Probing magnetic fields in high-redshift galactic systems is crucial to investigate galactic dynamics and evolution. Utilizing the rotation measure of the background quasars, we have developed a radial profile of the magnetic field in a typical high-$z$ galaxy. We have compiled a catalog of 59 confirmed quasar sightlines, having one intervening Mg \rom{2} absorber in the redshift range $0.372\leq z_{\text{abs}} \leq 0.8$. The presence of the foreground galaxy is ensured by comparing the photometric and spectroscopic redshifts within $3 σ_{z-\text{photo}}$ and visual checks. These quasar line-of-sights (LoS) pass through various impact parameters (D) up to $160$ kpc, covering the circumgalactic medium of a typical Milky-Way type galaxy. Utilizing the residual rotation measure (RRM) of these sightlines, we estimated the excess in RRM dispersion, $σ_{\text{ex}}^{\text{RRM}}$. We found $σ_{\text{ex}}^{\text{RRM}}$ decreases with increasing D. We translated $σ_{\text{ex}}^{\text{RRM}}$ to average LoS magnetic field strength, $\langle B_{\|}\rangle$ by considering a typical electron column density. Consequently, the decreasing trend is sustained in the magnetic field. In particular for sightlines with $\text{D} \leq 50$ kpc and $\text{D} > 50$ kpc, $\langle B_{\|}\rangle$ is found to be $2.39 \pm 0.7 \ μ$G and $1.67 \pm 0.38 \ μ$G, respectively. This suggests a clear indication of varying magnetic field from the disk to the circumgalactic medium. This work provides a methodology that, when applied to ongoing and future radio polarisation surveys such as LOFAR and SKA, promises to significantly enhance our understanding of magnetic field mapping in galactic systems.
We obtained rotation measures of 2642 quasars by cross-identification of the most updated quasar catalog and rotation measure catalog. After discounting the foreground Galactic Faraday rotation of the Milky Way, we get the residual rotation measure (RRM) of these quasars. We carefully discarded the effects from measurement and systematical uncertainties of RRMs as well as large RRMs from outliers, and get marginal evidence for the redshift evolution of real dispersion of RRMs which steady increases to 10 rad m$^{-2}$ from $z=0$ to $z\sim1$ and is saturated around the value at higher redshifts.…
The effect of gravitational Faraday rotation was predicted in the 1950s, but there is currently no practical method for measuring this effect. Measuring this effect is important because it will provide new evidence for correctness of general relativity, in particular, in the strong field limit. We predict that the observed degree and angle of the X-ray polarization of a cosmologically distant quasar microlensed by the random star field in a foreground galaxy or cluster lens vary rapidly and concurrently with flux during caustic-crossing events using the first simulation of quasar X-ray microle…
Through the use of a High Band Antenna system, the Low Frequency Array Two-Meter Sky Survey (LoTSS) is an attempt to complete a high-resolution survey of the northern celestial sky. To date, thousands of radio sources have been classified by LOFAR with most of them consisting of active galactic nuclei (AGN). The strong AGN emissions detected by LoTSS, it is thought, are powered by supermassive black holes (SMBHs) at the center of galaxies. During an analysis of 1500 images of these AGNs, we identified 10 radio sources with radial spokes emitted from an unknown source. According to LOFAR, the r…
We use X-ray and optical microlensing measurements to study the shape of the dark matter density profile in the lens galaxies and the size of the (soft) X-ray emission region. We show that single epoch X-ray microlensing is sensitive to the source size. Our results, in good agreement with previous estimates, show that the size of the X-ray emission region scales roughly linearly with the black hole mass, with a half light radius of $R_{1/2}\simeq(24\pm14) r_g$ where $r_g=GM_{BH}/c^2$. This corresponds to a size of $\log(R_{1/2}/cm)=15.6^{+0.3}_{-0.3}$ or $\sim$ 1 light day for a black hole mas…
Quasars whose broad emission lines show temporal, bulk radial velocity (RV) shifts have been proposed as candidate sub-parsec (sub-pc), binary supermassive black holes (BSBHs). We identified a sample of 16 BSBH candidates based on two-epoch spectroscopy among 52 quasars with significant RV shifts over a few rest-frame years. The candidates showed consistent velocity shifts independently measured from two broad lines (H$β$ and H$α$ or Mg${\rm \,II}$) without significant changes in the broad-line profiles. Here in the third paper of the series, we present further third- and fourth-epoch spectros…
