%0 Generic %1 chang2022radiative %A Chang, Seok-Jun %A Yang, Yujin %A Seon, Kwang-Il %A Zabludoff, Ann %A Lee, Hee-Won %D 2022 %K library %T Radiative Transfer in Ly\alpha Nebulae: I. Modeling a Continuous or Clumpy Spherical Halo with a Central Source %U http://arxiv.org/abs/2212.09630 %X To understand the mechanism behind high-$z$ Ly$\alpha$ nebulae, we simulate the scattering of Ly$\alpha$ in a $H\,I$ halo about a central Ly$\alpha$ source. For the first time, we consider both smooth and clumpy distributions of halo gas, as well as a range of outflow speeds, total $\rm H\,I$ column densities, $H\,I$ spatial concentrations, and central source galaxies (e.g., with Ly$\alpha$ line widths corresponding to those typical of AGN or star-forming galaxies). We compute the spatial-frequency diffusion and the polarization of the Ly$\alpha$ photons scattered by atomic hydrogen. Our scattering-only model reproduces the typical size of Ly$\alpha$ nebulae ($100\,$kpc) at total column densities $N_HI 10^20 \rm cm^-2$ and predicts a range of positive, flat, and negative polarization radial gradients. We also find two general classes of Ly$\alpha$ nebula morphologies: with and without bright cores. Cores are seen when $N_HI$ is low, i.e., when the central source is directly visible, and are associated with a polarization jump, a steep increase in the polarization radial profile just outside the halo center. Of all the parameters tested in our smooth or clumpy medium model, $N_HI$ dominates the trends. The radial behaviors of the Ly$\alpha$ surface brightness, spectral line shape, and polarization in the clumpy model with covering factor $f_c 5$ approach those of the smooth model at the same $N_HI$. A clumpy medium with high $N_HI$ and low $f_c 2$ generates Ly$\alpha$ features via scattering that the smooth model cannot: a bright core, symmetric line profile, and polarization jump.

@misc{chang2022radiative, abstract = {To understand the mechanism behind high-$z$ Ly${\alpha}$ nebulae, we simulate the scattering of Ly${\alpha}$ in a $\rm H\,I$ halo about a central Ly${\alpha}$ source. For the first time, we consider both smooth and clumpy distributions of halo gas, as well as a range of outflow speeds, total $\rm H\,I$ column densities, $\rm H\,I$ spatial concentrations, and central source galaxies (e.g., with Ly${\alpha}$ line widths corresponding to those typical of AGN or star-forming galaxies). We compute the spatial-frequency diffusion and the polarization of the Ly${\alpha}$ photons scattered by atomic hydrogen. Our scattering-only model reproduces the typical size of Ly${\alpha}$ nebulae ($\sim 100\,$kpc) at total column densities $N_{\rm HI} \geq 10^{20} \rm cm^{-2}$ and predicts a range of positive, flat, and negative polarization radial gradients. We also find two general classes of Ly${\alpha}$ nebula morphologies: with and without bright cores. Cores are seen when $N_{\rm HI}$ is low, i.e., when the central source is directly visible, and are associated with a polarization jump, a steep increase in the polarization radial profile just outside the halo center. Of all the parameters tested in our smooth or clumpy medium model, $N_{\rm HI}$ dominates the trends. The radial behaviors of the Ly${\alpha}$ surface brightness, spectral line shape, and polarization in the clumpy model with covering factor $f_c \gtrsim 5$ approach those of the smooth model at the same $N_{\rm HI}$. A clumpy medium with high $N_{\rm HI}$ and low $f_c \lesssim 2$ generates Ly${\alpha}$ features via scattering that the smooth model cannot: a bright core, symmetric line profile, and polarization jump.}, added-at = {2022-12-20T09:28:30.000+0100}, author = {Chang, Seok-Jun and Yang, Yujin and Seon, Kwang-Il and Zabludoff, Ann and Lee, Hee-Won}, biburl = {https://www.bibsonomy.org/bibtex/2bfcab2385f7dbb0983e414ace3b9985d/gpkulkarni}, description = {Radiative Transfer in Ly{\alpha} Nebulae: I. Modeling a Continuous or Clumpy Spherical Halo with a Central Source}, interhash = {a79d3a964c7e49639fda9a069825cbcb}, intrahash = {bfcab2385f7dbb0983e414ace3b9985d}, keywords = {library}, note = {cite arxiv:2212.09630Comment: 42 pages, 27 figures, accepted for publication in ApJ, Comments welcome!}, timestamp = {2022-12-20T09:28:30.000+0100}, title = {Radiative Transfer in Ly{\alpha} Nebulae: I. Modeling a Continuous or Clumpy Spherical Halo with a Central Source}, url = {http://arxiv.org/abs/2212.09630}, year = 2022 }