3,667 research outputs found
Football intermediaries and self‑regulation: the need for greater transparency through disciplinary law, sanctioning and qualifying criteria
This paper was first presented at the International Sports Law Conference in The Hague in October 2018. It summarises the author’s work and wider research on the introduction of new proposals for the regulation of football intermediaries (a term which the author finds unworkable and unorthodox). The author’s research critically analyses the current regulatory framework and identifies the elements that form the basis for the inadequacy and ineffectiveness of the regulations currently in force. With the use of case studies and examples drawn from the author’s private practice, recommendations are produced for new regulations that would promote transparency, equality and consistency. The author concludes that this can only be achieved via a blending of self-regulation and external regulation at an international setting
The Lennard-Jones-Devonshire cell model revisited
We reanalyse the cell theory of Lennard-Jones and Devonshire and find that in
addition to the critical point originally reported for the 12-6 potential (and
widely quoted in standard textbooks), the model exhibits a further critical
point. We show that the latter is actually a more appropriate candidate for
liquid-gas criticality than the original critical point.Comment: 5 pages, 3 figures, submitted to Mol. Phy
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
A Spectroscopic Redshift Measurement for a Luminous Lyman Break Galaxy at z=7.730 using Keck/MOSFIRE
We present a spectroscopic redshift measurement of a very bright Lyman break
galaxy at z=7.7302+-0.0006 using Keck/MOSFIRE. The source was pre-selected
photometrically in the EGS field as a robust z~8 candidate with H=25.0 mag
based on optical non-detections and a very red Spitzer/IRAC [3.6]-[4.5]
broad-band color driven by high equivalent width [OIII]+Hbeta line emission.
The Lyalpha line is reliably detected at 6.1 sigma and shows an asymmetric
profile as expected for a galaxy embedded in a relatively neutral
inter-galactic medium near the Planck peak of cosmic reionization. The line has
a rest-frame equivalent width of EW0=21+-4 A and is extended with
V_FWHM=360+90-70 km/s. The source is perhaps the brightest and most massive z~8
Lyman break galaxy in the full CANDELS and BoRG/HIPPIES surveys, having
assembled already 10^(9.9+-0.2) M_sol of stars at only 650 Myr after the Big
Bang. The spectroscopic redshift measurement sets a new redshift record for
galaxies. This enables reliable constraints on the stellar mass, star-formation
rate, formation epoch, as well as combined [OIII]+Hbeta line equivalent widths.
The redshift confirms that the IRAC [4.5] photometry is very likely dominated
by line emission with EW0(OIII+Hbeta)= 720-150+180 A. This detection thus adds
to the evidence that extreme rest-frame optical emission lines are a ubiquitous
feature of early galaxies promising very efficient spectroscopic follow-up in
the future with infrared spectroscopy using JWST and, later, ELTs.Comment: 6 pages, 4 figures, small updates to match ApJL accepted versio
UV Luminosity Functions at redshifts z~4 to z~10: 10000 Galaxies from HST Legacy Fields
The remarkable HST datasets from the CANDELS, HUDF09, HUDF12, ERS, and
BoRG/HIPPIES programs have allowed us to map out the evolution of the UV LF
from z~10 to z~4. We have identified 5859, 3001, 857, 481, 217, and 6 galaxy
candidates at z~4, z~5, z~6, z~7, z~8, and z~10, respectively from the ~1000
arcmin**2 area probed. The selection of z~4-8 galaxies over the five CANDELS
fields allows us to assess the cosmic variance; the largest variations are
apparent at z>=7. Our new LF determinations at z~4 and z~5 span a 6-mag
baseline (-22.5 to -16 AB mag). These determinations agree well with previous
estimates, but the larger samples and volumes probed here result in a more
reliable sampling of >L* galaxies and allow us to reassess the form of the UV
LFs. Our new LF results strengthen our earlier findings to 3.4 sigma
significance for a steeper faint-end slope to the UV LF at z>4, with alpha
evolving from alpha=-1.64+/-0.04 at z~4 to alpha=-2.06+/-0.13 at z~7 (and alpha
= -2.02+/-0.23 at z~8), consistent with that expected from the evolution of the
halo mass function. With our improved constraints at the bright end, we find
less evolution in the characteristic luminosity M* over the redshift range z~4
to z~7; the observed evolution in the LF is now largely represented by changes
in phi*. No evidence for a non-Schechter-like form to the z~4-8 LFs is found. A
simple conditional LF model based on halo growth and evolution in the M/L ratio
of halos ((1+z)**-1.5) provides a good representation of the observed
evolution.Comment: 53 pages, 28 figures, 11 tables, accepted for publication in the
Astrophysical Journa
Inductive learning spatial attention
This paper investigates the automatic induction of spatial attention
from the visual observation of objects manipulated
on a table top. In this work, space is represented in terms of
a novel observer-object relative reference system, named Local
Cardinal System, defined upon the local neighbourhood
of objects on the table. We present results of applying the
proposed methodology on five distinct scenarios involving
the construction of spatial patterns of coloured blocks
The Environment of M85 optical transient 2006-1: constraints on the progenitor age and mass
M85 optical transient 2006-1 (M85 OT 2006-1) is the most luminous member of
the small family of V838 Mon-like objects, whose nature is still a mystery.
