2,896 research outputs found
A sceptic looks at "housing theory"
A sceptic looks at "housing theory
Understanding contextualised rational action - author's response
Understanding contextualised rational action - author's respons
Note-based segmentation and hierarchy in the classification of digital musical instruments
The ability to automatically identify the musical instruments occurring in a recorded piece of music has important uses for various music-related applications. This paper examines the case of instrument classification where the raw data consists of musical phrases performed on digital instruments from eight instrument families. We compare the use of extracted features from a continuous sample of approximately one second, to the use of a systematic segmentation of the audio on note boundaries and using multiple, aligned note samples as input to classifiers. The accuracy of the segmented approach was greater than the one of the unsegmented approach. The best method was using a two-tiered hierarchical method which performed slightly better than the single-tiered flat approach. The best performing instrument category was woodwind, with an accuracy of 94% for the segmented approach, using the Bayesian network classifier. Distinguishing different types of pianos was difficult for all classifiers, with the segmented approach yielding an accuracy of 56%. For humans, broadly similar results were found, in that pianos were difficult to distinguish, along with woodwind and solo string instruments. However there was no symmetry between human comparisons of identical instruments and different instruments, with half of the broad instrument categories having widely different accuracies for the two cases
A Cosmic Variance Cookbook
Deep pencil beam surveys (<1 deg^2) are of fundamental importance for
studying the high-redshift universe. However, inferences about galaxy
population properties are in practice limited by 'cosmic variance'. This is the
uncertainty in observational estimates of the number density of galaxies
arising from the underlying large-scale density fluctuations. This source of
uncertainty can be significant, especially for surveys which cover only small
areas and for massive high-redshift galaxies. Cosmic variance for a given
galaxy population can be determined using predictions from cold dark matter
theory and the galaxy bias. In this paper we provide tools for experiment
design and interpretation. For a given survey geometry we present the cosmic
variance of dark matter as a function of mean redshift z and redshift bin size
Dz. Using a halo occupation model to predict galaxy clustering, we derive the
galaxy bias as a function of mean redshift for galaxy samples of a given
stellar mass range. In the linear regime, the cosmic variance of these galaxy
samples is the product of the galaxy bias and the dark matter cosmic variance.
We present a simple recipe using a fitting function to compute cosmic variance
as a function of the angular dimensions of the field, z, Dz and stellar mass
m*. We also provide tabulated values and a software tool. We find that for
GOODS at z=2 and with Dz=0.5 the relative cosmic variance of galaxies with
m*>10^11 Msun is ~38%, while it is ~27% for GEMS and ~12% for COSMOS. For
galaxies of m*~10^10 Msun the relative cosmic variance is ~19% for GOODS, ~13%
for GEMS and ~6% for COSMOS. This implies that cosmic variance is a significant
source of uncertainty at z=2 for small fields and massive galaxies, while for
larger fields and intermediate mass galaxies cosmic variance is less serious.Comment: 8 pages, 4 figures, 5 tables, submitted to Ap
The Role of Black Hole Feedback on Size and Structural Evolution in Massive Galaxies
We use cosmological hydrodynamical simulations to investigate the role of
feedback from accreting black holes on the evolution of sizes, compactness,
stellar core density and specific star-formation of massive galaxies with
stellar masses of . We perform two sets of
cosmological zoom-in simulations of 30 halos to z=0: (1) without black holes
and Active Galactic Nucleus (AGN) feedback and (2) with AGN feedback arising
from winds and X-ray radiation. We find that AGN feedback can alter the stellar
density distribution, reduce the core density within the central 1 kpc by 0.3
dex from z=1, and enhance the size growth of massive galaxies. We also find
that galaxies simulated with AGN feedback evolve along similar tracks to those
characterized by observations in specific star formation versus compactness. We
confirm that AGN feedback plays an important role in transforming galaxies from
blue compact galaxies into red extended galaxies in two ways: (1) it
effectively quenches the star formation, transforming blue compact galaxies
into compact quiescent galaxies and (2) it also removes and prevents new
