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Register a new userSpatially resolved rotation of the broad-line region of a quasar at sub-parsec scale
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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 are produced by orbiting gas clouds. Directly imaging such regions has not hitherto been possible because of their small angular sizes (< 0.1 milli-arcseconds). Here we report a spatial offset (with a spatial resolution of ten micro-arcseconds or about 0.03 parsecs for a distance of 550 million parsecs) between the red and blue photo-centres of the broad Paschen-{alpha} line of the quasar 3C 273 perpendicular to the direction of its radio jet. This spatial offset corresponds to a gradient in the velocity of the gas and thus implies that the gas is orbiting the central supermassive black hole. The data are well fitted by a broad-line-region model of a thick disk of gravitationally bound material orbiting a black hole of 300 million solar masses. We infer a disk radius of 150 light days; a radius of 100-400 light days was found previously using reverberation mapping. The rotation axis of the disk aligns in inclination and position angle with the radio jet. Our results support the methods that are often used to estimate the masses of accreting supermassive black holes and to study their evolution over cosmic time.
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We present new near-infrared VLTI/GRAVITY interferometric spectra that spatially resolve the broad Br$gamma$ emission line in the nucleus of the active galaxy IRAS 09149-6206. We use these data to measure the size of the broad line region (BLR) and estimate the mass of the central black hole. Using an improved phase calibration method that reduces the differential phase uncertainty to 0.05 degree per baseline across the spectrum, we detect a differential phase signal that reaches a maximum of ~0.5 degree between the line and continuum. This represents an offset of ~120 $mu$as (0.14 pc) between the BLR and the centroid of the hot dust distribution traced by the 2.3 $mu$m continuum. The offset is well within the dust sublimation region, which matches the measured ~0.6 mas (0.7 pc) diameter of the continuum. A clear velocity gradient, almost perpendicular to the offset, is traced by the reconstructed photocentres of the spectral channels of the Br$gamma$ line. We infer the radius of the BLR to be ~65 $mu$as (0.075 pc), which is consistent with the radius-luminosity relation of nearby active galactic nuclei derived based on the time lag of the H$beta$ line from reverberation mapping campaigns. Our dynamical modelling indicates the black hole mass is $sim 1times10^8,M_odot$, which is a little below, but consistent with, the standard $M_{rm BH}$-$sigma_*$ relation.
We present the results of integral field spectroscopy of the gravitational wave (GW) recoiling black hole candidate 3C 186. The goal of the observations is to study the kinematics of the [OIII]5007 narrow emission line region (NLR) of the quasar, and investigate the origin of the velocity offsets originally measured for different UV lines. The results show that i) the spatial structure of the NLR is complex. The [OIII]5007 line shows significant velocity offsets with respect to the systemic redshift of the source. Different components at different velocities (-670, -100, + 75 km s^-1) are produced in different regions of the source. ii) we detect both the narrow and the broad components of the Hbeta line. The narrow component generally follows the kinematics of the [OIII] line, while the broad component is significantly blue-shifted. The peak of the broad line is near the blue end, or possibly outside of the sensitivity band of the instrument, implying a velocity offset of >~1800 km s^-1. This result is in agreement with the interpretation of the QSO as a GW recoiling black hole. The properties of the NLR show that the observed outflows are most likely the effect of radiation pressure on the (photoionized) gas in the interstellar medium of the host galaxy.
We demonstrate a new technique for determining the physical conditions of the broad line emitting gas in quasars, using near-infrared hydrogen emission lines. Unlike higher ionisation species, hydrogen is an efficient line emitter for a very wide range of photoionisation conditions, and the observed line ratios depend strongly on the density and photoionisation state of the gas present. A locally optimally emitting cloud model of the broad emission line region was compared to measured emission lines of four nearby ($zapprox0.2$) quasars that have optical and NIR spectra of sufficient signal-to-noise to measure their Paschen lines. The model provides a good fit to three of the objects, and a fair fit to the fourth object, a ULIRG. We find that low incident ionising fluxes ($phih<10^{18}$cmsqs), and high gas densities ($ h>10^{12}$cmcu) are required to reproduce the observed hydrogen emission line ratios. This analysis demonstrates that the use of composite spectra in photoionisation modelling is inappropriate; models must be fitted to the individual spectra of quasars.
Using VLTI/GRAVITY and SINFONI data, we investigate the sub-pc gas and dust structure around the nearby type 1 AGN hosted by NGC 3783. The K-band coverage of GRAVITY uniquely allows a simultaneous analysis of the size and kinematics of the broad line region (BLR), the size and structure of the near-IR continuum emitting hot dust, and the size of the coronal line region (CLR). We find the BLR probed through broad Br$gamma$ emission is well described by a rotating, thick disk with a radial distribution of clouds peaking in the inner region. In our BLR model the physical mean radius of 16 light days is nearly twice the 10 day time lag that would be measured, which matches very well the 10 day time lag that has been measured by reverberation mapping. We measure a hot dust FWHM size of 0.74 mas (0.14 pc) and further reconstruct an image of the hot dust which reveals a faint (5% of the total flux) offset cloud which we interpret as an accreting cloud heated by the central AGN. Finally, we directly measure the FWHM size of the nuclear CLR as traced by the [CaVIII] and narrow Br$gamma$ line. We find a FWHM size of 2.2 mas (0.4 pc), fully in line with the expectation of the CLR located between the BLR and narrow line region. Combining all of these measurements together with larger scale near-IR integral field unit and mid-IR interferometry data, we are able to comprehensively map the structure and dynamics of gas and dust from 0.01--100 pc.
Despite extensive efforts, only two quasars have been found at $z>7$ to date due to a combination of low spatial density and high contamination from more ubiquitous Galactic cool dwarfs in quasar selection. This limits our current knowledge of the super-massive black hole (SMBH) growth mechanism and reionization history. In this letter, we report the discovery of a luminous quasar at $z=7.021$, DELS J003836.10$-$152723.6 (hereafter J0038$-$1527), selected using photometric data from DESI Legacy imaging Survey (DELS), Pan-STARRS1 (PS1) imaging Survey, as well as Wide-field Infrared Survey Explore ($WISE$) mid-infrared all-sky survey. With an absolute magnitude of $M_{1450}$=$-$27.1 and bolometric luminosity of $L_{rm Bol}$=5.6$times$10$^{13}$ $L_odot$, J0038$-$1527 is the most luminous quasar known at $z>7$. Deep optical to near infrared spectroscopic observations suggest that J0038-1527 hosts a 1.3 billion solar mass BH accreting at the Eddington limit, with an Eddington ratio of 1.25$pm$0.19. The CIV broad emission line of J0038$-$1527 is blue-shifted by more than 3000 km s$^{-1}$ to the systemic redshift. More detailed investigations of the high quality spectra reveal three extremely high velocity CIV broad absorption lines (BALs) with velocity from 0.08 to 0.14 times the speed of light and total balnicity index of more than 5000 km s$^{-1}$, suggesting the presence of relativistic outflows. J0038$-$1527 is the first quasar found at the epoch of reionization (EoR) with such strong outflows and provides a unique laboratory to investigate AGN feedback on the formation and growth of the most massive galaxies in the early universe.
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