Sky Variability in the y Band at the LSST Site

We have measured spatial and temporal variability in the y band sky brightness over the course of four nights above Cerro Tololo near Cerro Pachon, Chile, the planned site for the Large Synoptic Survey Telescope (LSST). Our wide-angle camera lens provided a 41 deg field of view and a 145 arcsec pixel scale. We minimized potential system throughput differences by deploying a deep depletion CCD and a filter that matches the proposed LSST y_3 band (970 nm-1030 nm). Images of the sky exhibited coherent wave structure, attributable to atmospheric gravity waves at 90 km altitude, creating 3%-4% rms spatial sky flux variability on scales of about 2 degrees and larger. Over the course of a full night the y_3 band additionally showed highly coherent temporal variability of up to a factor of 2 in flux. We estimate the mean absolute sky level to be approximately y_3 = 17.8 mag (Vega), or y_3 = 18.3 mag (AB). While our observations were made through a y_3 filter, the relative sky brightness variability should hold for all proposed y bands, whereas the absolute levels should more strongly depend on spectral response. The spatial variability presents a challenge to wide-field cameras that require illumination correction strategies that make use of stacked sky flats. The temporal variability may warrant an adaptive y band imaging strategy for LSST, to take advantage of times when the sky is darkest.Comment: 8 pages, 5 figures, accepted to PASP. Minor changes from referee report and editor's revisions

Metabolizable Energy Value of Crude Glycerol for Laying Hens

An experiment was conducted with laying hens to determine the nitrogen-corrected apparent metabolizable energy AMEn value of crude glycerol, a co-product of biodiesel production. Crude glycerol (87% glycerol, 9% water) was obtained from a commercial biodiesel production facility. A total of 48 40-week-old laying hens (Hy-Line W-36) was placed in metabolic cages (2 hens/cage) and given free access to the experimental diets. A corn and soybean meal–based basal diet was formulated with 15% glucose•H2O. Four dietary treatments were created by substituting 0, 5, 10, or 15% crude glycerol for glucose•H2O (3,640 kcal/kg AMEn). After 7 days of dietary adaptation, excreta were collected twice daily for 3 days, freeze-dried, and analyzed for contents of dry matter, nitrogen, acid-insoluble ash, and gross energy. Egg production was recorded daily, and eggs were collected on days 7 and 8 of the experiment for calculation of egg mass (egg production × egg weight). No significant treatment effects (P \u3e 0.1) were apparent for egg-production rate (93.0%), egg weight (56.1 g), egg mass (52.2 g/d), or feed consumption (104 g/d). Linear regression analysis (P \u3c 0.001, r 2 = 0.92, n = 24) revealed that the AMEn value of the crude glycerol used in this study was 3,805 kcal/kg (asis basis) for laying hens, slightly higher than that reported for corn grain and less than half of that reported for vegetable oil

The stellar mass - size relation for cluster galaxies at z=1 with high angular resolution from the Gemini/GeMS multi-conjugate adaptive optics system

We present the stellar mass - size relation for 49 galaxies within the $z$ = 1.067 cluster SPT-CL J0546$-$5345, with FWHM $\sim$80-120 mas $K_{\mathrm s}$-band data from the Gemini multi-conjugate adaptive optics system (GeMS/GSAOI). This is the first such measurement in a cluster environment, performed at sub-kpc resolution at rest-frame wavelengths dominated by the light of the underlying old stellar populations. The observed stellar mass - size relation is offset from the local relation by 0.21 dex, corresponding to a size evolution proportional to $(1+z)^{-1.25}$, consistent with the literature. The slope of the stellar mass - size relation $\beta$ = 0.74 $\pm$ 0.06, consistent with the local relation. The absence of slope evolution indicates that the amount of size growth is constant with stellar mass. This suggests that galaxies in massive clusters such as SPT-CL J0546$-$5345 grow via processes that increase the size without significant morphological interference, such as minor mergers and/or adiabatic expansion. The slope of the cluster stellar mass - size relation is significantly shallower if measured in $HST$/ACS imaging at wavelengths blueward of the Balmer break, similar to rest-frame UV relations at $z$ = 1 in the literature. The stellar mass - size relation must be measured at redder wavelengths, which are more sensitive to the old stellar population that dominates the stellar mass of the galaxies. The slope is unchanged when GeMS $K_s$-band imaging is degraded to the resolution of $K$-band HST/NICMOS resolution but dramatically affected when degraded to $K_s$-band Magellan/FourStar resolution. Such measurements must be made with AO in order to accurately characterise the sizes of compact, $z$ = 1 galaxies.Comment: 24 pages, 13 figures, 3 tables. Accepted for publication in MNRAS. Typos corrected, DOI adde

Stellar Locus Regression: Accurate Color Calibration, and the Real-time Determination of Galaxy Cluster Photometric Redshifts

We present Stellar Locus Regression (SLR), a method of directly adjusting the instrumental broadband optical colors of stars to bring them into accord with a universal stellar color-color locus, producing accurately calibrated colors for both stars and galaxies. This is achieved without first establishing individual zeropoints for each passband, and can be performed in real-time at the telescope. We demonstrate how SLR naturally makes one wholesale correction for differences in instrumental response, for atmospheric transparency, for atmospheric extinction, and for Galactic extinction. We perform an example SLR treatment of SDSS data over a wide range of Galactic dust values and independently recover the direction and magnitude of the canonical Galactic reddening vector with 14--18 mmag RMS uncertainties. We then isolate the effect of atmospheric extinction, showing that SLR accounts for this and returns precise colors over a wide of airmass, with 5--14 mmag RMS residuals. We demonstrate that SLR-corrected colors are sufficiently accurate to allow photometric redshift estimates for galaxy clusters (using red sequence galaxies) with an uncertainty sigma_z/(1+z) = 0.6% per cluster for redshifts 0.09<z<0.25. Finally, we identify our objects in the 2MASS all-sky catalog, and produce i-band zeropoints typically accurate to 18 mmag using only SLR. We offer open-source access to our IDL routines, validated and verified for the implementation of this technique, at http://stellar-locus-regression.googlecode.comComment: Submitted to AJ. The public code is available at http://stellar-locus-regression.googlecode.co

