A study of the core of the Shapley Concentration - I. The sample

Bardelli, S.; Zucca, E.; Vettolani, G.; Zamorani, G.; Scaramella, R.; Collins, Chris; MacGillivray, H. T.

doi:10.1093/mnras/267.3.665

Cited by 86 publications

(112 citation statements)

References 11 publications

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“…Formal errors of this task are smaller than true intrinsic ones (e.g. Bardelli et al 1994). This is because the error on the redshift estimate depends on several factors.…”

Section: Spectroscopic Galaxy Cataloguementioning

confidence: 97%

Deep spectroscopy of nearby galaxy clusters – I. Spectroscopic luminosity function of Abell 85

Agulli¹,

Aguerri²,

Sánchéz-Janssen³

et al. 2016

Mon. Not. R. Astron. Soc.

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We present a new deep spectroscopic catalogue for Abell 85, within 3.0 × 2.6 Mpc 2 and down to M r ∼ M * r +6. Using the Visible Multi-Object Spectrograph at the Very Large Telescope and the AutoFiber 2 at the William Herschel Telescope, we obtained almost 1430 new redshifts for galaxies with m r ≤ 21 mag and µ e,r ≤ 24 mag arcsec −2 . These redshifts, together with SDSS-DR6 and NED spectroscopic information, result in 460 confirmed cluster members. This data set allows the study of the luminosity function (LF) of the cluster galaxies covering three orders of magnitudes in luminosities. The total and radial LFs are best modelled by a double Schechter function. The normalized LFs show that their bright (M r ≤ −21.5) and faint (M r ≥ −18.0) ends are independent of clustercentric distance and similar to the field LFs unlike the intermediate luminosity range (−21.5 ≤ M r ≤ −18.0). Similar results are found for the LFs of the dominant types of galaxies: red, passive, virialized and early-infall members. On the contrary, the LFs of blue, star-forming, non-virialized and recent-infall galaxies are well described by a single Schechter function. These populations contribute to a small fraction of the galaxy density in the innermost cluster region. However, in the outskirts of the cluster, they have similar densities to red, passive, virialized and early-infall members at the LF faint end. These results confirm a clear dependence of the colour and star formation of Abell 85 members in the cluster centric distance.

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“…Formal errors of this task are smaller than true intrinsic ones (e.g. Bardelli et al 1994). This is because the error on the redshift estimate depends on several factors.…”

Section: Spectroscopic Galaxy Cataloguementioning

confidence: 97%

Deep spectroscopy of nearby galaxy clusters – I. Spectroscopic luminosity function of Abell 85

Agulli¹,

Aguerri²,

Sánchéz-Janssen³

et al. 2016

Mon. Not. R. Astron. Soc.

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“…The latter is actually the only galaxy with m r > 21 for which we measured the LOS velocity. The nominal uncertainties given by the cross-correlation algorithm are known to be smaller than the true ones (see, Malumuth et al 1992;Bardelli et al 1994;Ellingson & Yee 1994;Quintana et al 2000). The uncertainties obtained through the RVSAO procedure were multiplied by a factor 2, following previous analyses (Barrena et al 2009, and references therein) on data acquired with the same instrumental setup and with comparable quality or our own.…”

Section: Line Of Sight Velocity Measurementmentioning

confidence: 99%

Fossil group origins

Zarattini¹,

Barrena²,

Girardi³

et al. 2014

A&A

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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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“…Our spectroscopic survey in the field of A1240 consists of spectra for 118 galaxies with a median nominal error on cz of 50 km s −1 . The nominal errors given by the cross-correlation are known to be smaller than the true errors (e.g., Malumuth et al 1992;Bardelli et al 1994;Ellingson & Yee 1994;Quintana et al 2000;Boschin et al 2004). Double redshift determinations for four galaxies allowed us to estimate the true intrinsic errors.…”

Section: Introductionmentioning

confidence: 99%

Internal dynamics of Abell 1240: a galaxy cluster with symmetric double radio relics

Barrena¹,

Girardi

Boschin

et al. 2009

A&A

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Context. The mechanisms giving rise to diffuse radio emission in galaxy clusters, and in particular their connection with cluster mergers, are still debated. Aims. We aim to obtain new insights into the internal dynamics of the cluster Abell 1240, which appears to contain two roughly symmetric radio relics, separated by ∼2 h −1 70 Mpc. Methods. Our analysis is based mainly on redshift data for 145 galaxies mostly acquired at the Telescopio Nazionale Galileo and on new photometric data acquired at the Isaac Newton Telescope. We also use X-ray data from the Chandra archive and photometric data from the Sloan Digital Sky Survey (Data Release 7). We combine galaxy velocities and positions to select 89 cluster galaxies and analyze the internal dynamics of the Abell 1237 + Abell 1240 cluster complex, Abell 1237 being a close companion of Abell 1240 in its southern direction. Results. We estimate similar redshifts for Abell 1237 and Abell 1240, z = 0.1935 and z = 0.1948, respectively. For Abell 1237, we estimate a line-of-sight (LOS) velocity dispersion of σ V ∼ 740 km s −1 and a mass of M ∼ 6 × 10 14 h −1 70 M . For Abell 1240, we estimate a LOS σ V ∼ 870 km s −1 and a mass in the range M ∼ 0.9−1.9 × 10 15 h −1 70 M , which takes account of its complex dynamics. Abell 1240 is shown to have a bimodal structure with two galaxy clumps roughly aligned along its N-S direction, the same as defined by the elongation of its X-ray surface brightness and the axis of symmetry of the relics. The two brightest galaxies of Abell 1240, associated with the northern and southern clumps, are separated by a LOS rest-frame velocity difference V rf ∼ 400 km s −1 and a projected distance D ∼ 1.2 h −1 70 Mpc. The two-body model agrees with the hypothesis that we are looking at a cluster merger that occurred largely in the plane of the sky, the two galaxy clumps being separated by a rest-frame velocity difference V rf ∼ 2000 km s −1 at a time of 0.3 Gyr after the crossing core, while Abell 1237 is still infalling onto Abell 1240. Chandra archive data confirm the complex structure of Abell 1240 and allow us to estimate a global X-ray temperature of T X = 6.0 ± 0.5 keV. Conclusions. In agreement with the findings from radio data, our results for Abell 1240 strongly support the "outgoing merger shocks" model to explain the presence of the relics.

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A study of the core of the Shapley Concentration - I. The sample

Cited by 86 publications

References 11 publications

Deep spectroscopy of nearby galaxy clusters – I. Spectroscopic luminosity function of Abell 85

Deep spectroscopy of nearby galaxy clusters – I. Spectroscopic luminosity function of Abell 85

Fossil group origins

Internal dynamics of Abell 1240: a galaxy cluster with symmetric double radio relics

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