We investigate galactic-scale outflows in the redshift range 0.71 ≤ z ≤ 1.63, using 413 K-band selected galaxies observed in the spectroscopic follow-up of the UKIDSS Ultra-Deep Survey (UDSz). The ...galaxies have an average stellar mass of ∼109.5 M and span a wide range in rest-frame colours, representing typical star-forming galaxies at this epoch. We stack the spectra by various galaxy properties, including stellar mass, O ii equivalent width, star formation rate, specific star formation rate and rest-frame spectral indices. We find that outflows are present in virtually all spectral stacks, with velocities ranging from 100 to 1000 km s−1, indicating that large-scale outflowing winds are a common property at these redshifts. The highest velocity outflows (>500 km s−1) are found in galaxies with the highest stellar masses and the youngest stellar populations. Our findings suggest that high-velocity galactic outflows are mostly driven by star-forming processes rather than active galactic nuclei, with implied mass outflow rates comparable to the rates of star formation. Such behaviour is consistent with models required to reproduce the high-redshift mass-metallicity relation.
We use the United Kingdom Infrared Telescope Deep Sky Survey (UKIDSS) Ultra Deep Survey (UDS), the deepest degree-scale near-infrared survey to date, to investigate the clustering of star-forming and ...passive galaxies to z ∼ 3.5. Our new measurements include the first determination of the clustering for passive galaxies at z > 2, which we achieve using a cross-correlation technique. We find that passive galaxies are the most strongly clustered, typically hosted by massive dark matter haloes with M
halo > 5 × 1012 M irrespective of redshift or stellar mass. Our findings are consistent with models in which a critical halo mass determines the transition from star-forming to passive galaxies. Star-forming galaxies show no strong correlation between stellar mass and halo mass, but passive galaxies show evidence for an anticorrelation; low-mass passive galaxies appear, on average, to be located in the most massive haloes. These results can be understood if the termination of star formation is most efficient for galaxies of low stellar mass in very dense environments.
Purpose
Due to the electron return effect (ERE) during magnetic resonance imaging guided radiotherapy (MRIgRT), rectal gas during pelvic treatments can result in hot spots of over‐dosage in the ...rectal wall. Determining the clinical impact of this effect on rectal toxicity requires estimation of the amount and mobility (and stability) of rectal gas during treatment. We therefore investigated the amount of rectal gas and local inter‐ and intra‐fractional changes of rectal gas in pelvic cancer patients.
Methods
To estimate the volume of gas present at treatment planning, the rectal gas contents in the planning computed tomography (CT) scans of 124 bladder, 70 cervical and 2180 prostate cancer patients were calculated.
To estimate inter‐ and intra‐fractional variations in rectal gas, 174 and 131 T2‐w MRIs for six cervical and eleven bladder cancer patients were used. These scans were acquired during four scan‐sessions (~20–25 min each) at various time‐points. Additionally, 258 T2‐w MRIs of the first five prostate cancer patients treated using MRIgRT at our center, acquired during each fraction, were analyzed. Rectums were delineated on all scans.
The area of gas within the rectum delineations was identified on each MRI slice using thresholding techniques. The area of gas on each slice of the rectum was used to calculate the inter‐ and intra‐fractional group mean, systematic and random variations along the length of the rectum.
The cumulative dose perturbation as a result of the gas was estimated. Two approaches were explored: accounting or not accounting for the gas at the start of the scan‐session.
Results
Intra‐fractional variations in rectal gas are small compared to the absolute volume of rectal gas detected for all patient groups. That is, rectal gas is likely to remain stable for periods of 20–25 min. Larger volumes of gas and larger variations in gas volume were observed in bladder cancer patients compared with cervical and prostate cancer patients.
For all patients, local cumulative dose perturbations per beam over an entire treatment in the order of 60 % were estimated when gas had not been accounted for in the daily adaption. The calculated dose perturbation over the whole treatment was dramatically reduced in all patients when accounting for the gas in the daily set‐up image.
Conclusion
Rectal gas in pelvic cancer patients is likely to remain stable over the course of an MRIgRT fraction, and also likely to reappear in the same location in multiple fractions, and can therefore result in clinically relevant over‐dosage in the rectal wall. The over‐dosage is reduced when accounting for gas in the daily adaption.
Purpose
Dose deposition around unplanned air cavities during magnetic resonance‐guided radiotherapy (MRgRT) is influenced by the electron return effect (ERE). This is clinically relevant for gas ...forming close to or inside organs at risk (OARs) that lie in the path of a single beam, for example, intestinal track during pelvic treatment. This work aims to verify Monte Carlo calculations that predict the dosimetric effects of ERE around air cavities. For this, we use GafChromic EBT3 film inside poly‐methyl methacrylate (PMMA) –air phantoms.
Method
Four PMMA phantoms were produced. Three of the phantoms contained centrally located spherical air cavities (0.5, 3.5, 7.5 cm diameter), and one phantom contained no air. The phantoms were split to sandwich GafChromic EBT3 film in the center. The phantoms were irradiated on an Elekta Unity system using a single 10 × 10 cm2 7‐MV photon beam under the influence of a 1.5‐T transverse magnetic field. The measurements were replicated using the Elekta Monaco treatment planning system (TPS). Gamma analysis with pass criteria 3%/3 mm was used to compare the measured and calculated dose distributions. We also consider 3%/2 mm, 2%/3 mm, and 2%/2 mm pass criteria for interest.
