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[en] Purpose: This study reviews treatment related late complications following high dose rate endobronchial brachytherapy (HDR-EB) for primary lung cancers. Radiation dose contribution from HDR-EB treatment alone, or combined HDR-EB and external beam (EBRT) were analyzed in relation to the linear representation of the tracheobronchial anatomy. Results were presented in a dose volume histogram (DVH) analysis for the risk estimate of late complications from HDR-EB. Bronchial mucosal tolerance is estimated from the clinical experience study and histopathologic changes in laboratory animals treated with HDR-EB. Methods: 1.) There were forty one patients with primary lung cancer received HDR-EB as part of the radiation treatment between December 1990 and June 1994. Six of these developed late complications manifested as either fatal hemoptysis or endobronchial deposition of fibrinous material/bronchial stenosis. Treatment planning films were reviewed to map the volume treated with HDR-EB and EBRT along the tracheobronchial segments. DVH was constructed and compared for patients with and without late complications. Other clinical parameters of interest which were analyzed included: dose per fraction, EBRT total dose, HDR total dose, combined EBRT and HDR total dose, number of catheters per treatment, and points of prescriptions for HDR-EB. 2.) Forty four New Zealand White rabbits underwent HDR-EB of the major airway to a treatment length of 2 cm (1 cm above and below the carina) to a single fraction dose of 10 Gy, 30 Gy, or 50 Gy. Histopathologic changes were examined at 7, 14, 28, and 56 days post-treatment and compared with the control rabbits which received no irradiation. Results: 1.) The late complication rate is 14.5% with three patients developing fibrinous deposits/bronchial stenosis and four patients who experienced fatal hemoptysis in a total of six patients. There is a significant difference in DVH of HDR-EB treatment in the tracheobronchial high dose region comparing those patients with late complications to those without (p=0.001). In contrast, neither the HDR-EB dose alone (without accounting for the volume effect) or the DVH from combined HDR-EB and EBRT reached a significant value between the two groups. When separating the fatal hemoptysis complication from fibrinous deposit/bronchial stenosis, DVH difference of HDR-EB treatment showed an increased significance level to p=0.0007 comparing those with and without fatal hemoptysis. DVH difference of HDR-EB treatment for fibrinous deposit/bronchial stenosis alone failed to reached the significant p value (p=0.18). In those with a DVH less than 100 Gy-cm3, only one developed fibrinous deposits/bronchial stenosis out of 25 (4%). For DVH between 100 Gy-cm3 and 300 Gy-cm3, there were two fibrinous deposit/bronchial stenosis and three fatal hemoptysis out of 16 (31%). Two DVHs that were above 300 Gy-cm3 had fatal hemoptysis (100%). Other clinical parameters stated in the Methods failed to demonstrate a predictive value for late complications. (2) Animal study data showed loss of cilia, loss of organization of cilia, and squamous metaplasia starting at 10 Gy HDR-EB. There is progressive squamous metaplasia and increasing focal areas of thinning mucosa to only one to two cell layers above 30 Gy. Areas of thinning mucosa is at risk for hemorrhage because of the proximity to the rich submucosal vasculature and the pulmonary arteries and veins. Conclusions: 1.) Combining information from the clinical DVH data and the animal study, bronchial mucosal tolerance is likely between 20 Gy to 30 Gy. Data also support the fact that the risk of fatal complications from HDR-EB is a function of both the total HDR dose and the treatment length of tracheobronchial tree, but not the dose alone or the dose contribution from EBRT. 2.) Although the patient numbers are small, our data support a safe delivery of less than 100 Gy-cm3 with a 4% risk of severe complications. A risk of complications at approximately 30% for DVH between 100 Gy-cm3 and 300-cm3. When DVH is above 300 Gy-cm3 ( equivalent to approximately a total HDR-EB dose of 30 Gy to a 10 cm length), the risk of fatal hemoptysis is approaching 100%. 3.) As the DVH risk estimate for fatal hemoptysis is higher than for fibrinous deposit/bronchial stenosis, data suggest different mechanisms for these two types of late complications from HDR-EB treatment to the tracheobronchial tree
