Brightest cluster galaxies: the centre can(not?) hold

ABSTRACT We explore the persistence of the alignment of brightest cluster galaxies (BCGs) with their local environment. We find that a significant fraction of BCGs do not coincide with the centroid of the X-ray gas distribution and/or show peculiar velocities (they are not at rest with respect to the cluster mean). Despite this, we find that BCGs are generally aligned with the cluster mass distribution even when they have significant offsets from the X-ray centre and significant peculiar velocities. The large offsets are not consistent with simple theoretical models. To account for these observations BCGs must undergo mergers preferentially along their major axis, the main infall direction. Such BCGs may be oscillating within the cluster potential after having been displaced by mergers or collisions, or the dark matter halo itself may not yet be relaxed.

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Ellipticity of brightest cluster galaxies as tracer of halo orientation and weak-lensing mass bias

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2913 ◽

2019 ◽

Vol 490 (4) ◽

pp. 4889-4897 ◽

Cited By ~ 3

Author(s):

Ricardo Herbonnet ◽

Anja von der Linden ◽

Steven W Allen ◽

Adam B Mantz ◽

Pranati Modumudi ◽

...

Keyword(s):

Dark Matter ◽

Cold Dark Matter ◽

Dark Matter Halo ◽

Weak Lensing ◽

Cluster Galaxies ◽

Mass Bias ◽

Brightest Cluster Galaxies ◽

Cold Dark Matter Model ◽

Matter Model ◽

Dark Matter Model

ABSTRACT Weak-lensing measurements of the masses of galaxy clusters are commonly based on the assumption of spherically symmetric density profiles. Yet, the cold dark matter model predicts the shapes of dark matter haloes to be triaxial. Halo triaxiality, and the orientation of the major axis with respect to the line of sight, are expected to be the leading cause of intrinsic scatter in weak-lensing mass measurements. The shape of central cluster galaxies (brightest cluster galaxies; BCGs) is expected to follow the shape of the dark matter halo. Here we investigate the use of BCG ellipticity as predictor of the weak-lensing mass bias in individual clusters compared to the mean. Using weak-lensing masses $M^{\rm WL}_{500}$ from the Weighing the Giants project, and M500 derived from gas masses as low-scatter mass proxy, we find that, on average, the lensing masses of clusters with the roundest/most elliptical 25 per cent of BCGs are biased ∼20 per cent high/low compared to the average, as qualitatively predicted by the cold dark matter model. For cluster cosmology projects utilizing weak-lensing mass estimates, the shape of the BCG can thus contribute useful information on the effect of orientation bias in weak-lensing mass estimates as well as on cluster selection bias.

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The K-Band Hubble Diagram for X-Ray Selected Brightest Cluster Galaxies

New Horizons from Multi-Wavelength Sky Surveys ◽

10.1007/978-94-009-1485-8_81 ◽

1997 ◽

pp. 339-341

Author(s):

R. G. Mann ◽

C. A. Collins

Keyword(s):

Hubble Diagram ◽

X Ray ◽

Cluster Galaxies ◽

Brightest Cluster Galaxies ◽

K Band

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Shapes and alignments of dark matter haloes and their brightest cluster galaxies in 39 strong lensing clusters

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1479 ◽

2020 ◽

Vol 496 (3) ◽

pp. 2591-2604 ◽

Cited By ~ 2

Author(s):

Taizo Okabe ◽

Masamune Oguri ◽

Sébastien Peirani ◽

Yasushi Suto ◽

Yohan Dubois ◽

...

Keyword(s):

Dark Matter ◽

Gravitational Lensing ◽

Hubble Space Telescope ◽

Mean Value ◽

Cluster Galaxies ◽

Brightest Cluster Galaxies ◽

Strong Lensing ◽

The Mean ◽

The Difference ◽

Massive Clusters

ABSTRACT We study shapes and alignments of 45 dark matter (DM) haloes and their brightest cluster galaxies (BCGs) using a sample of 39 massive clusters from Hubble Frontier Field (HFF), Cluster Lensing And Supernova survey with Hubble (CLASH), and Reionization Lensing Cluster Survey (RELICS). We measure shapes of the DM haloes by strong gravitational lensing, whereas BCG shapes are derived from their light profiles in Hubble Space Telescope images. Our measurements from a large sample of massive clusters presented here provide new constraints on DM and cluster astrophysics. We find that DM haloes are on average highly elongated with the mean ellipticity of 0.482 ± 0.028, and position angles of major axes of DM haloes and their BCGs tend to be aligned well with the mean value of alignment angles of 22.2 ± 3.9 deg. We find that DM haloes in our sample are on average more elongated than their BCGs with the mean difference of their ellipticities of 0.11 ± 0.03. In contrast, the Horizon-AGN cosmological hydrodynamical simulation predicts on average similar ellipticities between DM haloes and their central galaxies. While such a difference between the observations and the simulation may well be explained by the difference of their halo mass scales, other possibilities include the bias inherent to strong lensing measurements, limited knowledge of baryon physics, or a limitation of cold DM.

