arXiv subjects

A. Schulze

Publications and source records attributed to A. Schulze.

17 recordsLinked to original sources

arXiv2024

The spatial clustering of ROSAT all-sky survey Active Galactic Nuclei: V. The evolution of broad-line AGN clustering properties in the last 6 Gyr

This is the fifth paper in a series of investigations of the clustering properties of luminous, broad-emission-line active galactic nuclei (AGN) identified in the ROSAT All-Sky Survey (RASS) and Sloan Digital Sky Survey (SDSS). In this work we measure the cross-correlation function (CCF) between RASS/SDSS DR14 AGN with the SDSS CMASS galaxy sample at $0.44<z<0.64$. We apply halo occupation distribution (HOD) modeling to the CCF along with the autocorrelation function of the CMASS galaxies. We find that X-ray and optically selected AGN at $0.44<z<0.64$ reside in statistically identical halos with a typical dark matter halo mass of $M_{\rm DMH}^{\rm typ,AGN} \sim 10^{12.7}\,h^{-1}\,\rm{M}_\odot$. The acceptable HOD parameter space for these two broad-line AGN samples have only statistically marginal differences caused by small deviations of the CCFs in the one-halo-dominated regime on small scales. In contrast to optically selected AGN, the X-ray AGN sample may contain a larger population of satellites at $M_{\rm DMH} \sim 10^{13}\,h^{-1}\,\rm{M}_\odot$. We compare our measurements in this work with our earlier studies at lower independent redshift ranges, spanning a look-back time of 6 Gyr. The comparison over this wider redshift range of $0.07<z<0.64$ reveals: (i) no significant difference between the typical DMH masses of X-ray and optically selected AGN, (ii) weak positive clustering dependencies of $M_{\rm DMH}^{\rm typ,AGN}$ with $L_{\rm X}$ and $M_{\rm BH}$, (iii) no significant dependence of $M_{\rm DMH}^{\rm typ,AGN}$ on Eddington ratio, and (iv) the same DMH masses host more-massive accreting black holes at high redshift than at low redshifts.

astro-ph.GA↗

arXiv2020

SUPER III. Broad Line Region properties of AGN at z$\sim$2

The SINFONI survey for Unveiling the Physics and Effect of Radiative feedback (SUPER) was designed to conduct a blind search for AGN-driven outflows on X-ray selected AGN at redshift z$\sim$2 with high ($\sim$2 kpc) spatial resolution, and correlate them to the properties of the host galaxy and central black hole. The main aims of this paper are: a) to derive reliable estimates for the BH mass and accretion rates for the Type-1 AGN in this survey; b) to characterize the properties of the AGN driven winds in the BLR. We analyzed rest-frame optical and UV spectra of 21 Type-1 AGN. We found that the BH masses estimated from H$α$ and H$β$ lines are in agreement. We estimate BH masses in the range Log(M$\rm_{BH}/M_{\odot}$)=8.4-10.8 and Eddington ratios $\rmλ_{Edd}$ =0.04-1.3. We confirm that the CIV line width does not correlate with the Balmer lines and the peak of the line profile is blue-shifted with respect to the [OIII]-based systemic redshift. These findings support the idea that the CIV line is tracing outflowing gas in the BLR, with velocities up to $\sim$4700 km/s. We confirm the strong dependence of the BLR wind velocity with the UV-to-Xray continuum slope, L$\rm_{Bol}$ and $\rmλ_{Edd}$. We inferred BLR mass outflow rates in the range 0.005-3 M$_{\odot}$/yr, showing a correlation with the bolometric luminosity consistent with that observed for ionized winds in the NLR and X-ray winds detected in local AGN, and kinetic power $\sim$10$^{[-7:-4]}\times$ L$\rm_{Bol}$. Finally, we found an anti-correlation between the equivalent width of the [OIII] line with respect to the CIV shift, and a positive correlation with [OIII] outflow velocity. These findings, for the first time in an unbiased sample of AGN at z$\sim$2, support a scenario where BLR winds are connected to galaxy scale detected outflows, and are capable of affecting the gas in the NLR located at kpc scale.

astro-ph.GA↗

arXiv2020

A significant excess in major merger rate for AGNs with the highest Eddington ratios at z<0.2

