Quasar Jets Research Articles

Jet collimation and acceleration in the flat spectrum radio quasar 1928+738

Using time-resolved multifrequency Very Long Baseline Array data and new KaVA (KVN and VERA Array) observations, we study the structure and kinematics of the jet of the flat spectrum radio quasar (FSRQ) 1928+738. We find two distinct jet geometries as a function of distance from the central black hole, with the inner jet having a parabolic shape, indicating collimation, and the outer jet having a conical shape, indicating free expansion of the jet plasma. Jet component speeds display a gradual outward acceleration up to a bulk Lorentz factor Γmax ≈ 10 followed by a deceleration further downstream. The location of the acceleration zone matches the region where the jet collimation occurs. Therefore, this is the first direct observation of an acceleration and collimation zone (ACZ) in an FSRQ. The ACZ terminates approximately at a distance of 5.6 × 106 gravitational radii, which is in good agreement with the sphere of gravitational influence of the supermassive black hole, implying that the physical extent of the ACZ is controlled by the black hole gravity. Our results suggest that confinement by an external medium is responsible for the jet collimation and that the jet is accelerated by converting Poynting flux energy to kinetic energy.

ЖИТТЯ ГАЛАКТИК У СПОСТЕРЕЖУВАНОМУ ВСЕСВІТІ. ЧАСТИНА 2

The exchange of hydrogen between galaxies and the galactic structures that ensure this process are considered. This exchange between the main objects of the Universe was given in the first part of the article, but it was not considered there as another and important process of the galactic cycle. However, the largest structures in the observable Universe are associated with the exchange of the lightest gas. This circumstance allows us to rightfully distinguish it as the next process of the galactic cycle. In the second process, determined by the phase of the quasar in the galactic core, stellar waste is disposed of. Weak quasar jets eject the results of recycling either into the halo of their own galaxy or into its immediate vicinity. From these emissions, stars are formed directly in the galaxy, or near it. As a rule, these are stars from the galaxy's own matter. High-speed jets contain particles at their bases that move at speeds faster than the speed of light. This allows jets to eject matter far beyond the boundaries of the parent galaxy. The matter of such a jet leaves the galaxy forever. Quasars turn on periodically and relatively rarely change the direction of their emissions. Therefore, they often send streams of matter in one direction. Observable intergalactic filaments are formed from energetic flows. Given that clusters contain many galaxies and each of them goes through quasar stages, several filaments may emerge from the cluster. Therefore, filaments begin and end on galaxies, or their clusters. Outgoing filaments, if they are located nearby and equally directed, can unite with each other, forming large filaments. The question of the forces contributing to the unification of almost parallel jets remains open. The filaments contain hot hydrogen, some dust, “metals,” stars and galaxies. Hydrogen in filaments is expected with a minimal percentage of “metals”. In the filaments, stars and galaxies can form from the available gas. This often happens where the threads intersect with each other. Filaments from other sources fall into the gravitational field of a galaxy, or cluster of galaxies. By delivering the necessary building material, filaments introduce new stellar life into the basic elements of the Universe. Therefore, filaments are channels that provide life to galaxies. This process of hydrogen exchange between galaxies is the fourth galactic process. He refines the model of galaxy life in the observable Universe, which is presented in the first part of the article

Superluminal Motion and Jet Parameters in the Gamma-ray-Emitting Narrow-Line Seyfert 1 Galaxy TXS 1206+549

Narrow-line Seyfert 1 (NLS1) galaxies are a peculiar subclass of active galactic nuclei (AGN). Among them, TXS 1206+549 belongs to a small group of radio-loud and γ-ray-emitting NLS1 galaxies. We focus on the radio properties of this galaxy by analysing archival, high-resolution, very long baseline interferometry (VLBI) imaging observations taken at 8 GHz frequency in six epochs between 1994 and 2018. Using the milliarcsecond-scale radio structure, we can resolve a core and a jet component whose angular separation increases by (0.055±0.006) mas yr−1. This corresponds to an apparent superluminal jet component motion of (3.5±0.4)c. From the core brightness temperature and the jet component proper motion, we determine the characteristic Doppler-boosting factor, the bulk Lorentz factor, and the jet viewing angle. We find no compelling evidence for a very closely aligned blazar-type jet. The parameters for TXS 1206+549 resemble those of radio-loud quasar jets with a moderate Lorentz factor (Γ≈4) and ϑ≈24∘ inclination to the line of sight.

