Survival of very small carbonaceous dust grains in the inner circumgalactic medium of NGC 891 from JWST/MIRI MRS
Abstract
We present new spectroscopic observations of the inner circumgalactic medium (CGM) of NGC 891 taken with the Mid-Infrared Imager/Medium Resolution Spectroscopy instrument on board JWST, in four positions: two near the bulge and two at galactocentric radii ( r ) of ∼1.5, 4.7 kpc. Each pair of pointings has one position along the minor axis ( h ) at ∼0.5 kpc and one at ∼1 kpc away from the mid-plane. We analysed 1D spectra and 3D cubes using the dust emission model PAHFIT to extract properties of typical mid-IR features. These spectra reveal that the earlier reported mid-IR emission out to 4 kpc is dominated by the emission of polycyclic aromatic hydrocarbons (PAHs), and not hot dust continuum, thus providing direct evidence of the survival of PAHs in the inner CGM of NGC 891. Comparing PAH band ratios with other environments (Orion, M51), it is obvious that the 11.2 μm PAH feature – and not the usual 7.7 μm – dominates in NGC 891, which seems to imply the presence of more neutral, large PAHs in the CGM. Overall, PAH-to-continuum ratios show little variations with scale-height and radius in NGC 891, which suggests little PAH processing. However, we do see a decrease in the PAH feature strengths with the [Ne III ]/[Ne II ] ratio, which points to elevated dust processing with increased radiation field hardness. We also confirm a tight correlation between H 2 and PAH features, which suggests that the two tracers must be co-spatial, and hence implies that PAH emission predominantly arises from cool dense parts of cloudlets entrained in galactic outflows. Finally, we report the clear detection of a previously unidentified PAH feature at 16.72 μm.
Related
- Catalytic formation of H2 on carbonaceous dust grains - implications for interstellar observations
- The multiphase circumgalactic medium in the epoch of reionization: CII and CIV absorbers around [OIII] emitters
- Using the Circumgalactic Medium of Dwarf Galaxies as a Calorimetric Dark Matter Detector
- Galactic Cosmic-Ray Transport in the Giant Circumgalactic Medium Halo
- Intrinsic Soft X-ray Emission from the Hot Circumgalactic Medium in IllustrisTNG
BibTeX
@article{chastenet2026survival,
title = {{Survival of very small carbonaceous dust grains in the inner circumgalactic medium of NGC 891 from JWST/MIRI MRS}},
author = {Jérémy Chastenet and Ilse De Looze and Karl Gordon and Suzanne Madden and Monica Relaño and Karin Sandstrom and Dries van de Putte and Maarten Baes and Simone Bianchi and Alberto Bolatto and Viviana Casasola and Daniel Dale and Sara Duval and Jacopo Fritz and Frédéric Galliano and Simon Glover and Stavroula Katsioli and Vasileios Katsis and Florian Kirchschlager and Ralf Klessen and Rebecca Levy and Sharon Meidt and Aleksandr Mosenkov and Kentaro Nagamine and Lara Pantoni and Helena Richie and Stefanie Walch and Thomas Williams and Emanuele Xilouris},
journal = {Astronomy \& Astrophysics - A\&A},
year = {2026},
month = aug,
doi = {10.1051/0004-6361/202558757},
eprint = {2605.26864},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05741200v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Survival of very small carbonaceous dust grains in the inner circumgalactic medium of NGC 891 from JWST/MIRI MRS
AU - Jérémy Chastenet
AU - Ilse De Looze
AU - Karl Gordon
AU - Suzanne Madden
AU - Monica Relaño
AU - Karin Sandstrom
AU - Dries van de Putte
AU - Maarten Baes
AU - Simone Bianchi
AU - Alberto Bolatto
AU - Viviana Casasola
AU - Daniel Dale
AU - Sara Duval
AU - Jacopo Fritz
AU - Frédéric Galliano
AU - Simon Glover
AU - Stavroula Katsioli
AU - Vasileios Katsis
AU - Florian Kirchschlager
AU - Ralf Klessen
AU - Rebecca Levy
AU - Sharon Meidt
AU - Aleksandr Mosenkov
AU - Kentaro Nagamine
AU - Lara Pantoni
AU - Helena Richie
AU - Stefanie Walch
AU - Thomas Williams
AU - Emanuele Xilouris
PY - 2026
DA - 2026/08/14
JO - Astronomy & Astrophysics - A&A
DO - 10.1051/0004-6361/202558757
UR - https://hal.science/hal-05741200v1
AB - We present new spectroscopic observations of the inner circumgalactic medium (CGM) of NGC 891 taken with the Mid-Infrared Imager/Medium Resolution Spectroscopy instrument on board JWST, in four positions: two near the bulge and two at galactocentric radii ( r ) of ∼1.5, 4.7 kpc. Each pair of pointings has one position along the minor axis ( h ) at ∼0.5 kpc and one at ∼1 kpc away from the mid-plane. We analysed 1D spectra and 3D cubes using the dust emission model PAHFIT to extract properties of typical mid-IR features. These spectra reveal that the earlier reported mid-IR emission out to 4 kpc is dominated by the emission of polycyclic aromatic hydrocarbons (PAHs), and not hot dust continuum, thus providing direct evidence of the survival of PAHs in the inner CGM of NGC 891. Comparing PAH band ratios with other environments (Orion, M51), it is obvious that the 11.2 μm PAH feature – and not the usual 7.7 μm – dominates in NGC 891, which seems to imply the presence of more neutral, large PAHs in the CGM. Overall, PAH-to-continuum ratios show little variations with scale-height and radius in NGC 891, which suggests little PAH processing. However, we do see a decrease in the PAH feature strengths with the [Ne III ]/[Ne II ] ratio, which points to elevated dust processing with increased radiation field hardness. We also confirm a tight correlation between H 2 and PAH features, which suggests that the two tracers must be co-spatial, and hence implies that PAH emission predominantly arises from cool dense parts of cloudlets entrained in galactic outflows. Finally, we report the clear detection of a previously unidentified PAH feature at 16.72 μm.
SN - 0004-6361
SN - 1432-0746
ER -