Cool outflows in galaxies and their implications

Neutral-atomic and molecular outflows are a common occurrence in galaxies, near and far. They operate over the full extent of their galaxy hosts, from the innermost regions of galactic nuclei to the outermost reaches of galaxy halos. They carry a substantial amount of material that would otherwise have been used to form new stars. These cool outflows may have a profound impact on the evolution of their host galaxies and environments. This article provides an overview of the basic physics of cool outflows, a comprehensive assessment of the observational techniques and diagnostic tools used to characterize them, a detailed description of the best-studied cases, and a more general discussion of the statistical properties of these outflows in the local and distant universe. The remaining outstanding issues that have not yet been resolved are summarized at the end of the review to inspire new research directions.STFC and ER

The Evolution of Galaxies and Their Environment

The Third Teton Summer School on Astrophysics discussed the formation of galaxies, star formation in galaxies, galaxies and quasars at high red shift, and the intergalactic and intercluster medium and cooling flows. Observation and theoretical research on these topics was presented at the meeting and summaries of the contributed papers are included in this volume

A multi-wavelength study of the evolution and pc-scale jet kinematics of active galaxies

Active galaxies have been in the forefront of astronomic research since their first discovery, at least 50 years ago . The putative supermassive black hole (SMBH) at their center characterizes their properties and regulates the evolution of these objects. I investigate the evolution of active galactic nuclei (AGN) in the context of a merger-driven evolution scheme. Under this assumption, galaxy mergers trigger activity in galaxies, both in the form of intense star-formation, as well as nuclear activity. This investigation uses the Caltech-Jodrell Bank flat-spectrum (CJF) sample, a statistically complete sample of compact, radio-loud AGN. I find evidence supporting the merger-driven evolution scheme of AGN, exhibiting the relevance of merger events in active galaxies. In particular, almost 30% of the CJF sources in the local Universe (z<0.4) show evidence of recent past, present, or possible future mergers. This is important in light of the unbiased selection effects of the CJF sample. In addition, I find a broken correlation between the near-infrared luminosity of the CJF sources and their total radio luminosity at 5 GHz. Low luminosity sources show an excess of near-infrared emission, compared to their high luminosity counterparts. A correlation between near-infrared colors and multiwavelength variability is also found. Finally, I trace the different stages of AGN evolution by selecting individual sources that fit the respective selection criteria, finding 14 promising candidates for binary black hole (BBH) systems in the CJF. One of the most prominent constituents of radio-loud active galaxies are their radio jets. The morphology, properties, and evolution of the CJF jet ridge lines are studied, in light of a recently revisited kinematic paradigm for BL Lac objects. Different measures for the width, the width evolution, the linear evolution, and the curvature of the jet ridge lines are developed and a statistical analysis of the whole sample on that basis is conducted. BL Lac objects are found to have substantially wider jets than quasars. They are also found to show larger changes in their widths, but significantly weaker linear evolution of their jet ridge lines. We find indications of active evolution of the jet length and linear evolution with time (as a function of redshift). An envelope is found confining a correlation between the total linear evolution of the CJF jet ridge lines and the radio luminosity of the corresponding sources. The above results are explained in terms of the combination of helical structure for AGN jets and projection effects. Coupled to the kinematics of the AGN jets is the emission of gamma-ray radiation. In light of the excellent quality of kinematic data available for the CJF, as well as the wealth of new gamma-ray information provided by the Fermi-LAT program, I investigate the gamma-ray properties of the CJF sample, in terms of their jet kinematics and properties. I find that gamma-ray detected sources show on average higher apparent velocities than their non-detected counterparts. I note however the existence of a low-velocity population of gamma-ray detected CJF sources, that put the argument of beaming as the source of gamma-ray photons under debate. I study a possible correlation between the gamma-ray detection of CJF sources, their luminosity, and their jet morphology. I find a correlation between the gamma-ray luminosity and the maximum apparent jet speed for the gamma-detected CJF sources. The correlation is stronger for variable sources and for those identified as BL Lacs. I find that gamma-detected sources show substantially wider jet ridge lines, with stronger evolution of their widths compared to non-detected sources. I find no significant difference between gamma-detected and non-detected sources concerning the linear evolution of their jet ridge lines. The absence of a strong correlation between gamma-ray properties of the CJF sources and their kinematics is interpreted in the context of a spine-sheath geometry of AGN jet, where, at the low observing frequency used for the CJF, only the slow outer sheath of the jet is uncovered. gamma-ray emission is assumed to originate in the ultra-relativistic spine of AGN jets

