A comparison of optical and near-infrared colours of Magellanic Cloud star clusters with predictions of simple stellar population models     

P. M. Pessev  P. Goudfrooij  T. H. Puzia  R. Chandar 《Monthly notices of the Royal Astronomical Society》2008,385(3):1535-1560

We present integrated JHK _S Two-Micron All-Sky Survey photometry and a compilation of integrated-light optical photoelectric measurements for 84 star clusters in the Magellanic Clouds. These clusters range in age from ≈200 Myr to >10 Gyr, and have [Fe/H] values from −2.2 to −0.1 dex. We find a spread in the intrinsic colours of clusters with similar ages and metallicities, at least some of which is due to stochastic fluctuations in the number of bright stars residing in low-mass clusters. We use 54 clusters with the most-reliable age and metallicity estimates as test particles to evaluate the performance of four widely used simple stellar population models in the optical/near-infrared (near-IR) colour–colour space. All models reproduce the reddening-corrected colours of the old (≥10 Gyr) globular clusters quite well, but model performance varies at younger ages. In order to account for the effects of stochastic fluctuations in individual clusters, we provide composite   B − V , B − J , V − J , V − K _S  and   J − K _S  colours for Magellanic Cloud clusters in several different age intervals. The accumulated masses for most composite clusters are higher than that needed to keep luminosity variations due to stochastic fluctuations below the 10 per cent level. The colours of the composite clusters are clearly distinct in optical–near-IR colour–colour space for the following intervals of age: >10 Gyr, 2–9 Gyr, 1–2 Gyr, and 200 Myr−1 Gyr. This suggests that a combination of optical plus near-IR colours can be used to differentiate clusters of different age and metallicity.  相似文献   

基于ASTER数据反演我国南方山地陆表温度   总被引：13，自引：1，他引：13  

王凤敏  田庆久  虢建宏 《国土资源遥感》2005,16(1):30-33

 以贵州省黎平县山地植被覆盖区为例，基于ASTER遥感数据进行15 m分辨率的归一化植被指数制图和地表发射率制图，在利用 MODTRAN 4大气辐射传输模型进行大气订正的基础上，基于普朗克辐射方程的推导反演陆表温度，取得了较为理想的结果。  相似文献   

白杨河超大型铍(铀)矿床中蓝柱石(BeAlSiO4(OH))的矿物特征与地质意义     

刘畅  田建吉  范光  赵晓波  王谋  衣龙升  邱林飞  吴玉  邹耀林 《矿物学报》2020,40(2):191-200

蓝柱石作为一种较为罕见的含铍矿物,通常产在过铝-准铝性的岩浆-热液演化系统中,或发育于富铝质岩石的低级变质过程中。本文通过偏光显微镜、电子探针、X射线粉晶衍射、激光拉曼光谱和红外光谱等多种手段方法,在白杨河超大型铍(铀)矿床首次发现了除羟硅铍石以外的另一种含铍矿物-蓝柱石。系统的矿物学研究表明蓝柱石应由花岗斑岩岩浆分异的岩浆热液直接沉淀而成,且形成于富F环境中。结合前人关于矿床地质特征、成矿年代学和地球化学等方面的研究,认为白杨河矿床中的铍矿化应是花岗斑岩深部岩浆房分异的岩浆热液,在不断演化过程中形成的,而与后期流体(包括幔源流体和大气降水)的淋滤作用无关或关系很小。  相似文献   

应用高频红外碳硫仪测定农用地土壤样品中有机质含量     

殷陶刚  窦向丽  张旺强  和振云 《岩矿测试》2020,39(4):631-638

应用高频红外碳硫仪测定农用地土壤样品中的有机质,避免了传统方法中的试样液体转化环节,测定效率高,但存在土壤样品电磁感应低和基体影响较大等问题。本文通过实验优化了样品称样量、助熔剂铁和钨的添加量等测定条件,结果表明：当样品称样量为0.05g、助熔剂铁添加量为0.40g、钨添加量为1.50g时,有机质测定效果最佳。通过土壤标准物质进行验证,方法检出限为0.003%,相对标准偏差（RSD,n=7）小于4%,测定值与认定值的相对误差小于5%,且不同分析人员的测定结果间没有显著差异。采用本法与重铬酸钾容量法对甘肃省农用地土壤样品进行测定,两种方法测定值的绝对误差为-0.25%~0.28%,测定结果之间呈极显著线性正相关（R²=0.9736）,表明两种方法的一致性很好。本方法的检出限、精密度、准确度均满足农用地土壤样品有机质测定要求。  相似文献   

恒星形成区NGC7538中的分子氢发射     

姚永强  陈亚峰  杨戟 《天文学报》2000,41(1):1-14

报告在ＮＧＣ７５３８中利用Ｈ２（２．１２μｍ）发射线测新发现的两个喷流和１８个近红外ＨＨ天体,在ＩＲＳ１－３星云中观测到了强Ｈ２发射壳层结构环绕在星云的北边。星云中红外源的ＵＶ辐射场的外流活动都可能导致这一Ｈ２发射。在ＨＲＳ１－３星云的南边和东边探测到了５个Ｈ２ｋｎｏｔｓ．在ＩＲＳ１南边发现的Ｈ２喷流暗示该区域有一个南北向的外流,在ＩＲＳ１１星团的周围发现了９个Ｈ２ｈｎｏｔｓ．在西北－东南方向和东  相似文献   

1–5 μm imaging of 3CRR galaxies: the K–z relation and the geometry of the torus     

Chris Simpson  Martin Ward  J. V. Wall 《Monthly notices of the Royal Astronomical Society》2000,319(3):963-976

