Fossil group origins

Zarattini, S.; Barrena, R.; Girardi, M.; Castro-Rodríguez, N.; Boschin, W.; Aguerri, J. A. L.; Méndez-Abreu, J.; Sánchéz-Janssen, R.; Catalán-Torrecilla, C.; Corsini, E. M.; Burgo, C. del; D’Onghia, Elena; Herrera-Ruiz, N.; Iglésias-Páramo, J.; Bailón, Elena Jiménez; Muoz, M. Lozada; Napolitano, N. R.; Vı́lchez, J. M.

doi:10.1051/0004-6361/201323351

Cited by 37 publications

(78 citation statements)

References 71 publications

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“…For example, Harrison et al (2012) show that both the absolute magnitude of the BGGs and the fraction of light contained in them are correlated with the magnitude gap, results that we have recently confirmed in Zarattini et al (2014). Moreover, their luminosity is correlated with the system velocity dispersion (Khosroshahi et al 2006).…”

Section: Introductionsupporting

confidence: 59%

“…They defined a system of galaxies as a fossil if it presents a magnitude gap of at least two magnitudes between the two brightest member galaxies (Δm 12 ≥ 2) in the r-band within half of its virial radius and if the central galaxy is surrounded by an extended X-ray halo of L X,bol > 10 42 h −2 50 erg s −1 . The latter criterion was adopted to distinguish large isolated galaxies from group-sized systems, but it is a lower limit, so it does not exclude the existence of "fossil clusters" (as proposed by Cypriano et al 2006;Mendes de Oliveira et al 2006;Zarattini et al 2014). For this reason, we refer to fossil systems, but we prefer to maintain the classical notation of FGs, which is usually accepted in the literature, as we did in the other papers of this series.…”

Section: Introductionmentioning

confidence: 99%

“…For this reason, we present a large study here of a sample of 110 systems, containing 19 confirmed fossils. The criteria in the definition of fossils are those reported in Zarattini et al (2014). With this unique data set, we are able to present the first study of the dependence of the LF on the magnitude gap in group-and cluster-sized systems within half the R 200 radius.…”

Section: Introductionmentioning

confidence: 99%

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Fossil group origins

Zarattini

Aguerri

Sánchéz-Janssen

et al. 2015

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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: Introductionsupporting

confidence: 59%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Fossil group origins

Zarattini

Aguerri

Sánchéz-Janssen

et al. 2015

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“…The spectroscopic observations went on until April 2012 thanks to additional time awarded at TNG through the Spanish and Italian Time Allocation Committees. The catalog is described in the companion study by Zarattini et al (2014;hereafter Paper IV).…”

Section: Introductionmentioning

confidence: 99%

Fossil group origins

Girardi¹,

Aguerri²,

Grandi³

et al. 2014

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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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“…Today, there is no consensus about the origin of fossil groups (Mulchaey & Zabludoff 1999;Cypriano et al 2006;Ponman et al 1994;Aguerri et al 2011;Proctor et al 2011;Girardi et al 2014;Zarattini et al 2014). Mulchaey & Zabludoff (1999) portrayed a fossil group as a "failed group" in which the majority of the baryonic materials were used in building up the giant elliptical galaxy, rather than in several massive L * galaxies.…”

Section: Introductionmentioning

confidence: 99%

Evolution of the galaxy luminosity function in progenitors of fossil groups

Gozaliasl

Khosroshahi

Dariush

et al. 2014

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Using the semi-analytic models based on the Millennium simulation, we trace back the evolution of the luminosity function of galaxies residing in progenitors of groups classified by the magnitude gap at redshift zero. We determine the luminosity function of galaxies within 0.25 R 200 , 0.5 R 200 , and R 200 for galaxy groups/clusters. The bright end of the galaxy luminosity function of fossil groups shows a significant evolution with redshift, with changes in M * by ∼1−2 mag between z ∼ 0.5 and z = 0 (for the central 0.5 R 200 ), suggesting that the formation of the most luminous galaxy in a fossil group has had a significant impact on the M * galaxies e.g. it is formed as a result of multiple mergers of M * galaxies within the last 5 Gyr. In contrast, the slope of the faint end, α, of the luminosity function shows no considerable redshift evolution and the number of dwarf galaxies in the fossil groups exhibits no evolution, unlike in non-fossil groups where it grows by ∼25−42% towards low redshifts. In agreement with previous studies, we also show that fossil groups accumulate most of their halo mass earlier than non-fossil groups. Selecting the fossils at a redshift of 1 and tracing them to a redshift 0, we show that 80% of the fossil groups (10 13 M h −1 < M 200 < 10 14 M h −1 ) will lose their large magnitude gap. However, about 40% of fossil clusters (M 200 > 10 14 M h −1 ) will retain their large gaps.

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Fossil group origins

Cited by 37 publications

References 71 publications

Fossil group origins

Fossil group origins

Fossil group origins

Evolution of the galaxy luminosity function in progenitors of fossil groups

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