accretion of cold gas, shutting down in-situ star formation and causing
subsequent mergers to be gas-poor or mixed. Gas poor minor mergers then build
up an extended stellar envelope. AGN feedback also puffs up the central region
through the fast AGN driven winds as well as the slow expulsion of gas while
the black hole is quiescent. Without AGN feedback, large amounts of gas
accumulate in the central region, triggering star formation and leading to
overly massive blue galaxies with dense stellar cores.Comment: 13 pages, 7 figures, Accepted for publication in Ap
Star formation in mergers with cosmologically motivated initial conditions
We use semi-analytic models and cosmological merger trees to provide the
initial conditions for multi-merger numerical hydrodynamic simulations, and
exploit these simulations to explore the effect of galaxy interaction and
merging on star formation (SF). We compute numerical realisations of twelve
merger trees from z=1.5 to z=0. We include the effects of the large hot gaseous
halo around all galaxies, following recent obervations and predictions of
galaxy formation models. We find that including the hot gaseous halo has a
number of important effects. Firstly, as expected, the star formation rate on
long timescales is increased due to cooling of the hot halo and refuelling of
the cold gas reservoir. Secondly, we find that interactions do not always
increase the SF in the long term. This is partially due to the orbiting
galaxies transferring gravitational energy to the hot gaseous haloes and
raising their temperature. Finally we find that the relative size of the
starburst, when including the hot halo, is much smaller than previous studies
showed. Our simulations also show that the order and timing of interactions are
important for the evolution of a galaxy. When multiple galaxies interact at the
same time, the SF enhancement is less than when galaxies interact in series.
All these effects show the importance of including hot gas and cosmologically
motivated merger trees in galaxy evolution models.Comment: 19 pages, 15 figures, 6 tables. Accepted for publication in MNRA
Sets and Sensibilities: The Excavation of Ideology in Upstate New York
A growing literature on the archaeology of farmsteads and rural domestic sites has examined commodity consumption as the means by which rural families created and maintained social networks and identities. During the nineteenth century, rural areas were increasingly influenced by the practices and values of the urban middle classes, although not every farmstead would, or could, participate in the same way. This paper examines a matching teacup and saucer recovered from the Spring House, a former commercial farmstead and hotel located southeastern Monroe County, Western New York State. The tea set is decorated with transfer print depictions of Faith, Hope, and Charity, the Three Virtues forming the basis of Christianity, and a motif popular in Victorian America. This paper considers how the tea set, recovered from a rural context, reflects social and genteel identity, and how the occupants of the Spring House used the set to create a sense of respectability through consumption and display
The nature of the ISM in galaxies during the star-formation activity peak of the Universe
We combine a semi-analytic model of galaxy formation, tracking atomic and
molecular phases of cold gas, with a three-dimensional radiative-transfer and
line tracing code to study the sub-mm emission from atomic and molecular
species (CO, HCN, [CI], [CII], [OI]) in galaxies. We compare the physics that
drives the formation of stars at the epoch of peak star formation (SF) in the
Universe (z = 2.0) with that in local galaxies. We find that normal
star-forming galaxies at high redshift have much higher CO-excitation peaks
than their local counterparts and that CO cooling takes place at higher
excitation levels. CO line ratios increase with redshift as a function of
galaxy star-formation rate, but are well correlated with H2 surface density
independent of redshift. We find an increase in the [OI]/[CII] line ratio in
typical star-forming galaxies at z = 1.2 and z = 2.0 with respect to
counterparts at z = 0. Our model results suggest that typical star-forming
galaxies at high redshift consist of much denser and warmer star-forming clouds
than their local counterparts. Galaxies belonging to the tail of the SF
activity peak at z = 1.2 are already less dense and cooler than counterparts
during the actual peak of SF activity (z = 2.0). We use our results to discuss
how future ALMA surveys can best confront our predictions and constrain models
of galaxy formation.Comment: 19 pages, 14 figures, accepted for publication in MNRA
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