IRAS observations of young stellar objects in the Corona Australis dark cloud

NASA Technical Reports Server (NTRS)

Wilking, Bruce A.; Greene, Thomas P.; Lada, Charles J.; Meyer, Michael R.; Young, Erick T.

1992-01-01

The young stellar object (YSO) population associated with the dark cloud complex in Corona Australis is studied by synthesizing IRAS data with newly obtained near-IR and mid-IR photometry and previously published optical/IR data. Twenty-four YSOs in the Cr A complex are identified. The observed range of spectral energy distribution shapes and bolometric luminosities are consistent with those observed in other dark clouds. The duration and efficiency of star formation are found to be similar to the Rho Ophiuchi IR cluster. The low number of YSOs compared to other dark clouds is understood by a reevaluation of the molecular mass of the R Cr A cloud which shows it to be much less massive than previously assumed.

A Herschel [C ii] Galactic plane survey. II. CO-dark H2 in clouds

NASA Astrophysics Data System (ADS)

Langer, W. D.; Velusamy, T.; Pineda, J. L.; Willacy, K.; Goldsmith, P. F.

2014-01-01

Context. H i and CO large scale surveys of the Milky Way trace the diffuse atomic clouds and the dense shielded regions of molecular hydrogen clouds, respectively. However, until recently, we have not had spectrally resolved C+ surveys in sufficient lines of sight to characterize the ionized and photon dominated components of the interstellar medium, in particular, the H2 gas without CO, referred to as CO-dark H2, in a large sample of interstellar clouds. Aims: We use a sparse Galactic plane survey of the 1.9 THz (158 μm) [C ii] spectral line from the Herschel open time key programme, Galactic Observations of Terahertz C+ (GOT C+), to characterize the H2 gas without CO in a statistically significant sample of interstellar clouds. Methods: We identify individual clouds in the inner Galaxy by fitting the [C ii] and CO isotopologue spectra along each line of sight. We then combine these spectra with those of H i and use them along with excitation models and cloud models of C+ to determine the column densities and fractional mass of CO-dark H2 clouds. Results: We identify1804 narrow velocity [C ii] components corresponding to interstellar clouds in different categories and evolutionary states. About 840 are diffuse molecular clouds with no CO, ~510 are transition clouds containing [C ii] and 12CO, but no 13CO, and the remainder are dense molecular clouds containing 13CO emission. The CO-dark H2 clouds are concentrated between Galactic radii of ~3.5 to 7.5 kpc and the column density of the CO-dark H2 layer varies significantly from cloud to cloud with a global average of 9 × 1020 cm-2. These clouds contain a significant fraction by mass of CO-dark H2, that varies from ~75% for diffuse molecular clouds to ~20% for dense molecular clouds. Conclusions: We find a significant fraction of the warm molecular ISM gas is invisible in H i and CO, but is detected in [C ii]. The fraction of CO-dark H2 is greatest in the diffuse clouds and decreases with increasing total column

The embedded young stars in the Taurus-Auriga molecular cloud. I - Models for spectral energy distributions

NASA Technical Reports Server (NTRS)

Kenyon, Scott J.; Calvet, Nuria; Hartmann, Lee

1993-01-01

We describe radiative transfer calculations of infalling, dusty envelopes surrounding pre-main-sequence stars and use these models to derive physical properties for a sample of 21 heavily reddened young stars in the Taurus-Auriga molecular cloud. The density distributions needed to match the FIR peaks in the spectral energy distributions of these embedded sources suggest mass infall rates similar to those predicted for simple thermally supported clouds with temperatures about 10 K. Unless the dust opacities are badly in error, our models require substantial departures from spherical symmetry in the envelopes of all sources. These flattened envelopes may be produced by a combination of rotation and cavities excavated by bipolar flows. The rotating infall models of Terebey et al. (1984) models indicate a centrifugal radius of about 70 AU for many objects if rotation is the only important physical effect, and this radius is reasonably consistent with typical estimates for the sizes of circumstellar disks around T Tauri stars.

Star Formation in Taurus: Preliminary Results from 2MASS

NASA Technical Reports Server (NTRS)

Beichman, C. A.; Jarrett, T.

1993-01-01

Data with the 2MASS prototype camera were obtained in a 2.3 sq. deg region in Taurus containing Heiles Cloud 2, a region known from IRAS observations to contain a number of very young solar type stars.

Dark Matter Reality Check: Chandra Casts Cloud On Alternative Theory

NASA Astrophysics Data System (ADS)

2002-10-01

New evidence from NASA's Chandra X-ray Observatory challenges an alternative theory of gravity that eliminates the need for dark matter. The observation also narrows the field for competing forms of dark matter, the elusive material thought to be the dominant form of matter in the universe. An observation of the galaxy NGC 720 shows it is enveloped in a slightly flattened, or ellipsoidal cloud of hot gas that has an orientation different from that of the optical image of the galaxy. The flattening is too large to be explained by theories in which stars and gas are assumed to contain most of the mass in the galaxy. "The shape and orientation of the hot gas cloud require it to be confined by an egg-shaped dark matter halo," said David Buote of the University of California, Irvine, and lead author of a report on this research in the 2002 September 20 issue of The Astrophysical Journal. "This means that dark matter is not just an illusion due to a shortcoming of the standard theory of gravity - it is real." According to the generally accepted standard theory of gravity, the hot X-ray cloud would need an additional source of gravity - a halo of dark matter - to keep the hot gas from expanding away. The mass of dark matter required would be about five to ten times the mass of the stars in the galaxy. If the dark matter tracked the optical light from the stars in the galaxy, the hot X-ray cloud would be more round than it is. The flattened shape of the hot gas cloud requires a flattened dark matter halo. An alternative theory of gravity called MOND, for Modified Newtonian Dynamics, was proposed in 1983 by Mordecai Milgrom of the Weizmann Institute in Israel, and has remained viable over the years. MOND does away with the need for dark matter by modifying the theory where the acceleration produced by gravity is very small, such as the outskirts of galaxies. However, MOND cannot explain the Chandra observation of NGC 720. This is apparently the first dynamical evidence that

IRAS images of nearby dark clouds

NASA Technical Reports Server (NTRS)

Wood, Douglas O. S.; Myers, Philip C.; Daugherty, Debra A.

1994-01-01

We have investigated approximately 100 nearby molecular clouds using the extensive, all-sky database of IRAS. The clouds in this study cover a wide range of physical properties including visual extinction, size, mass, degree of isolation, homogeneity and morphology. IRAS 100 and 60 micron co-added images were used to calculate the 100 micron optical depth of dust in the clouds. These images of dust optical depth compare very well with (12)CO and (13)CO observations, and can be related to H2 column density. From the optical depth images we locate the edges of dark clouds and the dense cores inside them. We have identified a total of 43 `IRAS clouds' (regions with A(sub v) greater than 2) which contain a total of 255 `IRAS cores' (regions with A(sub v) greater than 4) and we catalog their physical properties. We find that the clouds are remarkably filamentary, and that the cores within the clouds are often distributed along the filaments. The largest cores are usually connected to other large cores by filaments. We have developed selection criteria to search the IRAS Point Source Catalog for stars that are likely to be associated with the clouds and we catalog the IRAS sources in each cloud or core. Optically visible stars associated with the clouds have been identified from the Herbig and Bell catalog. From these data we characterize the physical properties of the clouds including their star-formation efficiency.

Precombination Cloud Collapse and Baryonic Dark Matter

NASA Technical Reports Server (NTRS)

Hogan, Craig J.

1993-01-01

A simple spherical model of dense baryon clouds in the hot big bang 'strongly nonlinear primordial isocurvature baryon fluctuations' is reviewed and used to describe the dependence of cloud behavior on the model parameters, baryon mass, and initial over-density. Gravitational collapse of clouds before and during recombination is considered including radiation diffusion and trapping, remnant type and mass, and effects on linear large-scale fluctuation modes. Sufficiently dense clouds collapse early into black holes with a minimum mass of approx. 1 solar mass, which behave dynamically like collisionless cold dark matter. Clouds below a critical over-density, however, delay collapse until recombination, remaining until then dynamically coupled to the radiation like ordinary diffuse baryons, and possibly producing remnants of other kinds and lower mass. The mean density in either type of baryonic remnant is unconstrained by observed element abundances. However, mixed or unmixed spatial variations in abundance may survive in the diffuse baryon and produce observable departures from standard predictions.

Detection of nitric oxide in the dark cloud L134N

NASA Technical Reports Server (NTRS)

Mcgonagle, D.; Irvine, W. M.; Minh, Y. C.; Ziurys, L. M.

1990-01-01

The first detection of interstellar nitric oxide (NO) in a cold dark cloud, L134N is reported. Nitric oxide was observed by means of its two 2 Pi 1/2, J = 3/2 - 1/2, rotational transitions at 150.2 and 150.5 GHz, which occur because of Lambda-doubling. The inferred column density for L134N is about 5 x 10 to the 14th/sq cm toward the SO peak in that cloud. This value corresponds to a fractional abundance relative to molecular hydrogen of about 6 x 10 to the -8th and is in good agreement with predictions of quiescent cloud ion-molecule chemistry. NO was not detected toward the dark cloud TMC-1 at an upper limit of 3 x 10 to the -8th or less.

Cyanide and isocyanide abundances in the cold, dark cloud TMC-1

NASA Technical Reports Server (NTRS)

Irvine, W. M.; Schloerb, F. P.

1984-01-01

Cold, dark molecular clouds are particularly useful for the study of interstellar chemistry because their physical parameters are better understood than those of heterogeneous, complex giant molecular clouds. Another advantage is their relatively small distance from the solar system. The present investigaation has the objective to provide accurate abundance ratios for several cyanides and isocyanides in order to constrain models of dark cloud chemistry. The relative abundances of such related species can be particularly useful for the study of chemical processes. The cloud TMC-1 considered in the current study has a remarkably high abundance of acetylene and polyacetylene derivatives. Data at 3 mm, corresponding to the J = 1 to 0 transitions of HCN, H(C-13)N, HN(C-13), HC(N-15), and H(N-15)C were obtained.

The CN/C15N isotopic ratio towards dark clouds

NASA Astrophysics Data System (ADS)

Hily-Blant, P.; Pineau des Forêts, G.; Faure, A.; Le Gal, R.; Padovani, M.

2013-09-01

Understanding the origin of the composition of solar system cosmomaterials is a central question, not only in the cosmochemistry and astrochemistry fields, and requires various approaches to be combined. Measurements of isotopic ratios in cometary materials provide strong constraints on the content of the protosolar nebula. Their relation with the composition of the parental dark clouds is, however, still very elusive. In this paper, we bring new constraints based on the isotopic composition of nitrogen in dark clouds, with the aim of understanding the chemical processes that are responsible for the observed isotopic ratios. We have observed and detected the fundamental rotational transition of C15N towards two starless dark clouds, L1544 and L1498. We were able to derive the column density ratio of C15N over 13CN towards the same clouds and obtain the CN/C15N isotopic ratios, which were found to be 500 ± 75 for both L1544 and L1498. These values are therefore marginally consistent with the protosolar value of 441. Moreover, this ratio is larger than the isotopic ratio of nitrogen measured in HCN. In addition, we present model calculations of the chemical fractionation of nitrogen in dark clouds, which make it possible to understand how CN can be deprived of 15N and HCN can simultaneously be enriched in heavy nitrogen. The non-fractionation of N2H+, however, remains an open issue, and we propose some chemical way of alleviating the discrepancy between model predictions and the observed ratios. Appendices are available in electronic form at http://www.aanda.orgThe reduced spectra (in FITS format) are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/557/A65

Red and nebulous objects in dark clouds - A survey

NASA Technical Reports Server (NTRS)

Cohen, M.

1980-01-01

A search on the NGS-PO Sky Survey photographs has revealed 150 interesting nebulous and/or red objects, mostly lying in dark clouds and not previously catalogued. Spectral classifications are presented for 55 objects. These indicate a small number of new members of the class of Herbig-Haro objects, a significant number of new T Tauri stars, and a few emission-line hot stars. It is argued that hot, high-mass stars form preferentially in the dense cores of dark clouds. The possible symbiosis of high and low mass stars is considered. A new morphology class is defined for cometary nebulae, in which a star lies on the periphery of a nebulous ring.

C+ detection of warm dark gas in diffuse clouds

NASA Astrophysics Data System (ADS)

Langer, W. D.; Velusamy, T.; Pineda, J. L.; Goldsmith, P. F.; Li, D.; Yorke, H. W.

2010-10-01

We present the first results of the Herschel open time key program, Galactic Observations of Terahertz C+ (GOT C+) survey of the [CII] 2P3/2-2P1/2 fine-structure line at 1.9 THz (158 μm) using the HIFI instrument on Herschel. We detected 146 interstellar clouds along sixteen lines-of-sight towards the inner Galaxy. We also acquired HI and CO isotopologue data along each line-of-sight for analysis of the physical conditions in these clouds. Here we analyze 29 diffuse clouds (AV < 1.3 mag) in this sample characterized by having [CII] and HI emission, but no detectable CO. We find that [CII] emission is generally stronger than expected for diffuse atomic clouds, and in a number of sources is much stronger than anticipated based on their HI column density. We show that excess [CII] emission in these clouds is best explained by the presence of a significant diffuse warm H2, dark gas, component. This first [CII] 158 μm detection of warm dark gas demonstrates the value of this tracer for mapping this gas throughout the Milky Way and in galaxies. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

The spectral energy distribution of the scattered light from dark clouds

NASA Technical Reports Server (NTRS)

Mattila, Kalevi; Schnur, G. F. O.

1989-01-01

A dark cloud is exposed to the ambient radiation field of integrated starlight in the Galaxy. Scattering of starlight by the dust particles gives rise to a diffuse surface brightness of the dark nebula. The intensity and the spectrum of this diffuse radiation can be used to investigate, e.g., the scattering parameters of the dust, the optical thickness of the cloud, and as a probe of the ambient radiation field at the location of the cloud. An understanding of the scattering process is also a prerequisite for the isolation of broad spectral features due to fluorescence or to any other non-scattering origin of the diffuse light. Model calculations are presented for multiple scattering in a spherical cloud. These calculations show that the different spectral shapes of the observed diffuse light can be reproduced with standard dust parameters. The possibility to use the observed spectrum as a diagnostic tool for analyzing the thickness of the cloud and the dust particle is discussed.

Grain Growth and Silicates in Dense Clouds

NASA Technical Reports Server (NTRS)

Pendeleton, Yvonne J.; Chiar, J. E.; Ennico, K.; Boogert, A.; Greene, T.; Knez, C.; Lada, C.; Roellig, T.; Tielens, A.; Werner, M.;

Clouds at CTIO and the Dark Energy Survey

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neilsen, Jr., Eric

An understanding of the weather patters at Cerro-Tololo Inter-American (CTIO) Observatory, the observing site for the Dark Energy Survey (DES), is important for assessing the efciency of DES operations in using observing time and for planning future operations. CTIO has maintained records of cloud-cover by quarters of nights since 1975. A comparison between these cloud records in the 2013-2014 DES observing season (DES year 1) and achieved observing efciency and exposure quality allows the DES collaboration to make better use of the historical records in survey planning. Plots and tables here relate human recorded cloud-cover to collection of good DESmore » data, show the variation of typical cloud-cover by month, and evaluate the relationship between the El Niño weather pattern and cloud-cover at CTIO.« less

Size-density relations in dark clouds: Non-LTE effects

NASA Technical Reports Server (NTRS)

Maloney, P.

1986-01-01

One of the major goals of molecular astronomy has been to understand the physics and dynamics of dense interstellar clouds. Because the interpretation of observations of giant molecular clouds is complicated by their very complex structure and the dynamical effects of star formation, a number of studies have concentrated on dark clouds. Leung, Kutner and Mead (1982) (hereafter LKM) and Myers (1983), in studies of CO and NH3 emission, concluded that dark clouds exhibit significant correlations between linewidth and cloud radius of the form delta v varies as R(0.5) and between mean density and radius of the form n varies as R(-1), as originally suggested by Larson (1981). This result suggests that these objects are in virial equilibrium. However, the mean densities inferred from the CO data of LKM are based on an local thermodynamic equilibrium (LTE) analysis of their 13CO data. At the very low mean densities inferred by LKM for the larger clouds in their samples, the assumption of LTE becomes very questionable. As most of the range in R in the density-size correlation comes from the clouds observed in CO, it seems worthwhile to examine how non-LTE effects will influence the derived densities. One way to assess the validity of LTE-derived densities is to construct cloud models and then to interpret them in the same way as the observed data. Microturbulent models of inhomogeneous clouds of varying central concentration with the linewidth-size and mean density-size relations found by Myers show sub-thermal excitation of the 13CO line in the larger clouds, with the result that LTE analysis considerbly underestimates the actual column density. A more general approach which doesn't require detailed modeling of the clouds is to consider whether the observed T sub R*(13CO)/T sub R*(12CO) ratios in the clouds studied by LKM are in the range where the LTE-derived optical depths (and hence column densities) can be seriously in error due to sub-thermal excitation of the 13CO

Large-Scale Structure of the Molecular Gas in Taurus Revealed by High Spatial Dynamic Range Spectral Line Mapping

NASA Technical Reports Server (NTRS)

Goldsmith, Paul F.

2008-01-01

Viewgraph topics include: optical image of Taurus; dust extinction in IR has provided a new tool for probing cloud morphology; observations of the gas can contribute critical information on gas temperature, gas column density and distribution, mass, and kinematics; the Taurus molecular cloud complex; average spectra in each mask region; mas 2 data; dealing with mask 1 data; behavior of mask 1 pixels; distribution of CO column densities; conversion to H2 column density; variable CO/H2 ratio with values much less than 10(exp -4) at low N indicated by UV results; histogram of N(H2) distribution; H2 column density distribution in Taurus; cumulative distribution of mass and area; lower CO fractional abundance in mask 0 and 1 regions greatly increases mass determined in the analysis; masses determined with variable X(CO) and including diffuse regions agrees well with the found from L(CO); distribution of young stars as a function of molecular column density; star formation efficiency; star formation rate and gas depletion; and enlarged images of some of the regions with numerous young stars. Additional slides examine the origin of the Taurus molecular cloud, evolution from HI gas, kinematics as a clue to its origin, and its relationship to star formation.

Chemical composition of rocks and soils at Taurus-Littrow

NASA Technical Reports Server (NTRS)

Rose, H. J., Jr.; Cuttitta, F.; Berman, S.; Brown, F. W.; Carron, M. K.; Christian, R. P.; Dwornik, E. J.; Greenland, L. P.

1974-01-01

Seventeen soils and seven rock samples were analyzed for major elements, minor elements, and trace elements. Unlike the soils at previous Apollo sites, which showed little difference in composition at each collection area, the soils at Taurus-Littrow vary widely. Three soil types are evident, representative of (1) the light mantle at the South Massif, (2) the dark mantle in the valley, and (3) the surface material at the North Massif. The dark-mantle soils are chemically similar to those at Tranquillitatis. Basalt samples from the dark mantle are chemically similar although they range from fine to coarse grained. It is suggested that they originated from the same source but crystallized at varying depths from the surface.

Dark matter annihilations in the Large Magellanic Cloud

NASA Astrophysics Data System (ADS)

Gondolo, Paolo

1994-05-01

I examine the possibility of detecting high energy γ-rays from non-baryonic dark matter annihilations in the central region of the Large Magellanic Cloud. Present address: LPTHE, Université Paris VII, Tour 24-14, 5 étage, 2 Place Jussieu, 75251 Paris Cédex 05, France;

Soft X-ray observation of the Rho Ophiuchus dark cloud region

NASA Technical Reports Server (NTRS)

Apparao, K. M. V.; Hayakawa, S.; Hearn, D. R.

1979-01-01

Soft X-rays (0.1-0.8 keV) from the region including the Rho Oph dark cloud were observed with the SAS-3 low-energy X-ray telescope. No X-ray absorption by the cloud was observed. This indicates that the diffuse component of soft X-rays in this region is mostly from the foreground of the Rho Oph cloud which is located at a distance of 160-200 pc.

Studies of Dark Spots and Their Companion Clouds on the Ice Giant Planets

NASA Astrophysics Data System (ADS)

Bhure, Sakhee; Sankar, Ramanakumar; Hadland, Nathan; Palotai, Csaba J.; Le Beau, Raymond P.; Koutas, Nikko

2017-10-01

Observations of ice giant planets in our Solar System have shown several large-scale dark spots with varying lifespans. Some of these features were directly observed, others were diagnosed from their orographic companion clouds. Historically, numerical simulations have been able to model certain characteristics of these storms such as the shape variability of the Neptune Great Dark Spot (GDS-89) (Deng and Le Beau, 2006), but have not been able to match observed drift rates and lifespans using the standard zonal wind profiles (Hammel et al. 2009). Common amongst these studies has been the lack of condensable species in the atmosphere and an explicit treatment of cloud microphysics. Yet, observations show that dark spots can affect neighboring cloud features, such as in the case of bright companion clouds or the “Berg” on Uranus. An analysis of the cloud structure is therefore required to gain a better understanding of the underlying atmospheric physics and dynamics of these vortices.For our simulations, we use the Explicit Planetary Isentropic Coordinate (EPIC) general circulation model (Dowling et al. 1998, 2006) and adapt its jovian cloud microphysics module which successfully reproduced the cloud structure of jovian storms, such as the Great Red Spot and the Oval BA (Palotai and Dowling 2008, Palotai et al. 2014). EPIC was recently updated to account for the condensation of methane and hydrogen sulfide (Palotai et al. 2016), which allows us to account for both the high-altitude methane ice-cloud and the deep atmosphere hydrogen sulfide ice-cloud layers.In this work, we simulate large-scale vortices on Uranus and Neptune with varying cloud microphysical parameters such as the deep abundance and the ambient supersaturation. We examine the effect of cloud formation on their lifespan and drift rates to better understand the underlying processes which drive these storms.

An assessment of Li abundances in weak-lined and classical T Tauri stars of the Taurus-Auriga association

NASA Astrophysics Data System (ADS)

Sestito, P.; Palla, F.; Randich, S.

2008-09-01

Context: Accurate measurements of lithium abundances in young low-mass stars provide an independent and reliable age diagnostics. Previous studies of nearby star forming regions have identified significant numbers of Li-depleted stars, often at levels inconsistent with the ages indicated by their luminosity. Aims: We aim at a new and accurate analysis of Li abundances in a sample of ~100 pre-main sequence stars in Taurus-Auriga using a homogeneous and updated set of stellar parameters and model atmospheres appropriate for the spectral types of the sample stars. Methods: We compute Li abundances using published values of the equivalent widths of the Li λ6708 Å doublet obtained from medium/high resolution spectra. Results: We find that the number of significantly Li-depleted stars in Taurus-Auriga is greatly reduced with respect to earlier results. Only 13 stars have abundances lower than the interstellar value by a factor of 5 or greater. All of them are weak-lined T Tauri stars drawn from X-ray surveys; with the exception of four stars located near the L1551 and L1489 dark clouds, all the Li-depleted stars belong to the class of dispersed low-mass stars, distributed around the main sites of current star formation. If located at the distance of Taurus-Auriga, the stellar ages implied by the derived Li abundances are in the range 3-30 Myr, greater than the bulk of the Li-rich population with implication on the star formation history of the region. Conclusions: In order to derive firm conclusions about the fraction of Li-depleted stars of Taurus-Auriga, Li measurements of the remaining members of the association should be obtained, in particular of the group of stars that fall in the Li-burning region of the HR diagram. Table [see full text] is only available in electronic form at http://www.aanda.org

DISTANCES TO DARK CLOUDS: COMPARING EXTINCTION DISTANCES TO MASER PARALLAX DISTANCES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Foster, Jonathan B.; Jackson, James M.; Stead, Joseph J.

We test two different methods of using near-infrared extinction to estimate distances to dark clouds in the first quadrant of the Galaxy using large near-infrared (Two Micron All Sky Survey and UKIRT Infrared Deep Sky Survey) surveys. Very long baseline interferometry parallax measurements of masers around massive young stars provide the most direct and bias-free measurement of the distance to these dark clouds. We compare the extinction distance estimates to these maser parallax distances. We also compare these distances to kinematic distances, including recent re-calibrations of the Galactic rotation curve. The extinction distance methods agree with the maser parallax distancesmore » (within the errors) between 66% and 100% of the time (depending on method and input survey) and between 85% and 100% of the time outside of the crowded Galactic center. Although the sample size is small, extinction distance methods reproduce maser parallax distances better than kinematic distances; furthermore, extinction distance methods do not suffer from the kinematic distance ambiguity. This validation gives us confidence that these extinction methods may be extended to additional dark clouds where maser parallaxes are not available.« less

Cosmic ray processing of N2-containing interstellar ice analogues at dark cloud conditions

NASA Astrophysics Data System (ADS)

Fedoseev, G.; Scirè, C.; Baratta, G. A.; Palumbo, M. E.

2018-04-01

N2 is believed to lock considerable part of nitrogen elemental budget and, therefore, to be one of the most abundant ice constituent in cold dark clouds. This laboratory-based research utilizes high energetic processing of N2 containing interstellar ice analogues using 200 keV H+ and He+ ions that mimics cosmic ray processing of the interstellar icy grains. It aims to investigate the formation of (iso)cyanates and cyanides in the ice mantles at the conditions typical for cold dark clouds and prestellar cores. Investigation of cosmic ray processing as a chemical trigger mechanism is explained by the high stability of N2 molecules that are chemically inert in most of the atom- and radical-addition reactions and cannot be efficiently dissociated by cosmic ray induced UV-field. Two sets of experiments are performed to closer address solid-state chemistry occurring in two distinct layers of the ice formed at different stages of dark cloud evolution, i.e. `H2O-rich' and `CO-rich' ice layers. Formation of HNCO and OCN- is discussed in all of the performed experiments. Corresponding kinetic curves for HNCO and OCN- are obtained. Furthermore, a feature around 2092 cm-1 assigned to the contributions of 13CO, CN-, and HCN is analysed. The kinetic curves for the combined HCN/CN- abundance are derived. In turn, normalized formation yields are evaluated by interpolation of the obtained results to the low irradiation doses relevant to dark cloud stage. The obtained values can be used to interpret future observations towards cold dark clouds using James Webb Space Telescope.

X-Ray Shadowing Experiments Toward Infrared Dark Clouds

NASA Technical Reports Server (NTRS)

Anderson, L. E.; Snowden, S.; Bania, T. M.

2009-01-01

We searched for X-ray shadowing toward two infrared dark clouds (IRDCs) using the MOS detectors on XMM-Newton to learn about the Galactic distribution of X-ray emitting plasma. IRDCs make ideal X-ray shadowing targets of 3/4 keY photons due to their high column densities, relatively large angular sizes, and known kinematic distances. Here we focus on two clouds near 30 deg Galactic longitude at distances of 2 and 5 kpc from the Sun. We derive the foreground and background column densities of molecular and atomic gas in the direction of the clouds. We find that the 3/4 ke V emission must be distributed throughout the Galactic disk. It is therefore linked to the structure of the cooler material of the ISM, and to the birth of stars.

Soft X-ray observations of pre-main sequence stars in the chamaeleon dark cloud

NASA Technical Reports Server (NTRS)

Feigelson, Eric D.; Kriss, Gerard A.

1987-01-01

Einstein IPC observations of the nearby Chamaeleon I star forming cloud show 22 well-resolved soft X-ray sources in a 1x2 deg region. Twelve are associated with H-alpha emission line pre-main sequence (PMS) stars, and four with optically selected PMS stars. Several X-ray sources have two or more PMS stars in their error circles. Optical spectra were obtained at CTIO of possible stellar counterparts of the remaining X-ray sources. They reveal 5 probable new cloud members, K7-MO stars with weak or absent emission lines. These naked X-ray selected PMS stars are similar to those found in the Taurus-Auriga cloud. The spatial distributions and H-R diagrams of the X-ray and optically selected PMS stars in the cloud are very similar. Luminosity functions indicate the Chamaeleon stars are on average approximately 5 times more X-ray luminous than Pleiad dwarfs. A significant correlation between L sub x and optical magnitude suggests this trend may continue within the PMS phase of stellar evolution. The relation of increasing X-ray luminosity with decreasing stellar ages is thus extended to stellar ages as young as 1 million years.

Last chance at Taurus-Littrow

NASA Technical Reports Server (NTRS)

Wilhelms, D. E.

1992-01-01

By the fall of 1971, it was known that only two more Apollos would land on the Moon. Most geoscientists agreed that both should concentrate on the previously neglected terrae (highlands). In June 1991, the Apollo Site Selection Board (ASSB) had chosen Descartes as the site of the Apollo 16 terra landing, scheduled for April 1972. Therefore, we had to assess how many pre-Apollo objectives the first four landings had met, how many Apollo 16 was likely to meet, and how to meet the remaining ones with Apollo 17. Geologists convened at Caltech in November 1971 and formulated a list of major lunar problems. An edited version of the list is presented, and how the remaining problems influenced the Apollo 16 and 17 landing site selection process is discussed with particular emphasis on the selection of Taurus-Littrow as the landing site for Apollo 17. Apollo 17 returned a fine collection from the massifs, bright mantle, Sculptured Hills, subfloor basalt, and dark mantle of Taurus-Littrow. They answered many of 1971's questions, showed others to have been wrongly asked, and left others for us to ponder still today. A brief discussion of the problems solved and the questions raised by the Apollo Program are presented.

School Consolidation: A Silver Lining in a Dark Cloud

ERIC Educational Resources Information Center

Waldfogel, Dean

2011-01-01

Everyone--board members, parents, and staff--loves small schools, bur it's no secret that small schools cost more to operate, particularly if administrative and teaching staff cannot be assigned efficiently. If there is a silver lining in this dark contextual cloud, it's that political support for consolidating schools has rarely been better. The…

The Relationship Between Infrared Dark Cloud and Stellar Properties

NASA Astrophysics Data System (ADS)

Calahan, Jenny; Hora, Joseph L.

