NGC 2775

NGC 2775, also known as Caldwell 48, is a spiral galaxy in the constellation Cancer. It is 67 million light-years (20.5 megaparsecs)^[3] away from the Milky Way. It was discovered by William Herschel in 1783. NGC 2775 belongs to the Antlia-Hydra Cluster^[10] of galaxies and is the most prominent member of the NGC 2775 Group, a small galaxy group in the Virgo Super-cluster, along with the Local Group. Other members of the NGC 2775 Group include NGC 2777 and UGC 4781.^[11]

NGC 2775
NGC 2775 imaged by the Hubble Space Telescope
Observation data (J2000 epoch)
Constellation	Cancer
Right ascension	09h 10m 20.112s[1]
Declination	+07° 02′ 16.53″[1]
Redshift	1,316.4±13.4 km/s[2]
Distance	67 Mly (20.5 Mpc)[3]
Apparent magnitude (V)	10.4[4]
Characteristics
Type	SAa[5] or SA(r)ab[6]
Size	79,000 ly (24.23 kpc) (estimated)[7]
Apparent size (V)	4.3′ × 3.3′[6]
Other designations
UGC 4820,[8] PGC 25861,[9] Caldwell 48

This object has a morphological classification of SA(r)ab,^[6] which indicates an unbarred spiral galaxy (SA) with a prominent ring structure (r) and flocculent,^[12] tightly wound spiral arms (ab).^[13] The galaxy is inclined by an angle of 44° to the line of sight from the Earth.^[6] The galactic nucleus is not active^[2] and the large nuclear bulge, which extends out to an angular radius of 0.4′,^[13] is relatively gas free.^[12] An explanation for the latter could be a high supernova rate.^[6] Although star formation is taking place in the dusty outer ring,^[13] NGC 2775 does not display any current starburst activity,^[14] and the galactic nucleus is virtually free of any star formation whatsoever.^[12]

The galaxy's hydrogen tail feature indicates a past interaction with a faint companion.^[6] A satellite galaxy appears to have orbited NGC 2775 multiple times, losing mass as it did so and creating faint, shell-like structures.^[13] Nearby irregular galaxy NGC 2777 displays a tidal tail of hydrogen gas that points back to NGC 2775, suggesting the two may be linked.^[15]

One supernova has been observed in NGC 2775. SN 1993Z (type Ia, mag. 13.9) was discovered by the Leuschner Observatory Supernova Search (LOSS) on 23 September 1993.^[16][17] By September 25, spectral analysis showed that it had peaked about four weeks earlier.^[16]

Gallery

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  NGC 2775 imaged with a 32-inch telescope.
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  Map showing the location of NGC 2775.
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  NGC 2775 (SDSS DR14)
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  NGC 2775 from the Hubble Space Telescope