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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

The 2.4 μ m Galaxy Luminosity Function as Measured Using WISE . III. Measurement Results

The Widefield Infrared Survey Explorer (WISE) satellite surveyed the entire sky multiple times in four infrared wavelengths (3.4, 4.6, 12, and 22 μm). The unprecedented combination of coverage area and depth gives us the opportunity to measure the luminosity function (LF) of galaxies, one of the fundamental quantities in the study of them, at 2.4 μm to an unparalleled level of formal statistical accuracy in the near-infrared. The big advantage of measuring LFs at wavelengths in the window of ≈2–3.5 μm is that it correlates more closely to the total stellar mass in galaxies than others. In this paper we report on the parameters of the 2.4 μm LF of galaxies obtained from applying the spectro-luminosity-functional-based methods to datasets from the previous papers in this series using the mean and covariance of 2.4 μm normalized spectral energy distributions (SEDs) from our previous work. In terms of the single Schechter function parameters evaluated at the present epoch, the combined result is: ${\phi }_{\star }=5.8\,\pm [{0.3}_{\mathrm{stat}},{0.4}_{\mathrm{sys}}]\times {10}^{-3}\,{\mathrm{Mpc}}^{-3}$, ${L}_{\star }=6.4\pm [{0.1}_{\mathrm{stat}},{0.3}_{\mathrm{sys}}]\times {10}^{10}\,{L}_{2.4\mu {\rm{m}}\odot }$ (M$_{\star}$ = -21.67 ± [0.02 stat , 0.05 sys ] AB mag), and $α$ = -1.050 ± [0.004 stat , 0.04 sys ]. The high statistical accuracy comes from combining public redshift surveys with the wide coverage from WISE, and the unevenness in statistical accuracy is a result of our efforts to work around biases of uncertain origin that affect resolved and marginally resolved galaxies. With further refinements, the techniques applied in this work promise to advance the study of the SED of the universe.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Discovery and Spectroscopic Confirmation of Aquarius III: A Low-mass Milky Way Satellite Galaxy

Abstract We present the discovery of Aquarius III, an ultra-faint Milky Way satellite galaxy identified in the second data release of the DECam Local Volume Exploration survey. Based on deeper follow-up imaging with DECam, we find that Aquarius III is a low-luminosity ( M V = − 2.5 − 0.5 + 0.3 ; L V = 850 − 260 + 380 L ⊙ ), extended ( r 1 / 2 = 41 − 8 + 9 pc) stellar system located in the outer halo ( D ⊙ = 85 ± 4 kpc). From medium-resolution Keck/DEIMOS spectroscopy, we identify 11 member stars and measure a mean heliocentric radial velocity of v sys = − 13.1 − 0.9 + 1.0 km s − 1 for the system and place an upper limit of σ v < 3.5 km s −1 ( σ v < 1.6 km s −1 ) on its velocity dispersion at the 95% (68%) credible level. Based on calcium-triplet metallicities of the six brightest red giant members, we find that Aquarius III is very metal-poor ([Fe/H]= − 2.61 ± 0.21) with a statistically significant metallicity spread ( σ [ Fe / H ] = 0.46 − 0.14 + 0.26 dex). We interpret this metallicity spread as strong evidence that the system is a dwarf galaxy as opposed to a star cluster. Combining our velocity measurement with Gaia proper motions, we find that Aquarius III is currently situated near its orbital pericenter in the outer halo ( r peri = 78 ± 7 kpc) and that it is plausibly on first infall onto the Milky Way. This orbital history likely precludes significant tidal disruption from the Galactic disk, notably unlike other satellites with comparably low velocity dispersion limits in the literature. Thus, if further velocity measurements confirm that its velocity dispersion is truly below σ v ≲ 2 km s −1 , Aquarius III may serve as a useful laboratory for probing galaxy formation physics in low-mass halos.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2026

Ultra-faint Milky Way Satellites Discovered in Carina, Phoenix, and Telescopium with DELVE Data Release 3

