Fire in the Heart: A Characterization of the High Kinetic Temperatures and Heating Sources in the Nucleus of NGC253

Abstract

The nuclear starburst within the central $\sim 15^{\prime \prime }$ ($\sim 250$ pc; $1^{\prime \prime }\simeq 17$ 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 $1{.}^{\prime \prime }5$ to $0{.}^{\prime \prime }4$ 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 (H${}_2$CO) molecule have been used to derive the kinetic temperature within the $\sim 0{.}^{\prime \prime }5$ to $5^{\prime \prime }$ dense-gas structures imaged. On $\sim 5^{\prime \prime }$ scales we measure $T_K\gtrsim 50$ K, while on size scales $\lesssim 1^{\prime \prime }$ we measure $T_K\gtrsim 300$ 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 (Br$\gamma$) 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.

60 pages, 25 figures (whew!), Accepted for publication in ApJ, Latest version includes minor corrections following proof submission

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Cited by in corpus (32)

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• The molecular outflow in NGC253 at a resolution of two parsecs
• ALMA view of the ${}^{12}$C/${}^{13}$C isotopic ratio in starburst galaxies
• Tracing Interstellar Heating: An ALCHEMI Measurement of the HCN Isomers in NGC 253
• The Distribution and Origin of C${}_2$H in NGC 253 from ALCHEMI
• First extragalactic detection of a phosphorus-bearing molecule with ALCHEMI: phosphorus nitride (PN)
• Starburst Energy Feedback Seen Through HCO${}^{+}$/HOC${}^{+}$ Emission in NGC 253 from ALCHEMI
• A Consistent Set of Empirical Scaling Relations for Spiral Galaxies: The $(v_{\max },M_{\mathrm{DM}})$-$({\sigma }_0,M_{\mathrm{BH}},\varphi )$ Relations
• Spatially resolved carbon and oxygen isotopic ratios in NGC 253 using optically thin tracers
• Energizing Star Formation: The Cosmic Ray Ionization Rate in NGC 253 Derived From ALCHEMI Measurements of H${}_3$O${}^{+}$ and SO
• A 2-3 mm high-resolution molecular line survey towards the centre of the nearby spiral galaxy NGC 6946
• The Molecular ISM in the Super Star Clusters of the Starburst NGC 253
• Kinetic temperature of massive star-forming molecular clumps measured with formaldehyde IV. The ALMA view of N113 and N159W in the LMC
• The turbulent gas structure in the centers of NGC253 and the Milky Way
• ALCHEMI finds a "shocking" carbon footprint in the starburst galaxy NGC~253
• Reconstructing the shock history in the CMZ of NGC 253 with ALCHEMI
• Discovery of Methanimine Megamasers Toward Compact Obscured Galaxy Nuclei
• The Opaque Heart of the Galaxy IC 860: Analogous Protostellar, Kinematics, Morphology, and Chemistry
• History-independent tracers: Forgetful molecular probes of the physical conditions of the dense interstellar medium
• Submillimeter observations of molecular gas interacting with the supernova remnant W28
• Kinetic temperature of massive star-forming molecular clumps measured with formaldehyde V. The massive filament DR21
• An ALCHEMI inspection of sulphur-bearing species towards the central molecular zone of NGC 253
• Sequential Star Formation in the Young SMC Region NGC 602: Insights from ALMA
• Molecular isotopologue measurements toward super star clusters and the relation to their ages in NGC253 with ALCHEMI
• APEX and NOEMA observations of H${}_2$S in nearby luminous galaxies and the ULIRG Mrk~231 -- Is there a relation between dense gas properties and molecular outflows?
• Unveiling Kinematic Structure in the Starburst Heart of NGC 253
• Shock-induced HCNH+ abundance enhancement in the heart of the starburst galaxy NGC 253 unveiled by ALCHEMI
• Complex Organic Molecules towards the central molecular zone of NGC 253
• Discovery of a giant molecular loop in the central region of NGC 253
• Chemical templates of the Central Molecular Zone. Shock and protostellar object signatures under Galactic Center conditions
• ArH+ and H2O+ absorption towards luminous galaxies
• First detection of a deuterated molecule in a starburst environment within NGC 253