Quasars and their emission lines as cosmological probes

Understand

Quasars are the most luminous sources in the Universe.

• They are currently observed out to redshift z ~ 7 when the Universe was less than one tenth of its present age.
• Since their discovery 50 years ago astronomers have dreamed of using them as standard candles.
• Unfortunately quasars cover a very large range (8 dex) of luminosity making them far from standard.