Arakelian Galaxies

An observing plan containing the Arakelian Galaxies has been posted recently to the Deep-Sky Planner Observing Plan Library (licensed users only.) This plan should be of particular interest to galaxy hunters, so more background is included here.

Russian astrophysicist Marat Arakelian published a paper in 1975 in which he studied the correlation between high surface brightness (HSB) galaxies and active galactic nuclei. Arakelian defined HSB as 22 magnitudes per square arc second (mpsas) or brighter.

Deep-Sky Planner shows surface brightness (SB) for galaxies when possible. The value comes either from catalogs when it is available, or it is calculated using a formula that is a little different from that used by Arakalian. Because of these differences, the plan has some SB values that are dimmer than 22. Most of the galaxies in the plan are smaller than 1 arc minute in size, thus contributing to high surface brightness. With this in mind, the observing plan contains about 500 of 591 galaxies with SB values of 22 or brighter. These galaxies (with SB <= 22) should be bright enough to be seen in large amateur telescopes in a dark sky location - those with skies perhaps 20.5 mpsas or darker.

Arakelian studied galaxies no further south than -3 degrees declination, so they are visible to northern hemisphere observers, and most are visible to observers at moderately southern latitudes.

The study found that there were more elliptical and lenticular galaxies in the study sample than one might find in a random sample, thus proving that there was a correlation between high surface brightness and active galactic nuclei. Arakelian's study was an important basis for further research. Arakelian himself had only a few years to explore the matter further since he died in 1983 at the young age of 52.

Integrated Flux Nebulae

I recently read about integrated flux nebulae (IFN), whose name was coined by amateur astronomer Steve Mandel. Steve photographed and cataloged a number of objects at high galactic latitudes that were wispy, dusty nebulae, though uncatalogued by professional astronomers.

A quick visit to Steve's web site reveals his personal pursuit of identifying these objects, and what his research has uncovered about them. Steve's work on these objects has been recognized by the American Astronomical Society (2008 Chambliss Award for Amateur Achievement) and the Astronomical Society of the Pacific (2008 Amateur Achievement Award). Professional astronomers have begun investigating these objects based on Steve's work.

In a recent email from Steve, he explains that the catalog will be renamed "Mandel Catalogue of Unexplored High-Latitude Galactic Dust Nebula". He continues his work on this project.

An observing plan containing the current list of integrated flux nebulae has been uploaded to the Plan Library which is available to licensed users of Deep-Sky Planner. It contains the list of objects and Steve's comments about each. Steve has kindly granted permission to use this information in Deep-Sky Planner.