|
Description
Simulations of the formation of large-scale structures predict that dark matter, low density highly ionized gas, and galaxies form 10 to 40Mpc scale filaments. These structures are easily recognized in the distribution of galaxies. Here we use Ly{alpha} absorption lines to study the gas in 30x6Mpc filament at cz~3500km/s, defined using a new catalog of nearby (cz<10000km/s) galaxies, which is complete down to a luminosity of about 0.05L_*_ for the region of space analyzed here. Using Hubble Space Telescope spectra of 24 active galactic nuclei, we sample the gas in this filament. All of our sightlines pass outside the virial radius of any known filament galaxy. Within 500kpc of the filament axis the detection rate is ~80%, but no detections are seen more than 2.1Mpc from the filament axis. The width of the Ly{alpha} lines correlates with filament impact parameter and the four BLAs in our sample occur within 400kpc of the filament axis, indicating increased temperature and/or turbulence. Comparing to simulations, we find that the recent Haardt & Madau extragalactic ionizing background predicts a factor of 3-5 too few ionizing photons. Using a more intense radiation field matches the hydrogen density profile within 2.1Mpc of the filament axis, but the simulations still overpredict the detection rate between 2.1 and 5Mpc from the axis. The baryonic mass inside filament galaxies is 1.4x10^13^M_{sun}_, while the mass of filament gas outside galaxy halos is found to be 5.2x10^13^M_{sun}_.
|
