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Dust extinction is one of the fundamental measurements of dust grain sizes, compositions, and shapes. Most of the wavelength-dependent variations seen in Milky Way extinction are strongly correlated with the single parameter R (V) = A (V)/ E (B − V). Existing R (V)-dependent extinction relationships use a mixture of spectroscopic and photometry observations, and hence do not fully capture all the important dust features or continuum variations. Using four existing samples of spectroscopically measured dust extinction curves, we consistently measure the R (V)-dependent extinction relationship spectroscopically from the far-ultraviolet (FUV) to mid-infrared for the first time. Linear fits of A (λ)/ A (V) dependent on R (V) are done using a method that fully accounts for their significant and correlated uncertainties. These linear parameters are fit with analytic wavelength-dependent functions to determine the smooth R (V) (2.3–5.6) and wavelength (912 Å–32 μ m) dependent extinction relationship. This relationship shows that the FUV rise, 2175 Å bump, and the three broad optical features are dependent on R (V), but the 10 and 20 μ m features are not. Existing literature relationships show significant deviations compared to this relationship especially in the FUV and infrared (IR). Extinction curves that clearly deviate from this relationship illustrate that this relationship only describes the average behavior versus R (V). We find tentative evidence that the relationship may not be linear with R (V)−1 especially in the ultraviolet (UV). For the first time, this relationship provides measurements of dust extinction that spectroscopically resolve the continuum and features in the UV, optical, and IR as a function of R (V), enabling detailed studies of dust grain properties and full spectroscopic accounting for the effects of dust extinction on astrophysical objects. [ABSTRACT FROM AUTHOR]

Interstellar dust extinction curves provide valuable information about dust properties, including the composition and size of the dust grains, and are essential to correct observations for the effects of interstellar dust. In this work, we measure a representative sample of near-infrared (NIR; 0.8â€"5.5 ÎĽ m) spectroscopic extinction curves for the first time, enabling us to investigate the extinction at wavelengths where it is usually only measured in broad photometric bands. We use IRTF/SpeX spectra of a sample of reddened and comparison stars to measure 15 extinction curves with the pair method. Our sample spans A (V) values from 0.78 to 5.65 and R (V) values from 2.43 to 5.33. We confirm that the NIR extinction curves are well fit by a power law, with indices and amplitudes differing from sight line to sight line. Our average diffuse NIR extinction curve can be represented by a single power law with index α = 1.7, but because of the sight line-to-sight line variations, the shape of any average curve will depend on the parental sample. We find that most of the variation in our sample can be linked to the ratio of total-to-selective extinction R (V), a rough measurement of the average dust grain size. Two sight lines in our sample clearly show the ice extinction feature at 3 ÎĽ m, which can be fitted by a modified Drude profile. We find tentative ice detections with slightly over 3 σ significance in two other sight lines. In our average diffuse extinction curve, we measure a 3 σ upper limit of A (ice)/ A (V) = 0.0021 for this ice feature. [ABSTRACT FROM AUTHOR]

We analyze low-resolution Spitzer infrared (IR) 5âˆ'14 ÎĽ m spectra of the diffuse emission toward a carefully selected sample of stars. The sample is composed of sight lines toward stars that have well-determined ultraviolet (UV) extinction curves and that are shown to lie beyond effectively all of the extinguishing and emitting dust along their lines of sight. Our sample includes sight lines whose UV curve extinction curves exhibit a wide range of curve morphology and that sample a variety of interstellar environments. As a result, this unique sample enabled us to study the connection between the extinction and emission properties of the same grains, and to examine their response to different physical environments. We quantify the emission features in terms of the polycyclic aromatic hydrocarbon (PAH) model given by Draine & Li and a set on additional features not known to be related to PAH emission. We compare the intensities of the different features in the Spitzer mid-infrared spectra with the Fitzpatrick & Massa parameters that describe the shapes of UV to near-infrared extinction curves. Our primary result is that there is a strong correlation between the area of the 2175 Ă... UV bump in the extinction curves of the program stars and the strengths of the major PAH emission features in the mid-infrared spectra for the same lines of sight. [ABSTRACT FROM AUTHOR]

We measured the mid-infrared (MIR) extinction using Spitzer photometry and spectroscopy (3.6–37 μm) for a sample of Milky Way sight lines (mostly) having measured ultraviolet extinction curves. We used the pair method to determine the MIR extinction that we then fit with a power law for the continuum and modified Drude profiles for the silicate features. We derived 16 extinction curves having a range of A(V) (1.8–5.5) and R(V) values (2.4–4.3). Our sample includes two dense sight lines that have 3 μm ice feature detections and weak 2175 Å bumps. The average A(λ)/A(V) diffuse sight-line extinction curve we calculate is lower than most previous literature measurements. This agrees better with literature diffuse dust grain models, though it is somewhat higher. The 10 μm silicate feature does not correlate with the 2175 Å bump, for the first time providing direct observational confirmation that these two features arise from different grain populations. The strength of the 10 μm silicate feature varies by ∼2.5 and is not correlated with A(V) or R(V). It is well fit by a modified Drude profile with strong correlations seen between the central wavelength, width, and asymmetry. We do not detect other features with limits in A(λ)/A(V) units of 0.0026 (5–10 μm), 0.004 (10–20 μm), and 0.008 (20–40 μm). We find that the standard prescription of estimating R(V) from C × E(Ks − V)/E(B − V) has C = −1.14 and a scatter of ∼7%. Using the IRAC 5.6 μm band instead of Ks gives C = −1.03 and the least scatter of ∼3%. [ABSTRACT FROM AUTHOR]

We describe the operations concept and data reduction plan for the Mid-Infrared Instrument (MIRI) for the James Webb Space Telescope (JWST). The overall JWST operations concept is to use observation templates (OTs) to provide a straightforward and intuitive way for users to specify observations. MIRI has four OTs that correspond to the four observing modes: (1) imaging, (2) coronagraphy, (3) low-resolution spectroscopy, and (4) medium-resolution spectroscopy. We outline the user choices and expansion of these choices into detailed instrument operations. The data reduction plans for MIRI are split into three stages, where the specificity of the reduction steps to the observation type increases with stage. The reduction starts with integration ramps: stage 1 yields uncalibrated slope images; stage 2 calibrates the slope images; and then stage 3 combines multiple calibrated slope images into high-level data products (e.g., mosaics, spectral cubes, and extracted source information). Finally, we give examples of the data and data products that will be derived from each of the four different OTs. [ABSTRACT FROM AUTHOR]

The measurement of precise absolute fluxes for stellar sources has been pursued with increased vigor since the discovery of dark energy and the realization that its detailed understanding requires accurate spectral energy distributions (SEDs) of redshifted la supernovae in the rest frame. The flux distributions of spectrophotometric standard stars were initially derived from the comparison of stars to laboratory sources of known flux but are now mostly based on calculated model atmospheres. For example, pure hydrogen white dwarf (WD) models provide the basis for the MST CALSPEC archive of flux standards. The basic equations for quantitative spectrophotometry and photometry are explained in detail. Several historical lab-based flux calibrations are reviewed; and the SEDs of stars in the major online astronomical databases are compared to the CALSPEC reference standard spectrophotometry. There is good evidence that relative fluxes from the visible to the near-IR wavelength of ~2.5 μm are currently accurate to 1% for the primary reference standards, and new comparisons with lab flux standards show promise for improving that precision. [ABSTRACT FROM AUTHOR]

