168 research outputs found
A Tale of Three Galaxies: Anomalous Dust Properties in IRASF10398+1455, IRASF21013-0739 and SDSSJ0808+3948
On a galactic scale the 9.7um silicate emission is usually only seen in type
1 active galactic nuclei (AGNs). They usually also display a flat emission
continuum at ~5--8um and the absence of polycyclic aromatic hydrocarbon (PAH)
emission bands. In contrast, starburst galaxies, luminous infrared (IR)
galaxies (LIRGs), and ultraluminous IR galaxies (ULIRGs) exhibit a red 5--8um
emission continuum, strong 10um and 18um silicate absorption features, and
strong PAH emission bands. Here we report the detection of anomalous dust
properties by Spitzer/Infrared Spectrograph in three galaxies (IRASF10398+1455,
IRASF21013-0739 and SDSSJ0808+3948) which are characterized by the simultaneous
detection of a red 5--8um emission continuum, the 9.7 and 18um silicate
emission features as well as strong PAH emission bands. These apparently
contradictory dust IR emission properties are discussed in terms of iron-poor
silicate composition, carbon dust deficit, small grain size and low dust
temperature in the young AGN phase of these three galaxies.Comment: accepted for publication in ApJ
A Tale of Three Galaxies: Deciphering the Infrared Emission of the Spectroscopically Anomalous Galaxies IRAS F10398+1455, IRAS F21013-0739 and SDSS J0808+3948
The \textit{Spitzer}/Infrared Spectrograph spectra of three spectroscopically
anomalous galaxies (IRAS~F10398+1455, IRAS~F21013-0739 and SDSS~J0808+3948) are
modeled in terms of a mixture of warm and cold silicate dust, and warm and cold
carbon dust. Their unique infrared (IR) emission spectra are characterized by a
steep \simali5--8\mum emission continuum, strong emission bands from
polycyclic aromatic hydrocarbon (PAH) molecules, and prominent silicate
emission. The steep \simali5--8\mum emission continuum and strong PAH
emission features suggest the dominance of starbursts, while the silicate
emission is indicative of significant heating from active galactic nuclei
(AGNs). With warm and cold silicate dust of various compositions ("astronomical
silicate," amorphous olivine, or amorphous pyroxene) combined with warm and
cold carbon dust (amorphous carbon, or graphite), we are able to closely
reproduce the observed IR emission of these %spectroscopically anomalous
galaxies. We find that the dust temperature is the primary cause in regulating
the steep 5--8\mum continuum and silicate emission, insensitive to the
exact silicate or carbon dust mineralogy and grain size as long as
a\simlt1\mum. More specifically, the temperature of the \simali5--8\mum
continuum emitter (which is essentially carbon dust) of these galaxies is
250--400\K, much lower than that of typical quasars which is
640\K. Moreover, it appears that larger dust grains are preferred in
quasars. The lower dust temperature and smaller grain sizes inferred for these
three galaxies compared with that of quasars could be due to the fact that they
may harbor a young/weak AGN which is not maturely developed yet.Comment: 31 pages, 14 figures, accepted for publication in Ap
Enhancing extraordinary transmission of light through a metallic nano slit with a nano cavity antenna
The extraordinary transmission of light through a nano slit in a metal film
is enhanced by introducing a nano cavity antenna formed by a nearby metallic
nano-strip over the slit opening. For a fixed wavelength, the width of the
metallic nano-strip should be chosen to make the horizontal
metal-insulator-metal waveguide of finite length resonant as a Fabry-Perot
cavity. When such a cavity antenna is used to enhance the transmission through
a non-resonant nano slit, the slit should be opened at a position with maximal
magnetic field in the horizontal resonant cavity. It is shown that an optimized
cavity antenna can enhance greatly the transmission of light through a
non-resonant nano slit (by about 20 times) or a resonant nano slit (by 124%).
The transmission spectrum of the nano slit can also be tuned by adjusting the
width of the metallic nano-strip. Such a transmission enhancement with a nano
cavity antenna is studied for the first time and the physical mechanism is
explained.Comment: 4 pages, 5 figure
Josephson current transport through a Quantum Dot in an Aharonov-Bohm Ring
The Josephson current through an Aharonov-Bohm (AB) interferometer, in which
a quantum dot (QD) is situated on one arm and a magnetic flux threads
through the ring, has been investigated. With the existence of the magnetic
flux, the relation of the Josephson current and the superconductor phase is
complex, and the system can be adjusted to junction by either modulating
the magnetic flux or the QD's energy level . Due to the
electron-hole symmetry, the Josephson current has the property
. The Josephson current
exhibits a jump when a pair of Andreev bound states aligns with the Fermi
energy. The condition for the current jump is given. In particularly, we find
that the position of the current jump and the position of the maximum value of
the critical current are identical. Due to the interference between the
two paths, the critical current versus the QD's level
shows a typical Fano shape, which is similar to the Fano effect in the
corresponding normal device. But they also show some differences. For example,
the critical current never reaches zero for any parameters, while the current
in the normal device can reach zero at the destruction point.Comment: 7 pages, 5 figure
Interregional and intersectoral interaction of digital economy in China
With the continuous advancement of the integration of the world’s digital economy, the economic development of various regions has become increasingly interdependent. However, the interregional interactions of digital industries have yet to be further elucidated. Here, based on the Multi-Regional Input-Output model, we take China, for example, and analyze the impact of digital industries on the economy from the industrial and regional. At the industry level, we discuss the economic spillover relationship between the digital industry and the three traditional industries, and analyzes the spatial and temporal differentiation in the inter-industry spillover status of China’s 30 provinces; at the regional level, we discuss the digital industrial economic spillover links and spillover states. The results show that: 1) The self-generating ability within the digital industry sector is the most significant factor influencing the industrial growth of China’s digital economy, followed by the interrelated effect between industry sectors, while the inter-industry feedback effect has a weak impact on the economic system. 2) There is a clear gap in the economic spillover capacity of the digital industry in 30 provinces, and the overall performance is decreasing in the eastern, central and western regions. 3) The intra-regional multiplier effect of digital industry shows a slowly decreasing trend, and the intra-regional digital economic spillover-feedback effect shows a growing trend. At the same time, the inter-regional digital economy interaction tends to decay in distance, indicating that regional accessibility has a significant impact on the inter-regional spillover effect
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