1,618 research outputs found
Inclination Dependence of Lyman-Alpha Properties in a Turbulent Disk Galaxy
We present simulations of Lyman-Alpha radiation transfer in an isolated disk
galaxy with a turbulence sub-grid model, multi-phase interstellar medium and
detailed star formation modelling. We investigate the influence of inclination
on the observed Lyman-Alpha properties for different snapshots. The Lyman-alpha
spectrum, equivalent width distribution and escape fractions vary significantly
with the detailed morphology of the disk, leading to variations from one
snapshot to another. In particular, we find that supernova-driven cavities near
star-forming regions in the simulation can dominate the transmitted Lyman-alpha
fraction, suggesting a variability of LAEs on the timescales of the star
formation activity.Comment: accepted for publication, 9 page
The Influence of Small-Scale Anisotropies and the Large-Scale Environment on the Observed Properties of Lyman-Alpha Emitters
Success Factors for an E-Government Strategy: Austrian Experiences, Indonesian Challenges
Focus of this paper are success factors for the implementation of an E-Government strategy. Whileconcepts for a sophisticated strategy process in Public Sector are delivered on a regular basis, the gapbetween ambitious planning and its implementation seems to get wider. Authors seek to define whatmakes a “good strategy” in order to enhance management capacity. Meanwhile some scholars fromPolitical Science see limitation of Governments on announcements which are not followed up bysufficient action rather as systematic problems, challenging concept and rules of liberal westerndemocracy, or owed to growing complexity of Governance under the conditions of globalization. Incontext of the introduction of New Public Management and its perception of citizens as customers andon the basis of new available technical options in Information Society, a key Governance reform projectin European and other Countries over the last fifteen years has been the introduction of E-Government.European market leader in this field is Austria. The author reviews concept and implementationexperiences of the Austrian E-Government strategy, analyzes key success factors and opens adiscussion, under which conditions a successful implementation of E-Government can take place inIndonesia
Educational Governance Today
In the communication and knowledge based globalvillage, under the conditions of dynamic Change inan economy driven world, education has become acomplex and challenging endeavor, both for individualsand organizations. Learning has changeddramatically: knowledge and skills are quickly outdatedand devaluated, giving education a new meaningwithin an individual biography; schools, universitiesand other providers of education go throughorganizational revolutions, who are challenging theirself-concept and management; governments areunder pressure to reshape Educational Governanceaccording to new paradigms with the overall goalto sustain national or regional competitiveness. Arekey actors in the education system ready to face thesechallenges and to modernize their organizations?Starting from an overview on the Complexity of Learningin modern societies, generalizable consequencesare reviewed in a case study on Germany. It leads toa framework for a necessary research project incountries such as Indonesia, which are still aheadof educational reform. The focus is on the organizationalmeso and macro level that is playing the keyrole in Educational Governance
The impact of Lyman- radiative transfer on large-scale clustering in the Illustris simulation
Lyman- emitters (LAEs) are a promising probe of the large-scale
structure at high redshift, . In particular, the Hobby-Eberly
Telescope Dark Energy Experiment aims at observing LAEs at 1.9 3.5 to
measure the Baryon Acoustic Oscillation (BAO) scale and the Redshift-Space
Distortion (RSD). However, Zheng et al. (2011) pointed out that the complicated
radiative transfer (RT) of the resonant Lyman- emission line generates
an anisotropic selection bias in the LAE clustering on large scales, Mpc. This effect could potentially induce a systematic error in the BAO and
RSD measurements. Also, Croft et al. (2016) claims an observational evidence of
the effect in the Lyman- intensity map, albeit statistically
insignificant. We aim at quantifying the impact of the Lyman- RT on the
large-scale galaxy clustering in detail. For this purpose, we study the
correlations between the large-scale environment and the ratio of an apparent
Lyman- luminosity to an intrinsic one, which we call the `observed
fraction', at . We apply our Lyman- RT code by post-processing
the full Illustris simulations. We simply assume that the intrinsic luminosity
of the Lyman- emission is proportional to the star formation rate of
galaxies in Illustris, yielding a sufficiently large sample of LAEs to measure
the anisotropic selection bias. We find little correlations between large-scale
environment and the observed fraction induced by the RT, and hence a smaller
anisotropic selection bias than what was claimed by Zheng et al. (2011). We
argue that the anisotropy was overestimated in the previous work due to the
insufficient spatial resolution: it is important to keep the resolution such
that it resolves the high density region down to the scale of the interstellar
medium, physical kpc. (abridged)Comment: 11 pages, published in A&
Ly{\alpha} emission from galaxies in the Epoch of Reionization
The intrinsic strength of the Ly line in young, star-forming systems
makes it a special tool for studying high-redshift galaxies. However,
interpreting observations remains challenging due to the complex radiative
transfer involved. Here, we combine state-of-the-art hydrodynamical simulations
of 'Althaea', a prototypical Lyman Break Galaxy (LBG, stellar mass
at , with detailed
radiative transfer computations of dust/continuum, [CII] 158 m, and
Ly to clarify the relation between the galaxy properties and its
Ly emission. Althaea exhibits low () Ly escape
fractions and Equivalent Widths, EW Angstrom for the simulated
