论文标题
火焰星云NGC 2024
Proplyds in the Flame Nebula NGC 2024
论文作者
论文摘要
对NGC 2024恒星形成区域内部0.35美元内部$ 0.35 \ times0.35 $ PC的调查显示，两个不同的毫米连续盘人群似乎在空间上被密集的云的边界隔离。东部（和更多嵌入式）人口为$ \ sim0.2-0.5 $ Myr，其ALMA MM Continuum Candum盘检测率约为$ 45 \ $ $，$％。但是，这在1myr西部人口中仅下降到$ \ sim15 $。在提出此结果时，van Terwisga等人。 （2020年）建议，两个主要的UV来源IRS 1（西部地区的B0.5V恒星）和IRS 2B（东部地区的O8V恒星，但嵌入了）都在蒸发西方人群中枯竭的光盘。 在本文中，我们报告了NGC 2024中的4个建议的档案HST数据中的企业发现和4个候选人的建议，证实了盘的外部光蒸发正在发生。但是，这些建议的位置改变了图片。其中只有三个是在西方人口耗尽的人群中，其蒸发由IRS 1支配，而IRS 2B没有明显影响。其他5套在东部地区，并被IRS 2B蒸发。我们建议两个种群都受到明显的外部光蒸发的影响，在整个圆盘都没有被星际培养基遮挡的地方，这在整个区域都会发生。在NGC 2024的0.2-0.5myr东部，即使是非常早期的行星形成，在0.2-0.5myr Eastern的外部光蒸发和严重耗竭也将在竞争中。
A recent survey of the inner $0.35\times0.35$pc of the NGC 2024 star forming region revealed two distinct millimetre continuum disc populations that appear to be spatially segregated by the boundary of a dense cloud. The eastern (and more embedded) population is $\sim0.2-0.5$Myr old, with an ALMA mm continuum disc detection rate of about $45\,$per cent. However this drops to only $\sim15$per cent in the 1Myr western population. When presenting this result, van Terwisga et al. (2020) suggested that the two main UV sources, IRS 1 (a B0.5V star in the western region) and IRS 2b (an O8V star in the eastern region, but embedded) have both been evaporating the discs in the depleted western population. In this paper we report the firm discovery in archival HST data of 4 proplyds and 4 further candidate proplyds in NGC 2024, confirming that external photoevaporation of discs is occurring. However, the locations of these proplyds changes the picture. Only three of them are in the depleted western population and their evaporation is dominated by IRS 1, with no obvious impact from IRS 2b. The other 5 proplyds are in the younger eastern region and being evaporated by IRS 2b. We propose that both populations are subject to significant external photoevaporation, which happens throughout the region wherever discs are not sufficiently shielded by the interstellar medium. The external photoevaporation and severe depletion of mm grains in the 0.2-0.5Myr eastern part of NGC 2024 would be in competition even with very early planet formation.
