Spatially Resolved [FeII] 1.64 \mu m Emission in NGC 5135. Clues for Understanding the Origin of the Hard X-rays in Luminous Infrared Galaxies

Spatially resolved near-IR and X-ray imaging of the central region of the Luminous Infrared Galaxy NGC 5135 is presented. The kinematical signatures of strong outflows are detected in the [FeII]1.64 \mu m emission line in a compact region at 0.9 kpc from the nucleus. The derived mechanical energy release is consistent with a supernova rate of 0.05-0.1 yr$^{-1}$. The apex of the outflowing gas spatially coincides with the strongest [FeII] emission peak and with the dominant component of the extranuclear hard X-ray emission. All these features provide evidence for a plausible direct physical link between supernova-driven outflows and the hard X-ray emitting gas in a LIRG. This result is consistent with model predictions of starbursts concentrated in small volumes and with high thermalization efficiencies. A single high-mass X-ray binary (HMXB) as the major source of the hard X-ray emission although not favoured, cannot be ruled out. Outside the AGN, the hard X-ray emission in NGC 5135 appears to be dominated by the hot ISM produced by supernova explosions in a compact star-forming region, and not by the emission due to HMXB. If this scenario is common to U/LIRGs, the hard X-rays would only trace the most compact (< 100 pc) regions with high supernova and star formation densities, therefore a lower limit to their integrated star formation. The SFR derived in NGC 5135 based on its hard X-ray luminosity is a factor of two and four lower than the values obtained from the 24 \mu m and soft X-ray luminosities, respectively.Comment: Accepted for Publication in ApJ, 18 pages, 2 figure

Chemical Abundances Of Open Clusters From High-Resolution Infrared Spectra. I. NGC 6940

We present near-infrared spectroscopic analysis of 12 red giant members of the Galactic open cluster NGC 6940. High-resolution (R$\simeq$45000) and high signal-to-noise ratio (S/N > 100) near-infrared H and K band spectra were gathered with the Immersion Grating Infrared Spectrograph (IGRINS) on the 2.7m Smith Telescope at McDonald Observatory. We obtained abundances of H-burning (C, N, O), ${\alpha}$ (Mg, Si, S, Ca), light odd-Z (Na, Al, P, K), Fe-group (Sc, Ti, Cr, Fe, Co, Ni) and neutron-capture (Ce, Nd, Yb) elements. We report the abundances of S, P, K, Ce, and Yb in NGC 6940 for the first time. Many OH and CN features in the H band were used to obtain O and N abundances. C abundances were measured from four different features: CO molecular lines in the K band, high excitation C I lines present in both near-infrared and optical, CH and $C_2$ bands in the optical region. We have also determined $^{12}C/^{13}C$ ratios from the R-branch band heads of first overtone (2-0) and (3-1) $^{12}CO$ (2-0) $^{13}CO$ lines near 23440 \overset{\lower.5em\circ}{\mathrm{A}} and (3-1) $^{13}CO$ lines at about 23730 \overset{\lower.5em\circ}{\mathrm{A}}. We have also investigated the HF feature at 23358.3 \overset{\lower.5em\circ}{\mathrm{A}}, finding solar fluorine abundances without ruling out a slight enhancement. For some elements (such as the ${\alpha}$ group), IGRINS data yield more internally self-consistent abundances. We also revisited the CMD of NGC 6940 by determining the most probable cluster members using Gaia DR2. Finally, we applied Victoria isochrones and MESA models in order to refine our estimates of the evolutionary stages of our targets.Comment: 16 pages, 10 figure

The dynamics and high-energy emission of conductive gas clouds in supernova-driven galactic superwinds

In this paper we present high-resolution hydrodynamical models of warm ionized clouds embedded in a superwind, and compare the OVI and soft X-ray properties to the existing observational data. These models include thermal conduction, which we show plays an important role in shaping both the dynamics and radiative properties of the resulting wind/cloud interaction. Heat conduction stabilizes the cloud by inhibiting the growth of K-H and R-T instabilities, and also generates a shock wave at the cloud's surface that compresses the cloud. This dynamical behaviour influences the observable properties. We find that while OVI emission and absorption always arises in cloud material at the periphery of the cloud, most of the soft X-ray arises in the region between the wind bow shock and the cloud surface, and probes either wind or cloud material depending on the strength of conduction and the relative abundances of the wind with respect to the cloud. In general only a small fraction (<1%) of the wind mechanical energy intersecting a cloud is radiated away at UV and X-ray wavelengths, with more wind energy going into accelerating the cloud. Models with heat conduction at Spitzer-levels are found to produce observational properties closer to those observed in superwinds than models with no thermal conduction, in particular in terms of the OVI-to-X-ray luminosity ratio, but cloud life times are uncomfortably short (<1Myr) compared to the dynamical ages of real winds. We experimented with reducing the thermal conductivity and found that even when we reduced conduction by a factor of 25 that the simulations retained the beneficial hydrodynamical stability and low O{\sc vi}-to-X-ray luminosity ratio found in the Spitzer-level conductive models, while also having reduced evaporation rates.Comment: 27 pages, 12 figures (4 in color), MNRAS accepte

Galactic Wind in the Nearby Starburst Galaxy NGC 253 Observed with the Kyoto3DII Fabry-Perot Mode

