|
The brightnesses of the globulars of M104
The question "How bright are the brightest globular clusters of M104?" has already been answered in several studies of the various brightnesses and sizes of the very numerous globulars belonging to the Sombrero.
In a paper by W.E. Harris et al., (see this preprint: arxiv 0909.4805 , which can be found at //arxiv.org), their
figure 10 shows a plot of the apparent magnitudes and B-V colours and B-R colours of a sample of the globular clusters belonging to M104.
From this graph, the following can confidently be said about how bright the many globulars are:
(1) There are a handful (say four or five) of very luminous globulars that are at an R-band (red) magnitude of around 18.3 , which corresponds to a B-band(blue) magnitude of around 19.6 (for a certain assumed colour of the clusters).
The most luminous globular clusters belonging to the Sombrero are therefore at a V-band (visual) magnitude of about 18.9
(2) These very luminous clusters are few in number, and are not representative of the overwhelmingly large numbers of fainter globulars that are found around M104.
(3) The system of multiple globular star clusters belonging to the Sombrero only starts to become reasonably populous at an R-band (red) magnitude of 19 or fainter, which corresponds to a B-band (blue) magnitude of 20.2 to 20.6
(4) The B-V optical colours of the numerous individual clusters around M104 vary between 0.65 and 1 . This is a substantial variation in colour.
Thus, it would seem that it would be quite a tough job to get that "swarm of bees" effect in an image of the the globular clusters of M104, as you would need to image at least two magnitudes deeper than the magnitudes I have mentioned!!
cheers,
madbadgalaxyman
|