Planar photonic crystal

We present results of guiding light in a single-line-defect planar photonic crystal (PPC) waveguide with 90° and 60° bends. The wave guiding is obtained by total internal reflection perpendicular to the plane of propagation and by the photonic band gap for the 2D photonic crystal in the plane. The results for photonic waveguiding are shown and demonstrated at 1.5 µm wavelength

Early Diagenesis of Plitvice Lakes Waterfall and Barrier Treavertine Deposits

Travertine forms spectacular waterfalls, barriers, and subaqueous finegrained lake-fill accumulations throughout the Plitvice National Park, Croatia, northwestern Yugoslavia. Barrier deposits form dams, behind which, the lakes of the Plitvice complex are situated. Three generations of low-magnesian calcite spar comprise the waterfall and barrier forming travertines. The initial precipitates generally are composed of cloudy, very finely to medium crystalline equant to bladed spar. A later generation is composed of clear, isopachous layers of medium to coarsely crystalline bladed crystals. Additionally, centimeter-thick laminated speleothem-like crusts, composed of clear, bladed to columnar spar, are the common precipitates around micritic accumulations within the older travertine. In comparison, the lake-fill deposits are primarily composed of moderately (recent lake-fill deposits) to well-developed (relict lake-fill deposits) 3-8 ^m calcite rhombohedrons. Petrographie analyses clearly show that cyanobacteria, fungi, and/or other microbial organisms bore into the spar and micritize it. This sparmicritization is pervasive throughout the waterfall and barrier deposits. Bladed spar crystals range from those which are pristine to those whose original bladed morphology can only be interpreted by comparison with laterally adjacent crystals. Individual samples display multiple generations of spar which have undergone various degrees of sparmicritization. Sparmicritization results in a thoroughly micritized accumulation in which evidence of the original spar composition has been completely obliterated.Le travertin est à l'origine de la formation de chutes spectaculaires, de barrières et de dépôts lacustres subaquatiques à grains fins partout dans le parc national Plitvice, en Croatie. Les barrières de travertin forment des barrages derrière lesquels est situé le complexe des lacs Plitvice. La chute et les barrières de travertin comprennent trois générations de sparites de calcite à basse teneur de magnésium. Les précipitations initiales sont généralement composées de sparite à cristaux impurs très fins à moyens allant de la forme isométrique à celle de la lame. Une génération subséquente est constituée de couches transparentes isopaques de cristaux plus ou moins fins en forme de lame. De plus, les croûtes laminées de l'ordre du centimètre, constituées de sparite en lame ou colonnaire, représentent le type de précipitations habituellement observées autour des accumulations de micrite à l'intérieur des plus anciens travertins. Par contre, les dépôts de remblaiement lacustre comprennent surtout des rhomboèdres de calcite de 3 à 8 p.m. Les analyses pétrographiques montrent clairement que les cyanobactéries, les champignons ou autres organismes microbiens creusent la sparite et la micritise. Cette micritisation de la sparite est répandue partout dans la chute et les dépôts de barrière. Les cristaux de sparite en lame comprennent ceux qui sont anciens et ceux dont la morphologie originelle en lame ne peut être interprétée qu'à l'aide des cristaux latéraux adjacents. Certains échantillons montrent de nombreuses générations de sparites qui ont subi une micritisation plus ou moins intense. La micritisation de la sparite résulte en une accumulation complètement micritisée où la composition originelle de la sparite a été oblitérée.Kaiktuff bildet pràchtige Wasserfàlle, Barrieren und feinkômige Unterwasser-Seeablagerungen quer durch den gesamten Nationalpark von Plitvice, Kroatien, nordwestliches Jugos-lawien. Die Travertin-Barrieren bilden Dàrnme, hinter denen sich die Gesamtheit der Seen von Plitvice befindet. Der Wasserfall und die Travertin-Barrieren umfassen drei Generationen von Kalkspat mit niedrigem Magnesiumgehalt. Die anfànglichen Ausscheidungen bestanden im allgemeinen aus Spat mit trùben, sehr feinen bis mittleren Kristallen von isometrischer Form bis Plàttchen-Form. Eine spâtere Generation besteht aus klaren, isopachen Schichten von mittleren bis grob kristallinischen Plâttchen-Kristallen. AuGerdem sind zentimeterdicke blàttrige Krusten, bestehend aus reinem blattbis saulenfôrmigem Spat die ùblichen Ausscheidungen um die mikritische Akkumulationen innerhalb der âlteren Travertine. Hingegen bestehen die See-auffùllungs-Ablagerungen vor allem aus mâBig (neuere Seeauffùllungs-Ablagerungen) bis gut entwickelten (frùhere See-auffùllungs-Ablagerungen) Kalkspat-Rhom-boedern von 3-8 jj.m. Die Gesteinsanalysen zeigen deutlich, daB die Zyanbakterien, Pilze und andere Mikroorganismen den Spat aushôhlen und ihn mikritisieren. Dièse Spat-Mikritisierung durchdringt den Wasserfall und die Barriereablagerungen. Die Spatplattchenkristalle reichen von den ursprùnglichen bis zu denen, deren ursprungliche Plâttchenmorphologie nur durch Vergleich mit lateral angrenzenden Kristallen interpretiert werden kann. Einzelne Proben zeigen zahlreiche Generationen von Spat, die verschiedene Grade der Spat-Mikritisierung durchlaufen haben. Spat-Mikritisierung fùhrt zu einer Mikritisierungs-Anhâufung, in welcher die ursprungliche Spatzusammensetzung getilgt worden ist

