Quasi-stellar objects (QSOs) are among the brightest objects in the universe. The origin of QSOs is still an important unsolved problems of modern astronomy. Current study suggests that the formation of QSOs and other less luminous active galactic nuclei (AGNs) is closely related to the formation of galaxies. In particular, the masses of the super mass black holes (SMBHs) of QSOs and the masses of galactic spheroids are closely correlated. For observed high-redshift QSOs, we expect that these QSOS should have huge SMBHs and galactic nuclei so they would be bright enough to be detectable. On the other hand, a high-redshift galaxy-QSO system should only be in the very early evolution stage of the galaxy-QSO system, so the galactic nucleus could not be too large. So what is the relationship between a QSO and its host galaxy at high redshifts? Or more generally, we might ask what kind of galaxies can host an AGN. For example, both barred spiral galaxies and merging/interacting galaxies were found to have more AGNs than normal spiral and non-interacting ones. What is the mechanism for the formation of AGNs in these galaxies? Another general problems include: Will different host galaxies affect the observed nature of AGNs, i.e., different types of AGNS have different host galaxies? Are different types of AGNs intrinsically different? What is the origin of the difference? The purpose of this project is to study on these important issues following our previous results.In the past few years, we have made some significant progress on the related issues. For example, we discovered several high-redshift (z>7) QSO candidates by using CO scanning observations of ALMA. We carried out optical-NIR observations for one candidate and confirmed that it was a QSO with a redshift of z = 7.09. The CO detection becomes the most distant molecular gas observed in human history. We also found a high-redshift QSO with a very luminous Lyman α emission line, but the Lyman α line width is very narrow. We also found that the color of red QSOs can vary significantly. Besides, we found that the host galaxies of Seyfert 1 and Seyfert 2 are very different. In addition, we found that nearby AGNs usually exists only in those galaxies that have experienced nuclear starbursts. We also found that some elliptical galaxies have high star formation rates, but the dynamics of the gas associated with the star formation activity is quite different from that of the stellar populations in the galaxies.In this project, we will use different observational techniques to probe relevant questions. Our study will utilize optical/near infrared spectral observations, millimeter and sub-millimeter observations, optical variability observations, and sky survey data analyses to investigate related problems in the connection of galaxy-AGN evolution. We will use a lot of telescopes in other countries, and thus require traveling budgets for oversea observations. This project will provide observational training for graduate students and postdocs. The results of this project are expected to have important impacts on the field of AGN researches.
|Effective start/end date||1/08/19 → 31/07/20|
In 2015, UN member states agreed to 17 global Sustainable Development Goals (SDGs) to end poverty, protect the planet and ensure prosperity for all. This project contributes towards the following SDG(s):