Cold molecular gas and PAH emission in Seyfert galaxies

Abstract

We investigate the relation between the detection of the $11.3\mu$m PAH feature in the nuclear ($\sim 24-230$pc) regions of 22 nearby Seyfert galaxies and the properties of the cold molecular gas. For the former we use ground-based (0.3-0.6" resolution) mid-infrared (mid-IR) spectroscopy. The cold molecular gas is traced by ALMA and NOEMA high (0.2-1.1") angular resolution observations of the CO(2-1) transition. Galaxies with a nuclear detection of the $11.3\mu$m PAH feature contain more cold molecular gas (median $1.6\times 10^7{M}_{\odot }$) and have higher column densities ($N({\mathrm{H}}_2)=2\times 10^{23}{\mathrm{cm}}^{-2}$) over the regions sampled by the mid-IR slits than those without a detection. This suggests that molecular gas plays a role in shielding the PAH molecules in the harsh environments of Seyfert nuclei. Choosing the PAH molecule naphthalene as an illustration, we compute its half-life in the nuclear regions of our sample when exposed to 2.5keV hard X-ray photons. We estimate shorter half-lives for naphthalene in nuclei without a $11.3\mu$m PAH detection than in those with a detection. The Spitzer/IRS PAH ratios on circumnuclear scales ($\sim$ 4" $\sim$ 0.25-1.3kpc) are in between model predictions for neutral and partly ionized PAHs. However, Seyfert galaxies in our sample with the highest nuclear H${}_2$ column densities are not generally closer to the neutral PAH tracks. This is because in the majority of our sample galaxies, the CO(2-1) emission in the inner $\sim$ 4" is not centrally peaked and in some galaxies traces circumnuclear sites of strong star formation activity. Spatially resolved observations with the MIRI medium-resolution spectrograph (MRS) on the James Webb Space Telescope will be able to distinguish the effects of an active galactic nucleus (AGN) and star formation on the PAH emission in nearby AGN.

Accepted for publication in A&A

References in corpus (27)

• BAT AGN Spectroscopic Survey - V. X-ray properties of the Swift/BAT 70-month AGN catalog
• A Close Look at Star Formation around Active Galactic Nuclei
• BAT AGN Spectroscopic Survey I: Spectral Measurements, Derived Quantities, and AGN Demographics
• Variations of the Mid-IR Aromatic Features Inside and Among Galaxies
• Spectral Mapping Reconstruction of Extended Sources
• Near-Infrared and Star-forming properties of Local Luminous Infrared Galaxies
• Molecular line emission in NGC1068 imaged with ALMA: II. The chemistry of the dense molecular gas
• ALMA images the many faces of the NGC1068 torus and its surroundings
• Spitzer/IRS 5-35 um Low-Resolution Spectroscopy of the 12 um Seyfert Sample
• Nuclear 11.3$\mu$m PAH emission in local active galactic nuclei
• The Effect of Active Galactic Nuclei on the Mid-Infrared Aromatic Features
• Coevolution of Supermassive Black Holes and Circumnuclear Disks
• AGN-Starburst connection in NGC7582: Gemini near-infrared spectrograph integral field unit observations
• Radio Variability in Seyfert Nuclei
• PAH features within few hundred parsecs of active galactic nuclei
• Understanding the 8 micron vs. Pa-alpha relationship on sub-arcsecond scales in Luminous Infrared Galaxies
• Starbursts and torus evolution in AGN
• The Origin of the Silicate Emission Features in the Seyfert 2 Galaxy, NGC 2110
• An accreting supermassive black hole irradiating molecular gas in NGC 2110
• A mid-infrared view of the inner parsecs of the Seyfert galaxy Mrk 1066 using CanariCam/GTC
• Circumnuclear Multi-phase Gas in Circinus Galaxy I: Non-LTE calculations of CO lines
• The nuclear and extended infrared emission of the Seyfert galaxy NGC 2992 and the interacting system Arp 245
• Nuclear kinematics in nearby AGN. I. An ALMA perspective on the Morphology and Kinematics of the molecular CO(2-1) emission
• Nuclear embedded star clusters in NGC 7582
• AGN torus detectability at sub-millimeter wavelengths: What to expect from ALMA continuum data
• Optical and near-infrared IFU spectroscopy of the nuclear region of the AGN-starburst galaxy NGC 7582
• Interstellar dehydrogenated PAH anions: vibrational spectra

Cited by in corpus (24)

• The Galaxy Activity, Torus and Outflow Survey (GATOS) I. ALMA images of dusty molecular tori in Seyfert galaxies
• A high angular resolution view of the PAH emission in Seyfert galaxies using JWST/MRS data
• Comprehensive Broadband X-ray and Multiwavelength Study of Active Galactic Nuclei in Local 57 Ultra/luminous Infrared Galaxies Observed with NuSTAR and/or Swift/BAT
• The Galaxy Activity, Torus and Outflow Survey (GATOS): II. Torus and polar dust emission in nearby Seyfert galaxies
• PHANGS-JWST First Results: Rapid Evolution of Star Formation in the Central Molecular Gas Ring of NGC1365
• Torus and polar dust dependence on AGN properties
• Deciphering the imprint of AGN feedback in Seyfert galaxies: Nuclear-scale molecular gas deficits
• Nuclear high-ionisation outflow in the Compton-thick AGN NGC6552 as seen by the JWST mid-infrared instrument
• Gemini NIFS survey of feeding and feedback processes in nearby Active Galaxies: VI -- Stellar Populations
• AGN feedback in action in the molecular gas ring of the Seyfert galaxy NGC7172
• The Ionization and Destruction of Polycyclic Aromatic Hydrocarbons in Powerful Quasars
• Chemical abundances in Seyfert galaxies -IX. Helium abundance estimates
• JWST MIRI reveals the diversity of nuclear mid-infrared spectra of nearby type-2 quasars
• The Black Hole-Galaxy Connection: Interplay between Feedback, Obscuration, and Host Galaxy Substructure
• Multiply charged naphthalene and its C10H8 isomers: bonding, spectroscopy and implications in AGN environments
• Absence of nuclear polycyclic aromatic hydrocarbon emission from a compact starburst: The case of the type-2 quasar Mrk 477
• The IBISCO survey: I. Multiphase discs and winds in the Seyfert galaxy Markarian 509
• Polycyclic Aromatic Hydrocarbon Emission in the Central Regions of Three Seyferts the Implication for Underlying Feedback Mechanisms
• LLAMA: Stellar populations in the nuclei of ultra hard X-ray selected AGN and matched inactive galaxies
• JWST Observations of Starbursts: Relations between PAH features and CO clouds in the starburst galaxy M 82
• Metallicity-PAH Relation of MIR-selected Star-forming Galaxies in AKARI North Ecliptic Pole-wide Survey
• WISDOM project -- XVIII. Molecular gas distributions and kinematics of three megamaser galaxies
• The Galaxy Activity, Torus, and Outflow Survey (GATOS): N. Unveiling physical processes in local active galaxies. Unsupervised hierarchical clustering of JWST MIRI/MRS observations
• A technique to select the most obscured galaxy nuclei