We have observed the central region of the nearby starburst galaxy NGC 253 with the Kyoto Tridimensional Spectrograph II (Kyoto3DII) Fabry-Perot mode in order to investigate the properties of its galactic wind. Since this galaxy has a large inclination, it is easy to observe its galactic wind. We produced the Ha, [N II]6583, and [S II]6716,6731 images, as well as those line ratio maps. The [N II]/Ha ratio in the galactic wind region is larger than those in H II regions in the galactic disk. The [N II]/Ha ratio in the southeastern filament, a part of the galactic wind, is the largest and reaches about 1.5. These large [N II]/Ha ratios are explained by shock ionization/excitation. Using the [S II]/Ha ratio map, we spatially separate the galactic wind region from the starburst region. The kinetic energy of the galactic wind can be sufficiently supplied by supernovae in a starburst region in the galactic center. The shape of the galactic wind and the line ratio maps are non-axisymmetric about the galactic minor axis, which is also seen in M82. In the [N II]6583/[S II]6716,6731 map, the positions with large ratios coincide with the positions of star clusters found in the Hubble Space Telescope (HST) observation. This means that intense star formation causes strong nitrogen enrichment in these regions. Our unique data of the line ratio maps including [S II] lines have demonstrated their effectiveness for clearly distinguishing between shocked gas regions and starburst regions, determining the extent of galactic wind and its mass and kinetic energy, and discovering regions with enhanced nitrogen abundance.Comment: 22 pages, 5 figures, 1 table, accepted for publication in Ap

Mapping Lyme Disease Incidence for Diagnostic and Preventive Decisions, Maryland

To support diagnostic and preventive decision making, we analyzed incidence of Lyme disease in Maryland on the zip code level. Areas of high incidence were identified on the Upper Eastern Shore of the Chesapeake Bay and in counties north and east of Baltimore City. These latter foci, especially, are not visible when mapping Lyme disease on the county level.

Production and Fate of Transparent Exopolymer Particles in the Ocean

The production and fate of transparent exopolymer particles (TEP) have been investigated in various oceanic regions (tropical, temperate, and polar), from the sea surface microlayer (SML) to the deep ocean. Accumulation of TEP within the mixed layer was observed even in the absence of phytoplankton blooms, indicating abiotic processes are important in TEP production. The abiotic TEP aggregation rates measured in the tropical and temperate North Pacific and the Arctic Ocean averaged between 8 and 12 μmol C L-1 d-1. Depth profiles from under sea ice in the Arctic revealed the highest TEP concentrations, potentially released by sympagic algal activity at the bottom of the sea ice. The aggregation rates in the SML, the interfacial layer between the ocean and atmosphere, were generally enhanced over those in the bulk surface waters by factors of 2 to 30. This finding further strengthens a developing consensus on the gelatinous nature of the SML, which will also affect microbial life, light penetration, and surface wave properties. We present a conceptual model implying that abiotic aggregation is an important factor for TEP production in the ocean, in particular in sea surface microlayers, while consumption by zooplankton and protists recycle TEP, providing a new pool of dissolved precursor material. Overall, TEP is recycled within the water column through heterotrophic grazing and degradation, providing a new pool of TEP precursor materials, while enhanced aggregation rates of TEP in the SML indicates the importance of this thin surface film in the marine carbon cycle

Observational Constraints on Superbubble X-ray Energy Budgets

The hot, X-ray-emitting gas in superbubbles imparts energy and enriched material to the interstellar medium (ISM) and generates the hot ionized medium, the ISM's high-temperature component. The evolution of superbubble energy budgets is not well understood, however, and the processes responsible for enhanced X-ray emission in superbubbles remain a matter of debate. We present Chandra ACIS-S observations of two X-ray-bright superbubbles in the Large Magellanic Cloud (LMC), DEM L50 (N186) and DEM L152 (N44), with an emphasis on disentangling the true superbubble X-ray emission from non-related diffuse emission and determining the spatial origin and spectral variation of the X-ray emission. An examination of the superbubble energy budgets shows that on the order of 50% of the X-ray emission comes from regions associated with supernova remnant (SNR) impacts. We find some evidence of mass-loading due to swept-up clouds and metallicity enrichment, but neither mechanism provides a significant contribution to the X-ray luminosities. We also find that one of the superbubbles, DEM L50, is likely not in collisional ionization equilibrium. We compare our observations to the predictions of the standard Weaver et al. model and to 1-D hydrodynamic simulations including cavity supernova impacts on the shell walls. Our observations show that mass-loading due to thermal evaporation from the shell walls and SNR impacts are the dominant source of enhanced X-ray luminosities in superbubbles. These two processes should affect most superbubbles, and their contribution to the X-ray luminosity must be considered when determining the energy available for transport to the ISM.Comment: 25 pages, 11 figures, accepted for publication in Ap

Mass-loaded spherical accretion flows

We have calculated the evolution of spherical accretion flows undergoing mass-loading from embedded clouds through either conduction or hydrodynamical ablation. We have observed the effect of varying the ratios of the mass-loading timescale and the cooling timescale to the ballistic crossing timescale through the mass-loading region. We have also varied the ratio of the potential energy of a particle injected into the flow near the outer region of mass-loading to the temperature at which a minimum occurs in the cooling curve. The two types of mass-loading produce qualitatively different types of behaviour in the accretion flow, since mass-loading through conduction requires the ambient gas to be hot, whereas mass ablation from clumps occurs throughout the flow. Higher ratios of injected to accreted mass typically occur with hydrodynamical ablation, in agreement with previous work on wind-blown bubbles and supernova remnants. We find that mass-loading damps the radiative overstability of such flows, in agreement with our earlier work. If the mass-loading is high enough it can stabilize the accretion shock at a constant radius, yielding an almost isothermal subsonic post-shock flow. Such solutions may be relevant to cooling flows onto massive galaxies. Mass-loading can also lead to the formation of isolated shells of high temperature material, separated by gas at cooler temperatures