The extended narrow line region in MKN 79. I. Observations.

We present deep long slit spectra of Mkn79 in position angles PA=12$^{o}$ and PA=50$^{o}$ obtained with the WHT. These data prove the existence of an extended narrow line region in PA=12$^{o}$, which coincides with the triplet radio structure (Ulvestad \& Wilson 1984) and the observed outflow of material from the nucleus at PA=10$^{o}$ (Whittle et al. 1988). The ratios of the high to low ionization lines indicate a higher level of gas excitation in PA=12$^{o}$ compared to PA=50$^{o}$. The [NII]$\lambda$6583/H$\alpha$ and [SII]$\lambda$6717,31/H$\alpha$ versus [OIII]$\lambda$5007/H$\beta$ line ratios are consistent with excitation by an AGN continuum rather than a HII region.Comment: uuencoded compressed postscript. The preprint is also available at http://www.ast.cam.ac.uk/preprint/PrePrint.htm

The effect of an attenuated continuum on the coronal line spectrum of NGC 1068 and the Circinus galaxy

We present photoionization models of the optical and IR coronal line spectrum in NGC1068 and the Circinus galaxy. The line fluxes have been calculated using (a) a non-thermal (nuclear) continuum source and (b) the non-thermal continuum plus a UV bump due to a stellar cluster. We take into account the effect of attenuation of these continua by gas with column density $10^{22} cm^{-2}$ located between the nucleus and the coronal line region. The calculated coronal line ratios are in a good agreement with those observed in NGC1068 for a model in which about 40% of the line emission comes from gas illuminated by unattenuated, non-thermal continuum, and about 60% from gas illuminated by attenuated, non-thermal continuum. The electron density of the coronal line emitting gas in NGC1068 is found to be $10^4 cm^{-3}$. In the Circinus galaxy the coronal line emission comes from gas with electron density $10^3 cm^{-3}$ illuminated entirely by attenuated, non-thermal continuum. The derived ionization parameters for both coronal line regions are very similar, but the different densities imply a higher ionizing photon flux in NGC1068, consistent with the higher observed excitation state of the line emitting gas in that galaxy. A possible geometry of the coronal line region of both galaxies is discussed, in which the distribution of the attenuating gas may be strongly affected by the relative strength of the nuclear radio-jet. The stronger radio-jet in NGC1068 may have cleared a channel through the NLR allowing some unattenuated nuclear continuum to illuminate part of the coronal line region.Comment: Accepted for publication in Astronomy and Astrophysics (main journal

Palaeoecological and palaeoclimatic conditions on the Karelian Isthmus (northwestern Russia) during the Holocene

© 2020 University of Washington. Published by Cambridge University Press. The Holocene evolution of climate in easternmost Fennoscandia and adjoining regions is poorly known, compared with regions to the west. To address this, a 224-cm-long sediment core from Lake Medvedevskoe, situated on the Central Upland of the Karelian Isthmus, northwestern Russia, was examined to investigate variations in the Holocene climate. Analyses indicate that the dry and cold late Pleistocene climate was replaced by the warmer and more humid early Holocene climate after ca. 10.5 cal ka BP. During the early Holocene, the lake transitioned from an oligotrophic to a mesotrophic state, characterized by a Corynocera ambigua/Microtendipes pedellus-type phase, which has been found in other lakes across Fennoscandia. Taxonomic shifts in the chironomid and cladoceran communities associated with climatic amelioration were identified at ca. 10.6 and 9.17 cal ka BP using breakpoint analysis. Reconstructed July temperatures indicate climatic patterns comparable to those seen in eastern Fennoscandia. The warm period between ca. 9.5 and 5.5 cal ka BP (T July 14.5-15°C) was interrupted by a slight cooling between ca. 8.5 and 8.1 cal ka BP, possibly relating to the 8.2 event, with peak temperature reached at ca. 7.8 cal ka BP. Neoglacial cooling started after ca. 5.5 cal ka BP, the median reconstructed July temperature dropped to 2-3°C cooler than present (mean T July 13.5°C) before recovering in recent time

Recent shift in biological communities: A case study from the Eastern European Russian Arctic (Bol`shezemelskaya Tundra)

Recent Arctic warming has major influences on biological communities, especially in freshwater environments. There is substantial evidence that lake ecosystems in the Canadian Arctic and Fennoscandia are undergoing changes that have been linked to human-induced climate warming during the past 150–100 years. However, only few data linking recent climatic changes with the changes in biological communities are available from the Russian Arctic. We investigated a short sediment core (bottom of the core dates to 1830 CE) from Lake Bolshoy Kharbey, the biggest lake of the Bol`shezemelskaya Tundra, western Russian Arctic, using chironomid, cladocera, diatom and palynological analyses. Variations in biological proxy were linked to regional meteorological data and compared with the available sub-recent palaeoecological and hydrobiological studies from the region. The overall change in species composition was the smallest for terrestrial vegetation (0.485 SD) followed by cladoceran communities (0.966 SD). Chironomid taxonomic turnover was 1.331 SD, and the greatest rate of change was observed in diatom assemblages (1.701 SD). Changes in biological communities demonstrated a correlation with meteorologically recorded climatic parameters (air temperature and precipitation). The strongest taxonomic shifts in biological communities took place in 1880 and 1980. Both dates can be linked with prominent and recent climatic events: 1880 can be related to the end of the Little Ice Age in the region and 1980 is the beginning of the modern accelerating warming

The Holocene environmental changes revealed from the sediments of the Yarkov sub-basin of Lake Chany, south-western Siberia

Lake Chany is the largest endorheic lake in Siberia whose catchment is entirely on the territory of Russia. Its geographical location on the climate-sensitive boundary of wet and dry landscapes provides an opportunity to gain more knowledge about environmental changes in the West Siberian interior during the Holocene and about the evolution of the lake itself. Sediment cores obtained from the Yarkov sub-basin of the lake in 2008 have been comprehensively studied by a number of approaches including sedimentology and AMS dating, pollen, diatom and chironomid analyses (with statistical interpretation of the results), mineralogy of authigenic minerals and geochemistry of plant lipids (biomarker analysis.). Synthesis of new results presented here and published data provides a good justification for our hypothesis that Lake Chany is very young, no older than 3.6 ka BP. Before that, between 9 and 3.6 ka BP, the Chany basin was a swampy landscape with a very low sedimentation rate; it could not be identified as a water body. In the early lake phase, between 3.6 and 1.5 ka BP, the lake was shallow, 1.2–3.5 m in depth, and it rose to its modern size, up to 6.5 m in depth, during the last millennium. Our data reveal important changes in the understanding of the history of this large endorheic lake, as before it was envisioned as a large lake with significant changes in water level since ca. 14 ka BP. In addition to hydrology, our proxies provide updates and details of the regional vegetation and climate change since ca. 4 ka BP in the West-Siberian forest-steppe and steppe. As evolution of the Chany basin is dependent on hydroclimatic changes in a large region of southern West Siberia, we compare lake-level change and climate-change proxies from the other recently and most comprehensively studied lakes of the region