Date:
Tue, 15/02/201112:30-13:30
(invited by Tsvi)
Title:
Probing the Missing Baryons through their Photoelectric X-Ray Absorption of High
Redshift Sources
Abstract:
Observations with the Swift satellite of X-ray afterglows of more than a hundred
gamma ray bursts (GRBs) reveal ubiquitous soft X-ray absorption. The directly measured optical depth at a given observed energy is found to be constant on average at high redshift z > 2. Such an asymptotic optical depth is expected if the foreground diffuse intergalactic medium (IGM) dominates the absorption effect,
and if the metallicity of the diffuse IGM is 0.2 − 0.4 solar at z = 0. Testing the IGM absorption hypothesis against a high-z quasar sample yields mixed results.
Four radio loud quasars (RLQs) at 2 < z < 2.5 do not show significant absorption
and the few available radio quiet quasars give only upper limits. Lack of quasar absorption poses a challenge to the IGM interpretation, and could allude to the opacity being rather due to the jets in RLQs and GRBs. Finally, a method for unambiguously distinguishing between IGM and host absorption will be described.
Title:
Probing the Missing Baryons through their Photoelectric X-Ray Absorption of High
Redshift Sources
Abstract:
Observations with the Swift satellite of X-ray afterglows of more than a hundred
gamma ray bursts (GRBs) reveal ubiquitous soft X-ray absorption. The directly measured optical depth at a given observed energy is found to be constant on average at high redshift z > 2. Such an asymptotic optical depth is expected if the foreground diffuse intergalactic medium (IGM) dominates the absorption effect,
and if the metallicity of the diffuse IGM is 0.2 − 0.4 solar at z = 0. Testing the IGM absorption hypothesis against a high-z quasar sample yields mixed results.
Four radio loud quasars (RLQs) at 2 < z < 2.5 do not show significant absorption
and the few available radio quiet quasars give only upper limits. Lack of quasar absorption poses a challenge to the IGM interpretation, and could allude to the opacity being rather due to the jets in RLQs and GRBs. Finally, a method for unambiguously distinguishing between IGM and host absorption will be described.