Evolution of the galaxy luminosity function in progenitors of fossil groups

Gozaliasl, G.; Khosroshahi, Habib G.; Dariush, A.; Finoguenov, A.; Jassur, D. M. Z.; Molaeinezhad, Alireza

doi:10.1051/0004-6361/201424075

Cited by 24 publications

(46 citation statements)

References 70 publications

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“…The median redshift value for subsamples with increasing magnitude gap are z = 0.064, 0.077, 0.088, and 0.11, respectively. Nevertheless, the differences in redshift are small, and Gozaliasl et al (2014) show that no evolution is expected in the faintend slope for both fossil and non-fossil systems since z = 1. Moreover, the lookback time at z = 0.1 is ∼1 Gyr, which is a small amount of time to see an evolution.…”

Section: Caveats Of the Resultsmentioning

confidence: 81%

“…Díaz-Giménez et al (2008) claim that the last major merger for the BGG occurs at a later time in fossil than in non-fossil systems. Gozaliasl et al (2014) suggest that the BGGs of fossil systems are the result of multiple mergers of M * galaxies in the past 5 Gyr. Moreover, von Benda-Beckmann et al (2008) claim that the fossil phase could be only transitional and that the interaction with other groups or clusters could erase the gap in magnitude.…”

Section: Introductionmentioning

confidence: 99%

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Fossil group origins

Zarattini

Aguerri

Sánchéz-Janssen

et al. 2015

A&A

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Context. In nature we observe galaxy aggregations that span a wide range of magnitude gaps between the two first-ranked galaxies of a system (Δm 12 ). Thus, there are systems with gaps close to zero (e.g., the Coma cluster), and at the other extreme of the distribution, the largest gaps are found among the so-called fossil systems. The observed distribution of magnitude gaps is thought to be a consequence of the orbital decay of M * galaxies in massive halos and the associated growth of the central object. As a result, to first order the amplitude of this gap is a good statistical proxy for the dynamical age of a system of galaxies. Fossil and non-fossil systems could therefore have different galaxy populations that should be reflected in their luminosity functions. Aims. In this work we study, for the first time, the dependence of the luminosity function parameters on Δm 12 using data obtained by the fossil group origins (FOGO) project. Methods. We constructed a hybrid luminosity function for 102 groups and clusters at z ≤ 0.25 using both photometric data from the SDSS-DR7 and redshifts from the DR7 and the FOGO surveys. The latter consists of ∼1200 new redshifts in 34 fossil system candidates. We stacked all the individual luminosity functions, dividing them into bins of Δm 12 , and studied their best-fit Schechter parameters. We additionally computed a "relative" luminosity function, expressed as a function of the central galaxy luminosity, which boosts our capacity to detect differences -especially at the bright end. Results. We find trends as a function of Δm 12 at both the bright and faint ends of the luminosity function. In particular, at the bright end, the larger the magnitude gap, the fainter the characteristic magnitude M * . The characteristic luminosity in systems with negligible gaps is more than a factor three brighter than in fossil-like ones. Remarkably, we also find differences at the faint end. In this region, the larger the gap, the flatter the faint-end slope α. Conclusions. The differences found at the bright end support a dissipationless, dynamical friction-driven merging model for the growth of the central galaxy in group-and cluster-sized halos. The differences in the faint end cannot be explained by this mechanism. Other processes -such as enhanced tidal disruption due to early infall and/or prevalence of eccentric orbits -may play a role. However, a larger sample of systems with Δm 12 > 1.5 is needed to establish the differences at the faint end.

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Section: Caveats Of the Resultsmentioning

confidence: 81%

Section: Introductionmentioning

confidence: 99%

Fossil group origins

Zarattini

Aguerri

Sánchéz-Janssen

et al. 2015

A&A

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“…This rapid growth in the number of faint galaxies could be a consequence of a smaller number of missing galaxies in fossils. Gozaliasl et al (2014) analysed the number of galaxies in the range of magnitudes between −18 to −16 that inhabit fossil and normal groups in the MS-I simulation and found no evolution in this population in fossil groups, while they observed an increase of ∼40% in normal groups towards low redshifts. In this work, we extended their analysis to fainter galaxies and found that the number of faint galaxies grows in both fossils and controls since z ∼ 1 to the present day, although this growth occurred in different ways, as we explained above.…”

