Understanding the Observed Evolution of the Galaxy Luminosity Function from z=6-10 in the Context of Hierarchical Structure Formation

Recent observations of the Lyman-break galaxy (LBG) luminosity function (LF) from z~6-10 show a steep decline in abundance with increasing redshift. However, the LF is a convolution of the mass function of dark matter halos (HMF)--which also declines sharply over this redshift range--and the galaxy-formation physics that maps halo mass to galaxy luminosity. We consider the strong observed evolution in the LF from z~6-10 in this context and determine whether it can be explained solely by the behavior of the HMF. From z~6-8, we find a residual change in the physics of galaxy formation corresponding to a ~0.5 dex increase in the average luminosity of a halo of fixed mass. On the other hand, our analysis of recent LF measurements at z~10 shows that the paucity of detected galaxies is consistent with almost no change in the average luminosity at fixed halo mass from z~8. The LF slope also constrains the variation about this mean such that the luminosity of galaxies hosted by halos of the same mass are all within about an order-of-magnitude of each other. We show that these results are well-described by a simple model of galaxy formation in which cold-flow accretion is balanced by star formation and momentum-driven outflows. If galaxy formation proceeds in halos with masses down to 10^8 Msun, then such a model predicts that LBGs at z~10 should be able to maintain an ionized intergalactic medium as long as the ratio of the clumping factor to the ionizing escape fraction is C/f_esc < 10.Comment: 15 pages, 2 figures; results unchanged; accepted by JCA

VLT/XSHOOTER and Subaru/MOIRCS spectroscopy of HUDF.YD3: no evidence for Lyman emission at z = 8.55

We present spectroscopic observations with VLT/XSHOOTER and Subaru/MOIRCS of a relatively bright Y-band drop-out galaxy in the Hubble Ultra Deep Field (HUDF), first selected by Bunker et al., McLure et al. and Bouwens et al. to be a likely z ≈ 8–9 galaxy on the basis of its colours in the Hubble Space Telescope (HST) Advanced Camera for Surveys and Wide Field Camera 3 images. This galaxy, HUDF.YD3 (also known as UDFy-38135539), has been targetted for VLT/SINFONI integral field spectroscopy by Lehnert et al., who published a candidate Lyman α emission line at z = 8.55 from this source. In our independent spectroscopy using two different infrared spectrographs (5 h with VLT/XSHOOTER and 11 h with Subaru/MOIRCS), we are unable to reproduce this line. We do not detect any emission line at the spectral and spatial location reported in Lehnert et al., despite the expected signal in our combined MOIRCS and XSHOOTER data being 5σ. The line emission also seems to be ruled out by the faintness of this object in recently extremely deep F105W (Y band) HST/WFC 3 imaging from HUDF12; the line would fall within this filter and such a galaxy should have been detected at YAB = 28.6 mag (∼20σ) rather than the marginal YAB ≈ 30 mag observed in the Y-band image, >3 times fainter than would be expected if the emission line was real. Hence, it appears highly unlikely that the reported Lyman α line emission at z > 8 is real, meaning that the highest redshift sources for which Lyman α emission has been seen are at z = 6.9-7.2. It is conceivable that Lyman α does not escape galaxies at higher redshifts, where the Gunn–Peterson absorption renders the Universe optically thick to this line. However, deeper spectroscopy on a larger sample of candidate z > 7 galaxies will be needed to test this

Brief of Interested Law Professors As \u3ci\u3eAmici Curiae\u3c/i\u3e Supporting Petitioner in \u3ci\u3eBrohl v. Direct Marketing Association\u3c/i\u3e

Amici curiae are 14 professors of law who have devoted much of their teaching and research to the area of state taxes and the role of state tax policy in our federal system. The names and affiliations (for identification purposes only) of amici are included in an addendum to this brief. The amici are concerned with the effect of this Court’s dormant Commerce Clause jurisprudence on the development of fair and efficient state tax systems. No decision of this Court has had more effect on state sales and use tax systems than Quill Corporation v. North Dakota. We believe the Tenth Circuit properly decided the case below. But if the Court decides to grant the Direct Marketing Association’s petition to review the issue of discrimination which it raises, we respectfully request that the Court also grant the conditional crosspetition filed by Executive Director Barbara J. Brohl of the Colorado Department of Revenue asking the Court to reconsider Quill. This brief sets forth the reasons for our support of that cross-petitio

Abnormal Cortical Development after Premature Birth Shown by Altered Allometric Scaling of Brain Growth

