Strong Nebular Line Ratios in the Spectra of z~2-3 Star-forming Galaxies: First Results from KBSS-MOSFIRE

We present initial results of a deep near-IR spectroscopic survey covering the 15 fields of the Keck Baryonic Structure Survey (KBSS) using MOSFIRE on the Keck 1 telescope, focusing on a sample of 251 galaxies with redshifts 2.0< z < 2.6, star-formation rates 2 < SFR < 200 M_sun/yr, and stellar masses 8.6 < log(M*/M_sun) < 11.4, with high-quality spectra in both H- and K-band atmospheric windows. We show unambiguously that the locus of z~2.3 galaxies in the "BPT" nebular diagnostic diagram exhibits a disjoint, yet similarly tight, relationship between the ratios [NII]6585/Halpha and [OIII]/Hbeta as compared to local galaxies. Using photoionization models, we argue that the offset of the z~2.3 locus relative to z~ 0 is explained by a combination of harder ionizing radiation field, higher ionization parameter, and higher N/O at a given O/H than applies to most local galaxies, and that the position of a galaxy along the z~2.3 star-forming BPT locus is surprisingly insensitive to gas-phase oxygen abundance. The observed nebular emission line ratios are most easily reproduced by models in which the net ionizing radiation field resembles a blackbody with effective temperature T_eff = 50000-60000 K and N/O close to the solar value at all O/H. We critically assess the applicability of commonly-used strong line indices for estimating gas-phase metallicities, and consider the implications of the small intrinsic scatter in the empirical relationship between excitation-sensitive line indices and stellar mass (i.e., the "mass-metallicity" relation), at z~2.3.Comment: 41 pages, 25 figures, accepted for publication in the Astrophysical Journal. Version with full-resolution figures available at http://www.astro.caltech.edu/~ccs/mos_bpt_submit.pd

SOFIA/EXES Observations of Water Absorption in the Protostar AFGL 2591 at High Spectral Resolution

We present high spectral resolution (~3 km/s) observations of the nu_2 ro-vibrational band of H2O in the 6.086--6.135 micron range toward the massive protostar AFGL 2591 using the Echelon-Cross-Echelle Spectrograph (EXES) on the Stratospheric Observatory for Infrared Astronomy (SOFIA). Ten absorption features are detected in total, with seven caused by transitions in the nu_2 band of H2O, two by transitions in the first vibrationally excited nu_2 band of H2O, and one by a transition in the nu_2 band of H2{18}O. Among the detected transitions is the nu_2 1(1,1)--0(0,0) line which probes the lowest lying rotational level of para-H2O. The stronger transitions appear to be optically thick, but reach maximum absorption at a depth of about 25%, suggesting that the background source is only partially covered by the absorbing gas, or that the absorption arises within the 6 micron emitting photosphere. Assuming a covering fraction of 25%, the H2O column density and rotational temperature that best fit the observed absorption lines are N(H2O)=(1.3+-0.3)*10^{19} cm^{-2} and T=640+-80 K.Comment: 6 pages, 3 figures, 1 table, accepted for publication in ApJ

APP Regulates Microglial Phenotype in a Mouse Model of Alzheimer\u27s Disease

Prior work suggests that amyloid precursor protein (APP) can function as a proinflammatory receptor on immune cells, such as monocytes and microglia. Therefore, we hypothesized that APP serves this function in microglia during Alzheimer\u27s disease. Although fibrillar amyloid β (Aβ)-stimulated cytokine secretion from both wild-type and APP knock-out (mAPP−/−) microglial cultures, oligomeric Aβ was unable to stimulate increased secretion from mAPP−/− cells. This was consistent with an ability of oligomeric Aβ to bind APP. Similarly, intracerebroventricular infusions of oligomeric Aβ produced less microgliosis in mAPP−/− mice compared with wild-type mice. The mAPP−/− mice crossed to an APP/PS1 transgenic mouse line demonstrated reduced microgliosis and cytokine levels and improved memory compared with wild-type mice despite robust fibrillar Aβ plaque deposition. These data define a novel function for microglial APP in regulating their ability to acquire a proinflammatory phenotype during disease. SIGNIFICANCE STATEMENT A hallmark of Alzheimer\u27s disease (AD) brains is the accumulation of amyloid β (Aβ) peptide within plaques robustly invested with reactive microglia. This supports the notion that Aβ stimulation of microglial activation is one source of brain inflammatory changes during disease. Aβ is a cleavage product of the ubiquitously expressed amyloid precursor protein (APP) and is able to self-associate into a wide variety of differently sized and structurally distinct multimers. In this study, we demonstrate both in vitro and in vivo that nonfibrillar, oligomeric forms of Aβ are able to interact with the parent APP protein to stimulate microglial activation. This provides a mechanism by which metabolism of APP results in possible autocrine or paracrine Aβ production to drive the microgliosis associated with AD brains

