Fossil groups in the Millennium simulation

Kanagusuku, María José; Díaz-Giménez, Eugenia; Zandivarez, Ariel

doi:10.1051/0004-6361/201527269

Cited by 16 publications

(15 citation statements)

References 40 publications

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“…This is in line with the more recent last major merger and recent significant growth of the BGG due to merging we find for fossils, and as has been found in other theoretical studies as well (e.g. Díaz-Giménez et al 2008;Kanagusuku et al 2016).…”

Section: Observational Implicationssupporting

confidence: 93%

“…We also find support for the idea of a 'fossil phase' (von Benda-Beckmann et al 2008) whereby groups only temporarily exist with a large magnitude gap due to recent mergers of satellites with the central without recent infall of new satellites, in good agreement with previous studies of simulated fossils (von Benda-Beckmann et al 2008;Dariush et al 2010;Gozaliasl et al 2014;Kanagusuku et al 2016). As can be seen in our Fig.…”

Section: Group Mass Assembly Historysupporting

confidence: 92%

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Are Fossil Groups Early-forming Galaxy Systems?

Kundert

D’Onghia

Aguerri

2017

ApJ

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Using the Illustris cosmological simulation, we investigate the origin of fossil groups in the M 200 = 10 13 − 10 13.5 M /h mass regime. We examine the formation of the two primary features of fossil groups: the large magnitude gap between their two brightest galaxies, and their exceptionally luminous brightest group galaxy (BGG). For fossils and non-fossils identified at z = 0, we find no difference in their halo mass assembly at early times, departing from previous studies. However, we do find a significant difference in the recent accretion history of fossil and non-fossil halos; in particular, fossil groups show a lack of recent accretion and have in majority assembled 80% of their M 200 (z = 0) mass before z ∼ 0.4. For fossils, massive satellite galaxies accreted during this period have enough time to merge with the BGG by the present day, producing a more massive central galaxy; and, the lack of recent group accretion prevents replenishment of the bright satellite population, allowing for a large magnitude gap to develop within the past few Gyr. We thus find that the origin of the magnitude gap and overmassive BGG of fossils in Illustris depends on the recent accretion history of the groups and merger history of the BGG after their collapse at z ∼ 1. This indicates that selecting galaxy groups by their magnitude gap does not guarantee obtaining neither early-forming galaxy systems nor undisturbed central galaxies.

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Section: Observational Implicationssupporting

confidence: 93%

Section: Group Mass Assembly Historysupporting

confidence: 92%

Are Fossil Groups Early-forming Galaxy Systems?

Kundert

D’Onghia

Aguerri

2017

ApJ

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“…We found that 23.1 ± 2.5% of the CASSOWARY systems are Jones fossil progenitors and 28.9 ± 2.5% are Dariush fossil progenitors. This higher rate of fossil progenitors in the CASSOWARY sample is not surprising considering that Kanagusuku et al (2016) found that in the Millennium Simulation, systems which were fossils at z = 0 finished forming their BGG (creating the required ∆m 12 /∆m 14 r-band magnitude gap) between 0.3 < z < 0.6 on average. Since the average redshift of the CASSOWARY members is z ∼ 0.4, we expect to see a collection of nearfossil systems, as we are seeing analogs to today's fossil systems in mid-cannibalization of their L * members.…”

Section: Cassowary Strong Lensing Samplementioning

confidence: 70%

“…The apparent fossil deficit could be accounted for due to the redshift range of our sample (0.2 < z < 0.7). Since most fossils discovered lie near z ∼ 0.1, and Kanagusuku et al (2016) found in the Millennium Simulation that most z = 0 fossils made the transition between 0.3 < z < 0.6, there could be a lower fossil fraction in our samples.…”

Section: Non-lensing Control Samplementioning

confidence: 84%

Using Strong Gravitational Lensing to Identify Fossil Group Progenitors

Johnson¹,

Irwin²,

White³

et al. 2018

ApJ

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Fossil galaxy systems are classically thought to be the end result of galaxy group/cluster evolution, as galaxies experiencing dynamical friction sink to the center of the group potential and merge into a single, giant elliptical that dominates the rest of the members in both mass and luminosity. Most fossil systems discovered lie within z < 0.2, which leads to the question: what were these systems' progenitors? Such progenitors are expected to have imminent or ongoing major merging near the brightest group galaxy (BGG) that, when concluded, will meet the fossil criteria within the look back time. Since strong gravitational lensing preferentially selects groups merging along the line of sight, or systems with a high mass concentration like fossil systems, we searched the CASSOWARY survey of strong lensing events with the goal of determining if lensing systems have any predisposition to being fossil systems or progenitors. We find that ∼13% of lensing groups are identified as traditional fossils while only ∼3% of non-lensing control groups are. We also find that ∼23% of lensing systems are traditional fossil progenitors compared to ∼17% for the control sample. Our findings show that strong lensing systems are more likely to be fossil/pre-fossil systems than comparable non-lensing systems. Cumulative galaxy luminosity functions of the lensing and non-lensing groups also indicate a possible, fundamental difference between strong lensing and non-lensing systems' galaxy populations with lensing systems housing a greater number of bright galaxies even in the outskirts of groups.

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“…Results from N-body simulations by von Benda-Beckmann et al (2008) supported the notion that not all fossils are old structures, as they found many instances of fossil systems being both formed and destroyed since z < 0.9 indicating this may be a phase of group evolution that all groups have a chance of passing into and out of. A later study by Kanagusuku et al (2016) found in the Millennium simulation that most groups which are classified as fossils at z = 0 assembled their BGGs between 0.3 < z < 0.6. These progenitors to today's fossils would be expected to exist near this redshift space and have imminent/ongoing major merging between intermediate mass galaxies and the BGG.…”

Section: Introductionmentioning

confidence: 95%

Chandra and HST Snapshots of Fossil System Progenitors

Johnson

Irwin

White

et al. 2018

ApJ

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The search for the progenitors to today's fossil galaxy systems has been restricted to N-body simulations until recently, where 12 fossil progenitors were identified in the CASSOWARY catalog of strong lensing systems. All 12 systems lie in the predicted redshift range for finding fossils in mid brightest group galaxy (BGG) assembly, and all show complex merging environments at their centers. None of these progenitors had archival X-ray data, and many were lacking high resolution optical data making precision photometry extremely difficult. Here, we present Chandra and Hubble Space Telescope (HST) snapshots of eight of these strong lensing fossil progenitors at varying stages of evolution. We find that our lensing progenitors exhibit higher than expected X-ray luminosities and temperatures consistent with previously observed non-lensing fossil systems. More precise galaxy luminosity functions are generated which strengthen past claims that progenitors are the transition phase between non-fossils and fossils. We also find evidence suggesting that the majority of differences between fossils and non-fossils lie in their BGGs and that fossil systems may themselves be a phase of galaxy system evolution and not a separate class of object.

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Fossil groups in the Millennium simulation

Cited by 16 publications

References 40 publications

Are Fossil Groups Early-forming Galaxy Systems?

Are Fossil Groups Early-forming Galaxy Systems?

Using Strong Gravitational Lensing to Identify Fossil Group Progenitors

Chandra and HST Snapshots of Fossil System Progenitors

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