MUSTANG Penetrates the Central Molecular Zone

image of the Milky Way, with a blow-up of the Galactic center
MUSTANG 2 view of Galactic Center. (NSF/AUI/GBO; photo, S.Brunier)

The MUSTANG 2 (Multiplexed SQUID TES Array for Ninety Gigahertz) receiver on the Green Bank Telescope observes the sky at a wavelength of 3 millimeters. Typical astronomical objects that emit light at these wavelengths is the dust in molecular clouds! Dense clouds in space contain tiny dust particles that radiate millimeter wavelength light in all directions. The Green Bank Telescope can pick up these signals and map regions of the sky that contain these clouds. One such region is the center of our Galaxy, located ~25,000 light years away in the direction of the constellation Sagittarius.

The center of our Galaxy (also known as the Central Molecular Zone) is one of the most dynamic regions in the Milky Way. The extreme environment of the Central Molecular Zone is 10 to 100 times hotter and denser than clouds near our Solar System. Dense clouds in this inner region of the galaxy tend to be very “dusty” and are therefore observable with the MUSTANG 2 receiver on the Green Bank Telescope (GBT).

This inner region of the galaxy is only observable with instruments like the Green Bank Telescope. Visible light that our eyes can detect are scattered and absorbed by the disk of the Milky Way galaxy. Longer wavelengths like radio waves, however, can pass through the disk of the galaxy and reach the Earth. Only radio telescopes like the Green Bank Telescope can see and map features in the Central Molecular Zone. (CMZ).

The Central Molecular Zone contains extended structures from past episodes of star formation along with bright knots of current star forming sites. One of the most prominent star forming sites in our galaxy is located within the CMZ and is commonly known in astronomy as the ‘Sgr B2 Complex’. The Sgr B2 Complex contains numerous knots of dusty emission and is a well known stellar nursery of star formation. The dust in this region is heated by embedded young stars that are ionizing the gas that cocoons them.

As the stars evolve they blow off the surrounding gas and dust to create extended structures that are several light years across. These extended structures will appear fainter and wispier than their younger counterparts. The most common material found in the these super-hot regions is hydrogen, and the presence of these extended ionized hydrogen regions is evidence of an eruption of massive star formation in the Central Molecular Zone a few million years ago.

It was during this massive star formation in the Central Molecular Zone that two very massive star clusters were created. The young protostars in the Sgr B2 Complex are believed to eventually form another massive star cluster.

Stars (and protostars!) are not all that reside in the center of our galaxy. The Central Molecular Zone is also harbors a supermassive black hole and the tidal forces from that object pull and stretch the nearby gas and dust, heating them to high temperatures. The gas and dust near this black hole have a spiral-like structure that is also known as the ‘mini-spiral’ or the ‘circumnuclear disk’.

This MUSTANG 2 picture represents just a small portion of a much larger survey of the Galactic Plane (PI Adam Ginsburg).

image showing the inner ~300 light years of our Galactic Center using the MUSTANG receiver at 3mm (PI Adam Ginsburg, data reduction by Simon Dicker and the GBT MUSTANG team). These observations show how dynamic (and dusty!) the center of our Galaxy is and how the GBT can recover the faint dust emission located in this distant part of the Galaxy.
Green Bank Telescope image showing the inner ~300 light years of our Galactic Center using the MUSTANG 2 receiver at 3mm (PI Adam Ginsburg, data reduction by Simon Dicker and the GBT MUSTANG team). These observations show how dynamic (and dusty!) the center of our Galaxy is and how the GBT can recover the faint dust emission located in this distant part of the Galaxy. (NSF/AUI/GBO)