[en] We report a highly significant Submillimeter Array (SMA) detection of the prototypical submillimeter source HDF 850.1, which is the brightest submillimeter source in the Hubble Deep Field-North proper. The detection yields an extremely precise position of R.A.(2000) = 12h36m51.s99 and Decl.(2000) = +62012'25.''83 with a 1σ positional uncertainty of 0.''17. The position is consistent with the location of a millimeter wavelength interferometric detection and with the locations of weak Very Large Array detections at 1.4 and 8.4 GHz, but it is not consistent with any previous optical/near-infrared identifications. The source appears point-like at the 2'' resolution of the SMA, and the detected flux of 7.8 ± 1.0 mJy is consistent with the measured Submillimeter Common-User Bolometer Array (SCUBA) fluxes. We tabulate fluxes and limits on HDF 850.1 at other wavelengths. Our redshift estimate for HDF 850.1 based on the radio through mid-infrared measurements is z = 4.1+0.5-0.6. The faintness of the source at optical/near-infrared wavelengths and the high estimated redshift suggest that HDF 850.1 may be an analog of the brighter submillimeter source GOODS 850-5, which is also thought to be at z > 4. The fact that a source like HDF 850.1 should have appeared in one of the very first blank-field SCUBA observations ever made suggests that such high-redshift sources are quite common. Thus, we are led to conclude that high-redshift star formation is dominated by giant dusty star-forming galaxies, just as it is at lower redshifts.
[en] We present new Expanded Very Large Array (EVLA) continuum observations at 7 mm of the 253-1536 binary disk system in the Orion Nebula Cluster. The measured fluxes were combined with data in the submillimeter to derive the millimeter spectral index of each individual disk component. We show how these observations can be used to test the models of dust evolution and early growth of solids in protoplanetary disks. Our analysis indicates that the disk with lower density and higher temperature hosts larger grains than the companion disk. This result is the opposite of what is predicted by the dust evolution models. The models and observational results can be reconciled if the viscosity α-parameter differs by more than a factor of 10 in the two disks, or if the distribution of solids in the disks is strongly affected by radial motions. This analysis can be applied to future high angular resolution observations of young disks with EVLA and ALMA to provide even stronger observational constraints to the models of dust evolution in protoplanetary disks.
[en] We carried out extremely sensitive Submillimeter Array (SMA) 340 GHz (860 μm) continuum imaging of a complete sample of SCUBA 850 μm sources (>4σ) with fluxes >3 mJy in the GOODS-N. Using these data and new SCUBA-2 data, we do not detect 4 of the 16 SCUBA sources, and we rule out the original SCUBA fluxes at the 4σ level. Three more resolve into multiple fainter SMA galaxies, suggesting that our understanding of the most luminous high-redshift dusty galaxies may not be as reliable as we thought. 10 of the 16 independent SMA sources have spectroscopic redshifts (optical/infrared or CO) up to z = 5.18. Using a new, ultradeep 20 cm image obtained with the Karl G. Jansky Very Large Array (rms of 2.5 μJy), we find that all 16 of the SMA sources are detected at >5σ. Using Herschel far-infrared (FIR) data, we show that the five isolated SMA sources with Herschel detections are well described by an Arp 220 spectral energy distribution template in the FIR. They also closely obey the local FIR-radio correlation, a result that does not suffer from a radio bias. We compute the contribution from the 16 SMA sources to the universal star formation rate (SFR) per comoving volume. With individual SFRs in the range 700-5000 M☉ yr–1, they contribute ∼30% of the extinction-corrected ultraviolet-selected SFR density from z = 1 to at least z = 5. Star formation histories determined from extinction-corrected ultraviolet populations and from submillimeter galaxy populations only partially overlap, due to the extreme ultraviolet faintness of some submillimeter galaxies.
