NGC 3147 | |
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![]() NGC 3147 imaged by the Hubble Space Telescope | |
Observation data (J2000 epoch) | |
Constellation | Draco |
Right ascension | 10h 16m 53.7s [1] |
Declination | +73° 24′ 03″ [1] |
Redshift | 0.009346 ± 0.000003 [1] |
Heliocentric radial velocity | 2,802 ± 1 km/s [1] |
Distance | 129 ± 29 Mly (39.6 ± 8.9 Mpc) [1] |
Apparent magnitude (V) | 10.6 |
Characteristics | |
Type | SA(rs)bc [1] |
Apparent size (V) | 3.9′ × 3.5′ [1] |
Notable features | Seyfert galaxy |
Other designations | |
UGC 5532, MCG +12-10-025, PGC 30019 [1] |
NGC 3147 is a spiral galaxy located in the constellation Draco. It is located at a distance of about 130 million light years from Earth, which, given its apparent dimensions, means that NGC 3147 is about 140,000 light years across. It was discovered by William Herschel on April 3, 1785. [2]
The galaxy has a small and bright nucleus and tightly wound multiple spiral arms. The overall appearance of the galaxy resembles that of NGC 488, however the nuclear bulge is smaller. The arms consist of spiral segments that branch after approximately one quarter of a revolution. HII regions can be detected in the arms. [3]
NGC 3147 has been characterised as a Seyfert II galaxy. It is considered the best candidate to be a true type II Seyfert galaxy, [4] galaxies which feature optical/UV spectrum lacking broad emission lines due to the lack of the broad line region rather than its obscuration, since the nucleus is simultaneously seen unobscured in the X-rays. [5]
The galaxy was observed simultaneously in the optical and X-ray spectrum by Bianchi et al. and concluded that the X-ray spectrum is unabsorbed while its optical spectrum lacks broad lines, a mismatch with respect to the Unification Model. [6] Birghtman et al. confirmed their findings and also noted that the hard X-ray flux dropped by a factor of ~2 between the observation by Chandra (2001) and XMM-Newton (2006). [7] Further flux variation was observed by Suzaku in 2010, confirming the variability of the source. [4] The nuclear emission in the UV band shows negligible variability. [8] Shi et al. used data from Spitzer Space Telescope and ground-based optical spectropolarimeteric observations and observed lack of polarised broad emission lines in NGC 3147. [9] NGC 3147 was observed by NuSTAR at the 3-40 keV X-ray spectrum, which is characterised by a simple power-law, with a standard Γ ~ 1.7 and an iron emission line, with no need for any further component up to ~ 40 keV. [5]
There is a debate whether the lack of broad lines detection observed with NGC 3147 is caused by the presence of a Compton-thick column with the presence of a highly ionised reflector to account for the X-ray spectrum or not. [5] Bianchi et al. rejected the presence of a Compton thick column on the grounds of low-equivalent width of the iron Kα line (≃130 eV), and of the large ratio between hard X-ray and [O III] fluxes. [6] Birghtman et al. confirmed their findings using data from XMM-Newton and Chandra. They also found that the X-ray flux is variable, meaning that the nucleus may be observed directly. However, they noted the presence of a Compton-thick column cannot be ruled out. [7] The observations by Suzaku in the hard X-rays spectrum did not cast more light, [4] but along with the observations performed by XMM-Newton put tight constraints on the column density. [5]
After the observations by NuStar in 2015, Bianchi et al. concluded that the spectral properties and the significant variability on time-scales as short as weeks strongly support an unobscured line-of-sight for the nucleus of NGC 3147 and the Compton-thick scenario is strongly disfavoured. [5]
In July 2019 researchers using the Hubble Space Telescope Imaging Spectrograph reported the presence of a thin disk of material around a supermassive black hole at the center of NGC 3147. The black hole is 250 million times as massive as the Sun. Black holes at the center of galaxies of such low activity have been considered to be "malnourished" or "starving", that is, little or no material would be falling into the black hole to feed it. The presence of a disk that is similar to the much brighter disks surrounding the black hole of more active galaxies was surprising, since models of low activity galaxies did not predict it. The disk is also unusual because it is deep within the gravitational well of the black hole and rotates around it at more than 10% of the speed of light. Its high velocity results in the effect known as relativistic beaming, in which the light coming from the side moving toward the Earth is brighter than that coming from the side that is receding. [11] [12]