Observational studies are increasingly finding evidence against major mergers being the dominant mechanism responsible for triggering AGN. After studying the connection between major mergers and AGN with the highest Eddington ratios at z=2, we here expand our analysis to z<0.2, exploring the same AGN parameter space. Using ESO VLT/FORS2 B-, V- and color images, we examine the morphologies of 17 galaxies hosting AGNs with Eddington ratios >0.3, and 25 mass- and redshift-matched control galaxies. To match the appearance of the two samples, we add synthetic point sources to the inactive comparison galaxies. The combined sample of AGN and inactive galaxies was independently ranked by 19 experts with respect to the degree of morphological distortion. We combine the resulting individual rankings into multiple overall rankings, from which we derive the respective major merger fractions of the two samples. With a best estimate of 0.41 $\pm$ 0.12 for the AGN host galaxies and 0.08 $\pm$ 0.06 for the inactive galaxies our results imply that our AGN host galaxies have a significantly higher merger rate, regardless of the observed wavelength or applied methodology. We conclude that although major mergers are an essential mechanism to trigger local high Eddington ratio AGNs at z<0.2, the origin of >=50% of this specific AGN subpopulation still remains unclear.

astro-ph.GA↗

arXiv2019

No signs of star formation being regulated in the most luminous quasars at z~2 with ALMA

We present ALMA Band~7 observations at $850μ$m of 20 luminous ($\log\, L_{\rm bol}>46.9$ [erg s$^{-1}$]) unobscured quasars at $z\sim2$. We detect continuum emission for 19/20 quasars. After subtracting an AGN contribution, we measure the total far-IR luminosity for 18 quasars, assuming a modified blackbody model, and attribute the emission as indicative of the star formation rate (SFR). Our sample can be characterized with a log-normal SFR distribution having a mean of 140 $M_\odot$ yr$^{-1}$ and a dispersion of 0.5 dex. Based on an inference of their stellar masses, the SFRs are similar, in both the mean and dispersion, with star-forming main-sequence galaxies at the equivalent epoch. Thus, there is no evidence for a systematic enhancement or suppression (i.e., regulation or quenching) of star formation in the hosts of the most luminous quasars at $z\sim2$. These results are consistent with the Magneticum cosmological simulation, while in disagreement with a widely recognized phenomenological model that predicts higher SFRs than observed here based on the high bolometric luminosities of this sample. Furthermore, there is only a weak relation between SFR and accretion rate onto their supermassive black holes both for average and individual measurements. We interpret these results as indicative of star formation and quasar accretion being fed from the available gas reservoir(s) in their host with a disconnect due to their different physical sizes, temporal scales, and means of gas processing.

astro-ph.GA↗

arXiv2019

Jet-driven galaxy-scale gas outflows in the hyper-luminous quasar 3C273

We present an unprecedented view on the morphology and kinematics of the extended narrow-line region (ENLR) and molecular gas around the prototypical hyper-luminous quasar 3C273 ($L\sim10^{47}$ erg/s at z=0.158) based on VLT-MUSE optical 3D spectroscopy and ALMA observations. We find that: 1) The ENLR size of 12.1$\pm$0.2kpc implies a smooth continuation of the size-luminosity relation out to large radii or a much larger break radius as previously proposed. 2) The kinematically disturbed ionized gas with line splits reaching 1000km/s out to 6.1$\pm$1.5kpc is aligned along the jet axis. 3) The extreme line broadening on kpc scales is caused by spatial and spectral blending of many distinct gas clouds separated on sub-arcsecond scales with different line-of-sight velocities. The ENLR velocity field combined with the known jet orientation rule out a simple scenario of a radiatively-driven radial expansion of the outflow. Instead we propose that a pressurized expanding hot gas cocoon created by the radio jet is impacting on an inclined gas disk leading to transverse and/or backflow motion with respect to our line-of-sight. The molecular gas morphology may either be explained by a density wave at the front of the outflow expanding along the jet direction as predicted by positive feedback scenario or the cold gas may be trapped in a stellar over-density caused by a recent merger event. Using 3C273 as a template for observations of high-redshift hyper-luminous AGN reveals that large-scale ENLRs and kpc scale outflows may often be missed due to the brightness of the nuclei and the limited sensitivity of current near-IR instrumentation.

