The Fornax Deep Survey with VST. II. Fornax A: a two-phase assembly caught on act

摘要: As part of the Fornax Deep Survey with ESO VLT Telescope, we present new $g$ and $r$ bands mosaics SW group cluster. It covers an area $3 \times 2$ square degrees around central galaxy NGC1316. The deep photometry, high spatial resolution OmegaCam large covered allow us to study structure, trace stellar halo formation look at environment. We map surface brightness profile out 33arcmin ($\sim 200$kpc $\sim15R_e$) from centre, down $\mu_g \sim 31$ mag arcsec$^{-2}$ $\mu_r 29$ arcsec$^{-2}$. This estimate scales main components dominating light distribution, which are spheroid, inside 5.5 arcmin ($\sim33$ kpc), outer envelope. Data analysis suggests that catching in act second phase mass assembly this galaxy, since accretion smaller satellites is going on both components. envelope NGC1316 still hosts remnants accreted satellite galaxies forming halo. discuss possible scenarios for NGC1316, by comparing observed properties (morphology, colors, gas content, kinematics dynamics) predictions cosmological simulations formation. find {\it i)} spheroid could result least one merging event, it be a pre-existing early-type disk lower companion, ii)} comes gradual small satellites.