We present the HIPASS Bright Galaxy Catalog (BGC), which contains the 1000 H I brightest galaxies in the southern sky as obtained from the H i Parkes All-Sky Survey ( HIPASS). The selection of the brightest sources is based on their H I peak flux density (S-peak greater than or similar to116 mJy) as measured from the spatially integrated HIPASS spectrum. The derived H I masses range from similar to10(7) to 4 x 10(10) M-.. While the BGC ( z 10degrees. Therefore, the BGC yields no evidence for a population of free-floating'' intergalactic H I clouds without associated optical counterparts. HIPASS provides a clear view of the local large-scale structure. The dominant features in the sky distribution of the BGC are the Supergalactic Plane and the Local Void. In addition, one can clearly see the Centaurus Wall, which connects via the Hydra and Antlia Clusters to the Puppis Filament. Some previously hardly noticable galaxy groups stand out quite distinctly in the H I sky distribution. Several new structures, including some not behind the Milky Way, are seen for the first time.

/pdf/the-1000-brightest-hipass-galaxies-h-i-properties-c93dxue76g.pdf

The 1000 Brightest HIPASS Galaxies: H I Properties

It has been known for a long time that the satellite galaxies of the Milky Way (MW) show a significant amount of phase-space correlation, they are distributed in a highly inclined Disc of Satellites (DoS). We have extended the previous studies on the DoS by analysing for the first time the orientations of streams of stars and gas, and the distributions of globular clusters within the halo of the MW. It is shown that the spatial distribution of MW globular clusters classified as young halo clusters (YH GC) is very similar to the DoS, while 7 of the 14 analysed streams align with the DoS. The probability to find the observed clustering of streams is only 0.3 per cent when assuming isotropy. The MW thus is surrounded by a vast polar structure (VPOS) of subsystems (satellite galaxies, globular clusters and streams), spreading from Galactocentric distances as small as 10 kpc out to 250 kpc. These findings demonstrate that a near-isotropic infall of cosmological sub-structure components onto the MW is essentially ruled out because a large number of infalling objects would have had to be highly correlated, to a degree not natural for dark matter sub-structures. The majority of satellites, streams and YH GCs had to be formed as a correlated population. This is possible in tidal tails consisting of material expelled from interacting galaxies. We discuss the tidal scenario for the formation of the VPOS, including successes and possible challenges. The potential consequences of the MW satellites being tidal dwarf galaxies are severe. If all the satellite galaxies and YH GCs have been formed in an encounter between the young MW and another gas-rich galaxy about 10-11 Gyr ago, then the MW does not have any luminous dark-matter substructures and the missing satellites problem becomes a catastrophic failure of the standard cosmological model.

/pdf/the-vpos-a-vast-polar-structure-of-satellite-galaxies-4mt0csk7fj.pdf

The VPOS: a vast polar structure of satellite galaxies, globular clusters and streams around the Milky Way

Original article can be found at: http://www.journals.uchicago.edu/AJ/--Copyright American Astronomical Society

/pdf/formation-of-a-tidal-dwarf-galaxy-in-the-interacting-system-3l87mqgtok.pdf

Formation of a tidal dwarf galaxy in the interacting system Arp 245 (NGC 2992/93)

We investigate the process of galaxy formation as can be observed in the only currently forming galaxies { the so-called Tidal Dwarf Galaxies, hereafter TDGs { through observations of the molecular gas detected via its CO (Carbon Monoxide) emission. These objects are formed of material torn o of the outer parts of a spiral disk due to tidal forces in a collision between two massive galaxies. Molecular gas is a key element in the galaxy formation process, providing the link between a cloud of gas and a bona de galaxy. We have detected CO in 8 TDGs (two of them have already been published in Braine et al. 2000, hereafter Paper I), with an overall detection rate of 80%, showing that molecular gas is abundant in TDGs, up to a few 10 8 M. The CO emission coincides both spatially and kinematically with the HI emission, indicating that the molecular gas forms from the atomic hydrogen where the HI column density is high. A possible trend of more evolved TDGs having greater molecular gas masses is observed, in accord with the transformation of HI into H2. Although TDGs share many of the properties of small irregulars, their CO luminosity is much greater (factor 100) than that of standard dwarf galaxies of comparable luminosity. This is most likely a consequence of the higher metallicity ( 1/3 solar) of TDGs which makes CO a good tracer of molecular gas. This allows us to study star formation in environments ordinarily inaccessible due to the extreme diculty of measuring the molecular gas mass. The star formation eciency, measured by the CO luminosity per H flux, is the same in TDGs and full-sized spirals. CO is likely the best tracer of the dynamics of these objects because some fraction of the HI near the TDGs may be part of the tidal tail and not bound to the TDG. Although uncertainties are large for individual objects, as the geometry is unknown, our sample is now of eight detected objects and we nd that the \dynamical" masses of TDGs, estimated from the CO line widths, seem not to be greater than the \visible" masses (HI + H2 + a stellar component). Although higher spatial resolution CO (and HI) observations would help reduce the uncertainties, we nd that TDGs require no dark matter, which would make them the only galaxy-sized systems where this is the case. Dark matter in spirals should then be in a halo and not a rotating disk. Most dwarf galaxies are dark matter-rich, implying that they are not of tidal origin. We provide strong evidence that TDGs are self-gravitating entities, implying that we are witnessing the ensemble of processes in galaxy formation: concentration of large amounts of gas in a bound object, condensation of the gas, which is atomic at this point, to form molecular gas and the subsequent star formation from the dense molecular component.

