Chandra Imaging and Spectroscopy of the Eastern XA Region of the Cygnus Loop Supernova Remnant

The XA region of the Cygnus Loop is a bright knot of X-ray emission on the eastern edge of the supernova remnant resulting from the interaction of the supernova blast wave with density enhancements at the edge of a precursor formed cavity. To study the nature and origin of the X-ray emission we use high spatial resolution images from Chandra. Our goal is to probe the density of various spectral extraction regions to form a picture of the cavity wall and characterize the interaction between this supernova and the local interstellar medium. We find that a series of regions along the edge of the X-ray emission appears to trace out the location of the cavity wall. The best fit plasma models result in two temperature component equilibrium models for each region. The low temperature components have densities that are an order of magnitude higher than the high temperature components. The high density plasma may exist in the cavity wall where it equilibrates rapidly and cools efficiently. The low density plasma is interior to the enhancement and heated further by a reverse shock from the wall. Calculations of shock velocities and timescales since shock heating are consistent with this interpretation. Furthermore, we find a bright knot of emission indicative of a discrete interaction of the blast wave with a high density cloud in the cavity wall with a size scale ~0.1 pc. Aside from this, other extractions made interior to the X-ray edge are confused by line of sight projection of various components. Some of these regions show evidence of detecting the cavity wall but their location makes the interpretation difficult. In general, the softer plasmas are well fit at temperatures kT~0.11 keV, with harder plasmas at temperatures of kT~0.27 keV. All regions display consistent metal depletions most notably in N, O, and Ne at an average of 0.54, 0.55, and 0.36 times solar

A Suborbital Payload for Soft X-ray Spectroscopy of Extended Sources

We present a suborbital rocket payload capable of performing soft X-ray spectroscopy on extended sources. The payload can reach resolutions of ~100(lambda/dlambda) over sources as large as 3.25 degrees in diameter in the 17-107 angstrom bandpass. This permits analysis of the overall energy balance of nearby supernova remnants and the detailed nature of the diffuse soft X-ray background. The main components of the instrument are: wire grid collimators, off-plane grating arrays and gaseous electron multiplier detectors. This payload is adaptable to longer duration orbital rockets given its comparatively simple pointing and telemetry requirements and an abundance of potential science targets.Comment: Accepted to Experimental Astronomy, 12 pages plus 1 table and 17 figure

HFPK 334: An unusual Supernova Remnant in the Small Magellanic Cloud

We present new Australia Telescope Compact Array (ATCA) radio-continuum and XMM-Newton/Chandra X-ray Observatory (CXO) observations of the unusual supernova remnant HFPK 334 in the Small Magellanic Cloud (SMC). The remnant follows a shell type morphology in the radio-continuum and has a size of $\sim$20~pc at the SMC distance. The X-ray morphology is similar, however, we detect a prominent point source close to the center of the SNR exhibiting a spectrum with a best fit powerlaw with a photon index of $\Gamma = 2.7 \pm 0.5$. This central point source is most likely a background object and cannot be directly associated with the remnant. The high temperature, nonequilibrium conditions in the diffuse region suggest that this gas has been recently shocked and point toward a younger SNR with an age of $\lesssim 1800$ years. With an average radio spectral index of $\alpha=-0.59\pm0.09$ we find that an equipartition magnetic field for the remnant is $\sim$90~$\mu$G, a value typical of younger SNRs in low-density environments. Also, we report detection of scattered radio polarisation across the remnant at 20~cm, with a peak fractional polarisation level of 25$\pm$5\%.Comment: 19 pages, 6-figures, submitted to A

The Relationship Between Baryons and Dark Matter in Extended Galaxy Halos

The relationship between gas-rich galaxies and Ly-alpha absorbers is addressed in this paper in the context of the baryonic content of galaxy halos. Deep Arecibo HI observations are presented of two gas-rich spiral galaxies within 125 kpc projected distance of a Ly-alpha absorber at a similar velocity. The galaxies investigated are close to edge-on and the absorbers lie almost along their major axes, allowing for a comparison of the Ly-alpha absorber velocities with galactic rotation. This comparison is used to examine whether the absorbers are diffuse gas rotating with the galaxies' halos, outflow material from the galaxies, or intergalactic gas in the low redshift cosmic web. The results indicate that if the gas resides in the galaxies' halos it is not rotating with the system and possibly counter-rotating. In addition, simple geometry indicates the gas was not ejected from the galaxies and there are no gas-rich satellites detected down to 3.6 - 7.5 x 10^6 Msun, or remnants of satellites to 5-6 x 10^{18} cm^{-2}. The gas could potentially be infalling from large radii, but the velocities and distances are rather high compared to the high velocity clouds around the Milky Way. The most likely explanation is the galaxies and absorbers are not directly associated, despite the vicinity of the spiral galaxies to the absorbers (58-77 kpc from the HI edge). The spiral galaxies reside in a filament of intergalactic gas, and the gas detected by the absorber has not yet come into equilibrium with the galaxy. These results also indicate that the massive, extended dark matter halos of spiral galaxies do not commonly have an associated diffuse baryonic component at large radii.Comment: Accepted by AJ, 33 pages preprint format, see http://www.astro.lsa.umich.edu/~mputman/putman1.pdf for a higher resolution versio

