HST images and properties of the most distant radio galaxies

We present Hubble Space Telescope images of 11 high redshift radio galaxies (between $z=2.3$ and $z=3.6$). The galaxies were observed with the WFPC2 camera in a broad band filter (F606W or F707W, roughly equivalent to V or R-band), for 2 orbits each. We find that on the scale of the HST observations there is a wide variety of morphological structures of the hosting galaxies: most objects have a clumpy, irregular appearance, consisting of a bright nucleus and a number of smaller components, suggestive of merging systems. Some observed structures could be due (at least partly) to the presence of dust distributed through the galaxies. The UV continuum emission is generally elongated and aligned with the axis of the radio sources, however the characteristics of the ``alignment effect'' differ from case to case, suggesting that the phenomenon cannot be explained by a single physical mechanism. We compare the properties of our radio galaxies with those of the UV dropout galaxies and conclude that (i) the most massive radio galaxies may well evolve from an aggregate of UV dropout galaxies and (ii) high redshift radio galaxies probably evolve into present day brightest cluster galaxies.Comment: 22 pages, 30 figures, accepted by A&

A moving target : matching graduate education with available careers for ocean scientists

Author Posting. © The Oceanography Society, 2016. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 29, no. 1 (2016): 22–30, doi:10.5670/oceanog.2016.05.The objective of this paper is to look at past assessments and available data to examine the match (or mismatch) between university curricula and programs available to graduate students in the ocean sciences and the career possibilities available to those students. We conclude there is a need for fundamental change in how we educate graduate students in the ocean sciences. The change should accommodate the interests of students as well as the needs of a changing society; the change should not be constrained by the traditions or resource challenges of the graduate institutions themselves. The limited data we have been able to obtain from schools and employers are consistent with this view: desirable careers for ocean scientists are moving rapidly toward interdisciplinary, collaborative, societally relevant activities, away from traditional academic-research/professorial jobs, but the training available to the students is not keeping pace. We offer some suggestions to mitigate the mismatch. Most importantly, although anecdotes and “gut feelings” abound, the quantitative data backing our conclusions and suggestions are very sparse and barely compelling; we urge better data collection to support curricular revision, perhaps with the involvement of professional societies

Computing NodeTrix Representations of Clustered Graphs

NodeTrix representations are a popular way to visualize clustered graphs; they represent clusters as adjacency matrices and inter-cluster edges as curves connecting the matrix boundaries. We study the complexity of constructing NodeTrix representations focusing on planarity testing problems, and we show several NP-completeness results and some polynomial-time algorithms. Building on such algorithms we develop a JavaScript library for NodeTrix representations aimed at reducing the crossings between edges incident to the same matrix.Comment: Appears in the Proceedings of the 24th International Symposium on Graph Drawing and Network Visualization (GD 2016

An optical spectroscopic survey of the 3CR sample of radio galaxies with z<0.3. III. Completing the sample

We present optical nuclear spectra for nine 3CR radio sources obtained with the Telescopio Nazionale Galileo, that complete our spectroscopic observations of the sample up to redshifts $<$ 0.3. We measure emission line luminosities and ratios, and derive a spectroscopic classification for these sources.Comment: Accepted for publication in A&A. We provide as additional material two tables presenting the main data for the whole sample, combining the results presented here with those of Paper I and Paper I

An arc tangent model of irradiance in the sea

The solar energy flux as a function of depth (the irradiance profile) in the ocean is an important function. It influences the dynamics of the mixed layer via the heat budget as well as the biology of the euphotic zone. The following three-parameter model can take into account the very rapid decrease near the surface due to absorption of long-wavelength radiation by water as well as the eventual exponential decrease at great depths. E(z) = E(0)e⁻K1z(1 – K₂ arctan K₃z), where E(z) is the irradiance at depth z and K₁, K₂, and K₃ are constants that depend on the optical properties of the water. The constants are determined for Jerlov’s water types. The constants can be readily calculated from any irradiance profile

An analysis of the optical features of the near-bottom and bottom nepheloid layers in the area of the Scotian Rise

Profiles of light transmission versus depth have been studied in the region of the Scotian Rise of the North Atlantic at bottom depths between 4900 and 5000 m. A component model has been developed and consists of three components of transmission which can be combined to duplicate accurately any given transmission profile. Two of the components are shown to be representative of several basic phenomena: the particle concentration within a uniform flow and the separation of a benthic nepheloid layer. In the case of a uniform flow it is the relative magnitudes of settling and eddy diffusion which determine the shape of the transmission profile. Separation of the benthic nepheloid layer was inferred to be caused by an occasional cross-slope velocity component. The physical interpretation of the third component was ambiguous. Eulerian and Lagrangian transformations of the data show that benthic 'storms' that were detected at one location and time appeared nearly identical at a later time downstream and that benthic 'storms' can be detected over a large distance. Distance and time scales obtained from these transformations show the area of the Scotian Rise to be one characterized by bottom 'storms' which keep their general form over periods of at least 2 weeks and for distances traveled of at least 400 km

Optical and Near-Infrared Observations of the Nearby Spiral Galaxy Maffei 2

Spectra, photographs, and photometric measurements have been used to show that Maffei 2 has a distance of 5 ± 2 Mpc and that it has a morphological type near Sbc II-in agreement with similar conclusions made earlier by radio observers. We discuss the possible relationships between Maffei 2 and the elliptical galaxy Maffei 1; there are serious inconsistencies in the existing data which bear on this question