Here is an excellent and
concise and
understandable set of lecture notes, quite descriptive, with only a few equations, about those gigantic spheroidal structures made of stars that we call
Bulges , together with a comparison of Bulges with
Elliptical Galaxies ::
http://arxiv.org/abs/1208.2295
This set of notes is by Dimitri Gadotti, a good and solid and practical Observational Extragalactic Astronomer who focusses on measuring the physical properties of galaxies, in the practical sense of assigning and measuring numerical parameters to various galaxies.
Wisely, in these notes, Gadotti prefers to use
graphs to display the relations between various numerical parameters, which makes this lecture much easier to understand for the "less mathematical brethren"
_____________________________
WANT
EVEN MORE DETAIL?!?! ...........@#@^%&^*^$#!!!??
The following review paper by Alister Graham is rather like an expanded version of Gadotti's lecture notes:
http://astronomy.swin.edu.au/~agraha.../Springer.html
This Long review paper has encyclopaedic coverage of
how the structure of Galaxy Bulges and Elliptical Galaxies is measured and described and classified by today's astronomers.
The classification & description of Elliptical Galaxies and of Galaxy Bulges by today's astronomers, has
little to do with the venerable Hubble galaxy classification system, as it is all about
measuring and graphing numerical parameters such as: surface brightness, galaxy shape, color index, rotational velocity, stellar orbits, etc.
In fact, work on a proper understanding and description and classification of these "big spheroidal structures" had to wait until the mid-1980s when CCDs became available ;
photographic photometry of galaxies had been possible, but it was difficult and slow, and it was often inaccurate!
This review is by Alister Graham, who - in my humble opinion - ranks as one of the top 5 quantitative galaxy morphologists and classifers, very much the heir of the formidable John Kormendy. We are lucky to have Graham in Australia, at Swinburne University.
The lore and mindset and classification terminology of those people who
classify and describe the morphology of bulges, spheroids and Elliptical Galaxies is
very different (and
less accessible to those amateurs who like things at the descriptive level) to the traditional Hubble-style Galaxy Classification efforts of people such as Ron Buta and Harold Corwin and Alan Sandage....... who primarily classify and describe the morphology of the
disk components within galaxies.
Graham is a brilliant example of someone who classifies and describes
spheroidal stellar structures, and this sort of work is not really burdened by the
historical baggage of the venerable Hubble classification system.
