MOND prediction of a new giant shell in the elliptical galaxy NGC3923

Abstract

Context. Stellar shells, which form axially symmetric systems of arcs in some elliptical galaxies, are most likely remnants of radial minor mergers. They are observed up a radius of $\sim$100 kpc. The stars in them oscillate in radial orbits. The radius of a shell depends on the free-fall time at the position of the shell and on the time since the merger. We previously verified the consistency of shell radii in the elliptical galaxy NGC 3923 with its most probable MOND potential. Our results implied that an as~yet undiscovered shell exists at the outskirts of the galaxy. Aims. We here extend our study by assuming more general models for the gravitational potential to verify the prediction of the new shell and to estimate its position. Methods. We tested the consistency of the shell radial distribution observed in NGC 3923 with a wide variety of MOND potentials of the galaxy. The potentials differed in the mass-to-light ratio and in distance to the galaxy. We considered different MOND interpolation functions, values of the acceleration constant $a_0$, and density profiles of the galaxy. We verified the functionality of our code on a Newtonian self-consistent simulation of the formation of a shell galaxy. Results. Our method reliably predicts that exactly one new outermost shell exists at a galactocentric radius of about 1900${}^{\prime \prime }$ ($\sim$210 kpc) on the southwestern side of the galaxy. Its estimated surface brightness is about 28 mag arcsec${}^{-2}$ in $B$ - a value accessible by current instruments. This prediction enables a rare test of MOND in an elliptical down to an acceleration of $a_0/10$. The predictive power of our method is verified by reconstructing the position of the largest known shell from the distribution of the remaining shells.

12 pages, 5 figures, 4 tables, accepted for publication in A&A

References in corpus (5)

• A Novel Test of the Modified Newtonian Dynamics with Gas Rich Galaxies
• THINGS about MOND
• Confrontation of MOND with the rotation curves of early-type disc galaxies
• Testing MOND Over a Wide Acceleration Range in X-Ray Ellipticals
• HST/ACS observations of shell galaxies: inner shells, shell colours and dust

Cited by in corpus (7)

• Shell galaxies as laboratories for testing MOND
• Lopsidedness of self-consistent galaxies by the external field effect of clusters
• Remnants of recent mergers in nearby early-type galaxies and their classification
• Ubiquitous signs of interactions in early-type galaxies with prolate rotation
• MOND implications for spectral line profiles of shell galaxies: shell formation history and mass-velocity scaling relations
• Type I shell galaxies as a test of gravity models
• Origin of the spectacular tidal shells of galaxy NGC474