astro-ph.GA↗

arXiv2019

Major mergers are not the dominant trigger for high-accretion AGNs at z = 2

Research over the past decade has shown diminishing empirical evidence for major galaxy mergers being a dominating or even important mechanism for the growth of supermassive black holes in galaxies and the triggering of optically or X-ray selected active galactic nuclei (AGN). We here for the first time test whether such a connection exists at least in the most plausible part of parameter space for this mechanism: the highest specific accretion rate broad-line AGNs at the peak epoch of black hole activity around z = 2. To that end we examine 21 galaxies hosting a high accreting black hole (L/Ledd > 0.7) observed with HST/WFC3 and 92 stellar mass- and redshift- matched inactive galaxies taken from the CANDELS survey. We removed the AGN point sources from their host galaxies and avoided bias in visual classification by adding and then subtracting mock point sources to and from the comparison galaxies, producing matched residual structures for both sets. The resulting samples were joined, randomized, and subsequently visually ranked with respect to perceived strength of structural distortions by 10 experts. The ensuing individual rankings were combined into a consensus sequence and from this we derived merger fractions for both samples. With the merger fractions f$_{m,agn}$ = 0.24 $\pm$ 0.09 for the AGN host galaxy sample and f$_{m,ina}$ = 0.19 $\pm$ 0.04 for the inactive galaxies, we find no significant difference between the AGN host galaxies and inactive galaxies. Also, both samples display comparable fractions of disk-dominated galaxies. These findings are consistent with previous studies for different AGN populations, and we conclude that even black hole growth at the highest specific accretion rates and at the peak of cosmic AGN activity is not predominantly caused by major mergers. (abriged)

astro-ph.GA↗

arXiv2018

An FMOS Survey of moderate-luminosity broad-line AGN in COSMOS, SXDS and E-CDF-S

We present near-IR spectroscopy in J- and H-band for a large sample of 243 X-ray selected moderate-luminosity type-1 AGN in the COSMOS, SXDS and E-CDF-S survey fields using the multi-object spectrograph Subaru/FMOS. Our sample covers the redshift range 0.5 0.4 dex). We extend a recently proposed correction based on the CIV blueshift to lower luminosities and black hole masses. While our sample shows an improvement in their CIV black hole mass estimates, the deficit of high blueshift sources reduces its overall importance for moderate-luminosity AGN, compared to the most luminous quasars. In addition, we revisit luminosity correlations between $L_{\rm{bol}}$, $L_X$, $L_{\rm{[OIII]}}$, $L_{5100}$ and $L_{\rm{H}α}$ and find them to be consistent with a simple empirical model, based on a small number of well-established scaling relations. We finally highlight our highest redshift AGN, CID 781, at z=4.6 which shows the lowest black hole mass ($\sim10^8$M$_\odot$) among current near-IR samples at this redshift, and is in a state of fast growth.

astro-ph.GA↗

arXiv2018

SUPER I. Toward an unbiased study of ionized outflows in z~2 active galactic nuclei: survey overview and sample characterization

Theoretical models of galaxy formation suggest that the presence of an active galactic nucleus (AGN) is required to regulate the growth of its host galaxy through feedback mechanisms, produced by e.g. AGN-driven outflows. Although such outflows are common both at low and high redshift, a comprehensive picture is still missing. The peak epoch of galaxy assembly (1<z<3) has been poorly explored so far, and current observations in this redshift range are mostly limited to targets with high chances to be in an outflowing phase. This paper introduces SUPER (a SINFONI Survey for Unveiling the Physics and Effect of Radiative feedback), an ongoing ESO's VLT/SINFONI Large Programme. SUPER will perform the first systematic investigation of ionized outflows in a sizeable and blindly-selected sample of 39 X-ray AGN at z~2, which reaches high spatial resolutions (~2 kpc) thanks to the adaptive optics-assisted IFU observations. The outflow morphology and star formation in the host galaxy will be mapped through the broad component of [OIII] and the narrow component of Ha emission lines. The main aim of our survey is to infer the impact of outflows on the on-going star formation and to link the outflow properties to a number of AGN and host galaxy properties. We describe here the survey characteristics and goals, as well as the selection of the target sample. Moreover, we present a full characterization of its multi-wavelength properties: we measure, via spectral energy distribution fitting of UV-to-FIR photometry, stellar masses (4x10^9-2x10^11 Msun), star formation rates (25-680 Msun yr^-1) and AGN bolometric luminosities (2x10^44-8x10^47 erg s^-1), along with obscuring column densities (<2x10^24 cm^-2) and 2-10 keV luminosities (2x10^43-6x10^45 erg s^-1) derived through X-ray spectral analysis. Finally, we classify our AGN as jetted or non-jetted according to their radio and FIR emission.

