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.