We report the discovery of three Milky Way satellite candidates: Carina IV, Phoenix III, and DELVE 7, in the third data release of the DECam Local Volume Exploration survey (DELVE). The candidate systems were identified by cross-matching results from two independent search algorithms. All three are extremely faint systems composed of old, metal-poor stellar populations (τ ≳ 10 Gyr, [Fe/H] ≲−1.4). Carina IV (M V = −2.8; r 1/2 = 40 pc) and Phoenix III (M V = −1.2; r 1/2 = 19 pc) have half-light radii that are consistent with the known population of dwarf galaxies, while DELVE 7 (M V = 1.2; r 1/2 = 2 pc) is very compact and seems more likely to be a star cluster, though its nature remains ambiguous without spectroscopic follow-up. The Gaia proper motions of stars in Carina IV ($M_{\star} = 2250^{+1180}_{-830} M_⊙$) indicate that it is unlikely to be associated with the LMC, while DECam CaHK photometry confirms that its member stars are metal poor. Phoenix III ($M_{\star} = 520^{+660}_{-290} M_⊙$) is the faintest known satellite in the extreme outer stellar halo (D GC > 100 kpc), while DELVE 7 ($M_{\star} = 60^{+120}_{-40} M_⊙$) is the faintest known satellite with D GC > 20 kpc.

Tan, Chin Yi [Univ. of Chicago, IL (United States)↗
DOE OSTI2017

An r -process enhanced star in the dwarf galaxy Tucana III

Chemically peculiar stars in dwarf galaxies provide a window for exploring the birth environment of stars with varying chemical enrichment. We present a chemical abundance analysis of the brightest star in the newly discovered ultra-faint dwarf galaxy candidate Tucana III. Because it is particularly bright for a star in an ultra-faint Milky Way (MW) satellite, we are able to measure the abundance of 28 elements, including 13 neutron-capture species. This star, DES J235532.66–593114.9 (DES J235532), shows a mild enhancement in neutron-capture elements associated with the r-process and can be classified as an r-I star. DES J235532 is the first r-I star to be discovered in an ultra-faint satellite, and Tuc III is the second extremely low-luminosity system found to contain r-process enriched material, after Reticulum II. Comparison of the abundance pattern of DES J235532 with r-I and r-II stars found in other dwarf galaxies and in the MW halo suggests a common astrophysical origin for the neutron-capture elements seen in all r-process enhanced stars. Furthermore, we explore both internal and external scenarios for the r-process enrichment of Tuc III and show that with abundance patterns for additional stars, it should be possible to distinguish between them.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Unveiling the First Black Holes With JWST:Multi-wavelength Spectral Predictions

Growing supermassive black holes (∼10{sup 9} M{sub ⊙}) that power luminous z>6 quasars from light seeds—the remnants of the first stars—within a Gyr of the Big Bang poses a timing challenge. The formation of massive black hole seeds via direct collapse with initial masses ∼10{sup 4}--10{sup 5} M{sub ⊙} alleviates this problem. Viable direct-collapse black hole formation sites, the satellite halos of star-forming galaxies, merge and acquire stars to produce a new, transient class of high-redshift objects, obese black hole galaxies (OBGs). The accretion luminosity outshines that of the stars in OBGs. We predict the multi-wavelength energy output of OBGs and growing Pop III remnants at z = 9 for standard and slim disk accretion, as well as high and low metallicities of the associated stellar population. We derive robust selection criteria for OBGs—a pre-selection to eliminate blue sources, followed by color–color cuts ([F{sub 090W}−F{sub 220W}]>0;−0.3<[F{sub 200W}−F{sub 444W}]<0.3) and the ratio of X-ray flux to rest-frame optical flux (F{sub X}/F{sub 444W}≫1). Our cuts sift out OBGs from other bright, high- and low-redshift contaminants in the infrared. OBGs with predicted M{sub AB}<25 are unambiguously detectable by the Mid-Infrared Instrument (MIRI), on the upcoming James Webb Space Telescope (JWST). For parameters explored here, growing Pop III remnants with predicted M{sub AB}<30 will likely be undetectable by JWST. We demonstrate that JWST has the power to discriminate between initial seeding mechanisms.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Source Physics Experiment: Rock Valley Interferometric Synthetic Aperture RADAR Earthquake Detection Study

