The Survey of Centaurus A's Baryonic Structures (SCABS) – II. The extended globular cluster system of NGC 5128 and its nearby environment - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Monthly Notices of the Royal Astronomical Society Année : 2017

The Survey of Centaurus A's Baryonic Structures (SCABS) – II. The extended globular cluster system of NGC 5128 and its nearby environment

Matthew A. Taylor
  • Fonction : Auteur
Thomas H. Puzia
  • Fonction : Auteur
Roberto P. Muñoz
  • Fonction : Auteur
Steffen Mieske
  • Fonction : Auteur
Hongxin Zhang
  • Fonction : Auteur
Paul Eigenthaler
  • Fonction : Auteur
Mia Sauda Bovill
  • Fonction : Auteur

Résumé

New wide-field u^΄g^΄r^΄i^΄z^΄Dark Energy Camera observations centred on the nearby giant elliptical galaxy NGC 5128 covering ∼21 deg^2 are used to compile a new catalogue of ∼3200 globular clusters (GCs). We report 2404 newly identified candidates, including the vast majority within ∼140 kpc of NGC 5128. We find evidence for a transition at a galactocentric radius of R_gc ≈ 55 kpc from GCs ‘intrinsic’ to NGC 5128 to those likely to have been accreted from dwarf galaxies or that may transition to the intragroup medium of the Centaurus A galaxy group. We fit power-law surface number density profiles of the form $$\Sigma _{N, R_{\rm gc}}\propto R_{\rm gc}^\Gamma$$ and find that inside the transition radius, the red GCs are more centrally concentrated than the blue, with Γ_inner, red ≈ −1.78 and Γ_inner, blue ≈ −1.40, respectively. Outside this region both profiles flatten, more dramatically for the red GCs (Γ_outer, red ≈ −0.33) compared to the blue (Γ_outer, blue ≈ −0.61), although the former is more likely to suffer contamination by background sources. The median (g^΄ − z^΄)_0 = 1.27 mag colour of the inner red population is consistent with arising from the amalgamation of two giant galaxies each less luminous than present-day NGC 5128. Both inwards and outwards of the transition radius, we find the fraction of blue GCs to dominate over the red GCs, indicating a lively history of minor mergers. Assuming the blue GCs to originate primarily in dwarf galaxies, we model the population required to explain them, while remaining consistent with NGC 5128’s present-day spheroid luminosity. We find that several dozen dwarfs of luminosities Ldw, V ≃ 10^6–9.3 LV, ⊙, following a Schechter luminosity function with a faint-end slope of −1.50 ≲ α ≲ −1.25 is favoured, many of which may have already been disrupted in NGC 5128’s tidal field.

Dates et versions

hal-01582689 , version 1 (06-09-2017)

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Matthew A. Taylor, Thomas H. Puzia, Roberto P. Muñoz, Steffen Mieske, Ariane Lançon, et al.. The Survey of Centaurus A's Baryonic Structures (SCABS) – II. The extended globular cluster system of NGC 5128 and its nearby environment. Monthly Notices of the Royal Astronomical Society, 2017, 469 (3), pp.3444-3467. ⟨10.1093/mnras/stx1021⟩. ⟨hal-01582689⟩
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