astro-ph.GA↗

arXiv2018

Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs). IV. Discovery of 41 Quasars and Luminous Galaxies at 5.7 < z < 6.9

We report discovery of 41 new high-z quasars and luminous galaxies, which were spectroscopically identified at 5.7 < z < 6.9. This is the fourth in a series of papers from the Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs) project, based on the deep multi-band imaging data collected by the Hyper Suprime-Cam (HSC) Subaru Strategic Program survey. We selected the photometric candidates by a Bayesian probabilistic algorithm, and then carried out follow-up spectroscopy with the Gran Telescopio Canarias and the Subaru Telescope. Combined with the sample presented in the previous papers, we have now spectroscopically identified 137 extremely-red HSC sources over about 650 deg2, which include 64 high-z quasars, 24 high-z luminous galaxies, 6 [O III] emitters at z ~ 0.8, and 43 Galactic cool dwarfs (low-mass stars and brown dwarfs). The new quasars span the luminosity range from M1450 ~ -26 to -22 mag, and continue to populate a few magnitude lower luminosities than have been probed by previous wide-field surveys. In a companion paper, we derive the quasar luminosity function at z ~ 6 over an unprecedentedly wide range of M1450 ~ -28 to -21 mag, exploiting the SHELLQs and other survey outcomes.

astro-ph.GA↗

arXiv2017

Observational constraints on the specific accretion-rate distribution of X-ray selected AGN

This paper estimates the specific accretion-rate distribution of AGN using a sample of 4821 X-ray sources from both deep and shallow surveys. The specific accretion-rate distribution is defined as the probability of a galaxy with a given stellar mass and redshift hosting an active nucleus with a certain specific accretion rate. We find that the probability of a galaxy hosting an AGN increases with decreasing specific accretion rate. There is evidence that this trend reverses at low specific accretion rates, $λ<10^{-4}-10^{-3}$ (in Eddington units). There is also a break close to the Eddington limit, above which the probability of an accretion event decreases steeply. The specific accretion-rate distribution evolves such that the fraction of AGN among galaxies drops toward lower redshifts. This decrease in the AGN duty cycle is responsible for the strong evolution of the accretion density of the Universe from redshift $z\approx1-1.5$ to the present day. Our analysis also suggests that this evolution is accompanied by a decoupling of accretion events onto black holes from the formation of stars in galaxies. There is also evidence that at earlier times the relative probability of high vs low specific accretion-rate events among galaxies increases. We argue that this differential redshift evolution of the AGN duty cycle with respect to $λ$ produces the AGN downsizing trend, whereby luminous sources peak at earlier epochs compared to less luminous ones. Finally, we also find a stellar-mass dependence of the specific accretion-rate distribution, with more massive galaxies avoiding high specific accretion-rate events.

astro-ph.HE↗

arXiv2017

X-ray constraints on the fraction of obscured AGN at high accretion luminosities

The wide-area XMM-XXL X-ray survey is used to explore the fraction of obscured AGN at high accretion luminosities, $L_X (\rm 2-10 \, keV) > 10^{44} \, erg \,s ^{-1}$, and out to redshift $z\approx1.5$. The sample covers an area of about $\rm14\,deg^2$ and provides constraints on the space density of powerful AGN over a wide range of neutral hydrogen column densities extending beyond the Compton-thick limit, $\rm N_H\approx10^{24}\,cm^{-2}$. The fraction of obscured Compton-thin ($\rm N_H=10^{22}-10^{24}\,cm^{-2}$) AGN is estimated to be $\approx0.35$ for luminosities $L_X(\rm 2-10\,keV)>10^{44}\,erg\,s^{-1}$ independent of redshift. For less luminous sources the fraction of obscured Compton-thin AGN increases from $0.45\pm0.10$ at $z=0.25$ to $0.75\pm0.05$ at $z=1.25$. Studies that select AGN in the infrared via template fits to the observed Spectral Energy Distribution of extragalactic sources estimate space densities at high accretion luminosities consistent with the XMM-XXL constraints. There is no evidence for a large population of AGN (e.g. heavily obscured) identified in the infrared and missed at X-ray wavelengths. We further explore the mid-infrared colours of XMM-XXL AGN as a function of accretion luminosity, column density and redshift. The fraction of XMM-XXL sources that lie within the mid-infrared colour wedges defined in the literature to select AGN is primarily a function of redshift. This fraction increases from about 20-30% at z=0.25 to about 50-70% at $z=1.5$.

astro-ph.HE↗

arXiv2016

Do the Most Massive Black Holes at $z=2$ Grow via Major Mergers?

