Maffei 1 Group
Encyclopedia
The IC 342/Maffei Group (also known as the IC 342 Group or the Maffei 1 Group) is the nearest group of galaxies to the Local Group
. The group can be described as a binary group; the member galaxies are mostly concentrated around either IC 342
or Maffei 1
, both of which are the brightest galaxies within the group. The group is one of many located within the Virgo Supercluster
(i.e. the Local Supercluster).
and Maffei 1
.
Additionally, KKH 37 is listed as possibly being a member of the IC 342 Subgroup, and KKH 6 is listed as possibly being a member of the Maffei 1 Subgroup.
(a region sometimes called the Zone of Avoidance
). Consequently, the light from many of the galaxies is severely affected by dust obscuration within the Milky Way
. This complicates observational studies of the group, as uncertainties in the dust obscuration also affect measurements of the galaxies' luminosities
and distances as well as other related quantities.
Moreover, the galaxies within the group have historically been difficult to identify. Many galaxies have only been discovered using late 20th century astronomical instrumentation. For example, while many fainter, more distant galaxies, such as the galaxies in the New General Catalogue
, were already identified visually by the end of the nineteenth century, Maffei 1
and Maffei 2
were only discovered in 1968 using infrared
photographic images of the region. Furthermore, it is difficult to determine whether some objects near IC 342 or Maffei 1 are galaxies associated with the IC 342/Maffei Group or diffuse foreground objects within the Milky Way that merely look like galaxies. For example, the objects MB 2 and Camelopardalis C were once thought to be dwarf galaxies in the IC 342/Maffei Group but are now known to be objects within the Milky Way
.
are located physically close to each other, the two groups may have influenced each other's evolution during the early stages of galaxy formation. An analysis of the velocities and distances to the IC 342/Maffei Group as measured by M. J. Valtonen and collaborators suggested that IC 342
and Maffei 1
were moving faster than what could be accounted for in the expansion of the universe. They therefore suggested that IC 342 and Maffei 1 were ejected from the Local Group after a violent gravitational interaction with the Andromeda Galaxy
during the early stages of the formation of the two groups.
However, this interpretation is dependent on the distances measured to the galaxies in the group, which in turn is dependent on accurately measuring the degree to which interstellar dust in the Milky Way
obscures the group. More recent observations have demonstrated that the dust obscuration may have been previously overestimated, so the distances may have been underestimated. If these new distance measurements are correct, then the galaxies in the IC 342/Maffei Group appear to be moving at the rate expected from the expansion of the universe, and the scenario of a collision between the IC 342/Maffei Group and the Local Group would be implausible.
Local Group
The Local Group is the group of galaxies that includes Earth's galaxy, the Milky Way. The group comprises more than 30 galaxies , with its gravitational center located somewhere between the Milky Way and the Andromeda Galaxy...
. The group can be described as a binary group; the member galaxies are mostly concentrated around either IC 342
IC 342
IC 342 is an intermediate spiral galaxy in the constellation Camelopardalis. The galaxy is located near the galactic equator where dust obscuration makes it a difficult object for both amateur and professional astronomers to observe.IC 342 is one of the brightest two galaxies in the IC 342/Maffei...
or Maffei 1
Maffei 1
Maffei 1 is a giant elliptical galaxy in the constellation Cassiopeia. It is the closest giant elliptical galaxy to the Milky Way. Once believed to be a member of the Local Group, it is now known to belong to the IC 342/Maffei Group...
, both of which are the brightest galaxies within the group. The group is one of many located within the Virgo Supercluster
Virgo Supercluster
The Virgo Supercluster or Local Supercluster is the irregular supercluster that contains the Virgo Cluster in addition to the Local Group, which in turn contains the Milky Way and Andromeda galaxies. At least 100 galaxy groups and clusters are located within its diameter of 33 megaparsecs...
(i.e. the Local Supercluster).
Members
The table below lists galaxies that have been identified as associated with the IC342/Maffei 1 Group by I. D. Karachentsev. Note that Karachentsev divides this group into two subgroups centered around IC 342IC 342
IC 342 is an intermediate spiral galaxy in the constellation Camelopardalis. The galaxy is located near the galactic equator where dust obscuration makes it a difficult object for both amateur and professional astronomers to observe.IC 342 is one of the brightest two galaxies in the IC 342/Maffei...
and Maffei 1
Maffei 1
Maffei 1 is a giant elliptical galaxy in the constellation Cassiopeia. It is the closest giant elliptical galaxy to the Milky Way. Once believed to be a member of the Local Group, it is now known to belong to the IC 342/Maffei Group...