There is evidence that magnetized material along the line of sight to distant quasars is detectable in the polarization properties of the background sources. The polarization properties appear to be correlated with the presence of intervening MgII absorption, which is thought to arise in outflowing material from star forming galaxies. In order to investigate this further, we have obtained high spectral resolution polarization measurements, with the VLA and ATCA, of a set of 49 unresolved quasars for which we have high quality optical spectra. These enable us to produce a Faraday Depth spectrum…
Radial gradients revealed by mutliscale outflows from down-the-barrel spectroscopy toward a quasar at redshift 3.4
Yunnan Observatories, Chinese Academy of Sciences（中国科学院云南天文台）；University of Washington Bothell（华盛顿大学博塞尔分校）；Zhuhai College of Science and Technology（珠海科技学院）；York University（约克大学）；University of Science and Technology of China（中国科学技术大学）；The Pennsylvania State University（宾夕法尼亚州立大学）；Peking University（北京大学）
Frequency and Abundance of Binary sUpermassive bLack holes from Optical Variability Surveys (FABULOVS): Hubble Space Telescope Imaging of Radial-Velocity Selected Binary Candidates
The source NRAO150 is a very prominent millimeter to radio emitting quasar at redshift z=1.52 for which previous millimeter VLBI observations revealed a fast counterclockwise rotation of the innermost regions of the jet. Here we present new polarimetric multi-epoch VLBI-imaging observations of NRAO150 performed at 8, 15, 22, 43, and 86GHz with the VLBA and GMVA between 2006 and 2010. All new and previous observational evidence are consistent with an interpretation of the source behavior where the jet is seen at an extremely small angle to the line of sight, and the high frequency emitting regi…
We present a detailed analysis of the single-slit optical spectrum of the Flat-Spectrum Radio Quasar (FSRQ) B2 0003+38A, taken by the Echellette Spectrograph and Imager (ESI) on the Keck II telescope. This classical low-redshift FSRQ ($z=0.22911$, as measured from the stellar absorption lines) remains underexplored in its emission lines, though its broad-band continuum properties from radio to X-ray is well-studied. After removing the unresolved quasar nucleus and the starlight from the host galaxy, we obtain a spatially-resolved 2-D spectrum, which clearly shows three components, indicating a…
We probed the magnetic fields in high-redshift galaxies using excess extragalactic contribution to residual rotation measure (RRM) for quasar sightlines with intervening Mg II absorbers. Based on a large sample of 1132 quasars, we have computed RRM distributions broadening using median absolute deviation from mean ($σ^{md}_{rrm}$), and found it to be 17.1$\pm0.7$ rad m$^{-2}$ for 352 sightlines having Mg II intervening absorbers in comparison to its value of $15.1\pm0.6$ rad m$^{-2}$ for 780 sightlines without such absorbers, resulting in an excess broadening ($σ_{rrm}^{ex}$) of $8.0\pm1.9$ ra…
We describe the kinematics of circumgalactic gas near the galactic plane, combining new measurements of galaxy rotation curves and spectroscopy of background quasars. The sightlines pass within 19--93 kpc of the target galaxy and generally detect Mg II absorption. The Mg II Doppler shifts have the same sign as the galactic rotation, so the cold gas co-rotates with the galaxy. Because the absorption spans a broader velocity range than disk rotation can explain, we explore simple models for the circumgalactic kinematics. Gas spiraling inwards (near the disk plane) offers a successful description…
The broad line region (BLR) of luminous active galactic nuclei (AGN) is a prominent observational signature of the accretion flow around supermassive black holes, which can be used to measure their masses (M_BH) over cosmic history. Due to the <100 μas angular size of the BLR, current direct constraints on BLR kinematics are limited to those provided by reverberation mapping studies, which are most efficiently carried out on low-luminosity L and low-redshift z AGN. We analyze the possibility to measure the BLR size and study its kinematic structure using spectroastrometry, whereby one measures…