In star-forming galaxies, dust plays a significant role in shaping the ultraviolet (UV) through infrared (IR) spectrum. Dust attenuates the radiation from stars, and re-radiates the energy through equilibrium and non-equilibrium emission. Polycyclic aromatic hydrocarbons (PAHs), graphite, and silicates contribute to different features in the spectral energy distribution; however, they are all highly opaque in the same spectral region--the UV. Compared to old stellar populations, young populations release a higher fraction of their total luminosity in the UV, making them a good source of the energetic UV photons that can power dust emission. However, given their relative abundance, the question of whether young or old stellar populations provide most of these photons that power the IR emission is an interesting question. Using three samples of galaxies observed with the Spitzer Space Telescope and our dusty radiative transfer model, we find that young stellar populations (on the order of 100 million years old) dominate the dust heating in star-forming galaxies, and old stellar populations (13 billion years old) generally contribute less than 20% of the far-IR luminosity. [ABSTRACT FROM AUTHOR]

Abstract: The Tetraviridae is a family of non-enveloped positive-stranded RNA insect viruses that is defined by the T=4 symmetry of virions. We report the complete Euprosterna elaeasa virus (EeV) genome sequence of 5698 nt with no poly(A) tail and two overlapping open reading frames, encoding the replicase and capsid precursor, with ∼67% amino acid identity to Thosea asigna virus (TaV). The N-terminally positioned 17 kDa protein is released from the capsid precursor by a NPGP motif. EeV has 40 nm non-enveloped isometric particles composed of 58 and 7 kDa proteins. The 3′-end of TaV/EeV is predicted to form a conserved pseudoknot. Replicases of TaV and EeV include a newly delineated VPg signal mediating the protein priming of RNA synthesis in dsRNA Birnaviridae. Results of rooted phylogenetic analysis of replicase and capsid proteins are presented to implicate recombination between monopartite tetraviruses, involving autonomization of a sgRNA, in the emergence of bipartite tetraviruses. They are also used to revise the Tetraviridae taxonomy. [Copyright &y& Elsevier]

Techniques of microscopy and histopathology were employed to study the positive-sense, single-stranded RNA virus, the Helicoverpa armigera stunt virus (HaSV; omegatetravirus, Tetraviridae) infecting its caterpillar host. Infection of the virus per os during the first three instars of larval development is virulent and leads to rapid stunting and mortality. In contrast, no detectable symptoms occur in later larval development, signifying a high degree of developmental resistance. A quantitative study of cell populations in the host midgut during this time showed that increased cell numbers during development alone could not account for the increase in resistance. HaSV infection was restricted to the midgut and three of its four cell types. In younger larvae, the virus initiated its infection in closely situated foci that appeared to expand to link with others to cover larger areas of the midgut. The midgut cells of the infected larvae responded with an increased rate of sloughing to an extent rendering the midgut incapable of maintenance or recovery of normal function. In contrast, infection of older larvae by HaSV did not lead to overt pathology although foci of HaSV infection were detected in their midguts. However, the foci were more sparsely situated, failed to expand, and eventually disappeared, presumably due to cell sloughing. These observations indicate that cell sloughing is an immune response existing throughout larval development but midguts of older larvae have an additional mechanism to account for the increased resistance. This second mechanism results in midgut cells becoming more refractory to infection and, combined with cell sloughing, allows the midguts of older larvae to recover more readily from HaSV infection. These two mechanisms are similar to those seen with host responses to baculoviruses, which display developmental resistance to a lesser degree against more general infections. HaSV remaining in the midgut appears to amplify the degree of developmental resistance. [Copyright &y& Elsevier]

A precise, reproducible deletion made during in vitro reverse transcription of RNA2 from the icosahedral positive-stranded Helicoverpa armigera stunt virus (Tetraviridae) is described. The deletion, located between two hexamer repeats, is a 50-base sequence that includes one copy of the hexamer repeat. Only the Moloney murine leukemia virus reverse transcriptase and its derivative Superscript I, carrying a deletion of the carboxy-terminal RNase H region, showed this response, indicating a template-switching mechanism different from one proposed that involves a RNase H– dependent strand transfer. Superscript II, however, which carries point mutations to reduce RNase H activity, does not cause a deletion. A possible mechanism involves the enzyme pausing at the 3' side of a stem-loop structure and the 3' end of the nascent DNA strand separating from the template and reannealing to the upstream hexamer repeat. [ABSTRACT FROM AUTHOR]

We present new JWST observations of the nearby, prototypical edge-on, spiral galaxy NGC 891. The northern half of the disk was observed with NIRCam in its F150W and F277W filters. Absorption is clearly visible in the mid-plane of the F150W image, along with vertical dusty plumes that closely resemble the ones seen in the optical. A ∼10 × 3 kpc2 area of the lower circumgalactic medium (CGM) was mapped with MIRI F770W at 12 pc scales. Thanks to the sensitivity and resolution of JWST, we detect dust emission out to ∼4 kpc from the disk, in the form of filaments, arcs, and super-bubbles. Some of these filaments can be traced back to regions with recent star formation activity, suggesting that feedback-driven galactic winds play an important role in regulating baryonic cycling. The presence of dust at these altitudes raises questions about the transport mechanisms at play and suggests that small dust grains are able to survive for several tens of million years after having been ejected by galactic winds in the disk-halo interface. We lay out several scenarios that could explain this emission: dust grains may be shielded in the outer layers of cool dense clouds expelled from the galaxy disk, and/or the emission comes from the mixing layers around these cool clumps where material from the hot gas is able to cool down and mix with these cool cloudlets. This first set of data and upcoming spectroscopy will be very helpful to understand the survival of dust grains in energetic environments, and their contribution to recycling baryonic material in the mid-plane of galaxies. [ABSTRACT FROM AUTHOR]

