Fossil groups origins

Aguerri, J. A. L.; Girardi, M.; Boschin, W.; Barrena, R.; Méndez-Abreu, J.; Sánchéz-Janssen, R.; Borgani, S.; Castro-Rodríguez, N.; Corsini, E. M.; Burgo, C. del; D’Onghia, Elena; Iglésias-Páramo, J.; Napolitano, N. R.; Vı́lchez, J. M.

doi:10.1051/0004-6361/201015364

Cited by 50 publications

(77 citation statements)

References 101 publications

(123 reference statements)

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“…In particular it is smaller than reported by Alamo-Martínez et al (2012) who find values of ∼3.9 in gand z-band. However, smaller values of n for fossil group central galaxies were already reported by the FOGO collaboration (Aguerri et al 2011;Méndez-Abreu et al 2012), who obtain a mean Sérsic index of n ∼ 3 for a sample of 21 FGs.…”

Section: The Brightest Group Galaxy Ngc 6482mentioning

confidence: 76%

“…Recently, Mendes de Oliveira et al (2009) has reanalyzed the FG used by D'Onghia & Lake (2004) and found a steeper faint end slope of −1.6 -comparable to clusters (e.g., Coma cluster: α = −1.4, Secker et al 1997). Other recent studies of FGs reveal shallower faint end slopes of α = −1.2 when determined out to ∼r vir Proctor et al 2011;Eigenthaler & Zeilinger 2012), whereas the restriction to 0.5r vir even reveals declining faint ends, i.e., α > −1.0 (Mendes de Aguerri et al 2011;Proctor et al 2011).…”

Section: Introductionmentioning

confidence: 76%

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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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Section: The Brightest Group Galaxy Ngc 6482mentioning

confidence: 76%

Section: Introductionmentioning

confidence: 76%

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

Lieder¹,

Mieske²,

Sánchéz-Janssen³

et al. 2013

A&A

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“…To achieve the best possible flat field correction, we obtained a super-flat field using a combination of the scientific images. Then we corrected the scientific images once again with such a new super-flat field (see Aguerri et al 2011, for details). The images were combined and calibrated using SDSS data of the unsaturated stars available in the field of view.…”

Section: Photometric Datamentioning

confidence: 99%

“…They found that the LF of these objects are well fitted by single Schechter function, but there is a large variety of values in the faint-end slope (α) of the LFs of FGs. In particular, the values of α measured goes from −1.6 to −0.6 (see Cypriano et al 2006; Khosroshahi et al 2006;Mendes de Oliveira et al 2006Zibetti et al 2009;Aguerri et al 2011;Lieder et al 2013). Unfortunately, all these studies were performed on single FGs or very small samples, and a systematic study of LFs of statistically meaningful samples of FGs remains to be done.…”

Section: Introductionmentioning

confidence: 98%

Fossil group origins

Zarattini¹,

Barrena²,

Girardi³

et al. 2014

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Context. Virialized halos grow by the accretion of smaller ones in the cold dark matter scenario. The rate of accretion depends on the different properties of the host halo. Those halos for which this accretion rate was very fast and efficient resulted in systems dominated by a central galaxy surrounded by smaller galaxies that were at least two magnitudes fainter. These galaxy systems are called fossil systems, and they can be the fossil relics of ancient galaxy structures. Aims. We started an extensive observational program to characterize a sample of 34 fossil group candidates spanning a broad range of physical properties. Methods. Deep r-band images were obtained with the 2.5-m Isaac Newton Telescope and Nordic Optic Telescope. Optical spectroscopic observations were performed at the 3.5-m Telescopio Nazionale Galileo for ∼1200 galaxies. This new dataset was completed with Sloan Digital Sky Survey Data Release 7 archival data to obtain robust cluster membership and global properties of each fossil group candidate. For each system, we recomputed the magnitude gaps between the two brightest galaxies (Δm 12 ) and the first and fourth ranked galaxies (Δm 14 ) within 0.5 R 200 . We consider fossil systems to be those with Δm 12 ≥ 2 mag or Δm 14 ≥ 2.5 mag within the errors. Results. We find that 15 candidates turned out to be fossil systems. Their observational properties agree with those of non-fossil systems. Both follow the same correlations, but the fossil systems are always extreme cases. In particular, they host the brightest central galaxies, and the fraction of total galaxy light enclosed in the brightest group galaxy is larger in fossil than in non-fossil systems. Finally, we confirm the existence of genuine fossil clusters. Conclusions. Combining our results with others in the literature, we favor the merging scenario in which fossil systems formed from mergers of L * galaxies. The large magnitude gap is a consequence of the extreme merger ratio within fossil systems and therefore it is an evolutionary effect. Moreover, we suggest that at least one fossil group candidate in our sample could represent a transitional fossil stage. This system could have been a fossil in the past, but not now owing to the recent accretion of another group of galaxies.

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“…In 2008 we started a large observational program of fossil systems, the Fossil group origins (FOGO) project (Aguerri et al 2011;hereafter Paper I). The aim of this project is to carry out a systematic, multiwavelength study of a sample of 34 fossil group candidates identified by Santos et al (2007, hereafter S07); here each system is denoted by FGS01, FGS02, etc., according to the S07 list.…”

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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Fossil groups origins

Cited by 50 publications

References 101 publications

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

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

Fossil group origins

Fossil group origins

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