Cosmo-tomography toward PKS 1830−211: Variability of the quasar and of its foreground molecular absorption monitored with ALMA

Context. Time variability of astronomical sources provides crude information on their typical size and on the implied physical mechanisms. PKS 1830−211 is a remarkable radio-bright lensed quasar with a foreground molecular absorber in the lens galaxy at z = 0.89. Small-scale morphological changes in the core–jet structure of the quasar – which is magnified by the lensing – result in a varying illumination of the absorber screen, which in turn causes variations in the absorption profile. Aims. We aim to study the time variations of the system (the two main lensed images of the quasar and the two corresponding sightlines in the absorber) in order to obtain constraints on both the quasar activity and small-scale structures in the interstellar medium of the absorber. Methods. We used ALMA to monitor the submillimeter continuum emission of PKS 1830−211, together with the absorption spectra of the H2O and CH molecules, with 17 visits spread over six months in 2016. Complementing this, we used available ALMA data to investigate changes in the system in the period 2012−2022. Results. From the continuum data, we followed the evolution of the flux density, flux-density ratio, spectral index, and differential polarization between the two lensed images of the quasar; all quantities show significant variations related to the intrinsic activity of the quasar. We propose a simple parametric model of a core plus a ballistic plasmon to account for the continuum evolution, from which we constrain a time delay of 25 ± 3 days between main lensed images. The spectral lines reveal significant variations in the foreground absorption profile. A principal component analysis highlights apparent wavy time variations, possibly linked to the helical jet precession period of the quasar. From the deep averaged spectra towards the southwest image, we detect the absorption of the rare isotopolog 13CH and estimate an abundance ratio of 12CH/13CH ∼ 150. We also measure the oxygen isotopic ratios, 16O/18O = 65.3 ± 0.7 and 18O/17O = 11.5 ± 0.5 in the z = 0.89 absorber. Finally, we find a remarkable continuous shallow trough in the water absorption spanning a velocity interval of nearly 500 km s−1. This broad absorption could be the signature of an extra-planar molecular component. Conclusions. All together, the system formed by the quasar PKS 1830−211 and its foreground lens–absorber acts as a powerful gravitational microscope, providing us with the possibility to dissect small-scale structures in both the ISM of the foreground absorber and the jet of the background quasar.

Jets in radio galaxies and quasars: an observational perspective

This article gives a brief historical introduction and reviews our current understanding of jets in radio galaxies and quasars from an observational perspective, with an emphasis on observations at radio wavelengths. Recent results on the Fanaroff-Riley classification scheme, and the nature of radio structures and jets in the FR classes as well as in high-excitation and low-excitation radio galaxies are summarized. The collimation and propagation of jets from nuclear sub-pc to hundreds of kpc scales from both observatinoal and theoretical work have been discussed. The jets exhibit evidence of interaction with a clumpy interstellar medium, especially in young radio sources, and could trigger both star formation as well as suppress star formation depending on the physical conditions. Observational evidence for such interactions and jet feedback which have profound implications in our understanding of galaxy evolution have been presented. Recurrent jet activity which has been seen over a wide range of projected linear size and time scales has been discussed. This review article concludes with a brief discussion of unresolved questions on jets which new telescopes should help address.

