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给出红外点源IRAS 20231 3440附近恒星形成区近红外．JHK’和H2成像观测结果，以及与该IRAS点源成协的近红外点源IRS1的K波段分光观测结果．．JHK’观测显示该区域存在嵌埋的年轻星天体，H2窄波段观测揭示了若干个氢分子发射结点，其中有几个结点排列成线形，暗示分子氢喷流的存在．喷流的北部与已知观测的分子外流成协，表明二者之间存在联系．喷流的走向提示IRS1可能是其激发源，对IRS1的K波段分光观测给出了进一步的证据．从近红外、MSX及IRAS资料估计出IRS1的能谱分布，表明它是一个处于ClassI状态的中等质量的年轻星天体． 相似文献
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报告分子外流源Ｌ１２１１ 中新发现的１２ 个近红外ＨＨ 天体．在Ｌ１２１１ 的～４’区域,取得了ＪＨＫ’宽带和Ｈ２ ｖ ＝ １０ Ｓ（１） 发射线窄带的近红外图像．分析表明,新探测到的许多红外源与浓密分子云物理成协,其中有２０ 多个源表现出典型的Ｔ Ｔａｕｒｉ 星、Ｈｅｒｂｉｇ Ａｅ／Ｂｅ星和原恒星的红外超．Ｌ１２１１ 中的ＩＲＡＳ点源没有被观测到,可能是更深地埋于分子云中．对红外观测和分子线观测消光估计的比较显示,小于２μｍ 的近红外观测还不足以揭示深埋于分子云的整个年轻星团．根据近红外ＨＨ 天体的形态分布和红外源性质,能进一步证认这些ＨＨ 天体的激发源．其结果表明,Ｌ１２１１ 分子云中具有多个红外源驱动的多个外流活动 相似文献
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以《Hipparcos星表》体现的国际天球参考架为基础 ,对球状星团M3(NGC 5 2 72 )中心附近 10 0′×10 0′天区内 5 34颗恒星 ,使用上海天文台佘山 4 0cm折射望远镜拍摄的底片资料 ,以 8颗《Hipparcos星表》中恒星和 4 9颗《Tycho - 2星表》中恒星的位置和绝对自行为参考 ,归算得到了位置和绝对自行 ,并估计了成员概率 相似文献
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热超短周期造父变星的周期≤0.~d1、变幅≥0.~m2、光谱型为A.在银河系中呈延仲球状分布;在银晕星族的球状星团和年老盘族的运动星群中都有.在色星等图上,处于造父不稳定带的左外侧而温度较高,故简称热造父变星.球状星团中超短周期造父变星现知五颗.三颗是热造父变星:半人马ω的V65星(M_v= 0.~m82),M56的V11星(M_v= 0.~m10)和M15的K1082星(M_v=0.~m09)。它们在色星等图上的位置紧邻,亮度和天琴RR型星相近,但色均较蓝.它们都处在银河系中呈延伸球状分布的贫金属星团中.银河系中已知超短周期造父变星的周期变幅图上,有可用0.~m2简示的变幅分布隙,和两条周期分布隙.其中变幅≥0.~m2、周期≤ 0.~d1的-群共九颗,是银河系一般星场的热造父变星.其银纬分布除一颗是b= 10°44′外,余均为|h|>20°.这九颗中的两颗是年老盘族的运动星群的成员,-颗具有空间速度高和金属线强度ΔS≥2的星族Ⅱ星的特点. 相似文献
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分子氢的红外振动发射线是显现年轻星质量外流的重要谱线之一。自Gautier等人1976年在猎户座发现年轻星质量外流的分子氢发射开始,人们在银河系内几乎所有的恒星形成区都发现了这种线发射。研究表明,分子氢发射与年轻星周围的其它活动现象（如分子外流和光学喷流）之间有着非常密切的联系。红外和光学喷流代表了年轻星剧烈活动的两个侧面,是喷流与周围介质相互作用强弱不同的表现,这种作用还拖带周围介质,产生分子外流,光学、红外喷流和分子外流组成了恒星形成区壮观的景象,它们是恒星形成活动的重要标志。随着红外探测技术的飞速发展,对年轻星外流活动现象的观测越来越丰富的详细,使人们对这种现象的本质越来越了解。在20世纪90年代NICMOS等大阵列红外探测器投入使用后,红外成像观测有了长足的进步。目前已在70个左右的区域里发现了H2发射,这一数字还在迅速增加,今后的研究主要可能向两个方向发展。其一是高分辨观测,进一步了解H2发射的结构以及与光学喷流和分子外流之间的关系;其二是天观测,了解银河系内的恒星形成H2区发射的大尺度结构和恒星形成的统计分布规律。 相似文献
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利用斯隆数字巡天（SDSS）第8次释放数据（DR8）的恒星光谱数据及2MASS（Two Micro All Sky Survey）近红外点源测光数据研究著名的疏散星团NGC 6791,得到该星团的视向速度与金属丰度分别为Vr=-46.4±0.2 km·s-1和[Fe/H]=0.32±0.11dex.利用星团中红团簇巨星作为理想"标准烛光",结合2MASS近红外点源测光数据计算了该星团的绝对距离模数为（m-M）0=13.02±0.08 mag或4.02±0.15 kpc.与其他研究者给出的结果进行了比较,金属丰度、视向速度及绝对距离模数都符合得比较好.主要结论有3点:（1）NGC 6791是个极度富金属的星团;（2）在SDSS的光谱分辨能力以内,分离出的87颗团星之间不存在明显的金属丰度差异;（3）得到的距离模数对年龄、金属丰度及尘埃消光不敏感,是一种可靠的间接测量. 相似文献
