Publication Date:
2013-03-16
Description:
We use sensitive observations of three high-redshift sources: [C ii ] $^2\text{P}_{3/2}$ -〉 $^2\text{P}_{1/2}$ fine-structure and CO ( J = 2 -〉 1) rotational transitions for the z = 6.4 quasar (QSO) host galaxy J1148+5251 taken with the Plateau de Bure Interferometer (PdBI) and Jansky Very Large Array, respectively, and [C ii ] and CO ( J = 5 -〉 4) transitions from the QSO BR1202–0725 and its companion sub-millimetre galaxy (SMG) at z = 4.7 taken with the Atacama Large Millimeter Array and the PdBI. We use these observations to place constraints on the quantity $\Delta z = z_{\rm CO} - z_{\text{C}{\,\small {ii}}}$ for each source where z CO and $z_{\text{C}{\,\small {ii}}}$ are the observed redshifts of the CO rotational transition and [C ii ] fine-structure transition, respectively, using a combination of approaches: (1) modelling the emission line profiles using ‘shapelets’ – a complete orthonormal set of basis functions that allow us to recreate most physical line shapes – to compare both the emission redshifts and the line profiles themselves, in order to make inferences about the intrinsic velocity differences between the molecular and atomic gas, and (2) performing a marginalization over all model parameters in order to calculate a non-parametric estimate of z . We derive 99 per cent confidence intervals for the marginalized posterior of z of (–1.9 ± 1.3) x 10 –3 , (–3 ± 8) x 10 –4 and (–2 ± 4) x 10 –3 for J1148+5251, and the BR1202–0725 QSO and SMG, respectively. We show that the [C ii ] and CO ( J = 2 -〉 1) line profiles for J1148+5251 are consistent with each other within the limits of the data, whilst the [C ii ] and CO ( J = 5 -〉 4) line profiles from the BR1202–0725 QSO and SMG, respectively, have 65 and 〉99.9 per cent probabilities of being inconsistent, with the CO ( J = 5 -〉 4) lines ~30 per cent wider than the [C ii ] lines. Therefore, whilst the observed values of z can correspond to variations in the quantity F / F with cosmic time, where F = α 2 /μ, with α the fine-structure constant and μ the proton-to-electron mass ratio, of both (–3.3 ± 2.3) x 10 –4 for a look-back time of 12.9 Gyr and of (–5 ± 15) x 10 –5 for a look-back time of 12.4 Gyr, we propose that they are the result of the two species of gas being spatially separated as indicated by the inconsistencies in their line profiles.
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
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