Near Infrared Observations of a Redshift 4.92 Galaxy: Evidence for Significant Dust Absorption

Near-infrared imaging and spectroscopy have been obtained of the gravitationally lensed galaxy at z=4.92 discovered in HST images by Franx et al. (1997). Images at 1.2, 1.6 and 2.2 microns show the same arc morphology as the HST images. The spectrum with resolution \lambda / \Delta\lambda ~ 70 shows no emission lines with equivalent width stronger than 100 A in the rest frame wavelength range 0.34 to 0.40 microns. In particular, [OII]3727 A and [NeIII]3869 A are not seen. The energy distribution is quite blue, as expected for a young stellar population with the observed Ly alpha flux. The spectral energy distribution can be fit satisfactorily for such a young stellar population when absorption by dust is included. The models imply a reddening 0.1 mag < E(B-V) < 0.4 mag. The stellar mass of the lensed galaxy lies in the range of 2 to 16 x 10^9 Msun. This is significantly higher than estimates based on the HST data alone. Our data imply that absorption by dust is important to redshifts of ~5.Comment: LaTeX with ApJ journal format, 2 postscript figures, ApJL, accepte

The effect of portacaval transposition on carbohydrate metabolism: Experimental and clinical observations

An investigation was conducted of the influence of portacaval transposition upon carbohydrate metabolism in 45 dogs. In 17 dogs, hepatic glycogen content was measured before and from 45 to 75 days after transposition. A reduction in glycogen content, principally in the TCA soluble fraction, was noted in 14 animals. The mean loss of total glycogen was 51 percent, and the mean loss of TCA soluble glycogen was 70 percent. In control animals hepatic deglycogenation did not occur. Despite the reduction in hepatic glycogen content, the animals were capable of glucagon-induced glycogenolysis using very small test doses. After transposition, a greater response to intraportal injection was noted as compared to that obtained with systemic venous infusions. Other alterations in carbohydrate metabolism were also measured. These included a reduction in the duration and magnitude of the hyperglycemic response to oral glucose loads. The profile of glycemic response under these conditions was studied, and demonstrated to be greatest in the portal vein, least in the peripheral venous blood, and of intermediate magnitude in the peripheral arteries. Based upon the hepatic deglycogenating effect of portacaval transposition in dogs, this operation was used for the treatment of an 8 1 2-year-old child with glycogen storage disease and concomitant portal cirrhosis. The portacaval transposition was performed in preference to a standard portacaval shunt. The enzyme defect in the patient was extensively studied before and after transposition. Prior to surgery, she was demonstrated to have Type IIIB glycogenosis (amylo-1,6-glucosidase deficiency confined to the liver). Eight and one half months after operation, the quantities of glycogen in liver and muscle and the enzyme activities showed no significant alteration. The clinical response to portacaval transposition was gratifying. There has been a decrease in the hepatosplenomegaly, rapid growth, a diminution in the pre-existing hypersplenism, and a considerable increase in the child's physical activity. Most of these benefits are ascribable to the effective portal decompressive procedure. Whether any metabolic benefit derived from the portacaval transposition is problematical. © 1965

Leadership development in a faith-based non-profit organisation using a relational leadership model: A case study

This paper describes a case study of a Leadership Development Program (LDP) which has been developed and conducted at a large faith-based non-profit organization providing aged and community care in Australia. Walter Wright's Relational Leadership model which used insights from Jude, Philemon and Colossians was adopted by the organization. Started as a pilot in 2003 the LDP was implemented in 2007 and has been run regularly since then. The LDP was systematically evaluated by an independent researcher recently. The evaluation concluded that the program has been effective and recommended that it continue with some minor modifications. The organization in which this program was developed is a partner in an Australian Research Council (ARC) linkage grant started in 2010 between three universities and two faith-based non-profit organizations providing aged care and community care. This paper has been written by four researchers involved in the linkage grant. Four interviews on participants in the LDP were conducted by the authors to evaluate the effectiveness of the leadership program in order to prepare this paper. The study was carried out to clarify the research aim for the principal author (who is a PhD student in the ARC grant) by trying to understand what the LDP program was aiming to achieve and to be presented at the Spirituality at Work conference at the University of Arkansas

Rest-Frame Optical Emission Lines in z~3.5 Lyman Break selected Galaxies: The Ubiquity of Unusually High [OIII]/Hbeta Ratios at 2 Gyr

We present K-band spectra of rest-frame optical emission lines for 24 star-forming galaxies at z~3.2-3.7 using MOSFIRE on the Keck 1 telescope. Strong rest-frame optical [O III] and Hbeta emission lines were detected in 18 LBGs. The median flux ratio of [O III]5007 to Hbeta is 5.1+/-0.5, a factor of 5-10x higher than in local galaxies with similar stellar masses. The observed Hbeta luminosities are in good agreement with expectations from the estimated star-formation rates, and none of our sources are detected in deep X-ray stacks, ruling out significant contamination by active galactic nuclei. Combining our sample with a variety of LBGs from the literature, including 49 galaxies selected in a very similar manner, we find a high median ratio of [OIII]/Hbeta = 4.8+0.8-1.7. This high ratio seems to be an ubiquitous feature of z~3-4 LBGs, very different from typical local star-forming galaxies at similar stellar masses. The only comparable systems at z~0 are those with similarly high specific star-formation rates, though ~5x lower stellar masses. High specific star-formation rates either result in a much higher ionization parameter or other unusual conditions for the interstellar medium, which result in a much higher [OIII]/Hbeta line ratio. This implies a strong relation between a global property of a galaxy, the specific star-formation rate, and the local conditions of ISM in star-forming regions.Comment: 14 pages, 8 figures, 5 color, published in ApJ, updated to reflect published versio

