68 research outputs found
Climate, landscape, habitat, and woodland management associations with hazel dormouse Muscardinus avellanarius population status
Although strictly protected, populations of the hazel dormouse Muscardinus avellanarius in the UK declined by 72% from 1993 to 2014. Using National Dormouse Monitoring Programme data from 300 sites throughout England and Wales, we investigated variation in hazel dormouse population status (expressed as Indices of Abundance, Breeding, and population Trend) in relation to climate, landscape, habitat, and woodland management. Dormice were more abundant and produced more litters on sites with warmer, sunnier springs, summers, and autumns. Dormouse abundance was also higher on sites with consistently cold local climate in winter. Habitat connectivity, woodland species composition, and active site management were all correlated with greater dormouse abundance and breeding. Abundances were also higher on sites with successional habitats, whereas the abundance of early successional bramble Rubus fruticosus habitat, woodland area, and landscape connectivity were important for population stability. Diversity in the structure of woodlands in Europe has decreased over the last 100 years, and the habitats we found to be associated with more favourable dormouse status have also been in decline. The conservation status of the hazel dormouse, and that of woodland birds and butterflies, may benefit from reinstatement or increased frequency of management practices, such as coppicing and glade management, that maintain successional and diverse habitats within woodland
Lensing-Induced Structure of Submillimeter Sources: Implications for the Microwave Background
We consider the effect of lensing by galaxy clusters on the angular
distribution of submillimeter wavelength objects. While lensing does not change
the total flux and number counts of submillimeter sources, it can affect the
number counts and fluxes of flux-limited samples. Therefore imposing a flux cut
on point sources not only reduces the overall Poisson noise, but imprints the
correlations between lensing clusters on the unresolved flux distribution.
Using a simple model, we quantify the lensing anisotropy induced in
flux-limited samples and compare this to Poisson noise. We find that while the
level of induced anisotropies on the scale of the cluster angular correlation
length is comparable to Poisson noise for a slowly evolving cluster model, it
is negligible for more realistic models of cluster evolution. Thus the removal
of point sources is not expected to induce measurable structure in the
microwave or far-infrared backgrounds.Comment: 22 pages, 9 figures, accepted to Astrophysical Journa
The Lifetime of FRIIs in Groups and Clusters: Implications for Radio-Mode Feedback
We determine the maximum lifetime t_max of 52 FRII radio sources found in 26
central group galaxies from cross correlation of the Berlind SDSS group catalog
with the VLA FIRST survey. Mock catalogs of FRII sources were produced to match
the selection criteria of FIRST and the redshift distribution of our parent
sample, while an analytical model was used to calculate source sizes and
luminosities. The maximum lifetime of FRII sources was then determined via a
comparison of the observed and model projected length distributions. We
estimate the average FRII lifetime is 1.5x10^7 years and the duty cycle is
~8x10^8 years. Degeneracies between t_max and the model parameters: jet power
distribution, axial ratio, energy injection index, and ambient density
introduce at most a factor of two uncertainty in our lifetime estimate. In
addition, we calculate the radio active galactic nuclei (AGN) fraction in
central group galaxies as a function of several group and host galaxy
properties. The lifetime of radio sources recorded here is consistent with the
quasar lifetime, even though these FRIIs have substantially sub-Eddington
accretion. These results suggest a fiducial time frame for energy injection
from AGN in feedback models. If the morphology of a given extended radio source
is set by large-scale environment, while the lifetime is determined by the
details of the accretion physics, this FRII lifetime is relevant for all
extended radio sources.Comment: 18 pages, 7 figures. Accepted for publication in ApJ. High resolution
paper available at http://www.astronomy.ohio-state.edu/~bird/BMK07.pd
Observational Limits on Type 1 AGN Accretion Rate in COSMOS
We present black hole masses and accretion rates for 182 Type 1 AGN in
COSMOS. We estimate masses using the scaling relations for the broad Hb, MgII,