Context. Mid-infrared emission features are important probes of the properties of ionized gas and hot or warm molecular gas, which are difficult to probe at other wavelengths. The Orion Bar photodissociation region (PDR) is a bright, nearby, and frequently studied target containing large amounts of gas under these conditions. Under the "PDRs4All" Early Release Science Program for JWST, a part of the Orion Bar was observed with MIRI integral field unit (IFU) spectroscopy, and these high-sensitivity IR spectroscopic images of very high angular resolution (0.2″) provide a rich observational inventory of the mid-infrared (MIR) emission lines, while resolving the H II region, the ionization front, and multiple dissociation fronts. Aims. We list, identify, and measure the most prominent gas emission lines in the Orion Bar using the new MIRI IFU data. An initial analysis summarizes the physical conditions of the gas and demonstrates the potential of these new data and future IFU observations with JWST. Methods. The MIRI IFU mosaic spatially resolves the substructure of the PDR, its footprint cutting perpendicularly across the ionization front and three dissociation fronts. We performed an up-to-date data reduction, and extracted five spectra that represent the ionized, atomic, and molecular gas layers. We identified the observed lines through a comparison with theoretical line lists derived from atomic data and simulated PDR models. The identified species and transitions are summarized in the main table of this work, with measurements of the line intensities and central wavelengths. Results. We identified around 100 lines and report an additional 18 lines that remain unidentified. The majority consists of H I recombination lines arising from the ionized gas layer bordering the PDR. The H I line ratios are well matched by emissivity coefficients from H recombination theory, but deviate by up to 10% because of contamination by He I lines. We report the observed emission lines of various ionization stages of Ne, P, S, Cl, Ar, Fe, and Ni. We show how the Ne III/Ne II, S IV/S III, and Ar III/Ar II ratios trace the conditions in the ionized layer bordering the PDR, while Fe III/Fe II and Ni III/Ni II exhibit a different behavior, as there are significant contributions to Fe II and Ni II from the neutral PDR gas. We observe the pure-rotational H2 lines in the vibrational ground state from 0–0 S(1) to 0–0 S (8), and in the first vibrationally excited state from 1–1 S (5) to 1–1 S(9). We derive H2 excitation diagrams, and for the three observed dissociation fronts, the rotational excitation can be approximated with one thermal (~700 K) component representative of an average gas temperature, and one nonthermal component (~2700 K) probing the effect of UV pumping. We compare these results to an existing model of the Orion Bar PDR, and find that the predicted excitation matches the data qualitatively, while adjustments to the parameters of the PDR model are required to reproduce the intensity of the 0–0 S (6) to S (8) lines. [ABSTRACT FROM AUTHOR]

Stress is a widespread phenomenon that all organisms must endure. Common in nature is oxidative stress, which can interrupt cell homeostasis to cause cell damage and may be derived from respiration or from environmental exposure through diet. As a result of the routine exposure from respiration, many organisms can mitigate the effects of oxidative stress, but less is known about responses to oxidative stress from other sources. Helicoverpa armigera is a major agricultural pest moth that causes significant damage to crops worldwide. Here, we examined the effects of oxidative stress on H. armigera by chronically exposing individuals to paraquat—a free radical producer—and measuring changes in development (weight, developmental rate, lifespan), and gene expression. We found that oxidative stress strongly affected development in H. armigera, with stressed samples spending more time as caterpillars than control samples (>24 vs. ~15 days, respectively) and therefore living longer overall. We found 1,618 up‐ and 761 down‐regulated genes, respectively, in stressed versus control samples. In the up‐regulated gene set, was an over‐representation of biological processes related to cuticle and chitin development, glycine metabolism, and oxidation–reduction. Oxidative stress clearly impacts physiology and biochemistry in H. armigera and the interesting finding of an extended lifespan in stressed individuals could demonstrate hormesis, the phenomenon whereby toxic compounds can actually be beneficial at low doses. Collectively, our findings provide new insights into physiological and gene expression responses to oxidative stress in invertebrates. [ABSTRACT FROM AUTHOR]

Background: Studies on Philippine Banaba native chickens and Philippine Mallard ducks were generally focused on their production and management. However, little is known on their immune responses to pathogens like Riemerella anatipestifer (R. anatipestifer), one of the economically important infectious disease-causing pathogens in Philippine Banaba native chickens and Philippine Mallard ducks. Methods: Chicken and duck embryonic fibroblasts (CEFs and DEFs) isolated from 11-day old healthy embryos were stimulated with heat-inactivated R. anatipestifer for 4, 8 and 24 h. The cells were collected at each time point and subjected to qRT-PCR for gene expression analyses. Results: Comparative gene expression analyses of immune-related cytokines revealed that the ex- pression levels of IL-17A, IL-17F, IL-1ß and IL-6 were significantly upregulated in both CEFs and DEFs stimulated with heat-inactivated R. anatipestifer serotype 7. However, levels were higher in DEFs compared to the corresponding levels in heat-inactivated R. anatipestifer stimulated CEFs. On the other hand, IFN-γ, IL-2, IL-4 and IL-10 expression levels of stimulated DEFs were also upregulated. In CEFs, it is interesting to note that IFN-γ level was significantly downregulated at 24 h while upregulated in DEFs. Conclusion: Results showed that the Philippine Banaba native chickens and Mallard ducks are also susceptible to R. anatipestifer infection. [ABSTRACT FROM AUTHOR]

The article reports on the two research regarding the potential use of RNA interference (RNAi) induced by hairpin RNAs as a new line of defense against coleopteran and lepidopteran pests. RNAi has been exploited in plants for applications ranging from functional genomics to provision of valuable crop traits such as resistance against viruses, bacteria and nematodes. The result of one research suggests that transgene-encoded ingestible double-stranded RNA may one day stand alongside Bacillus thuringiensis transgenes in insect management programs.

The spatial variations of the gas-to-dust ratio (GDR) provide constraints on the chemical evolution and lifecycle of dust in galaxies. We examine the relation between dust and gas at 10-50 pc resolution in the Large and Small Magellanic Clouds (LMC and SMC) based on Herschel far-infrared (FIR), H I 21 cm, CO, and Hα observations. In the diffuse atomic interstellar medium (ISM), we derive the GDR as the slope of the dust-gas relation and find GDRs of 380 3 in the LMC, and 1200 120 in the SMC, not including helium. The atomic-to-molecular transition is located at dust surface densities of 0.05 M☼ pc–2 in the LMC and 0.03 M☼ pc–2 in the SMC, corresponding to AV ∼ 0.4 and 0.2, respectively. We investigate the range of CO-to-H2 conversion factor to best account for all the molecular gas in the beam of the observations, and find upper limits on XCO to be 6 × 1020 cm–2 K–1 km–1 s in the LMC (Z = 0.5 Z☼) at 15 pc resolution, and 4 × 1021 cm–2 K–1 km–1 s in the SMC (Z = 0.2 Z☼) at 45 pc resolution. In the LMC, the slope of the dust-gas relation in the dense ISM is lower than in the diffuse ISM by a factor ∼2, even after accounting for the effects of CO-dark H2 in the translucent envelopes of molecular clouds. Coagulation of dust grains and the subsequent dust emissivity increase in molecular clouds, and/or accretion of gas-phase metals onto dust grains, and the subsequent dust abundance (dust-to-gas ratio) increase in molecular clouds could explain the observations. In the SMC, variations in the dust-gas slope caused by coagulation or accretion are degenerate with the effects of CO-dark H2. Within the expected 5-20 times Galactic XCO range, the dust-gas slope can be either constant or decrease by a factor of several across ISM phases. Further modeling and observations are required to break the degeneracy between dust grain coagulation, accretion, and CO-dark H2. Our analysis demonstrates that obtaining robust ISM masses remains a non-trivial endeavor even in the local Universe using state-of-the-art maps of thermal dust emission. [ABSTRACT FROM AUTHOR]

