High-redshift QSOs in the FIRST survey

In a pilot search for high-redshift radio quasi-stellar objects (QSOs), we have obtained spectra of 55 FIRST sources     with very red     starlike optical identifications. 10 of the candidates are QSOs with redshifts     (four were previously known), six with     . The remaining 45 candidates comprise: one     broad-absorption-line (BAL) QSO; three low-redshift galaxies with narrow emission lines; 18 probable radio galaxies; and 23 M stars (mainly misidentifications). The success rate (high-redshift QSOs / spectroscopically-observed candidates) for this search is 1/2 for     , and 1/9 for     . With an effective search area of 4030 deg², the surface density of high-redshift     QSOs discovered with this technique is 0.0015 deg⁻².     

Integral field observations of damped Lyman‐α galaxies

We report preliminary results from a targeted investigation on quasars containing damped Lyman‐α absorption (DLA) lines as well strong metal absorption lines, carried out with the Potsdam Multi Aperture Spectrophotometer (PMAS). We search for line‐emitting objects at the same redshift as the absorption lines and close to the line of sight of the QSOs. We have observed and detected the already confirmed absorbing galaxies in Q2233+131 (z_abs = 3.15) and Q0151+045 (z_abs=0.168), while failing to find spectral signatures for the z = 0.091 absorber in Q0738+313. From the Q2233+131 DLA galaxy, we have detected extended Lyα emission from an area of 3″ ×5″. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

VLT-SINFONI observations of Mrk 609 – A showcase for X-ray active galaxies chosen from a sample of AGN suitable for adaptive optics observations with natural guide stars

We will present first results of ESO-VLT AO-assisted integral-field spectroscopy of a sample of X-ray bright AGN with redshifts of 0.04 < z < 1. We constructed this sample by cross-correlating the SDSS and ROSAT surveys and utilizing typical AO constraints. This sample allows for a detailed study of the NIR properties of the nuclear and host environments with high spectral resolution on the 100 pc scale. These objects can then be compared directly to the local (z < 0.01) galaxy populations (observed without AO) at the same linear scale. As a current example, we will present observations of the z = 0.034 Seyfert 1.8 galaxy Mrk 609 with the new AO-assisted integral-field spectrometer SINFONI at the VLT. The successful observations show, that in the future – while having observed more objects – we will be able to determine the presence, frequency and importance of nuclear bars and/or circum-nuclear star forming rings in these objects and address the question of how these X-ray luminous AGN and their hosts are linked to optically/UV-bright QSOs, low-z QSOs/radio galaxies, or ULIRGs.     

Absorption features of QSOs

Absorption features shown by QSOs may be identified and measured as reported absorption redshift systems, or may remain unidentified and not measured. The features are believed to be observed in objects with high emission redshifts (z _em), although no quantitative analysis exists to examine any such preferential trend, except that by Basu (1982). However, redshift data have since increased enormously both in range of the redshift spectrum and in number. Furthermore, the earlier analysis was based on only the reported absorption redshifts while unidentified absorption features were not dealt with. The present paper analyses the updated data, both identified and unidentified features. It is found that absorption features may be expressed as exponential function ofz _em, and upper limits are set for the percentage of QSOs showing absorption features. Finally, an entirely new method of analysis confirms the earlier conclusion of Basu (1982) that the appearance of absorbing clouds is closely associated with the creation of the QSOs, the two may be having a common cause. It is suggested that absorption QSOs may be a separate class of QSOs whose birth is accompanied with creation of absorbing clouds.     

类星体色指数随红移的变化

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。     

Improved constraints on possible variation of physical constants from H i 21-cm and molecular QSO absorption lines

Quasar (QSO) absorption spectra provide an extremely useful probe of possible cosmological variation in various physical constants. Comparison of H  i 21-cm absorption with corresponding molecular (rotational) absorption spectra allows us to constrain variation in     , where α is the fine-structure constant and g _p is the proton g -factor. We analyse spectra of two QSOs, PKS 1413+135 and TXS 0218+357, and derive values of     at absorption redshifts of     and 0.6847 by simultaneous fitting of the H  i 21-cm and molecular lines. We find     and     respectively, indicating an insignificantly smaller y in the past. We compare our results with other constraints from the same two QSOs given recently by Drinkwater et al. and Carilli et al., and with our recent optical constraints, which indicated a smaller α at higher redshifts.     