The most frequently proposed model for the origin of quasars holds that the high accretion rates seen in luminous active galactic nuclei are primarily triggered during major mergers between gas-rich galaxies. While plausible for decades, this model has only begun to be tested with statistical rigor in the past few years. Here we report on a Hubble Space Telescope study to test this hypothesis for $z=2$ quasars with high super-massive black hole masses ($M_\mathrm{BH}=10^9-10^{10}~M_\odot{}$), which dominate cosmic black hole growth at this redshift. We compare Wide Field Camera 3 $F160W$ (rest-frame $V$-band) imaging of 19 point source-subtracted quasar hosts to a matched sample of 84 inactive galaxies, testing whether the quasar hosts have greater evidence for strong gravitational interactions. Using an expert ranking procedure, we find that the quasar hosts are uniformly distributed within the merger sequence of inactive galaxies, with no preference for quasars in high-distortion hosts. Using a merger/non-merger cutoff approach, we recover distortion fractions of $f_\mathrm{m,qso}=0.39\pm{}0.11$ for quasar hosts and $f_\mathrm{m,gal}=0.30\pm{}0.05$ for inactive galaxies (distribution modes, 68% confidence intervals), with both measurements subjected to the same observational conditions and limitations. The slight enhancement in distorted fraction for quasar hosts over inactive galaxies is not significant, with a probability that the quasar fraction is higher of $P(f_\mathrm{m,qso}>f_\mathrm{m,gal}) = 0.78$ ($0.78\,σ$), in line with results for lower mass and lower $z$ AGN. We find no evidence that major mergers are the primary triggering mechanism for the massive quasars that dominate accretion at the peak of cosmic quasar activity.

astro-ph.GA↗

arXiv2016

AGN host galaxy mass function in COSMOS: is AGN feedback responsible for the mass-quenching of galaxies?

We investigate the role of supermassive black holes in the global context of galaxy evolution by measuring the host galaxy stellar mass function (HGMF) and the specific accretion rate i.e., lambda_SAR, distribution function (SARDF) up to z~2.5 with ~1000 X-ray selected AGN from XMM-COSMOS. Using a maximum likelihood approach, we jointly fit the stellar mass function and specific accretion rate distribution function, with the X-ray luminosity function as an additional constraint. Our best fit model characterizes the SARDF as a double power-law with mass dependent but redshift independent break whose low lambda_SAR slope flattens with increasing redshift while the normalization increases. This implies that, for a given stellar mass, higher lambda_SAR objects have a peak in their space density at earlier epoch compared to the lower lambda_SAR ones, following and mimicking the well known AGN cosmic downsizing as observed in the AGN luminosity function. The mass function of active galaxies is described by a Schechter function with a almost constant Mstar* and a low mass slope alpha that flattens with redshift. Compared to the stellar mass function, we find that the HGMF has a similar shape and that, up to log((Mstar/Msun)~11.5 the ratio of AGN host galaxies to star forming galaxies is basically constant (~10%). Finally, the comparison of the AGN HGMF for different luminosity and specific accretion rate sub-classes with the phenomenological model prediction by Peng et al. (2010) for the "transient" population, i.e. galaxies in the process of being mass-quenched, reveals that low-luminosity AGN do not appear to be able to contribute significantly to the quenching and that at least at high masses, i.e. Mstar>10^(10.7) Msun , feedback from luminous AGN (log(Lbol)>~46 [erg/s]) may be responsible for the quenching of star formation in the host galaxy.

astro-ph.GA↗

arXiv2015

The cosmic growth of the active black hole population at 1<z<2 in zCOSMOS, VVDS and SDSS

We present a census of the active black hole population at 1<z<2, by constructing the bivariate distribution function of black hole mass and Eddington ratio, employing a maximum likelihood fitting technique. The study of the active black hole mass function (BHMF) and the Eddington ratio distribution function (ERDF) allows us to clearly disentangle the active galactic nuclei (AGN) downsizing phenomenon, present in the AGN luminosity function, into its physical processes of black hole mass downsizing and accretion rate evolution. We are utilizing type-1 AGN samples from three optical surveys (VVDS, zCOSMOS and SDSS), that cover a wide range of 3 dex in luminosity over our redshift interval of interest. We investigate the cosmic evolution of the AGN population as a function of AGN luminosity, black hole mass and accretion rate. Compared to z = 0, we find a distinct change in the shape of the BHMF and the ERDF, consistent with downsizing in black hole mass. The active fraction or duty cycle of type-1 AGN at z~1.5 is almost flat as a function of black hole mass, while it shows a strong decrease with increasing mass at z=0. We are witnessing a phase of intense black hole growth, which is largely driven by the onset of AGN activity in massive black holes towards z=2. We finally compare our results to numerical simulations and semi-empirical models and while we find reasonable agreement over certain parameter ranges, we highlight the need to refine these models in order to match our observations.

