Wolf-Lundmark-Melotte

From Wikipedia, the free encyclopedia

Wolf-Lundmark-Melotte Galaxy

Wolf-Lundmark-Mellote galaxy.
Observation data (J2000 epoch)
Constellation Cetus
Right ascension 00h 01m 58.1s[1]
Declination -15° 27′ 39″[1]
Redshift -122 ± 2 km/s[1]
Distance 3.04 ± 0.11 Mly (930 ± 30 kpc)[2]
Type IB(s)m[1]
Apparent dimensions (V) 11′.5 × 4′.2[1]
Apparent magnitude (V) 11.0[1]
Notable features -
Other designations
WLM,[1] DDO 221,[1] UGCA 444,[1] PGC 143[1]
See also: Galaxy, List of galaxies

The Wolf-Lundmark-Melotte (WLM) galaxy is an irregular galaxy discovered in 1909 by Max Wolf, and is located on the outer edges of the local group. The discovery of the nature of the galaxy was accredited to Knut Lundmark and Philibert Jacques Melotte in 1926. It is in the constellation Cetus.

[edit] Star formation

In 1999, A. E. Dolphin used the Hubble Space Telescope to create a color-magnitude diagram for WLM. It showed that around half of all the star formation in this galaxy occurred during a burst that started ~13 Gyr ago. During the burst, the metallicity of WLM rose from [Fe/H] ~ -2.2 to [Fe/H] -1.3. There being no horizontal-branch population, Dolphin concludes that no more than ~20 M☉ per Myr of star formation occurred in the period from 12 to 15 Gyr ago. From 2.5 to 9 Gyr ago, the mean rate of star formation was 100 to 200 M☉ per Myr.[3]

[edit] Globular cluster

WLM has one known globular cluster that Hodge et al. (1999) determined has Mv = -8.8 and [Fe/H] = -1.5 with an age of ~15 Gyr. This cluster has a luminosity that is slightly over the average for all globulars. The seeming lack of faint low-mass globular clusters can not be explained by the weak tidal forces of the WLM system.[3]

[edit] References

  1. ^ a b c d e f g h i j NASA/IPAC Extragalactic Database. Results for WLM. Retrieved on 2006-12-23.
  2. ^ McConnachie, A. W.; Irwin, M. J.; Ferguson, A. M. N.; Ibata, R. A.; Lewis, G. F.; Tanvir, N. (2005). "Distances and metallicities for 17 Local Group galaxies". Monthly Notices of the Royal Astronomical Society 356 (4): 979–997. doi:10.1111/j.1365-2966.2004.08514.x. 
  3. ^ a b van den Bergh, Sidney (April 2000), “Updated Information on the Local Group”, The Publications of the Astronomical Society of the Pacific 112 (770): 529-536, <http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2000PASP..112..529V>