Zusammenfassung
Using N-body/gasdynamic simulations of a Milky Way-like galaxy we analyse a
Kennicutt-Schmidt relation, \$\Sigma\_SFR \Sigma\_gas^N\$, at different
spatial scales. We simulate synthetic observations in CO lines and UV band. We
adopt the star formation rate defined in two ways: based on free fall collapse
of a molecular cloud - \$\Sigma\_SFR, cl\$, and calculated by using a UV flux
calibration - \$\Sigma\_SFR, UV\$. We study a KS relation for spatially smoothed
maps with effective spatial resolution from molecular cloud scales to several
hundred parsecs. We find that for spatially and kinematically resolved
molecular clouds the \$\Sigma\_SFR, cl \Sigma\_gas^N\$ relation
follows the power-law with index \$N 1.4\$. Using UV flux as SFR
calibrator we confirm a systematic offset between the \$\Sigma\_UV\$ and
\$\Sigma\_gas\$ distributions on scales compared to molecular cloud sizes.
Degrading resolution of our simulated maps for surface densities of gas and
star formation rates we establish that there is no relation \$\Sigma\_SFR,
UV - \Sigma\_gas\$ below the resolution \$50\$ pc. We find a transition
range around scales \$50-120\$ pc, where the power-law index \$N\$ increases
from 0 to 1-1.8 and saturates for scales larger \$120\$ pc. A value of the
index saturated depends on a surface gas density threshold and it becomes
steeper for higher \$\Sigma\_gas\$ threshold. Averaging over scales with size of
\$>150\$ pc the power-law index \$N\$ equals 1.3-1.4 for surface gas density
threshold \$5 M\_ødot\$pc\$^-2\$. At scales \$>120\$ pc surface SFR densities
determined by using CO data and UV flux, \$\Sigma\_SFR, UV/\Sigma\_SFR,
cl\$, demonstrate a discrepancy about a factor of 3. We argue that this may be
originated from overestimating (constant) values of conversion factor, star
formation efficiency or UV calibration used in our analysis.
Nutzer