Presented By: Department of Astronomy
Astronomy Colloquium Series Presents:
Dr. Jinyi Yang, Peter A. Strittmatter Fellow, The University of Arizona
Exploring Reionization-era Quasars: Cosmic Reionization History and the Early SMBH Growth
Our new reionization-era quasar survey has yielded more than 35 new luminous quasars at 6.3 < z <= 7.6, including the new redshift-record breaking quasar, which forms the first large statistical sample of quasars in the reionization epoch. I will first introduce this wide-field quasar survey and then present our recent works related to the intergalactic medium (IGM) evolution and the early supermassive black hole (SMBH) growth using our new quasar sample. We measure the Lyman-alpha and Lyman-beta effective optical depth at 5.3<z<6.5 using both individual sightlines and the stacked spectrum. Combining our new measurements and previous results, we obtain a best-fit evolution for the Lyman-alpha optical depth at z~5.3-6.1. We also build a large high redshift transmission spike sample including more than 400 Lyman-alpha or Lyman-beta transmission spikes at 5.5<z<6.3. The existence of these transmission spikes at redshift up to z~6.3 and its evolution suggests a rapid transition phase of IGM neutral fraction from z~7 to z~6.3. The study of damping wing features from our newly discovered z=7.52 quasar and the other z=7.0 quasar indicates a large scatter of the IGM neutral fraction from z=7.5 to z=7.0, indicative of a patchy reionization process. In addition, with data from the on-going near-infrared spectroscopic survey, we measure the BH mass and Eddington ratio, and investigate the properties of quasar broad emission lines. These quasars set new challenges to the formation and growth history of the earliest SMBHs. In particular, our newly discovered z=7.5 and 7.6 quasars hosting billion solar mass black holes require the most massive seed black holes compared to any other known quasars. The result is more consistent with a massive seed black hole model (e.g., direct collapse).
Should you require any accommodations to ensure equal access and opportunity related to this event, please contact Stacy Tiburzi at 734-764-3440 or [email protected].
Our new reionization-era quasar survey has yielded more than 35 new luminous quasars at 6.3 < z <= 7.6, including the new redshift-record breaking quasar, which forms the first large statistical sample of quasars in the reionization epoch. I will first introduce this wide-field quasar survey and then present our recent works related to the intergalactic medium (IGM) evolution and the early supermassive black hole (SMBH) growth using our new quasar sample. We measure the Lyman-alpha and Lyman-beta effective optical depth at 5.3<z<6.5 using both individual sightlines and the stacked spectrum. Combining our new measurements and previous results, we obtain a best-fit evolution for the Lyman-alpha optical depth at z~5.3-6.1. We also build a large high redshift transmission spike sample including more than 400 Lyman-alpha or Lyman-beta transmission spikes at 5.5<z<6.3. The existence of these transmission spikes at redshift up to z~6.3 and its evolution suggests a rapid transition phase of IGM neutral fraction from z~7 to z~6.3. The study of damping wing features from our newly discovered z=7.52 quasar and the other z=7.0 quasar indicates a large scatter of the IGM neutral fraction from z=7.5 to z=7.0, indicative of a patchy reionization process. In addition, with data from the on-going near-infrared spectroscopic survey, we measure the BH mass and Eddington ratio, and investigate the properties of quasar broad emission lines. These quasars set new challenges to the formation and growth history of the earliest SMBHs. In particular, our newly discovered z=7.5 and 7.6 quasars hosting billion solar mass black holes require the most massive seed black holes compared to any other known quasars. The result is more consistent with a massive seed black hole model (e.g., direct collapse).
Should you require any accommodations to ensure equal access and opportunity related to this event, please contact Stacy Tiburzi at 734-764-3440 or [email protected].
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