Thermal instability and the feedback regulation of hot haloes in clusters, groups and galaxies

By P. Sharma, Michael McCourt, E. Quataert, I. Parrish. 2011

255 citations recorded by the source corpus.

We present global multidimensional numerical simulations of the plasma that pervades the dark matter haloes of clusters, groups and massive galaxies (the ‘intracluster medium’; ICM). Observations of clusters and groups imply that such haloes are roughly in global thermal equilibrium, with heating balancing cooling when averaged over sufficiently long time- and length-scales; the ICM is, however, very likely to be locally thermally unstable. Using simple observationally motivated heating prescriptions, we show that local thermal instability (TI) can produce a multiphase medium – with ∼ 104 K cold filaments condensing out of the hot ICM – only when the ratio of the TI time-scale in the hot plasma (tTI) to the free-fall time-scale (tff) satisfies tTI/tff≲ 10. This criterion quantitatively explains why cold gas and star formation are preferentially observed in low-entropy clusters and groups. In addition, the interplay among heating, cooling and TI reduces the net cooling rate and the mass accretion rate at small radii by factors of ∼ 100 relative to cooling-flow models. This dramatic reduction is in line with observations. The feedback efficiency required to prevent a cooling flow is ∼ 10−3 for clusters and decreases for lower mass haloes; supernova heating may be energetically sufficient to balance cooling in galactic haloes. We further argue that the ICM self-adjusts so that tTI/tff≳ 10 at all radii. When this criterion is not satisfied, cold filaments condense out of the hot phase and reduce the density of the ICM. These cold filaments can power the black hole and/or stellar feedback required for global thermal balance, which drives tTI/tff≳ 10. In comparison to clusters, groups have central cores with lower densities and larger radii. This can account for the deviations from self-similarity in the X-ray luminosity–temperature () relation. The high-velocity clouds observed in the Galactic halo can be due to local TI producing multiphase gas close to the virial radius if the density of the hot plasma in the Galactic halo is >rsim 10−5 cm−3 at large radii.

Subfields: Astronomy and Astrophysics, Global and Planetary Change

View Paper: https://www.semanticscholar.org/paper/54ff6d62e7f23b4e3e7ae8e87e2174c97d4b168d

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Citations in the corpus

The impact of star formation feedback on the circumgalactic medium (2016, methodology): “For cluster and group mass haloes (> 1013 M⊙) thermal instability triggered feedback regulation (e.g., McCourt et al. 2012; Sharma et al. 2012a,b; Li et al. 2015) has proved successful in explaining some of the properties of both the cool and hot intracluster (intragroup) medium (Voit & Donahue…”
First results from the TNG50 simulation: galactic outflows driven by supernovae and black hole feedback (2019, background): “We speculate that they may arise from an in-situ, condensation-like process in the thermally unstable hot halo gas (Sharma et al. 2012; McCourt et al. 2012; Voit et al. 2015).”
LOCATING THE “MISSING” BARYONS WITH EXTRAGALACTIC DISPERSION MEASURE ESTIMATES (2013, methodology): “Sharma et al. (2012) find that halos with mh > 1013 M have the potential to retain most of their gas in a virialized intrahalo medium, whereas lower mass halos cannot as densities would be required that are thermally unstable.”
Formation of Galaxy Clusters (2012, background): “Generally, these processes cannot effectively regulate cooling in clusters by themselves (e.g.,Conroy & Ostriker 2008, Dolag et al. 2004), but they may play an important role when operating in concert with the AGN feedback (Voit 2011) or instabilities in plasma (e.g., Sharma et al. 2012).”
Neutral hydrogen in galaxy haloes at the peak of the cosmic star formation history (2014, background): “Another possibility is that the cool halo gas observed ∼ 100 kpc from quasars is not part of an outflow but rather a signature of how AGN feedback affects the thermal stability of gas in massive halos (e.g., Sharma et al. 2012; McCourt et al. 2012).”
Mechanical feedback from active galactic nuclei in galaxies, groups and clusters (2012, background): “Sharma et al (2012) suggested that for thermal instability to grow and for cooling gas to condense into stars, its growth time must also be shorter than about 10 free-fall times.”
Raining on black holes and massive galaxies: the top-down multiphase condensation model (2016, background): “…of warm gas condensation has been independently tested and corroborated by other groups (e.g. Quataert & Narayan 2000; Pizzolato & Soker 2005; Soker 2006; Barai, Proga & Nagamine 2012; McCourt et al. 2012; Mathews & Guo 2012; Sharma et al. 2012; Li & Bryan 2014; Valentini & Brighenti 2015).”
An origin for multiphase gas in galactic winds and haloes (2015, background): “An analogous situation can be seen in Fig A3 of Sharma et al. (2012) where an inhomogeneous cooling inflow (rather than a wind) with tcool ∼< tadv and initial density fluctuations generates significant multiphase structure.”
A Global Model for Circumgalactic and Cluster-core Precipitation (2016, methodology): “Taken together, the simulations of Sharma et al. (2012b) and Gaspari et al. (2013) have been viewed as support for the suggestion that systems in global thermal balance naturally stabilize near min(tcool/tff) ≈ 10, as observed in more realistic simulations of cluster cores regulated by…”