CO line and radio continuum study of elephant trunks: the Pillars of Creation in M16

Abstract

Molecular-line and radio continuum properties of the elephant trunks (ET, pillars of creation) in M16 are investigated by analyzing the 12 CO(J = 1 − 0) , 13 CO(J = 1 − 0) and C 18 O(J = 1 − 0) -line survey data with the Nobeyama 45-m telescope and the Galactic plane radio survey at 20 and 90 cm with the Very Large Array. The head clump of Pillar West I is found to be the brightest radio source in M16, showing thermal spectrum and property of a compact HII region with the nearest O5 star in NGC 6611 being the heating source. The radio pillars have cometary structure concave to the molecular trunk head, and the surface brightness distribution obeys a simple illumination law by a remote excitation source. The molecular density in the pillar head is estimated to be several 10 4 H 2 cm −3 and molecular mass ∼ 13 − 40M ⊙ . CO-line kinematics reveals random rotation of the clumps in the pillar tail at ∼ 1 − 2 km s −1 , comparable to the velocity dispersion and estimated Alfvén velocity. It is suggested that the random directions of velocity gradients would manifest a torsional magnetic oscillation of the clumps around the pillar axis.

Globules and pillars in Cygnus X

“…Possible rotation features in pillars were observed before (Gahm et al 2006;Sofue 2020). Gahm et al (2006) proposed for 'elephant trunks' in several sources observed in CO lines that rotation can be provoked by the formation of compressed magnetic filaments that were present in the parent molecular cloud and are now impacted by the expanding H II region.…”

“…The globule tail also shows a possible rotation, but the axis is less inclined and the velocity difference is smaller. The rotation is clock-wise around an axis located between the blue and red part of the tail if we view the globule from above.Possible rotation features in pillars were observed before(Gahm et al 2006;Sofue 2020) Gahm et al (2006). proposed for 'elephant trunks' in several sources observed in CO lines that rotation can be provoked by the formation of compressed magnetic filaments that were present in the parent molecular cloud and are now impacted by the expanding H II region.…”

SOFIA FEEDBACK Survey: The Pillars of Creation in [C ii] and Molecular Lines

“…Velocity gradients are detected in most lines both along and across the pillar body (Figures 8 and 9). Gradients across P1 and P2 were also observed by Sofue (2020). Line velocities are highest toward the northeastern side of the pillar head, and decrease both to the west across the head and to the south along the body.…”

“…We compare to the distances calculated by Sofue (2020) using peak radio continuum brightness. LOS separations from the plane of the cluster z = 1.8, 2.5, and 2.8 pc for P1a, P2, and P3 are calculated as = z D i cos( ) from the true distances D = 2.6, 3.2, and 3.6 pc and inclinations i = 47°, 40°, and 40°p resented by Sofue (2020). In both their and our estimates, P1a is nearest and P3 is farthest from the plane of the cluster.…”

Formation Mechanism of Laser-driven Magnetized “Pillars of Creation”

“…The gas emission in recombination radiation (e.g., H α or X-rays) is one of the most important observational features for the POC (Linsky et al 2007;Sofue 2020), and the most luminescent part is located at the pillar's head, followed by a long shadow tail (as shown in Figure 1(b)). In the experiments, the bremsstrahlung emission, as we mentioned above, is the main radiation mechanism for the high-temperature low-Z plasma (Nicolai et al 2006), and the radiation maps for medium-magnetized cases are shown in Figure 6.…”