NGC 2323 (Messier 50)

Posted on by Ben Humphries

Introduction

NGC 2323 is a intermediate age, open star cluster that is estimated to be around 1.4×10^8 years old. This star cluster, also known as Messier 50 was first documented by G. D. Cassini a year before it was formerly named and discovered by Charles Messier in 1772. NGC 2323 has a unique shape that resembles a heart and is quite easy to distinguish between other clusters due to its close proximity to the brightest star in the night sky: Sirius. 

In a recent study, J. J. Claria (1997) determined that the total span of NGC 2323 is believed to be roughly 20 light years across. Although, most of the stars; which is said to be around 200; are located in only a span of 10 light years. 

 

 https://www.messier-objects.com/messier-50-heart-shaped-cluster/

 

Procedure

In order to study NGC 2323, we need to explore and analyze relationships between colors, brightness, age, and overall chemical composition through Skynet. To capture this cluster effectively, 15 separate images with filters R, V, and B need to be taken with the Prompt5 telescope located in Cerro Tololo Inter-American Observatory. These images included: 5 B filter photographs with a 36.59s exposure length, 5 V filter photographs with a 12.29s exposure length, and 5 R filter photographs with a 12.29s exposure length. In addition, all images were taken with a 1s exposure duration to limit the number of photographs taken. 

Once all the images were finalized, I used Afterglow Access to generate a stacked image consisting of filters R, V and B to produce both a ISM-reddened image and a de-reddened image that are pictured below. These images where then further detailed by using Afterglows integrated tools. This consisted of changing the stretch mode to midtone, adding a midtone level percentile of 99, setting the background level percentile to roughly 35 and saturation level percentile to 99.999. These changes were done to increase the brightness and to make all notable stars more visible and identifiable.

 

Figure 1: The ISM-reddened image made using Afterglow Access.

 

Figure 2: The de-reddened image made using Afterglow Access.

 

Furthermore, I used Cluster Pro Plus, a plotting/graphing tool to load Gaia and 2MASS data on to my collected data to fit a isochrone model. This fit was fixed around the bottom of the main sequence of stars so values such as proper motions, distance, age, metallicity and E(B-V) would be most accurate. 

 

 

This same procedure was done, but this time with already generated data through the MWSC (The Milky Way Star Clusters Catalog). A isochrone model was fit and the same values were recorded.

 

 

Analysis

Through comparing and contrasting these plots and recorded values a table can be made:

Gaia and 2MASS Data MWSC Data
Proper Motion in RA (mas/yr) -0.864 +/- 0.252  -0.806 +/- 0.387
Proper Motion in Dec (mas/yr) -0.624 +/- 0.339 -0.657 +/- 0.508
Distance (kpc) 1.04 +/- 100% 0.902 +/- 100%
log(age) (log(yr)) 8.39 2.23
Metallicity (solar) -0.170 0
E(B-V) (mag) 0.210 0.229

 

The values of these two models yields no real significant error, except for the determined ages. The Gaia and 2MASS data generated a age of 2.34×10^8 yrs while the MWSC data had a age of 1.69×10^2 yrs. This is a very significant difference and is possibly why the MWSC plot has more prominent younger stars. In addition to this the presence of blue stars is evident in both plots as well as in the images. It is also clear that the isochrone fit in the MWSC graph does not fit as well to the main sequence, but still attributes to a accurate reading of these values for the cluster. Moreover, the presence of red giants is slightly visible on the Gaia and 2MASS plot, but even more visible on the MWSC plot. This could be due to the age difference. 

Some challenges that came from this analysis would be the initial plotting of the Gaia and 2MASS data on to my values. When determining and lining up the proper motions, the presence of a clear star cluster was not evident and could of have lead to some miscalculation. 

 

Conclusion

In conclusion, this project was a great deal of fun! The use of Afterglow to produce data and analyze it through Cluster Pro Plus was definitely challenging, but also furthered my knowledge in examining different types of stars and how to identify them in a cluster. Through this blog all my ideas came together in a coherent fashion that solidified my findings in FYRE Assignment 2.2 and I overall really enjoyed the process.

 

 

References:Â