In this letter we present the first systematic spectroscopic measurements of the Near-InfraRed (NIR) hydrogen recombination lines Paschen alpha ($Pa_{ \alpha}$ $\lambda = 1.875 \mu m$) and Brackett beta ($Br_{ \beta}$ $\lambda = 2.626 \mu m$), produced by pre-main-sequence (PMS) stars. These stars, consisting of T Tauri and Herbig AeBe stars are located in the massive Galactic star-formation region NGC 3603. The measurements were obtained from JWST NIRSpec, using multi-object spectroscopy (MOS) mode. Utilising existing empirical relations between $L_{ acc}$ and $L_{ Br_{ \gamma}}$, we have used our new measurements to formulate, for the first time, an empirical relationship between the accretion luminosity $L_{ acc}$ of the stars, and the line luminosities $L_{ line}$ of both $Pa_{ \alpha}$ and $Br_{ \beta}$. These relationships are: $\log_{ 10}( \frac{ L_{ acc}}{ L_{ \odot}}) = 1.42 (\pm 0.18) \times \log_{ 10}( \frac{ L_{ Pa_{ \alpha}}}{ L_{ \odot}}) + 3.33 (\pm 0.42)$ and $\log_{ 10}( \frac{ L_{ acc}}{ L_{ \odot}}) = 1.47 (\pm 0.18) \times \log_{ 10}( \frac{ L_{ Br_{ \beta}}}{ L_{ \odot}}) + 4.60 (\pm 0.57)$. These new relationships are key for roughly estimating the accretion rates for large samples of PMS stars with JWST.
Categories: astro-ph.SR astro-ph.GA