Spatially extended absorption around the z=2.63 radio galaxy MRC 2025-218: outflow or infall?

Abstract

We present an investigation into the absorber in front of the z=2.63 radio galaxy MRC 2025-218, using integral field spectroscopy obtained at the Very Large Telescope, and long slit spectroscopy obtained at the Keck II telescope. The properties of MRC 2025-218 are particularly conducive to study the nature of the absorbing gas, i.e., this galaxy shows bright and spatially extended Ly-alpha emission, along with bright continuum emission from the active nucleus. Ly-alpha absorption is detected across ~40x30 kpc^2, has a covering factor of ~1, and shows remarkably little variation in its properties across its entire spatial extent. This absorber is kinematically detached from the extended emission line region (EELR). Its properties suggest that the absorber is outside of the EELR. We derive lower limits to the HI, HII and H column densities for this absorber of 3x10^16, 7x10^17 and 2x10^18 cm^-2, respectively. Moreover, the relatively bright emission from the active nucleus has allowed us to measure a number of metal absorption lines: CI, CII, CIV, NV, OI, SiII, SiIV, AlII and AlIII. The column density ratios are most naturally explained using photoionization by a hard continuum, with an ionization parameter U~0.0005-0.005. Shocks or photoionization by young stars cannot reproduce satisfactorily the measured column ratios. Using the ratio between the SiII* and SiII column densities, we derive a lower limit of >10 cm^-3 for the electron density of the absorber. The data do not allow useful constraints to be placed on the metallicity of the absorber. We consider two possibilities for the nature of this absorber: the cosmological infall of gas, and an outflow driven by supernovae or the radio-jets.

Accepted for publication in MNRAS

References in corpus (9)

• Extreme gas kinematics in the z=2.2 powerful radio galaxy MRC1138-262: Evidence for efficient AGN feedback in the early Universe?
• The Massive Hosts of Radio Galaxies Across Cosmic Time
• Deep spectroscopy of the FUV-optical emission lines from a sample of radio galaxies at z~2.5: metallicity and ionization
• The Lyman-alpha glow of gas falling into the dark matter halo of a z=3 galaxy
• VIMOS-VLT spectroscopy of the giant Ly-alpha nebulae associated with three z~2.5 radio galaxies
• Integral field spectroscopy of H-alpha emission in cooling flow cluster cores: disturbing the molecular gas reservoir
• Jet-gas interactions in z~2.5 radio galaxies: evolution of the ultraviolet line and continuum emission with radio morphology
• Giant Lyman-alpha nebulae around z>2 radio galaxies: evidence for infall
• Ionization of large-scale absorbing haloes and feedback events from high-redshift radio galaxies

Cited by in corpus (5)

• The MUSE 3D view of feedback in a high-metallicity radio galaxy at z = 2.9
• Ionization and feedback in Ly$\alpha$ halos around two radio galaxies at z$\sim$2.5
• CO survey of high-z radio galaxies, revisited with ALMA: Jet-cloud Alignments and Synchrotron Brightening by Molecular Gas in the Circumgalactic Environment
• The Dragonfly Galaxy. III. Jet-brightening of a High-redshift Radio Source Caught in a Violent Merger of Disk Galaxies
• Carbon-loud SDSS BOSS QSO2s at z > 2: High density gas or secondary production of Carbon?