Seismic signals from 1993 show a series of magnitude (Mw) 3.7 or less seismic events in Rock Valley on the Nevada National Security Site (NNSS). Historic synthetic aperture radar images of that location were found that could provide interferometric synthetic aperture radar (InSAR) measures of the ground height during 1993. Given this historic SAR imagery, we explore answering the question if ground movement from the 1993 Rock Valley earthquake activity could be sensed by remote sensing means. Finding earthquake surface movement would assist in locating the Rock Valley fault and the 1993 earthquake hypocenter where the Source Physics Experiment Phase III series of experiments will be conducted. In this report, we show that InSAR can sense very small height differences, and for the European Radar Satellite-1 InSAR collections during 1992 and 1993 over Rock Valley earth surface movements were measured with 8 mm uplift and 12.5 mm subsidence over isolated areas. One of these earth movement areas coincides with an InSAR image pair coherence drop between March 5, 1993 and June 18, 1993. The coherence drop is over an approximately 13 square km area south southeast of Skull Mountain centered at 36° 43' 30" N latitude and 116° 05' 00" W longitude. Measured small surface movement and a loss of InSAR coherence may be caused by the series of earthquakes. The location of these InSAR detections may also coincide with water drainage or erosion displacement. There are no records to disambiguate the earthquake and erosion earth surface motion possibilities. Therefore, the InSAR findings of earth surface movement by InSAR are inconclusive.

58 GEOSCIENCES↗
DOE OSTI2015

The star formation histories of local group dwarf galaxies. III. Characterizing quenching in low-mass galaxies

We explore the quenching of low-mass galaxies (10{sup 4} ≲ M{sub ⋆} ≲ 10{sup 8} M{sub ⊙}) as a function of lookback time using the star formation histories (SFHs) of 38 Local Group dwarf galaxies. The SFHs were derived by analyzing color–magnitude diagrams of resolved stellar populations in archival Hubble Space Telescope/Wide Field Planetary Camera 2 imaging. We find: (1) lower-mass galaxies quench earlier than higher-mass galaxies; (2) inside of R{sub virial} there is no correlation between a satellite’s current proximity to a massive host and its quenching epoch; and (3) there are hints of systematic differences in the quenching times of M31 and Milky Way (MW) satellites, although the sample size and uncertainties in the SFHs of M31 dwarfs prohibit definitive conclusions. Combined with results from the literature, we qualitatively consider the redshift evolution (z = 0–1) of the quenched galaxy fraction over ∼7 dex in stellar mass (10{sup 4} ≲ M{sub ⋆} ≲ 10{sup 11.5} M{sub ⊙}). The quenched fraction of all galaxies generally increases toward the present, with both the lowest and highest-mass systems exhibiting the largest quenched fractions at all redshifts. In contrast, galaxies between M{sub ⋆} ∼ 10{sup 8}–10{sup 10} M{sub ⊙} have the lowest quenched fractions. We suggest that such intermediate-mass galaxies are the least efficient at quenching. Finally, we compare our quenching times with predictions for infall times for low-mass galaxies associated with the MW. We find that some of the lowest-mass satellites (e.g., CVn II, Leo IV) may have been quenched before infall, while higher-mass satellites (e.g., Leo I, Fornax) typically quench ∼1–4 Gyr after infall.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

The impact of environmental effects on active galactic nuclei: A decline in the incidence of ionized outflows

