Explaining the Entropy Excess in Clusters and Groups of Galaxies without Additional Heating

Bryan, Greg L.

doi:10.1086/317289

Cited by 139 publications

(201 citation statements)

References 38 publications

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“…In the pioneering work of Bryan (2000), an overall agreement between the predicted and observed L X -T relations and entropy distributions has been essentially found, although at low temperature T < 1 keV, the observed L X -T relation falls below the theoretical prediction. Motivated by these successes and their profound implications for our understanding of the formation and evolution of the galaxies and gas in groups and clusters, we wish to conduct an extensive comparison of the theoretically predicted properties of the intragroup/intracluster gas by the GG model with those revealed by current X-ray observations.…”

Section: Introductionmentioning

confidence: 71%

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Reexamination of the Galaxy Formation–regulated Gas Evolution Model in Groups and Clusters

Xue

2002

ApJ

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As an alternative explanation of the entropy excess and the steepening of the X-ray luminosity-temperature relation in groups and clusters, the galaxy formation-regulated gas evolution (GG) model proposed recently by Bryan makes an attempt to incorporate the formation of galaxies into the evolution of gas without additional heating by nongravitational processes. This seems to provide a unified scheme for our understanding of the structures and evolution of both galaxies and gas in groups and clusters. In this paper, we present an extensive comparison of the X-ray properties of groups and clusters predicted by the GG model and those revealed by current X-ray observations, using various large data sources in the literature and also taking the observational selection effects into account. These include an independent check of the fundamental working hypothesis of the GG model (i.e., galaxy formation was less efficient in rich clusters than in groups), a new test of the radial gas distributions revealed by both the gas mass fraction and the X-ray surface brightness profiles, and a reexamination of the X-ray luminosity-temperature and entropy-temperature relations. In particular, it shows that the overall X-ray surface brightness profiles predicted by the GG model are very similar in shape and insensitive to the X-ray temperature and that the shallower X-ray surface brightness profiles seen at low-temperature systems may arise from the current observational selection effect. This can be used as the simplest approach to distinguishing between the GG model and the preheating scenario. The latter yields an intrinsically shallower gas distribution in groups than in rich clusters.

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Section: Introductionmentioning

confidence: 71%

“…Based on three independent studies of 33 groups and clusters in the literature, Bryan (2000) derived the following empirical formula, regardless of the large scatter of the data points especially for low-temperature groups: …”

Section: Reexamination Of the Working Hypothesismentioning

confidence: 99%

Reexamination of the Galaxy Formation–regulated Gas Evolution Model in Groups and Clusters

Xue

2002

ApJ

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“…Again, the former result is well known (e.g. Bryan 2000;Muanwong et al 2001), being due to the effect of cooling removing the dense, low-entropy gas. However, this effect produces density (or entropy) profiles with the wrong shape: the density is too low beyond the core and too high in the centre.…”

Section: The L Bol -M 500 Relationmentioning

confidence: 81%

Cosmological simulations of galaxy clusters with feedback from active galactic nuclei: profiles and scaling relations

Pike

Kay

Newton

et al. 2014

Monthly Notices of the Royal Astronomical Society

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We present results from a new set of 30 cosmological simulations of galaxy clusters, including the effects of radiative cooling, star formation, supernova feedback, black hole growth and AGN feedback. We first demonstrate that our AGN model is capable of reproducing the observed cluster pressure profile at redshift, z 0, once the AGN heating temperature of the targeted particles is made to scale with the final virial temperature of the halo. This allows the ejected gas to reach larger radii in highermass clusters than would be possible had a fixed heating temperature been used. Such a model also successfully reduces the star formation rate in brightest cluster galaxies and broadly reproduces a number of other observational properties at low redshift, including baryon, gas and star fractions; entropy profiles outside the core; and the Xray luminosity-mass relation. Our results are consistent with the notion that the excess entropy is generated via selective removal of the densest material through radiative cooling; supernova and AGN feedback largely serve as regulation mechanisms, moving heated gas out of galaxies and away from cluster cores. However, our simulations fail to address a number of serious issues; for example, they are incapable of reproducing the shape and diversity of the observed entropy profiles within the core region. We also show that the stellar and black hole masses are sensitive to numerical resolution, particularly the gravitational softening length; a smaller value leads to more efficient black hole growth at early times and a smaller central galaxy.

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“…When radiative cooling is included, the entropy profile can be modified. Using a simplified model, Bryan (2000) argued that because rapid cooling always happens in lowentropy gas, and the high-entropy gas will expand adiabatically to occupy the volume of the halo, resulting in a flatter entropy profile. However, Tang et al (2009) found that cooling in Milky Way sized halos is a runaway process in their simulations, and the resulting entropy profile remains a power-law.…”

Section: Configuration Of the Hot Halo Gasmentioning

confidence: 99%

Formation of disc galaxies in preheated media: a preventative feedback model

Lu¹,

Mo²

2014

Monthly Notices of the Royal Astronomical Society

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We introduce a semi-analytic galaxy formation model implementing a self-consistent treatment for the hot halo gas configuration and the assembly of central disks. Using the model, we explore a preventative feedback model, in which the circum-halo medium is assumed to be preheated up to a certain entropy level by early starbursts or other processes, and compare it with an ejective feedback model, in which baryons are first accreted into dark matter halos and subsequently ejected out by feedback. The model demonstrates that when the medium is preheated to an entropy comparable to the halo virial entropy the baryon accretion can be largely reduced and delayed. In addition, the preheated medium can establish an extended low density gaseous halo when it accretes into the dark matter halos, and result in a specific angular momentum of the cooling gas large enough to form central disks as extended as those observed. Combined with simulated halo assembly histories, the preventative feedback model can reproduce remarkably well a number of observational scaling relations. These include the cold baryon (stellar plus cold gas) mass fraction-halo mass relations, star formation histories, disk size-stellar mass relation and its evolution, and the number density of low-mass galaxies as a function of redshift. In contrast, the conventional ejective feedback model fails to reproduce these observational trends. Using the model, we demonstrate that the properties of disk galaxies are closely tied to the thermal state of hot halo gas and even possibly the circum-halo medium, which suggests that observational data for the disk properties and circum-galactic hot/warm medium may jointly provide interesting constraints for galaxy formation models.

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Explaining the Entropy Excess in Clusters and Groups of Galaxies without Additional Heating

Cited by 139 publications

References 38 publications

Reexamination of the Galaxy Formation–regulated Gas Evolution Model in Groups and Clusters

Reexamination of the Galaxy Formation–regulated Gas Evolution Model in Groups and Clusters

Cosmological simulations of galaxy clusters with feedback from active galactic nuclei: profiles and scaling relations

Formation of disc galaxies in preheated media: a preventative feedback model

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