A tidally distorted dwarf galaxy near NGC 4449

Дата и время публикации : 2012-02-10T17:43:52Z

Авторы публикации и институты :
R. M. Rich
M. L. M. Collins
C. M. Black
F. M. Longstaff
A. Koch
A. Benson
D. B. Reitzel

Ссылка на журнал-издание: Nature 2012 482, 192-194
Коментарии к cтатье: Published in Nature, February 9, 2012. Nature, 482, 192-194 Published article available at http://www.nature.com/nature/journal/v482/n7384//full/nature10837.html
Первичная категория: astro-ph.CO

Все категории : astro-ph.CO, astro-ph.GA

Краткий обзор статьи: NGC 4449 is a nearby Magellanic irregular starburst galaxy with a B-band absolute magnitude of -18 and a prominent, massive, intermediate-age nucleus at a distance from Earth of 3.8 megaparsecs. It is wreathed in an extraordinary neutral hydrogen (H I) complex, which includes rings, shells and a counter-rotating core, spanning 90 kiloparsecs. NGC 4449 is relatively isolated, although an interaction with its nearest known companion-the galaxy DDO 125, some 40 kpc to the south-has been proposed as being responsible for the complexity of its HI structure. Here we report the presence of a dwarf galaxy companion to NGC 4449, namely NGC 4449B. This companion has a V-band absolute magnitude of -13.4 and a half-light radius of 2.7 kpc, with a full extent of around 8 kpc. It is in a transient stage of tidal disruption, similar to that of the Sagittarius dwarf near the Milky Way. NGC 4449B exhibits a striking S-shaped morphology that has been predicted for disrupting galaxies but has hitherto been seen only in a dissolving globular cluster. We also detect an additional arc or disk ripple embedded in a two-component stellar halo, including a component extending twice as far as previously known, to about 20 kpc from the galaxy’s centre.

Category: Physics