Maffei 1
| Maffei 1 | |
|---|---|
 |
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| Observation data (J2000 epoch) | |
| Constellation | Cassiopeia |
| Right ascension | 02h 36m 35.4s[1] |
| Declination | +59° 39′ 19″[1] |
| Helio radial velocity | 66.4 ± 5.0 km/s[2] |
| Distance | 2.85 ± 0.36 Mpc[3] 4.4+0.6 −0.5 Mpc[4] |
| Type | E3 |
| Apparent dimensions (V) | 3′.36 × 1′.68[1] |
| Apparent magnitude (V) | 11.14 ± 0.06 (V-band)[2] |
| Other designations | |
| PGC 9892,[1] Sharpless 191 | |
| See also: Galaxy, List of galaxies | |
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. It was named after Paolo Maffei, who discovered it and the neighboring Maffei 2 in 1968 from their infrared emissions.
Maffei 1 a slightly flattened core type boxy elliptical galaxy made mainly of old stars. It has a small blue nucleus where stars continue to form. Like any large elliptical it contains a significant population of globular clusters. The distance to Maffei 1 is 3–4 Mpc. It may be the closest giant elliptical galaxy to the Milky Way.
Maffei 1 lies in the Zone of Avoidance and is heavily obscured by the Milky Way's stars and dust. If it were not obscured, it would be one of the largest, brightest and best known galaxies in the sky. Contrary to common belief, it is possible to observe it visually, using a 30–40 cm or bigger telescope under a very dark sky.
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[edit] Discovery
Maffei 1 was discovered by Paolo Maffei on photographic plates he obtained with the Schmidt telescope at Asiago Observatory. He searched for diffuse nebulae and T Tauri stars but found Maffei 1 together with its companion spiral galaxy Maffei 2.[2]
[edit] Distance
Maffei 1 is located only 0.55° from the galactic plane in the middle of the zone of avoidance and suffers from about 4.7 magnitude of extinction (about 70 times) in the visible light. In addition to the extinction it is covered by myriads of faint galactic stars, which can be easily confused with the stars belonging to Maffei 1. These circumstances have seriously hampered distance determination to it.[2]
In 1971 soon after its discovery Hyron Spinrad estimated the distance to Maffei 1 at about 1 Mpc, which would place it within the Local Group of galaxies. In 1983 this estimate was revised up to 2.1+1.3
−0.8 Mpc by Ronald Buta and Marshall McCall using the general relation between the luminosity and velocity dispersion for elliptical galaxies.[2] At that distance Maffei 1 was well outside the Local Group, but could have still influenced it in the past.[4]
In 1993 Gerard Luppino and John Tonry used surface brightness fluctuations to derive a new distance estimate to Maffei 1—4.15 ± 0.5 Mpc. Later in 2001 Tim Davidge and Sidney van den Bergh used adaptive optics to observe the brightest Asymptotic Giant Branch stars in Maffei 1 and concluded that it is located at the distance 4.4+0.6
−0.5 Mpc from the Sun.[4][2] The latest determination of the distance to Maffei 1, which is based on the re-calibrated luminosity/velocity dispersion relation for the elliptical galaxies and the updated extinction, is 2.85 ± 0.36 Mpc.
