Giant stellar arcs in the Large Magellanic Cloud: a possible link with past activity of the Milky Way nucleus

TL;DR

The paper proposes that the giant stellar arcs in the Large Magellanic Cloud resulted from past jet activity of the Milky Way's nucleus, which triggered star formation and created the observed arcs.

Contribution

It introduces a novel hypothesis linking the Milky Way's past activity to the formation of stellar arcs in the LMC, supported by new observational data.

Findings

Radial velocities support the jet-induced star formation hypothesis.

The arcs' orientation points toward the Milky Way's center.

Evidence suggests a past energetic jet from the Milky Way influenced the LMC.

Abstract

The origin of the giant stellar arcs in the LMC remains a controversial issue, discussed since 1966. No other stellar arc is so perfect a segment of a circle, moreover, there is another similar arc nearby. Many hypotheses were advanced to explain these arcs, and all but one of these were disproved. It was proposed in 2004 that origin of these arcs was due to the bow shock from the jet, which is intermittently fired by the Milky Way nucleus and during the last episode of its activity the jet was pointed to the LMC. Quite recently evidence for such a jet has really appeared. We suppose it was once energetic enough to trigger star formation in the LMC, and if the jet opening angle was about 2{\deg}, it could push out HI gas from the region of about 2 kpc in size, forming a cavity LMC4, but also squeezed two dense clouds, which occurred in the same area, causing the formation of stars along their surfaces facing the core of the MW. In result, spherical segments of the stellar shells might arise, visible now as the arcs of Quadrant and Sextant, the apices of which point to the center of the MW. This orientation of both arcs can be the key to unlocking their origin. Here we give data which confirm the above hypothesis, amongst which are radial velocities of stars inside and outside the larger one of the LMC arcs. The probability is low that a jet from an AGN points to a nearby galaxy and triggers star formation there, but a few other examples are now known or suspected.