The Herschel Virgo Cluster Survey. VI. The far-infrared view of M87

The origin of the far-infrared emission from the nearby radio galaxy M87 remains a matter of debate. Some studies find evidence of a far-infrared excess due to thermal dust emission, whereas others propose that the far-infrared emission can be explained by synchrotron emission without the need for an additional dust emission component. We present Herschel PACS and SPIRE observations of M87, taken as part of the science demonstration phase observations of the Herschel Virgo Cluster Survey. We compare these data with a synchrotron model based on mid-infrared, far-infrared, submm and radio data from the literature to investigate the origin of the far-infrared emission. Both the integrated SED and the Herschel surface brightness maps are adequately explained by synchrotron emission. At odds with previous claims, we find no evidence of a diffuse dust component in M87, which is not unexpected in the harsh X-ray environment of this radio galaxy sitting at the core of the Virgo cluster

Engaged Lecturing in Lecture-Based Courses

Numerous teaching styles are implemented by educators to capture the attention and interest of engineering students. Lecture-based courses can be significantly less engaging than inductive or project-based courses, however, lectures continue to be necessary. For this reason, there is a deliberate effort to explore all avenues that aid retaining the student’s interest-level and content-assimilation while participating in long (50 to 75 minute) lecture sessions. In this paper, we specifically discuss simple methods (systemic pauses and group in-class assignments) that can be used in any lecture-based course. These methods were implemented at our lecture sessions. To gauge the efficacy of these methods, collaboration between two instructors was established and these methods were implemented simultaneously in different lecture based classrooms. Our goal is for students to retain the subject matter of a course and achieve mastery of the course learning outcomes. As methods to evaluate goal attainment, we provide an overall assessment of student interest-level and understanding of the course materials over the duration of lecture sessions. It is noted that, while we present the impact engaged lecturing has with students, we also discuss the process (orientation to teaching techniques, feedback/assessment practices) that goes with instructors to establish a culture of engaged learning in a program.Cockrell School of Engineerin

The Herschel Virgo Cluster Survey - V. Star-forming dwarf galaxies – dust in metal-poor environments

We present the dust properties of a small sample of Virgo cluster dwarf galaxies drawn from the science demonstration phase data set of the Herschel Virgo Cluster Survey. These galaxies have low metallicities (7.8 < 12 + log(O/H) < 8.3) and star-formation rates ≲10^(-1) M_☉ yr^(-1). We measure the spectral energy distribution (SED) from 100 to 500 μm and derive dust temperatures and dust masses. The SEDs are fitted by a cool component of temperature T ≲ 20 K, implying dust masses around 10^5 M_☉ and dust-to-gas ratios within the range 10^(-3)–10^(-2). The completion of the full survey will yield a larger set of galaxies, which will provide more stringent constraints on the dust content of star-forming dwarf galaxies

Heat Transfer Activity for a First-Year Mechanical Engineering Course

A heat transfer educational activity is designed for freshman students who declare a mechanical engineering major. This activity is part of an introductory course given during the first year to introduce students to mechanical engineering and give them tools to use in while pursuing their Bachelors of Science degree in mechanical engineering. The activity is designed to challenge students in learning heat transfer concepts. However, its rigor is planned for students (at the freshman level) who have not yet taken the prerequisites required for heat transfer. The activity is scalable and can be easily deployed in other educational institutes. It is presented with its goals, goal attainment measures, and feedback representing the student perception.Cockrell School of Engineerin

A Conceptual Mechanism Design Activity for an Introduction to Mechanical Engineering Course

A conceptual design activity is presented in this paper to introduce freshman students to motion transmission with simple gear train mechanisms. The activity requires students to select components from a catalog and perform kinematic simulations using CAD software. The activity described in this paper was implemented in an introduction to mechanical engineering course but it could also be deployed in an upper-level, undergraduate mechanisms course. The activity was successfully administered to a class of 221 students during the Spring 2017 semester but can be administered to smaller classes as well. A description of the activity is presented along with a discussion of the resources and personnel required (instructors and teaching assistants). The activity is considered simple to implement, requiring only a computer station with CAD software available in most engineering schools. Continuous improvements to the project are made based on faculty observations and assessments, as well as a survey administered to the students.Cockrell School of Engineerin

The hunt for red AGN: a new infrared diagnostic

We introduce a new infrared diagnostic to separate galaxies on the basis of their dominant infrared emission: stellar or nuclear. The main novelty with respect to existing diagnostics, is the usage of a broad band encompassing at the same time the 9.7micron Silicate absorption feature and one of the adjacent broad PAH (polycyclic aromatic hydrocarbon) features. This provides a robust estimate of the near- to mid-infrared continuum slope and enables a clear distinction among different classes of galaxies up to a redshift z=2.5. The diagnostic can be applied to a wealth of archival data from the ISO, Spitzer, and Akari surveys as well as future JWST surveys. Based on data in the GOODS, Lockman Hole, and North Ecliptic Pole (NEP) fields, we find out that approximately 70% active galactic nuclei detected with X-ray and optical spectroscopy dominate the total mid-infrared emission. Finally, we estimate that AGN contribute less than 30% of the mid-infrared extragalactic integrated emission.Comment: 5 pages, 4 figures, accepted for publication in MNRA

The Herschel Virgo Cluster Survey - II. Truncated dust disks in H I-deficient spirals

By combining Herschel-SPIRE observations obtained as part of the Herschel Virgo Cluster Survey with 21 cm Hi data from the literature, we investigate the role of the cluster environment on the dust content of Virgo spiral galaxies. We show for the first time that the extent of the dust disk is significantly reduced in Hi-deficient galaxies, following remarkably well the observed “truncation” of the Hi disk. The ratio of the submillimetre-to-optical diameter correlates with the Hi-deficiency, suggesting that the cluster environment is able to strip dust as well as gas. These results provide important insights not only into the evolution of cluster galaxies but also into the metal enrichment of the intra-cluster medium

The Herschel Virgo Cluster Survey - I. Luminosity function

We describe the Herschel Virgo Cluster Survey (HeViCS) and the first data obtained as part of the science demonstration phase (SDP). The data cover a central 4×4 sq deg region of the cluster. We use SPIRE and PACS photometry data to produce 100, 160, 250, 350 and 500 μm luminosity functions (LFs) for optically bright galaxies that are selected at 500 μm and detected in all bands. We compare these LFs with those previously derived using IRAS, BLAST and Herschel-ATLAS data. The Virgo cluster LFs do not have the large numbers of faint galaxies or examples of very luminous galaxies seen previously in surveys covering less dense environments