Preprint

Observational signatures of the dust size evolution in isolated galaxy simulations

Kosei MatsumotoDepartment of Physics, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, JapanHiroyuki HirashitaInstitute of Astronomy and Astrophysics, Academia Sinica, Astronomy-Mathematics Building, No. 1, Section 4, Roosevelt Road, Taipei 10617, TaiwanKentaro NagamineDepartment of Physics and Astronomy, University of Nevada, Las Vegas, 4505 S. Maryland Pkwy, Las Vegas, NV 89154-4002, USAStefan van der GiessenDept. Física Teórica y del Cosmos, Universidad de Granada, SpainLeonard E. C. RomanoExcellence Cluster ORIGINS, Boltzmannstr. 2, 85748 Garching, GermanyM. RelañoDept. Física Teórica y del Cosmos, Universidad de Granada, SpainIlse De LoozeSterrenkundig Observatorium Department of Physics and Astronomy Universiteit Gent, Krijgslaan 281 S9, 9000 Gent, BelgiumM. BaesSterrenkundig Observatorium Department of Physics and Astronomy Universiteit Gent, Krijgslaan 281 S9, 9000 Gent, BelgiumAngelos NersesianSTAR Institute, Université de Liège, Quartier Agora, Allée du six Aout 19c, 4000 Liege, BelgiumPeter CampsSterrenkundig Observatorium Department of Physics and Astronomy Universiteit Gent, Krijgslaan 281 S9, 9000 Gent, BelgiumKuan-Chou HouPhysics Department, Ben-Gurion University of the Negev, Be’er-Sheva 84105, IsraelYuri OkuTheoretical Astrophysics, Department of Earth and Space Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan

2024en

ABI

Annotatsiya

Aims . We aim to provide observational signatures of the dust size evolution in the interstellar medium. In particular, we explore indicators of the polycyclic aromatic hydrocarbon (PAH) mass fraction ( q PAH ), defined as the mass fraction of PAHs relative to the total dust grains. In addition, we validate our dust evolution model by comparing the observational signatures from our simulations to observations. Methods . We used the hydrodynamic simulation code, GADGET4-OSAKA to model the dust properties of Milky Way-like and NGC 628-like galaxies representing star-forming galaxies. This code incorporates the evolution of grain size distributions driven by dust production and interstellar processing. Furthermore, we performed post-processing dust radiative transfer calculations with SKIRT based on the hydrodynamic simulations to predict the observational properties of the simulations. Results . We find that the intensity ratio between 8 and 24 μm ( I ν (8 μm)/ I ν (24 μm)) is correlated with q PAH and can be used as an indicator of the PAH mass fraction. However, this ratio is influenced by the local radiation field. We suggest the 8 μm-to-total infrared intensity ratio ( νI ν (8 μm)/ I TIR ) as another indicator of the PAH mass fraction, since it is tightly correlated with the PAH mass fraction. Furthermore, we explored the spatially resolved evolutionary properties of the PAH mass fraction in the simulated Milky Way-like galaxy using νI ν (8 μm)/ I TIR . We find that the spatially resolved PAH mass fraction increases with metallicity at Z ≲ 0.2 Z ⊙ due to the interplay between accretion and shattering, whereas it decreases at Z ≳ 0.2 Z ⊙ because of coagulation. Also, coagulation decreases the PAH mass fraction in regions with a high hydrogen surface density. Finally, we compared the above indicators in the NGC 628-like simulation with those observed in NGC 628 by Herschel, Spitzer, and JWST . Consequently, we find that our simulation underestimates the PAH mass fraction throughout the entire galaxy by a factor of ~8 on average. This could be due to the efficient loss of PAHs by coagulation in our model, suggesting that our treatment of PAHs in dense regions needs to be improved.

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DOI: 10.1051/0004-6361/202449454

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