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Session: Extragalactic Astronomy and Astrophysics

Name: Dr. Alexandros Maragkoudakis (NASA Ames Research Center)
Coauthors: No coauthors were included.
Type: Oral
Title: Spectral variations among different scenarios of PAH processing or formation
Abstract:

Utilizing the NASA Ames PAH IR Spectroscopic Database, we examine the variations in the spectral characteristics and intensities of polycyclic aromatic hydrocarbons (PAHs) in two different scenarios of PAH processing (or formation): (1) small PAHs are being destroyed (or equivalently large PAHs are being formed, referred to as SPR case) and (2) large PAHs are being destroyed (or equivalently small PAHs are being formed, referred to as LPR case). The variation in the PAH band intensities as a function of the average number of carbon atoms ⟨Nc⟩ has the highest dynamic range in the SPR case, suggesting that smaller PAHs have higher impact on the PAH band strengths. PAH plateaus show overall declining emission with ⟨Nc⟩, and their higher dynamic range in the SPR case also suggests that smaller PAHs are mainly contributing to the plateau emission. The 7.7/(11.0 + 11.2) μm PAH band ratio presents the least amount of variance with the lowest dynamic range, rendering this ratio as the better choice for tracing PAH charge. The 3.3/(11.2 + 11.0) μm PAH band ratio is the only ratio that has both a monotonic variance and fully separated values among the SPR and LPR scenarios, highlighting its efficiency as PAH size tracer but also allowing the characterization of the dominant scenario of processing or formation in a given region or source. We present new PAH charge-size diagnostic diagrams, which can provide insights into the average, maximum, or minimum NC within astrophysical sources.