Jets and outflows are ubiquitous in the process of formation of stars since outflow is intimately associated with accretion. Free–free (thermal) radio continuum emission in the centimeter domain is associated with these jets. The emission is relatively weak and compact, and sensitive radio interferometers of high angular resolution are required to detect and study it. One of the key problems in the study of outflows is to determine how they are accelerated and collimated. Observations in the cm range are most useful to trace the base of the ionized jets, close to the young central object and the inner parts of its accretion disk, where optical or near-IR imaging is made difficult by the high extinction present. Radio recombination lines in jets (in combination with proper motions) should provide their 3D kinematics at very small scale (near their origin). Future instruments such as the Square Kilometre Array (SKA) and the Next Generation Very Large Array (ngVLA) will be crucial to perform this kind of sensitive observations. Thermal jets are associated with both high and low mass protostars and possibly even with objects in the substellar domain. The ionizing mechanism of these radio jets appears to be related to shocks in the associated outflows, as suggested by the observed correlation between the centimeter luminosity and the outflow momentum rate. From this correlation and that of the centimeter luminosity with the bolometric luminosity of the system it will be possible to discriminate between unresolved HII regions and jets, and to infer additional physical properties of the embedded objects. Some jets associated with young stellar objects (YSOs) show indications of non-thermal emission (negative spectral indices) in part of their lobes. Linearly polarized synchrotron emission has been found in the jet of HH 80–81, allowing one to measure the direction and intensity of the jet magnetic field, a key ingredient to determine the collimation and ejection mechanisms. As only a fraction of the emission is polarized, very sensitive observations such as those that will be feasible with the interferometers previously mentioned are required to perform studies in a large sample of sources. Jets are present in many kinds of astrophysical scenarios. Characterizing radio jets in YSOs, where thermal emission allows one to determine their physical conditions in a reliable way, would also be useful in understanding acceleration and collimation mechanisms in all kinds of astrophysical jets, such as those associated with stellar and supermassive black holes and planetary nebulae.

由于流出与吸积密切相关，喷流和流出在恒星形成过程中无处不在。厘米域内的自由-自由（热）射电连续谱发射与这些射流相关。发射相对较弱且紧凑，需要高角分辨率的灵敏射电干涉仪来检测和研究它。研究资本外流的关键问题之一是确定资本外流如何加速和校准。厘米范围内的观测对于追踪电离射流的底部最有用，靠近年轻的中心物体及其吸积盘的内部，在这些地方，光学或近红外成像由于存在高消光而变得困难。射流中的无线电重组线（与自行结合）应提供非常小比例（靠近其原点）的 3D 运动学。平方公里阵列 (SKA) 和下一代甚大阵列 (ngVLA) 等未来仪器对于执行此类敏感观测至关重要。热喷流与高质量和低质量的原恒星有关，甚至可能与星际域中的物体有关。这些射电射流的电离机制似乎与相关流出中的冲击有关，正如观察到的厘米光度与流出动量率之间的相关性所表明的那样。根据这种相关性以及厘米光度与系统的测辐射热光度的相关性，将可以区分未解析的 HII 区域和射流，并推断嵌入物体的其他物理特性。一些与年轻恒星物体（YSO）相关的喷流在其部分波瓣中显示出非热发射（负光谱指数）的迹象。 在 HH 80-81 的射流中发现了线性偏振同步加速器发射，使人们能够测量射流磁场的方向和强度，这是确定准直和喷射机制的关键因素。由于只有一小部分发射是偏振的，因此需要非常敏感的观测（例如使用前面提到的干涉仪进行的观测）才能对大量源样本进行研究。喷气机出现在多种天体物理场景中。表征 YSO 中的射电喷流，其中热发射允许人们以可靠的方式确定其物理条件，也有助于理解各种天体物理喷流的加速和准直机制，例如与恒星和超大质量黑洞和行星相关的喷流。星云。