lines of sight, with a large scatter. The correlation between escape fraction
and inclination is weak, as a result of the rather chaotic structure of
high-redshift galaxies. Low values persist even if we artificially
remove neutral gas around star forming regions to mimick the presence of HII
regions. The high attenuation is primarily caused by dust clumps co-located
with young stellar clusters. We can turn Althaea into a Lyman Alpha Emitter
(LAE) only if we artificially remove dust from the clumps, yielding EWs up to
Angstrom. Our study suggests that the LBG-LAE duty-cycle required by
recent clustering measurements poses the challenging problem of a dynamically
changing dust attenuation. Finally, we find an anti-correlation between the
magnitude of Ly-[CII] line velocity shift and Ly luminosity.Comment: published in MNRA
Analysis of slow (theta) oscillations as a potential temporal reference frame for information coding in sensory cortices
While sensory neurons carry behaviorally relevant information in responses that often extend over hundreds of milliseconds, the key units of neural information likely consist of much shorter and temporally precise spike patterns. The mechanisms and temporal reference frames by which sensory networks partition responses into these shorter units of information remain unknown. One hypothesis holds that slow oscillations provide a network-intrinsic reference to temporally partitioned spike trains without exploiting the millisecond-precise alignment of spikes to sensory stimuli. We tested this hypothesis on neural responses recorded in visual and auditory cortices of macaque monkeys in response to natural stimuli. Comparing different schemes for response partitioning revealed that theta band oscillations provide a temporal reference that permits extracting significantly more information than can be obtained from spike counts, and sometimes almost as much information as obtained by partitioning spike trains using precisely stimulus-locked time bins. We further tested the robustness of these partitioning schemes to temporal uncertainty in the decoding process and to noise in the sensory input. This revealed that partitioning using an oscillatory reference provides greater robustness than partitioning using precisely stimulus-locked time bins. Overall, these results provide a computational proof of concept for the hypothesis that slow rhythmic network activity may serve as internal reference frame for information coding in sensory cortices and they foster the notion that slow oscillations serve as key elements for the computations underlying perception
Performance-based Remuneration for Civil Servants
Within the ongoing discussion about the Governance system in Indonesia and a reform of its PublicAdministration according to principles of Good Governance, a new remuneration system for civilservants is regarded a strategic key issue. The article outlines dimensions of the issue and gives aninsight on discourse and current reform approaches. An outlook on necessary steps ahead stresses, thatAdministrative Reform is not a topic for th
Beamed Lyman Alpha Emission through Outflow-Driven Cavities
We investigate the radiative transfer of Lyman alpha photons through
simplified anisotropic gas distributions, which represent physically motivated
extensions of the popular 'shell-models'. Our study is motivated by the notion
that (i) shell models do not always reproduce observed Lyman alpha spectral
line profiles, (ii) (typical) shell models do not allow for the escape of
ionizing photons, and (iii) the observation & expectation that winds are more
complex, anisotropic phenomena. We examine the influence of inclination on the
Lyman alpha spectra, relative fluxes and escape fractions. We find the flux to
be enhanced/suppressed by factors up to a few depending on the parameter range
of the models, corresponding to a boost in equivalent width of the same
amplitude if we neglect dust. In general, lower mean optical depths tend to
reduce the impact of anisotropies as is expected. We find a correlation between
an observed peak in the -- occasionally triple-peaked -- spectrum at the
systemic velocity and the existence of a low optical depth cavity along the
line of sight. This can be of importance in the search for ionizing photons
leaking from high- redshift galaxies since these photons will also be able to
escape through the cavity.Comment: 11 pages, accepted for publication in A&
Radiative Transfer Distortions of Lyman Α Emitters: A New Fingers-Of-God Damping in the Clustering in Redshift Space
Complex radiative transfer (RT) of the Lyman α photons poses a theoretical challenge to galaxy surveys that infer the large-scale structure with Lyman α emitters (LAEs). Guided by RT simulations, prior studies investigated the impact of RT on the large-scale LAE clustering, and claimed that RT induces a selection effect which results in an anisotropic distortion even in real space but in an otherwise negligible effect in redshift space. However, our previous study, which relies on a full RT code run on the Illustris simulations, shows that the anisotropic selection effect was drastically reduced with higher spatial resolution. Adopting the same simulation framework, we further study the impact of RT on the LAE clustering in redshift space. Since we measure LAE\u27s radial position through a spectral peak of Lyman α emission, the frequency shift due to RT contaminates the redshift measurement and hence the inferred radial position in redshift space. We demonstrate that this additional RT offset suppresses the LAE clustering along the line of sight, which can be interpreted as a novel Fingers-of- God (FoG) effect. To assess the FoG effect, we develop a theoretical framework modelling the impact of the RT similar to that of the small-scale peculiar velocity which is commonly studied in the context of the redshift space distortion (RSD). Although our findings strongly encourage a more careful RSD modelling in LAE surveys, we also seek a method to mitigate the additional FoG effect due to RT by making use of other information in a Lyman α spectrum
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