Multi-waveband observations of colliding galaxies

Colliding galaxies represent a major challenge to both theorists and observers because of the large variety of phenomena which are expected to come into play during the interaction. Strong gravitational fluctuations may drive non-linear waves and instabilities throughout the stars and gas leading to enhanced star formation, nuclear activity and ultimately a mixing of the morphological components of the original galaxies. One relatively uncomplicated class of colliding galaxy where stellar waves play an important role in star formation are ring galaxies. Ring galaxies are probably formed when a companion galaxy passes through the center of a disk system driving circular waves through the disk (Lynds and Toomre 1976, Toomre 1978, Struck-Marcell 1990). Off-center collisions can generate non-circular waves and can be loosely described as banana-shaped although they may exhibit more complex forms as the waves expand into the disk. The propagation of such stellar and gaseous waves through the disk leads to enhanced star formation (e.g., Appleton and Struck-Marcell 1987a; Jeske 1986) and provides a unique probe of the response of the interstellar medium (ISM) to a propagating wave (see Appleton and Struck-Marcell 1987b). Here, the authors report results for 3 systems; the irregular ring Arp 143 (=VV 117); Wakamatsu's Seyfert ring (A0959-755; see Wakamatsu and Nishida 1987) and the brighter member of the pair of ring galaxies comprising of AM 1358-221. The most complete multi-wavelength data is for Arp 143. Optical charge coupled device (CCD) observations made with the 60 inch Palomar telescope at BV and r band, near-IR images at J (1.25 microns), H (1.65 microns) and k (2.2 microns) bands from the infrared camera (IRCAM) InSb array camera on the 3.8m United Kingdon Infrared Telescope (UKIRT) telescope and very large array (VLA) observations at 20cm in both the neutral hydrogen line and radio continuum are described. The observations of Wakamatsu's ring and AM 1358 were made only in the near-IR, and a comparison is made with available optical plate material

The design and fabrication of microstrip omnidirectional array antennas for aerospace applications

A microstrip antenna design concept was developed that will provide quasi-omnidirectional radiation pattern characteristics about cylindrical and conical aerospace structures. L-band and S-band antenna arrays were designed, fabricated, and, in some cases, flight tested for rocket, satellite, and aircraft drone applications. Each type of array design is discussed along with a thermal cover design that was required for the sounding rocket applications

Cloud fluid models of gas dynamics and star formation in galaxies

The large dynamic range of star formation in galaxies, and the apparently complex environmental influences involved in triggering or suppressing star formation, challenges the understanding. The key to this understanding may be the detailed study of simple physical models for the dominant nonlinear interactions in interstellar cloud systems. One such model is described, a generalized Oort model cloud fluid, and two simple applications of it are explored. The first of these is the relaxation of an isolated volume of cloud fluid following a disturbance. Though very idealized, this closed box study suggests a physical mechanism for starbursts, which is based on the approximate commensurability of massive cloud lifetimes and cloud collisional growth times. The second application is to the modeling of colliding ring galaxies. In this case, the driving processes operating on a dynamical timescale interact with the local cloud processes operating on the above timescale. The results is a variety of interesting nonequilibrium behaviors, including spatial variations of star formation that do not depend monotonically on gas density

Protocol for a longitudinal qualitative interview study: maintaining psychological well-being in advanced cancer - what can we learn from patients' and carers' own coping strategies?

IntroductionPeople with advanced cancer and their carers experience stress and uncertainty which affects the quality of life and physical and mental health. This study aims to understand how patients and carers recover or maintain psychological well-being by exploring the strategies employed to self-manage stress and uncertainty.Methods and analysisA longitudinal qualitative interview approach with 30 patients with advanced cancer and 30 associated family or informal carers allows the exploration of contexts, mechanisms and outcomes at an individual level. Two interviews, 4–12?weeks apart, will not only enable the exploration of individuals’ evolving coping strategies in response to changing contexts but also how patients’ and carers’ strategies inter-relate. Patient and Carer focus groups will then consider how the findings may be used in developing an intervention. Recruiting through two major tertiary cancer centres in the North West and using deliberately broad and inclusive criteria will enable the sample to capture demographic and experiential breadth.Ethics and disseminationThe research team will draw on their considerable experience to ensure that the study is sensitive to a patient and carer group, which may be considered vulnerable but still values being able to contribute its views. Public and patient involvement (PPI) is integral to the design and is evidenced by: a research advisory group incorporating patient and carers, prestudy consultations with the PPI group at one of the study sites and a user as the named applicant. The study team will use multiple methods to disseminate the findings to clinical, policy and academic audiences. A key element will be engaging health professionals in patient and carer ideas for promoting self-management of psychological well-being. The study has ethical approval from the North West Research Ethics Committee and the appropriate NHS governance clearance.RegistrationNational Institute for Health Research (NIHR) Clinical Studies Portfolio, UK Clinical Research Network (UKCRN) Study number 11725

