Context. Hydrodynamical simulations of planet-disk interactions suggest that planets may be responsible for a number of the substructures frequently observed in disks in both scattered light and... Show moreContext. Hydrodynamical simulations of planet-disk interactions suggest that planets may be responsible for a number of the substructures frequently observed in disks in both scattered light and dust thermal emission. Despite the ubiquity of these features, direct evidence of planets embedded in disks and of the specific interaction features like spiral arms within planetary gaps are still rare.Aims. In this study we discuss recent observational results in the context of hydrodynamical simulations in order to infer the properties of a putative embedded planet in the cavity of a transition disk.Methods. We imaged the transition disk SR 21 in H-band in scattered light with SPHERE/IRDIS and in thermal dust emission with ALMA band 3 (3 mm) observations at a spatial resolution of 0.1 ''. We combine these datasets with existing Band 9 (430 mu m) and Band 7 (870 mu m) ALMA continuum data.Results. The Band 3 continuum data reveals a large cavity and a bright ring peaking at 53 au strongly suggestive of dust trapping. The ring shows a pronounced azimuthal asymmetry, with a bright region in the northwest that we interpret as a dust overdensity. A similarly asymmetric ring is revealed at the same location in polarized scattered light, in addition to a set of bright spirals inside the millimeter cavity and a fainter spiral bridging the gap to the outer ring. These features are consistent with a number of previous hydrodynamical models of planet-disk interactions, and suggest the presence of a similar to 1 M-Jup planet at 44 au and PA = 11 deg. This makes SR21 the first disk showing spiral arms inside the millimeter cavity, and the first disk for which the location of a putative planet can be precisely inferred.Conclusions. The main features of SR 21 in both scattered light and thermal emission are consistent with hydrodynamical predictions of planet-disk interactions. With the location of a possible planet being well constrained by observations, it is an ideal candidate for follow-up observations to search for direct evidence of a planetary companion still embedded in its disk. Show less
Muro-Arena, G.A.; Ginski, C.; Dominik, C.; Benisty, M.; Pinilla, P.; Bohn, A.J.; ... ; Rabou, P. 2020
Context. Shadows in scattered light images of protoplanetary disks are a common feature and support the presence of warps or misalignments between disk regions. These warps are possibly caused by... Show moreContext. Shadows in scattered light images of protoplanetary disks are a common feature and support the presence of warps or misalignments between disk regions. These warps are possibly caused by an inclined (sub-)stellar companion embedded in the disk.Aims. We aim to study the morphology of the protoplanetary disk around the Herbig Ae star HD 139614 based on the first scattered light observations of this disk, which we model with the radiative transfer code MCMax3D.Methods. We obtained J- and H-band observations that show strong azimuthal asymmetries in polarized scattered light with VLT/SPHERE. In the outer disk, beyond similar to 30 au, a broad shadow spans a range of similar to 240 deg in position angle, in the east. A bright ring at similar to 16 au also shows an azimuthally asymmetric brightness, with the faintest side roughly coincidental with the brightest region of the outer disk. Additionally, two arcs are detected at similar to 34 and similar to 50 au. We created a simple four-zone approximation to a warped disk model of HD 139614 in order to qualitatively reproduce these features. The location and misalignment of the disk components were constrained from the shape and location of the shadows they cast.Results. We find that the shadow on the outer disk covers a range of position angles too wide to be explained by a single inner misaligned component. Our model requires a minimum of two separate misaligned zones - or a continuously warped region - to cast this broad shadow on the outer disk. A small misalignment of similar to 4 degrees between adjacent components can reproduce most of the observed shadow features.Conclusions. Multiple misaligned disk zones, potentially mimicking a warp, can explain the observed broad shadows in the HD 139614 disk. A planetary mass companion in the disk, located on an inclined orbit, could be responsible for such a feature and for the dust-depleted gap responsible for a dip in the SED. Show less
Snellen, I.A.G.; Albrecht, S.; Anglada-Escude, G.; Baraffe, I.; Baudoz, P.; Benz, W.; ... ; Visser, P. de 2019
