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1.
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 −1Mpc  , 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   

2.
Image processing performed on a series of photographs of the superluminal Seyfert galaxy, 3C 120, shows the outer optical disc to consist of fragmented segments generally pointing toward the centre. One long arm of peculiar, separated knots comes off to the W and SW. A peculiar companion is seen along the line of the NW radio jet. In the interior, optical jets are detected which are aligned along the direction of the outer radio jets. A region of the sky 45 ×; 25 degrees around 3C120 is investigated. It is found that:
  1. A nebulous filament about 3/4 degree in length points to 3C 120.
  2. Hydrogen clouds of redshiftz = ?130 and ?210 km s?1 are situated at 3 and 1 degrees on either side of 3C 120.
  3. Eleven low-surface-brightness galaxies with 4500 <z < 5300 km s?1 fall within a radius of 8 degrees.
  4. Seven quasars withz ? 1.35 and radio fluxesS b ? 0.3 fall within a radius of 10 degrees.
It is concluded that the concentration of these objects in the vicinity of this unique, active galaxy has a negligible chance of being accidental and that all those objects of diverse redshift are at the same nearby distance. This smaller distance reduces the supposed superluminal motions in 3C 120 to quite precedented ejection velocities.  相似文献   

3.
《New Astronomy Reviews》2002,46(2-7):349-351
Our HST WFPC2 survey of 110 BL Lac objects, from six complete X-ray-, radio-, and optically-selected catalogs, probes the host galaxies of low-luminosity radio sources in the redshift range 0<z<1.35. The host galaxies are luminous ellipticals, well matched in radio power and galaxy magnitude to FR I radio galaxies. Similarly, the host galaxies of high luminosity quasars occupy the same region of this plane as FR II radio galaxies (matched in redshift). This strongly supports the unification of radio-loud AGN, and suggests that studying blazars at high redshift is a proxy for investigating less luminous (to us) but intrinsically identical radio galaxies, which are harder to find at high z. Accordingly, the difference between low-power jets in BL Lac objects and high-power jets in quasars can then be related to the FR I/FR II dichotomy; and the evolution of blazar host galaxies or their nuclei (jets) should correspond to the evolution of radio galaxies.  相似文献   

4.
We have compiled a catalog of 903 candidates for type 1 quasars at redshifts 3 < z < 5.5 selected among the X-ray sources of the “serendipitous” XMM-Newton survey presented in the 3XMMDR4 catalog (the median X-ray flux is ≈5 × 10?15 erg s?1 cm?2 in the 0.5–2 keV energy band) and located at high Galactic latitudes |b| > 20° in Sloan Digital Sky Survey (SDSS) fields with a total area of about 300 deg2. Photometric SDSS data as well infrared 2MASS and WISE data were used to select the objects. We selected the point sources from the photometric SDSS catalog with a magnitude error δ mz′ < 0.2 and a color i′ ? z′ < 0.6 (to first eliminate the M-type stars). For the selected sources, we have calculated the dependences χ2(z) for various spectral templates from the library that we compiled for these purposes using the EAZY software. Based on these data, we have rejected the objects whose spectral energy distributions are better described by the templates of stars at z = 0 and obtained a sample of quasars with photometric redshift estimates 2.75 < z phot < 5.5. The selection completeness of known quasars at z spec > 3 in the investigated fields is shown to be about 80%. The normalized median absolute deviation (Δz = |z spec ? z phot|) is σ Δz /(1+z spec) = 0.07, while the outlier fraction is η = 9% when Δz/(1 + z спек.) > 0.2. The number of objects per unit area in our sample exceeds the number of quasars in the spectroscopic SDSS sample at the same redshifts approximately by a factor of 1.5. The subsequent spectroscopic testing of the redshifts of our selected candidates for quasars at 3 < z < 5.5 will allow the purity of this sample to be estimated more accurately.  相似文献   

5.
We examine the recent report by Prochter et al. that gamma-ray burst (GRB) sight lines have a much higher incidence of strong Mg II absorption than quasar sight lines. We propose that the discrepancy is due to the different beam sizes of GRBs and quasars, and that the intervening Mg II systems are clumpy with the dense part of each cloudlet of a similar size as the quasars, i.e. ≲1016 cm, but bigger than GRBs. We also discuss observational predictions of our proposed model. Most notably, in some cases the intervening Mg II absorbers in GRB spectra should be seen varying, and quasars with smaller sizes should show an increased rate of strong Mg II absorbers. In fact, our prediction of variable Mg II lines in the GRB spectra has been now confirmed by Hao et al., who observed intervening Fe II and Mg II lines at z=1.48 to be strongly variable in the multi-epoch spectra of z=4.05 GRB 060206.  相似文献   