Active galactic nuclei (AGNs) have generally been considered to be less frequent in denser environments due to a lower number of galaxy-galaxy interactions and/or the removal of their gas-rich reservoirs by the dense intergalactic medium. However, recent observational and theoretical works suggest that the effect of ram-pressure stripping acting on galaxies in dense environments might reduce the angular momentum of their gas, causing it to infall towards the super massive black hole at their centre, activating the AGN phase. In this work we explore the connection between environment and nuclear activity by evaluating the variation in the incidence of ionized outflows, a common phenomenon associated with nuclear activity, in AGNs across different environments. We select a sample of approximately 3300 optical AGNs from the Sloan Digital Sky Survey Data Release 13, which we match with a group catalogue to identify galaxies in isolation or residing in groups. We further probe their environments through the projected distance to the central galaxy of the group or cluster and the projected surface density to the fifth neighbour (δ 5 ). The presence of ionized outflows is determined through the modelling of the [O III] λ5007 emission line. We find that at lower masses (< 10 10.3 M ⊙ ), the fraction of ionized outflows is significantly lower in satellite AGNs (~7%) than in isolated (~22%) AGNs, probably due to their different AGN luminosity, L [O III] , in this stellar mass range. The fraction of outflows decreases at distances closer to the central galaxy of the group or cluster for all satellite AGNs; however, only the lower-mass ones (10 9 - 10 10.3 M ⊙ ) display a significant decline with δ 5 . Although this study does not include AGNs in the densest regions of galaxy clusters, our findings suggest that AGNs in dense environments accrete less gas than those in the field, potentially due to the removal of the gas reservoirs via stripping or starvation, leading to a negative connection between environment and AGN activity. Based on our results, we propose that the observed change in the incidence of outflows when moving towards denser regions of groups and clusters could contribute to the higher gas metallicities of cluster galaxies compared to field galaxies, especially at lower masses.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Spectral Energy Distributions for 258 Local Volume Galaxies

We present model spectral energy distribution (SED) fits to ultraviolet/optical/infrared observations for the 258 nearby galaxies in the Local Volume Legacy survey, a sample dominated by lower-luminosity dwarf irregular systems. The data for each galaxy include up to 26 spatially-integrated broadband and narrowband fluxes from the Galaxy Evolution Explorer, Spitzer Space Telescope, and Infrared Astronomical Satellite space-based platforms, and from the Sloan Digital Sky Survey, Two Micron All Sky Survey, and other ground-based efforts. The CIGALE SED fitting package is employed using a delayed star-formation history with an optional late burst or quenching episode to constrain 11 different free parameters that characterize the properties of each galaxy's stellar and dust emission, with the overriding constraint that the ultraviolet/optical emission absorbed by interstellar dust grains is emitted in equal energy portions at infrared wavelengths. The main results are: (i) 94% of the SED fits yield reduced χ 2 values less than 3; (ii) the modeled stellar masses agree with those derived from 3.6 μm-based measures with a scatter of 0.07 dex; (iii) for a typical galaxy in the sample the SED-derived star-formation rate averaged over the past 100 Myr is about 88% of the value derived from standard hybrid indicators on similar timescales; and (iv) there is a statistically significant inverse relation between the stellar mass fraction appearing in the late burst and the total stellar mass. These results build upon prior SED modeling efforts in the local volume and lay the groundwork for future studies of more distant low-metallicity galaxies with JWST.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Clustering properties of g -selected galaxies at z ~ 0.8

In current and future large redshift surveys, as the Sloan Digital Sky Survey IV extended Baryon Oscillation Spectroscopic Survey (SDSS-IV/eBOSS) or the Dark Energy Spectroscopic Instrument (DESI), we will use emission-line galaxies (ELGs) to probe cosmological models by mapping the large-scale structure of the Universe in the redshift range 0.6 < z < 1.7. We explore the halo-galaxy connection, with current data and by measuring three clustering properties of g-selected ELGs as matter tracers in the redshift range 0.6 < z < 1: (i) the redshift-space two-point correlation function using spectroscopic redshifts from the BOSS ELG sample and VIPERS; (ii) the angular two-point correlation function on the footprint of the CFHT-LS; (iii) the galaxy-galaxy lensing signal around the ELGs using the CFHTLenS. Furthermore, we interpret these observations by mapping them on to the latest high-resolution MultiDark Planck N-body simulation, using a novel (Sub)Halo-Abundance Matching technique that accounts for the ELG incompleteness. ELGs at z ~ 0.8 live in haloes of (1 ± 0.5) × 10 12 h -1 M⊙ and 22.5 ± 2.5 per cent of them are satellites belonging to a larger halo. The halo occupation distribution of ELGs indicates that we are sampling the galaxies in which stars form in the most efficient way, according to their stellar-to-halo mass ratio.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

