213 research outputs found
E-Business and the Semiconductor Industry Value Chain: Implications for Vertical Specialization and Integrated Semiconductor Manufacturers
Intellectual property disclosure in standards development
Firms often collaborate to produce inter-operability standards so that independently designed products can work together. When this process takes place in a Standard Setting Organization (SSO), participants are typically required to disclose any intellectual property rights (IP) that would be infringed by a proposed standard, and asked for a commitment to license their essential IP on fair, reasonable and non-discriminatory terms. This paper describes the IP disclosure process, and provides an overview of a publicly available IP disclosure dataset that the authors have compiled using the archives of thirteen major SSOs. We use these new data to illustrate several major trends in standards development, and to show how "declared essential" patents differ from a random sample of patents of the same vintage covering similar technology
The Sunburst Arc: Direct Lyman {\alpha} escape observed in the brightest known lensed galaxy
We present rest-frame ultraviolet and optical spectroscopy of the brightest
lensed galaxy yet discovered, at redshift z = 2.4. This source reveals a
characteristic, triple-peaked Lyman {\alpha} profile which has been predicted
by various theoretical works but to our knowledge has not been unambiguously
observed previously. The feature is well fit by a superposition of two
components: a double-peak profile emerging from substantial radiative transfer,
and a narrow, central component resulting from directly escaping Lyman {\alpha}
photons; but is poorly fit by either component alone. We demonstrate that the
feature is unlikely to contain contamination from nearby sources, and that the
central peak is unaffected by radiative transfer effects apart from very slight
absorption. The feature is detected at signal-to-noise ratios exceeding 80 per
pixel at line center, and bears strong resemblance to synthetic profiles
predicted by numerical models.Comment: Accepted for publication in Astronomy & Astrophysics. 4 pages, 5
figure
Clues to the nature of high-redshift OVI absorption systems from their (lack of) small-scale structure
We present results of the first survey of high-redshift ( ~ 2.3) OVI
absorption systems along parallel lines of sight toward two lensed QSOs. After
a careful and well-defined search, we find ten intervening OVI systems. Within
the errors, all OVI systems appear at the same redshift and have similar line
strengths in front of both QSO images, whereas in most cases CIV or SiIV show
more differences across the lines of sight, either in radial velocity or line
strength. We conclude that (1) the coherence length of OVI must be much larger
than ~ 1 kpc, and (2) an important fraction of the CIV absorbers may not reside
in the same volume as OVI. Since Doppler parameters are consistent with
photoionization, we propose a model in which CIV occurs in two different
photoionized phases, one large, with characteristic sizes of a few hundred kpc
and bearing OVI, and another one a factor of ten smaller and containing CIII.
This model is able to explain the various transverse differences observed in
column density and kinematics. We apply the model successfully to 2 kinds of
absorbers, with low and high metallicity. In the low-metallicity regime, [C/H]
\~ -2, we find that [C/O] ~ -0.7 is required to explain the observations, which
hints at late (z < 6) rather than early metal enrichment. In the
high-metallicity regime, the observed dissociation between OVI and CIV gas
might be produced by galactic outflows. Altogether, the relative abundances,
inhomogeneous CIV and featureless OVI are consistent with gas that has been
processed recently before the absorption occurred (thus close to star-forming
regions). Finally, we discuss briefly three associated systems (z_abs ~ z_em)
that also show OVI. (abridged)Comment: Accepted by A&A, 22 page
MASE: A New Data--Reduction Pipeline for the Magellan Echellette Spectrograph
We introduce a data reduction package written in Interactive Data Language
(IDL) for the Magellan Echellete Spectrograph (MAGE). MAGE is a
medium-resolution (R ~4100), cross-dispersed, optical spectrograph, with
coverage from ~3000-10000 Angstroms. The MAGE Spectral Extractor (MASE)
incorporates the entire image reduction and calibration process, including bias
subtraction, flat fielding, wavelength calibration, sky subtraction, object
extraction and flux calibration of point sources. We include examples of the
user interface and reduced spectra. We show that the wavelength calibration is
sufficient to achieve ~5 km/s RMS accuracy and relative flux calibrations
better than 10%. A light-weight version of the full reduction pipeline has been
included for real-time source extraction and signal-to-noise estimation at the
telescope.Comment: 10 pages (ApJ format), accepted PAS
Metal-enriched, subkiloparsec gas clumps in the circumgalactic medium of a faint z = 2.5 galaxy
We report the serendipitous detection of a 0.2 L*, Lyα emitting galaxy at redshift 2.5 at an impact parameter of 50 kpc from a bright background QSO sightline. A high-resolution spectrum of the QSO reveals a partial Lyman-limit absorption system (NHi=1016.94±0.10 cmâ2) with many associated metal absorption lines at the same redshift as the foreground galaxy. Using photoionization models that carefully treat measurement errors and marginalize over uncertainties in the shape and normalization of the ionizing radiation spectrum, we derive the total hydrogen column density NH=1019.4±0.3cmâ2, and show that all the absorbing clouds are metal enriched, with Z = 0.1â0.6âZâ. These metallicities and the system's large velocity width (436 kmâsâ 1) suggest the gas is produced by an outflowing wind. Using an expanding shell model we estimate a mass outflow rate of âŒ5âMââyrâ1. Our photoionization model yields extremely small sizes (<100â500 pc) for the absorbing clouds, which we argue is typical of high column density absorbers in the circumgalactic medium (CGM). Given these small sizes and extreme kinematics, it is unclear how the clumps survive in the CGM without being destroyed by hydrodynamic instabilities. The small cloud sizes imply that even state-of-the-art cosmological simulations require more than a 1000-fold improvement in mass resolution to resolve the hydrodynamics relevant for cool gas in the CGM
