Optical imaging of L723: the structure of HH 223

Abstract

We imaged the Lynds 723 dark nebula (L723) with the aim of studying the morphology of the Herbig-Haro object HH 223 and other line-emission nebula detected in the region. We obtained deep narrow-band images in the Halpha and [SII] lines and in the continuum nearby Halpha of a field of ~5' of the L723 dark nebula centered on HH 223. The Halpha and [SII] images reveal the detailed morphology of HH 223, unresolved in previous optical images. Both images show a quite complex knotty, wiggling structure embedded in a low-emission nebula. Comparison between the [SII] and Halpha fluxes of the knots are indicative of variations in the excitation conditions through HH 223. In addition, several other faint nebula are detected in Halpha a few arcmin to the SE and to the NW of HH 223, all of them lying projected onto the east-west pair of lobes of the quadrupolar CO outflow. Comparison between the Halpha and the continuum images confirms the HH-like nature of the Vrba object V83, while the Vrba objects V84 and V85 are identified as faint field stars.