240 research outputs found
CuPc Adsorption on Au(110)-(1 × 2): From a Monomer to a Periodic Chain
Using scanning tunneling microscopy (STM), we study the adsorption of copper-phthalocyanine (CuPc) on the anisotropic Au(110)-(1 × 2) surface as a function of coverage. For the initial adsorption at room temperature, we observe CuPc monomers as well as a molecular chain that forms along the step edge. By STM manipulation, we reveal that the CuPc adsorption is accompanied by surface reconstruction from the initial adsorption stage; the periodicity beneath the monomer and the chain changes locally from (1 × 2) to (1 × 1) and (1 × 3), respectively. This finding highlights that the Au atom mobility of the surface plays an essential role in CuPc adsorption. At higher coverage, we observe the development of CuPc chains along the [110] direction on the terrace with periodicities of (7 × 5) and (5 × 5), and compare the obtained results with those from the previous studies by diffraction methods
A new design of nanocrystalline silicon optical devices based on 3-dimensional photonic crystal structures
We propose a new design of nanocrystalline silicon optical devices which are based on control of electromagnetic fields, electronic states, as well as the phonon dispersion of size-controlled silicon quantum dots
First Detection of Near-Infrared Intraday Variations in the Seyfert 1 Nucleus NGC4395
We carried out a one-night optical V and near-infrared JHK monitoring
observation of the least luminous Seyfert 1 galaxy, NGC4395, on 2004 May 1, and
detected for the first time the intraday flux variations in the J and H bands,
while such variation was not clearly seen for the K band. The detected J and H
variations are synchronized with the flux variation in the V band, which
indicates that the intraday-variable component of near-infrared continuum
emission of the NGC4395 nucleus is an extension of power-law continuum emission
to the near-infrared and originates in an outer region of the central accretion
disk. On the other hand, from our regular program of long-term optical BVI and
near-infrared JHK monitoring observation of NGC4395 from 2004 February 12 until
2005 January 22, we found large flux variations in all the bands on time scales
of days to months. The optical BVI variations are almost synchronized with each
other, but not completely with the near-infrared JHK variations. The color
temperature of the near-infrared variable component is estimated to be
T=1320-1710 K, in agreement with thermal emission from hot dust tori in active
galactic nuclei (AGNs). We therefore conclude that the near-infrared variation
consists of two components having different time scales, so that a small K-flux
variation on a time scale of a few hours would possibly be veiled by large
variation of thermal dust emission on a time scale of days.Comment: 4 pages including figures, accepted for publication in ApJ
Dust emission from a parsec-scale structure in the Seyfert 1 nucleus of NGC 4151
We report mid-IR interferometric measurements with \sim 10 mas resolution,
which resolve the warm (T = 285 +25 / -50 K) thermal emission at the center of
NGC 4151. Using pairs of VLT 8.2 m telescopes with MIDI and by comparing the
data to a Gaussian model, we determined the diameter of the dust emission
region, albeit only along one position angle, to be 2.0 +/- 0.4 pc (FWHM). This
is the first size and temperature estimate for the nuclear warm dust
distribution in a Seyfert 1 galaxy. The parameters found are comparable to
those in Seyfert 2 galaxies, thus providing direct support for the unified
model. Using simple analytic temperature distributions, we find that the
mid-infrared emission is probably not the smooth continuation of the hot
nuclear source that is marginally resolved with K band interferometry. We also
detected weak excess emission around 10.5 micron in our shorter baseline
observation, possibly indicating that silicate emission is extended to the
parsec scale.Comment: 5 pages, 4 figures, accepted for publication in The Astrophysical
Journal Letter
Reverberation Measurements of the Inner Radius of the Dust Torus in Nearby Seyfert 1 Galaxies
The most intense monitoring observations yet made in the optical (UBV) and
near-infrared (JHK) wave bands were carried out for nearby Seyfert1 galaxies of
NGC 5548, NGC 4051, NGC 3227, and NGC 7469. Over three years of observations
with MAGNUM telescope since early 2001, clear time-delayed response of the