Six supernovae have been discovered in NGC 3147:
NGC 3147 is the brightest galaxy in the NGC 3147 group, which also includes NGC 3155, UGC 5570, UGC 5686, and UGC 5689. A bit further away lie NGC 3183, NGC 3348, NGC 3364, and NGC 3516. [24]
Messier 61 is an intermediate barred spiral galaxy in the Virgo Cluster of galaxies. It was first discovered by Barnaba Oriani on May 5, 1779, six days before Charles Messier discovered the same galaxy. Messier had observed it on the same night as Oriani but had mistaken it for a comet. Its distance has been estimated to be 45.61 million light years from the Milky Way Galaxy. It is a member of the M61 Group of galaxies, which is a member of the Virgo II Groups, a series of galaxies and galaxy clusters strung out from the southern edge of the Virgo Supercluster.
NGC 3184, the Little Pinwheel Galaxy, is an unbarred spiral galaxy approximately 40 million light-years away in the constellation Ursa Major. Its name comes from its resemblance to the Pinwheel Galaxy. It was discovered on 18 March 1787 by German-British astronomer William Herschel. It has two HII regions named NGC 3180 and NGC 3181.
NGC 1097 is a barred spiral galaxy about 45 million light years away in the constellation Fornax. It was discovered by William Herschel on 9 October 1790. It is a severely interacting galaxy with obvious tidal debris and distortions caused by interaction with the companion galaxy NGC 1097A.
NGC 1316 is a lenticular galaxy about 60 million light-years away in the constellation Fornax. It is a radio galaxy and at 1400 MHz is the fourth-brightest radio source in the sky.
NGC 5033 is an inclined spiral galaxy located in the constellation Canes Venatici. Distance estimates vary from between 38 and 60 million light years from the Milky Way. The galaxy has a very bright nucleus and a relatively faint disk. Significant warping is visible in the southern half of the disk. The galaxy's relatively large angular size and relatively high surface brightness make it an object that can be viewed and imaged by amateur astronomers. The galaxy's location relatively near Earth and its active galactic nucleus make it a commonly studied object for professional astronomers.
NGC 4639 is a barred spiral galaxy located in the equatorial constellation of Virgo. It was discovered by German-born astronomer William Herschel on 12 April 1784. John L. E. Dreyer described it as "pretty bright, small, extended, mottled but not resolved, 12th magnitude star 1 arcmin to southeast". This is a relatively nearby galaxy, lying approximately 72 million light-years away from the Milky Way. It is a companion to NGC 4654, and the two appear to have interacted roughly 500 million years ago. NGC 4639 is a member of the Virgo Cluster.
NGC 5584 is a barred spiral galaxy in the constellation Virgo. It was discovered July 27, 1881 by American astronomer E. E. Barnard. Distance determination using Cepheid variable measurements gives an estimate of 75 million light years, whereas the tip of the red-giant branch approach yields a distance of 73.4 million light years. It is receding with a heliocentric radial velocity of 1,637 km/s. It is a member of the Virgo III Groups, a series of galaxies and galaxy clusters strung out to the east of the Virgo Supercluster of galaxies.
NGC 1084 is an unbarred spiral galaxy in the constellation Eridanus. It is located at a distance of about 63 million light-years away from the Milky Way. The galaxy was discovered by William Herschel on 10 January 1785. It has multiple spiral arms, which are not well defined. It belongs in the same galaxy group with NGC 988, NGC 991, NGC 1022, NGC 1035, NGC 1042, NGC 1047, NGC 1052 and NGC 1110. This group is in turn associated with the Messier 77 group.
