NGC 2903棒星形成的多波长研究
Multiwavelength study of the star formation in the bar of NGC 2903
摘要：
NGC 2903是一个临近的棒旋星系，中心有一个活跃的星暴，而Hii区域则分布在棒旋星系的棒上。我们的目的是分析NGC 2903的酒吧区的恒星形成的性质，并研究与典型的酒吧形态特征的联系。从远紫外到亚毫米光谱范围的空间和地面数据的组合被用来创建NGC 2903酒吧的全色视图。我们提供两个目录：一个用于当前的恒星形成区域，由halpha紧凑发射跟踪，第二个用于紫外线（UV）发射结，包含位置和光度。从中我们得到了紫外色、恒星形成率、尘埃衰减和halpha EWs，并分析了它们的空间分布。星团的年龄已经用恒星星族合成模型（Starburst 99）估算过。NGC 2903是一个复杂的星系，在每个光谱带上都有非常不同的形态。CO（J=1-0）和3.6 μ m发射相互跟踪，呈明显的条状结构，而halpha则引领两个分量，呈s形分布。紫外线发射是不规则的，不像一个酒吧。紫外线辐射的特征还在于许多区域相对于星系中心对称，几乎垂直于棒，呈螺旋形，覆盖内部~2.5 kpc。这些区域未显示出显著的halpha或24微米发射。我们估计这些区域的年龄在1.5亿到3.2亿年之间，比其他年龄低于1000万年的紫外线结要老。根据UV发射计算的SFR约为0.4 M $_{\odot}$ /年，与根据halpha校准（M $_{\odot}$ /年）得出的SFR兼容。
英文摘要：
NGC 2903 is a nearby barred spiral with an active starburst in the center and Hii regions distributed along its bar. We aim to analyse the star formation properties in the bar region of NGC 2903 and study the links with the typical bar morphological features. A combination of space and ground-based data from the far-ultraviolet to the sub-millimeter spectral ranges is used to create a panchromatic view of the NGC 2903 bar. We produce two catalogues: one for the current star formation regions, as traced by the halpha compact emission, and a second one for the ultraviolet (UV) emitting knots, containing positions and luminosities. From them we have obtained ultraviolet colours, star formation rates, dust attenuation and halpha EWs, and their spatial distribution have been analysed. Stellar cluster ages have been estimated using stellar population synthesis models (Starburst99). NGC 2903 is a complex galaxy, with a very different morphology on each spectral band. The CO(J=1-0) and the 3.6 micron emission trace each other in a clear barred structure, while the halpha leads both components and it has an s-shape distribution. The UV emission is patchy and does not resemble a bar. The UV emission is also characterised by a number of regions located symmetrically with respect to the galaxy center, almost perpendicular to the bar, in a spiral shape covering the inner ~2.5 kpc. These regions do not show a significant halpha nor 24 micron emission. We have estimated ages for these regions ranging from 150 to 320 Myr, being older than the rest of the UV knots, which have ages lower than 10 Myr. The SFR calculated from the UV emission is ~0.4 M$_{\odot}$/yr, compatible with the SFR as derived from halpha calibrations (M$_{\odot}$/yr).
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