2018-01-01

Massive stars are known to form within infrared dark clouds (IRDCs), but many details about how molecular clouds collapse and form stars remain poorly understood.We determine the relationship between the dark cloud mass and the population of young stellar objects (YSOs) associated with the cloud to shed light on the physical processes occurring within these star forming regions. We chose to use a sample of IRDCs and YSOs within the Cygnus-X region, a close-by giant star formation complex that has every stage of star formation represented. Using observations from IRAC, MIPS, PACS, and SPIRE on Spitzer and Herschel we identified a sample of 30,903 YSOs and 167 IRDCs. We derived the class of each YSO as well as the mass of YSO and IRDCs from the flux information. Using these parameters, as well as their locations in the cloud, we were sorted IRDC fragments into larger filaments and associate a set of YSOs with each IRDC. By measuring and comparing parameters such as YSO total mass, number of YSOs, Class 0, Class I, and Class II populations, distance from host filament, and filament mass we tested for correlations between the YSO and IRDC parameters. Using this treasure trove of information, we find that Class 0 and I objects are located more closely to their host IRDC than their Class II counterparts. We also find that high-density IRDCs are better environments for star formation than low-density IRDCs. However, we find no correlation between the total mass of the IRDC and the largest YSO mass in the IRDC, suggesting that IRDCs of any mass can have massive YSOs associated with them.The SAO REU program is funded by the National Science Foundation REU and Department of Defense ASSURE programs under NSF Grant AST-1659473, and by the Smithsonian Institution.

Molecules in interstellar clouds. [physical and chemical conditions of star formation and biological evolution

NASA Technical Reports Server (NTRS)

Irvine, W. M.; Hjalmarson, A.; Rydbeck, O. E. H.

1981-01-01

The physical conditions and chemical compositions of the gas in interstellar clouds are reviewed in light of the importance of interstellar clouds for star formation and the origin of life. The Orion A region is discussed as an example of a giant molecular cloud where massive stars are being formed, and it is pointed out that conditions in the core of the cloud, with a kinetic temperature of about 75 K and a density of 100,000-1,000,000 molecules/cu cm, may support gas phase ion-molecule chemistry. The Taurus Molecular Clouds are then considered as examples of cold, dark, relatively dense interstellar clouds which may be the birthplaces of solar-type stars and which have been found to contain the heaviest interstellar molecules yet discovered. The molecular species identified in each of these regions are tabulated, including such building blocks of biological monomers as H2O, NH3, H2CO, CO, H2S, CH3CN and H2, and more complex species such as HCOOCH3 and CH3CH2CN.

Effect of monensin withdrawal on intake, digestion, and ruminal fermentation parameters by Bos taurus indicus and Bos taurus taurus steers consuming bermudagrass hay

USDA-ARS?s Scientific Manuscript database

Effects of monensin withdrawal and cattle subspecies on the utilization of bermudagrass hay (14.3% CP, 72.3% NDF, and 36.9% ADF) were evaluated using ruminally cannulated steers (5 Bos Taurus indicus [BI] and 5 Bos taurus taurus [BT]). Subspecies were concurrently subjected to a 2-period, 2-treatme...

Is the filamentary dark cloud GF 6 a star forming region? — Stability analysis and infrared properties

NASA Astrophysics Data System (ADS)

Kim, Jaeheon; Kim, Hyun-Goo; Kim, Sang Joon; Zhang, Bo

2017-12-01

We present the results of mapping observations and stability analyses toward the filamentary dark cloud GF 6. We investigate the internal structures of a typical filamentary dark cloud GF 6 to know whether the filamentary dark cloud will form stars. We perform radio observations with both 12CO (J=1-0) and 13CO (J=1-0) emission lines to examine the mass distribution and its evolutionary status. The 13CO gas column density map shows eight subclumps in the GF 6 region with sizes on a sub-pc scale. The resulting local thermodynamic equilibrium masses of all the subclumps are too low to form stars against the turbulent dissipation. We also investigate the properties of embedded infrared point sources to know whether they are newly formed stars. The infrared properties also indicate that these point sources are not related to star forming activities associated with GF 6. Both radio and infrared properties indicate that the filamentary dark cloud GF 6 is too light to contract gravitationally and will eventually be dissipated away.

Anomalous 13C isotope abundances in C3S and C4H observed toward the cold interstellar cloud, Taurus Molecular Cloud-1.

PubMed

Sakai, Nami; Takano, Shuro; Sakai, Takeshi; Shiba, Shoichi; Sumiyoshi, Yoshihiro; Endo, Yasuki; Yamamoto, Satoshi

2013-10-03

We have studied the abundances of the (13)C isotopic species of C3S and C4H in the cold molecular cloud, Taurus Molecular Cloud-1 (Cyanopolyyne Peak), by radioastronomical observations of their rotational emission lines. The CCCS/(13)CCCS and CCCS/C(13)CCS ratios are determined to be >206 and 48 ± 15, respectively. The CC(13)CS line is identified with the aid of laboratory microwave spectroscopy, and the range of the CCCS/CC(13)CS ratio is found to be from 30 to 206. The abundances of at least two (13)C isotopic species of C3S are thus found to be different. Similarly, it is found that the abundances of the four (13)C isotopic species of C4H are not equivalent. The CCCCH/(13)CCCCH, CCCCH/C(13)CCCH, CCCCH/CC(13)CCH, and CCCCH/CCC(13)CH ratios are evaluated to be 141 ± 44, 97 ± 27, 82 ± 15, and 118 ± 23, respectively. Here the errors denote 3 times the standard deviation. These results will constrain the formation pathways of C3S and C4H, if the nonequivalence is caused during the formation processes of these molecules. The exchange reactions after the formation of these two molecules may also contribute to the nonequivalence. In addition, we have confirmed that the (12)C/(13)C ratio of some species are significantly higher than the interstellar elemental (12)C/(13)C ratio of 60-70. The observations of the (13)C isotopic species provide us with rich information on chemical processes in cold interstellar clouds.

Effect of monensin inclusion on intake, digestion, and ruminal fermentation parameters by Bos taurus indicus and Bos taurus taurus steers consuming bermudagrass hay

USDA-ARS?s Scientific Manuscript database

Effects of monensin inclusion and cattle subspecies on utilization of bermudagrass hay (13.7% CP, 77.3% NDF, and 38.8% ADF) were evaluated using ruminally cannulated steers (5 Bos taurus indicus [BI] and 5 Bos taurus taurus [BT]; 398 kg BW). Subspecies were concurrently subjected to a 2-period, 2-t...

Far-infrared Extinction Mapping of Infrared Dark Clouds

NASA Astrophysics Data System (ADS)

Lim, Wanggi; Tan, Jonathan C.

2014-01-01

Progress in understanding star formation requires detailed observational constraints on the initial conditions, i.e., dense clumps and cores in giant molecular clouds that are on the verge of gravitational instability. Such structures have been studied by their extinction of near-infrared and, more recently, mid-infrared (MIR) background light. It has been somewhat more of a surprise to find that there are regions that appear as dark shadows at far-infrared (FIR) wavelengths as long as ~100 μm! Here we develop analysis methods of FIR images from Spitzer-MIPS and Herschel-PACS that allow quantitative measurements of cloud mass surface density, Σ. The method builds on that developed for MIR extinction mapping by Butler & Tan, in particular involving a search for independently saturated, i.e., very opaque, regions that allow measurement of the foreground intensity. We focus on three massive starless core/clumps in the Infrared Dark Cloud (IRDC) G028.37+00.07, deriving mass surface density maps from 3.5 to 70 μm. A by-product of this analysis is the measurement of the spectral energy distribution of the diffuse foreground emission. The lower opacity at 70 μm allows us to probe to higher Σ values, up to ~1 g cm-2 in the densest parts of the core/clumps. Comparison of the Σ maps at different wavelengths constrains the shape of the MIR-FIR dust opacity law in IRDCs. We find that it is most consistent with the thick ice mantle models of Ossenkopf & Henning. There is tentative evidence for grain ice mantle growth as one goes from lower to higher Σ regions.

Transitions from order to disorder in multiple dark and multiple dark-bright soliton atomic clouds.

PubMed

Wang, Wenlong; Kevrekidis, P G

2015-03-01

We have performed a systematic study quantifying the variation of solitary wave behavior from that of an ordered cloud resembling a "crystalline" configuration to that of a disordered state that can be characterized as a soliton "gas." As our illustrative examples, we use both one-component, as well as two-component, one-dimensional atomic gases very close to zero temperature, where in the presence of repulsive interatomic interactions and of a parabolic trap, a cloud of dark (dark-bright) solitons can form in the one- (two-) component system. We corroborate our findings through three distinct types of approaches, namely a Gross-Pitaevskii type of partial differential equation, particle-based ordinary differential equations describing the soliton dynamical system, and Monte Carlo simulations for the particle system. We define an "empirical" order parameter to characterize the order of the soliton lattices and study how this changes as a function of the strength of the "thermally" (i.e., kinetically) induced perturbations. As may be anticipated by the one-dimensional nature of our system, the transition from order to disorder is gradual without, apparently, a genuine phase transition ensuing in the intermediate regime.

FAR-INFRARED EXTINCTION MAPPING OF INFRARED DARK CLOUDS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lim, Wanggi; Tan, Jonathan C.

Progress in understanding star formation requires detailed observational constraints on the initial conditions, i.e., dense clumps and cores in giant molecular clouds that are on the verge of gravitational instability. Such structures have been studied by their extinction of near-infrared and, more recently, mid-infrared (MIR) background light. It has been somewhat more of a surprise to find that there are regions that appear as dark shadows at far-infrared (FIR) wavelengths as long as ∼100 μm! Here we develop analysis methods of FIR images from Spitzer-MIPS and Herschel-PACS that allow quantitative measurements of cloud mass surface density, Σ. The method buildsmore » on that developed for MIR extinction mapping by Butler and Tan, in particular involving a search for independently saturated, i.e., very opaque, regions that allow measurement of the foreground intensity. We focus on three massive starless core/clumps in the Infrared Dark Cloud (IRDC) G028.37+00.07, deriving mass surface density maps from 3.5 to 70 μm. A by-product of this analysis is the measurement of the spectral energy distribution of the diffuse foreground emission. The lower opacity at 70 μm allows us to probe to higher Σ values, up to ∼1 g cm{sup –2} in the densest parts of the core/clumps. Comparison of the Σ maps at different wavelengths constrains the shape of the MIR-FIR dust opacity law in IRDCs. We find that it is most consistent with the thick ice mantle models of Ossenkopf and Henning. There is tentative evidence for grain ice mantle growth as one goes from lower to higher Σ regions.« less

A CENSUS OF ROTATION AND VARIABILITY IN L1495: A UNIFORM ANALYSIS OF TRANS-ATLANTIC EXOPLANET SURVEY LIGHT CURVES FOR PRE-MAIN-SEQUENCE STARS IN TAURUS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xiao Hongyu; Covey, Kevin R.; Lloyd, James P.

2012-09-15

We analyze light curves obtained by the Trans-atlantic Exoplanet Survey (TrES) for a field centered on the L1495 dark cloud in Taurus. The Spitzer Taurus Legacy Survey catalog identifies 179 bona fide Taurus members within the TrES field; 48 of the known Taurus members are detected by TrES, as well as 26 candidate members identified by the Spitzer Legacy team. We quantify the variability of each star in our sample using the ratio of the standard deviation of the original light curve ({sigma}{sub orig.}) to the standard deviation of a light curve that has been smoothed by 9 or 1001more » epochs ({sigma}{sub 9} and {sigma}{sub 1001}, respectively). Known Taurus members typically demonstrate ({sigma}{sub orig.}/{sigma}{sub 9}) < 2.0, and ({sigma}{sub orig.}/{sigma}{sub 1001}) < 5, while field stars reveal ({sigma}{sub orig.}/{sigma}{sub 9}) {approx} 3.0 and ({sigma}{sub orig.}/{sigma}{sub 1001}) {approx} 10, as expected for light curves dominated by unstructured white noise. Of the 74 Taurus members/candidates with TrES light curves, we detect significant variability in 49 sources. Adapting a quantitative metric originally developed to assess the reliability of transit detections, we measure the amount of red and white noise in each light curve and identify 18 known or candidate Taurus members with highly significant period measurements. These appear to be the first periods measured for four of these sources (HD 282276, CX Tau, FP Tau, TrES J042423+265008), and in two other cases, the first non-aliased periods (LkCa 21 and DK Tau AB). For the remainder, the TrES measurements typically agree very well ({delta}P < 1%) with previously reported values. Including periods measured at lower confidence for 15 additional sources, we report periods for 11 objects where no previous periods were found, including 8 confirmed Taurus members. We also identify 10 of the 26 candidate Taurus members that demonstrate variability levels consistent with being bona fide T Tauri stars. A

Ultra-High Spectral Resolution Observations of Fragmentation in Dark Cloud Cores

NASA Technical Reports Server (NTRS)

Velusamy, T.; Langer, W.; Kuiper, T; Levin, S.; Olsen, E.

1993-01-01

This paper presents new evidence of the fragmentary structure of dense cores in dark clouds using the high resolution spectra of the carbon chain molecule CCS transition (J subscript N = 2 subscript 1 - 1 subscript o) at 22.344033 GHz with 0.008 km s superscript -1 resolution.

Transitions from order to disorder in multiple dark and multiple dark-bright soliton atomic clouds

DOE PAGES

Wang, Wenlong; Kevrekidis, P. G.

2015-03-09

We have performed a systematic study quantifying the variation of solitary wave behavior from that of an ordered cloud resembling a “crystalline” configuration to that of a disordered state that can be characterized as a soliton “gas.” As our illustrative examples, we use both one-component, as well as two-component, one-dimensional atomic gases very close to zero temperature, where in the presence of repulsive interatomic interactions and of a parabolic trap, a cloud of dark (dark-bright) solitons can form in the one- (two-) component system. We corroborate our findings through three distinct types of approaches, namely a Gross-Pitaevskii type of partialmore » differential equation, particle-based ordinary differential equations describing the soliton dynamical system, and Monte Carlo simulations for the particle system. In addition, we define an “empirical” order parameter to characterize the order of the soliton lattices and study how this changes as a function of the strength of the “thermally” (i.e., kinetically) induced perturbations. As may be anticipated by the one-dimensional nature of our system, the transition from order to disorder is gradual without, apparently, a genuine phase transition ensuing in the intermediate regime.« less

The Gould's Belt Distances Survey (GOBELINS). IV. Distance, Depth, and Kinematics of the Taurus Star-forming Region

NASA Astrophysics Data System (ADS)

Galli, Phillip A. B.; Loinard, Laurent; Ortiz-Léon, Gisela N.; Kounkel, Marina; Dzib, Sergio A.; Mioduszewski, Amy J.; Rodríguez, Luis F.; Hartmann, Lee; Teixeira, Ramachrisna; Torres, Rosa M.; Rivera, Juana L.; Boden, Andrew F.; Evans, Neal J., II; Briceño, Cesar; Tobin, John J.; Heyer, Mark

2018-05-01

We present new trigonometric parallaxes and proper motions of young stellar objects in the Taurus molecular cloud complex from observations collected with the Very Long Baseline Array as part of the Gould’s Belt Distances Survey. We detected 26 young stellar objects and derived trigonometric parallaxes for 18 stars with an accuracy of 0.3% to a few percent. We modeled the orbits of six binaries and determined the dynamical masses of the individual components in four of these systems (V1023 Tau, T Tau S, V807 Tau, and V1000 Tau). Our results are consistent with the first trigonometric parallaxes delivered by the Gaia satellite and reveal the existence of significant depth effects. We find that the central portion of the dark cloud Lynds 1495 is located at d =129.5 ± 0.3 pc, while the B216 clump in the filamentary structure connected to it is at d = 158.1 ± 1.2 pc. The closest and remotest stars in our sample are located at d = 126.6 ± 1.7 pc and d = 162.7 ± 0.8 pc, yielding a distance difference of about 36 pc. We also provide a new distance estimate for HL Tau that was recently imaged. Finally, we compute the spatial velocity of the stars with published radial velocity and investigate the kinematic properties of the various clouds and gas structures in this region.

The Nature of Carbon Dioxide Bearing Ices in Quiescent Molecular Clouds

NASA Astrophysics Data System (ADS)

Whittet, D. C. B.; Cook, A. M.; Chiar, J. E.; Pendleton, Y. J.; Shenoy, S. S.; Gerakines, P. A.

2009-04-01

The properties of the ices that form in dense molecular clouds represent an important set of initial conditions in the evolution of interstellar and preplanetary matter in regions of active star formation. Of the various spectral features available for study, the bending mode of solid CO2 near 15 μm has proven to be a particularly sensitive probe of physical conditions, especially temperature. We present new observations of this absorption feature in the spectrum of Q21-1, a background field star located behind a dark filament in the Cocoon Nebula (IC 5146). We show the profile of the feature to be consistent with a two-component (polar + nonpolar) model for the ices, based on spectra of laboratory analogs with temperatures in the range 10-20 K. The polar component accounts for ~85% of the CO2 in the line of sight. We compare for the first time 15 μm profiles in three widely separated dark clouds (Taurus, Serpens, and IC 5146), and show that they are indistinguishable to within observational scatter. Systematic differences in the observed CO2/H2O ratio in the three clouds have little or no effect on the 15 μm profile. The abundance of elemental oxygen in the ices appears to be a unifying factor, displaying consistent behavior in the three clouds. We conclude that the ice formation process is robust and uniformly efficient, notwithstanding compositional variations arising from differences in how the O is distributed between the primary species (H2O, CO2, and CO) in the ices.

Similar complex kinematics within two massive, filamentary infrared dark clouds

NASA Astrophysics Data System (ADS)

Barnes, A. T.; Henshaw, J. D.; Caselli, P.; Jiménez-Serra, I.; Tan, J. C.; Fontani, F.; Pon, A.; Ragan, S.

2018-04-01

Infrared dark clouds (IRDCs) are thought to be potential hosts of the elusive early phases of high-mass star formation. Here, we conduct an in-depth kinematic analysis of one such IRDC, G034.43+00.24 (Cloud F), using high sensitivity and high spectral resolution IRAM-30m N2H+ (1-0) and C18O (1-0) observations. To disentangle the complex velocity structure within this cloud, we use Gaussian decomposition and hierarchical clustering algorithms. We find that four distinct coherent velocity components are present within Cloud F. The properties of these components are compared to those found in a similar IRDC, G035.39-00.33 (Cloud H). We find that the components in both clouds have high densities (inferred by their identification in N2H+), trans-to-supersonic non-thermal velocity dispersions with Mach numbers of ˜1.5-4, a separation in velocity of ˜3 km s-1, and a mean red-shift of ˜0.3 km s-1 between the N2H+ (dense gas) and C18O emission (envelope gas). The latter of these could suggest that these clouds share a common formation scenario. We investigate the kinematics of the larger-scale Cloud F structures, using lower-density-tracing 13CO(1-0) observations. A good correspondence is found between the components identified in the IRAM-30m observations and the most prominent component in the 13CO data. We find that the IRDC Cloud F is only a small part of a much larger structure, which appears to be an inter-arm filament of the Milky Way.

A GALEX-BASED SEARCH FOR THE SPARSE YOUNG STELLAR POPULATION IN THE TAURUS-AURIGAE STAR FORMING REGION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gómez de Castro, Ana I.; Lopez-Santiago, Javier; López-Martínez, Fatima

2015-02-01

In this work, we identify 63 bona fide new candidates to T Tauri stars (TTSs) in the Taurus-Auriga region, using its ultraviolet excess as our baseline. The initial data set was defined from the GALEX all sky survey (AIS). The GALEX satellite obtained images in the near-ultraviolet (NUV) and far-ultraviolet (FUV) bands where TTSs show a prominent excess compared with main-sequence or giants stars. GALEX AIS surveyed the Taurus-Auriga molecular complex, as well as a fraction of the California Nebula and the Perseus complex; bright sources and dark clouds were avoided. The properties of TTSs in the ultraviolet (GALEX), opticalmore » (UCAC4), and infrared (2MASS) have been defined using the TTSs observed with the International Ultraviolet Explorer reference sample. The candidates were identified by means of a mixed ultraviolet-optical-infrared excess set of colors; we found that the FUV-NUV versus J–K color-color diagram is ideally suited for this purpose. From an initial sample of 163,313 bona fide NUV sources, a final list of 63 new candidates to TTSs in the region was produced. The search procedure has been validated by its ability to detect all known TTSs in the area surveyed: 31 TTSs. Also, we show that the weak-lined TTSs are located in a well-defined stripe in the FUV-NUV versus J–K diagram. Moreover, in this work, we provide a list of TTSs photometric standards for future GALEX-based studies of the young stellar population in star forming regions.« less

Thoughts About Nursing Curricula: Dark Clouds and Bright Lights.

PubMed

Turkel, Marian C; Fawcett, Jacqueline; Amankwaa, Linda; Clarke, Pamela N; Dee, Vivien; Eustace, Rosemary; Hansell, Phyllis Shanley; Jones, Dorothy A; Smith, Marlaine C; Zahourek, Rothlyn

2018-04-01

In this essay, several nurse scholars who are particularly concerned about the contemporary state of nursing science present their concerns about the inclusion of nursing conceptual models and theories in the curricula of nursing programs (dark clouds) and ways in which the concerns have been addressed (bright lights). This essay is the second of two essays that were catalyzed by Barrett's paper, "Again, What Is Nursing Science?" The first essay was published in the previous issue of Nursing Science Quarterly.

A survey of carbon monoxide emission in dark clouds. [cosmic dust

NASA Technical Reports Server (NTRS)

Dickman, R. L.

1975-01-01

Results are reported of a CO and (C-13)O survey of 68 dark clouds from the Lynds catalog. CO was detected in 63 of the 64 sources in which it was searched for, and the (C-13)O line was seen in 52 of 55 clouds. There is a rather narrow distribution of CO peak line radiation temperatures about a mean of 6 K; this may reflect the presence of a roughly uniform kinetic temperature of 9.5 K in the sources. Despite the probably subthermal excitation temperature of the (C-13)O transition observed, derived (C-13)O column densities are most likely good to within a factor of 2. Typical CO column densities for the clouds surveyed are 5 x 10 to the 17-th power per sq cm, assuming a terrestrial carbon isotope ratio. All 68 clouds have previously been studied by Dieter in 6-cm H2CO absorption; a comparison of line widths shows the (C-13)O lines to generally be wider than their formaldehyde counterparts. Possible explanations of this fact in terms of internal cloud motions are discussed.

IRAS observations of dust heating and energy balance in the Rho Ophiuchi dark cloud

NASA Technical Reports Server (NTRS)

Greene, Thomas P.; Young, Erick T.

1989-01-01

The equilibrium process dust emission in the Rho Ophiuchi dark cloud is studied. The luminosity of the cloud is found to closely match the luminosity of the clouds's known embedded and external radiation sources. There is no evidence for a large population of undetected low-luminosity sources within the cloud and unknown external heating is also only a minor source of energy. Most of the cloud's luminosity is emitted in the mid-to-far-IR. Dust temperature maps indicate that the dust is not hot enough to heat the gas to observed temperatures. A simple cloud model with a radiation field composed of flux HD 147889, S1, and Sco OB2 associations predicts the observed IRAS 60 to 100 micron in-band flux ratios for a mean cloud density n(H2) = 1400. Flattened 12 and 25 micron observations show much extended emission in these bands, suggesting stochastic heating of very small grains or large molecules.

Water and complex organic chemistry in the cold dark cloud Barnard 5: Observations and Models

NASA Astrophysics Data System (ADS)

Wirström, Eva; Charnley, Steven B.; Taquet, Vianney; Persson, Carina M.

2015-08-01

Studies of complex organic molecule (COM) formation have traditionally been focused on hot cores in regions of massive star formation, where chemistry is driven by the elevated temperatures - evaporating ices and allowing for endothermic reactions in the gas-phase. As more sensitive instruments have become available, the types of objects known to harbour COMs like acetaldehyde (CH3CHO), dimethyl ether (CH3OCH3), methyl formate (CH3OCHO), and ketene (CH2CO) have expanded to include low mass protostars and, recently, even pre-stellar cores. We here report on the first in a new category of objects harbouring COMs: the cold dark cloud Barnard 5 where non-thermal ice desorption induce complex organic chemistry entirely unrelated to local star-formation.Methanol, which only forms efficiently on the surfaces of dust grains, provide evidence of efficient non-thermal desorption of ices in the form of prominent emission peaks offset from protostellar activity and high density tracers in cold molecular clouds. A study with Herschel targeting such methanol emission peaks resulted in the first ever detection of gas-phase water offset from protostellar activity in a dark cloud, at the so called methanol hotspot in Barnard 5.To model the effect a transient injection of ices into the gas-phase has on the chemistry of a cold, dark cloud we have included gas-grain interactions in an existing gas-phase chemical model and connected it to a chemical reaction network updated and expanded to include the formation and destruction paths of the most common COMs. Results from this model will be presented.Ground-based follow-up studies toward the methanol hotspot in B5 have resulted in the detection of a number of COMs, including CH2CO, CH3CHO, CH3OCH3, and CH3OCHO, as well as deuterated methanol (CH2DOH). Observations have also confirmed that COM emission is extended and not localised to a core structure. The implications of these observational and theoretical studies of B5 will be discussed

Models of bright storm clouds and related dark ovals in Saturn's Storm Alley as constrained by 2008 Cassini/VIMS spectra

NASA Astrophysics Data System (ADS)

Sromovsky, L. A.; Baines, K. H.; Fry, P. M.

2018-03-01

A 5° latitude band on Saturn centered near planetocentric latitude 36°S is known as "Storm Alley" because it has been for several extended periods a site of frequent lightning activity and associated thunderstorms, first identified by Porco et al. (2005). The thunderstorms appeared as bright clouds at short and long continuum wavelengths, and over a period of a week or so transformed into dark ovals (Dyudina et al., 2007). The ovals were found to be dark over a wide spectral range, which led Baines et al. (2009) to suggest the possibility that a broadband absorber such as soot produced by lightning could play a significant role in darkening the clouds relative to their surroundings. Here we show that an alternative explanation, which is that the clouds are less reflective because of reduced optical depth, provides an excellent fit to near infrared spectra of similar features obtained by the Cassini Visual and Infrared Mapping Spectrometer (VIMS) in 2008, and leads to a plausible scenario for cloud evolution. We find that the background clouds and the oval clouds are both dominated by the optical properties of a ubiquitous upper cloud layer, which has the same particle size in both regions, but about half the optical depth and physical thickness in the dark oval regions. The dark oval regions are also marked by enhanced emissions in the 5-μm window region, a result of lower optical depth of the deep cloud layer near 3.1-3.8 bar, presumably composed of ammonium hydrosulfide (NH4SH). The bright storm clouds completely block this deep thermal emission with a thick layer of ammonia (NH3) clouds extending from the middle of the main visible cloud layer probably as deep as the 1.7-bar NH3 condensation level. Other condensates might also be present at higher pressures, but are obscured by the NH3 cloud. The strong 3-μm spectral absorption that was displayed by Saturn's Great Storm of 2010-2011 (Sromovsky et al., 2013) is weaker in these storms because the contrast is

Thoughts About Advancement of the Discipline: Dark Clouds and Bright Lights.

PubMed

Turkel, Marian; Fawcett, Jacqueline; Chinn, Peggy L; Eustace, Rosemary; Hansell, Phyllis Shanley; Smith, Marlaine C; Watson, Jean; Zahourek, Rothlyn

2018-01-01

In this essay, several nurse scholars who are particularly concerned about the contemporary state of nursing science present their specific concerns (dark clouds) about the advancement of our discipline and the ways in which the concerns have been addressed (bright lights). This essay is the first of two essays that were catalyzed by Barrett's paper, "Again, What Is Nursing Science?" The second essay will be published in the next issue Nursing Science Quarterly.

The 15 273 Å diffuse interstellar band in the dark cloud Barnard 68

NASA Astrophysics Data System (ADS)

Elyajouri, Meriem; Cox, Nick L. J.; Lallement, Rosine

2017-09-01

High obscuration of background stars behind dark clouds precludes the detection of optical diffuse interstellar bands (DIBs) and hence our knowledge of DIB carriers in these environments. Taking advantage of the reduced obscuration of starlight in the near-infrared (NIR) we used one of the strongest NIR DIBs at 15 273 Å to probe the presence and properties of its carrier throughout the nearby interstellar dark cloud Barnard 68. We measured equivalent widths (EW) for different ranges of visual extinction AV, using VLT/KMOS H-band (1.46-1.85 μm) moderate-resolution (R 4000) spectra of 43 stars situated behind the cloud. To do so, we fitted the data with synthetic stellar spectra from the APOGEE project and TAPAS synthetic telluric transmissions appropriate for the observing site and time period. The results show an increase of DIB EW with increasing AV. However, the rate of increase is much flatter than expected from the EW-AV quasi-proportionality established for this DIB in the Galactic diffuse interstellar medium. Based on a simplified inversion assuming sphericity, it is found that the volume density of the DIB carrier is 2.7 and 7.9 times lower than this expected average value in the external and central regions of the cloud, which have nH≃ 0.4 and 3.5 × 105 cm-3, respectively. Further measurements with multiplex NIR spectrographs should allow detailed modeling of such an edge effect of this DIB and other bands and help clarify its actual origin. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme 096.C-0931(A).

A study of the large-scale infrared emission from a selected dark cloud

NASA Technical Reports Server (NTRS)

Young, Erick T.

1993-01-01

An investigation of the infrared emission energetics and embedded population in the rho Ophiuchi dark cloud is summarized. With a distance of approximately 140 pc, the rho Ophiuchi cloud is one of the closest regions of recent star formation. It is also one of the best studied such regions with numerous observations at all wavelengths. The Infrared Astronomy Satellite (IRAS) data of the cloud provided a new glimpse of the overall structure of the cloud. In particular, the interaction of radiation from the Sco-Oph OB Association on the external heating of the cloud was very evident on Skyflux and Survey CO-Add images produced by IRAS. The infrared survey also revealed a number of new embedded sources in the cloud which have subsequently been observed from the ground. In earlier study, the overall energies of the cloud using the IRAS data was explored. The main conclusions of that work were: (1) the overall luminosity of the cloud is well explained by the emission of the known B-stars, HD 147889, SR-3, and S1, along with a 15 percent contribution from the external radiation field; (2) the dust physical temperatures were significantly lower than the observed CO gas temperatures; and (3) dust grains are heated to only 10 percent to 20 percent of the total depth into the cloud. This analysis was extended by drawing on data from large-scale CO maps of Loren (1989) and from near-infrared surveys of the embedded population.

