869 research outputs found
Multi-phase Nature of a Radiation-Driven Fountain with Nuclear Starburst in a Low-mass Active Galactic Nucleus
The structures and dynamics of molecular, atomic, and ionized gases are
studied around a low-luminosity active galactic nucleus (AGN) with a small
() black hole using 3D radiation hydrodynamic
simulations. We studied, for the first time, the non-equilibrium chemistry for
the X-ray dominated region in the "radiation-driven fountain" (Wada 2012) with
supernova feedback. A double hollow cone structure is naturally formed without
postulating a thick "torus" around a central source. The cone is occupied with
an inhomogeneous, diffuse ionized gas and surrounded by a geometrically thick
() atomic gas. Dense molecular gases are distributed near the
equatorial plane, and energy feedback from supernovae enhances their scale
height. Molecular hydrogen exists in a hot phase ( > 1000 K) as well as in a
cold ( cm) phase. The velocity dispersion of
H in the vertical direction is comparable to the rotational velocity, which
is consistent with near infrared observations of nearby Seyfert galaxies. Using
3D radiation transfer calculations for the dust emission, we find polar
emission in the mid-infrared band (12), which is associated with bipolar
outflows, as suggested in recent interferometric observations of nearby AGNs.
If the viewing angle for the nucleus is larger than 75 deg, the spectral energy
distribution (~ 2 -- 60 ) of this model is consistent with that of the
Circinus galaxy. The multi-phase interstellar medium observed in
optical/infrared and X-ray observations is also discussed.Comment: 9 pages, 5 figures. Accepted for ApJL. A movie file for Fig.5b can be
downloaded from http://astrophysics.jp/Circinus
Songlines from Direct Collapse Seed Black Holes: Effects of X-rays on Black Hole Growth and Stellar Populations
In the last decade, the growth of supermassive black holes (SMBHs) has been
intricately linked to galaxy formation and evolution and is a key ingredient in
the assembly of galaxies. To investigate the origin of SMBHs, we perform
cosmological simulations that target the direct collapse black hole (DCBH) seed
formation scenario in the presence of two different strong Lyman-Werner (LW)
background fields. These simulations include the X-ray irradiation from a
central massive black hole (MBH), self-shielding and stellar
feedback from metal-free and metal-enriched stars. We find in both simulations
that local X-ray feedback induces metal-free star formation Myr
after the MBH forms. The MBH accretion rate reaches a maximum of
yr in both simulations. However, the duty cycle differs
which is derived to be and for high and low LW cases,
respectively. The MBH in the high LW case grows only in 100 Myr
compared to in the low LW case. We find that the maximum accretion rate
is determined by the local gas thermodynamics whereas the duty cycle is
determined by the large scale gas dynamics and gas reservoir. We conclude that
radiative feedback from the central MBH plays an important role in star
formation in the nuclear regions and stifling initial MBH growth, relative to
the typical Eddington rate argument, and that initial MBH growth might be
affected by the local LW radiation field.Comment: 8 pages, 6 figures. Accepted for publication in ApJ, with minor
changes to submitted versio
Tracing the Physical Conditions in Active Galactic Nuclei with Time-Dependent Chemistry
We present an extension of the code ProDiMo that allows for a modeling of
processes pertinent to active galactic nuclei and to an ambient chemistry that
is time dependent. We present a proof-of-concept and focus on a few
astrophysically relevant species, e.g., H+, H2+ and H3+; C+ and N+; C and O; CO
and H2O; OH+, H2O+ and H3O+; HCN and HCO+. We find that the freeze-out of water
is strongly suppressed and that this affects the bulk of the oxygen and carbon
chemistry occurring in AGN. The commonly used AGN tracer HCN/HCO+ is strongly
time-dependent, with ratios that vary over orders of magnitude for times longer
than 10^4 years. Through ALMA observations this ratio can be used to probe how
the narrow-line region evolves under large fluctuations in the SMBH accretion
rate. Strong evolutionary trends, on time scales of 10^4-10^8 years, are also
found in species such as H3O+, CO, and H2O. These reflect, respectively, time
dependent effects in the ionization balance, the transient nature of the
production of molecular gas, and the freeze-out/sublimation of water.Comment: Accepted for publication at the Journal of Physical Chemistry A "Oka
Festschrift: Celebrating 45 Years of Astrochemistry
On the Detection of High Redshift Black Holes with ALMA through CO and H2 Emission
Many present-day galaxies are known to harbor supermassive, >10^6 Mo, black
holes. These central black holes must have grown through accretion from less
massive seeds in the early universe. The molecules CO and H2 can be used to
trace this young population of accreting massive black holes through the X-ray
irradiation of ambient gas. The X-rays drive a low-metallicity ion-molecule
chemistry that leads to the formation and excitation of CO and H2 in
100<T<1,000 K gas. H2 traces very low metallicity gas, ~10^-3 solar or less,
while some pollution by metals, ~10^-2 solar or more, must have taken place to
form CO. Strong CO J>15 and H2 S(0) & S(1) emission is found that allows one to
constrain ambient conditions. Comparable line strengths cannot be produced by
FUV or cosmic ray irradiation. Weak, but perhaps detectable, H3+ (2,2) - (1,1)
emission is found and discussed. The models predict that black hole masses
larger than 10^5 Mo can be detected with ALMA, over a redshift range of 5-20,
provided that the black holes radiate close to Eddington.Comment: 12 pages, 3 figures, ApJL accepted; minor typographical change
