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Short GMC lifetimes : an observational estimate with the PdBI Arcsecond Whirlpool Survey (PAWS)

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Abstract
We describe and execute a novel approach to observationally estimate the lifetimes of giant molecular clouds (GMCs). We focus on the cloud population between the two main spiral arms in M51 (the inter-arm region) where cloud destruction via shear and star formation feedback dominates over formation processes. By monitoring the change in GMC number densities and properties across the inter-arm, we estimate the lifetime as a fraction of the inter-arm travel time. We find that GMC lifetimes in M51's inter-arm are finite and short, 20-30 Myr. Over most of the region under investigation shear appears to regulate the lifetime. As the shear timescale increases with galactocentric radius, we expect cloud destruction to switch primarily to feedback at larger radii. We identify a transition from shear-to feedback-dominated disruption, finding that shear is more efficient at dispersing clouds, whereas feedback transforms the population, e.g., by fragmenting high-mass clouds into lower mass pieces. Compared to the characteristic timescale for molecular hydrogen in M51, our short lifetimes suggest that gas can remain molecular while clouds disperse and reassemble. We propose that galaxy dynamics regulates the cycling of molecular material from diffuse to bound (and ultimately star-forming) objects, contributing to long observed molecular depletion times in normal disk galaxies. We also speculate that, in extreme environments like elliptical galaxies and concentrated galaxy centers, star formation can be suppressed when the shear timescale is short enough that some clouds will not survive to form stars.
Keywords
GIANT MOLECULAR CLOUDS, LARGE-MAGELLANIC-CLOUD, STAR-FORMATION, EFFICIENCY, INTERSTELLAR-MEDIUM, SPIRAL GALAXIES, M51, EVOLUTION, GAS, CLUSTERS, TURBULENCE, galaxies: individual (M51), ISM: clouds, ISM: kinematics and dynamics

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MLA
van der Wel, Sharon Meidt, et al. “Short GMC Lifetimes : An Observational Estimate with the PdBI Arcsecond Whirlpool Survey (PAWS).” ASTROPHYSICAL JOURNAL, vol. 806, no. 1, 2015.
APA
van der Wel, S. M., Hughes, A., Dobbs, C. L., Pety, J., Thompson, T. A., Garcia-Burillo, S., … Dumas, G. (2015). Short GMC lifetimes : an observational estimate with the PdBI Arcsecond Whirlpool Survey (PAWS). ASTROPHYSICAL JOURNAL, 806(1).
Chicago author-date
Wel, Sharon Meidt van der, Annie Hughes, Clare L Dobbs, Jerome Pety, Todd A Thompson, Santiago Garcia-Burillo, Adam K Leroy, et al. 2015. “Short GMC Lifetimes : An Observational Estimate with the PdBI Arcsecond Whirlpool Survey (PAWS).” ASTROPHYSICAL JOURNAL 806 (1).
Chicago author-date (all authors)
van der Wel, Sharon Meidt, Annie Hughes, Clare L Dobbs, Jerome Pety, Todd A Thompson, Santiago Garcia-Burillo, Adam K Leroy, Eva Schinnerer, Dario Colombo, Miguel Querejeta, Carsten Kramer, Karl F Schuster, and Gaelle Dumas. 2015. “Short GMC Lifetimes : An Observational Estimate with the PdBI Arcsecond Whirlpool Survey (PAWS).” ASTROPHYSICAL JOURNAL 806 (1).
Vancouver
1.
van der Wel SM, Hughes A, Dobbs CL, Pety J, Thompson TA, Garcia-Burillo S, et al. Short GMC lifetimes : an observational estimate with the PdBI Arcsecond Whirlpool Survey (PAWS). ASTROPHYSICAL JOURNAL. 2015;806(1).
IEEE
[1]
S. M. van der Wel et al., “Short GMC lifetimes : an observational estimate with the PdBI Arcsecond Whirlpool Survey (PAWS),” ASTROPHYSICAL JOURNAL, vol. 806, no. 1, 2015.
@article{8622286,
  abstract     = {We describe and execute a novel approach to observationally estimate the lifetimes of giant molecular clouds (GMCs). We focus on the cloud population between the two main spiral arms in M51 (the inter-arm region) where cloud destruction via shear and star formation feedback dominates over formation processes. By monitoring the change in GMC number densities and properties across the inter-arm, we estimate the lifetime as a fraction of the inter-arm travel time. We find that GMC lifetimes in M51's inter-arm are finite and short, 20-30 Myr. Over most of the region under investigation shear appears to regulate the lifetime. As the shear timescale increases with galactocentric radius, we expect cloud destruction to switch primarily to feedback at larger radii. We identify a transition from shear-to feedback-dominated disruption, finding that shear is more efficient at dispersing clouds, whereas feedback transforms the population, e.g., by fragmenting high-mass clouds into lower mass pieces. Compared to the characteristic timescale for molecular hydrogen in M51, our short lifetimes suggest that gas can remain molecular while clouds disperse and reassemble. We propose that galaxy dynamics regulates the cycling of molecular material from diffuse to bound (and ultimately star-forming) objects, contributing to long observed molecular depletion times in normal disk galaxies. We also speculate that, in extreme environments like elliptical galaxies and concentrated galaxy centers, star formation can be suppressed when the shear timescale is short enough that some clouds will not survive to form stars.},
  articleno    = {72},
  author       = {van der Wel, Sharon Meidt and Hughes, Annie and Dobbs, Clare L and Pety, Jerome and Thompson, Todd A and Garcia-Burillo, Santiago and Leroy, Adam K and Schinnerer, Eva and Colombo, Dario and Querejeta, Miguel and Kramer, Carsten and Schuster, Karl F and Dumas, Gaelle},
  issn         = {0004-637X},
  journal      = {ASTROPHYSICAL JOURNAL},
  keywords     = {GIANT MOLECULAR CLOUDS,LARGE-MAGELLANIC-CLOUD,STAR-FORMATION,EFFICIENCY,INTERSTELLAR-MEDIUM,SPIRAL GALAXIES,M51,EVOLUTION,GAS,CLUSTERS,TURBULENCE,galaxies: individual (M51),ISM: clouds,ISM: kinematics and dynamics},
  language     = {eng},
  number       = {1},
  pages        = {13},
  title        = {Short GMC lifetimes : an observational estimate with the PdBI Arcsecond Whirlpool Survey (PAWS)},
  url          = {http://dx.doi.org/10.1088/0004-637X/806/1/72},
  volume       = {806},
  year         = {2015},
}

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