Taurus lightweight manned spacecraft Earth orbiting vehicle

NASA Technical Reports Server (NTRS)

Chase, Kevin A.; Vandersall, Eric J.; Plotkin, Jennifer; Travisano, Jeffrey J.; Loveless, Dennis; Kaczmarek, Michael; White, Anthony G.; Est, Andy; Bulla, Gregory; Henry, Chris

1991-01-01

The Taurus Lightweight Manned Spacecraft (LMS) was developed by students of the University of Maryland's Aerospace Engineering course in Space Vehicle Design. That course required students to design an Alternative Manned Spacecraft (AMS) to augment or replace the Space Transportation System and meet the following design requirements: (1) launch on the Taurus Booster being developed by Orbital Sciences Corporation; (2) 99.9 percent assured crew survival rate; (3) technology cutoff data of 1 Jan. 1991; (4) compatibility with current space administration infrastructure; and (5) first flight by May 1995. The Taurus LMS design meets the above requirements and represents an initial step towards larger and more complex spacecraft. The Taurus LMS has a very limited application when compared to the Space Shuttle, but it demonstrates that the U.S. can have a safe, reliable, and low cost space system. The Taurus LMS is a short mission duration spacecraft designed to place one man into low earth orbit (LEO). The driving factor for this design was the low payload carrying capabilities of the Taurus Booster--1300 kg to a 300 km orbit. The Taurus LMS design is divided into six major design sections. The human factors system deals with the problems of life support and spacecraft cooling. The propulsion section contains the abort system, the Orbital Maneuvering System (OMS), the Reaction Control System (RCS), and power generation. The thermal protection systems and spacecraft structure are contained in the structures section. The avionics section includes navigation, attitude determination, data processing, communication systems, and sensors. The mission analysis section was responsible for ground processing and spacecraft astrodynamics. The systems integration section pulled the above sections together into one spacecraft and addressed costing and reliability.

Taurus Lightweight Manned Spacecraft Earth orbiting vehicle

NASA Technical Reports Server (NTRS)

Bosset, M.

1991-01-01

The Taurus Lightweight Manned Spacecraft (LMS) was developed by students of the University of Maryland's Aerospace Engineering course in Space Vehicle Design. That course required students to design an Alternative Manned Spacecraft (AMS) to augment or replace the Space Transportation System and meet the following design requirements: (1) launch on the Taurus Booster being developed by Orbital Sciences Corporation; (2) 99.9 percent assured crew survival rate; (3) technology cutoff date of 1 Jan. 1991; (4) compatibility with current space administration infrastructure; and (5) first flight by May 1995. The Taurus LMS design meets the above requirements and represents an initial step toward larger and more complex spacecraft. The Taurus LMS has a very limited application when compared to the space shuttle, but it demonstrates that the U.S. can have a safe, reliable, and low-cost space system. The Taurus LMS is a short mission duration spacecraft designed to place one man into low Earth orbit (LEO). The driving factor for this design was the low payload carrying capabilities of the Taurus Booster - 1300 kg to a 300-km orbit. The Taurus LMS design is divided into six major design sections. The Human Factors section deals with the problems of life support and spacecraft cooling. The Propulsion section contains the Abort System, the Orbital Maneuvering System (OMS), the Reaction Control System (RCS), and Power Generation. The thermal protection systems and spacecraft structure are contained in the Structures section. The Avionics section includes Navigation, Attitude Determination, Data Processing, Communication systems, and Sensors. The Mission Analysis section was responsible for ground processing and spacecraft astrodynamics. The Systems Integration Section pulled the above sections together into one spacecraft, and addressed costing and reliability.

Physical properties of Southern infrared dark clouds

NASA Astrophysics Data System (ADS)

Vasyunina, T.; Linz, H.; Henning, Th.; Stecklum, B.; Klose, S.; Nyman, L.-Å.

2009-05-01

Context: What are the mechanisms by which massive stars form? What are the initial conditions for these processes? It is commonly assumed that cold and dense Infrared Dark Clouds (IRDCs) represent the birth-sites of massive stars. Therefore, these clouds have been receiving an increasing amount of attention, and their analysis offers the opportunity to tackle the afore mentioned questions. Aims: To enlarge the sample of well-characterised IRDCs in the southern hemisphere, where ALMA will play a major role in the near future, we have developed a program to study the gas and dust of southern infrared dark clouds. The present paper attempts to characterize the continuum properties of this sample of IRDCs. Methods: We cross-correlated 1.2 mm continuum data from SIMBA bolometer array mounted on SEST telescope with Spitzer/GLIMPSE images to establish the connection between emission sources at millimeter wavelengths and the IRDCs that we observe at 8 μm in absorption against the bright PAH background. Analysing the dust emission and extinction enables us to determine the masses and column densities, which are important quantities in characterizing the initial conditions of massive star formation. We also evaluated the limitations of the emission and extinction methods. Results: The morphology of the 1.2 mm continuum emission is in all cases in close agreement with the mid-infrared extinction. The total masses of the IRDCs were found to range from 150 to 1150 M_⊙ (emission data) and from 300 to 1750 M_⊙ (extinction data). We derived peak column densities of between 0.9 and 4.6 × 1022 cm-2 (emission data) and 2.1 and 5.4 × 1022 cm-2 (extinction data). We demonstrate that the extinction method is unreliable at very high extinction values (and column densities) beyond AV values of roughly 75 mag according to the Weingartner & Draine (2001) extinction relation RV = 5.5 model B (around 200 mag when following the common Mathis (1990, ApJ, 548, 296) extinction calibration

Hydroxyl as a Tracer of Dark Gas in a Diffuse Molecular Cloud

NASA Astrophysics Data System (ADS)

White, Josh; Donate, Emmanuel; Magnani, Loris A.

2017-06-01

In an attempt to determine the extent of dark molecular gas at high Galactic latitudes, we have conducted a survey of OH at 18 cm in a region containing the diffuse molecular cloud MBM 53. Dark molecular gas is a term that refers to molecular hydrogen that is either difficult or impossible to detect by conventional spectroscopic means. While models of photo-dissociation regions predict that some molecular hydrogen is found under conditions where other species are too low in abundance to be detected by radio spectroscopy, recent estimates have predicted that as much dark molecular gas exists as that normally detected by CO(1-0) surveys. However, more sensitive surveys either in the CO(1-0) line or other tracers should detect some of this gas. We observed 44 lines of sight at 18 cm to see if very sensitive OH observations could detect some of the dark molecular gas in the Pegasus-Pisces region. Our data were taken with the 305 m Arecibo radiotelescope and have typical rms values of 6-7 mK. We compared our OH observations with the Georgia/Harvard-Smithsonian CfA high-latitude CO(1-0) survey. Of 8 OH detections at 1667 MHz, 5 were not detected by the CO survey and indicate that at least some of the dark molecular gas may be traced by sensitive OH observations.

Cosmic-rays, gas, and dust in nearby anticentre clouds. II. Interstellar phase transitions and the dark neutral medium

NASA Astrophysics Data System (ADS)

Remy, Q.; Grenier, I. A.; Marshall, D. J.; Casandjian, J. M.

2018-03-01

Aim. H I 21-cm and 12CO 2.6-mm line emissions trace the atomic and molecular gas phases, respectively, but they miss most of the opaque H I and diffuse H2 present in the dark neutral medium (DNM) at the transition between the H I-bright and CO-bright regions. Jointly probing H I, CO, and DNM gas, we aim to constrain the threshold of the H I-H2 transition in visual extinction, AV, and in total hydrogen column densities, NHtot. We also aim to measure gas mass fractions in the different phases and to test their relation to cloud properties. Methods: We have used dust optical depth measurements at 353 GHz, γ-ray maps at GeV energies, and H I and CO line data to trace the gas column densities and map the DNM in nearby clouds toward the Galactic anticentre and Chamaeleon regions. We have selected a subset of 15 individual clouds, from diffuse to star-forming structures, in order to study the different phases across each cloud and to probe changes from cloud to cloud. Results: The atomic fraction of the total hydrogen column density is observed to decrease in the (0.6-1) × 1021 cm-2 range in NHtot (AV ≈ 0.4 mag) because of the formation of H2 molecules. The onset of detectable CO intensities varies by only a factor of 4 from cloud to cloud, between 0.6 × 1021 cm-2 and 2.5 × 1021 cm-2 in total gas column density. We observe larger H2 column densities than linearly inferred from the CO intensities at AV > 3 mag because of the large CO optical thickness; the additional H2 mass in this regime represents on average 20% of the CO-inferred molecular mass. In the DNM envelopes, we find that the fraction of diffuse CO-dark H2 in the molecular column densities decreases with increasing AV in a cloud. For a half molecular DNM, the fraction decreases from more than 80% at 0.4 mag to less than 20% beyond 2 mag. In mass, the DNM fraction varies with the cloud properties. Clouds with low peak CO intensities exhibit large CO-dark H2 fractions in molecular mass, in particular the

Classifying the embedded young stellar population in Perseus and Taurus and the LOMASS database

NASA Astrophysics Data System (ADS)

Carney, M. T.; Yıldız, U. A.; Mottram, J. C.; van Dishoeck, E. F.; Ramchandani, J.; Jørgensen, J. K.

2016-02-01

Context. The classification of young stellar objects (YSOs) is typically done using the infrared spectral slope or bolometric temperature, but either can result in contamination of samples. More accurate methods to determine the evolutionary stage of YSOs will improve the reliability of statistics for the embedded YSO population and provide more robust stage lifetimes. Aims: We aim to separate the truly embedded YSOs from more evolved sources. Methods: Maps of HCO+J = 4-3 and C18O J = 3-2 were observed with HARP on the James Clerk Maxwell Telescope (JCMT) for a sample of 56 candidate YSOs in Perseus and Taurus in order to characterize the presence and morphology of emission from high density (ncrit > 106 cm-3) and high column density gas, respectively. These are supplemented with archival dust continuum maps observed with SCUBA on the JCMT and Herschel PACS to compare the morphology of the gas and dust in the protostellar envelopes. The spatial concentration of HCO+J = 4-3 and 850 μm dust emission are used to classify the embedded nature of YSOs. Results: Approximately 30% of Class 0+I sources in Perseus and Taurus are not Stage I, but are likely to be more evolved Stage II pre-main sequence (PMS) stars with disks. An additional 16% are confused sources with an uncertain evolutionary stage. Outflows are found to make a negligible contribution to the integrated HCO+ intensity for the majority of sources in this study. Conclusions: Separating classifications by cloud reveals that a high percentage of the Class 0+I sources in the Perseus star forming region are truly embedded Stage I sources (71%), while the Taurus cloud hosts a majority of evolved PMS stars with disks (68%). The concentration factor method is useful to correct misidentified embedded YSOs, yielding higher accuracy for YSO population statistics and Stage timescales. Current estimates (0.54 Myr) may overpredict the Stage I lifetime on the order of 30%, resulting in timescales down to 0.38 Myr for the

Search for gamma-ray emission from dark matter annihilation in the Small Magellanic Cloud with the Fermi Large Area Telescope

DOE PAGES

Caputo, Regina; Buckley, Matthew R.; Martin, Pierrick; ...

2016-03-22

The Small Magellanic Cloud (SMC) is the second-largest satellite galaxy of the Milky Way and is only 60 kpc away. As a nearby, massive, and dense object with relatively low astrophysical backgrounds, it is a natural target for dark matter indirect detection searches. In this work, we use six years of Pass 8 data from the Fermi Large Area Telescope to search for gamma-ray signals of dark matter annihilation in the SMC. Using data-driven fits to the gamma-ray backgrounds, and a combination of N-body simulations and direct measurements of rotation curves to estimate the SMC DM density profile, we found that themore » SMC was well described by standard astrophysical sources, and no signal from dark matter annihilation was detected. We set conservative upper limits on the dark matter annihilation cross section. Furthermore, these constraints are in agreement with stronger constraints set by searches in the Large Magellanic Cloud and approach the canonical thermal relic cross section at dark matter masses lower than 10 GeV in the bb¯ and τ +τ - channels.« less

A New Dark Vortex

NASA Astrophysics Data System (ADS)

Wong, Michael

2015-10-01

A bright, unusually long-lived outburst of cloud activity on Neptune was observed in 2015. This led to speculation about whether the clouds were convective in nature, or bright companions to an unseen dark vortex (similar to the Great Dark Spot studied in detail by Voyager 2). HST OPAL images at blue wavelengths finally answered this question by discovering a new dark vortex at 45 deg S. We call this feature SDS-2015, for southern dark spot discovered in 2015.Dark vortices on Neptune are rare; SDS-2015 is only the fifth ever seen. All five were diverse in terms of size and shape, the distribution of bright companion clouds, and horizontal motions (oscillations and drifts). The drift of these vortices is highly sensitive to horizontal and vertical wind shear, making them valuable probes into the structure of Neptune's atmospheric jets. We have traced oscillations in the longitudinal positions of bright companion clouds of SDS-2015, but a second epoch of HST imaging is needed to measure latitudinal motion of the dark vortex itself.Only HST can image dark vortices on Neptune. Ground-based facilities lack the resolution to detect these low-contrast features at blue optical wavelengths, while infrared observations don't detect the dark spots themselves, only their bright companion features. We propose observations of SDS-2015, in order to measure its size, drift rate, and aerosol structure, and to trace its temporal evolution. The observations will improve our understanding of the life cycle of neptunian vortices, of their influence on the surrounding atmosphere, and of the structure of planetary jets.

The Pan-STARRS1 Proper-motion Survey for Young Brown Dwarfs in Nearby Star-forming Regions. I. Taurus Discoveries and a Reddening-free Classification Method for Ultracool Dwarfs

NASA Astrophysics Data System (ADS)

Zhang, Zhoujian; Liu, Michael C.; Best, William M. J.; Magnier, Eugene A.; Aller, Kimberly M.; Chambers, K. C.; Draper, P. W.; Flewelling, H.; Hodapp, K. W.; Kaiser, N.; Kudritzki, R.-P.; Metcalfe, N.; Wainscoat, R. J.; Waters, C.

2018-05-01

We are conducting a proper-motion survey for young brown dwarfs in the Taurus-Auriga molecular cloud based on the Pan-STARRS1 3π Survey. Our search uses multi-band photometry and astrometry to select candidates, and is wider (370 deg2) and deeper (down to ≈3 M Jup) than previous searches. We present here our search methods and spectroscopic follow-up of our high-priority candidates. Since extinction complicates spectral classification, we have developed a new approach using low-resolution (R ≈ 100) near-infrared spectra to quantify reddening-free spectral types, extinctions, and gravity classifications for mid-M to late-L ultracool dwarfs (≲100–3 M Jup in Taurus). We have discovered 25 low-gravity (VL-G) and the first 11 intermediate-gravity (INT-G) substellar (M6–L1) members of Taurus, constituting the largest single increase of Taurus brown dwarfs to date. We have also discovered 1 new Pleiades member and 13 new members of the Perseus OB2 association, including a candidate very wide separation (58 kau) binary. We homogeneously reclassify the spectral types and extinctions of all previously known Taurus brown dwarfs. Altogether our discoveries have thus far increased the substellar census in Taurus by ≈40% and added three more L-type members (≲5–10 M Jup). Most notably, our discoveries reveal an older (>10 Myr) low-mass population in Taurus, in accord with recent studies of the higher-mass stellar members. The mass function appears to differ between the younger and older Taurus populations, possibly due to incompleteness of the older stellar members or different star formation processes.

CO Column Density and Extinction in the Chamaeleon II--III Dark-Cloud Complex

NASA Astrophysics Data System (ADS)

Hayakawa, Takahiro; Cambrésy, Laurent; Onishi, Toshikazu; Mizuno, Akira; Fukui, Yasuo

2001-12-01

We carried out 13CO (J = 1 -- 0) and C18O (J = 1 -- 0) observations of the Chamaeleon II--III dark-cloud complex with the NANTEN radio telescope. The column densities of both molecular isotopes were derived assuming LTE. The AV values were obtained by scaling the AV values that were derived using an adaptive-grid star-count method applied to the DENIS J-band data. We established the AV--CO isotope column-density relations in Cha II and III, and compared them with those in Cha I. The slopes of the AV--13CO relations for Cha II and III are steeper than that for Cha I. Those of the AV -- C18O relations are similar among the three clouds. The total column density ratio, N(13O) / N(C18O, in Cha I tends to be small compared with those in Cha II or Cha III; the ratios range from ~ 5 to ~ 25 at low extinction in Cha II and III, but at most ~ 10 in Cha I. We suggest that the increase of N(13CO) due to the 13CO formation process causes cloud-to-cloud variations in the AV -- N(13CO) correlation.

X-ray emitting class I protostars in the Serpens dark cloud

NASA Astrophysics Data System (ADS)

Preibisch, T.

2004-12-01

We analyze a set of three individual XMM-Newton X-ray observation of the Serpens dark cloud. In addition to the 45 sources already reported in the analysis of the first of these XMM-Newton observations by Preibisch (\\cite{Preibisch2003), the complete combined data set leads to the detection of X-ray emission from four of the 19 known class I protostars in the region. The set of three observations allows us to study the variability of the sources on timescales from minutes to several months. The lightcurves of two of the four X-ray detected class I protostars show evidence for significant variability; the data suggest at least four flare-like events on these objects. This relatively high level of variability in the X-ray emission from the class I protostars is in qualitative agreement with the result by Imanishi et al. (\\cite{Imanishi2001}), who found that the class I protostars in the ρ Ophiuchi dark cloud show a higher level of variability than that of more evolved class II and class III young stellar objects. This may support non-coronal X-ray emission mechanisms for class I protostars and is in agreement with the predictions of models that assume magnetic interactions between the protostar and its surrounding disk as a source of high-energy emission. We also find a strong variation (by a factor of ˜10) in the X-ray luminosity of the class II object EC 74 between the three observations, which may be explained by a long duration flare or by rotational modulation. Finally, we find no evidence for X-ray emission from the five class 0 protostars in the region.

Using binary statistics in Taurus-Auriga to distinguish between brown dwarf formation processes

NASA Astrophysics Data System (ADS)

Marks, M.; Martín, E. L.; Béjar, V. J. S.; Lodieu, N.; Kroupa, P.; Manjavacas, E.; Thies, I.; Rebolo López, R.; Velasco, S.

2017-08-01

Context. One of the key questions of the star formation problem is whether brown dwarfs (BDs) form in the manner of stars directly from the gravitational collapse of a molecular cloud core (star-like) or whether BDs and some very low-mass stars (VLMSs) constitute a separate population that forms alongside stars comparable to the population of planets, for example through circumstellar disk (peripheral) fragmentation. Aims: For young stars in Taurus-Auriga the binary fraction has been shown to be large with little dependence on primary mass above ≈ 0.2 M⊙, while for BDs the binary fraction is < 10%. Here we investigate a case in which BDs in Taurus formed dominantly, but not exclusively, through peripheral fragmentation, which naturally results in small binary fractions. The decline of the binary frequency in the transition region between star-like formation and peripheral formation is modelled. Methods: We employed a dynamical population synthesis model in which stellar binary formation is universal with a large binary fraction close to unity. Peripheral objects form separately in circumstellar disks with a distinctive initial mass function (IMF), their own orbital parameter distributions for binaries, and small binary fractions, according to observations and expectations from smoothed particle hydrodynamics (SPH) and grid-based computations. A small amount of dynamical processing of the stellar component was accounted for as appropriate for the low-density Taurus-Auriga embedded clusters. Results: The binary fraction declines strongly in the transition region between star-like and peripheral formation, exhibiting characteristic features. The location of these features and the steepness of this trend depend on the mass limits for star-like and peripheral formation. Such a trend might be unique to low density regions, such as Taurus, which host binary populations that are largely unprocessed dynamically in which the binary fraction is large for stars down to M

A New Dark Vortex on Neptune

NASA Astrophysics Data System (ADS)

Wong, Michael H.; Tollefson, Joshua; Hsu, Andrew I.; de Pater, Imke; Simon, Amy A.; Hueso, Ricardo; Sánchez-Lavega, Agustín; Sromovsky, Lawrence; Fry, Patrick; Luszcz-Cook, Statia; Hammel, Heidi; Delcroix, Marc; de Kleer, Katherine; Orton, Glenn S.; Baranec, Christoph

2018-03-01

An outburst of cloud activity on Neptune in 2015 led to speculation about whether the clouds were convective in nature, a wave phenomenon, or bright companions to an unseen dark vortex (similar to the Great Dark Spot studied in detail by Voyager 2). The Hubble Space Telescope (HST) finally answered this question by discovering a new dark vortex at 45 degrees south planetographic latitude, named SDS-2015 for “southern dark spot discovered in 2015.” SDS-2015 is only the fifth dark vortex ever seen on Neptune. In this paper, we report on imaging of SDS-2015 using HST’s Wide Field Camera 3 across four epochs: 2015 September, 2016 May, 2016 October, and 2017 October. We find that the size of SDS-2015 did not exceed 20 degrees of longitude, more than a factor of two smaller than the Voyager dark spots, but only slightly smaller than previous northern-hemisphere dark spots. A slow (1.7–2.5 deg/year) poleward drift was observed for the vortex. Properties of SDS-2015 and its surroundings suggest that the meridional wind shear may be twice as strong at the deep level of the vortex as it is at the level of cloud-tracked winds. Over the 2015–2017 period, the dark spot’s contrast weakened from about -7 % to about -3 % , while companion clouds shifted from offset to centered, a similar evolution to some historical dark spots. The properties and evolution of SDS-2015 highlight the diversity of Neptune’s dark spots and the need for faster cadence dark spot observations in the future.

Imaging diffuse clouds: bright and dark gas mapped in CO

NASA Astrophysics Data System (ADS)

Liszt, H. S.; Pety, J.

2012-05-01

Aims: We wish to relate the degree scale structure of galactic diffuse clouds to sub-arcsecond atomic and molecular absorption spectra obtained against extragalactic continuum background sources. Methods: We used the ARO 12 m telescope to map J = 1-0 CO emission at 1' resolution over 30' fields around the positions of 11 background sources occulted by 20 molecular absorption line components, of which 11 had CO emission counterparts. We compared maps of CO emission to sub-arcsec atomic and molecular absorption spectra and to the large-scale distribution of interstellar reddening. Results: 1) The same clouds, identified by their velocity, were seen in absorption and emission and atomic and molecular phases, not necessarily in the same direction. Sub-arcsecond absorption spectra are a preview of what is seen in CO emission away from the continuum. 2) The CO emission structure was amorphous in 9 cases, quasi-periodic or wave-like around B0528+134 and tangled and filamentary around BL Lac. 3) Strong emission, typically 4-5 K at EB - V ≤ 0.15 mag and up to 10-12 K at EB - V ≲ 0.3 mag was found, much brighter than toward the background targets. Typical covering factors of individual features at the 1 K km s-1 level were 20%. 4) CO-H2 conversion factors as much as 4-5 times below the mean value N(H2)/WCO = 2 × 1020 H2 cm-2 (K km s-1)-1 are required to explain the luminosity of CO emission at/above the level of 1 K km s-1. Small conversion factors and sharp variability of the conversion factor on arcminute scales are due primarily to CO chemistry and need not represent unresolved variations in reddening or total column density. Conclusions: Like Fermi and Planck we see some gas that is dark in CO and other gas in which CO is overluminous per H2. A standard CO-H2 conversion factor applies overall owing to balance between the luminosities per H2 and surface covering factors of bright and dark CO, but with wide variations between sightlines and across the faces of

Widespread SiO and CH3OH emission in filamentary infrared dark clouds

NASA Astrophysics Data System (ADS)

Cosentino, G.; Jiménez-Serra, I.; Henshaw, J. D.; Caselli, P.; Viti, S.; Barnes, A. T.; Fontani, F.; Tan, J. C.; Pon, A.

2018-03-01

Infrared dark clouds (IRDCs) are cold, dense regions of high (optical and infrared) extinction, believed to be the birthplace of high-mass stars and stellar clusters. The physical mechanisms leading to the formation of these IRDCs are not completely understood and it is thus important to study their molecular gas kinematics and chemical content to search for any signature of the IRDCs formation process. Using the 30-m-diameter antenna at the Instituto de Radioastronomía Milimétrica (IRAM), we have obtained emission maps of dense gas tracers (H13CO+ and HN13C) and typical shock tracers (SiO and CH3OH) towards three IRDCs, G028.37+00.07, G034.43+00.24, and G034.77-00.55 (clouds C, F, and G, respectively). We have studied the molecular gas kinematics in these clouds and, consistent with previous works towards other IRDCs, the clouds show complex gas kinematics with several velocity-coherent substructures separated in velocity space by a few km s-1. Correlated with these complex kinematic structures, widespread (parsec-scale) emission of SiO and CH3OH is present in all the three clouds. For clouds C and F, known to be actively forming stars, widespread SiO and CH3OH is likely associated with on-going star formation activity. However, for cloud G, which lacks either 8 or 24 μm sources and 4.5 μm H2 shock-excited emission, the detected widespread SiO and CH3OH emission may have originated in a large-scale shock interaction, although a scenario involving a population of low-mass stars driving molecular outflows cannot be fully ruled out.

Dark Spot and Jovian Galaxy

NASA Image and Video Library

2017-03-24

This enhanced-color image of a mysterious dark spot on Jupiter seems to reveal a Jovian "galaxy" of swirling storms. Juno acquired this JunoCam image on Feb. 2, 2017, at 5:13 a.m. PDT (8:13 a.m. EDT), at an altitude of 9,000 miles (14,500 kilometers) above the giant planet's cloud tops. This publicly selected target was simply titled "Dark Spot." In ground-based images it was difficult to tell that it is a dark storm. Citizen scientist Roman Tkachenko enhanced the color to bring out the rich detail in the storm and surrounding clouds. Just south of the dark storm is a bright, oval-shaped storm with high, bright, white clouds, reminiscent of a swirling galaxy. As a final touch, he rotated the image 90 degrees, turning the picture into a work of art. http://photojournal.jpl.nasa.gov/catalog/PIA21386

A new interstellar molecule - Tricarbon monoxide

NASA Technical Reports Server (NTRS)

Matthews, H. E.; Irvine, W. M.; Friberg, P.; Brown, R. D.; Godfrey, P. D.

1984-01-01

The C3O molecule, whose pure rotational spectrum has only recently been studied in the laboratory, has been detected in the cold, dark interstellar Taurus Molecular Cloud 1. Since C3O is the first interstelar carbon chain molecule to contain oxygen, its existence places an important new constraint on chemical schemes for cold interstellar clouds. The abundance of C3O can be understood in terms of purely gas-phase ion-molecule chemistry.

Instability analysis of cosmic viscoelastic gyro-gravitating clouds in the presence of dark matter

NASA Astrophysics Data System (ADS)

Karmakar, Pralay Kumar; Das, Papari

2017-08-01

A classical formalism for the weakly nonlinear instability analysis of a gravitating rotating viscoelastic gaseous cloud in the presence of gyratory dark matter is presented on the cosmic Jeans flat scales of space and time. The constituent neutral gaseous fluid (NGF) and dark matter fluid (DMF) are inter-coupled frictionally via mutual gravity alone. Application of standard nonlinear perturbation techniques over the complex gyro-gravitating clouds results in a unique conjugated pair of viscoelastic forced Burgers (VFB) equations. The VFB pair is conjointly twinned by correlational viscoelastic effects. There is no regular damping term here, unlike, in the conventional Burgers equation for the luminous (bright) matter solely. Instead, an interesting linear self-consistent derivative force-term naturalistically appears. A numerical illustrative platform is provided to reveal the micro-physical insights behind the weakly non-linear natural diffusive eigen-modes. It is fantastically seen that the perturbed NGF evolves as extended compressive solitons and compressive shock-like structures. In contrast, the perturbed DMF grows as rarefactive extended solitons and hybrid shocks. The latter is micro-physically composed of rarefactive solitons and compressive shocks. The consistency and reliability of the results are validated in the panoptic light of the existing reports based on the preeminent nonlinear advection-diffusion-based Burgers fabric. At the last, we highlight the main implications and non-trivial futuristic applications of the explored findings.

Dynamical Timescale of Pre-collapse Evolution Inferred from Chemical Distribution in the Taurus Molecular Cloud-1 (TMC-1) Filament

DOE Office of Scientific and Technical Information (OSTI.GOV)

Choi, Yunhee; Lee, Jeong-Eun; Bourke, Tyler L.

We present observations and analyses of the low-mass star-forming region, Taurus Molecular Cloud-1 (TMC-1). CS ( J = 2–1)/N{sub 2}H{sup +} ( J = 1–0) and C{sup 17}O ( J = 2–1)/C{sup 18}O ( J = 2–1) were observed with the Five College Radio Astronomy Observatory and the Seoul Radio Astronomy Observatory, respectively. In addition, Spitzer infrared data and 1.2 mm continuum data observed with Max-Planck Millimetre Bolometer are used. We also perform chemical modeling to investigate the relative molecular distributions of the TMC-1 filament. Based on Spitzer observations, there is no young stellar object along the TMC-1 filament, while five Classmore » II and one Class I young stellar objects are identified outside the filament. The comparison between column densities calculated from dust continuum and C{sup 17}O 2–1 line emission shows that CO is depleted much more significantly in the ammonia peak than in the cyanopolyyne peak, while the column densities calculated from the dust continuum are similar at the two peaks. N{sub 2}H{sup +} is not depleted much in either peak. According to our chemical calculation, the differential chemical distribution in the two peaks can be explained by different timescales required to reach the same density, i.e., by different dynamical processes.« less

Star Formation in the Filamentary Dark Cloud GF-9: a Multi-Wavelength Intra-Cloud Comparative Study

NASA Astrophysics Data System (ADS)

Ciardi, David Robert

Filamentary dark clouds (FDCs) are a subclass of small molecular clouds containing small numbers of somewhat regularly spaced dense cores connected by lower density gas and dust. Most of the previous work performed on FDCs has concerned the star formation properties of individual dense cores within the FDCs and has not concerned the FDCs as entities of their own. As a result little is known about the general star formation properties of FDCs. The primary question addressed in this work is 'Within filamentary dark clouds, how does the star formation process within a core region compare to that within a filamentary region?' In order to address the above question, a multi-wavelength observational comparative study has been performed upon a representative dense core (hereafter, GF9-Core) and filamentary region (hereafter, GF9-Fila) within the FDC GF-9 (LDN 1082). At the Five College Radio Astronomy Observatory, the core and filamentary region were observed in the rotational transitions of 12CO/ (J=1/to0),/ 13CO/ (J=1/to0)/ and/ CS/ (J=2/to1) covering a region of 10' x 8'. The temperature, density and kinematic structures of the two regions were deduced from the radio imaging spectroscopy data and were used to estimate the energy balance of the regions. We also obtained 70, 100, 135 and 200 μm images from the Infrared Space Observatory (ISO) covering approximately 12' x 9' which were used to investigate the temperature and density distributions of the dust within the two regions. Finally, at the Wyoming Infrared Observatory using the Aerospace Corporation NICMOS3 camera, the core and filament were imaged in the near-infrared broadband filters J, H, and K-short covering a slightly smaller region of 7' x 7'. The near-infrared survey data were used to search for embedded Class I and Class II protostars and to investigate the density distribution of the dust. We have found that the evolutionary processes of the core region and the filament region proceed along similar

Search for gamma-ray emission from dark matter annihilation in the large magellanic cloud with the fermi large area telescope

DOE PAGES

Buckley, Matthew R.; Charles, Eric; Gaskins, Jennifer M.; ...

