Fossil group origins IX. Probing the formation of fossil galaxy groups with stellar population gradients of their central galaxies

Abstract

Fossil groups (FGs) are galaxy aggregates with an extended and luminous X-ray halo, which are dominated by a very massive early-type galaxy and lack of L* objects. FGs are indeed characterized by a large magnitude gap between their central and surrounding galaxies. This is explained by either speculating that FGs are failed groups that formed without bright satellite galaxies and did not suffer any major merger, or by suggesting that FGs are very old systems that had enough time to exhaust their bright satellite galaxies through multiple major mergers. Since major mergers leave signatures in the stellar populations of the resulting galaxy, we study the stellar population parameters of the brightest central galaxies (BCGs) of FGs as a benchmark against which the formation and evolution scenarios of FGs can be compared. We present long-slit spectroscopic observations along different axes of NGC 6482 and NGC 7556, which are the BCGs of two nearby FGs. The measurements include spatially resolved stellar kinematics and radial profiles of line-strength indices, which we converted into stellar population parameters using single stellar-population models. NGC 6482 and NGC 7556 are very massive and large galaxies and host a centrally concentrated stellar population, which is significantly younger and more metal rich than the rest of the galaxy. The age gradients of both galaxies are somewhat larger than those of the other FG BCGs studied so far, whereas their metallicity gradients are similarly negative and shallow. They have negligible gradients of alpha-element abundance ratio. The measured metallicity gradients are less steep than those predicted for massive galaxies that formed monolithically and evolved without experiencing any major merger. We conclude that the observed FGs formed through major mergers rather than being failed groups that lacked bright satellite galaxies from the beginning.

arXiv comment17 pages, 9 figures, A&A in press, corrected proofs

References in corpus (81)

