Deep in our Milky Way galaxy's center, a candy cane emerges as the centerpiece of a new, colorful composite image from a NASA camera, just in time for the holidays.
The image--captured by a NASA-designed and built instrument called the Goddard-IRAM Superconducting 2-Millimeter Observer, or GISMO--shows the inner part of our galaxy, which hosts the largest, densest collection of giant molecular clouds in the Milky Way. These vast, cool clouds contain enough dense gas and dust to form tens of millions of stars like the Sun. The view spans a part of the sky about 1.5 degrees across, equivalent to roughly three times the apparent size of the Moon.
Two papers describing the image, one led by Johannes Staguhn at The Johns Hopkins University and the other led by Richard Arendt at The University of Maryland, were recently published in The Astrophysical Journal.
"The galactic center is an enigmatic region with extreme conditions where velocities are higher and objects frequently collide with each other," says Staguhn, who leads the GISMO team at NASA'S Goddard Space Flight Center.
"GISMO gives us the opportunity to observe microwaves with a wavelength of 2 millimeters at a large scale, combined with an angular resolution that perfectly matches the size of galactic center features we are interested in. Such detailed, large-scale observations have never been done before."
The studies detail how, after spending 8 hours looking at the sky and collecting data, GISMO detected the most prominent radio filament in the galactic center, making this the shortest wavelength where these curious structures have been observed. Scientists say the filaments delineate the edges of a large bubble produced by some energetic event at the galactic center.
"We're very intrigued by the beauty of this image; it's exotic. When you look at it, you feel like you're looking at some really special forces of nature in the universe," muses Staguhn.
The image is a composite of different color codes for emission mechanisms. Blue and cyan features reveal cold dust in molecular clouds where star formation is still in its infancy. Yellow features reveal the presence of ionized gas and show well-developed star factories; this light comes from electrons that are slowed but not captured by gas ions, a process also known as free-free emission. Red and orange regions show areas where synchrotron emission occurs, such as in the prominent Radio Arc and Sagittarius A, the bright source at the galaxy's center that hosts its supermassive black hole.
To make the image, the team acquired GISMO data, shown in green, in April and November 2012. They then used archival observations from the European Space Agency's Herschel satellite to model the far-infrared glow of cold dust, which they then subtracted from the GISMO data. Next, they added, in blue, existing 850-micrometer infrared data from the SCUBA-2 instrument on the James Clerk Maxwell Telescope. Finally, they added, in red, archival longer-wavelength 19.5-centimeter radio observations from the National Science Foundation's Karl G. Jansky Very Large Array. The higher-resolution infrared and radio data were then processed to match the lower-resolution GISMO observations. The team used GISMO in concert with a 30-meter radio telescope located on Pico Veleta, Spain.
Moving forward, Staguhn hopes to upgrade and take GISMO to the Greenland Telescope to make large surveys on the sky looking for the first galaxies in the universe where stars formed.
"There's a good chance that a significant part of star formation that occurred during the universe's infancy is obscured and can't be detected by tools we've been using, and GISMO will be able to help detect what was previously unobservable," says Staguhn.
The Astrophysical Journal