Archived HST/ACS F814W image of the host of GRB 050709 and its AG taken in July and August 2005 (HST program ID 10624, principal investigator: D. Fox). Labels indicate the AG (blue), the optically brightest part of the host (B), and potentially star-forming regions or young luminous stellar clusters placed along tidal arms (C and D). The apparently faint western region of the host (H) is filled with ionized gas (Sect. 4). “Q” is an anonymous point-like emission-line object, which we have used as a reference for the astrometry between HST and VLT/MUSE (see Sect. 3.4). Coordinate values are given in units of arcseconds relative to object Q. The inset shows an optical contour plot that reveals two peaks inside region B that are 030 (0.85 kpc) apart from each other. (For the original image, see Fox et al. 2005).