An isolated, compact early-type galaxy with a diffuse stellar component: merger origin?

Abstract

The relation between the size and luminosity for both bright and faint early-type galaxies has been repeatedly discussed as a crucial proxy for understanding evolutionary scenarios, as galaxies grow and lose their stellar mass in different physical processes. The class of compact early-type galaxies (cEs) are, however, distinct outliers from this relation and mainly found around massive galaxies in the centres of groups and clusters. The recent discovery of a cE in isolation provided a new opportunity to understand their formation scenario in a different environment. Here, we report the discovery of an isolated cE, CGCG 036-042, using imagery from the Sloan Digital Sky Survey (SDSS). The CGCG 036-042 has an $r$-band absolute magnitude (M${}_r$) of $-$18.21 mag and a half-light radius (R${}_e$) of 559 pc. Interestingly, it possesses a faint outer stellar component, which extends up to 10 kpc from its centre and has a nearly constant $r$-band surface brightness of $\sim$26 mag/arcsec${}^2$. ESO-VLT long-slit spectroscopic data reveal that the simple stellar population (SSP) properties are fairly similar to those of previously identified cEs, with an intermediate-age of 7.15$\pm$1.17 Gyr, a metallicity of --0.18$\pm$0.07 dex and a supersolar alpha-element abundance of 0.2$\pm$0.05 dex. The SSP metallicity also shows a significant decline outward from the center, by 0.5 dex over one half light radius. We discuss the possible origin of this galaxy and suggest that it might have originated from a merger of even smaller objects -- a well established scenario for the formation of massive early-type galaxies.

8 pages, Accepted for publication in MNRAS

References in corpus (51)

• The Sloan Digital Sky Survey: Technical Summary
• Measuring Reddening with SDSS Stellar Spectra and Recalibrating SFD
• Detailed Structural Decomposition of Galaxy Images
• Galaxy Harassment and the Evolution of Clusters of Galaxies
• The epochs of early-type galaxy formation as a function of environment
• The Ninth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the SDSS-III Baryon Oscillation Spectroscopic Survey
• The formation history of elliptical galaxies
• Structure and Formation of Elliptical and Spheroidal Galaxies
• Environmental Effects on Late-Type Galaxies in Nearby Clusters
• Stellar population models of Lick indices with variable element abundance ratios
• Evolutionary Stellar Population Synthesis with MILES. Part I: The Base Models and a New Line Index System
• Confirmation of the remarkable compactness of massive quiescent galaxies at z~2.3: early-type galaxies did not form in a simple monolithic collapse
• Old Stellar Populations. VI. Absorption-Line Spectra of Galaxy Nuclei and Globular Clusters
• The Luminosity Function of Galaxies in SDSS Commissioning Data
• A concise reference to (projected) Sersic R^{1/n} quantities, including Concentration, Profile Slopes, Petrosian indices, and Kron Magnitudes
• The ACS Virgo Cluster Survey. VI. Isophotal Analysis and the Structure of Early-Type Galaxies
• The HST Key Project on the Extragalactic Distance Scale. XXVIII. Combining the Constraints on the Hubble Constant
• HST photometry of dwarf elliptical galaxies in Coma, and an explanation for the alleged structural dichotomy between dwarf and bright elliptical galaxies
• ULySS: A Full Spectrum Fitting Package
• Preparing Red-Green-Blue (RGB) Images from CCD Data
• Formation of early-type galaxies from cosmological initial conditions
• Inclination- and dust-corrected galaxy parameters: Bulge-to-disc ratios and size-luminosity relations
• Hydrodynamics of high-redshift galaxy collisions: From gas-rich disks to dispersion-dominated mergers and compact spheroids
• Dissipation and Extra Light in Galactic Nuclei: II. 'Cusp' Ellipticals
• Compact High-Redshift Galaxies Are the Cores of the Most Massive Present-Day Spheroids
• SDSSJ150634.27+013331.6: the second compact elliptical galaxy in the NGC5846 group
• Observing the dark matter density profile of isolated galaxies
• Galaxy groups and clouds in the Local (z~0.01) universe
• Families of dynamically hot stellar systems over ten orders of magnitude in mass
• Tidal Interaction of M32 and NGC 205 with M31: Surface Photometry and Numerical Simulations
• Early-type galaxies in low-density environments
• The regeneration of stellar bars by tidal interactions. Numerical simulations of fly-by encounters
• A new formation model for M32: A threshed early-type spiral?
• Evolution of dwarf early-type galaxies I. Spatially resolved stellar populations and internal kinematics of Virgo cluster dE/dS0 galaxies
• A Population of Compact Elliptical Galaxies Detected with the Virtual Observatory
• The Atlas-3D project - IX. The merger origin of a fast and a slow rotating Early-Type Galaxy revealed with deep optical imaging: first results
• The remnant of a merger between two dwarf galaxies in Andromeda II
• A tidally distorted dwarf galaxy near NGC 4449
• A near-infrared census of the multi-component stellar structure of early-type dwarf galaxies in the Virgo cluster
• The HST/ACS Coma Cluster Survey: V - Compact Stellar Systems in the Coma Cluster
• The grouping, merging and survival of subhaloes in the simulated Local Group
• The Sizes of Early-type Galaxies
• The early early type: discovery of a passive galaxy at z=3
• The Next Generation Virgo Cluster Survey. IV. NGC 4216: A Bombarded Spiral in the Virgo Cluster
• Signatures of the M31-M32 Galactic Collision
• Tidal streams in newly discovered M32 analogues: evidence for the stripping scenario
• Discovery of a new M32-like "Compact Elliptical" galaxy in the halo of the Abell 496 cD galaxy
• Discovery of an isolated compact elliptical galaxy in the field
• Pre-existing dwarfs, tidal knots and a tidal dwarf galaxy: an unbiased HI study of the gas-rich interacting galaxy group NGC 3166/9
• Long slit spectroscopy of a sample of isolated spirals with and without an AGN
• Tidal interactions at the edge of the Local Group: New evidence for tidal features in the Antlia Dwarf Galaxy