The larger (≥3 Mpc) distances reported in the past 20 years mean that Maffei 1 has never been close enough to the Local Group to significantly influence its dynamic.[3]
[edit] Physical properties
[edit] Size and shape
Maffei 1 is a giant elliptical galaxy classified as E3 type in the Hubble classification scheme.[5] This means that it is slightly flattened with its semi-minor axis being 70% of its semi-major axis. Maffei 1 has also a boxy shape (E(b)3 type), while its central part (radius ≈ 34 pc) is deficient of light as compared to the r1/4 law meaning that Maffei 1 is a core type elliptical. Both the boxy shape and the core are typical of intermediate to massive ellipticals.[6]
The apparent dimension of Maffei 1 strongly depends on the wavelength of light because of the heavy obscuration by the Milky Way. In the blue light it is 1–2′ across while in the near infrared its major axis reaches 23′—more than 3/4 of the Moon's diameter. At the distance of 3 Mpc this corresponds to approximately 23 kpc.[5] The total visible absolute magnitude of Maffei 1, MV=−20.8, is comparable to that of Milky Way.[3]
[edit] Nucleus
In the center of Maffei 1 there exists a small blue nucleus approximately 1.2 pc across. It contains ionized hydrogen with the mass of about 29 solar masses.[6] This implies a recent star formation activity in the nucleus. There is no signs of an active galactic nucleus (AGN) in the center of Maffei 1. The X-ray emission from the center is extended and likely comes from a number of stellar sources.[7]
[edit] Stars and stellar clusters
Maffei 1 is mainly made of old metal rich stars more than 10 billion years in age.[7] As a large elliptical galaxy Maffei 1 is expected to host a significant (about 1100) population of globular clusters. However due to heavy extinction ground-based observations for the long time failed to identify any of them.[7] Only observations by Hubble Space Telescope in 2000 revealed about 20 of globular clusters candidates in the central region of the galaxy.[6] Later infrared ground based observations also found a population of bright globular cluster candidates.[8]
[edit] Group membership
Maffei 1 is a principle member of a nearby group of galaxies. Other its members are giant spiral galaxies IC 342 and Maffei 2. Maffei 1 has also a small satellite spiral galaxy Dwingeloo 1 as well as a number of dwarf satellites like MB1. IC 342/Maffei Group is one the closest galaxy groups to the Milky Way galaxy.[9]
[edit] References
- ^ a b c d "NASA/IPAC Extragalactic Database". Results for NGC 404. http://nedwww.ipac.caltech.edu/. Retrieved 2006-11-18.
- ^ a b c d e f Fingerhut, R. L.; McCall, M. L.; De Robertis, M.; Kingsburgh, R. L.; Komljenovic, M.; Lee, H.; Buta, R. J. (2003). "The Extinction and Distance of Maffei 1". The Astrophysical Journal 587 (2): 672. doi:10.1086/368339.
- ^ a b c Fingerhut, R. L.; Lee, H.; McCall, M. L.; Richer, M. G. (2007). "The Extinction and Distance of Maffei 2 and a New View of the IC 342/Maffei Group". The Astrophysical Journal 655 (2): 814. doi:10.1086/509862.
- ^ a b c Davidge, T. J.; Van Den Bergh, S. (2001). "The Detection of Bright Asymptotic Giant Branch Stars in the Nearby Elliptical Galaxy Maffei 1". The Astrophysical Journal 553 (2): L133. doi:10.1086/320692.
- ^ a b Buta, R. J.; McCall, M. L. (1999). "The IC 342/Maffei Group Revealed". The Astrophysical Journal Supplement Series 124: 33. doi:10.1086/313255.
- ^ a b c Buta, R.; McCall, M. L. (2003). "Maffei 1 with the Hubble Space Telescope". The Astronomical Journal 125 (3): 1150. doi:10.1086/367789.
- ^ a b c Davidge, T. J. (2002). "The Upper Asymptotic Giant Branch of the Elliptical Galaxy Maffei 1 and Comparisons with M32 and NGC 5128". The Astronomical Journal 124 (4): 2012. doi:10.1086/342535.
- ^ Davidge, T. J.; Van Den Bergh, S. (2005). "The Globular Cluster Content of Maffei 1". Publications of the Astronomical Society of the Pacific 117 (832): 589. doi:10.1086/430367.
- ^ Karachentsev, I. D.; Sharina, M. E.; Dolphin, A. E.; Grebel, E. K. (2003). "Distances to nearby galaxies around IC 342". Astronomy and Astrophysics 408: 111. doi:10.1051/0004-6361:20030912.
[edit] External links
- Maffei 1
- SEDS: Maffei 1
- Maffei 1 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images
- Galaxies Beyond the Heart: Maffei 1 and 2 - Astronomy Picture of the Day 2010 March 9
