12 research outputs found
Diagnostic value of far-IR water ice features in T Tauri disks
This paper investigates how the far-IR water ice features can be used to
infer properties of disks around T Tauri stars and the water ice thermal
history. We explore the power of future observations with SOFIA/HIRMES and
SPICA's proposed far-IR instrument SAFARI. A series of detailed radiative
transfer disk models around a representative T Tauri star are used to
investigate how the far-IR water ice features at 45 and 63 micron change with
key disk properties: disk size, grain sizes, disk dust mass, dust settling, and
ice thickness. In addition, a series of models is devised to calculate the
water ice emission features from warmup, direct deposit and cooldown scenarios
of the water ice in disks. Photodesorption from icy grains in disk surfaces
weakens the mid-IR water ice features by factors 4-5. The far-IR water ice
emission features originate from small grains at the surface snow line in disks
at distance of 10-100 au. Unless this reservoir is missing in disks (e.g.
transitional disks with large cavities), the feature strength is not changing.
Grains larger than 10 micron do not contribute to the features. Grain settling
(using turbulent description) is affecting the strength of the ice features by
at most 15%. The strength of the ice feature scales with the disk dust mass and
water ice fraction on the grains, but saturates for dust masses larger than
1.e-4 Msun and for ice mantles that increase the dust mass by more than 50%.
The various thermal histories of water ice leave an imprint on the shape of the
features (crystalline/amorphous) as well as on the peak strength and position
of the 45 micron feature. SOFIA/HIRMES can only detect crystalline ice features
much stronger than simulated in our standard T Tauri disk model in deep
exposures (1 hr). SPICA/SAFARI can detect the typical ice features in our
standard T Tauri disk model in short exposures (10 min). (abbreviated)Comment: accepted for publication in A&
A tunnel and a traffic jam: How transition disks maintain a detectable warm dust component despite the presence of a large planet-carved gap
We combined hydrodynamical simulations of planet-disk interactions with dust
evolution models that include coagulation and fragmentation of dust grains over
a large range of radii and derived observational properties using radiative
transfer calculations. We studied the role of the snow line in the survival of
the inner disk of transition disks. Inside the snow line, the lack of ice
mantles in dust particles decreases the sticking efficiency between grains. As
a consequence, particles fragment at lower collision velocities than in regions
beyond the snow line. This effect allows small particles to be maintained for
up to a few Myrs within the first astronomical unit. These particles are
closely coupled to the gas and do not drift significantly with respect to the
gas. For lower mass planets (1), the pre-transition appearance
can be maintained even longer because dust still trickles through the gap
created by the planet, moves invisibly and quickly in the form of relatively
large grains through the gap, and becomes visible again as it fragments and
gets slowed down inside of the snow line. The global study of dust evolution of
a disk with an embedded planet, including the changes of the dust aerodynamics
near the snow line, can explain the concentration of millimetre-sized particles
in the outer disk and the survival of the dust in the inner disk if a large
dust trap is present in the outer disk. This behaviour solves the conundrum of
the combination of both near-infrared excess and ring-like millimetre emission
observed in several transition disks.Comment: Accepted for publication in A&A (including acknowledgments
GLI1 Confers Profound Phenotypic Changes upon LNCaP Prostate Cancer Cells That Include the Acquisition of a Hormone Independent State
The GLI (GLI1/GLI2) transcription factors have been implicated in the development
and progression of prostate cancer although our understanding of how they
actually contribute to the biology of these common tumours is limited. We
observed that GLI reporter activity was higher in normal (PNT-2) and
tumourigenic (DU145 and PC-3) androgen-independent cells compared to
androgen-dependent LNCaP prostate cancer cells and, accordingly, GLI mRNA levels
were also elevated. Ectopic expression of GLI1 or the constitutively active
ΔNGLI2 mutant induced a distinct cobblestone-like morphology in LNCaP cells
that, regarding the former, correlated with increased GLI2 as well as expression
of the basal/stem-like markers CD44, β1-integrin, ΔNp63 and BMI1, and
decreased expression of the luminal marker AR (androgen receptor). LNCaP-GLI1
cells were viable in the presence of the AR inhibitor bicalutamide and gene
expression profiling revealed that the transcriptome of LNCaP-GLI1 cells was
significantly closer to DU145 and PC-3 cells than to control LNCaP-pBP (empty
vector) cells, as well as identifying LCN2/NGAL as a highly induced transcript
which is associated with hormone independence in breast and prostate cancer.
