Artist's impression of the heart of a quasar, where a black hole is hidden in a disk of gas and dust.
Credit: NASA Education and Public Outreach at Sonoma State University - Aurore Simonnet.
The thermal state of the intergalactic medium (IGM) provides an indirect probe of both the HI and He II reionisation epochs. Current constraints on the IGM temperature from the Lyα forest are restricted to the redshift range 2 z 4.5, limiting the ability to probe the thermal memory of HI reionisation toward higher redshift. In this work, the authors using a high resolution Keck/HIRES spectrum in combination with detailed numerical modelling present the first direct measurement of the IGM temperature around a z = 6 quasar by analysing the Doppler widths of Ly_ absorption lines in the proximity zone of SDSS J0818+1722.(read more)