We analyze Herschel Space Observatory observations of 104 young stellar objects with protoplanetary disks in the ∼1.5 Myr star-forming region Lynds 1641 (L1641) within the Orion A Molecular Cloud. We ...present spectral energy distributions from the optical to the far-infrared including new photometry from the Herschel Photodetector Array Camera and Spectrometer at 70 m. Our sample, taken as part of the Herschel Orion Protostar Survey, contains 24 transitional disks, 8 of which we identify for the first time in this work. We analyze the full disks (FDs) with irradiated accretion disk models to infer dust settling properties. Using forward modeling to reproduce the observed n K S − 70 index for the FD sample, we find the observed disk indices are consistent with models that have depletion of dust in the upper layers of the disk relative to the midplane, indicating significant dust settling. We perform the same analysis on FDs in Taurus with Herschel data and find that Taurus is slightly more evolved, although both samples show signs of dust settling. These results add to the growing literature that significant dust evolution can occur in disks by ∼1.5 Myr.
Abstract
We present JWST-MIRI Medium Resolution Spectrometer (MRS) spectra of the protoplanetary disk around the low-mass T Tauri star GW Lup from the MIRI mid-INfrared Disk Survey Guaranteed Time ...Observations program. Emission from
12
CO
2
,
13
CO
2
, H
2
O, HCN, C
2
H
2
, and OH is identified with
13
CO
2
being detected for the first time in a protoplanetary disk. We characterize the chemical and physical conditions in the inner few astronomical units of the GW Lup disk using these molecules as probes. The spectral resolution of JWST-MIRI MRS paired with high signal-to-noise data is essential to identify these species and determine their column densities and temperatures. The
Q
branches of these molecules, including those of hot bands, are particularly sensitive to temperature and column density. We find that the
12
CO
2
emission in the GW Lup disk is coming from optically thick emission at a temperature of ∼400 K.
13
CO
2
is optically thinner and based on a lower temperature of ∼325 K, and thus may be tracing deeper into the disk and/or a larger emitting radius than
12
CO
2
. The derived
N
CO
2
/
N
H
2
O
ratio is orders of magnitude higher than previously derived for GW Lup and other targets based on Spitzer-InfraRed-Spectrograph data. This high column density ratio may be due to an inner cavity with a radius in between the H
2
O and CO
2
snowlines and/or an overall lower disk temperature. This paper demonstrates the unique ability of JWST to probe inner disk structures and chemistry through weak, previously unseen molecular features.
The accretion of material from protoplanetary disks onto their central stars is a fundamental process in the evolution of these systems and a key diagnostic in constraining the disk lifetime. We ...analyze the relationship between the stellar accretion rate and the disk mass in 32 intermediate-mass Herbig Ae/Be systems and compare them to their lower-mass counterparts, T Tauri stars. We find that the $\dot{M}$ – M _disk relationship for Herbig Ae/Be stars is largely flat at ∼10 ^−7 M _☉ yr ^−1 over 3 orders of magnitude in dust mass. While most of the sample follows the T Tauri trend, a subset of objects with high accretion rates and low dust masses are identified. These outliers (12 out of 32 sources) have an inferred disk lifetime of less than 0.01 Myr and are dominated by objects with low infrared excess. This outlier sample is likely identified in part by the bias in classifying Herbig Ae/Be stars, which requires evidence of accretion that can only be reliably measured above a rate of ∼10 ^−9 M _☉ yr ^−1 for these spectral types. If the disk masses are not underestimated and the accretion rates are not overestimated, this implies that these disks may be on the verge of dispersal, which may be due to efficient radial drift of material or outer disk depletion by photoevaporation and/or truncation by companions. This outlier sample likely represents a small subset of the larger young, intermediate-mass stellar population, the majority of which would have already stopped accreting and cleared their disks.