/pdf/abundant-molecular-gas-in-tidal-dwarf-galaxies-on-going-1ephfn594p.pdf

Abundant molecular gas in tidal dwarf galaxies: On-going galaxy formation

As small satellites become more popular and capable, strategies to provide in-space propulsion increase in importance. Applications range from orbital changes and maintenance, attitude control and desaturation of reaction wheels to drag compensation and de-orbit at spacecraft end-of-life. Space propulsion can be enabled by chemical or electric means, each having different performance and scalability properties. The purpose of this review is to describe the working principles of space propulsion technologies proposed so far for small spacecraft. Given the size, mass, power, and operational constraints of small satellites, not all types of propulsion can be used and very few have seen actual implementation in space. Emphasis is given in those strategies that have the potential of miniaturization to be used in all classes of vehicles, down to the popular 1-L, 1-kg CubeSats and smaller.

/pdf/space-propulsion-technology-for-small-spacecraft-2ayk72ioi6.pdf

Space Propulsion Technology for Small Spacecraft

KySat1 is a 1 kilogram picoclass satellite being developed by college students across the state of Kentucky. To the best of our knowledge, the KySat effort is the first by a state to develop a satellite. The consortium assembled to fund and develop KySat includes public, private and educational partners throughout Kentucky. While the primary mission of KySat1 is educational outreach, the goals of the KySat program include (1) Educational experience for secondary and post secondary students (2) Cultivate an aerospace and satellite technology base in Kentucky (3) Develop a reliable reusable satellite bus that will form the basis for future education and commercial KySat missions. The timeline for KySat1 is aggressive and off-the-shelf technology is leveraged whenever possible. This paper overviews the KySat1 design and development.

Development of an Off-the-Shelf Bus for Small Satellites

/pdf/3d-printing-and-mems-propulsion-for-the-rampart-2u-cubesat-3seuy21zfw.pdf

3D Printing and MEMS Propulsion for the RAMPART 2U CUBESAT

The launch and successful operation of the Mars Cube One (MarCO) CubeSats in May of 2018 ushered in a new era of solar system exploration. The 13 interplanetary CubeSats slated to fly on Artemis 1 in 2020 along with MarCO represent the beginning of a new paradigm of planetary exploration—one that utilizes the CubeSat form factor as both primary and supporting exploration platforms. Enabling technologies required by interplanetary CubeSats including relatively high Δv propulsion systems, capable high-frequency transponders, radiation-tolerant components, and extremely capable miniaturized science instruments are now becoming commercially available making these missions possible. Interplanetary CubeSats require different and more sophisticated spacecraft systems architectures and must utilize different and more sophisticated ground station systems than LEO missions. These differences are discussed in this chapter in detail, using specific examples from current and planned missions.

Interplanetary CubeSat missions

Busek, in partnership with Morehead State University (MSU), is developing a versatile 6U CubeSat platform nicknamed “LunarCube” that can undertake missions beyond LEO. The spacecraft can host a variety of science payloads, and its mission capability is highlighted by >3km/s of delta-V maneuverability with a groundbreaking ion propulsion system heretofore unavailable to CubeSats. Salient features of this propulsion system include innovative use of solid iodine propellant and a 60W class mini RF ion thruster that is capable of 1.3mN thrust and 3250sec specific impulse (Isp). The primary objective of the LunarCube program is to support a deep space CubeSat mission to the Moon from GEO or a translunar trajectory (such as the SLS/EM-1 drop-off) and carry out a lunar science campaign as a technology demonstration of the platform. A secondary objective is to showcase that much of the spacecraft’s miniaturized avionics and power system can survive the harsh radiation environment. The LunarCube concept, especially its ion propulsion element, has received significant attention from the CubeSat user community targeting near-term lunar flights. In fact, the platform has already morphed into an EM-1 CubeSat mission known as “Lunar IceCube”, selected for flight by NASA’s Next Space Technologies for Exploration Partnerships (NextSTEP) program.

/pdf/lunarcube-a-deep-space-6u-cubesat-with-mission-enabling-ion-y4iap6hw1n.pdf

LunarCube: A Deep Space 6U CubeSat with Mission Enabling Ion Propulsion Technology

P. E. Clark, Ben Malphrus, Kevin Brown, Dennis Reuter, Robert MacDowall, David Folta, Avi Mandell, Terry Hurford, Cliff Brambora, Deepak Patel, Stuart Banks, William Farrell, Noah Petro, Michael Tsay, V. Hruby, Carl Brandon, Peter Chapin, Jet Propulsion Laboratory, California Institute of Technology (pamela.e.clark@jpl.nasa.gov), Morehead State University, NASA/GSFC, Busek, Vermont Technical College.

Lunar Ice Cube Mission: Determining Lunar Water Dynamics with a First Generation Deep Space CubeSat

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