Collimation of the Relativistic Jet in the Quasar 3C 273

The collimation of relativistic jets launched from the vicinity of supermassive black holes (SMBHs) at the centers of active galactic nuclei (AGNs) is one of the key questions to understand the nature of AGN jets. However, little is known about the detailed jet structure for AGN like quasars since very high angular resolutions are required to resolve these objects. We present very long baseline interferometry (VLBI) observations of the archetypical quasar 3C 273 at 86 GHz, performed with the Global Millimeter VLBI Array, for the first time including the Atacama Large Millimeter/submillimeter Array. Our observations achieve a high angular resolution down to ∼60 μas, resolving the innermost part of the jet ever on scales of ∼105 Schwarzschild radii. Our observations, including close-in-time High Sensitivity Array observations of 3C 273 at 15, 22, and 43 GHz, suggest that the inner jet collimates parabolically, while the outer jet expands conically, similar to jets from other nearby low-luminosity AGNs. We discovered the jet collimation break around 107 Schwarzschild radii, providing the first compelling evidence for structural transition in a quasar jet. The location of the collimation break for 3C 273 is farther downstream from the sphere of gravitational influence (SGI) from the central SMBH. With the results for other AGN jets, our results show that the end of the collimation zone in AGN jets is governed not only by the SGI of the SMBH but also by the more diverse properties of the central nuclei.

Detections of inflowing gas from narrow absorption lines at parsec scales

The detection of inflows at the scale of the dusty torus and smaller is crucial for investigating the process of supermassive black hole (SMBH) accretion. However, only a few cases of inflowing gas at small scales have been reported through redshifted broad absorption lines so far. Here we report nine redshifted narrow absorption lines (NALs) of Mg+ions with inflowing speeds of 1071–1979 km s−1, which are likely along the directions close to the axes of accretion disks. The quasars showing inflowing Mg IINALs have, on average, slightly smaller Eddington ratios than the sources with outflowing Mg IINALs. The upper limits on the locations of the detected NALs are at parsec scale, that is, the distance from dusty tori to their central SMBHs. One possible origin of these infalling NALs is from dusty tori. However, these infalling NALs could also be naturally explained by chaotic cold accretion resulting from the nonlinear interaction of active galactic nucleus (AGN) jets with the interstellar medium (ISM), and these cold gaseous blobs may originally precipitate in metal-rich trailing outflows uplifted by AGN jet ejecta. The infalling NALs may therefore provide direct evidence for cold gas precipitation and accretion in AGN feedback processes, and provide direct evidence of inflowing gas along the directions close to quasar jets and at parsec scale. Regardless of whether these infalling NALs are from the dusty tori or the interaction of AGN jets with the ISM, the infalling NALs cannot provide sufficient fuel to power the quasars.

Multiphase Outflows in High-redshift Quasar Host Galaxies

Abstract We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of six radio-loud quasar host galaxies at z = 1.4–2.3. We combine the kiloparsec-scale resolution ALMA observations with high spatial resolution adaptive optics integral field spectrograph data of the ionized gas. We detect molecular gas emission in five quasar host galaxies and resolve the molecular interstellar medium using the CO (3–2) or CO (4–3) rotational transitions. Clumpy molecular outflows are detected in four quasar host galaxies and a merger system 21 kpc away from one quasar. Between the ionized and cold molecular gas phases, the majority of the outflowing mass is in a molecular phase, while for three out of four detected multiphase gas outflows, the majority of the kinetic luminosity and momentum flux is in the ionized phase. Combining the energetics of the multiphase outflows, we find that their driving mechanism is consistent with energy-conserving shocks produced by the impact of the quasar jets with the gas in the galaxy. By assessing the molecular gas mass to the dynamics of the outflows, we estimate a molecular gas depletion timescale of a few megayears. The gas outflow rates exceed the star formation rates, suggesting that quasar feedback is a major mechanism of gas depletion at the present time. The coupling efficiency between the kinetic luminosity of the outflows and the bolometric luminosity of the quasar of 0.1%–1% is consistent with theoretical predictions. Studying multiphase gas outflows at high redshift is important for quantifying the impact of negative feedback in shaping the evolution of massive galaxies.

