探宝梅西叶（7）

球状星团M79 基本资料： 梅西叶编号：M79 NGC编号：NGC1904     

探宝梅西叶（2）

靓丽的七姐妹——昴星团（M45） 梅西叶编号：M45 类型：疏散星团 NGC编号：无 赤经：03h47m24s     

M32：M31的致密伴星系还是普通的背景星系？

我们的银河系,是一个称为本星系群的星系部落中的第二大成员。这个星系部落中最大的星系就是我们熟知的旋涡星系—仙女座大星云,M31（或称NGC224）,一般认为,它至少被四个“早型星系”所环绕：M32（或称NGC221）、H110（或称NGC205）、NGC185和NGC147①,以及一些没有NGC编号（因为它们的发现时间相对比较靠后）的更小的卫星星系。     

实现Johnson标准UBV系统中的某些问题(英)

Odewahn等人发表的CCD标准星区NGC7790的目录是挑选过的非密集星目录．在其证认图上都为单星或仅有相对很暗的近星,但在深度露光图上许多星显出有近星,有的貌似单星但实际上是双星或三重星．本文给出这些（光学）伴星的相对距离和星等差,以便测光工作者挑选标准星时参考使用．另外,比对NGC7790的CCD测光与光电和照相测光,发现Sandage的光电内插照相星等有系统偏离,远大于其测光误差．检验Sandage及其合作者的其 他类似工作可知Johnson等人的工作（M67, M11）,在误差范围内,内插照相值的确和光电值在同一系统．Sandage和Walker的NGC4147,所说的照相光电一致与事实不符．Burbidge和Sandage的NGC7789,在改正了照相值的系统偏离后仍没有全改掉．Sandage和Walker的M92,真正改掉了小的非线性偏离．Sandage和Wildey的NGC7006,由于星暗难测,其照相值不能坚持光电内插的原则,结果不但有明显的颜色方程,而且星等有大的标度误差．CCD测光也应从中吸取经验教训.     

双鱼座中的旋涡星系M74

M74(NGC628)的赤道坐标为:赤经1时36.7分,赤纬15°47′;视星等为9.4等,(O'Meara),面亮度14.4,角径10.′5x9′.5,距离3200万光年。发现者:Pierre Méchain(1780)。梅西叶1780年10月18日对它的观察记录如下:一个没有星的星云,靠近双鱼座内连接两鱼尾丝带中的η星,他对 M74研究的结果与 M.Méchain 于1780年9月的结论     

追星一族

M105,9.2等,明亮的椭圆星系,15cm口径望远镜可以看见,但要分辨出其核心和外围,需30cm口径望远镜。M105与NGC3384和NGC3389构成了一个三合星系,在观测条件较好的情况下,用15Cm望远镜可以看见。M96,10cm以上望远镜观测较为合适。NGC2903.旋涡星系,非常明亮,10cm望远镜可见。     

Spatially-resolved stellar population properties of the M51–NGC 5195 system from multi-wavelength photometric data

Using multi-band photometric images of M51 and its companion NGC 5195 from ultraviolet to optical and infrared,we investigate spatially resolved stellar population properties of this interacting system with stellar population synthesis models.The observed infrared excess(IRX)is used to constrain dust extinction.Stellar mass is also inferred from the model fitting.By fitting observed spectral energy distributions(SEDs)with synthetical ones,we derive two-dimensional distributions of stellar age,metallicity,dust extinction and stellar mass.In M51,two grand-designed spiral arms extending from the bulge show young age,rich metallicity and abundant dust.The inter-arm regions are filled with older,metalpoorer and less dusty stellar populations.Except for the spiral arm extending from M51 into NGC 5195,the stellar population properties of NGC 5195 are quite featureless.NGC 5195 is much older than M51,and its core is very dusty with AV up to 1.67 mag and dense in stellar mass surface density.The close encounters might drive the dust in the spiral arm of M51 into the center of NGC 5195.     

