283 research outputs found
Finite-difference distributions for the Ginibre ensemble
The Ginibre ensemble of complex random matrices is studied. The complex
valued random variable of second difference of complex energy levels is
defined. For the N=3 dimensional ensemble are calculated distributions of
second difference, of real and imaginary parts of second difference, as well as
of its radius and of its argument (angle). For the generic N-dimensional
Ginibre ensemble an exact analytical formula for second difference's
distribution is derived. The comparison with real valued random variable of
second difference of adjacent real valued energy levels for Gaussian
orthogonal, unitary, and symplectic, ensemble of random matrices as well as for
Poisson ensemble is provided.Comment: 8 pages, a number of small changes in the tex
The WISSH quasars Project: II. Giant star nurseries in hyper-luminous quasars
Studying the coupling between the energy output produced by the central
quasar and the host galaxy is fundamental to fully understand galaxy evolution.
Quasar feedback is indeed supposed to dramatically affect the galaxy properties
by depositing large amounts of energy and momentum into the ISM. In order to
gain further insights on this process, we study the SEDs of sources at the
brightest end of the quasar luminosity function, for which the feedback
mechanism is supposed to be at its maximum. We model the rest-frame UV-to-FIR
SEDs of 16 WISE-SDSS Selected Hyper-luminous (WISSH) quasars at 1.8 < z < 4.6
disentangling the different emission components and deriving physical
parameters of both the nuclear component and the host galaxy. We also use a
radiative transfer code to account for the contribution of the quasar-related
emission to the FIR fluxes. Most SEDs are well described by a standard
combination of accretion disk+torus and cold dust emission. However, about 30%
of them require an additional emission component in the NIR, with temperatures
peaking at 750K, which indicates the presence of a hotter dust component in
these powerful quasars. We measure extreme values of both AGN bolometric
luminosity (LBOL > 10^47 erg/s) and SFR (up to 2000 Msun/yr). A new relation
between quasar and star-formation luminosity is derived (LSF propto
LQSO^(0.73)) by combining several Herschel-detected quasar samples from z=0 to
4. Future observations will be crucial to measure the molecular gas content in
these systems, probe the impact between quasar-driven outflows and on-going
star-formation, and reveal the presence of merger signatures in their host
galaxies.Comment: 19 pages, 12 figures; Accepted for publication in Astronomy &
Astrophysics on June 13, 201
The WISSH Quasars Project III. X-ray properties of hyper-luminous quasars
We perform a survey of the X-ray properties of 41 objects from the WISE/SDSS
selected Hyper-luminous (WISSH) quasars sample, composed by 86 broad-line
quasars (QSOs) with bolometric luminosity , at z~2-4. All but 3 QSOs show unabsorbed 2-10 keV luminosities
. Thanks to their extreme radiative output
across the Mid-IR-to-X-ray range, WISSH QSOs offer the opportunity to
significantly extend and validate the existing relations involving .
We study as a function of (i) X-ray-to-Optical (X/O) flux ratio,
(ii) mid-IR luminosity (), (iii) as well as (iv)
vs. the 2500 luminosity. We find that WISSH QSOs
show very low X/O(<0.1) compared to typical AGN values;
ratios significantly smaller than those derived for AGN with lower luminosity;
large X-ray bolometric corrections 100-1000; and steep
. These results lead to a scenario where the X-ray
emission of hyper-luminous quasars is relatively weaker compared to
lower-luminosity AGN. Models predict that such an X-ray weakness can be
relevant for the acceleration of powerful high-ionization emission line-driven
winds, commonly detected in the UV spectra of WISSH QSOs, which can in turn
perturb the X-ray corona and weaken its emission. Accordingly, hyper-luminous
QSOs represent the ideal laboratory to study the link between the AGN energy
output and wind acceleration. Additionally, WISSH QSOs show very large BH
masses (>9.5). This enables a more robust modeling
of the relation by increasing the statistics at high masses. We
derive a flatter dependence than previously found over the broad range
5 < < 11.Comment: 20 pages, 14 Figures. Accepted for publication on A&
Particle-in-cell Simulation Concerning Heat-flux Mitigation Using Electromagnetic Fields
The Particle-in-Cell (PIC) method was used to study heat flux mitigation experiments with argon. In the experiment it was shown that a magnetic field allows to reduce the heat flux towards a target. PIC is well-suited for plasma simulation, giving the chance to get a better basic understanding of the underlying physics. The simulation demonstrates the importance of a self-consistent neutral-plasma description to understand the effect of heat flux reduction
Atmospheric energy spectra in global kilometre-scale models
