Draft:Early-type galaxy
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An early-type galaxy (ETG) is an elliptical or lenticular galaxy in the Hubble sequence. These galaxies usually have smooth light distributions and no prominent spiral arms.[1] The word early refers to their place in the classification sequence, not to their age or stage of evolution.[2]
Most nearby early-type galaxies are dominated by older stars and lie on the red sequence. They generally contain less cold gas and have lower rates of star formation than spiral galaxies, although some retain molecular gas.[1] The ATLAS3D survey detected carbon monoxide, a tracer of molecular gas, in 56 of 259 early-type galaxies, giving a detection rate of 22 ± 3 per cent.[3]
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Integral field spectroscopy has revealed differences in their internal stellar motions. Fast rotators show strong, ordered rotation and often retain flattened, disc-like structures, while slow rotators have lower stellar angular momentum and tend to be rounder and more massive.[1] Slow rotators accounted for 14 ± 2 per cent of the 260 galaxies examined by the ATLAS3D survey.[4]
See also
[edit]References
[edit]- 1 2 3 Cappellari, Michele (2016). "Structure and Kinematics of Early-Type Galaxies from Integral-Field Spectroscopy". Annual Review of Astronomy and Astrophysics. 54: 597–665. arXiv:1602.04267. Bibcode:2016ARA&A..54..597C. doi:10.1146/annurev-astro-082214-122432.
- ↑ Baldry, Ivan K. (2008). "Hubble's galaxy nomenclature". Astronomy & Geophysics. 49 (5): 5.25 – 5.26. arXiv:0809.0125. Bibcode:2008A&G....49e..25B. doi:10.1111/j.1468-4004.2008.49525.x.
- ↑ Young, Lisa M.; Bureau, Martin; Davis, Timothy A.; Combes, Françoise; et al. (2011). "The ATLAS3D project – IV. The molecular gas content of early-type galaxies". Monthly Notices of the Royal Astronomical Society. 414 (2): 940–967. arXiv:1102.4633. Bibcode:2011MNRAS.414..940Y. doi:10.1111/j.1365-2966.2011.18561.x.
- ↑ Emsellem, Eric; Cappellari, Michele; Krajnović, Davor; Alatalo, Katherine; et al. (2011). "The ATLAS3D project – III. A census of the stellar angular momentum within the effective radius of early-type galaxies: unveiling the distribution of fast and slow rotators". Monthly Notices of the Royal Astronomical Society. 414 (2): 888–912. arXiv:1102.4444. Bibcode:2011MNRAS.414..888E. doi:10.1111/j.1365-2966.2011.18496.x.