| 11. |
- Hess, K. M., et al.
(author)
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Apertif view of the OH megamaser IRAS 10597+5926: OH 18 cm satellite lines in wide-area H i surveys
- 2021
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 647
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Journal article (peer-reviewed)abstract
- We present the serendipitous detection of the two main OH maser lines at 1667 and 1665 MHz associated with IRAS 10597+5926 at zpdbl = 0.19612 in the untargeted Apertif Wide-area Extragalactic imaging Survey (AWES), and the subsequent measurement of the OH 1612 MHz satellite line in the same source. With a total OH luminosity of log(L/Lpdbl ) = 3.90 ± 0.03, IRAS 10597+5926 is the fourth brightest OH megamaser (OHM) known. We measure a lower limit for the 1667/1612 ratio of R1612 > 45.9, which is the highest limiting ratio measured for the 1612 MHz OH satellite line to date. OH satellite line measurements provide a potentially valuable constraint by which to compare detailed models of OH maser pumping mechanisms. Optical imaging shows that the galaxy is likely a late-stage merger. Based on published infrared and far ultraviolet fluxes, we find that the galaxy is an ultra-luminous infrared galaxy (ULIRG) with log(LTIR/Lpdbl) = 12.24 that is undergoing a starburst with an estimated star formation rate of 179 ± 40 Mpdbl yr-1. These host galaxy properties are consistent with the physical conditions responsible for very bright OHM emission. Finally, we provide an update on the predicted number of OH masers that may be found in AWES and estimate the total number of OH masers that will be detected in each of the individual main and satellite OH 18 cm lines.
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| 12. |
- Adebahr, B., et al.
(author)
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The Apertif science verification campaign: Characteristics of polarised radio sources
- 2022
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 663
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Journal article (peer-reviewed)abstract
- Context. The characteristics of the polarised radio sky are a key ingredient in constraining evolutionary models of magnetic fields in the Universe and their role in feedback processes. The origin of the polarised emission and the characteristics of the intergalactic medium on the line of sight can be investigated using large samples of polarised sources. Ancillary infrared (IR) and optical data can be used to study the nature of the emitting objects. Aims. We analyse five early science datasets from the APERture Tile in Focus (Apertif) phased array feed system to verify the polarisation capabilities of Apertif in view of future larger data releases. We aim to characterise the source population of the polarised sky in the L-Band using polarised source information in combination with IR and optical data. Methods. We use automatic routines to generate full field-of-view Q- and U-cubes and perform rotation measure (RM)-Synthesis, source finding, and cross-matching with published radio, optical, and IR data to generate polarised source catalogues. All sources were inspected individually by eye for verification of their IR and optical counterparts. Spectral energy distribution (SED)-fitting routines were used to determine photometric redshifts, star-formation rates, and galaxy masses. IR colour information was used to classify sources as active galactic nuclei (AGN) or star-forming-dominated and early- or late-type. Results. We surveyed an area of 56 deg2 and detected 1357 polarised source components in 1170 sources. The fraction of polarised sources is 10.57% with a median fractional polarisation of 4.70 ± 0.14%. We confirmed the reliability of the Apertif measurements by comparing them with polarised cross-identified NVSS sources. Average RMs of the individual fields lie within the error of the best Milky Way foreground measurements. All of our polarised sources were found to be dominated by AGN activity in the radio regime with most of them being radio-loud (79%) and of the Fanaroff-Riley (FR)II class (87%). The host galaxies of our polarised source sample are dominated by intermediate disc and star-forming disc galaxies. The contribution of star formation to the radio emission is on the order of a few percent for 10% of the polarised sources while for 90% it is completely dominated by the AGN. We do not see any change in fractional polarisation for different star-formation rates of the AGN host galaxies. Conclusions. The Apertif system is suitable for large-area high-sensitivity polarised sky surveys. The data products of the polarisation analysis pipeline can be used to investigate the Milky Way magnetic field on projected scales of several arcminutes as well as the origin of the polarised emission in AGN and the properties of their host galaxies.
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| 13. |
- Kukreti, P., et al.
(author)
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Seeing the forest and the trees: A radio investigation of the ULIRG Mrk 273
- 2022
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 664
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Journal article (peer-reviewed)abstract
- Galaxy mergers have been observed to trigger nuclear activity by feeding gas to the central supermassive black hole. One such class of objects are Ultra Luminous InfraRed Galaxies (ULIRGs), which are mostly late stage major mergers of gas-rich galaxies. Recently, large-scale (100 kpc) radio continuum emission has been detected in a select number of ULIRGs, all of which also harbour powerful Active Galactic Nuclei (AGN). This hints at the presence of large-scale radio emission being evidence for nuclear activity. Exploring the origin of this radio emission and its link to nuclear activity requires high sensitivity multi-frequency data. We present such an analysis of the ULIRG Mrk 273. Using the International LOFAR telescope (ILT), we detected spectacular large-scale arcs in this system. This detection includes, for the first time, a giant 190 kpc arc in the north. We propose these arcs are fuelled by a low power radio AGN triggered by the merger. We also identified a bright 45 kpc radio ridge, which is likely related to the ionised gas nebula in that region. We combined this with high sensitivity data from APERture Tile In Focus (Apertif) and archival data from the Very Large Array (VLA) to explore the spectral properties. The ILT simultaneously allowed us to probe the nucleus at a resolution of 0.3, where we detected three components, and, for the first time, diffuse emission around these components. Combining this with archival high frequency VLA images of the nucleus allowed us to detect absorption in one component, and a steep spectrum radio AGN in another. We then extrapolate from this case study to the importance of investigating the presence of radio emission in more ULIRGs and what it can tell us about the link between mergers and the presence of radio activity.
