The LOFAR Two-metre Sky Survey Deep Fields A new analysis of low-frequency radio luminosity as a star-formation tracer in the Lockman Hole region
The LOFAR Two-metre Sky Survey Deep Fields A new analysis of low-frequency radio luminosity as a star-formation tracer in the Lockman Hole region
复制标题
LOFAR 两米巡天深场对低频射电光度作为洛克曼霍尔地区恒星形成示踪剂的新分析
DOI：
10.1051/0004-6361/202141286
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发表时间：
2021
影响因子：
6.5
通讯作者：
Bonato M
中科院分区：
文献类型：
--
作者：
Bonato M
我们利用 LOFAR 对 150 MHz 洛克曼霍尔场的深度观测来研究恒星形成星系 (SFG) 的射电光度与其恒星形成速率 (SFR) 之间的关系，以及其对恒星质量和红移的依赖性。所采用的源分类、恒星形成率和恒星质量是基于四种不同光谱能量分布拟合方法组合的一致估计。我们注意到，绝大多数低于 ∼1.4 GHz 的源的无线电频谱变得平坦。因此，此类源在 150 MHz 处的“无线电响度”水平低于使用平均频谱指数从 1.4 GHz 推断的预期水平。我们发现恒星质量 M⋆ 较高时，SFR/L150 MHz 比率呈较低趋势，趋势较弱。我们认为，这种趋势可能解释了 L150 MHz/SFR 比率的大部分明显红移演化，与之前的工作一致。我们的数据表明，进化程度比之前的一些分析所发现的要弱。我们还发现特定恒星形成率红移的演化比之前几项（但不是全部）研究发现的更弱。我们的无线电选择提供了 SFR–M⋆平面中星系分布的视图，与光学和近红外选择的视图互补。它表明星系恒星形成历史的均匀性比光学和近红外数据的一些分析所暗示的更高。我们导出了 SFG 和射电安静 (RQ) AGN 在各种红移下的 150 MHz 光度函数。我们的结果与 T-RECS 模拟和文献估计非常一致。我们还根据我们的射电勘测数据，对 SFG 和 RQ AGN 在几个红移处的 SFR 函数进行了明确的估计。
We have exploited LOFAR deep observations of the Lockman Hole field at 150 MHz to investigate the relation between the radio luminosity of star-forming galaxies (SFGs) and their star-formation rates (SFRs), as well as its dependence on stellar mass and redshift. The adopted source classification, SFRs, and stellar masses are consensus estimates based on a combination of four different spectral energy distribution fitting methods. We note a flattening of the radio spectra of a substantial minority of sources below ∼1.4 GHz. Such sources have thus a lower ‘radio-loudness’ level at 150 MHz than expected from extrapolations from 1.4 GHz using the average spectral index. We found a weak trend towards a lower SFR/L150 MHzratio for higher stellar mass,M⋆. We argue that such a trend may account for most of the apparent redshift evolution of theL150 MHz/SFR ratio, in line with previous work. Our data indicate a weaker evolution than found by some previous analyses. We also find a weaker evolution with redshift of the specific SFR than found by several (but not all) previous studies. Our radio selection provides a view of the distribution of galaxies in the SFR–M⋆plane complementary to that of optical and near-IR selection. It suggests a higher uniformity of the star-formation history of galaxies than implied by some analyses of optical and near-IR data. We have derived luminosity functions at 150 MHz of both SFGs and radio-quiet (RQ) AGN at various redshifts. Our results are in very good agreement with the T-RECS simulations and with literature estimates. We also present explicit estimates of SFR functions of SFGs and RQ AGN at several redshifts derived from our radio survey data.