and CIV emission lines in the redshift ranges 0.16<z<0.88, 1<z<2.4, and
2.7<z<4.9. We estimate the accretion rate using an Eddington ratio L_I/L_Edd
estimated from optical and X-ray data. We find that very few Type 1 AGN accrete
below L_I/L_Edd ~ 0.01, despite simulations of synthetic spectra which show
that the survey is sensitive to such Type 1 AGN. At lower accretion rates the
BLR may become obscured, diluted or nonexistent. We find evidence that Type 1
AGN at higher accretion rates have higher optical luminosities, as more of
their emission comes from the cool (optical) accretion disk with respect to
shorter wavelengths. We measure a larger range in accretion rate than previous
works, suggesting that COSMOS is more efficient at finding low accretion rate
Type 1 AGN. However the measured range in accretion rate is still comparable to
the intrinsic scatter from the scaling relations, suggesting that Type 1 AGN
accrete at a narrow range of Eddington ratio, with L_I/L_Edd ~ 0.1.Comment: Accepted for pulication in ApJ. 7 pages, 5 figures, table 1 available
on reques
Seasonal Consumptive Demand and Prey Use by Stocked Saugeyes in Ohio Reservoirs
Community structure and species composition may be strongly influenced by predator-prey interactions resulting from and leading to episodes of population abundance or scarcity. We quantified diets of stocked saugeyes (female walleye Sander vitreus × male sauger S. canadensis) and estimated biomass of their primary prey, gizzard shad Dorosoma cepedianum, in three Ohio reservoirs at quarterly intervals during July 2002-July 2003 to determine whether saugeye consumptive demand could exceed the supply of available gizzard shad prey, resulting in a shift to alternative prey. We incorporated water temperature and saugeye diet composition, growth, and mortality into walleye bioenergetics models, which allowed us to compare estimated prey-specific consumption rates by saugeyes with gizzard shad standing stocks estimated with acoustics. Spring and summer were critical seasons. During spring, gizzard shad biomass was low, saugeye consumptive demand was low, and saugeyes consumed primarily alternative prey. During summer, when age-0 gizzard shad became available as prey, saugeyes consumed similar proportions of gizzard shad and alternative prey. Saugeye cumulative consumptive demand in summer was high and approached the gizzard shad standing stock. However, during fall and winter, gizzard shad supply was adequate to support high (fall) or declining (winter) saugeye consumptive demand. Across reservoirs and seasons, saugeyes consumed alternative prey to varying degrees, primarily sunfishes Lepomis spp., yellow perch Perca flavescens, logperch Percina caprodes, and minnows Pimephales spp. Seasonal asynchrony between saugeye consumptive demand and gizzard shad biomass during spring and summer indicated that a saugeye population with high survival, growth, and consumptive demand will opportunistically increase use of prey other than gizzard shad. The manner in which saugeye predation quantitatively influences these prey species could not be assessed. However, overexploitation of gizzard shad prey appears to be unlikely at current saugeye population sizes, particularly considering the opportunistic use of alternative prey and the high reproductive potential of gizzard shad.Funding for this research was provided by the Ohio Department of Natural Resources, Division of Wildlife; Federal Aid in Sport Fish Restoration Project F-69-P, Fish Management in Ohio; and the Department of Evolution, Ecology, and Organismal Biology at The Ohio State University
The James Webb Space Telescope
The James Webb Space Telescope (JWST) is a large (6.6m), cold (50K),
infrared-optimized space observatory that will be launched early in the next
decade. The observatory will have four instruments: a near-infrared camera, a
near-infrared multi-object spectrograph, and a tunable filter imager will cover
the wavelength range, 0.6 to 5.0 microns, while the mid-infrared instrument
will do both imaging and spectroscopy from 5.0 to 29 microns. The JWST science
goals are divided into four themes. The End of the Dark Ages: First Light and
Reionization theme seeks to identify the first luminous sources to form and to
determine the ionization history of the early universe. The Assembly of
Galaxies theme seeks to determine how galaxies and the dark matter, gas, stars,
metals, morphological structures, and active nuclei within them evolved from
the epoch of reionization to the present day. The Birth of Stars and