Implementasi Metode Backpropagation Untuk Memprediksi Pemakaian Obat Di Puskesmas Oesapa
The medicine management incommunity health clinic is one of important aspect, because the health community clinic will have negative impact in costs if there is inefficiency in managing the medicine, the most used medicine will be out of stock before the re-order due date. In artificial neural network backpropagation method is classified as algorithm learning or traning tend to supervised and using rules of quality correction. Backpropagation is using error output to change the value of qualities in two ways, in backward and forward propagation. In this research, writer applying backpropagation method to predicting the medicine USAge in oesapa community health clinic. The data was taken from USAge report and medicine order receipt in 2014-2016. Where at 2014-2015 was data training and 2016 was data test. Which is the result of data training has ±99% accuracy and the data test has 70,66% accuracy
Mapping the e-Learning Assessment Domain: Concept Maps for Orientation and Navigation
Concept or Topic Maps have long been used as a method of categorizing and organizing information about a domain. Building them can help people conceptualize an area and spot trends or gaps, and as a presentation method they quickly provide an overview and general impression of a space. We are currently constructing a Reference Model of the Assessment Domain that takes the form of a highly interlinked dynamic website. This represents the assessment domain via the software, projects, standards and use cases of which it is composed. In this paper we present our efforts to create complimentary concept maps of the assessment domain, not as an overview, but for navigation and orientation within the domain. These concept maps, which model resources and activities independently, have been corroborated with practitioners in the e-learning community
A New Raytracer for Modeling AU-Scale Imaging of Lines from Protoplanetary Disks
The material that formed the present-day solar system originated in feeding zones in the inner solar nebula located at distances within ~20 AU from the Sun, known as the planet-forming zone. Meteoritic and cometary material contain abundant evidence for the presence of a rich and active chemistry in the planet-forming zone during the gas-rich phase of solar system formation. It is a natural conjecture that analogs can be found among the zoo of protoplanetary disks around nearby young stars. The study of the chemistry and dynamics of planet formation requires: (1) tracers of dense gas at 100-1000 K and (2) imaging capabilities of such tracers with 5-100 mas (0.5-20 AU) resolution, corresponding to the planet-forming zone at the distance of the closest star-forming regions. Recognizing that the rich infrared (2-200 μm) molecular spectrum recently discovered to be common in protoplanetary disks represents such a tracer, we present a new general ray-tracing code, RADLite, that is optimized for producing infrared line spectra and images from axisymmetric structures. RADLite can consistently deal with a wide range of velocity gradients, such as those typical for the inner regions of protoplanetary disks. The code is intended as a back-end for chemical and excitation codes, and can rapidly produce spectra of thousands of lines for grids of models for comparison with observations. Such radiative transfer tools will be crucial for constraining both the structure and chemistry of planet-forming regions, including data from current infrared imaging spectrometers and extending to the Atacama Large Millimeter Array and the next generation of Extremely Large Telescopes, the James Webb Space Telescope and beyond
A Spitzer survey of mid-infrared molecular emission from protoplanetary disks I: Detection rates
We present a Spitzer InfraRed Spectrometer search for 10-36 micron molecular
emission from a large sample of protoplanetary disks, including lines from H2O,
OH, C2H2, HCN and CO2. This paper describes the sample and data processing and
derives the detection rate of mid-infrared molecular emission as a function of
stellar mass. The sample covers a range of spectral type from early M to A, and
is supplemented by archival spectra of disks around A and B stars. It is drawn
from a variety of nearby star forming regions, including Ophiuchus, Lupus and
Chamaeleon. In total, we identify 22 T Tauri stars with strong mid-infrared H2O
emission. Integrated water line luminosities, where water vapor is detected,
range from 5x10^-4 to 9x10^-3 Lsun, likely making water the dominant line
coolant of inner disk surfaces in classical T Tauri stars. None of the 5
transitional disks in the sample show detectable gaseous molecular emission
with Spitzer upper limits at the 1% level in terms of line-to-continuum ratios
(apart from H2). We find a strong dependence on detection rate with spectral
type; no disks around our sample of 25 A and B stars were found to exhibit
water emission, down to 1-2% line-to-continuum ratios, in the mid-infrared,
while almost 2/3 of the disks around K stars show sufficiently intense water
emission to be detected by Spitzer. Some Herbig Ae/Be stars show tentative
H2O/OH emission features beyond 20 micron at the 1-2 level, however, and one of
them shows CO2 in emission. We argue that the observed differences between T
Tauri disks and Herbig Ae/Be disks is due to a difference in excitation and/or
chemistry depending on spectral type and suggest that photochemistry may be
playing an important role in the observable characteristics of mid-infrared
molecular line emission from protoplanetary disks.Comment: 19 pages, accepted for publication in Ap
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