88 research outputs found
Numerical modeling of thermal dust polarization from aligned grains in the envelope of evolved stars with updated POLARIS
Magnetic fields are thought to influence the formation and evolution of
evolved star envelopes. Thermal dust polarization from magnetically aligned
grains is potentially a powerful tool for probing magnetic fields and dust
properties in these circumstellar environments. In this paper, we present
numerical modeling of thermal dust polarization from the envelope of IK Tau
using the magnetically enhanced radiative torque (MRAT) alignment theory
implemented in our updated POLARIS code. Due to the strong stellar radiation
field, the minimum size required for RAT alignment of silicate grains is . Additionally, ordinary paramagnetic grains can achieve
perfect alignment by MRAT in the inner regions of due to
stronger magnetic fields of mG - 1G, producing thermal dust
polarization degree of . The polarization degree can be enhanced
to for grains with embedded iron inclusions. We also find that
the magnetic field geometry affects the alignment size and the resulting
polarization degree due to the projection effect in the plane-of-sky. We also
study the spectrum of polarized thermal dust emission and find the increased
polarization degree toward due to the alignment of
small grains by MRAT. Furthermore, we investigate the impact of rotational
disruption by RATs (RAT-D) and find the RAT-D effect cause a decrease in the
dust polarization fraction. Finally, we compare our numerical results with
available polarization data observed by SOFIA/HAWC+ for constraining dust
properties, suggesting grains are unlikely to have embedded iron clusters and
might have slightly elongated shapes. Our modeling results suggest further
observational studies at far-infrared/sub-millimeter wavelengths to understand
the properties of magnetic fields and dust in AGB envelopes.Comment: 27 pages, 23 figures, 1 table, to be submitte
AGN X-ray irradiation of CO gas in NGC 2110 revealed by and ALMA
We report spatial distributions of the Fe-K line at 6.4 keV and the
CO( = 2--1) line at 230.538 GHz in NGC 2110, which are respectively revealed
by and ALMA at 0.5 arcsec. A 6.2--6.5
keV-to-3.0--6.0 keV image suggests that the Fe-K emission extends
preferentially in a northwest-to-southeast direction out to 3 arcsec, or
500 pc, on each side. Spatially-resolved spectral analyses support this by
finding significant Fe-K emission lines only in northwest and southeast
regions. Moreover, their equivalent widths are found 1.5 keV, indicative
for the fluorescence by nuclear X-ray irradiation as the physical origin. By
contrast, CO( = 2--1) emission is weak therein. For quantitative discussion,
we derive ionization parameters by following an X-ray dominated region (XDR)
model. We then find them high enough to interpret the weakness as the result of
X-ray dissociation of CO and/or H. Another possibility also remains that CO
molecules follow a super-thermal distribution, resulting in brighter emission
in higher- lines. Further follow-up observations are encouraged to draw a
conclusion on what predominantly changes the inter-stellar matter properties,
and whether the X-ray irradiation eventually affects the surrounding star
formation as an AGN feedback.Comment: 15 pages, 11 figures, 3 tables. Accepted for publication in Ap
Effect of the initial mass function on the dynamical SMBH mass estimate in the nucleated early-type galaxy FCC 47
Supermassive black holes (SMBHs) and nuclear star clusters (NSCs) co-exist in
many galaxies. While the formation history of the black hole is essentially
lost, NSCs preserve their evolutionary history imprinted onto their stellar
populations and kinematics. Studying SMBHs and NSCs in tandem might help us to
ultimately reveal the build-up of galaxy centres. In this study, we combine
large-scale VLT/MUSE and high-resolution adaptive-optics-assisted VLT/SINFONI
observations of the early-type galaxy FCC 47 with the goal being to assess the
effect of a spatially (non-)variable initial mass function (IMF) on the
determination of the mass of the putative SMBH in this galaxy. We achieve this
by performing DYNAMITE Schwarzschild orbit-superposition modelling of the
galaxy and its NSC. In order to properly take account of the stellar mass
contribution to the galaxy potential, we create mass maps using a varying
stellar mass-to-light ratio derived from single stellar population models with
fixed and with spatially varying IMFs. Using the two mass maps, we estimate
black hole masses of and
at signifance,
respectively. Compared to models with constant stellar-mass-to-light ratio, the
black hole masses decrease by 15% and 48%, respectively. Therefore, a varying
IMF, both in its functional form and spatially across the galaxy, has a
non-negligible effect on the SMBH mass estimate. Furthermore, we find that the
SMBH in FCC 47 has probably not grown over-massive compared to its very
over-massive NSC.Comment: 23 pages 19 Figures, accepted for publication in A&
ALMA 0.02"-resolution observations reveal HCN-abundance-enhanced counter-rotating and outflowing dense molecular gas at the NGC 1068 nucleus
We present ALMA ~0.02"-resolution observations of the nucleus of the nearby
(~14 Mpc) type-2 AGN NGC 1068 at HCN/HCO+/HNC J=3-2 lines, as well as at their
13C isotopologue and vibrationally excited lines, to scrutinize the
morphological/dynamical/chemical/physical properties of dense molecular gas in
the putative dusty molecular torus around a mass-accreting supermassive black
hole. We confirm almost east-west-oriented dense molecular gas emission both
morphologically and dynamically, which we regard as coming from the torus.
Bright emission is compact (<3 pc), and low-surface-brightness emission extends
out to 5-7 pc. These dense molecular gas properties are not symmetric between
the eastern and western torus. The HCN J=3-2 emission is stronger than the HCO+
J=3-2 emission within the ~7 pc torus region, with an estimated dense molecular
mass of (0.4-1.0)x10^6Msun. We interpret that HCN abundance is enhanced in the
torus. We detect signatures of outflowing dense molecular gas and a
vibrationally excited HCN J=3-2 line. Finally, we find that in the innermost
(<1 pc) part of the torus, the dense molecular line rotation velocity, relative
to the systemic velocity, is the opposite of that in the outer (>2 pc) part, in
both the eastern and western torus. We prefer a scenario of counter-rotating
dense molecular gas with innermost almost-Keplerian-rotation and outer slowly
rotating (far below Keplerian) components. Our high-spatial-resolution dense
molecular line data reveal that torus properties of NGC 1068 are much more
complicated than the simple axi-symmetrically rotating torus picture in the
classical AGN unification paradigm.Comment: 45 pages, 20 Figures. Accepted for publication in Ap
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