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DDO 44

Coordinates: Sky map 07h 34m 11.5s, +66° 52′ 47″
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DDO 44
An image of DDO 44, as taken by the Hubble Space Telescope
Observation data (J2000 epoch)
ConstellationCamelopardalis
Right ascension07h 34m 11.5s [1]
Declination+66° 52′ 47″ [1]
Redshift0.000711 [1]
Distance9.82 ± 0.59 Mly
Apparent magnitude (V)15.6 [2]
Characteristics
TypedSph [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.

Structure

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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]

References

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  1. ^ a b c d e f "UGCA 133 -- Galaxy". SIMBAD. Retrieved 19 August 2020.
  2. ^ "NASA/IPAC Intergalactic Database". Retrieved 20 August 2020.
  3. ^ a b Karachentsev et al. 2011, p. L34.
  4. ^ Carlin et al. 2019, p. 1.
  5. ^ a b c d Alonso‐García et al. 2006, p. 580.
  6. ^ Carlin et al. 2019, p. 2.
  7. ^ Carlin et al. 2019, p. 4.
  8. ^ Karachentsev et al. 1999, p. 5.
  9. ^ Karachentsev et al. 1999, p. 7.
  10. ^ Karachentsev et al. 2011, p. L33.
  11. ^ Alonso‐García et al. 2006, p. 581.
  12. ^ a b Carlin et al. 2019, p. 8.

Bibliography

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