Bias and consistency in time delay estimation methods: case of the double quasar HE 1104-1805

We present a short re-evaluation of a recently published time delay estimate for the gravitational lens system HE 1104-1805 with emphasis on important methodological aspects: bias of the statistics, inconsistency of the methods and use of the purposeful selection of data points(or so-called "cleaning") at the preprocessing stage. We show how the inadequate use of simple analysis methods can lead to too strong conclusions. Our analysis shows that there are indications for the time delay in HE 1104-1805 to be between -0.9 and -0.7 years, but still with a large uncertainty.Comment: 5 pages, 5 figures, accepted as a Letter to the Editor in A&

Three photometric methods tested on ground-based data of Q 2237+0305

The Einstein Cross, Q~2237+0305, has been photometrically observed in four bands on two successive nights at NOT (La Palma, Spain) in October 1995. Three independent algorithms have been used to analyse the data: an automatic image decomposition technique, a CLEAN algorithm and the new MCS deconvolution code. The photometric and astrometric results obtained with the three methods are presented. No photometric variations were found in the four quasar images. Comparison of the photometry from the three techniques shows that both systematic and random errors affect each method. When the seeing is worse than 1.0", the errors from the automatic image decomposition technique and the Clean algorithm tend to be large (0.04-0.1 magnitudes) while the deconvolution code still gives accurate results (1{sigma} error below 0.04) even for frames with seeing as bad as 1.7". Reddening is observed in the quasar images and is found to be compatible with either extinction from the lensing galaxy or colour dependent microlensing. The photometric accuracy depends on the light distribution used to model the lensing galaxy. In particular, using a numerical galaxy model, as done with the MCS algorithm, makes the method less seeing dependent. Another advantage of using a numerical model is that eventual non-homogeneous structures in the galaxy can be modeled. Finally, we propose an observational strategy for a future photometric monitoring of the Einstein Cross.Comment: 9 pages, accepted for publication in A&

Absolute diffuse calibration of IRAC through mid-infrared and radio study of HII regions

We investigate the diffuse absolute calibration of the InfraRed Array Camera on the Spitzer Space Telescope at 8.0microns using a sample of 43 HII regions with a wide range of morphologies near GLON=312deg. For each region we carefully measure sky-subtracted,point-source- subtracted, areally-integrated IRAC 8.0-micron fluxes and compare these with Midcourse Space eXperiment (MSX) 8.3-micron images at two different spatial resolutions, and with radio continuum maps. We determine an accurate median ratio of IRAC 8.0-micron/MSX\8.3-micron fluxes, of 1.55+/-0.15. From robust spectral energy distributions of these regions we conclude that the present 8.0-micron diffuse calibration of the SST is 36% too high compared with the MSX validated calibration, perhaps due to scattered light inside the camera. This is an independent confirmation of the result derived for the diffuse calibration of IRAC by the Spitzer Science Center (SSC). From regression analyses we find that 843-MHz radio fluxes of HII regions and mid-infrared (MIR) fluxes are linearly related for MSX at 8.3-microns and Spitzer at 8.0 microns, confirming the earlier MSX result by Cohen & Green. The median ratio of MIR/843-MHz diffuse continuum fluxes is 600 times smaller in nonthermal than thermal regions, making it a sharp discriminant. The ratios are largely independent of morphology up to a size of ~24 arcsec. We provide homogeneous radio and MIR morphologies for all sources. MIR morphology is not uniquely related to radio structure. Compact regions may have MIR filaments and/or diffuse haloes, perhaps infrared counter- parts to weakly ionized radio haloes found around compact HII regions. We offer two IRAC colour-colour plots as quantitative diagnostics of diffuse HII regions.Comment: 29 pages, LaTeX (aastex), incl. 31 PostScript (ps,eps) figures and 5 tables. Accepted by MNRAS (main journal). Replaced an unused file and added this URL for people wishing to download a version with high-resolution images: http://www.astro.wisc.edu/sirtf/martin.hii.accepted.pd

Systemic linear polyethylenimine (L‐PEI)‐mediated gene delivery in the mouse

Background Several nonviral vectors including linear polyethylenimine(L‐PEI) confer a pronounced lung tropism to plasmid DNA when injected into the mouse tail vein in a nonionic solution. Methods and results We have optimized this route by injecting 50 µg DNA with excess L‐PEI (PEI nitrogen/DNA phosphate=10) in a large volume of 5% glucose (0.4 ml). In these conditions, 1–5% of lung cells were transfected (corresponding to 2 ng luciferase/mg protein), the other organs remaining essentially refractory to transfection (1–10 pg luciferase/mg protein).β‐Galactosidase histochemistry confirmed alveolar cells, including pneumocytes, to be the main target, thus leading to the puzzling observation that the lung microvasculature must be permeable to cationic L‐PEI/DNA particles of ca 60 nm. A smaller injected volume, premixing of the complexes with autologous mouse serum, as well as removal of excess free L‐PEI, all severely decreased transgene expression in the lung. Arterial or portal vein delivery did not increase transgene expression in other organs. Conclusions These observations suggest that effective lung transfection primarily depends on the injection conditions: the large nonionic glucose bolus prevents aggregation as well as mixing of the cationic complexes and excess free L‐PEI with blood. This may favour vascular leakage in the region where the vasculature is dense and fragile, i.e. around the lung alveoli. Cationic particles can thus reach the epithelium from the basolateral side where their receptors (heparan sulphate proteoglycans) are abundant