6.
The results of a comprehensive analysis of continuous radio spectra of a sample of Gigahertz-Peaked Spectrum (GPS) sources are reported. The sources are selected from a flux-density-complete sample (S ν ≥ 200 mJy at 4.8 or 5 GHz) using multifrequency measurements of the RATAN-600 radio telescope and data from the CATS astrophysical catalogs support system. The analysis revealed a very small number (1–2%) of “classical” GPS objects, which is significantly less than the expected fraction of 10%. GPS galaxies are found to have narrower and steeper radio spectra than quasars. The low-frequency part of the spectrum is seen to become steeper with increasing redshift. Galaxies and quasars at the same z have comparable angular sizes, whereas their luminosities may differ by one order of magnitude. At large redshifts there is a deficit of objects with low (several GHZ) peak frequencies. The number of GPS galaxies decreases sharply with redshift, and most of them are found at z between 0.01 and 1.81. GPS quasars are found at large redshifts, from 0.11 to 3.99. A quarter of the sample consists of blazars whose spectra may temporarily have a convex shape when the object is in active state.  相似文献   

7.
We present the results of optical spectroscopy for 19 quasar candidates at photometric redshifts z phot ? 3, 18 of which enter into the Khorunzhev et al. (2016) catalog (K16). This is a catalog of quasar candidates and known type 1 quasars selected among the X-ray sources of the 3XMM-DR4 catalog of the XMM-Newton serendipitous survey. We have performed spectroscopy for a quasi-random sample of new candidates at the 1.6-m AZT-33IK telescope of the Sayan Solar Observatory and the 6-m BTA telescope of the Special Astrophysical Observatory. The spectra at AZT-33IK were taken with the new low- and medium-resolution ADAM spectrograph that was produced and installed on the telescope in 2015. Fourteen of the 18 candidates actually have turned out to be quasars; 10 of them are at spectroscopic redshifts z spec > 3. The high purity of the sample of new candidates suggests that the purity of the entire K16 catalog of quasars is probably 70–80%. One of the most distant (z spec = 5.08) optically bright (i′ ? 21) quasars ever detected in X-ray surveys has been discovered.  相似文献   

8.
《New Astronomy Reviews》2000,44(7-9):503-510
AGNs with narrow Balmer lines show various extreme properties. In particular, rapid X-ray variability, steep X-ray spectra, peculiar optical and UV line ratios, and possibly peculiar line profiles. Since all these phenomena occur together they are likely to be related to one specific underlying physical parameter. I review recent evidence, based on HST imaging of low z quasars, which suggests that the Hβ line width and continuum luminosity of quasars provide a reasonably accurate estimate of the black hole mass. This implies that narrow-line AGN have relatively low black hole masses, and thus high L/LEdd, as independently suggested based on their steep X-ray spectra. I present additional evidence suggesting that the X-ray variability and the radio loudness are primarily driven by the black hole mass. The high mass inflow rate into the core of narrow-line AGNs may produce a denser and more enriched BLR, a high column radiation pressure driven outflow, and a smaller illumination angle for the NLR, as suggested by the observed emission line properties. Narrow-line AGNs may thus provide important clues for understanding the rich overall phenomenology of AGNs.  相似文献   

9.
We investigate the properties of the Lα absorption lines in the high resolution spectra of nine quasars, B2 1225+31.7, PKS 2126-158, Q 0002-422, Q 1453-423, PHL 957, PKS 0528-250, PKS 0805+046, PKS 1448-232 and PKS 1442+101. Their emission line redshift range is 2.20 ? zem ? 3.54; a total of 350 Lα absorption lines cover the range 1.70 ? zabs ? 3.54. Our analysis support the following conclusions; 1) the number density of Lα absorption lines is not significantly different in different quasars. 2) The number density does not vary significantly with redshift. 3) Their equivalent width spectrum does not vary significantly with redshift. 4) Their properties are the same whether in the wing of the Lα emission or in the continuum. 5) Their two-point correlation function is flat within the limit of resolution, which is different from the behaviour of galaxies. These results show that the Lα absorption lines in high-redshift quasars are very probably produced by intergalactic hydrogen clouds uniformly distributed throughout space.  相似文献   

