NGC 6503

NGC 6503 is a field^[8] dwarf spiral galaxy ^{[dubious – discuss]} in the northern constellation of Draco. It was discovered by German astronomer Arthur von Auwers on July 22, 1854.^[5] The galaxy has an angular size of 7.1′ × 2.4′^[7] and an apparent visual magnitude of 10.2.^[5] It is located at the distance of 18 million light years away from the Milky Way galaxy.^[4] NGC 6503 may form the remote tip of a long chain of galaxies that extends out into the Local Void, forming a galaxy filament spanning 26 million light-years (8 Mpc).^[9]

NGC 6503
HST image of NGC 6503's spiral arms[1]
Observation data (J2000 epoch)
Constellation	Draco
Right ascension	17h 49m 26.4207s[2]
Declination	+70° 08′ 39.587″[2]
Redshift	0.000143[3]
Heliocentric radial velocity	28[4] km/s
Distance	20.9 ± 2.2 Mly (6.40 ± 0.66 Mpc)[4]
Apparent magnitude (V)	10.2[5]
Characteristics
Type	SAB:(s)bc[6]
Apparent size (V)	7.1′ × 2.4′[7]
Other designations
IRAS 17499+7009, 2MASX J17492651+7008396, UGC 11012, LEDA 60921, MCG +12-17-009[3]

The galactic plane of this galaxy is inclined at an angle of 78°±3° to the plane of the sky,^[4] with the major axis of its oval profile being aligned along a position angle of 121°.^[10] The morphological classification of NGC 6502 is SAB:(s)bc. This indicates a barred spiral galaxy (SAB:) with no inner ring structure (s) and moderately wound spiral arms (bc). However, the ':' notation indicates some uncertainty about the classification. Older works gave it a class of SA(s)bc; i.e. no bar.^[6]

A possible bar system has been reported via infrared observations, being viewed end-on from the perspective of the Earth.^[11][12] Ultraviolet observations show a young, inner star forming ring encircling the bar.^[12] The ring has a radius between 1 and 2.5 kpc from the core.^[13] There is a disk of neutral hydrogen that is larger in extent than the optical disk of the galaxy. This extra-planar gas is mostly the result of star formation activity, rather than cold gas that is being accreted.^[14] There is evidence for a LINER-type or Seyfert 2 nucleus.^[12]

NGC 6503 has one known satellite galaxy,^[15] known as KK 242. With a stellar mass of about 3 million solar masses, KK 242 is on the border between a dwarf irregular galaxy (dIrr) and a dwarf spheroidal galaxy (dSph).^[16]

Gallery

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  NGC 6503 by Hubble Space Telescope
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  NGC 6503 (HST)
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  NGC 6503 from Hubble.