ГУСТИНА СЕРЕДОВИЩА ВЕЛЕТЕНСЬКОЇ РАДІОСТРУКТУРИ ДЛЯ ГАЛАКТИК І КВАЗАРІВ З КРУТИМИ РАДІОСПЕКТРАМИ

Purpose: Estimate of the environment density of giant (with the linear size of about megaparsec) radio structures for galaxies and quasars with steep low-frequency spectra taken from the UTR-2 catalogue. Study of the cosmological evolution of environment density of giant radio sources. Determination of dependence of contribution of radio lobes into the emission of giant sources with respect to their environment density. Design/methodology/approach: We use the sample of sources from the UTR-2 catalogue of extragalactic sources to estimate the environment density for giant sources with steep low-frequency spectra. The selection criteria for the examined objects are the following: 1) the spectral index value is equal or larger than 1; 2) the fl ux density of emission at the frequency of 25 MHz is larger than 10 Jy; 3) the sample sources are optically identifi ed. The value of environment density of examined sources is obtained with the assumption of equality of source jet luminosity (at the synchrotron mechanism of radio emission) and its corresponding kinetic luminosity. The analysis of the estimates of environment densities is made for different classes of the sample objects (for galaxies and quasars with linear steep spectra and with break steep spectra). Findings: The estimates of environment density have been derived for giant radio structures formed by the jets of sources with steep spectrum from the UTR-2 catalogue. On the average, the environment density for the quasar structure (~ 10-28 g/sm3) is lesser than the one for the galaxies (~ 10-27 g/sm3 to ~ 10-26 g/sm3). The larger jet environment density is typical for the galaxies and quasars with the break steep spectra than for those with the linear steep spectra. The inverse power relation of the jet environment density and the source redshift (the cosmological evolution of the jet environment density) has been derived. The contribution of jet-related radio lobes into the emission of sources displays the inverse power relation for the environment density of the corresponding radio structures. Conclusions: The mean values of obtained estimates of environment density of giant jets of radio sources with steep low-frequency spectra indicate the lesser environment density of quasar jets than that for the galaxy jets. Giant radio sources with steep low-frequency spectrum (especially, with break steep spectrum) reveal considerable evolution of environment density of jets. The larger contribution of radio lobes (jets) into the emission of sources corresponds to the lesser environment density of sources taken from the UTR-2 catalogue. It can be due to propagation of jets (surrounded by radio lobes) from powerful radio sources to distances of about megaparsec, until the balance of source’s environment density and extragalactic environment density is reached. Key words: steep low-frequency radio spectrum; giant radio structure; jets; radio lobes; galaxies; quasars; environment density

Enhanced X-Ray Emission from the Most Radio-powerful Quasar in the Universe’s First Billion Years

Abstract We present deep (265 ks) Chandra X-ray observations of PSO J352.4034−15.3373, a quasar at z = 5.831 that, with a radio-to-optical flux ratio of R > 1000, is one of the radio-loudest quasars in the early universe and is the only quasar with observed extended radio jets of kiloparsec scale at z ≳ 6. Modeling the X-ray spectrum of the quasar with a power law, we find a best fit of Γ = 1.99 − 0.28 + 0.29 , leading to an X-ray luminosity of L 2 – 10 = 1.26 − 0.33 + 0.45 × 10 45 erg s − 1 and an X-ray to UV brightness ratio of α OX = −1.45 ± −0.11. We identify a diffuse structure 50 kpc (∼8″) to the NW of the quasar along the jet axis that corresponds to a 3σ enhancement in the angular density of emission and can be ruled out as a background fluctuation with a probability of P = 0.9985. While with few detected photons the spectral fit of the structure is uncertain, we find that it has a luminosity of L 2–10 ∼ 1044 erg s−1. These observations therefore potentially represent the most distant quasar jet yet seen in X-rays. We find no evidence for excess X-ray emission where the previously reported radio jets are seen (which have an overall linear extent of 0.″28), and a bright X-ray point source located along the jet axis to the SE is revealed by optical and NIR imaging to not be associated with the quasar.

