| NGC 3166 | |
|---|---|
 NGC 3166 (right) withNGC 3169 (left) imaged byLa Silla Observatory | |
| Observation data (J2000epoch) | |
| Constellation | Sextans |
| Right ascension | 10h 13m 45.6784s[1] |
| Declination | +03° 25′ 29.294″[1] |
| Redshift | 0.003946 ± 0.000005[1] |
| Heliocentric radial velocity | 1,183 ± 1 km/s[1] |
| Distance | 61.3 – 71.7Mly (18.8 – 22Mpc)[1] |
| Group orcluster | NGC 3166 Group |
| Apparent magnitude (V) | 10.5[2] |
| Characteristics | |
| Type | SAB(rs)0/a[1] |
| Size | ~107,900 ly (33.09 kpc) (estimated)[1] |
| Apparent size (V) | 4.8′ × 2.3′[1] |
| Notable features | Interacting with NGC 3169 |
| Other designations | |
| HOLM 173A,IRAS 10111+0340,UGC 5516,MCG +01-26-024,PGC 29814,CGCG 036-064[1] | |
NGC 3166 is alenticular galaxy in the constellationSextans. The galaxy lies about 65 millionlight years away from Earth, which means, given its apparent dimensions, that NGC 3166 is approximately 105,000 light years across.[1] It was discovered byWilliam Herschel on December 19, 1783.[3]
NGC 3166 has a bright, elongated nucleus, surrounded by an elliptical brightbulge, elongated along a nearly east-west axis.[4] In the central 6-7 arcseconds there is evidence of a circumnuclear star disk. The age of the stars in the nucleus is estimated to be no older than two billion years.[5] A low-surface-brightnessbar is visible lying nearly perpendicular to that. The fainter parts of the bulge are nearly circular, about one arcminute in diameter, and with spiral whorls. Beyond that lies a low-surface-brightness disk, withoutspiral arms or knots.[4] Dust lanes are visible over the disk of the galaxy.[6] The stars in the disk have sub-solarmetallicity, indicating the stars are more than 8 billion years old there.[7]
Inultraviolet the galaxy is asymmetric, with stronger emission west of the nucleus. That region, at the western tidal arm, is the only in the galaxy that has a spectrum similar to anHII region and is indicative of the presence of young stars. There is hydrogen emission east of the nucleus. This asymmetry could be the result of recent gas accretion, and a complete star formation ring hasn't yet formed.[8] The currentstar formation rate of the galaxy is estimated to be0.06±0.01 M☉ per year.[9] An arm is visible inH-alpha 100 arcseconds west of the nucleus. The outer regions of the galaxy appear lopsided.[8]
Onesupernova has been detected in NGC 3166.SN 2012cw (Type Ic, mag. 16.5) was discovered byKōichi Itagaki on 14 June 2012.[10][11] Its progenitor couldn't be detected in archive images byHubble Space Telescope, indicating it had anabsolute magnitude of less than -7.[12]
NGC 3166 forms aninteracting pair withNGC 3169, which lies at a separation of 7.5 arcminutes. Another companion galaxy,NGC 3165, lies 4.5 arcminutes to the southwest.[6] Atidal tail connecting NGC 3166 with NGC 3169 extending south of the galaxy is visible in radiowaves, in thehydrogen line. The total mass of hydrogen in the tail is estimated to be108 M☉.[13] At the end of the tail a tidaldwarf galaxy, AGC 208457, has formed.[14] Some other gas clumps have also been detected. Three of them are classical dwarf irregular galaxies.[9] There is extended hydrogen emission surrounding the group.[13] These galaxies, along withNGC 3156, form the NGC 3169 Group, which is part of theLeo II Groups, a large cloud of galaxies in theVirgo Supercluster.[15]
