Mexican researcher heads int’l project on globular clusters

Mexico City — Rosa Amelia Gonzalez Lopezlira, a researcher with the National Autonomous University of Mexico (UNAM), headed an international scientific project that discovered globular clusters in the Messier 106 spiral galaxy that formed relatively soon after the Big Bang, UNAM announced on Sunday.

Globular clusters are very brilliant nearly spherical whirling conglomerations of between 100,000 and a million stars in galaxies, including the Milky Way, which has at least 160 of them, UNAM said in a bulletin.

These objects formed shortly after the Big Bang some 13.8 billion years ago and shortly before the cosmic rate of star formation reached its maximum some 10 billion years ago, the milestone known among scientists as “cosmic noon.”

Because of their great age, the clusters preserve information about that early epoch and can provide keys as to how galaxies formed.

According to the findings of the study, the stellar concentrations in M106, which were observed and analyzed with two international telescopes, are part of a disk that spins as rapidly as the galaxy’s disk of gas. “This had never been observed before,” said the researcher with UNAM’s Radio Astronomy and Astrophysics Institute (IRyA).

The results of the study were published on May 1 in The Astrophysical Journal.

“The hypothesis is that the spatial distribution (of the clusters) that we observe today is the same that they had when they formed. So, that disk of clusters which has not been perturbed could give us information about the very early phases of the evolution of the Universe,” Gonzalez Lopezlira said.

Collaborating on this international project were 13 scientists from Australia, Germany, Brazil, Chile, France, Denmark and Mexico.

The Mexican contingent was headed by Gonzalez Lopezlira as the primary author and included secondary author Divaraka Mayya, a researcher with the National Institute of Astrophysics, Optics and Electronics (INAOE), Laurent Loinard with IRyA and doctoral student Luis Lomeli with INAOE.

As part of their research, the astrophysicists first used the Canada-France-Hawaii telescope located on the Pacific island and then the Gran Telescopio Canarias, on the Spanish island of La Palma in the Canary Islands.

“Thanks to the fact that Mexico is participating in the Gran Telescopio Canarias, the largest in the world, we could perform part of the research there. We used a multi-object spectrograph called OSIRIS, with which several spectra can be obtained at the same time. We observed 23 globular cluster candidates in two fields,” Gonzalez Lopezlira said.

The researchers found that the number of globular clusters in M106 - a spiral galaxy like the Milky Way - is proportional to the mass of the supermassive black hole at the center of that galaxy, just as occurs in elliptical galaxies.

The black hole in M106 - which is located between 22 and 25 million light years away from Earth - has a mass 40 million times that of the Sun and 10 times more than the Milky Way’s own central black hole.

The Mexican researcher said that studies of this kind on more spiral galaxies could clarify how galaxies, their globular cluster systems and their black holes formed.