The Hydra I cluster core

Hilker, M.; Richtler, T.; Barbosa, C. E.; Arnaboldi, M.; Coccato, L.; Oliveira, C. Mendes de

doi:10.1051/0004-6361/201731737

Cited by 33 publications

(41 citation statements)

References 65 publications

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“…The g−r colours and absolute magnitudes in the r band (M r ) are used to derive the stellar mass for all UDG candidates, using the relation given by Into & Portinari (2013). Values are listed in Table 1.…”

Section: Stellar Mass Versus Dm Contentmentioning

confidence: 99%

“…The cluster core is dominated by the two brightest early-type galaxies, NGC 3309 and NGC 3311, embedded in an extended diffuse stellar halo (Arnaboldi et al 2012). Most of the recent studies of Hydra I focused on the light distribution and kinematics in the cluster core, which showed the presence of ongoing interactions and traced the extended mass assembly around NGC 3311 (Ventimiglia et al 2011;Richtler et al 2011;Coccato et al 2011;Misgeld et al 2008Misgeld et al , 2011Arnaboldi et al 2012;Koch et al 2012;Barbosa et al 2018;Hilker et al 2018). We carried out the first search for UDGs enabled by a new wide area and deepimaging dataset.…”

Section: Introductionmentioning

confidence: 99%

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The first detection of ultra-diffuse galaxies in the Hydra I cluster from the VEGAS survey

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Hilker

et al. 2020

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In this paper, we report the discovery of 27 low-surface brightness galaxies, of which 12 are candidates for ultra-diffuse galaxies (UDG) in the Hydra I cluster, based on deep observations taken as part of the VST Early-type Galaxy Survey (VEGAS). This first sample of UDG candidates in the Hydra I cluster represents an important step in our project that aims to enlarge the number of confirmed UDGs and, through study of statistically relevant samples, constrain the nature and formation of UDGs. This study presents the main properties of this class of galaxies in the Hydra I cluster. For all UDGs, we analysed the light and colour distribution, and we provide a census of the globular cluster (GC) systems around them. Given the limitations of a reliable GC selection based on two relatively close optical bands only, we find that half of the UDG candidates have a total GC population consistent with zero. Of the other half, two galaxies have a total population larger than zero at 2σ level. We estimate the stellar mass, the total number of GCs, and the GC specific frequency (SN). Most of the candidates span a range of stellar masses of 107 − 108 M⊙. Based on the GC population of these newly discovered UDGs, we conclude that most of these galaxies have a standard or low dark matter content, with a halo mass of ≤1010 M⊙.

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Section: Stellar Mass Versus Dm Contentmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The first detection of ultra-diffuse galaxies in the Hydra I cluster from the VEGAS survey

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Cantiello

Hilker

et al. 2020

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“…For example, the group around NGC 4472 (M49), with the largest N V is deep in the virgo cluster. The second group , "NGC 3311", is the Hydra I cluster (Abel 1060), whose baryons are dominated by hot gas [28,29]. The group "NGC 4696" is Centaurus.…”

Section: The Samplementioning

confidence: 99%

MOND in galaxy groups: A superior sample

Milgrom

2019

Phys. Rev. D

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Intermediate-richness galaxy groups are an important testing ground for MOND. First, they constitute a distinct type of galactic systems, with their own evolution histories and underlying physical processes; second, they probe little-chartered regions of parameter space, as they have baryonic masses similar to massive galaxies, and similar velocity dispersions, but much larger sizes -similar to cluster cores (or even to clusters), but much lower dispersions. Importantly in the context of MOND, they have the lowest internal accelerations reachable inside galactic systems. Following my recent analysis of MOND in galaxy groups, I came across a much superior sample, which I analyze here. This extensive catalog permits strict quality cuts that still leave a large sample of 56 mediumrichness groups, better suited for dynamical analysis -e.g., in having a large number (≥ 15) of members with measured velocities. I find that these groups obey the deep-MOND relation between baryonic mass, MM , and velocity dispersion, σ: MM Ga0 = (81/4)σ 4 , with individual, MOND, mass-to-light ratios, MM /LK of order 1 M /LK, , and a sample median value of (MM /LK) med = 0.7 M /LK, . These compare well with stellar values deduced for single galaxies, and with values deduced from population-synthesis analyses. In contrast, the dynamical, Newtonian M d /LK values are much larger -several tens solar units, and (M d /LK) med = 37 M /LK, . The same MOND relation describes (isolated) dwarf spheroidals -two-three orders smaller in size, and seven-eight orders lower in mass. The groups conformation to the MOND relation is equivalent to their lying on the deep-MOND branch of the "mass-discrepancy-acceleration relation", g ≈ (gN a0) 1/2 , for g as low as a few percents of a0 (gN is the Newtonian, baryonic, gravitational acceleration, and g the actual one). This argues against systematic departure from MOND at extremely low accelerations (as has been suggested). This conformation also argues against the hypothesis that the remaining MOND conundrum in cluster cores bespeaks a breakdown of MOND on large-distance scales; our groups are as large as cluster cores, but do not show obvious disagreement with MOND. I also discuss the possible presence of the idiosyncratic, MOND external-field effect.PACS numbers: 04.50. Kd, 95.35.+d