It has been claimed by Taylor et al. that the low-redshift end of the K – z relation for radio galaxies is too bright by about half a magnitude owing to contributions from the obscured quasar nuclei. Such a result has major implications for the use of the K -band Hubble diagram in understanding the cosmological evolution of radio galaxies. In this paper we present 1–5-μm imaging data of a nearly complete sample of low-redshift radio galaxies; this approach allows us to determine accurately the strengths of any unresolved nuclear components in the galaxies. We detect nuclear sources in five targets, whose broad-band colours are consistent with reddened quasar spectra. In all the five cases the ratio of the inferred intrinsic near-infrared luminosity to the narrow-line luminosity is typical of quasars. We find a correlation between the inferred nuclear extinction and core-to-lobe ratio, which places constraints on the geometry of the torus. We find evidence for a shift of the K – z relation to fainter magnitudes, but by a much smaller amount (∼0.1 mag) than determined by Taylor et al. Under the assumption that the nuclear sources in radio galaxies have the same intrinsic near-infrared spectra as quasars, our multiwavelength images allow us to limit any possible shift to less than 0.3 mag.  相似文献   

Three quasars from a survey of strong 25-μm emitters     

R. D. Wolstencroft  Q. A. Parker  C. J. Lonsdale  S. M. Scarrott 《Monthly notices of the Royal Astronomical Society》2000,311(3):541-554

We have carried out a spectroscopic survey of 750 sources that are strong 25-μm emitters from the IRAS Faint Source data base. Many of these sources are previously unknown active galactic nuclei including new IRAS quasars, three of which we describe here: F21382−2659, Z06367−6845 and Z05558−5008. They are all radio and X-ray quiet, and compared to the known IRAS quasars they have similar 25-μm luminosities, L (25 μm), but lower values of L (25 μm)/ L ( B ). Their F (25 μm)/ F (60 μm) IRAS colours lie in the range 0.33 to 1.08, indicating the presence of relatively warm dust, presumably in a dusty torus surrounding the central source, and with temperatures similar to those of the known IRAS quasars. The quasar with the warmest dust, F21382−2659, exhibits broad (full width at half-maximum ∼4000 km s⁻¹) asymmetric Balmer lines with H γ having an opposite asymmetry to the other broad lines; also H β (only) is double-peaked. Fe  ii is very weak in F21382−2659 but strong in the other two quasars, and the anticorrelation between Fe  ii and [O  iii ] holds as anticipated. Two of the quasars are unpolarized: although F21382−2659 is optically polarized (2.1 per cent at 4950 Å), we argue that this provides little insight into the orientation of its dust torus relative to the line of sight.  相似文献   

The 3.4-μm absorption feature towards three obscured active galactic nuclei     

M. Imanishi 《Monthly notices of the Royal Astronomical Society》2000,319(1):331-336

The results of 3–4-μm spectroscopy towards the nuclei of NGC 3094, 7172, and 7479 are reported. In ground-based 8–13-μm spectra, all the sources have strong absorption-like features at ∼10 μm, but they do not have detectable polycyclic aromatic hydrocarbon (PAH) emission features. The 3.4-μm carbonaceous dust absorption features are detected towards all nuclei. NGC 3094 shows a detectable 3.3-μm PAH emission feature, while NGC 7172 and 7479 do not. Nuclear emission whose spectrum shows dust absorption features but no PAH emission features, is thought to be dominated by highly obscured active galactic nuclei (AGNs) activity. For NGC 7172, 7479, and three other such nuclei in the literature, we investigate the optical depth ratios between the 3.4-μm carbonaceous dust and 9.7-μm silicate dust absorption     The     ratios towards three highly obscured AGNs with face-on host galaxies are systematically larger than the ratios in the Galactic diffuse interstellar medium or the ratios for two highly obscured AGNs with edge-on host galaxies. We suggest that the larger ratios can be explained if the obscuring dust is so close to the central AGNs that a temperature gradient occurs in it. If this idea is correct, our results may provide spectroscopic evidence for the presence of the putative 'dusty tori' in the close vicinity of AGNs.  相似文献   

Near-infrared adaptive optics imaging of nuclear spiral structure in the Seyfert galaxy NGC 3227     

Scott C. Chapman  †‡  Simon L. Morris ‡  Gordon A. H. Walker 《Monthly notices of the Royal Astronomical Society》2000,319(3):666-676

We present high spatial resolution, near-infrared images in J , H and K of the nucleus of NGC 3227, obtained with the Adaptive Optics Bonnette on the Canada–France–Hawaii Telescope. The ∼0.15 arcsec (17 pc) resolution allows structures to be probed in the core region. Dust obscuration becomes significantly less pronounced at longer wavelengths, revealing the true geometry of the core region. We are able to identify two main features in our maps: (i) a spiralling association of knots with a counterpart in a Hubble Space Telescope F606W image; and (ii) a smaller-scale annulus, orthogonal to the spiral of knots. These features may provide a means to transport material inwards to fuel the active nucleus.  相似文献   

红外线和植物生长物质对紫球藻生长及代谢的影响     

萧华山  林和  范子南  张文焕  谢志强  郭建生 《热带海洋学报》2000,19(2):64-68

特定红外辐射能促进紫球藻Porphyridium purpareum生长 ;植物生长物质 ,即吲哚丁酸(IBA)、三十烷醇 (TA)及其复配形式对紫球藻的光合作用、呼吸作用、生长繁殖等生理过程皆有促进作用 ;正交实验结果表明 ,植物生长物质最佳组合为TA 1 .0 μg·ml- 1 ,IBA 0 .1 μg·ml- 1( 1 0∶1 )。  相似文献