NGC 1218
Galaxy in the constellation Cetus
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NGC 1218 is a lenticular galaxy in Cetus that hosts the radio source 3C 78. It was discovered in 1886 by American astronomer Lewis A. Swift. It is located at l = 174.86, b = -44.51 in the galactic coordinate system.[1]
| NGC 1218 | |
|---|---|
NGC 1218 as viewed by the Hubble Space Telescope.[Note 1] | |
| Observation data (J2000.0 epoch) | |
| Constellation | Cetus |
| Right ascension | 03h 08m 26.2s[1] |
| Declination | +04° 06′ 39.3″[1] |
| Redshift | 0.0288[2] |
| Heliocentric radial velocity | 8,485±15 km/s[3] |
| Galactocentric velocity | 8,488±15 km/s[3] |
| Distance | 378,600,000 ly (116.08 Mpc)[1] |
| Group or cluster | [CHM 2007] LDC 223[1] |
| Apparent magnitude (V) | 8.460[3] |
| Apparent magnitude (B) | 12.84[4] |
| Absolute magnitude (V) | -2.70[3] |
| Surface brightness | 1.19×10−1[3] |
| Characteristics | |
| Type | S0/a[3] |
| Size | 225,400 ly (69.11 kpc) (diameter)[3] |
| Apparent size (V) | 1.147′ × 0.917′[1] |
| Other designations | |
| 2MASS J03082623+0406390, 2MASX J03082624+0406388, Gaia DR1 2673462523030912, UGC 2555, LEDA 11749, MCG +01-09-001, PGC 011749, CGCG 0305.8+0355[1][3][Note 2] | |
History
Discovered by Lewis Swift on September 6, 1886,[5] NGC 1218 was one of the original objects included in the New General Catalogue.[6] 3C 78 was discovered c. 1957, and subsequently included in the Third Cambridge Catalogue of Radio Sources (3C).[7]
In 1982, it was found that the nucleus of NGC 1218 emits a radio jet.[8] A follow-up study in 1986 corroborated the presence of the jet, as well as finding evidence of a possible weak counter-jet.[9] The Hubble Space Telescope observed NGC 1218 on August 17, 1994. An optical jet of synchrotron radiation similar to that of Messier 87 was subsequently found.[10]
On September 6, 2000, a type Ia supernova was detected in NGC 1218. A 2002 study found that the previously identified radio jet was the cause.[11]
In 2023, the proper motion of 3C 78 was determined using observations from the Very Large Array (VLA), as well as a single observation from the Atacama Large Millimeter/submillimeter Array (ALMA).[12]
Composition and structure
NGC 1218 is a lenticular (S/0a) radio galaxy, with a radio halo roughly equivalent in size to the optical halo's extent.[8] The observable synchrotron jet has a total length of 1.37 arcseconds (0.75 kpc), and expands substantially at 0.5 arcseconds from the nucleus.[10]
NGC 1218 has an approximate hydrogen mass of <36×109 M☉.[9]
3C 78
3C 78 is an astronomical radio source with an angular extent of approximately 80 × 55 arcseconds squared.[9] According to Tabara and Inoue (1980), 3C 78 has a rotation measure of 8.7 ± 1.9 m−2 and an intrinsic position angle of 87° ± 4°, although Simard-Normandin, Kronberg, and Button (1981) claim that it has a rotation measure of 14 ± 2 m−2 and an intrinsic position angle of 85° ± 3°.[13][14]
It possesses a radio jet approximately one arcsecond (0.58 kpc) in length, with three bright, compact inhomogeneities (or "knots"), with the second and thirds ones being the most prominent. The second knot has a longitudinal motion of approximately 0.51 ± 0.14c at roughly 200 pc, and the third knot had an apparent superluminal backwards motion of −2.6 ± 2c prior to 2000, followed by a forward motion of 0.5 ± 2c, both at roughly 300 pc. [12]
Notes
- Color rendered with the Aladin Sky Atlas
- There are a total of 76 identifiers used. The NGC, 3C, and CGCG designations are the most common