Free Astronomy Magazine July-August 2019

45 JULY-AUGUST 2019 SPACE CHRONICLES F alse color image of M106. The figure combines neutral hydrogen data taken using the Westerbrook Synthesis Radio Telescope (WSRT) in blue, with optical images ob- tained with the (CFHT) in green and red. The yellow circles highlight the observed globular clusters, which are arranged on a disk that rotates in phase and at the same speed as the neutral gas. [Divakara Mayya (INAOE)] globular clusters and to distinguish them from other ap- parent point sources such as stars, and distant galaxies. To do that one needs to take spectra to show that each clus- ter has a coeval population of old stars and really belongs to the galaxy under study. For Divakara Mayya, a researcher at the Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE), the second author of the article “The observations with the GTC and OSIRIS are essential for the success of the study, because the objects are quite far away, and so they need expo- sures of more than one hour with the largest optical-in- frared telescope in the world to be able to extract the relevant information from the spectra. The OSIRIS instru- ment (Optical System for Imaging and low-Intermediate- Resolution Integrated Spectroscopy) is a multi-object spectrograph built at the Instituto de Astrofísica de Ca- narias (IAC) in collaboration with Mexico, which is capable of observing several objects at a time.” “To have this capacity for multiplexing, that is to obtain several spectra simultaneously, is fundamental for this type of studies, and it is offered on three of the current instruments on the GTC, covering the optical and the in- frared” explains Antonio Cabrera, head of scientific oper- ations on the GTC. For this work, 23 candidate globular clusters in two fields were observed. This article is one result from a wider project which will study the systems of globular clusters in nine spiral galax- ies within a radius of 52 million light years, in order to look into the relation between the number of globular clusters and the mass of the central black hole in spiral galaxies. “This relation if very tight for elliptical galaxies, but it is not so clear in spiral galaxies, such as the Milky Way,” comments researcher Lopezlira. “The nine galaxies which we plan to study have good estimates of the masses of their central black holes, and lie at distances where we can make good studies of their globular clusters.” This recent study confirms that there is a correlation be- tween the number of globular clusters and the mass of the central black hole in M106 and proves the accuracy of the photometric method used at the GTC. “Studies of this type in more spiral galaxies can clarify the role of the dif- ferent hypotheses proposed for galaxy assembly, and that of the globular clusters and central black holes” claims the first author of the work. !