Study of the dynamic tear film aberrations using a curvature sensing setup

The advancement in adaptive optics in recent years has increased the interest in the dynamic aberrations of the eye, including those introduced by the first optical surface provided by the tear film. A curvature sensing system to measure the dynamic topography of the tear film is described. This optical system was used to measure the aberrations of the tear film on 14 eyes. The evolution of this surface is monitored through videos of the tear film topography. The effect on optical quality is studied from the time-evolution of the RMS wavefront error showing non-negligible aberration variations attributed to the tear film layer; the effect of tear film break-up on the ocular optical quality is also discussed. Furthermore, the aberration maps are decomposed into their constituent Zernike components showing stronger contributions from 4th order terms, and also from those components with vertical symmetry which can be attributed to the effect of the eye lids on the tear film. Finally, the power spectra of the RMS wavefront error evolution show that the strongest contributions of the tear film aberrations are to be found at low frequencies, typically below 2Hz

Fragmented molecular complexes: The role of the magnetic field in feeding internal supersonic motions

A hierarchical structure for molecular complexes in their cold phase i.e., preceeding the formation of massive stars, was derived from extensive large scale CO(13)(J=1=0) observations: the mass is found to be distributed into virialized clouds which fill only a very low fraction approx. 01 of the volume of the complex and are supported against gravity by internal supersonic motions. An efficient mechanism was found to transfer kinetic energy from the orbital motions of the clouds to their internal random motions. The large perturbations of the magnetic field induced at the cloud boundaries by their interactions with their neighbors generate systems of hydromagnetic waves trapped inside the clouds. The magnetic field lines being closely coupled to the gas at the densities which prevail in the bulk of the clouds volume, internal velocity dispersion is thus generated. Some conclusions derived from this data are given

MM Observations of IRAS Galaxies: Dust Properties, Luminosity Functions and Contributions to the Sub-MM Background

We have studied the FIR/{\it mm} spectrum of IR galaxies by combining IRAS photometry with new {\it mm} data on a complete southern IRAS galaxy sample. The observed spectra and a dust model emphasize a dicothomy in the galaxy population: half of the objects with a lot of warm dust are characterized by higher values of the bolometric (UV-FIR) luminosity, of the dust-to-gas mass ratio, of the dust optical depths and extinction, while those dominated by cold ({\it cirrus}) dust show opposite trends. From these data we derive the {\it mm} luminosity function of galaxies and estimate their contribution to the sub-{\it mm} background (BKG).Comment: 4 pg Latex file (using included crckapb.sty) gzip'd tar'd file including 3 ps figures. Proceedings of 'Cold dust Morphology Conference', Johannesburg, South Africa, January 21-26 1996 A wrong figure is replace

Anisotropy Studies of the Unresolved Far-infrared Background

Dusty, starforming galaxies and active galactic nuclei that contribute to the integrated background intensity at far-infrared wavelengths trace the large-scale structure. Below the point source detection limit, correlations in the large-scale structure lead to clustered anisotropies in the unresolved component of the far-infrared background (FIRB). The angular power spectrum of the FIRB anisotropies could be measured in large-area surveys with the Spectral and Photometric Imaging Receiver (SPIRE) on the upcoming Herschel observatory. To study statistical properties of these anisotropies, the confusion from foreground Galactic dust emission needs to be reduced even in the ``cleanest'' regions of the sky.The multi-frequency coverage of SPIRE allows the foreground dust to be partly separated from the extragalactic background composed of dusty starforming galaxies as well as faint normal galaxies. The separation improves for fields with sizes greater than a few hundred square degrees and when combined with Planck data. We show that an area of about $\sim$ 400 degrees$^2$ observed for about 1000 hours with Herschel-SPIRE and complemented by Planck provides maximal information on the anisotropy power spectrum. We discuss the scientific studies that can be done with measurements of the unresolved FIRB anisotropies including a determination of the large scale bias and the small-scale halo occupation distribution of FIRB sources with fluxes below the point-source detection level.Comment: 10 pages, 8 figures, replaced to match the extended version, accepted by Ap

On the carbon abundance in Comet Halley derived from the 3 micron feature: Comparison with interstellar dust

In spite of some similarities with the infrared features observed in the interstellar medium, the 3 micron signature observed in comet Halley's spectrum shows two distinct differences: (1) the 3.28 micron and 3.37 micron cometary features are both in emission, while the 3.37 micron interstellar feature is most often observed in absorption; and (2) there is no associated emission feature beyond 6 micron in the cometary spectrum. These two facts can be simply explained if it is assumed that the excitation mechanism is resonance fluorescence by the solar IR radiation field. With this assumption, it is found that hydrocarbons are present in roughly equal quantities in both the saturated forms, with a total carbon abundance of about 30 percent of H2O. This carbon abundance can be compared with the abundances derived for the interstellar dust when all condensed (or condensable) components are considered

FIRBACK: II. Data Reduction and Calibration of the 170 micron ISO Deep Cosmological Survey

We present the final reduction and calibration of the FIRBACK ISOPHOT data. FIRBACK is a deep cosmological survey performed at 170 microns. This paper deals with the ISOPHOT C200 camera with the C160 filter. We review the whole data reduction process and compare our final calibration with DIRBE (for the extended emission) and IRAS (for point sources). The FIRBACK source extraction and galaxy counts is discussed in a companion paper (Dole et al., 2001).Comment: Accepted for publication in A&A. 9 pages, includes new aa.cls. Also available (with better quality figures) at http://wwwfirback.ias.u-psud.fr and http://mips.as.arizona.edu/~hdole/firback (new aa.cls is here