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DDO 44
An image of DDO 44, as taken by the Hubble Space Telescope
Observation data (J2000 epoch)
Constellation	Camelopardalis
Right ascension	07 34 11.5
Declination	+66° 52′ 47″
Redshift	0.000711
Distance	9.82 ± 0.59 Mly
Apparent magnitude (V)	15.6
Characteristics
Type	dSph
Apparent size (V)	1′.51 × 0′.998
Other designations
UGCA 133, Anon 0729+66, LEDA 21302, KK98a 61, KK98a 072913.1+665940

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

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. It has an estimated metallicity () of -1.54 ± 0.14. Due to its proximity and relative velocity to the larger NGC 2403, it is believed to be NGC 2403's satellite galaxy. Stellar streams has been observed to originate from DDO 44, flowing towards and away for NGC 2403, indicating tidal disruptions. Around 20 percent of the galaxy's stars are believed to be of intermediate age (between 2-8 Gya), with the most recent stellar formation being estimated at 300 Mya due to a lack of young bright blue stars. This lack of bright stars caused DDO 44 to have a relatively low level of brightness.

It is located approximately 3 million parsecs away from the Milky Way, and 79 arcminutes towards north-northwest from NGC 2403 (or approximately 75 kpc). Mass estimates based on luminosity measurements give a galactic mass of 2×10–6×10 M_☉. 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 ~10 M_☉. H_I observations place an upper limit for DDO 44's hydrogen gas mass at 4×10 M_☉.

References

1. ^ "UGCA 133 -- Galaxy". SIMBAD. Retrieved 19 August 2020.
2. "NASA/IPAC Intergalactic Database". Retrieved 20 August 2020.
3. ^ Karachentsev et al. 2011, p. L34.
4. Carlin et al. 2019, p. 1.
5. ^ 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. ^ Carlin et al. 2019, p. 8.

Bibliography

• Alonso-García, Javier; Mateo, Mario; Aparicio, Antonio (2006). "DDO 44 and UGC 4998: Distances, Metallicities, and Star Formation Histories". Publications of the Astronomical Society of the Pacific. 118 (842): 580–589. Bibcode:2006PASP..118..580A. doi:10.1086/502984. ISSN 0004-6280. S2CID 120814156.
• Carlin, Jeffrey L.; Garling, Christopher T.; Peter, Annika H. G.; Crnojević, Denija; Forbes, Duncan A.; Hargis, Jonathan R.; Mutlu-Pakdil, Burçin; Pucha, Ragadeepika; Romanowsky, Aaron J.; Sand, David J.; Spekkens, Kristine; Strader, Jay; Willman, Beth (2019). "Tidal Destruction in a Low-mass Galaxy Environment: The Discovery of Tidal Tails around DDO 44". The Astrophysical Journal. 886 (2): 109. arXiv:1906.08260. Bibcode:2019ApJ...886..109C. doi:10.3847/1538-4357/ab4c32. ISSN 1538-4357. S2CID 195218404.
• 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.
• Karachentsev, Igor; Kaisina, Elena; Kaisin, Serafim; Makarova, Lidia (2011). "Emission sparks around M 81 and in some dwarf spheroidal galaxies: Emission sparks in dSph galaxies". Monthly Notices of the Royal Astronomical Society: Letters. 415 (1): L31 – L34. arXiv:1104.5318. doi:10.1111/j.1745-3933.2011.01069.x.

v t e Constellation of Camelopardalis
Camelopardalis in Chinese astronomy List of stars in Camelopardalis
Stars	Bayer α β γ Flamsteed 1 2 3 4 5 7 8 11 12 14 15 16 17 18 19 20 21 22 23 24 26 28 29 30 31 33 34 35 36 37 38 39 40 41 42 43 49 51 53 Variable U Z RU ST TX VZ BD BE BK BN CE CO CQ CS DD MY HR 967 1046 1073 1112 1124 1129 1138 1158 1192 1204 1205 1241 1242 1305 1313 1314 1327 1335 1342 1401 1440 1491 1527 1561 1624 1636 (Mago) 1675 1683 1686 1720 1844 1916 2209 2363 2396 2401 2527 2581 2830 3075 3082 3216 4062 4084 4609 (Tonatiuh) 4892 4893 5009 5091 5203 HD 35759 Other 2MASS J05325346+8246465 Gliese 445 NGC 2363-V1 PSR B0329+54 Stein 2051 Struve 1694 XO-3 XO-6
Exoplanets HD 32518 b HD 33564 b HD 104985 b XO-3b XO-6b
Star clusters NGC 1502
Nebulae IC 3568 (Lemon Slice Nebula) M4-18 NGC 1501 NGC 2404
Galaxies	NGC 1530 1560 1569 1573 1573A 1961 2146 2336 2363 2366 2403 2441 2460 2523 2655 2715 2748 5640 Other DDO 44 IC 342 IRAS 07598+6508 MACS0647-JD UGC 3478 UGC 3730 UGCA 86
Galaxy clusters MACS J0647.7+7015 MS 0735.6+7421
Astronomical events SN 1996ah GRB 970508 SN 2004dj SN 2010lt
Category

• Dwarf spheroidal galaxies
• M81 Group
• UGCA objects
• Camelopardalis