M51的观测研究进展

M51系统包含巨旋涡星系M51和相对较大且较近的伴星系NGC 5195。M51离银河系较近,由尘埃消光带来的观测不确定性也就不十分显著,从而可以得到较详细的星系结构。自M51被发现至今,从射电波段到X射线波段都已获得了丰富的观测资料。主要介绍了M51的多波段观测成果和数值模拟研究,并概述了对其伴星系NGC 5195的观测。     

宇宙画廊

星系烟花[图片来自NASA]每逢春节,我国各地都会上演绚丽的烟花秀。如果想感受节日氛围,还想兼顾空气质量,该怎么办呢?最佳选项是:来看一场星系烟花秀。这场烟花不用纸和火药粉末,纯粹由巨大的黑洞、冲击波以及大量的气体合作而成。演出场地位于2300万光年外的一个星系中,星系的编号是NGC 4258,也称M 106。     

追星一族

二月的夜空,依然灿烂。让我们面北而立,从天顶附近看起。御夫座中疏散星团NGC2281进入我们的视野。NGC2281用7×50双筒望远镜可以观测,如果用16cm30倍率以上的望远镜观测,则可见十几颗较亮的星交织在一起。向北偏西方向,是英仙座的弥漫星云NGC1499、疏散星团M34、NGC1342     

在球状星团 M79中发现的两颗变星

在1957—1958年间,作者使用上海天文台佘山工作站的口径40厘米折光望远镜,以柯达103a-0底片,对天兔座的球状星团 M79(NGC 1904)拍摄了9张底片(佘 M79I-Ⅸ).这架望远镜的情况可参阅文献.当时从这9张底片中发现了两颗以前未经查到的变星.依照发现时序,这两颗变星的编号,当继罗西诺(L.Rosino)在这个星团中所发现的变星之后,而列为第7号和第8号变星.     

Chemo-dynamical modelling with Schwarzschild's method

We extend Schwarzschild's dynamical modelling method to model absorption line strength data as well as the more usual luminosity and kinematic data.Our approach draws on earlier published work by the first author with the Syer Tremaine made-to-measure(M2M) dynamical modelling method and uses similar ideas to create a chemo-Schwarzschild method.We apply our extended Schwarzschild method to the same four early type galaxies(NGC 1248, NGC 3838, NGC 4452,NGC 4551) as the chemo-M2M work, and are able to recover successfully the 2D absorption line strength for the three lines we model(Hβ, Fe5015, Mg b).We believe that this is the first time Schwarzschild's method has been used in this way.The techniques developed can be applied to modelling other aspects of galaxies, for example age and metallicity data coming from stellar population modelling, and are not specific to absorption line strength data.     

追寻科德韦尔天体（7）

C32（NGC4631）使用100mm左右的望远镜就可以看见它：C33（NGC6992）和C34（NGC6960）与其旁边的几片星云共同构成了帷幕星云,通常认为它比较难用目视观测,但使用特殊的O III滤镜则可以比较容易地看到它：C35（NGC4889）和C36（NGC4559）都比较暗,不过使用4英寸（116毫米）的望远镜都可以看到;而C37（NGC6885）本身亮度不算太暗,     

Made-to-measure galaxy modelling utilising absorption line strength data

We enhance the Syer Tremaine made-to-measure(M2M) particle method of stellar dynamical modelling to model simultaneously both kinematic data and absorption line strength data, thus creating a‘chemo-M2M' modelling scheme. We apply the enhanced method to four galaxies(NGC 1248, NGC 3838,NGC 4452, NGC 4551) observed using the SAURON integral-field spectrograph as part of the ATLAS3 D programme. We are able to reproduce successfully the 2D line strength data achieving mean χ2per bin values of ≈ 1 with 95% of particles having converged weights. Because M2 M uses a 3D particle system,we are also able to examine the underlying 3D line strength distributions. The extent to which these distributions are plausible representations of real galaxies requires further consideration. Overall, we consider the modelling exercise to be a promising first step in developing a ‘chemo-M2M' modelling system and in understanding some of the issues to be addressed. While the made-to-measure techniques developed have been applied to absorption line strength data, they are in fact general and may be of value in modelling other aspects of galaxies.     

