The effect of viewing angle on the Kennicutt-Schmidt relation of the local molecular clouds
Journal article, 2022

The Gaia data give us an unprecedented view to the three-dimensional (3D) structure of molecular clouds in the solar neighbourhood. We study how the projected areas and masses of clouds, and consequently the Kennicutt-Schmidt (KS) relation, depend on the viewing angle. We derive the probability distributions of the projected areas and masses for nine clouds within 400 pc of the Sun using 3D dust distribution data from the literature. We find that the viewing angle can have a dramatic effect on the observed areas and masses of individual clouds. The joint probability distributions of the areas and masses are strongly correlated, relatively flat, and can show multiple peaks. The typical ranges and 50% quartiles of the distributions are roughly 100-200% and 20-80% of the median value, respectively, making viewing angle effects important for all individual clouds. The threshold value used to define the cloud areas is also important; our analysis suggests that the clouds become more anisotropic for smaller thresholds (larger scales). On average, the areas and masses of the plane-of-the-sky and face-on projections agree, albeit with a large scatter. This suggests that sample averages of areas and masses are relatively free of viewing angle effects, which is important to facilitate comparisons of extragalactic and Galactic data. Ultimately, our results demonstrate that a cloud's location in the KS relation is affected by the viewing angle in a non-trivial manner. However, the KS relation of our sample as a whole is not strongly affected by these effects, because the covariance of the areas and masses causes the observed mean column density to remain relatively constant.

stars

structure

ISM

clouds

formation

ISM

Author

Jouni Kainulainen

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

Sara Rezaeikhoshbakht

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

Max Planck Society

Andri Spilker

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

Jan Orkisz

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 659 L6

Turbulensdiagnostik i molekylmolnen i solens närhet

Swedish Research Council (VR) (2017-03864), 2018-01-01 -- 2020-12-31.

Subject Categories

Analytical Chemistry

Meteorology and Atmospheric Sciences

Astronomy, Astrophysics and Cosmology

DOI

10.1051/0004-6361/202142420

More information

Latest update

4/4/2022 9