Absorption line redshifts of QSOs in relation to their emission line redshifts

Analysis of the recent data indicate that absorption line redshifts of QSOs are significantly correlated to their emission line redshifts. It is concluded that the absorption lines originate in materials intrinsic to the QSOs.     

The redshift dependence of spectral index in powerful radio galaxies

We present and discuss in this paper the rest frame radio spectra (1–25 GHz) of a sample of fourteen radio galaxies atz >2 from the newly defined MRC/1Jy complete sample of 558 radio sources. These galaxies are among the most powerful radio sources known and range in luminosity from 1028-1028·8 watt Hz-1 at 1 GHz. We find that the median rest frame spectral index of this sample of galaxies atz >2 is significantly steeper than that of a matched luminosity sample of 3CRR galaxies which are at a much lower redshift (0.85 <z < 1.7). This indicates that spectral index correlates primarily with redshift, at least in the luminosity range considered here. The difference between the distributions of rest frame spectral curvatures for the two samples does not appear to be statistically significant. We suggest a new explanation for the steeper spectra of radio galaxies at high redshift involving steeper electron energy spectra at injection. Electron energy spectra are expected to steepen in a first-order Fermi acceleration process, at both non-relativistic and relativistic shock fronts, as the upstream fluid velocity decreases. This may well be the case at high redshifts: the hotter and denser circum-galactic medium at high redshifts could result in slower speeds for the hotspot and the jet material behind it. The smaller sizes of radio sources at higher redshifts provide support to this scenario. Since deceased.     

The X-ray variability of high-redshift QSOs

We present an analysis of X-ray variability in a sample of 156 radio-quiet quasars taken from the ROSAT archive, covering a redshift range  0.12)  in the sense that QSOs of the same X-ray luminosity are more variable at  z>2  . We discuss possible explanations for this effect. The simplest explanation may be that high-redshift QSOs are accreting at a larger fraction of the Eddington limit than local AGNs.     

The Hubble relation for a comprehensive sample of QSOs

A correlation between redshifts (z) and apparent magnitudes (V) (Hubble relation) of Quasi Stellar Objects (QSOs) has long been sought. Such a correlation exists for galaxies whose redshifts are of cosmological origin. However, a plot of the two quantities representing the Hubble diagram for QSOs exhibits, in general, a wild scatter. This raises the question whether redshifts of QSOs are cosmological. On the other hand, most luminous QSOs in groups, and subsamples with particular properties, have been reported to show the Hubble relation. In the present paper, we analyse all optically non-variable QSOs in a comprehensive sample. In our analysis we grouped the objects into certain intervals of apparent magnitudes. Correlations obtained between redshifts and magnitudes are all statistically robust. Also, the Hubble relation in the usual formV = 5 logz +C is obeyed very convincingly for QSOs withV < 19.5.     

Hydrogen-like nitrogen radio line from hot interstellar and warm-hot intergalactic gas

The hyperfine-structure lines of highly charged ions may allow one to look at hot rarefied astrophysical plasmas from a new perspective. In this paper, we discuss the spectral lines of ions and isotopes abundant at temperatures 10⁵–10⁷ K characteristic of a warm-hot intergalactic gas, a hot interstellar medium, starburst galaxies, their superwinds, and young supernova remnants. Observations of these lines will make it possible to study the bulk and turbulent motions in the observed objects and will supplement the information about the ionization state and chemical and isotopic compositions of the gas. The line of the main nitrogen isotope with wavelength λ = 5.65 mm is of particular interest. The wavelength of this line is well suited for observations of objects at z ≈ 0.15−0.6, when it is redshifted to the spectral range 6.5–9 mm widely used in ground-based radio observations, and, for example, for z ≥ 1.3, when the line is redshifted to 1.3 cm or farther. Modern and future radio telescopes and interferometers are capable of observing the ¹⁴N VII absorption by the warm-hot intergalactic gas at redshifts higher than z ≈ 0.15 in the spectra of the brightest millimeter-band sources. The submillimeter emission lines of the most abundant isotopes with hyperfine splitting may also be detected in the spectra of young supernova remnants. The article was translated by the authors.     

