The 1999 Quadrantids and the lunar Na atmosphere

Enhancements of the Na emission and temperature from the lunar atmosphere were reported during the Leonid meteor showers of 1995, 1997 and 1998. Here we report a search for similar enhancement during the 1999 Quadrantids, which have the highest mass flux of any of the major streams. No enhancements were detected. We suggest that different chemical-physical properties of the Leonid and Quadrantid streams may be responsible for the differenc

VLBA imaging of radio-loud BAL QSOs

Broad Absorption Line Quasars (BAL QSOs) have been found to be associated with extremely compact radio sources. These reduced dimensions can be either due to projection effects or these objects might actually be intrinsically small. Exploring these two hypotheses is important to understand the nature and origin of the BAL phenomenon because orientation effects are an important discriminant between the different models proposed to explain this phenomenon. In this work we present VLBA observations of 5 BAL QSOs and discuss their pc-scale morpholog

Morphology and orientation of radio-loud Broad Absorption Line quasars

ABSTRACT: BAL QSOs are still a not-well understood class of objects. In the UV spectra they show Broad Absorption Lines (BALs) in the blue wings of the UV resonance lines, due to ionized gas with outflow velocities up to 0.2 c. Two different models have been proposed to explain this phenomenon: in the orientation model BAL-producing outflows should be present in all QSOs, but seen only when they intercept the observer’s line of sight. In the evolutionary model BAL QSOs are young sources still expelling their dust cocoon. We performed VLBI observations with both the EVN (4.8 GHz) and VLBA (4.8 and 8.4 GHz) to map the pc-scale structure of the brightest radio-loud objects of our sample. A variety of morphologies and orientations have been found: 5 BAL QSOs in a total of 9 observed sources have a resolved structure, with a linear size < 1 kpc. In some cases the spectral index analysis of single components suggests a beamed emission toward the observer, in other cases a symmetric structure is evident from the map. From VLBI observations BAL QSOs do not seem to have a preferred orientation. Dimensions are typical of young GPS-CSS sources. This evidence could indicate an evolutionary scenario for the origin of this class of quasars

1999 Quadrantids and the lunar Na atmosphere

Enhancements of the Na emission and temperature from the lunar atmosphere were reported during the Leonids meteor showers of 1995, 1997 and 1998. Here we report a search for similar enhancement during the 1999 Quadrantids, which have the highest mass flux of any of the major streams. No enhancements were detected. We suggest that different chemical-physical properties of the Leonid and Quadrantid streams may be responsible for the difference.Comment: 5 pages, 1 figure, accepted for publication in MNRA

Evidence for rapid ice flow and proglacial lake evolution around the central Strait of Magellan region, southernmost Patagonia

This paper presents a detailed palaeoglaciological reconstruction of ice sheet dynamics in the Seno Skyring, Seno Otway and Strait of Magellan region of the former Patagonian Ice Sheet, with a particular focus on previously hypothesised zones of rapid ice flow and the evolution of proglacial lakes. Geomorphological mapping from a combination of satellite imagery and oblique and vertical aerial photographs reveals a variety of glacial landforms that are grouped into several discrete flow-sets and associated ice margin positions. The most distinct features are represented by flow-sets of highly elongate streamlined glacial lineations on both sides of the Strait of Magellan. Based on the shape and dimensions of the flow-sets and their abrupt lateral margins, a transverse and longitudinal variation in glacial lineation length and elongation ratio, and the reported presence of a potentially deformable bed and thrust moraines, the flow-sets are interpreted as zones of rapid ice flow within the Otway and Magellan lobes. We hypothesise that this provides evidence for contemporaneous surge-like advances within the lobes, which may explain the asymmetry in the lobate margin positions on either side of the strait. The mechanisms that initiated rapid flow are unclear, but are likely to have been influenced by internal factors such as a change in thermal/hydrological conditions at the bed. The topography of the region suggests ice-dammed lakes would have formed as the ice lobes retreated. The westernmost of the former lakes, Lake Skyring, is delimited by a series of palaeo-shorelines surrounding the present-day lake Laguna Blanca and we reconstruct lake evolution based on manipulation of a digital elevation model. The size and orientation of meltwater channels and a large outwash plain indicate that Lake Skyring drained eastwards towards the Strait of Magellan, probably quite rapidly. We conclude that the potential for quasi-independent surge-like behaviour within adjacent lobes raises the possibility that, during climate-driven ice expansion, some advances in this region may have been partly controlled by secondary internal feedback mechanisms

K-band imaging of 52 B3-VLA quasars: Nucleus and host properties

We present K-band imaging and photometry of a sample of 52 radio-loud quasars (RQs) selected from the B3 survey with flux densities greater than 0.5 Jy at 408 MHz. The optical completeness of the sample is 90%, and the quasars cover the redshift range 0.4-2.3. For ? 57% of the sources for which the quality of the images allowed a detailed morphological study (16/28), resolved extended emission was detected around the QSO, and its K flux was measured. Interpreting this "fuzz" as starlight emission from the host galaxy, its location on the K-z plane at z < 1 is consistent with radio quasars being hosted by galaxies similar to radio galaxies (RGs) or giant ellipticals (gE's). At higher redshifts the detected host galaxies of RQs are more luminous than are typical RGs and gE's, although some weak detections or upper limits are consistent with a similar fraction of RQs being hosted by galaxies with the expected luminosities for RGs or gE's. The study of the B-K color distribution of the QSO nuclei, after removing the contribution of K emission from the host galaxy, confirm that these sources are not reddened by large amounts of dust, with an estimated extinction Av < 1.0 mag at z ? 1. We find a significant correlation between radio power and nuclear infrared luminosity, indicating a direct link between the radio synchrotron emission and the nuclear emission in K. This correlation is more tight for the steep-spectrum sources (99.97% significance). In addition, a trend is found between radio power and infrared luminosity of the host galaxy (or mass), in the sense that the most powerful quasars inhabit the most luminous galaxies. The similarity of this tendency with that found for powerful FR II radio galaxies is consistent with the unification model for radio sources.We have made use of the APM Catalogues. We thank the referee, R. Antonucci, for valuable comments and suggestions that improved the paper. We also thank S. Charlot for providing us with the GISSEL package, and L. Cayo n and I. Ferreras for their help in obtaining the k- and evolutionary corrections from the GISSEL models. The William Herschel Telescope is operated by the Royal Greenwich Observatory at the Spanish Observatorio del Roque de Los Muchachos of the Instituto de Astrofísica de Canarias on behalf of the Science and Engineering Research Council of the United Kingdom and the Netherlands Organization for ScientiÐc Research. Financial support was provided under DGICYT project PB92 0501, DGES project PB95 0122, and by the Comision Mixta Caja Cantabria Universidad de Cantabria

Limits on dust extinction in B3 QSOS

The broad range of optical?infrared colours of radio QSOs, 1 < B ? K < 6, has been cited as evidence for several mag of dust extinction (Webster et al., 1995). If such large extinctions are typical, the implications for our understanding of the space density of optically selected QSOs are profound. We have previously found that the host galaxies of several of the reddest B3 QSOs are readily detectable in K-band images. This suggests contamination of the K apparent magnitudes by starlight, i.e. the redness in B ? K may be due to excess light in K, rather than to dust extinction of the B light. We have now imaged the B3 QSOs in UBV R, and we use the range of observed optical and optical?IR colours to place an upper limit on the amount of dust extinction present, rest-frame AV < 1.5 ma