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The UV/optical variation, likely driven by accretion disc turbulence, is a defining characteristic of type 1 active galactic nuclei (AGNs) and quasars. In this work we investigate an interesting consequence of such turbulence using quasars in SDSS Stripe 82 for which the measurements of the UV/optical variability amplitude are available from $sim$ 10 years long light curves. We discover positive correlations between UV/optical variability amplitude $sigma_{rms}$ and equivalent widths of CIV, Mg II and [OIII]5007 emission lines. Such correlations remain statistically robust through partial correlation analyses, i.e., after controlling the effects of other variables including bolometric luminosity, central supermassive black hole mass, Eddington ratio and redshift. This, for the first time, indicates a causal link between disc turbulence and emission line production. We propose two potential underlying mechanisms both of which may be involved: 1) quasars with stronger disc turbulence have on average bluer/harder broadband SED, an expected effect of the disc thermal fluctuation model; 2) stronger disc turbulence could lead to launch of emission line regions with larger covering factors.
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We derive a fine-grained uncertainty relation for the measurement of two incompatible observables on a single quantum system of continuous variables, and show that continuous variable systems are more uncertain than discrete variable systems. Using the derived fine-grained uncertainty relation, we formulate stronger steering criterion that is able to reveal the steerability of N00N states that has hitherto not been possible using other criteria. We further obtain a monogamy relation for our steering inequality which leads to an, in principle, improved lower bound on the secret key rate of a one-sided device independent quantum key distribution protocol for continuous variables.
We identify a sample of 74 high-redshift quasars (z>3) with weak emission lines from the Fifth Data Release of the Sloan Digital Sky Survey and present infrared, optical, and radio observations of a subsample of four objects at z>4. These weak emission-line quasars (WLQs) constitute a prominent tail of the Lya+NV equivalent width distribution, and we compare them to quasars with more typical emission-line properties and to low-redshift active galactic nuclei with weak/absent emission lines, namely BL Lac objects. We find that WLQs exhibit hot (T~1000 K) thermal dust emission and have rest-frame 0.1-5 micron spectral energy distributions that are quite similar to those of normal quasars. The variability, polarization, and radio properties of WLQs are also different from those of BL Lacs, making continuum boosting by a relativistic jet an unlikely physical interpretation. The most probable scenario for WLQs involves broad-line region properties that are physically distinct from those of normal quasars.
The EUV provides most of the ionization that creates the high equivalent width (EW) broad and narrow emission lines (BELs, NELs) of quasars. Spectra of Hypermassive Schwarzschild black holes (HMBHs, $M_{BH} geq 10^{10} M_{odot}$) with $alpha$-discs, decline rapidly in the EUV suggesting much lower EWs. Model spectra for black holes of mass $10^{6}-10^{12} M_{odot}$ and accretion rates $0.03 leq L_{bol}/L_{edd} leq 1.0$ were input to the CLOUDY photoionization code. BELs become $sim$100 times weaker in EW from $M_{BH} sim 10^8 M_{odot}$ to $M_{BH} sim 10^{10} M_{odot}$. The high ionization BELs (O VI 1034 $overset{circ}{mathrm {A}}$, C IV 1549 $overset{circ}{mathrm {A}}$, He II 1640 $overset{circ}{mathrm {A}}$) decline in EW from ($M_{BH} geq 10^6 M_{odot}$, reproducing the Baldwin effect, but regain EW for $M_{BH} geq 10^{10} M_{odot}$). The low ionization lines (MgII 2798 $overset{circ}{mathrm {A}}$, H$beta$ 4861 $overset{circ}{mathrm {A}}$ and H$alpha$ 6563 $overset{circ}{mathrm {A}}$) remain weak. Lines for maximally spinning HMBHs behave similarly. Line ratio diagrams for the BELs show that high OVI/H$beta$ and low CIV/H$alpha$ may pick out HMBH, although OVI is often hard to observe. In NEL BPT diagrams HMBHs lie among star-forming regions, except for highly spinning, high accretion rate HMBHs. In summary, the BELs expected from HMBHs would be hard to detect using the current optical facilities. From 100 to $10^{12} M_{odot}$, the emission lines used to detect AGN only have high EW in the $10^6 - 10^9 M_{odot}$ window, where most AGN are found. This selection effect may be distorting reported distributions of $M_{BH}$.
We present Atacama Large Millimiter/submillimiter Array (ALMA) observations of eight highly excited CO (J$_{rm up}>8$) lines and continuum emission in two $zsim6$ quasars: SDSS J231038.88+185519.7 (hereafter J2310), for which CO(8-7), CO(9-8), and CO(17-16) lines have been observed, and ULAS J131911.29+095951.4 (J1319), observed in the CO(14-13), CO(17-16) and CO(19-18) lines. The continuum emission of both quasars arises from a compact region ($< 0.9$ kpc). By assuming a modified black-body law, we estimate dust masses of Log$(M_{rm dust}/M_{odot})=8.75pm0.07$ and Log$(M_{rm dust}/M_{odot})=8.8pm0.2$ and dust temperatures of $T_{rm dust}=76pm3~{rm K}$ and $T_{rm dust}=66^{+15}_{-10}~{rm K}$, respectively for J2310 and J1319. Only CO(8-7) and CO(9-8) in J2310 are detected, while $3sigma$ upper limits on luminosities are reported for the other lines of both quasars. The CO line luminosities and upper limits measured in J2310 and J1319 are consistent with those observed in local AGN and starburst galaxies, and other $zsim 6$ quasars, except for SDSS J1148+5251 (J1148), the only quasar at $z=6.4$ with a previous CO(17-16) line detection. By computing the CO SLEDs normalised to the CO(6-5) line and FIR luminosities for J2310, J1319, and J1149, we conclude that different gas heating mechanisms (X-ray radiation and/or shocks) may explain the different CO luminosities observed in these $zsim6$ quasar. Future J$_{rm up}>8$ CO observations will be crucial to understand the processes responsible for molecular gas excitation in luminous high-$z$ quasars.
We investigate the distribution of companion galaxies around quasars using {em Hubble Space Telescope} ({em HST}) Advanced Camera for Surveys Wide Field Camera (ACS/WFC) archival images. Our master sample contains 532 quasars which have been observed by {em HST} ACS/WFC, spanning a wide range of luminosity $(-31<M_i(z=2)<-23)$ and redshift ($0.3<z<3$). We search for companions around the quasars with projected distance of $10text{ kpc}<d<100text{ kpc}$. PSF subtraction is performed to enhance the completeness for close companions. The completeness is estimated to be high $(>90%)$ even for the faintest companions of interest. The number of physical companions is estimated by subtracting a background density from the number density of projected companions. We divide all the companions into three groups (faint, intermediate and bright) according to their fluxes. A control sample of galaxies is constructed to have similar redshift distribution and stellar mass range as the quasar sample using the data from {em HST} deep fields. We find that quasars and control sample galaxies have similar numbers of faint and bright companions, while quasars show a $3.7sigma$ deficit of intermediate companions compared to galaxies. The numbers of companions in all three groups do not show strong evolution with redshift, and the number of intermediate companions around quasars decreases with quasar luminosity. Assuming that merger-triggered quasars have entered the final coalescence stage during which individual companions are no longer detectable at large separations, our result is consistent with a picture in which a significant fraction of quasars is triggered by mergers.
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