Dependence of galaxy clustering on UV-luminosity and stellar mass at z∼4−7z \sim 4 - 7

We investigate the dependence of galaxy clustering at $z \sim 4 - 7$ on UV-luminosity and stellar mass. Our sample consists of $\sim$ 10,000 Lyman-break galaxies (LBGs) in the XDF and CANDELS fields. As part of our analysis, the $M_\star - M_{\rm UV}$ relation is estimated for the sample, which is found to have a nearly linear slope of $d\log_{10} M_\star / d M_{\rm UV} \sim 0.44$. We subsequently measure the angular correlation function and bias in different stellar mass and luminosity bins. We focus on comparing the clustering dependence on these two properties. While UV-luminosity is only related to recent starbursts of a galaxy, stellar mass reflects the integrated build-up of the whole star formation history, which should make it more tightly correlated with halo mass. Hence, the clustering segregation with stellar mass is expected to be larger than with luminosity. However, our measurements suggest that the segregation with luminosity is larger with $\simeq 90\%$ confidence (neglecting contributions from systematic errors). We compare this unexpected result with predictions from the \textsc{Meraxes} semi-analytic galaxy formation model. Interestingly, the model reproduces the observed angular correlation functions, and also suggests stronger clustering segregation with luminosity. The comparison between our observations and the model provides evidence of multiple halo occupation in the small scale clustering.Comment: 10 pages, 6 figures, 2 tables, accepted for publication in MNRA

A Rest-frame Optical View on z~4 Galaxies I: Color and Age Distributions from Deep IRAC Photometry of the IUDF10 and GOODS Surveys

We present a study of rest-frame UV-to-optical color distributions for z~4 galaxies based on the combination of deep HST/ACS+WFC3/IR data with Spitzer/IRAC imaging. In particular, we use new, ultra-deep data from the IRAC Ultradeep Field program (IUDF10). Our sample contains a total of ~2600 galaxies selected as B-dropout Lyman Break Galaxies (LBGs) in the HUDF and one of its deep parallel fields, the HUDF09-2, as well as GOODS-North and South. This sample is used to investigate the UV continuum slopes beta and Balmer break colors (J_125-[4.5]) as a function of rest-frame optical luminosity. The [4.5] filter is chosen to avoid potential contamination by strong rest-frame optical emission lines. We find that galaxies at M_z<-21.5 (roughly corresponding to L*[z~4]) are significantly redder than their lower luminosity counterparts. The UV continuum slopes and the J_125-[4.5] colors are well correlated. The most simple explanation for this correlation is that the dust reddening at these redshifts is better described by an SMC-like extinction curve, rather than the typically assumed Calzetti reddening. After correcting for dust, we find that the galaxy population shows mean stellar population ages in the range 10^8.5 to 10^9 yr, with a dispersion of ~0.5 dex, and only weak trends as a function of luminosity. In contrast to some results from the literature, we find that only a small fraction of galaxies shows Balmer break colors which are consistent with extremely young ages, younger than 100 Myr. Under the assumption of smooth star-formation histories, this fraction is only 12-19% for galaxies at M_z<-19.75. Our results are consistent with a gradual build-up of stars and dust in galaxies at z>4, with only a small fraction of stars being formed in short, intense bursts of star-formation.Comment: 11 pages, 10 figures; submitted to Ap

The Impact of Strong Gravitational Lensing on Observed Lyman-Break Galaxy Numbers at 4<z<8 in the GOODS and the XDF Blank Fields

Detection of Lyman-Break Galaxies (LBGs) at high-redshift can be affected by gravitational lensing induced by foreground deflectors not only in galaxy clusters, but also in blank fields. We quantify the impact of strong magnification in the samples of $B$, $V$, $i$, $z$ $\&$ $Y$ LBGs ($4\lesssim z \lesssim8$) observed in the XDF and GOODS/CANDELS fields, by investigating the proximity of dropouts to foreground objects. We find that $\sim6\%$ of bright LBGs ($m_{H_{160}}2$) by foreground objects. This fraction decreases from $\sim 3.5\%$ at $z\sim6$ to $\sim1.5\%$ at $z\sim4$. Since the observed fraction of strongly lensed galaxies is a function of the shape of the luminosity function (LF), it can be used to derive Schechter parameters, $\alpha$ and $M_{\star}$, independently from galaxy number counts. Our magnification bias analysis yields Schechter-function parameters in close agreement with those determined from galaxy counts albeit with larger uncertainties. Extrapolation of our analysis to $z\gtrsim 8$ suggests that future surveys with JSWT, WFIRST and EUCLID should find excess LBGs at the bright-end, even if there is an intrinsic exponential cutoff of number counts. Finally, we highlight how the magnification bias measurement near the detection limit can be used as probe of the population of galaxies too faint to be detected. Preliminary results using this novel idea suggest that the magnification bias at $M_{UV}\sim -18$ is not as strong as expected if $\alpha\lesssim -1.7$ extends well below the current detection limits in the XDF. At face value this implies a flattening of the LF at $M_{UV}\gtrsim-16.5$. However, selection effects and completeness estimates are difficult to quantify precisely. Thus, we do not rule out a steep LF extending to $M_{UV}\gtrsim -15$.Comment: Submitted to ApJ on 18/12/201