OPINION Sierra L. Smith; Anna A. Sher; Grant, Thomas A
Restoration ecology,
09/2007, Volume:
15, Issue:
3
Journal Article
Peer reviewed
The ever increasing demand for native plants and seed for use in restoration and revegetation has created a sizable industry. The large-scale production and planting of native plants have given rise ...to a suite of ecological concerns including collection impacts, genetic diversity, and provenance. This study examines the practices and beliefs of 12 restoration plant production companies in Colorado with regard to arising ecological issues and identifies where further research is needed. We found that native seed collection in Colorado was largely unregulated and unmonitored and impacts were unknown. Maintaining genetic diversity in restoration materials is costly and does not have universal support. The use of provenance material (or local ecotypes) was hotly contested with strong and sound arguments on both sides of the issue. Procurement of pure ecotypes was difficult because of the variety of institutions involved in production and complications such as artificial selection and cross-pollination. PUBLICATION ABSTRACT
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The accretion of material from protoplanetary disks onto their central stars
is a fundamental process in the evolution of these systems and a key diagnostic
in constraining the disk lifetime. We ...analyze the relationship between the
stellar accretion rate and the disk mass in 32 intermediate-mass Herbig Ae/Be
systems and compare them to their lower-mass counterparts, T Tauri stars. We
find that the $\dot{M}$--$M_{\rm{disk}}$ relationship for Herbig Ae/Be stars is
largely flat at $\sim$10$^{-7}$ M$_{\odot}$ yr$^{-1}$ across over three orders
of magnitude in dust mass. While most of the sample follows the T Tauri trend,
a subset of objects with high accretion rates and low dust masses are
identified. These outliers (12 out of 32 sources) have an inferred disk
lifetime of less than 0.01 Myr and are dominated by objects with low infrared
excess. This outlier sample is likely identified in part by the bias in
classifying Herbig Ae/Be stars, which requires evidence of accretion that can
only be reliably measured above a rate of $\sim$10$^{-9}$ M$_{\odot}$ yr$^{-1}$
for these spectral types. If the disk masses are not underestimated and the
accretion rates are not overestimated, this implies that these disks may be on
the verge of dispersal, which may be due to efficient radial drift of material
or outer disk depletion by photoevaporation and/or truncation by companions.
This outlier sample likely represents a small subset of the larger young,
intermediate-mass stellar population, the majority of which would have already
stopped accreting and cleared their disks.
The Cryogenic IR echelle Spectrometer (CRIRES) instrument at the Very Large Telescope (VLT) was in operation from 2006 to 2014. Great strides in characterizing the inner regions of protoplanetary ...disks were made using CRIRES observations in the L- and M-band at this time. The upgraded instrument, CRIRES+, became available in 2021 and covers a larger wavelength range simultaneously. Here we present new CRIRES+ Science Verification data of the binary system S Coronae Australis (S CrA). We aim to characterize the upgraded CRIRES+ instrument for disk studies and provide new insight into the gas in the inner disk of the S CrA N and S systems. We analyze the CRIRES+ data taken in all available L- and M-band settings, providing spectral coverage from 2.9 to 5.5 \(\mu\)m. We detect emission from \(^{12}\)CO (v=1-0, v=2-1, and v=3-2), \(^{13}\)CO (v=1-0), hydrogen recombination lines, OH, and H\(_2\)O in the S CrA N disk. In the fainter S CrA S system, only the \(^{12}\)CO v=1-0 and the hydrogen recombination lines are detected. The \(^{12}\)CO v=1-0 emission in S CrA N and S shows two velocity components, a broad component coming from \(\sim\)0.1 au in S CrA N and \(\sim\)0.03 au in S CrA S and a narrow component coming from \(\sim\)3 au in S CrA N and \(\sim\)5 au in S CrA S. We fit local thermodynamic equilibrium slab models to the rotation diagrams of the two S CrA N velocity components and find that they have similar column densities (\(\sim\)1-7\(\times\)10\(^{17}\) cm\(^{-2}\)), but that the broad component is coming from a hotter and narrower region. Two filter settings, M4211 and M4368, provide sufficient wavelength coverage for characterizing CO and H\(_2\)O at \(\sim\)5 \(\mu\)m, in particular covering low- and high-\(J\) lines. CRIRES+ provides spectral coverage and resolution that are crucial complements to low-resolution observations, such as those with JWST, where multiple velocity components cannot be distinguished.
Accretion plays an important role in protoplanetary disk evolution, and it is thought that the accretion mechanism changes between low- and high-mass stars. Here, we characterize accretion in ...intermediate-mass, pre-main-sequence Herbig Ae/Be (HAeBe) stars to search for correlations between accretion and system properties. We present new high-resolution, near-infrared spectra from the Immersion GRating INfrared Spectrograph for 102 HAeBes and analyze the accretion-tracing Br\(\gamma\) line at 2.166 \(\mu\)m. We also include the samples of Fairlamb et al. and Donehew & Brittain, for a total of 155 targets. We find a positive correlation between the Br\(\gamma\) and stellar luminosity, with a change in the slope between the Herbig Aes and Herbig Bes. We use \(L_{Br\gamma}\) to determine the accretion luminosity and accretion rate. We find that the accretion luminosity and rate depend on stellar mass and age; however, the trend disappears when normalizing the accretion luminosity by the stellar luminosity. We classify the objects into flared (Group I) or flat (Group II) disks and find that there is no trend with accretion luminosity or rate, indicating that the disk dust structure is not impacting accretion. We test for Br\(\gamma\) variability in objects that are common to our sample and previous studies. We find that the Br\(\gamma\) line equivalent width is largely consistent between the literature observations and those that we present here, except in a few cases where we may be seeing changes in the accretion rate.