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• Hiding in plain sight: An abundance of compact massive spheroids in the local Universe
• A catalog of merging dwarf galaxies in the local universe
• The AIMSS Project III: The Stellar Populations of Compact Stellar Systems
• Isolated compact elliptical galaxies: Stellar systems that ran away
• Implications for the origin of dwarf early-type galaxies: a detailed look at the isolated rotating dwarf early-type galaxy CG 611, with ramifications for the Fundamental Plane's (S_K)^2 kinematic scaling and the spin-ellipticity diagram
• THE NEXT GENERATION VIRGO CLUSTER SURVEY. XIV. Shell feature early-type dwarf galaxies in the Virgo cluster
• The Formation of Compact Elliptical Galaxies in The Vicinity of A Massive Galaxy: The Role of Ram-pressure Confinement
• On the formation mechanisms of compact elliptical galaxies
• Tidal Interaction as the origin of early-type dwarf galaxies in group environment
• An Extensive Catalog of Early-type Dwarf Galaxies in the Local Universe: Morphology and Environment
• Low-mass compact elliptical galaxies: spatially-resolved stellar populations and kinematics with the Keck Cosmic Web Imager
• Compact elliptical galaxies in different local environments: a mixture of galaxies with different origins?
• SDSS-IV MaNGA: Environmental dependence of the Mgb/<Fe>-sigma_* relation for nearby galaxies
• Large-scale structure and galaxy motions in the Leo/Cancer constellations
• Starbursting Nuclei in Old Dwarf Galaxies
• SDSS J085431.18+173730.5: The First Compact Elliptical Galaxy Hosting an Active Nucleus
• Discovery of a Bimodal Environmental Distribution of Compact Ellipticals in the Local Universe
• The Influence of Environment on the Chemical Evolution in Low-mass Galaxies
• Compact elliptical galaxies hosting active galactic nuclei in isolated environment
• SDSS J122958.84+000138.0: A Compact, Optically red galaxy
• Early-type Dwarf Galaxies in the Local Universe. Evidence of Ex-situ Growth
• An isolated early-type dwarf galaxy that ran away from the group environment
• Stealing galaxies from galaxy clusters