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The polycyclic aromatic hydrocarbon (PAH) hypothesis proposes that the aromatic infrared bands (AIBs) observed at 3.3, 6.2, 7.7, 8.6, 11.3, and 12.7 mic originate from gas-phase PAH molecules. These bands exhibit consistent peak wavelengths…

Astrophysics of Galaxies · Physics 2025-11-03 Alan T. Tokunaga , Lawrence S. Bernstein , Takashi Onaka

Polycyclic aromatic hydrocarbons (PAHs) appear to be ubiquitous in terrestrial atmosphere as well as in the interstellar medium (ISM). In the astrophysical context presence of PAHs is interpreted by the observations of mid-IR emission bands…

Chemical Physics · Physics 2019-03-26 Rashmi Singh , Shantanu Rastogi

We reanalyze the mid-infrared (5-40 $\mu$m) Spitzer spectra of 86 low-redshift ($z < 0.5$) Palomar-Green quasars to investigate the nature of polycyclic aromatic hydrocarbon (PAH) emission and its utility as a star formation rate (SFR)…

Astrophysics of Galaxies · Physics 2022-02-16 Yanxia Xie , Luis C. Ho

Ratios of polycyclic aromatic hydrocarbon (PAH) vibrational bands are a promising tool for measuring the properties of the PAH population and their effect on star formation. The photometric bands of the MIRI and NIRCam instruments on JWST…

We decompose the observed 7.7 $\mu$m polycyclic aromatic hydrocarbon (PAH) emission complexes in a large sample of over 7000 mid-infrared spectra of the interstellar medium (ISM) using spectral cubes observed with the Spitzer/IRS-SL…

Astrophysics of Galaxies · Physics 2017-03-22 D. J. Stock , E. Peeters

Computational study of polycyclic aromatic hydrocarbons (PAHs) with phenyl side group substituted at different positions is reported. The infrared spectral variations due to the position of phenyl substitution, ionization state and the size…

Astrophysics of Galaxies · Physics 2022-11-28 Anju Maurya , Rashmi Singh , Shantanu Rastogi

We calibrate the integrated luminosity from the polycyclic aromatic hydrocarbon (PAH) features at 6.2\micron, 7.7\micron\ and 11.3\micron\ in galaxies as a measure of the star-formation rate (SFR). These features are strong (containing as…

Astrophysics of Galaxies · Physics 2016-02-17 Heath V. Shipley , Casey Papovich , George H. Rieke , Michael J. I. Brown , John Moustakas

The aromatic infrared bands (AIBs) observed in the mid infrared spectrum are attributed to Polycyclic Aromatic Hydrocarbons (PAHs). We observe the NGC 7023-North West (NW) PDR in the mid-infrared (10 - 19.5 micron) using the Infrared…

Astrophysics of Galaxies · Physics 2015-05-28 M. J. F. Rosenberg , O. Berné , C. Boersma , L. J. Allamandola , A. G. G. M Tielens

Recurrent fluorescence (RF) is an important relaxation mechanism in polycyclic aromatic hydrocarbons (PAHs), which could stabilize them and contribute to the production of aromatic infrared bands that are observed in the infrared spectra of…

Chemical Physics · Physics 2026-04-01 Damien Borja , Florent Calvo , Pascal Parneix , Cyril Falvo

Polycyclic aromatic hydrocarbon (PAH) molecules, as revealed by the distinctive set of emission bands at 3.3, 6.2, 7.7, 8.6, 11.3 and 12.7 $\mu$m characteristic of their vibrational modes, are abundant and widespread throughout the…

Astrophysics of Galaxies · Physics 2020-03-25 Aigen Li

This work presents theoretical calculations of infrared spectra of nitrogen (N)-containing polycyclic aromatic hydrocarbon (PAH) molecules with incorporation of N, NH and NH$_2$ using density functional theory (DFT). The properties of their…

Astrophysics of Galaxies · Physics 2021-12-30 Akant Vats , Amit Pathak , Takashi Onaka , Mridusmita Buragohain , Itsuki Sakon , Izumi Endo

We present a new method to decompose the emission features of polycyclic aromatic hydrocarbons (PAHs) from mid-infrared spectra using theoretical PAH templates in conjunction with modified blackbody components for the dust continuum and an…

Astrophysics of Galaxies · Physics 2018-06-26 Yanxia Xie , Luis C. Ho , Aigen Li , Jinyi Shangguan

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

The integrated luminosity from the features of the polycyclic aromatic hydrocarbons (PAHs) exceeds the luminosity from atomic and molecular emission lines in the star-forming regions in galaxies and is a potential tracer of galaxy-scale…

Intensity ratios of aromatic emission features are widely used to diagnose the size and ionization state of polycyclic aromatic hydrocarbons (PAHs) in astronomical environments. However, PAHs are known to typically carry aliphatic side…

Astrophysics of Galaxies · Physics 2026-05-12 Zhuang Zhang , Yong Zhang

Using a large collection of near-infrared spectra (2.5-5.4 um) of Galactic HII regions and HII region-like objects, we perform a systematic investigation of the astronomical polycyclic aromatic hydrocarbon (PAH) features. 36 objects were…

Astrophysics of Galaxies · Physics 2015-06-18 Tamami I. Mori , Takashi Onaka , Itsuki Sakon , Daisuke Ishihara , Takashi Shimonishi , Ryou Ohsawa , Aaron C. Bell

In this Letter we report the results of density functional theory calculations on medium-sized neutral Polycyclic Aromatic Hydrocarbon (PAH) molecules with armchair edges. These PAH molecules possess strong C-H stretching and bending modes…

Astrophysics of Galaxies · Physics 2014-10-09 A. Candian , P. J. Sarre , A. G. G. M. Tielens

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 Str\"omgren sphere of young, massive stars. We apply a…

Astrophysics of Galaxies · Physics 2019-11-06 Yanxia Xie , Luis C. Ho

The so-called aromatic infrared bands are attributed to emission of polycyclic aromatic hydrocarbons. The observed variations toward different regions in space are believed to be caused by contributions of different classes of PAH…

Astrophysics of Galaxies · Physics 2021-04-14 Shreyak Banhatti , Julianna Palotás , Pavol Jusko , Britta Redlich , Jos Oomens , Stephan Schlemmer , Sandra Brünken

We have conducted a sensitivity analysis on the mid-infrared spectral decomposition of galaxies and the modeling of the PAH emission spectrum with the NASA Ames PAH Infrared Spectroscopic Database (PAHdb) to assess the variance on the…