ISO far infrared observations of the high latitude cloud L 1642 ^*

I. The density and temperature structure

¹ Observatory, Tähtitorninmäki, PO Box 14, University of Helsinki, 00014 Helsinki, Finland e-mail: kimmo.lehtinen@helsinki.fi
² Laboratoire d'Astrophysique de Marseille, 2 place Le Verrier, 13004 Marseille, France
³ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany

Received: 16 January 2004
Accepted: 28 April 2004

Abstract

We have performed a large-scale mapping of the high-latitude, moderate extinction dark cloud L 1642 with ISO (Infrared Space Observatory) at 200 μm to study the properties of dust, the virial equilibrium condition of the cloud, and their relation to star formation. The cloud consists of three denser regions which are connected by diffuse material. Only one of the regions, the one most massive and with the greatest optical depth, is related to a temperature mimimum. The pre-main sequence binary stars IRAS 04325-1419 and IRAS 04327-1419, probably born within the cloud, are located close to this temperature mimimum coinciding with the column density maximum. The minimum dust temperature is ~13.8 K. The ratio / for the star-forming region is about 1.2, and thus it is close to being gravitationally bound. However, the other regions are not gravitationally bound. On a 1´-10´  spatial scale the radial density distributions, derived from far-infared optical depth maps, are similar between the star-forming and non star-forming regions. The differences that distinguish the star-forming core appear to be its higher density and lower dust temperature.