K-band flux variations to the V-band flux variations was detected for all of
these galaxies. Their H-K color temperature was estimated to be 1500-1800 K
from the observed flux variation gradients, which supports a view that the bulk
of the K flux should originate in the thermal radiation of hot dust that
surrounds the central engine. Cross-correlation analysis was performed to
quantify the lag time corresponding to the light-travel distance of the hot
dust region from the central engine. The measured lag time is 47-53 days for
NGC 5548, 11-18 days for NGC 4051, about 20 days for NGC 3227, and 65-87 days
for NGC 7469. We found that the lag time is tightly correlated with the optical
luminosity as expected from dust reverberation (),
while only weakly with the central virial mass, which suggests that an inner
radius of the dust torus around the active nucleus has a one-to-one
correspondence to central luminosity. In the lag time versus central luminosity
diagram, the K-band lag times place an upper boundary on the similar lag times
of broad-emission lines in the literature. This not only supports the unified
scheme of AGNs, but also implies a physical transition from the BLR out to the
dust torus that encircles the BLR. Furthermore, our V-band flux variations of
NGC 5548 on timescales of up to 10 days are found to correlate with X-ray
variations and delay behind them by one or two days, indicating the thermal
reprocessing of X-ray emission by the central accretion flow.Comment: ApJ, March 2006, v639 issue, 24 pages, 33 figures, 10 table
Development of Syowa-Iceland ULF spectrogram database and some applications to Pc1 pearl analysis
第3回極域科学シンポジウム/第36回極域宙空圏シンポジウム 11月26日(月)、27日(火) 国立極地研究所 2階ラウン
Multiple Regression Analysis of the Variable Component in the Near-Infrared Region for Type 1 AGN MCG+08-11-011
We propose a new method of analysing a variable component for type 1 active
galactic nuclei (AGNs) in the near-infrared wavelength region. This analysis
uses a multiple regression technique and divides the variable component into
two components originating in the accretion disk at the center of AGNs and from
the dust torus that far surrounds the disk. Applying this analysis to the
long-term monitoring data of MCG+08-11-011 that were obtained by the
MAGNUM project, we found that the -color temperature of the dust
component is K K, which agrees with the sublimation
temperature of dust grains, and that the time delay of to variations is
days, which indicates the existence of a radial temperature
gradient in the dust torus. As for the disk component, we found that the
power-law spectrum of in the to near-infrared
bands varies with a fixed index of -- +0.4, which is
broadly consistent with the irradiated standard disk model. The outer part of
the disk therefore extends out to a radial distance where the temperature
decreases to radiate the light in the near-infrared.Comment: 10pages + 5figures, accepted by ApJ
A dust-parallax distance of 19 megaparsecs to the supermassive black hole in NGC 4151
The active galaxy NGC 4151 has a crucial role as one of only two active
galactic nuclei for which black hole mass measurements based on emission line
reverberation mapping can be calibrated against other dynamical methods.
Unfortunately, effective calibration requires an accurate distance to NGC 4151,
which is currently not available. Recently reported distances range from 4 to
29 megaparsecs (Mpc). Strong peculiar motions make a redshift-based distance
very uncertain, and the geometry of the galaxy and its nucleus prohibit
accurate measurements using other techniques. Here we report a dust-parallax
distance to NGC 4151 of Mpc. The measurement is
based on an adaptation of a geometric method proposed previously using the
emission line regions of active galaxies. Since this region is too small for
current imaging capabilities, we use instead the ratio of the
physical-to-angular sizes of the more extended hot dust emission as determined
from time-delays and infrared interferometry. This new distance leads to an
approximately 1.4-fold increase in the dynamical black hole mass, implying a
corresponding correction to emission line reverberation masses of black holes
if they are calibrated against the two objects with additional dynamical
masses.Comment: Authors' version of a letter published in Nature (27 November 2014);
8 pages, 5 figures, 1 tabl
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