The search for quasars within the Southern Photometric Local Universe Survey (S-PLUS)


Horário de início



Aud. Prof. Paulo Benevides Soares – IAG/USP (Rua do Matão, 1226 - Cidade Universitária) - Palestrante presencial



The search for quasars within the Southern Photometric Local Universe Survey (S-PLUS)

Lilianne Nakazono


Quasars are known to be the most energetic objects in the Universe. They are key to understanding the physics surrounding supermassive black holes, the evolution of galaxies, and the properties of the intergalactic medium. Since the first quasar discovery in 1963, the number of confirmed quasars increased to about a million. The Sloan Digital Sky Survey, among many surveys, has provided the largest number of confirmations with more than 700 thousand quasars in two decades. This would have not been possible without an understanding of the quasar's photometric space in the optical (broad bands) and near-infrared colors.
We want to search for new quasars in the southern hemisphere using data from the Southern Photometric Local Universe Survey (S-PLUS). S-PLUS will observe a total area of ~9300 squared degrees with a 0.8m telescope at the Cerro Tololo Inter-American Observatory (CTIO, Chile). Up to this date, S-PLUS has provided observations with the highest number of narrow bands and the largest area in the southern hemisphere (~3000 squared degrees in S-PLUS DR4). This makes S-PLUS a good laboratory for empirically evaluating the narrow-band importance, which will be useful for the next generation of surveys, including LSST after their 10-year survey.
In this talk, I will present our efforts in constructing a quasar candidate catalog for S-PLUS. This involves developing an object classifier that will return the most probable class (quasar, star, or galaxy) for each detected source in S-PLUS. Afterward, we estimate photometric redshifts for our quasar candidates so we can select the best candidates for spectroscopic follow-up. We also study how informative the S-PLUS narrow-band photometry is for these specific tasks. I will finish this talk with our prospects on identifying anomalous quasars and mention my collaboration on some side projects, such as the classification of white dwarfs and giant stars for S-PLUS.

Lilianne Nakazono obtained her bachelor's degree in Statistics in 2013 from Instituto de Matemática e Estatística (USP). In 2016 she obtained her bachelor's degree in Astronomy at IAG-USP and then joined a Ph.D. program at the same institute in 2018. During her Ph.D., she made a short-term visit to the University of Florida to work with quasar classification. More recently, she visited the University of Washington, where she spent one year in an internship at DiRAC. She is an active member of the S-PLUS collaboration, having been involved in the data releases development since 2020 with the S-PLUS DR2. She is former director (2022) and former vice-director (2023) of Research and Development of Turing USP, a student organization focused on artificial intelligence. She strives to foster a more collaborative environment between Astrophysics, Statistics, Computer Science, and Software Engineering.

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