The end of the arm is largely dark. That's the top of the ChemCam housing on the RSM - no doubt about it.
It was Sol 2423 for MSL
Images
https://mars.jpl.nasa.gov/msl/multimedia/ra...00#/?slide=2423Plan Description
https://mars.jpl.nasa.gov/msl/mission/mars-...cks-at-our-feet"Then on the second sol ChemCam will acquire observations on 2 autonomously selected AEGIS targets, along with some Navcam dust devil and suprahorizon observations to monitor the atmosphere."
It's the second sol of a 2 sol plan that had a drive on the first sol - therefore the arm remains stowed.
That includes a ChemCam AEGIS block (Navcam images with a CCAM sequence ID are AEGIS) a dust devil movie and supra-horizon movie, and then the RSM would have stowed - which is 0az, -48 deg in rover frame. i.e. pointing forward and down.
The arm was stowed at the time it was taken.