1,201 research outputs found
A model for the infrared dust emission from forming galaxies
In the early epoch of galaxy evolution, dust is only supplied by supernovae
(SNe). With the aid of a new physical model of dust production by SNe developed
by Nozawa et al. (2003) (N03), we constructed a model of dust emission from
forming galaxies on the basis of the theoretical framework of Takeuchi et al.
(2003) (T03). N03 showed that the produced dust species depends strongly on the
mixing within SNe. We treated both unmixed and mixed cases and calculated the
infrared (IR) spectral energy distribution (SED) of forming galaxies for both
cases. Our model SED is less luminous than the SED of T03 model by a factor of
2-3. The difference is due to our improved treatment of UV photon absorption
cross section, as well as different grain size and species newly adopted in
this work. The SED for the unmixed case is found to have an enhanced near to
mid-IR (N-MIR) continuum radiation in its early phase of the evolution (age <
10^{7.25} yr) compared with that for the mixed case. The strong N--MIR
continuum is due to the emission from Si grains, which only exist in the
species of the unmixed dust production. We also calculated the IR extinction
curves for forming galaxies. Then we calculated the SED of a local starbursting
dwarf galaxy SBS 0335-052. Our present model SED naturally reproduced the
strong N--MIR continuum and the lack of cold FIR emission of SBS 0335-052. We
found that only the SED of unmixed case can reproduce the NIR continuum of this
galaxy. We then made a prediction for the SED of another typical star-forming
dwarf, I Zw 18. We also presented the evolution of the SED of LBGs. Finally, we
discussed the possibility of observing forming galaxies at z > 5.Comment: MNRAS, in press. 18 pages, 15 figures. Abstract abridge
The clinical significance of the arterial ketone body ratio as an early indicator of graft viabilityin human liver transplantation
Arterial ketone body ratio (AKBR) was measured sequentially in 84 liver transplantations (OLTx). These transplantation procedures were classified into 3 groups with respect to graft survival and patient condition at the end of the first month (Group A, the grafts survived longer than 1 month with satisfactory patient condition; Group B, the grafts survived longer than 1 month but the patients were ICU-bound; Group C, the grafts were lost and the patients died or underwent re-OLTx). In Group A, the AKBR was elevated to above 1.0 by the second postoperative day. In Group B, the AKBR was elevated to above 0.7 but stayed below 1.0 during this period. In Group C, the AKBR remained below 0.7 longer than 2 days after operation. Although conventional liver function tests showed significant increases in Groups B and C as compared with Group A, they were less specific in predicting ultimate graft survival. © 1991 by Williams & Wilkins
Detection of Excess Hard X-ray Emission from the Group of Galaxies HCG62
From the group of galaxies HCG62, we detected an excess hard X-ray emission
in energies above keV with \A SCA. The excess emission is spatially
extended up to from the group center, and somewhat enhanced toward
north. Its spectrum can be represented by either a power-law of photon index
0.8-2.7, or a Bremsstrahlung of temperature keV. In the 2-10 keV range,
the observed hard X-ray flux, erg cm
s, implies a luminosity of erg s for a
Hubble constant of 50 km s Mpc. The emission is thus too luminous
to be attributed to X-ray binaries in the memb er galaxies. We discuss possible
origin of the hard X-ray emission.Comment: 6 pages, 3 Postscript figures, uses emulateapj.sty. Accepted for
publication in the Astrophysical Journal Letter
Extinction curves flattened by reverse shocks in supernovae
We investigate the extinction curves of young galaxies in which dust is
supplied from Type II supernovae (SNe II) and/or pair instability supernovae
(PISNe). Since at high redshift (z>5), low-mass stars cannot be dominant
sources for dust grains, SNe II and PISNe, whose progenitors are massive stars
with short lifetimes, should govern the dust production. Here, we theoretically
investigate the extinction curves of dust produced by SNe II and PISNe, taking
into account reverse shock destruction induced by collision with ambient
interstellar medium. We find that the extinction curve is sensitive to the
ambient gas density around a SN, since the efficiency of reverse shock
destruction strongly depends on it. The destruction is particularly efficient
for small-sized grains, leading to a flat extinction curve in the optical and
ultraviolet wavelengths. Such a large ambient density as n_H > 1 cm^{-3}
produces too flat an extinction curve to be consistent with the observed
extinction curve for SDSS J104845.05+463718.3 at z=6.2. Although the extinction
curve is highly sensitive to the ambient density, the hypothesis that the dust
is predominantly formed by SNe at z~6 is still allowed by the current
observational constraints. For further quantification, the ambient density
should be obtained by some other methods. Finally we also discuss the
importance of our results for observations of high-z galaxies, stressing a
possibility of flat extinction curves.Comment: 8 pages, 5 figures, Accepted for publication in MNRA
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