The dust properties in the Large and Small Magellanic clouds (LMC/SMC) are studied using the HERITAGE Herschel Key Project photometric data in five bands from 100 to 500 μm. Three simple models of dust emission were fit to the observations: a single temperature blackbody modified by a power-law emissivity (SMBB), a single temperature blackbody modified by a broken power-law emissivity (BEMBB), and two blackbodies with different temperatures, both modified by the same power-law emissivity (TTMBB). Using these models, we investigate the origin of the submillimeter excess, defined as the submillimeter emission above that expected from SMBB models fit to observations <200 μm. We find that the BEMBB model produces the lowest fit residuals with pixel-averaged 500 μm submillimeter excesses of 27% and 43% for the LMC and SMC, respectively. Adopting gas masses from previous works, the gas-to-dust ratios calculated from our fitting results show that the TTMBB fits require significantly more dust than are available even if all the metals present in the interstellar medium (ISM) were condensed into dust. This indicates that the submillimeter excess is more likely to be due to emissivity variations than a second population of colder dust. We derive integrated dust masses of (7.3 ± 1.7) × 105 and (8.3 ± 2.1) × 104M☼ for the LMC and SMC, respectively. We find significant correlations between the submillimeter excess and other dust properties; further work is needed to determine the relative contributions of fitting noise and ISM physics to the correlations. [ABSTRACT FROM AUTHOR]

A correction to the article "Fuse Measurements of Far-Ultraviolet Extinction. III. The Dependence on R(V) and Discrete Feature Limits From 75 Galactic Sightlines" by Karl D. Gordon, Stefan Cartledge and Geoffrey C. Clayton in a 2009 issue of the journal is presented.

Context: Dust modeling is crucial to infer dust properties and budget for galaxy studies. However, there are systematic disparities between dust grain models that result in corresponding systematic differences in the inferred dust properties of galaxies. Quantifying these systematics requires a consistent fitting analysis. Aims: We compare the output dust parameters and assess the differences between two dust grain models, the DustEM model and THEMIS. In this study, we use a single fitting method applied to all the models to extract a coherent and unique statistical analysis. Methods: We fit the models to the dust emission seen by Spitzer and Herschel in the Small and Large Magellanic Clouds (SMC and LMC). The observations cover the infrared (IR) spectrum from a few microns to the sub-millimeter range. For each fitted pixel, we calculate the full n-D likelihood based on a previously described method. The free parameters are both environmental (U, the interstellar radiation field strength; αISRF, power-law coefficient for a multi-U environment; Ω∗, the starlight strength) and intrinsic to the model (Yi: abundances of the grain species i; αsCM20, coefficient in the small carbon grain size distribution). Results: Fractional residuals of five different sets of parameters show that fitting THEMIS brings a more accurate reproduction of the observations than the DustEM model. However, independent variations of the dust species show strong model-dependencies. We find that the abundance of silicates can only be constrained to an upper-limit and that the silicate/carbon ratio is different than that seen in our Galaxy. In the LMC, our fits result in dust masses slightly lower than those found in the literature, by a factor lower than 2. In the SMC, we find dust masses in agreement with previous studies. [ABSTRACT FROM AUTHOR]

The draft assembly of the honey bee Apis mellifera genome sequence reveals that the 17 centromeric-distal telomeres are of a simple, shared, and canonical structure, with 3-4 kb of a unique subtelomeric sequence, followed by several kilobases of TTAGG or variant telomeric repeats. This simple subtelomeric structure differs from the centromeric-proximal telomeres on the short arms of the 15 acrocentric chromosomes, which are apparently composed primarily of the 176-bp AluI tandem repeat. This dichotomy between the distal and proximal telomeres may involve differential participation of the telomeres of the 15 acrocentric chromosomes in the Rab1 configuration after mitosis and the chromosome bouquet in meiotic prophase I. As expected from the presence of canonical TTAGG telomeric repeats, we identified a candidate telomerase gene in the bee, as well as the silkmoth Bombyx mori and the flour beetle Tribolium castaneum. [ABSTRACT FROM AUTHOR]

The fall armyworm (FAW; Spodoptera frugiperda) is one of the major agricultural pest insects. FAW is native to the Americas, and its invasion was first reported in West Africa in 2016. Then it quickly spread through Africa, Asia, and Oceania, becoming one of the main threats to corn production. We analyzed whole genome sequences of 177 FAW individuals from 12 locations on four continents to infer evolutionary processes of invasion. Principal component analysis from the TPI gene and whole genome sequences shows that invasive FAW populations originated from the corn strain. Ancestry coefficient and phylogenetic analyses from the nuclear genome indicate that invasive populations are derived from a single ancestry, distinct from native populations, while the mitochondrial phylogenetic tree supports the hypothesis of multiple introductions. Adaptive evolution specific to invasive populations was observed in detoxification, chemosensory, and digestion genes. We concluded that extant invasive FAW populations originated from the corn strain with potential contributions of adaptive evolution. [ABSTRACT FROM AUTHOR]

Native to the Americas, the invasive Spodoptera frugiperda (fall armyworm; FAW) was reported in West Africa in 2016, followed by its chronological detection across the Old World and the hypothesis of an eastward Asia expansion. We explored population genomic signatures of American and Old World FAW and identified 12 maternal mitochondrial DNA genome lineages across the invasive range. 870 high-quality nuclear single nucleotide polymorphic DNA markers identified five distinct New World population clusters, broadly reflecting FAW native geographical ranges and the absence of host-plant preferences. We identified unique admixed Old World populations, and admixed and non-admixed Asian FAW individuals, all of which suggested multiple introductions underpinning the pest's global spread. Directional gene flow from the East into eastern Africa was also detected, in contrast to the west-to-east spread hypothesis. Our study demonstrated the potential of population genomic approaches via international partnership to address global emerging pest threats and biosecurity challenges. This population genomics study identifies the complex multiple introduction history of Spodoptera frugiperda (fall armyworm) from the Americas, into Africa and Asia. This provides new insight into the 'east-to-west' directionality of gene flow, and suggests ample genomic exchange at the nuclear level. [ABSTRACT FROM AUTHOR]

Cosmic dust is present in many astrophysical objects, and recent observations across the electromagnetic spectrum show that the dust distribution is often strongly three-dimensional (3D). Dust grains are effective in absorbing and scattering ultraviolet (UV)/optical radiation, and they re-emit the absorbed energy at infrared wavelengths. Understanding the intrinsic properties of these objects, including the dust itself, therefore requires 3D dust radiative transfer (RT) calculations. Unfortunately, the 3D dust RT problem is nonlocal and nonlinear, which makes it one of the hardest challenges in computational astrophysics. Nevertheless, significant progress has been made in the past decade, with an increasing number of codes capable of dealing with the complete 3D dust RT problem. We discuss the complexity of this problem, the two most successful solution techniques [ray-tracing (RayT) and Monte Carlo (MC)], and the state of the art in modeling observational data using 3D dust RT codes. We end with an outlook on the bright future of this field. [ABSTRACT FROM AUTHOR]

