Satellite systems around galaxies in hydrodynamic simulations

We investigate the properties of satellite galaxies formed in N -body/SPH simulations of galaxy formation in the ΛCDM cosmology. The simulations include the main physical effects thought to be important in galaxy formation and, in several cases, produce realistic spiral discs. In total, a sample of nine galaxies of luminosity comparable to the Milky Way was obtained. At magnitudes brighter than the resolution limit,   M_V =−12  , the luminosity function of the satellite galaxies in the simulations is in excellent agreement with data for the Local Group. The radial number density profile of the model satellites, as well as their gas fractions also match observations very well. In agreement with previous N -body studies, we find that the satellites tend to be distributed in highly flattened configurations whose major axis is aligned with the major axis of the (generally triaxial) dark halo. In two out of three systems with sufficiently large satellite populations, the satellite system is nearly perpendicular to the plane of the galactic disc, a configuration analogous to that observed in the Milk Way. The discs themselves are perpendicular to the minor axis of their host haloes in the inner parts, and the correlation between the orientation of the galaxy and the shape of the halo persists even out to the virial radius. However, in one case the disc's minor axis ends up, at the virial radius, perpendicular to the minor axis of the halo. The angular momenta of the galaxies and their host halo tend to be well aligned.     

Astrobiological molecularly imprinted polymer sensors

The purpose of the Astrobiological MIP Sensor (AMS) Project is to develop reliable, low-cost, low-mass, low-power consumption detection technologies for in situ analysis of biochemical markers, and other indicators of astrobiological importance. To this end, we are investigating the potential role that molecularly imprinted polymers (MIP) could serve in the recognition of pre-biotic and biotic compounds in planetary, astrobiological and geochemical mission profiles. While MIPs are effective molecular recognition tools, a signal transduction method must be developed so that the recognition of analytes can be realized. In the course of this study, surface plasmon resonance (SPR) will be the detection method of the MIP recognition event. In addition, MIP-coated SPR substrates were subjected to vibration, temperature and radiation testing to demonstrate that they could withstand the rigors of space travel. The methods developed in this study require capture of the biomarkers onto the SPR sensor chip, followed by addition of a MIP. It is the binding of the MIP to the SPR bound analyte that amplifies the SPR signal associated with binding of the low molecular weight analyte. The MIPs, developed in this study are water-soluble processable star polymers while the SPR device used was SensíQ™ by Nomatics. Proof-of-principal experiments were first demonstrated using amino biotin.     

Explaining the energetic AGN outburst of MS 0735+7421 with massive slow jets

By conducting axisymmetrical hydrodynamical numerical simulations (2.5 dimensional code) we show that slow, massive, wide jets can reproduce the morphology of the huge X-ray deficient bubble pair in the cluster of galaxies MS 0735+7421. The total energy of the jets, composed of the energy in the bubble pair and in the shock wave, is constrained by observations conducted by McNamara et al. to be  ∼10⁶² erg  . We show that two opposite jets that are active for ∼100 Myr, each with a launching half opening angle of  α≃ 70°  , an initial velocity of   v _j∼ 0.1 c   and a total mass loss rate of the two jets of     , can account for the observed morphology. Rapidly precessing narrow jets can be used instead of wide jets. In our model the cluster suffered from a cooling catastrophe ∼100 Myr ago. Most of the mass that cooled,  ∼10¹⁰ M_⊙  , was expelled back to the intracluster medium by the active galactic nuclei activity and is inside the bubbles now, ∼10 per cent formed stars and ∼10 per cent of the cold gas was accreted by the central black hole and was the source of the outburst energy. This type of activity is similar to that expected to occur in galaxy formation.     

Magnetic field, dust and axisymmetrical mass loss on the asymptotic giant branch

I propose a mechanism for axisymmetrical mass loss on the asymptotic giant branch (AGB) that may account for the axially symmetric structure of elliptical planetary nebulae. The proposed model operates for slowly rotating AGB stars, having angular velocities in the range of 10⁻⁴ω _Kep  ω  10⁻² ω_Kep, where ω_Kep is the equatorial Keplerian angular velocity. Such angular velocities could be gained from a planet companion of mass  0.1  M _Jupiter, which deposits its orbital angular momentum to the envelope at late stages, or even from single stars that are fast rotators on the main sequence. The model assumes that dynamo magnetic activity results in the formation of cool spots, above which dust forms much more easily. The enhanced magnetic activity towards the equator results in a higher dust formation rate there, and hence higher mass-loss rate. As the star ascends the AGB, both the mass-loss rate and magnetic activity increase rapidly, and hence the mass loss becomes more asymmetrical, with higher mass-loss rate closer to the equatorial plane.     