In this white paper, we recommend the European Space Agency plays a proactive role in developing a global collaborative effort to construct a large high-contrast imaging space telescope, e.g. as... Show moreIn this white paper, we recommend the European Space Agency plays a proactive role in developing a global collaborative effort to construct a large high-contrast imaging space telescope, e.g. as currently under study by NASA. Such a mission will be needed to characterize a sizable sample of temperate Earth-like planets in the habitable zones of nearby Sun-like stars and to search for extraterrestrial biological activity. We provide an overview of relevant European expertise, and advocate ESA to start a technology development program towards detecting life outside the Solar system. Show less
Exoplanet science is one of the most thriving fields of modern astrophysics. A major goal is the atmospheric characterization of dozens of small, terrestrial exoplanets in order to search for... Show moreExoplanet science is one of the most thriving fields of modern astrophysics. A major goal is the atmospheric characterization of dozens of small, terrestrial exoplanets in order to search for signatures in their atmospheres that indicate biological activity, assess their ability to provide conditions for life as we know it, and investigate their expected atmospheric diversity. None of the currently adopted projects or missions, from ground or in space, can address these goals. In this White Paper we argue that a large space-based mission designed to detect and investigate thermal emission spectra of terrestrial exoplanets in the MIR wavelength range provides unique scientific potential to address these goals and surpasses the capabilities of other approaches. While NASA might be focusing on large missions that aim to detect terrestrial planets in reflected light, ESA has the opportunity to take leadership and spearhead the development of a large MIR exoplanet mission within the scope of the "Voyage 2050" long-term plan establishing Europe at the forefront of exoplanet science for decades to come. Given the ambitious science goals of such a mission, additional international partners might be interested in participating and contributing to a roadmap that, in the long run, leads to a successful implementation. A new, dedicated development program funded by ESA to help reduce development and implementation cost and further push some of the required key technologies would be a first important step in this direction. Ultimately, a large MIR exoplanet imaging mission will be needed to help answer one of mankind's most fundamental questions: "How unique is our Earth?" Show less
Hifinger, M.; Ramiro, S.; Putrik, P.; Eijk-Hustings, Y. van; Woolf, A.; Smolen, J.S.; ... ; Boonen, A. 2018
On 15 December 2006 Marloes Janson (Zentrum Moderner Orient, Berlin) and Dorothea Schulz (Indiana University) convened a workshop titled “Piety, Responsibility, Subjectivity: Reconfigurations of... Show moreOn 15 December 2006 Marloes Janson (Zentrum Moderner Orient, Berlin) and Dorothea Schulz (Indiana University) convened a workshop titled “Piety, Responsibility, Subjectivity: Reconfigurations of the Moral Economy of Gender Relations in Contemporary Muslim Africa” at the Snoeck Hurgronje Huis, Leiden. The workshop and the subsequent public event were sponsored by ISIM, in cooperation with the Knowledge Centre Religion and Development and ZemZem, Journal for the Middle East, North Africa, and Islam. Show less
Over the years, the Tablighi Jamaat has expanded into what is probably indeed the largest Islamic movement of contemporary times. Despite its magnitude, its impact in sub-Saharan Africa has been... Show moreOver the years, the Tablighi Jamaat has expanded into what is probably indeed the largest Islamic movement of contemporary times. Despite its magnitude, its impact in sub-Saharan Africa has been largely neglected. This article, based on ethnographic field research, focuses on the Jamaat in The Gambia (West Africa) where particularly youth convert to Tablighi ideology, in what could be seen as a form of rebellion against the authority of their elders. In the process, established religious and social values are redefined. Show less
Gambian griottes, or female bards, are in a serious predicament. Islamic ethics prescribe that women should behave in a modest way, while conversely the griottes' very profession implies that they... Show moreGambian griottes, or female bards, are in a serious predicament. Islamic ethics prescribe that women should behave in a modest way, while conversely the griottes' very profession implies that they stand out by their behaviour and the way they dress. How do these women reconcile their identity as female performers with Islamic values? The Gambia is an interesting setting in which to explore this question because of its long history with Islam. There was even talk that President Jammeh wanted to impose the sharica in this small West African country. Show less
