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These notes correspond to a couple of Lectures given at the School of Astrophysics "F. Lucchin" for PhD students and young researchers, held in Erice, Italy, in September 2011. One of the two subjects of the School was Galaxy Bulges, and the presentation slides are available online 1. The content in the slides is significantly more extended than what the limited space here allows, and I stay considerably on the deceptively simple, difficult subject of bulge definitions. Current literature abounds with confusion, and I thus dedicate space to try and shed some light on this topic, not only for those beginning their way, but hopefully also for a broader audience in need.

I would like to right away acknowledge reference publications which have influenced my view substantially. These are Binney & Tremaine (1987), Wyse et al. (1997), Binney & Merrifield (1998), Kormendy & Kennicutt (2004) and Athanassoula (2005). Also important are the relatively recent Conference Proceedings of the IAU Symp. 245, and the recent review by Graham (2011). Although I did my best to cope with the enormous body of literature covering the subject, the reference list is but a tiny fraction of it. In order to minimize this inherent bias in these Notes, Fig. 1 displays word-clouds with the first authors of papers on galaxy bulges published in two different periods: 1970-2000 and 2001-2012 (mid-May). Font sizes are porportional to number of papers, rather than citations, as the latter are also biased to some extent. I hope that this will alert the reader to authors and studies other than those I quote here. Figure 1 also shows word-clouds made with common words in the abstracts of these publications. It is interesting to see that these words have not changed much in the two periods, with few notable exceptions, including the word `black-hole'.

Figure 1

Figure 1. Top left: authors with first-author papers in the period 1970-2000 in ApJ, AJ, MNRAS and A&A with the words `bulge(s)' and `galaxy(ies)' in the abstract. The word-cloud is limited to authors with three or more publications, and the font size is proportional to the number of papers. Bottom left: most common relevant words in the abstracts of all such publications in the period. Top right and bottom right are the corresponding word clouds for the period 2001-2012 (mid-May). In the 1970-2000 period, this search returns 1562 published papers, and 143 authors with more than three first-author papers. For the period 2001-2012, these figures change to 1999 papers and 178 authors.

1 See Back.

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