We present a characterization of the close environment of GRB 980425 based on 5-160 µm spectro-imaging obtained with Spitzer. The gamma-ray burst GRB 980425 occurred in a nearby (z = 0.0085) SBc-type dwarf galaxy at a projected distance of 900 pc from an H II region with strong signatures of Wolf--Rayet (WR) stars. While this "WR region" produces less than 5% of the B-band emission of the host, we find that it is responsible for 45% ± 10% of the total infrared luminosity, with a maximum contribution reaching 75% at 25-30 µm. This atypical property is rarely observed among morphologically relaxed dwarfs, suggesting a strong causal link with the gamma-ray burst (GRB) event. The luminosity of the WR region (L8-1000 µm = 4.6 x 108 L⊙), the peak of its spectral energy distribution at ≲ 100 µm, and the presence of highly ionized emission lines (e.g., [Ne III]) also reveal extremely young (<5 Myr) star-forming activity, with a typical timescale of only 47 Myr to double the stellar mass already built. Finally, the mid-IR over B-band luminosity ratio in this region is substantially higher than in star-forming galaxies with similar LIR, but it is lower than in young dust-enshrouded stellar clusters. Considering the modest obscuration measured from the silicate features (τ9.7 µm ~ 0.015), this suggests that the WR region is dominated by one or several star clusters that have either partly escaped or cleared out their parent molecular cloud. Combined with the properties characterizing the whole population of GRB hosts, our results reinforce the idea that long GRBs mostly happen within or in the vicinity of relatively unobscured galactic regions harboring very recent star formation. [ABSTRACT FROM AUTHOR]

We estimate the conversion factor relating CO emission to H2 mass, αCO, in five Local Group galaxies that span approximately an order of magnitude in metallicity--M 31, M 33, the Large Magellanic Cloud (LMC), NGC 6822, and the Small Magellanic Cloud (SMC). We model the dust mass along the line of sight from infrared (IR) emission and then solve for the αCO that best allows a single gas-to-dust ratio (δGDR) to describe each system. This approach remains sensitive to CO-dark envelopes H2 surrounding molecular clouds. In M 31, M 33, and the LMC we find αCO ≈ 3-9 M⊙ pc-2 (K km s-1)-1, consistent with the Milky Way value within the uncertainties. The two lowest metallicity galaxies in our sample, NGC 6822 and the SMC (12 + log(O/H) ≈ 8.2 and 8.0), exhibit a much higher αCO. Our best estimates are Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. and Due to image rights restrictions, multiple line equation(s) cannot be graphically displayed. These results are consistent with the conversion factor becoming a strong function of metallicity around 12 + log(O/H) ~ 8.4-8.2. We favor an interpretation where decreased dust shielding leads to the dominance of CO-free envelopes around molecular clouds below this metallicity. [ABSTRACT FROM AUTHOR]

An abstract of the article "Downregulation of a Chitin Deacetylase-Like Protein in Response to Baculovirus Infection and Its Application for Improving Baculovirus Infectivity," by Agata K. Jakubowska, Silvia Caccia, Karl H. Gordon, Juan Ferré, and Salvador Herrero is presented.

The fall armyworm (FAW), Spodoptera frugiperda, is a major pest native to the Americas that has recently invaded the Old World. Point mutations in the target‐site proteins acetylcholinesterase‐1 (ace‐1), voltage‐gated sodium channel (VGSC) and ryanodine receptor (RyR) have been identified in S. frugiperda as major resistance mechanisms to organophosphate, pyrethroid and diamide insecticides respectively. Mutations in the adenosine triphosphate‐binding cassette transporter C2 gene (ABCC2) have also been identified to confer resistance to Cry1F protein. In this study, we applied a whole‐genome sequencing (WGS) approach to identify point mutations in the target‐site genes in 150 FAW individuals collected from China, Malawi, Uganda and Brazil. This approach revealed three amino acid substitutions (A201S, G227A and F290V) of S. frugiperda ace‐1, which are known to be associated with organophosphate resistance. The Brazilian population had all three ace‐1 point mutations and the 227A allele (mean frequency = 0.54) was the most common. Populations from China, Malawi and Uganda harbored two of the three ace‐1 point mutations (A201S and F290V) with the 290V allele (0.47–0.58) as the dominant allele. Point mutations in VGSC (T929I, L932F and L1014F) and RyR (I4790M and G4946E) were not detected in any of the 150 individuals. A novel 12‐bp insertion mutation in exon 15 of the ABCC2 gene was identified in some of the Brazilian individuals but absent in the invasive populations. Our results not only demonstrate robustness of the WGS‐based genomic approach for detection of resistance mutations, but also provide insights for improvement of resistance management tactics in S. frugiperda. [ABSTRACT FROM AUTHOR]

The nucleotide sequence of the 3035 residues of RNA 2(MΓ 1.03 x 106) of the Q strain of cucumber mosaic virus (CMV) was determined by sequencing M13 clones of the RNA 2 cDNA and by dideoxy sequencing using primers prepared either from M13 clones or by chemical synthesis. A single long open reading frame starts at the second AUG from the 5' end of RNA 2 and encodes 839 amino acids (MΓ 94 333). This frame has flanking reion of 92 nucleotides at the 5' terminus and 423 nucleotides at the 3' terminus. Computer analysis of the nucleotide sequence showed that CMV RNA 2 has a significant homology with RNA 2 of brome mosaic virus (BMV) and alfalfa mosaic virus (AMV) and also with a region for tobacco mosaic virus (TMV) RNA encoding the read-through part of the 183-kDa protein. About 400 amino acids in the central region of the CMV RNA 2 translation product have a striking homology with the corresponding proteins encoded by BMV and AMV and with the read-through part of the TMV 183-kDa protein. Hydrophobicity plots of CMV and BMV RNA translation products also had apparent similarities. It is concluded that CMV is related to BMV, AMV and TMV in order of increasing evolutionary divergence. [ABSTRACT FROM AUTHOR]

The chloroplast genomes of Euglena gracilis and Spinacia oleracea were investigated in their compositional heterogeneity, by using several different experimental approaches. Euglena chloroplast DNA has a dG + dC content of 28%. Preparations averaging 20 x 10[sup6] in molecular weight exhibit a gross heterogeneity in their elution profiles from hydroxyapatite and in their buoyant densities because the rRNA genes have a high rG + rC content. Finer analysis by melting, buoyant density of restriction fragments and micrococcal nuclease degradation have revealed an extended compositional heterogeneity. From micrococcal nuclease digestion data, approximately 30 % of the chloroplast genome is as low as 12 % in its dG + dC content, whereas 10% is higher than 60% dG + dC. Since the average dG + dC content of large restriction endonuclease fragments varied to a lesser extent, most of dA + dT-rich sequences must occur in short stretches interspersed with dG + dC-rich stretches. Spinach chloroplast DNA (dG + dC = 36.5%) did not exhibit any gross compositional heterogeneity in its hydroxyapatite elution or in its buoyant density profile. But the higher resolution methods of melting, buoyant densities of restriction fragments and micrococcal nuclease degradation revealed a high degree of heterogeneity which appears to be due to interspersion of short DNA stretches of different base composition. About 30 % of genome is as low as 22 % in dG + dC, while 10 % is higher than 60 % in dG + dC. [ABSTRACT FROM AUTHOR]

We present a comparative study of four physical dust models and two single-temperature modified blackbody models by fitting them to the resolved WISE, Spitzer, and Herschel photometry of M101 (NGC 5457). Using identical data and a grid-based fitting technique, we compare the resulting dust and radiation field properties derived from the models. We find that the dust mass yielded by the different models can vary by up to a factor of 3 (factor of 1.4 between physical models only), although the fits have similar quality. Despite differences in their definition of the carriers of the mid-IR aromatic features, all physical models show the same spatial variations for the abundance of that grain population. Using the well-determined metallicity gradient in M101 and resolved gas maps, we calculate an approximate upper limit on the dust mass as a function of radius. All physical dust models are found to exceed this maximum estimate over some range of galactocentric radii. We show that renormalizing the models to match the same Milky Way high-latitude cirrus spectrum and abundance constraints can reduce the dust mass differences between models and bring the total dust mass below the maximum estimate at all radii. [ABSTRACT FROM AUTHOR]

