3,292 research outputs found
Addressing Indiaâs water challenge 2050: the virtual water trade option
The Government of India, on directions from the Supreme Court in 2002 and advice from the National Water Development Agency (NWDA), proposed an estimated US$120 billion National River Linking Project (NRLP) which envisages linking 37 Himalayan and Peninsular rivers (Figure 1; NCIWRD 1999). Doing this will form a gigantic South Asian water grid which will annually handle 178Ă109 m3/yr of interbasin water transfer; build 12,500 km of canals; generate 34 gigawatts of hydropower; add 35 million hectares (Mha) to Indiaâs irrigated areas; and generate inland navigation benefits (IWMI 2003; NWDA 2006; Gupta and van der Zaag 2007)
PKS 1004+13: A High-Inclination, Highly-Absorbed Radio-Loud QSO -- The First Radio-Loud BAL QSO at Low Redshift?
The existence of BAL outflows in only radio-quiet QSOs was thought to be an
important clue to mass ejection and the radio-loud - radio-quiet dichotomy.
Recently a few radio-loud BAL QSOs have been discovered at high redshift. We
present evidence that PKS 1004+13 is a radio-loud BAL QSO. It would be the
first known at low-redshift (z = 0.24), and one of the most radio luminous. For
PKS 1004+13, there appear to be broad absorption troughs of O VI, N V, Si IV,
and C IV, indicating high-ionization outflows up to about 10,000 km/s. There
are also two strong, broad (~500 km/s), high-ionization, associated absorption
systems that show partial covering of the continuum source. The strong UV
absorption we have detected suggests that the extreme soft-X-ray weakness of
PKS 1004+13 is primarily the result of absorption. The large radio-lobe
dominance indicates BAL and associated gas at high inclinations to the central
engine axis, perhaps in a line-of-sight that passes through an accretion disk
wind.Comment: To appear in Ap.J. Letters, 1999 (June or July); 4 pages, 5 figure
Constraints on Omega_m and sigma_8 from weak lensing in RCS fields
We have analysed 53 square degrees of imaging data from the Red-Sequence
Cluster Survey (RCS), and measured the excess correlations in the shapes of
galaxies on scales out to ~1.5 degrees. We separate the signal into an ``E''-
(lensing) and ``B''-mode (systematics), which allows us to study residual
systematics. On scales larger than 10 arcminutes, we find no ``B''-mode. On
smaller scales we find a small, but significant ``B''-mode. This signal is also
present when we select a sample of bright galaxies. These galaxies are rather
insensitive to observational distortions, and we therefore conclude that the
oberved ``B''-mode is likely to be caused by intrinsic alignments. We therefore
limit the cosmic shear analysis to galaxies with 22<R_C<24. We derive joint
constraints on Omega_m and sigma_8, by marginalizing over Gamma, Omega_Lambda
and the source redshift distribution, using different priors. We obtain a
conservative constraint of
(95% confidence). A better constraint is derived when we use Gaussian priors
redshift distribution. For this choice of priors, we find
(95% confidence). Using our
setof Gaussian priors, we find that we can place a lower bound on Gamma:
Gamma>0.1+0.16\Omega_m$ (95% confidence). Comparison of the RCS results with
three other recent cosmic shear measurements shows excellent agreement. The
current weak lensing results are also in good agreement with CMB measurements,
when we allow the reionization optical depth tau and the spectral index n_s to
vary. We present a simple demonstration of how the weak lensing results can be
used as a prior in the parameter estimation from CMB measurements to derive
constraints on the reionization optical depth tau. (abridged)Comment: 9 pages, 6 figures, Accepted for publication in the Astrophysical
Journa
Finding halo streams with a pencil-beam survey: new wraps in the Sagittarius stream
We use data from two CFHT-MegaCam photometric pencil-beam surveys in the g'
and the r' bands to measure distances to the Sagittarius, the Palomar 5 and the
Orphan stream. We show that, using a cross-correlation algorithm to detect the
turnoff point of the main sequence, it is possible to overcome the main
limitation of a two-bands pencil-beam survey, namely the lack of adjacent
control-fields that can be used to subtract the foreground and background stars
to enhance the signal on the colour-magnitude diagrams (CMDs). We describe the
cross-correlation algorithm and its implementation. We combine the resulting
main sequence turnoff points with theoretical isochrones to derive photometric
distances to the streams. Our results (31 detections on the Sagittarius stream
and one each for the Palomar 5 and the Orphan streams) confirm the findings by
previous studies, expand the distance trend for the Sagittarius faint southern
branch and, for the first time, trace the Sagittarius faint branch of the
northern-leading arm out to 56 kpc. In addition, they show evidence for new
substructure: we argue that these detections trace the continuation of the
Sagittarius northern-leading arm into the southern hemisphere, and find a
nearby branch of the Sagittarius trailing wrap in the northern hemisphere.Comment: 16 pages, 15 figures, 2 table
A skewer survey of the Galactic halo from deep CFHT and INT images
We study the density profile and shape of the Galactic halo using deep
multicolour images from the MENeaCS and CCCP projects, over 33 fields selected
to avoid overlap with the Galactic plane. Using multicolour selection and PSF
homogenization techniques we obtain catalogues of F stars (near-main sequence
turnoff stars) out to Galactocentric distances up to 60kpc. Grouping nearby
lines of sight, we construct the stellar density profiles through the halo in
eight different directions by means of photometric parallaxes. Smooth halo
models are then fitted to these profiles. We find clear evidence for a
steepening of the density profile power law index around R=20 kpc, from -2.50
+- 0.04 to -4.85 +- 0.04, and for a flattening of the halo towards the poles
with best-fit axis ratio 0.63 +- 0.02. Furthermore, we cannot rule out a mild
triaxiality (w>=0.8). We recover the signatures of well-known substructure and
streams that intersect our lines of sight. These results are consistent with
those derived from wider but shallower surveys, and augur well for upcoming,
wide-field surveys of comparable depth to our pencil beam surveys.Comment: 14 pages, 8 figures, 6 table
Multiwavelength Mass Comparisons of the z~0.3 CNOC Cluster Sample
Results are presented from a detailed analysis of optical and X-ray
observations of moderate-redshift galaxy clusters from the Canadian Network for
Observational Cosmology (CNOC) subsample of the EMSS. The combination of
extensive optical and deep X-ray observations of these clusters make them ideal
candidates for multiwavelength mass comparison studies. X-ray surface
brightness profiles of 14 clusters with 0.17<z<0.55 are constructed from
Chandra observations and fit to single and double beta-models. Spatially
resolved temperature analysis is performed, indicating that five of the
clusters in this sample exhibit temperature gradients within their inner 60-200
kpc. Integrated spectra extracted within R_2500 provide temperature, abundance,
and luminosity information. Under assumptions of hydrostatic equilibrium and
spherical symmetry, we derive gas and total masses within R_2500 and R_200. We
find an average gas mass fraction within R_200 of 0.136 +/- 0.004, resulting in
Omega_m=0.28 +/- 0.01 (formal error). We also derive dynamical masses for these
clusters to R_200. We find no systematic bias between X-ray and dynamical
methods across the sample, with an average M(dyn)/M(X-ray) = 0.97 +/- 0.05. We
also compare X-ray masses to weak lensing mass estimates of a subset of our
sample, resulting in a weighted average of M(lens)/M(X-ray) of 0.99 +/- 0.07.
