Spatially Resolved Gas Kinematics within a Lyα\alpha Nebula: Evidence for Large-scale Rotation

We use spatially extended measurements of Ly$\alpha$ as well as less optically thick emission lines from an $\approx$80 kpc Ly$\alpha$ nebula at $z\approx1.67$ to assess the role of resonant scattering and to disentangle kinematic signatures from Ly$\alpha$ radiative transfer effects. We find that the Ly$\alpha$, CIV, HeII, and CIII] emission lines all tell a similar story in this system, and that the kinematics are broadly consistent with large-scale rotation. First, the observed surface brightness profiles are similar in extent in all four lines, strongly favoring a picture in which the Ly$\alpha$ photons are produced in situ instead of being resonantly scattered from a central source. Second, we see low kinematic offsets between Ly$\alpha$ and the less optically thick HeII line ($\sim$100-200 km s$^{-1}$), providing further support for the argument that the Ly$\alpha$ and other emission lines are all being produced within the spatially extended gas. Finally, the full velocity field of the system shows coherent velocity shear in all emission lines: $\approx$500 km s$^{-1}$ over the central $\approx$50 kpc of the nebula. The kinematic profiles are broadly consistent with large-scale rotation in a gas disk that is at least partially stable against collapse. These observations suggest that the Ly$\alpha$ nebula represents accreting material that is illuminated by an offset, hidden AGN or distributed star formation, and that is undergoing rotation in a clumpy and turbulent gas disk. With an implied mass of M(<R=20 kpc)$\sim3\times10^{11}$ $M_{\odot}$, this system may represent the early formation of a large Milky Way mass galaxy or galaxy group.Comment: Accepted to ApJ; 25 pages in emulateapj format; 15 figures, 4 table

Circumnuclear star formation in Mrk 42 mapped with Gemini Near-infrared Integral Field Spectrograph

We present Gemini Near-infrared Integral Field Spectrograph (NIFS) observations of the inner $1.5\times1.5$ kpc$^2$ of the narrow-line Seyfert 1 galaxy Mrk 42 at a spatial resolution of 60 pc and spectral resolution of 40 km s$^{-1}$. The emission-line flux and equivalent width maps clearly show a ring of circumnuclear star formation regions (CNSFRs) surrounding the nucleus with radius of $\sim$500 pc. The spectra of some of these regions show molecular absorption features which are probably of CN, TiO or VO, indicating the presence of massive evolved stars in the thermally pulsing asymptotic giant branch (TP-AGB) phase. The gas kinematics of the ring is dominated by rotation in the plane of the galaxy, following the large scale disk geometry, while at the nucleus an additional outflowing component is detected blueshifted by 300-500 kms$^{-1}$, relative to the systemic velocity of the galaxy. Based on the equivalent width of Br$\gamma$, we find evidences of gradients in the age of HII regions along the ring of Mrk 42, favoring the pearls on a string scenario of star formation. The broad component of Pa$\beta$ emission line presents a Full Width at Half Maximum (FWHM) of $\sim$1480 kms$^{-1}$, implying in a mass of $\sim\,2.5\times10^{6}$~M$_{\odot}$ for the central supermassive black hole. Based on emission-line ratios we conclude that besides the active galactic nucleus, Mrk 42 presents nuclear Starburst activity.Comment: 14 pages, MNRAS accepte

Understanding the circumgalactic medium is critical for understanding galaxy evolution

Galaxies evolve under the influence of gas flows between their interstellar medium and their surrounding gaseous halos known as the circumgalactic medium (CGM). The CGM is a major reservoir of galactic baryons and metals, and plays a key role in the long cycles of accretion, feedback, and recycling of gas that drive star formation. In order to fully understand the physical processes at work within galaxies, it is therefore essential to have a firm understanding of the composition, structure, kinematics, thermodynamics, and evolution of the CGM. In this white paper we outline connections between the CGM and galactic star formation histories, internal kinematics, chemical evolution, quenching, satellite evolution, dark matter halo occupation, and the reionization of the larger-scale intergalactic medium in light of the advances that will be made on these topics in the 2020s. We argue that, in the next decade, fundamental progress on all of these major issues depends critically on improved empirical characterization and theoretical understanding of the CGM. In particular, we discuss how future advances in spatially-resolved CGM observations at high spectral resolution, broader characterization of the CGM across galaxy mass and redshift, and expected breakthroughs in cosmological hydrodynamic simulations will help resolve these major problems in galaxy evolution.Comment: Astro2020 Decadal Science White Pape

Summary of environmental mercury concentrations and assessment of risk to public health from mercury at the geysers

Ambient mercury data were investigated in relation to the environment and public health at and near the vicinity of The Geysers, California. Mercury was found to occur naturally in the environment (air, water, soil, etc.) and as a result of industrial activities, although the exact contribution of each source could not be determined. Ambient air concentrations ranged from non-detectable to 630 ng/m3 . Concentrations in ambient waters ranged from non-detectable to 2.9 Mg/1; the highest value exceeds all water quality criteria for the protection of health and is 30% below the level set to protect freshwater organisms from acute toxicity. Little data are available on concentrations of mercury in fish; however, the existing data suggest that some fish may be bioconcentrating the mercury. Reported data for mercury in fish were above applicable health standards (for food) in most cases. Soil mercury levels ranged from less than the detection limit to 11 Mg/g. Mercury was not detected in small animals, and low and relatively insignificant mercury concentrations were found in bulk atmospheric deposition samples and in foliage. Because total human exposure data in or near The Geysers area are not available, the above environmental data were compiled and used to assess the worst-case potential risk to public health as a result of mercury emissions (natural and industrial) at The Geysers. The results of this study show that the highest mercury exposure to humans occurs from ingesting inorganic mercury in food. The concentrations of mercury in food are not expected to be impacted by activities at The Geysers. Under normal conditions. mercury in food accounts for approximately 99% of the total exposure to mercury. Regardless of the route of exposure (air, water, or food), the daily total exposure of mercury to the public living at The Geysers is predicted to be 28 Mg/day. According to the EPA, national average mercury exposures are approximately 25 Mg/day. It is very unlikely that any public health effects would occur since exposures of 200 Mg/day of methyl mercury are necessary for toxic response to be noticeable.Pacific Gas and Electric Compan

Polymers of 3-hydroxyacids in plants

Polyhydroxyalkanoates (PHA) are polyesters of bacterial origin that have properties of biodegradable plastics and elastomers. Synthesis of PHA in crop plants would allow the large-scale production and use of these biodegradable and renewable polymers as substitutes for petroleum-derived plastics. Synthesis of a diversity of PHAs in plants, such as Arabidopsis thaliana, rapeseed, corn and cotton, has been demonstrated through the genetic engineering of metabolic pathways in the cytoplasm, plastid and peroxisome. PHA can also be used as a novel tool to study various aspects of plant metabolism, such as the regulation of carbon flux to the fatty acid biosynthetic and degradation pathways

Synthesis of novel biomaterials in plants.

Metabolic engineering of plants allows the possibility of using crops for the synthesis of novel polymers having useful material properties. Strong and flexible protein-based polymers, which are based on the structure of silk and elastin have been synthesized in transgenic plants. A wide range of polyhydroxyalkanoates having properties ranging from stiff plastics to soft elastomers and glues have been synthesized in various compartments of plants, such as the cytoplasm, plastid and peroxisome. These plant biomaterials could replace, in part, the synthetic plastics, fibers and elastomers produced from petroleum, thus offering the advantage of renewability, sustainability and biodegradability