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1.
对于具有吸收线红移大于发射线红移的吸收体,如果吸收体具有比较大的多普勒速度,吸收体有可能是正在向类星体中心移动.在SDSS J101108 +553407的光谱中认证了3个Lyα吸收体,其吸收线红移均大于发射线红移,吸收线红移分别是:3.3442、3.3496和3.3553,对应的多普勒速度分别是401 km/s、773 km/s和1166 km/s.这3个吸收体的运动情况和起源均不相同:具有最大多普勒红移的一个吸收体,可能起源于类星体物质外流的回落,而另外两个吸收体很可能起源于绕天体中心转动的云团,并且这些云团位于寄主星系中. 相似文献
2.
分析类星体吸收线红移和发射线红移的特征。我们从Hewitt和Burbidge ( 1 993 )的星表中选择了吸收线红移和发射线红移都同时提供的类星体 ,得到了包含 4 0 1个对象的样本。这是至今对类星体红移研究的最大样本。我们从吸收线红移和发射线红移之间的关系图发现绝大多数 ( 93 .6% )对象的吸收线红移都小于相应的发射线红移。这个结论人们在 2 0世纪 70年代已经从很小的类星体样本 (样本大小 50左右 )中得到。本文进一步支持了这个结论。它表明类星体红移确实是距离的指示器。这跟宇宙学对类星体红移的解释是一致的 相似文献
3.
本文对16个高红移类星体的L_α森林吸收线密度N(z_(abs))统计分析的结果,表明它明显地依赖于类星体自身的发射红移z_(em)。这不仅表现在z(em)越大的类星体其全部L_α吸收线的平均数密度N(z_(abs))也越大;更重要的是,对于相同的吸收红移值z_(abs),而言,N(z_(abs))在统计意义上明显地随着类星体z_(em)的增大而增大。另一方面,本文也在“吸收体源自类星体抛射”的框架下作了统计,结果仍表明z_(em)对L_α森林吸收线密度有显著影响,但抛射速度却对被抛射体的数目无显著影响。最后,对所得的结果以及可能影响N(z_(abs))的若干因素作了讨论。 相似文献
4.
根据红移定义１＋ｚ＝λｉ／λ０ｉ，我们认为类星体红移分布ｌｎ（１＋ｚ）周期性受两个因素影响。首先，决定类星体红移的主要线（如Ｌα１２１６，ＣＩＶ１５４９，ＣＩＩＩ１９０９，ＭｇＩＩ２７９８，ＮｅＶ３４２６，ＯＩＩ３７２７，ＮｅＩＩＩ３８６８，Ｈγ４３４０，Ｈβ４８６１，ＯＩＩＩ５００７）固有波长可能构成０．２０５的周期性；另外，这些谱线的观测波长进入一定光学窗口对红移有一定限制，在一定条件下，它正好在某些红移出现峰值，并与ｌｎ（１＋ｚ）＝０．２０５预言峰值一致。我们还在这两个基本考虑下进行模拟取样，发现有明显周期性，定量上证实了我们的基本考虑。本文是类星体红移分布的一种解释，它能说明为什么统计分布不同样品能得到不同的结论。进而，我们认为红移分布周期性不能成为内禀红移观点的观测支持。 相似文献
5.
分析类星体吸收线红移和发射线红移的特征。我们从Hewitt和Burbidge（1993）的星表中选择了吸收线红称和发射线红移都同时提供的类星体，得到了包含401个对象的样本。这是至今对类星体红移研究的最大样本。我们从吸收线红移和发射线红移之间的关系图发现绝大多数（93．6％）对象的吸收线红移都小于相应的发射线红移。这个结论人们在20世纪70年代已经从很小的类星体样本（样本大小50左右）中得到。本文进一步支持了这个结论。它表明类星体红移确实是距离的指示器。这跟宇宙学对类星体红移的解释是一致的。 相似文献
6.
本文讨论了类星体成团随红移的变化。利用Hewitt-Burbidge类星体星表和寻找类星体对的统计方法,分析结果表明类星体成团主要是由于小红移类星体的贡献,大红移类星体没有成团分布的证据。进一步分析表明不同红移类星体在成团分布上的区别并不是由于样品的绝对光度不同而引起的选择效应,而是反映了类星体团随宇宙时间变化的演化效应。 相似文献
7.
本文是系列文章Ⅱ的第2篇.根据前文的统计结果,我们确认了成协吸收系统的存在.本文在此基础上,对成协吸收系统出现频率与类星体红移、光学亮度、X射线波段和红外波段辐射性质的相关性进行了讨论.结果表明成协吸收系统与类星体X射线波段性质无关,而与类星体的红移和光学亮度有关,表现为低红移(z<2.0)低光度(M_v≥-27~m) 的类星体中成协系统的出现频率明显地比其它样本高得多. 相似文献
8.
