52970930
Variable X-ray absorption in the mini-BAL QSO PG 1126-041
Context. X-ray studies of AGN with powerful nuclear winds are important to constrain the physics of the inner accretion/ejection flow around SMBH, and to understand the impact of such winds on the AGN environment. Aims. Our main scientific goal is to constrain the properties of a va riable outflowing absorber that is thought to be launched nea r the SMBH of the mini-BAL QSO PG 1126-041 using a multi-epoch observational campaign performed with XMM-Newton. Methods. We performed temporally resolved X-ray spectroscopy and simultaneous UV and X-ray photometry on the most complete set of observations and on the deepest X-ray exposure of a mini-BAL QSO to date. Results. We found complex X-ray spectral variability on time scales of both months and hours, best reproduced by means of variable massive ionized absorbers along the line of sight. As a consequence, the observed optical-to-X-ray spectral index is found to be variable with time. In the highest signal-to-noise observa tion we detected highly ionized X-ray absorbing material outflowing much faster (υX∼ 16 500 km s −1 ) than the UV absorbing one (υuv∼ 5 000 km s −1 ). This highly ionized absorber is found to be variable on very short (a few kiloseconds) time scales. Conclusions. Our findings are qualitatively consistent with line driven a ccretion disk winds scenarios. Our observations have opened the time-resolved X-ray spectral analysis field for mini-BA L QSOs; only with future deep studies will we be able to map the dynamics of the inner flow and understand the physics of AGN winds and th eir impact on the environment.
118758635
First Results from a XMM-Newton Survey of a Distance-Limited (D<22 Mpc) Sample of Seyfert Galaxies: I- the Agns
We report here preliminary results from a survey of nearby Seyfert galaxies using the EPIC CCDs on board XMM-Newton. The total sample consists of 28 Seyfert galaxies, and constitute a well-defined, complete (B 0 deg.) hemisphere. The survey has been initiated in June, 2001, and we report here the results for the 6 objects analyzed so far, namely: NGC3185, NGC3486, NGC3941, NGC4138, NGC4565, and NGC5033. The main goal of this survey is to obtain a better and unbiased understanding of the ``typical'' Seyfert X-ray spectrum (e.g. the distribution of their absorption column density) in the local Universe. This is crucial to verify the predictions and, thus, to validate unified models, and is a fundamental parameter of synthesis models for the X-ray background. A companion poster (paper II: L. Foschini et al., these proceedings) illustrates how this survey will also allow a comprehensive spectral study of the brightest (highest-luminosity) off-nuclear sources in the galaxies.
119331878
MOLECULAR LINES IN BOK GLOBULES AND AROUND HERBIG AE/BE STARS
This paper is intended as part of a more extensive molecular line survey in star forming regions along the evolutionary track of a collapsing cloud toward a young stellar object. We have studied a sample of seven small dark clouds (Bok globules) and eight Herbig Ae/Be stars in the J=1->0 transition of HCO$^{+}$, H$^{13}$CO$^{+}$, HCN and H$^{13}$CN. The choice of these molecules is determined by the simple chemistry and the predicted high abundance of the reactants leading to their formation. The isotopically substituted species (isotopomers), H$^{13}$CO$^{+}$ and H$^{13}$CN, were observed in order to determine, whenever possible, the optical thickness of the main species. The most abundant isotopomers were found in almost all the sources (detection rate 70-90\%). Those sources which exhibited the strongest signals were also searched for the $^{13}$C isotopomers. H$^{13}$CO$^{+}$ was found in one dark cloud and around three Herbig Ae/Be stars, while H$^{13}$CN around only one star. The column densities for each species and the physical conditions of the objects were derived whenever the observational data allowed it.
73549569
Warm absorber energetics in broad-line radio galaxies
We review the soft X-ray properties of 3C 390.3, 3C 120, 3C 382 and 3C 445, the only broad-line radio galaxies (BLRGs) for which good quality gratings data are currently available. The XMM–Newton/Reflection Grating Spectrometer data of 3C 390.3 and 3C 120 were re-analysed searching for warm absorbers, already discovered in 3C 382 and 3C 445. We confirm the absence of ionized absorption features in 3C 120, but find signatures of outflowing gas (vout∼ 102 km s−1) in 3C 390.3. Its warm absorber (log ξ∼ 2 erg cm s−1, NH∼ 1020 cm−2), similar to that observed in 3C 382, is probably placed in the narrow-line regions. Its gas content is slower and less dense than the accretion disc wind discovered in 3C 445. Independently from the location of the warm gas, the outflowing masses () of BLRGs are significantly (but improbably) predominant with respect to the accretion masses (), suggesting a clumpy configuration of the warm absorber. However, even assuming overestimated values of , the kinetic luminosity of the outflow () is well below 1 per cent of the kinetic power of the jet (Pjet). Thus, the jet remains the major driver of the radio-loud active galactic nucleus (AGN) feedback at least on a parsec scale and beyond. The warm absorber parameters (NH, ξ) of BLRGs span a similar range of values to type 1 radio-quiet AGNs. However, when the mass outflow rate of BLRGs and Seyfert 1s is plotted as a function of the radio loudness, R = log [νLν(5 GHz)/L(2-10 keV)], the mass outflow rate seems to increase with radio power.
