2015/12/31 by Prakriti Pal Choudhury, Prateek Sharma · 4 citations
Physics and Astronomy · #Astrophysics #Astrophysics and Star Formation Studies #Classical mechanics #Condensation #Galaxies: Formation, Evolution, Phenomena #Galaxy #Gamma-ray bursts and supernovae #Geometry #Gravitation #Gravitational acceleration #Instability #Mechanics #Physics #Plane (geometry) #Thermodynamics #Virial theorem #astro-ph.GA
paper · pdf · doi:10.1093/mnras/stw152
published as MNRAS (2016) 457, 2554-2568 · 17 pages, 16 figures, 2 tables, version accepted in MNRAS. Links to python codes for global stability analysis: https://drive.google.com/folderview?id=0B2HaDXI2USsZWUdESVVsN2RGeVU&usp=sharing
arxiv created 2016/01/20 · openalex publication_date 2016/02/10 · arxiv updated 2016/02/15 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We perform global linear stability analysis and idealized numerical simulations in global thermal balance to understand the condensation of cold gas from hot/virial atmospheres (coronae), in particular the intracluster medium (ICM). We pay particular attention to geometry (e.g. spherical versus plane-parallel) and the nature of the gravitational potential. Global linear analysis gives a similar value for the fastest growing thermal instability modes in spherical and Cartesian geometries. Simulations and observations suggest that cooling in haloes critically depends on the ratio of the cooling time to the free-fall time (tcool/tff). Extended cold gas condenses out of the ICM only if this ratio is smaller than a threshold value close to 10. Previous works highlighted the difference between the nature of cold gas condensation in spherical and plane-parallel atmospheres; namely, cold gas condensation appeared easier in spherical atmospheres. This apparent difference due to geometry arises because the previous plane-parallel simulations focused on in situ condensation of multiphase gas but spherical simulations studied condensation anywhere in the box. Unlike previous claims, our non-linear simulations show that there are only minor differences in cold gas condensation, either in situ or anywhere, for different geometries. The amount of cold gas depends on the shape of tcool/tff; gas has more time to condense if gravitational acceleration decreases towards the centre. In our idealized plane-parallel simulations with heating balancing cooling in each layer, there can be significant mass/energy/momentum transfer across layers that can trigger condensation and drive tcool/tff far beyond the critical value close to 10.