34 research outputs found
Supernova Feedback in Molecular Clouds: Global Evolution and Dynamics
We use magnetohydrodynamical simulations of converging warm neutral medium
flows to analyse the formation and global evolution of magnetised and turbulent
molecular clouds subject to supernova feedback from massive stars. We show that
supernova feedback alone fails to disrupt entire, gravitationally bound,
molecular clouds, but is able to disperse small--sized (~10 pc) regions on
timescales of less than 1 Myr. Efficient radiative cooling of the supernova
remnant as well as strong compression of the surrounding gas result in
non-persistent energy and momentum input from the supernovae. However, if the
time between subsequent supernovae is short and they are clustered, large hot
bubbles form that disperse larger regions of the parental cloud. On longer
timescales, supernova feedback increases the amount of gas with moderate
temperatures (T~300-3000 K). Despite its inability to disrupt molecular clouds,
supernova feedback leaves a strong imprint on the star formation process. We
find an overall reduction of the star formation efficiency by a factor of 2 and
of the star formation rate by roughly factors of 2-4.Comment: 16 pages, 12 figures (2 in appendix), revised version, submitted to
MNRA
Relation between suppressiveness to tomato fusarium wilt and microbial populations in different growth media
Simulated observations of star formation regions: infrared evolution of globally collapsing clouds
The direct comparison between hydrodynamical simulations and observations is
needed to improve the physics included in the former and test biases in the
latter. Post-processing radiative transfer and synthetic observations are now
the standard way to do this. We report on the first application of the
\texttt{SKIRT} radiative transfer code to simulations of a star-forming cloud.
The synthetic observations are then analyzed following traditional
observational workflows. We find that in the early stages of the simulation,
stellar radiation is inefficient in heating dust to the temperatures observed
in Galactic clouds, thus the addition of an interstellar radiation field is
necessary. The spectral energy distribution of the cloud settles rather quickly
after Myr of evolution from the onset of star formation, but its
morphology continues to evolve for Myr due to the expansion of
\textsc{Hii} regions and the respective creation of cavities, filaments, and
ridges. Modeling synthetic \textit{Herschel} fluxes with 1- or 2-component
modified black bodies underestimates total dust masses by a factor of .
Spatially-resolved fitting recovers up to about of the intrinsic value.
This ``missing mass'' is located in a very cold dust component with
temperatures below K, which does not contribute appreciably to the
far-infrared flux. This effect could bias real observations if such dust exists
in large amounts. Finally, we tested observational calibrations of the SFR
based on infrared fluxes and concluded that they are in agreement when compared
to the intrinsic SFR of the simulation averaged over Myr
Structure and Expansion Law of HII Regions in structured Molecular Clouds
We present radiation-magnetohydrodynamic simulations aimed at studying
evolutionary properties of H\,{\normalsize II} regions in turbulent,
magnetised, and collapsing molecular clouds formed by converging flows in the
warm neutral medium. We focus on the structure, dynamics and expansion laws of
these regions. Once a massive star forms in our highly structured clouds, its
ionising radiation eventually stops the accretion (through filaments) toward
the massive star-forming regions. The new over-pressured H\,{\normalsize II}
regions push away the dense gas, thus disrupting the more massive collapse
centres. Also, because of the complex density structure in the cloud, the
H\,{\normalsize II} regions expand in a hybrid manner: they virtually do not
expand toward the densest regions (cores), while they expand according to the
classical analytical result towards the rest of the cloud, and in an
accelerated way, as a blister region, towards the diffuse medium. Thus, the
ionised regions grow anisotropically, and the ionising stars generally appear
off-centre of the regions. Finally, we find that the hypotheses assumed in
standard H\,{\normalsize II}-region expansion models (fully embedded region,
blister-type, or expansion in a density gradient) apply simultaneously in
different parts of our simulated H\,{\normalsize II} regions, producing a net
expansion law (, with in the range of 0.93-1.47
and a mean value of ) that differs from any of those of the
standard models.Comment: Accepted for publication in MNRA