Galactic Center Photo Contest

The NRAO Photo Contest

The Galactic Center and the surrounding Central Molecular Zone comprise the most active star formation region in the Milky Way. This 2 x 1 degree field was imaged at 20 cm (purple) with the NRAO Very Large Array, tracing H II regions that are illuminated by hot, massive stars, supernova remnants, and synchrotron emission. Emission at 1.1 mm (orange) was observed with the Caltech Submillimeter Observatory and highlights cold (20-30 K) dust associated with molecular gas. Some of this material will form stars within in the next few million years; the remainder will be blown away. The diffuse cyan and colored star images are from the Spitzer Space Observatory's Infrared Array Camera. The cyan is primarily emission from stars, the point sources, and from polycyclic aromatic hydrocarbons (PAHs), the diffuse component.

My view of the Galactic Center is the winner of this year's NRAO photo contest. It displays a multiwavelength view of the galactic center. The caption at the NRAO photo contest (reproduced above) describes it well, but I will go into further depth here.

The 'arches' are the large purple filamentary structures seen near the brightest point in the map, Sgr A*, the center of our galaxy. They are thought to be large scale magnetic fields possibly generated by winds from hot stars. Farhad Yusef-Zadeh, my collaborator on the photo, leads the study of radio emission from the Galactic Center.

The orange color is 1.1mm emission, which means that we're seeing something completely different. This light actually comes from dust. We usually see dust in absorption because in the optical, it blocks light. There is so much dust between us and the Galactic Center that we can't see it at all at optical wavelengths.

Sagittarius B2 is the bright blob just to the left of center. It is the most massive collection of gas and dust in our galaxy. It is full of different types of molecules including complex organic molecules. A new generation of massive stars is thought to be forming there.

Spitzer's 8 micron view is presented in cyan. Mostly this comes from PAH, Polycyclic Aromatic Hydrocarbon, emission. PAHs are big molecules with lots of Carbon and Hydrogen chained together. Stars are visible at these wavelengths because the dust isn't as effective at blocking out infrared light - but look closely at the orange regions on the right side of the image. You might notice that not only is there dust there, but there's also less PAH emission visible. This is because on the right side of the Galactic Center, the spiral arm is behind the dust, and on the left side it is in front. When dust blocks out infrared light, the object we see is called an 'infrared dark cloud'. These clouds are usually places where star formation has not yet started, but will soon.

This image was created using GIMP, the Gnu Image Manipulation Program, using a variety of layers, opacities, etc.