229 research outputs found
Food and Agriculture in PNG
Agriculture dominates the rural economy of Papua New Guinea (PNG). More than five million rural dwellers (80% of the population) earn a living from subsistence agriculture and selling crops in domestic and international markets. Many aspects of agriculture in PNG are described in this data-rich book. Topics include agricultural environments in which crops are grown; production of food crops, cash crops and animals; land use; soils; demography; migration; the macro-economic environment; gender issues; governance of agricultural institutions; and transport. The history of agriculture over the 50 000 years that PNG has been occupied by humans is summarised. Much of the information presented is not readily available within PNG. The book contains results of many new analyses, including a food budget for the entire nation. The text is supported by 165 tables and 215 maps and figures
A Systematic Search for Molecular Outflows Toward Candidate Low-Luminosity Protostars and Very Low Luminosity Objects
We present a systematic single-dish search for molecular outflows toward a
sample of 9 candidate low-luminosity protostars and 30 candidate Very Low
Luminosity Objects (VeLLOs; L_int < 0.1 L_sun). The sources are identified
using data from the Spitzer Space Telescope catalogued by Dunham et al. toward
nearby (D < 400 pc) star forming regions. Each object was observed in 12CO and
13CO J = 2-1 simultaneously using the sideband separating ALMA Band-6 prototype
receiver on the Heinrich Hertz Telescope at 30 arcsecond resolution. Using
5-point grid maps we identify five new potential outflow candidates and make
on-the-fly maps of the regions surrounding sources in the dense cores B59,
L1148, L1228, and L1165. Of these new outflow candidates, only the map of B59
shows a candidate blue outflow lobe associated with a source in our survey. We
also present larger and more sensitive maps of the previously detected L673-7
and the L1251-A IRS4 outflows and analyze their properties in comparison to
other outflows from VeLLOs. The accretion luminosities derived from the outflow
properties of the VeLLOs with detected CO outflows are higher than the observed
internal luminosity of the protostars, indicating that these sources likely had
higher accretion rates in the past. The known L1251-A IRS3 outflow is detected
but not remapped. We do not detect clear, unconfused signatures of red and blue
molecular wings toward the other 31 sources in the survey indicating that
large-scale, distinct outflows are rare toward this sample of candidate
protostars. Several potential outflows are confused with kinematic structure in
the surrounding core and cloud. Interferometric imaging is needed to
disentangle large-scale molecular cloud kinematics from these potentially weak
protostellar outflows.Comment: 42 pages, 19 figures, Accepted for publication in the Astronomical
Journa
The Ages of Galactic Bulge Stars with Realistic Uncertainties
Using modern isochrones with customized physics and carefully considered
statistical techniques, we recompute the age distribution for a sample of 91
micro-lensed dwarfs in the Galactic bulge presented by Bensby et al. (2017) and
do not produce an age distribution consistent with their results. In
particular, our analysis finds that only 15 of 91 stars have ages younger than
7 Gyr, compared to their finding of 42 young stars in the same sample. While we
do not find a constituency of very young stars, our results do suggest the
presence of an Gyr population at the highest metallicities, thus
contributing to long-standing debate about the age--metallicity distribution of
the Galactic bulge. We supplement this with attempts at independent age
determinations from two sources of photometry, BDBS and \textit{Gaia}, but find
that the imprecision of photometric measurements prevents reliable age and age
uncertainty determinations. Lastly, we present age uncertainties derived using
a first-order consideration of global modeling uncertainties in addition to
standard observational uncertainties. The theoretical uncertainties are based
on the known variance of free parameters in the 1D stellar evolution models
used to generate isochrones, and when included, result in age uncertainties of
-- Gyr for this spectroscopically well-constrained sample. These error
bars, which are roughly twice as large as typical literature values, constitute
realistic lower limits on the true age uncertainties.Comment: accepted to ApJ; revisions complet
Protostellar accretion traced with chemistry. High resolution C18O and continuum observations towards deeply embedded protostars in Perseus
Context: Understanding how accretion proceeds is a key question of star
formation, with important implications for both the physical and chemical
evolution of young stellar objects. In particular, very little is known about
the accretion variability in the earliest stages of star formation.
Aims: To characterise protostellar accretion histories towards individual
sources by utilising sublimation and freeze-out chemistry of CO.
Methods: A sample of 24 embedded protostars are observed with the
Submillimeter Array (SMA) in context of the large program "Mass Assembly of
Stellar Systems and their Evolution with the SMA" (MASSES). The size of the
CO emitting region, where CO has sublimated into the gas-phase, is
measured towards each source and compared to the expected size of the region
given the current luminosity. The SMA observations also include 1.3 mm
continuum data, which are used to investigate whether a link can be established
between accretion bursts and massive circumstellar disks.
