Context : The heavy mass loss observed in evolved stars on the asymptotic giant branch ( AGB ) is usually attributed to dust-driven winds , but it is still an open question how much AGB stars contribute to the dust production in the interstellar medium , especially at lower metallicities .
In the case of C-type AGB stars , where the wind is thought to be driven by radiation pressure on amorphous carbon grains , there should be significant dust production even in metal-poor environments .
Carbon stars can manufacture the building blocks needed to form the wind-driving dust species themselves , irrespective of the chemical composition they have , by dredging up carbon from the stellar interior during thermal pulses .

Aims : We investigate how the mass loss in carbon stars is affected by a low-metallicity environment , similar to the Large and Small Magellanic Clouds ( LMC and SMC ) .

Methods : The atmospheres and winds of C-type AGB stars are modeled with the 1D spherically symmetric radiation-hydrodynamical code Dynamic Atmosphere and Radiation-driven Wind models based on Implicit Numerics ( DARWIN ) .
The models include a time-dependent description for nucleation , growth , and evaporation of amorphous carbon grains directly out of the gas phase .
To explore the metallicity-dependence of mass loss we calculate model grids at three different chemical abundances ( solar , LMC , and SMC ) .
Since carbon may be dredged up during the thermal pulses as AGB stars evolve , we keep the carbon abundance as a free parameter .
The models in these three different grids all have a current mass of one solar mass ; effective temperatures of 2600 K , 2800 K , 3000 K , or 3200 K ; and stellar luminosities equal to \log L _ { * } / L _ { \odot } = 3.70 , 3.85 , or 4.00 .

Results : The DARWIN models show that mass loss in carbon stars is facilitated by high luminosities , low effective temperatures , and a high carbon excess ( C-O ) at both solar and subsolar metallicities .
Similar combinations of effective temperature , luminosity , and carbon excess produce outflows at both solar and subsolar metallicities .
There are no large systematic differences in the mass-loss rates and wind velocities produced by these wind models with respect to metallicity , nor any systematic difference concerning the distribution of grain sizes or how much carbon is condensed into dust .
DARWIN models at subsolar metallicity have approximately 15 % lower mass-loss rates compared to DARWIN models at solar metallicity with the same stellar parameters and carbon excess .
For both solar and subsolar environments typical grain sizes range between 0.1 and 0.5 \mu m , the degree of condensed carbon varies between 5 % and 40 % , and the gas-to-dust ratios between 500 and 10000 .

Conclusions : C-type AGB stars can contribute to the dust production at subsolar metallicities ( down to at least \mathrm { [ Fe / H ] } = -1 ) as long as they dredge up sufficient amounts of carbon from the stellar interior .
Furthermore , stellar evolution models can use the mass-loss rates calculated from DARWIN models at solar metallicity when modeling the AGB phase at subsolar metallicities if carbon excess is used as the critical abundance parameter instead of the C/O ratio .