ГАЛАКТИЧНІ СЛІДИ РЕГЕНЕРАЦІЇ ВОДНЮ

The article discusses direct consequences of hydrogen regeneration mechanisms observed in galaxies when galactic nuclei are active. Previously, these mechanisms have been presented by describing the work of structures that form quasar jets. Based on evaluation of the findings obtained through observation of our Galaxy and intergalactic space, the present article gives direct evidence that the aforementioned processes exist. The adduced evidence is astronomical objects that have come into existence as a result of hydrogen ejected by jets together with plasma and dust. In terms of the Milky Way galaxy, this fact is emphasised by direct astronomical observation of its elements. There are also evidential findings among intergalactic astronomy observational data, whose origin is explained comprehensively in terms of the present approach. However, the provided findings are traditionally regarded from the prevailing Big Bang theory perspective. For instance, according to this theory, huge intergalactic hydrogen clouds are interpreted as residual hydrogen left from the primary explosion. The Milky Way observation results include data indicative of alleged contribution of the given processes to formation of some of its structural elements, including a number of satellite galaxies. There is a criterion whereby it is possible to distinguish galactic gas clouds and star clusters formed of galactic matter itself. This matter containing a great deal of regenerated hydrogen was ejected from a galactic nucleus during the period of its activity. Based on the example of a spiral galaxy, it is assumed that active galactic nuclei are possibly involved in the formation of its morphology. It is concluded that, when being active, a central supermassive object performs its primary function, which is to process waste produced during the life of stars. This process is the final link in the galactic life cycle, which consists of two reciprocal processes. The first one is about hydrogen burning continuously in stars, while the second one is about episodic activity of the galactic nucleus, which results in star waste that contributes to regeneration of hydrogen needed to maintain direct processes within the galaxy. The two specified processes are associated with one more process: stellar electromagnetic radiation energy extended beyond the galaxy partially returns to it. The process is completed due to a fragment of dark matter. The overarching conclusion can be drawn: as a functional system, the Universe is well-organised and self-sufficient to last forever.

Inverse Compton Scattering of Radiation from a Central Source as a Possible Mechanism for the Formation of X-Ray Radiation from Kiloparsec Jets of Core-Dominated Quasars

For the interpretation of X-ray radiation from kiloparsec jets of quasars, the inverse Compton scattering of the cosmic microwave background has been widely used for almost 20 years. A recent analysis of the Fermi-LAT observational data showed that this assumption is inapplicable for jets of several quasars. In this paper, we consider the inverse Compton scattering of photons from a central source as a possible mechanism for the formation of X-ray radiation from kiloparsec jets of the quasars PKS 0637-752, 3C 273, PKS 1510-089, and PKS 1045-188. Estimates for the angle between the line of sight and the velocity of kiloparsec-scale jets are obtained. The predicted gamma-ray flux for all objects turned out to be below the upper limit on the flux from a kiloparsec jet obtained from the Fermi-LAT data. It is shown that our assumption about the mechanism of kiloparsec jets X-ray radiation is consistent with all data of multiwavelength observations available to date.

Unraveling the Physics of Quasar Jets: Optical Polarimetry and Implications for the X-ray Emission Process

Since the launch of Chandra twenty years ago, one of the greatest mysteries surrounding Quasar Jets is the production mechanism for their extremely high X-ray luminosity. Two mechanisms have been proposed. In the first view, the X-ray emission is inverse-Comptonized CMB photons. This view requires a jet that is highly relativistic (bulk Lorentz factor >20–40) on scales of hundreds of kiloparsecs, and a jet that is comparably or more powerful than the black hole’s Eddington luminosity. The second possibility is synchrotron emission from a high-energy population of electrons. This requires a much less powerful jet that does not need to be relativistically beamed, but it imposes other extreme requirements, namely the need to accelerate particles to >100 TeV energies at distances of hundreds of kiloparsecs from the active nucleus. We are exploring these questions using a suite of observations from a diverse group of telescopes, including the Hubble Space Telescope (HST), Chandra X-ray Observatory (CXO), Fermi Gamma-ray Space Telescope and various radio telescope arrays. Our results strongly favor the hypothesis that the X-ray emission is synchrotron radiation from a separate, high-energy electron population. We discuss the observations, results and new questions brought up by these surprising results. We investigate the physical processes and magnetic field structure that may help to accelerate particles to such extreme energies.