BACKGROUND: We postulated that during ontogenesis cortical surface area and cerebral volume are related by a scaling law whose exponent gives a quantitative measure of cortical development. We used this approach to investigate the hypothesis that premature termination of the intrauterine environment by preterm birth reduces cortical development in a dose-dependent manner, providing a neural substrate for functional impairment. METHODS AND FINDINGS: We analyzed 274 magnetic resonance images that recorded brain growth from 23 to 48 wk of gestation in 113 extremely preterm infants born at 22 to 29 wk of gestation, 63 of whom underwent neurodevelopmental assessment at a median age of 2 y. Cortical surface area was related to cerebral volume by a scaling law with an exponent of 1.29 (95% confidence interval, 1.25–1.33), which was proportional to later neurodevelopmental impairment. Increasing prematurity and male gender were associated with a lower scaling exponent (p < 0.0001) independent of intrauterine or postnatal somatic growth. CONCLUSIONS: Human brain growth obeys an allometric scaling relation that is disrupted by preterm birth in a dose-dependent, sexually dimorphic fashion that directly parallels the incidence of neurodevelopmental impairments in preterm infants. This result focuses attention on brain growth and cortical development during the weeks following preterm delivery as a neural substrate for neurodevelopmental impairment after premature delivery

THE ROLE OF INTERDEPENDENCE IN THE MICRO-FOUNDATIONS OF ORGANIZATION DESIGN: TASK, GOAL, AND KNOWLEDGE INTERDEPENDENCE

Interdependence is a core concept in organization design, yet one that has remained consistently understudied. Current notions of interdependence remain rooted in seminal works, produced at a time when managers’ near-perfect understanding of the task at hand drove the organization design process. In this context, task interdependence was rightly assumed to be exogenously determined by characteristics of the work and the technology. We no longer live in that world, yet our view of interdependence has remained exceedingly task-centric and our treatment of interdependence overly deterministic. As organizations face increasingly unpredictable workstreams and workers co-design the organization alongside managers, our field requires a more comprehensive toolbox that incorporates aspects of agent-based interdependence. In this paper, we synthesize research in organization design, organizational behavior, and other related literatures to examine three types of interdependence that characterize organizations’ workflows: task, goal, and knowledge interdependence. We offer clear definitions for each construct, analyze how each arises endogenously in the design process, explore their interrelations, and pose questions to guide future research

Single hadron response measurement and calorimeter jet energy scale uncertainty with the ATLAS detector at the LHC

The uncertainty on the calorimeter energy response to jets of particles is derived for the ATLAS experiment at the Large Hadron Collider (LHC). First, the calorimeter response to single isolated charged hadrons is measured and compared to the Monte Carlo simulation using proton-proton collisions at centre-of-mass energies of sqrt(s) = 900 GeV and 7 TeV collected during 2009 and 2010. Then, using the decay of K_s and Lambda particles, the calorimeter response to specific types of particles (positively and negatively charged pions, protons, and anti-protons) is measured and compared to the Monte Carlo predictions. Finally, the jet energy scale uncertainty is determined by propagating the response uncertainty for single charged and neutral particles to jets. The response uncertainty is 2-5% for central isolated hadrons and 1-3% for the final calorimeter jet energy scale.Comment: 24 pages plus author list (36 pages total), 23 figures, 1 table, submitted to European Physical Journal

Lyman-alpha Forest Tomography from Background Galaxies: The First Megaparsec-Resolution Large-Scale Structure Map at z>2

We present the first observations of foreground Lyman-$\alpha$ forest absorption from high-redshift galaxies, targeting 24 star-forming galaxies (SFGs) with $z\sim 2.3-2.8$ within a $5' \times 15'$ region of the COSMOS field. The transverse sightline separation is $\sim 2\,h^{-1}\mathrm{Mpc}$ comoving, allowing us to create a tomographic reconstruction of the 3D Ly$\alpha$ forest absorption field over the redshift range $2.20\leq z\leq 2.45$. The resulting map covers $6\,h^{-1}\mathrm{Mpc} \times 14\,h^{-1}\mathrm{Mpc}$ in the transverse plane and $230\,h^{-1}\mathrm{Mpc}$ along the line-of-sight with a spatial resolution of $\approx 3.5\,h^{-1}\mathrm{Mpc}$, and is the first high-fidelity map of large-scale structure on $\sim\mathrm{Mpc}$ scales at $z>2$. Our map reveals significant structures with $\gtrsim 10\,h^{-1}\mathrm{Mpc}$ extent, including several spanning the entire transverse breadth, providing qualitative evidence for the filamentary structures predicted to exist in the high-redshift cosmic web. Simulated reconstructions with the same sightline sampling, spectral resolution, and signal-to-noise ratio recover the salient structures present in the underlying 3D absorption fields. Using data from other surveys, we identified 18 galaxies with known redshifts coeval with our map volume enabling a direct comparison to our tomographic map. This shows that galaxies preferentially occupy high-density regions, in qualitative agreement with the same comparison applied to simulations. Our results establishes the feasibility of the CLAMATO survey, which aims to obtain Ly$\alpha$ forest spectra for $\sim 1000$ SFGs over $\sim 1 \,\mathrm{deg}^2$ of the COSMOS field, in order to map out IGM large-scale structure at $\langle z \rangle \sim 2.3$ over a large volume $(100\,h^{-1}\mathrm{Mpc})^3$.Comment: Accepted for publication in Astrophysical Journal Letters; 8 pages and 5 figure