10.
Polarization observations of the H2O maser emission at 1.35 cm from the active region Orion KL were carried out at epoch 2011.7 on the Svetloe-Zelenchukskaya radio interferometer. The observational data have been processed on the correlator of the QUASAR network. Fragments of the structure have been identified; the line velocities and profile widths and the emission polarization have been determined. The component at the radial velocity V = 7.0 km s?1 has been taken as a reference one. Its effective size in the Gaussian approximation is 1.5 mas, the axial ratio is Major/Minor = 3.3, and the orientation is PA = 11°. The component V = 7.6 km s?1 corresponds to a bipolar outflow with an effective size of 6.2 mas, the axial ratio is Major/Minor = 5.3, and the orientation ?32°. The bipolar outflow is 10 mas away from the reference feature in the direction of 173°. The longitudinal velocity components of the NW and SE parts of the bipolar outflow in the local standard of rest are +0.15 and ?0.15 km s?1, respectively. The degrees of polarization of the emission from the reference feature (7.0 km s?1) and the bipolar outflow are m = 39 and 52%, respectively. The difference in polarization orientations of both components ?? ?? does not exceed 3°.  相似文献   

11.
Co-evolution of Galaxies and AGNs in Hierarchical Galaxy Formation Models   总被引：1，自引：0，他引：1  
  相似文献   

12.
《Icarus》1987,72(3):555-567
The behavior of isolated pure and dusty gas jets ejected from an active spot on the sunlit side of the nucleus surface is hydrodynamically investigated in the inner coma of an H2O-dominated comet that is assumed to have no ambient ejection of the gas and dust from the dust-covered surface except the active spot. Steady-state solutions of the expanding jets are obtained by numerically solving the axisymmetric, time-dependent, coupled hydrodynamic equations of H2O gas and the dust in polar coordinates (r, θ, φ). The dust particles are treated as multicomponents composed of the three radii of a = 0.01, 0.1, and 1 μm. The boundary conditions of a slip wall are applied to the dust-covered surface. Discussion is given on the no-slip-wall conditions. Compared with the previous study on the jets surrounded by ambient gas and dust ejected from a nonactive region by Y. Kitamura (1986, Icarus 66, 241–257), the jet features can be clearly discerned even at large distances from the nucleus center, and the shift of the density peaks from the central axis to the wings, which was seen in the previous study, does not occur, because the jets can freely expand in the θ direction without being decelerated by the ambient gas and dust. The gas flow in the θ direction is supersonic, and consequently it is predicted that the shock waves are formed in the interactive regions among several jets. For the isolated jets with no ambient ejection, it is to be noted that the flow of the gas and dust along the nucleus surface arises in spite of the radial ejection from the active spot, and that this flow may change the surface structure. In the dusty case, the gas temperature increases immediately from 200 to ∼275°K in the vicinity of the surface owing to strong heating by the fine dust particles with the radius as small as 0.01 μm. In addition to the fine dust, the hot dust mantle (300–400°K) on the surface may considerably heat the gas near the mantle.  相似文献   

13.
The X-ray luminosity function of distant (3 < z < 5.1) type 1 quasars has been measured. A sample of distant high-luminosity (1045 erg s?1 ≤ LX,2?10 < 7.5×1045 erg s?1 in the 2–10 keV energy band) quasars from the catalog by Khorunzhev et al. (2016) compiled from the data of the 3XMM-DR4 catalog of the XMM-Newton serendipitous survey and the Sloan Digital Sky Survey (SDSS) has been used. This sample consists of 101 sources. Most of them (90) have spectroscopic redshifts zspec ? 3; the remaining ones are quasar candidates with photometric redshift estimates zphot ? 3. The spectroscopic redshifts of eight sources have been measured with the BTA and AZT-33IK telescopes. Owing to the record sky coverage area (?250 sq. deg at X-ray fluxes ~10?14 erg s?1 cm?2 in the 0.5–2 keVband) from which the sample was drawn, we have managed to obtain reliable estimates of the space density of distant X-ray quasars with luminosities LX,2?10 > 2×1045 erg s?1 for the first time. Their comoving space density remains constant as the redshift increases from z = 3 to 5 to within a factor of 2. The power-law slope of the X-ray luminosity function of distant quasars at its bright end (above the break) has been reliably constrained for the first time. The range of possible slopes for the quasar luminosity and density evolution model is γ2 = 2.72 ?0.12 +0.19 ± 0.21, where initially the lower and upper boundaries of γ2 with the remaining uncertainty in the detection completeness of X-ray sources in SDSS and subsequently the statistical error of the slope are specified.  相似文献   

