The case for inflow of the broad-line region of active galactic nuclei

The high-ionization lines of the broad-line region (BLR) of thermal active galactic nuclei (AGNs) show blueshifts of a few hundred km/s to several thousand km/sec with respect to the low-ionization lines. This has long been thought to be due to the high-ionization lines of the BLR arising in a wind of which the far side of the outflow is blocked from our view by the accretion disc. Evidence for and against the disc-wind model is discussed. The biggest problem for the model is that velocity-resolved reverberation mapping repeatedly fails to show the expected kinematic signature of outflow of the BLR. The disc-wind model also cannot readily reproduce the red side of the line profiles of high-ionization lines. The rapidly falling density in an outflow makes it difficult to obtain high equivalent widths. We point out a number of major problems with associating the BLR with the outflows producing broad absorption lines. An explanation which avoids all these problems and satisfies the constraints of both the line profiles and velocity-resolved reverberation-mapping is a model in which the blueshifting is due to scattering off material spiraling inwards with an inflow velocity of half the velocity of the blueshifting. We discuss how recent reverberation mapping results are consistent with the scattering-plus-inflow model but do not support a disc-wind model. We propose that the anti-correlation of the apparent redshifting of H$\beta$ with the blueshifting of CIV is a consequence of contamination of the red wings of H$\beta$ by the broad wings of [O III].Comment: 15 pages, 15 figures. To appear in special issue of Astrophysics and Space Science, "Spectral Line Shapes in Astrophysics

Line Shifts, Broad-Line Region Inflow, And The Feeding Of Active Galactic Nuclei

Velocity-resolved reverberation mapping suggests that the broad-line regions (BLRs) of active galactic nuclei (AGNs) can have significant net inflow. We use the STOKES radiative transfer code to show that electron and Rayleigh scattering off the BLR and torus naturally explains the blueshifted profiles of high-ionization lines and the ionization dependence of the blueshifts. This result is insensitive to the geometry of the scattering region. If correct, then this model resolves the long-standing conflict between the absence of outflow implied by velocity-resolved reverberation mapping and the need for outflow if the blueshifting is the result of obscuration. The accretion rate implied by the inflow is sufficient to power the AGN. We suggest that the BLR is part of the outer accretion disk and that similar magnetohydrodynamic processes are operating. In the scattering model, the blueshifting is proportional to the accretion rate so high-accretion-rate AGNs will show greater high-ionization line blueshifts, as is observed. Scattering can lead to systematically too high black hole mass estimates from the C IV line. We note many similarities between narrow-line region (NLR) and BLR blueshiftings, and suggest that NLR blueshiftings have a similar explanation. Our model explains the higher blueshifts of broad absorption line QSOs if they are more highly inclined. Rayleigh scattering from the BLR and torus could be more important in the UV than electron scattering for predominantly neutral material around AGNs. The importance of Rayleigh scattering versus electron scattering can be assessed by comparing line profiles at different wavelengths arising from the same emission-line region.US National Science Foundation AST 03-07912, AST 08-03883Space Telescope Science Institute AR-09926.01GEMINI-CONICYT Fund of Chile 32070017FONDECYT of Chile 1120957French GdR PCHECenter for Theoretical Astrophysics (CTA) through Czech Ministry of Education, Youth and Sports LC06014ANR-11-JS56-013-01Astronom

Internal and external R&DF complements or substitutes? Evidence from a dynamic panel data model

We examine the impact of internal and external R&D on labor productivity in a 6-year panel of 304 innovating firms. We apply a dynamic linear panel data model that allows for decreasing returns to scale in internal and external R&D with a non-linear approximation of changes in the knowledge stock. We find complementarity between internal and external R&D, with a positive impact of external R&D only evident in case of sufficient internal R&D. The findings confirm the role of internal R&D in enhancing absorptive capacity and hence the effective utilization of external knowledge. These results suggest that empirical studies examining complementarities between continuously measured practices should adopt more general non-linear specifications to allow for correct inferences.R&D, Innovation, Complementarity, Dynamic panel data, Productivity

