WHAT DOES A SUBMILLIMETER GALAXY SELECTION ACTUALLY SELECT? THE DEPENDENCE OF SUBMILLIMETER FLUX DENSITY ON STAR FORMATION RATE AND DUST MASS
WHAT DOES A SUBMILLIMETER GALAXY SELECTION ACTUALLY SELECT? THE DEPENDENCE OF SUBMILLIMETER FLUX DENSITY ON STAR FORMATION RATE AND DUST MASS
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DOI：
10.1088/0004-637x/743/2/159
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发表时间：
2010-12
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影响因子：
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通讯作者：
C. Hayward;D. Keres̆;P. Jonsson;D. Narayanan;T. J. Cox;L. Hernquist
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作者：
C. Hayward;D. Keres̆;P. Jonsson;D. Narayanan;T. J. Cox;L. Hernquist
我们对孤立和合并的盘状星系的流体动力学模拟进行三维尘埃辐射传输（RT）计算，以便定量研究观测框架亚毫米（submm）通量密度对星系特性的依赖性。我们发现，对于静止的恒星形成星系和星暴来说，亚毫米通量密度和恒星形成率（SFR）之间的关联方式截然不同。由于合并引起的星暴中形成的恒星并不主导辐射光度，并且尘埃质量的快速下降和更紧凑的几何结构导致爆发期间尘埃温度急剧升高，因此星暴在提高亚毫米通量密度方面非常低效（例如，恒星形成率增加≳ 16倍，亚毫米通量密度会增加≲ 2倍）。此外，亚毫米磁通密度与 SFR 的比率在两种模式之间存在显着差异；因此，我们不能假设具有最高亚毫米通量密度的星系一定是具有最高辐射光度或恒星形成率的星系。这些结果对明亮的亚毫米选择星系（SMG）群体具有重要影响。其中包括： (1) SMG 人群具有异质性。除了合并驱动的星暴之外，还有一个星系对子群，其中两个正在经历重大合并但尚未强烈相互作用的盘被混合成一个亚毫米源，因为单盘亚毫米望远镜的光束很大（≳ 15”或〜130 kpc，z = 2）。（2）SMG必须非常巨大（M⋆≳6×1010 M☉）。（3）坠落 阶段使得 SMG 占空比比合并驱动的星爆的预期大几倍。最后，我们提供了 SCUBA 和 AzTEC 亚毫米通量密度的拟合函数，作为 SFR 和灰尘质量以及辐射光度和灰尘质量的函数；当执行完整的 RT 在计算上不可行时，这些对于计算半解析模型和宇宙学模拟中的亚毫米通量密度很有用。
We perform three-dimensional dust radiative transfer (RT) calculations on hydrodynamic simulations of isolated and merging disk galaxies in order to quantitatively study the dependence of observed-frame submillimeter (submm) flux density on galaxy properties. We find that submm flux density and star formation rate (SFR) are related in dramatically different ways for quiescently star-forming galaxies and starbursts. Because the stars formed in the merger-induced starburst do not dominate the bolometric luminosity and the rapid drop in dust mass and more compact geometry cause a sharp increase in dust temperature during the burst, starbursts are very inefficient at boosting submm flux density (e.g., a ≳ 16 × boost in SFR yields a ≲ 2 × boost in submm flux density). Moreover, the ratio of submm flux density to SFR differs significantly between the two modes; thus one cannot assume that the galaxies with highest submm flux density are necessarily those with the highest bolometric luminosity or SFR. These results have important consequences for the bright submillimeter-selected galaxy (SMG) population. Among them are: (1) The SMG population is heterogeneous. In addition to merger-driven starbursts, there is a subpopulation of galaxy pairs, where two disks undergoing a major merger but not yet strongly interacting are blended into one submm source because of the large (≳ 15” or ∼130 kpc at z = 2) beam of single-dish submm telescopes. (2) SMGs must be very massive (M⋆ ≳ 6 × 1010 M☉). (3) The infall phase makes the SMG duty cycle a factor of a few greater than what is expected for a merger-driven starburst. Finally, we provide fitting functions for SCUBA and AzTEC submm flux densities as a function of SFR and dust mass and bolometric luminosity and dust mass; these should be useful for calculating submm flux density in semi-analytic models and cosmological simulations when performing full RT is computationally not feasible.