Do galaxies form a spectroscopic sequence?
Abstract
We identify a spectroscopic sequence of galaxies, analogous to the Hubble sequence of morphological types, based on the Automatic Spectroscopic K-means-based (ASK) classification. Considering galaxy spectra as multidimensional vectors, the majority of the spectral classes are distributed along a well-defined curve going from the earliest to the latest types, suggesting that the optical spectra of normal galaxies can be described in terms of a single affine parameter. Optically bright active galaxies, however, appear as an independent, roughly orthogonal branch that intersects the main sequence exactly at the transition between early and late types.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- August 2011
- DOI:
- 10.1111/j.1365-2966.2011.18869.x
- arXiv:
- arXiv:1104.1388
- Bibcode:
- 2011MNRAS.415.2417A
- Keywords:
-
- methods: data analysis;
- methods: statistical;
- galaxies: fundamental parameters;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- 10 pages, 11 figures, accepted by MNRAS