The Lutz-Kelker bias in trigonometric parallaxes

The theoretical prediction that trigonometric parallaxes suffer from a statistical effect, has become topical again now that the results of the Hipparcos satellite have become available. This statistical effect, the so-called Lutz-Kelker bias, causes measured parallaxes to be too large. This has the implication that inferred distances, and hence inferred luminosities are too small. Published analytic calculations of the Lutz-Kelker bias indicate that the inferred luminosity of an object is, on average, 30% too small when the error in the parallax is only 17.5%. Yet, this bias has never been determined empirically. In this paper we investigate whether there is such a bias by comparing the best Hipparcos parallaxes which ground-based measurements. We find that there is indeed a large bias affecting parallaxes, with an average and scatter comparable to predictions. We propose a simple method to correct for the LK bias, and apply it successfully to a sub-sample of our stars. We then analyze the sample of 26 `best' Cepheids used by Feast & Catchpole (1997) to derive the zero-point of the fundamental mode pulsators and leads to a distance modulus to the Large Magellanic Cloud - based on Cepheid parallaxes- of 18.56 +/- 0.08, consistent with previous estimates.Comment: MNRAS Letters in press; 6 pages LaTeX, 6 ps figure

Phylogenomics of Lanternfishes and the Evolution of Feeding Structures

Mechanisms of speciation in the deep-sea, an environment with few physical isolating barriers, are relatively understudied in deep-sea fishes. This research focuses on the lanternfishes (Myctophiformes ~250 species) as a study system to investigate speciation in deep-sea environments and to test new phylogenomic approaches at resolving contested phylogenetic relationships. Previous phylogenetic hypotheses of lanternfishes identify two monophyletic families (Myctophidae and Neoscopelidae) and two monophyletic subfamilies within Myctophidae (Myctophine and Lampanyctinae), based on morphological and molecular data. Although subfamily relationships have generally remained the same, hypotheses of higher order (tribe, genus, species) relationships lack resolution. This study is the first to infer the evolutionary relationships of lanternfishes with a genome scale target-enrichment approach with ultraconserved elements (UCEs), which are noncoding areas of the genome that are highly conserved across distantly related taxa. Our results infer a phylogeny of lanternfishes that includes a monophyletic Neoscopelidae, a monophyletic Myctophinae, and a paraphyletic Lampanyctinae. We elevate two tribes to subfamilies (Gymnoscopelinae and Diaphinae both previously within Lampanyctinae) in addition to Lampanyctinae and Myctophinae. Gymnoscopelinae was resolved as the stem myctophid group and Diaphinae as sister to Myctophinae. Little is known regarding how lanternfish achieved such high species richness in the deep sea, and many studies have focused on their bioluminescence. This study also focuses on the evolution of feeding structures in lanternfishes and the potential for niche differentiation in this group. Geometric morphometrics were performed on 955 lanternfish specimens, and an ancestral character-state reconstruction was used to examine patterns of evolution in mouth size in lanternfishes. We identify that mouth size in lanternfishes is highly variable, with general trends towards larger mouths in Lampanyctinae and Gymnoscopelinae and shorter mouths in Myctophinae. Of particular note, Diaphinae was found to occupy a large range of morphospace, with broad plasticity in mouth size among the examined species. To further investigate the evolution of feeding structures, we examined 229 lanternfish specimens within Myctophiformes, assessing variation in tooth anatomy, presence on tooth bearing bones, and presence of heterodonty. An ancestral character-state reconstruction was also used to examine the evolution of heterodonty in this group. Our results support at least four separate evolutions of heterodonty in lanternfishes. Once in the common ancestor of the tribe Lampanyctini, once in Diogenichthys, once in Centrobranchus, and possible multiple evolutions in Diaphus. Heterodonty tooth types are expressed by four different anatomical variations around a global ‘hook’ shape, which have allowed for specialization in feeding