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Probing the cold and warm molecular gas in the Whirlpool Galaxy : Herschel SPIRE-FTS observations of the central region of M51 (NGC 5194)

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Abstract
We present Herschel Spectral and Photometric Imaging Receiver (SPIRE)-Fourier Transform Spectrometer (FTS) intermediate-sampled mapping observations of the central similar to 8 kpc (similar to 150 arcsec) of M51, with a spatial resolution of 40 arcsec. We detect four (CO)-C-12 transitions (J = 4-3 to J = 7-6) and the [C i] P-3(2)-P-3(1) and P-3(1)-P-3(0) transitions. We supplement these observations with ground-based observations of (CO)-C-12 J = 1-0 to J = 3-2 and perform a two-component non-local thermodynamic equilibrium analysis. We find that the molecular gas in the nucleus and centre regions has a cool component (T-kin similar to 10-20 K) with a moderate but poorly constrained density (n(H-2) similar to 10(3)-10(6) cm(-3)), as well as significant molecular gas in a warmer (T-kin similar to 300-3000 K), lower density (n(H-2) similar to 10(1.6)-10(2.5) cm(-3)) component. We compare our CO line ratios and calculated densities along with ratios of CO to total infrared luminosity to a grid of photon-dominated region (PDR) models and find that the cold molecular gas likely resides in PDRs with a field strength of G(0) similar to 10(2). The warm component likely requires an additional source of mechanical heating, from supernovae and stellar winds or possibly shocks produced in the strong spiral density wave. When compared to similar two-component models of other star-forming galaxies published as part of the Very Nearby Galaxies Survey (Arp 220, M82 and NGC 4038/39), M51 has the lowest density for the warm component, while having a warm gas mass fraction that is comparable to those of Arp 220 and M82, and significantly higher than that of NGC 4038/39.
Keywords
ISM: molecules, galaxies: individual: NGC 5194, galaxies: ISM, STAR-FORMATION, PHOTODISSOCIATION REGIONS, INTERSTELLAR-MEDIUM, RADIO-CONTINUUM, NEARBY GALAXIES, ARP 220, EMISSION, CLOUDS, CALIBRATION, SPITZER

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Chicago
Schirm, MRP, CD Wilson, J Kamenetzky, TJ Parkin, J Glenn, P Maloney, N Rangwala, et al. 2017. “Probing the Cold and Warm Molecular Gas in the Whirlpool Galaxy : Herschel SPIRE-FTS Observations of the Central Region of M51 (NGC 5194).” Monthly Notices of the Royal Astronomical Society 470 (4): 4989–5006.
APA
Schirm, M., Wilson, C., Kamenetzky, J., Parkin, T., Glenn, J., Maloney, P., Rangwala, N., et al. (2017). Probing the cold and warm molecular gas in the Whirlpool Galaxy : Herschel SPIRE-FTS observations of the central region of M51 (NGC 5194). MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 470(4), 4989–5006.
Vancouver
1.
Schirm M, Wilson C, Kamenetzky J, Parkin T, Glenn J, Maloney P, et al. Probing the cold and warm molecular gas in the Whirlpool Galaxy : Herschel SPIRE-FTS observations of the central region of M51 (NGC 5194). MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY. 2017;470(4):4989–5006.
MLA
Schirm, MRP, CD Wilson, J Kamenetzky, et al. “Probing the Cold and Warm Molecular Gas in the Whirlpool Galaxy : Herschel SPIRE-FTS Observations of the Central Region of M51 (NGC 5194).” MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 470.4 (2017): 4989–5006. Print.
@article{8538459,
  abstract     = {We present Herschel Spectral and Photometric Imaging Receiver (SPIRE)-Fourier Transform Spectrometer (FTS) intermediate-sampled mapping observations of the central similar to 8 kpc (similar to 150 arcsec) of M51, with a spatial resolution of 40 arcsec. We detect four (CO)-C-12 transitions (J = 4-3 to J = 7-6) and the [C i] P-3(2)-P-3(1) and P-3(1)-P-3(0) transitions. We supplement these observations with ground-based observations of (CO)-C-12 J = 1-0 to J = 3-2 and perform a two-component non-local thermodynamic equilibrium analysis. We find that the molecular gas in the nucleus and centre regions has a cool component (T-kin similar to 10-20 K) with a moderate but poorly constrained density (n(H-2) similar to 10(3)-10(6) cm(-3)), as well as significant molecular gas in a warmer (T-kin similar to 300-3000 K), lower density (n(H-2) similar to 10(1.6)-10(2.5) cm(-3)) component. We compare our CO line ratios and calculated densities along with ratios of CO to total infrared luminosity to a grid of photon-dominated region (PDR) models and find that the cold molecular gas likely resides in PDRs with a field strength of G(0) similar to 10(2). The warm component likely requires an additional source of mechanical heating, from supernovae and stellar winds or possibly shocks produced in the strong spiral density wave. When compared to similar two-component models of other star-forming galaxies published as part of the Very Nearby Galaxies Survey (Arp 220, M82 and NGC 4038/39), M51 has the lowest density for the warm component, while having a warm gas mass fraction that is comparable to those of Arp 220 and M82, and significantly higher than that of NGC 4038/39.},
  author       = {Schirm, MRP and Wilson, CD and Kamenetzky, J and Parkin, TJ and Glenn, J and Maloney, P and Rangwala, N and Spinoglio, L and Baes, Maarten and Boselli, A and Cooray, A and De Looze, Ilse and Fern{\'a}ndez-Ontiveros, JA and Karczewski, O\unmatched{0141} and Wu, R},
  issn         = {0035-8711},
  journal      = {MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY},
  keyword      = {ISM: molecules,galaxies: individual: NGC 5194,galaxies: ISM,STAR-FORMATION,PHOTODISSOCIATION REGIONS,INTERSTELLAR-MEDIUM,RADIO-CONTINUUM,NEARBY GALAXIES,ARP 220,EMISSION,CLOUDS,CALIBRATION,SPITZER},
  language     = {eng},
  number       = {4},
  pages        = {4989--5006},
  title        = {Probing the cold and warm molecular gas in the Whirlpool Galaxy : Herschel SPIRE-FTS observations of the central region of M51 (NGC 5194)},
  url          = {http://dx.doi.org/10.1093/mnras/stx1554},
  volume       = {470},
  year         = {2017},
}

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