Results: Depending on the adopted sublimation temperature of the CO ice,
between 20% and 50% of the sources in the sample show extended CO
emission indicating that the gas was warm enough in the past that CO sublimated
and is currently in the process of refreezing; something which we attribute to
a recent accretion burst. Given the fraction of sources with extended CO
emission, we estimate an average interval between bursts of 20000-50000 yr,
which is consistent with previous estimates. No clear link can be established
between the presence of circumstellar disks and accretion bursts, however the
three closest known binaries in the sample (projected separations <20 AU) all
show evidence of a past accretion burst, indicating that close binary
interactions may also play a role in inducing accretion variability.Comment: Accepted for publication in A&A, 21 pages, 13 figure
The Nakanai Mountain Ranges of East New Britain, Papua New Guinea
This E-Book on the Nakanai Mountains of East New Britain is in four parts. The first section provides an overview of the karst and cave attributes which led to the listing of Nakanai on the Tentative World Heritage List in a Serial Site known as The Sublime Karsts of Papua New Guinea. The next section provides a brief history of the region involving European encounters. This is followed with a brief overview of the archaeology of East New Britain. The fourth section highlights some of the unique flora and fauna of the Nakanai. The final section includes the UNESCO Justification for Significance on the Tentative World Heritage List
An ALMA Search for Substructure, Fragmentation, and Hidden Protostars in Starless Cores in Chamaeleon I
We present an Atacama Large Millimeter/submillimeter Array (ALMA) 106 GHz
(Band 3) continuum survey of the complete population of dense cores in the
Chamaeleon I molecular cloud. We detect a total of 24 continuum sources in 19
different target fields. All previously known Class 0 and Class I protostars in
Chamaeleon I are detected, whereas all of the 56 starless cores in our sample
are undetected. We show that the Spitzer+Herschel census of protostars in
Chamaeleon I is complete, with the rate at which protostellar cores have been
misclassified as starless cores calculated as <1/56, or < 2%. We use synthetic
observations to show that starless cores collapsing following the turbulent
fragmentation scenario are detectable by our ALMA observations when their
central densities exceed ~10^8 cm^-3, with the exact density dependent on the
viewing geometry. Bonnor-Ebert spheres, on the other hand, remain undetected to
central densities at least as high as 10^10 cm^-3. Our starless core
non-detections are used to infer that either the star formation rate is
declining in Chamaeleon I and most of the starless cores are not collapsing,
matching the findings of previous studies, or that the evolution of starless
cores are more accurately described by models that develop less substructure
than predicted by the turbulent fragmentation scenario, such as Bonnor-Ebert
spheres. We outline future work necessary to distinguish between these two
possibilities.Comment: Accepted by Ap
The Spitzer Survey of Interstellar Clouds in the Gould Belt. VI. The Auriga-California Molecular Cloud observed with IRAC and MIPS
We present observations of the Auriga-California Molecular Cloud (AMC) at
3.6, 4.5, 5.8, 8.0, 24, 70 and 160 micron observed with the IRAC and MIPS
detectors as part of the Spitzer Gould Belt Legacy Survey. The total mapped
areas are 2.5 sq-deg with IRAC and 10.47 sq-deg with MIPS. This giant molecular
cloud is one of two in the nearby Gould Belt of star-forming regions, the other
being the Orion A Molecular Cloud (OMC). We compare source counts, colors and
magnitudes in our observed region to a subset of the SWIRE data that was
processed through our pipeline. Using color-magnitude and color-color diagrams,
we find evidence for a substantial population of 166 young stellar objects
(YSOs) in the cloud, many of which were previously unknown. Most of this
population is concentrated around the LkHalpha 101 cluster and the filament
extending from it. We present a quantitative description of the degree of
clustering and discuss the fraction of YSOs in the region with disks relative
to an estimate of the diskless YSO population. Although the AMC is similar in
mass, size and distance to the OMC, it is forming about 15 - 20 times fewer
stars.Comment: (30 pages, 17 figures (2 multipage figures), accepted for publication
in ApJ
Preventing species extinctions: A global conservation consortium for Erica
Societal Impact Statement
Human-caused habitat destruction and transformation is resulting in a cascade of impacts to biological diversity, of which arguably the most fundamental is species extinctions. The Global Conservation Consortia (GCC) are a means to pool efforts and expertise across national boundaries and between disciplines in the attempt to prevent such losses in focal plant groups. GCC Erica coordinates an international response to extinction threats in one such group, the heaths, or heathers, of which hundreds of species are found only in South Africa's spectacularly diverse Cape Floristic Region.
Summary
Effectively combating the biodiversity crisis requires coordinated conservation efforts. Botanic Gardens Conservation International (BGCI) and numerous partners have established Global Conservation Consortia (GCC) to collaboratively develop and implement comprehensive conservation strategies for priority threatened plant groups. Through these networks, institutions with specialised collections and staff can leverage ongoing work to optimise impact for threatened plant species. The genus Erica poses a challenge similar in scale to that of the largest other GCC group, Rhododendron, but almost 700 of the around 800 known species of Erica are concentrated in a single biodiversity hotspot, the Cape Floristic Region (CFR) of South Africa. Many species are known to be threatened, suffering the immediate impacts of habitat destruction, invasive species, changes in natural fire regimes and climate change. Efforts to counter these threats face general challenges: disproportionate burden of in situ conservation falling on a minority of the community, limited knowledge of species-rich groups, shortfalls in assessing and monitoring threat, lack of resources for in situ and limitations of knowledge for ex situ conservation efforts and in communicating the value of biological diversity to a public who may never encounter it in the wild. GCC Erica brings together the world's Erica experts, conservationists and the botanical community, including botanic gardens, seed banks and organisations in Africa, Madagascar, Europe, the United States, Australia and beyond. We are collaboratively pooling our unique sets of skills and resources to address these challenges in working groups for conservation prioritisation, conservation in situ, horticulture, seed banking, systematic research and outreach.publishedVersio
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