Tracing the merger-driven evolution of active galaxies using the CJF sample

In the context of the evolution of large structures in the Universe, it is unclear whether active galaxies are a phase which each galaxy undergoes, and what is the importance of the evolution of black holes in their centers. Binary black hole (BBH) systems could play a key role in our understanding of the above question. We investigate the Caltech-Jodrell Bank flat-spectrum (CJF) sample for evidence in favor of the merger-driven evolution scheme of active galaxies and search tracer-systems of AGN evolution and possible indications of BBH candidates. We discuss the validity and ambiguity of such indications and formulate a set of selection criteria for the detection of such systems. We conduct an extensive literature search for all available multi-wavelength information, concentrating on the optical and infrared regime, in addition to morphological information of the CJF sources. We analyze the statistics of this sample, in terms of these properties. We find 1 ULIRG (Mrk 231) included in the CJF, prototype of a transitory system. In total 28.6% of the CJF sources with z<0.4 are distorted or have a companion. Given the unbiased sample used here, this provides strong evidence for the ubiquity of the merger phenomenon in the context of active galaxies. We find a correlation between the radio and the near-infrared luminosity for the high-luminosity sources, interpreted in the context of the interplay between a star-formation and AGN component. We find a connection between variability and evolutionary transitory systems, as selected through their near-infrared colors. We select 28 sources that trace the different evolution phases of an AGN, as well as a number of the most promising BBH candidates. We find 4 sources with almost periodical variability in the optical and radio on similar timescales.Comment: 18 pages, 6 figures, accepted for publication in A&A (updated to match proofs

Massive star evolution: Luminous Blue Variables as unexpected Supernova progenitors

Stars more massive than about 8 Msun end their lives as a Supernova (SN), an event of fundamental importance Universe-wide. Theoretically, these stars have been expected to be either at the red supergiant, blue supergiant, or Wolf-Rayet stage before the explosion. We performed coupled stellar evolution and atmospheric modeling of stars with initial masses between 20 Msun and 120 Msun. We found that the 20 Msun and 25 Msun rotating models, before exploding as SN, have spectra that do not resemble any of the aforementioned classes of massive stars. Rather, they have remarkable similarities with rare, unstable massive stars known as Luminous Blue Variables (LBV). While observations show that some SNe seem to have had LBVs as progenitors, no theoretical model had yet predicted that a star could explode at this stage. Our models provide theoretical support for relatively low-luminosity LBVs exploding as SN in the framework of single stellar evolution. This is a significant shift in paradigm, meaning that a fraction of LBVs could be the end stage of massive star evolution, rather than a transitory evolutionary phase. We suggest that type IIb SN could have LBV as progenitors, and a prime example could be SN 2008ax.Comment: 4 pages, 3 figures, accepted for publication in Astronomy and Astrophysic

The inflation Targeting effect on the inflation series: ANew Analysis Approach of evolutionary spectral analysis

In this work, we study the inflation targeting effect on the inflation dynamics in the case of four industrial countries. Our objective is to check whether the inflation targeting policy (ITP) has a significant impact on the change of the inflation path. We use a non-parametric approach that doesn't require any previous modelling. This is the evolutionary spectral analysis, as defined by Priestley (1965-1996). Then, we use a test that can detect many break points on the timeseries. This test is inspired by Subba Rao (1981). We use an extension to this test to allow the detection of multiple breaks. We base this on the extension ofAhamada and Boutahar (2002). This is the first time that this method is used in the case of inflation-targeting countries. We find that the inflation-targeting policyhad a transition period for countries that had a high and volatile inflation experience before the inflation-targeting adoption. There is the case of New Zealand,Canada and Sweden. In these countries, we identify a structural change in the inflation series resulting to the inflation targeting intervention. However, In thecase of other countries like United Kingdom that have a relatively lower inflation rate experience before the ITP adoption, we didn't find a break point caused by this monetary policy intervention. In this case, the ITP had a role of ensuring this price stability. This result is explained by the fact that the inflation targetingis relevant when the initial inflation to be stabilized is near the target range (Artus, 2004). So, in this paper we justify the intuition of Artus (2004). The second result in our paper consists on the nature of inflation stabilization during the inflation-targeting period. The results proof a long-term stabilization on the inflation dynamic in the period of IT. These results traduce the success of this new framework to anchor the inflation expectation anchoring. So, we can conclude thatthis policy is preferment to ensure price stability in the case of industrials countries.inflation targeting, spectral analysis and structural change

The transition period before the inflation targeting policy

In this paper, we study the inflation dynamics in an industrial inflation-targeting country (New Zealand). Our objective is to check if the inflation targeting policy has a transition period or not. Loosely speaking, we try to give some response to the famous debate: if the inflation targeting is a framework or a simple monetaryrule. For this purpose, we use a frequency approach: Evolutionary Spectral Analysis, as defined by Priestley (1965-1996). Then, we detect endogenously a structuralbreak point in inflation series, by applying a non-parametric test. This is the first time that this method is used in the case of inflation-targeting countries. Our main finding is that the adoption of the inflation-targeting policy in New Zealand was characterized by a transition period before the adoption of this framework. This period was characterized by many radical reforms, which caused a structuralbreak in the New Zealand inflation series. These reforms were made to lead back the inflation close to the initial target. In addition, these reforms increased the transparency and the credibility of the monetary policy. We conclude from our frequency analysis that the inflation series becomes stable in long-term after the adoption of the inflation targeting. This can be a justification of the effectiveness of this policy to ensure the price stability.New Zealand; inflation targeting; spectral analysis and structural change

The tourist area lifecycle and the unit roots test. A new economic perspective for a classic paradigm in tourism.