A multiwavelength view of the ISM in the merger remnant galaxy Fornax A

We present multi-wavelength imagery of the merger remnant galaxy NGC 1316 with an objective to study the dust content and its association with the other phases of the interstellar medium. Color-index maps as well as extinction maps derived for this galaxy reveal an intricate and complex dust morphology in NGC 1316, i.e. there is a prominent lane in the inner part, while at about 6-7 kpc it apparently takes the form of an arc-like pattern extending along the northeast direction. In addition to this, several other dust clumps and knots are also evident in this galaxy. The dust emission mapped using Spitzer data at 8 μm indicates even more complex morphological structures of the dust in NGC 1316. The extinction curve derived over the optical to near-IR bands closely follows the standard Galactic curve, suggesting similar properties of the dust grains. The dust content of NGC 1316, estimated from optical extinction, is ～ 2.13 105M⊙ . This is a lower limit compared to that estimated using the IRAS flux densities of ～5.17×106M⊙ and the flux densities at 24, 70 and 160 μm from MIPS ～3.2×107M⊙ . High resolution Chandra observations of this merger remnant system have provided an unprecedented view of the complex nature exhibited by the distribution of hot gas in NGC 1316, which closely matches the morphology of ionized gas and to some extent also the dust. X-ray color-color plots for the resolved sources within the optical D 25 extent of NGC 1316 have enabled us to separate them into different classes.     

Searching for Variable Stars in and around Open Clusters

We present a snapshot of our recent results of a variable star survey in 1 degree fields around three open clusters: NGC 188, NGC 7789 and M67. A total number of 39 variable stars are newly discovered, including 22 W UMa stars, 10 EA (Algol) type binaries, one RR-lyr and one RRd pulsator, and five unclassified variables.     

行星状星云M97

行星状星云 M97(NGC3587)位于大熊星座,其赤道坐标为:赤经11时14.8分,赤纬 55°01′;视星等:9.9,角径:170″,距离:1630光年,发现者:Pierre Mechain,1781年。梅西叶1781年3月24日的观测记录如下:它是靠近大熊座β星的一个星云。1781年2月16日 Mechain 首次发现的,该星云在天空的位置也是他提供的。NGC 的描述:极显著的星云,很亮且大,圆形,角径150″,从周边向中心逐步增亮,最后突然大亮。这一有特色的星云具有一副猫头鹰(至少从其照片上看去)一样的面相,故我国天文学家称其为枭状星云。关于观察 M97的难易程度,有不同的看法。Johnesr 认为用口径小于6英寸的望远镜有可能什么也看不到,至少需要12英寸的望远镜去观看枭的“眼睛”。     

后发座内的M88和M91

旋涡星系 M88(NGC4501)的赤道坐标为赤经12时32.0分,赤纬 14°25′:视星等9.6,面亮度12.6,角径6.9′x3.7′,距离5500万光年。梅西叶1781年3月18日对它的观测记录如下:"室女座内一无星的星云,位于两暗星与一颗6等星之间,这三颗星与该星云一同出现在望远镜的视场内,星云外形与室女座 M58相似。"NGC 的简述:亮,很大,延伸得很宽。John Mallas 认为在很小的尺度上 M88与仙女     

疏散星团NGC2286的研究

本文利用疏散昨团NGC2286天区内250颗恒星的相对自行及成员概率判定资料，首次对该星团的半径、光度函数以及内部运动等做较深入的研究，分析表明对NGC2286这个中等年龄的星团，正处于动力学演化的初级阶段，在空间和速度上都没有表现出象年老疏散星团M67那样较为明显的分层效应。     

巨椭圆星系M87

M87(NGC4486)的赤道坐标为:赤经12时30.8分,赤纬 12°24′;视星等8.6,面亮度:12.7,角经8.3′×6.6′。距离:5 500万光年。梅西叶发现它时(1781年3月18日)的记录如下:室女座中无星的星云,星云的上端紧挨着一颗8等星,该星与M87有相同的赤经,但赤纬为 13°42′21″。此星云显得与另两个星云M84和M86有相同的亮度。 NGC的简述:很亮、很大、圆形,中部非常之亮,三者中这第三(最东端)。 M87可以称得上是—能量巨大的星系,其质量是太阳的8000亿倍,是最大的星系之一,也是室女座较亮的