Distribution function approach to redshift space distortions. Part III: halos and galaxies

It was recently shown that the power spectrum in redshift space can be written as a sum of cross-power spectra between number weighted velocity moments, of which the lowest are density and momentum density. We investigate numerically the properties of these power spectra for simulated galaxies and dark matter halos and compare them to the dark matter power spectra, generalizing the concept of the bias in density-density power spectra. Because all of the quantities are number weighted this approach is well defined even for sparse systems such as massive halos. This contrasts to the previous approaches to RSD where velocity correlations have been explored, but velocity field is a poorly defined concept for sparse systems. We find that the number density weighting leads to a strong scale dependence of the bias terms for momentum density auto-correlation and cross-correlation with density. This trend becomes more significant for the more biased halos and leads to an enhancement of RSD power relative to the linear theory. Fingers-of-god effects, which in this formalism come from the correlations of the higher order moments beyond the momentum density, lead to smoothing of the power spectrum and can reduce this enhancement of power from the scale dependent bias, but are relatively small for halos with no small scale velocity dispersion. In comparison, for a more realistic galaxy sample with satellites the small scale velocity dispersion generated by satellite motions inside the halos leads to a larger power suppression on small scales, but this depends on the satellite fraction and on the details of how the satellites are distributed inside the halo. We investigate several statistics such as the two-dimensional power spectrum P(k,μ), where μ is the angle between the Fourier mode and line of sight, its multipole moments, its powers of μ{sup 2}, and configuration space statistics. Overall we find that the nonlinear effects in realistic galaxy samples such as luminous red galaxies affect the redshift space clustering on very large scales: for example, the quadrupole moment is affected by 10% for k < 0.1hMpc{sup −1}, which means that these effects need to be understood if we want to extract cosmological information from the redshift space distortions.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Geodetic measurements and numerical models of transient deformation at Raft River geothermal field, Idaho, USA

Here, we perform synthetic aperture radar interferometry using data acquired between 2004 and 2016 by the Envisat, and ALOS-2 satellite missions to measure transient deformation at the Raft River geothermal field in Cassia County in Southern Idaho where geothermal production began in late 2007. Time-series analysis of multiple interferometric pairs indicates uplift at an exponentially decaying rate, over an ~8 km-by-5 km area centered near three injection wells that recycle produced brine. Similarly, subsidence at an exponentially decaying rate is observed in a 4 km-by-4 km area west of the production wells. These two signatures stay in the same location in all of the well-correlated Envisat interferometric pairs spanning the time interval between 2007 and 2010. The boundary separating the uplifting and subsiding areas is associated with the steeply dipping Bridge fault zone. Using two-dimensional numerical models, we explore first-order, bi-directional coupling between hydrological and mechanical processes. Our results suggest that: (i) most of the deformation occurs due to pore pressure changes following the start of geothermal production, (ii) the rate of deformation decays to zero over a time scale on the order of ~5 years as the system reaches steady state, and (iii) a reservoir-scale permeability of the order of ~1E–14 m 2 is required to explain the transient deformation.

15 GEOTHERMAL ENERGY↗
DOE OSTI2017

The Dehydration of Water Worlds via Atmospheric Losses

We present a three-species multi-fluid magnetohydrodynamic model (H{sup +}, H{sub 2}O{sup +}, and e {sup −}), endowed with the requisite atmospheric chemistry, that is capable of accurately quantifying the magnitude of water ion losses from exoplanets. We apply this model to a water world with Earth-like parameters orbiting a Sun-like star for three cases: (i) current normal solar wind conditions, (ii) ancient normal solar wind conditions, and (iii) one extreme “Carrington-type” space weather event. We demonstrate that the ion escape rate for (ii), with a value of 6.0 × 10{sup 26} s{sup −1}, is about an order of magnitude higher than the corresponding value of 6.7 × 10{sup 25} s{sup −1} for (i). Studies of ion losses induced by space weather events, where the ion escape rates can reach ∼10{sup 28} s{sup −1}, are crucial for understanding how an active, early solar-type star (e.g., with frequent coronal mass ejections) could have accelerated the depletion of the exoplanet’s atmosphere. We briefly explore the ramifications arising from the loss of water ions, especially for planets orbiting M-dwarfs where such effects are likely to be significant.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2018

