Galaxy evolution across the optical emission-line diagnostic diagrams?

The discovery of the M-sigma relation, the local galaxy bimodality, and the link between black-hole and host-galaxy properties, have raised the question whether AGN play a role in galaxy evolution. Several theoretical models implement AGN feedback to explain the observed galaxy luminosity function, and possibly the color and morphological transformation of spiral galaxies into passive ellipticals. To understand the importance of AGN feedback, a study of the AGN populations in the radio-optical domain is crucial. A mass sequence linking star-forming galaxies and AGN has been already noted in previous works, and it is now investigated as possible evolutionary sequence. We observed a sample of 119 intermediate-redshift (0.04<z<0.4) SDSS-FIRST radio emitters with the Effelsberg 100-m telescope at 4.85 and 10.45 GHz and obtained spectral indices. We find indications of spectral index flattening in high-metallicity star-forming galaxies, composite galaxies, and Seyferts. This "flattening sequence" along the [NII]-based emission-line diagnostic diagram is consistent with the hardening of galaxy ionizing field, due to nuclear activity. After combining our data with FIRST measurements at 1.4 GHz, we find that the three-point radio spectra of Seyferts and LINERs show substantial differences, attributable to small radio core components and larger (arcsecond sized) jet/lobe components, respectively. A visual inspection of FIRST images seems to confirm this hypothesis. Galaxies along this sequence are hypothesized to be transitioning from the active star-forming galaxies (blue cloud) to the passive elliptical galaxies (red sequence). This supports the suggestion that AGN play a role in shutting down star-formation, and allow the transition from one galaxy class to the other.Comment: 20 pages, 19 figures, accepted for publication in A&

A Unified Theory for the Atmospheres of the Hot and Very Hot Jupiters: Two Classes of Irradiated Atmospheres

We highlight the importance of gaseous TiO and VO opacity on the highly irradiated close-in giant planets. The atmospheres of these planets naturally fall into two classes that are somewhat analogous to the M- and L-type dwarfs. Those that are warm enough to have appreciable opacity due to TiO and VO gases we term the ``pM Class'' planets, and those that are cooler we term ``pL Class'' planets. We calculate model atmospheres for these planets, including pressure-temperature profiles, spectra, and characteristic radiative time constants. We show that pM Class planets have hot stratospheres $\sim$2000 K and appear ``anomalously'' bright in the mid infrared secondary eclipse, as was recently found for planets HD 149026b and HD 209458b. This class of planets absorbs incident flux and emits thermal flux from high in their atmospheres. Consequently, they will have large day/night temperature contrasts and negligible phase shifts between orbital phase and thermal emission light curves, because radiative timescales are much shorter than possible dynamical timescales. The pL Class planets absorb incident flux deeper in the atmosphere where atmospheric dynamics will more readily redistribute absorbed energy. This will lead to cooler day sides, warmer night sides, and larger phase shifts in thermal emission light curves. Around a Sun-like primary this boundary occurs at $\sim$0.04-0.05 AU. The eccentric transiting planets HD 147506b and HD 17156b alternate between the classes. Thermal emission in the optical from pM Class planets is significant red-ward of 400 nm, making these planets attractive targets for optical detection. The difference in the observed day/night contrast between ups Andromeda b (pM Class) and HD 189733b (pL Class) is naturally explained in this scenario. (Abridged.)Comment: Accepted to the Astrophysical Journa

On four numerical schemes for a unipolar degenerate drift-diffusion model

International audienceWe consider a unipolar degenerate drift-diffusion system where the relation between the concentration of the charged species c and the chemical potential h is $h(c) = log(c/(1−c))$. For four different finite volume schemes based on four different formulations of the fluxes of the problem, we discuss stability and existence results. For two of them, we report a convergence proof. Numerical experiments illustrate the behaviour of the different schemes

From Solar Proton Burning to Pionic Deuterium through the Nambu-Jona-Lasinio model of light nuclei

Within the Nambu-Jona-Lasinio model of light nuclei (the NNJL model), describing strong low-energy nuclear interactions, we compute the width of the energy level of the ground state of pionic deuterium. The theoretical value fits well the experimental data. Using the cross sections for the reactions nu_e + d -> p + p + e^- and nu_e + d -> p + n + nu_e, computed in the NNJL model, and the experimental values of the events of these reactions, detected by the SNO Collaboration, we compute the boron neutrino fluxes. The theoretical values agree well with the experimental data and the theoretical predictions within the Standard Solar Model by Bahcall. We argue the applicability of the constraints on the astrophysical factor for the solar proton burning, imposed by helioseismology, to the width of the energy level of the ground state of pionic deuterium. We show that the experimental data on the width satisfy these constraints. This testifies an indirect measurement of the recommended value of the astrophysical factor for the solar proton burning in terrestrial laboratories in terms of the width of the energy level of the ground state of pionic deuterium.Comment: 10 pages, no figures, Late

Dynamic modulation of photonic crystal nanocavities using gigahertz acoustic phonons

Photonic crystal membranes (PCM) provide a versatile planar platform for on-chip implementations of photonic quantum circuits. One prominent quantum element is a coupled system consisting of a nanocavity and a single quantum dot (QD) which forms a fundamental building block for elaborate quantum information networks and a cavity quantum electrodynamic (cQED) system controlled by single photons. So far no fast tuning mechanism is available to achieve control within the system coherence time. Here we demonstrate dynamic tuning by monochromatic coherent acoustic phonons formed by a surface acoustic wave (SAW) with frequencies exceeding 1.7 gigahertz, one order of magnitude faster than alternative approaches. We resolve a periodic modulation of the optical mode exceeding eight times its linewidth, preserving both the spatial mode profile and a high quality factor. Since PCMs confine photonic and phononic excitations, coupling optical to acoustic frequencies, our technique opens ways towards coherent acoustic control of optomechanical crystals.Comment: 11 pages 4 figure

A Consistency Test of Spectroscopic Gravities for Late-Type Stars

Chemical analyses of late-type stars are usually carried out following the classical recipe: LTE line formation and homogeneous, plane-parallel, flux-constant, and LTE model atmospheres. We review different results in the literature that have suggested significant inconsistencies in the spectroscopic analyses, pointing out the difficulties in deriving independent estimates of the stellar fundamental parameters and hence,detecting systematic errors. The trigonometric parallaxes measured by the HIPPARCOS mission provide accurate appraisals of the stellar surface gravity for nearby stars, which are used here to check the gravities obtained from the photospheric iron ionization balance. We find an approximate agreement for stars in the metallicity range -1 <= [Fe/H] <= 0, but the comparison shows that the differences between the spectroscopic and trigonometric gravities decrease towards lower metallicities for more metal-deficient dwarfs (-2.5 <= [Fe/H] <= -1.0), which casts a shadow upon the abundance analyses for extreme metal-poor stars that make use of the ionization equilibrium to constrain the gravity. The comparison with the strong-line gravities derived by Edvardsson (1988) and Fuhrmann (1998a) confirms that this method provides systematically larger gravities than the ionization balance. The strong-line gravities get closer to the physical ones for the stars analyzed by Fuhrmann, but they are even further away than the iron ionization gravities for the stars of lower gravities in Edvardsson's sample. The confrontation of the deviations of the iron ionization gravities in metal-poor stars reported here with departures from the excitation balance found in the literature, show that they are likely to be induced by the same physical mechanism(s).Comment: AAS LaTeX v4.0, 35 pages, 10 PostScript files; to appear in The Astrophysical Journa