The transcriptional response of Caenorhabditis elegans to ivermectin exposure identifies novel genes involved in the response to reduced food intake

We have examined the transcriptional response of Caenorhabditis elegans following exposure to the anthelmintic drug ivermectin (IVM) using whole genome microarrays and real-time QPCR. Our original aim was to identify candidate molecules involved in IVM metabolism and/or excretion. For this reason the IVM tolerant strain, DA1316, was used to minimise transcriptomic changes related to the phenotype of drug exposure. However, unlike equivalent work with benzimidazole drugs, very few of the induced genes were members of xenobiotic metabolising enzyme families. Instead, the transcriptional response was dominated by genes associated with fat mobilization and fatty acid metabolism including catalase, esterase, and fatty acid CoA synthetase genes. This is consistent with the reduction in pharyngeal pumping, and consequential reduction in food intake, upon exposure of DA1316 worms to IVM. Genes with the highest fold change in response to IVM exposure, cyp-37B1, mtl-1 and scl-2, were comparably up-regulated in response to short–term food withdrawal (4 hr) independent of IVM exposure, and GFP reporter constructs confirm their expression in tissues associated with fat storage (intestine and hypodermis). These experiments have serendipitously identified novel genes involved in an early response of C. elegans to reduced food intake and may provide insight into similar processes in higher organisms

An HST/WFC3-IR Morphological Survey of Galaxies at z = 1.5-3.6: II. The Relation between Morphology and Gas-Phase Kinematics

We analyze rest-frame optical morphologies and gas-phase kinematics as traced by rest-frame far-UV and optical spectra for a sample of 204 star forming galaxies in the redshift range z ~ 2-3 drawn from the Keck Baryonic Structure Survey (KBSS). We find that spectroscopic properties and gas-phase kinematics are closely linked to morphology: compact galaxies with semi-major axis radii r <~ 2 kpc are substantially more likely than their larger counterparts to exhibit LyA in emission. Although LyA emission strength varies widely within galaxies of a given morphological type, all but one of 19 galaxies with LyA equivalent width W_LyA > 20 Angstroms have compact and/or multiple-component morphologies with r <= 2.5 kpc. The velocity structure of absorption lines in the galactic continuum spectra also varies as a function of morphology. Galaxies of all morphological types drive similarly strong outflows (as traced by the blue wing of interstellar absorption line features), but the outflows of larger galaxies are less highly ionized and exhibit larger optical depth at the systemic redshift that may correspond to a decreasing efficiency of feedback in evacuating gas from the galaxy. This v ~ 0 km/s gas is responsible both for shifting the mean absorption line redshift and attenuating W_LyA (via a longer resonant scattering path) in galaxies with larger rest-optical half light radii. In contrast to galaxies at lower redshifts, there is no evidence for a correlation between outflow velocity and inclination, suggesting that outflows from these puffy and irregular systems may be poorly collimated. (Abbrev.)Comment: 18 pages, 11 figures. Revised version accepted for publication in ApJ. Version with full-resolution figures is available at http://di.utoronto.ca/~drlaw/Papers/wfc3_uvspec.pd

The Lyα Properties of Faint Galaxies at z ~ 2-3 with Systemic Redshifts and Velocity Dispersions from Keck-MOSFIRE