The Energetics of Launching the Most Powerful Jets in Quasars: A Study of 3C 82

Abstract 3C 82 at a redshift of 2.87 is the most distant 3C (Third Cambridge Catalogue) quasar. Thus, it is a strong candidate to have the most-luminous radio lobes in the universe. 3C 82 belongs to the class of compact steep-spectrum radio sources. We use single-dish and interferometric radio observations in order to model the plasma state of these powerful radio lobes. It is estimated that the long-term time-averaged jet power required to fill these lobes with leptonic plasma is , among the largest time-averaged jet powers from a quasar. Positing protonic lobes is not tenable as they would require two orders of magnitude more mass transport to the lobes than was accreted to the central black hole during their formation. The first high signal-to-noise optical spectroscopic observation obtained of this object indicates that there is a powerful high-ionization broad-line wind with a kinetic power of ∼1045 erg s−1 and a velocity of ∼0.01c. We also estimate from the broad lines in 2018 and the UV continuum in three epochs spread out over three decades that the accretion flow bolometric luminosity is L bol ≈ 3.2–5.8 × 1046 erg s−1. The ratio of is perhaps the largest of any known quasar. Extremely powerful jets tend to strongly suppress powerful winds of ionized baryonic matter. Consequently, 3C 82 provides a unique laboratory for studying the dynamical limits of the central engine of outflow initiation in quasars.

Inverse-Compton scattering in the resolved jet of the high-redshift quasar PKS J1421−0643

ABSTRACT Despite the fact that kpc-scale inverse-Compton (iC) scattering of cosmic microwave background (CMB) photons into the X-ray band is mandated, proof of detection in resolved quasar jets is often insecure. High redshift provides favourable conditions due to the increased energy density of the CMB, and it allows constraints to be placed on the radio synchrotron-emitting electron component at high energies that are otherwise inaccessible. We present new X-ray, optical, and radio results from Chandra, HST, and the VLA for the core and resolved jet in the z = 3.69 quasar PKS J1421−0643. The X-ray jet extends for about 4.5 arcsec (32 kpc projected length). The jet’s radio spectrum is abnormally steep and consistent with electrons being accelerated to a maximum Lorentz factor of about 5000. Results argue in favour of the detection of iC X-rays for modest magnetic field strength of a few nT, Doppler factor of about 4, and viewing angle of about 15°, and predict the jet to be largely invisible in most other spectral bands including the far- and mid-infrared and high-energy gamma-ray. The jet power is estimated to be about 3 × 1046 erg s−1 which is of order a tenth of the quasar bolometric power, for an electron–positron jet. The jet radiative power is only about 0.07 per cent of the jet power, with a smaller radiated power ratio if the jet contains heavy particles, so most of the jet power is available for heating the intergalactic medium.

Jet efficiencies and black hole spins in jetted quasars

ABSTRACT The mechanisms responsible for the production of relativistic jets from supermassive black holes (SMBHs) accreting at near-Eddington rates are not well understood. Simple theoretical expectations indicate that SMBHs in quasars accrete via thin discs which should produce at most very weak jets. This is contradicted by observations of powerful jets in flat-spectrum radio quasars (FSRQs). We use gamma-ray luminosities observed with the Fermi Large Area Telescope as a proxy of the jet power for a population of 154 FSRQs. Assuming typical quasar accretion rates and using black hole (BH) mass measurements from a variety of methods, we find a mean jet production efficiency of about 10 per cent for FSRQs, with values as high as 222 per cent. We find that this is consistent with FSRQs hosting moderately thin, magnetically arrested accretion discs around rapidly spinning BHs. Modelling our observations using general relativistic magnetohydrodynamic (GRMHD) simulations of jets from thin discs, we find an average lower limit of a* = 0.59 for the SMBH spins of FSRQs, with tendency for the spins to decrease as the BH mass increases. Our results are consistent with the merger-driven evolution of SMBHs. 3 per cent of the sample cannot be explained by current GRMHD models of jet production from Kerr BHs due to the high efficiencies. Along the way, we find a correlation between BH masses and Lγ which may be an useful mass estimator in blazar gamma-ray studies.

