LEDA 074886: A remarkable rectangular-looking galaxy

TL;DR

The paper reports the discovery of LEDA 074886, a rare rectangular-shaped galaxy with an embedded stellar disk, suggesting a complex merger history that challenges existing galaxy evolution models.

Contribution

It introduces a unique rectangular galaxy with an embedded disk, proposing a merger origin and highlighting the need to combine wet and dry merger simulations.

Findings

Galaxy exhibits a rectangular shape with boxy isophotes.

Presence of an embedded, edge-on stellar disk.

Implication of a merger origin for this unusual morphology.

Abstract

We report the discovery of an interesting and rare, rectangular-shaped galaxy. At a distance of 21 Mpc, the dwarf galaxy LEDA 074886 has an absolute R-band magnitude of -17.3 mag. Adding to this galaxy's intrigue is the presence of an embedded, edge-on stellar disk (of extent 2R_{e,disk} = 12 arcsec = 1.2 kpc) for which Forbes et al. reported V_rot/sigma ~ 1.4. We speculate that this galaxy may be the remnant of two (nearly edge-one) merged disk galaxies in which the initial gas was driven inward and subsequently formed the inner disk, while the stars at larger radii effectively experienced a dissipationless merger event resulting in this `emerald cut galaxy' having very boxy isophotes with a_4/a = -0.05 to -0.08 from 3 to 5 kpc. This galaxy suggests that knowledge from simulations of both `wet' and `dry' galaxy mergers may need to be combined to properly understand the various paths that galaxy evolution can take, with a particular relevance to blue elliptical galaxies.