The fossil phase in the life of a galaxy group

Benda‐Beckmann, Alexander M. von; D’Onghia, Elena; Gottlöber, Stefan; Hoeft, M.; Khalatyan, A.; Klypin, Anatoly; Müller, V.

doi:10.1111/j.1365-2966.2008.13221.x

Cited by 86 publications

(170 citation statements)

References 49 publications

(118 reference statements)

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“…We particularly note that the De Lucia & Blaizot model is one of the best at reproducing the bright end of the luminosity function (Bertone et al 2007), which is of particular importance when measuring the ΔM 12 parameter that defines fossil groups. We note that our fossil sample is comprised of groups that exhibit ΔM 12 > 2 at z = 0, and does not include groups that had ΔM 12 > 2 at higher redshift, but became "normal" again by z = 0 (as suggested by von Benda-Beckmann et al 2008). The presence of these groups in our normal group samples can only serve to reduce any differences between our fossil and non-fossil samples and therefore does not affect our qualitative analysis.…”

Section: The Samplesmentioning

confidence: 98%

“…However, observationally, it has been suggested that fossil systems inhabit under-dense regions (Jones et al 2003). On the other hand, von Benda-Beckmann et al (2008) used numerical simulations to conclude that there is no tendency for fossil systems to be preferentially located in low density environments. They also showed that many galaxy groups and clusters may undergo a fossil phase in their lives, but may not necessarily still be fossil systems at z = 0 because of the infall of L galaxies from the large-scale environment.…”

Section: Introductionmentioning

confidence: 99%

“…Much effort has been devoted to answering this question. Beside minor differences in the definition of fossil groups, the fossil group phenomenon has been studied from the broad range of observational, analytical, numerical, and semi-analytical points of view (Vikhlinin et al 1999;Jones et al 2003;D'Onghia et al 2005;Mendes de Oliveira et al 2006;Cypriano et al 2006;Khosroshahi et al 2006;Milosavljević et al 2006;van den Bosch et al 2007;Sales et al 2007;von Benda-Beckmann et al 2008;Mendes de Oliveira & et al 2009). Most of these works have been motivated by the questions of whether the large magnitude difference in fossil groups implies that they are a distinct class of objects or they simply represent a tail of the cluster distribution.…”

Section: Introductionmentioning

confidence: 99%

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Fossil groups in the Millennium simulation

Díaz-Giménez

Zandivarez

Proctor³

et al. 2011

A&A

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Context. Fossil systems are defined to be X-ray bright galaxy groups (or clusters) with a two-magnitude difference between their two brightest galaxies within half the projected virial radius, and represent an interesting extreme of the population of galaxy agglomerations. However, the physical conditions and processes leading to their formation are still poorly constrained. Aims. We compare the outskirts of fossil systems with that of normal groups to understand whether environmental conditions play a significant role in their formation. We study the groups of galaxies in both, numerical simulations and observations. Methods. We use a variety of statistical tools including the spatial cross-correlation function and the local density parameter Δ 5 to probe differences in the density and structure of the environments of "normal" and "fossil" systems in the Millennium simulation. Results. We find that the number density of galaxies surrounding fossil systems evolves from greater than that observed around normal systems at z = 0.69, to lower than the normal systems by z = 0. Both fossil and normal systems exhibit an increment in their otherwise radially declining local density measure (Δ 5 ) at distances of order 2.5 r vir from the system centre. We show that this increment is more noticeable for fossil systems than normal systems and demonstrate that this difference is linked to the earlier formation epoch of fossil groups. Despite the importance of the assembly time, we show that the environment is different for fossil and non-fossil systems with similar masses and formation times along their evolution. We also confirm that the physical characteristics identified in the Millennium simulation can also be detected in SDSS observations. Conclusions. Our results confirm the commonly held belief that fossil systems assembled earlier than normal systems but also show that the surroundings of fossil groups could be responsible for the formation of their large magnitude gap.

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Section: The Samplesmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Fossil groups in the Millennium simulation

Díaz-Giménez

Zandivarez

Proctor³

et al. 2011

A&A

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“…Some more recent studies suggest that FGs may only be a transient phase in a group's evolution (von Benda-Beckmann et al 2008;Dariush et al 2010;Cui et al 2011). Dariush et al (2010) argue that most of the early formed systems are not in a "fossil phase" at z = 0, but were so at some earlier point during their evolution.…”

Section: Introductionmentioning

confidence: 99%

A normal abundance of faint satellites in the fossil group NGC 6482

Lieder¹,

Mieske²,

Sánchéz-Janssen³

et al. 2013

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A fossil group is considered the end product in a galaxy group's evolution. It is a massive central galaxy that dominates the luminosity budget of the group, and is the outcome of efficient merging between intermediate-luminosity members. Little is known, however, about the faint satellite systems of fossil groups. Here we present a Subaru/Suprime-Cam wide-field, deep imaging study in the B− and R−bands of the nearest fossil group NGC 6482 (M tot ∼ 4 × 10 12 M ), covering the virial radius out to 310 kpc. We performed detailed completeness estimations and selected group member candidates by a combination of automated object detection and visual inspection. A fiducial sample of 48 member candidates down to M R ∼ −10.5 mag is detected, making this study the deepest of a fossil group to now. We investigate the photometric scaling relations, the color-magnitude relation, and the luminosity function of our galaxy sample. We find evidence of recent and ongoing merger events among bright group galaxies. The color-magnitude relation is comparable to that of nearby galaxy clusters, and it exhibits significant scatter at the faintest luminosities. The completeness-corrected luminosity function is dominated by early-type dwarfs and is characterized by a faint end slope α = −1.32 ± 0.05. We conclude that the NGC 6482 fossil group shows photometric properties consistent with those of regular galaxy clusters and groups, including a normal abundance of faint satellites.

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“…Alternative criteria for their definition (e.g., Dariush et al 2007) and the concept of fossil clusters for massive systems (e.g., Cypriano et al 2006) have been proposed. Moreover, studies based on N-body numerical simulations have suggested that many systems go through an optical fossil phase during their life (e.g., von Benda-Beckmann et al 2008;Cui et al 2011).…”

Section: Introductionmentioning

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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The fossil phase in the life of a galaxy group

Cited by 86 publications

References 49 publications

Fossil groups in the Millennium simulation

Fossil groups in the Millennium simulation

A normal abundance of faint satellites in the fossil group NGC 6482

Fossil group origins

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