NGC 2276 is an intermediate spiral galaxy in the constellation Cepheus. The galaxy lies 120 million light-years away from Earth. NGC 2276 has an asymmetrical appearance, most likely caused by gravitational interactions with its neighbor, elliptical galaxy NGC 2300. NGC 2276 is traveling with an orbital velocity of about 968 km/s due to its neighbor. Trailing NGC 2276 is a long tail of interstellar medium about 300,000 light-years long, formed by ram pressure stripping.
NGC 1448 is an unbarred spiral galaxy seen nearly edge-on in the constellation Horologium. It is at a distance of 55 million light years from Earth. It was discovered by British astronomer John Herschel on 24 October 1835. Herschel observed the galaxy again on 14 December 1835, resulting in it being listed twice in the New General Catalogue, as NGC 1448 and as NGC 1457.
NGC 1961 is a spiral galaxy in the constellation Camelopardalis. It was discovered by William Herschel on 3 December 1788. It is at a distance of about 200 million light years from Earth, which, given its apparent dimensions, means that NGC 1961 is more than 220,000 light years across.
NGC 5643 is an intermediate spiral galaxy in the constellation Lupus. Based on the tip of the red-giant branch distance indicator, it is located at a distance of about 40 million light-years. NGC 5643 has an active galactic nucleus and is a type II Seyfert galaxy.
NGC 4699 is an intermediate spiral galaxy located in the constellation Virgo. It is located at a distance of about 65 million light years from Earth, which, given its apparent dimensions, means that NGC 4699 is about 85,000 light years across. It was discovered by William Herschel in 1786. It is a member of the NGC 4699 Group of galaxies, which is a member of the Virgo II Groups, a series of galaxies and galaxy clusters strung out from the southern edge of the Virgo Supercluster.
NGC 3941 is a barred lenticular galaxy located in the constellation Ursa Major. It is located at a distance of circa 40 million light years from Earth, which, given its apparent dimensions, means that NGC 3941 is about 40,000 light years across. It was discovered by William Herschel in 1787.
NGC 5468 is an intermediate spiral galaxy located in the constellation Virgo. It is located at a distance of about 140 million light-years from Earth, which, given its apparent dimensions, means that NGC 5468 is about 110,000 light-years across. It was discovered by William Herschel on 5 March 1785.
NGC 3367 is a barred spiral galaxy located in the constellation Leo. It is located at a distance of about 120 million light years from Earth, which, given its apparent dimensions, means that NGC 3367 is about 85,000 light years across. It was discovered by William Herschel on March 19, 1784.
NGC 4939 is a large spiral galaxy located in the constellation Virgo. It is located at a distance of about 120 million light years from Earth, which, given its apparent dimensions, means that NGC 4939 is about 190,000 light years across. It was discovered by William Herschel on March 25, 1786.
NGC 6951 is a barred spiral galaxy located in the constellation Cepheus. It is located at a distance of about 75 million light-years from Earth, which, given its apparent dimensions, means that NGC 6951 is about 100,000 light-years across. It was discovered by Jérôme Eugène Coggia in 1877 and independently by Lewis Swift in 1878.
NGC 7678 is an intermediate spiral galaxy located in the constellation Pegasus. It is located at a distance of about 130 million light years from Earth, which, given its apparent dimensions, means that NGC 7678 is about 95,000 light years across. It was discovered by William Herschel on September 15, 1784.
NGC 1320 is a spiral galaxy located in the constellation Eridanus. Its speed relative to the cosmic microwave background is 2,620 ± 15 km/s, which corresponds to a Hubble distance of 38.6 ± 2.7 Mpc. It was discovered by the German-British astronomer William Herschel in 1784.