NGC 7625

NGC 7625, or Arp 212, is a peculiar galaxy in the constellation of Pegasus. It was discovered on October 15, 1784, by William Herschel.^[8] In his New General Catalogue (1888), J. L. E. Dreyer described it as pretty bright, considerably small, round, with a suddenly much brighter middle.^[9] It is located at an estimated distance of 78 million light-years (24.0 megaparsecs) from the Milky Way galaxy.^[3]

NGC 7625
Sloan Digital Sky Survey image of NGC 7625
Observation data (J2000 epoch)
Constellation	Pegasus
Right ascension	23h 20m 30.132s[1]
Declination	+17° 13′ 32.16″[1]
Heliocentric radial velocity	1,630±3 km/s[2]
Distance	78.3 ± 7.5 Mly (24.0 ± 2.3 Mpc)[3]
Apparent magnitude (V)	12.9[4]
Apparent magnitude (B)	12.94[5]
Characteristics
Type	Sa/S pec[6]
Mass/Light ratio	2.5[4] M☉/L☉
Apparent size (V)	1.6′ × 1.4′[5]
Other designations
NGC 7625, Arp 212, UGC 12529, LEDA 71133, MCG +03-59-038, PGC 71133[7]

Halton Arp included NGC 7625 as object 212 in his Atlas of Peculiar Galaxies, indicating it displayed unexplained physical processes.^[10] In the Third Reference Catalogue of Bright Galaxies, NGC 7625 was assigned a morphological classification of SA(rs)a pec, which indicates a peculiar spiral galaxy (SA) with a transitional ring structure (rs) and tightly wound spiral arms (a).^[11] In 1981 it was designated a blue compact dwarf by T. X. Thaun and G. E. Martin on the basis of strong emission lines from ionized gas.^[12] A prominent visible feature is an open ring of dust lanes with an angular radius of about 15″–20″.^[13]

NGC 7625 displays indications of a recent interaction with another galaxy. Velocity measurements suggest the inner part of the galaxy is rotating in a different plane than the outer parts. The angle between these two planes increases with distance from the galactic center, reaching 50° at a radius of 6 kpc. Hence this may be a polar-ring galaxy, with the added gas accreted from the dwarf satellite galaxy UGC 12549.^[13] There is a large amount of gas and dust undergoing significant star formation, with emission of H-alpha concentrated at the core and in separate knots along exterior curved structures.^[6]

On October 28, 2023 type Ia supernova SN 2023vyl was discovered in this galaxy by ATLAS.^[14][15]