Sweating the small stuff: simulating dwarf galaxies, ultra-faint dwarf galaxies, and their own tiny satellites

We present FIRE/Gizmo hydrodynamic zoom-in simulations of isolated dark matter halos, two each at the mass of classical dwarf galaxies ($M_{\rm vir} \simeq 10^{10} M_{\odot}$) and ultra-faint galaxies ($M_{\rm vir} \simeq 10^9 M_{\odot}$), and with two feedback implementations. The resultant central galaxies lie on an extrapolated abundance matching relation from $M_{\star} \simeq 10^6$ to $10^4 M_{\odot}$ without a break. Every host is filled with subhalos, many of which form stars. Our dwarfs with $M_{\star} \simeq 10^6 M_{\odot}$ each have 1-2 well-resolved satellites with $M_{\star} = 3-200 \times 10^3 M_{\odot}$. Even our isolated ultra-faint galaxies have star-forming subhalos. If this is representative, dwarf galaxies throughout the universe should commonly host tiny satellite galaxies of their own. We combine our results with the ELVIS simulations to show that targeting $\sim 50~ \rm kpc$ regions around nearby isolated dwarfs could increase the chances of discovering ultra-faint galaxies by $\sim 35\%$ compared to random halo pointings, and specifically identify the region around the Phoenix dwarf galaxy as a good potential target. The well-resolved ultra-faint galaxies in our simulations ($M_{\star} \simeq 3 - 30 \times 10^3 M_{\odot}$) form within $M_{\rm peak} \simeq 0.5 - 3 \times 10^9 M_{\odot}$ halos. Each has a uniformly ancient stellar population ($> 10~ \rm Gyr$) owing to reionization-related quenching. More massive systems, in contrast, all have late-time star formation. Our results suggest that $M_{\rm halo} \simeq 5 \times 10^9 M_{\odot}$ is a probable dividing line between halos hosting reionization "fossils" and those hosting dwarfs that can continue to form stars in isolation after reionization.Comment: 12 pages, 6 figures, 1 table, submitted to MNRA

Birth and death: Infant burials from Vlasac and Lepenski Vir

Why were infants buried beneath house-floors at the Mesolithic and early Neolithic site of Lepenski Vir? Undertaking a new analysis of the neonate remains at Vlasac and Lepenski Vir the authors reject the idea of sacrificial infanticide, and demonstrate a consistency of respect in these burials. They suggest that the deaths were mourned and the dead, like the living, were given protection by the houses they were buried in. The treatment of mothers and children suggests increasing social cohesion from the Mesolithic at Vlasac to the early Neolithic at Lepenski Vir

A Predicted Correlation Between Age Gradient and Star Formation History in FIRE Dwarf Galaxies

