Spiral and dwarf galaxies' kinematics and optical instrumentation

我们不同研究项目的主要目标是确定螺旋星系和矮星系中暗物质的物理参数（例如密度定律，总范围）。采用的方法如下。首先，从甚大阵（新墨西哥州）、韦斯特博克（荷兰）、澳大利亚望远镜和DRAO（彭蒂克顿，不列颠哥伦比亚省）获得的21厘米HI观测结果中，有可能推导出这些星系在其光学直径的2至5倍范围内的旋转曲线，从而测量到最后测量的速度点的质量（运动学质量）。这些观测也给了我们气体质量，在某些矮星系中，气体质量有时比恒星质量更重要。然后，光分布（表面测光）允许我们推导恒星质量（使用近红外数据，例如斯皮策）。因此，运动质量和发光质量（恒星和气体）之间的差异是暗物质成分的量度。由于质量模型对旋转曲线的上升部分非常敏感，因此必须将从法布里-珀罗干涉法获得的更高分辨率的3D数据与内部部件的HI数据相结合（以避免HI数据的光束拖尾效应）。如果有人想确定暗物质密度分布在内部是平坦的（例如等温）还是尖锐的（例如NFW），这一点尤其重要，正如冷暗物质宇宙学模拟所预测的那样。为了在非常关键的内部部分获得尽可能高的信噪比数据，我们建立了自己的图像光子计数系统（IPCS），称为FaNTOmM，我们不仅在Observatoire du mont Mégantic的1.6米望远镜上使用，而且还在加拿大-法国-夏威夷（CFHT）和ESO（La Silla）的3.6米望远镜上使用。第一代FaNTOmM使用GaAs增强管，其DQE约为30%（意味着30%的入射光子被检测到），而旧IPCS的DQE约为4-5%，我们正在研究基于L3 CCD芯片的第二代相机，其DQE应> 80%。

The main goal of our different research projects is to determine the physical parameters (e.g. density laws, total extent) of the Dark Matter present in spiral and dwarf galaxies. The methodology used is the following. First, from 21cm HI observations obtained at the Very Large Array (New-Mexico), Westerbork (Holland), the Australia Telescope, and at DRAO (Penticton, BC), it is possible to derive the rotation curves of those galaxies over 2 to 5 times their optical diameters and thus to measure the mass present out to the last measured velocity point (kinematical mass). Those observations also give us the gas mass, which can sometimes be more important than the stellar mass in certain dwarf galaxies. Then, the light distribution (surface photometry) allows us to derive the stellar mass (using near infrared data, e.g. Spitzer). The difference between the kinematical mass and the luminous mass (stars & gas) is thus a measure of the Dark Matter component. Since the mass models are very sensitive to the rising part of the rotation curves, higher resolution 3D data, obtained from Fabry-Perot interferometry, must be combined to the HI data for the inner parts (to avoid the beam smearing effect of HI data). This is especially important if someone wants to determine whether the dark matter density profiles are flat (e.g. isothermal) or cuspy (e.g. NFW) in the very inner parts, as predicted by Cold Dark Matter cosmological simulations. In order to get the highest Signal-to-Noise data possible in the very critical inner parts, we built our own Image Photon Counting System (IPCS) called FaNTOmM, which we used not only on the 1,6m telescope of the Observatoire du mont Mégantic, but also on the 3,6m telescopes of the Canada-France-Hawaii (CFHT) and of the ESO (La Silla). The first generation of FaNTOmM used a GaAs intensifier tube which gives a DQE ~ 30% (meaning that 30% of the incoming photons are detected), as compared to ~4-5% for the old IPCS and we are working on the second generation camera based on a L3CCD chip which should provide a DQE > 80%.