This event took place in the Virgo cluster of galaxies and peaked at an
absolute magnitude of I~-13. Here we present Hubble Space Telescope images of
M85 OT 2006-1 and its environment, taken before and after the eruption, along
with a spectrum of the host galaxy at the transient location. We find that the
progenitor of M85 OT 2006-1 was not associated with any star forming region.
The g and z-band absolute magnitudes of the progenitor were fainter than about
-4 and -6 mag, respectively. Therefore, we can set a lower limit of ~50 Myr on
the age of the youngest stars at the location of the progenitor that
corresponds to a mass of <7 solar mass. Previously published line indices
suggest that M85 has a mean stellar age of 1.6+/-0.3 Gyr. If this mean age is
representative of the progenitor of M85 OT 2006-1, then we can further
constrain its mass to be less than 2 solar mass. We compare the energetics and
mass limit derived for the M85 OT 2006-1 progenitor with those expected from a
simple model of violent stellar mergers. Combined with further modeling, these
new clues may ultimately reveal the true nature of these puzzling events.Comment: 4 pages, accepted to Ap
An Ontology of Soil Properties and Processes
Assessing the Underworld (ATU) is a large interdisciplinary UK research project, which addresses challenges in integrated inter-asset maintenance. As assets on the surface of the ground (e.g. roads or pave- ments) and those buried under it (e.g. pipes and cables) are supported by the ground, the properties and processes of soil a ect the performance of these assets to a signi cant degree. In order to make integrated deci- sions, it is necessary to combine the knowledge and expertise in multiple areas, such as roads, soil, buried assets, sensing, etc. This requires an underpinning knowledge model, in the form of an ontology. Within this context, we present a new ontology for describing soil properties (e.g. soil strength) and processes (e.g. soil compaction), as well as how they a ect each other. This ontology can be used to express how the ground a ects and is a ected by assets buried under the ground or on the ground surface. The ontology is written in OWL 2 and openly available from the University of Leeds data repository: http://doi.org/10.5518/54
The Most Luminous z~9-10 Galaxy Candidates yet Found: The Luminosity Function, Cosmic Star-Formation Rate, and the First Mass Density Estimate at 500 Myr
[abridged] We present the discovery of four surprisingly bright (H_160 ~ 26 -
27 mag AB) galaxy candidates at z~9-10 in the complete HST CANDELS WFC3/IR
GOODS-N imaging data, doubling the number of z~10 galaxy candidates that are
known, just ~500 Myr after the Big Bang. Two similarly bright sources are also
detected in a systematic re-analysis of the GOODS-S data set. Three of the four
galaxies in GOODS-N are significantly detected at 4.5-6.2sigma in the very deep
Spitzer/IRAC 4.5 micron data, as is one of the GOODS-S candidates. Furthermore,
the brightest of our candidates (at z=10.2+-0.4) is robustly detected also at
3.6 micron (6.9sigma), revealing a flat UV spectral energy distribution with a
slope beta=-2.0+-0.2, consistent with demonstrated trends with luminosity at
high redshift. The abundance of such luminous candidates suggests that the
luminosity function evolves more significantly in phi_* than in L_* at z>~8
with a higher number density of bright sources than previously expected.
Despite the discovery of these luminous candidates, the cosmic star formation
rate density for galaxies with SFR >0.7 M_sun/yr shows an order-of-magnitude
increase in only 170 Myr from z ~ 10 to z ~ 8, consistent with previous
results. Based on the IRAC detections, we derive galaxy stellar masses at z~10,
finding that these luminous objects are typically 10^9 M_sun. The cosmic
stellar mass density at z~10 is log10 rho_* = 4.7^+0.5_-0.8 M_sun Mpc^-3 for
galaxies brighter than M_UV~-18. The remarkable brightness, and hence
luminosity, of these z~9-10 candidates highlights the opportunity for deep
spectroscopy to determine their redshift and nature, demonstrates the value of
additional search fields covering a wider area to understand star-formation in
the very early universe, and highlights the opportunities for JWST to map the
buildup of galaxies at redshifts much earlier than z~10.Comment: 20 pages, 12 figures, changed to match resubmitted version to Ap
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