本文讨论了类星体各光谱特征对其色指数的影响以及色指数随红移的变化，随着红移的增加，位于Ｌｙａ发射线短波方向的各种吸收特征进入了可见光区，内禀的禀的幂律谱和发射线强度的分布对类星体色指数及其弥散的影响将是次要的，各种吸收系统的作用将改变类星体色指数随红移变化的趋势，其中，Ｌｙｍａｎ系限吸收系统的影响最大，利用ＩＵＥ观测的类星体光谱求得色指数随红移的变化，对上述结果进行了验证。 相似文献
9.
文［１］提出，类星体红移分布周期性可能由两点因素造成：首先是主要谱线固有波长呈周期性；其次是光学窗口对谱线红移范围的限制．本文赞同上述第二论点，同时论证了上述第一论点不能成立．此外，该文在处理方法上也有一些不当之处．本文屏弃上述第一论点，仅从第二论点出发，应用概率分析方法，得到类星体相对观测几率－红移分布．此分布与部分观测结果符合较好，大致可解释类星体红移周期分布现象． 相似文献
10.
本文讨论了类星体各光谱特征对其色指数的影响以及色指数随红移的变化．随着红移的增加，位于Ｌｙα发射线短波方向的各种吸收特征进入了可见光区，内禀的幂律谱和发射线强度的分布对类星体色指数及其弥散的影响将是次要的，各种吸收系统的作用将改变类星体色指数随红移变化的趋势，其中，Ｌｙｍａｎ系限吸收系统的影响最大。利用ＩＵＥ观测的类星体光谱求得色指数随红移的变化，对上述结果进行了验证。 相似文献
11.
Vivienne Wild Guinevere Kauffmann Simon White Donald York Matthew Lehnert Timothy Heckman Patrick B. Hall Pushpa Khare Britt Lundgren Donald P. Schneider Daniel Vanden Berk 《Monthly notices of the Royal Astronomical Society》2008,388(1):227-241
Using data from the Sloan Digital Sky Survey data release 3 (SDSS DR3), we investigate how narrow (<700 km s−1 ) C iv and Mg ii quasar absorption-line systems are distributed around quasars. The C iv absorbers lie in the redshift range 1.6 < z < 4 and the Mg ii absorbers in the range 0.4 < z < 2.2. By correlating absorbers with quasars on different but neighbouring lines of sight, we measure the clustering of absorbers around quasars on comoving scales between 4 and 30 Mpc. The observed comoving correlation lengths are r o ∼ 5 h −1 Mpc , similar to those observed for bright galaxies at these redshifts. Comparing correlations between absorbers and the quasars, in whose spectra they are identified, then implies: (i) that quasars destroy absorbers to comoving distances of ∼300 kpc (C iv ) and ∼800 kpc (Mg ii ) along their lines of sight; (ii) that ≳40 per cent of C iv absorbers within 3000 km s−1 of the quasi-stellar object are not a result of large-scale clustering but rather are directly associated with the quasar itself; (iii) that this intrinsic absorber population extends to outflow velocities of the order of 12 000 km s−1 ; (iv) that this outflow component is present in both radio-loud and radio-quiet quasars and (v) that a small high-velocity outflow component is also observed in the Mg ii population. We also find an indication that absorption systems within 3000 km s−1 are more abundant for radio-loud quasars than for radio-quiet quasars. This suggests either that radio-loud objects live in more massive haloes, or that their radio activity generates an additional low-velocity outflow, or both. 相似文献
12.
Doppler redshifts of a sample of Mg II associated absorbers of SDSS DR7 quasars are analysed. We find that there might be three Gaussian components in the distribution of the Doppler redshift. The first Gaussian component, with the peak being located at z Dopp?=???0.0074, probably arises from absorbers with outflow histories observed in the direction close to jets of quasars. The second Gaussian component, with the peak being located at z Dopp?=???0.0017, possibly arises from absorbers with outflow histories observed in the direction far away from jets of quasars. Whereas, the third Gaussian component, with the peak being located at z Dopp?=???0.0004, might arise from the random motion of absorbers with respect to quasars. 相似文献
13.
Xue-Bing Wu Wen-Wen Zuo Qian Yang Wei-Min Yi Chen-Wei Yang Wen-Juan Liu Peng Jiang Xin-Wen Shu and Hong-Yan Zhou 《天文和天体物理学研究(英文版)》2012,(9):1185-1190
Quasars with redshifts greater than 4 are rare, and can be used to probe the structure and evolution of the early universe. Here we report the discovery of six new quasars with i-band magnitudes brighter than 19.5 and redshifts between 2.4 and 4.6 from spectroscopy with the Yunnan Faint Object Spectrograph and Camera (YFOSC) at the Lijiang 2.4 m telescope in February, 2012. These quasars are in the list of z > 3.6 quasar candidates selected by using our proposed J K/i Y criterion and the photometric redshift estimations from the SDSS optical and UKIDSS near-IR photometric data. Nine candidates were observed by YFOSC, and five among six new quasars were identified as z > 3.6 quasars. One of the other three objects was identified as a star and the other two were unidentified due to the lower signal-to-noise ratio of their spectra. This is the first time that z > 4 quasars have been discovered using a telescope in China. Thanks to the Chinese Telescope Access Program (TAP), the redshift of 4.6 for one of these quasars was confirmed by the Multiple Mirror Telescope (MMT) Red Channel spectroscopy. The continuum and emission line properties of these six quasars, as well as their central black hole masses and Eddington ratios, were obtained. 相似文献
14.