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基于高分辨率、高信噪比光谱观测资料，确定了19颗贫金属红团簇巨星的恒星大气参数，得到样本星4种α族元素(O、Mg、Ca、Si)的化学丰度．讨论了铁丰度与恒星大气参数的相关性以及α族元素丰度随金属丰度的变化，计算了共58颗红团簇巨星在I、K波段的绝对星等，讨论了它们与恒星铁丰度之间的关系．结果表明，在分析铁丰度范围内相对于I波段，K波段的绝对星等与铁丰度的相关性更弱，并且与利用理论模型得到的红团簇巨星I、K波段绝对星等与铁丰度的关系进行了比较与验证。 相似文献
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本文利用中国科学院上海天文台４０厘米双筒天体照相仪所拍摄得的１０对底片（历元差１６─７０年），经ＰＤＳ测量仪测量，共确定了疏散星团Ｍｌｌ天区８７２颗恒星的相对自行，其中８５％以上恒星的自行测定精度好于±０″．１／百年．利用所测得的相对自行和新的数学模型，确定了不同星等组恒星的分布参数并计算了团中心距ｒ≤２５＇内７８５颗恒星的成员概率，其中成员概率大于０．７的恒星共有５４１颗．详细的讨论表明，新方法不仅在理论上更为严格，实用上也是可行的，可以使星团成员确定取得更为合理的结果． 相似文献
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恒星形成于分子云之中, 分子外向流是恒星形成正在进行的重要动力学特征, 也是研究和认识恒星形成的重要契入点. 利用紫金山天文台青海观测站德令哈13.7m毫米波望远镜, 采用5种分子谱线探针(包括12CO、13CO、C18O、HCO$^+$ $J=1-0$和CS $J=2-1$, J为角动量量子数), 对一个包含IRAS 19230+1506、IRAS 19232+1504和G050.3179--00.4186这3个源的大质量恒星形成复合体进行了成图观测研究. 通过对以上分子谱线数据并结合红外波段巡天数据的分析, 在这3个源中首次探测到了分子外向流活动, 并确定了分子外向流的中心驱动源. 最后对这3个源进行了分子外向流相关物理量参数的计算, 分析了这些物理量参数之间的关系, 结果表明分子外向流的性质与中心驱动源的性质息息相关. 相似文献
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We present results of near infrared observation of 21 molecular outflow sources and two non-outflow sources with compact cores. Combined with IRAS and other surface station observations we analyse their spectra and find that the outflow sources have, on average, steeper spectral gradients than the non-outflow sources in the range 2.28–25 μ. Most of the bipolar outflow sources have gradients greater than 2.0. Using a revised blackbody photosphere model we calculate the contributions to the JHK fluxes by the central young star and the circumstellar envelope. For the sources with known bolometric luminosity we derive the photospheric temperature of the central star and the circumstellar extinction. Results show that most of the young stars associated with molecular outflows are probably T Tauri stars (5000–7000 K) or emission line stars (9000–26000 K). The circumstellar extinction in JHK is around 10 to 20 magnitudes. These facts show that molecular outflow sources are young objects still embedded deep inside or around the interior of compact cores. Fitting the 3.5– 25 μ and 60–100 μ spectra with a λ-1 dust emission model to five source gives a negative power law for the temperature profile of the circumstellar shell with exponents between 0.39 and 0.48, close to the theoretical results for molecular clouds associated with HI I regions. 相似文献