14.
Two quasars SDSS J010013.02+280225.8 and J030642.51+185315.8 with redshifts z = 6.30 and z = 5.363 were recently discovered. Their apparent magnitudes in the standard cosmological model give the luminosities of Lbol ～ 4.3 × 1014L⊙ and Lbol ～ 3.4 × 1014L⊙. In the framework of modern concepts it is accepted that the energy release of quasars is provided by the accretion onto black holes with masses of 1.24 ± 0.19 × 1010M⊙ and 1.07 ± 0.27 × 1010M⊙. As within the standard cosmological model the ages of these objects are about one billion years, this creates serious difficulties for the scenario of formation of such objects. Here we interpret the ultra-high luminosities of quasars as the effect of lensing of their radiation by the foreground globular clusters or dwarf galaxies.  相似文献   

15.
We report on the results of a wide field near infrared survey for protostellar jets identified via their emission in the 2.12μm line of shock heated molecular hydrogen, done over a 1.2 square degree area in Orion A. We derive an evolutionary sequence for protostellar jets, based on the observed lenghts and H2 luminosities as well as the evolutionary stage and bolometric luminosity of their driving sources. Protostellar jets start from zero length, evolve quickly to parsec scale extents during the Class 0 phase, and shrink during the Class I and Class II phase. They are first very bright in H2 emission, and fade later on. This is indicative of strongly time-variably mass accretion onto the driving protostar, with a peak early on, and a subsequent continous decay of accretion activity. Finally, we present evidence for a molecular CO jet from a Class 0 object, supporting the idea that a very efficient outflow phase at very early evolutionary stages should produce very dense, molecular jets.  相似文献   

16.
Observations of three different sized regions centered on the optical jet spiral, NGC 1097 have been made with ROSAT. The PSPC observations show a striking excess of bright and medium flux X-ray sources around this hot spot nucleus, Seyfert 1 galaxy. The brightest of these sources are catalogued quasars which suggests the fainter X-ray sources are predominantly quasars also. If so, of the order of at least 10 and possibly considerably more X-ray quasars appear to be associated with NGC 1097 within a radius of 20. There is a marked segregation, with bright X-ray sources on the side of the bright optical jets and weak X-ray sources on the side of the fainter optical jets. Some, but not all, of this asymmetry could be accounted for by absorption in the plane of the spiral being tilted towards us on the weak source side. Both optical and X-ray evidence point to strong absorption in the disk of NGC 1097 which reaches far beyond the optical limits. High resolution imaging (HRI) of regions closer to NGC 1097 reveal some fainter pairs and lines of X-ray sources aligned across the nucleus near the cones defined by the optical jets. Filaments and patches of ultraviolet emission (1500–1700Å) appear to fill in the region between the strong optical jets in the direction of the bright X-ray quasars, suggesting physical association of the ultraviolet emission with the quasars and the galaxy. Finally, ROSAT SURVEY observations have been examined over a 4 × 4 degree field centered on NGC 1097. A line of X-ray sources going through the galaxy in the direction of the strongest optical jet includes a strong X-ray quasar with its X-ray isophotes extended toward NGC 1097. In approximately the opposite direction, 1.9 degrees distant, is a strong X-ray source (.5cts s-1) which is here identified with a 16.5 mag BL Lac object.  相似文献   

17.
We investigate the optical colors and radio morphologies of 214 broad absorption line (BAL) quasars with FIRST detections in the redshift range 1.68≤z≤4.93 drawn from the Sloan Digital Sky Survey (SDSS) Data Release 5 (DR5) quasar catalog. The radio-detected SDSS BAL quasars are found to have Δ(g?i) colors significantly redder than their non-BAL counterparts, with a mean color difference of 0.52 mag, in good agreement with the O–E (roughly B–R) color difference between radio-selected BAL and non-BAL quasars in the FIRST Bright Quasar Survey (FBQS). The vast majority (～90 %) of the radio-detected BAL quasars are found to be core-only sources, most of which show compact radio morphologies, consistent with the morphological results for the FBQS sample. Moreover, within the FIRST-detected SDSS sample, BAL quasars with GB6 detections are found to span a wide range in radio spectral indices, indistinguishable from that of non-BAL quasars, indicating no special line of sight for the presence of BALs. The properties of the present SDSS sample are more consistent with the evolutionary model, in which BALs are at an early evolutionary stage of quasars.  相似文献   

