%0 Generic %1 bisbas2015starbench %A Bisbas, T. G. %A Haworth, T. J. %A Williams, R. J. R. %A Mackey, J. %A Tremblin, P. %A Raga, A. C. %A Arthur, S. J. %A Baczynski, C. %A Dale, J. E. %A Frostholm, T. %A Geen, S. %A Haugboelle, T. %A Hubber, D. %A Iliev, I. T. %A Kuiper, R. %A Rosdahl, J. %A Sullivan, D. %A Walch, S. %A Wuensch, R. %D 2015 %K HII code comparison expansion region %T StarBench: The D-type expansion of an HII region %U http://arxiv.org/abs/1507.05621 %X StarBench is a project focused on benchmarking and validating different star-formation and stellar feedback codes. In this first StarBench paper we perform a comparison study of the D-type expansion of an HII region. The aim of this work is to understand the differences observed between the twelve participating numerical codes against the various analytical expressions examining the D-type phase of HII region expansion. To do this, we propose two well-defined tests which are tackled by 1D and 3D grid- and SPH- based codes. The first test examines the `early phase' D-type scenario during which the mechanical pressure driving the expansion is significantly larger than the thermal pressure of the neutral medium. The second test examines the `late phase' D-type scenario during which the system relaxes to pressure equilibrium with the external medium. Although they are mutually in excellent agreement, all twelve participating codes follow a modified expansion law that deviates significantly from the classical Spitzer solution in both scenarios. We present a semi-empirical formula combining the two different solutions appropriate to both early and late phases that agrees with high-resolution simulations to $łesssim2\%$. This formula provides a much better benchmark solution for code validation than the Spitzer solution. The present comparison has validated the participating codes and through this project we provide a dataset for calibrating the treatment of ionizing radiation hydrodynamics codes.

@misc{bisbas2015starbench, abstract = {StarBench is a project focused on benchmarking and validating different star-formation and stellar feedback codes. In this first StarBench paper we perform a comparison study of the D-type expansion of an HII region. The aim of this work is to understand the differences observed between the twelve participating numerical codes against the various analytical expressions examining the D-type phase of HII region expansion. To do this, we propose two well-defined tests which are tackled by 1D and 3D grid- and SPH- based codes. The first test examines the `early phase' D-type scenario during which the mechanical pressure driving the expansion is significantly larger than the thermal pressure of the neutral medium. The second test examines the `late phase' D-type scenario during which the system relaxes to pressure equilibrium with the external medium. Although they are mutually in excellent agreement, all twelve participating codes follow a modified expansion law that deviates significantly from the classical Spitzer solution in both scenarios. We present a semi-empirical formula combining the two different solutions appropriate to both early and late phases that agrees with high-resolution simulations to $\lesssim2\%$. This formula provides a much better benchmark solution for code validation than the Spitzer solution. The present comparison has validated the participating codes and through this project we provide a dataset for calibrating the treatment of ionizing radiation hydrodynamics codes.}, added-at = {2015-07-22T09:48:31.000+0200}, author = {Bisbas, T. G. and Haworth, T. J. and Williams, R. J. R. and Mackey, J. and Tremblin, P. and Raga, A. C. and Arthur, S. J. and Baczynski, C. and Dale, J. E. and Frostholm, T. and Geen, S. and Haugboelle, T. and Hubber, D. and Iliev, I. T. and Kuiper, R. and Rosdahl, J. and Sullivan, D. and Walch, S. and Wuensch, R.}, biburl = {https://www.bibsonomy.org/bibtex/2736be2caef66f20caf49efd94de08d88/miki}, description = {[1507.05621] StarBench: The D-type expansion of an HII region}, interhash = {93e0efffeac563ec7374ec793aea6bf1}, intrahash = {736be2caef66f20caf49efd94de08d88}, keywords = {HII code comparison expansion region}, note = {cite arxiv:1507.05621Comment: 20 pages, 12 Figures, 4 Tables. Accepted for publication in MNRAS. Comments are welcome. Participation in future StarBench tests is also welcome}, timestamp = {2015-07-22T09:48:31.000+0200}, title = {StarBench: The D-type expansion of an HII region}, url = {http://arxiv.org/abs/1507.05621}, year = 2015 }