NGC 615

Source: Wikipedia, the free encyclopedia.
85 ± 11 Mly (26.1 ± 3.3 Mpc)[1]
Apparent magnitude (V)11.5
Characteristics
TypeSA(rs)b [1]
Apparent size (V)3.6′ × 1.4′[1]
Other designations
MCG -01-05-008, PGC 5897[1]

NGC 615 is an unbarred

light years from Earth, which, given its apparent dimensions, means that NGC 615 is about 75,000 light years across. It was discovered by William Herschel on January 10, 1785.[2] NGC 615 belongs to the NGC 584 galaxy group, which also includes the galaxies NGC 584, NGC 596, NGC 600, and NGC 636.[3]

The galaxy is included in the Herschel 400 Catalogue. It lies about three degrees northeast from Theta Ceti.[4]

Characteristics

The galaxy has been found to possess a chemically and dynamically decoupled nucleus.[5] Further observations revealed two decoupled components, with the outer one identified as a disk. In the centre of the galaxy (<3" / 0.3 kpc) was found to exist an inclined circumnuclear disk. The stars in the circumnuclear disk have solar metallicity and their median age was determined at 5 billion years. In the bulge of NGC 615 (3"-6") was detected a counterrotating gaseous component.[5]

Further away of the centre (8-30") lies the inner decoupled component, where

HII regions, with the most prominent of them in Hα imaging being a pair located symmetrically with respect to the nucleus at the radius of 20"-23".[6] The mean stellar age in the inner disk outside the HII regions is 5 billion years.[5] The presence of a chemically decoupled nucleus and inner disk suggest a secondary burst of star formation, perhaps provoked by the close passage of another galaxy some gigayears ago.[5]

The outer disk demonstrates a pair of low-contrast outer spiral arms or, more likely, a ring. Its inclination with respect to the line of sight is no more than 60°.[5]

References

  1. ^ a b c d e f g h "NASA/IPAC Extragalactic Database". Results for NGC 615. Retrieved 2016-01-18.
  2. ^ Seligman, Courtney. "NGC 615 (= PGC 5897)". Celestial Atlas. Retrieved 19 November 2018.
  3. S2CID 119194025
    .
  4. ISBN 978-0521858939
    .
  5. ^
    doi:10.1086/320368
    .
  6. S2CID 39130734
    .
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