Lyman alpha halos around radio-loud quasars
Billion solar mass black holes existed within a billion years of the Big Bang, and growing them that fast takes an enormous supply of gas. That supply is the circumgalactic medium, the gas sitting around a galaxy inside its halo but outside the disk. Around powerful quasars it is cool and dense enough to shine in the Lyman alpha line, as halos stretching tens to hundreds of kiloparsecs.
Radio jets are found in more than 10% of quasars and may matter a great deal to how a black hole and its galaxy grow together. What those jets do to the gas around them was an open question, with no systematic comparison between radio-loud and radio-quiet quasars.
How different are the diffuse gas structures around radio-loud and radio-quiet quasars, and does the powerful jet interact strongly with the CGM?
This project is the first systematic survey of extended Lyman alpha halos around 15 radio-loud quasars, observed with VLT/MUSE at 3.66 < z < 6.44. I reduced the data, subtracted each quasar’s own point spread function, and searched what remained for diffuse emission.
We detect extended Lyman alpha emission around 9 of the 15 quasars, a detection rate of 60%, above the 39% measured for a radio-quiet sample matched in redshift. The halos reach luminosities of 2 to 17 × 1043 erg s-1, maximum projected extents of 17.5 to 47.4 kpc, and line widths of 925 to 2937 km s-1, and their stacked profiles come out systematically more compact than those reported for radio-quiet samples.
Taken together this suggests that jetted systems host a brighter cool CGM. Whether the jets drive that brighter emission, or simply mark the dense environments that produce it, is the next question. The paper is in internal review and will be submitted soon.
