Possible evolution of the circum-galactic medium around QSOs with QSO age and cosmic time revealed by Ly α haloes
Abstract
We first present new Subaru narrow-band observations of the Ly α halo around the quasi-stellar object (QSO) CFHQ J232908-030158 at z = 6.42, which appears the most luminous and extended halo at z > 5 (LLy α = 9.8 × 1043 erg s-1 within 37 pkpc diameter). Then, combining these measurements with available data in the literature, we find two different evolutions of QSOs' Ly α haloes. First is a possible short-term evolution with QSO age seen in four z > 6 QSOs. We find the anticorrelation between the Ly α halo scales with QSOs' infrared (IR) luminosity, with J2329-0301's halo being the brightest and largest. It indicates that ionizing photons escape more easily out to circum-galactic regions when host galaxies are less dusty. We also find a positive correlation between IR luminosity and black hole mass (MBH). Given MBH as an indicator of QSO age, we propose a hypothesis that a large Ly α halo mainly exists around QSOs in the young phase of their activity due to a small amount of dust. The second is an evolution with cosmic time seen over z ∼ 2-5. We find the increase of surface brightness towards lower redshift with a similar growth rate to that of dark matter haloes (DHs) that evolve to MDH = 1012-1013 M⊙ at z = 2. The extent of Ly α haloes is also found to increase at a rate scaling with the virial radius of growing DHs, r_vir ∝ M_DH^{1/3}(1+z)^{-1}. These increases are consistent with a scenario that the circum-galactic medium around QSOs evolves in mass and size keeping pace with hosting DHs.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- September 2019
- DOI:
- 10.1093/mnras/stz1707
- arXiv:
- arXiv:1809.10916
- Bibcode:
- 2019MNRAS.488..120M
- Keywords:
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- galaxies: evolution;
- galaxies: haloes;
- galaxies: high-redshift;
- quasars: general;
- quasars: individual: J2329-0301;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 16 pages, 7 figures, published by MNRAS