ALMA 50-parsec-resolution Imaging of Jet–ISM Interaction in the Lensed Quasar MG J0414+0534

Abstract We report our high-resolution (0.″03–0.″07) Atacama Large Millimeter/submillimeter Array (ALMA) imaging of the quadruply lensed radio-loud quasar MG J0414+0534 at redshift z = 2.639 in the continuum and the broad CO(11−10) line at ∼340 GHz. With the help of strong lensing magnification and ALMA’s high resolution, we succeeded in resolving the jet/dust and CO gas in the quasar host galaxy, both extending up to ∼1 kpc, with a resolution of ∼50 pc for the first time. Both the continuum emission and the CO(11−10) line have a similar bimodal structure aligned with the quasar jets (∼200 pc) observed by Very Long Baseline Interferometry at 5 and 8.4 GHz. The CO gas in the vicinity of both the eastern and western jet components at the location of ∼80 pc from the quasar core are moving at high velocities, up to ±600 km s−1 relative to the core. The observed features show clear evidence of strong interaction between the jets and interstellar medium (ISM). High temperature and high-density environments in the ISM of the quasar host galaxy, as suggested from CO line ratios, also support this result. The small scale of the jets, the jet–ISM interaction, and the continuum spectral energy distribution of this source indicate that we are watching the infancy stage of quasar radio activity.

A Tentative Observation Design for Investigating the Morphology of Dark Matter in the Universe

Unlike the luminous objects observed, dark matter does not emit light but can be only detected by its gravitational effect. Modern cosmology considers that most matter in Universe is dark matter. However, it is still not clear what the dark matter was. Two origins have been proposed by astrophysicists, astrophysics candidates and particle physics candidates. The most differences are their morphology, the former are compact objects and the latter are dispersed. Under Einstein’s theory of general relativity, light bends as it passes near a compact object, creating a convergence effect like a lens. When background light source, intervening lense and the observer lie on a straight line, the brightness of the background source will be significantly magnified. In astrophysics, this effect is called microlensing. If compact dark matter is abundant in the universe, it is possible to frequently observe “microlensing” events when observing high redshift objects, i.e. the objects temporarily brighten for a certain time. The microlensing technique has been applied to study the dark matter in halo of Milky Way. The difficulty occurs when applying to study the cosmic dark matter as the crossing time of cosmic microlensing events is too long for observations. Apparent superluminal jets in bright quasars are idea background objects, significantly enhancing the efficiency of cosmic microlensing survey. Here, we tentatively designed an observational experiment to study the morphology of dark matter in Universe via statistics of microlensing events towards luminous quasars with apparent superluminal jets.

Exploring the Morphology and Origins of the 4C 38.41 Jet

Abstract We study the properties of the innermost jet of the flat spectrum radio quasar 1633+382 (4C 38.41) based on very long baseline interferometry (VLBI) data from the radio monitoring observations of the Boston University VLBI program at 43 GHz. Analysis of the components suggests a semi-parabolic jet geometry with jet radius R following the relation R ∝ r 0.7 with distance r, with indications of a jet geometry break toward a conical geometry. Brightness temperature falls with distance following T B ∝ r −2.1. Combining this information, magnetic field and electron densities are found to fall along the jet as B ∝ r −1.5 and n ∝ r −1.1, respectively, suggesting that the magnetic configuration in the jet may be dominated by the poloidal component. Our analysis of the jet structure suggests that the innermost jet regions do not follow a ballistic trajectory and, instead, match a sinusoidal morphology, which could be due to jet precession from a helical pattern or Kelvin–Helmholtz instabilities.

Inverse Compton Scattering of the Central Source Photons as an X-Ray Emission Mechanism on Kiloparsec Scales in PKS 1127–145

Abstract The beamed inverse Compton/cosmic microwave background model has generally been used for the interpretation of X-ray radiation from kiloparsec-scale jets of core-dominated quasars. Recent Fermi-LAT and HST observations have brought this model into question. We examine the assumption that X-rays from the kiloparsec-scale jet of the quasar PKS 1127−145 are produced by inverse Compton scattering of the central source emission. In this context, we show that both similarity and distinction between the observed radio and X-ray spectral indices for some of the jet knots can be explained under a single power-law electron energy distribution. We derive that the viewing angle of the kiloparsec-scale jet is about 35° and the jet has a moderate relativistic speed of ≈0.8c. The predicted gamma-ray flux of the jet is found to be a few orders of magnitude lower than the minimum flux level measured by Fermi-LAT, further supporting our scenario.