Gaseous Galaxy Halos

Galactic halo gas traces inflowing star formation fuel and feedback from a galaxy's disk and is therefore crucial to our understanding of galaxy evolution. In this review, we summarize the multi-wavelength observational properties and origin models of Galactic and low redshift spiral galaxy halo gas. Galactic halos contain multiphase gas flows that are dominated in mass by the ionized component and extend to large radii. The densest, coldest halo gas observed in neutral hydrogen (HI) is generally closest to the disk (< 20 kpc), and absorption line results indicate warm and warm-hot diffuse halo gas is present throughout a galaxy's halo. The hot halo gas detected is not a significant fraction of a galaxy's baryons. The disk-halo interface is where the multiphase flows are integrated into the star forming disk, and there is evidence for both feedback and fueling at this interface from the temperature and kinematic gradient of the gas and HI structures. The origin and fate of halo gas is considered in the context of cosmological and idealized local simulations. Accretion along cosmic filaments occurs in both a hot (> 10^5.5 K) and cold mode in simulations, with the compressed material close to the disk the coldest and densest, in agreement with observations. There is evidence in halo gas observations for radiative and mechanical feedback mechanisms, including escaping photons from the disk, supernova-driven winds, and a galactic fountain. Satellite accretion also leaves behind abundant halo gas. This satellite gas interacts with the existing halo medium, and much of this gas will become part of the diffuse halo before it can reach the disk. The accretion rate from cold and warm halo gas is generally below a galaxy disk's star formation rate, but gas at the disk-halo interface and stellar feedback may be important additional fuel sources.Comment: 50 pages, 9 figures (1 in 3D, view with a current version of Adobe), to appear in ARA&A, 50, 49

Discovery of molecular hydrogen in a high-velocity cloud of the Galactic halo

We report the discovery of molecular hydrogen absorption in a Galactic high-velocity cloud (HVC) in the direction of the Large Magellanic Cloud. For the same HVC we derive an iron abundance which is half of the solar value. Thus, all evidence points to a Galactic origin for high-velocity cloud complex in front of the LMC.Comment: Published in Nature, this week; 14 pages, 3 figure

Near-identical star formation rate densities from Hα and FUV at redshift zero

For the first time both H$\alpha$ and far-ultraviolet (FUV) observations from an HI-selected sample are used to determine the dust-corrected star formation rate density (SFRD: $\dot{\rho}$) in the local Universe. Applying the two star formation rate indicators on 294 local galaxies we determine log($\dot{\rho}$$_{H\alpha}) = -1.68~^{+0.13}_{-0.05}$ [M$_{\odot}$ yr$^{-1}$ Mpc$^{-3}]$ and log($\dot{\rho}_{FUV}$) $= -1.71~^{+0.12}_{-0.13}$ [M$_\odot$ yr$^{-1}$ Mpc$^{-3}]$. These values are derived from scaling H$\alpha$ and FUV observations to the HI mass function. Galaxies were selected to uniformly sample the full HI mass (M$_{HI}$) range of the HI Parkes All-Sky Survey (M$_{HI} \sim10^{7}$ to $\sim10^{10.7}$ M$_{\odot}$). The approach leads to relatively larger sampling of dwarf galaxies compared to optically-selected surveys. The low HI mass, low luminosity and low surface brightness galaxy populations have, on average, lower H$\alpha$/FUV flux ratios than the remaining galaxy populations, consistent with the earlier results of Meurer. The near-identical H$\alpha$- and FUV-derived SFRD values arise with the low H$\alpha$/FUV flux ratios of some galaxies being offset by enhanced H$\alpha$ from the brightest and high mass galaxy populations. Our findings confirm the necessity to fully sample the HI mass range for a complete census of local star formation to include lower stellar mass galaxies which dominate the local Universe.Partial funding for the SINGG and SUNGG surveys came from NASA grants NAG5-13083 (LTSA program), GALEX GI04- 0105-0009 (NASA GALEX Guest Investigator grant) and NNX09AF85G (GALEX archival grant) to G.R. Meurer. FAR acknowledges partial funding from the Department of Physics, University of Western Australia. This research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration

Biodegradation of Pig Manure by the Housefly, Musca domestica: A Viable Ecological Strategy for Pig Manure Management

The technology for biodegradation of pig manure by using houseflies in a pilot plant capable of processing 500–700 kg of pig manure per week is described. A single adult cage loaded with 25,000 pupae produced 177.7±32.0 ml of eggs in a 15-day egg-collection period. With an inoculation ratio of 0.4–1.0 ml eggs/kg of manure, the amount of eggs produced by a single cage can suffice for the biodegradation of 178–444 kg of manure. Larval development varied among four different types of pig manure (centrifuged slurry, fresh manure, manure with sawdust, manure without sawdust). Larval survival ranged from 46.9±2.1%, in manure without sawdust, to 76.8±11.9% in centrifuged slurry. Larval development took 6–11 days, depending on the manure type. Processing of 1 kg of wet manure produced 43.9–74.3 g of housefly pupae and the weight of the residue after biodegradation decreased to 0.18–0.65 kg, with marked differences among manure types. Recommendations for the operation of industrial-scale biodegradation facilities are presented and discussed

AMPK α1 Activation Is Required for Stimulation of Glucose Uptake by Twitch Contraction, but Not by H2O2, in Mouse Skeletal Muscle