We investigate X-ray scaling relationships and find powerlaw slopes which are
slightly steeper than the predictions of self-similar models, with an E(z)^(-1)
Lx-Tx slope of 2.4 +/- 0.2 and an E(z) M_2500-Tx slope of 1.7 +/- 0.1.
Relationships between red-sequence optical richness (B_gc,red) and global
cluster X-ray properties (Tx, Lx and M_2500) are also examined and fitted.Comment: Astrophysical Journal, 48 pages, 11 figures, LaTeX. Added correction
to surface brightness normalization of MS1512.4+3647, corrections to sample
gas mass fractions and calculated value of Omega_m. Figure resolution has
been reduced to comply with astro-ph upload requirement
Factors determining household market participation in small ruminant production in the highlands of Ethiopia
Small ruminants, which account for more than half of the domesticated ruminants in the world, are an important component of the farming systems in most developing countries. Despite their economic and social importance, socioeconomic and marketing research on small ruminants has so far been limited, a fact which also holds strongly true in Ethiopia. This study, based on survey data of 5004 Ethiopian smallholder households, uses analysis of descriptive information and econometric analysis to draw implications to promote market orientation. Econometric results are based on estimation of bivariate, ordinal, and multinomial probit models. We find that herd size, herd structure, access to livestock market, and involvement in the institutional services of extension and credit stand out as the most important factors affecting market participation behaviour of households. Our results imply that an effective package of interventions to promote market-oriented small ruminant production will need to include development of livestock market infrastructure and market institutions, improved access to extension and credit use, efficient animal reproduction and management, and proper animal health care
The dependence of intrinsic alignment of galaxies on wavelength using KiDS and GAMA
The outer regions of galaxies are more susceptible to the tidal interactions
that lead to intrinsic alignments of galaxies. The resulting alignment signal
may therefore depend on the passband if the colours of galaxies vary spatially.
To quantify this, we measured the shapes of galaxies with spectroscopic
redshifts from the GAMA survey using deep gri imaging data from the KiloDegree
Survey. The performance of the moment-based shape measurement algorithm DEIMOS
was assessed using dedicated image simulations, which showed that the
ellipticities could be determined with an accuracy better than 1% in all bands.
Additional tests for potential systematic errors did not reveal any issues. We
measure a significant difference of the alignment signal between the g,r and
i-band observations. This difference exceeds the amplitude of the linear
alignment model on scales below 2 Mpc/h. Separating the sample into
central/satellite and red/blue galaxies, we find that that the difference is
dominated by red satellite galaxies.Comment: 16 pages, 13 figures, accepted, to appear in A&
A Multiwavelength Analysis of the Strong Lensing Cluster RCS 022434-0002.5 at z=0.778
We present the results of two (101 ks total) Chandra observations of the
z=0.778 optically selected lensing cluster RCS022434-0002.5, along with weak
lensing and dynamical analyses of this object. An X-ray spectrum extracted
within R(2500) (362 h(70)^(-1) kpc) results in an integrated cluster
temperature of 5.1 (+0.9,-0.5) keV. The surface brightness profile of
RCS022434-0002.5 indicates the presence of a slight excess of emission in the
core. A hardness ratio image of this object reveals that this central emission
is primarily produced by soft X-rays. Further investigation yields a cluster
cooling time of 3.3 times 10^9 years, which is less than half of the age of the
universe at this redshift given the current LCDM cosmology. A weak lensing
analysis is performed using HST images, and our weak lensing mass estimate is
found to be in good agreement with the X-ray determined mass of the cluster.
Spectroscopic analysis reveals that RCS022434-0002.5 has a velocity dispersion
of 900 +/- 180 km/s, consistent with its X-ray temperature. The core gas mass
fraction of RCS022434-0002.5 is, however, found to be three times lower than
expected universal values. The radial distribution of X-ray point sources
within R(200) of this cluster peaks at ~0.7 R(200), possibly indicating that
the cluster potential is influencing AGN activity at that radius. Correlations
between X-ray and radio (VLA) point source positions are also examined.Comment: 32 pages, 9 figures. Accepted for publication in The Astrophysical
Journa
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