Evolution of interstellar dust with Herschel . First results in the photodissociation regions of NGC 7023
Evolution of interstellar dust with Herschel . First results in the photodissociation regions of NGC 7023
复制标题
赫歇尔的星际尘埃演化。
DOI：
10.1051/0004-6361/201014643
复制
发表时间：
2010
影响因子：
6.5
通讯作者：
Abergel A
中科院分区：
文献类型：
--
作者：
Abergel A
在光离解区域（PDR），物理条件和激发在短的空间尺度上作为云内深度的函数而演变，这为研究尘埃和气体种群如何随着激发和物理条件而演变提供了独特的机会。NGC 7023中PDR的绘图是在Herschelis的科学演示阶段进行的，是“星际尘埃演化”关键计划的一部分。本项目的目标是建立一个关于从弥漫云到星星形成点的星际尘埃辐射的数据库，目的是研究PDR及其周围较暗区域的远红外/亚毫米辐射。我们结合联合收割机的赫歇尔和斯皮策地图，以获得在每个位置的所有尘埃成分的全部发射光谱，我们比较灰尘和辐射传输模型，以了解空间变化的激发条件和灰尘property.MethodsWe调整发射光谱来自PACS和SPIRE地图使用修改的黑体，以获得温度和发射率指数β的灰尘在热平衡，辐射场。我们提出了第一个建模的NGC 7023-E PDR与标准的灰尘属性和abundances.ResultsAt峰位置，β值等于2是兼容的数据。辐射传输效应对探测到的光谱和空间结构有很大影响。我们能够再现从Herschel映射推导出的尘埃粒子在热平衡时发射的峰值位置处的光谱，以及从近红外到亚毫米波段观测到的空间结构的演化。另一方面，随机加热的较小粒子的发射被高估了约2倍。
ContextIn photodissociation regions (PDRs), the physical conditions and the excitation evolve on short spatial scales as a function of depth within the cloud, providing a unique opportunity to study how the dust and gas populations evolve with the excitation and physical conditions. The mapping of the PDRs in NGC 7023 performed during the science demonstration phase ofHerschelis part of the “Evolution of interstellar dust” key program. The goal of this project is to build a coherent database on interstellar dust emission from diffuse clouds to the sites of star formation.AimsWe study the far-infrared/submillimeter emission of the PDRs and their fainter surrounding regions. We combine theHerschelandSpitzermaps to derive at each position the full emission spectrum of all dust components, which we compare to dust and radiative transfer models in order to learn about the spatial variations in both the excitation conditions and the dust properties.MethodsWe adjust the emission spectra derived from PACS and SPIRE maps using modified black bodies to derive the temperature and the emissivity indexβof the dust in thermal equilibrium with the radiation field. We present a first modeling of the NGC 7023-E PDR with standard dust properties and abundances.ResultsAt the peak positions, a value ofβequal to 2 is compatible with the data. The detected spectra and the spatial structures are strongly influenced by radiative transfer effects. We are able to reproduce the spectra at the peak positions deduced fromHerschelmaps and emitted by dust particles at thermal equilibrium, and also the evolution of the spatial structures observed from the near infrared to the submillimeter. On the other hand, the emission of the stochastically heated smaller particles is overestimated by a factor ~2.