Black Hole TON618 - Wavelength Spectrum

[nanjo]

Several websites quote the Lyman-alpha wavelength as 121.567nm for black hole TON618. Is this value the observed wavelength or the source wavelength? As both values are required to determine z, can anyone tell me what the value of the missing wavelength is?

 

[Orodruin]

The Lyman-alpha emitted wavelength is 121.567 nm.

You can easily compute the observed wavelength from the redshift value z = 2.219.

 

[nanjo]

Thanks Orodruin for your prompt reply and confirming that the 121.567nm is the emitted wavelength at TON618. The value z = 2.219 is stated as a fact in the data provided for TON618. It is calculated from knowledge of the source and emitted wavelengths. What I need to know is the spectrum value initially observed, from which the value of z was originally derived.

 

[Ibix]

Observed wavelength is $(1+z)$ times the emitted wavelength, so you can calculate the observed wavelength from the two numbers you have.