1997A&A...323..541G

An optical study (high resolution images and long-slit spectra in the Hα range) of the Serpens reflection nebula (SRN) is presented. The SRN is a bipolar nebula illuminated by the low mass pre-main-sequence (PMS) star Serpens/SVS 2. The Hα profile of Serpens/SVS 2 is shown to be very broad (the width at a 10% of the peak intensity is 13.1Å (∼600km/s)). The profile has three emission peaks centered at -137, 5 and 100km/s. The relative strength of the peaks varies with the slit orientation. The blue and redshifted components have similar intensities at low inclinations (5 and 0) while at high inclinations the blueshifted component is weaker than the redshifted suggesting a significant contribution of absorption by low latitude outflowing gas. These profiles could be produced in a rotating, latitude dependent wind with the outflow axis parallel to the disk axis. The nebular Hα profile is double peaked; it has a blue and a redshifted component at the same velocities as the star. The profile shows no significant variations along a given PA; the emission is best explained by single scattering of the stellar radiation. The absence of the 0-velocity emission component is suggestive of the presence of warm absorbing gas within a few stellar radii. There are several knots of gas and dust embedded within the north-western (NW) nebular lobe. These knots are connected by a faint emission, defining a helical path around the major axis of the nebula. This area is also characterized by an unusually large polarization that reaches a 30-40% at 0.95µm that is consistent with a concentration of large and reflecting dust grains that are presumably ice coated carbon grains. This region coincides with a ridge of hot (T≃35K) dust detected by IRAS along the major axis of the SRN.