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| 14. |
- Kutkin, A. M., et al.
(author)
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Apertif 1.4 GHz continuum observations of the Boötes field and their combined view with LOFAR
- 2023
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In: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 676
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Journal article (peer-reviewed)abstract
- We present a new image of a 26.5 square degrees region in the Boötes constellation obtained at 1.4 GHz using the Aperture Tile in Focus (Apertif) system on the Westerbork Synthesis Radio Telescope. We use a newly developed processing pipeline that includes direction-dependent self-calibration, which provides a significant improvement in the quality of the images compared to those released as part of the Apertif first data release. For the Boötes region, we mosaicked 187 Apertif images and extracted a source catalog. The mosaic image has an angular resolution of 27 × 11.5″ and a median background noise of 40 μJy beam-1. The catalog has 8994 sources and is complete down to the 0.3 mJy level. We combined the Apertif image with LOFAR images of the Boötes field at 54 and 150 MHz to study the spectral properties of the sources. We find a spectral flattening toward sources with a low flux density. Using the spectral index limits from Apertif nondetections, we derive that up to 9% of the sources have ultrasteep spectra with a slope below -1.2. A steepening of the spectral index with increasing redshift is also seen in the data, which shows a different dependence for the low-and high-frequency spectral index. The explanation probably is that a population of sources has concave radio spectra with a turnover frequency of about the LOFAR band. Additionally, we discuss cases of individual extended sources with an interesting resolved spectral structure. With the improved pipeline, we aim to continue to process data from the Apertif wide-area surveys and release the improved 1.4-GHz images of several well-known fields.
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| 15. |
- Pastor-Marazuela, Ines, et al.
(author)
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Chromatic periodic activity down to 120 megahertz in a fast radio burst
- 2021
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In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 596:7873, s. 505-508
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Journal article (peer-reviewed)abstract
- Fast radio bursts (FRBs) are extragalactic astrophysical transients(1) whose brightness requires emitters that are highly energetic yet compact enough to produce the short, millisecond-duration bursts. FRBs have thus far been detected at frequencies from 8 gigahertz (ref. (2)) down to 300 megahertz (ref. (3)), but lower-frequency emission has remained elusive. Some FRBs repeat(4-6), and one of the most frequently detected, FRB 20180916B(7), has a periodicity cycle of 16.35 days (ref. (8)). Using simultaneous radio data spanning a wide range of wavelengths (a factor of more than 10), here we show that FRB 20180916B emits down to 120 megahertz, and that its activity window is frequency dependent (that is, chromatic). The window is both narrower and earlier at higher frequencies. Binary wind interaction models predict a wider window at higher frequencies, the opposite of our observations. Our full-cycle coverage shows that the 16.3-day periodicity is not aliased. We establish that low-frequency FRB emission can escape the local medium. For bursts of the same fluence, FRB 20180916B is more active below 200 megahertz than at 1.4 gigahertz. Combining our results with previous upper limits on the all-sky FRB rate at 150 megahertz, we find there are 3-450 FRBs in the sky per day above 50 Jy ms. Our chromatic results strongly disfavour scenarios in which absorption from strong stellar winds causes FRB periodicity. We demonstrate that some FRBs are found in 'clean' environments that do not absorb or scatter low-frequency radiation. The fast radio burst FRB 20180916B repeats with a periodicity of 16 days, and is now found to emit down to a frequency of 120 MHz, much lower than previously observed.
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| 16. |
- Anderson, Christopher J., et al.
(author)
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Response to Comment on "Estimating the reproducibility of psychological science"
- 2016
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In: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 351:6277
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Journal article (other academic/artistic)abstract
- Gilbert et al. conclude that evidence from the Open Science Collaboration's Reproducibility Project: Psychology indicates high reproducibility, given the study methodology. Their very optimistic assessment is limited by statistical misconceptions and by causal inferences from selectively interpreted, correlational data. Using the Reproducibility Project: Psychology data, both optimistic and pessimistic conclusions about reproducibility are possible, and neither are yet warranted.
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| 17. |
- Smeele, Hansje P., et al.