Eleven 40-day long integrations of five different global models with horizontal resolutions of less than 9 km are compared in terms of their global energy spectra. The method of normal-mode function decomposition is used to distinguish between balanced (Rossby wave; RW) and unbalanced (inertia-gravity wave; IGW) circulation. The simulations produce the expected canonical shape of the spectra, but their spectral slopes at mesoscales, and the zonal scale at which RW and IGW spectra intersect differ significantly. The partitioning of total wave energies into RWs an IGWs is most sensitive to the turbulence closure scheme and this partitioning is what determines the spectral crossing scale in the simulations, which differs by a factor of up to two. It implies that care must be taken when using simple spatial filtering to compare gravity wave phenomena in storm-resolving simulations, even when the model horizontal resolutions are similar. In contrast to the energy partitioning between the RWs and IGWs, changes in turbulence closure schemes do not seem to strongly affect spectral slopes, which only exhibit major differences at mesoscales. Despite their minor contribution to the global (horizontal kinetic plus potential available) energy, small scales are important for driving the global mean circulation. Our results support the conclusions of previous studies that the strength of convection is a relevant factor for explaining discrepancies in the energies at small scales. The models studied here produce the major large-scale features of tropical precipitation patterns. However, particularly at large horizontal wavenumbers, the spectra of upper tropospheric vertical velocity, which is a good indicator for the strength of deep convection, differ by factors of three or more in energy. High vertical kinetic energies at small scales are mostly found in those models that do not use any convective parameterisation
The WISSH Project: Winds in the BLR
(On behalf of the WISSH collaboration) The WISE/SDSS-selected hyper-luminous quasar (WISSH) survey is an extensive multi-band observing program to investigate the role of nuclear activity in SMBH-galaxy self-regulated growth via extended outflows. Our ongoing project is designed to accurately probe the relationship between nuclear and host galaxy ISM properties in a large sample of ~90 quasars at the brightest end of the AGN luminosity function (log LBol > 47.3) and at the peak of their number density (z~2.5-3.5)We will report on the discovery of highly accreting (0.3-3Ledd), ten billion solar masses SMBHs being able to produce very powerful (up to ~ 4% of L_bol) ionized outflows and accretion disk windsThe impact of AGN-driven feedback on their host galaxies will be also discussed
The WISSH quasars project: VIII. Outflows and metals in the circum-galactic medium around the hyper-luminous z 3c 3.6 quasar J1538+08
Context. In recent years, Ly\u3b1 nebulae have been routinely detected around high redshift, radio-quiet quasars thanks to the advent of the highly sensitive integral field spectrographs. Constraining the physical properties of the Ly\u3b1 nebulae is crucial for a full understanding of the circum-galactic medium (CGM). The CGM acts both as a repository for intergalactic and galactic baryons as well as a venue of feeding and feedback processes. The most luminous quasars are privileged test-beds to study these processes, given their large ionising fluxes and dense CGM environments in which they are expected to be embedded. Aims. We aim to characterise the rest-frame ultraviolet (UV) emission lines in the CGM around a hyper-luminous, broad emission line, radio-quiet quasar at z 3c 3.6, which exhibits powerful outflows at both nuclear and host galaxy scales. Methods. We analyse VLT/MUSE observations of the quasar J1538+08 (Lbol = 6
7 1047 erg s-1), and we performed a search for extended UV emission lines to characterise its morphology, emissivity, kinematics, and metal content. Results. We report the discovery of a very luminous ( 3c2
7 1044 erg s-1), giant Ly\u3b1 nebula and a likely associated extended (75 kpc) CIV nebula. The Ly\u3b1 nebula emission exhibits moderate blueshift ( 3c440 km s-1) compared to the quasar systemic redshift and a large average velocity dispersion (\u3c3\u304v 3c700 km s-1) across the nebula, while the CIV nebula shows average velocity dispersion of \u3c3\u304v 3c350 km s-1. The Ly\u3b1 line profile exhibits a significant asymmetry towards negative velocity values at 20-30 kpc south of the quasar and is well parametrised by the following two Gaussian components: a narrow (\u3c3 3c 470 km s-1) systemic one plus a broad (\u3c3 3c 1200 km s-1), blueshifted ( 3c1500 km s-1) one. Conclusions. Our analysis of the MUSE observation of J1538+08 reveals metal-enriched CGM around this hyper-luminous quasar. Furthermore, our detection of blueshifted emission in the emission profile of the Ly\u3b1 nebula suggests that powerful nuclear outflows can propagate through the CGM over tens of kiloparsecs
The hyperluminous Compton-Thick z ⌠2 quasar nucleus of the hot DOG W1835+4355 observed by NuSTAR
We present a 155ks NuSTAR observation of the hot dust-obscured
galaxy (hot DOG) W1835+4355. We extracted spectra from the two NuSTAR detectors
and analyzed them jointly with the archival XMM PN and MOS spectra. We
performed a spectroscopic analysis based on both phenomenological and
physically motivated models employing toroidal and spherical geometry for the
obscurer. In all the modelings, the source exhibits a Compton-thick column
density cm, a 2-10 keV luminosity
erg s , and a prominent soft excess
( % of the primary radiative output), which translates into a
luminosity erg s. We modeled the spectral energy
distribution from 1.6 to 850 using a clumpy two-phase dusty torus model
