Determining the Nature of the Extended HI Structure Around LITTLE THINGS Dwarf Galaxy NGC 1569

TL;DR

This study maps the extended neutral hydrogen around dwarf galaxy NGC 1569, revealing filamentary structures and potential interaction remnants that shed light on its starburst activity and past interactions.

Contribution

First detailed HI mapping of NGC 1569's surroundings, identifying structures suggestive of galaxy interactions and providing insights into its peculiar kinematics.

Findings

Detected a large HI cloud sharing position and velocity with NGC 1569.

Discovered filamentary structures extending 77 kpc from NGC 1569.

Identified possible tidal tails and HI bridges indicating past interactions.

Abstract

This work presents an extended, neutral Hydrogen emission map around Magellanic-type dwarf irregular galaxy (dIm) NGC 1569. In the Spring of 2010, the Robert C. Byrd Green Bank Telescope (GBT) was used to map a 9 degree x 2 degree region in HI line emission that includes NGC 1569 and IC 342 as well as two other dwarf galaxies. The primary objective for these observations was to search for structures potentially connecting NGC 1569 with IC 342 group members in order to trace previous interactions and thus, provide an explanation for the starburst and peculiar kinematics prevalent in NGC 1569. A large, half-degree diameter HI cloud was detected that shares the same position and velocity as NGC 1569. Also, two long structures were discovered that are reminiscent of intergalactic filaments extending out in a v-shaped manner from NGC 1569 toward UGCA 92, a nearby dwarf galaxy. These filamentary structures extend for about 1.5 degrees, which is 77 kpc at NGC 1569. There is a continuous velocity succession with the 0.5 degree HI cloud, filaments, and main body of the galaxy. The 0.5 degree HI cloud and filamentary structures may be foreground Milky Way, but are suggestive as possible remnants of an interaction between NGC 1569 and UGCA 92. The data also show two tidal tails extending from UGCA 86 and IC 342, respectively. These structures may be part of a continuous HI bridge but more data are needed to determine if this is the case.