(author)
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Breast reconstruction timing and modality in context : A cross-sectional study in Uppsala, Maastricht, and Rome
- 2023
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In: European journal of plastic surgery. - : Springer. - 0930-343X .- 1435-0130. ; 47:1
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Journal article (peer-reviewed)abstract
- BackgroundWith the development and refinement of techniques most mastectomy patients nowadays are candidates for breast reconstruction. No one surgical technique fits all, however. Treatment choices are driven by patient characteristics and preferences, alongside policy and operational factors. These, in turn, might be expected to differ on several levels of aggregation, for example, countries, regions, and hospitals. The aim of this study was to compare choices for breast reconstruction timing and modality in Uppsala (Sweden), Maastricht (the Netherlands), and Rome (Italy).MethodsIn this cross-sectional study, patients presenting for first-time post-mastectomy breast reconstruction in three teaching hospitals were included. The primary study outcomes were breast reconstruction timing and modality. Covariables were body habitus (i.e., body mass index, waist circumference, and mastectomy weight), health-related quality of life assessed with the BREAST-Q Reconstruction module, patient preferences assessed with a self-constructed questionnaire, and shared decision making assessed with the CollaboRATE questionnaire. Statistical tests were used to compare data across study sites.ResultsSixty-six participants were included. The most common choices for breast reconstruction timing and modality were delayed DIEP flaps in Uppsala (53%), immediate DIEP flaps in Maastricht (44%), and immediate prepectoral implants in Rome (92%). Participants in Rome were much slenderer than participants in Uppsala and Maastricht (mean body mass index 21.6, 26.2, and 26.3 kg/m2, respectively; p < 0.05). Participants in Uppsala and Maastricht highly valued material used for the reconstruction; participants in Rome were significantly more concerned with complications, scars, and recovery duration associated with the reconstruction.ConclusionsThis study shows large differences in choices for breast reconstruction timing and modality in Uppsala, Maastricht, and Rome. Possible reasons for the observed variation include differences in patient characteristics, patient preferences, reconstructive techniques available, and reimbursement.Level of evidenceLevel IV, Therapeutic study.
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| 18. |
- Noorishad, P., et al.
(author)
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Redundancy calibration of phased-array stations
- 2012
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 545, s. A108 (article no.)-
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Journal article (peer-reviewed)abstract
- Aims. We assess the benefits and limitations of using the redundant visibility information in regular phased-array systems to improve the quality of the calibration. Methods. Regular arrays offer the possibility of using redundant visibility information to constrain the calibration of the array independently of a sky model and a beam model of the station elements. This requires a regular arrangement of the configuration of array elements and identical beam patterns. Results. We revised a previously developed calibration method for phased-array stations using the redundant visibility information in the system and applied it successfully to a LOFAR station. The performance and limitations of the method were demonstrated by comparing its application to real and simulated data. The main limitation is the mutual coupling between the station elements, which leads to non-identical beams and stronger baseline-dependent noise. Comparing the variance in the estimated complex gains with the Cramer-Rao Bound indicates that redundancy is a stable and optimum method for calibrating the complex gains of the system. Conclusions. Our study shows that the use of the redundant visibility does improve the quality of the calibration in phased-array systems. In addition, it provides a powerful tool obtaining system diagnostics. Our results demonstrate that designing redundancy in both the station layout and the array configuration of future aperture arrays is strongly recommended. This is particularly true in the case of the Square Kilometre Array (SKA) with its dynamic range requirement that surpasses any existing array by an order of magnitude.
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| 19. |
- Enajat, Morteza, et al.
(author)
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The deep inferior epigastric artery perforator flap for autologous reconstruction of large partial mastectomy defects
- 2011
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In: Microsurgery. - : Wiley. - 0738-1085 .- 1098-2752. ; 31:1, s. 12-17
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Journal article (peer-reviewed)abstract
- Background: Breast conservation surgery in the treatment of early stage breast cancer has become increasingly utilized as a means to avoiding mastectomy. While partial mastectomy defects (PMDs) may often be cosmetically acceptable, some cases warrant consideration of reconstructive options, and while several reconstructive options have been described in this role, a series of deep inferior epigastric perforator (DIEP) flaps has not been reported to date. Methods: A cohort of 18 patients undergoing PMD reconstruction with a DIEP flap were included. Patient-specific data, operation details, cosmetic results, and complication rates were assessed. Oncologic outcomes, in particular recurrence rates, were also evaluated. Results: In our series there were no cases of partial or total flap necrosis, and overall complications were low. There were two cases of wound infection (both had undergone radiotherapy), managed conservatively, and one case of reoperation due to hematoma. There were no cancer recurrences or effect on oncologic management. Cosmetic outcome was rated as high by both patients and surgeon. The results were thus comparable with other reconstructive options. Conclusion: Although autologous reconstruction has an established complication rate, our results suggest that the DIEP flap may be of considerable value for delayed reconstruction of selected larger partial mastectomy defects.
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