Results
The gamma analysis showed that >95% of the points agreed between the TPS‐calculated and measured dose distributions, using 3%/3 mm criteria. The phantom containing the largest air cavity had the lowest agreement, with most of the disagreeing points lying inside the air cavity (dose to air region).
Conclusions
The dose effects due to ERE around spherical air cavities are being calculated in the TPS with sufficient accuracy for clinical use.
We report the results of a comprehensive study of the relationship between galaxy size, stellar mass and specific star formation rate (sSFR) at redshifts 1.3 < z < 1.5. Based on a mass-complete (M
≥ ...6 × 1010 M), spectroscopic sample from the UK Infrared Deep Sky Survey (UKIDSS) Ultradeep Survey, with accurate stellar-mass measurements derived from spectro-photometric fitting, we find that at z 1.4 the location of massive galaxies on the size-mass plane is determined primarily by their sSFR. At this epoch, we find that massive galaxies which are passive (sSFR ≤ 0.1 Gyr−1) follow a tight size-mass relation, with half-light radii a factor of f
g = 2.4 ± 0.2 smaller than their local counterparts. Moreover, amongst the passive sub-sample we find no evidence that the off-set from the local size-mass relation is a function of stellar population age. In contrast, we find that massive star-forming galaxies at this epoch lie closer to the local late-type size-mass relation and are only a factor of f
g = 1.6 ± 0.2 smaller than observed locally. Based on a sub-sample with dynamical-mass estimates, which consists of both passive and star-forming objects, we also derive an independent estimate of f
g = 2.3 ± 0.3 for the typical growth in half-light radius between z 1.4 and the present day. Focusing on the passive sub-sample, we conclude that to produce the necessary evolution predominantly via major mergers would require an unfeasible number of merger events and overpopulate the high-mass end of the local stellar-mass function. In contrast, we find that a scenario in which mass accretion is dominated by minor mergers can comfortably produce the necessary evolution, whereby an increase in stellar mass of only a factor of 2, accompanied by size growth of a factor of 3.5, is required to reconcile the size-mass relation at z 1.4 with that observed locally. Finally, we note that a significant fraction (44 ± 12 per cent) of the passive galaxies in our sample have a disc-like morphology, providing additional evidence that separate physical processes are responsible for the quenching of star formation and morphological transformation in massive galaxies.
We present spectroscopic confirmation of 10 highly luminous (L≥ 2L
★) Lyα emitters (LAEs) in the redshift range 6.01 < z < 6.49 (nine galaxies and one active galactic nucleus), initially drawn from a ...sample of 14 z
phot≥ 6 Lyman-break galaxies (LBGs) selected from an area of 0.25 deg2 within the UK Infrared Deep Sky Survey (UKIDSS) Ultra-Deep Survey (UDS). Overall, our high rate of spectroscopic confirmation (≥71 per cent) and low rate of contamination provides a strong vindication of the photometric redshift analysis used to define the original sample. By considering star formation rate estimates based on the Lyα and ultraviolet continuum luminosity we conclude that our sample is consistent with a Lyα escape fraction of ≃25 per cent. Moreover, after careful consideration of the potential uncertainties and biases, we find that 40-50 per cent of our sample of L≥ 2L
★ galaxies at 6.0 < z < 6.5 display strong Lyα emission (rest-frame equivalent width ≥25 Å), a fraction which is a factor of ≃2 higher than previously reported for L≤L
★ galaxies at z≃ 6. Our results suggest that, as the epoch of reionization is approached, it is plausible that the LAE fraction amongst luminous (L≥ 2L
★) LBGs shows a similarly sharp increase to that observed in their lower luminosity (L≤L
★) counterparts.
•MR based deep learning auto-contouring is effective for head and neck OAR delineation.•A model created on diagnostic MR scans works well on similar scans and on RTP scans but needs optimisation on ...MR Linac sequences.•Performance of the MR based model is superior to the CT based model on respective radiotherapy planning scans.
Auto contouring models help consistently define volumes and reduce clinical workload. This study aimed to evaluate the cross acquisition of a Magnetic Resonance (MR) deep learning auto contouring model for organ at risk (OAR) delineation in head and neck radiotherapy.
Two auto contouring models were evaluated using deep learning contouring expert (DLCExpert) for OAR delineation: a CT model (modelCT) and an MR model (modelMRI). Models were trained to generate auto contours for the bilateral parotid glands and submandibular glands. Auto-contours for modelMRI were trained on diagnostic images and tested on 10 diagnostic, 10 MR radiotherapy planning (RTP), eight MR-Linac (MRL) scans and, by modelCT, on 10 CT planning scans. Goodness of fit scores, dice similarity coefficient (DSC) and distance to agreement (DTA) were calculated for comparison.
ModelMRI contours improved the mean DSC and DTA compared with manual contours for the bilateral parotid glands and submandibular glands on the diagnostic and RTP MRs compared with the MRL sequence. There were statistically significant differences seen for modelMRI compared to modelCT for the left parotid (mean DTA 2.3 v 2.8 mm), right parotid (mean DTA 1.9 v 2.7 mm), left submandibular gland (mean DTA 2.2 v 2.4 mm) and right submandibular gland (mean DTA 1.6 v 3.2 mm).
A deep learning MR auto-contouring model shows promise for OAR auto-contouring with statistically improved performance vs a CT based model. Performance is affected by the method of MR acquisition and further work is needed to improve its use with MRL images.
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