2,136 research outputs found
Acoustic schwannoma of traumatic origin? A temporal bone study
A tumour of the singular nerve was found on examination of the temporal bones of a child who died 13 months after meningitis. The tumour consisted of a main mass with the appearance of an acoustic neuroma but close by and not connected were some nests of tumour cells inside the vestibule. This very unusual finding raises questions of the aetiology of this tumour which may have a bearing on the aetiology of other tumours of the VIIIth. nerv
Ear, nose and throat manifestations of Lyme disease
The manifestations of Lyme disease as they may present to the ENT surgeon are discussed. The most important ENT symptom is facial palsy. Particularly when combined with other cranial palsies, systemic illness or signs of meningeal irritation, the diagnosis must be considered. Three case reports are used to illustrate the presentation and diagnosis and treatment of Lyme disease. The characteristics of the disease are reviewed and the limitations of serological testing outlined. The literature has concentrated on bilateral or relapsing facial palsy. A review of palsies in Zurich that presented to the ENT clinic found only unilateral and partial palsies. The diagnosis should be considered in every case of facial palsy of unknown aetiology especially in childre
Report of the ultraviolet and visible sensors panel
In order to meet the science objectives of the Astrotech 21 mission set the Ultraviolet (UV) and Visible Sensors Panel made a number of recommendations. In the UV wavelength range of 0.01 to 0.3 micro-m the focus is on the need for large format high quantum efficiency, radiation hard 'solar-blind' detectors. Options recommended for support include Si and non-Si charge coupled devices (CCDs) as well as photocathodes with improved microchannel plate readouts. For the 0.3 to 0.9 micro-m range, it was felt that Si CCDs offer the best option for high quantum efficiencies at these wavelengths. In the 0.9 to 2.5 micro-m the panel recommended support for the investigation of monolithic arrays. Finally, the panel noted that the implementation of very large arrays will require new data transmission, data recording, and data handling technologies
An extended view of the Pisces Overdensity from the SCUSS survey
SCUSS is a u-band photometric survey covering about 4000 square degree of the
South Galactic Cap, reaching depths of up to 23 mag. By extending around 1.5
mag deeper than SDSS single-epoch u data, SCUSS is able to probe much a larger
volume of the outer halo, i.e. with SCUSS data blue horizontal branch (BHB)
stars can trace the outer halo of the Milky Way as far as 100-150 kpc.
Utilizing this advantage we combine SCUSS u band with SDSS DR9 gri photometric
bands to identify BHB stars and explore halo substructures. We confirm the
existence of the Pisces overdensity, which is a structure in the outer halo (at
around 80 kpc) that was discovered using RR Lyrae stars. For the first time we
are able to determine its spatial extent, finding that it appears to be part of
a stream with a clear distance gradient. The stream, which is ~5 degrees wide
and stretches along ~25 degrees, consists of 20-30 BHBs with a total
significance of around 6sigma over the background. Assuming we have detected
the entire stream and that the progenitor has fully disrupted, then the number
of BHBs suggests the original system was similar to smaller classical or a
larger ultra-faint dwarf galaxy. On the other hand, if the progenitor still
exists, it can be hunted for by reconstructing its orbit from the distance
gradient of the stream. This new picture of the Pisces overdensity sheds new
light on the origin of this intriguing system.Comment: 8 pages, 4 figures, accepted by Ap
The SDSS-IV extended Baryon Oscillation Spectroscopic Survey: selecting emission line galaxies using the Fisher discriminant
We present a new selection technique of producing spectroscopic target
catalogues for massive spectroscopic surveys for cosmology. This work was
conducted in the context of the extended Baryon Oscillation Spectroscopic
Survey (eBOSS), which will use ~200 000 emission line galaxies (ELGs) at
0.6<zspec<1.0 to obtain a precise baryon acoustic oscillation measurement. Our
proposed selection technique is based on optical and near-infrared broad-band
filter photometry. We used a training sample to define a quantity, the Fisher
discriminant (linear combination of colours), which correlates best with the
desired properties of the target: redshift and [OII] flux. The proposed
selections are simply done by applying a cut on magnitudes and this Fisher
discriminant. We used public data and dedicated SDSS spectroscopy to quantify
the redshift distribution and [OII] flux of our ELG target selections. We
demonstrate that two of our selections fulfil the initial eBOSS/ELG redshift
requirements: for a target density of 180 deg^2, ~70% of the selected objects
have 0.6<zspec<1.0 and only ~1% of those galaxies in the range 0.6<zspec<1.0
are expected to have a catastrophic zspec estimate. Additionally, the stacked
spectra and stacked deep images for those two selections show characteristic
features of star-forming galaxies. The proposed approach using the Fisher
discriminant could, however, be used to efficiently select other galaxy
populations, based on multi-band photometry, providing that spectroscopic
information is available. This technique could thus be useful for other future
massive spectroscopic surveys such as PFS, DESI, and 4MOST.Comment: Version published in A&
Large format heterodyne arrays for observing far-infrared lines with SOFIA
