Open AccessThe mysterious absence of neutral hydrogen within 1 Mpc of a luminous quasar at redshift 2.168
Author(s) -
Francis Paul J.,
BlandHawthorn Joss
Publication year - 2004
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2004.08068.x
Subject(s) - physics , astrophysics , quasar , redshift , galaxy , astronomy , surface brightness , emission spectrum , population , photoevaporation , brightness , spectral line , star formation , demography , sociology
The intense ultraviolet (UV) radiation from a highly luminous quasi‐stellar object (QSO) should excite fluorescent Lyman α (Lyα) emission from any nearby neutral hydrogen clouds. We present a very deep narrow‐band search for such emission near the z = 2.168 quasar PKS 0424‐131, obtained with the Taurus Tunable Filter on the Anglo‐Australian Telescope. By working in the UV, at high spectral resolution and by using charge shuffling, we have been able to reach surface brightness limits as faint as 4.7 × 10 −19 erg cm −2 s −1 arcsec −2 . No fluorescent Lyα emission is seen, whereas QSO absorption‐line statistics suggest that we should have seen ≳ 6 clouds, unless the clouds are larger than ∼100 kpc in size. Furthermore, we do not even see the normal population of Lyα‐emitting galaxies found by other surveys at this redshift. This is very different from observations of high‐redshift radio galaxies, which seem to be surrounded by clusters of Lyα emitters. We tentatively conclude that there is a deficit of neutral hydrogen close to this quasar, perhaps owing to the photoevaporation of nearby dwarf galaxies.