On the Radio Detectability of Circumplanetary Discs

Discs around young planets, so-called circumplanetary discs (CPDs), are essential for planet growth, satellite formation, and planet detection. We study the millimetre and centimetre emission from accreting CPDs by using the simple α disc model. We find that it is easier to detect CPDs at shorter radio wavelengths (e.g. λ ≲ 1 mm). For example, if the system is 140 pc away from us, deep observations (e.g. 5 h) at ALMA Band 7 (0.87 mm) are sensitive to as small as 0.03 lunar mass of dust in CPDs. If the CPD is around a Jupiter mass planet 20 au away from the host star and has a viscosity parameter α ≲ 0.001, ALMA can detect this disc when it accretes faster than 10−10M⊙yr−110−10M⊙yr−1 . ALMA can also detect the \u27minimum mass sub-nebulae\u27 disc if such a disc exists around a young planet in young stellar objects. However, to distinguish the embedded compact CPD from the circumstellar disc material, we should observe circumstellar discs with large gaps/cavities using the highest resolution possible. We also calculate the CPD fluxes at VLA bands, and discuss the possibility of detecting radio emission from jets/winds launched in CPDs. Finally we argue that, if the radial drift of dust particles is considered, the drifting time-scale for millimetre dust in CPDs can be extremely short. It only takes 102–103 yr for CPDs to lose millimetre dust. Thus, for CPDs to be detectable at radio wavelengths, mm-sized dust in CPDs needs to be replenished continuously, or the disc has a significant fraction of micron-sized dust or a high gas surface density so that the particle drifting time-scale is long, or the radial drift is prevented by other means (e.g. pressure traps)

What is hegemony now? Transformations in media, political economy, and cultural studies

The basic theoretical framework of Cultural Studies scholarship was forged in an era of nearly unrivaled corporate media hegemony, with most communities finding a limited number of national and multinational corporations transmitting one-way broadcasts to idle consumers whose only agency was in the act of reading ideologies with or against the grain. Likewise, the dominant political economic model in the North was one of expanding social democracy, leading the many strains of the New Left to operate on the presumption that the political economic system will remain as it was: the state would remain as an organ of control over the economy, making the Gramscian concept of hegemony essential to the overall strategy—and the cultural realm a key target for undermining the current reproduction. It is now an accepted commonplace that emergent technologies have changed the way many of us make, distribute, and consume media. The continued dominance of corporate media hegemony is simultaneously aided and hampered by the tenuous system of national segmentations, streaming service overlap and often unenforceable intellectual property rights. And the neoliberal state has effectively ceded the ideological work of the mass media to competing ideoscapes, often funded by wealthy donors with little interest in a functioning public sphere: as long as they can monetize the property or the platform, its ideological content is irrelevant. In this conjuncture, Cultural Studies must reconsider - and reconstitute - its understanding of how hegemony functions and the role that the (transformed) culture industries play in maintaining it

The Dispersal of Protoplanetary Disks

Protoplanetary disks are the sites of planet formation, and the evolution and eventual dispersal of these disks strongly influences the formation of planetary systems. Disk evolution during the planet-forming epoch is driven by accretion and mass-loss due to winds, and in typical environments photoevaporation by high-energy radiation from the central star is likely to dominate final gas disk dispersal. We present a critical review of current theoretical models, and discuss the observations that are used to test these models and inform our understanding of the underlying physics. We also discuss the role disk dispersal plays in shaping planetary systems, considering its influence on both the process(es) of planet formation and the architectures of planetary systems. We conclude by presenting a schematic picture of protoplanetary disk evolution and dispersal, and discussing prospects for future work.Comment: 23 pages, 6 figures. Refereed review chapter, accepted for publication in Protostars & Planets VI, University of Arizona Press (2014), eds. H.Beuther, C.Dullemond, Th.Henning, R.Klesse