2,918 research outputs found
Spectral Models for Low-luminosity Active Galactic Nuclei in LINERs: The Role of Advection-dominated Accretion and Jets
We perform an exploratory study of the physical properties of accretion flows
and jets in low-luminosity active galactic nuclei (LLAGNs) by modeling the
spectral energy distributions (SEDs) of 12 LLAGNs in low-ionization nuclear
emission-line regions (LINERs). These SEDs we constructed from high-resolution
radio, X-ray and optical/UV observations of the immediate vicinity of the black
hole. We adopt a coupled accretion-jet model comprising an inner
advection-dominated accretion flow (ADAF) and an outer standard thin disk. We
present best-fit models in which either the ADAF or the jet dominate the X-ray
emission. Six sources in our sample display an optical-UV excess with respect
to ADAF and jet models; this excess can be explained as emission from the
truncated disk with transition radii 30-225 Rs in four of them. In almost all
sources the optical emission can also be attributed to unresolved, old stellar
clusters with masses ~1E7-1E8 Msun. We find evidence for a correlation between
the accretion rate and jet power and an anti-correlation between the
radio-loudness and the accretion rate. We confirm previous findings that the
radio emission is severely underpredicted by ADAF models and explained by the
relativistic jet. We find evidence for a nonlinear relation between the X-ray
and bolometric luminosities and a slight IR excess in the average model SED
compared to that of quasars. We suggest that the hardness of the X-ray spectrum
can be used to identify the X-ray emission mechanism and discuss directions for
progress in understanding the origin of the X-rays.Comment: Accepted for publication in MNRAS. 27 pages, 22 figures. arXiv admin
note: substantial text overlap with arXiv:1112.464
2D stellar population and gas kinematics of the inner 1.5 kpc of the post-starburst quasar SDSS J0210-0903
Post-Starburst Quasars (PSQs) are hypothesized to represent a stage in the
evolution of massive galaxies in which the star formation has been recently
quenched due to the feedback of the nuclear activity. In this paper our goal is
to test this scenario with a resolved stellar population study of the PSQ
J0210-0903, as well as of its emitting gas kinematics and excitation. We have
used optical Integral Field Spectroscopy obtained with the Gemini GMOS
instrument at a velocity resolution of ~120 km/s and spatial resolution of ~0.5
kpc. We find that old stars dominate the luminosity (at 4700 \AA) in the inner
0.3 kpc (radius), while beyond this region (at ~0.8 kpc) the stellar population
is dominated by both intermediate age and young ionizing stars. The gas
emission-line ratios are typical of Seyfert nuclei in the inner 0.3 kpc, where
an outflow is observed. Beyond this region the line ratios are typical of
LINERs and may result from the combination of diluted radiation from the
nucleus and ionization from young stars. The gas kinematics show a combination
of rotation in the plane of the galaxy and outflows, observed with a maximum
blueshift of -670 km/s. We have estimated a mass outflow rate in ionized gas in
the range 0.3--1.1 M_sun/yr and a kinetic power for the outflow of dE/dt ~
1.4--5.0 x 10^40 erg/s ~0.03% - 0.1% x L_bol. This outflow rate is two orders
of magnitude higher than the nuclear accretion rate of ~8.7 x 10^-3 M_sun/yr,
thus being the result of mass loading of the nuclear outflow by circumnuclear
galactic gas. Our observations support an evolutionary scenario in which the
feeding of gas to the nuclear region has triggered a circumnuclear starburst
100's Myr ago, followed by the triggering of the nuclear activity, producing
the observed gas outflow which may have quenched further star formation in the
inner 0.3 kpc.Comment: 17 pages, 9 Figures, 2 Table
2D stellar population and gas kinematics of the inner kiloparsec of the post-starburst quasar SDSS J0330-0532
We have used optical Integral Field Spectroscopy in order to map the star
formation history of the inner kiloparsec of the Post-Starburst Quasar (PSQ)
J0330--0532 and to map its gas and stellar kinematics as well as the gas
excitation. PSQs are hypothesized to represent a stage in the evolution of
galaxies in which the star formation has been recently quenched due to the
feedback of the nuclear activity, as suggested by the presence of the
post-starburst population at the nucleus. We have found that the old stellar
population (age 2.5 Gyr) dominates the flux at 5100 \AA\ in the inner
0.26 kpc, while both the post-starburst (100 Myr age 2.5 Gyr) and
starburst (age 100 Myr) components dominate the flux in a circumnuclear
ring at 0.5 kpc from the nucleus. With our spatially resolved study we
do not have found any post-starburst stellar population in the inner 0.26\,kpc.
On the other hand, we do see the signature of AGN feedback in this region,
which does not reach the circumnuclear ring where the post-starburst population
is observed. We thus do not support the quenching scenario for the J0330-0532.
In addition, we have concluded that the strong signature of the post-starburst
population in larger aperture spectra (e.g. from Sloan Digital Sky Survey) is
partially due to the combination of the young and old age components. Based on
the M relationship and the stellar kinematics we
have estimated a mass for the supermassive black hole of 1.48 0.66
10 M.Comment: 16 pages, 11 figures. arXiv admin note: text overlap with
arXiv:1210.120
Integrated Data as backbone of e-Navigation
e-Navigation, a theme introduced but IMO to improve safety of navigation at sea, is starting to gain traction in various organizations. As the concept develops, the importance of data, both static as well as dynamic, is more and more realized. IALA and IHO, in their efforts to help making e-Navigation a reality, have agreed to propose the IHO GI Register (often known as S-100 Register) as the conceptual basis for the Common Maritime Data Structure (CMDS). Utilizing this common understanding of key players in e-Navigation arena, the IMO e-Navigation Correspondence Group has firmed up the overarching architecture, enabling a series to test beds proving the concept of integration of various data streams to enable improved communication between the stakeholders on shore or at sea.
 The integration of pre-composed, expert generated navigational data with real time and semi real-time data like Virtual AtoNs, Tide Gages Data or MSI transmission from VTS into a single e-Navigation display, if correctly developed, implemented and executed, will be the enabler of increased situational awareness
Modest Molinism: An Explanation and Defense
Molinism, which says that God has middle knowledge, offers one of the most impressive and popular ways of combining libertarian creaturely freedom with full providential control by God. The aim of this paper is to explain, motivate, and defend a heretofore overlooked version of Molinism that I call ‘Modest Molinism’. In Section 1, I explain Modest Molinism and make an initial case for it. Then, in Sections 2 and 3, I defend Modest Molinism against Dean Zimmerman’s anti-Molinist argument, which is directed at all versions of Molinism, including Modest Molinism. Zimmerman’s anti-Molinist argument combines two distinct and separable challenges to Molinism that I call the ‘Irrelevance Objection’ and the ‘Extreme Manipulation Objection’. Despite the fact that Zimmerman intertwines these two objections, they require separate treatment. Thus, Section 2 will raise concerns about Zimmerman’s Irrelevance Objection and Section 3 will focus on concerns about Zimmerman’s Extreme Manipulation Objection
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