.
| Name | Type | R.A. Right ascension Right ascension is the astronomical term for one of the two coordinates of a point on the celestial sphere when using the equatorial coordinate system. The other coordinate is the declination.-Explanation:... (J2000) |
Dec. Declination In astronomy, declination is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. Declination in astronomy is comparable to geographic latitude, but projected onto the celestial sphere. Declination is measured in degrees north and... (J2000) |
Redshift Redshift In physics , redshift happens when light seen coming from an object is proportionally increased in wavelength, or shifted to the red end of the spectrum... (km/s Second The second is a unit of measurement of time, and is the International System of Units base unit of time. It may be measured using a clock.... ) |
Apparent Magnitude Apparent magnitude The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere... |
|---|---|---|---|---|---|
| Camelopardalis A | Irr | -46 ± 1 | 14.8 | ||
| Camelopardalis B | Irr | 77 | 16.1 | ||
| Cassiopeia 1 | dIrr | 35 | 16.4 | ||
| IC 342 IC 342 IC 342 is an intermediate spiral galaxy in the constellation Camelopardalis. The galaxy is located near the galactic equator where dust obscuration makes it a difficult object for both amateur and professional astronomers to observe.IC 342 is one of the brightest two galaxies in the IC 342/Maffei... |
SAB(rs)cd | 31 ± 3 | 9.1 | ||
| KK 35 | Irr | 105 ± 1 | 17.2 | ||
| NGC 1560 | SA(s)d | -36 ± 5 | 12.2 | ||
| UGCA 86 | Im | 67 ± 4 | 13.5 | ||
| UGCA 105 | Im | 111 ± 5 | 13.9 | ||
| Name | Type | R.A. Right ascension Right ascension is the astronomical term for one of the two coordinates of a point on the celestial sphere when using the equatorial coordinate system. The other coordinate is the declination.-Explanation:... (J2000) |
Dec. Declination In astronomy, declination is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. Declination in astronomy is comparable to geographic latitude, but projected onto the celestial sphere. Declination is measured in degrees north and... (J2000) |
Redshift Redshift In physics , redshift happens when light seen coming from an object is proportionally increased in wavelength, or shifted to the red end of the spectrum... (km/s Second The second is a unit of measurement of time, and is the International System of Units base unit of time. It may be measured using a clock.... ) |
Apparent Magnitude Apparent magnitude The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere... |
|---|---|---|---|---|---|
| Dwingeloo 1 Dwingeloo 1 Dwingeloo 1 is a barred spiral galaxy about 10 million light-years away from the Earth, in the constellation Cassiopeia. It lies in the Zone of Avoidance and is heavily obscured by the Milky Way... |
SB(s)cd | 110 | 8.3 | ||
| Dwingeloo 2 Dwingeloo 2 Dwingeloo 2 is a small irregular galaxy discovered in 1996 and located about 10 million light-years away from the Earth. Its discovery was a result of Dwingeloo Obscured Galaxy Survey of the Zone of Avoidance... |
Im | 94 ± 1 | 20.5 | ||
| KKH 11 | dE | 310 | 16.2 | ||
| KKH 12 | Irr | 70 | 17.8 | ||
| Maffei 1 Maffei 1 Maffei 1 is a giant elliptical galaxy in the constellation Cassiopeia. It is the closest giant elliptical galaxy to the Milky Way. Once believed to be a member of the Local Group, it is now known to belong to the IC 342/Maffei Group... |
S0 pec | 13 ± 22 | 11.4 | ||
| Maffei 2 Maffei 2 Maffei 2 is an intermediate spiral galaxy about 10 million light-years away in the constellation Cassiopeia. Maffei 2 and Maffei 1 were both discovered by Paolo Maffei in 1968 from their infrared emission. Maffei 2 lies in the Zone of Avoidance and is about 99.5% obscured by the Milky Way's... |
SAB(rs)bc | -17 ± 5 | 16.0 | ||
| MB 1 | SAB(s)d | 190 ± 1 | 20.5 | ||
| MB 3 MB 3 MB3 is a dwarf spheroidal galaxy discovered in 1997 and located about 10 million light-years away from the Earth. It was discovered during an optical survey of the IC 342/Maffei group to which the galaxy is a member. MB3 is a companion galaxy of Dwingeloo 1 and situated in the Zone of Avoidance... |
dSph | 59 ± 1 | 17.33 | ||
Additionally, KKH 37 is listed as possibly being a member of the IC 342 Subgroup, and KKH 6 is listed as possibly being a member of the Maffei 1 Subgroup.
