201 research outputs found
JWST imaging of edge-on protoplanetary disks II. Appearance of edge-on disks with a tilted inner region: case study of IRAS04302+2247
We present JWST imaging from 2m to 21m of the edge-on
protoplanetary disk around the embedded young star IRAS04302+2247. The
structure of the source shows two reflection nebulae separated by a dark lane.
The source extent is dominated by the extended filamentary envelope at
4.4m and shorter wavelengths, transitioning at 7m and longer
wavelengths to more compact lobes of scattered light from the disk itself. The
dark lane thickness does not vary significantly with wavelength, which we
interpret as an indication for intermediate-sized (m) grains in the
upper layers of the disk. Intriguingly, we find that the brightest nebula of
IRAS40302 switches side between 12.8m and 21m. We explore the effect
of a tilted inner region on the general appearance of edge-on disks. We find
that radiative transfer models of a disk including a tilted inner region can
reproduce an inversion in the brightest nebula. In addition, for specific
orientations, the model also predicts strong lateral asymmetries, which can
occur for more than half possible viewing azimuths. A large number of edge-on
protoplanetary disks observed in scattered light show such lateral asymmetries
(15/20), which suggests that a large fraction of protoplanetary disks might
host a tilted inner region. Stellar spots may also induce lateral asymmetries,
which are expected to vary over a significantly shorter timescale. Variability
studies of edge-on disks would allow to test the dominant scenario for the
origin of these asymmetries.Comment: Accepted for publication in Ap
JWST imaging of edge-on protoplanetary disks. I. Fully vertically mixed 10m grains in the outer regions of a 1000 au disk
Scattered light imaging of protoplanetary disks provides key insights on the
geometry and dust properties in the disk surface. Here we present JWST
2--21\,m images of a 1000\,au-radius edge-on protoplanetary disk
surrounding an 0.4\, young star in Taurus, 2MASS\,J04202144+2813491.
These observations represent the longest wavelengths at which a protoplanetary
disk is spatially resolved in scattered light. We combine these observations
with HST optical images and ALMA continuum and CO mapping. We find that the
changes in the scattered light disk morphology are remarkably small across a
factor of 30 in wavelength, indicating that dust in the disk surface layers is
characterized by an almost gray opacity law. Using radiative transfer models,
we conclude that grains up to m in size are fully coupled to
the gas in this system, whereas grains m are strongly settled
towards the midplane. Further analyses of these observations, and similar ones
of other edge-on disks, will provide strong empirical constraints on disk
dynamics and evolution and grain growth models. In addition, the 7.7 and
12.\,m JWST images reveal an X-shaped feature located above the warm
molecular layer traced by CO line emission. The highest elevations at which
this feature is detectable roughly match the maximal extent of the disk in
visible wavelength scattered light as well as of an unusual kinematic signature
in CO. We propose that these phenomena could be related to a disk wind
entraining small dust grains.Comment: Accepted for publication in the Astronomical Journa
Modest dust settling in the IRAS04302+2247 Class I protoplanetary disk
We present new VLA observations, between 6.8mm and 66mm, of the edge-on
Class~I disk IRAS04302+2247. Observations at 6.8mm and 9.2mm lead to the
detection of thermal emission from the disk, while shallow observations at the
other wavelengths are used to correct for emission from other processes. The
disk radial brightness profile transitions from broadly extended in previous
ALMA 0.9mm and 2.1mm observations to much more centrally brightened at 6.8mm
and 9.2mm, which can be explained by optical depth effects. The radiative
transfer modeling of the 0.9mm, 2.1mm, and 9.2mm data suggests that the grains
are smaller than 1cm in the outer regions of the disk and allows us to obtain
the first lower limit for the scale height of grains emitting at millimeter
wavelengths in a protoplanetary disk. We find that the millimeter dust scale
height is between 1au and 6au at a radius 100au from the central star, while
the gas scale height is estimated to be about 7au, indicating a modest level of