[en] Mid-infrared spectrophotometric observations have revealed a small subclass of circumstellar disks with spectral energy distributions (SEDs) suggestive of large inner gaps with low dust content. However, such data provide only an indirect and model-dependent method of finding central holes. Imaging of protoplanetry disks provides an independent check of SED modeling. We present here the direct characterization of three 33-47 AU radii inner gaps, in the disks around LkHα 330, SR 21N, and HD 135344B, via 340 GHz (880 μm) dust continuum aperture synthesis observations obtained with the Submillimeter Array (SMA). The large gaps are fully resolved at ∼0.''3 by the SMA data and mostly empty of dust, with less than (1-7.5) x 10-6 Msun of fine grained solids inside the holes. Gas (as traced by atomic accretion markers and CO 4.7 μm rovibrational emission) is still present in the inner regions of all three disks. For each, the inner hole exhibits a relatively steep rise in dust emission to the outer disk, a feature more likely to originate from the gravitational influence of a companion body than from a process expected to show a more shallow gradient like grain growth. Importantly, the good agreement between the spatially resolved data and spectrophotometry-based models lends confidence to current interpretations of SEDs, wherein the significant dust emission deficits arise from disks with inner gaps or holes. Further SED-based searches can therefore be expected to yield numerous additional candidates that can be examined at high spatial resolution.
[en] We use the James Clerk Maxwell Telescope's SCUBA-2 camera to image a 400 arcmin2 area surrounding the GOODS-N field. The 850 μm rms noise ranges from a value of 0.49 mJy in the central region to 3.5 mJy at the outside edge. From these data, we construct an 850 μm source catalog to 2 mJy containing 49 sources detected above the 4σ level. We use an ultradeep (11.5 μJy at 5σ) 1.4 GHz image obtained with the Karl G. Jansky Very Large Array together with observations made with the Submillimeter Array to identify counterparts to the submillimeter galaxies. For most cases of multiple radio counterparts, we can identify the correct counterpart from new and existing Submillimeter Array data. We have spectroscopic redshifts for 62% of the radio sources in the 9' radius highest sensitivity region (556/894) and 67% of the radio sources in the GOODS-N region (367/543). We supplement these with a modest number of additional photometric redshifts in the GOODS-N region (30). We measure millimetric redshifts from the radio to submillimeter flux ratios for the unidentified submillimeter sample, assuming an Arp 220 spectral energy distribution. We find a radio-flux-dependent K – z relation for the radio sources, which we use to estimate redshifts for the remaining radio sources. We determine the star formation rates (SFRs) of the submillimeter sources based on their radio powers and their submillimeter fluxes and find that they agree well. The radio data are deep enough to detect star-forming galaxies with SFRs >2000 M ☉ yr–1 to z ∼ 6. We find galaxies with SFRs up to ∼6000 M ☉ yr–1 over the redshift range z = 1.5-6, but we see evidence for a turn-down in the SFR distribution function above 2000 M ☉ yr–1.
[en] We have obtained a full suite of Spitzer observations to characterize the debris disk around HR 8799 and to explore how its properties are related to the recently discovered set of three massive planets orbiting the star. We distinguish three components to the debris system: (1) warm dust (T ∼ 150 K) orbiting within the innermost planet; (2) a broad zone of cold dust (T ∼ 45 K) with a sharp inner edge orbiting just outside the outermost planet and presumably sculpted by it; and (3) a dramatic halo of small grains originating in the cold dust component. The high level of dynamical activity implied by this halo may arise due to enhanced gravitational stirring by the massive planets. The relatively young age of HR 8799 places it in an important early stage of development and may provide some help in understanding the interaction of planets and planetary debris, an important process in the evolution of our own solar system.