Foreground dust obscuration
As seen from Earth, the group lies near the plane of the Milky WayMilky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
(a region sometimes called the Zone of Avoidance
Zone of Avoidance
The Zone of Avoidance is the area of the night sky that is obscured by our own galaxy, the Milky Way.-Term:The ZOA was originally called the "Zone of Few Nebulae" in an 1878 paper by English astronomer Richard Proctor that referred to the distribution of "nebulae" in Sir John Herschel's General...
). Consequently, the light from many of the galaxies is severely affected by dust obscuration within the Milky Way
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
. This complicates observational studies of the group, as uncertainties in the dust obscuration also affect measurements of the galaxies' luminosities
Luminosity
Luminosity is a measurement of brightness.-In photometry and color imaging:In photometry, luminosity is sometimes incorrectly used to refer to luminance, which is the density of luminous intensity in a given direction. The SI unit for luminance is candela per square metre.The luminosity function...
and distances as well as other related quantities.
Moreover, the galaxies within the group have historically been difficult to identify. Many galaxies have only been discovered using late 20th century astronomical instrumentation. For example, while many fainter, more distant galaxies, such as the galaxies in the New General Catalogue
New General Catalogue
The New General Catalogue of Nebulae and Clusters of Stars is a well-known catalogue of deep sky objects in astronomy. It contains 7,840 objects, known as the NGC objects...
, were already identified visually by the end of the nineteenth century, Maffei 1
Maffei 1
Maffei 1 is a giant elliptical galaxy in the constellation Cassiopeia. It is the closest giant elliptical galaxy to the Milky Way. Once believed to be a member of the Local Group, it is now known to belong to the IC 342/Maffei Group...
and Maffei 2
Maffei 2
Maffei 2 is an intermediate spiral galaxy about 10 million light-years away in the constellation Cassiopeia. Maffei 2 and Maffei 1 were both discovered by Paolo Maffei in 1968 from their infrared emission. Maffei 2 lies in the Zone of Avoidance and is about 99.5% obscured by the Milky Way's...
were only discovered in 1968 using infrared
Infrared
Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...
photographic images of the region. Furthermore, it is difficult to determine whether some objects near IC 342 or Maffei 1 are galaxies associated with the IC 342/Maffei Group or diffuse foreground objects within the Milky Way that merely look like galaxies. For example, the objects MB 2 and Camelopardalis C were once thought to be dwarf galaxies in the IC 342/Maffei Group but are now known to be objects within the Milky Way
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
.
Group formation and possible interactions with the Local Group
Since the IC 342/Maffei Group and the Local GroupLocal Group
The Local Group is the group of galaxies that includes Earth's galaxy, the Milky Way. The group comprises more than 30 galaxies , with its gravitational center located somewhere between the Milky Way and the Andromeda Galaxy...
are located physically close to each other, the two groups may have influenced each other's evolution during the early stages of galaxy formation. An analysis of the velocities and distances to the IC 342/Maffei Group as measured by M. J. Valtonen and collaborators suggested that IC 342
IC 342
IC 342 is an intermediate spiral galaxy in the constellation Camelopardalis. The galaxy is located near the galactic equator where dust obscuration makes it a difficult object for both amateur and professional astronomers to observe.IC 342 is one of the brightest two galaxies in the IC 342/Maffei...
and Maffei 1
Maffei 1
Maffei 1 is a giant elliptical galaxy in the constellation Cassiopeia. It is the closest giant elliptical galaxy to the Milky Way. Once believed to be a member of the Local Group, it is now known to belong to the IC 342/Maffei Group...
were moving faster than what could be accounted for in the expansion of the universe. They therefore suggested that IC 342 and Maffei 1 were ejected from the Local Group after a violent gravitational interaction with the Andromeda Galaxy
Andromeda Galaxy
The Andromeda Galaxy is a spiral galaxy approximately 2.5 million light-years from Earth in the constellation Andromeda. It is also known as Messier 31, M31, or NGC 224, and is often referred to as the Great Andromeda Nebula in older texts. Andromeda is the nearest spiral galaxy to the...
during the early stages of the formation of the two groups.
However, this interpretation is dependent on the distances measured to the galaxies in the group, which in turn is dependent on accurately measuring the degree to which interstellar dust in the Milky Way
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
obscures the group. More recent observations have demonstrated that the dust obscuration may have been previously overestimated, so the distances may have been underestimated. If these new distance measurements are correct, then the galaxies in the IC 342/Maffei Group appear to be moving at the rate expected from the expansion of the universe, and the scenario of a collision between the IC 342/Maffei Group and the Local Group would be implausible.