2018/12/31 by Jeffrey G. Mangum, Adam G. Ginsburg, Christian Henkel +3 · 1 citation
Physics and Astronomy · #astro-ph.GA
paper · pdf · doi:10.3847/1538-4357/aafa15
60 pages, 25 figures (whew!), Accepted for publication in ApJ, Latest version includes minor corrections following proof submission
arxiv created 2019/01/18 · arxiv updated 2019/09/25
The nuclear starburst within the central ∼ 15′′ (∼ 250 pc; 1′′ ≃ 17 pc) of NGC253 has been extensively studied as a prototype for the starburst phase in galactic evolution. Atacama Large Millimeter/submillimeter Array (ALMA) imaging within receiver Bands 6 and 7 have been used to investigate the dense gas structure, kinetic temperature, and heating processes which drive the NGC253 starburst. Twenty-nine transitions from fifteen molecular species/isotopologues have been identified and imaged at 1.′′5 to 0.′′4 resolution, allowing for the identification of five of the previously-studied giant molecular clouds (GMCs) within the central molecular zone (CMZ) of NGC253. Ten transitions from the formaldehyde (H2CO) molecule have been used to derive the kinetic temperature within the ∼ 0.′′5 to 5′′ dense-gas structures imaged. On ∼ 5′′ scales we measure TK \gtrsim 50 K, while on size scales \lesssim 1′′ we measure TK \gtrsim 300 K. These kinetic temperature measurements further delineate the association between potential sources of dense gas heating. We have investigated potential heating sources by comparing our measurements to models which predict the physical conditions associated with dense molecular clouds that possess a variety of heating mechanisms. This comparison has been supplemented with tracers of recently-formed massive stars (Brγ) and shocks ([FeII]). Derived molecular column densities point to a radially-decreasing abundance of molecules with sensitivity to cosmic ray and mechanical heating within the NGC253 CMZ. These measurements are consistent with radio spectral index calculations which suggest a higher concentration of cosmic ray producing supernova remnants within the central 10 pc of NGC253.