Dust, Gas, and the Evolutionary Status of the Radio Galaxy 8C 1435+635 at z = 4.25
Dust, Gas, and the Evolutionary Status of the Radio Galaxy 8C 1435+635 at z = 4.25
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灰尘、气体和射电星系 8C 1435 635 在 z = 4.25 时的演化状态
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发表时间：
1997
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通讯作者：
W. Gear
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作者：
R. Ivison;J. Dunlop;D. Hughes;E. Archibald;J. Stevens;W. Holland;E. I. Robson;S. Eales;S. Rawlings;A. Dey;W. Gear
我们提出了对z = 4.25射电星系8C 1435+635的新静止框架远红外观测结果，这不仅证实了它含有大量的尘埃（这是1995年Ivison首次从毫米波探测中推断出来的），而且还允许对这种尘埃和伴生气体的质量进行第一次有意义的限制。新的测量结果包括：(1)在James Clerk Maxwell望远镜上使用新型亚毫米辐射热计阵列SCUBA获得了λobs = 450和850 μm的亚毫米连续辐射的清晰探测；(2)在红外空间天文台上使用SCUBA和PHT远红外相机获得了λobs = 350、750和175 μm的连续辐射上限；(3)使用IRAM 30 m毫米射电望远镜获得了CO（4-3）线通量的灵敏上限。由此得到的静止框架33-238 μm连续体覆盖范围使我们能够推断出在40±5 K温度下2 × 108 M☉的尘埃是观测到的毫米/亚毫米辐射的原因。利用CO上限，将MH2/Md限制在950以下，我们继续计算总气体储量（H2 + H I）的稳健极限，从而将其限制在4 × 1010和1.2 × 1012 M☉之间。因此，8C 1435+635的亚毫米特性与z = 3.80射电星系4C 41.17的亚毫米特性惊人地相似，4C 41.17是迄今为止唯一一个在亚毫米波长上被探测到的高红移星系，其特性似乎没有被引力透镜放大。推断出的两个天体的气体质量都足够大，表明大质量椭圆星系的形成恒星爆发仍在z≃4处进行。为了确定8c1435 +635和4c41.17的远红外特性主要是由于它们的极端红移还是由于它们的极端射电光度，需要对跨越红移和射电光度范围的射电星系的完整样本进行观测。
We present the results of new rest-frame far-IR observations of the z = 4.25 radio galaxy 8C 1435+635, which not only confirm that it contains an enormous quantity of dust (as first inferred from its millimeter-wave detection by Ivison in 1995), but also allow the first meaningful constraints to be placed on the mass of this dust and associated gas. The new measurements consist of (1) clear detections of submillimeter continuum emission at λobs = 450 and 850 μm obtained with the new submillimeter bolometer array, SCUBA, on the James Clerk Maxwell Telescope, (2) continuum upper limits at λobs = 350, 750, and 175 μm obtained with SCUBA and the PHT far-IR camera aboard the Infrared Space Observatory, and (3) a sensitive upper limit on the CO (4-3) line flux obtained with the IRAM 30 m Millimeter Radio Telescope. The resulting rest-frame 33-238 μm continuum coverage allows us to deduce that 2 × 108 M☉ of dust at a temperature of 40 ± 5 K is responsible for the observed millimeter/submillimeter emission. Using our CO upper limit, which constrains MH2/Md to less than 950, we go on to calculate robust limits on the total gas reserves (H2 + H I), which are thereby constrained to between 4 × 1010 and 1.2 × 1012 M☉. The submillimeter properties of 8C 1435+635 are thus strikingly similar to those of the z = 3.80 radio galaxy 4C 41.17, the only other high-redshift galaxy detected to date at submillimeter wavelengths whose properties appear not to be exaggerated by gravitational lensing. The inferred gas masses of both objects are sufficiently large to suggest that the formative starbursts of massive elliptical galaxies are still in progress at z ≃ 4. Observations of complete samples of radio galaxies spanning a range of redshifts and radio luminosities will be required to determine whether the spectacular far-IR properties of 8C 1435+635 and 4C 41.17 are primarily due to their extreme redshifts or to their extreme radio luminosities.