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The polycyclic aromatic hydrocarbon mass fraction on a 10 pc scale in the magellanic clouds

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Abstract
We present maps of the dust properties in the Small and Large Magellanic Clouds (SMC, LMC) from fitting Spitzer and Herschel observations with the Draine & Li dust model. We derive the abundance of the small carbonaceous grain (or polycyclic aromatic hydrocarbon; PAH) component. The global PAH fraction (q(PAH), the fraction of the dust mass in the form of PAHs) is smaller in the SMC (1.0(-0.3)(+0.3)%) than in the LMC (3.3(-1.3)(+1.4)%). We measure the PAH fraction in different gas phases (H II regions, ionized gas outside of H II regions, molecular gas, and diffuse neutral gas). H II regions appear as distinctive holes in the spatial distribution of the PAH fraction. In both galaxies, the PAH fraction in the diffuse neutral medium is higher than in the ionized gas, but similar to the molecular gas. Even at equal radiation field intensity, the PAH fraction is lower in the ionized gas than in the diffuse neutral gas. We investigate the PAH life-cycle as a function of metallicity between the two galaxies. The PAH fraction in the diffuse neutral medium of the LMC is similar to that of the Milky Way (similar to 4.6%), while it is significantly lower in the SMC. Plausible explanations for the higher PAH fraction in the diffuse neutral medium of the LMC compared to the SMC include: more effective PAH production by fragmentation of large grains at higher metallicity, and/or the growth of PAHs in molecular gas.
Keywords
dust, extinction, ISM: abundances, Magellanic Clouds, LOW-METALLICITY ENVIRONMENTS, POINT-SOURCE CLASSIFICATION, INFRARED-EMISSION BANDS, SPITZER LEGACY PROGRAM, GALAXY EVOLUTION SAGE, WARM IONIZED MEDIUM, MU-M PAH, INTERSTELLAR DUST, MILKY-WAY, PHOTOMETRIC SURVEY

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MLA
Chastenet, Jérémy, et al. “The Polycyclic Aromatic Hydrocarbon Mass Fraction on a 10 Pc Scale in the Magellanic Clouds.” ASTROPHYSICAL JOURNAL, vol. 876, no. 1, 2019.
APA
Chastenet, J., Sandstrom, K., Chiang, I.-D., Leroy, A. K., Utomo, D., Bot, C., … Tsuge, K. (2019). The polycyclic aromatic hydrocarbon mass fraction on a 10 pc scale in the magellanic clouds. ASTROPHYSICAL JOURNAL, 876(1).
Chicago author-date
Chastenet, Jérémy, Karin Sandstrom, I-Da Chiang, Adam K. Leroy, Dyas Utomo, Caroline Bot, Karl Gordon, et al. 2019. “The Polycyclic Aromatic Hydrocarbon Mass Fraction on a 10 Pc Scale in the Magellanic Clouds.” ASTROPHYSICAL JOURNAL 876 (1).
Chicago author-date (all authors)
Chastenet, Jérémy, Karin Sandstrom, I-Da Chiang, Adam K. Leroy, Dyas Utomo, Caroline Bot, Karl Gordon, Bruce T. Draine, Yasuo Fukui, Toshikazu Onishi, and Kisetsu Tsuge. 2019. “The Polycyclic Aromatic Hydrocarbon Mass Fraction on a 10 Pc Scale in the Magellanic Clouds.” ASTROPHYSICAL JOURNAL 876 (1).
Vancouver
1.
Chastenet J, Sandstrom K, Chiang I-D, Leroy AK, Utomo D, Bot C, et al. The polycyclic aromatic hydrocarbon mass fraction on a 10 pc scale in the magellanic clouds. ASTROPHYSICAL JOURNAL. 2019;876(1).
IEEE
[1]
J. Chastenet et al., “The polycyclic aromatic hydrocarbon mass fraction on a 10 pc scale in the magellanic clouds,” ASTROPHYSICAL JOURNAL, vol. 876, no. 1, 2019.
@article{8656150,
  abstract     = {We present maps of the dust properties in the Small and Large Magellanic Clouds (SMC, LMC) from fitting Spitzer and Herschel observations with the Draine & Li dust model. We derive the abundance of the small carbonaceous grain (or polycyclic aromatic hydrocarbon; PAH) component. The global PAH fraction (q(PAH), the fraction of the dust mass in the form of PAHs) is smaller in the SMC (1.0(-0.3)(+0.3)%) than in the LMC (3.3(-1.3)(+1.4)%). We measure the PAH fraction in different gas phases (H II regions, ionized gas outside of H II regions, molecular gas, and diffuse neutral gas). H II regions appear as distinctive holes in the spatial distribution of the PAH fraction. In both galaxies, the PAH fraction in the diffuse neutral medium is higher than in the ionized gas, but similar to the molecular gas. Even at equal radiation field intensity, the PAH fraction is lower in the ionized gas than in the diffuse neutral gas. We investigate the PAH life-cycle as a function of metallicity between the two galaxies. The PAH fraction in the diffuse neutral medium of the LMC is similar to that of the Milky Way (similar to 4.6%), while it is significantly lower in the SMC. Plausible explanations for the higher PAH fraction in the diffuse neutral medium of the LMC compared to the SMC include: more effective PAH production by fragmentation of large grains at higher metallicity, and/or the growth of PAHs in molecular gas.},
  articleno    = {62},
  author       = {Chastenet, Jérémy and Sandstrom, Karin and Chiang, I-Da and Leroy, Adam K. and Utomo, Dyas and Bot, Caroline and Gordon, Karl and Draine, Bruce T. and Fukui, Yasuo and Onishi, Toshikazu and Tsuge, Kisetsu},
  issn         = {0004-637X},
  journal      = {ASTROPHYSICAL JOURNAL},
  keywords     = {dust,extinction,ISM: abundances,Magellanic Clouds,LOW-METALLICITY ENVIRONMENTS,POINT-SOURCE CLASSIFICATION,INFRARED-EMISSION BANDS,SPITZER LEGACY PROGRAM,GALAXY EVOLUTION SAGE,WARM IONIZED MEDIUM,MU-M PAH,INTERSTELLAR DUST,MILKY-WAY,PHOTOMETRIC SURVEY},
  language     = {eng},
  number       = {1},
  pages        = {14},
  title        = {The polycyclic aromatic hydrocarbon mass fraction on a 10 pc scale in the magellanic clouds},
  url          = {http://dx.doi.org/10.3847/1538-4357/ab16cf},
  volume       = {876},
  year         = {2019},
}

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