Stellar Locus Regression: Accurate Color Calibration, and the Real-time Determination of Galaxy Cluster Photometric Redshifts

We present Stellar Locus Regression (SLR), a method of directly adjusting the instrumental broadband optical colors of stars to bring them into accord with a universal stellar color-color locus, producing accurately calibrated colors for both stars and galaxies. This is achieved without first establishing individual zeropoints for each passband, and can be performed in real-time at the telescope. We demonstrate how SLR naturally makes one wholesale correction for differences in instrumental response, for atmospheric transparency, for atmospheric extinction, and for Galactic extinction. We perform an example SLR treatment of SDSS data over a wide range of Galactic dust values and independently recover the direction and magnitude of the canonical Galactic reddening vector with 14--18 mmag RMS uncertainties. We then isolate the effect of atmospheric extinction, showing that SLR accounts for this and returns precise colors over a wide of airmass, with 5--14 mmag RMS residuals. We demonstrate that SLR-corrected colors are sufficiently accurate to allow photometric redshift estimates for galaxy clusters (using red sequence galaxies) with an uncertainty $\sigma(z)/(1+z)$ = 0.6% per cluster for redshifts 0.09< $z$ <0.25. Finally, we identify our objects in the 2MASS all-sky catalog, and produce i-band zeropoints typically accurate to 18 mmag using only SLR. We offer open-source access to our IDL routines, validated and verified for the implementation of this technique, at http://stellar-locus-regression.googlecode.comPhysic

Disappearance and Appearance of an Indigestible Marker in Feces from Growing Pigs as Affected by Previous- and Current-Diet Composition

Background: Indigestible markers are commonly utilized in digestion studies, but the complete disappearance or maximum appearance of a marker in feces can be affected by diet composition, feed intake, or an animal’s BW. The objectives of this study were to determine the impact of previous (Phase 1, P1) and current- (Phase 2, P2) diet composition on marker disappearance (Cr) and appearance (Ti) in pigs fed 3 diets differing in NDF content. Results: When pigs were maintained on the 25.1, 72.5, and 125.0 g/kg NDF diets, it took 5.1, 4.1, and 2.5 d, respectively, for Cr levels to decrease below the limit of quantitation; or 4.6, 3.7, or 2.8 d, respectively, for Ti to be maximized. These effects were not, however, independent of the previous diet as indicated by the interaction between P1 and P2 diets on fecal marker concentrations (P \u3c 0.01). When dietary NDF increased from P1 to P2, it took less time for fecal Cr to decrease or fecal Ti to be maximized (an average of 2.5 d), than if NDF decreased from P1 to P2 where it took longer for fecal Cr to decrease or fecal Ti to be maximized (an average of 3.4 d). Conclusions: Because of the wide range in excretion times reported in the literature and improved laboratory methods for elemental detection, the data suggests that caution must be taken in considering dietary fiber concentrations of the past and currently fed diets so that no previous dietary marker addition remains in the digestive tract or feces such that a small amount of maker is present to confound subsequent experimental results, and that marker concentration have stabilized when these samples are collected

The Effects of Dietary Omega 3 Fatty Acids on Commercial Broiler Behavior from Hatch to Market Weight

The objective of this experiment was to investigate how different dietary omega-3 sources affect commercial broiler behavior from hatch to market weight. One hundred and twenty male 308 Ross broiler chicks were enrolled into the study. Three dietary treatments were compared; Control, Flaxseed-and Fish-oil. Fifteen pens were randomly selected and onefocal-bird was watched continually for three periods of time. One behavior, two postures,and an unknown category were collected. Week by dietary treatment interaction was not significant for any broiler behaviors (P ≥ 0.49). There was no dietary treatment effect observed for any broiler behaviors (P≥ 0.32). There was no observed difference for percentage of time spent at the feeder between week 1 and 4 (P =0.14). However, there was a difference for percentage of time spent active (P \u3c 0.0001), inactive (P = 0.0004) and unknown (P = 0.01) between week 1 and 4. Within the context of this work, the selected omega-3 dietary sources did not affect broiler behavior between weeks 1 and 4. Independent of dietary treatment, broilers increased the percentage of time spent inactive by week 4 of the study

The Effects of Dietary Omega 3 Fatty Acids on Commercial Broiler Lameness and Bone Integrity from Hatching to Market

The objective of this experiment was to investigate how different dietary ω-3 sources affect lameness and bone integrity of commercial broiler chickens from hatching to finishing.One hundred and twenty male Ross308broiler chicks were assigned to three dietary treatments; control, flaxseed oil and fish oil for 4 consecutive weeks. From week 1 to 4, broilers were visually assigned a lameness score (2 non-lame to 5 non-ambulatory) anda bone integrity score (score 2 normal bones to 5 bird was non-ambulatory and was removed from the trial).There were no observed differences for the dietary treatmentand week interaction for lameness or bone integrity (P= 1.00). There wasno observed lameness or bone integrity differences (P≥0.93) between dietary treatments. There were no observed differences for lameness (P= 0.92) and bone integrity differences(P= 1.00) over the four consecutive weeks. In conclusion, regardless of dietary treatment, birds in this study were not lame and had normal bone integrity