Characterizing Spatial Variations of PAH Emission in the Reflection Nebula NGC 1333

Abstract

Infrared emission features at 3.3, 6.2, 7.7, 8.6, and 11.2 $\mu$m, attributed to polycyclic aromatic hydrocarbons, show variations in relative intensity, shape, and peak position. These variations depend on the physical conditions of the photodissociation region (PDR) in which strong PAH emission arises, but their relationship has yet to be fully quantified. We aim to better calibrate the response of PAH species to their environment using observations with matching apertures and spatial resolution. We present observations from the Field-Imaging Far-Infrared Line Spectrometer (FIFI-LS) on board the Stratospheric Observatory for Infrared Astronomy (SOFIA) of the gas cooling lines [OI] 63, 146 $\mu$m and [CII] 158 $\mu$m in the reflection nebula NGC 1333 and use archival dust continuum observations from the Photodetector Array Camera and Spectrometer (PACS) on board Herschel. We employ PDR modelling to derive the physical conditions and compare these with the characteristics of the PAH emission as observed with the Infrared Spectrometer (IRS) on board Spitzer. We find distinct spatial characteristics for the various PAH spectral components. We conclude that the ionic bands (6.2, 7.7, 8.6, and 11.0) and the 7-9 $\mu$m emission are due to multiple PAH sub-populations and that the plateaus are distinct from the features perched on top. The 6-9 $\mu$m PAH emission exhibit a significant change in behaviour between the irradiated PDR and diffuse outskirts, confirming these bands arise from multiple PAH sub-populations with different underlying molecular properties. We find multiple promising relationships between PAH ratios and the FUV radiation field strength but no clear correlations with the PAH ionization parameter.

arXiv comment22 pages, 21 figures, to be published in MNRAS

References in corpus (40)

• Herschel Space Observatory - An ESA facility for far-infrared and submillimetre astronomy
• The Spitzer Space Telescope Mission
• The Photodetector Array Camera and Spectrometer (PACS) on the Herschel Space Observatory
• The Dark Molecular Gas
• Far Infrared and Submillimeter Emission from Galactic and Extragalactic Photo-Dissociation Regions
• The rich 6 to 9 um spectrum of interstellar PAHs
• Photodissociation and photoionisation of atoms and molecules of astrophysical interest
• Spitzer Observations of NGC 1333: A Study of Structure and Evolution in a Nearby Embedded Cluster
• Mid-IR Galaxy Classification Based on Silicate Obscuration and PAH Equivalent Width
• The CH out-of-plane bending modes of PAH molecules in astrophysical environments
• Formation of buckminsterfullerene (C60) in interstellar space
• Variations of the Mid-IR Aromatic Features Inside and Among Galaxies
• The profiles of the 3 to 12 $\mu$m PAH features
• Astrometry of Water Maser Sources in Nearby Molecular Clouds with VERA - II. SVS 13 in NGC 1333
• Interstellar Carbon in Translucent Sightlines
• Spectral Mapping Reconstruction of Extended Sources
• Analysis of the emission of very small dust particles from Spitzer spectro-imagery data using blind signal separation methods
• The infrared spectra of very large, compact, highly symmetric, polycyclic aromatic hydrocarbons (PAHs)
• The aromatic infrared bands as seen by ISO-SWS: probing the PAH model
• The Infrared Spectra of Very Large Irregular Polycyclic Aromatic Hydrocarbons (PAHs): Observational Probes of Astronomical PAH Geometry, Size and Charge
• Evaporating Very Small Grains as tracers of the UV radiation field in Photo-dissociation Regions
• Mapping PAH sizes in NGC 7023 with SOFIA
• The PAH emission characteristics of the reflection nebula NGC2023
• Direct spectroscopic evidence for ionized PAHs in the interstellar medium
• Mixed aliphatic and aromatic composition of evaporating very small grains in NGC 7023 revealed by the 3.4/3.3 $\mu$m ratio
• Variations of the Mid-IR Emission Spectrum in Reflection Nebulae
• The 15-20 um emission in the reflection nebula NGC2023
• The chemistry of interstellar argonium and other probes of the molecular fraction in diffuse clouds
• Examining the class B-to-A shift of the 7.7 $\mu$m PAH band with the NASA Ames PAH IR Spectroscopic Database
• Polycyclic Aromatic Hydrocarbon emission in Spitzer/IRS maps I: Catalog and simple diagnostics
• Polycyclic Aromatic Hydrocarbon emission in Spitzer/IRS maps II: A direct link between band profiles and the radiation field strength
• Probing the Ionization States of Polycyclic Aromatic Hydrocarbons via the 15-20 μm Emission Bands
• Interpreting the subtle spectral variations of the 11.2 and 12.7 μm polycyclic aromatic hydrocarbon bands
• The mid-infrared appearance of the Galactic Mini-Starburst W49A
• A Principal Component Analysis of polycyclic aromatic hydrocarbon emission in NGC 2023
• The fine structure line deficit in S 140
• Extinction and PAH intensity variations across the HII region IRAS 12063-6259
• Astronomical Image Processing with Array Detectors
• Tracing PAH Size in Prominent Nearby Mid-Infrared Environments
• Characterizing the PAH Emission in the Orion Bar