birth cloud dust attenuation applied beyond dust_tesc

I ran into the following issue regarding the birth cloud dust attenuation:

I'm running StellarPopulation with dust_tesc=7.0, which I think means that only stellar populations with age < 1e7 should be affected by birth cloud dust attenuation. However, I find that when birth cloud dust attenuation is applied to stellar populations with age 1.1e7.

Below is an illustration. I generate spectra for a stellar population with tage=1.1e7. In one of the spectra, I set dust1 = 0.9; in the other I set dust1=0. Since tage > dust_tesc, I didn't expect there to be a difference between the two spectra but the figure below shows a significant difference.

I find that for dust_tesc=7.0, birth cloud dust attenuation is applied up to tage=1.12e7yr

まず StellarPopulation における dust_tesc と dust1 の処理を確認し、次に tage=1.1e7 と dust_tesc=7.0 で報告されたケースを再現しながら、dust1=0.9 と dust1=0 を比較します。設定されたしきい値を超える年齢では誕生雲減衰によってスペクトルが変化しなくなり、報告された境界の挙動がカバレッジされていれば完了です。