A new eye on the cosmos

How are galaxies formed and evolve? And how do central supermassive black holes form in galaxies and influence their hosts? These are two of the big questions that Tufts astronomers hope to answer when they begin to use a new, extremely sensitive instrument that should be on line in a few years on a historic Hawaiian telescope.

Danilo Marchesini and Anna Sajina, both associate professors, are part of a major international group in charge of building the state-of-the-art Focus Focus (PFS) spectrograph, which will be located on the Mauna Kea summit in Hawaii.

The PFS will use 2,400 optical fibers at the top of Subaru's existing 8.2-meter telescope, enabling it to simultaneously display 2,400 astronomical objects in the night sky. These data will be introduced into four spectrographs, each connected to 600 optical fibers. Spectrographs separate the light into different wavelengths, thus collecting information about the invisible light for the eyes. "They basically consist of three cameras: an ultraviolet camera, an optical-visual camera and a near infrared camera," said Marchesini.

The tests will start in 2020 and the PFS is expected to be fully operational by the end of 2021 or early 2022. The multinational team responsible for the construction of the instrument is led by scientists from Japanese, Taiwanese, Brazilian, Chinese institutions , French and American, including CalTech Johns Hopkins University and Princeton.

Tufts is part of the PFS Northeastern Participation Group (NEPG), whose other members are professors from the University of Connecticut, from the University of Illinois at Urbana-Champaign, from the University of Connecticut. Columbia University and the University of Pittsburgh. Marchesini is the NEPG President and represents him as a member of the PFS Steering Committee.

Being part of the PFS team means that Tufts astronomers have access to the instrument for 300 to 350 nights over a period of about five or six years for a series of research experiments. and that they will have immediate access to the generated data. While Sajina and Marchesini are studying the formation of galaxies and actively growing supermassive black holes, other groups will explore the origins of dark matter and black energy, as well as the history of our own Milky Way and its satellite galaxies.

In astronomy, access to these new instruments is highly sought after, said Marchesini. "Anna and I are part of PFS, so we each have four junior members of our research group with the same unlimited and unlimited access to data, which includes post-docs, graduate students and undergraduates," he said. declared Marchesini.

This greatly expands opportunities for Tufts students and post-docs, who will have access to data generated by PFS and who could also potentially participate in other areas of PFS research. "It is possible to create at Tufts a new scientific world that previously was not available internally," said Marchesini.

Being part of PFS and having so many nights of guaranteed data will also contribute to the search for funding for further astronomy research. "Because we already have guaranteed data, we do not need to prove to the funding agency that we will be able to obtain such advanced data," said Marchesini.

He noted that this access to PFS had already proved beneficial. Sajina, who is on sabbatical this semester to do research at CalTech, is the principal investigator of a research project using NASA's Spitzer Space Telescope, which was funded partly on the basis of his participation in PFS.

Supermassive black holes and the evolution of galaxies

Sajina and Marchesini already have detailed plans for their nights on the PFS. Their primary goal is to use it to understand how galaxies are formed and evolve, and in particular how supermassive black holes located at the center of galaxies affect the evolution of all galaxies. They examine what are called active galactic nuclei: when materials fall into supermassive black holes and emit enormous amounts of radiation.

They will use at least 100 nights to study the connection between these active galactic nuclei and the evolution of galaxies. To do this, they will examine the light of the part of the spectrum related to what is called the cosmic midi, the period of formation of active stars in the universe there are about 10 billion d & # 39; 39; years.

They will also examine how galaxies stop their star formation – "for example, the physical mechanisms to extinguish star formation, passing them from galaxies into star formation at resting galaxies" said Marchesini.

They also hope to learn how the environment of a galaxy affects it. Galaxies are not uniformly distributed in the universe. There is "a sort of distribution of spider web galaxies, with filaments," said Marchesini. "When these filaments meet, you get clusters of galaxies." A big question is how does this global environment of large structures affect the evolution of the galaxy.The PFS will allow us to study this, for the first time at cosmic noon. "