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The K-Band Hubble Diagram for X-Ray Selected Brightest Cluster Galaxies

Symposium - International Astronomical Union ◽

10.1017/s0074180900128955 ◽

1998 ◽

Vol 179 ◽

pp. 339-341

Author(s):

R.G. Mann ◽

C.A. Collins

Keyword(s):

Star Formation ◽

List Type ◽

Type Number ◽

Hubble Diagram ◽

Technical Problems ◽

X Ray ◽

Cluster Galaxies ◽

Brightest Cluster Galaxies ◽

The Absolute ◽

Small Dispersion

The Hubble (magnitude-redshift) diagram for brightest cluster galaxies (BCGs) is a classic cosmological tool, widely studied because of the remarkably small dispersion (∼ 0.3 mag) in the absolute optical magnitudes of low redshift BCGs (Postman and Lauer 1995). Extending the BCG Hubble diagram to higher redshifts would greatly enhance its role as a cosmological probe, but this has been frustrated by several technical problems: – the conventional means of cluster selection in the optical become increasingly compromised by projection effects at z > 0.1– at higher redshifts the interpretation of optical magnitudes becomes increasingly complicated by the effects of possible star formation.

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Spectroscopic Evidences for Star Formation in Cooling Flow Galaxies

Symposium - International Astronomical Union ◽

10.1017/s0074180900232683 ◽

1996 ◽

Vol 171 ◽

pp. 349-349

Author(s):

N. Cardiel ◽

J. Gorgas ◽

A. Aragon-Salamanca

Keyword(s):

Star Formation ◽

Galaxy Clusters ◽

X Ray ◽

Cluster Galaxies ◽

Cooling Flows ◽

Cooling Flow ◽

Brightest Cluster Galaxies

X-ray observations have led to the conclusion that many galaxy clusters are hosting cooling flows. The brightest cluster galaxies could have accreted masses of the order of 1011–1012M⊙, but is still uncertain what the final fate of the accreted gas may be.

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Gas Density and X‐Ray Surface Brightness Profiles of Clusters of Galaxies from Dark Matter Halo Potentials: Beyond the Isothermal β‐Model

The Astrophysical Journal ◽

10.1086/306520 ◽

1998 ◽

Vol 509 (2) ◽

pp. 544-550 ◽

Cited By ~ 86

Author(s):

Yasushi Suto ◽

Shin Sasaki ◽

Nobuyoshi Makino

Keyword(s):

Dark Matter ◽

Surface Brightness ◽

Dark Matter Halo ◽

Clusters Of Galaxies ◽

Gas Density ◽

X Ray

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Stellar population gradients in brightest cluster galaxies

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313005188 ◽

2012 ◽

Vol 8 (S295) ◽

pp. 316-316

Author(s):

S. I. Loubser ◽

P. Sánchez-Blázquez

Keyword(s):

Stellar Population ◽

Velocity Dispersion ◽

Elliptical Galaxies ◽

Negative Slope ◽

High Quality ◽

X Ray ◽

Cluster Galaxies ◽

Central Galaxy ◽

Brightest Cluster Galaxies

AbstractWe present the stellar population and velocity dispersion gradients for a sample of 24 brightest cluster galaxies (BCGs) in the nearby Universe for which we have obtained high quality long-slit spectra at the Gemini telescopes. With the aim of studying the possible connection between the formation of the BCGs and their host clusters, we explore the relations between the stellar population gradients and properties of the host clusters, as well as the possible connections between the stellar population gradients and other properties of the galaxies. We find mean stellar population gradients (negative Δ[Z/H]/log r gradient of − 0.285 ± 0.064; small positive Δlog(age)/log r gradient of +0.069 ± 0.049; and null Δ[E/Fe]/log r gradient of -0.008 ± 0.032), that are consistent with those of normal massive elliptical galaxies. However, we find a trend between metallicity gradients and velocity dispersion (with a negative slope of − 1.616 ± 0.539), that is not found for the most massive ellipticals. Furthermore, we find trends between the metallicity gradients and K-band luminosities (with a slope of 0.173 ± 0.081) as well as the distance from the BCG to the X-ray peak of the host cluster (with a slope of − 7.546 ± 2.752). The latter indicates a possible relation between the formation of the cluster and that of the central galaxy.

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