Subaru IR Echelle Spectroscopy of Herbig‐Haro Driving Sources. I. H2and [Feii] Emission

Abstract

We present infrared echelle spectroscopy of three Herbig-Haro (HH) driving sources (SVS 13, B5-IRS 1, and HH 34 IRS) using Subaru IRCS. The large diameter of the telescope and wide spectral coverage of the spectrograph allowedustodetectseveralH2and[Feii]linesinthe HandKbands.TheseincludeH2linesarisingfromv ¼ 1 3and J ¼ 1 11, and [Fe ii] lines with upper level energies ofE/k ¼ (1:1 2:7) ; 10 4 K. For all objects the outflow is found to have two velocity components: (1) a high-velocity (� 70 to � 130 km s � 1 ) component (HVC), seen in [Fe ii ]o r H2 emission and associated with a collimated jet; and (2) a low-velocity (� 10 to � 30 km s � 1 ) component (LVC), which is seen in H2 emission only and is spatially more compact. Such a kinematic structure resembles optical forbidden emission line outflows associated with classical T Tauri stars, whereas the presence of H2 emission reflects the lowexcitation nature of the outflowing gas close to these protostars. Theobserved H2flux ratios indicate a temperature of (2 3) ;10 3 Kandagasdensityof10 5 cm � 3 ormore,supportingshocksastheheatingmechanism.B5-IRS1exhibits faint extended emission associated with the H2-LVC, in which the radial velocity slowly increases with distance from the protostar (by � 20 km s � 1 at � 500 AU). This is explained as warm molecular gas entrained by an unseen wideangled wind. The [Fe ii] flux ratios indicate electron densities to be � 10 4 cm � 3 or greater, similar to forbidden-line outflowsassociated withclassicalT Tauristars.Finally,thekinematic structureof the[Feii] emissionassociated with the base of the B5-IRS 1 and HH 34 IRS outflows is shown to support disk-wind models. Subject headingg ISM: Herbig-Haro objects — ISM: individual (B5-IRS 1, HH 34 IRS, SVS 13) — ISM: jets and outflows — ISM: kinematics and dynamics — line: formation — stars: formation