We present ultra-deep, matched-resolution Karl G. Jansky Very Large Array (VLA) observations at 10 and $3$ GHz in the COSMOS field: the COSMOS-XS survey. The final 10 and $3$ GHz images cover $\sim16\rm{arcmin}^{2}$ and $\sim180\rm{arcmin}^{2}$ and reach median rms values of $0.41\mu\rm{Jy\,beam}^{-1}$ and $0.53\mu\rm{Jy\,beam}^{-1}$, respectively. Both images have an angular resolution of $\sim 2.0''$. To fully account for the spectral shape and resolution variations across the broad bands, we image all data with a multi-scale, multi-frequency synthesis algorithm. We present source catalogs for the 10 and $3$ GHz image with 91 and 1498 sources, respectively, above a peak brightness threshold of $5\sigma$. We present source counts with completeness corrections included that are computed via Monte Carlo simulations. Our corrected radio counts at $3$ GHz with direct detections down to $\sim2.8\mu$Jy are consistent within the uncertainties with other results at 3 and 1.4 GHz, but extend to fainter flux densities than previous direct detections. The ultra-faint $3$ GHz number counts are found to exceed the counts predicted by the semi-empirical radio sky simulations developed in the framework of the SKA Simulated Skies project, consistent with previous P(D) analyses. Our measured source counts suggest a steeper luminosity function evolution for these faint star-forming sources. The semi-empirical Tiered Radio Extragalactic Continuum Simulation (T-RECS) predicts this steeper evolution and is in better agreement with our results. The $10$ GHz radio number counts also agree with the counts predicted by the T-RECS simulation within the expected variations from cosmic variance. In summary, the multi-band, matched-resolution COSMOS-XS survey in the well-studied COSMOS field provides a high-resolution view of the ultra-faint radio sky that can help guide next generation radio facilities.

中文翻译：

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微弱无线电天空的超深多波段 VLA 巡天 (COSMOS-XS)：源目录和数量计数

我们展示了 COSMOS 领域中 10 GHz 和 $3$ GHz 的超深、匹配分辨率 Karl G. Jansky 甚大阵列 (VLA) 观测：COSMOS-XS 调查。最后的 10 GHz 和 $3$ GHz 图像覆盖 $\sim16\rm{arcmin}^{2}$ 和 $\sim180\rm{arcmin}^{2}$ 并达到 $0.41\mu\rm{Jy\ ,beam}^{-1}$ 和 $0.53\mu\rm{Jy\,beam}^{-1}$ 分别。两幅图像的角分辨率均为 $\sim 2.0''$。为了充分考虑宽带上的光谱形状和分辨率变化，我们使用多尺度、多频率合成算法对所有数据进行成像。我们提供了 10 和 3 美元 GHz 图像的源目录，分别有 91 和 1498 个源，高于 5 美元/西格玛的峰值亮度阈值。我们提供了包含通过蒙特卡罗模拟计算的完整性校正的源计数。我们校正后的无线电计数为 $3$ GHz，直接检测低至 $\sim2.8\mu$Jy，在不确定性范围内与 3 GHz 和 1.4 GHz 的其他结果一致，但扩展到比以前的直接检测更微弱的通量密度。发现超微弱的 3 美元 GHz 数字计数超过了在 SKA 模拟天空项目框架中开发的半经验射电天空模拟预测的计数，与之前的 P(D) 分析一致。我们测量的源计数表明这些微弱的恒星形成源具有更陡峭的光度函数演化。半经验分层无线电河外连续体模拟 (T-RECS) 预测了这种更陡峭的演变，并且与我们的结果更加吻合。10 美元 GHz 无线电数量计数也与 T-RECS 模拟预测的计数一致，符合宇宙方差的预期变化。总而言之，经过深入研究的 COSMOS 领域中的多波段、分辨率匹配的 COSMOS-XS 巡天提供了超微弱无线电天空的高分辨率视图，有助于指导下一代无线电设施。