Extended Hot Gas in the Galactic Center
Abstract
The inner 300--500 pc of the Milky Way, the Central Molecular Zone (CMZ), is one of the most extreme environments for molecular gas in our Galaxy. Physical properties of the CMZ, including temperature, density, thermal pressure, and turbulent pressure, are key factors for characterizing gas energetics, kinematics, and evolution. In order to better understand the extreme environments in the CMZ, we must better understand the physical conditions of the molecular gas across the entire CMZ. Many of these physical conditions can be derived from observation of ammonia (NH3). We observe NH3 J,K=(1,1)-(6,6) inversion transitions, up to 408K above the ground state, from SWAG (Survey of Water and Ammonia in the Galactic Center) using the Australia Telescope Compact Array (ATCA). We generate maps of the gas kinetic temperature, density, and kinematics covering the entire CMZ. These maps quantitatively agree with previous studies of selected regions at lower resolution which have indicated the presence of multiple temperature components. Rotational temperatures average ∼60K across the CMZ, though several regions, excluding Sgr B2 and Sgr A, exhibit temperatures of 150-200K and higher. Additionally, we observe higher NH3 transitions of J,K=(8,8)-(13,13) (E_{up}=1690 K) in a sample of clouds using the 100m Robert C. Byrd Green Bank Telescope (GBT) toward selected regions across the CMZ. These higher transitions probe higher temperatures, and we find rotational temperatures greater than 400K for CMZ clouds out to a radius of 400 pc. We identify some of the most extreme molecular gas temperatures detected in the Galactic center thus far. However, with this sample, we do not find a correlation between the hot temperature component and galactocentric radius, nor do we find a relationship between these high temperatures and actively star-forming clouds.
- Publication:
-
The 35th Annual New Mexico Symposium
- Pub Date:
- February 2020
- Bibcode:
- 2020anms.conf...16C