A key component of the baryon cycle in galaxies is the depletion of metals from the gas to the dust phase in the neutral interstellar medium (ISM). The METAL (Metal Evolution, Transport, and Abundance in the Large Magellanic Cloud) program on the Hubble Space Telescope acquired UV spectra toward 32 sight lines in the half-solar metallicity LMC, from which we derive interstellar depletions (gas-phase fractions) of Mg, Si, Fe, Ni, S, Zn, Cr, and Cu. The depletions of different elements are tightly correlated, indicating a common origin. Hydrogen column density is the main driver for depletion variations. Correlations are weaker with volume density, probed by C i fine-structure lines, and distance to the LMC center. The latter correlation results from an east–west variation of the gas-phase metallicity. Gas in the east, compressed side of the LMC encompassing 30 Doradus and the southeast H i over-density is enriched by up to +0.3 dex, while gas in the west side is metal deficient by up to −0.5 dex. Within the parameter space probed by METAL, no correlation with molecular fraction or radiation-field intensity are found. We confirm the factor of three to four increase in dust-to-metal and dust-to-gas ratios between the diffuse (log N(H) ∼ 20 cm−2) and molecular (log N(H) ∼ 22 cm−2) ISM observed from far-infrared, 21 cm, and CO observations. The variations of dust-to-metal and dust-to-gas ratios with column density have important implications for the sub-grid physics of chemical evolution, gas and dust mass estimates throughout cosmic times, and for the chemical enrichment of the Universe measured via spectroscopy of damped Lyα systems. [ABSTRACT FROM AUTHOR]

We demonstrate a new method for measuring the escape fraction of ionizing photons using Hubble Space Telescope imaging of resolved stars in NGC 4214, a local analog of high-redshift starburst galaxies that are thought to be responsible for cosmic reionization. Specifically, we forward model the UV through near-IR spectral energy distributions of ∼83,000 resolved stars to infer their individual ionizing flux outputs. We constrain the local escape fraction by comparing the number of ionizing photons produced by stars to the number that are either absorbed by dust or consumed by ionizing the surrounding neutral hydrogen in individual star-forming regions. We find substantial spatial variation in the escape fraction (0%–40%). Integrating over the entire galaxy yields a global escape fraction of %. This value is much higher than previous escape fractions of zero reported for this galaxy. We discuss the sources of this apparent tension and demonstrate that the viewing angle and 3D interstellar medium geometric effects are the cause. If we assume that NGC 4214 has no internal dust, like many high-redshift galaxies, we find an escape fraction of 59% (an upper limit for NGC 4214). This is the first nonzero escape fraction measurement for UV-faint (M = −15.9) galaxies at any redshift and supports the idea that starburst UV-faint dwarf galaxies can provide a sufficient number of ionizing photons to the intergalactic medium. [ABSTRACT FROM AUTHOR]

The Old World cotton bollworm Helicoverpa armigera was first detected in Brazil with subsequent reports from Paraguay, Argentina, Bolivia, and Uruguay. This pattern suggests that the H. armigera spread across the South American continent following incursions into northern/central Brazil, however, this hypothesis has not been tested. Here we compare northern and central Brazilian H. armigera mtDNA COI haplotypes with those from southern Brazil, Uruguay, Argentina, and Paraguay. We infer spatial genetic and gene flow patterns of this dispersive pest in the agricultural landscape of South America. We show that the spatial distribution of H. armigera mtDNA haplotypes and its inferred gene flow patterns in the southwestern region of South America exhibited signatures inconsistent with a single incursion hypothesis. Simulations on spatial distribution patterns show that the detection of rare and/or the absence of dominant mtDNA haplotypes in southern H. armigera populations are inconsistent with genetic signatures observed in northern and central Brazil. Incursions of H. armigera into the New World are therefore likely to have involved independent events in northern/central Brazil, and southern Brazil/Uruguay-Argentina-Paraguay. This study demonstrates the significant biosecurity challenges facing the South American continent, and highlights alternate pathways for introductions of alien species into the New World. [ABSTRACT FROM AUTHOR]

Five species of noctuid moths, Helicoverpa armigera, H. punctigera, H. assulta, H. zea, and H. gelotopoeon, are major agricultural pests inhabiting various and often overlapping global distributions. Visual identification of these species requires a great deal of expertise and misidentification can have repercussions for pest management and agricultural biosecurity. Here, we report on the complete mitochondrial genomes of H. assulta assulta and H. assulta afra, H. gelotopoeon, H. punctigera, H. zea, and H. armigera armigera and H. armigera conferta' assembled from high‐throughput sequencing data. This study significantly increases the mitogenome resources for these five agricultural pests with sequences assembled from across different continents, including an H. armigera individual collected from an invasive population in Brazil. We infer the phylogenetic relationships of these five Helicoverpa species based on the 13 mitochondrial DNA protein‐coding genes (PCG's) and show that two publicly available mitogenomes of H. assulta (KP015198 and KR149448) have been misidentified or incorrectly assembled. We further consolidate existing PCR‐RFLP methods to cover all five Helicoverpa pest species, providing an updated method that will contribute to species differentiation and to future monitoring efforts of Helicoverpa pest species across different continents. We discuss the value of Helicoverpa mitogenomes to assist with species identification in view of the context of the rapid spread of H. armigera in the New World. With this work, we provide the molecular resources necessary for future studies of the evolutionary history and ecology of these species. Five species of noctuid moths, Helicoverpa armigera, H. punctigera, H. assulta, H. zea, and H. gelotopoeon, are major agricultural pests inhabiting various and often overlapping global distributions. Here, we report on the complete mitochondrial genomes of these species assembled from high‐throughput sequencing data. We infer the phylogenetic relationships, consolidate existing PCR‐RFLP methods, and provide the molecular resources necessary for future studies of the evolutionary history and ecology of these species. [ABSTRACT FROM AUTHOR]

We report the complete mitochondrial DNA genome of the soybean stem fly (SSF)Melanagromyza sojaefrom Brazil Santa Catarina state based on Illumina MiSeq sequence data. The estimated mitogenome is 15 475 base pairs (bp) (KT597923), with 13 protein-coding genes (PCGs), two ribosomal RNA (rRNA) genes, and 22 tRNAs, and an estimated 579 bp AT-rich control region. Similar to other insects, the SSF mitogenome is A–T bias with 40.9% A, 36.7% T, 13.6% C, and 8.8% G. Molecular characterization of SSF mitogenome will facilitate the development of effective molecular markers, and robust and rapid identification of suspected biosecurity incursions and field infestations of this insect pest. [ABSTRACT FROM AUTHOR]

