Abstract:
Bright-rimmed clouds (BRCs) are ideal candidates to study radiation-driven implosion mode of star formation as they are
potential sites of triggered star formation, located at the edges of HII regions, showing evidence of ongoing star formation
processes. BRC 18 is located towards the eastern edge of relatively closer (∼400 pc) H II region excited by λ Ori. We made
R-band polarimetric observations of 17 candidate young stellar objects (YSOs) located towards BRC 18 to investigate any
preferred orientation of the discs with respect to the ambient magnetic field and the direction of energetic photons from λ Ori.
We found that the discs are oriented randomly with respect to the projected magnetic field. Using distances and proper motions
from the Gaia EDR3 of the candidate YSOs, we investigated the possible acceleration of BRC 18, away from λ Ori due to the
well-known ‘Rocket Effect’, by assuming that both the candidate YSOs and BRC 18 are kinematically coupled. The relative
proper motions of the candidate YSOs are found to show a trend of moving away from λ Ori. We computed the offset between
the angle of the direction of the ionization front and the relative proper motion of the candidate YSOs and found it to lie close
to being parallel to each other. Additionally, we found 12 sources that are co-moving with the known candidate YSOs towards
BRC 18. These co-moving sources are most likely to be young and are missed in previous surveys conducted to identify potential
YSOs of the region.
