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1. Introduction

Systematic studies of dense molecular cores in regions of high mass star formation (HMSF) are of great importance for understanding their general properties. In comparison with low mass star-forming regions, extended samples of which have been observed in various molecular lines, only a few, rather arbitrarily selected cores associated with HMSF regions have been investigated in some detail (for a review see, e.g., Walmsley & Güsten 1994).

The goal of the present study was twofold: (1) to investigate in more detail the structure of selected HMSF cores and (2) to extend our previous ammonia survey of bright FIR sources (Schreyer et al. 1996; hereafter Paper I) to another part of the Galaxy.

We selected (1, 1) and (2, 2) ammonia lines for this study because they allow for the derivation of the core temperatures and can be directly compared with our previous results. At the same time we bear in mind that the ammonia distribution in many cases differs significantly from distributions of other high-density tracers (e.g. Zhou et al. 1989, 1991; Zinchenko et al. 1994, hereafter Paper II). The reasons for this difference should be further investigated.

This work is a continuation of the investigation of dense cores in molecular clouds associated with Sharpless HII regions in the J=1-0 HCN and tex2html_wrap_inline1585 lines by Burov et al. (1988), Zinchenko et al. (1989) and Zinchenko et al. (1990). Several clouds from this sample have been subject to a detailed study in the CS J=2-1 line in Paper II. A part of them has been mapped in the (1, 1) and (2, 2) tex2html_wrap_inline1589 lines by Harju et al. (1993). Ammonia is a convenient ``thermometer" for dense cores and provides information on their density and kinematics too. In addition, the comparison of the CS and ammonia maps can be informative for understanding the cloud structure and chemistry. Thus, similar ammonia data for the remaining cores were highly desirable.

This sample overlaps partly with the sample of bright FIR sources in the outer Galaxy which has been investigated already in various molecular lines and continuum emission by Snell et al. (1988, 1990), Carpenter et al. (1990, 1993) and Henning et al. (1992). Recently we surveyed these objects in the (1, 1) and (2, 2) tex2html_wrap_inline1591 lines and in the J=1-0 tex2html_wrap_inline1595 line (Paper I). The detection rate in the tex2html_wrap_inline1597 (1, 1) line was 37%. An extension of this survey to the inner Galaxy should be important taking into account that there are hints on a galacto-centric dependence of the mean core density (e.g. Zinchenko 1995). We selected targets for the present study from the list of FIR sources in Sharpless clouds using the same criterion as in Paper I, i.e. the flux in the IRAS Point Source Catalogue at tex2html_wrap_inline1599 tex2html_wrap_inline1601 should be larger than 500 Jy applying it to another range of right ascension. Of course, there is a number of other powerful FIR sources in the inner Galaxy which are not associated with Sharpless clouds.

Most of the cores surveyed in ammonia lines in Paper I have not been mapped in these lines. However, in order to obtain a complete physical representation of these objects such maps are very important. Thus, we included in the list several strong sources from this survey.

Here we present the results of the observations of 17 clouds in the (1, 1) and (2, 2) tex2html_wrap_inline1603 lines. Ten of them (all sufficiently strong detections) have been mapped in these lines. The relevant physical properties are estimated and briefly discussed. A more detailed analysis of the data on some individual objects will be a subject of subsequent publications.

In Sect. 2 (click here) we describe the observations and data analysis. In Sect. 3 (click here) we present the observational results and derive the physical parameters of the sources. In Sect. 4 (click here) the results are discussed and in Sect. 5 (click here) we present our conclusions.


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