There is the configuration parameter "azimuth_window": [0, 36000], and I'm able to adjust it using
"set_config_param azimuth_window [0, 18000]" to only transmit the left half of the image on my OS-1-16-A2 with FW v1.13.0 (I also tried [0, 4500] and that worked as expected, returning leftmost 45° of image).
Note that I'm using my own SW framework which makes use of commands described in SW user guide v1.13.0 to achieve this, I cannot tell you much about ROS driver or Ouster studio.
Even that azimuth_window is not explicitly listed in 'set_param' section, it is working as expected, but you'll need to call 'reininitialize' for it to take effect.
As far I observed, this limits the amount of Lidar packets transmitted.