557 research outputs found
Galaxy Evolution from Emission Linewidths
The major thrust of the Tully-Fisher (TF) surveys of distant galaxies is the
measurement of linewidths rather than mere redshifts or colors. Linewidths are
a measure of galaxy mass and should therefore be a more stable indicator of
size than galaxy brightness, which can be badly affected by luminosity
evolution. Masses may provide the best way to relate galaxies at different
epochs, but for such a program to work, we must control systematic effects that
could bias linewidth measurements at high redshift and skew comparisons with
local Tully-Fisher calibrations. Potential sources of confusion in TF studies
of galaxy structure and evolution include central or extended star bursts,
infalling gas, turbulence and outflows, dust extinction, calibration of
emission linewidths, and improper application of local TF calibrations to high
redshift galaxies.Comment: 7 pages, 3 figures; Proceedings contribution in The Mass of Galaxies
at Low and High Redshift, eds. R. Bender and A. Renzini (ESO Astrophysics
Symposia
PAGaN I: Multi-Frequency Polarimetry of AGN Jets with KVN
Active Galactic Nuclei (AGN) with bright radio jets offer the opportunity to
study the structure of and physical conditions in relativistic outflows. For
such studies, multi-frequency polarimetric very long baseline interferometric
(VLBI) observations are important as they directly probe particle densities,
magnetic field geometries, and several other parameters. We present results
from first-epoch data obtained by the Korean VLBI Network (KVN) within the
frame of the Plasma Physics of Active Galactic Nuclei (PAGaN) project. We
observed seven radio-bright nearby AGN at frequencies of 22, 43, 86, and 129
GHz in dual polarization mode. Our observations constrain apparent brightness
temperatures of jet components and radio cores in our sample to K
and K, respectively. Degrees of linear polarization are
relatively low overall: less than 10%. This indicates suppression of
polarization by strong turbulence in the jets. We found an exceptionally high
degree of polarization in a jet component of BL Lac at 43 GHz, with 40%. Assuming a transverse shock front propagating downstream along the
jet, the shock front being almost parallel to the line of sight can explain the
high degree of polarization.Comment: 14 pages, 17 figures, 4 tables. To appear in JKAS (received 2015 July
27; accepted 2015 October 25). Note the PAGaN II companion paper by J. Oh et
a
PAGaN II: The Evolution of AGN Jets on Sub-Parsec Scales
We report first results from KVN and VERA Array (KaVA) VLBI observations
obtained in the frame of our Plasma-physics of Active Galactic Nuclei (PAGaN)
project. We observed eight selected AGN at 22 and 43 GHz in single polarization
(LCP) between March 2014 and April 2015. Each source was observed for 6 to 8
hours per observing run to maximize the coverage. We obtained a total of
15 deep high-resolution images permitting the identification of individual
circular Gaussian jet components and three spectral index maps of BL Lac, 3C
111 and 3C 345 from simultaneous dual-frequency observations. The spectral
index maps show trends in agreement with general expectations -- flat core and
steep jets -- while the actual value of the spectral index for jets shows
indications for a dependence on AGN type. We analyzed the kinematics of jet
components of BL Lac and 3C 111, detecting superluminal proper motions with
maximum apparent speeds of about . This constrains the lower limits of the
intrinsic component velocities to and the upper limits of the angle
between jet and line of sight to 20. In agreement with global jet
expansion, jet components show systematically larger diameters at larger
core distances , following the global relation , albeit within
substantial scatter.Comment: 13 pages, 15 figures, 4 tables. To appear in JKAS (received 2015
August 31; accepted 2015 October 15). Note the PAGaN I companion paper by
J.-Y. Kim et a
A Case of Autoimmune Pancreatitis Manifested by a Pseudocyst and IgG4-Associated Cholangitis
Autoimmune pancreatitis (AIP) is a benign disorder and a unique form of chronic pancreatitis with several characteristic features. A cystic formation that mimics a pseudocyst is a rare finding. There have been a few reports of AIP complicated by pancreatic cysts. We present a case of AIP with multiple pseudocysts and obstructive jaundice caused by IgG4-associated cholangitis. We initially missed the diagnosis due to the pseudocyst. Based on the computed tomography images, laboratory findings and the therapeutic response to steroids, the case was diagnosed as AIP with pseudocysts and associated cholangiopathy
Have different kinds of photon-pair sources the same indistinguishability in quantum silicon photonics?
In the same silicon photonic integrated circuit, we compare two types of
integrated degenerate photon-pair sources (microring resonators or waveguides)
by means of Hong-Ou-Mandel (HOM) interference experiments. Two nominally
identical microring resonators are coupled to two nominally identical
waveguides which form the arms of a Mach-Zehnder interferometer. This is pumped
by two lasers at two different wavelengths to generate by spontaneous four-wave
mixing degenerate photon pairs. In particular, the microring resonators can be
thermally tuned in or out of resonance with the pump wavelengths, thus choosing
either the microring resonators or the waveguides as photon-pair sources,
respectively. In this way, an on-chip HOM visibility of 94% with microring
resonators and 99% with straight waveguides is measured. We compare our
experimental results with theoretical simulations of the joint spectral
intensity and the purity of the degenerate photon pairs. We verify that the
visibility is connected to the sources' indistinguishability, which can be
quantified by the overlap between the joint spectral amplitudes (JSA) of the
photon pairs generated by the two sources. We estimate a JSA overlap of 98%
with waveguides and 89% with microring resonators
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