403 research outputs found
Further multiwavelength observations of the SSA22 Ly_alpha emitting `blob'
We present new follow-up observations of the sub-mm luminous
Ly_alpha-emitting object in the SSA22 z=3.09 galaxy overdensity, referred to as
`Blob 1' by Steidel et al.(2000). In particular we discuss high resolution
Hubble Space Telescope optical imaging, Owens Valley Radio Observatory spectral
imaging, Keck spectroscopy, VLA 20cm radio continuum imaging, and Chandra X-ray
observations. We also present a more complete analysis of the existing James
Clerk Maxwell Telescope sub-mm data. We detect several optical continuum
components which may be associated with the core of the submillimeter emitting
region. A radio source at the position of one of the HST components
(22:17:25.94, +00:12:38.9) identifies it as the likely counterpart to the
submillimeter source. We also tentatively detect the CO(4-3) molecular line,
centered on the radio position. We use the CO(4-3) intensity to estimate a
limit on the gas mass for the system. The optical morphology of sources within
the Ly_alpha cloud appears to be filamentary, while the optical source
identified with the radio source has a dense knot which may be an AGN or
compact starburst. We obtain a Keck-LRIS spectrum of this object, despite its
faintness (R=26.8). The spectrum reveals weak Ly_alpha emission, but no other
obvious features, suggesting that the source is not an energetic AGN (or that
it is extremely obscured). We use non-detections in deep Chandra X-ray images
to constrain the nature of the `Blob'. Although conclusive evidence regarding
the nature of the object remains hard to obtain at this redshift, the evidence
presented here is at least consistent with a dust-obscured AGN surrounded by a
starburst situated at the heart of this giant Ly_alpha cloud.Comment: 8 pages, 9figs (low res), to appear in ApJ, for higher res figures,
http://www.submm.caltech.edu/~schapman/sa22_sept4.ps.g
Data processing pipeline for Herschel HIFI
Context. The HIFI instrument on the Herschel Space Observatory performed over 9100 astronomical observations, almost 900 of which were calibration observations in the course of the nearly four-year Herschel mission. The data from each observation had to be converted from raw telemetry into calibrated products and were included in the Herschel Science Archive.
Aims. The HIFI pipeline was designed to provide robust conversion from raw telemetry into calibrated data throughout all phases of the HIFI missions. Pre-launch laboratory testing was supported as were routine mission operations.
Methods. A modular software design allowed components to be easily added, removed, amended and/or extended as the understanding of the HIFI data developed during and after mission operations.
Results. The HIFI pipeline processed data from all HIFI observing modes within the Herschel automated processing environment as well as within an interactive environment. The same software can be used by the general astronomical community to reprocess any standard HIFI observation. The pipeline also recorded the consistency of processing results and provided automated quality reports. Many pipeline modules were in use since the HIFI pre-launch instrument level testing.
Conclusions. Processing in steps facilitated data analysis to discover and address instrument artefacts and uncertainties. The availability of the same pipeline components from pre-launch throughout the mission made for well-understood, tested, and stable processing. A smooth transition from one phase to the next significantly enhanced processing reliability and robustness
Electrically driven photon emission from individual atomic defects in monolayer WS2.
Quantum dot-like single-photon sources in transition metal dichalcogenides (TMDs) exhibit appealing quantum optical properties but lack a well-defined atomic structure and are subject to large spectral variability. Here, we demonstrate electrically stimulated photon emission from individual atomic defects in monolayer WS2 and directly correlate the emission with the local atomic and electronic structure. Radiative transitions are locally excited by sequential inelastic electron tunneling from a metallic tip into selected discrete defect states in the WS2 bandgap. Coupling to the optical far field is mediated by tip plasmons, which transduce the excess energy into a single photon. The applied tip-sample voltage determines the transition energy. Atomically resolved emission maps of individual point defects closely resemble electronic defect orbitals, the final states of the optical transitions. Inelastic charge carrier injection into localized defect states of two-dimensional materials provides a powerful platform for electrically driven, broadly tunable, atomic-scale single-photon sources
Dust Distribution during Reionization
The dust produced by the first generation of stars will be a foreground to
cosmic microwave background. In order to evaluate the effect of this early
dust, we calculate the power spectrum of the dust emission anisotropies and
compare it with the sensitivity limit of the Planck satellite. The spatial
distribution of the dust is estimated through the distribution of dark matter.
