of two Milky Way-mass galaxies to demonstrate the impact of cosmic-ray pressure on the kinematics of cool and warm circumgalactic gas. Consistent with previous studies, we find that cosmic-ray pressure can…

Due to their long mean free path, X-rays are expected to have an important impact on cosmic reionization by heating and ionizing the IGM on large scales, especially after simulations have suggested that Population III stars may form in…

Cosmology and Nongalactic Astrophysics · Physics 2014-08-06 Hao Xu , Kyungjin Ahn , John H. Wise , Michael L. Norman , Brian W. O'Shea

We investigate the effects of cosmic ray (CR) dynamics on cold, dense clouds embedded in a hot, tenuous galactic halo. If the magnetic field does not increase too much inside the cloud, the local reduction in Alfv\'en speed imposes a…

High Energy Astrophysical Phenomena · Physics 2017-01-25 Joshua Wiener , S. Peng Oh , Ellen G. Zweibel

Low-metallicity environments are subject to inefficient cooling. They also have low dust-to-gas ratios and therefore less efficient photoelectric (PE) heating than in solar-neighbourhood conditions, where PE heating is one of the most…

We investigate a mechanism for accelerating cool (10$^4$ K) clouds in the circumgalactic medium (CGM) with cosmic rays (CRs), possibly explaining some characteristics of observed high velocity clouds (HVCs). Enforcing CRs to stream down…

Astrophysics of Galaxies · Physics 2019-07-31 Joshua Wiener , Ellen G. Zweibel , Mateusz Ruszkowski