The Sarah's Galaxy - July 2011

About the image…

Image Subject – NGC 3628, the Sarah's Galaxy.
Location Taken – Teide Observatory (Canary Islands – Spain; 16º 30' 35" W, 28º 18' 00" N).
Telescope – IAC80.
Instrument – CCD E2V 42-40.
Focal Ratio –
Cassegrain f/11.3.
Exposure –
Mosaic of 2x1 images. B: 6 x 600 s, V: 6 x 600 s, R: 3 x 600 s, H-alfa: 3 x 1200 s.
Image Size –
2994 x 1932 pixels (15.2 x 9.8 arcminutes).
Software – IRAF, PixInsight.
Images taken and reduced by –
Pablo Rodríguez-Gil and Pablo Bonet.
Pablo Rodríguez-Gil.

Overlooked by Charles Messier, NGC 3628 is a member of the Leo triplet of galaxies sharing its neighbourhood with M65 and M66. It was discovered by William Herschel in 1784 and can be found at about 35 million light-years from Earth in the northern constellation Leo. Sarah's Galaxy is believed to be a SAb spiral. Its extreme inclination emphasizes prominent dust lines as can be seen in this mosaic of two images taken with the IAC80 telescope. NGC 3628 is peculiar in that its disc clearly fans out near the edges. Because of its appearance, NGC 3628 was catalogued as Arp 317 in the Atlas of Peculiar Galaxies, published in 1966, which aimed to characterize a large sample of odd objects that fell outside the standard Hubble classification, to aid understanding of how galaxies evolve. The galaxy also exhibits a faint tidal tail extending some 300000 light years towards the east (outside the field of view of this image), a result of gravitational interaction with the other two members of the Leo triplet. This month's AIM also reveals a large number of galaxies of different shapes and colours, some of which lie much further away than NGC 3628. Particularly noticeable is the fuzzy blob just to the south of NGC 3628, which is a diffuse satellite galaxy. A number of globular clusters can be seen as fuzzy reddish spots in the halo of the galaxy. Also visible as bright red spots, especially to the west, are star forming regions, recorded in the H-alpha channel of this composite image.