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Cosmic rays are an essential ingredient in the evolution of the interstellar medium, as they dominate the ionisation of the dense molecular gas, where stars and planets form. However, since they are efficiently scattered by the galactic…

Astrophysics of Galaxies · Physics 2014-09-05 Solenn Vaupré , Pierre Hily-Blant , Cecilia Ceccarelli , Guillaume Dubus , Stefano Gabici , Thierry Montmerle

Hydrocarbons play a key role in shaping the chemistry of the interstellar medium (ISM), but their enrichment and relationship with carbonaceous grains and polycyclic aromatic hydrocarbons (PAHs) still lack clear observational constraints.…

Depending on whom you ask, PAHs are either the smallest dust particles or the largest gas-phase molecules in space. Whether referred to as gas or dust, these PAHs can contain up to 20% of the total cosmic carbon abundance and as such also…

Solar and Stellar Astrophysics · Physics 2015-05-20 Inga Kamp

The infrared signature of polycyclic aromatic hydrocarbons (PAHs) are present in many protostellar disks and these speciesare thought to play an important role in heating of the gas in the photosphere. We aim to consider PAH cluster…

Earth and Planetary Astrophysics · Physics 2021-09-01 K. Lange , C. Dominik , A. G. G. M. Tielens

Context. Cosmic ray particles that hit interstellar grains in dark molecular cores may induce whole-grain heating. The high temperature of a CR-heated grain allows energy barriers for bulk diffusion and reactions to be overcome.…

Astrophysics of Galaxies · Physics 2014-12-17 Juris Kalvans

We present a study for a sample of galaxies with active nuclei to characterize the main type of PAH molecules present in these objects and the local physical conditions of their irradiating sources, as well as the characteristics of the…

Spectral features from PAH molecules observed in the mid-IR range are typically used to infer the amount of recent and ongoing star formation (SF) on kpc scales around AGN where more traditional methods fail. This assumes that the observed…

Astrophysics of Galaxies · Physics 2017-07-26 J. J. Jensen , S. F. Hönig , S. Rakshit , A. Alonso-Herrero , D. Asmus , P. Gandhi , M. Kishimoto , A. Smette , K. R. W. Tristram

In this work, we study the photodissociation processes of small PAH clusters (e.g., pyrene clusters). The experiments are carried out using a quadrupole ion trap in combination with time-of-flight (QIT-TOF) mass spectrometry. The results…

Instrumentation and Methods for Astrophysics · Physics 2018-09-27 Junfeng Zhen , Tao Chen , Alexander G. G. M. Tielens

Polycyclic aromatic hydrocarbon (PAH) dust emission has been proposed as an effective extinction-independent star formation rate (SFR) indicator in the mid-infrared (MIR), but this may depend on conditions in the interstellar medium. The…

Polycyclic aromatic hydrocarbons (PAHs) are responsible for strong mid-IR emission features near star-forming regions. It is well known that low-metallicity environments exhibit weaker PAH emission, but it is not clear how the metallicity…

Astrophysics of Galaxies · Physics 2025-06-09 Congcong Zhang , Joelene Hales , Els Peeters , Jan Cami , Ameek Sidhu , Junfeng Zhen

Cosmic rays are the only agent capable of ionizing the interior of dense molecular clouds and, thus, they are believed to play an essential role in determining the physical and chemical evolution of star-forming regions. In this work, we…

High Energy Astrophysical Phenomena · Physics 2024-02-09 Vo Hong Minh Phan , Enrico Peretti , Pierre Cristofari , Antoine Gusdorf , Philipp Mertsch

The main goal of the present lectures is to outline the key particle interactions and energy loss mechanisms in the Galactic medium that high-energy particles are subject to. These interactions are an important ingredient entering the…

High Energy Astrophysical Phenomena · Physics 2024-04-09 Pasquale Dario Serpico

A proper modelling of the cosmic-ray ionisation rate within gas clouds is crucial to describe their chemical evolution accurately. However, this modelling is computationally demanding because it requires the propagation of cosmic rays…

Astrophysics of Galaxies · Physics 2025-07-08 G. Latrille , A. Lupi , S. Bovino , T. Grassi , G. Sabatini , M. Padovani

We investigate in the mid-IR the spatial properties of the PAHs emission in the disk of HD179218. We obtained mid-IR images in the PAH1, PAH2 and Si6 filters at 8.6, 11.3 and 12.5 mu, and N band low-resolution spectra using CanariCam on the…

We present Gran Telescopio CANARIAS CanariCam 8.7$\mu$m imaging and 7.5-13$\mu$m spectroscopy of six local systems known to host an active galactic nucleus (AGN) and have nuclear star formation. Our main goal is to investigate whether the…

The infrared (IR) emission of polycyclic aromatic hydrocarbons (PAHs) permeates our universe; astronomers have detected the IR signatures of PAHs around many interstellar objects. The IR emission of interstellar PAHs differs from their…

Astrophysics of Galaxies · Physics 2018-10-05 Cameron J. Mackie , Tao Chen , Alessandra Candian , Timothy J. Lee , Alexander G. G. M. Tielens

Cosmic rays are the main agents in controlling the chemical evolution and setting the ambipolar diffusion time of a molecular cloud. We summarise the processes causing the energy degradation of cosmic rays due to their interaction with…

Astrophysics of Galaxies · Physics 2014-06-11 Marco Padovani , Patrick Hennebelle , Daniele Galli

Galaxies at high redshifts with strong star formation are sources of high-energy cosmic rays. These cosmic rays interact with the baryon and radiation fields of the galactic environment via photo-pair, photo-pion and proton-proton processes…

High Energy Astrophysical Phenomena · Physics 2017-08-24 Ellis R. Owen , Kinwah Wu , Pooja Surajbali , Idunn B. Jacobsen

The PHANGS survey uses ALMA, HST, VLT, and JWST to obtain an unprecedented high-resolution view of nearby galaxies, covering millions of spatially independent regions. The high dimensionality of such a diverse multi-wavelength dataset makes…