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“…Investigations of mass assembly in the outskirts of galaxies have also been conducted by means of stellar kinematics and population properties (e.g. Coccato et al 2010Coccato et al , 2011Ma et al 2014;Barbosa et al 2018;Veale et al 2018;Hilker et al 2018;Greene et al 2019) and kinematics of discrete tracers such as globular clusters (GCs) and planetary nebulae (PNe; e.g. Coccato et al 2013;Longobardi et al 2013;Spiniello et al 2018;Hartke et al 2018;Prole et al 2019;Napolitano et al 2002;Pota et al 2018).…”

Section: Introductionmentioning

confidence: 99%

The Fornax Deep Survey with VST

Spavone

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Ven

et al. 2020

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Context. This work is based on deep multi-band (g, r, i) data from the Fornax Deep Survey with the VLT Survey Telescope (VST). We analyse the surface brightness profiles of the 19 bright early-type galaxies (ETGs; mB ≤ 15 mag) inside the virial radius of the Fornax cluster (Rvir ∼ 0.7 Mpc), in the mass range 8 × 108 ≤ M* ≤ 1.2 × 1011 M⊙. Aims. The main aim of this work is to identify signatures of accretion onto galaxies by studying the presence of outer stellar haloes and to understand their nature and occurrence. Our analysis also provides a new and accurate estimate of the intra-cluster light inside the virial radius of Fornax. Methods. We performed multi-component fits to the azimuthally averaged surface brightness profiles available for all sample galaxies. This allows us to quantify the relative weight of all components in the galaxy structure that contribute to the total light. In addition, we derived the average g − i colours in each component identified by the fit, as well as the azimuthally averaged g − i colour profiles, to correlate them with the stellar mass of each galaxy and the location inside the cluster. Results. We find that in the most massive (1010 ≤ M ≤ 1011 M⊙) and reddest ETGs the fraction of light in, probably accreted, haloes (50%–90%) is much larger than in the other galaxies. All of these are located in the high-density region of the cluster (≤0.4Rvir ∼ 0.3 Mpc), belonging to the north-south clump (NS clump). Less massive galaxies (109 ≤ M ≤ 1010 M⊙) have an accreted mass fraction that is lower than 30%, have bluer colours, and reside in the low-density regions of the cluster. The colour profiles of the ETGs with the largest accreted mass fraction tend to flatten in the outskirts of the galaxy, that is beyond the transition radius from the central in situ to the ex situ accreted component. Inside the virial radius of the cluster (∼0.7 Mpc), the total luminosity of the intra-cluster light, compared with the total luminosity of all cluster members (bright galaxies and dwarfs), is about 34%. Conclusions. Inside the Fornax cluster there is a clear correlation between the amount of accreted material in the stellar haloes of galaxies and the density of the environment in which those galaxies reside. By comparing this quantity with theoretical predictions and previous observational estimates, there is a clear indication that the driving factor for the accretion process is the total stellar mass of the galaxy, which agrees with the hierarchical accretion scenario. Massive galaxies in the NS clump, with the largest accreted mass fractions, went through pre-processing in a group environment before this group merged with the main cluster early on. At the present epoch of the Fornax assembly history, these galaxies are the major contribution to the stellar density in the core of the cluster.

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The Hydra I cluster core

Cited by 33 publications

References 65 publications

The first detection of ultra-diffuse galaxies in the Hydra I cluster from the VEGAS survey

The first detection of ultra-diffuse galaxies in the Hydra I cluster from the VEGAS survey

MOND in galaxy groups: A superior sample

The Fornax Deep Survey with VST

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