astro-ph.GA↗

arXiv2014

The Dark Matter Halos of Moderate Luminosity X-ray AGN as Determined from Weak Gravitational Lensing and Host Stellar Masses

Understanding the relationship between galaxies hosting active galactic nuclei (AGN) and the dark matter halos in which they reside is key to constraining how black-hole fueling is triggered and regulated. Previous efforts have relied on simple halo mass estimates inferred from clustering, weak gravitational lensing, or halo occupation distribution modeling. In practice, these approaches remain uncertain because AGN, no matter how they are identified, potentially live a wide range of halo masses with an occupation function whose general shape and normalization are poorly known. In this work, we show that better constraints can be achieved through a rigorous comparison of the clustering, lensing, and cross-correlation signals of AGN hosts to a fiducial stellar-to-halo mass relation (SHMR) derived for all galaxies. Our technique exploits the fact that the global SHMR can be measured with much higher accuracy than any statistic derived from AGN samples alone. Using 382 moderate luminosity X-ray AGN at z<1 from the COSMOS field, we report the first measurements of weak gravitational lensing from an X-ray selected sample. Comparing this signal to predictions from the global SHMR, we find that, contrary to previous results, most X-ray AGN do not live in medium size groups ---nearly half reside in relatively low mass halos with Mh~10^12.5 Msun. The AGN occupation function is well described by the same form derived for all galaxies but with a lower normalization---the fraction of halos with AGN in our sample is a few percent. By highlighting the relatively "normal" way in which moderate luminosity X-ray AGN hosts occupy halos, our results suggest that the environmental signature of distinct fueling modes for luminous QSOs compared to moderate luminosity X-ray AGN is less obvious than previously claimed.

astro-ph.GA↗

arXiv2014

The M_BH - M_star relation for X-ray obscured, red QSOs at 1.2< z <2.6

We present near-infrared spectra, obtained with SINFONI and XShooter observations at ESO VLT, of nine dusty, red QSOs at 1.2 10^{21} - 10^{22} cm^{-2}) and show a broad Ha component in the NIR spectra. We complement this sample with twelve additional sources taken from the literature with similar properties resulting in a total sample of 21 X-ray obscured, intermediate type (1.8-1.9), dusty reddened QSOs. From the broad Ha line we have computed the BH masses through the virial formula and derived Eddington ratios. Moreover, from optical/IR multi-component SED fitting we have derived the stellar mass of their host galaxies and their SFRs. We find that most of the sources in our sample are hosted in starburst and main sequence star-forming galaxies with Eddington ratios lambda>0.1. We find a strong trend with the BH mass i.e. less massive objects are scattered below and above the local relation while the most massive ones are mainly located above it. We also studied the evolution of these sources on the M_BH-M_star plane compared to a sample of optically blue type--1 QSOs and we find that obscured red QSOs show a ratio of M_BH to M_star that increases with redshift which is consistent with or slightly lower than what has been found for blue QSOs. These sources may represent the blow-out phase at the end of the rapid BH growth and immediately preceding the classical blue QSOs typically sampled in optical surveys. They in fact show evidence of outflows in the ionized gas component, but their BH has already fully formed.

astro-ph.GA↗

arXiv2004

Two-dimensional Bloch oscillations: A Lie-algebraic approach

A Lie-algebraic approach successfully used to describe one-dimensional Bloch oscillations in a tight-binding approximation is extended to two dimensions. This extension has the same algebraic structure as the one-dimensional case while the dynamics shows a much richer behaviour. The Bloch oscillations are discussed using analytical expressions for expectation values and widths of the operators of the algebra. It is shown under which conditions the oscillations survive in two dimensions and the centre of mass of a wave packet shows a Lissajous like motion. In contrast to the one-dimensional case, a wavepacket shows systematic dispersion that depends on the direction of the field and the dispersion relation of the field free system.

quant-ph↗