Metal-enriched, subkiloparsec gas clumps in the circumgalactic medium of a faint z = 2.5 galaxy
We report the serendipitous detection of a 0.2 L*, Lyα emitting galaxy at redshift 2.5 at an impact parameter of 50 kpc from a bright background QSO sightline. A high-resolution spectrum of the QSO reveals a partial Lyman-limit absorption system (N[subscript Hi] = 10[superscript 16.94±0.10] cm[superscript â2]) with many associated metal absorption lines at the same redshift as the foreground galaxy. Using photoionization models that carefully treat measurement errors and marginalize over uncertainties in the shape and normalization of the ionizing radiation spectrum, we derive the total hydrogen column density N[subscript H] = 10[superscript 19.4±0.3] cm[superscript â2], and show that all the absorbing clouds are metal enriched, with Z = 0.1â0.6âZ[subscript â]. These metallicities and the system's large velocity width (436 kmâs[superscript â1]) suggest the gas is produced by an outflowing wind. Using an expanding shell model we estimate a mass outflow rate of ~5âM[subscript â]âyr[superscript â1]. Our photoionization model yields extremely small sizes (<100â500 pc) for the absorbing clouds, which we argue is typical of high column density absorbers in the circumgalactic medium (CGM). Given these small sizes and extreme kinematics, it is unclear how the clumps survive in the CGM without being destroyed by hydrodynamic instabilities. The small cloud sizes imply that even state-of-the-art cosmological simulations require more than a 1000-fold improvement in mass resolution to resolve the hydrodynamics relevant for cool gas in the CGM
A Structure for Quasars
This paper proposes a simple, empirically derived, unifying structure for the
inner regions of quasars. This structure is constructed to explain the broad
absorption line (BAL) regions, the narrow `associated' ultraviolet and X-ray
warm absorbers (NALs); and is also found to explain the broad emission line
regions (BELR), and several scattering features, including a substantial
fraction of the broad X-ray Iron-K emission line, and the bi-conical extended
narrow emission line region (ENLR) structures seen on large kiloparsec scales
in Seyfert images. Small extensions of the model to allow luminosity dependent
changes in the structure may explain the UV and X-ray Baldwin effects and the
greater prevalence of obscuration in low luminosity AGN.Comment: 35 pages, including 8 color figures (figures 4abc are big).
Astrophysical Journal, in press. Expanded version of conference paper
astro-ph/000516
An 800-million-solar-mass black hole in a significantly neutral Universe at redshift 7.5
Quasars are the most luminous non-transient objects known and as a result
they enable studies of the Universe at the earliest cosmic epochs. Despite
extensive efforts, however, the quasar ULAS J1120+0641 at z=7.09 has remained
the only one known at z>7 for more than half a decade. Here we report
observations of the quasar ULAS J134208.10+092838.61 (hereafter J1342+0928) at
redshift z=7.54. This quasar has a bolometric luminosity of 4e13 times the
luminosity of the Sun and a black hole mass of 8e8 solar masses. The existence
of this supermassive black hole when the Universe was only 690 million years
old---just five percent of its current age---reinforces models of early
black-hole growth that allow black holes with initial masses of more than about
1e4 solar masses or episodic hyper-Eddington accretion. We see strong evidence
of absorption of the spectrum of the quasar redwards of the Lyman alpha
emission line (the Gunn-Peterson damping wing), as would be expected if a
significant amount (more than 10 per cent) of the hydrogen in the intergalactic
medium surrounding J1342+0928 is neutral. We derive a significant fraction of
neutral hydrogen, although the exact fraction depends on the modelling.
However, even in our most conservative analysis we find a fraction of more than
0.33 (0.11) at 68 per cent (95 per cent) probability, indicating that we are
probing well within the reionization epoch of the Universe.Comment: Updated to match the final journal versio
Slicing the Torus: Obscuring Structures in Quasars
Quasars and Active Galactic Nuclei (AGNs) are often obscured by dust and gas.
It is normally assumed that the obscuration occurs in an oblate "obscuring
torus", that begins at the radius at which the most refractive dust can remain
solid. The most famous form of this torus is a donut-shaped region of molecular
gas with a large scale-height. While this model is elegant and accounts for
many phenomena at once, it does not hold up to detailed tests. Instead the
obscuration in AGNs must occur on a wide range of scales and be due to a
minimum of three physically distinct absorbers. Slicing the "torus" into these
three regions will allow interesting physics of the AGN to be extracted.Comment: 8 pages, 1 figure. To appear in the proceedings of the conference
"The central kiloparsec in Galactic Nuclei:Astronomy at High Angular
Resolution 2011", open access Journal of Physics: Conference Series (JPCS),
published by IOP Publishin
- âŠ