18.
The superfine structure of the bulge of the galaxy NGC 4258 has been investigated in H2O maser emission at the epochs on February 4, 2013, and November 29, 2013. The peak intensities of the spectral components reached F ≈ 5 Jy. The emission of the component at v = 476 km s-1 dominated at the beginning of this period; the second component at v = 487 km s-1 was observed at the end of the period. The structure is a chain of compact components up to 200 µas or 7mpc in extent. The velocity of the local standard of rest is v LSR = 482 km s-1. Two bright compact components with a separation between them Δρ ≈ 35 µas or 1.3 mpc and a pair of components spaced 13 µas apart, whose brightness reaches 30% of the peak value corresponding to a brightness temperature T b ≈ 1018 K, are located at the center. The sizes of the components are ~2–3 µas. A splitting and a shift of the two pairs of components relative to each other by 8 µas or 0.3 mpc in the 45° direction are observed at the end of the period. The velocity gradient of the structure is dV/dρ = 224 km s-1 mas-1, suggesting a solid-body rotation with a period T ≈ 760 years. The compact components correspond to the tangential directions of the arm. Two parallel chains of components corresponding to the tangential directions of the walls of the bipolar outflow carrying away an excess angular momentum are ejected from the central part of the bulge, two sources. The outflow is oriented at an angle X ≈ 15° relative to the disk axis. The brightness of the outflow fragments does not exceed 1.5% of the peak value. The ejection of material from the central part in the northward direction at a level up to 0.2%, T b ≈ 1015 K, is observed at the epoch on February 4, 2013, at v = 478 km s-1. The core structure suggests a double system: parallel disks–vortices spaced 0.25 mpc apart.  相似文献   

19.
In this paper, I have analysed the subarcsecond polarization structure of two high-z compact steep-spectrum quasars. Morphology suggests that the jets are interacting strongly with intergalactic medium. Models of bending by ram pressure equilibrium in a cooling flow and alignment of magnetic field lines by jet-IGM shock suggest that the CSS jets are light, supersonic and mildly relativistic. Particle energy index variations along the jet suggests replenishment triggered by such interactions.  相似文献   

20.
We present the results of a study which uses a sample of 1822 Sloan Digital Sky Survey (SDSS) quasars with reliable Wide-field Infrared Survey Explorer (WISE) detections in the redshift range 1.7≤z≤4.38 to investigate the mid-infrared fraction of broad absorption line (BAL) quasars. The BAL quasars in the sample include both high-ionization BAL (HiBAL) quasars that show broad absorption from C?iv and low-ionization BAL (LoBAL) quasars that show additional broad absorption from Mg?ii. The fraction of C?iv BAL quasars with nonzero absorption index (AI) is found to be 38.7±1.2 %, in good agreement with that derived for the Two Micron All Sky Survey (2MASS) sample. The C?iv BAL quasar fractions remain constant with magnitude in the WISE 3.4 μm (W1) and 4.6 μm (W2) bands, and increase rapidly with decreasing magnitude in the WISE 12 μm (W3) and 22 μm (W4) bands. The nonzero AI fraction of 44.5±2.1 % determined in the WISE W4 band is more likely to represent the intrinsic BAL quasar fraction. No evidence that the fraction is a strong function of redshift is found. At 1.7≤z≤2.15, the overall mid-infrared LoBAL fraction is $3.3^{+0.6}_{-0.5}~\%$ and the fractions increase significantly with decreasing magnitude in all four of WISE bands. Moreover, it is found that the mean optical-to-WISE colors of BAL quasars are ?0.2 mag redder than that of non-BAL quasars, while the traditional (nonzero balnicity) BAL quasars are redder than the nontraditional BAL quasars by ?0.15 mag, which suggest a continuum of more reddening from non-BAL to nontraditional BAL to traditional BAL. No evidence that nontraditional BALs are a distinct class from traditional BALs is found. Finally, it is shown that the mean optical-to-WISE colors of LoBALs are ?0.4 mag redder than that of HiBALs at 1.7≤z≤2.15.  相似文献   

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