Deriving the Faraday rotation measure (RM) of quasar absorption line systems, which are tracers of high-redshift galaxies intervening background quasars, is a powerful tool for probing magnetic fields in distant galaxies. Statistically comparing the RM distributions of two quasar samples, with and without absorption line systems, allows one to infer magnetic field properties of the intervening galaxy population. Here, we have derived the analytical form of the probability distribution function (PDF) of RM produced by a single galaxy with an axisymmetric large-scale magnetic field. We then furt…
Velocity offsets in the broad Balmer lines of quasars and their temporal variations serve as indirect evidence for bound supermassive black hole binaries (SBHBs) at sub-parsec separations. In this work, we test the SBHB hypothesis for 14 quasars with double-peaked broad emission lines using their long-term (14--41 years) radial velocity curves. We improve on previous work by (a) using elliptical instead of circular orbits for the SBHBs, (b) adopting a statistical model for radial velocity jitter, (c) employing a Markov Chain Monte Carlo method to explore the orbital parameter space efficiently…
Using spectra taken with the AAOmega spectrograph, we measure the radial velocities of over 100 stars, many of which are intermediate age carbon stars, in the direction of the dwarf irregular galaxy NGC 6822. Kinematic analysis suggests that the carbon stars in the sample are associated with NGC 6822, and estimates of its radial velocity and galactic rotation are made from a star-by-star analysis of its carbon star population. We calculate a heliocentric radial velocity for NGC 6822 of $-51\pm3$ \kms\ and show that the population rotates with a mean rotation speed of $11.2\pm2.1$ \kms\ at a me…
We present the largest ever sample of radio polarization properties for $z>4$ sources, with 14 sources having significant polarization detections. Using wideband data from the Karl G. Jansky Very Large Array, we obtained the rest-frame total intensity and polarization properties of 37 radio sources, nine of which have spectroscopic redshifts in the range $1 \le z \le 1.4$, with the other 28 having spectroscopic redshifts in the range $3.5 \le z \le 6.21$. Fits are performed for the Stokes $I$ and fractional polarization spectra, and Faraday rotation measures are derived using Rotation measure …
Gaia data release 2 (DR2) provides the best non-rotating optical frame aligned with the radio frame (ICRF) thanks to the inclusion of about half-million quasars in the 5-parameter astrometric solution. Given their crucial diagnostic role for characterizing the properties of the celestial reference frame, we aim to make an independent assessment of the astrometry of quasars in DR2. We cross-match with Gaia DR2 the quasars from LQAC3, SDSS and LAMOST, obtaining 208743 new sources (denominated as KQCG). With the quasars already identified in DR2, we estimate the global offsets of parallaxes and p…
We investigate the properties of the galaxy environment of a sample of 14 low redshift (z $<$ 0.85) quasar physical pairs extracted from SDSS DR10 archives. The pairs have a systemic radial velocity difference $ΔV_\parallel \leqslant$ 600 $km \ s^{-1}$ (based on [OIII]5007 Å\ line) and projected distance $ R_\bot \leqslant$ 600 kpc. The physical association of the pairs is statistically confirmed at a level of $\sim$ 90 %. For most of the images of these quasars we are able to resolve their host galaxies that turn out to be on average similar to those of quasars not in pairs. We also found tha…
The broadening of atomic emission lines by high-velocity motion of gas near accreting supermassive black holes is an observational hallmark of quasars. Observations of broad emission lines could potentially constrain the mechanism for transporting gas inwards through accretion disks or outwards through winds. The size of this broad-line region has been estimated by measuring the light travel time delay between the variable nuclear continuum and the emission lines - a method known as reverberation mapping. In some models the emission lines arise from a continuous outflow, whereas in others they…
We constrain gas inflow speeds in star-forming galaxies with color gradients consistent with inside-out disk growth. Our method combines new measurements of disk orientation with previously described circumgalactic absorption in background quasar spectra. Two quantities, a position angle and an axis ratio, describe the projected shape of each galactic disk on the sky, leaving an ambiguity about which side of the minor axis is tipped toward the observer. This degeneracy regarding the 3D orientation of disks has compromised previous efforts to measure gas inflow speeds. We present HST and Keck/L…