The MRS mode of the JWST-MIRI instrument gives insights into the chemical
richness and complexity of the inner regions of planet-forming disks. Here, we
analyse the H$_2$O-rich spectrum of the ...compact disk DR Tau. We probe the
excitation conditions of the H$_2$O transitions observed in different
wavelength regions across the entire spectrum using LTE slab models, probing
both the rovibrational and rotational transitions. These regions suggest a
radial temperature gradient, as the excitation temperature (emitting radius)
decreases (increases) with increasing wavelength. To explain the derived
emitting radii, we require a larger inclination for the inner disk (i~20-23
degrees) compared to the outer disk (i~5 degrees), agreeing with our previous
analysis on CO. We also analyse the pure rotational spectrum (<10 micron) using
a large, structured disk (CI Tau) as a template, confirming the presence of the
radial gradient, and by fitting multiple components to further characterise the
radial and vertical temperature gradients present in the spectrum. At least
three temperature components (T~180-800 K) are required to reproduce the
rotational spectrum of H$_2$O arising from the inner ~0.3-8 au. These
components describe a radial temperature gradient that scales roughly as
~R$^{-0.5}$ in the emitting layers. As the H$_2$O is mainly optically thick, we
derive a lower limit on the abundance ratio of H$_2$O/CO~0.17, suggesting a
potential depletion of H$_2$O. Similarly to previous work, we detect a cold
H$_2$O component (T~180 K) originating from near the snowline. We cannot
conclude if an enhancement of the H$_2$O reservoir is observed following radial
drift. A consistent analysis of a larger sample of compact disks is necessary
to study the importance of drift in enhancing the H$_2$O abundances.
SY Cha is a T Tauri star surrounded by a protoplanetary disk with a large cavity seen in the millimeter continuum but has the spectral energy distribution (SED) of a full disk. Here we report the ...first results from JWST-MIRI Medium Resolution Spectrometer (MRS) observations taken as part of the MIRI mid-INfrared Disk Survey (MINDS) GTO Program. The much improved resolution and sensitivity of MIRI-MRS compared to Spitzer enables a robust analysis of the previously detected H2O, CO, HCN, and CO2 emission as well as a marginal detection of C2H2. We also report the first robust detection of mid-infrared OH and ro-vibrational CO emission in this source. The derived molecular column densities reveal the inner disk of SY Cha to be rich in both oxygen and carbon bearing molecules. This is in contrast to PDS 70, another protoplanetary disk with a large cavity observed with JWST, which displays much weaker line emission. In the SY Cha disk, the continuum, and potentially the line, flux varies substantially between the new JWST observations and archival Spitzer observations, indicative of a highly dynamic inner disk.
Most stars form in multiple systems whose properties can significantly impact circumstellar disk evolution. We investigate the physical and chemical properties of the equal-mass, small separation ...(~66 mas, ~9 au) DF Tau binary system. Previous observations indicated that only DF Tau A has a circumstellar disk. We present JWST-MIRI MRS observations of DF Tau. The MIRI spectrum shows a forest of H2O lines and emission from CO, C2H2, HCN, CO2, and OH. LTE slab models are used to determine the properties of the gas, and we analyze high angular spatial and spectral resolution data from ALMA, VLTI-GRAVITY, and IRTF-iSHELL to aid in the interpretation of the JWST data. The 1.3 mm ALMA continuum data show two equal-brightness sources of compact (R<3 au) emission, with separations and movement consistent with astrometry from VLTI-GRAVITY and the known orbit. This is interpreted as a robust detection of a disk around DF Tau B, which we suggest may host a small (~1 au) cavity to reconcile all observations. The disk around DF Tau A is expected to be a full disk, and spatially and spectrally resolved dust and gas emission points to hot, close-in (<0.2 au) material. Hot (~500-1000 K) H2O, HCN, and C2H2 emission in the MIRI data likely originate in the DF Tau A disk, while a cold (<200 K) H2O component with an extended emitting area is consistent with an origin from both disks. Despite the very compact outer disks, the inner disk composition and conditions are similar to isolated systems, suggesting that the close binary nature is not a driving factor in setting the inner disk chemistry. However, constraining the geometry of the disks, for instance, via higher resolution ALMA observations, would provide additional insight into the mid-infrared gas emission. JWST observations of spatially resolved binaries will be important for understanding the impact of binarity on inner disk chemistry more generally.
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