We present the results from a full polarization study carried out with the Atacama Large Millimeter/submillimeter Array (ALMA) during the first Very Long Baseline Interferometry (VLBI) campaign, which was conducted in 2017 April in the λ3 mm and λ1.3 mm bands, in concert with the Global mm-VLBI Array (GMVA) and the Event Horizon Telescope (EHT), respectively. We determine the polarization and Faraday properties of all VLBI targets, including Sgr A*, M87, and a dozen radio-loud active galactic nuclei (AGNs), in the two bands at several epochs in a time window of 10 days. We detect high linear polarization fractions (2%–15%) and large rotation measures (RM > 10^3.3–10^5.5 rad m⁻²), confirming the trends of previous AGN studies at millimeter wavelengths. We find that blazars are more strongly polarized than other AGNs in the sample, while exhibiting (on average) order-of-magnitude lower RM values, consistent with the AGN viewing angle unification scheme. For Sgr A* we report a mean RM of (−4.2 0.3) 10⁵ rad m⁻² at 1.3 mm, consistent with measurements over the past decade and, for the first time, an RM of (–2.1 0.1) 10⁵ rad m⁻² at 3 mm, suggesting that about half of the Faraday rotation at 1.3 mm may occur between the 3 mm photosphere and the 1.3 mm source. We also report the first unambiguous measurement of RM toward the M87 nucleus at millimeter wavelengths, which undergoes significant changes in magnitude and sign reversals on a one year timescale, spanning the range from −1.2 to 0.3 10⁵ rad m⁻² at 3 mm and −4.1 to 1.5 10⁵ rad m⁻² at 1.3 mm. Given this time variability, we argue that, unlike the case of Sgr A*, the RM in M87 does not provide an accurate estimate of the mass accretion rate onto the black hole. We put forward a two-component model, comprised of a variable compact region and a static extended region, that can simultaneously explain the polarimetric properties observed by both the EHT (on horizon scales) and ALMA (which observes the combined emission from both components). These measurements provide critical constraints for the calibration, analysis, and interpretation of simultaneously obtained VLBI data with the EHT and GMVA.

我们展示了在 2017 年 4 月在λ 3 毫米和λ 1.3 毫米波段进行的第一次甚长基线干涉测量 (VLBI) 活动期间使用阿塔卡马大型毫米/亚毫米阵列 (ALMA) 进行的全偏振研究的结果，分别与全球 mm-VLBI 阵列 (GMVA) 和事件视界望远镜 (EHT) 配合使用。我们确定了所有 VLBI 目标的极化和法拉第特性，包括人马座 A*、M87 和十几个射电响亮的活动星系核 (AGN)，在 10 天的时间窗口内的几个时代的两个波段中。我们检测到高线性极化分数 (2%–15%) 和大旋转测量 (RM > 10 ^3.3 –10 ^5.5 rad m ^-2)，证实了以前在毫米波长下 AGN 研究的趋势。我们发现耀变体比样本中的其他 AGN 更强烈地极化，同时表现出（平均）数量级较低的 RM 值，与 AGN 视角统一方案一致。对于 Sgr A*，我们报告了在 1.3 mm 处的平均 RM 为 (-4.2 0.3) 10 ⁵ rad m ^-2，与过去十年的测量结果一致，并且首次出现了 (–2.1 0.1) 10 ⁵ rad的 RM米^-2在 3 mm 处，表明 1.3 mm 处的法拉第旋转的大约一半可能发生在 3 mm 光球层和 1.3 mm 光源之间。我们还报告了第一次在毫米波长下对 M87 核的 RM 的明确测量，它在一年的时间尺度上经历了幅度和符号反转的显着变化，范围从 -1.2 到 0.3 10 ⁵ rad m ^-2在 3 mm 和−4.1 至 1.5 10 ⁵弧度米^-2在 1.3 毫米。鉴于这种时间可变性，我们认为，与人马座 A* 的情况不同，M87 中的 RM 没有提供对黑洞质量吸积率的准确估计。我们提出了一个由可变紧凑区域和静态扩展区域组成的双分量模型，它可以同时解释 EHT（在水平尺度上）和 ALMA（观察两个分量的组合发射）观测到的极化特性。 . 这些测量为使用 EHT 和 GMVA 同时获得的 VLBI 数据的校准、分析和解释提供了关键约束。