DATA SET

A data set of 113 galaxies was presented by Zsolt Frei, Puragra Guhathakurta, and James E. Gunn at Princeton University and J. Anthony Tyson at AT&T Bell Laboratories (1996). The galaxies were chosen to span the Hubble classification classes. All the galaxies in the set are nearby, well resolved and bright with the faintest having the total magnitude B_T of 12.90. The sample was chosen to be suitable to test automatic galaxy classification techniques with the idea that automatic methods of classifying galaxies are necessary to handle the huge amount of data that will soon be available from large survey projects, such as the Sloan Digital Sky Survey. All the images of the set were recorded with charge coupled devices (CCDs) at the Palomar Observatory with the 1.5 meter telescope and at the Lowell Observatory with the 1.1 meter telescope. The images were stored in FITS (Flexible Image Transport System) format with important data on these galaxies published in the Third Reference Catalog of Bright Galaxies (de Vaucouleurs et al., 1991). Table 3 shows the number of spiral and elliptical galaxies observed at both of the observatories along with the broad band pass wavelengths of the filters through which they were observed.

 

Table 3: Data set

Observatory	Spiral Galaxies	Elliptical Galaxies	Bands (nanometer)
Palomar	31	0	500, 650 and 820
Lowell	58	14	450 and 650

The images were processed to a point where the flat field and bias corrections were made and stars were removed from them. It can be seen from Figures 4 through 6, which contain scaled down versions of the all the images from the catalog, that the collection contains a wide range of galaxy classes.

 

Figure 4: Data Set: NGC 2403 to NGC 4242

 

Figure 5: Data Set: NGC 4254 to NGC 5248

 

Figure 6: Data Set: NGC 5322 to NGC 6503