Spectral properties and geologic processes on Eros from combined NEAR NIS and MSI data sets

Abstract— From April 24 to May 14, 2000, the Near Earth Asteroid Rendezvous (NEAR) Shoemaker mission's near infrared spectrometer (NIS) obtained its highest resolution data of 433 Eros. High signal‐to‐noise ratio NIS reflectance spectra cover a wavelength range of 800–2400 nm, with footprint sizes from 213 times 427 m to 394 times 788 m. This paper describes improvement in instrument calibration by remediation of internally scattered light; derivation of a “pseudo channel” for NIS at 754 nm using Multispectral Imager (MSI) Eros approach maps at 951 and 754 nm; synthesis of a 3127‐spectrum high‐resolution data set with the improved calibration and expanded wavelength coverage; and investigation of global and localized spectral variation with respect to mineralogy, composition, and space weathering of Eros, comparing the findings with previous analyses. Scattered light removal reduces the “red” slope of Eros spectra, though not to the level seen by telescopic observations. The pseudo channel completes sampling of Eros' 1 micron (Band I) absorption feature, enabling direct comparison of NIS data with other asteroid and meteorite spectra without additional scaling or correction. Following scattered light removal and wavelength range extension, the spectral parameters of average Eros plot well inside the S(IV) field of Gaffey et al. (1993) and are consistent with the L6 chondrite meteorite fields of Gaffey and Gilbert (1998). Although Eros shows no evidence of mineralogical heterogeneity, modest spectral variations correlate with morphologically and geographically distinct areas of the asteroid. Eros bright‐to‐dark spectral ratios are largely consistent with laboratory “space weathering” experiment results and modeling of space weathering effects. Eros brightness variation unaccompanied by significant spectral variation departs from “lunar‐type”—where band depths, slopes, and albedoes all correlate—and “Ida‐type”—where significant spectral variation is unaccompanied by corresponding brightness variation. The brightest areas on Eros—steep crater walls—have lesser spectral slope and deeper Band I, consistent with exposure of “fresher,” less space weathered materials. Bright crater slope materials have opx/(opx + olv) of 0.24–0.29 and may be more representative of the subsurface mineralogy than “average” Eros, which is probably affected by space weathering. The floors of the large craters Psyche and Himeros have lower albedo and contain the most degraded or altered looking materials. NIS spectra retain a “red” spectral slope at greater than 2 microns. The recalibrated and expanded NIS spectra show better agreements with mixing models based on space weathering of chondritic mixtures.     

Harnessing Crowdsourced Data and Prevalent Technologies for Atmospheric Research

The knowledge garnered in environmental science takes a crucial part in informing decision-making in various fields,including agriculture, transportation, energy, public health and safety, and more. Understanding the basic processes in each of these fields relies greatly on progress being made in conceptual, observational and technological approaches. However,existing instruments for environmental observations are often limited as a result of technical and practical constraints. Current technologies, including remote sensing systems and ground-level measuring means, may suffer from obstacles such as low spatial representativity or a lack of precision when measuring near ground-level. These constraints often limit the ability to carry out extensive meteorological observations and, as a result, the capacity to deepen the existing understanding of atmospheric phenomena and processes. Multi-system informatics and sensing technology have become increasingly distributed as they are embedded into our environment. As they become more widely deployed, these technologies create unprecedented data streams with extraordinary levels of coverage and immediacy, providing a growing opportunity to complement traditional observation techniques using the large volumes of data created. Commercial microwave links that comprise the data transfer infrastructure of cellular communication networks are an example of these types of systems. This viewpoint letter briefly reviews various works on the subject and presents aspects concerning the added value that may be obtained as a result of the integration of these new means, which are becoming available for the first time in this era, for studying and monitoring atmospheric phenomena.     

Perchlorate accumulation and migration in the deep vadose zone in a semiarid region

For 25 years, a plant in Israel manufacturing ammonium perchlorate disposed of untreated wastewater in four unlined ponds. This study explores the transport mechanisms of perchlorate infiltrated from 1965 to 1990 from one of these active storage ponds into a deep (40 m) layered vadose zone and the underlying Israeli coastal aquifer. Perchlorate migration from 1990, when wastewater disposal ceased, until today, with infiltration due only to natural rain (500 mm y⁻¹), was also studied. Several indirect methods were used, including: mass balance in the unsaturated zone profile, δ¹⁸O and δ²H profiles below the pond, and a comparison of the same sediment profiles in 2005 and 2007. The isotopic composition of the pore water could be divided into two separate groups: lighter (depleted) and heavier (enriched) samples. All samples in the lighter group were from the shallow vadose zone, above two clayey layers, and represent natural infiltration of rainwater. The enriched samples were from the deeper section of the unsaturated zone (20–40 m) and represent water used for perchlorate manufacturing 14 years prior to drilling. Consequently, the overall maximum infiltration rate was estimated to be 1.4 m y⁻¹. Below the clayey layer almost identical perchlorate concentrations were found along the sediment profile in 2005 and 2007 (two boreholes, 3 m apart). Very different perchlorate profiles were observed above the clayey layers. This suggests that perchlorate below the clay layers (20–40 m) is practically stagnant under the current natural conditions. The reduction in perchlorate concentration in groundwater below the ponds vs. its increased concentration further downgradient supports the contention that the current migration of perchlorate from the vadose zone to the groundwater is very small. We estimate that perchlorate concentration in the groundwater under the infiltration pond, which was 187 mg l⁻¹ in 2004, will reach 10 μg l⁻¹ within about 14 years. The existence of a clayey layer crossing the thick vadose zone was thus found to significantly change the infiltration rate when ponded conditions were replaced with natural precipitation.