settling. The estimated dust height is intermediate between less evolved Class
0 sources, that are found to be vertically thick, and more evolved Class II
sources, which show a significant level of settling. This suggests that we are
witnessing an intermediate stage of dust settling.Comment: Accepted for publication in the Astrophysical Journa
Probing protoplanetary disk evolution in the Chamaeleon II region
Context. Characterizing the evolution of protoplanetary disks is necessary to
improve our understanding of planet formation. Constraints on both dust and gas
are needed to determine the dominant disk dissipation mechanisms. Aims. We aim
to compare the disk dust masses in the Chamaeleon II (Cha II) star-forming
region with other regions with ages between 1 and 10Myr. Methods. We use ALMA
band 6 observations (1.3 mm) to survey 29 protoplanetary disks in Cha II. Dust
mass estimates are derived from the continuum data. Results. Out of our initial
sample of 29 disks, we detect 22 sources in the continuum, 10 in 12CO, 3 in
13CO, and none in C18O (J=2-1). Additionally, we detect two companion
candidates in the continuum and 12CO emission. Most disk dust masses are lower
than 10Mearth, assuming thermal emission from optically thin dust. We compare
consistent estimations of the distributions of the disk dust mass and the
disk-to-stellar mass ratios in Cha II with six other low mass and isolated
star-forming regions in the age range of 1-10Myr: Upper Sco, CrA, IC 348, Cha
I, Lupus, and Taurus. When comparing the dust-to-stellar mass ratio, we find
that the masses of disks in Cha II are statistically different from those in
Upper Sco and Taurus, and we confirm that disks in Upper Sco, the oldest region
of the sample, are statistically less massive than in all other regions.
Performing a second statistical test of the dust mass distributions from
similar mass bins, we find no statistical differences between these regions and
Cha II. Conclusions. We interpret these trends, most simply, as a sign of
decline in the disk dust masses with time or dust evolution. Different global
initial conditions in star-forming regions may also play a role, but their
impact on the properties of a disk population is difficult to isolate in
star-forming regions lacking nearby massive stars.Comment: Accepted for publication in A&
Gas- and particle-phase products from the photooxidation of acenaphthene and acenaphthylene by OH radicals
This work is focused on the gas-phase oxidation of acenaphthylene and acenaphthene by OH radicals and associated secondary organic aerosol (SOA) formation under low and high-NOx conditions. Experiments were carried out in an atmospheric simulation chamber using a proton transfer reaction time-of-flight-mass spectrometer (PTR-TOF-MS) and an aerosol time-of-flight-mass spectrometer (ATOFMS) to chemically characterize the gas- and particle-phase products, respectively. Due to the structures of these two aromatic compounds, the proposed chemical mechanisms exhibit some differences. In the case of acenaphthene, H-atom abstraction from the saturated cyclopenta-fused ring was found to be competitive with the OH-addition to the aromatic rings. During the photooxidation of acenaphthene using nitrous acid (HONO), aromatic ring-opening products such as indanone and indanone carbaldehyde, generated through OH addition to the aromatic ring, were formed in higher yields compared to low-NOx conditions. In the case of acenaphthylene, OH addition to the unsaturated cyclopenta-fused ring was strongly favored. Hence, ring-retaining species such as acenaphthenone and acenaphthenequinone, were identified as the main reaction products in both gas- and particle-phases, especially under high-NOx conditions. Subsequent SOA formation was observed in all experiments and SOA yields were determined under low/high-NOx conditions to be 0.61/0.46 and 0.68/0.55 from the OH-initiated oxidation of acenaphthylene and acenaphthene, respectively
Spectro-Photo-Interferometry of Stellar Pulsation (SPIPS)
We present our implementation of the parallax of pulsation method which integrates all observables and physical modelling of the photosphere to get the best statistical precision and controlled biases. This method has been validated on well known stars and used to estimate observationally the projection factor of the HST-FGS sample. Our future developments include application to the Gaia Cepheids and modelling of the spectrum
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