Section: Discussionmentioning

confidence: 99%

“…However, more substantial evidence is needed to confirm these observational findings. Gozaliasl et al (2014) explored the influence of the faint galaxy population in the formation history of fossil systems and used the MS-I to study the evolution of the luminosity function parameters in fossil and non-fossil systems. They confirmed that roughly 80% of the fossil systems identified at early epochs (z ∼ 1) have lost their magnitude gaps before reaching the present time.…”

Section: Introductionmentioning

confidence: 99%

Fossil groups in the Millennium simulation

Kanagusuku

Díaz-Giménez

Zandivarez

2016

A&A

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Aims. We investigate the evolution of bright and faint galaxies in fossil and non-fossil groups. Methods. We used mock galaxies constructed based on the Millennium run simulation II. We identified fossil groups at redshift zero according to two different selection criteria, and then built reliable control samples of non-fossil groups that reproduce the fossil virial mass and assembly time distributions. The faint galaxies were defined as having r-band absolute magnitudes in the range [−16, −11]. We analysed the properties of the bright and faint galaxies in fossil and non-fossil groups during the past 8 Gyr.Results. We observed that the brightest galaxy in fossil groups is typically brighter and more massive than their counterparts in control groups. Fossil groups developed their large magnitude gap between the brightest galaxies around 3.5 Gyr ago. The brightest galaxy stellar masses of all groups show a notorious increment at that time. By analysing the behaviour of the magnitude gap between the first and the second, third, and fourth ranked galaxies, we found that at earlier times, fossil groups comprised two large brightest galaxies with similar magnitudes surrounded by much fainter galaxies, while in control groups these magnitude gaps were never as large as in fossils. At early times, fossil groups in the faint population were denser than non-fossil groups, then this trend reversed, and finally they became similar at the present day. The mean number of faint galaxies in non-fossil systems increases in an almost constant rate towards later times, while this number in fossil groups reaches a plateau at z ∼ 0.6 that lasts ∼2 Gyr, and then starts growing again more rapidly. Conclusions. The formation of fossil groups is defined at the very beginning of the groups according to their galaxy luminosity sampling, which could be determined by their merging rate at early times.

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“…The small difference between the adopted Δm 12 =1.7 limit used for the selection of the relaxed groups and the one conventionally used in previous studies of fossil groups, Δm 12 =2.0, is to ensure a statistically meaningful number of galaxies in both the above samples. Other authors have also adapted similar variations in the sample selection of fossil galaxy groups (e.g., Gozaliasl et al 2014). …”

Section: Data and Sample Selectionmentioning

confidence: 99%

Galaxy And Mass Assembly (GAMA): A “No Smoking” Zone for Giant Elliptical Galaxies?

Khosroshahi

Raouf

Miraghaei

et al. 2017

ApJ

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We study the radio emission of the most massive galaxies in a sample of dynamically relaxed and unrelaxed galaxy groups from the Galaxy and Mass Assembly survey. The dynamical state of the group is defined by the stellar dominance of the brightest group galaxy (BGG), e.g., the luminosity gap between the two most luminous members, and the offset between the position of the BGG and the luminosity centroid of the group. We find that the radio luminosity of the largest galaxy in the group strongly depends on its environment, such that the BGGs in dynamically young (evolving) groups are an order of magnitude more luminous in the radio than those with a similar stellar mass but residing in dynamically old (relaxed) groups. This observation has been successfully reproduced by a newly developed semi-analytic model that allows us to explore the various causes of these findings. We find that the fraction of radio-loud BGGs in the observed dynamically young groups is ∼2 times that of the dynamically old groups. We discuss the implications of this observational constraint on the central galaxy properties in the context of galaxy mergers and the super massive black hole accretion rate.

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Evolution of the galaxy luminosity function in progenitors of fossil groups

Cited by 24 publications

References 70 publications

Fossil group origins

Fossil group origins

Fossil groups in the Millennium simulation

Galaxy And Mass Assembly (GAMA): A “No Smoking” Zone for Giant Elliptical Galaxies?

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