1 Introduction

Bok globules are isolated clouds of dense molecular gas (Bok & Reilly 1947). They are recognised in the optical as sharply outlined dark patches against a background of stars. Bok & Reilly's (1947) statement that the globules were probably sites where stars would form has been confirmed (e.g., Yun & Clemens 1990). We have begun a project to study Bok globules, to determine how they form, evolve and disperse. Their significance lies not only in their illustration of a distinct mechanism leading to stars but also that a considerable proportion of gas in the Galaxy is processed through them. A total of 10¹⁰$M_\odot$ is processed in the lifetime of the Galaxy, given a globule lifetime of 10⁶ years (Launhardt & Henning 1997), a number of 10⁵ (Clemens et al. 1991), along with a mass of 10$M_\odot$. Hence, many field stars including our Sun, as well as the enigmatic isolated T Tauri stars (Yun et al. 1997; Launhardt & Henning 1997), could find their origin in Bok globules.

Globules are not a homogeneous group of objects. They span a range in masses from $\sim$1-100$M_\odot$ and their angular sizes are typically a few arcminutes which corresponds to sizes of 0.1-1 parsec, according to their distance. Therefore, a single low-mass star could form or a small group including high-mass stars could result. Moreover, we cannot expect to uncover a single evolutionary scheme for all Bok globules, if any scheme exists. Bok globules could (1) form spontaneously from small growing perturbations, (2) be triggered by a large pressure wave or (3) evolve after fragmenting from a larger molecular cloud. They are not perfectly isolated. Usually, some connection with a distant molecular cloud complex is found.

We present here near-infrared and millimetre data for the Bok globule CB34 (Clemens & Barvanis 1988), in order to determine its evolutionary stage. CB34 belongs to a class of distant massive globules. We thus wish to examine if a few powerful outflows, corresponding to those expected from high-mass stars, are being generated. The Gemini OB1 cloud is $\approx$2$^\circ$ east of CB34 at an estimated distance of 1.5kpc from us. Supposing that the two formed at the same time, with the early CB34 being stripped off from the main outskirts of the cloud and separating at 10kms^-1, would then yield an age of at least 5$\times$10⁶yr. This is uncomfortably old, being equal to the average age for globule dispersal derived by Launhardt & Henning (1997).

CB34 is certainly in an advanced stage. It has successfully formed dense molecular clumps and protostars (Launhardt & Henning 1997; Huard et al. 2000) as well as being associated with young stars (Alves et al. 1997). The chemical age of the globule exceeds 10⁵yr (Scappini et al. 1998) (although this result is sensitive to the assumed density of 10⁴cm^-3). Collimated outflows also testify to active star formation. A bipolar CO outflow from cool gas (Yun & Clemens 1994), shocked optical knots of atomic emission lines from radiative shocks (Herbig-Haro objects), as well as an infrared outflow from vibrationally-excited molecular hydrogen (Yun & Clemens 1994) have been reported. Protostellar outflows can be several parsecs long. Therefore, to search for evidence for evolved outflows, we chose CB34 for wide-field infrared observations in the 2.12 $\mu$m H₂ line.

We also present JHK photometry for CB34 and compare it to previous results of Moreira & Yun (1995). We discuss the depth in the globule and the protostellar stage of individual stars. Finally, we have obtained velocity-channel maps in CO, H¹³CO⁺ and SiO, in order to determine the location of the densest cores and to search for further outflows.