NGC 1546

Lore & Background

NGC 1546 was discovered by John Herschel on December 5, 1834. The galaxy is seen nearly edge-on, with an inclination of 70°. Its multiple spiral arms resemble those of an Sc spiral galaxy, but earlier images showed no structure in the disk, leading to its lenticular classification. The H-alpha and [N II] emission is distributed in a flocculent pattern. The galaxy features an inner ring with a radius of 26 arcseconds and an outer pseudoring 0.96 arcminutes across, both detected in infrared and far ultraviolet, with H II regions present at both rings. The total star formation rate is estimated at 0.83 solar masses per year.

A series of dust lanes, some backlit by the galaxy's core, absorb light from the core, reddening it and making the dust appear rusty-brown. The core glows brightly in yellowish light, indicating an older population of stars, while brilliant-blue regions of active star formation sparkle through the dust. The galaxy shows no evidence of an outflow from the nucleus. Diffuse far ultraviolet emission comes from the outer regions, and a diffuse halo is present. A faint shell is visible southeast of the galaxy.

Reader's Guide

NGC 1546 is significant as a member of the Dorado Group, one of the nearest galaxy groups to the Local Group, and it lies in the central part of that group. Its classification history illustrates how improved imaging can reveal hidden structure: originally categorized as a lenticular galaxy due to an apparently featureless disk, later observations uncovered a high surface brightness spiral arm pattern similar to an Sc spiral. The galaxy's inner ring and outer pseudoring, detected in both infrared and far ultraviolet, along with H II regions at both rings, indicate ongoing star formation at a rate of 0.83 solar masses per year. The presence of dust lanes backlit by the core, which redden and color the dust rusty-brown, and the contrast between the yellowish core (older stars) and blue star-forming regions, provide a clear example of galactic structure and stellar population differences. The absence of a nuclear outflow and the presence of diffuse far ultraviolet emission and a faint shell add to its interest as a relatively quiescent but active galaxy. Its compact grouping with NGC 1549, NGC 1553, and IC 2058 makes it a valuable target for studying galaxy interactions and evolution within a group environment.