2015-05-05

At a distance of 50 kpc and with a dark matter mass of ~10 10 M ⊙, the large magellanic cloud (LMC) is a natural target for indirect dark matter searches. We use five years of data from the Fermi Large Area Telescope (LAT) and updated models of the gamma-ray emission from standard astrophysical components to search for a dark matter annihilation signal from the LMC. We perform a rotation curve analysis to determine the dark matter distribution, setting a robust minimum on the amount of dark matter in the LMC, which we use to set conservative bounds on the annihilationmore » cross section. The LMC emission is generally very well described by the standard astrophysical sources, with at most a 1–2σ excess identified near the kinematic center of the LMC once systematic uncertainties are taken into account. As a result, we place competitive bounds on the dark matter annihilation cross section as a function of dark matter particle mass and annihilation channel.« less

Tharsis Limb Cloud

NASA Technical Reports Server (NTRS)

2005-01-01

[figure removed for brevity, see original site] Annotated image of Tharsis Limb Cloud

7 September 2005 This composite of red and blue Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) daily global images acquired on 6 July 2005 shows an isolated water ice cloud extending more than 30 kilometers (more than 18 miles) above the martian surface. Clouds such as this are common in late spring over the terrain located southwest of the Arsia Mons volcano. Arsia Mons is the dark, oval feature near the limb, just to the left of the 'T' in the 'Tharsis Montes' label. The dark, nearly circular feature above the 'S' in 'Tharsis' is the volcano, Pavonis Mons, and the other dark circular feature, above and to the right of 's' in 'Montes,' is Ascraeus Mons. Illumination is from the left/lower left.

Season: Northern Autumn/Southern Spring

NARROW Na AND K ABSORPTION LINES TOWARD T TAURI STARS: TRACING THE ATOMIC ENVELOPE OF MOLECULAR CLOUDS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pascucci, I.; Simon, M. N.; Edwards, S.

2015-11-20

We present a detailed analysis of narrow Na i and K i absorption resonance lines toward nearly 40 T Tauri stars in Taurus with the goal of clarifying their origin. The Na i λ5889.95 line is detected toward all but one source, while the weaker K i λ7698.96 line is detected in about two-thirds of the sample. The similarity in their peak centroids and the significant positive correlation between their equivalent widths demonstrate that these transitions trace the same atomic gas. The absorption lines are present toward both disk and diskless young stellar objects, which excludes cold gas within themore » circumstellar disk as the absorbing material. A comparison of Na i and CO detections and peak centroids demonstrates that the atomic gas and molecular gas are not co-located, the atomic gas being more extended than the molecular gas. The width of the atomic lines corroborates this finding and points to atomic gas about an order of magnitude warmer than the molecular gas. The distribution of Na i radial velocities shows a clear spatial gradient along the length of the Taurus molecular cloud filaments. This suggests that absorption is associated with the Taurus molecular cloud. Assuming that the gradient is due to cloud rotation, the rotation of the atomic gas is consistent with differential galactic rotation, whereas the rotation of the molecular gas, although with the same rotation axis, is retrograde. Our analysis shows that narrow Na i and K i absorption resonance lines are useful tracers of the atomic envelope of molecular clouds. In line with recent findings from giant molecular clouds, our results demonstrate that the velocity fields of the atomic and molecular gas are misaligned. The angular momentum of a molecular cloud is not simply inherited from the rotating Galactic disk from which it formed but may be redistributed by cloud–cloud interactions.« less

ScienceCast 88: Dark Lightning

NASA Image and Video Library

2013-01-07

Researchers studying thunderstorms have made a surprising discovery: The lightning we see with our eyes has a dark competitor that discharges storm clouds and flings antimatter into space. Scientists are scrambling to understand "dark lightning."

Genetic variation in bison (bison bison) subspecies and cattle (Bos taurus) breeds and subspecies

USDA-ARS?s Scientific Manuscript database

Genetic variation was quantified at 29 polymorphic microsatellite DNA loci in nine herds of plains bison (Bison bison bison), three herds of wood bison (B.b. athabascae), fourteen breeds of taurine cattle (Bos Taurus Taurus), and two breeds of indicine cattle (Bos Taurus indicus). Genetic distances,...

A search for the 13175 A infrared diffuse band in dense environments

NASA Technical Reports Server (NTRS)

Adamson, A. J.; Kerr, Tom H.; Whittet, D. C. B.; Duley, Walter W.

1994-01-01

Models of ionized interstellar C60 predict a strong transition in the 1.2 micrometer region, and two candidate bands have recently been detected in reddened stars. We have searched for the stronger of these bands (at 13175 A) in the Taurus dark cloud complex, to determine its response to the dark-cloud environment. None of the three lines of sight studied (two near the cloud surface, one reaching A(sub V) greater than 20(sup m)) give rise to a detectable band; in one case the equivalent width is a factor of order three below that predicted. Since such behaviour is also shown by the optical Diffuse Interstellar Bands, we suggest that the 13175 A band is a genuine DIB, but we caution against an automatic interpretation in terms of an ionic carrier.

La Freccia Rossa: An IR-dark cloud hosting the Milky Way intermediate-mass black hole candidate

NASA Astrophysics Data System (ADS)

Ravi, Vikram; Vedantham, Harish; Phinney, E. Sterl

2018-05-01

The dynamics of the high-velocity compact molecular cloud CO-0.40-0.22 have been interpreted as evidence for a ˜105M⊙ black hole within 60 pc of Sgr A*. Recently, Oka et al. have identified a compact millimetre-continuum source, CO-0.40-0.22*, with this candidate black hole. Here we present a collation of radio and infrared data at this location. ATCA constraints on the radio spectrum, and the detection of a mid-infrared counterpart, are in tension with an Sgr A*-like model for CO-0.40-0.22* despite the comparable bolometric to Eddington luminosity ratios under the IMBH interpretation. A protostellar-disk scenario is, however, tenable. CO-0.40-0.22(*) is positionally coincident with an arrowhead-shaped infrared-dark cloud (which we call the Freccia Rossa). If the VLSR ≈ 70 km s-1 systemic velocity of CO-0.40-0.22 is common to the entire Freccia Rossa system, we hypothesise that it is the remnant of a high-velocity cloud that has plunged into the Milky Way from the Galactic halo.

Jovian Dark Spot

NASA Technical Reports Server (NTRS)

1998-01-01

A recently discovered black spot in Jupiter's clouds is darker than any feature ever before observed on the giant planet. The spot may be the result of a downward spiraling wind that blows away high clouds and reveals deeper, very dark cloud layers. These three panels depict the same area of Jupiter's atmosphere. A map of Jovian temperatures near 250 millibar pressure (top) panel is derived from the photopolarimeter-radiometer instrument on NASA's Galileo Jupiter orbiter. This map is compared with maps derived from images of the same area in visible light (middle panel)and thermal radiation sensitive to cloud-top temperatures (bottom panel).

The single downward-pointing arrow in the top panel indicates the location of a warm area that corresponds to the position of a so-called 'black spot'(shown in the middle panel), a feature that is about a year old. Features this dark are rare on Jupiter. The bottom panel, sensitive to temperatures at Jupiter's cloud tops, shows this feature as a bright object, meaning that upper-level cold clouds are missing - allowing us to see deeper into Jupiter's warmer interior. The dark visible appearance of the feature than most likely represents the color of very deep clouds. The warm temperatures and cloud-free conditions imply that this feature is a region where dry upper-atmospheric gas is being forced to converge, is warmed up and then forced to descend, clearing out clouds. It is the opposite of wet, upwelling gas in areas such as Jupiter's Great Red Spot or white ovals. On the other hand, it is unlike the dry and relatively cloudless feature into which the Galileo probe descended in 1995, because that region had the same temperatures as its surroundings and did not appear nearly as dark as this new spot.

The temperatures sampled by the photopolarimeter radiometer are near the top of Jupiter's troposphere, where wind motions control the atmosphere. The top row of arrows shows the location of temperature waves in a warm region

Magnetic fields in the Perseus Spiral Arm and in Infrared Dark Clouds

NASA Astrophysics Data System (ADS)

Hoq, Sadia

2017-04-01

The magnetic (B) field is ubiquitous throughout the Milky Way. Several fundamental questions about the B-field in the cool, star-forming interstellar medium (ISM) remain unanswered. In this dissertation, near-infrared (NIR) polarimetric observations are used to study the large-scale Galactic B-field in the cool ISM in a spiral arm and to determine the role of B-fields in the formation of Infrared Dark Clouds (IRDCs). NIR polarimetry of 31 star clusters, located in and around the Perseus spiral arm, were obtained to determine the orientation of the plane-of-sky B-field in the outer Galaxy, and whether the presence of a spiral arm influenced B-field properties. Cluster distances, which provide upper limits to the B-field probed by observations, were estimated by developing a maximum likelihood method to fit theoretical stellar isochrones to stars in cluster color-magnitude diagrams (CMDs). Using the distance estimates, the cluster locations relative to the Perseus arm were found. The cluster polarization percentages and orientations were compared between clusters foreground to the arm and clusters inside or behind the arm. The cluster polarization orientations are predominantly parallel to the Galactic plane. Clusters inside and behind the arm have larger polarization percentages, likely a result of more polarizing material along the line of sight. The cluster polarization data were also compared to optical, inner Galaxy NIR, and Planck submm polarimetry data, and showed agreement with all three data sets. The polarimetric properties of one IRDC, G28.23, were determined using deep NIR observations. The polarization orientations relative to the cloud major axis were found to change directions with distance from the cloud axis. The B-field strength was estimated to be 10 to 100microG. Despite these large inferred B-field strengths, the B-field was found not to be the dominant force in the formation of the IRDC, though the B-field morphology was influenced by the cloud

Far-infrared observations of young clusters embedded in the R Coronae Australis and Rho Ophiuchi dark clouds

NASA Technical Reports Server (NTRS)

Wilking, B. A.; Harvey, P. M.; Joy, M.; Hyland, A. R.; Jones, T. J.

1985-01-01

Multicolor far-infrared maps in two nearby dark clouds, R Coronae Australis and Rho Ophiuchi, have been made in order to investigate the individual contribution of low-mass stars to the energetics and dynamics of the surrounding gas and dust. Emission from cool dust associated with five low-mass stars has been detected in CrA and four in Rho Oph; their far-infrared luminosities range from 2 solar luminosities to 40 solar luminosities. When an estimate of the bolometric luminosity was possible, it was found that typically more than 50 percent of the star's energy was radiated longward of 20 microns. Meaningful limits to the far-infrared luminosities of an additional 11 association members in CrA and two in Rho Oph were also obtained. The dust optical depth surrounding the star R CrA appears to be asymmetric and may control the dynamics of the surrounding molecular gas. The implications of these results for the cloud energetics and star formation efficiency in these two clouds are discussed.

Far-infrared observations of young clusters embedded in the R Coronae Austrinae and RHO Ophiuchi dark clouds

NASA Technical Reports Server (NTRS)

Wilking, B. A.; Harvey, P. M.; Joy, M.; Hyland, A. R.; Jones, T. J.

1985-01-01

Multicolor far infrared maps in two nearby dark clouds, R Coronae Austrinae and rho Ophiuchi, were made in order to investigate the individual contribution of low mass stars to the energetics and dynamics of the surrounding gas and dust. Emission from cool dust associated with five low mass stars in Cr A and four in rho Oph was detected; their far infrared luminosities range from 2 far infrared luminosities L. up to 40 far infrared luminosities. When an estimate of the bolometric luminosity was possible, it was found that typically more than 50% of the star's energy was radiated longward of 20 micrometers. meaningful limits to the far infrared luminosities of an additional eleven association members in Cr A and two in rho Oph were also obtained. The dust optical depth surrounding the star R Cr A appears to be asymmetric and may control the dynamics of the surrounding molecular gas. The implications of the results for the cloud energetics and star formation efficiency in these two clouds are discussed.

La Freccia Rossa: an IR-dark cloud hosting the Milky Way intermediate-mass black hole candidate

NASA Astrophysics Data System (ADS)

Ravi, Vikram; Vedantham, Harish; Phinney, E. Sterl

2018-07-01

The dynamics of the high-velocity compact molecular cloud CO-0.40-0.22 have been interpreted as evidence for a ˜105 M⊙ black hole within 60 pc of Sgr A*. Recently, Oka et al. have identified a compact millimetre-continuum source, CO-0.40-0.22*, with this candidate black hole. Here we present a collation of radio and infrared data at this location. Australia Telescope Compact Array constraints on the radio spectrum, and the detection of a mid-infrared counterpart, are in tension with an Sgr A*-like model for CO-0.40-0.22* despite the comparable bolometric to the Eddington luminosity ratios under the intermediate-mass black hole interpretation. A protostellar-disc scenario is, however, tenable. CO-0.40-0.22(*) is positionally coincident with an arrowhead-shaped infrared-dark cloud (which we call the Freccia Rossa). If the VLSR ≈ 70 km s-1 systemic velocity of CO-0.40-0.22 is common to the entire Freccia Rossa system, we hypothesize that it is the remnant of a high-velocity cloud that has plunged into the Milky Way from the Galactic halo.

Four Brown Dwarfs in the Taurus Star-Forming Region

NASA Astrophysics Data System (ADS)

Martín, E. L.; Dougados, C.; Magnier, E.; Ménard, F.; Magazzù, A.; Cuillandre, J.-C.; Delfosse, X.

2001-11-01

We have identified four brown dwarfs in the Taurus star-forming region. They were first selected from R and I CCD photometry of 2.29 deg2 obtained at the Canada-France-Hawaii Telescope. Subsequently, they were recovered in the Two Micron All Sky Survey second incremental data release point source catalog. Low-resolution optical spectra obtained at the William Herschel Telescope allow us to derive spectral types in the range M7-M9. One of the brown dwarfs has very strong Hα emission (EW=-340 Å). It also displays Brγ emission in an infrared spectrum obtained with the Infrared Camera and Spectrograph on the Subaru telescope, suggesting that it is accreting matter from a disk. The K I resonance doublet and the Na I subordinate doublet at 818.3 and 819.5 nm in these Taurus objects are weaker than in field dwarfs of similar spectral type, consistent with low surface gravities as expected for young brown dwarfs. Two of the objects are cooler and fainter than GG Tau Bb, the lowest mass known member of the Taurus association. We estimate masses of only 0.03 Msolar for them. The spatial distribution of brown dwarfs in Taurus hints at a possible anticorrelation between the density of stars and the density of brown dwarfs. Based on data collected at the Canada-France-Hawaii Telescope and the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

Organic Species in Infrared Dark Clouds

NASA Astrophysics Data System (ADS)

Vasyunina, T.; Vasyunin, A. I.; Herbst, Eric; Linz, Hendrik; Voronkov, Maxim; Britton, Tui; Zinchenko, Igor; Schuller, Frederic

2014-01-01

It is currently assumed that infrared dark clouds (IRDCs) represent the earliest evolutionary stages of high-mass stars (>8 M ⊙). Submillimeter and millimeter-wave studies performed over the past 15 yr show that IRDCs possess a broad variety of properties, and hence a wide range of problems and questions that can be tackled. In this paper, we report an investigation of the molecular composition and chemical processes in two groups of IRDCs. Using the Mopra, APEX, and IRAM radio telescopes over the last four years, we have collected molecular line data for CO, H2CO, HNCO, CH3CCH, CH3OH, CH3CHO, CH3OCHO, and CH3OCH3. For all of these species we estimated molecular abundances. We then undertook chemical modeling studies, concentrating on the source IRDC028.34+0.06, and compared observed and modeled abundances. This comparison showed that to reproduce observed abundances of complex organic molecules, a zero-dimensional gas-grain model with constant physical conditions is not sufficient. We achieved greater success with the use of a warm-up model, in which warm-up from 10 K to 30 K occurs following a cold phase. Based on observations carried out with the IRAM 30 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain). This publication is based on data acquired with the Atacama Pathfinder Experiment (APEX). APEX is a collaboration between the Max-Planck-Institut für Radioastronomie, the European Southern Observatory, and the Onsala Space Observatory. The 22 m Mopra antenna is part of the Australia Telescope, which is funded by the Commonwealth of Australia for operations as a National Facility managed by CSIRO. The University of New South Wales Digital Filter Bank used for the observations with the Mopra Telescope was provided with support from the Australian Research Council.

Genetic variation and differentiation of bison (Bison bison) subspecies and cattle (Bos taurus) breeds and subspecies

USDA-ARS?s Scientific Manuscript database

Genetic variation was quantified at 29 polymorphic microsatellite DNA loci in nine herds of plains bison (Bison bison bison), three herds of wood bison (B. b. athabascae), fourteen breeds of taurine cattle (Bos taurus taurus), and two breeds of indicine cattle (Bos taurus indicus). Genetic distances...

HUBBLE FINDS NEW DARK SPOT ON NEPTUNE

NASA Technical Reports Server (NTRS)

2002-01-01

NASA's Hubble Space Telescope has discovered a new great dark spot, located in the northern hemisphere of the planet Neptune. Because the planet's northern hemisphere is now tilted away from Earth, the new feature appears near the limb of the planet. The spot is a near mirror-image to a similar southern hemisphere dark spot that was discovered in 1989 by the Voyager 2 probe. In 1994, Hubble showed that the southern dark spot had disappeared. Like its predecessor, the new spot has high altitude clouds along its edge, caused by gasses that have been pushed to higher altitudes where they cool to form methane ice crystal clouds. The dark spot may be a zone of clear gas that is a window to a cloud deck lower in the atmosphere. Planetary scientists don t know how long lived this new feature might be. Hubble's high resolution will allow astronomers to follow the spot's evolution and other unexpected changes in Neptune's dynamic atmosphere. The image was taken on November 2, 1994 with Hubble's Wide Field Planetary Camera 2, when Neptune was 2.8 billion miles (4.5 billion kilometers) from Earth. Hubble can resolve features as small as 625 miles (1,000 kilometers) across in Neptune's cloud tops. Credit: H. Hammel (Massachusetts Institute of Technology) and NASA

A Catalog of Distances to Molecular Clouds from Pan-STARRS1

NASA Astrophysics Data System (ADS)

Schlafly, Eddie; Green, G.; Finkbeiner, D. P.; Rix, H.

2014-01-01

We present a catalog of distances to molecular clouds, derived from PanSTARRS-1 photometry. We simultaneously infer the full probability distribution function of reddening and distance of the stars towards these clouds using the technique of Green et al. (2013) (see neighboring poster). We fit the resulting measurements using a simple dust screen model to infer the distance to each cloud. The result is a large, homogeneous catalog of distances to molecular clouds. For clouds with heliocentric distances greater than about 200 pc, typical statistical uncertainties in the distances are 5%, with systematic uncertainty stemming from the quality of our stellar models of about 10%. We have applied this analysis to many of the most well-studied clouds in the δ > -30° sky, including Orion, California, Taurus, Perseus, and Cepheus. We have also studied the entire catalog of Magnani, Blitz, and Mundy (1985; MBM), though for about half of those clouds we can provide only upper limits on the distances. We compare our distances with distances from the literature, when available, and find good agreement.

Dark clouds in the vicinity of the emission nebula Sh2-205: interstellar extinction and distances

NASA Astrophysics Data System (ADS)

Straižys, V.; Čepas, V.; Boyle, R. P.; Zdanavičius, J.; Maskoliūnas, M.; Kazlauskas, A.; Zdanavičius, K.; Černis, K.

2016-05-01

Results of CCD photometry in the seven-colour Vilnius system for 922 stars down to V = 16-17 mag and for 302 stars down to 19.5 mag are used to investigate the interstellar extinction in an area of 1.5 square degrees in the direction of the P7 and P8 clumps of the dark cloud TGU H942, which lies in the vicinity of the emission nebula Sh2-205. In addition, we used 662 red clump giants that were identified by combining the 2MASS and WISE infrared surveys. The resulting plots of extinction versus distance were compared with previous results of the distribution and radial velocities of CO clouds and with dust maps in different passbands of the IRAS and WISE orbiting observatories. A possible distance of the front edge of the nearest cloud layer at 130 ± 10 pc was found. This dust layer probably covers all the investigated area, which results in extinction of up to 1.8 mag in some directions. A second rise of the extinction seems to be present at 500-600 pc. Within this layer, the clumps P7 and P8 of the dust cloud TGU H942, the Sh2-205 emission nebula, and the infrared cluster FSR 655 are probably located. In the direction of these clouds, we identified 88 young stellar objects and a new infrared cluster. Full Tables 1 and 2 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/590/A21

Extragalactic background light: a measurement at 400 nm using dark cloud shadow*†- I. Low surface brightness spectrophotometry in the area of Lynds 1642

NASA Astrophysics Data System (ADS)

Mattila, K.; Lehtinen, K.; Väisänen, P.; von Appen-Schnur, G.; Leinert, Ch.

2017-09-01

We present the method and observations for the measurement of the Extragalactic Background Light (EBL) utilizing the shadowing effect of a dark cloud. We measure the surface brightness difference between the opaque cloud core and its unobscured surroundings. In the difference the large atmospheric and Zodiacal light components are eliminated and the only remaining foreground component is the scattered starlight from the cloud itself. Although much smaller, its separation is the key problem in the method. For its separation we use spectroscopy. While the scattered starlight has the characteristic Fraunhofer lines and 400 nm discontinuity, the EBL spectrum is smooth and without these features. Medium resolution spectrophotometry at λ = 380-580 nm was performed with VLT/FORS at ESO of the surface brightness in and around the high-galactic-latitude dark cloud Lynds 1642. Besides the spectrum for the core with AV ≳ 15 mag, further spectra were obtained for intermediate-opacity cloud positions. They are used as proxy for the spectrum of the impinging starlight spectrum and to facilitate the separation of the scattered starlight (cf. Paper II; Mattila et al.). Our spectra reach a precision of ≲ 0.5 × 10-9 erg cm-2 s-1 sr-1 Å-1 as required to measure an EBL intensity in range of ˜1 to a few times 10-9 erg cm-2 s-1 sr-1 Å-1. Because all surface brightness components are measured using the same equipment, the method does not require unusually high absolute calibration accuracy, a condition that has been a problem for some previous EBL projects.

LUMINOSITY FUNCTIONS OF SPITZER-IDENTIFIED PROTOSTARS IN NINE NEARBY MOLECULAR CLOUDS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kryukova, E.; Megeath, S. T.; Allen, T. S.

2012-08-15

We identify protostars in Spitzer surveys of nine star-forming (SF) molecular clouds within 1 kpc: Serpens, Perseus, Ophiuchus, Chamaeleon, Lupus, Taurus, Orion, Cep OB3, and Mon R2, which combined host over 700 protostar candidates. These clouds encompass a variety of SF environments, including both low-mass and high-mass SF regions, as well as dense clusters and regions of sparsely distributed star formation. Our diverse cloud sample allows us to compare protostar luminosity functions in these varied environments. We combine near- and mid-infrared photometry from the Two Micron All Sky Survey and Spitzer to create 1-24 {mu}m spectral energy distributions (SEDs). Usingmore » protostars from the c2d survey with well-determined bolometric luminosities, we derive a relationship between bolometric luminosity, mid-IR luminosity (integrated from 1-24 {mu}m), and SED slope. Estimations of the bolometric luminosities for protostar candidates are combined to create luminosity functions for each cloud. Contamination due to edge-on disks, reddened Class II sources, and galaxies is estimated and removed from the luminosity functions. We find that luminosity functions for high-mass SF clouds (Orion, Mon R2, and Cep OB3) peak near 1 L{sub Sun} and show a tail extending toward luminosities above 100 L{sub Sun }. The luminosity functions of the low-mass SF clouds (Serpens, Perseus, Ophiuchus, Taurus, Lupus, and Chamaeleon) do not exhibit a common peak, however the combined luminosity function of these regions peaks below 1 L{sub Sun }. Finally, we examine the luminosity functions as a function of the local surface density of young stellar objects. In the Orion molecular clouds, we find a significant difference between the luminosity functions of protostars in regions of high and low stellar density, the former of which is biased toward more luminous sources. This may be the result of primordial mass segregation, although this interpretation is not unique. We compare our

Peering into the heart of galactic star formation: A detailed characterization of infrared-dark clouds

NASA Astrophysics Data System (ADS)

Ragan, Sarah E.

2009-09-01

Everything we know about other galaxies is based on light from massive stars, yet, in our own Galaxy, it's the formation of massive stars that is the least understood. Star formation studies to date have focused on nearby, low-mass regions, but the bulk of star formation takes place in massive clusters, which takes place primarily in the inner-Galaxy, where the bulk of the molecular gas resides. To learn about the conditions under which massive clusters form, we seek out their precursors, called infrared-dark clouds (IRDCs). We present the results of a high-resolution multi-wavelength observational study of IRDCs, which vastly improves our knowledge of the initial conditions of cluster formation. Beginning with IRDC candidates identified with Midcourse Science Experiment (MSX) survey data, we map 41 IRDCs in the N 2 H + 1 [arrow right] 0, CS 2 [arrow right] 1 and C 18 O 1 [arrow right] 0 molecular transitions using the Five College Radio Astronomy Observatory. We examine the stellar content and absorption structure with Spitzer Space Telescope observations of eleven IRDCs, and we use Very Large Array NH 3 observations to probe the kinematics and chemistry of six IRDCs. Our comprehensive high-resolution study of IRDCs confirms that these objects are cold and dense precursors to massive stars and clusters. For the first time. we quantify IRDC sub-structure on sub-parsec scales and show the kinematic structure of IRDCs is diverse and depends on associated local star- formation activity. Overall, IRDCs exhibit non-thermal dynamics, suggesting that turbulence and systematic motions dominate. IRDC temperatures are between 8 and 16 K and are mostly flat with hints of a rise near the edges due to external heating. This study shows that IRDCs are a unique star-forming environment, one that dominates the star formation in the Milky Way. Using high-resolution observations, we have quantified the structure, star formation, kinematics, and chemistry of infrared-dark clouds. Our

ISOCAM observations of the Chamaeleon I dark cloud

NASA Astrophysics Data System (ADS)

Persi, P.; Marenzi, A. R.; Olofsson, G.; Kaas, A. A.; Nordh, L.; Huldtgren, M.; Abergel, A.; André, P.; Bontemps, S.; Boulanger, F.; Burggdorf, M.; Casali, M. M.; Cesarsky, C. J.; Copet, E.; Davies, J.; Falgarone, E.; Montmerle, T.; Perault, M.; Prusti, T.; Puget, J. L.; Sibille, F.

2000-05-01

We present the results of an ISOCAM survey of the Chamaeleon I dark cloud conducted in two broad-band filters at 6.7 and 14.3 mu m. In an area of 0.59 sq.deg. we have detected a total of 282 mid-IR sources with 103 sources observed in both filters. Combining the ISOCAM observations with the I, J, and K_s data obtained with DENIS, we have found 108 pre-main-sequence (PMS) stars in the region, of which 34 were previously unidentified. Several of these newly discovered young stellar objects are relatively faint suggesting a population in Cha I of very low mass objects that probably includes brown dwarfs in their early contraction phases. Finally, most of the PMS stars show the spectral index computed between 2.2 and 14.3 mu m typical of Class II sources. The luminosity function (LF) derived for our detected PMS stars is discussed. ISO is an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) and with the participation of ISAS and NASA. Tables 1 and 2 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html Tables 3 and 4 are only available with the on-line publication at http://link.springer.de/link/service/journals/00230/

Measurements of the H2(13)CO ortho/para ratio in cold dark molecular clouds

NASA Technical Reports Server (NTRS)

Minh, Y. C.; Dickens, J. E.; Irvine, W. M.; McGonagle, D.

1995-01-01

H2(13)CO has been detected for the first time toward cold dark molecular clouds using the NRAO 12 m telescope. The H2(13)CO ortho/para abundance ratio R for B335, which we report as R approximately 1.7, suggests equilibrium at the local kinetic temperature and appears to be distinctly different from that for both TMC-1 and L134N, where R is close to or higher than the statistical value 3. Since only B335 among the observed positions includes an imbedded IR source, this difference may result from heating of the grain surfaces, providing the energy necessary for desorption of formaldehyde formed on the grains.

VizieR Online Data Catalog: Taurus ultra-wide pairs (Joncour+, 2017)

NASA Astrophysics Data System (ADS)

Joncour, I.; Duchene, G.; Moraux, E.

2017-05-01

Although a recent catalog of Taurus members has been released including newly detected mid-infrared Wide-field Infrared Survey Explorer (WISE) sources (Esplin et al., 2014, Cat. J/ApJ/784/126), we adopted the catalog containing 352 Taurus members that offers a full census of members down to 0.02 Mȯ(Luhman et al., 2010, Cat. J/ApJS/186/111; Rebull et al., 2010, Cat. J/ApJS/186/259), which we supplemented with stellar multiplicity data. (3 data files).

Apollo 17: At Taurus Littrow

NASA Technical Reports Server (NTRS)

Anderton, D. A.

1973-01-01

A summation, with color illustrations, is presented on the Apollo 17 mission. The height, weight, and thrust specifications are given on the launch vehicle. Presentations are given on: the night launch; earth to moon ascent; separation and descent; EVA, the sixth lunar surface expedition; ascent from Taurus-Littrow; the America to Challenger rendezvous; return, reentry, and recovery; the scientific results of the mission; background information on the astronauts; and the future projects.

The inception of star cluster formation revealed by [C II] emission around an Infrared Dark Cloud

NASA Astrophysics Data System (ADS)

Bisbas, Thomas G.; Tan, Jonathan C.; Csengeri, Timea; Wu, Benjamin; Lim, Wanggi; Caselli, Paola; Güsten, Rolf; Ricken, Oliver; Riquelme, Denise

2018-07-01

We present SOFIA-upGREAT observations of [C II] emission of Infrared Dark Cloud (IRDC) G035.39-00.33, designed to trace its atomic gas envelope and thus test models of the origins of such clouds. Several velocity components of [C II] emission are detected, tracing structures that are at a wide range of distances in the Galactic plane. We find a main component that is likely associated with the IRDC and its immediate surroundings. This strongest emission component has a velocity similar to that of the 13CO(2-1) emission of the IRDC, but offset by ˜3 km s-1 and with a larger velocity width of ˜9 km s-1. The spatial distribution of the [C II] emission of this component is also offset predominantly to one side of the dense filamentary structure of the IRDC. The C II column density is estimated to be of the order of ˜1017-1018 cm-2. We compare these results to the [C II] emission from numerical simulations of magnetized, dense gas filaments formed from giant molecular cloud (GMC) collisions, finding similar spatial and kinematic offsets. These observations and modellingof [C II] add further to the evidence that IRDC G035.39-00.33 has been formed by a process of GMC-GMC collision, which may thus be an important mechanism for initiating star cluster formation.

