Advanced search
1 file | 2.05 MB Add to list

Resolving the far-IR line deficit : photoelectric heating and far-IR line cooling in NGC 1097 and NGC 4559

Author
Organization
Abstract
The physical state of interstellar gas and dust is dependent on the processes which heat and cool this medium. To probe heating and cooling of the interstellar medium over a large range of infrared surface brightness, on sub-kiloparsec scales, we employ line maps of [C II] 158 mu m, [O I] 63 mu m, and [N II] 122 mu m in NGC 1097 and NGC 4559, obtained with the Photodetector Array Camera & Spectrometer on board Herschel. We matched new observations to existing Spitzer Infrared Spectrograph data that trace the total emission of polycyclic aromatic hydrocarbons (PAHs). We confirm at small scales in these galaxies that the canonical measure of photoelectric heating efficiency, ([C II] + [O I])/TIR, decreases as the far-infrared (far-IR) color, nu f(nu)(70 mu m) nu f(nu)(100 mu m), increases. In contrast, the ratio of far-IR cooling to total PAH emission, ([C II] + [O I])/PAH, is a near constant similar to 6% over a wide range of far-IR color, 0.5 < nu f(nu)(70 mu m) nu f(nu)(100 mu m) less than or similar to 0.95. In the warmest regions, where nu f(nu)(70 mu m) nu f(nu)(100 mu m) greater than or similar to 0.95, the ratio ([C II] + [O I])/PAH drops rapidly to 4%. We derived representative values of the local ultraviolet radiation density, G(0), and the gas density, n(H), by comparing our observations to models of photodissociation regions. The ratio G(0)/n(H), derived from fine-structure lines, is found to correlate with the mean dust-weighted starlight intensity, < U >, derived from models of the IR spectral energy distribution. Emission from regions that exhibit a line deficit is characterized by an intense radiation field, indicating that small grains are susceptible to ionization effects. We note that there is a shift in the 7.7/11.3 mu m PAH ratio in regions that exhibit a deficit in ([C II] + [O I])/PAH, suggesting that small grains are ionized in these environments.
Keywords
ULTRALUMINOUS INFRARED GALAXIES, SPECTRAL ENERGY-DISTRIBUTIONS, STAR-FORMING REGIONS, C-II, NEARBY GALAXIES, PHOTODISSOCIATION REGIONS, INTERSTELLAR-MEDIUM, PHYSICAL CONDITIONS, TRANSLUCENT CLOUDS, RADIATIVE, RATES, galaxies: individual (NGC 1097, NGC 4559), galaxies: ISM, ISM: lines and bands

Downloads

  • Resolving the Far-IR Line Deficit- Photoelectric Heating and Far-IR Line Cooling in NGC 1097 and NGC 4559.pdf
    • full text
    • |
    • open access
    • |
    • PDF
    • |
    • 2.05 MB

Citation

Please use this url to cite or link to this publication:

