Measuring molecular abundances in comet C/2014 Q2 (Lovejoy) using the APEX telescope

Comet composition provides critical information on the chemical and physical processes that took place during the formation of the Solar system. We report here on millimetre spectroscopic observations of the long-period bright comet C/2014 Q2 (Lovejoy) using the Atacama Pathfinder Experiment (APEX) band 1 receiver between 2015 January UT 16.948 to 18.120, when the comet was at heliocentric distance of 1.30 AU and geocentric distance of 0.53 AU. Bright comets allow for sensitive observations of gaseous volatiles that sublimate in their coma. These observations allowed us to detect HCN, CH3OH (multiple transitions), H2CO and CO, and to measure precise molecular production rates. Additionally, sensitive upper limits were derived on the complex molecules acetaldehyde (CH3CHO) and formamide (NH2CHO) based on the average of the strongest lines in the targeted spectral range to improve the signal-to-noise ratio. Gas production rates are derived using a non-LTE molecular excitation calculation involving collisions with H2O and radiative pumping that becomes important in the outer coma due to solar radiation. We find a depletion of CO in C/2014 Q2 (Lovejoy) with a production rate relative to water of 2 per cent, and relatively low abundances of Q(HCN)/Q(H2O), 0.1 per cent, and Q(H2CO)/Q(H2O), 0.2 per cent. In contrast the CH3OH relative abundance Q(CH3OH)/Q(H2O), 2.2 per cent, is close to the mean value observed in other comets. The measured production rates are consistent with values derived for this object from other facilities at similar wavelengths taking into account the difference in the fields of view. Based on the observed mixing ratios of organic molecules in four bright comets including C/2014 Q2, we find some support for atom addition reactions on cold dust being the origin of some of the molecules.Comment: 10 pages, 7 figures, to be published in MNRA

Sub-millimeter images of a dusty Kuiper belt around eta Corvi

We present sub-millimeter and mid-infrared images of the circumstellar disk around the nearby F2V star eta Corvi. The disk is resolved at 850um with a size of ~100AU. At 450um the emission is found to be extended at all position angles, with significant elongation along a position angle of 130+-10deg; at the highest resolution (9.3") this emission is resolved into two peaks which are to within the uncertainties offset symmetrically from the star at 100AU projected separation. Modeling the appearance of emission from a narrow ring in the sub-mm images shows the observed structure cannot be caused by an edge-on or face-on axisymmetric ring; the observations are consistent with a ring of radius 150+-20AU seen at 45+-25deg inclination. More face-on orientations are possible if the dust distribution includes two clumps similar to Vega; we show how such a clumpy structure could arise from the migration over 25Myr of a Neptune mass planet from 80-105AU. The inner 100AU of the system appears relatively empty of sub-mm emitting dust, indicating that this region may have been cleared by the formation of planets, but the disk emission spectrum shows that IRAS detected an additional hot component with a characteristic temperature of 370+-60K (implying a distance of 1-2AU). At 11.9um we found the emission to be unresolved with no background sources which could be contaminating the fluxes measured by IRAS. The age of this star is estimated to be ~1Gyr. It is very unusual for such an old main sequence star to exhibit significant mid-IR emission. The proximity of this source makes it a perfect candidate for further study from optical to mm wavelengths to determine the distribution of its dust.Comment: 22 pages, 4 figures. Scheduled for publication in ApJ 10 February 2005 issu

Field testing methodology for investigating the effect of systemic insecticides on honey bees

contribution to session IVTest methodolog

Unsuccessful dispersal affects life history characteristics of natal populations: The role of dispersal related variation in vital rates

International audienceIndividuals that disperse from one habitat to another has consequences for individual fitness, population dynamics and gene flow. The fitness benefits accrued in the new habitat are traded off against costs associated with dispersal. Most studies focus on costs at settlement and effects on settlement populations; the influence of dispersal to natal populations is assessed by monitoring change in numbers due to emigration. However, the extent to which natal populations are affected when individuals that invest in dispersal fail to disperse/emigrate is unclear. Here, we use an Integral Projection Model (IPM) to assess how developing into a disperser affects natal population structure and growth. We do so using the bulb mite (Rhizoglyphus robini) as a study system. Bulb mites, in unfavourable environments, develop into a dispersal (deutonymph) stage during ontogeny; these individuals are called dispersers with individuals not developing into this stage called non-dispersers. We varied disperser expression and parameterised IPMs to describe three simulations of successful and unsuccessful dispersal: (i) ‘no dispersal’ - dispersal stage is excluded and demographic data are from non-disperser individuals; (ii) ‘false dispersal’ - dispersal stage included and demographic data from non-disperser individuals are used; (iii) ‘true dispersal’ - dispersal stage included and demographic data are from individuals that go through the dispersal stage and from non-disperser individuals. We found that the type of dispersal simulation (no dispersal < false dispersal < true dispersal) and disperser expression increases generation time and reduces lifetime reproductive success and population growth rate. Our findings show that disperser individuals that fail to leave, can change the structure and growth of natal populations

