星系周围延展莱曼α发射的两个域：从局域辐射到环境调控
Two domains of extended Lyman-alpha emission around galaxies: from local radiation to environmental regulation
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中文总结 AI 辅助
本研究利用MXDF巡天，对3<z<4的21个LAE的Lyα晕进行分析，发现其Lyα发射在$1r_\text{vir}$内外分别由SFR和环境密度调控，外晕发射源自弥散气体。
中文摘要 AI 辅助
我们研究高红移星系周围延展莱曼α（Lyα）晕与驱动这类晕中发射的主要因素之间的关系，尤其是在约一个维里半径$r_\text{vir}$及更远的距离处。为达到所需的面亮度灵敏度，我们利用了MUSE极深场（MXDF）巡天，该巡天可探测单个Lyα晕中暗至约$10^{-20}$ erg cm$^{-2}$ s$^{-1}$ arcsec$^{-2}$的水平。我们的样本由MXDF中$3<z<4$的21个视核与晕最亮（但本征光度较低，$\text{log}_{10}L_{\text{Ly}\beta}<42.3$ erg s$^{-1}$）的莱曼α发射体（LAE）组成，其典型维里半径约为20 kpc。我们测量它们延伸至50 kpc（超过$2r_\text{vir}$）的径向面亮度轮廓，并研究面亮度与内部因素（宿主星系的恒星形成率SFR）或外部影响（环境密度$\text{δ}+1$）之间的相关性。我们发现这些相关性在约$1r_\text{vir}$或稍小的半径处存在明显的断点：断点以内，发射与SFR紧密相关（符合预期），与$\text{δ}+1$完全无关；在约$1r_\text{vir}$（20 kpc）以外，我们观察到相反的趋势，与SFR无关，但与$\text{δ}+1$的相关性逐渐显现。我们将测量结果与极暗、未被单独探测到的LAE的预期积分面亮度进行比较，发现后者不足以驱动观测到的相关性。我们得出结论，外部晕的Lyα发射由周围环境调控，但主要源自弥散气体而非离散源。
英文摘要
We examine the relation between extended Ly$α$ halos around high-redshift galaxies and the main factors responsible for driving the emission in such halos, in particular at distances around and beyond one virial radius $r_\mathrm{vir}$. To reach the required surface brightness sensitivity we take advantage of the MUSE eXtremely Deep Field (MXDF) survey, allowing us to probe levels as faint as $\sim 10^{-20}$ erg cm$^{-2}$ s$^{-1}$ arcsec$^{-2}$ in individual Ly$α$ halos. Our sample consists of the 21 apparently core- and halo-brightest (yet intrinsically low luminosity $\log_{10}$L$_{\mathrm{Ly}α} < 42.3$ erg s$^{-1}$) Ly$α$ emitters (LAEs) in the MXDF at $3<z<4$, with typical virial radii around 20 kpc. We measure their radial surface brightness profiles out to 50 kpc (more than $2r_{\mathrm{vir}}$) and investigate the correlations between surface brightness and internal (star formation rates of the host galaxies, SFR) or external influences (environmental density, $δ+1$). We find a clear break in these correlations at radii around or just below $1r_{\mathrm{vir}}$. Below this break the emission correlates tightly with SFR (as expected) and not at all with $δ+1$. Beyond $\sim 1r_\mathrm{vir}$(20 kpc) we observe the opposite trend with no dependence on SFR, but an emerging correlation with $δ+1$. We compare our measurements with the expected integrated surface brightness from ultrafaint, individually undetected LAEs and find that the latter is insufficient to drive the observed correlation. We conclude that Ly$α$ emission from the outer halos is regulated by the surrounding environment, but originates mostly from diffuse gas rather than discrete sources.