Star Formation in Collision Debris: Insights from the modeling of their Spectral Energy Distribution

During galaxy-galaxy interactions, massive gas clouds can be injected into the intergalactic medium which in turn become gravitationally bound, collapse and form stars, star clusters or even dwarf galaxies. The objects resulting from this process are both "pristine", as they are forming their first generation of stars, and chemically evolved because the metallicity inherited from their parent galaxies is high. Such characteristics make them particularly interesting laboratories to study star formation. After having investigated their star-forming properties, we use photospheric, nebular and dust modeling to analyze here their spectral energy distribution (SED) from the far-ultraviolet to the mid-infrared regime for a sample of 7 star-forming regions. Our analysis confirms that the intergalactic star forming regions in Stephan's Quintet, around Arp 105, and NGC 5291, appear devoid of stellar populations older than 10^9 years. We also find an excess of light in the near-infrared regime (from 2 to 4.5 microns) which cannot be attributed to stellar photospheric or nebular contributions. This excess is correlated with the star formation rate intensity suggesting that it is probably due to emission by very small grains fluctuating in temperature as well as the polycyclic aromatic hydrocarbons (PAH) line at 3.3 micron. Comparing the attenuation via the Balmer decrement to the mid-infrared emission allows us to check the reliability of the attenuation estimate. It suggests the presence of embedded star forming regions in NGC 5291 and NGC 7252. Overall the SED of star-forming regions in collision debris (and Tidal Dwarf Galaxies) resemble more that of dusty star-forming regions in galactic disks than to that of typical star-forming dwarf galaxies.Comment: 22 pages, 24 figures, accepted for publication in A

Observations and modeling of the dust emission from the H_2-bright galaxy-wide shock in Stephan's Quintet

Context. Spitzer Space Telescope observations have detected powerful mid-infrared (mid-IR) H_2 rotational line emission from the X-ray emitting large-scale shock (~15 × 35 kpc^2) associated with a galaxy collision in Stephan's Quintet (SQ). Because H_2 forms on dust grains, the presence of H_2 is physically linked to the survival of dust, and we expect some dust emission to originate in the molecular gas. Aims. To test this interpretation, IR observations and dust modeling are used to identify and characterize the thermal dust emission from the shocked molecular gas. Methods. The spatial distribution of the IR emission allows us to isolate the faint PAH and dust continuum emission associated with the molecular gas in the SQ shock. We model the spectral energy distribution (SED) of this emission, and fit it to Spitzer observations. The radiation field is determined with GALEX UV, HST V-band, and ground-based near-IR observations. We consider two limiting cases for the structure of the H_2 gas: it is either diffuse and penetrated by UV radiation, or fragmented into clouds that are optically thick to UV. Results. Faint PAH and dust continuum emission are detected in the SQ shock, outside star-forming regions. The 12/24 μm flux ratio in the shock is remarkably close to that of the diffuse Galactic interstellar medium, leading to a Galactic PAH/VSG abundance ratio. However, the properties of the shock inferred from the PAH emission spectrum differ from those of the Galaxy, which may be indicative of an enhanced fraction of large and neutrals PAHs. In both models (diffuse or clumpy H_2 gas), the IR SED is consistent with the expected emission from dust associated with the warm (> 150 K) H_2 gas, heated by a UV radiation field of intensity comparable to that of the solar neighborhood. This is in agreement with GALEX UV observations that show that the intensity of the radiation field in the shock is GUV = 1.4±0.2 [Habing units]. Conclusions. The presence of PAHs and dust grains in the high-speed (~1000 km s^(-1)) galaxy collision suggests that dust survives. We propose that the dust that survived destruction was in pre-shock gas at densites higher than a few 0.1 cm^(-3), which was not shocked at velocities larger than ~200 km s^(-1). Our model assumes a Galactic dust-to-gas mass ratio and size distribution, and current data do not allow us to identify any significant deviations of the abundances and size distribution of dust grains from those of the Galaxy. Our model calculations show that far-IR Herschel observations will help in constraining the structure of the molecular gas, and the dust size distribution, and thereby to look for signatures of dust processing in the SQ shock