The relative impact of photoionizing radiation and stellar winds on
  different environments
  Photoionizing radiation and stellar winds from massive stars deposit energy
and momentum into the interstellar medium (ISM). They might disperse the local
ISM, change its turbulent multi-phase structure, and even regulate star
formation. Ionizing radiation dominates the massive stars' energy output, but
the relative effect of winds might change with stellar mass and the properties
of the ambient ISM. We present simulations of the interaction of stellar winds
and ionizing radiation of 12, 23, and 60 M$_{\odot}$ stars within a cold
neutral (CNM, $n_{0}$ = 100 cm$^{-3}$), warm neutral (WNM, $n_{0}$ = 1, 10
cm$^{-3}$) or warm ionized (WIM, $n_{0}$ = 0.1 cm$^{-3}$) medium. The FLASH
simulations adopt the novel tree-based radiation transfer algorithm TreeRay.
With the On-the-Spot approximation and a temperature-dependent recombination
coefficient, it is coupled to a chemical network with radiative heating and
cooling. In the homogeneous CNM, the total momentum injection ranges from
1.6$\times$10$^{4}$ to 4$\times$10$^{5}$ M$_{\odot}$ km s$^{-1}$ and is always
dominated by the expansion of the ionized H$_{\text{II}}$ region. In the WIM,
stellar winds dominate (2$\times$10$^{2}$ to 5$\times$10$^{3}$ M$_{\odot}$ km
s$^{-1}$), while the input from radiation is small ($\sim$ 10$^{2}$ M$_{\odot}$
km s$^{-1}$). The WNM ($n_{0}$ = 1 cm$^{-3}$) is a transition regime.
Energetically, stellar winds couple more efficiently to the ISM ($\sim$ 0.1
percent of wind luminosity) than radiation ($<$ 0.001 percent of ionizing
luminosity). For estimating the impact of massive stars, the strongly
mass-dependent ratios of wind to ionizing luminosity and the properties of the
ambient medium have to be considered.
