Molecular Gas in a Submillimeter Galaxy at z = 4.5: Evidence for a Major Merger at 1 Billion Years after the Big Bang
Molecular Gas in a Submillimeter Galaxy at z = 4.5: Evidence for a Major Merger at 1 Billion Years after the Big Bang
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DOI：
10.1086/595680
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发表时间：
2008-10
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通讯作者：
E. Schinnerer;C. Carilli;P. Capak;A. Martínez-Sansigre;N. Scoville;V. Smolčić;Y. Taniguchi;Min S. Yun;F. Bertoldi;O. Fèvre;L. Ravel
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作者：
E. Schinnerer;C. Carilli;P. Capak;A. Martínez-Sansigre;N. Scoville;V. Smolčić;Y. Taniguchi;Min S. Yun;F. Bertoldi;O. Fèvre;L. Ravel
本文报道了利用IRAM Plateau de Bure干涉仪（PdBI）和NRAO甚大阵（VLA）对Z = 4.5毫米探测星系COSMOS J100054+023436（以下简称J1000+0234）中CO分子谱线发射的探测。用PdBI观测到的12 CO（4-3）线的全线宽约为1000 km s−1，积分线通量为0.66 Jy km s−1，CO光度为3.2 × 1010 L。与VLA对CO（2-1）谱线发射的3.3 σ探测结果的比较表明，该分子气体可能被热化到J = 4-3跃迁能级。相应的分子气体质量为2.6 × 1010 M，假设是ULIRG的转换因子。根据红移和蓝移谱线峰值的空间偏移和谱线宽度，假设合并的情况下，估计动力学质量为1.1 × 1011 M。分子气体分布与物体的静止坐标系光学和射电位置相一致，同时与先前探测到的Lyα发射偏移0.5″。J1000+0234表现出非常典型的低红移（z ≥ 2）亚毫米星系（SMG）的性质，因此很可能是这个族群中长期以来一直在寻找的高红移（z > 4）天体之一。大的CO（4-3）谱线宽度和它的高度扰动的静止框架紫外几何一起表明，在大爆炸后大约10亿年，一个正在进行的大合并。考虑到它的大星星形成速率（SFR）大于1000 M yr−1，并且含有分子气体，这个天体可能是在z = 2的红移处观测到的“红死”椭圆的前兆。
We report the detection of CO molecular line emission in the z = 4.5 millimeter-detected galaxy COSMOS J100054+023436 (hereafter J1000+0234) using the IRAM Plateau de Bure interferometer (PdBI) and NRAO’s Very Large Array (VLA). The 12CO(4-3) line as observed with PdBI has a full line width of ~1000 km s−1, an integrated line flux of 0.66 Jy km s−1, and a CO luminosity of 3.2 × 1010 L☉. Comparison to the 3.3 σ detection of the CO(2-1) line emission with the VLA suggests that the molecular gas is likely thermalized to the J = 4–3 transition level. The corresponding molecular gas mass is 2.6 × 1010 M☉ assuming an ULIRG-like conversion factor. From the spatial offset of the red- and blueshifted line peaks and the line width a dynamical mass of 1.1 × 1011 M☉ is estimated assuming a merging scenario. The molecular gas distribution coincides with the rest-frame optical and radio position of the object while being offset by 0.5″ from the previously detected Lyα emission. J1000+0234 exhibits very typical properties for lower redshift (z ∼ 2) submillimeter galaxies (SMGs) and thus is very likely one of the long sought after high-redshift (z > 4) objects of this population. The large CO(4-3) line width taken together with its highly disturbed rest-frame UV geometry suggest an ongoing major merger about a billion years after the big bang. Given its large star formation rate (SFR) of >1000 M☉ yr−1 and molecular gas content this object could be the precursor of a “red and dead” elliptical observed at a redshift of z = 2.