Search for C II emission on cosmological scales at redshift Z ~ 2.6

We present a search for C II emission over cosmological scales at high redshifts. The C II line is a prime candidate to be a tracer of star formation over large-scale structure since it is one of the brightest emission lines from galaxies. Redshifted C II emission appears in the submillimeter regime, which means it could potentially be present in the higher frequency intensity data from the Planck satellite is used to measure the cosmic infrared background (CIB). We search for C II emission over redshifts z = 2–3.2 in the Planck 545 GHz intensity map by cross-correlating the three highest frequency Planck maps with spectroscopic quasars and CMASS galaxies from the Sloan Digital Sky Survey III, which we then use to jointly fit C II intensity, CIB parameters, and thermal Sunyaev–Zeldovich (SZ) emission. We report a measurement of an anomalous emission I ν = 6.6 +5.0 –4.8 × 10 4 Jy sr –1 at 95 percent confidence, which could be explained by C II emission, favouring collisional excitation models of C II emission that tend to be more optimistic than models based on C II luminosity scaling relations from local measurements; however, a comparison of Bayesian information criteria reveals that this model and the CIB & SZ model are equally plausible. Thus, more sensitive measurements will be needed to confirm the existence of a large-scale C II emission at high redshifts. Lastly, we forecast that intensity maps from Planck cross-correlated with quasars from the Dark Energy Spectroscopic Instrument would increase our sensitivity to C II emission by a factor of 5, while the proposed Primordial Inflation Explorer could increase the sensitivity further.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

The MOSDEF survey: detection of [O {sub III}]λ4363 and the direct-method oxygen abundance of a star-forming galaxy at z = 3.08

We present measurements of the electron-temperature-based oxygen abundance for a highly star-forming galaxy at z = 3.08, COSMOS-1908. This is the highest redshift at which [O iii]λ4363 has been detected and the first time that this line has been measured at z>2. We estimate an oxygen abundance of 12+log(O/H)=8.00{sub −0.14}{sup +0.13}. This galaxy is a low-mass (10{sup 9.3} M{sub ⊙}), highly star-forming (∼50 M{sub ⊙} yr{sup −1}) system that hosts a young stellar population (∼160 Myr). We investigate the physical conditions of the ionized gas in COSMOS-1908 and find that this galaxy has a high ionization parameter, little nebular reddening (E(B−V){sub gas}<0.14), and a high electron density (n{sub e}∼500 cm{sup −3}). We compare the ratios of strong oxygen, neon, and hydrogen lines to the direct-method oxygen abundance for COSMOS-1908 and additional star-forming galaxies at z=0−1.8 with [O iii]λ4363 measurements and show that galaxies at z∼1--3 follow the same strong-line correlations as galaxies in the local universe. This agreement suggests that the relationship between ionization parameter and O/H is similar for z∼0 and high-redshift galaxies. These results imply that metallicity calibrations based on lines of oxygen, neon, and hydrogen do not strongly evolve with redshift and can reliably estimate abundances out to z∼3, paving the way for robust measurements of the evolution of the mass–metallicity relation to high redshift.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

