We report on the X-ray observation of a strong lensing selected group , SL2S J08544-0121 , with a total mass of 2.4 \pm 0.6 \times 10 ^ { 14 } { M _ { \odot } } Â which revealed a separation of 124 \pm 20 kpc between the X-ray emitting collisional gas and the collisionless galaxies and dark matter ( DM ) , traced by strong lensing .
This source allows to put an order of magnitude estimate to the upper limit to the interaction cross section of DM of 10 cm ^ { 2 } g ^ { -1 } .
It is the lowest mass object found to date showing a DM-baryons separation and it reveals that the detection of bullet-like objects is not rare and confined to mergers of massive objects opening the possibility of a statistical detection of DM-baryons separation with future surveys .