We study the Lyα profiles of 36 spectroscopically detected Lyα-emitters (LAEs) at z ~ 2-3, using Keck MOSFIRE to measure systemic redshifts and velocity dispersions from rest-frame optical nebular emission lines. The sample has a median optical magnitude R = 26.0, and ranges from R ≃ 23 to R > 27, corresponding to rest-frame UV absolute magnitudes M _(UV) ≃ –22 to M ^(UV) > –18.2. Dynamical masses range from M_(dyn) 3σ significance: brighter galaxies with larger velocity dispersions tend to have larger values of Δv Lyα. We also make use of a comparison sample of 122 UV-color-selected R < 25.5 galaxies at z ~ 2, all with Lyα emission and systemic redshifts measured from nebular emission lines. Using the combined LAE and comparison samples for a total of 158 individual galaxies, we find that Δv_(Lyα) is anti-correlated with the Lyα equivalent width with 7σ significance. Our results are consistent with a scenario in which the Lyα profile is determined primarily by the properties of the gas near the systemic redshift; in such a scenario, the opacity to Lyα photons in lower mass galaxies may be reduced if large gaseous disks have not yet developed and if the gas is ionized by the harder spectrum of young, low metallicity stars

Gene Expression Modifications by Temperature-Toxicants Interactions in Caenorhabditis elegans

Although organophosphorus pesticides (OP) share a common mode of action, there is increased awareness that they elicit a diverse range of gene expression responses. As yet however, there is no clear understanding of these responses and how they interact with ambient environmental conditions. In the present study, we investigated genome-wide gene expression profiles in the nematode Caenorhabditis elegans exposed to two OP, chlorpyrifos and diazinon, in single and combined treatments at different temperatures. Our results show that chlorpyrifos and diazinon induced expression of different genes and that temperature affected the response of detoxification genes to the pesticides. The analysis of transcriptional responses to a combination of chlorpyrifos and diazinon shows interactions between toxicants that affect gene expression. Furthermore, our combined analysis of the transcriptional responses to OP at different temperatures suggests that the combination of OP and high temperatures affect detoxification genes and modified the toxic levels of the pesticides

A Novel 3-Hydroxysteroid Dehydrogenase That Regulates Reproductive Development and Longevity

A multidisciplinary approach identifies novel biochemical activities involved in the synthesisof C. elegans bile acid-like steroids, which act as hormones that regulate sterol metabolism and longevity

First light for GRAVITY: Phase referencing optical interferometry for the Very Large Telescope Interferometer

This is the author accepted manuscript. the final version is available from EDP Sciences via the DOI in this recordGRAVITY is a new instrument to coherently combine the light of the European Southern Observatory Very Large Telescope Interferometer to form a telescope with an equivalent 130 m diameter angular resolution and a collecting area of 200 m2. The instrument comprises fiber fed integrated optics beam combination, high resolution spectroscopy, built-in beam analysis and control, near-infrared wavefront sensing, phase-tracking, dual-beam operation, and laser metrology. GRAVITY opens up to optical/infrared interferometry the techniques of phase referenced imaging and narrow angle astrometry, in many aspects following the concepts of radio interferometry. This article gives an overview of GRAVITY and reports on the performance and the first astronomical observations during commissioning in 2015/16. We demonstrate phase-tracking on stars as faint as mK ≈ 10 mag, phase-referenced interferometry of objects fainter than mK ≈ 15 mag with a limiting magnitude of mK ≈ 17 mag, minute long coherent integrations, a visibility accuracy of better than 0.25%, and spectro-differential phase and closure phase accuracy better than 0.5°, corresponding to a differential astrometric precision of better than ten microarcseconds (μas). The dual-beam astrometry, measuring the phase difference of two objects with laser metrology, is still under commissioning. First observations show residuals as low as 50 μas when following objects over several months. We illustrate the instrument performance with the observations of archetypical objects for the different instrument modes. Examples include the Galactic center supermassive black hole and its fast orbiting star S2 for phase referenced dual-beam observations and infrared wavefront sensing, the high mass X-ray binary BP Cru and the active galactic nucleus of PDS 456 for a few μas spectro-differential astrometry, the T Tauri star S CrA for a spectro-differential visibility analysis, ξ Tel and 24 Cap for high accuracy visibility observations, and η Car for interferometric imaging with GRAVITY.Agence Nationale de la RechercheAlexander von Humboldt FoundationEuropean Union, Seventh Framework Programm