17,547 research outputs found
The WISE AGN Catalog
We present two large catalogs of AGN candidates identified across ~75% of the
sky from the Wide-field Infrared Survey Explorer's AllWISE Data Release. Both
catalogs, some of the largest such catalogs published to date, are selected
purely on the basis of mid-IR photometry in the WISE W1 and W2 bands. The
catalogs are designed to be appropriate for a broad range of scientific
investigations, with one catalog emphasizing reliability while the other
emphasizes completeness. Specifically, the R90 catalog consists of 4,543,530
AGN candidates with 90% reliability, while the C75 catalog consists of
20,907,127 AGN candidates with 75% completeness. We provide a detailed
discussion of potential artifacts, and excise portions of the sky close to the
Galactic Center, Galactic Plane, nearby galaxies, and other expected
contaminating sources. Our final catalogs cover 30,093 deg^2 of extragalactic
sky. These catalogs are expected to enable a broad range of science, and we
present a few simple illustrative cases. From the R90 sample we identify 45
highly variable AGN lacking radio counterparts in the FIRST survey, implying
they are unlikely to be blazars. One of these sources, WISEA
J142846.71+172353.1, is a mid-IR-identified changing-look quasar at z=0.104. We
characterize our catalogs by comparing them to large, wide-area AGN catalogs in
the literature, specifically UV-to-near-IR quasar selections from SDSS and
XDQSOz, mid-IR selection from Secrest et al. (2015) and X-ray selection from
ROSAT. From the latter work, we identify four ROSAT X-ray sources that each are
matched to three WISE-selected AGN in the R90 sample within 30". Palomar
spectroscopy reveals one of these systems, 2RXS J150158.6+691029, to consist of
a triplet of quasars at z=1.133 +/- 0.004, suggestive of a rich group or
forming galaxy cluster.(Abridged)Comment: Accepted for publication in the Astrophysical Journal Supplements.
Updated with comments from the referee. 20 pages, 15 figures, 8 tables. The
WISE AGN Catalogs can be made available upon request by writing to
[email protected]
The role of the resonance in the reaction
We investigate the photo-production in the reaction within the effective Lagrangian method near
threshold. In addition to the "background" contributions from the contact,
channel exchange, and channel nucleon pole terms, which were
already considered in previous works, the contribution from the nucleon
resonance (spin-parity ) is also considered. We show
that the inclusion of the nucleon resonance leads to a fairly good
description of the new LEPS differential cross section data, and that these
measurements can be used to determine some of the properties of this latter
resonance. However, serious discrepancies appear when the predictions of the
model are compared to the photon-beam asymmetry also measured by the LEPS
Collaboration.Comment: 9 pages,6 figures, 1 tabl
Thermodynamic of the Ghost Dark Energy Universe
Recently, the vacuum energy of the QCD ghost in a time-dependent background
is proposed as a kind of dark energy candidate to explain the acceleration of
the Universe. In this model, the energy density of the dark energy is
proportional to the Hubble parameter , which is the Hawking temperature on
the Hubble horizon of the Friedmann-Robertson-Walker (FRW) Universe. In this
paper, we generalized this model and choice the Hawking temperature on the
so-called trapping horizon, which will coincides with the Hubble temperature in
the context of flat FRW Universe dominated by the dark energy component. We
study the thermodynamics of Universe with this kind of dark energy and find
that the entropy-area relation is modified, namely, there is an another new
term besides the area term.Comment: 8 pages, no figure
Non-linear Spectroscopy of Sr Atoms in an Optical Cavity for Laser Stabilization
We study the non-linear interaction of a cold sample of strontium-88 atoms
coupled to a single mode of a low finesse optical cavity in the so-called bad
cavity limit and investigate the implications for applications to laser
stabilization. The atoms are probed on the weak inter-combination line \lvert
5s^{2} \, ^1 \textrm{S}_0 \rangle \,-\, \lvert 5s5p \, ^3 \textrm{P}_1 \rangle
at 689 nm in a strongly saturated regime. Our measured observables include the
atomic induced phase shift and absorption of the light field transmitted
through the cavity represented by the complex cavity transmission coefficient.