Within the mega-pest lineage of heliothine moths are a number of polyphagous, highly mobile species for which the exchange of adaptive traits through hybridization would affect their properties as pests. The recent invasion of South America by one of the most significant agricultural pests, Helicoverpa armigera, raises concerns for the formation of novel combinations of adaptive genes following hybridization with the closely related Helicoverpa zea. To investigate the propensity for hybridization within the genus Helicoverpa, we carried out whole-genome resequencing of samples from six species, focusing in particular upon H. armigera population structure and its relationship with H. zea. We show that both H. armigera subspecies have greater genetic diversity and effective population sizes than do the other species. We find no signals for gene flow among the six species, other than between H. armigera and H. zea, with nine Brazilian individuals proving to be hybrids of those two species. Eight had largely H. armigera genomes with some introgressed DNA from H. zea scattered throughout. The ninth resembled an F1 hybrid but with stretches of homozygosity for each parental species that reflect previous hybridization. Regions homozygous for H. armigera-derived DNA in this individual included one containing a gustatory receptor and esterase genes previously associated with host range, while another encoded a cytochrome P450 that confers insecticide resistance. Our data point toward the emergence of novel hybrid ecotypes and highlight the importance of monitoring H. armigera genotypes as they spread through the Americas. [ABSTRACT FROM AUTHOR]

Molecular species identification using suboptimal PCR primers can over-estimate species diversity due to coamplification of nuclear mitochondrial (NUMT) DNA/pseudogenes. For the agriculturally important whitefly Bemisia tabaci cryptic pest species complex, species identification depends primarily on characterization of themitochondrialDNAcytochromeoxidase I (mtDNACOI) gene. The lack of robust PCR primers for the mtDNA COI gene can undermine correct species identification which in turn compromises management strategies. This problemis identified in the B. tabaci Africa/Middle East/AsiaMinor cladewhich comprises the globally invasive Mediterranean (MED) andMiddle East AsiaMinor I (MEAM1) species,Middle East AsiaMinor 2 (MEAM2), and the Indian Ocean (IO) species. Initially identified from the Indian Ocean island of Réunion,MEAM2 has since been reported from Japan, Peru, Turkey and Iraq.We identified MEAM2 individuals from a Peruvian population via Sanger sequencing of the mtDNA COI gene. In attempting to characterize the MEAM2 mitogenome, we instead characterized mitogenomes of MEAM1. We also report on the mitogenomes of MED, AUS, and IO thereby increasing genomic resources for members of this complex. Gene synteny (i.e., same gene composition and orientation) was observed with published B. tabaci cryptic species mitogenomes. Pseudogene fragments matching MEAM2 partial mtDNA COI gene exhibited low frequency single nucleotide polymorphisms that matched low copy number DNA fragments (<3%) of MEAM1 genomes, whereas presence of internal stop codons, loss of expected stop codons and poor primer annealing sites, all suggested MEAM2 as a pseudogene artifact and so not a real species. [ABSTRACT FROM AUTHOR]

The use of conventional chemical insecticides and bacterial toxins to control lepidopteran pests of global agriculture has imposed significant selection pressure leading to the rapid evolution of insecticide resistance. Transgenic crops (e.g., cotton) expressing the Bt Cry toxins are now used world wide to control these pests, including the highly polyphagous and invasive cotton bollworm Helicoverpa armigera. Since 2004, the Cry2Ab toxin has become widely used for controlling H. armigera, often used in combination with Cry1Ac to delay resistance evolution. Isolation of H. armigera and H. punctigera individuals heterozygous for Cry2Ab resistance in 2002 and 2004, respectively, allowed aspects of Cry2Ab resistance (level, fitness costs, genetic dominance, complementation tests) to be characterised in both species. However, the gene identity and genetic changes conferring this resistance were unknown, as was the detailed Cry2Ab mode of action. No cross-resistance to Cry1Ac was observed in mutant lines. Biphasic linkage analysis of a Cry2Ab-resistant H. armigera family followed by exon-primed intron-crossing (EPIC) marker mapping and candidate gene sequencing identified three independent resistance-associated INDEL mutations in an ATP-Binding Cassette (ABC) transporter gene we named HaABCA2. A deletion mutation was also identified in the H. punctigera homolog from the resistant line. All mutations truncate the ABCA2 protein. Isolation of further Cry2Ab resistance alleles in the same gene from field H. armigera populations indicates unequal resistance allele frequencies and the potential for Bt resistance evolution. Identification of the gene involved in resistance as an ABC transporter of the A subfamily adds to the body of evidence on the crucial role this gene family plays in the mode of action of the Bt Cry toxins. The structural differences between the ABCA2, and that of the C subfamily required for Cry1Ac toxicity, indicate differences in the detailed mode-of-action of the two Bt Cry toxins. [ABSTRACT FROM AUTHOR]

Context. Thermal emission by stochastically heated dust grains (SHGs) plays an important role in the radiative transfer (RT) problem for a dusty medium. It is therefore essential to verify that RT codes properly calculate the dust emission before studying the effects of spatial distribution and other model parameters on the simulated observables. Aims. We define an appropriate problem for benchmarking dust emissivity calculations in the context of RT simulations, specifically including the emission from SHGs. Our aim is to provide a self-contained guide for implementors of such functionality and to offer insight into the effects of the various approximations and heuristics implemented by the participating codes to accelerate the calculations. Methods. The benchmark problem definition includes the optical and calorimetric material properties and the grain size distributions for a typical astronomical dust mixture with silicate, graphite, and PAH components. It also includes a series of analytically defined radiation fields to which the dust population is to be exposed and instructions for the desired output. We processed this problem using six RT codes participating in this benchmark effort and compared the results to a reference solution computed with the publicly available dust emission code DustEM. Results. The participating codes implement different heuristics to keep the calculation time at an acceptable level. We study the effects of these mechanisms on the calculated solutions and report on the level of (dis)agreement between the participating codes. For all but the most extreme input fields, we find agreement within 10% across the important wavelength range 3 μm < λ < 1000 μm. Conclusions. We conclude that the relevant modules in RT codes can and do produce fairly consistent results for the emissivity spectra of SHGs. This work can serve as a reference for implementors of dust RT codes, and it will pave the way for a more extensive benchmark effort focusing on the RT aspects of the various codes. [ABSTRACT FROM AUTHOR]

The Magellanic Bridge is the nearest low-metallicity, tidally stripped environment, offering a unique high-resolution view of physical conditions in merging and forming galaxies. In this paper, we present an analysis of candidate massive young stellar objects (YSOs), i.e., in situ, current massive star formation (MSF) in the Bridge using Spitzer mid-IR and complementary optical and near-IR photometry. While we definitely find YSOs in the Bridge, the most massive are ∼10 M☼, ≪45 M☼ found in the LMC. The intensity of MSF in the Bridge also appears to be decreasing, as the most massive YSOs are less massive than those formed in the past. To investigate environmental effects on MSF, we have compared properties of massive YSOs in the Bridge to those in the LMC. First, YSOs in the Bridge are apparently less embedded than in the LMC: 81% of Bridge YSOs show optical counterparts, compared to only 56% of LMC sources with the same range of mass, circumstellar dust mass, and line-of-sight extinction. Circumstellar envelopes are evidently more porous or clumpy in the Bridge's low-metallicity environment. Second, we have used whole samples of YSOs in the LMC and the Bridge to estimate the probability of finding YSOs at a given H I column density, N(H I). We found that the LMC has ∼3 × higher probability than the Bridge for N(H I) >12 × 1020 cm–2, but the trend reverses at lower N(H I). Investigating whether this lower efficiency relative to H I is due to less efficient molecular cloud formation or to less efficient cloud collapse, or to both, will require sensitive molecular gas observations. [ABSTRACT FROM AUTHOR]

