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14/10/2019-18/10/2019

SHAO Astrophysics Colloquium 

Title: Highlights in cosmology 2019  

Speaker: Charling Tao (Centre de Physique des Particules de Marseilles) 

    Time: 3:00 pm, October 17th (Thursday)  

Location: Lecture hall, 3rd floor 

Abstract: After a brief reminder of the basics of cosmology, I will discuss some of the present issues and the results of some present and future projects that addresses those issues.  

Brief biographical sketch:  

Charling Tao is a mother of twins and grandmother of two boys. She trained as a particle physicist, designing detectors to detect the invisible world of neutrinos and Dark Matter. She tested quantum chromodynamics (QCD) with Deep inelastic scattering, discovered the W and Z0 mediators of the Weak interaction with the UA1 experiment at CERN. She became an astrophysicist, to understand the mystery of the missing solar neutrinos. GALLEX in Gran Sasso (LNGS) was the first experiment to measure the contribution of the pp neutrinos. She designed the DAMA experiment with NaI(Tl) crystals but protested the claim of a DM signal at Gran Sasso. She joined and designed the first prototype of the undersea ANTARES detector. The mystery of the Dark Energy converted her into a cosmologist. Since 2005, she is testing  ΛCDM with Supernovae, Baryonic Oscillations and Weak Lensing. Charling Tao is a director of research in CNRS, France, and emeritus professor in DOA, Tsinghua University. She is currently co-leading the transient science working group in the European Euclid space cosmology project and studies the complementarity with the Chinese space project CSS-OS and with LSST and SKA. She is also testing a directional Dark Matter detector. 

  


SHAO Astrophysics Special Colloquium
    Title: First discovery of inflows fueling supermassive black hole accretion disks  

Speaker: Professor Hongyan Zhou 

    Time: 3:00 pm, October 14th (Monday)  

Location: Lecture Hall, 3rd floor
    Abstract:   

Research group from Polar Research Institute of China (PRIC) recently identified a fast gaseous inflow fueling the accretion disk around a supermassive black hole in the quasar J1035+1422, traced by a redshifted broad-absorption-line system. Located around the outer radius of the accretion disk, this inflow is the first case reported actually reaching the disk. The result is published in a letter "Fast inflows as the adjacent fuel of supermassive black hole accretion disks in quasars" in Nature on Sep 4, 2019 (https://www.nature.com/articles/s41586-019-1510-y).  

  

The absorption-line system was originally detected through a systematic search in ~10^5 SDSS quasar with z<1.3. In the follow-up campaign with the DBSP and TripleSpec spectrographs, the system was confirmed using H I Balmer absorptions from H\alpha to H\eta and metastable He I multiplets He I* \lambda\lambda3,188,3,889,10,830 in the optical and near-infrared spectra. The absorption trough spreads 0~5000 km s^-1 redshifted to the quasar's rest frame, which is the fastest and broadest in the sample of redshifted broad- or mini-broad-absorption-line systems, inferring a fast inward motion. The photoionization simulation suggested that the inflow is about 1,100 gravitational radii from the central engine, overlapping with the outer accretion disk. The inflow could be originated from the inner surface of the dusty torus, and the mass flux rate is therefore about 15-36 solar mass per year, sufficient to power the quasar radiation and the outflow.
Such inflow directly feeding the accretion disk is considered the last piece of the puzzle of quasar black hole accretion. Due to the obscuring effect of the dusty torus, the inflow discovered here might be much more common in quasars than they appear in ultraviolet and optical spectra. Absorption/emission lines in the infrared, (sub)millimetre and radio wavelengths, where dust obscuration is slight or negligible, could be even more powerful probers to unveil the nature of disk-feeding inflow.  

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