Neptune's New Dark Vortex: Imaging with HST/WFC3

NASA Astrophysics Data System (ADS)

Wong, M. H.; Tollefson, J.; De Pater, I.; de Kleer, K.; Hammel, H. B.; Luszcz-Cook, S.; Hueso, R.; Sanchez-Lavega, A.; Simon, A. A.; Delcroix, M.; Sromovsky, L. A.; Fry, P. M.; Orton, G. S.; Baranec, C.

2016-12-01

A bright, unusually long-lived outburst of cloud activity on Neptune was observed in 2015 (Hueso et al. 2015, DPS 400.02). This led to speculation about whether the clouds were convective in nature, or bright companions to an unseen dark vortex (similar to the Great Dark Spot studied in detail by Voyager 2: Smith et al. 1989, Science 246, 1422). HST OPAL images at blue wavelengths finally answered this question by discovering a new dark vortex at 45 deg S. We call this feature SDS-2015, for "southern dark spot discovered in 2015" (Wong et al. 2016, CBET 4278). Dark vortices on Neptune are rare; SDS-2015 is only the fifth ever seen. All five were diverse in terms of size and shape, the distribution of bright companion clouds, and horizontal motions (oscillations and drifts). The drift of these vortices is highly sensitive to horizontal and vertical wind shear, making them valuable probes into the structure of Neptune's atmospheric jets. We will present imaging observations of SDS-2015 obtained with the WFC3/UVIS camera on the Hubble Space Telescope, covering the discovery of the vortex in September 2015 and follow-up observations in May 2016. No significant latitudinal drift was seen over this time span. We will compare size estimates, which are complicated by the continual presence of companion clouds, and by the low contrast between the vortex and its surroundings. The 2015 observations included 7 filters spanning 467-845 nm, weighted toward longer wavelengths to study general cloud motions and vertical distributions. The 2016 observations included 7 filters spanning 336-763 nm, weighted toward shorter wavelengths where the dark spot itself can be detected. A companion abstract (Tollefson et al., this meeting) will present results from radiative transfer modeling of the multispectral data. [This conference abstract is based on observations made with the NASA/ESA Hubble Space Telescope, associated with programs GO-13937 ("OPAL") and GO-14492.

15N fractionation in infrared-dark cloud cores

NASA Astrophysics Data System (ADS)

Zeng, S.; Jiménez-Serra, I.; Cosentino, G.; Viti, S.; Barnes, A. T.; Henshaw, J. D.; Caselli, P.; Fontani, F.; Hily-Blant, P.

2017-07-01

Context. Nitrogen is one of the most abundant elements in the Universe and its 14N/15N isotopic ratio has the potential to provide information about the initial environment in which our Sun formed. Recent findings suggest that the solar system may have formed in a massive cluster since the presence of short-lived radioisotopes in meteorites can only be explained by the influence of a supernova. Aims: We seek to determine the 14N/15N ratio towards a sample of cold and dense cores at the initial stages in their evolution. Methods: We observed the J = 1 → 0 transitions of HCN, H13CN, HC15N, HN13C, and H15NC towards a sample of 22 cores in four infrared-dark clouds (IRDCs) which are believed to be the precursors of high-mass stars and star clusters. Assuming LTE and a temperature of 15 K, the column densities of HCN, H13CN, HC15N, HN13C, and H15NC are calculated and their 14N/15N ratio is determined for each core. Results: The 14N/15N ratios measured in our sample of IRDC cores range between 70 and ≥763 in HCN and between 161 and 541 in HNC. These ratios are consistent with the terrestrial atmosphere (TA) and protosolar nebula (PSN) values, and with the ratios measured in low-mass prestellar cores. However, the 14N/15N ratios measured in cores C1, C3, F1, F2, and G2 do not agree with the results from similar studies towards the same cores using nitrogen bearing molecules with nitrile functional group (-CN) and nitrogen hydrides (-NH) although the ratio spread covers a similar range. Conclusions: Relatively low 14N/15N ratios amongst the four-IRDCs were measured in IRDC G which are comparable to those measured in small cosmomaterials and protoplanetary disks. The low average gas density of this cloud suggests that the gas density, rather than the gas temperature, may be the dominant parameter influencing the initial nitrogen isotopic composition in young PSN. The reduced spectra (FITS files) are only available at the CDS via anonymous ftp to http

New T Tauri stars in Chamaeleon I and Chamaeleon II

NASA Technical Reports Server (NTRS)

Hartigan, Patrick

1993-01-01

A new objective prism survey of the entire Chamaeleon I dark cloud and 2/3 of the Chamaeleon II cloud has uncovered 26 new H-alpha emission line objects that were missed by previous H-alpha plate surveys. The new H-alpha emission line objects have similar IR colors and spatial distributions to the known T Tauri stars in these dark clouds, and could represent the very low mass end of the stellar population in these clouds or an older, less active component to the usual classical T Tauri star population. The new H-alpha survey identified 70 percent of the total known Young Stellar Objects (YSOs) in Cha I, compared with 35 percent for IRAS, and 25 percent from the Einstein X-ray survey. Ten of the new objects are weak-lined stars, with H-alpha equivalent widths less than 10 A. Weak-lined T Tauri stars make up about half of the total population of young stars in the Chamaeleon I cloud, a proportion similar to the Taurus-Auriga cloud. Presented are coordinates, finding charts, and optical and IR photometry of the new emission-line objects.

Simulating the evolution of optically dark HI clouds in the Virgo cluster : will no-one rid me of this turbulent sphere ?

NASA Astrophysics Data System (ADS)

Taylor, R.; Wünsch, R.; Palouš, J.

2018-05-01

Most detected neutral atomic hydrogen (HI) at low redshift is associated with optically bright galaxies. However, a handful of HI clouds are known which appear to be optically dark and have no nearby potential progenitor galaxies, making tidal debris an unlikely explanation. In particular, 6 clouds identified by the Arecibo Galaxy Environment Survey are interesting due to the combination of their small size, isolation, and especially their broad line widths atypical of other such clouds. A recent suggestion is that these clouds exist in pressure equilibrium with the intracluster medium, with the line width arising from turbulent internal motions. Here we explore that possibility by using the FLASH code to perform a series of 3D hydro simulations. Our clouds are modelled using spherical Gaussian density profiles, embedded in a hot, low-density gas representing the intracluster medium. The simulations account for heating and cooling of the gas, and we vary the structure and strength of their internal motions. We create synthetic HI spectra, and find that none of our simulations reproduce the observed cloud parameters for longer than ˜100 Myr : the clouds either collapse, disperse, or experience rapid heating which would cause ionisation and render them undetectable to HI surveys. While the turbulent motions required to explain the high line widths generate structures which appear to be inherently unstable, making this an unlikely explanation for the observed clouds, these simulations demonstrate the importance of including the intracluster medium in any model seeking to explain the existence of these objects.

Searching for dark clouds in the outer galactic plane. I. A statistical approach for identifying extended red(dened) regions in 2MASS

NASA Astrophysics Data System (ADS)

Frieswijk, W. W. F.; Shipman, R. F.

2010-06-01

Context. Most of what is known about clustered star formation to date comes from well studied star forming regions located relatively nearby, such as Rho-Ophiuchus, Serpens and Perseus. However, the recent discovery of infrared dark clouds may give new insights in our understanding of this dominant mode of star formation in the Galaxy. Though the exact role of infrared dark clouds in the formation process is still somewhat unclear, they seem to provide useful laboratories to study the very early stages of clustered star formation. Infrared dark clouds have been identified predominantly toward the bright inner parts of the galactic plane. The low background emission makes it more difficult to identify similar objects in mid-infrared absorption in the outer parts. This is unfortunate, because the outer Galaxy represents the only nearby region where we can study effects of different (external) conditions on the star formation process. Aims: The aim of this paper is to identify extended red regions in the outer galactic plane based on reddening of stars in the near-infrared. We argue that these regions appear reddened mainly due to extinction caused by molecular clouds and young stellar objects. The work presented here is used as a basis for identifying star forming regions and in particular the very early stages. An accompanying paper describes the cross-identification of the identified regions with existing data, uncovering more on the nature of the reddening. Methods: We use the Mann-Whitney U-test, in combination with a friends-of-friends algorithm, to identify extended reddened regions in the 2MASS all-sky JHK survey. We process the data on a regular grid using two different resolutions, 60´´ and 90´´. The two resolutions have been chosen because the stellar surface density varies between the crowded spiral arm regions and the sparsely populated galactic anti-center region. Results: We identify 1320 extended red regions at the higher resolution and 1589 in the

Measuring the Internal Structure and Physical Conditions in Star and Planet Forming Clouds Cores: Towards a Quantitative Description of Cloud Evolution

NASA Technical Reports Server (NTRS)

Lada, Charles J.

2004-01-01

This grant funds a research program to use infrared extinction measurements to probe the detailed structure of dark molecular cloud cores and investigate the physical conditions which give rise to star and planet formation. The goals of this program are to acquire, reduce and analyze deep infrared and molecular-line observations of a carefully selected sample of nearby dark clouds in order to determine the detailed initial conditions for star formation from quantitative measurements of the internal structure of starless cloud cores and to quantitatively investigate the evolution of such structure through the star and planet formation process.

Measuring the Internal Structure and Physical Conditions in Star and Planet Forming Clouds Core: Toward a Quantitative Description of Cloud Evolution

NASA Technical Reports Server (NTRS)

Lada, Charles J.

2005-01-01

This grant funds a research program to use infrared extinction measurements to probe the detailed structure of dark molecular cloud cores and investigate the physical conditions which give rise to star and planet formation. The goals of this program are to acquire, reduce and analyze deep infrared and molecular-line observations of a carefully selected sample of nearby dark clouds in order to internal structure of starless cloud cores and to quantitatively investigate the evolution of such structure through the star and planet formation process. During the second year of this grant, progress toward these goals is discussed.

Neptune's New Dark Vortex: Aerosol Properties from Optical Data

NASA Astrophysics Data System (ADS)

Tollefson, J.; Luszcz-Cook, S.; Wong, M. H.; De Pater, I.

2016-12-01

Over the past year, amateur and professional astronomers alike have monitored the appearance of a new dark vortex on Neptune, dubbed SDS-2015 for "southern dark spot discovered in 2015" (Wong et al. 2016; CBET 4278). The discovery of SDS-2015 is fortuitous, being one of only five dark spots observed on Neptune since Voyager 2 imaged the Great Dark Spot (Smith et al. 1989, Science 246, 1422). A companion abstract (Wong et al., this meeting) will present Hubble Space Telescope images of SDS-2015, showcasing the discovery of the vortex in September 2015 and subsequent observations in May 2016. These observations span the optical regime. Longer wavelengths track bright companion clouds thought to form as air is diverted around SDS-2015. Shorter wavelengths reveal the dark spot itself. Combined, these data probe the vertical extent of the dark spot and Neptune's surrounding upper atmosphere. We present preliminary radiative transfer analyses of SDS-2015 using our multispectral data. Our model is the same as that in Luszcz-Cook et al. (2016, Icarus 276, 52) but extended to optical wavelengths. Prior to this work, little was known about the composition and vertical extent of Neptune's dark spots. Only data at optical wavelengths reveal these vortices, suggesting they consist of clearings in the background of fine, evenly-distributed haze particle. Alternatively, the spots may consist of low-albedo aerosols, causing their apparent darkness. Radiative transfer modeling is also one way to determine the vortex top altitude. Simulations of the Great Dark Spot by Stratman et al. (2001, Icarus 151, 275) found that the vortex top altitude is coupled to the brightness of companion clouds, where cloud opacity weakened as the top of the vortex reached higher into the tropopause region. The modeling presented here will compare these hypotheses and provide the first glimpses into the vertical structure of SDS-2015.

Neptune Great Dark Spot in High Resolution

NASA Image and Video Library

1999-08-30

This photograph shows the last face on view of the Great Dark Spot that Voyager will make with the narrow angle camera. The image was shuttered 45 hours before closest approach at a distance of 2.8 million kilometers (1.7 million miles). The smallest structures that can be seen are of an order of 50 kilometers (31 miles). The image shows feathery white clouds that overlie the boundary of the dark and light blue regions. The pinwheel (spiral) structure of both the dark boundary and the white cirrus suggest a storm system rotating counterclockwise. Periodic small scale patterns in the white cloud, possibly waves, are short lived and do not persist from one Neptunian rotation to the next. This color composite was made from the clear and green filters of the narrow-angle camera. http://photojournal.jpl.nasa.gov/catalog/PIA00052

Hubble Finds New Dark Spot on Neptune

NASA Technical Reports Server (NTRS)

1995-01-01

NASA's Hubble Space Telescope has discovered a new great dark spot, located in the northern hemisphere of the planet Neptune. Because the planet's northern hemisphere is now tilted away from Earth, the new feature appears near the limb of the planet.

The spot is a near mirror-image to a similar southern hemisphere dark spot that was discovered in 1989 by the Voyager 2 probe. In 1994, Hubble showed that the southern dark spot had disappeared.

Like its predecessor, the new spot has high altitude clouds along its edge, caused by gasses that have been pushed to higher altitudes where they cool to form methane ice crystal clouds. The dark spot may be a zone of clear gas that is a window to a cloud deck lower in the atmosphere.

Planetary scientists don t know how long lived this new feature might be. Hubble's high resolution will allow astronomers to follow the spot's evolution and other unexpected changes in Neptune's dynamic atmosphere.

The image was taken on November 2, 1994 with Hubble's Wide Field Planetary Camera 2, when Neptune was 2.8 billion miles (4.5 billion kilometers) from Earth. Hubble can resolve features as small as 625 miles (1,000 kilometers) across in Neptune's cloud tops.

The Wide Field/Planetary Camera 2 was developed by the Jet Propulsion Laboratory and managed by the Goddard Spaced Flight Center for NASA's Office of Space Science.

This image and other images and data received from the Hubble Space Telescope are posted on the World Wide Web on the Space Telescope Science Institute home page at URL http://oposite.stsci.edu/pubinfo/

Physiological responses of Bos taurus and Bos indicus cattle to prolonged, continuous heat and humidity.

PubMed

Beatty, D T; Barnes, A; Taylor, E; Pethick, D; McCarthy, M; Maloney, S K

2006-04-01

Two experiments were conducted to investigate the physiological responses of Bos taurus (Angus cross, n = 6) and Bos indicus (Brahman, n = 6) cattle to prolonged heat and humidity, as can occur during live export by sea. Each experiment was carried out in climate-controlled rooms, where heifers were exposed to 15 d of sustained heat and humidity. The treatment was designed to be representative of a long-haul, live-export voyage leaving a southern Australian winter and traveling to a Middle Eastern summer. Wet bulb temperature (WBT) was used to give a combined measure of dry bulb temperature and relative humidity and was increased over several days, culminating in 5 d at 32 degrees C WBT between d 7 and 11. By d 11, the respiratory rate and core body temperature increased (P < 0.001) compared with values at lower ambient temperature on d 1 and 2 when climate-controlled rooms were not operating. Feed intake of Bos taurus was reduced (P < 0.001) by d 11, whereas that of Bos indicus did not change (P = 0.14). Despite no diurnal variation in climatic conditions, core body temperature of both Bos taurus and Bos indicus continued to show a circadian amplitude of approximately 1 degrees C throughout the hottest period. This amplitude increased during the recovery period after heat was removed (up to 1.8 degrees C for Bos indicus and 1.6 degrees C for Bos taurus). Water intake for both Bos taurus and Bos indicus increased when WBT increased (P < 0.01 on d 11). Significant acid-base and blood electrolyte imbalances occurred in both Bos taurus and Bos indicus, with changes in Bos taurus being more substantial and prolonged. The increase in respiratory rate coincided with a decrease in the partial pressures of carbon dioxide and bicarbonate in venous blood. However, during the hottest period, average daily venous blood pH remained unchanged. When the heat load was reduced after d 11, the blood pH decreased, indicating metabolic acidosis. Blood pH declined from 7.44 to 7.36 for

New insights on multiplicity and clustering in Taurus.

NASA Astrophysics Data System (ADS)

Joncour, Isabelle; Duchene, Gaspard; Moraux, Estelle; Mundy, Lee

2018-01-01

Multiplicity and clustering of young stars are critical clues to constraint star formation process. The Taurus molecular complex is the archetype of a quiescent star forming region that may retain primeval signature of star formation.Using statistical and clustering tools such as nearest neighbor statistics, correlation functions and the density-Based Spatial Clustering of Applications with Noise (DBSCAN) algorithm, this work reveals new spatial substructures in Taurus.We have identified unexpected ultra wide pairs (UWPs) candidates of high order multiplicity in Taurus in the 5-60 kAU separation range (Joncour et al 2017), beyond the separation assessed for wide pairs (Kraus & Hillenbrand 2009).Our work reveals 20 local stellar substructures, the Nested Elementary Structures (NESTs). These NESTs contain nearly half the stars of Taurus and 75% of the Class 0/I objects probing that they are the preferred sites of star formation (Joncour et al, sub.). The NESTs size ranges from few kAU up to 80 kAU making a length scale bridge between wide pairs and loose group (few hundreds kAU, Kirk & Myers, 2011). The NESTs mass ranges from 0.5-10 solar mass. The balance between Class I, II and III in NESTs suggests that they may be ordered as an evolutionary temporal scheme, some of them got infertile, while other shelter stars in infancy.The UWPs and the NESTs may be pristine imprints of their spatial configuration at birth. The UWPs population may result from a cascade fragmentation scenario of the natal molecular core. They could be the older counterparts, to the 0.5 Myr prestellar cores/Class 0 multiple objects observed at radio/millimeter wavelengths (Tobin et al 2010, 2016) and the precursors of the large number of UWPs (10–100 kAU) recently identified in older moving groups (Floriano-Alonso et al, 2015 ; Elliot et al 2016). The NESTs may result from the gravitational collapse of a gas clump that fragments to give a tight collection of stars within few millions years

Bands of Clouds and Lace

NASA Image and Video Library

2004-05-13

As Cassini nears its rendezvous with Saturn, new detail in the banded clouds of the planet's atmosphere are becoming visible. Cassini began the journey to the ringed world of Saturn nearly seven years ago and is now less than two months away from orbit insertion on June 30. Cassini’s narrow-angle camera took this image on April 16, 2004, when the spacecraft was 38.5 million kilometers (23.9 million miles) from Saturn. Dark regions are generally areas free of high clouds, and bright areas are places with high, thick clouds which shield the view of the darker areas below. A dark spot is visible at the south pole, which is remarkable to scientists because it is so small and centered. The spot could be affected by Saturn's magnetic field, which is nearly aligned with the planet's rotation axis, unlike the magnetic fields of Jupiter and Earth. From south to north, other notable features are the two white spots just above the dark spot toward the right, and the large dark oblong-shaped feature that extends across the middle. The darker band beneath the oblong-shaped feature has begun to show a lacy pattern of lighter-colored, high altitude clouds, indicative of turbulent atmospheric conditions. The cloud bands move at different speeds, and their irregularities may be due to either the different motions between them or to disturbances below the visible cloud layer. Such disturbances might be powered by the planet's internal heat; Saturn radiates more energy than it receives from the Sun. The moon Mimas (396 kilometers, 245 miles across) is visible to the left of the south pole. Saturn currently has 31 known moons. Since launch, 13 new moons have been discovered by ground-based telescopes. Cassini will get a closer look and may discover new moons, perhaps embedded within the planet’s magnificent rings. This image was taken using a filter sensitive to light near 727 nanometers, one of the near-infrared absorption bands of methane gas, which is one of the ingredients in

Long Carbon Chains in the Warm Carbon-chain-chemistry Source L1527: First Detection of C7H in Molecular Clouds

NASA Astrophysics Data System (ADS)

Araki, Mitsunori; Takano, Shuro; Sakai, Nami; Yamamoto, Satoshi; Oyama, Takahiro; Kuze, Nobuhiko; Tsukiyama, Koichi

2017-09-01

Long carbon-chain molecules were searched for toward the low-mass star-forming region L1527, which is a prototypical source of warm carbon-chain chemistry (WCCC), using the 100 m Green Bank Telescope. Long carbon-chain molecules, C7H (2Π1/2), C6H (2Π3/2 and 2Π1/2), CH3C4H, and C6H2 (cumulene carbene, CCCCCCH2), and cyclic species of C3H and C3H2O were detected. In particular, C7H was detected for the first time in molecular clouds. The column density of C7H is determined to be 6 × 1010 cm-2. The column densities of the carbon-chain molecules including CH3C4H and C6H in L1527 relative to those in the starless dark cloud Taurus Molecular Cloud-1 Cyanopolyyne Peak (TMC-1 CP) tend to be systematically lower for long carbon-chain lengths. However, the column densities of C7H and C6H2 do not follow this trend and are found to be relatively abundant in L1527. This result implies that these long carbon-chain molecules are remnants of the cold starless phase. The results—that both the remnants and WCCC products are observed toward L1527—are consistent with the suggestion that the protostar can also be born in the parent core at a relatively early stage in the chemical evolution.

A quantitative analysis of IRAS maps of molecular clouds

NASA Technical Reports Server (NTRS)

Wiseman, Jennifer J.; Adams, Fred C.

1994-01-01

We present an analysis of IRAS maps of five molecular clouds: Orion, Ophiuchus, Perseus, Taurus, and Lupus. For the classification and description of these astrophysical maps, we use a newly developed technique which considers all maps of a given type to be elements of a pseudometric space. For each physical characteristic of interest, this formal system assigns a distance function (a pseudometric) to the space of all maps: this procedure allows us to measure quantitatively the difference between any two maps and to order the space of all maps. We thus obtain a quantitative classification scheme for molecular clouds. In this present study we use the IRAS continuum maps at 100 and 60 micrometer(s) to produce column density (or optical depth) maps for the five molecular cloud regions given above. For this sample of clouds, we compute the 'output' functions which measure the distribution of density, the distribution of topological components, the self-gravity, and the filamentary nature of the clouds. The results of this work provide a quantitative description of the structure in these molecular cloud regions. We then order the clouds according to the overall environmental 'complexity' of these star-forming regions. Finally, we compare our results with the observed populations of young stellar objects in these clouds and discuss the possible environmental effects on the star-formation process. Our results are consistent with the recently stated conjecture that more massive stars tend to form in more 'complex' environments.

The nature of the embedded population in the Rho Ophiuchi dark cloud - Mid-infrared observations

NASA Technical Reports Server (NTRS)

Lada, C. J.; Wilking, B. A.

1984-01-01

In combination with previous IR and optical data, the present 10-20 micron observations of previously identified members of the embedded population of the Rho Ophiuchi dark cloud allow determinations to be made of the broadband energy distributions for 32 of the 44 sources. The majority of the sources are found to emit the bulk of their luminosity in the 1-20 micron range, and to be surrounded by dust shells. Because they are, in light of these characteristics, probably premain-sequence in nature, relatively accurate bolometric luminosities for these objects can be obtained through integration of their energy distributions. It is found that 44 percent of the sources are less luminous than the sun, and are among the lowest luminosity premain-sequence/protostellar objects observed to date.

Opacity broadening and interpretation of suprathermal CO linewidths: Macroscopic turbulence and tangled molecular clouds

NASA Astrophysics Data System (ADS)

Hacar, A.; Alves, J.; Burkert, A.; Goldsmith, P.

2016-06-01

Context. Since their first detection in the interestellar medium, (sub-)millimeter line observations of different CO isotopic variants have routinely been employed to characterize the kinematic properties of the gas in molecular clouds. Many of these lines exhibit broad linewidths that greatly exceed the thermal broadening expected for the low temperatures found within these objects. These observed suprathermal CO linewidths are assumed to originate from unresolved supersonic motions inside clouds. Aims: The lowest rotational J transitions of some of the most abundant CO isotopologues, 12CO and 13CO, are found to present large optical depths. In addition to well-known line saturation effects, these large opacities present a non-negligible contribution to their observed linewidths. Typically overlooked in the literature, in this paper we aim to quantify the impact of these opacity broadening effects on the current interpretation of the CO suprathermal line profiles. Methods: Combining large-scale observations and LTE modeling of the ground J = 1-0 transitions of the main 12CO, 13CO, C18O isotopologues, we have investigated the correlation of the observed linewidths as a function of the line opacity in different regions of the Taurus molecular cloud. Results: Without any additional contributions to the gas velocity field, a large fraction of the apparently supersonic (ℳ ~ 2-3) linewidths measured in both 12CO and 13CO (J = 1-0) lines can be explained by the saturation of their corresponding sonic-like, optically thin C18O counterparts assuming standard isotopic fractionation. Combined with the presence of multiple components detected in some of our C18O spectra, these opacity effects also seem to be responsible for most of the highly supersonic linewidths (ℳ > 8-10) detected in some of the broadest 12CO and 13CO spectra in Taurus. Conclusions: Our results demonstrate that most of the suprathermal 12CO and 13CO linewidths reported in nearby clouds like Taurus

Chemical transitions for interstellar C2 and CN in cloud envelopes

NASA Technical Reports Server (NTRS)

Federman, S. R.; Strom, C. J.; Lambert, D. L.; Cardelli, Jason A.; Smith, V. V.; Joseph, C. L.

1994-01-01

Observations were made of absorption from CH, C2, and CN toward moderately reddened stars in Sco, OB2, Ceo OB3, and Taurus/Auriga. For these directions, most of the reddening is associated with a single cloud complex, for example, the rho Ophiuchus molecular cloud, and as a result, the observations probe moderately dense material. When combined with avaliable data for nearby directions, the survey provides the basis for a comprehensive analysis of the chemistry for these species. The chemical transitions affecting C2 and CN in cloud envelopes were analyzed. The depth into a cloud at which a transition takes place was characterized by tau(sub uv), the grain optical depth at 1000 A. One transition at tau(sub uv) approx. = 2, which arises from, the conversion of C(+) into CO, affects the chemistries for both molecules because of the key role this ion plays. A second one involving production terms in the CN chemistry occurs at tau(sub uv) of approx. = 3; neutral reactions which C2 and CH is more important at larger values for tau(sub uv). The transition from photodissociation to chemical destruction takes place at tau(sub uv) approx. = 4.5 for C2 and CN. The observational data for stars in Sco OB2, Cep OB3, and Taurus/Auriga were studied with chemical rate equations containing the most important production and destruction mechanisms. Because the sample of stars in Sco OB2 includes sight lines with A(sub v) ranging from 1-4 mag, sight lines dominated by photochemistry could be analyzed separately from those controlled by gas-phase destruction. The analysis yielded values for two poorly known rate constants for reactions involved in the production of CN; the reactions are C2 + N yields CN + C and C(+) + NH yields all products. The other directions were analyzed with the inferred values. The predicted column densities for C2 and CN agree with the observed values to better than 50%, and in most instances 20%. When combining the estimates for density and temperature derived

A search for planemos in L 1495. (Spanish Title: Búsqueda de planemos en L 1495)

NASA Astrophysics Data System (ADS)

Heredia, L.; Gómez, M.; Bravo-Alfaro, H.

In this contribution we present a search for planemos (planetary mass objects) in the L 1495 dark cloud, belonging to the Taurus molecular complex. The observations were obtained in the K (2.2 micron) and H (1.6 micron) bands with the near-IR instrument CAMILA, attached to the 2.1-m telescope of the San Pedro Mártir Observatory, in Baja California, México. These observations have been supplemented with data from the 2MASS, which cover a larger area and provide magnitudes in the J (1.25 micron) band. We used the Baraffe et al. (1998, 2002) and Chabrier et al. (2000) pre-main sequence evolutionary models to select approximately 90 planetary mass candidates with magnitudes and colors roughly corresponding to objects with masses between 4 and 15 Jupiter masses and ages of a few million years, in the Taurus molecular cloud. However, more accurate photometry is necessary to confirm the magnitudes and colors of these candidate objects. If confirmed, this result may indicate that planemos are very common in our Galaxy.

Mid-J CO Shock Tracing Observations of Infrared Dark Clouds. III. SLED Fitting

NASA Astrophysics Data System (ADS)

Pon, A.; Kaufman, M. J.; Johnstone, D.; Caselli, P.; Fontani, F.; Butler, M. J.; Jiménez-Serra, I.; Palau, A.; Tan, J. C.

2016-08-01

Giant molecular clouds contain supersonic turbulence that can locally heat small fractions of gas to over 100 K. We run shock models for low-velocity, C-type shocks propagating into gas with densities between 103 and 105 cm-3 and find that CO lines are the most important cooling lines. Comparison to photodissociation region (PDR) models indicates that mid-J CO lines (J = 8 \\to 7 and higher) should be dominated by emission from shocked gas. In Papers I and II we presented CO J = 3 \\to 2, 8 \\to 7, and 9 \\to 8 observations toward four primarily quiescent clumps within infrared dark clouds. Here we fit PDR models to the combined spectral line energy distributions and show that the PDR models that best fit the low-J CO emission underpredict the mid-J CO emission by orders of magnitude, strongly hinting at a hot gas component within these clumps. The low-J CO data clearly show that the integrated intensities of both the CO J = 8 \\to 7 and 9 \\to 8 lines are anomalously high, such that the line ratio can be used to characterize the hot gas component. Shock models are reasonably consistent with the observed mid-J CO emission, with models with densities near {10}4.5 cm-3 providing the best agreement. Where this mid-J CO is detected, the mean volume filling factor of the hot gas is 0.1%. Much of the observed mid-J CO emission, however, is also associated with known protostars and may be due to protostellar feedback.

Catching the Drift: Simulating Dark Spots and Bright Companions on the Ice Giants

NASA Astrophysics Data System (ADS)

LeBeau, R. P., Jr.; Koutas, N.; Palotai, C. J.; Bhure, S.; Hadland, N.; Sankar, R.

