Tierra Candelaria

The central ∼300 pc of the Galaxy is known as the Central Molecular Zone (CMZ). It is the closest galactic nucleus, contains ∼10% of the total molecular gas in the galaxy, and is considered to be extreme in terms of gas and star formation properties when compared to the disk of the galaxy. This makes it optimal for studying molecular gas in extreme environments. Star formation in the CMZ is high, but is around an order of magnitude lower than expected given the amount of dense gas in this region. Gas is the building block of star formation, so understanding the gas is essential for providing insight on star formation in this extreme environment. We combine interferometric ammonia (NH3) data from the Survey for Water and Ammonia in the Galactic center (SWAG) with single dish data from the H2O Southern Galactic Plane Survey (HOPS) to form a data set called SWAPS. This data set has more transitions, higher resolution, and a larger field of view than any other CMZ ammonia survey to date. Our goals are to quantify the temperatures across the CMZ and to determine the heating mechanism responsible for the elevated temperatures. We find a fairly uniform temperature component of ∼80–100 K across the CMZ with SWAPS. We do not observe a spatial dependence, nor do we find a correlation between galactocentric radius and temperature or linewidths. In order to reproduce the temperature map in SWAPS, we must implement a lower limit for the cosmic ray ionization rates of ∼10−15 s−1, from which we calculate heating rates for cosmic ray heating and turbulent heating. Additionally, using SWAPS and supplemental Green Bank Telescope (GBT) data, we investigate hotter temperatures using even higher rotational transitions of NH3. We find hot temperatures are spread throughout the CMZ and conclude that turbulent heating alone is capable of heating the gas to the temperature we see, but we cannot rule out cosmic rays as a contributor to heating in some part of the CMZ. The CMZ remains one of the most complex and compelling regions in the Milky Way, offering a window into understanding molecular gas as the birthplace for star formation under extreme conditions.

Zoom Link: https://nmt-edu.zoom.us/j/98411502294?pwd=Hd5aavhYcZGMk7jealLhJ3tqjeGyC8.1