2,757 research outputs found
Short time-scale optical variability of the dwarf Seyfert nucleus in NGC 4395
We present optical spectroscopic observations of the least-luminous known
Seyfert 1 galaxy, NGC 4395, which was monitored every half-hour over the course
of 3 nights. The continuum emission varied by ~35 per cent over the course of 3
nights, and we find marginal evidence for greater variability in the blue
continuum than the red. A number of diagnostic checks were performed on the
data in order to constrain any systematic or aperture effects. No correlations
were found that adequately explained the observed variability, hence we
conclude that we have observed real intrinsic variability of the nuclear
source. No simultaneous variability was measured in the broad H-beta line,
although given the difficulty in deblending the broad and narrow components it
is difficult to comment on the significance of this result. The observed short
time-scale continuum variability is consistent with NGC 4395 having an
intermediate-mass (~10^5 solar masses) central supermassive black hole, rather
than a very low accretion rate. Comparison with the Seyfert 1 galaxy NGC 5548
shows that the observed variability seems to scale with black hole mass in
roughly the manner expected in accretion models. However the absolute
time-scale of variability differs by several orders of magnitude from that
expected in simple accretion disc models in both cases.Comment: 16 pages, 14 figures, 5 tables, accepted for publication in MNRA
Investigations of Inhibition of Asphaltene Precipitation at High Pressure Using Bottomhole Samples
Searching for molecular outflows in Hyper-Luminous Infrared Galaxies
We present constraints on the molecular outflows in a sample of five
Hyper-Luminous Infrared Galaxies using Herschel observations of the OH doublet
at 119 {\mu}m. We have detected the OH doublet in three cases: one purely in
emission and two purely in absorption. The observed emission profile has a
significant blueshifted wing suggesting the possibility of tracing an outflow.
Out of the two absorption profiles, one seems to be consistent with the
systemic velocity while the other clearly indicates the presence of a molecular
outflow whose maximum velocity is about ~1500 km/s. Our analysis shows that
this system is in general agreement with previous results on Ultra-luminous
Infrared Galaxies and QSOs, whose outflow velocities do not seem to correlate
with stellar masses or starburst luminosities (star formation rates). Instead
the galaxy outflow likely arises from an embedded AGN.Comment: Accepted for publication in MNRAS. 13 pages, 11 figures, 4 table
Quantum gravity and Riemannian geometry on the fuzzy sphere
We study the quantum geometry of the fuzzy sphere defined as the angular
momentum algebra modulo setting
to a constant, using a recently introduced 3D rotationally
invariant differential structure. Metrics are given by symmetric
matrices and we show that for each metric there is a unique quantum
Levi-Civita connection with constant coefficients, with scalar curvature . As an
application, we construct Euclidean quantum gravity on the fuzzy unit sphere.
We also calculate the charge 1 monopole for the 3D differential structure.Comment: 15 pages latex, 1 figur
Geometric Dirac operator on noncommutative torus and
We solve for quantum-geometrically realised spectral triples or `Dirac
operators' on the noncommutative torus and on the algebra
of matrices with their standard quantum metrics and
associated quantum Levi-Civita connections. For , we obtain
an even standard spectral triple but now uniquely determined by full geometric
realisability. For , we are forced to the flat quantum Levi-Civita
connection and again obtain a natural fully geometrically realised even
spectral triple. In both case there is also an odd spectral triple for a
different choice of a sign parameter. We also consider an alternate quantum
metric on with curved quantum Levi-Civita connection and find a
natural 2-parameter of almost spectral triple in that fails to be
antihermitian. In all cases, we split the construction into a local tensorial
level related to the quantum geometry, where we classify the results more
broadly, and the further requirements relating to the Hilbert space structure.
We also illustrate the Lichnerowicz formula for which applies in the case
of a full geometric realisation.Comment: 33 pages latex no figures. Moved the less interesting second quantum
metric on M_2(C) into an appendix, corrected typos and added details of
Lichnerowicz theorem related D^2 and Laplacian. This is a sequel to
2104.13212 (math.QA
Asymmetric fiscal and monetary policies: a two country model of european integration
We use a 2-country model to analyze fiscal and monetary interactions in a Monetary union.Both countries are integrated and experience spillovers from their partners’ fiscal policies. Wesolve for Monetary Leadership - the Central Bank commits to an inflation target and the fiscalpolicymakers optimize spending - and for Fiscal Leadership - the Central Bank chooses its pre-ferred rate given exogenously defined fiscal policies. High inflation aversion and small outputgaps in one country can generate overspending in their integrated partners. Country weights determined by the Central Bank affect its policy making by overlooking smaller countries
An infrared study of the double nucleus in NGC3256
We present new resolved near and mid-IR imaging and N-band spectroscopy of
the two nuclei in the merger system NGCA3256, the most IR luminous galaxy in
the nearby universe. The results from the SED fit to the data are consistent
with previous estimates of the amount of obscuration towards the nuclei and the
nuclear star formation rates. However, we also find substantial differences in
the infrared emission from the two nuclei which cannot be explained by
obscuration alone. We conclude that the northern nucleus requires an additional
component of warm dust in order to explain its properties. This suggests that
local starforming conditions can vary significantly within the environment of a
single system.Comment: Accepted for publication (MNRAS
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