标题： Ap 2-1星云和环绕的分子云G35.2-0.74：一个活跃的恒星形成区 显示英文标题

标题： The Ap 2-1 nebula and the surrounding molecular cloud G35.2-0.74: an active star forming region

摘要： 利用来自大规模巡天调查的数据：2MASS、GLIMPSE、MIPSGAL、VGPS、GRS 和 IPHAS，我们对大约 20' × 20' 大小的分子云 G35.2-0.74 方向的星际介质进行了多波段研究。此外，投影在分子云上的 Ap 2-1 星云使用阿根廷 CASLEO 的 2.15 米望远镜获得的光学数据进行了研究。 通过 HI 吸收研究，我们估计 Ap 2-1 的距离约为 2 千秒差距，证实该星云嵌套在分子云 G35.2-0.74 的南部分区。 通过对可能嵌入云中的源进行测光研究并分析它们的谱能量分布，我们确认该区域在恒星形成方面非常活跃，特别是在北部，我们在那里发现了一个年轻恒星天体的星团。 从 Hα 和 [NII] 线中，我们得到了 Ap 2-1 星云的 LSR 径向速度 v_LSR ≈ 31 km/s，与分子云的速度一致。 最后，我们得出结论，Ap 2-1 是一个很可能由早期 B 型星激发的 HII 区域。 显示英文摘要

摘要： Using data from large-scale surveys: 2MASS, GLIMPSE, MIPSGAL, VGPS, GRS, and IPHAS, we performed a multiwavelength study of the ISM in a region of about 20' x 20' towards the molecular cloud G35.2-0.74. Additionally, the Ap 2-1 nebula, that is seen in projection over the molecular cloud, was studied using optical data obtained with the 2.15 m telescope at CASLEO, Argentina. From the HI absorption study we estimate a distance of ~2 kpc for Ap 2-1 confirming that the nebula is embedded in the south portion of the molecular cloud G35.2-0.74. Performing a photometric study and analysing the spectral energy distributions of the sources likely embedded in the cloud, we confirm that this region is very active in star formation, mainly towards the north, where we discover a cluster of young stellar objects. From the H_alpha and [NII] lines we obtain a radial velocity of v_LSR ~ 31 km/s for the Ap 2-1 nebula, in coincidence with the velocity of the molecular cloud. Finally, we conclude that Ap 2-1 is an HII region probably excited by an early B-type star.