Recently, astroimager and longtime Astronomy magazine contributor Ken Crawford from Camino, California, sent me a note regarding some astronomical research he had collaborated in.
Ken Crawford stands next to his 20-inch RC Optical Systems Ritchey-Chrétien reflector in his observatory in Rancho Del Sol Camino, California. Crawford used this telescope to take the images of NGC 7600 he discusses in this blog.Some of you might know Ken in a different capacity. He’s one of the prime movers of the Advanced Imaging Conference held in Santa Clara, California, each year. What follows is a great response to someone who asks, “What do amateur astronomers contribute to science?”
Dear Michael,
“It Matters.”
I am excited to bring you some news about a special event that just occurred. I apologize for the long post, but some background needs to go with this story.
Cold Dark Matter is a theory that most of the material in the universe cannot be seen (it’s dark) and that it moves very slowly (it’s cold). It is the leading theory explaining the formation of galaxies, galaxy groups, and even the current known structure of the universe. One of the problems with the theory is that it predicts large amounts of small satellite galaxies called dwarf galaxies. These tiny galaxies are about 1/1000 the mass of our Milky Way, but the problem is that nobody has observed them. If this theory is correct, then where are all the dwarf galaxies that should be there?
Enter professional star-stream hunter David Martinez-Delgado. David is the principal investigator of the Stellar Tidal Stream Survey at the Max Planck Institute in Heidelberg, Germany. He believes the reason we do not see large amounts of dwarf galaxies is because larger galaxies absorb them as part of their formation process. If this is correct, then we should find remnants of these mergers in astronomical observations. These leftovers would show up as trails of dwarf galaxy debris made up mostly of stars. Astronomers call these debris trails star streams.
An international team of professional astronomers led by Martinez-Delgado has identified enormous star streams on the periphery of nearby spiral galaxies. With long-exposure images, the team showed the process of galactic cannibalism theorized between the Milky Way and the Sagittarius Dwarf galaxy. This is happening in our own backyard! Part of the work involves using computer modeling to show how larger galaxies merge and absorb the smaller ones.
Enter the amateurs. David recruited a small group of astroimagers to help search for and detect these stellar fossils. The team leader is R. Jay GaBany [another longtime Astronomy contributor], and you can read more about the Pilot Star Stream Survey here: http://www.cosmotography.com/images/stellar_stream_survey_overview.html.
Several years ago, GaBany asked me to become part of this team, and I have made several contributions to the survey. I am excited to announce that my latest contribution has resulted in a professional letter that has been accepted by The Astronomical Journal.
What makes this special is that Carlos Frenk, the director of the Institute for Computational Cosmology at Durham University in England, and his team found that my image of galaxy NGC 7600 helped validate their computer model. In particular, my picture helped explain how larger galaxies form by absorbing satellite dwarf galaxies and why we do not see large number of dwarf galaxies today. Carlos has appeared on several shows on the Science and Discovery channels, to name a few, to explain and show some of these amazing simulations. You can read more about Carlos here: http://www.iau.org/public_press/images/detail/iau1103c.
Of course, I got excited about my participation in this pro-am collaboration. The target galaxy has some special features called shells. I had to take long exposures and then carefully process the images to detect these structures and show the delicate anatomy within. Previous images of NGC 7600’s shell structures have not shown them this well. I also included two movies below the images on this website: http://www.imagingdeepsky.com/Galaxies/NGC7600/NGC7600.htm. The top one shows my image of NGC 7600 blending into the simulation at about the point when the shells start to form. The bottom movie shows the complete simulation. Don’t forget to click the full-screen button to zoom and pan around for the details.
What is groundbreaking scientifically is that the simulation uses the Cold Dark Matter theory modeling the dark matter halos of the galaxies. As you can see, it is pretty convincing. So now you know why we do not observe lots of dwarf galaxies in the universe. And it took an amateur’s help to find out.
Here is a link to The Astronomical Journal Letters paper: http://arxiv.org/abs/1111.2864.
Kindest Regards,
Ken Crawford
www.imagingdeepsky.com
Great work, Ken, and congratulations! And keep those images coming.
Astronomy.com blog