In the wavelength regime between 60 and 300 microns there are a number of atomic and molecular emission lines that are key diagnostic probes of the interstellar medium. These include transitions of [CII], [NII], [OI], HD, H_2D^+, OH, CO, and H_2O, some of which are among the brightest global and local far-infrared lines in the Galaxy. In Giant Molecular Clouds (GMCs), evolved star envelopes, and planetary nebulae, these emission lines can be extended over many arc minutes and possess complicated, often self absorbed, line profiles. High spectral resolution (R > 10^5) observations of these lines at sub-arcminute angular resolution are crucial to understanding the complicated interplay between the interstellar medium and the stars that form from it. This feedback is central to all theories of galactic evolution. Large format heterodyne array receivers can provide the spectral resolution and spatial coverage to probe these lines over extended regions. The advent of large format (~100 pixel) spectroscopic imaging cameras in the far-infrared (FIR) will fundamentally change the way astronomy is performed in this important wavelength regime. While the possibility of such instruments has been discussed for more than two decades, only recently have advances in mixer and local oscillator technology, device fabrication, micromachining, and digital signal processing made the construction of such instruments tractable. These technologies can be implemented to construct a sensitive, flexible, heterodyne array facility instrument for SOFIA. The instrument concept for StratoSTAR: Stratospheric Submm/THz Array Receiver includes a common user mounting, control system, IF processor, spectrometer, and cryogenic system. The cryogenic system will be designed to accept a frontend insert. The frontend insert and associated local oscillator system/relay optics would be provided by individual user groups and reflect their scientific interests. Rapid technology development in this field makes SOFIA the ideal platform to operate such a modular, continuously evolving instrument
The Luminosity Function of Early-Type Galaxies at z~0.75
We measure the luminosity function of morphologically selected E/S0 galaxies
from to using deep high resolution Advanced Camera for Surveys
imaging data. Our analysis covers an area of 48\Box\arcmin (8 the
area of the HDF-N) and extends 2 magnitudes deeper ( mag) than was
possible in the Deep Groth Strip Survey (DGSS). At , we find
and , and at
, we find . These luminosity
functions are similar in both shape and number density to the luminosity
function using morphological selection (e.g., DGSS), but are much steeper than
the luminosity functions of samples selected using morphological proxies like
the color or spectral energy distribution (e.g., CFRS, CADIS, or COMBO-17). The
difference is due to the `blue', , E/S0 galaxies, which make up to
of the sample at all magnitudes and an increasing proportion of faint
galaxies. We thereby demonstrate the need for {\it both morphological and
structural information} to constrain the evolution of galaxies.
We find that the `blue' E/S0 galaxies have the same average sizes and Sersic
parameters as the `red', , E/S0 galaxies at brighter luminosities
(), but are increasingly different at fainter magnitudes where
`blue' galaxies are both smaller and have lower Sersic parameters. Fits of the
colors to stellar population models suggest that most E/S0 galaxies have short
star-formation time scales ( Gyr), and that galaxies have formed at an
increasing rate from until after which there has been a
gradual decline.Comment: 39 pages, 21 figures, accepted in A
The Morphology - Density Relation in z ~ 1 Clusters
We measure the morphology--density relation (MDR) and morphology-radius
relation (MRR) for galaxies in seven z ~ 1 clusters that have been observed
with the Advanced Camera for Surveys on board the Hubble Space Telescope.
Simulations and independent comparisons of ourvisually derived morphologies
indicate that ACS allows one to distinguish between E, S0, and spiral
morphologies down to zmag = 24, corresponding to L/L* = 0.21 and 0.30 at z =
0.83 and z = 1.24, respectively. We adopt density and radius estimation methods
that match those used at lower redshift in order to study the evolution of the
MDR and MRR. We detect a change in the MDR between 0.8 < z < 1.2 and that
observed at z ~ 0, consistent with recent work -- specifically, the growth in
the bulge-dominated galaxy fraction, f_E+SO, with increasing density proceeds
less rapidly at z ~ 1 than it does at z ~ 0. At z ~ 1 and density <= 500
galaxies/Mpc^2, we find = 0.72 +/- 0.10. At z ~ 0, an E+S0 population
fraction of this magnitude occurs at densities about 5 times smaller. The
evolution in the MDR is confined to densities >= 40 galaxies/Mpc^2 and appears
to be primarily due to a deficit of S0 galaxies and an excess of Spiral+Irr
galaxies relative to the local galaxy population. The Elliptical fraction -
density relation exhibits no significant evolution between z = 1 and z = 0. We
find mild evidence to suggest that the MDR is dependent on the bolometric X-ray
luminosity of the intracluster medium. Implications for the evolution of the
disk galaxy population in dense regions are discussed in the context of these
observations.Comment: 30 pages, 18 figures. Accepted for publication in ApJ. Full
resolution versions of figs 2,3,6,8 are available at
http://www.stsci.edu/~postman/mdr_figure
Discovery of Globular Clusters in the Proto-Spiral NGC2915: Implications for Hierarchical Galaxy Evolution
We have discovered three globular clusters beyond the Holmberg radius in
Hubble Space Telescope Advanced Camera for Surveys images of the gas-rich dark
matter dominated blue compact dwarf galaxy NGC2915. The clusters, all of which
start to resolve into stars, have M_{V606} = -8.9 to -9.8 mag, significantly
brighter than the peak of the luminosity function of Milky Way globular
clusters. Their colors suggest a metallicity [Fe/H] ~ -1.9 dex, typical of
metal-poor Galactic globular clusters. The specific frequency of clusters is at
a minimum normal, compared to spiral galaxies. However, since only a small
portion of the system has been surveyed it is more likely that the luminosity
and mass normalized cluster content is higher, like that seen in elliptical
galaxies and galaxy clusters. This suggests that NGC2915 resembles a key phase
in the early hierarchical assembly of galaxies - the epoch when much of the old
stellar population has formed, but little of the stellar disk. Depending on the
subsequent interaction history, such systems could go on to build-up larger
elliptical galaxies, evolve into normal spirals, or in rare circumstances
remain suspended in their development to become systems like NGC2915.Comment: ApJ Letters accepted; 6 pages, 2 figures, 3 table
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