911 research outputs found
Reconstruction of the extinct Ezo wolf's diet
On Hokkaido, Japan, the Ezo wolf (Canis lupus hattai), an apex predator, became extinct at the end of the 19th century owing to human activities. Top predators often have an important role in their ecosystems, yet we have no scientific information on the feeding habits of the Ezo wolf. We performed carbon and nitrogen stable isotope analysis and radiocarbon dating of specimens of the wolf (n = 7) and its prey species and estimated the components of the wolves' diet using an isotope mixing model. Radiocarbon dating suggested that most of the wolves examined came from different populations or generations. The mean stable isotope ratios of the wolves were −19.5 ‰ (± 1.9 ‰ SD) for δ13C and 8.7 ‰ (± 2.6 ‰ SD) for δ15N. The discrimination-corrected isotopic ratios of five of the seven wolves were almost the same as those of Sika deer at the same sites. In contrast, those of two wolves had clearly higher isotopic values than those of deer, suggesting that these wolves depended partly on marine prey such as salmon and marine mammals. Thus, Ezo wolves had similar ecological roles to Canadian grey wolves, and were a second subspecies shown to have fed on a marine diet, in addition to the "coastal wolves" of British Columbia
Discontinuous Transition from a Real Bound State to Virtual Bound State in a Mixed-Valence State of SmS
Golden SmS is a paramagnetic, mixed-valence system with a pseudogap. With
increasing pressure across a critical pressure Pc, the system undergoes a
discontinuous transition into a metallic, anti-ferromagnetically ordered state.
By using a combination of thermodynamic, transport, and magnetic measurements,
we show that the pseudogap results from the formation of a local bound state
with spin singlet. We further argue that the transition Pc is regarded as a
transition from an insulating electron-hole gas to a Kondo metal, i.e., from a
spatially bound state to a Kondo virtually bound state between 4f and
conduction electrons.Comment: 5 pages, 5 figure
Ionization Source of a Minor-axis Cloud in the Outer Halo of M82
The M82 `cap' is a gas cloud at a projected radius of 11.6 kpc along the
minor axis of this well known superwind source. The cap has been detected in
optical line emission and X-ray emission and therefore provides an important
probe of the wind energetics. In order to investigate the ionization source of
the cap, we observed it with the Kyoto3DII Fabry-Perot instrument mounted on
the Subaru Telescope. Deep continuum, Ha, [NII]6583/Ha, and [SII]6716,6731/Ha
maps were obtained with sub-arcsecond resolution. The superior spatial
resolution compared to earlier studies reveals a number of bright Ha emitting
clouds within the cap. The emission line widths (< 100 km s^-1 FWHM) and line
ratios in the newly identified knots are most reasonably explained by slow to
moderate shocks velocities (v_shock = 40--80 km s^-1) driven by a fast wind
into dense clouds. The momentum input from the M82 nuclear starburst region is
enough to produce the observed shock. Consequently, earlier claims of
photoionization by the central starburst are ruled out because they cannot
explain the observed fluxes of the densest knots unless the UV escape fraction
is very high (f_esc > 60%), i.e., an order of magnitude higher than observed in
dwarf galaxies to date. Using these results, we discuss the evolutionary
history of the M82 superwind. Future UV/X-ray surveys are expected to confirm
that the temperature of the gas is consistent with our moderate shock model.Comment: 7 pages, 5 figures, 2 tables; Accepted for publication in Ap
Post-starburst Tidal Tails in the Archetypical Ultra Luminous Infrared Galaxy Arp 220
We present our new deep optical imaging and long-slit spectroscopy for Arp
220 that is the archetypical ULIRG in the local universe. Our sensitive Ha
imaging has newly revealed large-scale, Ha absorption, i.e., post-starburst
regions in this merger; one is found in the eastern superbubble and the other
is in the two tidal tails that are clearly reveled in our deep optical imaging.
The size of Ha absorption region in the eastern bubble is 5 kpc x 7.5 kpc and
the observed Ha equivalent widths are ~2 A +- 0.2 A. The sizes of the northern
and southern Ha-absorption tidal tails are ~5 kpc x 10 kpc and ~6 kpc x 20 kpc,
respectively. The observed Ha equivalent widths range from 4 A to 7 A. In order
to explain the presence of the two post-starburst tails, we suggest a possible
multiple-merger scenario for Arp 220 in which two post-starburst disk-like
structures merged into one, and then caused the two tails. This favors that Arp
220 is a multiple merging system composed of four or more galaxies, arising
from a compact group of galaxies. Taking our new results into account, we
discuss a star formation history in the last 1 Gyr in Arp 220.Comment: 6 pages, 7 figures, Accepted for publication in the Astrophysical
Journa
Measuring the spin of the primary black hole in OJ287
The compact binary system in OJ287 is modelled to contain a spinning primary
black hole with an accretion disk and a non-spinning secondary black hole.
Using Post Newtonian (PN) accurate equations that include 2.5PN accurate
non-spinning contributions, the leading order general relativistic and
classical spin-orbit terms, the orbit of the binary black hole in OJ287 is
calculated and as expected it depends on the spin of the primary black hole.
Using the orbital solution, the specific times when the orbit of the secondary
crosses the accretion disk of the primary are evaluated such that the record of
observed outbursts from 1913 up to 2007 is reproduced. The timings of the
outbursts are quite sensitive to the spin value. In order to reproduce all the
known outbursts, including a newly discovered one in 1957, the Kerr parameter
of the primary has to be . The quadrupole-moment contributions
to the equations of motion allow us to constrain the `no-hair' parameter to be
where 0.3 is the one sigma error. This supports the `black hole
no-hair theorem' within the achievable precision.
It should be possible to test the present estimate in 2015 when the next
outburst is due. The timing of the 2015 outburst is a strong function of the
spin: if the spin is 0.36 of the maximal value allowed in general relativity,
the outburst begins in early November 2015, while the same event starts in the
end of January 2016 if the spin is 0.2Comment: 12 pages, 6 figure
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