2017-12-01

Starting with the original Great Dark Spot (GDS-89) observed by Voyager 2, roughly a half-dozen large geophysical vortices have been observed on the Ice Giants, the most recent in 2015 on Neptune (Wong et al., 2016). While the presumption is that these Dark Spots are similar in structure to the large vortices on Jupiter, in some cases the Dark Spots exhibit dynamical motions such as the shape oscillations and latitudinal drift of GDS-89 (Smith et al., 1989) or the possible vortex drift underlying the "Berg" cloud feature on Uranus (de Pater et al., 2011). Others, like NGDS-1998, have remained largely stable across years of observation (Sromovsky et al., 2002). In addition, several of the vortices are linked with Bright Companion clouds which are presumed to be orographic features formed as the atmosphere rises over the vortex. The numerical simulation of these features has evolved with each new observation. Prior simulations have captured the forms if not all the specifics of observed Dark Spot dynamics (LeBeau and Dowling, 1998; LeBeau and Deng, 2006); likewise, numerical models have demonstrated the potential for orographic companion clouds (Stratman et al., 2001). However, as more knowledge of the Ice Giant atmospheres has been obtained, it has proven challenging to generate consistent dynamical models that capture the details of the Dark Spot variations and are physically consistent with known observations. In particular, current simulations indicate that the addition of a companion cloud can alter the vortex dynamics, both in terms of drift and oscillations. Given the impact of these clouds, a new parametric simulation study uses an updated microphysics model, implemented in the Explicit Planetary Isentropic Coordinate (EPIC) general circulation model (Dowling et al., 1998, 2006), to account for the condensation of methane and hydrogen sulfide (Palotai et al., 2016). Simulations of dark spots with varying sizes, strengths, and locations are conducted with

Isolation and genetic diversity of endangered grey nurse shark (Carcharias taurus) populations.

PubMed

Stow, Adam; Zenger, Kyall; Briscoe, David; Gillings, Michael; Peddemors, Victor; Otway, Nicholas; Harcourt, Robert

2006-06-22

Anthropogenic impacts are believed to be the primary threats to the eastern Australian population of grey nurse sharks (Carcharias taurus), which is listed as critically endangered, and the most threatened population globally. Analyses of 235 polymorphic amplified fragment length polymorphisms (AFLP) loci and 700 base pairs of mitochondrial DNA control region provide the first account of genetic variation and geographical partitioning (east and west coasts of Australia, South Africa) in C. taurus. Assignment tests, analysis of relatedness and Fst values all indicate that the Australian populations are isolated from South Africa, with negligible migration between the east and west Australian coasts. There are significant differences in levels of genetic variation among regions. Australian C. taurus, particularly the eastern population, has significantly less AFLP variation than the other sampling localities. Further, the eastern Australian sharks possess only a single mitochondrial haplotype, also suggesting a small number of founding individuals. Therefore, historical, rather than anthropogenic processes most likely account for their depauperate genetic variation. These findings have implications for the viability of the eastern Australian population of grey nurse sharks.

Dark Targets, Aerosols, Clouds and Toys

NASA Astrophysics Data System (ADS)

Remer, L. A.

2015-12-01

Today if you use the Thomson-Reuters Science Citations Index to search for "aerosol*", across all scientific disciplines and years, with no constraints, and you sort by number of citations, you will find a 2005 paper published in the Journal of the Atmospheric Sciences in the top 20. This is the "The MODIS Aerosol Algorithm, Products and Validation". Although I am the first author, there are in total 12 co-authors who each made a significant intellectual contribution to the paper or to the algorithm, products and validation described. This paper, that algorithm, those people lie at the heart of a lineage of scientists whose collaborations and linked individual pursuits have made a significant contribution to our understanding of radiative transfer and climate, of aerosol properties and the global aerosol system, of cloud physics and aerosol-cloud interaction, and how to measure these parameters and maximize the science that can be obtained from those measurements. The 'lineage' had its origins across the globe, from Soviet Russia to France, from the U.S. to Israel, from the Himalayas, the Sahel, the metropolises of Sao Paulo, Taipei, and the cities of east and south Asia. It came together in the 1990s and 2000s at the NASA Goddard Space Flight Center, using cultural diversity as a strength to form a common culture of scientific creativity that continues to this day. The original algorithm has spawned daughter algorithms that are being applied to new satellite and airborne sensors. The original MODIS products have been fundamental to analyses as diverse as air quality monitoring and aerosol-cloud forcing. AERONET, designed originally for the need of validation, is now its own thriving institution, and the lineage continues to push forward to provide new technology for the coming generations.

A SURVEY FOR NEW MEMBERS OF THE TAURUS STAR-FORMING REGION WITH THE SLOAN DIGITAL SKY SURVEY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luhman, K. L.; Mamajek, E. E.; Shukla, S. J.

Previous studies have found that ∼1 deg{sup 2} fields surrounding the stellar aggregates in the Taurus star-forming region exhibit a surplus of solar-mass stars relative to denser clusters like IC 348 and the Orion Nebula Cluster. To test whether this difference reflects mass segregation in Taurus or a variation in the initial mass function, we have performed a survey for members of Taurus across a large field (∼40 deg{sup 2}) that was imaged by the Sloan Digital Sky Survey (SDSS). We obtained optical and near-infrared spectra of candidate members identified with those images and the Two Micron All Sky Survey, as wellmore » as miscellaneous candidates that were selected with several other diagnostics of membership. We have classified 22 of the candidates as new members of Taurus, which includes one of the coolest known members (M9.75). Our updated census of members within the SDSS field shows a surplus of solar-mass stars relative to clusters, although it is less pronounced than in the smaller fields toward the stellar aggregates that were surveyed for previously measured mass functions in Taurus. In addition to spectra of our new members, we include in our study near-IR spectra of roughly half of the known members of Taurus, which are used to refine their spectral types and extinctions. We also present an updated set of near-IR standard spectra for classifying young stars and brown dwarfs at M and L types.« less

Neptune's small dark spot (D2)

NASA Technical Reports Server (NTRS)

1999-01-01

This bulls-eye view of Neptune's small dark spot (D2) was obtained by Voyager 2's narrow-angle camera. Banding surrounding the feature indicates unseen strong winds, while structures within the bright spot suggest both active upwelling of clouds and rotation about the center. A rotation rate has not yet been measured, but the V-shaped structure near the right edge of the bright area indicates that the spot rotates clockwise. Unlike the Great Red Spot on Jupiter, which rotates counterclockwise, if the D2 spot on Neptune rotates clockwise, the material will be descending in the dark oval region. The fact that infrared data will yield temperature information about the region above the clouds makes this observation especially valuable. The Voyager Mission is conducted by JPL for NASA's Office of Space Science and Applications.

Mapping of the extinction in giant molecular clouds using optical star counts

NASA Astrophysics Data System (ADS)

Cambrésy, L.

1999-05-01

This paper presents large scale extinction maps of most nearby Giant Molecular Clouds of the Galaxy (Lupus, rho Ophiuchus, Scorpius, Coalsack, Taurus, Chamaeleon, Musca, Corona Australis, Serpens, IC 5146, Vela, Orion, Monoceros R1 and R2, Rosette, Carina) derived from a star count method using an adaptive grid and a wavelet decomposition applied to the optical data provided by the USNO-Precision Measuring Machine. The distribution of the extinction in the clouds leads to estimate their total individual masses M and their maximum of extinction. I show that the relation between the mass contained within an iso-extinction contour and the extinction is similar from cloud to cloud and allows the extrapolation of the maximum of extinction in the range 5.7 to 25.5 magnitudes. I found that about half of the mass is contained in regions where the visual extinction is smaller than 1 magnitude. The star count method used on large scale ( ~ 250 square degrees) is a powerful and relatively straightforward method to estimate the mass of molecular complexes. A systematic study of the all sky would lead to discover new clouds as I did in the Lupus complex for which I found a sixth cloud of about 10(4) M_⊙.

Genetic effects on beef tenderness in Bos indicus composite and Bos taurus cattle.

PubMed

O'Connor, S F; Tatum, J D; Wulf, D M; Green, R D; Smith, G C

1997-07-01

Bos indicus composite and Bos taurus cattle, originating from diverse production environments, were used to quantify genetic variation in marbling, 24-h calpastatin activity, and beef tenderness and to identify strategies for prevention of beef tenderness problems in Bos indicus composite cattle. Comparisons among 3/8 Bos indicus breeds (Braford, Red Brangus, Simbrah) revealed significant differences in marbling and 24-h calpastatin activity, but not in tenderness. Compared with Bos taurus cattle, 3/ 8 Bos indicus cattle had similar marbling scores but higher 24-h calpastatin activities. Also, beef from 3/8 Bos indicus composites aged more slowly from 1 to 7 d and was less tender at 4, 7, 14, 21, and 35 d postmortem than beef from Bos taurus cattle. However, beef from 3/8 Bos indicus cattle was relatively tender if it was aged for a sufficient period of time (21 d). The delayed response to aging and greater toughness of beef from 3/8 Bos indicus cattle was associated with Brahman breed effects and was not related to the Bos taurus germplasm source. Marbling was moderately heritable (.52 +/- .21) but exhibited positive genetic correlations with shear force at d 1 through 14 of aging, suggesting that, in these cattle, selection for increased marbling would have an unfavorable effect on beef tenderness. A low heritability estimate for 24-h calpastatin activity (.15 +/- .15), coupled with low genetic correlations between calpastatin activity and shear force at 7, 14, and 35 d, suggested that selection for low calpastatin activity would have little effect on aged beef tenderness. Panel tenderness and shear force at 7, 14, and 21 d were moderately heritable (.27 to .47), indicating that aged beef tenderness could be improved by direct selection (via progeny testing). Comparisons among Simbrah, Senegus x Simbrah, and Red Angus x Simmental steers showed that inclusion of a tropically adapted Bos taurus breed (Senepol) could be an effective strategy for preventing beef

The clouds and winds of Neptune

NASA Astrophysics Data System (ADS)

Beebe, R.

1992-04-01

The atmospheric features of Neptune are described based on the images from Voyager 2 with comparisons made to the atmosphere of Uranus. Specific attention is given to the clear atmosphere's methane content and lack of the smog associated with Uranus. Neptune absorbs only a small amount of energy from sunlight and radiates about 2.7 times as much as it absorbs. The mechanisms that keep Neptune's atmosphere free of smog are thought to be upwelling enhanced by an outward heat flow and melting ice. The Voyager photographs show streaks of white clouds indicating strong winds and probably white ice in the upper atmosphere. The Great Dark Spot and a small triangular cloud are described in terms of their periods of rotation, and the wind speed is discussed in terms of cloud variations. The Great Dark Spot drifted equatorward during the observational period, and the drift yields some important clues regarding the nature of the Neptunian atmosphere and climate.

The Gould's Belt Very Large Array Survey. IV. The Taurus-Auriga Complex

NASA Astrophysics Data System (ADS)

Dzib, Sergio A.; Loinard, Laurent; Rodríguez, Luis F.; Mioduszewski, Amy J.; Ortiz-León, Gisela N.; Kounkel, Marina A.; Pech, Gerardo; Rivera, Juana L.; Torres, Rosa M.; Boden, Andrew F.; Hartmann, Lee; Evans, Neal J., II; Briceño, Cesar; Tobin, John

2015-03-01

We present a multi-epoch radio study of the Taurus-Auriga star-forming complex made with the Karl G. Jansky Very Large Array at frequencies of 4.5 GHz and 7.5 GHz. We detect a total of 610 sources, 59 of which are related to young stellar objects (YSOs) and 18 to field stars. The properties of 56% of the young stars are compatible with non-thermal radio emission. We also show that the radio emission of more evolved YSOs tends to be more non-thermal in origin and, in general, that their radio properties are compatible with those found in other star-forming regions. By comparing our results with previously reported X-ray observations, we notice that YSOs in Taurus-Auriga follow a Güdel-Benz relation with κ = 0.03, as we previously suggested for other regions of star formation. In general, YSOs in Taurus-Auriga and in all the previous studied regions seem to follow this relation with a dispersion of ~1 dex. Finally, we propose that most of the remaining sources are related with extragalactic objects but provide a list of 46 unidentified radio sources whose radio properties are compatible with a YSO nature.

The Taurus Boundary of Stellar/Substellar (TBOSS) Survey. II. Disk Masses from ALMA Continuum Observations

NASA Astrophysics Data System (ADS)

Ward-Duong, K.; Patience, J.; Bulger, J.; van der Plas, G.; Ménard, F.; Pinte, C.; Jackson, A. P.; Bryden, G.; Turner, N. J.; Harvey, P.; Hales, A.; De Rosa, R. J.

2018-02-01

We report 885 μm ALMA continuum flux densities for 24 Taurus members spanning the stellar/substellar boundary with spectral types from M4 to M7.75. Of the 24 systems, 22 are detected at levels ranging from 1.0 to 55.7 mJy. The two nondetections are transition disks, though other transition disks in the sample are detected. Converting ALMA continuum measurements to masses using standard scaling laws and radiative transfer modeling yields dust mass estimates ranging from ∼0.3 to 20 M ⊕. The dust mass shows a declining trend with central object mass when combined with results from submillimeter surveys of more massive Taurus members. The substellar disks appear as part of a continuous sequence and not a distinct population. Compared to older Upper Sco members with similar masses across the substellar limit, the Taurus disks are brighter and more massive. Both Taurus and Upper Sco populations are consistent with an approximately linear relationship in M dust to M star, although derived power-law slopes depend strongly upon choices of stellar evolutionary model and dust temperature relation. The median disk around early-M stars in Taurus contains a comparable amount of mass in small solids as the average amount of heavy elements in Kepler planetary systems on short-period orbits around M-dwarf stars, with an order of magnitude spread in disk dust mass about the median value. Assuming a gas-to-dust ratio of 100:1, only a small number of low-mass stars and brown dwarfs have a total disk mass amenable to giant planet formation, consistent with the low frequency of giant planets orbiting M dwarfs.

Jupiter's Bands of Clouds

NASA Image and Video Library

2017-06-22

This enhanced-color image of Jupiter's bands of light and dark clouds was created by citizen scientists Gerald Eichstädt and Seán Doran using data from the JunoCam imager on NASA's Juno spacecraft. Three of the white oval storms known as the "String of Pearls" are visible near the top of the image. Each of the alternating light and dark atmospheric bands in this image is wider than Earth, and each rages around Jupiter at hundreds of miles (kilometers) per hour. The lighter areas are regions where gas is rising, and the darker bands are regions where gas is sinking. Juno acquired the image on May 19, 2017, at 11:30 a.m. PST (2:30 p.m. EST) from an altitude of about 20,800 miles (33,400 kilometers) above Jupiter's cloud tops. https://photojournal.jpl.nasa.gov/catalog/PIA21393

Mare volcanism in the Taurus-Littrow region

NASA Technical Reports Server (NTRS)

Delano, J. W.

1992-01-01

The products of mare volcanism at Taurus-Littrow occur in the form of crystalline basalts and volcanic glass beads. Both categories of samples define a compositionally diverse, but petrogenetically unrelated, suite of magmas derived by partial melting of a heterogenous, differentiated mantle beneath the region of the Apollo 17 landing site. This is a brief review of what is known and what is not known about mare volcanism at this location on the Moon.

The Dark Heart of the King

NASA Image and Video Library

2010-09-29

NASA Wide-field Infrared Survey Explorer captured this image of a hidden star-forming cloud of dust and gas located in the constellation of Cepheus. What appears to the naked eye as the blackness of space is in fact a dark nebula.

The dependence of stellar properties on initial cloud density

NASA Astrophysics Data System (ADS)

Jones, Michael O.; Bate, Matthew R.

2018-05-01

We investigate the dependence of stellar properties on the initial mean density of the molecular cloud in which stellar clusters form using radiation hydrodynamical simulations that resolve the opacity limit for fragmentation. We have simulated the formation of three star clusters from the gravitational collapse of molecular clouds whose densities vary by a factor of a hundred. As with previous calculations including radiative feedback, we find that the dependence of the characteristic stellar mass, Mc, on the initial mean density of the cloud, ρ, is weaker than the dependence of the thermal Jeans mass. However, unlike previous calculations, which found no statistically significant variation in the median mass with density, we find a weak dependence approximately of the form Mc∝ρ-1/5. The distributions of properties of multiple systems do not vary significantly between the calculations. We compare our results to the result of observational surveys of star-forming regions, and suggest that the similarities between the properties of our lowest density calculation and the nearby Taurus-Auriga region indicate that the apparent excess of solar-type stars observed may be due to the region's low density.

Analysis of interstellar cloud structure based on IRAS images

NASA Technical Reports Server (NTRS)

Scalo, John M.

1992-01-01

The goal of this project was to develop new tools for the analysis of the structure of densely sampled maps of interstellar star-forming regions. A particular emphasis was on the recognition and characterization of nested hierarchical structure and fractal irregularity, and their relation to the level of star formation activity. The panoramic IRAS images provided data with the required range in spatial scale, greater than a factor of 100, and in column density, greater than a factor of 50. In order to construct densely sampled column density maps of star-forming clouds, column density images of four nearby cloud complexes were constructed from IRAS data. The regions have various degrees of star formation activity, and most of them have probably not been affected much by the disruptive effects of young massive stars. The largest region, the Scorpius-Ophiuchus cloud complex, covers about 1000 square degrees (it was subdivided into a few smaller regions for analysis). Much of the work during the early part of the project focused on an 80 square degree region in the core of the Taurus complex, a well-studied region of low-mass star formation.

Formation of stellar clusters in magnetized, filamentary infrared dark clouds

NASA Astrophysics Data System (ADS)

Li, Pak Shing; Klein, Richard I.; McKee, Christopher F.

2018-01-01

Star formation in a filamentary infrared dark cloud (IRDC) is simulated over the dynamic range of 4.2 pc to 28 au for a period of 3.5 × 105 yr, including magnetic fields and both radiative and outflow feedback from the protostars. At the end of the simulation, the star formation efficiency is 4.3 per cent and the star formation rate per free-fall time is εff ≃ 0.04, within the range of observed values. The total stellar mass increases as ∼t2, whereas the number of protostars increases as ∼t1.5. We find that the density profile around most of the simulated protostars is ∼ρ ∝ r-1.5. At the end of the simulation, the protostellar mass function approaches the Chabrier stellar initial mass function. We infer that the time to form a star of median mass 0.2 M⊙ is about 1.4 × 105 yr from the median mass accretion rate. We find good agreement among the protostellar luminosities observed in the large sample of Dunham et al., our simulation and a theoretical estimate, and we conclude that the classical protostellar luminosity problem is resolved. The multiplicity of the stellar systems in the simulation agrees, to within a factor of 2, with observations of Class I young stellar objects; most of the simulated multiple systems are unbound. Bipolar protostellar outflows are launched using a subgrid model, and extend up to 1 pc from their host star. The mass-velocity relation of the simulated outflows is consistent with both observation and theory.

Gas-phase chemistry in dense interstellar clouds including grain surface molecular depletion and desorption

NASA Technical Reports Server (NTRS)

Bergin, E. A.; Langer, W. D.; Goldsmith, P. F.

1995-01-01

We present time-dependent models of the chemical evolution of molecular clouds which include depletion of atoms and molecules onto grain surfaces and desorption, as well as gas-phase interactions. We have included three mechanisms to remove species from the grain mantles: thermal evaporation, cosmic-ray-induced heating, and photodesorption. A wide range of parameter space has been explored to examine the abundance of species present both on the grain mantles and in the gas phase as a function of both position in the cloud (visual extinction) and of evolutionary state (time). The dominant mechanism that removes molecules from the grain mantles is cosmic-ray desorption. At times greater than the depletion timescale, the abundances of some simple species agree with abundances observed in the cold dark cloud TMC-1. Even though cosmic-ray desorption preserves the gas-phase chemistry at late times, molecules do show significant depletions from the gas phase. Examination of the dependence of depletion as a function of density shows that when the density increases from 10(exp 3)/cc to 10(exp 5)/cc several species including HCO(+), HCN, and CN show gas-phase abundance reductions of over an order of magnitude. The CO: H2O ratio in the grain mantles for our standard model is on the order of 10:1, in reasonable agreement with observations of nonpolar CO ice features in rho Ophiuchus and Serpens. We have also examined the interdependence of CO depletion with the space density of molecular hydrogen and binding energy to the grain surface. We find that the observed depletion of CO in Taurus in inconsistent with CO bonding in an H2O rich mantle, in agreement with observations. We suggest that if interstellar grains consist of an outer layer of CO ice, then the binding energies for many species to the grain mantle may be lower than commonly used, and a significant portion of molecular material may be maintained in the gas phase.

Optical spectroscopy of X-ray sources in the Taurus molecular cloud: discovery of ten new pre-main sequence stars

NASA Astrophysics Data System (ADS)

Scelsi, L.; Sacco, G.; Affer, L.; Argiroffi, C.; Pillitteri, I.; Maggio, A.; Micela, G.

2008-11-01

Aims: We have analyzed optical spectra of 25 X-ray sources identified as potential new members of the Taurus molecular cloud (TMC), in order to confirm their membership in this star-forming region. Methods: Fifty-seven candidate members were previously selected among the X-ray sources in the XEST survey, having a 2MASS counterpart compatible with a pre-main sequence star based on color-magnitude and color-color diagrams. We obtained high-resolution optical spectra for 7 of these candidates with the SARG spectrograph at the TNG telescope, which were used to search for lithium absorption and to measure the Hα line and the radial and rotational velocities. Then, 18 low-resolution optical spectra obtained with the instrument DOLORES for other candidate members were used for spectral classification, for Hα measurements, and to assess membership together with IR color-color and color-magnitude diagrams and additional information from the X-ray data. Results: We found that 3 sources show lithium absorption, with equivalent widths (EWs) of 500 mÅ, broad spectral line profiles, indicating rotational velocities of 20{-}40 km s-1, radial velocities consistent with those for known members, and Hα emission. Two of them are classified as new weak-lined T Tauri stars, while the EW ( -9 Å) of the Hα line and its broad asymmetric profile clearly indicate that the third star (XEST-26-062) is a classical T Tauri star. Fourteen sources observed with DOLORES are M-type stars. Fifteen sources show Hα emission. Six of them have spectra that indicate surface gravity lower than in main sequence stars, and their de-reddened positions in IR color-magnitude diagrams are consistent with their derived spectral type and with pre-main sequence models at the distance of the TMC. The K-type star XEST-11-078 is confirmed as a new member on the basis of the strength of the Hα emission line. Overall, we confirm membership to the TMC for 10 out of 25 X-ray sources observed in the optical. Three

SCUBA and HIRES Results for Protostellar Cores in the MON OB1 Dark Cloud

NASA Astrophysics Data System (ADS)

Wolf-Chase, G.; Moriarty-Schieven, G.; Fich, M.; Barsony, M.

1999-05-01

We have used HIRES-processing of IRAS data and point-source modelling techniques (Hurt & Barsony 1996; O'Linger 1997; Barsony et al. 1998), together with submillimeter continuum imaging using the Submillimeter Common-User Bolometer Array (SCUBA) on the 15-meter James Clerk Maxwell Telescope (JCMT), to search CS cores in the Mon OB1 dark cloud (Wolf-Chase, Walker, & Lada 1995; Wolf-Chase & Walker 1995) for deeply embedded sources. These observations, as well as follow-up millimeter photometry at the National Radio Astronomy Observatory (NRAO) 12-meter telescope on Kitt Peak, have lead to the identification of two Class 0 protostellar candidates, which were previously unresolved from two brighter IRAS point sources (IRAS 06382+0939 & IRAS 06381+1039) in this cloud. Until now, only one Class 0 object had been confirmed in Mon OB1; the driving source of the highly-collimated outflow NGC 2264 G (Ward-Thompson, Eiroa, & Casali 1995; Margulis et al. 1990; Lada & Fich 1996), which lies well outside the extended CS cores. One of the new Class 0 candidates may be an intermediate-mass source associated with an H_2O maser, and the other object is a low-mass source which may be associated with a near-infrared jet, and possibly with a molecular outflow. We report accurate positions for the new Class 0 candidates, based on the SCUBA images, and present new SEDs for these sources, as well as for the brighter IRAS point sources. A portion of this work was performed while GWC held a President's Fellowship from the University of California. MB and GWC gratefully acknowledge financial support from MB's NSF CAREER Grant, AST97-9753229.

Molecular Anions in Protostars, Prestellar Cores and Dark Clouds

NASA Technical Reports Server (NTRS)

Cordiner, Martin; Charnley, Steven; Buckle, Jane; Wash, Catherine; Millar, Tom

2011-01-01

From our recent survey work using the Green Bank Telescope, microwave emission lines from the hydrocarbon anion C6H(-) and its parent neutral C6H have been detected in six new sources. Using HC3N = 10(exp -9) emission maps, we targeted the most carbon-chain-rich sources for our anion survey, which included the low-mass Class 0 protostar L1251A-IRS3, the prestellar cores L1389-SMM1 and L1512, and the interstellar clouds Ll172A, TMC-1C and L1495B. Derived [C6H(-)]/[C6H] anion-to-neutral ratios are approximately 1-10. The greatest C6H(-) column densities are found in the quiescent clouds TMC-1C and L1495B, but the anion-to-neutral ratios are greatest in the prestellar cores and protostars. These results are interpreted in terms of the physical and chemical properties of the sources, and the implications for molecular cloud chemistry are discussed.

A whole-genome assembly of the domestic cow, Bos taurus

USDA-ARS?s Scientific Manuscript database

Background: The genome of the domestic cow, Bos taurus, was sequenced using a mixture of hierarchical and whole-genome shotgun sequencing methods. Results: We have assembled the 35 million sequence reads and applied a variety of assembly improvement techniques, creating an assembly of 2.86 billion b...

Islands in the Sky: Ecophysiological Cloud-Vegetation Linkages in Southern Appalachian Mountain Cloud Forests

NASA Astrophysics Data System (ADS)

Reinhardt, K.; Emanuel, R. E.; Johnson, D. M.

2013-12-01

Mountain cloud forest (MCF) ecosystems are characterized by a high frequency of cloud fog, with vegetation enshrouded in fog. The altitudinal boundaries of cloud-fog zones co-occur with conspicuous, sharp vegetation ecotones between MCF- and non-MCF-vegetation. This suggests linkages between cloud-fog and vegetation physiology and ecosystem functioning. However, very few studies have provided a mechanistic explanation for the sharp changes in vegetation communities, or how (if) cloud-fog and vegetation are linked. We investigated ecophysiological linkages between clouds and trees in Southern Appalachian spruce-fir MCF. These refugial forests occur in only six mountain-top, sky-island populations, and are immersed in clouds on up to 80% of all growing season days. Our fundamental research questions was: How are cloud-fog and cloud-forest trees linked? We measured microclimate and physiology of canopy tree species across a range of sky conditions (cloud immersed, partly cloudy, sunny). Measurements included: 1) sunlight intensity and spectral quality; 2) carbon gain and photosynthetic capacity at leaf (gas exchange) and ecosystem (eddy covariance) scales; and 3) relative limitations to carbon gain (biochemical, stomatal, hydraulic). RESULTS: 1) Midday sunlight intensity ranged from very dark (<30 μmol m-2 s-1, under cloud-immersed conditions) to very bright (>2500 μmol m-2 s-1), and was highly variable on minute-to-minute timescales whenever clouds were present in the sky. Clouds and cloud-fog increased the proportion of blue-light wavelengths 5-15% compared to sunny conditions, and altered blue:red and red:far red ratios, both of which have been shown to strongly affect stomatal functioning. 2) Cloud-fog resulted in ~50% decreased carbon gain at leaf and ecosystem scales, due to sunlight levels below photosynthetic light-saturation-points. However, greenhouse studies and light-response-curve analyses demonstrated that MCF tree species have low light

Subsonic islands within a high-mass star-forming infrared dark cloud

NASA Astrophysics Data System (ADS)

Sokolov, Vlas; Wang, Ke; Pineda, Jaime E.; Caselli, Paola; Henshaw, Jonathan D.; Barnes, Ashley T.; Tan, Jonathan C.; Fontani, Francesco; Jiménez-Serra, Izaskun; Zhang, Qizhou

2018-03-01

High-mass star forming regions are typically thought to be dominated by supersonic motions. We present combined Very Large Array and Green Bank Telescope (VLA+GBT) observations of NH3 (1,1) and (2,2) in the infrared dark cloud (IRDC) G035.39-00.33, tracing cold and dense gas down to scales of 0.07 pc. We find that, in contrast to previous, similar studies of IRDCs, more than a third of the fitted ammonia spectra show subsonic non-thermal motions (mean line width of 0.71 km s-1), and sonic Mach number distribution peaks around ℳ = 1. As possible observational and instrumental biases would only broaden the line profiles, our results provide strong upper limits to the actual value of ℳ, further strengthening our findings of narrow line widths. This finding calls for a re-evaluation of the role of turbulent dissipation and subsonic regions in massive-star and cluster formation. Based on our findings in G035.39, we further speculate that the coarser spectral resolution used in the previous VLA NH3 studies may have inhibited the detection of subsonic turbulence in IRDCs. The reduced turbulent support suggests that dynamically important magnetic fields of the 1 mG order would be required to support against possible gravitational collapse. Our results offer valuable input into the theories and simulations that aim to recreate the initial conditions of high-mass star and cluster formation.

Shedding light on baryonic dark matter

NASA Technical Reports Server (NTRS)

Silk, Joseph

1991-01-01

Halo dark matter, if it is baryonic, may plausibly consist of compact stellar remnants. Jeans mass clouds containing 10 to the 6th to 10 to the 8th solar masses could have efficiently formed stars in the early universe and could plausibly have generated, for a suitably top-heavy stellar initial mass function, a high abundance of neutron stars as well as a small admixture of long-lived low mass stars. Within the resulting clusters of dark remnants, which eventually are tidally disrupted when halos eventually form, captures of neutron stars by nondegenerate stars resulted in formation of close binaries. These evolve to produce, by the present epoch, an observable X-ray signal associated with dark matter aggregations in galaxy cluster cores.

Shedding light on baryonic dark matter.

PubMed

Silk, J

1991-02-01

Halo dark matter, if it is baryonic, may plausibly consist of compact stellar remnants. Jeans mass clouds containing 10(6) to 10(8) solar masses could have efficiently formed stars in the early universe and could plausibly have generated, for a suitably top-heavy stellar initial mass function, a high abundance of neutron stars as well as a small admixture of long-lived low mass stars. Within the resulting clusters of dark remnants, which eventually are tidally disrupted when halos eventually form, captures of neutron stars by non-degenerate stars resulted in formation of close binaries. These evolve to produce, by the present epoch, an observable x-ray signal associated with dark matter aggregations in galaxy halos and galaxy cluster cores.