Spectropolarimetric observations of Herbig Ae/Be Stars I: HiVIS spectropolarimetric calibration and reduction techniques

Using the HiVIS spectropolarimeter built for the Haleakala 3.7m AEOS telescope in Hawaii, we are collecting a large number of high precision spectropolarimetrc observations of stars. In order to precisely measure very small polarization changes, we have performed a number of polarization calibration techniques on the AEOS telescope and HiVIS spectrograph. We have extended our dedicated IDL reduction package and have performed some hardware upgrades to the instrument. We have also used the ESPaDOnS spectropolarimeter on CFHT to verify the HiVIS results with back-to-back observations of MWC 361 and HD163296. Comparision of this and other HiVIS data with stellar observations from the ISIS and WW spectropolarimeters in the literature further shows the usefulness of this instrument.Comment: 35 pages, 44 figures, Accepted by PAS

CO emission from discs around isolated HAeBe and Vega-excess stars

We describe results from a survey for J=3-2 12CO emission from visible stars with an infrared excess. The line is clearly detected in 21 objects, with molecular gas (>10^-3 Jupiter masses) common in targets with infrared excesses >0.01 (>56% of objects). Such high excesses indicate the presence of a disc of opening angle >12 degrees; within this, the optically thick disc prevents CO photodissociation. Two or three stars with associated CO have an excess <0.01, implying a disc opening angle <1 degree. Most line profiles are double-peaked or relatively broad. Model fits, assuming a Keplerian disc, indicate outer radii, R_out, of ~20-300 au. As many as 5 discs have outer radii smaller than the Solar System (50 au), and a further 4 have gas at radii <20 au. R_out is independent of the stellar spectral type (from K through to B9), but is correlated with total dust mass. R_out appears to decrease with time: discs around stars of age 3-7 Myr have a mean radius of ~210 au, whereas discs of age 7-20 Myr are a factor of 3 smaller. The only bona fide debris disc with detected CO is HD9672; this has a double peaked line profile and is the most compact gas disc observed, with a modelled radius 17 au). A fit to HD141569 suggests the gas lies in two rings of radii 90 and 250 au, similar to the scattered light structure. In both AB Aur and HD163296 the sizes of the molecular and dust scattering discs are also similar, suggesting that the gas and small dust grains are co-located.Comment: 16 pages, 5 figures MNRAS - accepte

Phonons in graphene with point defects

The phonon density of states (DOS) of graphene with different types of point defects (carbon isotopes, substitution atoms, vacancies) is considered. Using a solvable model which is based on the harmonic approximation and the assumption that the elastic forces act only between nearest neighboring ions we calculate corrections to graphene DOS dependent on type and concentration of defects. In particular the correction due to isotopic dimers is determined. It is shown that a relatively small concentration of defects may lead to significant and specific changes in the DOS, especially at low frequencies, near the Van Hove points and in the vicinity of the K-points of the Brillouin zone. In some cases defects generate one or several narrow gaps near the critical points of the phonon DOS as well as resonance states in the Brillouin zone regular points. All types of defects are characterized by the appearance of one or more additional Van Hove peaks near the (Dirac) K points and their singular contribution may be comparable with the effect of electron-phonon interaction. Besides, for low frequencies and near the critical points the relative change in density of states may be many times higher than the concentration of defects.Comment: 19 pages, 7 figure

Quantum marginal problem and N-representability

A variant of the quantum marginal problem was known from early sixties as N-representability problem. In 1995 it was designated by National Research Council of USA as one of ten most prominent research challenges in quantum chemistry. In spite of this recognition the progress was very slow, until a couple of years ago the problem came into focus again, now in framework of quantum information theory. In the paper I give an account of the recent development.Comment: A talk at 12 Central European workshop on Quantum Optics, July 2005, Bilkent University, Turke