DDO 44 | |
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![]() An image of DDO 44, as taken by the
Hubble Space Telescope | |
Observation data ( J2000 epoch) | |
Constellation | Camelopardalis |
Right ascension | 07h 34m 11.5s [1] |
Declination | +66° 52′ 47″ [1] |
Redshift | 0.000711 [1] |
Distance | 9.82 ± 0.59 Mly |
Apparent magnitude (V) | 15.6 [2] |
Characteristics | |
Type | dSph [3] |
Apparent size (V) | 1′.51 × 0′.998 [1] |
Other designations | |
UGCA 133, Anon 0729+66, LEDA 21302, KK98a 61, KK98a 072913.1+665940 [1] |
DDO 44 (or UGCA 133) is a dwarf spheroidal galaxy in the M81 Group, believed to be a satellite galaxy of the nearby NGC 2403.
DDO 44 is a relatively large dwarf galaxy, and it has been observed to possess a tidal tail extending at least 50,000 parsecs from its center. [4] It has an estimated metallicity ([Fe/H]) of -1.54 ± 0.14. [5] Due to its proximity and relative velocity to the larger NGC 2403, it is believed to be NGC 2403's satellite galaxy. [6] Stellar streams has been observed to originate from DDO 44, flowing towards and away for NGC 2403, indicating tidal disruptions. [7] Around 20 percent of the galaxy's stars are believed to be of intermediate age (between 2-8 Gya), [5] with the most recent stellar formation being estimated at 300 Mya due to a lack of young bright blue stars. [8] This lack of bright stars caused DDO 44 to have a relatively low level of brightness. [5]
It is located approximately 3 million parsecs away from the Milky Way, [5] [9] and 79 arcminutes towards north-northwest from NGC 2403 (or approximately 75 kpc). [10] [11] Mass estimates based on luminosity measurements give a galactic mass of 2×107–6×107 M☉. [12] This makes DDO 44 by far NGC 2403's most massive known satellite galaxy, with the other known satellite galaxy (MADCASH J074238+652501-dw) having a mass of just ~105 M☉. [12] HI observations place an upper limit for DDO 44's hydrogen gas mass at 4×105 M☉. [3]