1 Introduction

Statistical properties of dense molecular cores in regions of high mass star formation (HMSF) and their possible variations on the galactic scale have not been sufficiently investigated yet despite of a large amount of new observational data. The relevant data are provided mainly by extensive surveys of HMSF signposts (water masers, strong FIR sources, ultracompact H II regions) in lines of high density tracers like CS (Anglada et al. 1996; Bronfman et al. 1996; Juvela 1996; Plume et al. 1992, 1997; Zinchenko et al. 1995, hereafter Paper I). Unfortunately (though inevitably), most of these surveys are limited to one-point observations towards the indicators mentioned above.

In Paper I we started a survey of southern H₂O and OH non-stellar masers in the CS and C³⁴S J=2-1 lines with SEST. This survey covered 30 objects in the longitude range $l =260^\circ - 310^\circ$.All detected sources were mapped in the CS line. From the analysis of these data we obtained statistical distributions of the core parameters (Zinchenko 1995, hereafter Paper II). One of the most interesting results was a hint on the galactic gradient of the mean core density.

The goal of the present study is to extend this survey to the outer Galaxy in order to improve the statistics and to investigate possible gradients of the core parameters in a larger interval of galactocentric distances.

We use the same selection criteria as in Paper I and the same observing and data analysis procedures. The observations were performed with the 20-m Onsala radio telescope. The difference in the beam sizes of Onsala and SEST is not very significant and has been approximately accounted for by using a simple deconvolution procedure.

In this paper we present the results of our J=2-1 CS and C³⁴S as well as J=1-0 CO observations towards 55 H₂O masers in the longitude range $l=120^\circ - 210^\circ$. We have mapped most of the detected cores in the CS line. The C³⁴S and CO observations are limited to the positions of the CS emission peaks.

The structure of the paper is as follows: In Sect. 2 we describe the observations and data analysis. In Sect. 3 we present the observational results. In Sect. 4 we derive some physical parameters of the sources and discuss their properties. In Sect. 5 we present our conclusions.