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arXiv 1005.2497astro-ph.CO
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确定赫歇尔时代的尘埃温度和质量:200微米观测的重要性

Determining dust temperatures and masses in the Herschel era: the importance of observations longward of 200 micron

K. D. Gordon, F. Galliano, S. Hony, J. -P. Bernard, A. Bolatto, C. Bot, C. Engelbracht, A. Hughes, F. P. Israel, F. Kemper, S. Kim, A. Li, S. C. Madden, M. Mats… 展开作者

K. D. Gordon, F. Galliano, S. Hony, J. -P. Bernard, A. Bolatto, C. Bot, C. Engelbracht, A. Hughes, F. P. Israel, F. Kemper, S. Kim, A. Li, S. C. Madden, M. Matsuura, M. Meixner, K. Misselt, K. Okumura, P. Panuzzo, M. Rubio, W. T. Reach, J. Roman-Duval, M. Sauvage, R. Skibba, A. G. G. M. Tielens

摘要:

尘埃颗粒的性质(例如,温度和质量)可以从拟合远红外SED(>100微米)得到。只有赫歇尔上的SPIRE才有可能获得200到500微米的高空间分辨率,这超过了大多数星系尘埃排放的峰值(~160微米)。我们研究了仅使用200微米数据(新的SPIRE观测)确定的拟合尘埃温度和质量的差异<200 micron data and then also including >,以确定拥有&gt;200微米数据对于推导这些尘埃属性的重要性。我们拟合的大麦云云(LMC)的100至350微米的观测点逐点的模型,由一个单一的温度和固定的发射率的法律。所使用的数据是现有的100和160微米的观测数据(来自IRAS和斯皮策)和新的SPIRE观测的1/4的LMC观测的遗产关键项目作为赫歇尔科学示范阶段的一部分。仅使用100和160微米数据计算的尘埃温度和质量与包括SPIRE 250和350微米数据的数据分别相差10%和36%。我们发现,与λ ^-1.5成正比的发射率定律使100-350微米的部分残差最小化。我们发现,在500微米处的发射比从外推在较短波长处进行的拟合所预期的高约10%。我们发现分数500微米的过量是弱反相关的MIPS 24微米通量和总气体表面密度。这反对通量校准误差作为500微米过量的起源。我们的研究结果不允许我们区分系统的变化,在波长依赖的发射率的法律或人口非常冷的灰尘,只有在λ&gt; 500微米的起源超过500微米的检测。

英文摘要:

The properties of the dust grains (e.g., temperature and mass) can be derived from fitting far-IR SEDs (>100 micron). Only with SPIRE on Herschel has it been possible to get high spatial resolution at 200 to 500 micron that is beyond the peak (~160 micron) of dust emission in most galaxies. We investigate the differences in the fitted dust temperatures and masses determined using only <200 micron data and then also including >200 micron data (new SPIRE observations) to determine how important having >200 micron data is for deriving these dust properties. We fit the 100 to 350 micron observations of the Large Magellanic Cloud (LMC) point-by-point with a model that consists of a single temperature and fixed emissivity law. The data used are existing observations at 100 and 160 micron (from IRAS and Spitzer) and new SPIRE observations of 1/4 of the LMC observed for the HERITAGE Key Project as part of the Herschel Science Demonstration phase. The dust temperatures and masses computed using only 100 and 160 micron data can differ by up to 10% and 36%, respectively, from those that also include the SPIRE 250 & 350 micron data. We find that an emissivity law proportional to lambda^-1.5 minimizes the 100-350 micron fractional residuals. We find that the emission at 500 micron is ~10% higher than expected from extrapolating the fits made at shorter wavelengths. We find the fractional 500 micron excess is weakly anti-correlated with MIPS 24 micron flux and the total gas surface density. This argues against a flux calibration error as the origin of the 500 micron excess. Our results do not allow us to distinguish between a systematic variation in the wavelength dependent emissivity law or a population of very cold dust only detectable at lambda > 500 micron for the origin of the 500 micron excess.

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