Functionally, LNCaP-GLI1 cells displayed greater clonal growth and were more
invasive than control cells but they did not form colonies in soft agar or
prostaspheres in suspension suggesting that they do not possess inherent stem
cell properties. Moreover, targeted suppression of GLI1 or GLI2 with siRNA did
not reverse the transformed phenotype of LNCaP-GLI1 cells nor did double
GLI1/GLI2 knockdowns activate AR expression in DU145 or PC-3 cells. As such,
early targeting of the GLI oncoproteins may hinder progression to a hormone
independent state but a more detailed understanding of the mechanisms that
maintain this phenotype is required to determine if their inhibition will
enhance the efficacy of anti-hormonal therapy through the induction of a luminal
phenotype and increased dependency upon AR function
A Realistic Roadmap to Formation Flying Space Interferometry
The ultimate astronomical observatory would be a formation flying space interferometer, combining sensitivity and stability with high angular resolution. The smallSat revolution offers a new and maturing prototyping platform for space interferometry and we put forward a realistic plan for achieving first stellar fringes in space by 2030
Thermal imaging of dust hiding the black hole in NGC 1068
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Thermal imaging of dust hiding the black hole in the Active Galaxy NGC 1068
In the widely accepted 'Unified Model' solution of the classification puzzle of Active Galactic Nuclei, the orientation of a dusty accretion torus around the central black hole dominates their appearance. In 'type-1' systems, the bright nucleus is visible at the centre of a face-on torus. In 'type-2' systems the thick, nearly edge-on torus hides the central engine. Later studies suggested evolutionary effects and added dusty clumps and polar winds but left the basic picture intact. However, recent high-resolution images of the archetypal type-2 galaxy NGC 1068 suggested a more radical revision. They displayed a ring-like emission feature which the authors advocated to be hot dust surrounding the black hole at the radius where the radiation from the central engine evaporates the dust. That ring is too thin and too far tilted from edge-on to hide the central engine, and ad hoc foreground extinction is needed to explain the type-2 classification. These images quickly generated reinterpretations of the type 1-2 dichotomy. Here we present new multi-band mid-infrared images of NGC1068 that detail the dust temperature distribution and reaffirm the original model. Combined with radio data, our maps locate the central engine below the previously reported ring and obscured by a thick, nearly edge-on disk, as predicted by the Unified Model. We also identify emission from polar flows and absorbing dust that is mineralogically distinct from that towards the Milky Way centre
Thermal imaging of dust hiding the black hole in the Active Galaxy NGC 1068
In the widely accepted 'Unified Model' solution of the classification puzzle of Active Galactic Nuclei, the orientation of a dusty accretion torus around the central black hole dominates their appearance. In 'type-1' systems, the bright nucleus is visible at the centre of a face-on torus. In 'type-2' systems the thick, nearly edge-on torus hides the central engine. Later studies suggested evolutionary effects and added dusty clumps and polar winds but left the basic picture intact. However, recent high-resolution images of the archetypal type-2 galaxy NGC 1068 suggested a more radical revision. They displayed a ring-like emission feature which the authors advocated to be hot dust surrounding the black hole at the radius where the radiation from the central engine evaporates the dust. That ring is too thin and too far tilted from edge-on to hide the central engine, and ad hoc foreground extinction is needed to explain the type-2 classification. These images quickly generated reinterpretations of the type 1-2 dichotomy. Here we present new multi-band mid-infrared images of NGC1068 that detail the dust temperature distribution and reaffirm the original model. Combined with radio data, our maps locate the central engine below the previously reported ring and obscured by a thick, nearly edge-on disk, as predicted by the Unified Model. We also identify emission from polar flows and absorbing dust that is mineralogically distinct from that towards the Milky Way centre
Thermal imaging of dust hiding the black hole in the Active Galaxy NGC 1068
In the widely accepted 'Unified Model' solution of the classification puzzle of Active Galactic Nuclei, the orientation of a dusty accretion torus around the central black hole dominates their appearance. In 'type-1' systems, the bright nucleus is visible at the centre of a face-on torus. In 'type-2' systems the thick, nearly edge-on torus hides the central engine. Later studies suggested evolutionary effects and added dusty clumps and polar winds but left the basic picture intact. However, recent high-resolution images of the archetypal type-2 galaxy NGC 1068 suggested a more radical revision. They displayed a ring-like emission feature which the authors advocated to be hot dust surrounding the black hole at the radius where the radiation from the central engine evaporates the dust. That ring is too thin and too far tilted from edge-on to hide the central engine, and ad hoc foreground extinction is needed to explain the type-2 classification. These images quickly generated reinterpretations of the type 1-2 dichotomy. Here we present new multi-band mid-infrared images of NGC1068 that detail the dust temperature distribution and reaffirm the original model. Combined with radio data, our maps locate the central engine below the previously reported ring and obscured by a thick, nearly edge-on disk, as predicted by the Unified Model. We also identify emission from polar flows and absorbing dust that is mineralogically distinct from that towards the Milky Way centre
Thermal imaging of dust hiding the black hole in the Active Galaxy NGC 1068
In press at NatureIn the widely accepted 'Unified Model' solution of the classification puzzle of Active Galactic Nuclei, the orientation of a dusty accretion torus around the central black hole dominates their appearance. In 'type-1' systems, the bright nucleus is visible at the centre of a face-on torus. In 'type-2' systems the thick, nearly edge-on torus hides the central engine. Later studies suggested evolutionary effects and added dusty clumps and polar winds but left the basic picture intact. However, recent high-resolution images of the archetypal type-2 galaxy NGC 1068 suggested a more radical revision. They displayed a ring-like emission feature which the authors advocated to be hot dust surrounding the black hole at the radius where the radiation from the central engine evaporates the dust. That ring is too thin and too far tilted from edge-on to hide the central engine, and ad hoc foreground extinction is needed to explain the type-2 classification. These images quickly generated reinterpretations of the type 1-2 dichotomy. Here we present new multi-band mid-infrared images of NGC1068 that detail the dust temperature distribution and reaffirm the original model. Combined with radio data, our maps locate the central engine below the previously reported ring and obscured by a thick, nearly edge-on disk, as predicted by the Unified Model. We also identify emission from polar flows and absorbing dust that is mineralogically distinct from that towards the Milky Way centre
Astro2020 Science White Paper. The Future of Exoplanet Direct Detection
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