As many traditional tourist destinations have experienced a slow down in tourist arrivals and expenditure, Butler’s (1980) Tourist Area Life Cycle (TALC) model seems to attract new attention from tourist researchers. The TALC describes the evolution of a tourist area from its discovery to its final stage picturing an evolutionary path represented with an S shaped curve associated to the logistic function. The limits of growth and the shape of the curve represent the existence of congestion problems and upper carrying capacity limits. But the TALC has been repeatedly criticized by its lack of operability and its departures from the anticipated curve. An alternative way to test its existence is to estimate its theoretical logistic curve and test the presence of unit roots. The application of this new technique to Majorca concludes that the evolutionary path predicted by the TALC does not apply in this particular case. Even more, the empirical results could imply that shocks that affect to this destination will have not temporary but permanent effects, encouraging the adoption of pro-active policy measures.Destination lifecycle, carrying capacity, logistic function, unit root test

Sounding stellar cores with mixed modes

The space-borne missions CoRoT and Kepler have opened a new era in stellar physics, especially for evolved stars, with precise asteroseismic measurements that help determine precise stellar parameters and perform ensemble astero seismology. This paper deals with the quality of the information that we can retrieve from the oscillations. It focusses on the conditions for obtaining the most accurate measurement of the radial and non-radial oscillation patterns. This accuracy is a prerequisite for making the best with asteroseismic data. From radial modes, we derive proxies of the stellar mass and radii with an unprecedented accuracy for field stars. For dozens of subgiants and thousands of red giants, the identification of mixed modes (corresponding to gravity waves propagating in the core coupled to pressure waves propagating in the envelope) indicates unambiguously their evolutionary status. As probes of the stellar core, these mixed modes also reveal the internal differential rotation and show the spinning down of the core rotation of stars ascending the red giant branch. A toy model of the coupling of waves constructing mixed modes is exposed, for illustrating many of their features.Comment: Meeting: New advances in stellar physics: from microscopic to macroscopic processes Roscoff, 27-31 May 201

Searching for Hydrogen in Type Ib Supernovae

We present synthetic spectral fits of the typical Type Ib SN 1999dn and the Hydrogen Rich Ib SN 2000H using the generalized non-local thermodynamic equilibrium stellar atmospheres code \phx. We fit model spectra to five epochs of SN 1999dn ranging from ten days pre-maximum light to 17 days post-maximum light and the two earliest epochs of SN 2000H available, maximum light and six days post-maximum. Our goal is to investigate the possibility of hydrogen in Type Ib Supernovae (SNe Ib), specifically a feature around 6200\AA\ which has previously been attributed to high velocity H-alpha. In earlier work on SN 1999dn we found the most plausible alternative to H-alpha to be a blend of Si II and Fe II lines which can be adjusted to fit by increasing the metallicity. Our models are simple; they assume a powerlaw density profile with radius, homologous expansion, and solar compositions. The helium core is produced by burning 4H --> He in order to conserve nucleon number. For models with hydrogen the outer skin of the model consists of a shell of solar composition. The hydrogen mass of the standard solar composition shell is M_H less than about 0.001 times the mass of the sun in SN 1999dn and M_H less than about 0.2 times the mass of the sun for SN 2000H. Our models fit the observed spectra reasonably well, successfully reproducing most features including the characteristic He I absorptions. The hydrogen feature in SN 1999dn is clear, but much more pronounced in SN 2000H. We discuss a possible evolutionary scenario that accounts for the dichotomy in the hydrogen shell mass between these two supernovae.Comment: 20 pages, 11 figures, ApJ, in pres

Submm-bright QSOs at z~2: signposts of co-evolution at high z

We have assembled a sample of 5 X-ray and submm-luminous z~2 QSOs which are therefore both growing their central black holes through accretion and forming stars copiously at a critical epoch. Hence, they are good laboratories to investigate the co-evolution of star formation and AGN. We have performed a preliminary analysis of the AGN and SF contributions to their UV-to-FIR SEDs, fitting them with simple direct (disk), reprocessed (torus) and star formation components. All three are required by the data and hence we confirm that these objects are undergoing strong star formation in their host galaxies at rates 500-2000 Msun/y. Estimates of their covering factors are between about 30 and 90%. In the future, we will assess the dependence of these results on the particular models used for the components and relate their observed properties to the intrinsice of the central engine and the SF material, as well as their relevance for AGN-galaxy coevolution.Comment: 6 pages, 2 figures, contributed talk to "Nuclei of Seyfert galaxies and QSOs - Central engine & conditions of star formation" November 6-8, 2012. MPIfR, Bonn, Germany. Po