Roger G. Clowes † Luis E. Campusano Matthew J. Graham ‡ 《Monthly notices of the Royal Astronomical Society》1999,309(1):48-62
We present the spectra and redshifts of 62 quasars, from observations made with the Cerro Tololo Inter-American Observatory (CTIO) 4-m Blanco Telescope. These quasars form part of a total sample of 118 (with 56 having been published previously), which is being used for analysis of structure in the early universe. Quasars of particular interest are noted, including eight broad absorption line (BAL) quasars and two quasars with unusual emission spectra. Finally, we include a short summary of the present status of the large quasar group (LQG) that was discovered by Clowes & Campusano from the earlier observations. The quasars are from an area ∼25.3 deg2 of ESO/SERC field 927, which is centred at (1950) 10h 40m 00s , 05°00'00'. 相似文献
15.
D. Nestor F. Hamann P. Rodriguez Hidalgo 《Monthly notices of the Royal Astronomical Society》2008,386(4):2055-2064
We report on a survey for narrow (full widths at half-minimum <600 km s−1 ) C iv absorption lines in a sample of bright quasars at redshifts 1.8 ≤ z < 2.25 in the Sloan Digital Sky Survey. Our main goal is to understand the relationship of narrow C iv absorbers to quasar outflows and, more generally, to quasar environments. We determine velocity zero-points using the broad Mg ii emission line, and then measure the absorbers' quasar-frame velocity distribution. We examine the distribution of lines arising in quasar outflows by subtracting model fits to the contributions from cosmologically intervening absorbers and absorption due to the quasar host galaxy or cluster environment. We find that a substantial number ( ≥43 ± 6 per cent) of absorbers with W λ1548 0 > 0.3 Å in the velocity range +750 ≲ v ≲+ 12 000 km s−1 are intrinsic to the active galactic nucleus outflow. This 'outflow fraction' peaks near v =+2000 km s−1 with a value of f outflow ≃ 0.81 ± 0.13 . At velocities below v ≈+ 2000 km s−1 , the incidence of outflowing systems drops, possibly due to geometric effects or to the over-ionization of gas that is nearer the accretion disc. Furthermore, we find that outflow absorbers are on average broader and stronger than cosmologically intervening systems. Finally, we find that ∼14 per cent of the quasars in our sample exhibit narrow, outflowing C iv absorption with W λ1548 0 > 0.3 Å, slightly larger than that for broad absorption line systems. 相似文献
16.
Astronomy Letters - We propose a method of analyzing the absorption spectra of quasars that allows the physical parameters of absorbing clouds, absorbers, to be roughly estimated: their masses,... 相似文献
17.
Xue-Bing Wu Wei Zhang Xu Zhou Department of Astronomy School of Physics Peking University Beijing National Astronomical Observatories Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2004,4(1):17-27
With a recently constructed composite quasar spectrum and the X2 minimization technique, we describe a general method for estimating the photometric redshifts of a large sample of quasars by deriving theoretical color-redshift relations and comparing the theoretical colors with the observed ones. We estimated the photometric redshifts from the 5-band SDSS photometric data of 18678 quasars in the first major data release of SDSS and compared them with their spectroscopic redshifts. The difference is less than 0.1 for 47% of the quasars and less than 0.2 for 68%. Based on the calculation of the theoretical color-color diagrams of stars, galaxies and quasars both on the SDSS system and on the BATC system, we expect that we would be able to select candidates of high redshift quasars more efficaciously with the latter than with the former, provided the BATC survey can detect objects with magnitudes fainter than 21. 相似文献
18.
J. G. Hartnett 《Astrophysics and Space Science》2009,324(1):13-16
Discrete Fourier analysis on the quasar number count, as a function of redshift, z, calculated from the Sloan Digital Sky Survey DR6 release appears to indicate that quasars have preferred periodic redshifts
with redshift intervals of 0.258, 0.312, 0.44, 0.63, and 1.1. However the same periods are found in the mean of the zConf parameter used to flag the reliability of the spectroscopic measurements. It follows that these redshift periods must result
from some selection effect, as yet undetermined. It does not signal any intrinsic (quantized) redshifts in the quasars in
Sloan survey data. However this result does not rule out the possibility as found in earlier studies of other data. 相似文献
19.
The large-scale angular distribution of quasars from a complete sample of extragalactic radio sources is examined at different
redshifts. The sample contains 264 quasars which have been found so far among the complete sample of 518 radio sources stronger
than. 1 Jy at 5 GHz. Of these, 19 quasars have redshift z > 2. Dividing the entire sky into three separate declination zones
of equal area, the counts of quasars seem to indicate a deficit of high redshift quasars in the northernmost declination zone.
On the other hand, the Iow-redshift quasars (z < 1) appear fairly uniformly distributed. We discuss some possible selection
effects that might have led to the apparent anomaly at high redshifts and estimate the expected number of high-redshift quasars
amongst the radio sources in the sample for which redshifts are presently not available. 相似文献