Protoplanetary Systems theme seeks to unravel the birth and early evolution of
stars, from infall on to dust-enshrouded protostars to the genesis of planetary
systems. The Planetary Systems and the Origins of Life theme seeks to determine
the physical and chemical properties of planetary systems including our own,
and investigate the potential for the origins of life in those systems. To
enable these observations, JWST consists of a telescope, an instrument package,
a spacecraft and a sunshield. The telescope consists of 18 beryllium segments,
some of which are deployed. The segments will be brought into optical alignment
on-orbit through a process of periodic wavefront sensing and control. The JWST
operations plan is based on that used for previous space observatories, and the
majority of JWST observing time will be allocated to the international
astronomical community through annual peer-reviewed proposal opportunities.Comment: 96 pages, including 48 figures and 15 tables, accepted by Space
Science Review
Prospects for Indirect Detection of Neutralino Dark Matter
Dark matter candidates arising in models of particle physics incorporating
weak scale supersymmetry may produce detectable signals through their
annihilation into neutrinos, photons, or positrons. A large number of relevant
experiments are planned or underway. The `logically possible' parameter space
is unwieldy. By working in the framework of minimal supergravity, we can survey
the implications of the experiments for each other, as well as for direct
searches, collider searches, low-energy experiments, and naturalness in a
transparent fashion. We find that a wide variety of experiments provide
interesting probes. Particularly promising signals arise in the mixed
gaugino-Higgsino region. This region is favored by low-energy particle physics
constraints and arises naturally from minimal supergravity due to the focus
point mechanism. Indirect dark matter searches and traditional particle
searches are highly complementary. In cosmologically preferred models, if there
are charged superpartners with masses below 250 GeV, then some signature of
supersymmetry must appear before the LHC begins operation.Comment: 37 pages, 20 figures. Latest Super-Kamiokande result included,
expected sensitivities of HESS and CANGAROO updated, references added.
Version to appear in Phys. Rev.
Observations of Ly Emitters at High Redshift
In this series of lectures, I review our observational understanding of
high- Ly emitters (LAEs) and relevant scientific topics. Since the
discovery of LAEs in the late 1990s, more than ten (one) thousand(s) of LAEs
have been identified photometrically (spectroscopically) at to . These large samples of LAEs are useful to address two major astrophysical
issues, galaxy formation and cosmic reionization. Statistical studies have
revealed the general picture of LAEs' physical properties: young stellar
populations, remarkable luminosity function evolutions, compact morphologies,
highly ionized inter-stellar media (ISM) with low metal/dust contents, low
masses of dark-matter halos. Typical LAEs represent low-mass high- galaxies,
high- analogs of dwarf galaxies, some of which are thought to be candidates
of population III galaxies. These observational studies have also pinpointed
rare bright Ly sources extended over kpc, dubbed
Ly blobs, whose physical origins are under debate. LAEs are used as
probes of cosmic reionization history through the Ly damping wing
absorption given by the neutral hydrogen of the inter-galactic medium (IGM),
which complement the cosmic microwave background radiation and 21cm
observations. The low-mass and highly-ionized population of LAEs can be major
sources of cosmic reionization. The budget of ionizing photons for cosmic
reionization has been constrained, although there remain large observational
uncertainties in the parameters. Beyond galaxy formation and cosmic
reionization, several new usages of LAEs for science frontiers have been
suggested such as the distribution of {\sc Hi} gas in the circum-galactic
medium and filaments of large-scale structures. On-going programs and future
telescope projects, such as JWST, ELTs, and SKA, will push the horizons of the
science frontiers.Comment: Lecture notes for `Lyman-alpha as an Astrophysical and Cosmological
Tool', Saas-Fee Advanced Course 46. Verhamme, A., North, P., Cantalupo, S., &
Atek, H. (eds.) --- 147 pages, 103 figures. Abstract abridged. Link to the
lecture program including the video recording and ppt files :
https://obswww.unige.ch/Courses/saas-fee-2016/program.cg
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