plus a modified blackbody to account for emission powered by star formation in
the far-infrared. We employed several geometrical configurations consistent
with those applied in the X-ray analysis. In all cases we obtained a bolometric
luminosity erg s, which confirms
the hyperluminous nature of this active galactic nucleus. Finally, we estimate
a prodigious star formation rate of 3000 , which is
consistent with the rates inferred for hyperluminous type I
quasars. The heavily obscured nature, together with , the ratio of
X-ray to mid-infrared luminosity, the rest-frame optical morphology, and the
host star formation rate are indicative of its evolutionary stage. We can
interpret this as a late-stage merger event in the transitional,
dust-enshrouded, evolutionary phase eventually leading to an optically bright
AGN.ERC
STF
Probing the AGN/galaxy coevolution in the widest dynamical range ever
The existence of a long-lasting link between the central black hole mass and various physical properties of their host spheroids is now a matter of fact. Studying the correlations between the two at different ages is then the best way to rebuild their cosmic evolution. Within this scenario, we have built up two complementary AGN samples able to probe the accreting phases at both a) very high luminosity (>1047 erg/s) and BH masses (109-10 Msol), i.e. the WISSH Sample, and b) very low luminosities ( 1043 erg/s) and BH masses ( 105 Msol), i.e. studying sources extracted from the SWIFT/BAT catalog. By performing AGN-dedicated SED-fitting procedures we derived the main physical properties of both the nuclear engine and the host galaxy of these sources, i.e. bolometric luminosities, star formation rates and stellar masses. We will present the accreting and star formation properties of these sources, comparing the two classes of objects. Moreover, we are able to constrain the BH-galaxy scaling relation over three orders of magnitudes in mass and to follow its evolution from z 3 to z 0. I will show that while the more massive galaxies populate the typical region of the already observed MBH-Mstar relation, the less massive ones are still on their way to reach the MBH-Mstar locus, especially obscured AGN which seem to be hosted in less massive galaxies compared to unobscured ones, given the same BH. We will also present a new bolometric correction, separately for AGN2 and AGN1, which spans five orders of luminosity thus allowing to derive more accurate predictions on the accretion history of the AGN and their host galaxies
The WISSH quasars project IV. Broad line region versus kiloparsec-scale winds
Winds accelerated by active galactic nuclei (AGNs) are invoked in the most successful models of galaxy evolution to explain the observed physical and evolutionary properties of massive galaxies. Winds are expected to deposit energy and momentum into the interstellar medium (ISM), thus regulating both star formation and supermassive black hole (SMBH) growth. We undertook a multiband observing program aimed at obtaining a complete census of winds in a sample of WISE/SDSS selected hyper-luminous (WISSH) quasars (QSOs) at z â 2â4. We analyzed the rest-frame optical (i.e. LBT/LUCI and VLT/SINFONI) and UV (i.e. SDSS) spectra of 18 randomly selected WISSH QSOs to measure the SMBH mass and study the properties of winds both in the narrow line region (NLR) and broad line region (BLR) traced by blueshifted or skewed [OIII] and CIV emission lines, respectively. These WISSH QSOs are powered by SMBH with masses âł109 Mâ accreting at 0.4 < λEdd < 3.1. We found the existence of two subpopulations of hyper-luminous QSOs characterized by the presence of outflows at different distances from the SMBH. One population (i.e. [OIII] sources) exhibits powerful [OIII] outflows, a rest-frame equivalent width (REW) of the CIV emission REWCIV â 20â40 â«, and modest CIV velocity shift (vCIVpeak) with respect to the systemic redshift (vCIVpeak <~ 2000 km sâ1). The second population (i.e. Weak [OIII] sources), representing ~70% of the analyzed WISSH QSOs, shows weak or absent [OIII] emission and an extremely large blueshifted CIV emission (vCIVpeak up to ~8000 km sâ1 and REWCIV <~ 20 â«). We propose two explanations for the observed behavior of the strength of the [OIII] emission in terms of the orientation effects of the line of sight and ionization cone. The dichotomy in the presence of BLR and NLR winds could be likely due to inclination effects considering a polar geometry scenario for the BLR winds. In a few cases these winds are remarkably as powerful as those revealed in the NLR in the [OIII] QSOs (Äkin ~ 1044â45 erg sâ1). We also investigated the dependence of these CIV winds on fundamental AGN parameters such as bolometric luminosity (LBol), Eddington ratio (λEdd), and UV-to-X-ray continuum slope (αOX). We found a strong correlation with LBol and an anti-correlation with αOX whereby the higher the luminosity, the steeper the ionizing continuum described by means of αOX and the larger the blueshift of the CIV emission line. Finally, the observed dependence vCIVpeak â LBol0.28 ± 0.04 is consistent with a radiatively-driven-winds scenario, where a strong UV continuum is necessary to launch the wind and a weakness of the X-rayemission is fundamental to prevent overionization of the wind itself
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