[en] The σ Orionis cluster is important for studying protoplanetary disk evolution, as its intermediate age (∼3–5 Myr) is comparable to the median disk lifetime. We use ALMA to conduct a high-sensitivity survey of dust and gas in 92 protoplanetary disks around σ Orionis members with M * ≳ 0.1 M ⊙. Our observations cover the 1.33 mm continuum and several CO J = 2–1 lines: out of 92 sources, we detect 37 in the millimeter continuum and 6 in 12CO, 3 in 13CO, and none in C18O. Using the continuum emission to estimate dust mass, we find only 11 disks with M dust ≳ 10 M ⊕, indicating that after only a few Myr of evolution most disks lack sufficient dust to form giant planet cores. Stacking the individually undetected continuum sources limits their average dust mass to 5× lower than that of the faintest detected disk, supporting theoretical models that indicate rapid dissipation once disk clearing begins. Comparing the protoplanetary disk population in σ Orionis to those of other star-forming regions supports the steady decline in average dust mass and the steepening of the M dust– M * relation with age; studying these evolutionary trends can inform the relative importance of different disk processes during key eras of planet formation. External photoevaporation from the central O9 star is influencing disk evolution throughout the region: dust masses clearly decline with decreasing separation from the photoionizing source, and the handful of CO detections exist at projected separations of >1.5 pc. Collectively, our findings indicate that giant planet formation is inherently rare and/or well underway by a few Myr of age.
[en] We present ten young (≲10 Myr) late-K and M dwarf stars observed in K2 Campaign 2 that host protoplanetary disks and exhibit quasi-periodic or aperiodic dimming events. Their optical light curves show ∼10–20 dips in flux over the 80-day observing campaign with durations of ∼0.5–2 days and depths of up to ∼40%. These stars are all members of the ρ Ophiuchus (∼1 Myr) or Upper Scorpius (∼10 Myr) star-forming regions. To investigate the nature of these “dippers” we obtained: optical and near-infrared spectra to determine stellar properties and identify accretion signatures; adaptive optics imaging to search for close companions that could cause optical variations and/or influence disk evolution; and millimeter-wavelength observations to constrain disk dust and gas masses. The spectra reveal Li i absorption and Hα emission consistent with stellar youth (<50 Myr), but also accretion rates spanning those of classical and weak-line T Tauri stars. Infrared excesses are consistent with protoplanetary disks extending to within ∼10 stellar radii in most cases; however, the sub-millimeter observations imply disk masses that are an order of magnitude below those of typical protoplanetary disks. We find a positive correlation between dip depth and WISE-2 (Wide-field Infrared Survey Explorer-2) excess, which we interpret as evidence that the dipper phenomenon is related to occulting structures in the inner disk, although this is difficult to reconcile with the weakly accreting aperiodic dippers. We consider three mechanisms to explain the dipper phenomenon: inner disk warps near the co-rotation radius related to accretion; vortices at the inner disk edge produced by the Rossby Wave Instability; and clumps of circumstellar material related to planetesimal formation
[en] We present high-resolution (R ∼ 100,000) L-band spectroscopy of 11 Herbig AeBe stars with circumstellar disks. The observations were obtained with the VLT/CRIRES to detect hot water and hydroxyl radical emission lines previously detected in disks around T Tauri stars. OH emission lines are detected toward four disks. The OH 2Π3/2 P4.5 (1+,1-) doublet is spectrally resolved as well as the velocity profile of each component of the doublet. Its characteristic double-peak profile demonstrates that the gas is in Keplerian rotation and points to an emitting region extending out to ∼15-30 AU. The OH emission correlates with disk geometry as it is mostly detected toward flaring disks. None of the Herbig stars analyzed here show evidence of hot water vapor at a sensitivity similar to that of the OH lines. The non-detection of hot water vapor emission indicates that the atmospheres of disks around Herbig AeBe stars are depleted of water molecules. Assuming LTE and optically thin emission we derive a lower limit to the OH/H2O column density ratio >1-25 in contrast to T Tauri disks for which the column density ratio is 0.3-0.4.