PAHs and star formation in the H ii regions of nearby galaxies M83 and M33

Maragkoudakis, Alexandros; Ivkovich, Nina; Peeters, E.; Stock, D. J.; Hemachandra, Dimuthu; Tielens, A. G. G. M.

doi:10.1093/mnras/sty2658

Cited by 42 publications

(43 citation statements)

References 71 publications

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“…We scale the larger aperture (10.7 ) long-low spectrum to match the short-low spectrum using their common overlapping region, making the explicit assumption that the mid-IR spectrum does not change dramatically between these two apertures. This generally holds for nearby galaxies that have been studied with spatially resolved mid-IR observations (e.g., Maragkoudakis et al 2018).…”

Section: Datamentioning

confidence: 76%

A New Calibration of Star Formation Rate in Galaxies Based on Polycyclic Aromatic Hydrocarbon Emission

Xie

2019

ApJ

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Polycyclic aromatic hydrocarbon (PAH) emission has long been proposed to be a potential star formation rate indicator, as it arises from the photodissociation region bordering the Strömgren sphere of young, massive stars. We apply a recently developed technique of mid-infrared spectral decomposition to obtain a uniform set of PAH measurements from Spitzer low-resolution spectra of a large sample of star-forming galaxies spanning a wide range in stellar mass (M ≈ 10 6 − 10 11.4 M ) and star formation rate (∼ 0.1 − 2000 M yr −1 ). High-resolution spectra are also analyzed to measure [Ne II] 12.8 µm and [Ne III] 15.6 µm, which effectively trace the Lyman continuum. We present a new relation between PAH luminosity and star formation rate based on the [Ne II] and [Ne III] lines. Calibrations are given for the integrated 5-15 µm PAH emission, the individual features at 6.2, 7.7, 8.6, and 11.3 µm, as well as several mid-infrared bandpasses sensitive to PAH. We confirm that PAH emission is suppressed in low-mass, dwarf galaxies, and we discuss the possible physical origin of this effect.

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Section: Datamentioning

confidence: 76%

A New Calibration of Star Formation Rate in Galaxies Based on Polycyclic Aromatic Hydrocarbon Emission

Xie

2019

ApJ

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“…As such, a popular approach in the literature for determining average PAH sizes, especially for extragalactic astrophysical sources (e.g. O'Dowd et al 2009;Diamond-Stanic & Rieke 2010;Sandstrom et al 2012;Stierwalt et al 2014;Maragkoudakis et al 2018), is based on the usage of the Draine & Li (2001) (hereafter DL01) models, and specifically the employment of the 7.7/11.2 and 6.2/7.7 ratios (DL01; their Fig. 16) to track PAH charge and size respectively.…”

Section: The 62/77 Ratiomentioning

confidence: 99%

“…As a result, the strength of the 11.2/7.7 ratio in neutral PAHs will always be higher compared to the 11.0/7.7 ratio in cations, leading to an effective separation of the two populations. Maragkoudakis et al (2018) have initially presented the 11.2(11.0)/7.7 -11.2(11.0)/3.3 plane and questioned whether the 6.2/7.7 ratio is effective in tracking PAH size, using a small sample of 34 symmetric pure PAH molecules (including the families of coronene and ovalene) with 24 < NC < 170 drawn from the v3.00 PAHdb libraries. In this paper we vastly expand the work of Maragkoudakis et al cation PAH pairs (266 PAH molecules), including straight edge molecules from the next release of the PAHdb (v3.10); ii) using molecules with a large diversity of symmetries; and iii) covering a broad range of molecule sizes: 22 < NC < 216.…”

Section: The 33 µM -Nc Relationmentioning

confidence: 99%

“…PAH emission has been calibrated from spectroscopic and photometric bands and used for the estimation of star-formation rates on both galaxy-wide and spatially resolved galactic scales (e.g. Peeters et al 2004;Farrah et al 2007;Calzetti et al 2007;Shipley et al 2016;Maragkoudakis et al 2018), particularly in the cases of metal-rich and dust-rich environments. In addition, the existence of a galaxy-wide correlation between PAH and CO emission (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…Comparison between the diagnostic diagrams ofDraine & Li (2001) (left panel) and the new PAH charge -size diagram defined inMaragkoudakis et al (2018) and this work (right panel). Both panels are populated with the PAHdb sample molecules calculated with the ISRF, with triangles and circles representing neutral and cationic PAHs respectively, color-coded based on the number of their carbon atoms (N C ).…”