At small angular scales () the dust signal is found to be
noticeable with the Planck detector for certain values of dust lifetime and
production rates. The dust signal is also compared to sensitivities of other
instruments. The early dust emission anisotropies are finally compared to those
of local dust and they are found to be similar in magnitude at mm wavelengths.Comment: 6 pages, 6 figures; Typos fixed. Clarifications in the abstract,
sections 2 and 4.1 and fig
Effective land management in Ukraine using accounting and analytical support
Unique nature of land resources determines the specifics of constructing a land management and registration system, which includes accumulation, systematization, processing and analysis of economic information about their quantitative, qualitative, monetary and legal data in the state. The economic, social, and ecological safety of the state and living standards of the population depend on the effective land use. Consequently, there is a need for continuous improvement of the regulatory and legislative framework, development of a methodology for land registration and fixing land accounting operations. The article deals with the current state and problems of the development of synthetic and analytical registration of land resources in Ukraine. The variability of the representation of land relations in the accounting system is also considered. The current system of agricultural land registration in Ukraine does not allow to reflect the full range of characteristics of land plots for external and internal users in order to profit and increase the investment attractiveness of enterprises. It is established that reliable and accurate assessment and registration of land plots have significant influence on the agricultural enterprise position
Safety and reactogenicity of the 10-valent pneumococcal non-typeable Haemophilus influenzae protein D conjugate vaccine (PHiD-CV) co-administered with DTPa-HBV-IPV/Hib in Vietnamese infants
Understanding the nature of the optically faint radio sources and their connection to the submillimeter population
We present a sample of 43 submillimeter sources detected (at >3 sigma), drawn
from our program to follow-up optically faint radio sources with SCUBA. These
sources already have associated radio and in many cases optical
identifications, and many are also detected at 450 microns. We compare these
with 12 submillimeter sources drawn from the literature, which were discovered
in blank field mapping campaigns, but also have radio detections. We then use
this total sample (55 sources) to study and model the evolution of dusty
galaxies. A correlation is observed in the sub-mm/radio color-magnitude
diagram, which can be modeled by strong luminosity evolution. The selection
effects of the radio/optical pre-selection technique are determined from the
models, and a corrected redshift distribution is constrained using a range of
model assumptions. The temperature/redshift effects on the 450 microns detected
subset of our sample are studied in relation to the models, and prospects for
improved measurements in the shorter sub-mm wavelength windows (450 microns and
350 microns) are explored.Comment: to appear in ApJ, 19 pages, 9 figure
First Constraints on Source Counts at 350 Microns
We have imaged a 6 arcminute region in the Bo\"otes Deep Field
using the 350 m-optimised second generation Submillimeter High Angular
Resolution Camera (SHARC II), achieving a peak 1 sensitivity of 5
mJy. We detect three sources above 3, and determine a spurious source
detection rate of 1.09 in our maps. In the absence of detections, we
rely on deep 24 m and 20 cm imaging to deduce which sources are most
likely to be genuine, giving two real sources. From this we derive an integral
source count of 0.84 sources arcmin at mJy,
which is consistent with 350 m source count models that have an
IR-luminous galaxy population evolving with redshift. We use these constraints
to consider the future for ground-based short-submillimetre surveys.Comment: accepted for publication in The Astrophysical Journa
Environment of MAMBO galaxies in the COSMOS field
Submillimeter galaxies (SMG) represent a dust-obscured high-redshift
population undergoing massive star formation activity. Their properties and
space density have suggested that they may evolve into spheroidal galaxies
residing in galaxy clusters. In this paper, we report the discovery of compact
(~10"-20") galaxy overdensities centered at the position of three SMGs detected
with the Max-Planck Millimeter Bolometer camera (MAMBO) in the COSMOS field.
These associations are statistically significant. The photometric redshifts of
galaxies in these structures are consistent with their associated SMGs; all of
them are between z=1.4-2.5, implying projected physical sizes of ~170 kpc for
the overdensities. Our results suggest that about 30% of the radio-identified
bright SMGs in that redshift range form in galaxy density peaks in the crucial
epoch when most stars formed.Comment: Accepted for publication in ApJ Letter
- …