Radio spectra and polarization properties of radio-loud broad absorption-line quasars

We present multifrequency observations of a sample of 15 radio-emitting broad absorption-line quasars (BAL QSOs), covering a spectral range between 74 MHz and 43 GHz. They mostly display convex radio spectra which typically peak at about 1–5 GHz (in the observer's rest frame), flatten at MHz frequencies, probably due to synchrotron self-absorption, and become steeper at high frequencies, i.e. ν≳ 20 GHz. Very Large Array (VLA) 22-GHz maps (HPBW ∼80 mas) show unresolved or very compact sources, with linear projected sizes of ≤1 kpc. About two-thirds of the sample looks unpolarized or weakly polarized at 8.4 GHz, frequency in which reasonable upper limits could be obtained for polarized intensity. Statistical comparisons have been made between the spectral index distributions of samples of BAL and non-BAL QSOs, both in the observed and in the rest frame, finding steeper spectra among non-BAL QSOs. However, constraining this comparison to compact sources results in no significant differences between both distributions. This comparison is consistent with BAL QSOs not being oriented along a particular line of sight. In addition, our analysis of the spectral shape, variability and polarization properties shows that radio BAL QSOs share several properties common to young radio sources like compact steep spectrum or gigahertz peaked spectrum sources.     

Are QSOs local objects?

The similarities of the spectra of QSOs with those of Wolf-Rayet stars are pointed out. The emission spectrum of the earliest discovered QSO, 3C 273, in the ultraviolet and visible regions is interpreted as that of an object deficient in hydrogen like Wolf-Rayet stars but havingno redshift. The visible emission spectra of two other QSOs, 3C 48 and 3C 280.1, are also similarly interpreted. It is further assumed that the absorption lines of QSOs are produced in an expanding atmosphere so that they are violet shifted as in Wolf-Rayet stars. Fifty-four out of 55 narrow absorption lines of the QSO Q 1246-057 are interpreted on the assumption that the average velocity of the absorbing ions is 500 km s^–1, although the redshift theory can explain only 23 lines by invoking six different redshifts: Four of the five emission lines of the same object can be identified assuming no shift. Since the QSOs are here assumed to be comparatively local objects, the problems of energy supply, superluminal velocities, etc., raised by the conventional explanation do not arise in this case.Presently at the Institut für Physikalische und Theoretische Chemie, Universität Erlangen, F.R.G.     

Properties of Broad Band Continuum of Narrow Line Seyfert 1 Galaxies

We have performed a statistical study of the properties of the broadband continuum of Narrow Line Seyfert 1 galaxies (NLS1s) by collecting ratio,infrared, optical and X-ray continuum data from various databases and comparedthe results with control samples of Broad Line Seyfert 1 galaxies (BLSls). We findthat the fraction (～ 6%) of Radio Loud (RL) NLSls is significantly less than thatof BLS1s (～ 13%), which is caused by the lack of radio-very-loud sources in theformer. The rarity of RL NLS1s, especially radio-very-loud ones, is consistent withthe scenario of small black hole and high accretion rate for NLSls. Six new radio loudNLSls are found and five RL NLS1 candidates are presented. In comparison withthe BLS1s, the NLS1s tend to have stronger far infrared emission, cooler infraredcolors and redder B- K color, which suggests that NLS1s are hosted by dust-richernuclei. The NLS1s also show steeper soft X-ray spectrum and large soft X-rayto optical flux ratio, while a significant fraction show fiat soft X-ray spectra. Atleast two factors can account for this, absorption and spectral variability. We alsoperform a correlation analysis between various broad band data. It is found thatmost correlations identified for NLS1s are also valid for radio quiet BLS1s: (1) theoptical colors are anti-correlated with X-ray spectral index; (2) higher optical, X-ray and NIR luminosity objects show bluer optical colors and red H - K color; (3)higher luminosity objects show warmer IRAS color; (4) the radio loudness correlateswith B - K and X-ray to optical flux ratio. Radio loud objects behave somewhatdifferently in a few correlations.     

Ejections of population III objects seen as blueshifted QSOs?