Frequencies of polymorphisms associated with BSE resistance differ significantly between Bos taurus, Bos indicus, and composite cattle

PubMed Central

Brunelle, Brian W; Greenlee, Justin J; Seabury, Christopher M; Brown, Charles E; Nicholson, Eric M

2008-01-01

Background Transmissible spongiform encephalopathies (TSEs) are neurodegenerative diseases that affect several mammalian species. At least three factors related to the host prion protein are known to modulate susceptibility or resistance to a TSE: amino acid sequence, atypical number of octapeptide repeats, and expression level. These factors have been extensively studied in breeds of Bos taurus cattle in relation to classical bovine spongiform encephalopathy (BSE). However, little is currently known about these factors in Bos indicus purebred or B. indicus × B. taurus composite cattle. The goal of our study was to establish the frequency of markers associated with enhanced susceptibility or resistance to classical BSE in B. indicus purebred and composite cattle. Results No novel or TSE-associated PRNP-encoded amino acid polymorphisms were observed for B. indicus purebred and composite cattle, and all had the typical number of octapeptide repeats. However, differences were observed in the frequencies of the 23-bp and 12-bp insertion/deletion (indel) polymorphisms associated with two bovine PRNP transcription regulatory sites. Compared to B. taurus, B. indicus purebred and composite cattle had a significantly lower frequency of 23-bp insertion alleles and homozygous genotypes. Conversely, B. indicus purebred cattle had a significantly higher frequency of 12-bp insertion alleles and homozygous genotypes in relation to both B. taurus and composite cattle. The origin of these disparities can be attributed to a significantly different haplotype structure within each species. Conclusion The frequencies of the 23-bp and 12-bp indels were significantly different between B. indicus and B. taurus cattle. No other known or potential risk factors were detected for the B. indicus purebred and composite cattle. To date, no consensus exists regarding which bovine PRNP indel region is more influential with respect to classical BSE. Should one particular indel region and

Storm clouds on Saturn: Lightning-induced chemistry and associated materials consistent with Cassini/VIMS spectra

USGS Publications Warehouse

Baines, K.H.; Delitsky, M.L.; Momary, T.W.; Brown, R.H.; Buratti, B.J.; Clark, R.N.; Nicholson, P.D.

2009-01-01

Thunderstorm activity on Saturn is associated with optically detectable clouds that are atypically dark throughout the near-infrared. As observed by Cassini/VIMS, these clouds are ~20% less reflective than typical neighboring clouds throughout the spectral range from 0.8 ??m to at least 4.1 ??m. We propose that active thunderstorms originating in the 10-20 bar water-condensation region vertically transport dark materials at depth to the ~1 bar level where they can be observed. These materials in part may be produced by chemical processes associated with lightning, likely within the water clouds near the ~10 bar freezing level of water, as detected by the electrostatic discharge of lightning flashes observed by Cassini/RPWS (e.g., Fischer et al. 2008, Space Sci. Rev., 137, 271-285). We review lightning-induced pyrolytic chemistry involving a variety of Saturnian constituents, including hydrogen, methane, ammonia, hydrogen sulfide, phosphine, and water. We find that the lack of absorption in the 1-2 ??m spectral region by lightning-generated sulfuric and phosphorous condensates renders these constituents as minor players in determining the color of the dark storm clouds. Relatively small particulates of elemental carbon, formed by lightning-induced dissociation of methane and subsequently upwelled from depth - perhaps embedded within and on the surface of spectrally bright condensates such as ammonium hydrosulfide or ammonia - may be a dominant optical material within the dark thunderstorm-related clouds of Saturn. ?? 2009 Elsevier Ltd. All rights reserved.

Neptune - Changes in Great Dark Spot

NASA Technical Reports Server (NTRS)

1989-01-01

These images show changes in the clouds around Neptune's Great Dark Spot (GDS) over a four and one-half-day period. From top to bottom the images show successive rotations of the planet an interval of about 18 hours. The GDS is at a mean latitude of 20 degrees south, and covers about 30 degrees of longitude. The violet filter of the Voyager narrow angle camera was used to produce these images at distances ranging from 17 million kilometers (10.5 million miles) at the top, to 10 million kilometers (6.2 million miles) at bottom. The images have been mapped on to a rectangular latitude longitude grid to remove the effects of changing viewing geometry and the changing distance to Neptune. The sequence shows a large change in the western end (left side) of the GDS, where a dark extension apparent in the earlier images converges into an extended string of small dark spots over the next five rotations. This 'string of beads' extends from the GDS at a surprisingly large angle relative to horizontal lines of constant latitude. The large bright cloud at the southern (bottom) border of the GDS is a more or less permanent companion of the GDS. The apparent motion of smaller clouds at the periphery of the GDS suggests a counterclockwise rotation of the GDS reminiscent of flow around the Great Red Spot in Jupiter's atmosphere. This activity of the GDS is surprising because the total energy flux from the sun and from Neptune's interior is only 5 percent as large as the total energy flux on Jupiter.

Dark Murky Clouds in the Bright Milky Way

NASA Image and Video Library

2011-08-24

This infrared image from NASA Wide-field Infrared Survey Explorer shows exceptionally cold, dense cloud cores seen in silhouette against the bright diffuse infrared glow of the plane of the Milky Way galaxy.

Jovian cloud structure from 5-mu M images

NASA Astrophysics Data System (ADS)

Ortiz, J. L.; Moreno, F.; Molina, A.; Roos-Serote, M.; Orton, G. S.

1999-09-01

Most radiative transfer studies place the cloud clearings responsible for the 5-mu m bright areas at pressure levels greater than 1.5 bar whereas the low-albedo clouds are placed at lower pressure levels, in the so-called ammonia cloud. If this picture is correct, and assuming that the strong vertical shear of the zonal wind detected by the Galileo Entry Probe exists at all latitudes in Jupiter, the bright areas at 5 mu m should drift faster than the dark clouds, which is not observed. At the Galileo Probe Entry latitude this can be explained by a wave, but this is not a likely explanation for all regions where the anticorrelation between 5-mu m brightness and red-nIR reflectivity is observed. Therefore, either the vertical zonal wind shears are not global or cloud clearings and dark clouds are located at the same pressure level. We have developed a multiple scattering radiative transfer code to model the limb-darkening at several jovian features derived from IRTF 4.8-mu m images, in order to retrieve information on the cloud levels. The limb darkening coefficients range from 1.4 at hot spots to 0.58 at the Equatorial Region. We also find that reflected light is dominant over thermal emission in the Equatorial Region, as already pointed out by other investigators. Preliminary results from our code tend to favor the idea that the ammonia cloud is a very high-albedo cloud with little influence on the contrast seen in the red and nIR and that a deeper cloud at P >1.5 bar can be responsible for the cloud clearings and for the low-albedo features simultaneously. This research was supported by the Comision Interministerial de Ciencia y Tecnologia under contract ESP96-0623.

Stellar Clustering in the Dark Filament IRDC 321.706+0.066

NASA Astrophysics Data System (ADS)

Soto King, Piera

2017-06-01

We investigate the star formation process in the infrared dark cloud IRDC 321.706+0.066, where are located three infrared clusters recently discovered by Barbá et al. (2015) using images of the VISTA Variables in the Vía Láctea public survey: La Serena 210, 211 and 212. The aim is to characterize the stellar content of the three clusters and to investigate the star formation sequence in a filamentary dark cloud. We present a new photometric analysis of VVV images, and we use data from others surveys. We confirmed the presence of the three VVV clusters. And also, we propose a new cluster

Genetic variation and differentiation of bison (Bison bison) subspecies and cattle (Bos taurus) breeds and subspecies.

PubMed

Cronin, Matthew A; MacNeil, Michael D; Vu, Ninh; Leesburg, Vicki; Blackburn, Harvey D; Derr, James N

2013-01-01

The genetic relationship of American plains bison (Bison bison bison) and wood bison (Bison bison athabascae) was quantified and compared with that among breeds and subspecies of cattle. Plains bison from 9 herds (N = 136), wood bison from 3 herds (N = 65), taurine cattle (Bos taurus taurus) from 14 breeds (N = 244), and indicine cattle (Bos taurus indicus) from 2 breeds (N = 53) were genotyped for 29 polymorphic microsatellite loci. Bayesian cluster analyses indicate 3 groups, 2 of which are plains bison and 1 of which is wood bison with some admixture, and genetic distances do not show plains bison and wood bison as distinct groups. Differentiation of wood bison and plains bison is also significantly less than that of cattle breeds and subspecies. These and other genetic data and historical interbreeding of bison do not support recognition of extant plains bison and wood bison as phylogenetically distinct subspecies.

An X-ray Observation of the L1251 Dark Cloud

NASA Technical Reports Server (NTRS)

Simon, Theodore

2006-01-01

An X-ray image of the L1251 dark cloud in Cepheus was obtained with the XMM-Newton telescope. More than three dozen sources were detected above a 3 delta limit in X-ray luminosity of L(sub X = 10(exp 29) ergs/s. Among the detections are eight optically visible T Tauri stars, which had been identified in earlier work from their emission at H(alpha). The two strongest X-ray sources have steady luminosities of L(sub X) approx. 10(exp 31) ergs/s and are at the saturation limit for X-ray activity in late-type stars, L(sub X)/L(sub bol) approx. 10(exp -3). X-ray emission was also observed from two CO emission cores in L1251, core C (L1251A) and core E (L1251B). Both regions contain high-velocity molecular gas, bright IRAS sources (Class I protostars), thermal radio sources, and Herbig-Haro (HH) jets. In L1251A strong X-ray emission was discovered in close proximity to the near-inbred and radio source IRSA/VLA 7 and to IRAS 22343+7501. IRSA/VLA 7 thus appears to be the most likely source of the molecular and HH outflows in L1251A. In L1251B X-ray emission was observed from a visible T Tauri star, KP2-44, which is thought to be the driving source for HH 189. Also reported is the tentative detection of X-ray emission from VLA 3, a thermal radio continuum source in L1251B that is closely associated with the extreme Class I protostar IRAS 22376+7455.

Looking at the bright side of the rho Ophiuchi dark cloud. Far infrared spectrophotometric observations of the rho Oph cloud with the ISO

NASA Astrophysics Data System (ADS)

Liseau, R.; White, G. J.; Larsson, B.; Sidher, S.; Olofsson, G.; Kaas, A.; Nordh, L.; Caux, E.; Lorenzetti, D.; Molinari, S.; Nisini, B.; Sibille, F.

1999-04-01

We present far infrared (45-195 mu m) spectrophotometric observations with the Iso-Lws of the active star forming rho Oph main cloud (L 1688). The [C ii] 158 mu m and [O i] 63 mu m lines were detected at each of the 33 positions observed, whereas the [O i] 145 mu m line was clearly seen toward twelve. The principal observational result is that the [C ii] 158 mu m line fluxes exhibit a clear correlation with projected distance from the dominant stellar source in the field (HD 147889). We interpret this in terms of Pdr-type emission from the surface layers of the rho Ophc. The observed [C ii] 158 mu m/[O i] 63 mu m flux ratios are larger than unity everywhere. A comparison of the [C ii] 158 mu m line emission and the Fir dust continuum fluxes yields estimates of the efficiency at which the gas in the cloud converts stellar to [C ii] 158 mu m photons (chi_ {_C II},>_{ ~ },0.5%). We first develop an empirical model, which provides us with a three dimensional view of the far and bright side of the dark rho Ophc, showing that the cloud surface towards the putative energy source is concave. This model also yields quantitative estimates of the incident flux of ultraviolet radiation (G_0 ~ , \\powten{1} - \\powten{2}) and of the degree of clumpiness/texture of the cloud surface (filling of the 80({') '} beam ~ ,0.2). Subsequently, we use theoretical models of Pdr s to derive the particle density, n(H), and the temperature structures, for T_gas and T_dust, in the surface layers of the rho Ophc. T_gas is relatively low, ~ ,60 K, but higher than T_dust ( ~ ,30 K), and densities are generally found within the interval (1-3) \\powten{4} cm(-3) . These Pdr models are moderately successful in explaining the Lws observations. They correctly predict the [O i] 63 mu m and [C ii] 158 mu m line intensities and the observed absence of any molecular line emission. The models do fail, however, to reproduce the observed small [O i] 63 mu m/[O i] 145 mu m ratios. We examine several possible

Absolute extinction and the influence of environment - Dark cloud sight lines toward VCT 10, 30, and Walker 67

NASA Technical Reports Server (NTRS)

Cardelli, Jason A.; Clayton, Geoffrey C.

1991-01-01

The range of validity of the average absolute extinction law (AAEL) proposed by Cardelli et al. (1988 and 1989) is investigated, combining published visible and NIR data with IUE UV observations for three lines of sight through dense dark cloud environments with high values of total-to-selective extinction. The characteristics of the data sets and the reduction and parameterization methods applied are described in detail, and the results are presented in extensive tables and graphs. Good agreement with the AAEL is demonstrated for wavelengths from 3.4 microns to 250 nm, but significant deviations are found at shorter wavelengths (where previous studies of lines of sight through bright nebulosity found good agreement with the AAEL). These differences are attributed to the effects of coatings on small-bump and FUV grains.

Testing the variability of the proton-to-electron mass ratio from observations of methanol in the dark cloud core L1498

NASA Astrophysics Data System (ADS)

Daprà, M.; Henkel, C.; Levshakov, S. A.; Menten, K. M.; Muller, S.; Bethlem, H. L.; Leurini, S.; Lapinov, A. V.; Ubachs, W.

2017-12-01

The dependence of the proton-to-electron mass ratio, μ, on the local matter density was investigated using methanol emission in the dense dark cloud core L1498. Towards two different positions in L1498, five methanol transitions were detected and an extra line was tentatively detected at a lower confidence level in one of the positions. The observed centroid frequencies were then compared with their rest-frame frequencies derived from least-squares fitting to a large data set. Systematic effects, as the underlying methanol hyperfine structure and the Doppler tracking of the telescope, were investigated and their effects were included in the total error budget. The comparison between the observations and the rest-frame frequencies constrains potential μ variation at the level of Δμ/μ < 6 × 10-8, at a 3σ confidence level. For the dark cloud, we determine a total CH3OH (A+E) beam averaged column density of ∼3-4 × 1012 cm-2 (within roughly a factor of two), an E- to A-type methanol column density ratio of N(A-CH3OH)/N(E-CH3OH) ∼1.00 ± 0.15, a density of n(H2) = 3 × 105 cm-3 (again within a factor of two) and a kinetic temperature of Tkin = 6 ± 1 K. In a kinetic model including the line intensities observed for the methanol lines, the n(H2) density is higher and the temperature is lower than that derived in previous studies based on different molecular species; the intensity of the 10 → 1-1 E line strength is not well reproduced.

Twomey Effect in Subtropical Stratocumulus Clouds from UV Depolarization LIDAR

NASA Astrophysics Data System (ADS)

de Graaf, Martin; Brown, Jessica; Donovan, David

2018-04-01

Marine stratocumulus clouds are important climate regulators, reflecting sunlight over a dark ocean background. A UV-depolarization lidar on Ascension, a small remote island in the south Atlantic, measured cloud droplet sizes and number concentration using an inversion method based on Monte Carlo (MC) modelling of multiple scattering in idealised semiadiabatic clouds. The droplet size and number concentration weremodulated due to smoke from the African continent, measured by the same instrument.

Far-infrared observations of a star-forming region in the Corona Australis dark cloud

NASA Technical Reports Server (NTRS)

Cruz-Gonzalez, I.; Mcbreen, B.; Fazio, G. G.

1984-01-01

A high-resolution far-IR (40-250-micron) survey of a 0.9-sq-deg section of the core region of the Corona Australis dark cloud (containing very young stellar objects such as T Tauri stars, Herbig Ae and Be stars, Herbig-Haro objects, and compact H II regions) is presented. Two extended far-IR sources were found, one associated with the Herbig emission-line star R CrA and the other with the irregular emission-line variable star TY CrA. The two sources have substantially more far-IR radiation than could be expected from a blackbody extrapolation of their near-IR fluxes. The total luminosities of these sources are 145 and 58 solar luminosity, respectively, implying that the embedded objects are of intermediate or low mass. The infrared observations of the sources associated with R CrA and TY CrA are consistent with models of the evolution of protostellar envelopes of intermediate mass. However, the TY CrA source appears to have passed the evolutionary stage of expelling most of the hot dust near the central source, yielding an age of about 1 Myr.

The new Be-type star HD 147196 in the Rho Ophiuchi dark cloud region

NASA Technical Reports Server (NTRS)

The, P. S.; Perez, M. R.; De Winter, D.; Van Den Ancker, M. E.

1993-01-01

The newly discovered hot-emission line star, HD 147196 in the Rho Oph dark cloud region was observed spectroscopically and photometrically and high and low resolution IUE spectra were obtained. The finding of Irvine (1990) that this relatively bright star show its H-alpha-line in emission is confirmed. Previous H-alpha-surveys of the Rho Oph star-forming region did not detect HD 147196 as an H-alpha-emission star, meaning that it must recently be very active and has perhaps transformed itself from a B-type star at shell phase to a Be-phase. The Mg II h + k resonance lines are in absorption and they appear to be interstellar in nature, which means that either the abundance of Mg in the extended atmosphere of the star is low or that the shell is not extended enough to produce emission lines of Mg II. Photometric observations of this B8 V type star do not show any variations during at least the years covered by our monitoring or any excess of NIR radiation in its spectral energy distribution up to the M-passband at 4.8 microns.

Distance to Dark Bodies

NASA Technical Reports Server (NTRS)

2007-01-01

Using the unique orbit of NASA's Spitzer Space Telescope and a depth-perceiving trick called parallax, astronomers have determined the distance to an invisible Milky Way object called OGLE-2005-SMC-001. This artist's concept illustrates how this trick works: different views from both Spitzer and telescopes on Earth are combined to give depth perception.

Our Milky Way galaxy is heavier than it looks, and scientists use the term 'dark matter' to describe all the 'heavy stuff' in the universe that seems to be present but invisible to our telescopes. While much of this dark matter is likely made up of exotic materials, different from the ordinary particles that make up the world around us, some may consist of dark celestial bodies -- like planets, black holes, or failed stars -- that do not produce light or are too faint to detect from Earth. OGLE-2005-SMC-001 is one of these dark celestial bodies.

Although astronomers cannot see a dark body, they can sense its presence from the way light acts around it. When a dark body like OGLE-2005-SMC-001 passes in front of a bright star, its gravity causes the background starlight to bend and brighten, a process called gravitational microlensing. When the observing telescope, dark body, and star system are closely aligned, the microlensing event reaches maximum, or peak, brightness.

A team of astronomers first sensed OGLE-2005-SMC-001's presence when it passed in front of a star in a neighboring satellite galaxy called the Small Magellanic Cloud. In this artist's rendering, the satellite galaxy is depicted as the fuzzy structure sitting to the left of Earth. Once they detected this microlensing event, the scientists used Spitzer and the principle of parallax to figure out its distance. Humans naturally use parallax to determine distance. Each eye sees the distance of an object differently. The brain takes each eye's perspective and instantaneously calculates how far away the object is.

To determine OGLE

Newly detected molecules in dense interstellar clouds

NASA Astrophysics Data System (ADS)

Irvine, William M.; Avery, L. W.; Friberg, P.; Matthews, H. E.; Ziurys, L. M.

Several new interstellar molecules have been identified including C2S, C3S, C5H, C6H and (probably) HC2CHO in the cold, dark cloud TMC-1; and the discovery of the first interstellar phosphorus-containing molecule, PN, in the Orion "plateau" source. Further results include the observations of 13C3H2 and C3HD, and the first detection of HCOOH (formic acid) in a cold cloud.

Clouds on Hot Jupiters Illustration

NASA Image and Video Library

2016-10-18

Hot Jupiters are exoplanets that orbit their stars so tightly that their temperatures are extremely high, reaching over 2,400 degrees Fahrenheit (1600 Kelvin). They are also tidally locked, so one side of the planet always faces the sun and the other is in permanent darkness. Research suggests that the "dayside" is largely free of clouds, while the "nightside" is heavily clouded. This illustration represents how hot Jupiters of different temperatures and different cloud compositions might appear to a person flying over the dayside of these planets on a spaceship, based on computer modeling. Cooler planets are entirely cloudy, whereas hotter planets have morning clouds only. Clouds of different composition have different colors, whereas the clear sky is bluer than on Earth. For the hottest planets, the atmosphere is hot enough on the evening side to glow like a charcoal. Figure 1 shows an approximation of what various hot Jupiters might look like based on a combination of computer modeling and data from NASA's Kepler Space Telescope. From left to right it shows: sodium sulfide clouds (1000 to 1200 Kelvin), manganese sulfide clouds (1200 to 1600 Kelvin), magnesium silicate clouds (1600 to 1800 Kelvin), magnesium silicate and aluminum oxide clouds (1800 Kelvin) and clouds composed of magnesium silicate, aluminum oxide, iron and calcium titanate (1900 to 2200 Kelvin). http://photojournal.jpl.nasa.gov/catalog/PIA21074

A simple model for the cloud adjacency effect and the apparent bluing of aerosols near clouds

NASA Astrophysics Data System (ADS)

Marshak, Alexander; Wen, Guoyong; Coakley, James A.; Remer, Lorraine A.; Loeb, Norman G.; Cahalan, Robert F.

2008-07-01

In determining aerosol-cloud interactions, the properties of aerosols must be characterized in the vicinity of clouds. Numerous studies based on satellite observations have reported that aerosol optical depths increase with increasing cloud cover. Part of the increase comes from the humidification and consequent growth of aerosol particles in the moist cloud environment, but part comes from 3-D cloud-radiative transfer effects on the retrieved aerosol properties. Often, discerning whether the observed increases in aerosol optical depths are artifacts or real proves difficult. The paper only addresses the cloud-clear sky radiative transfer interaction part. It provides a simple model that quantifies the enhanced illumination of cloud-free columns in the vicinity of clouds that are used in the aerosol retrievals. This model is based on the assumption that the enhancement in the cloud-free column radiance comes from enhanced Rayleigh scattering that results from the presence of the nearby clouds. This assumption leads to a larger increase of AOT for shorter wavelengths, or to a "bluing" of aerosols near clouds. The assumption that contribution from molecular scattering dominates over aerosol scattering and surface reflection is justified for the case of shorter wavelengths, dark surfaces, and an aerosol layer below the cloud tops. The enhancement in Rayleigh scattering is estimated using a stochastic cloud model to obtain the radiative flux reflected by broken clouds and comparing this flux with that obtained with the molecules in the atmosphere causing extinction, but no scattering.

Screaming Clouds

NASA Astrophysics Data System (ADS)

Fikke, Svein; Egill Kristjánsson, Jón; Nordli, Øyvind

2017-04-01

"Mother-of-pearl clouds" appear irregularly in the winter stratosphere at high northern latitudes, about 20-30 km above the surface of the Earth. The size range of the cloud particles is near that of visible light, which explains their extraordinary beautiful colours. We argue that the Norwegian painter Edvard Munch could well have been terrified when the sky all of a sudden turned "bloodish red" after sunset, when darkness was expected. Hence, there is a high probability that it was an event of mother-of-pearl clouds which was the background for Munch's experience in nature, and for his iconic Scream. Currently, the leading hypothesis for explaining the dramatic colours of the sky in Munch's famous painting is that the artist was captivated by colourful sunsets following the enormous Krakatoa eruption in 1883. After carefully considering the historical accounts of some of Munch's contemporaries, especially the physicist Carl Störmer, we suggest an alternative hypothesis, namely that Munch was inspired by spectacular occurrences of mother-of-pearl clouds. Such clouds, which have a wave-like structure akin to that seen in the Scream were first observed and described only a few years before the first version of this motive was released in 1892. Unlike clouds related to conventional weather systems in the troposphere, mother-of-pearl clouds appear in the stratosphere, where significantly different physical conditions prevail. This result in droplet sizes within the range of visible light, creating the spectacular colour patterns these clouds are famous for. Carl Störmer observed such clouds, and described them in minute details at the age of 16, but already with a profound interest in science. He later noted that "..these mother-of-pearl clouds was a vision of indescribable beauty!" The authors find it logical that the same vision could appear scaring in the sensible mind of a young artist unknown to such phenomena.

Star counts and visual extinctions in dark nebulae

NASA Technical Reports Server (NTRS)

Dickman, R. L.

1978-01-01

Application of star count techniques to the determination of visual extinctions in compact, fairly high-extinction dark nebulae is discussed. Particular attention is devoted to the determination of visual extinctions for a cloud having a possibly anomalous ratio of total to selective extinction. The techniques discussed are illustrated in application at two colors to four well-known compact dust clouds or Bok globules: Barnard 92, B 133, B 134, and B 335. Minimum masses and lower limits to the central extinction of these objects are presented.

The relative influence of temperature and humidity on cutaneous function in Bos indicus and Bos taurus females

NASA Astrophysics Data System (ADS)

Egbunike, G. N.; Ogunmola, A. L.; Amakiri, S. F.

1983-09-01

The relative importance of dry- and wet-bulb temperatures on cutaneous function in Bos indicus and Bos taurus females under humid tropical climatic conditions was evaluated. The parameters investigated were sweating rate and skin temperature, while the species utilised were zebu White Fulani ( Bos indicus) and German Brown and German Black and White ( Bos taurus). The sweating rate, irrespective of breed, differed with the site of sampling and was more influenced by dry-bulb (59%) than by wet-bulb temperature (41%). Skin temperature responded more to wet-bulb temperature in White Fulani and German Black and White cattle, but not in German Brown cattle. It is concluded that the response of the animals, with respect to sweating, was similar but that the efficiency of sweating, judged by the lowering of skin temperature, was higher in Bos indicus than in Bos taurus. This, in part, may explain the higher degree of comfort demonstrated by Bos indicus under tropical conditions.

Genotype x environment interactions for fatty acid profiles in Bos indicus and Bos taurus finished on pasture or grain.

PubMed

Bressan, M C; Rossato, L V; Rodrigues, E C; Alves, S P; Bessa, R J B; Ramos, E M; Gama, L T

2011-01-01

A study was conducted to characterize lipid profiles in the M. longissimus thoracis of commercial Brazilian beef and to assess how those profiles are influenced by finishing system, genetic group, and their interaction. Intramuscular fat (IMF) and fatty acid (FA) profiles were determined in 160 bulls of the Bos taurus (n = 75) and Bos indicus (n = 85) genetic groups, finished on pasture (n = 46) or with grain supplementation (n = 114) and slaughtered in a commercial abattoir. Finishing system had a major impact on the deposition of IMF, as well as on the concentration of SFA, PUFA, and their ratio, but genetic groups showed important differences in the ability to convert SFA into cis-9 MUFA and to convert 16:0 into 18:0. When compared with pasture-finished animals, those finished with grain had greater content of IMF and SFA (P < 0.01), similar amounts of MUFA (P > 0.05), and about one-half the amount of PUFA (P < 0.01). Except for MUFA, differences in FA profiles among finishing systems were mostly mediated through their effect on IMF, even though the relationship of IMF with groups of FA differed among finishing systems. Under grain finishing, B. taurus had less SFA and greater MUFA than B. indicus (P < 0.01), but no differences were observed in PUFA (P > 0.05). With pasture-finishing, no differences were observed among the 2 genetic groups in SFA and MUFA (P > 0.05), but PUFA were decreased in B. taurus (P < 0.01). When genetic groups were compared in grain-finishing, B. taurus had a decreased ability for elongation and B. indicus had a decreased aptitude for desaturation of FA. On the other hand, with pasture-finishing a greater deposition of intermediate FA from ruminal biohydrogenation was observed in B. indicus than in B. taurus. Overall, FA profiles were affected more by finishing system in B. indicus than in B. taurus.

GOT C+ Survey of [CII] 158 Micrometer Emission: Atomic to Molecular Cloud Transitions in the Inner Galaxy

NASA Technical Reports Server (NTRS)

Velusamy, T.; Langer, W. D.; Willacy, K.; Pineda, J. L.; Goldsmith, P. F.

2012-01-01

We present the results of the distribution of CO-dark H2 gas in a sample of 2200 interstellar clouds in the inner Galaxy (l = 90 deg to +57 deg) detected in the velocity resolved [CII] spectra observed in the GOT C+ survey using the Herschel HIFI. We analyze the [CII] intensities along with the ancillary HI, (12)CO and (13)CO data for each cloud to determine their evolutionary state and to derive the H2 column densities in the C(+) and C(+)/CO transition layers in the cloud. We discuss the overall Galactic distribution of the [CII] clouds and their properties as a function Galactic radius. GOT C+ results on the global distribution of [CII] clouds and CO-dark H2 gas traces the FUV and star formation rates in the Galactic disk.

Featured Image: A New Dark Vortex on Neptune

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2018-03-01

This remarkable series of images by the Hubble Space Telescope (click for the full view) track a dark vortex only the fifth ever observed on Neptune as it evolves in Neptunes atmosphere. These Hubble images, presented in a recent study led by Michael Wong (University of California, Berkeley), were taken in 2015 September, 2016 May, 2016 October, and 2017 October; the observations have monitored the evolution of the vortex as it has gradually weakened and drifted polewards. Confirmation of the vortex solved a puzzle that arose in 2015, when astronomers spotted an unexplained outburst of cloud activity on Neptune. This outburst was likely a group of bright companion clouds that form as air flows over high-pressure dark vortices, causing gases to freeze into methane ice crystals. To learn more about what the authors have since learned by studying this vortex, check out the paper below.CitationMichael H. Wong et al 2018 AJ 155 117. doi:10.3847/1538-3881/aaa6d6

Iapetus Bright and Dark Terrains

NASA Technical Reports Server (NTRS)

1990-01-01

Saturn's outermost large moon, Iapetus, has a bright, heavily cratered icy terrain and a dark terrain, as shown in this Voyager 2 image taken on August 22, 1981. Amazingly, the dark material covers precisely the side of Iapetus that leads in the direction of orbital motion around Saturn (except for the poles), whereas the bright material occurs on the trailing hemisphere and at the poles. The bright terrain is made of dirty ice, and the dark terrain is surfaced by carbonaceous molecules, according to measurements made with Earth-based telescopes. Iapetus' dark hemisphere has been likened to tar or asphalt and is so dark that no details within this terrain were visible to Voyager 2. The bright icy hemisphere, likened to dirty snow, shows many large impact craters. The closest approach by Voyager 2 to Iapetus was a relatively distant 600,000 miles, so that our best images, such as this, have a resolution of about 12 miles. The dark material is made of organic substances, probably including poisonous cyano compounds such as frozen hydrogen cyanide polymers. Though we know a little about the dark terrain's chemical nature, we do not understand its origin. Two theories have been developed, but neither is fully satisfactory--(1) the dark material may be organic dust knocked off the small neighboring satellite Phoebe and 'painted' onto the leading side of Iapetus as the dust spirals toward Saturn and Iapetus hurtles through the tenuous dust cloud, or (2) the dark material may be made of icy-cold carbonaceous 'cryovolcanic' lavas that were erupted from Iapetus' interior and then blackened by solar radiation, charged particles, and cosmic rays. A determination of the actual cause, as well as discovery of any other geologic features smaller than 12 miles across, awaits the Cassini Saturn orbiter to arrive in 2004.