We demonstrate high signal-to-noise-ratio measurements of both quadratures -
the cavity transmitted phase and absorption - by employing FM spectroscopy
(NICE-OHMS). We also show that when FM spectroscopy is employed in connection
with a cavity locked to the probe light, observables are substantially modified
compared to the free space situation where no cavity is present. Furthermore,
the non-linear dynamics of the phase dispersion slope is experimentally
investigated and the optimal conditions for laser stabilization are
established. Our experimental results are compared to state-of-the-art cavity
QED theoretical calculations.Comment: 7 pages, 4 figure
Arbitrary Dimensional Schwarzschild-FRW Black Holes
The metric of arbitrary dimensional Schwarzschild black hole in the
background of Friedman-Robertson-Walker universe is presented in the cosmic
coordinates system. In particular, the arbitrary dimensional Schwarzschild-de
Sitter metric is rewritten in the Schwarzschild coordinates system and basing
on which the even more generalized higher dimensional Schwarzschild-de Sitter
metric with another extra dimensions is found. The generalized solution shows
that the cosmological constant may roots in the extra dimensions of space.Comment: 10 page
Assessing the regional impact of Indonesian biomass burning emissions based on organic molecular tracers and chemical mass balance modeling
Biomass burning activities commonly occur in Southeast Asia (SEA), and are particularly intense in Indonesia during the dry seasons. The effect of biomass smoke emissions on air quality in the city state of Singapore was investigated during a haze episode in October 2006. Substantially increased levels of airborne particulate matter (PM) and associated chemical species were observed during the haze period. Specifically, the enhancement in the concentration of molecular tracers for biomass combustion such as levoglucosan by as much as two orders of magnitude and the diagnostic ratios of individual organic compounds indicated that biomass burning emissions caused a regional smoke haze episode due to their long-range transport by prevailing winds. With the aid of air mass backward trajectories and chemical mass balance modeling, large-scale forest and peat fires in Sumatra and Kalimantan were identified as the sources of the smoke aerosol, exerting a significant impact on air quality in downwind areas, such as Singapore
Dependence of Spiral Galaxy Distribution on Viewing Angle in RC3
The normalized inclination distributions are presented for the spiral
galaxies in RC3. The results show that, except for the bin of
-, in which the apparent minor isophotal diameters that
are used to obtain the inclinations, are affected by the central bulges, the
distributions for Sa, Sab, Scd and Sd are well consistent with the Monte-Carlo
simulation of random inclinations within 3-, and Sb and Sbc almost, but
Sc is different. One reason for the difference between the real distribution
and the Monte-Carlo simulation of Sc may be that some quite inclined spirals,
the arms of which are inherently loosely wound on the galactic plane and should
be classified to Sc galaxies, have been incorrectly classified to the earlier
ones, because the tightness of spiral arms which is one of the criteria of the
Hubble classification in RC3 is different between on the galactic plane and on
the tangent plane of the celestial sphere. Our result also implies that there
might exist biases in the luminosity functions of individual Hubble types if
spiral galaxies are only classified visually.Comment: 5 pages + 8 figures, LaTe
Canonical Charmonium Interpretation for Y(4360) and Y(4660)
In this work, we consider the canonical charmonium assignments for Y(4360)
and Y(4660). Y(4660) is good candidate of state, the
possibility of Y(4360) as a state is studied, and the
charmonium hybrid interpretation of Y(4360) can not be excluded completely. We
evaluate the leptonic widths, E1 transitions, M1 transitions and
the open flavor strong decays of Y(4360) and Y(4660). Experimental tests for
the charmonium assignments are suggested.Comment: 32 pages, 4 figure
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