MLA
Croxall, Kevin V., et al. “Resolving the Far-IR Line Deficit : Photoelectric Heating and Far-IR Line Cooling in NGC 1097 and NGC 4559.” ASTROPHYSICAL JOURNAL, vol. 747, no. 1, 2012.
APA
Croxall, K. V., Smith, J., Wolfire, M., Roussel, H., Sandstrom, K., Draine, B., … Wilson, C. (2012). Resolving the far-IR line deficit : photoelectric heating and far-IR line cooling in NGC 1097 and NGC 4559. ASTROPHYSICAL JOURNAL, 747(1).
Chicago author-date
Croxall, Kevin V, JD Smith, MG Wolfire, H Roussel, KM Sandstrom, BT Draine, G Aniano, et al. 2012. “Resolving the Far-IR Line Deficit : Photoelectric Heating and Far-IR Line Cooling in NGC 1097 and NGC 4559.” ASTROPHYSICAL JOURNAL 747 (1).
Chicago author-date (all authors)
Croxall, Kevin V, JD Smith, MG Wolfire, H Roussel, KM Sandstrom, BT Draine, G Aniano, DA Dale, L Armus, P Beirao, G Helou, AD Bolatto, PN Appleton, BR Brandl, D Calzetti, AF Crocker, M Galametz, BA Groves, C-N Hao, LK Hunt, BD Johnson, RC Kennicutt, J Koda, O Krause, Y Li, Sharon Meidt van der Wel, EJ Murphy, N Rahman, H-W Rix, M Sauvage, E Schinnerer, F Walter, and CD Wilson. 2012. “Resolving the Far-IR Line Deficit : Photoelectric Heating and Far-IR Line Cooling in NGC 1097 and NGC 4559.” ASTROPHYSICAL JOURNAL 747 (1).
Vancouver
1.
Croxall KV, Smith J, Wolfire M, Roussel H, Sandstrom K, Draine B, et al. Resolving the far-IR line deficit : photoelectric heating and far-IR line cooling in NGC 1097 and NGC 4559. ASTROPHYSICAL JOURNAL. 2012;747(1).
IEEE
[1]
K. V. Croxall et al., “Resolving the far-IR line deficit : photoelectric heating and far-IR line cooling in NGC 1097 and NGC 4559,” ASTROPHYSICAL JOURNAL, vol. 747, no. 1, 2012.
@article{8622860,
  abstract     = {The physical state of interstellar gas and dust is dependent on the processes which heat and cool this medium. To probe heating and cooling of the interstellar medium over a large range of infrared surface brightness, on sub-kiloparsec scales, we employ line maps of [C II] 158 mu m, [O I] 63 mu m, and [N II] 122 mu m in NGC 1097 and NGC 4559, obtained with the Photodetector Array Camera & Spectrometer on board Herschel. We matched new observations to existing Spitzer Infrared Spectrograph data that trace the total emission of polycyclic aromatic hydrocarbons (PAHs). We confirm at small scales in these galaxies that the canonical measure of photoelectric heating efficiency, ([C II] + [O I])/TIR, decreases as the far-infrared (far-IR) color, nu f(nu)(70 mu m) nu f(nu)(100 mu m), increases. In contrast, the ratio of far-IR cooling to total PAH emission, ([C II] + [O I])/PAH, is a near constant similar to 6% over a wide range of far-IR color, 0.5 < nu f(nu)(70 mu m) nu f(nu)(100 mu m) less than or similar to 0.95. In the warmest regions, where nu f(nu)(70 mu m) nu f(nu)(100 mu m) greater than or similar to 0.95, the ratio ([C II] + [O I])/PAH drops rapidly to 4%. We derived representative values of the local ultraviolet radiation density, G(0), and the gas density, n(H), by comparing our observations to models of photodissociation regions. The ratio G(0)/n(H), derived from fine-structure lines, is found to correlate with the mean dust-weighted starlight intensity, < U >, derived from models of the IR spectral energy distribution. Emission from regions that exhibit a line deficit is characterized by an intense radiation field, indicating that small grains are susceptible to ionization effects. We note that there is a shift in the 7.7/11.3 mu m PAH ratio in regions that exhibit a deficit in ([C II] + [O I])/PAH, suggesting that small grains are ionized in these environments.},
  articleno    = {81},
  author       = {Croxall, Kevin V and Smith, JD and Wolfire, MG and Roussel, H and Sandstrom, KM and Draine, BT and Aniano, G and Dale, DA and Armus, L and Beirao, P and Helou, G and Bolatto, AD and Appleton, PN and Brandl, BR and Calzetti, D and Crocker, AF and Galametz, M and Groves, BA and Hao, C-N and Hunt, LK and Johnson, BD and Kennicutt, RC and Koda, J and Krause, O and Li, Y and van der Wel, Sharon Meidt and Murphy, EJ and Rahman, N and Rix, H-W and Sauvage, M and Schinnerer, E and Walter, F and Wilson, CD},
  issn         = {0004-637X},
  journal      = {ASTROPHYSICAL JOURNAL},
  keywords     = {ULTRALUMINOUS INFRARED GALAXIES,SPECTRAL ENERGY-DISTRIBUTIONS,STAR-FORMING REGIONS,C-II,NEARBY GALAXIES,PHOTODISSOCIATION REGIONS,INTERSTELLAR-MEDIUM,PHYSICAL CONDITIONS,TRANSLUCENT CLOUDS,RADIATIVE,RATES,galaxies: individual (NGC 1097,NGC 4559),galaxies: ISM,ISM: lines and bands},
  language     = {eng},
  number       = {1},
  pages        = {18},
  title        = {Resolving the far-IR line deficit : photoelectric heating and far-IR line cooling in NGC 1097 and NGC 4559},
  url          = {http://dx.doi.org/10.1088/0004-637X/747/1/81},
  volume       = {747},
  year         = {2012},
}

Altmetric
View in Altmetric
Web of Science
Times cited: