# Significantly blueshifted Lyman-$\alpha$

Lyman-$$\alpha$$ line in galaxies is notably known to show a double peaked profile, mainly due to its scattering in a moving medium, see e.g., the very recent Matthee et al. 2021, The X-SHOOTER Lyman-α survey at z=2 (XLS-z2) I: the panchromatic spectrum of typical Lyman-α emitters.

Reading through some literature I learned that most of the time the blue peak is reduced and the red one is enhanced because of the presence of outflowing medium, commonly present in star-forming galaxies. The peak separation is of the order of a few hundreds of $$\rm km ~s^{-1}$$. In case of inflowing medium (rarer) the situation is inverted. I have in hands a spectrum of a galaxies with a Lyman-$$\alpha$$ absorbed at the systemic redshift and with a narrow component blueshifted by $$>1000 ~\rm km ~s^{-1}$$, whit no red peak. Is there any known mechanism that could explain this?

• Does the absorption go all the way to zero flux? Could you show the spectrum? What redshift is it? Which instrument did you use? Are you Tony P.?
– pela
Feb 26 at 15:09