The Pristine dwarf galaxy survey-V. The edges of the dwarf galaxy Hercules

We present a new spectroscopic study of 175 stars in the vicinity of the dwarf galaxy Hercules (d similar to 132 kpc) with data from the Anglo-Australian Telescope and its AAOmega spectrograph together with the Two Degree Field multi-object system to solve the conundrum that whether Hercules is tidally disrupting. We combine broad-band photometry, proper motions from Gaia, and our Pristine narrow-band and metallicity-sensitive photometry to efficiently weed out the Milky Way contamination. Such cleaning is particularly critical in this kinematic regime, as both the transverse and heliocentric velocities of Milky Way populations o v erlap with Hercules. Thanks to this method, three new member stars are identified, including one at almost 10rh of the satellite. All three hav e v elocities and metallicities consistent with that of the main body. Combining this new data set with the entire literature cleaned out from contamination shows that Hercules does not exhibit a velocity gradient (d(v)/d x = 0 . 1 (+ 0.4) (-0.2) km s (-1) arcmin (-1), 1.6 km s (-1) arcmin (-1) as a 3s upper limit) and, as such, does not show evidence to undergo tidal disruption.