Speeding up Simplification of Polygonal Curves using Nested Approximations

We develop a multiresolution approach to the problem of polygonal curve approximation. We show theoretically and experimentally that, if the simplification algorithm A used between any two successive levels of resolution satisfies some conditions, the multiresolution algorithm MR will have a complexity lower than the complexity of A. In particular, we show that if A has a O(N2/K) complexity (the complexity of a reduced search dynamic solution approach), where N and K are respectively the initial and the final number of segments, the complexity of MR is in O(N).We experimentally compare the outcomes of MR with those of the optimal "full search" dynamic programming solution and of classical merge and split approaches. The experimental evaluations confirm the theoretical derivations and show that the proposed approach evaluated on 2D coastal maps either shows a lower complexity or provides polygonal approximations closer to the initial curves.Comment: 12 pages + figure

Temporal evolution of sand corridors in a <i>Posidonia oceanica</i> seascape: a 15-year study

The spatial dynamic of Posidonia oceanica meadows is a process extending over centuries. This paper shows evidence of the natural dynamics of P. oceanica “shifting intermattes” or “sand corridors” (hereafter SCs): unvegetated patches within a dense meadow. We studied features and temporal evolution (2001-2015) of 5 SCs in the Calvi Bay (Corsica) at 15 m depth and followed the characteristics the P. oceanica meadow lining the edge of patches. All SCs show a similar topography. The eroded side is a vertical edge where roots, rhizomes and sediments are visible, when on the opposite colonized side, the sand is at the same level as the continuous meadow. The vertical edge reaches a maximum height of 160 cm and is eroded by orbital bottom currents with a maximum speed of 12 cm.s-1, the erosion speed ranging from 0.6 to 15 cm.y-1. SCs progress toward the coastline with a mean speed of 10 cm.y-1, the rate of colonization by P. oceanica shoots ranging from 1.5 to 21 cm.y-1. We calculated that the studied SCs would reach the coastline within 500 to 600 years. We finally discuss the implication of such dynamic in the framework of meadows’ colonization assessment and the seascape dynamic

A resolved analysis of cold dust and gas in the nearby edge-on spiral NGC 891

We investigate the connection between dust and gas in the nearby edge-on spiral galaxy NGC 891. High resolution Herschel PACS and SPIRE 70, 100, 160, 250, 350, and 500 $\mu$m images are combined with JCMT SCUBA 850 $\mu$m observations to trace the far-infrared/submillimetre spectral energy distribution (SED). Maps of the HI 21 cm line and CO(J=3-2) emission trace the atomic and molecular hydrogen gas, respectively. We fit one-component modified blackbody models to the integrated SED, finding a global dust mass of 8.5$\times$10$^{7}$ M$_{\odot}$ and an average temperature of 23$\pm$2 K. We also fit the pixel-by-pixel SEDs to produce maps of the dust mass and temperature. The dust mass distribution correlates with the total stellar population as traced by the 3.6 $\mu$m emission. The derived dust temperature, which ranges from approximately 17 to 24 K, is found to correlate with the 24 $\mu$m emission. Allowing the dust emissivity index to vary, we find an average value of $\beta$ = 1.9$\pm$0.3. We confirm an inverse relation between the dust emissivity spectral index and dust temperature, but do not observe any variation of this relationship with vertical height from the mid-plane of the disk. A comparison of the dust properties with the gaseous components of the ISM reveals strong spatial correlations between the surface mass densities of dust and the molecular hydrogen and total gas surface densities. Observed asymmetries in the dust temperature, and the H$_{2}$-to-dust and total gas-to-dust ratios hint that an enhancement in the star formation rate may be the result of larger quantities of molecular gas available to fuel star formation in the NE compared to the SW. Whilst the asymmetry likely arises from dust obscuration due to the geometry of the line-of-sight projection of the spiral arms, we cannot exclude an enhancement in the star formation rate in the NE side of the disk.Comment: Accepted for publication in A&A. 21 pages, including 13 figures and 4 table

Biomass Burning Aerosols in the Amazon Basin, Characterised by Lidar, Optical Particle Counters, and Modelling

This is the final version. Available from EDP Sciences via the DOI in this record. This article has no abstract.Natural Environment Research Council (NERC)Met Offic