BACKGROUND: AMPK is a promising pharmacological target in relation to metabolic disorders partly due to its non-insulin dependent glucose uptake promoting role in skeletal muscle. Of the 2 catalytic alpha-AMPK isoforms, alpha(2) AMPK is clearly required for stimulation of glucose transport into muscle by certain stimuli. In contrast, no clear function has yet been determined for alpha(1) AMPK in skeletal muscle, possibly due to alpha-AMPK isoform signaling redundancy. By applying low-intensity twitch-contraction and H(2)O(2) stimulation to activate alpha(1) AMPK, but not alpha(2) AMPK, in wildtype and alpha-AMPK transgenic mouse muscles, this study aimed to define conditions where alpha(1) AMPK is required to increase muscle glucose uptake. METHODOLOGY/PRINCIPAL FINDINGS: Following stimulation with H(2)O(2) (3 mM, 20 min) or twitch-contraction (0.1 ms pulse, 2 Hz, 2 min), signaling and 2-deoxyglucose uptake were measured in incubated soleus muscles from wildtype and muscle-specific kinase-dead AMPK (KD), alpha(1) AMPK knockout or alpha(2) AMPK knockout mice. H(2)O(2) increased the activity of both alpha(1) and alpha(2) AMPK in addition to Akt phosphorylation, and H(2)O(2)-stimulated glucose uptake was not reduced in any of the AMPK transgenic mouse models compared with wild type. In contrast, twitch-contraction increased the activity of alpha(1) AMPK, but not alpha(2) AMPK activity nor Akt or AS160 phosphorylation. Glucose uptake was markedly lower in alpha(1) AMPK knockout and KD AMPK muscles, but not in alpha(2) AMPK knockout muscles, following twitch stimulation. CONCLUSIONS/SIGNIFICANCE: These results provide strong genetic evidence that alpha(1) AMPK, but not alpha(2) AMPK, Akt or AS160, is necessary for regulation of twitch-contraction stimulated glucose uptake. To our knowledge, this is the first report to show a major and essential role of alpha(1) AMPK in regulating a physiological endpoint in skeletal muscle. In contrast, AMPK is not essential for H(2)O(2)-stimulated muscle glucose uptake, as proposed by recent studies

Which Factors Determine Spatial Segregation in the South American Opossums (Didelphis aurita and D. albiventris)? An Ecological Niche Modelling and Geometric Morphometrics Approach

Didelphis albiventris and D. aurita are Neotropical marsupials that share a unique evolutionary history and both are largely distributed throughout South America, being primarily allopatric throughout their ranges. In the Araucaria moist forest of Southern Brazil these species are sympatric and they might potentially compete having similar ecology. For this reason, they are ideal biological models to address questions about ecological character displacement and how closely related species might share their geographic space. Little is known about how two morphologically similar species of marsupials may affect each other through competition, if by competitive exclusion and competitive release. We combined ecological niche modeling and geometric morphometrics to explore the possible effects of competition on their distributional ranges and skull morphology. Ecological niche modeling was used to predict their potential distribution and this method enabled us to identify a case of biotic exclusion where the habit generalist D. albiventris is excluded by the presence of the specialist D. aurita. The morphometric analyses show that a degree of shape discrimination occurs between the species, strengthened by allometric differences, which possibly allowed them to occupy marginally different feeding niches supplemented by behavioral shift in contact areas. Overlap in skull morphology is shown between sympatric and allopatric specimens and a significant, but weak, shift in shape occurs only in D. aurita in sympatric areas. This could be a residual evidence of a higher past competition between both species, when contact zones were possibly larger than today. Therefore, the specialist D. aurita acts a biotic barrier to D. albiventris when niche diversity is not available for coexistence. On the other hand, when there is niche diversification (e.g. habitat mosaic), both species are capable to coexist with a minimal competitive effect on the morphology of D. aurita

Colonization history of the western corn rootworm (Diabrotica virgifera virgifera) in North America: insights from random forest ABC using microsatellite data

First described from western Kansas, USA, the western corn rootworm, Diabrotica virgifera virgifera, is one of the worst pests of maize. The species is generally thought to be of Mexican origin and to have incidentally followed the expansion of maize cultivation into North America thousands of years ago. However, this hypothesis has never been investigated formally. In this study, the genetic variability of samples collected throughout North America was analysed at 13 microsatellite marker loci to explore precisely the population genetic structure and colonization history of D. v. virgifera. In particular, we used up-to-date approximate Bayesian computation methods based on random forest algorithms to test a Mexican versus a central-USA origin of the species, and to compare various possible timings of colonization. This analysis provided strong evidence that the origin of D. v. virgifera was southern (Mexico, or even further south). Surprisingly, we also found that the expansion of the species north of its origin was recent—probably not before 1100 years ago—thus indicating it was not directly associated with the early history of maize expansion out of Mexico, a far more ancient event

Variability of Female Responses to Conspecific vs. Heterospecific Male Mating Calls in Polygynous Deer: An Open Door to Hybridization?

Males of all polygynous deer species (Cervinae) give conspicuous calls during the reproductive season. The extreme interspecific diversity that characterizes these vocalizations suggests that they play a strong role in species discrimination. However, interbreeding between several species of Cervinae indicates permeable interspecific reproductive barriers. This study examines the contribution of vocal behavior to female species discrimination and mating preferences in two closely related polygynous deer species known to hybridize in the wild after introductions. Specifically, we investigate the reaction of estrous female red deer (Cervus elaphus) to playbacks of red deer vs. sika deer (Cervus nippon) male mating calls, with the prediction that females will prefer conspecific calls. While on average female red deer preferred male red deer roars, two out of twenty females spent more time in close proximity to the speaker broadcasting male sika deer moans. We suggest that this absence of strict vocal preference for species-specific mating calls may contribute to the permeability of pre-zygotic reproductive barriers observed between these species. Our results also highlight the importance of examining inter-individual variation when studying the role of female preferences in species discrimination and intraspecific mate selection