论文标题
Lyman-Alpha的MMT光谱z $ \ simeq $ 7：围绕大型星系加速电离的证据
MMT Spectroscopy of Lyman-alpha at z$\simeq$7: Evidence for Accelerated Reionization Around Massive Galaxies
论文作者
论文摘要
电离时代的星系倾向于表现出弱$α$排放，这可能反映出越来越中性的IgM的衰减。最近的观察已经开始揭示这张图片的例外，现在在烛台中最大的Z = 7 $ -9 $ 9的星系中出现了强烈的$α$排放，所有这些都表现出强烈的[oiii] $+$+$ h $β$排放（ew $> $> $ 800 $ \ $ 800 $ \ x MATHRM \ MATHRM {\ MATHRM {\ MATHRIM {a} a}}}}。为了更好地理解为什么ly $α$在大型z $ \ simeq $ 7 $ - $ 9星系中匿名强劲，我们已经开始了针对类似发光的较大样品（$ \ simeq $ 1 $ 1 $ -6 l $^$^{\ ast} $^{\ ast} $}的MMT/BINOSPEC调查（n = 22） z $ \ simeq $ 7的星系在非常广阔的区域（$ \ sim $ 3 v $^2 $）上选择。我们自信（$> $ 7 $σ$）在78％（7/9）的星系中检测出强大[OIII] $+$ H $β$ sistions（ew $> $ 800 $ \ Mathrm {\ Mathring {\ Mathring {a}} $），而与8％（1/12）的$ 8％（1/12）的$ 8％（EW $ 800 $> $ 800 $ \ $ 800 $ \ $> $ 800 $ \ $ 800 $ \ $ 800 $ \ 800 $ \ $ 800）（1/12） $ \ mathrm {\ Mathring {a}} $）[OIII] $+$ h $β$。我们认为，由于其大型SSFRS（$ \ gtrsim $ 30 Gyr $^{ - 1} $），较高的[OIII] $+$+$ h $β$种群的较高$α$ ews可能反映了电离光子生产效率的增强。我们还发现证据表明，与低质量透镜系统相比，来自大型星系的Ly $α$传输速度速度超过$ 6 <7 $。特别是，我们的数据表明在LY $α$传输中没有强烈的演变，这与图片一致，其中大量Z $ \ simeq $ 7星系通常位于大型电离区域。我们在样本中检测到三个紧密分隔（$ r $ = 1.7物理MPC）z $ \ simeq $ 7 ly $α$发射器，可以想象，可以追溯到与这张图片一致的大电离结构。我们检测到该区域过度密度的暂定证据，这意味着周围的体积中有大量的电离光子预算。
Reionization-era galaxies tend to exhibit weak Ly$α$ emission, likely reflecting attenuation from an increasingly neutral IGM. Recent observations have begun to reveal exceptions to this picture, with strong Ly$α$ emission now known in four of the most massive z=7$-$9 galaxies in the CANDELS fields, all of which also exhibit intense [OIII]$+$H$β$ emission (EW$>$800 $\mathrm{\mathring{A}}$). To better understand why Ly$α$ is anonymously strong in a subset of massive z$\simeq$7$-$9 galaxies, we have initiated an MMT/Binospec survey targeting a larger sample (N=22) of similarly luminous ($\simeq$1$-$6 L$^{\ast}_{\mathrm{UV}}$) z$\simeq$7 galaxies selected over very wide-area fields ($\sim$3 deg$^2$). We confidently ($>$7$σ$) detect Ly$α$ in 78% (7/9) of galaxies with strong [OIII]$+$H$β$ emission (EW$>$800 $\mathrm{\mathring{A}}$) as opposed to only 8% (1/12) of galaxies with more moderate (EW=200$-$800 $\mathrm{\mathring{A}}$) [OIII]$+$H$β$. We argue that the higher Ly$α$ EWs of the strong [OIII]$+$H$β$ population likely reflect enhanced ionizing photon production efficiency owing to their large sSFRs ($\gtrsim$30 Gyr$^{-1}$). We also find evidence that Ly$α$ transmission from massive galaxies declines less rapidly over $6<z<7$ than in low-mass lensed systems. In particular, our data suggest no strong evolution in Ly$α$ transmission, consistent with a picture wherein massive z$\simeq$7 galaxies often reside in large ionized regions. We detect three closely-separated ($R$ = 1.7 physical Mpc) z$\simeq$7 Ly$α$ emitters in our sample, conceivably tracing a large ionized structure that is consistent with this picture. We detect tentative evidence for an overdensity in this region, implying a large ionizing photon budget in the surrounding volume.