15312636
Probing the Hard X-Ray Properties of High-Redshift Radio-Quiet Quasars with ASCA
This paper reports the X-ray spectral analysis of five high-redshift (z≥2), radio-quiet quasars observed by ASCA. A simple power-law continuum plus cold Galactic absorption model well fits all the spectra (typically between ~2 and 30 keV in the sources frame). Neither the X-ray spectral hardening, which is attributed to a reflection component and observed in Seyfert galaxies, nor the excess absorption previously detected in high-redshift, radio-loud quasars have been revealed. Only marginal evidence of a neutral or mildly ionized FeKα line is found in one of the quasars. The average spectral slope in the observed 0.7-10 keV energy range, Γ=1.67 ± 0.11 (dispersion σ ~0.07), appears to be flatter than that of low-z, radio-quiet quasars (Γ 1.9-2) and slightly steeper but consistent with Γ=1.61 ± 0.04 (σ ~0.10) of high-z, radio-loud quasars.
122093176
Broad-Line Radio Galaxies: Jet Contribution to the Nuclear X-Ray Continuum
It is shown that for broad-line radio galaxies the strength of the nonthermal beamed radiation, when present, is always smaller than the accretion flow by a factor of <0.7 in the 2-10 keV band. This result has been obtained using the procedure adopted for disentangling the flat-spectrum radio quasar 3C 273. Although this implies a significantly smaller nonthermal flux in radio galaxies when compared to blazars, the jet component, if present, could be important at very high energies and thus easily detectable with GLAST.
120919640
Gravitational Behaviour of an Effective Topological Field Theory
Effective topological field theories describe the properties of Dirac fermions in the low-energy regime. In this work, we introduce a new emergent gravity model by considering Dirac fermions invariant under local de Sitter transformations in four-dimensional open manifolds. In the context of Cartan geometry, fermions couple to spacetime through a $Spin(5)$ Cartan connection that can be decomposed in spin connection and tetrads. In presence of a gravitational instanton background, we show that the corresponding effective topological field theory becomes equivalent to a dynamical gravitational theory with positive cosmological constant and Barbero-Immirzi parameter. At classical level and in absence of matter, this theory is compatible with general relativity.
73703329
Non-Abelian Chern-Simons Theory from a Hubbard-like Model
Here, we provide a simple Hubbard-like model of spin-1/2 fermions that gives rise to the SU(2)-symmetric Thirring model that is equivalent, in the low-energy limit, to the Yang-Mills-Chern-Simons model. First, we identify the regime that simulates the SU(2) Yang-Mills theory. Then, we suitably extend this model so that it gives rise to the SU(2) Chern-Simons theory with level k≥2 that can support non-Abelian anyons. This is achieved by introducing multiple fermionic species and modifying the Thirring interactions, while preserving the SU(2) symmetry. Our proposal provides the means to theoretically and experimentally probe non-Abelian SU(2) level k topological phases.
96459470
(3+1) -dimensional topological quantum field theory from a tight-binding model of interacting spinless fermions
Currently, there is much interest in discovering analytically tractable (3+1)-dimensional models that describe interacting fermions with emerging topological properties. Towards that end we present a three-dimensional tight-binding model of spinless interacting fermions that reproduces, in the low-energy limit, a (3+1)-dimensional Abelian topological quantum field theory called the BF model. By employing a mechanism equivalent to Haldane's Chern insulator, we can turn the noninteracting model into a three-dimensional chiral topological insulator. We then isolate energetically one of the two Fermi points of the lattice model. In the presence of suitable fermionic interactions, the system, in the continuum limit, is equivalent to a generalized (3+1)-dimensional Thirring model. The low-energy limit of this model is faithfully described by the BF theory. Our approach directly establishes the presence of (2+1)-dimensional BF theory at the boundary of the lattice and it provides a way to detect the topological order of the model through fermionic density measurements.
117979829
A crucial hypothesis for Inflation
As is well known there are many different inflationary models that can explain the accelerated expansion occurred in the early Universe. It is possible that there exists a fundamental property of this period that could provide the corresponding field theory. Our hypothesis is that the Ricci scalar should assume a positive constant value during Inflation. Considering a single scalar field that drives the inflationary phase, we obtain uniquely the scalar potential and the coupling term between the scalar field and spacetime geometry. For this potential, that is well known in the inflationary scenario, the theoretical prediction of the spectral index ns is in perfect agreement with the experimental data. Interestingly in two dimensions, our model is equivalent to Liouville gravity.
2580056
Skyrmion Superfluidity in Two-Dimensional Interacting Fermionic Systems
In this article we describe a multi-layered honeycomb lattice model of interacting fermions which supports a new kind of parity-preserving skyrmion superfluidity. We derive the low-energy field theory describing a non-BCS fermionic superfluid phase by means of functional fermionization. Such effective theory is a new kind of non-linear sigma model, which we call double skyrmion model. In the bi-layer case, the quasiparticles of the system (skyrmions) have bosonic statistics and replace the Cooper-pairs role. Moreover, we show that the model is also equivalent to a Maxwell-BF theory, which naturally establishes an effective Meissner effect without requiring a breaking of the gauge symmetry. Finally, we map effective superfluidity effects to identities among fermionic observables for the lattice model. This provides a signature of our theoretical skyrmion superfluidy that can be detected in a possible implementation of the lattice model in a real quantum system.