Ammonia Emission in Various Star-forming Environments: A Pilot Study of Planck Galactic Cold Clumps

The Planck Catalogue of Galactic Cold Clumps provides an all-sky sample of potential star-forming regions based on the submillimeter emission of their dust content. Around 1000 of these Planck objects were mapped with the James Clerk Maxwell telescope in the submillimeter range during the SCOPE survey, identifying prestellar and protostellar dense clumps inside them. We used the Effelsberg 100 m telescope to observe the emission lines of the NH3 inversion transitions toward a sample of 97 dense objects in varying environments in order to assess the physical parameters of their gas content. We derive their temperature, density, and velocity dispersion, correlating the resulting parameters with the environmental and evolutionary characteristics of the targets and with regard to their distance and physical size. We examine the dependence of physical parameters on distance and Galactic position and compare the gas-based and dust-continuum-based temperatures and densities. Together with the presence of maser emission and higher inversion transitions of ammonia, we may differentiate between certain groups of targets, e.g., filamentary, protostellar clumps, and high-latitude, core-sized, starless sources.

‘I’m your automatic colour’ La colorazione automatica delle immagini in antropologia

Colour photographs now represent almost all the images produced with the new reality capture tools, mobile phones, which in 2020 ‘took’ 90% of all photos of that year. Black and white is relegated to artistic expression, even newspapers have converted to colour for some years. In the history of photography, although research on colour is attempted from the early stages, it is necessary to wait until 1861 with the experiences of James Clerk Maxwell who created a stable colour image. However, it is from the fifties of the twentieth century that the use of colour becomes ‘popular’ even in a more aesthetic dimension than an objective reproduction of reality. Part of the ethnographic, anthropological, archaeological and field research, on the other hand still makes use of consolidated and inexpensive black and white for a long time. On these images largely available online and open source you can conduct automatic colouring experiences. The procedure, managed with artificial intelligence algorithms with deep learning processes, is always more widely used with free applications and allows to obtain qualitatively more and more relevant results, even if some critical analysis is still necessary. This article presents the state of the art to 2021 of automatic colouring, with the comparison between algorithms developed since 2016 and showing with experimental examples both the possibilities of rendering and even the critical issues that emerged with the application in anthropological photographs, with the aim of extracting information that is not very evident in the originals in black and white.

A demon of a puzzle

In 1871 James Clerk Maxwell proposed a puzzle now known as “Maxwell’s Demon” in his book Theory of Heat. We celebrate its 150th anniversary in this thermodynamics-themed cryptic crossword compiled by Ian Randall.

The JCMT BISTRO Survey: Evidence for Pinched Magnetic Fields in Quiescent Filaments of NGC 1333

We investigate the internal 3D magnetic structure of dense interstellar filaments within NGC 1333 using polarization data at 850 μm from the B-fields In STar-forming Region Observations survey at the James Clerk Maxwell Telescope. Theoretical models predict that the magnetic field lines in a filament will tend to be dragged radially inward (i.e., pinched) toward the central axis due to the filament’s self-gravity. We study the cross-sectional profiles of the total intensity (I) and polarized intensity (PI) of dust emission in four segments of filaments unaffected by local star formation that are expected to retain a pristine magnetic field structure. We find that the filaments’ FWHMs in PI are not the same as those in I, with two segments being appreciably narrower in PI (FWHM ratio ≃0.7–0.8) and one segment being wider (FWHM ratio ≃1.3). The filament profiles of the polarization fraction (P) do not show a minimum at the spine of the filament, which is not in line with an anticorrelation between P and I normally seen in molecular clouds and protostellar cores. Dust grain alignment variation with density cannot reproduce the observed P distribution. We demonstrate numerically that the I and PI cross-sectional profiles of filaments in magnetohydrostatic equilibrium will have differing relative widths depending on the viewing angle. The observed variations of FWHM ratios in NGC 1333 are therefore consistent with models of pinched magnetic field structures inside filaments, especially if they are magnetically near-critical or supercritical.

Editorial

In 1969, T.F. Torrance published Space, Time, and Incarnation. This brought together recent work in philosophy and science on the nature of space and time in order to explore the implications for theology. Torrance’s theology engaged with the scientific thought of Albert Einstein and James Clerk Maxwell, as well as the temporal logic of A.N. Prior. The influence of this work on subsequent Christian theology cannot be overstated. Yet, a great deal has changed since 1969, and most contemporary discussions in systematic theology show little awareness of recent advancements in the metaphysics of time and space.

XXIII Semana de la Enseñanza de La Física. 200 años del Electromagnetismo.

Evento desarrollado del 23 al 27 de noviembre de 2020, en el Proyecto Curricular de Licenciatura en Física, de la Facultad de Ciencias y Educación. Universidad Distrital Francisco José de Caldas, Bogotá, Colombia. A comienzos de 1820 el físico danés Hans Christian Ørsted descubrió experimentalmente la relación existente entre el magnetismo y la electricidad, publicando su descubrimiento en un corto artículo titulado: Experimenta circa effectum conflictus electrici in acum magneticam. Dando origen al electromagnetismo y a una serie de trabajos de diversos científicos, que culminaron con la unificación, lograda por James Clerk Maxwell, de la electricidad, el magnetismo y la luz como diversas manifestaciones de un mismo fenómeno físico. Trabajo que fue publicado bajo el título de: A Dynamical Theory of the Electromagnetic Field. Se cumplen así 200 años de un descubrimiento que cambiaría la concepción física de la época y potenciaría un desarrollo que aún hoy día continúa.

The Confined Atom: James Clerk Maxwell on the Fundamental Particles and the Limits of Scientific Knowledge

This paper distinguishes in Maxwell’s thought between “atomic molecules” and “ultimate atoms,” and arrives at a set of properties that characterize each type of atom. It concludes that Maxwell is a mathematical atomist, an approach that entails the notion that although it is impossible to observe the ultimate atoms as free particles, we can nevertheless study them as mathematical observables, on the caveat that mathematical formalism remains tied to phenomenalism and to theoretical interpretations of such phenomena as, for example, mass and force variations, gravitational pull, gas diffusion and viscosity, and heat conduction.