NGC 3147 | |
---|---|
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.
Messier 66 or M66, also known as NGC 3627, is an intermediate spiral galaxy in the southern, equatorial half of Leo. It was discovered by French astronomer Charles Messier on 1 March 1780, who described it as "very long and very faint". This galaxy is a member of a small group of galaxies that includes M65 and NGC 3628, known as the Leo Triplet or the M66 Group. M65 and M66 are a common object for amateur astronomic observation, being separated by only 20′.
NGC 2403 is an intermediate spiral galaxy in the constellation Camelopardalis. It is an outlying member of the M81 Group, and is approximately 8 million light-years distant. It bears a similarity to M33, being about 50,000 light years in diameter and containing numerous star-forming H II regions. The northern spiral arm connects it to the star forming region NGC 2404. NGC 2403 can be observed using 10×50 binoculars. NGC 2404 is 940 light-years in diameter, making it one of the largest known H II regions. This H II region represents striking similarity with NGC 604 in M33, both in size and location in galaxy.
Messier 84 or M84, also known as NGC 4374, is a giant elliptical or lenticular galaxy in the constellation Virgo. Charles Messier discovered the object in 1781 in a systematic search for "nebulous objects" in the night sky. It is the 84th object in the Messier Catalogue and in the heavily populated core of the Virgo Cluster of galaxies, part of the local supercluster.
NGC 3184, the Little Pinwheel Galaxy, is a 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 1275 is a type 1.5 Seyfert galaxy located around 237 million light-years away in the direction of the constellation Perseus. NGC 1275 is a member of the large Perseus Cluster of galaxies.
NGC 4725 is an intermediate barred spiral galaxy with a prominent ring structure, located in the northern constellation of Coma Berenices near the north galactic pole. It was discovered by German-born British astronomer William Herschel on April 6, 1785. The galaxy lies at a distance of approximately 40 megalight-years from the Milky Way. NGC 4725 is the brightest member of the Coma I Group of the Coma-Sculptor Cloud, although it is relatively isolated from the other members of this group. This galaxy is strongly disturbed and is interacting with neighboring spiral galaxy NGC 4747, with its spiral arms showing indications of warping. The pair have an angular separation of 24′, which corresponds to a projected linear separation of 370 kly. A tidal plume extends from NGC 4747 toward NGC 4725.
NGC 2841 is an unbarred spiral galaxy in the northern circumpolar constellation of Ursa Major. It was discovered on 9 March, 1788 by German-born astronomer William Herschel. J. L. E. Dreyer, the author of the New General Catalogue, described it as, "very bright, large, very much extended 151°, very suddenly much brighter middle equal to 10th magnitude star". Initially thought to be about 30 million light-years distant, a 2001 Hubble Space Telescope survey of the galaxy's Cepheid variables determined its distance to be approximately 14.1 megaparsecs or 46 million light-years. The optical size of the galaxy is 8.1′ × 3.5′.
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 April 12, 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 3938 is an unbarred spiral galaxy in the Ursa Major constellation. It was discovered on 6 February 1788 by William Herschel. It is one of the brightest spiral galaxies in the Ursa Major South galaxy group and is roughly 67,000 light years in diameter. It is approximately 43 million light years away from Earth. NGC 3938 is classified as type Sc under the Hubble sequence, a loosely wound spiral galaxy with a smaller and dimmer bulge. The spiral arms of the galaxy contain many areas of ionized atomic hydrogen gas, more so towards the center.
NGC 4102 is an intermediate barred spiral galaxy located in the northern constellation of Ursa Major. It is visible in a small telescope and has an apparent visual magnitude of 11.2. The galaxy was discovered April 12, 1789 by William Herschel. J. L. E. Dreyer described it as "bright, pretty small, round, brighter middle and bright nucleus". This galaxy is located at a distance of 60 million light years and is receding with a heliocentric radial velocity of 837 km/s. It is a member of the Ursa Major group of galaxies.
NGC 2748 is a spiral galaxy in the northern circumpolar constellation of Camelopardalis, located at a distance of 61.3 megalight-years from the Milky Way. It was discovered September 2, 1828 by John Herschel. The morphological classification of SAbc indicates this is an unbarred spiral with moderate to loosely-wound spiral arms. It is a disk-like peculiar galaxy with a stellar shell that is rotating about the main galactic axis. This shell was most likely formed through the capture and disruption of a dwarf companion. The galactic nucleus likely contains a supermassive black hole with a mass of 4.4+3.5
−3.6×107 M☉, or 44 million times the mass of the Sun.
NGC 3021 is a spiral galaxy in the northern constellation of Leo Minor. It is about 93 million light-years away from Earth, and is receding with a heliocentric radial velocity of 1,537±4 km/s. This galaxy was discovered December 7, 1785 by Anglo-German astronomer William Herschel. The morphological classification of NGC 3021 is SA(rs)bc, which indicates a spiral galaxy with no central bar (SA), an incomplete inner ring structure (rs), and moderate to loosely wound spiral arms (bc).
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 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 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 March 5, 1785.
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.