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We present infrared spectroscopy of the Antennae galaxies (NGC 4038/9) with the near-infrared spectrometer (NIRSPEC) at the W. M. Keck Observatory. We imaged the star clusters in the vicinity of the southern nucleus (NGC 4039) with 0&farcs;39 seeing in the K band using NIRSPEC's slit-viewing camera. The brightest star cluster revealed in the near-IR [MK&parl0;0&parr0; approximately -17.9] is insignificant optically but is coincident with the highest surface brightness peak in the mid-IR (12-18 μm) Infrared Space Observatory image presented by Mirabel et al. We obtained high signal-to-noise ratio 2.03-2.45 μm spectra of the nucleus and the obscured star cluster at R approximately 1900. The cluster is very young ( approximately 4 Myr), massive (M approximately 16x106 M middle dot in circle), and compact (with a density of approximately 115 M middle dot in circle pc-3 within a 32 pc half-light radius), assuming a Salpeter initial mass function (0.1-100 M middle dot in circle). Its hot stars have a radiation field characterized by Teff approximately 39,000 K, and they ionize a compact H ii region with ne approximately 104 cm-3. The stars are deeply embedded in gas and dust (AV approximately 9-10 mag), and their strong far-ultraviolet field powers a clumpy photodissociation region with densities nH greater, similar105 cm-3 on scales of approximately 200 pc, radiating LH21-0S&parl0;1&parr0;=9600 L middle dot in circle. 相似文献
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Yao Bao-an Sheng Chang-jung Zhang Chun-sheng Lin Qing 《Chinese Astronomy and Astrophysics》2004,28(4):399-403
G302 = L3107 is a red star located at the lowest end of the red giant branch of the globular cluster M4. According to its location on the C-M diagram, G302 may be a cluster member. No proper motion or radial velocity determinations are available up to date.
