Optical Luminosities and Mass‐to‐Light Ratios of Nearby Galaxy Clusters

Girardi, M.; Borgani, S.; Giuricin, G.; Mardirossian, F.; Mezzetti, M.

doi:10.1086/308342

Cited by 77 publications

(112 citation statements)

References 99 publications

(163 reference statements)

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“…However, it seems equally possible that this gas is in the form of stars. This would also be consistent with a higher mass-to-light ratio for large clusters than for groups (Girardi et al 2000;Adami et al 1998;Hradecky et al 2000;Ramella, Pisani, & Geller 1997), although see David, Jones, & Forman (1995). Weak lensing of groups should provide useful constraints; preliminary results indicate the mass-to-light ratios of groups are somewhat lower than those of clusters (Hoekstra, Franx, & Kuijken 2000).…”

Section: The Modelmentioning

confidence: 54%

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

Bryan¹

2000

The Astrophysical Journal

138

172

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The X-ray luminosity and temperature of clusters and groups of galaxies do not scale in a self-similar manner. This has often been interpreted as a sign that the intracluster medium has been substantially heated by nongravitational sources. In this Letter, we propose a simple model that instead uses the properties of galaxy formation to explain the available observations. Drawing on available observations, we show that there is evidence that the efficiency of galaxy formation was higher in groups than in clusters. If confirmed, this would deplete the low-entropy gas in groups, increase their central entropy, and decrease their X-ray luminosity. A simple, empirical, hydrostatic model appears to match both the luminosity-temperature relation of clusters and the properties of their internal structure.

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Section: The Modelmentioning

confidence: 54%

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

Bryan¹

2000

The Astrophysical Journal

138

172

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“…Note that such a trend of Ç is in agreement not only with the expectations of equation (8) Table 2). In addition, Ç $ 280 h ðM =LÞ for M '10 14 h À1 M clusters and Ç $ 475 h ðM =LÞ for M ' 10 15 h À1 M clusters are values well within the range of the various estimates for galaxy clusters (e.g., Adami et al 1998b;Mellier 1999;Wilson, Kaiser, & Luppino 2001;Girardi et al 2000Girardi et al , 2002. It is also remarkable (since it is not a necessary consequence) that by adopting equation (11) the face-on FP and the FJ and Kormendy relations are also very well reproduced, as apparent from Figs.…”

Section: From the Simulated To The Observed Scaling Relationsmentioning

confidence: 54%

The Scaling Relations of Galaxy Clusters and Their Dark Matter Halos

Lanzoni

Ciotti

Cappi

et al. 2004

ApJ

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Like early-type galaxies, nearby galaxy clusters also define fundamental plane, luminosity-radius, and luminosity-velocity dispersion relations, whose physical origins are still unclear. By means of high-resolution N-body simulations of massive dark matter halos in a ÃCDM (Ã cold dark matter) cosmology, we find that scaling relations similar to those observed for galaxy clusters are already defined by their dark matter hosts. The slopes, however, are not the same, and among the various possibilities in principle able to bring the simulated and the observed scaling relations into mutual agreement, we show that the preferred solution is a luminositydependent mass-to-light ratio (M =L / L $0:3 ) that corresponds well to what is inferred observationally. We then show that at galactic scales there is a conflict between the cosmological predictions of structure formation, the observed trend of the mass-to-light ratio in elliptical galaxies, and the slope of their luminosity-velocity dispersion relation (which significantly differs from the analogous one followed by clusters). The conclusion is that the scaling laws of elliptical galaxies might be the combined result of the cosmological collapse of density fluctuations at the epoch when galactic scales became nonlinear plus important modifications afterward due to early-time dissipative merging. Finally, we briefly discuss the possible evolution of the cluster scaling relations with redshift.

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“…We computed L opt within R 500 (and 0.5R 200 ) following standard procedures for photometric samples (e.g., Girardi et al 2000;P04). In particular, P04 suggests that the count-based L opt estimation has to be preferred to the fit-based one in the study of the correlation between optical and X-ray properties (see their Sect.…”

Section: Computing L Optmentioning

confidence: 99%

“…We adopted the LF parameters determined by Popesso et al (2005), i.e., the L * value corresponding to the absolute magnitude M * r = −22.12 + 5log h 70 and α = −1.30 as listed in the first part of their Table 2 (second line). Following previous studies (Lumsden et al 1997;Girardi et al 2000), the Φ * parameter is determined from the (corrected) galaxy number counts in a magnitude interval around M * to obtain a more robust value. We used N corr (−19, −23) computed for −23 ≤ M r ≤ −19 to obtain…”

Section: Computing L Optmentioning

confidence: 99%

Fossil group origins

Girardi¹,

Aguerri²,

Grandi³

et al. 2014

A&A

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Aims. This study is part of the Fossil group origins (FOGO) project which aims to carry out a systematic and multiwavelength study of a large sample of fossil systems. Here we focus on the relation between the optical luminosity (L opt ) and X-ray luminosity (L X ). Methods. Out of a total sample of 28 candidate fossil systems, we consider a sample of 12 systems whose fossil classification has been confirmed by a companion study. They are compared with the complementary sample of 16 systems whose fossil nature has not been confirmed and with a subsample of 102 galaxy systems from the RASS-SDSS galaxy cluster survey. Fossil and normal systems span the same redshift range 0 < z < 0.5 and have the same L X distribution. For each fossil system, the L X in the 0.1−2.4 keV band is computed using data from the ROSAT All Sky Survey to be comparable to the estimates of the comparison sample. For each fossil and normal system we homogeneously compute L opt in the r-band within the characteristic cluster radius, using data from the Sloan Digital Sky Survey Data Release 7. Results. We sample the L X -L opt relation over two orders of magnitude in L X . Our analysis shows that fossil systems are not statistically distinguishable from the normal systems through the 2D Kolmogorov-Smirnov test nor the fit of the L X -L opt relation. Thus, the optical luminosity of the galaxy system does strongly correlate with the X-ray luminosity of the hot gas component, independently of whether the system is fossil or not. We discuss our results in comparison with previous literature. Conclusions. We conclude that our results are consistent with the classical merging scenario of the brightest galaxy formed via merger/cannibalism of other group galaxies with conservation of the optical light. We find no evidence for a peculiar state of the hot intracluster medium.

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Optical Luminosities and Mass‐to‐Light Ratios of Nearby Galaxy Clusters

Cited by 77 publications

References 99 publications

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

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

The Scaling Relations of Galaxy Clusters and Their Dark Matter Halos

Fossil group origins

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