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arXiv 1607.07534astro-ph.GA
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两个$z \sim 5$ SMG的K波段SINFONI光谱:从[O II ]光发射谱线搜索得到的未遮蔽恒星形成的上限

K band SINFONI spectra of two $z \sim 5$ SMGs: upper limits to the un-obscured star formation from [O II] optical emission line searches

Guilherme S. Couto, Luis Colina, Javier Piqueras López, Thaisa Storchi-Bergmann, Santiago Arribas

摘要:

本文给出了两个亚毫米(SMG)星系BR 1202-0725和J1000+0234的深SINFONI K带积分场谱。在两个系统中提取的每个物体的光谱没有显示出任何[O II] $λλ$ 3726,29 $\,$发射线的特征,分别为BR 1202-0725和J1000+0234设置了$3.9$和$2.5 \times 10^{-18}\,$ ${\rm erg\,s^{-1}\,\,cm^{-2} \,}$的通量上限。利用Kennicutt(1998)提出的[O II]双峰光度与恒星形成率之间的关系,我们分别估算了两个系统天体的$\sim$ $10-15\,\rm M_\odot\,yr^{-1} \,$和$\sim$ $30-40\,\rm M_\odot\,yr^{-1} \,$的无遮蔽SFR上限。对于SMG,这些值比从SED和IR光度导出的值低至少两个数量级。SFR值的差异将分别对应于BR 1202-0725和J1000+0234 SMG目视检查中至少$3.4 - 4.9$和$2.1 - 3.6$ mag的内部消光。BR 1202 -0725系统中LAE之一(Ly $\alpha2$)中[O II]衍生SFR的上限至少比先前从红外示踪剂衍生的SFR低一个数量级,而Ly $α$ 1的两个估计值都非常一致。这两个莱曼α发射体(LAE)的内部消光的下限分别为$0.6$和$1.3$。在我们的数据中没有发现先前声称的(Ohta等人,2000年)与Ly $α$ 1相关的[O II]发射的证据,这意味着在中波段成像数据中减去K波段天空发射线后的残差可以提供足够的通量。

英文摘要:

We present deep SINFONI K band integral field spectra of two submillimeter (SMG) galaxy systems: BR 1202-0725 and J1000+0234, at $z=4.69$ and $4.55$ respectively. Spectra extracted for each object in the two systems do not show any signature of the [O II]$λλ$3726,29Å$\,$ emission-lines, placing upper flux limits of $3.9$ and $2.5 \times 10^{-18}\,$${\rm erg\,s^{-1}\,\,cm^{-2} \,}$ for BR 1202-0725 and J1000+0234, respectively. Using the relation between the star formation rate (SFR) and the luminosity of the [O II] doublet from Kennicutt (1998), we estimate unobscured SFR upper limits of $\sim$ $10-15\,\rm M_\odot\,yr^{-1} \,$ and $\sim$ $30-40\,\rm M_\odot\,yr^{-1} \,$ for the objects of the two systems, respectively. For the SMGs, these values are at least two orders of magnitude lower than those derived from SED and IR luminosities. The differences on the SFR values would correspond to internal extinction of, at least, $3.4 - 4.9$ and $2.1 - 3.6$ mag in the visual for BR 1202-0725 and J1000+0234 SMGs, respectively. The upper limit for the [O II]-derived SFR in one of the LAEs (Ly$\alpha2$) in the BR1202-0725 system is at least one order of magnitude lower than the previous SFR derived from infrared tracers, while both estimates are in good agreement for Ly$α$1. The lower limits to the internal extinction in these two Lyman-alpha emitters (LAEs) are $0.6$ mag and $1.3$ mag, respectively. No evidence for the previously claimed (Ohta et al. 2000) [O II] emission associated with Ly$α$1 is identified in our data, implying that residuals of the K-band sky emission lines after subtraction in medium-band imaging data could provide the adequate flux.

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