ROBO-AO KEPLER PLANETARY CANDIDATE SURVEY. III. ADAPTIVE OPTICS IMAGING OF 1629 KEPLER EXOPLANET CANDIDATE HOST STARS

The Robo-AO Kepler Planetary Candidate Survey is observing every Kepler planet candidate host star with laser adaptive optics imaging to search for blended nearby stars, which may be physically associated companions and/or responsible for transit false positives. In this paper, we present the results of our search for stars nearby 1629 Kepler planet candidate hosts. With survey sensitivity to objects as close as ∼0.″15, and magnitude differences Δm ⩽6, we find 223 stars in the vicinity of 206 target KOIs; 209 of these nearby stars have not been previously imaged in high resolution. We measure an overall nearby-star probability for Kepler planet candidates of 12.6%±0.9% at separations between 0.″15 and 4.″0. Particularly interesting KOI systems are discussed, including 26 stars with detected companions that host rocky, habitable zone candidates and five new candidate planet-hosting quadruple star systems. We explore the broad correlations between planetary systems and stellar binarity, using the combined data set of Baranec et al. and this paper. Our previous 2σ result of a low detected nearby star fraction of KOIs hosting close-in giant planets is less apparent in this larger data set. We also find a significant correlation between detected nearby star fraction and KOI number, suggesting possible variation between early and late Kepler data releases.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Electron-impact excitation collision strengths and theoretical line intensities for transitions in S III

We present Maxwellian-averaged effective collision strengths for the electron-impact excitation of S III over a wide range of electron temperatures of astrophysical importance, log T{sub e} (K) = 3.0-6.0. The calculation incorporates 53 fine-structure levels arising from the six configurations—3s {sup 2}3p {sup 2}, 3s3p {sup 3}, 3s {sup 2}3p3d, 3s {sup 2}3p4s, 3s {sup 2}3p4p, and 3s {sup 2}3p4d—giving rise to 1378 individual lines and is undertaken using the recently developed RMATRX II plus FINE95 suite of codes. A detailed comparison is made with a previous R-matrix calculation and significant differences are found for some transitions. The atomic data are subsequently incorporated into the modeling code CLOUDY to generate line intensities for a range of plasma parameters, with emphasis on allowed ultraviolet extreme-ultraviolet emission lines detected from the Io plasma torus. Electron density-sensitive line ratios are calculated with the present atomic data and compared with those from CHIANTI v7.1, as well as with Io plasma torus spectra obtained by Far-Ultraviolet Spectroscopic Explorer and Extreme-Ultraviolet Explorer. The present line intensities are found to agree well with the observational results and provide a noticeable improvement on the values predicted by CHIANTI.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

Structure of dark matter halos in warm dark matter models and in models with long-lived charged massive particles

We study the formation of non-linear structures in warm dark matter (WDM) models and in a long-lived charged massive particle (CHAMP) model. CHAMPs with a decay lifetime of about 1 yr induce characteristic suppression in the matter power spectrum at subgalactic scales through acoustic oscillations in the thermal background. We explore structure formation in such a model. We also study three WDM models, where the dark matter particles are produced through the following mechanisms: i) WDM particles are produced in the thermal background and then kinematically decoupled; ii) WDM particles are fermions produced by the decay of thermal heavy bosons; and iii) WDM particles are produced by the decay of non-relativistic heavy particles. We show that the linear matter power spectra for the three models are all characterised by the comoving Jeans scale at the matter-radiation equality. Furthermore, we can also describe the linear matter power spectrum for the long-lived CHAMP model in terms of a suitably defined characteristic cut-off scale k{sub Ch}, similarly to the WDM models. We perform large cosmological N-body simulations to study the non-linear growth of structures in these four models. We compare the halo mass functions, the subhalo mass functions, and the radial distributions of subhalos in simulated Milky Way-size halos. For the characteristic cut-off scale k{sub cut} = 51 h Mpc{sup −1}, the subhalo abundance ( ∼ 10{sup 9}M{sub sun}) is suppressed by a factor of ∼ 10 compared with the standard ΛCDM model. We then study the models with k{sub cut} ≅ 51, 410, 820 h Mpc{sup −1}, and confirm that the halo and the subhalo abundances and the radial distributions of subhalos are indeed similar between the different WDM models and the long-lived CHAMP model. The result suggests that the cut-off scale k{sub cut} not only characterises the linear power spectra but also can be used to predict the non-linear clustering properties. The radial distribution of subhalos in Milky Way-size halos is consistent with the observed distribution for k{sub cut} ∼ 50−800 h Mpc{sup −1}; such models resolve the so-called ''missing satellite problem''.

79 ASTRONOMY AND ASTROPHYSICS↗