Angular Misalignment Measurements for an Off-Plane Reflection Grating Module

We present an analysis of an alignment technique used for an off-plane reflection grating system that, if proven to be feasible, would ideally be utilized for future astronomical x-ray spectrometers. The use of reflection gratings allows for the production of both high throughput and spectral resolution. As such, they are a candidate grating technology for future soft X-ray spectroscopy missions. To be viable for these missions, however, a low-cost optical technique for co-aligning multiple gratings into a module for use in a spectrograph must be demonstrated. The off-plane grating module was built to contain fifteen gratings with proper relative alignment to one another for a converging X-ray beam. The module was coupled with a silicon pore optic mirror to produce a spectrum of reflected and diffracted light onto a CCD camera at the focal plane. The alignment performance of the module’s grating system was assessed both before and after a series of vibrational and thermal tests were conducted at the NASA Marshall Space Flight Center. Data reduction was done in order to identify the number and position of photon events from the diffraction spots for each grating, and raytracing analysis was conducted in order to calculate the induced grating-to-grating angular misalignments. Finally, these measurements were compared to theoretical alignment tolerances derived using analytical techniques. The grating system yielded misalignments within a factor of 2-3 of the analytical tolerances, which is very encouraging for a first attempt. Further refinement and troubleshooting is required to see whether or not this alignment technique can be used in the future

Development of the X-ray camera for the OGRE sub-orbital rocket

Current theories regarding the matter composition of the universe suggest that half of the expected baryonic matter is missing. One region this could be residing in is intergalactic filaments which absorb strongly in the X-ray regime. Present space based technology is limited when it comes to imaging at these wavelengths and so new techniques are required. The Off-Plane Grating Rocket Experiment (OGRE) aims to produce the highest resolution spectrum of the binary star system Capella, a well-known X-ray source, in the soft X-ray range (0.2keV to 2keV). This will be achieved using a specialised payload combining three low technology readiness level components placed on-board a sub-orbital rocket. These three components consist of an array of large format off-plane X-ray diffraction gratings, a Wolter Type 1 mirror made using single crystal silicon, and the use of EM-CCDs to capture soft X-rays. Each of these components have been previously reviewed with OGRE being the first project to utilise them in a space observation mission. This paper focuses on the EM-CCDs (CCD207-40 by e2v) that will be used and their optimisation with a camera purposely designed for OGRE. Electron Multiplying gain curves were produced for the back-illuminated devices at -80 degrees Celsius. Further tests which will need to be carried out are discussed and the impact of the OGRE mission on future projects mentioned

Lynx X-Ray Observatory: An Overview

Lynx, one of the four strategic mission concepts under study for the 2020 Astrophysics Decadal Survey, provides leaps in capability over previous and planned x-ray missions and provides synergistic observations in the 2030s to a multitude of space- and ground-based observatories across all wavelengths. Lynx provides orders of magnitude improvement in sensitivity, on-axis subarcsecond imaging with arcsecond angular resolution over a large field of view, and high-resolution spectroscopy for point-like and extended sources in the 0.2- to 10-keV range. The Lynx architecture enables a broad range of unique and compelling science to be carried out mainly through a General Observer Program. This program is envisioned to include detecting the very first seed black holes, revealing the high-energy drivers of galaxy formation and evolution, and characterizing the mechanisms that govern stellar evolution and stellar ecosystems. The Lynx optics and science instruments are carefully designed to optimize the science capability and, when combined, form an exciting architecture that utilizes relatively mature technologies for a cost that is compatible with the projected NASA Astrophysics budget

Optical design of the Off-plane Grating Rocket Experiment

The Off-plane Grating Rocket Experiment (OGRE) is a soft X-ray spectroscopy suborbital rocket payload scheduled for launch in Q3 2020 from Wallops Flight Facility. The payload will serve as a testbed for several key technologies which can help achieve the desired performance increases for the next generation of X-ray spectrographs and other space-based missions: monocrystalline silicon X-ray mirrors developed at NASA Goddard Space Flight Center, reflection gratings manufactured at The Pennsylvania State University, and electron-multiplying CCDs developed by the Open University and XCAM Ltd. With these three technologies, OGRE hopes to obtain the highest-resolution on-sky soft X-ray spectrum to date. We discuss the optical design of the OGRE payload

The Off-plane Grating Rocket Experiment (OGRE) system overview

The Off-plane Grating Rocket Experiment (OGRE) is a sub-orbital rocket payload that will make the highest spectral resolution astronomical observation of the soft X-ray Universe to date. Capella, OGRE’s science target, has a well-defined line emission spectrum and is frequently used as a calibration source for X-ray observatories such as Chandra. This makes Capella an excellent target to test the technologies on OGRE, many of which have not previously flown. Through the use of state-of-the-art X-ray optics, co-aligned arrays of off-plane reflection gratings, and an X-ray camera based around four Electron Multiplying CCDs, OGRE will act as a proving ground for next generation X-ray spectrometers

Future instrumentation for the study of the Warm-Hot Intergalactic Medium

We briefly review capabilities and requirements for future instrumentation in UV- and X-ray astronomy that can contribute to advancing our understanding of the diffuse, highly ionised intergalactic medium.Comment: 16 pages, 4 figures, accepted for publication in Space Science Reviews, special issue "Clusters of galaxies: beyond the thermal view", Editor J.S. Kaastra, Chapter 19; work done by an international team at the International Space Science Institute (ISSI), Bern, organised by J.S. Kaastra, A.M. Bykov, S. Schindler & J.A.M. Bleeke