The filamentary structures in the CO emission toward the Milky Way disk

Soler, J. D.; Beuther, H.; Syed, J.; Wang, Y.; Henning, Th.; Glover, Simon C. O.; Klessen, Ralf S.; Sormani, Mattia C.; Smith, Rowan J.; Urquhart, J. S.; Yang, Ji; Su, Yang; Zhou, Xin

doi:10.1051/0004-6361/202141327

Cited by 8 publications

(4 citation statements)

References 60 publications

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“…The cold neutral media has a generally large aspect ratio along B-field, which is suggested by a number of authors observationally (Clark et al 2015;Soler et al 2021). The aspect ratio of CNM filaments is in average 60 (visual inspection of (Clark, Peek, & Putman 2014)) and can be as large as private communication).…”

Section: Introductionmentioning

confidence: 87%

How the existence of unstable neutral media restricts the aspect ratio of cold neutral media?

Ho¹,

Yuen²,

Lazarían³

2021

Preprint

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The ubiquity of very thin and lengthy cold neutral media (CNM) has been reported by multiple authors in the HI community. Yet, the reason of how the CNM can be so long and lengthy is still in debate. In this paper, we recognize a new type of instability due to the attractive nature of the pressure force in the unstable phase. We provide a new estimation of the average CNM filament aspect ratio with the consideration of force balances at the phase boundary, which is roughly 5-20 in common CNM environment. We show that most of the cold filaments are less filamentary than what usually predicted via MHD turbulence theory or inferred from observations: The average length of CNM filament is roughly 1/2 of that in isothermal MHD turbulence with similar turbulence conditions. This suggests that the "cold filaments" that is identified in observations might not be in pressure equilibrium or generated via other mechanisms.

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Section: Introductionmentioning

confidence: 87%

How the existence of unstable neutral media restricts the aspect ratio of cold neutral media?

Ho¹,

Yuen²,

Lazarían³

2021

Preprint

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“…We selected the filamentary structures using the Hessian matrix technique as implemented in Soler et al (2021) and coded in the hessiananalysis routine of the magnetar software package 5 (Soler 2020). This method is less computationally demanding than other filament identification methods, such as the rolling Hough transform (RHT, Clark et al 2014) or FILFINDER (Koch & Rosolowsky 2015), and yields similar results for the filament orientation, as detailed in Appendix C of Soler et al (2020).…”

Section: Analysis Of Filamentary Structurementioning

confidence: 99%

“…Similar observations for the outer regions toward the outer third and fourth quadrants have not been made. Thus, it is hard at the moment to estimate if the HI filaments inherit their elongation and orientation into molecular clouds that they may help form within them, in contrast with the general trend for the clouds traced by CO in the inner Galaxy (Soler et al 2021). Yet, the outer Galaxy reveals as an attractive laboratory to test our theories of molecular cloud formation and the coupling between the ISM phases.…”

Section: Properties Of Atomic Filamentsmentioning

confidence: 99%

The Galactic dynamics revealed by the filamentary structure in atomic hydrogen emission

Soler

Miville-Deschênes

Molinari

et al. 2022

A&A

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We present a study of the filamentary structure in the neutral atomic hydrogen (H I) emission at the 21 cm wavelength toward the Galactic plane using the 16′.2-resolution observations in the H I 4π (HI4PI) survey. Using the Hessian matrix method across radial velocity channels, we identified the filamentary structures and quantified their orientations using circular statistics. We found that the regions of the Milky Way’s disk beyond 10 kpc and up to roughly 18 kpc from the Galactic center display H I filamentary structures predominantly parallel to the Galactic plane. For regions at lower Galactocentric radii, we found that the H I filaments are mostly perpendicular or do not have a preferred orientation with respect to the Galactic plane. We interpret these results as the imprint of supernova feedback in the inner Galaxy and Galactic rotation and shear in the outer Milky Way. We found that the H I filamentary structures follow the Galactic warp and flaring and that they highlight some of the variations interpreted as the effect of the gravitational interaction with satellite galaxies. In addition, the mean scale height of the filamentary structures is lower than that sampled by the bulk of the H I emission, thus indicating that the cold and warm atomic hydrogen phases have different scale heights in the outer galaxy. Finally, we found that the fraction of the column density in H I filaments is almost constant up to approximately 18 kpc from the Galactic center. This is possibly a result of the roughly constant ratio between the cold and warm atomic hydrogen phases inferred from the H I absorption studies. Our results indicate that the H I filamentary structures provide insight into the dynamical processes shaping the Galactic disk. Their orientations record how and where the stellar energy input, the Galactic fountain process, the cosmic ray diffusion, and the gas accretion have molded the diffuse interstellar medium in the Galactic plane.

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“…Similar observations for the outer regions toward the outer third and forth quadrants have not been made. Thus, it is hard at the moment to estimate if the Hi filaments inherit their elongation and orientation into molecular clouds that they may help form within them, in contrast with the general trend for the clouds traced by CO in the inner Galaxy (Soler et al 2021). Yet, the outer Galaxy reveals as an attractive laboratory to test our theories of molecular cloud formation and the coupling between the ISM phases.…”

Section: Properties Of Atomic Filamentsmentioning

confidence: 99%

The Galactic dynamics revealed by the filamentary structure in atomic hydrogen emission

Soler,

Miville-Deschênes,

Molinari

et al. 2022

Preprint

View full text Add to dashboard Cite

We present a study of the filamentary structure in the neutral atomic hydrogen (Hi) emission at the 21 cm wavelength toward the Galactic plane using the 16. 2-resolution observations in the Hi 4π (HI4PI) survey. Using the Hessian matrix method across radial velocity channels, we identified the filamentary structures and quantified their orientations using circular statistics. We found that the regions of the Milky Way's disk beyond 10 kpc and up to roughly 18 kpc from the Galactic center display Hi filamentary structures predominantly parallel to the Galactic plane. For regions at lower Galactocentric radii, we found that the Hi filaments are mostly perpendicular or do not have a preferred orientation with respect to the Galactic plane. We interpret these results as the imprint of supernova feedback in the inner Galaxy and Galactic rotation and shear in the outer Milky Way. We found that the Hi filamentary structures follow the Galactic warp and flaring and that they highlight some of the variations interpreted as the effect of the gravitational interaction with satellite galaxies. In addition, the mean scale height of the filamentary structures is lower than that sampled by the bulk of the Hi emission, thus indicating that the cold and warm atomic hydrogen phases have different scale heights in the outer galaxy. Finally, we found that the fraction of the column density in Hi filaments is almost constant up to approximately 18 kpc from the Galactic center. This is possibly a result of the roughly constant ratio between the cold and warm atomic hydrogen phases inferred from the Hi absorption studies. Our results indicate that the Hi filamentary structures provide insight into the dynamical processes shaping the Galactic disk. Their orientations record how and where the stellar energy input, the Galactic fountain process, the cosmic ray diffusion, and the gas accretion have molded the diffuse interstellar medium in the Galactic plane.

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The filamentary structures in the CO emission toward the Milky Way disk

Cited by 8 publications

References 60 publications

How the existence of unstable neutral media restricts the aspect ratio of cold neutral media?

How the existence of unstable neutral media restricts the aspect ratio of cold neutral media?

The Galactic dynamics revealed by the filamentary structure in atomic hydrogen emission

The Galactic dynamics revealed by the filamentary structure in atomic hydrogen emission

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