Thermal emission from bow shocks I: 2D Hydrodynamic Models of the Bubble Nebula

摘要: The Bubble Nebula (or NGC 7635) is a parsec-scale seemingly spherical wind-blown bubble around the relatively unevolved O star BD+60$^\circ$2522. small dynamical age of nebula and significant space velocity suggest that might be bow shock. We have run 2D hydrodynamic simulations to model interaction central star's wind with interstellar medium (ISM). models cover range possible ISM number densities $n=50-200 {\rm cm}^{-3}$ stellar velocities $v_{\star}=20-40$ km s$^{-1}$. Synthetic H$\alpha$ 24 $\mu$m emission maps predict same apparent shape quantitative properties similar observations. synthetic also maximum brightness from observations agree at apex best-matching simulation had $v_{\star}\approx20$ s$^{-1}$ into an $n\sim100 cm}^{-3}$, angle 60$^\circ$ respect line sight. soft ($0.3-2$ keV) hard ($2-10$ X-ray show brightest region in wake behind not shock itself. unabsorbed X-rays luminosity $\sim10^{32}-10^{33}$ erg are fainter, $\sim 10^{30} - 10^{31}$ s$^{-1}$, may too faint for current instruments successfully observe. Our results imply creates as it moves through turn asymmetric visible optical infrared wavelengths, predicted X-rays. does appear unique, could just favourably oriented very dense surrounding BD+60$^\circ$2522 its strong good candidate detecting non-thermal emission.