SHAO Astrophysics Colloquium

标题: Star Formation Across Cosmic Time

报告人: Yong Shi (Nanjing University)

时间： 3pm, Dec. 14(Thursday)

地点: Lecture Hall, 3rd floor

摘要: Stars including our Sun are born in clouds of cold gas. Understanding how gas converts into stars across cosmic time is a big challenge in modern astronomy. In the early universe, primordial gas with little or no metals collapse into early-generation stars whose radiation re-ionizes the universe. The subsequent rising of the cosmic star-formation-rate (SFR) density until z∼2 follows by a rapid decline toward the current universe. The driving mechanism of this cosmic SFR evolution is related to the cold gas reservoir available within the galaxies and its capability of forming new stars. In this talk, I will review recent progresses including our own works in understanding the evolution of cosmic star formation, with the focus on answering three key questions: how does cosmic star formation start, how does cosmic star formation evolve, and how does star formation stop?

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Special Colloquium

标题: Searching for Habitable Worlds Using Artificial Intelligence

报告人: Prof. Jian Ge (University of Florida)

时间： 10:30 am, Dec. 13 (Wednesday)

地点: Lecture Hall, 3rd floor

摘要: Detecting habitable worlds around nearby stars and searching for life among them is one of the main goals of science. However, it is extremely challenging to detect them with the ground-based Doppler spectroscopy and space-based transit photometry as their signals are extremely weak. We launched the Dharma Planet Survey (DPS) using the TOU very high precision Doppler spectrograph at the fully dedicated 50-inch Automatic Dharma Endowment Foundation Telescope (DEFT) on Mt. Lemmon in 2016 to search for habitable planets around nearby FGKM dwarfs. To date, more than 80 survey targets have been observed with more than 10 times each. Seven low-mass planet candidates have been detected. In the meantime, we are developing deep neural networks to capture weak long-period transit signals from habitable Earth-like planets in the Kepler photometry data, taking advantage of the newly established NSF deep learning (DL) center at UF. An early DL model was able to detect over 20,000 weak metal absorption lines among SDSS 50,000 quasar spectra at better than 90% accuracy in an extremely short time of only 20 seconds. This DL method is being implemented in Kepler data and will be implemented in DPS spectroscopy data to significantly boost search speed to detect weak habitable planet signals and optimize DPS operation efficiency. Early results will be presented.

Group meetings

Black hole Accretion and High-energy Astrophysics /Black Hole Feedback and Cosmic Ray Astrophysics Seminar

Location: 1608

Time: 14:00-16:00, Wednesday (Dec. 13th)

Speaker: Maochun Wu
Title: Radiative efficiency, variability and Bondi accretion on to massive black holes: the transition from radio AGN to quasars in brightest cluster galaxies
http://adsabs.harvard.edu/abs/2013MNRAS.432..530R

Speaker: Hai Yang

Title: The Properties of Reconnection Current Sheets in GRMHD Simulations of Radiatively Inefficient Accretion Flows
http://adsabs.harvard.edu/abs/2017arXiv170506293B