The open clusters NGC 6604 and NGC 6704

Abstract

At the suggestion of Dr. D.L. DuPuy, the young open clusters of NGC 6604 and NGC 6704 were observed in the UBV wide-band system in order to obtain improved colour-magnitude diagrams and estimates of distance. A short introduction serves to present basic information and review previous studies of the two clusters, and to demonstrate their potential importance in determining the spiral structure of the Galaxy near the Sun. The second and third chapters describe the photoelectric and photographic observations and reductions, including a section on difficulties encountered with the iris photometer used to measure the plates. A section on results contains two appendices, giving approximately 100 UBV measures in the fields of both clusters. The methods of determining reddening corrections, cluster membership, and distance moduli are discussed is some detail in Chapter 4. Chapter 5 is a discussion of the colour-magnitude diagrams for both clusters. Age estimates are also derived; NGC 6604 is found to have an estimated age of ~4 million years, and NGC 6704 an estimated age of 20 million years. The relation of both clusters to the local spiral structure is the topic of Chapter 6, but due to the small sample, there is little new information gained. A discussion of possible future work towards determining the spiral structure between galactic longitudes [lowercase script l] = 20 [degree sign]-70 [degree sign] at distances greater than 2 kpc from the Sun, and investigating the possible pre-main-sequence stars which may be members of NGC 6604, concludes the study.