The impact of galactic disc environment on star-forming clouds

Nguyen, Ngan K.; Pettitt, Alex R.; Tasker, Elizabeth J.; Okamoto, Takashi

doi:10.1093/mnras/stx3143

Cited by 20 publications

(19 citation statements)

References 117 publications

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“…If we assume our model is correct, then we can interpret the relative differences in σ − L relations between differing spiral galaxies as due to differences in the strength of spiral shocks, at least where they interact with molecular gas (cf Nguyen et al 2018). More explicitly, the spiral shocks of NGC 4526 must be weaker than those of the Milky Way to be consistent with the model.…”

Section: Discussionmentioning

confidence: 99%

Clumpy shocks as the driver of velocity dispersion in molecular clouds: the effects of self-gravity and magnetic fields

Forgan

Bonnell

2018

Monthly Notices of the Royal Astronomical Society

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We revisit an alternate explanation for the turbulent nature of molecular cloudsnamely, that velocity dispersions matching classical predictions of driven turbulence can be generated by the passage of clumpy material through a shock. While previous work suggested this mechanism can reproduce the observed Larson relation between velocity dispersion and size scale (σ ∝ L Γ with Γ ≈ 0.5), the effects of self-gravity and magnetic fields were not considered. We run a series of smoothed particle magnetohydrodynamics experiments, passing clumpy gas through a shock in the presence of a combination of self-gravity and magnetic fields. We find powerlaw relations between σ and L throughout, with indices ranging from Γ = 0.3 − 1.2. These results are relatively insensitive to the strength and geometry of magnetic fields, provided that the shock is relatively strong. Γ is strongly sensitive to the angle between the gas' bulk velocity and the shock front, and the shock strength (compared to the gravitational boundness of the pre-shock gas). If the origin of the σ − L relation is in clumpy shocks, deviations from the standard Larson relation constrain the strength and behaviour of shocks in spiral galaxies.

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Section: Discussionmentioning

confidence: 99%

Clumpy shocks as the driver of velocity dispersion in molecular clouds: the effects of self-gravity and magnetic fields

Forgan

Bonnell

2018

Monthly Notices of the Royal Astronomical Society

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“…Exactly how clouds depend on the non-axisymmetric spiral structure has been the subject of only a few studies. Nguyen et al (2018) found E-mail: alex@astro1.sci.hokudai.ac.jp that the impact of spiral features vastly exceeds changes possible from differing rotation curves (i.e. differing shear rates).…”

Section: Introductionmentioning

confidence: 99%

How do different spiral arm models impact the ISM and GMC population?

Pettitt

Dobbs

Baba

et al. 2020

Monthly Notices of the Royal Astronomical Society

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The nature of galactic spiral arms in disc galaxies remains elusive. Regardless of the spiral model, arms are expected to play a role in sculpting the star-forming interstellar medium. As such, different arm models may result in differences in the structure of the interstellar medium and molecular cloud properties. In this study we present simulations of galactic discs subject to spiral arm perturbations of different natures. We find very little difference in how the cloud population or gas kinematics vary between the different grand-design spirals, indicting that the interstellar medium on cloud scales cares little about where spiral arms come from. We do, however, see a difference in the interarm/arm mass spectra, and minor differences in tails of the distributions of cloud properties (as well as radial variations in the stellar/gaseous velocity dispersions). These features can be attributed to differences in the radial dependence of the pattern speeds between the different spiral models, and could act as a metric of the nature of spiral structure in observational studies.

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“…They also observe a population of unbound objects that are typically observed as a product of cloud interactions in dense filamentary structures. Similarly, Nguyen et al (2018) find that simulations that include spiral perturbation tend to generate a high degree of agglomeration of clouds within the spiral arms, with a general decrease in the number of small and medium-sized objects (with masses < 10 6 M ) in the disc, together with an incremental increase in the size of the unbound population. Cloud properties do not appear to be strongly influenced by the kind of spiral perturbation (flocculent, granddesign, or perturbed by a companion iteration), as shown by Pettitt et al (2020), who nevertheless found that the cloud mass spectra and contrast between arms and inter-arm regions di↵er depending on the type of spiral arms.…”

Section: Introductionmentioning

confidence: 78%