Working Papers: Astronomy and Astrophysics Panel Reports

The papers of the panels appointed by the Astronomy and Astrophysics survey Committee are compiled. These papers were advisory to the survey committee and represent the opinions of the members of each panel in the context of their individual charges. The following subject areas are covered: radio astronomy, infrared astronomy, optical/IR from ground, UV-optical from space, interferometry, high energy from space, particle astrophysics, theory and laboratory astrophysics, solar astronomy, planetary astronomy, computing and data processing, policy opportunities, benefits to the nation from astronomy and astrophysics, status of the profession, and science opportunities

Optical design study, testing and qualification of a Schwarzschild-Couder telescope for CTA and an assessment on the Intensity Interferometry capabilities with CTA

There is a growing common effort in the very high energy community towards the development of new research infrastructures to answer the fundamental questions of modern high-energy astrophysics and astroparticle physics. The Cherenkov Telescope Array Observatory (CTAO) is an international project aiming to deploy two separate arrays to observe the whole VHE sky between E = 20 GeV up to E = 300 TeV in a long term plan of about 30 years of operations. CTA is designed to increase the sensitivity by a factor 10 at 1 TeV, to enlarge the detection area, the angular resolution and the field of view over the facilities operating today. The observatory will be characterized by high flexibility, enhanced monitoring and deep survey capabilities, short time scale and simultaneous observations in multiple fields. This PhD thesis addresses the optical design study and testing of dual mirror Imaging Atmospheric Cherenkov Telescopes (IACTs) for the incoming CTAO. All of the IACTs facilities currently operating rely on single mirror solutions, which are mostly parabolic or Davies-Cotton optical designs, however there is a novel interest in the development of dual mirror configurations following the Schwarzschild-Couder optical design. This peculiar design, based on two highly aspherical mirrors promises wide-field, aplanatic telescopes characterized by small f-numbers and more compact structures. Dual mirror solutions allow use smaller camera pixels (3-6 mm) based on Silicon Photo Multiplier technology in substitution of the larger Photo Multiplier Tubes (1 inch) currently in use. The increased complexity in terms of optics manufacturing, replication and alignment is motivated from the attractive new capabilities of such configuration. In this context the Italian National Institute for Astrophysics (INAF) supported by the Italian Ministry of Education, University and Research (MIUR), is developing a small sized telescope prototype for CTA, named ASTRI, which is based upon the Schwarzschild-Couder optical design. The present work deals with the challenging realization of this optical configuration that has never been applied to IACTs. After two introductory chapters on the gamma-ray astronomy and the ASTRI optical design and its main subsystems (chapters 1 and 2), the performances of this system are compared with those of the other common wide-field telescopes in use for Cherenkov observations and for other applications in astrophysics (chapter 3). This comparative study is based on a commercial ray tracing software into which the optical designs of the envisaged telescopes are reproduced. Subsequently in chapter 4, an extended study of the ASTRI capabilities in relation to the performance and environmental requirements issued by CTA is presented in a detailed analysis of compliance supported by ray tracing simulations, finite element analysis and tolerance studies. In chapter 5 the work on the qualification tests of the secondary mirror gives an insight into the complexity of the Schwarzschild-Couder optics. The realization of this optical element is challenging in relation to currently available technologies, in particular concerning the cost requirements imposed by the CTA project. These constraints and the large sagitta of the mirror (190 mm) requires the use of the hot slumping technique in substitution of the cold slumping and diamond milling approaches usually used in the manufacturing of mirrors for Cherenkov applications. The results of a careful and extended test campaign on a mirror prototype have indicated that this manufacturing technique can provide a reliable engineering process of production for such large, highly aspherical optics. With a perspective on the science with future large telescopes as those provided by CTA, an assessment study upon the potentialities of the Intensity Interferometry (II) technique is carried out in chapter 6. In particular, a new kind of observation based on II is explored; the method aims to estimate the direct distance of the celestial objects. The order of magnitudes of the problem parameters space and the sensitivity that CTA and other future large observatories should achieve is estimated by means of numerical simulations. A short-term concept of experiment to assess the reliability of this new method is also discussed in relation to a pilot measurement that could be pursued with the state of the art technology

Washington University Senior Honor Thesis Abstracts (WUSHTA), Spring 2017

Complete issue of the Washington University Senior Honors Thesis Abstracts (WUSHTA), Spring 2017. Published by the Office of Undergraduate Research. Joy Zalis Kiefer, Director of Undergraduate Research and Associate Dean in the College of Arts & Sciences; Lindsey Paunovich Editor; Kristin G. Sobotka, Programs Manager; Jennifer Kohl