NGC 3109

Template:Short description Template:Infobox Galaxy

NGC 3109 is a small barred Magellanic type spiral or irregular galaxy around 4.35 Mly away in the direction of the constellation of Hydra. NGC 3109 is believed to be tidally interacting with the dwarf elliptical galaxy Antlia Dwarf.<ref>Grebel, Gallagher, Harbeck, p.7</ref> It was discovered by John Herschel on March 24, 1835 while he was in what is now South Africa.<ref name=Ign>Irregular Galaxy NGC 3109 Template:Webarchive</ref>

Size and morphologyEdit

NGC 3109 is classified as a Magellanic type irregular galaxy,<ref name="AparicoEtAl">Template:Cite book</ref> but it may in fact be a small spiral galaxy. Based on the D_25.5 isophote at the B-band with an angular diameter of Template:Val arcseconds, it has an isophotal diameter approximately Template:Convert across, slightly larger than the Large Magellanic Cloud but smaller than the Triangulum Galaxy.<ref name="ned" /> If it is a spiral galaxy, it would be the smallest in the Local Group.<ref name="SauvageEtAl">Template:Cite book</ref> NGC 3109 has a mass of about Template:Val times the mass of the Sun (Template:Solar mass), of which 20% is in the form of neutral hydrogen.<ref name="Vandenbergh">Template:Cite book</ref> It is oriented edge-on from our point of view, and may contain a disk and a halo.<ref name="SauvageEtAl"/> The disk appears to be composed of stars of all ages, whereas the halo contains only very old and metal-poor stars.<ref name="HidalgoEtAl">Template:Cite journal</ref> NGC 3109 does not appear to possess a galactic nucleus.<ref name="Vandenbergh"/>

From measurements of the neutral atomic hydrogen in the galaxy, it has been found that the disk of NGC 3109 is warped. The warp has the same radial velocity as gas in the Antlia Dwarf galaxy, indicating that the two galaxies had a close encounter approximately one billion years ago.<ref name="BarnesdeBlok">Template:Cite journal</ref>

CompositionEdit

Based on spectroscopy of blue supergiants in NGC 3109, it is known that the galaxy has a low metallicity, similar to that of the Small Magellanic Cloud.<ref name="EvansEtAl"/> It is one of the most metal-poor star-forming galaxies in the Local group.<ref name="Pena">Template:Cite journal</ref> NGC 3109 seems to contain an unusually large number of planetary nebulae for its luminosity.<ref name="RicherMcCall">Template:Cite journal</ref> It also contains a substantial amount of dark matter.<ref name="JobinCarignan"> Template:Cite journal</ref>

LocationEdit

NGC 3109 is located about Template:Convert away, in the constellation Hydra. This puts it at the very outskirts of the Local Group.<ref name="EvansEtAl">Template:Cite journal</ref> Its membership of the Local Group has been questioned, because it seems to be receding faster than estimates of the Local Group's escape velocity.<ref name="Plotner">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> It is distant enough from the largest members of the Local Group that it has not been tidally influenced by them.<ref name="Pena"/>

Luminous Blue VariableEdit

Although no supernovae have been observed in NGC 3109 yet, a luminous blue variable, designated ATTemplate:Nbsp2018akx (type LBV, mag. 17.5), was discovered by the All Sky Automated Survey for SuperNovae on 22 March 2018.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>