We measure the extinction curve in the central 200 pc of M31 at mid-ultraviolet to near-infrared wavelengths (from 1928 Å to 1.5 μm), using Swift/UVOT and Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3)/Advanced Camera for Surveys (ACS) observations in 13 bands. Taking advantage of the high angular resolution of the HST/WFC3 and ACS detectors, we develop a method to simultaneously determine the relative extinction and the fraction of obscured starlight for five dusty complexes located in the circumnuclear region. The extinction curves of these clumps (RV = 2.4-2.5) are steeper than the average Galactic one (RV = 3.1), but are similar to optical and near-infrared curves recently measured toward the Galactic bulge (RV ∼ 2.5). This similarity suggests that steep extinction curves may be common in the inner bulge of galaxies. In the ultraviolet, the extinction curves of these clumps are also unusual. We find that one dusty clump (size < 2 pc) exhibits a strong UV bump (extinction at 2175 Å), more than three standard deviation higher than that predicted by common models. Although the high stellar metallicity of the M31 bulge indicates that there are sufficient carbon and silicon to produce large dust grains, the grains may have been destroyed by supernova explosions or past activity of the central supermassive black hole, resulting in the observed steepened extinction curve. [ABSTRACT FROM AUTHOR]

We report on recent observations of molecular clouds in the tidal Magellanic Bridge; specifically, the ∼kpc-long, tidally extended “tail” of the Small Magellanic Cloud. In particular, we identify an unusually high 12CO(3–2)/12CO(1–0) ratio of 2–3 to 1, toward one of the clouds, suggesting a warm and dense molecular material associated with imminent or current formation of stars. Our ∼ 6 pc-resolution observations show that the target clouds have only a general correlation with bright 24 μm emission regions, occasionally offset by up to ∼ 15 pc. These detections support the scenario that stars are actively being created in this uniquely nearby tidal filament, in the present epoch, and that star formation is ongoing at a range of evolutionary stages or rates. [ABSTRACT FROM AUTHOR]

Galaxies observed at redshift z > 6, when the Universe was less than a billion years old, thus far very rarely show evidence of the cold dust that accompanies star formation in the local Universe, where the dust-to-gas mass ratio is around one per cent. A prototypical example is the galaxy Himiko (z = 6.6), which-a mere 840 million years after the Big Bang-is forming stars at a rate of 30-100 solar masses per year, yielding a mass assembly time of about 150 × 106 years. Himiko is thought to have a low fraction (2-3 per cent of the Sun's) of elements heavier than helium (low metallicity), and although its gas mass cannot yet be determined its dust-to-stellar mass ratio is constrained to be less than 0.05 per cent. The local dwarf galaxy I Zwicky 18, which has a metallicity about 4 per cent that of the Sun's and is forming stars less rapidly (assembly time about 1.6 × 109 years) than Himiko but still vigorously for its mass, is also very dust deficient and is perhaps one of the best analogues of primitive galaxies accessible to detailed study. Here we report observations of dust emission from I Zw 18, from which we determine its dust mass to be 450-1,800 solar masses, yielding a dust-to-stellar mass ratio of about 10−6 to 10−5 and a dust-to-gas mass ratio of 3.2-13 × 10−6. If I Zw 18 is a reasonable analogue of Himiko, then Himiko's dust mass must be around 50,000 solar masses, a factor of 100 below the current upper limit. These numbers are quite uncertain, but if most high-z galaxies are more like Himiko than like the very-high-dust-mass galaxy SDSS J114816.64 + 525150.3 at z ≈ 6, which hosts a quasar, then our prospects for detecting the gas and dust inside such galaxies are much poorer than hitherto anticipated. [ABSTRACT FROM AUTHOR]

A correction to the article "Ultraviolet Extinction Properties in the Milky Way," by Lynne A. Valencic and colleagues that was published in the September 5, 2014 issue is presented.

Motivated by recent interstellar medium studies, we present high quality MMT and Gemini spectroscopic observations of H II regions in the nearby spiral galaxies NGC 628 and NGC 2403 in order to measure their chemical abundance gradients. Using long-slit and multi-object mask optical spectroscopy, we obtained measurements of the temperature sensitive auroral lines [O III] λ4363 and/or [N II] λ5755 at a strength of 4σ or greater in 11 H II regions in NGC 628 and 7 regions in NGC 2403. These observations allow us, for the first time, to derive an oxygen abundance gradient in NGC 628 based solely on “direct” oxygen abundances of H II regions: 12 + log(O/H) = (8.43 ± 0.03) + (–0.017 ± 0.002) × Rg (dex kpc–1), with a dispersion in log(O/H) of σ = 0.10 dex, from 14 regions with a radial coverage of ∼2-19 kpc. This is a significantly shallower slope than found by previous “strong-line” abundance studies. In NGC 2403, we derive an oxygen abundance gradient of 12 + log(O/H) = (8.48 ± 0.04) + (–0.032 ± 0.007)× Rg (dex kpc–1), with a dispersion in log(O/H) of σ = 0.07 dex, from seven H II with a radial coverage of ∼1-10 kpc. Additionally, we measure the N, S, Ne, and Ar abundances. We find the N/O ratio decreases with increasing radius for the inner disk, but reaches a plateau past R25 in NGC 628. NGC 2403 also has a negative N/O gradient with radius, but we do not sample the outer disk of the galaxy past R25 and so do not see evidence for a plateau. This bi-modal pattern measured for NGC 628 indicates dominant contributions from secondary nitrogen inside of the R25 transition and dominantly primary nitrogen farther out. As expected for α-process elements, S/O, Ne/O, and Ar/O are consistent with constant values over a range in oxygen abundance. [ABSTRACT FROM AUTHOR]

Dust has long been identified as a barrier to measuring inherent galaxy properties. However, the link between dust and attenuation is not straightforward and depends on both the amount of dust and its distribution. Herschel imaging of nearby galaxies undertaken as part of the KINGFISH project allows us to map the dust as seen in emission with unprecedented sensitivity and ~1 kpc resolution. We present here new optical integral field unit spectroscopy for eight of these galaxies that provides complementary 100-200 pc scale maps of the dust attenuation through observation of the reddening in both the Balmer decrement and the stellar continuum. The stellar continuum reddening, which is systematically less than that observed in the Balmer decrement, shows no clear correlation with the dust, suggesting that the distribution of stellar reddening acts as a poor tracer of the overall dust content. The brightest Hii regions are observed to be preferentially located in dusty regions, and we do find a correlation between the Balmer line reddening and the dust mass surface density for which we provide an empirical relation. Some of the high-inclination systems in our sample exhibit high extinction, but we also find evidence that unresolved variations in the dust distribution on scales smaller than 500 pc may contribute to the scatter in this relation. We caution against the use of integrated AV measures to infer global dust properties. [ABSTRACT FROM AUTHOR]