NGC 2403

NGC 2403 (also known as Caldwell 7) is an intermediate spiral galaxy in the constellation Camelopardalis. It is an outlying member of the M81 Group,[3] and is approximately 8 million light-years distant. It bears a similarity to M33, being about 50,000 light years in diameter and containing numerous star-forming H II regions.[4] The northern spiral arm connects it to the star forming region NGC 2404.[3] NGC 2403 can be observed using 10×50 binoculars.[3] NGC 2404 is 940 light-years in diameter, making it one of the largest known H II regions. This H II region represents striking similarity with NGC 604 in M33, both in size and location in galaxy.

NGC 2403
A Hubble Space Telescope (HST), and Subaru image of NGC 2403. NGC 2404 is visible
Observation data (J2000 epoch)
ConstellationCamelopardalis
Right ascension07h 36m 51.4s[1]
Declination+65° 36′ 09″[1]
Redshift131 ± 3 km/s[1]
Distance9.65 Mly (2.96 Mpc)[2]
Apparent magnitude (V)8.9[1]
Characteristics
TypeSAB(s)cd[1]
Apparent size (V)21.9′ × 12.3′[1]
Other designations
UGC 3918,[1] PGC 21396,[1] Caldwell 7

Supernovae

There have been two reported supernovae in the galaxy: SN 1954J, which attained a magnitude of 16 at its brightest, and SN 2004dj. SN 2004dj was the nearest and brightest supernovae in the past 17 years. It remains nearest and brightest supernova in 21st century.

History

The galaxy was discovered by William Herschel in 1788. Edwin Hubble detected Cepheid variables in NGC 2403 using the Hale telescope, making it the first galaxy beyond the Local Group within which a Cepheid was discovered.[3] By 1963, 59 variables had been found in NGC 2403, of which 17 were eventually confirmed as Cepheids, with periods between 20 and 87 days. As late as 1950 Hubble was using a distance of just under 2 million light years for the galaxy's distance, but by 1968 the analysis of the Cepheids increased this by almost a factor of five, to within 0.2 magnitudes of the current value.

Companions

NGC 2403 has two known companions. One is the relatively massive dwarf galaxy DDO 44. It is currently being disrupted by NGC 2403, as evidenced by a tidal stream extending 82 kly (25 kpc) on both sides of DDO 44. DDO 44 is approaching NGC 2403 at a distance much closer than typical for dwarf galaxy interactions. It currently has a V-band absolute magnitude of −12.9, but its progenitor was even more luminous.[2]

The other known companion is officially named MADCASH J074238+652501-dw, although it is nicknamed MADCASH-1. The name refers to the MADCASH (Magellanic Analog Dwarf Companions and Stellar Halos) project. MADCASH-1 is similar to typical dwarf spheroidal galaxies in the Local Group; it is quite faint, with an absolute V-band magnitude of −7.81, and has only an ancient, metal-poor population of red giant stars.[5]

A Galaxy of Birth and Death

See also

References
  1. "NASA/IPAC Extragalactic Database". Results for NGC 2403. Retrieved 2006-11-21.
  2. 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. S2CID 195218404.
  3. Kepple, George Robert; Glen W. Sanner (1998). The Night Sky Observer's Guide. Vol. 1. Willmann-Bell, Inc. p. 73. ISBN 978-0-943396-58-3.
  4. Ho, Luis C.; Filippenko, Alexei V.; Sargent, Wallace L. W. (October 1997). "A Search for "Dwarf" Seyfert Nuclei. III. Spectroscopic Parameters and Properties of the Host Galaxies". Astrophysical Journal Supplement. 112 (2): 315–390. arXiv:astro-ph/9704107. Bibcode:1997ApJS..112..315H. doi:10.1086/313041. S2CID 17086638.
  5. Carlin, Jeffrey L.; Mutlu-Pakdil, Burçin; Crnojević, Denija; Garling, Christopher T.; Karunakaran, Ananthan; Peter, Annika H. G.; Tollerud, Erik; Forbes, Duncan A.; Hargis, Jonathan R.; Lim, Sungsoon; Romanowsky, Aaron J.; Sand, David J.; Spekkens, Kristine; Strader, Jay (2021). "Hubble Space Telescope Observations of Two Faint Dwarf Satellites of Nearby LMC Analogs from MADCASH". The Astrophysical Journal. 909 (2): 211. arXiv:2012.09174. Bibcode:2021ApJ...909..211C. doi:10.3847/1538-4357/abe040. S2CID 229297953.
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