Recent observational evidence indicates that the center of our Milky Way harbours a super-massive object with ultra-strong radial magnetic field (Eatough et al., 2013). Here we demonstrate that the radiations observed in the vicinity of the Galactic Center (GC) (Falcke and Marko 2013) cannot be emitted by the gas of the accretion disk since the accreting plasma is prevented from approaching to the GC by the abnormally strong radial magnetic field. These fields obstruct the infalling accretion flow from the inner region of the disk and the central massive black hole in the standard model. It is…
Multi-frequency Very Long Baseline Array (VLBA) polarimetry observation of the GHz-Peaked Spectrum (GPS) quasar OQ172 (J1445+0958) has been performed at 1.6, 2.2, 4.8, 8.3 and 15.3 GHz in 2005. Core-jet structures are detected in all bands with the jet strongly bent at about 3 mas from the core. The radio emission of the source is polarised at all five bands. We study the Faraday Rotation in the core and jet components at all five bands, and find good linear fits of Faraday Rotation in the core and jet components at 4.8 and 8.3 GHz. At these two frequencies, the Rotation Measure (RM) is $\sim …
We present the first luminous, spatially resolved binary quasar that clearly inhabits an ongoing galaxy merger. SDSS J125455.09+084653.9 and SDSS J125454.87+084652.1 (SDSS J1254+0846 hereafter) are two luminous z=0.44 radio quiet quasars, with a radial velocity difference of just 215 km/s, separated on the sky by 21 kpc in a disturbed host galaxy merger showing obvious tidal tails. The pair was targeted as part of a complete sample of binary quasar candidates with small transverse separations drawn from SDSS DR6 photometry. We present follow-up optical imaging which shows broad, symmetrical ti…
The Tantalizing Case of the Quasar J0950+5128 -- I. Presentation of the Data and Detailed Exploration of the Binary Supermassive Black Hole Scenario
Penn State University（宾夕法尼亚州立大学）；Fisk University（菲斯克大学）；Vanderbilt University（范德堡大学）；Georgia Institute of Technology（佐治亚理工学院）；California Institute of Technology（加州理工学院）；Jet Propulsion Laboratory（喷气推进实验室）
We present ALMA 0.28"x0.20" (1.4kpc x 1.0kpc) resolution observations of the [CII] 158um line and underlying dust continuum in the host galaxy of the most distant quasar currently known, ULAS J1342+0928 at z=7.5413. Both the [CII] and continuum are detected and spatially resolved. The [CII] line is ~1.5 times more extended than the continuum emission, showing an elongated and complex structure of approximately 3.2kpc x 6.4kpc. Two separate peaks are clearly seen (>6sigma each) in three 100 km/s width [CII] channel maps. The velocity field of the [CII] gas does not show evidence of a coherent r…
We have derived exact axisymmetric solutions of the two-dimensional Lane-Emden equations with rotation. These solutions are intrinsically favored by the differential equations regardless of any adopted boundary conditions and the physical solutions of the Cauchy problem are bound to oscillate about and remain close to these intrinsic solutions. The isothermal solutions are described by power-law density profiles in the radial direction, whereas the polytropic solutions are described by radial density profiles that are powers of the zeroth-order Bessel function of the first kind. Both families …
There is growing observational evidence of high-redshift quasars launching energetic, fast outflows, but the effects that these have on their host galaxies is poorly understood. We employ the moving-mesh code AREPO to study the feedback from a quasar that has grown to $\sim 10^9 M_\odot$ by $z \sim 5$ and the impact that this has on its host galaxy. Our simulations use a super-Lagrangian refinement technique to increase the accuracy with which the interface of the quasar-driven wind and the surrounding gas is resolved. We find that the feedback injected in these simulations is less efficient a…
Context: Chromospheric activity produces both photometric and spectroscopic variations that can be mistaken as planets. Large spots crossing the stellar disc can produce planet-like periodic variations in the light curve of a star. These spots clearly affect the spectral line profiles and their perturbations alter the line centroids creating a radial velocity jitter that might contaminate" the variations induced by a planet. Precise chromospheric activity measurements are needed to estimate the activity-induced noise that should be expected for a given star. Aims: We obtain precise chromospher…
