A Pilot Survey
or the past few years an international team of professional researchers, led by Dr. David Martinez-Delgado (Max Planck Institute for Astronomy
), has conducted a preliminary survey of selected nearby galaxies seeking evidence of galactic mergers. Initially, the group relied exclusively on telescopes at major observatories. But, availability to large instruments is limited and competition for observing time is highly competitive requiring the submission and acceptance of proposals months in advance with the hope of being awarded only a precious few nights for observations each year. Since the number of candidate galaxies is large, the chances for quickly studying more than a few was daunting.
- The .5 meter telescope at Blackbird Observatory is located in the south central Sacramento Mountains of New Mexico at 7,300 feet above sea level.
- Photo credit: Ron Wodaski
So, the team leader decided to take a decidedly different approach by enlisting the help of a private observatory equipped with a relatively modest .5 meter telescope
. Since private observers have unfettered access to the night sky, his decision would enable a larger number of observations in a shorter period of time if the small instrument could produce usable scientific data
Initial tests proved surprisingly successful. For example, based on typical exposures reaching 8 hours or longer, the data collected by the .5 meter telescope reached magnitude 28, which is 10 times deeper than images produced by the Sloan Digital Sky Survey
- Rings and arcs aren't the only evidence of an ancient satellite mergers. This animation simulates the merger of numerous companion galaxies and demonstrates that plumes, spears, spikes and shells that surround the primary galaxy are also possible.
- Model animation credit: James Bullock (UC Irvine)
As a result, the first projects were able to provide conclusive evidence of ancient galactic mergers in near by galaxies that were heretofore unsuspected.
For example, both NGC4013
were shown to be surrounded by enormous tidal structures. Both images show vast rings that possibly trace the final orbits of long lost small companion galaxies whose constituents were shorn into streams of stars as the satellites were gravitationally disrupted and subsequently absorbed by their more massive parent.
But, according to the standard model, rings and loops aren't the only structures that can be produced when a satellite merges with its parent. So, a further investigation was launched and eight additional local galaxies were studied using several more
small private telescopes.
The results of the just released pilot survey
exhibit a host of amazing merger fossils.
The Umbrella Galaxy, NGC4651, is located in the constellation of Coma Berenices and situated about 35 million light years from our planet. This new view displays evidence of previous mergers with one or more satellite galaxies.
The shell of stellar debris apparently pierced by a narrow tidal 'spear' is consistent with predictions based on the standard model.
- Photo credit: R. Jay GaBany Cosmotography.com
For example, the first image of a set
that will be released over the next few months is focused on the Umbrella Galaxy, NGC4651
, a spiral located about 35 million light-years from Earth in the northern constellation of Coma Berenices. This star system has a diameter of about 50,000 light years and is approximately half the size of our home galaxy, the Milky Way.
The team's deep image reveals a shell of debris surrounding this galaxy which, according to the model, is indicative of an ancient satellite merger. Also evident is a narrow tidal spear that is superimposed over the face of the galaxy. Both ends of this structure are sheared providing further evidence of the titanic gravitational forces that ripped the satellite into shreds as it was flung back and forth. This image was produced by combining an hour of exposure through the Isaac Newton Telescope
, located on the Spanish island of La Palma, with over 13 hours of imagery obtained with the .5 meter telescope at the Blackbird Observatory
in New Mexico (USA).
The team has now embarked on a larger multi-year survey that encompasses 50 local galaxies. This investigation will conduct a statistical analysis to determine the percentage of star systems with ancient merger activity. Additional private observers have been recruited in hopes the survey can be completed and reported as early as 2012.