We discuss the origin of the optical jets and the apparently associated cloud of QSOs in NGC 1097. There is a simple explanation for the jets in terms of ejection trails of supermassive black holes. In this interpretation, the trails provide the first direct evidence for the non-conservation of linear momentum in a two black hole collision. The cluster of quasars at the end of the jets is then naturally associated with objects which have been ejected by the merging pair of black holes. It is possible to interpret the spectral lines of these QSOs such that half of them are blueshifted relative to NGC 1097 while the other half is redshifted. We infer that the objects in the QSO cluster are not real QSOs but probably collapsed objects of lower mass. We argue that these objects are likely to represent the hypothetical population III black holes of Carretal.     

Magnitude and redshift distributions of QSOs

The peak in the distribution of apparent magnitude (V) of QSOs at 18.0 can be explained by loss of QSOs forV<-18.0 arising out of selection effects due to the availability of search lines necessary for the determination of redshifts and due to the misidentification of QSOs as Main-Sequence stars. ForV>18.0, the number of objects seem to fall off as they become progressively fainter and detection efficiency goes down. The present analysis also shows that a strong correlation exists between apparent magnitude and redshift of QSOs indicating redshifts are of cosmological origin.     

Detecting the most distant (z>7) objects with ALMA

Detecting and studying objects at the highest redshifts, out to the end of Cosmic Reionization at z>7, is clearly a key science goal of ALMA. ALMA will in principle be able to detect objects in this redshift range both from high-J (J>7) CO transitions and emission from ionized carbon, [CII], which is one of the main cooling lines of the ISM. ALMA will even be able to resolve this emission for individual targets, which will be one of the few ways to determine dynamical masses for systems in the Epoch of Reionization. We discuss some of the current problems regarding the detection and characterization of objects at high redshifts and how ALMA will eliminate most (but not all) of them.     

The proximity effect in a close group of QSOs

We present an analysis of the proximity effect in a sample of 10 2-Å-resolution QSO spectra of the Ly α forest at     . Rather than investigating variations in the number density of individual absorption lines, we employ a novel technique that is based on the statistics of the transmitted flux itself. We confirm the existence of the proximity effect at the > 99 per cent confidence level. We derive a value for the mean intensity of the extragalactic background radiation at the Lyman limit of     . This value assumes that QSO redshifts measured from high-ionization lines differ from the true systemic redshifts by     . We find evidence at a level of 2.6 σ that the significance of the proximity effect is correlated with QSO Lyman limit luminosity. Allowing for known QSO variability, the significance of the correlation reduces to 2.1 σ .
The QSOs form a close group on the sky and the sample is thus well suited for an investigation of the foreground proximity effect, where the Ly α forest of a background QSO is influenced by the UV radiation from a nearby foreground QSO. From the complete sample we find no evidence for the existence of this effect, implying either that     or that QSOs emit at least a factor of 1.4 less ionizing radiation in the plane of the sky than along the line of sight to Earth. We do, however, find one counter-example. Our sample includes the fortunate constellation of a foreground QSO surrounded by four nearby background QSOs. These four spectra all show underdense absorption within ±3000 km s⁻¹ of the redshift of the foreground QSO.     

Periodicity in quasar redshifts or selection effects?

Peaks at high redshifts in individual samples of quasars can be explained as due to selection effects. It is concluded that peaks in quasar redshift distribution do not obey any generalformula that can constitute a periodicity, even though individual samples may favour some redshifts of smaller values, viz. z < 1.     

An X-ray hubble diagram for quasi-stellar objects

To form the Hubble diagram for quasi-stellar objects (QSOs),we have made use of the recently published data on X-ray fluxes of 159 QSOs observed from the Einstein Observatory. The scatter in the Hubble diagram and the lack of an obvious redshift-flux density correlation for these QSOs have been attributed to the observational selection effect that the intrinsically less luminous QSOs can be detected only in the nearby region of space. When the optical, radio and X-ray selection effects are removed, keeping only the intrinsically brighter sources, we obtain a sample of 16 QSOs having a small dispersion in X-ray luminosities (〈 logL _x〉) = 46.12 ± 0.28), a statistically significant linear correlation between (logf _x, logcz) pairs and a slopeA =-1.906 ± 0.061 of the linear regression oflog f _x on logcz. This slope is consistent, at a confidence level of 95 per cent or greater, with the slope of-2.0 expected theoretically based on the assumption that the redshifts of QSOs are cosmological in nature.