We explore the radial variation of star formation histories in dwarf galaxies simulated with Feedback In Realistic Environments (FIRE) physics. The sample contains 9 low-mass field dwarfs with M_ star = 10^5 - 10^7 M_sun from previous FIRE results, and a new suite of 17 higher mass field dwarfs with M_star = 10^7 - 10^9 M_sun introduced here. We find that age gradients are common in our dwarfs, with older stars dominant at large radii. The strength of the gradient correlates with overall galaxy age such that earlier star formation produces a more pronounced gradient. The relation between formation time and strength of the gradient is driven by both mergers and star-formation feedback. Mergers can both steepen and flatten the age gradient depending on the timing of the merger and star formation history of the merging galaxy. In galaxies without significant mergers, early feedback pushes stars to the outskirts at early times. Interestingly, among galaxies without mergers, those with large dark matter cores have flatter age gradients because these galaxies have more late-time feedback. If real galaxies have age gradients as we predict, stellar population studies that rely on sampling a limited fraction of a galaxy can give a biased view of its global star formation history. We show that central fields can be biased young by a few Gyrs while outer fields are biased old. Fields positioned near the 2D half-light radius will provide the least biased measure of a dwarf galaxy's global star formation history.Comment: 13 pages, 8 figures. Submitted to MNRAS, comments welcom

CO Luminosity Functions For FIR and B-band Selected Galaxies and the First Estimate for Omega_{HI+H2}

We derive a non-parametric CO luminosity function using a FIR and an optical B-band selected sample of the galaxies included in the FCRAO Extragalactic CO Survey. The FIR selected sample is defined using the IRAS Bright Galaxy Surveys (BGS; IRAS 60 micron flux density >= 5.24 Jy). Although our CO sample is not complete, the normalization using the BGS reproduces the IRAS 60 micron luminosity function in excellent agreement with those found in the literature. Similarly, a B-band selected sample defined using the Revised Shapley-Ames (RSA) catalog is used to derive a CO luminosity function for a comparison. A Schechter function describes the both derived CO luminosity functions reasonably well. Adopting the standard CO-to-H2 conversion factor, we derive a molecular gas density of rho_{H2}=(3.1\pm 1.2)*10^7h Mo Mpc^{-3} for the local volume. Combining with the measurements of the local HI mass density and the helium contribution, we estimate that the total mass density of cold neutral gas in the local universe is Omega_{gas} =(4.3 \pm 1.1)*10^{-4} h^{-1}, which is about 20% of the total stellar mass density Omega_{stars}.Comment: 16 pages, 11 figures uses aastex.cls and emulateapj5.sty. Accepted for publication in Ap

Polarimetric radar observations and interpretation of co-cross-polar correlation coefficients

Includes bibliographical references (page 354).Preliminary analysis of all components of the polarimetric radar covariance matrix for precipitation measured with the NCAR S-band dual-polarization Doppler radar (S-Pol) and the Colorado State University-University of Chicago-Illinois State Water Survey (CSU-CHILL) radars is presented. Radar reflectivity at horizontal polarization Zh, differential reflectivity ZDR, linear depolarization ratio LDR, specific differential phase KDP, crosscorrelation coefficient | ρhv | , and two co-cross-polar correlation coefficients, ρxh and ρxv, have been measured and examined for two rain events: the 14 August 1998 case in Florida and the 8 August 1998 case in Colorado. Examination of the coefficients ρxh and ρxv is the major focus of the study. It is shown that hydrometeors with different types of orientation can be better delineated if the coefficients ρxv and ρxv are used. Rough estimates of the raindrop mean canting angles and the rms width of the canting angle distribution are obtained from the co-cross-polar correlation coefficients in combination with other polarimetric variables. Analysis of the two cases indicates that the raindrop net canting angles averaged over the propagation paths near the ground in typical convective cells do not exceed 2.5°. Nonetheless, the mean canting angles in individual radar resolution volumes in rain can be noticeably higher. Although the net canting angle for individual convective cells can deviate by a few degrees from zero, the average over a long propagation path along several cells is close to zero, likely because canting angles in different cells vary in sign. The rms width of the canting angle distribution in rain is estimated to vary mainly between 5° and 15° with the median value slightly below 10°