We discovered that C302 is a new variable star with a main period of 1.24719 day and a peak to peak amplitude of about 0.3 mag in V. It may have a second period of 2.38249 day with an amplitude of about 0.05 mag. If it is a cluster member, then there will be interesting implications for the the theory of stellar evolution. 相似文献
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I. Waddington R. A. Windhorst J. S. Dunlop D. C. Koo J. A. Peacock 《Monthly notices of the Royal Astronomical Society》2000,317(4):801-824
The results are presented of an extensive programme of optical and infrared imaging of radio sources in a complete subsample of the Leiden–Berkeley Deep Survey. The LBDS Hercules sample consists of 72 sources observed at 1.4 GHz, with flux densities S 1.4 1.0 mJy, in a 1.2 deg2 region of Hercules. This sample is almost completely identified in the g , r , i and K bands, with some additional data available at J and H . The magnitude distributions peak at r ≃22 mag, K ≃16 mag and extend down to r ≃26 mag, K ≃21 mag. The K -band magnitude distributions for the radio galaxies and quasars are compared with those of other radio surveys. At S 1.4 GHz ≲1 Jy, the K -band distribution does not change significantly with radio flux density. The sources span a broad range of colours, with several being extremely red ( r − K ≳6). Though small, this is the most optically complete sample of mJy radio sources available at 1.4 GHz, and is ideally suited for studying the evolution of the radio luminosity function out to high redshifts. 相似文献
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A-Ran Lyo Inseok Song Warrick A. Lawson M. S. Bessell B. Zuckerman 《Monthly notices of the Royal Astronomical Society》2006,368(3):1451-1455
We report the outcome of the deep optical/infrared photometric survey of the central region (33 × 33 arcmin2 or 0.9 pc2 ) of the η Chamaeleontis (η Cha) pre-main sequence star cluster. The completeness limits of the photometry are I = 19.1, J = 18.2 and H = 17.6, faint enough to reveal low-mass members down to the brown dwarf and planet boundary of ≈13 MJup . We found no such low-mass members in this region. Our result combined with a previous shallower ( I = 17) but larger area survey indicates that low-mass objects (0.013 < M /M⊙ < 0.075) were either not created in the η Cha cluster or lost due to the early dynamical history of the cluster and ejected to outside the surveyed areas. 相似文献
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We present a comprehensive study of star formation toward the H II region Sharpless 155(S155).Star-formation activities therein were investigated based on multi-wavelength data from optical to the far-infrared.The surface density distribution of selected 2MASS sources toward S155 indicates the existence of a compact cluster,which is spatially consistent with the position of the exciting source of the H II region,HD 217086.A sample of more than 200 sources with excessive emission in the infrared were selected based on their 2MASS color indices.The spatial distribution of the sample sources reveals the existence of three young subclusters in this region,among which subcluster A is spatially coincident with the bright rim of the H II region.In addition,photometric data from the WISE survey were used to identify and classify young stellar objects(YSOs).To further explore the evolutionary stages of the candidate YSOs,we fit the spectral energy distributions of 44 sources,which led to the identification of 14 Class I,27 Class II and 3 Class HI YSOs.The spatial distribution of the classified YSOs at different evolutionary stages presents a spatiotemporal gradient,which is consistent with a scenario of sequential star formation.On the other hand,Herschel PACS observations toward the interface between S155 and the ambient molecular cloud disclose an arc-shaped dust layer,the origin of which could be attributed to the UV dissipation from early type stars,e.g.HD 217061,in S155.Four dusty cores were revealed by the Herschel data,which hints at new generations of star formation. 相似文献
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V. S. Shevchenko O. V. Ezhkova M. A. Ibrahimov M. E. van den Ancker H. R. E. Tjin A Djie 《Monthly notices of the Royal Astronomical Society》1999,310(1):210-222
A new photometric and spectroscopic survey of the star formation region (SFR) CMa R1 is described. In a sample of 165 stars brighter than 13th mag, 88 stars were found to be probable members of the SFR. They are defined as early-type stars with E ( B − V )0.16 mag, which corresponds to a distance of about 1 kpc. 74 of the probable members are B stars. 19 stars are possibly associated with an IRAS point source. We derive a most probable distance of 1050±150 pc to the association. It appears that about 80 candidate members are pre-main-sequence stars with ages lower than 6 million years, while the main sequence extends over 6.0–7.6 mag, which is consistent with star formation starting about 8 million years ago and continuing until at least half a million years ago. Two bright B stars in the association (GU CMa and FZ CMa) seem to be much older and probably do not originate from the same star formation episode. The star formation efficiency appears to increase roughly monotonically with time up to half a million years ago. From our data, we conclude that only a minor fraction of the stars has been created through the scenario suggested by Herbst & Assousa, in which the members of CMa R1 form by compression of ambient material by a supernova shock wave. An extensive search for candidate members with H α emission did not reveal new Herbig Ae/Be candidates, so that the number of stars in this class seems to be limited to four: Z CMa, LkH α 218, LkH α 220 and possibly HD 53367. 相似文献