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首页> 外文期刊>The Astrophysical journal >MOLECULAR GAS IN THE LENSED LYMAN BREAK GALAXY cB58
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MOLECULAR GAS IN THE LENSED LYMAN BREAK GALAXY cB58

机译：莱曼BREAK影驰cB58中的分子气体

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摘要

We have used the IRAM Plateau de Bure Interferometer to map CO (3-2) emission from the gravitationally lensed Lyman break galaxy MS 1512-cB58. This is the first detection of a molecular emission line in any Lyman break system; its integrated intensity implies a total molecular gas mass of (6.6_(-4.3)~(+5.8)) x 10~9 h_(0.7)~(-2)solar mass, while its width implies a dynamical mass of (1.0_(-0.4)~(+0.6)) x 10~(10) csc~2 I h_(0.7)~(-1) solar mass (for a flat Ω_Λ = 0.7 cosmology). These estimates are in excellent concordance with nearly all parameters of the system measured at other wavelengths and yield a consistent picture of past and future star formation with no obvious discrepancies requiring explanation by differential lensing. In particular, we find that the age and remaining lifetime of the current episode of star formation are likely to be similar, the surface densities of star formation and molecular gas mass are related by a Schmidt law, and the fraction of baryonic mass already converted into stars is sufficient to account for the observed enrichment of the interstellar medium to 0.4 Z_☉. Barring substantial gas inflow or a major merger, the stars forming in the current episode will have mass and coevality at z = 0 similar to those of a spiral bulge. Assuming that cB58 is a typical Lyman break galaxy apart from its magnification, its global parameters suggest that the prescriptions for star formation used in some semianalytic models of galaxy evolution require moderate revision, although the general prediction that gas mass fraction should increase with redshift is validated. The length of cB58's star formation episode relative to the time elapsed over the redshift range 2.5 ≤ z ≤ 3.5 strongly argues against scenarios in which observed LBGs cohabit their halos with a large number of similar but "dormant" systems whose starbursts have faded or not yet begun. As a useful empirical result, we find that the observed line/continuum ratio for cB58 is similar to those of high-redshift systems with quite different dust luminosities and nuclear activity levels. Finally, we report the detection of a second source close to the position of the cD elliptical in the z = 0.37 lensing cluster, which may be nonthermal continuum emission from the cD or CO line emission from a hitherto unknown background galaxy at z ～1.48 or～2.73.
机译：我们已经使用IRAM高原德伯干涉仪来绘制由重力透镜组成的莱曼断裂星系MS 1512-cB58产生的CO（3-2）发射图。这是在任何莱曼断裂系统中首次检测到分子发射线;其积分强度表示总分子气体质量为（6.6 _（-4.3）〜（+5.8））x 10〜9 h_（0.7）〜（-2）太阳能质量，而其宽度表示动态质量为（1.0_ （-0.4）〜（+0.6））x 10〜（10）csc〜2 I h_（0.7）〜（-1）太阳质量（对于平坦的Ω_Λ= 0.7宇宙学）。这些估计值与在其他波长下测量的系统几乎所有参数都非常一致，并且可以提供过去和将来恒星形成的一致图像，而没有明显的差异需要通过差动透镜进行解释。特别是，我们发现当前恒星形成事件的年龄和剩余寿命很可能相似，恒星形成的表面密度与分子气体质量之间的关系通过施密特定律（Schmidt law），并且重子质量分数已转换为恒星足以说明所观察到的星际介质富集至0.4Z_☉。除非有大量的气体流入或大量合并，否则当前事件中形成的恒星在z = 0时的质量和凸度将类似于螺旋形凸起的质量和凸度。假设cB58除了是一个典型的莱曼破裂星系，其放大倍数也是如此，其总体参数表明，在某些星系演化半解析模型中使用的恒星形成处方需要进行适度修正，尽管验证了气体质量分数应随红移而增加的一般预测。 cB58的恒星形成情节相对于在2.5≤z≤3.5的红移范围内经过的时间的长度强烈反对以下情形：观察到的LBG与大量类似但休眠的系统共同存在于它们的光晕中，而这些系统的星爆尚未消失开始。作为有用的经验结果，我们发现cB58的观测线/连续谱比与尘埃发光度和核活性水平完全不同的高红移系统的相近。最后，我们报告了在z = 0.37透镜簇中检测到接近cD椭圆位置的第二个源，这可能是cD的非热连续辐射或迄今未知的背景星系在z〜1.48或CO线发射。 〜2.73。

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