Colloquium on May. 13, 2021

ALMA observations of z > 6 low-luminosity quasars: unbiased view on the early co-evolution and feedback

Speaker:Takuma Izumi (NAOJ)

Venue:Video Conference

Time:16:00 PM, Thursday, May. 13, 2021

Abstract:

I will review our multi-wavelength campaign observations toward z > 6 optically "low-luminosity” quasars (w/ emphasis on my ALMA works), most of which were discovered by our on-going wide-field Subaru Hyper Suprime-Cam (HSC) optical imaging survey. Our HSC quasars are an order of magnitude fainter at rest-UV than previously-known luminous quasars. Subsequent NIR spectroscopic follow-up observations revealed a wide spread in their BH mass, consequently Eddington ratio. We have also been carrying out a series of ALMA observations ([CII] line and FIR continuum emission) toward a sample of HSC quasars. We found that their host galaxies are basically FIR-faint with moderate SFR (< 100 Msun/yr). Using the [CII]-based dynamical mass as a surrogate for bulge-scale stellar mass, we found that a significant fraction of these low-luminosity quasars are located on or even below the local BH mass-bulge mass scaling relation, suggesting that the rapid emergence of the "co-evolution" already at z > 6. I will also talk about one particular case, z = 7.07 HSC quasar J1243+0100, in which we found a vigorous starburst and, surprisingly, fast and massive [CII] outflows (indeed this is the highest redshift large-scale outflow ever detected!). Various considerations have led us conclude that this outflow is quasar-driven. This manifests that the “negative feedback” on the host galaxy, which is often invoked to drive the co-evolution, has indeed occurred at that very early universe.

Report PPT:SWIFAR_Takuma Izumi.pdf