• Measuring Reddening with SDSS Stellar Spectra and Recalibrating SFD
• The Eleventh and Twelfth Data Releases of the Sloan Digital Sky Survey: Final Data from SDSS-III
• The Optical and Near-Infrared Properties of Galaxies: I. Luminosity and Stellar Mass Functions
• Introducing the Illustris Project: Simulating the coevolution of dark and visible matter in the Universe
• Parametric Recovery of Line-of-Sight Velocity Distributions from Absorption-Line Spectra of Galaxies via Penalized Likelihood
• MILES: A Medium resolution INT Library of Empirical Spectra
• 2MASS Extended Source Catalog: Overview and Algorithms
• Stellar population models of Lick indices with variable element abundance ratios
• The SAURON project - V. Integral-field emission-line kinematics of 48 elliptical and lenticular galaxies
• An updated MILES stellar library and stellar population models
• Galaxies in a simulated $\Lambda$CDM Universe I: cold mode and hot cores
• Old Stellar Populations. VI. Absorption-Line Spectra of Galaxy Nuclei and Globular Clusters
• The Stellar Population Histories of Local Early-Type Galaxies. I. Population Parameters
• On the shape of the light profiles of early-type galaxies
• K-band Properties of Galaxy Clusters and Groups: Brightest Cluster Galaxies and Intracluster Light
• The structure of galactic disks: Studying late-type spiral galaxies using SDSS
• Galaxy Evolution in Cosmological Simulations With Outflows I: Stellar Masses and Star Formation Rates
• The nature and space density of fossil groups of galaxies
• GRAPE-SPH Chemodynamical Simulation of Elliptical Galaxies I: Evolution of Metallicity Gradients
• Spatially resolved spectroscopy of Coma cluster early -- type galaxies: III. The stellar population gradients
• The MASSIVE Survey - I. A Volume-Limited Integral-Field Spectroscopic Study of the Most Massive Early-Type Galaxies within 108 Mpc
• Cool Core Clusters from Cosmological Simulations
• Stellar populations of early-type galaxies in different environments II. Ages and metallicities
• SDSSJ150634.27+013331.6: the second compact elliptical galaxy in the NGC5846 group
• The Formation of Fossil Galaxy Groups in the hierarchical Universe
• Age and metallicity gradients in early-type galaxies: A dwarf to giant sequence
• Brightest Cluster Galaxies at the Present Epoch
• Redshift-Distance Survey of Early-Type Galaxies: Spectroscopic Data
• Why Do Only Some Galaxy Clusters Have Cool Cores?
• Two-dimensional multi-component photometric decomposition of CALIFA galaxies
• Scaling relations in fossil galaxy groups
• On the survival of metallicity gradients to major dry-mergers
• An old galaxy group: Chandra X-ray observations of the nearby fossil group NGC 6482
• The MASSIVE Survey - V. Spatially-Resolved Stellar Angular Momentum, Velocity Dispersion, and Higher Moments of the 41 Most Massive Local Early-Type Galaxies
• Ages and Metallicities of Hickson Compact Group Galaxies
• The Fossil Phase in the Life of a Galaxy Group
• The Stellar Halos of Massive Elliptical Galaxies II: Detailed Abundance Ratios at Large Radius
• Secular- and merger-built bulges in barred galaxies
• Abundance gradient slopes versus mass in spheroids: predictions by monolithic models
• Spatially resolved kinematics and stellar populations of brightest cluster and group galaxies
• Stellar populations of early-type galaxies in different environments III. Line-strength gradients
• On the spectral resolution of the MILES stellar library
• Fossil Groups in the Sloan Digital Sky Survey
• Stellar Populations of Bulges in 14 Cluster Disc Galaxies
• The luminosity function of the fossil group RX J1552.2+2013
• The central elliptical galaxy in fossil groups and formation of BCGs
• The XMM Cluster Survey: The Stellar Mass Assembly of Fossil Galaxies
• On the Nature of Fossil Galaxy Groups: Are they really fossils ?
• The formation of the [alpha/Fe] radial gradients in the stars of elliptical galaxies
• Evolution of BCGs structural parameters in the last $\sim$6 Gyr: feedback processes versus merger events
• Fossil Systems in the 400d Cluster Catalog
• Fossil Groups Origins: I. RX J105453.3+552102 a very massive and relaxed system at z~0.5
• On the mass-to-light ratios of fossil groups. Are they simply dark clusters?
• Ages, metallicities and $\alpha$-element enhancement for galaxies in Hickson compact groups
• Cold Dark Matter's Small Scale Crisis Grows Up
• Testing adiabatic contraction of dark matter in fossil group candidates
• Structure and dynamics of galaxies with a low surface-brightness disc - II. Stellar populations of bulges
• Stellar populations in the bulges of isolated galaxies
• Fossil Groups Origins III. The relation between optical and X-ray luminosities
• Fossil Groups in the Millennium Simulation. Evolution of the Brightest Galaxies
• The Stellar Haloes of Massive Elliptical Galaxies III: Kinematics at Large Radius
• Fossil groups origins II. Unveiling the formation of the brightest group galaxies through their scaling relations
• Properties of fossil groups in cosmological simulations and galaxy formation models
• Age and metallicity gradients in fossil ellipticals
• The Cluster Gas Mass - Temperature Relation: Evidence for a High Level of Preheating
• Stellar population gradients in brightest cluster galaxies
• Gravitational Quenching by Clumpy Accretion in Cool Core Clusters: Convective Dynamical Response to Overheating
• Study of the stellar population properties in the discs of ten spiral galaxies
• Do the stellar populations of the brightest two group galaxies depend on the magnitude gap?
• Evolution of compact and fossil groups of galaxies from semi-analytical models of galaxy formation
• Fossil group origins V. The dependence of the luminosity function on the magnitude gap
• Are fossil groups early-forming galaxy systems?
• Fossil Group Origins VII. Galaxy substructures in fossil systems
• Evolution of the galaxy luminosity function in progenitors of fossil groups
• Comparison of the properties of two fossil groups of galaxies with the normal group NGC 6034 based on multiband imaging and optical spectroscopy
• Optically selected fossil groups; X-ray observations and galaxy properties
• Fossil group origins - VI. Global X-ray scaling relations of fossil galaxy clusters
• The density of dark matter haloes of early-type galaxies in low-density environments
• A Normal Abundance of Faint Satellites in the Fossil Group NGC 6482
• Spatially resolved stellar population parameters in the BCGs of two fossil groups
• Fossil group origins: VIII RXJ075243.6+455653 a transitionary fossil group

Cited by in corpus (11)

• Dependency of halo concentration on mass, redshift and fossilness in Magneticum hydrodynamic simulations
• Cosmology dependency of halo masses and concentrations in hydrodynamic simulations
• The Fornax3D project: Assembly histories of lenticular galaxies from a combined dynamical and population orbital analysis
• Evidence of a fast bar in the weakly-interacting galaxy NGC 4264 with MUSE
• Aging Halos: Implications of the Magnitude Gap on Conditional Statistics of Stellar and Gas Properties of Massive Halos
• A slow bar in the lenticular barred galaxy NGC 4277
• A search for ionised gas outflows in an Halpha imaging atlas of nearby LINERs
• Fossil group origins. XI. The dependence of galaxy orbits on the magnitude gap
• Fossil group origins XII. Large-scale environment around fossil systems
• Fossil group origins XIII. A paradigm shift: fossil groups as isolated structures rather than relics of the ancient Universe
• Fornax 3D project: assessing the diversity of IMF and stellar population maps within the Fornax Cluster