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]
Karachentsev, I. D.; Sharina, M. E.; Grebel, E. K.; Dolphin, A. E.; Geisler, D.; Guhathakurta, P.; Hodge, P. W.; Karachentseva, V. E.; Sarajedini, A.; Seitzer, P. (1999). "The dwarf spheroidal galaxy DDO 44: stellar populations and distance". Astronomy and Astrophysics. 352: 399. arXiv:astro-ph/9910402. Bibcode:1999A&A...352..399K.
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