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Probing the size and charge of polycyclic aromatic hydrocarbons

Maragkoudakis

Peeters

Ricca

2020

Monthly Notices of the Royal Astronomical Society

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We present a new method to accurately describe the ionization fraction and the size distribution of polycyclic aromatic hydrocarbons (PAHs) within astrophysical sources. To this purpose, we have computed the mid-infrared emission spectra of 308 PAH molecules of varying sizes, symmetries, and compactness, generated in a range of radiation fields. We show that the intensity ratio of the solo CH out-of-plane bending mode in PAH cations and anions (referred to as the 11.0 µm band, falling in the 11.0-11.3 µm region for cations and anions) to their 3.3 µm emission, scales with PAH size, similarly to the scaling of the 11.2/3.3 ratio with the number of carbon atoms (N C ) for neutral molecules. Among the different PAH emission bands, it is the 3.3 µm band intensity which has the strongest correlation with N C , and drives the reported PAH intensity ratio correlations with N C for both neutral and ionized PAHs. The 6.2/7.7 intensity ratio, previously adopted to track PAH size, shows no evident scaling with N C in our large sample. We define a new diagnostic grid space to probe PAH charge and size, using the (11.2+11.0)/7.7 and (11.2+11.0)/3.3 PAH intensity ratios respectively. We demonstrate the application of the (11.2+11.0)/7.7 -(11.2+11.0)/3.3 diagnostic grid for galaxies M82 and NGC 253, for the planetary nebula NGC 7027, and the reflection nebulae NGC 2023 and NGC 7023. Finally, we provide quantitative relations for PAH size determination depending on the ionization fraction of the PAHs and the radiation field they are exposed to.

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A Spectroscopic View on Cosmic PAH Emission

et al. 2021

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Metrics & MoreArticle Recommendations CONSPECTUS: Polycyclic aromatic hydrocarbon molecules (PAHs) are ubiquitously present at high abundances in the Universe. They are detected through their infrared (IR) fluorescence UV pumped by nearby massive stars. Hence, their infrared emission is used to determine the star formation rate in galaxies, one of the key indicators for understanding the evolution of galaxies. Together with fullerenes, PAHs are the largest molecules found in space. They significantly partake in a variety of physical and chemical processes in space, influencing star and planet formation as well as galaxy evolution.Since the IR features from PAHs originate from chemical bonds involving only nearest neighbor atoms, they have only a weak dependence on the size and structure of the molecule, and it is therefore not possible to identify the individual PAH molecules that make up the cosmic PAH family. This strongly hampers the interpretation of their astronomical fingerprints. Despite the lack of identification, constraints can be set on the characteristics of the cosmic PAH family thanks to a joint effort of astronomers, physicists, and chemists. This Account presents the spectroscopic properties of the cosmic PAH emission as well as the intrinsic spectroscopic properties of PAHs and astronomical modeling of the PAH evolution required for the interpretation of the cosmic PAH characteristics. We discuss the observed spectral signatures tracing PAH properties such as charge, size, and structure and highlight the related challenges. We discuss the recent success of anharmonic calculations of PAH infrared absorption and emission spectra and outline the path forward. Finally, we illustrate the importance of models on PAH processing for the interpretation of the astronomical data in terms of the charge balance and PAH destruction. Throughout this Account, we emphasize that huge progress is on the horizon on the astronomical front. Indeed, the world is eagerly awaiting the launch of the James Webb Space Telescope (JWST). With its incredible improvement in spatial resolution, combined with its complete spectral coverage of the PAH infrared emission bands at medium spectral resolution and superb sensitivity, the JWST will revolutionize PAH research. Previous observations could only present spectra averaged over regions with vastly different properties, thus greatly confusing their interpretation. The amazing spatial resolution of JWST will disentangle these different regions. This will allow us to quantify precisely how PAHs are modified by the physical conditions of their host environment and thus trace how PAHs evolve across space. However, this will only be achieved when the necessary (and still missing) fundamental properties of PAHs, outlined in this Account, are known. We strongly encourage you to join this effort.

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PAHs and star formation in the H ii regions of nearby galaxies M83 and M33

Cited by 42 publications

References 71 publications

A New Calibration of Star Formation Rate in Galaxies Based on Polycyclic Aromatic Hydrocarbon Emission

A New Calibration of Star Formation Rate in Galaxies Based on Polycyclic Aromatic Hydrocarbon Emission

Probing the size and charge of polycyclic aromatic hydrocarbons

A Spectroscopic View on Cosmic PAH Emission

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