Jupiter's Colorful Cloud Belts

NASA Image and Video Library

2018-01-12

Colorful swirling cloud belts dominate Jupiter's southern hemisphere in this image captured by NASA's Juno spacecraft. Jupiter appears in this color-enhanced image as a tapestry of vibrant cloud bands and storms. The dark region in the far left is called the South Temperate Belt. Intersecting the belt is a ghost-like feature of slithering white clouds. This is the largest feature in Jupiter's low latitudes that's a cyclone (rotating with clockwise motion). This image was taken on Dec. 16, 2017 at 10:12 PST (1:12 p.m. EST), as Juno performed its tenth close flyby of Jupiter. At the time the image was taken, the spacecraft was about 8,453 miles (13,604 kilometers) from the tops of the clouds of the planet at a latitude of 27.9 degrees south. The spatial scale in this image is 5.6 miles/pixel (9.1 kilometers/pixel). Citizen scientist Kevin M. Gill processed this image using data from the JunoCam imager. https://photojournal.jpl.nasa.gov/catalog/PIA21974

Understanding the Star Formation Process in the Filamentary Dark Cloud GF 9: Near-Infrared Observations

NASA Technical Reports Server (NTRS)

Ciardi, David R.; Woodward, Charles E.; Clemens, Dan P.; Harker, David E.; Rudy, Richard J.

1998-01-01

We have performed a near-infrared JHK survey of a dense core and a diffuse filament region within the filamentary dark cloud GF 9 (LDN 1082). The core region is associated with the IRAS point source PSC 20503+6006 and is suspected of being a site of star formation. The diffuse filament region has no associated IRAS point sources and is likely quiescent. We find that neither the core nor the filament region appears to contain a Class I or Class II young stellar object. As traced by the dust extinction, the core and filament regions contain 26 and 22 solar mass, respectively, with an average H2 volume density for both regions of approximately 2500/cu cm. The core region contains a centrally condensed extinction maximum with a peak extinction of A(sub v) greater than or approximately equal to 10 mag that appears to be associated with the IRAS point source. The average H2 volume density of the extinction core is approximately 8000/cu cm. The dust within the filament, however, shows no sign of a central condensation and is consistent with a uniform-density cylindrical distribution.

Movie of High Clouds on Jupiter

NASA Technical Reports Server (NTRS)

2000-01-01

Jupiter's high-altitude clouds are seen in this brief movie made from seven frames taken by the narrow-angle camera of NASA's Cassini spacecraft. This is the first time a movie sequence of Jupiter has been made that illustrates the motions of the high-altitude clouds on a global scale.

The images were taken at a wavelength that is absorbed by methane, one chemical in Jupiter's lower clouds. So, dark areas are relatively free of high clouds, and the camera sees through to the methane in a lower level. Bright areas are places with high, thick clouds that shield the methane below.

Jupiter's equator and Great Red Spot are covered with high-altitude, hazy clouds.

The movie covers the time period between Oct. 1 and Oct. 5, 2000, latitudes from 50 degrees north to 50 degrees south, and a 100-degree sweep of longitude. Those factors were the same for a Cassini movie of cloud motions previously released (PIA02829), but that movie used frames taken through a blue filter, which showed deeper cloud levels and sharper detail. Features in this methane-filter movie appear more diffuse.

Among the nearly stationary features are the Red Spot and some bright ovals at mid-latitudes in both hemispheres. These are anticyclonic (counter-clockwise rotating) storms. They are bright in the methane band because of their high clouds associated with rising gas. They behave differently from terrestrial cyclones, which swirl in the opposite direction. The mechanism making the Red Spot and similar spots stable apparently has no similarity to the mechanism which feeds terrestrial cyclones.

Some small-scale features are fascinating because of their brightness fluctuations. Such fluctuations observed in the methane band are probably caused by strong vertical motions, which form clouds rapidly, as in Earth's thunderstorms. Near the upper left corner in this movie, a number of smaller clouds appear to circulate counterclockwise around a dark spot, and these clouds fluctuate in

Venus Cloud Patterns (colorized and filtered)

NASA Technical Reports Server (NTRS)

1990-01-01

This picture of Venus was taken by the Galileo spacecrafts Solid State Imaging System on February 14, 1990, at a range of almost 1.7 million miles from the planet. A highpass spatial filter has been applied in order to emphasize the smaller scale cloud features, and the rendition has been colorized to a bluish hue in order to emphasize the subtle contrasts in the cloud markings and to indicate that it was taken through a violet filter. The sulfuric acid clouds indicate considerable convective activity, in the equatorial regions of the planet to the left and downwind of the subsolar point (afternoon on Venus). They are analogous to 'fair weather clouds' on Earth. The filamentary dark features visible in the colorized image are here revealed to be composed of several dark nodules, like beads on a string, each about 60 miles across. The Galileo Project is managed for NASA's Office of Space Science and Applications by the Jet Propulsion Laboratory; its mission is to study Jupiter and its satellites and magnetosphere after multiple gravity assist flybys at Venus and Earth. These images of the Venus clouds were taken by Galileo's Solid State Imaging System February 13, 1990, at a range of about 1 million miles. The smallest detail visible is about 20 miles. The two right images show Venus in violet light, the top one at a time six hours later than the bottom one. They show the state of the clouds near the top of Venus's cloud deck. A right to left motion of the cloud features is evident and is consistent with westward winds of about 230 mph. The two left images show Venus in near infrared light, at the same times as the two right images. Sunlight penetrates through the clouds more deeply at the near infrared wavelengths, allowing a view near the bottom of the cloud deck. The westward motion of the clouds is slower (about 150 mph) at the lower altitude. The clouds are composed of sulfuric acid droplets and occupy a range of altitudes from 30 to 45 miles. The images have

Photometry and Classification of Stars in the Direction of the Dark Cloud Tgu 619 IN Cepheus. I. a Catalog of Magnitudes, Color Indices and Spectral Types of 1304 Stars

NASA Astrophysics Data System (ADS)

Zdanavičius, K.; Zdanavičius, J.; Straižys, V.; Maskoliūnas, M.

The catalog contains magnitudes and color indices of 1304 stars down to ˜ 16.6 mag in V measured in the seven-color Vilnius photometric system in the area of 1.5 square degrees with the center at Galactic coordinates 102.4°, +15.5°, containing the dark cloud TGU 619 in the Cepheus Flare. For most of the stars spectral and luminosity classes determined from the photometric data are given.

Differences of skin morphology in Bos indicus, Bos taurus, and their crossbreds

NASA Astrophysics Data System (ADS)

Jian, Wang; Duangjinda, M.; Vajrabukka, C.; Katawatin, Suporn

2014-08-01

Cutaneous evaporation is the main avenue by which cattle dissipate heat via the involvement of sweat glands and other skin components. The difference in skin morphology between B. indicus and B. taurus has been recognized, as well as differences in their ability to tolerate heat. The objective of this study was to compare skin morphology between B. indicus, B. taurus, and their crossbreds. Skin samples of Sahiwal ( B. indicus) ( n = 10, reddish brown skin) and Holstein Friesian (HF) ( B. taurus) ( n = 10, black and white skin) and crossbred of HF75% ( n = 10, black and white skin) and HF87.5 % ( n = 10, black and white skin) were biopsied for histological study, followed by measurement of skin components. The results indicated that breed significantly affected sweat gland morphology. The shape of the sweat gland, as indicated by the ratio of length/diameter, in Sahiwal was baggier in shape compared to HF (5.99 and 9.52) while values for crossbreds were intermediate (7.82, 8.45). The density and volume of sweat glands in Sahiwal (1,058 glands/cm2; 1.60 μ3 × 10-6) were higher than in HF (920 glands/cm2; 0.51 μ3x10-6) and crossbreds, both HF 75 % (709 glands/cm2; 0.68 μ3 × 10-6) and HF 87.5 % (691 glands/cm2; 0.61 μ3 × 10-6) respectively. However, capillary surface area was greater for HF (2.07 cm2) compared to Sahiwal (1.79 cm2); accordingly, the lower genetic fraction of HF in crossbred cattle showed less capillary surface area (1.83 and 1.9 cm2 for HF75% and HF87.5 %) ( P < 0.01). Nerve density was not significantly different between Sahiwal and HF but was higher in the crossbred ( P < 0.01) cattle. Moreover, the effect of skin color (black and white) was evaluated and it was found that there was an interaction ( P < 0.01) between breed and skin color on the skin components. This study reveals that there are differences in skin morphology among B. indicus, B. taurus and their crossbreds, with these differences being more or less related to the genetic

The chemistry of dense interstellar clouds

NASA Technical Reports Server (NTRS)

Irvine, W. M.

1991-01-01

The basic theme of this program is the study of molecular complexity and evolution in interstellar and circumstellar clouds incorporating the biogenic elements. Recent results include the identification of a new astronomical carbon-chain molecule, C4Si. This species was detected in the envelope expelled from the evolved star IRC+10216 in observations at the Nobeyama Radio Observatory in Japan. C4Si is the carrier of six unidentified lines which had previously been observed. This detection reveals the existence of a new series of carbon-chain molecules, C sub n Si (n equals 1, 2, 4). Such molecules may well be formed from the reaction of Si(+) with acetylene and acetylene derivatives. Other recent research has concentrated on the chemical composition of the cold, dark interstellar clouds, the nearest dense molecular clouds to the solar system. Such regions have very low kinetic temperatures, on the order of 10 K, and are known to be formation sites for solar-type stars. We have recently identified for the first time in such regions the species of H2S, NO, HCOOH (formic acid). The H2S abundance appears to exceed that predicted by gas-phase models of ion-molecule chemistry, perhaps suggesting the importance of synthesis on grain surfaces. Additional observations in dark clouds have studied the ratio of ortho- to para-thioformaldehyde. Since this ratio is expected to be unaffected by both radiative and ordinary collisional processes in the cloud, it may well reflect the formation conditions for this molecule. The ratio is observed to depart from that expected under conditions of chemical equilibrium at formation, perhaps reflecting efficient interchange between cold dust grains in the gas phase.

A multiwavelength observation and investigation of six infrared dark clouds

NASA Astrophysics Data System (ADS)

Zhang, Chuan-Peng; Yuan, Jing-Hua; Li, Guang-Xing; Zhou, Jian-Jun; Wang, Jun-Jie

2017-02-01

Context. Infrared dark clouds (IRDCs) are ubiquitous in the Milky Way, yet they play a crucial role in breeding newly-formed stars. Aims: With the aim of further understanding the dynamics, chemistry, and evolution of IRDCs, we carried out multiwavelength observations on a small sample. Methods: We performed new observations with the IRAM 30 m and CSO 10.4 m telescopes, with tracers HCO+, HCN, N2H+, C18O, DCO+, SiO, and DCN toward six IRDCs G031.97+00.07, G033.69-00.01, G034.43+00.24, G035.39-00.33, G038.95-00.47, and G053.11+00.05. Results: We investigated 44 cores including 37 cores reported in previous work and seven newly-identified cores. Toward the dense cores, we detected 6 DCO+, and 5 DCN lines. Using pixel-by-pixel spectral energy distribution (SED) fits of the Herschel 70 to 500 μm, we obtained dust temperature and column density distributions of the IRDCs. We found that N2H+ emission has a strong correlation with the dust temperature and column density distributions, while C18O showed the weakest correlation. It is suggested that N2H+ is indeed a good tracer in very dense conditions, but C18O is an unreliable one, as it has a relatively low critical density and is vulnerable to freezing-out onto the surface of cold dust grains. The dynamics within IRDCs are active, with infall, outflow, and collapse; the spectra are abundant especially in deuterium species. Conclusions: We observe many blueshifted and redshifted profiles, respectively, with HCO+ and C18O toward the same core. This case can be well explained by model "envelope expansion with core collapse (EECC)". The final datacubes (HCO+, HCN, N2H+, C18O) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/598/A76

Modeling the chemistry of the dense interstellar clouds. I - Observational constraints for the chemistry

NASA Technical Reports Server (NTRS)

Federman, S. R.; Huntress, W. T., Jr.; Prasad, S. S.

1990-01-01

A search for correlations arising from molecular line data is made in order to place constraints on the chemical models of interstellar clouds. At 10 to the 21st H2/sq cm, N(CO) for dark clouds is a factor of six greater than the value for diffuse clouds. This implies that the strength of the UV radiation field where CO shields itself from dissociation is about one-half the strength of the average Galactic field. The dark cloud data indicate that the abundance of CO continues to increase with A(V) for directions with A(V) of 4 mag or less, although less steeply with N(H2) than for diffuse clouds. For H2CO, a quadratic relationship is obtained in plots versus H2 column density. The data suggest a possible turnover at the highest values for A(V). NH3 shows no correlation with H2, C(O-18), HC3N, or HC5N; a strong correlation is found between HC5N and HC3N, indicating a chemical link between the cyanopolyynes.

GOT C+ Survey of [CII] 158 μm Emission: Atomic to Molecular Cloud Transitions in the Inner Galaxy

NASA Astrophysics Data System (ADS)

Velusamy, T.; Langer, W. D.; Willacy, K.; Pineda, J. L.; Goldsmith, P. F.

2013-03-01

We present the results of the distribution of CO-dark H2 gas in a sample of 2223 interstellar clouds in the inner Galaxy (l=-90° to +57°) detected in the velocity resolved [CII] spectra observed in the GOT C+ survey using the Herschel HIFI. We analyze the [CII] intensities along with the ancillary HI, 12CO and 13CO data for each cloud to determine their evolutionary state and to derive the H2 column densities in the C+ and C+/CO transition layers in the cloud. We discuss the overall Galactic distribution of the [CII] clouds and their properties as a function Galactic radius. GOT C+ results on the global distribution of [CII] clouds and CO-dark H2 gas traces the FUV intensity and star formation rate in the Galactic disk.

Ammonia Ice Clouds on Jupiter

NASA Technical Reports Server (NTRS)

2007-01-01

The top cloud layer on Jupiter is thought to consist of ammonia ice, but most of that ammonia 'hides' from spectrometers. It does not absorb light in the same way ammonia does. To many scientists, this implies that ammonia churned up from lower layers of the atmosphere 'ages' in some way after it condenses, possibly by being covered with a photochemically generated hydrocarbon mixture. The New Horizons Linear Etalon Imaging Spectral Array (LEISA), the half of the Ralph instrument that is able to 'see' in infrared wavelengths that are absorbed by ammonia ice, spotted these clouds and watched them evolve over five Jupiter days (about 40 Earth hours). In these images, spectroscopically identified fresh ammonia clouds are shown in bright blue. The largest cloud appeared as a localized source on day 1, intensified and broadened on day 2, became more diffuse on days 3 and 4, and disappeared on day 5. The diffusion seemed to follow the movement of a dark spot along the boundary of the oval region. Because the source of this ammonia lies deeper than the cloud, images like these can tell scientists much about the dynamics and heat conduction in Jupiter's lower atmosphere.

Making and Breaking Clouds

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-10-01

Molecular clouds which youre likely familiar with from stunning popular astronomy imagery lead complicated, tumultuous lives. A recent study has now found that these features must be rapidly built and destroyed.Star-Forming CollapseA Hubble view of a molecular cloud, roughly two light-years long, that has broken off of the Carina Nebula. [NASA/ESA, N. Smith (University of California, Berkeley)/The Hubble Heritage Team (STScI/AURA)]Molecular gas can be found throughout our galaxy in the form of eminently photogenic clouds (as featured throughout this post). Dense, cold molecular gas makes up more than 20% of the Milky Ways total gas mass, and gravitational instabilities within these clouds lead them to collapse under their own weight, resulting in the formation of our galaxys stars.How does this collapse occur? The simplest explanation is that the clouds simply collapse in free fall, with no source of support to counter their contraction. But if all the molecular gas we observe collapsed on free-fall timescales, star formation in our galaxy would churn a rate thats at least an order of magnitude higher than the observed 12 solar masses per year in the Milky Way.Destruction by FeedbackAstronomers have theorized that there may be some mechanism that supports these clouds against gravity, slowing their collapse. But both theoretical studies and observations of the clouds have ruled out most of these potential mechanisms, and mounting evidence supports the original interpretation that molecular clouds are simply gravitationally collapsing.A sub-mm image from ESOs APEX telescope of part of the Taurus molecular cloud, roughly ten light-years long, superimposed on a visible-light image of the region. [ESO/APEX (MPIfR/ESO/OSO)/A. Hacar et al./Digitized Sky Survey 2. Acknowledgment: Davide De Martin]If this is indeed the case, then one explanation for our low observed star formation rate could be that molecular clouds are rapidly destroyed by feedback from the very stars

Resource availability at Taurus-Littrow

NASA Technical Reports Server (NTRS)

Haskin, Larry A.; Colson, R. O.

1992-01-01

Early lunar technologies will probably use a common lunar material as ore. They will be robust to minor fluctuations in feedstock composition and will not require appreciable feedstock beneficiation such as rock grinding or mineral concentration. Technologies using unprocessed soil and indifferent to its composition will have the advantage. Nevertheless, the size and grade of the ore body must be confirmed for even the most indiscriminate process. Simple uses such as heaping unprocessed lunar soil for thermal insulation or radiation shielding onto a habitat require that we know the depth of the regolith, the size distributions of its soils, the locations of large boulders, and the ease of excavation. Costs of detailed site surveys trade against restrictions on site selection and conservative engineering design to accommodate unknown conditions of a poorly explored site. Given the above considerations, we consider briefly some abundant lunar materials, their proposed uses, and technologies for their preparation, with particular attention to the Taurus-Littrow site.

Angular momentum of the N2H+ cores in the Orion A cloud

NASA Astrophysics Data System (ADS)

Tatematsu, Ken'ichi; Ohashi, Satoshi; Sanhueza, Patricio; Nguyen Luong, Quang; Umemoto, Tomofumi; Mizuno, Norikazu

2016-04-01

We have analyzed the angular momentum of the molecular cloud cores in the Orion A giant molecular cloud observed in the N2H+ J = 1-0 line with the Nobeyama 45 m radio telescope. We have measured the velocity gradient using position-velocity diagrams passing through core centers, and made sinusoidal fits against the position angle. Twenty-seven out of 34 N2H+ cores allowed us to measure the velocity gradient without serious confusion. The derived velocity gradient ranges from 0.5 to 7.8 km s-1 pc-1. We marginally found that the specific angular momentum J/M (against the core radius R) of the Orion N2H+ cores tends to be systematically larger than that of molecular cloud cores in cold dark clouds obtained by Goodman et al., in the J/M-R relation. The ratio β of rotational to gravitational energy is derived to be β = 10-2.3±0.7, and is similar to that obtained for cold dark cloud cores in a consistent definition. The large-scale rotation of the ∫-shaped filament of the Orion A giant molecular cloud does not likely govern the core rotation at smaller scales.

Physical properties of CO-dark molecular gas traced by C+

NASA Astrophysics Data System (ADS)

Tang, Ningyu; Li, Di; Heiles, Carl; Wang, Shen; Pan, Zhichen; Wang, Jun-Jie

2016-09-01

Context. Neither Hi nor CO emission can reveal a significant quantity of so-called dark gas in the interstellar medium (ISM). It is considered that CO-dark molecular gas (DMG), the molecular gas with no or weak CO emission, dominates dark gas. Determination of physical properties of DMG is critical for understanding ISM evolution. Previous studies of DMG in the Galactic plane are based on assumptions of excitation temperature and volume density. Independent measurements of temperature and volume density are necessary. Aims: We intend to characterize physical properties of DMG in the Galactic plane based on C+ data from the Herschel open time key program, namely Galactic Observations of Terahertz C+ (GOT C+) and Hi narrow self-absorption (HINSA) data from international Hi 21 cm Galactic plane surveys. Methods: We identified DMG clouds with HINSA features by comparing Hi, C+, and CO spectra. We derived the Hi excitation temperature and Hi column density through spectral analysis of HINSA features. The Hi volume density was determined by utilizing the on-the-sky dimension of the cold foreground Hi cloud under the assumption of axial symmetry. The column and volume density of H2 were derived through excitation analysis of C+ emission. The derived parameters were then compared with a chemical evolutionary model. Results: We identified 36 DMG clouds with HINSA features. Based on uncertainty analysis, optical depth of HiτHi of 1 is a reasonable value for most clouds. With the assumption of τHi = 1, these clouds were characterized by excitation temperatures in a range of 20 K to 92 K with a median value of 55 K and volume densities in the range of 6.2 × 101 cm-3 to 1.2 × 103 cm-3 with a median value of 2.3 × 102 cm-3. The fraction of DMG column density in the cloud (fDMG) decreases with increasing excitation temperature following an empirical relation fDMG =-2.1 × 10-3Tex,(τHi = 1) + 1.0. The relation between fDMG and total hydrogen column density NH is given by f

Still from High-Clouds Jupiter Movie

NASA Technical Reports Server (NTRS)

2000-01-01

This image is one of seven from the narrow-angle camera on NASA's Cassini spacecraft assembled as a brief movie of high-altitude cloud movements on Jupiter. It was taken in early October 2000.

The images were taken at a wavelength that is absorbed by methane, one chemical in Jupiter's lower clouds. So, dark areas are relatively free of high clouds, and the camera sees through to the methane in a lower level. Bright areas are places with high, thick clouds that shield the methane below.

The area shown covers latitudes from 50 degrees north to 50 degrees south and a 100-degree sweep of longitude.

Cassini is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini mission for NASA's Office of Space Science, Washington, D.C.

A Survey For Planetary-mass Brown Dwarfs in the Taurus and Perseus Star-forming Regions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Esplin, T. L.; Luhman, K. L., E-mail: taran.esplin@psu.edu

We present the initial results from a survey for planetary-mass brown dwarfs in the Taurus star-forming region. We have identified brown dwarf candidates in Taurus using proper motions and photometry from several ground- and space-based facilities. Through spectroscopy of some of the more promising candidates, we have found 18 new members of Taurus. They have spectral types ranging from mid-M to early-L, and they include the four faintest known members in extinction-corrected K{sub s}, which should have masses as low as ∼4–5 M {sub Jup} according to evolutionary models. Two of the coolest new members (M9.25, M9.5) have mid-IR excessesmore » that indicate the presence of disks. Two fainter objects with types of M9–L2 and M9–L3 also have red mid-IR colors relative to photospheres at ≤L0, but since the photospheric colors are poorly defined at >L0, it is unclear whether they have excesses from disks. We also have obtained spectra of candidate members of the IC 348 and NGC 1333 clusters in Perseus that were identified by Luhman et al. Eight candidates are found to be probable members, three of which are among the faintest and least-massive known members of the clusters (∼5 M{sub Jup}).« less

Detection of quantitative trait loci in Bos indicus and Bos taurus cattle using genome-wide association studies

PubMed Central

2013-01-01

Background The apparent effect of a single nucleotide polymorphism (SNP) on phenotype depends on the linkage disequilibrium (LD) between the SNP and a quantitative trait locus (QTL). However, the phase of LD between a SNP and a QTL may differ between Bos indicus and Bos taurus because they diverged at least one hundred thousand years ago. Here, we test the hypothesis that the apparent effect of a SNP on a quantitative trait depends on whether the SNP allele is inherited from a Bos taurus or Bos indicus ancestor. Methods Phenotype data on one or more traits and SNP genotype data for 10 181 cattle from Bos taurus, Bos indicus and composite breeds were used. All animals had genotypes for 729 068 SNPs (real or imputed). Chromosome segments were classified as originating from B. indicus or B. taurus on the basis of the haplotype of SNP alleles they contained. Consequently, SNP alleles were classified according to their sub-species origin. Three models were used for the association study: (1) conventional GWAS (genome-wide association study), fitting a single SNP effect regardless of subspecies origin, (2) interaction GWAS, fitting an interaction between SNP and subspecies-origin, and (3) best variable GWAS, fitting the most significant combination of SNP and sub-species origin. Results Fitting an interaction between SNP and subspecies origin resulted in more significant SNPs (i.e. more power) than a conventional GWAS. Thus, the effect of a SNP depends on the subspecies that the allele originates from. Also, most QTL segregated in only one subspecies, suggesting that many mutations that affect the traits studied occurred after divergence of the subspecies or the mutation became fixed or was lost in one of the subspecies. Conclusions The results imply that GWAS and genomic selection could gain power by distinguishing SNP alleles based on their subspecies origin, and that only few QTL segregate in both B. indicus and B. taurus cattle. Thus, the QTL that segregate in

Bill E. Kunkle Interdisciplinary Beef Symposium: Temperament and acclimation to human handling influence growth, health, and reproductive responses in Bos taurus and Bos indicus cattle.

PubMed

Cooke, R F

2014-12-01

Temperament in cattle is defined as the fear-related behavioral responses when exposed to human handling. Our group evaluates cattle temperament using 1) chute score on a 1 to 5 scale that increases according to excitable behavior during restraint in a squeeze chute, 2) exit velocity (speed of an animal exiting the squeeze chute), 3) exit score (dividing cattle according to exit velocity into quintiles using a 1 to 5 scale where 1=cattle in the slowest quintile and 5=cattle in the fastest quintile), and 4) temperament score (average of chute and exit scores). Subsequently, cattle are assigned a temperament type of adequate temperament (ADQ; temperament score≤3) or excitable temperament (EXC; temperament score>3). To assess the impacts of temperament on various beef production systems, our group associated these evaluation criteria with productive, reproductive, and health characteristics of Bos taurus and Bos indicus-influenced cattle. As expected, EXC cattle had greater plasma cortisol vs. ADQ cattle during handling, independent of breed type (B. indicus×B. taurus, P<0.01; B. taurus, P<0.01; B. indicus, P=0.04) or age (cows, P<0.01; heifers or steers, P<0.01). In regards to reproduction, EXC females had reduced annual pregnancy rates vs. ADQ cohorts across breed types (B. taurus, P=0.03; B. indicus, P=0.05). Moreover, B. taurus EXC cows also had decreased calving rate (P=0.04), weaning rate (P=0.09), and kilograms of calf weaned/cow exposed to breeding (P=0.08) vs. ADQ cohorts. In regards to feedlot cattle, B. indicus EXC steers had reduced ADG (P=0.02) and G:F (P=0.03) during a 109-d finishing period compared with ADQ cohorts. Bos taurus EXC cattle had reduced weaning BW (P=0.04), greater acute-phase protein response on feedlot entry (P≤0.05), impaired feedlot receiving ADG (P=0.05), and reduced carcass weight (P=0.07) vs. ADQ cohorts. Acclimating B. indicus×B. taurus or B. taurus heifers to human handling improved temperament (P≤0.02), reduced plasma

The OGLE view of microlensing towards the Magellanic Clouds - II. OGLE-II Small Magellanic Cloud data

NASA Astrophysics Data System (ADS)

Wyrzykowski, Ł.; Kozłowski, S.; Skowron, J.; Belokurov, V.; Smith, M. C.; Udalski, A.; Szymański, M. K.; Kubiak, M.; Pietrzyński, G.; Soszyński, I.; Szewczyk, O.

2010-09-01

The primary goal of this paper is to provide evidence that can prove true or false the hypothesis that dark matter in the Galactic halo can clump into stellar-mass compact objects. If such objects exist, they would act as lenses to external sources in the Magellanic Clouds, giving rise to an observable effect of microlensing. We present the results of our search for such events, based on data from the second phase of the OGLE survey (1996-2000) towards the Small Magellanic Cloud (SMC). The data set we used comprises 2.1 million monitored sources distributed over an area of 2.4deg2. We found only one microlensing event candidate, however its poor-quality light curve limited our discussion of the exact distance to the lensing object. Given a single event, taking blending (crowding of stars) into account for the detection-efficiency simulations and deriving the Hubble Space Telescope (HST)-corrected number of monitored stars, the microlensing optical depth is τ = (1.55 +/- 1.55) × 10-7. This result is consistent with the expected SMC self-lensing signal, with no need to introduce dark matter microlenses. Rejecting the unconvincing event leads to an upper limit on the fraction of dark matter in the form of massive compact halo objects (MACHOs) of f < 20 per cent for deflector masses around 0.4Msolar and f < 11 per cent for masses between 0.003 and 0.2Msolar (95 per cent confidence limit). Our result indicates that the Milky Way's dark matter is unlikely to be clumpy and to form compact objects in the subsolar-mass range. Based on observations obtained with the 1.3-m Warsaw Telescope at the Las Campanas Observatory of the Carnegie Institution of Washington. E-mail: wyrzykow@ast.cam.ac.uk ‡ Name pronunciation: Woocash Vizhikovsky

Above-Cloud Precipitable Water Retrievals using the MODIS 0.94 micron Band with Applications for Multi-Layer Cloud Detection

NASA Technical Reports Server (NTRS)

Platnick, S.; Wind, G.

2004-01-01

In order to perform satellite retrievals of cloud properties, it is important to account for the effect of the above-cloud atmosphere on the observations. The solar bands used in the operational MODIS Terra and Aqua cloud optical and microphysical algorithms (visible, NIR, and SWIR spectral windows) are primarily affected by water vapor, and to a lesser extent by well-mixed gases. For water vapor, the above-cloud column amount, or precipitable water, provides adequate information for an atmospheric correction; details of the vertical vapor distribution are not typically necessary for the level of correction required. Cloud-top pressure has a secondary effect due to pressure broadening influences. For well- mixed gases, cloud-top pressure is also required for estimates of above-cloud abundances. We present a method for obtaining above-cloud precipitable water over dark Ocean surfaces using the MODIS 0.94 pm vapor absorption band. The retrieval includes an iterative procedure for establishing cloud-top temperature and pressure, and is useful for both single layer water and ice clouds. Knowledge of cloud thermodynamic phase is fundamental in retrieving cloud optical and microphysical properties. However, in cases of optically thin cirrus overlapping lower water clouds, the concept of a single unique phase is ill- defined and depends, at least, on the spectral region of interest. We will present a method for multi-layer and multi-phase cloud detection which uses above-cloud precipitable water retrievals along with several existing MODIS operational cloud products (cloud-top pressure derived from a C02 slicing algorithm, IR and SWIR phase retrievals). Results are catagorized by whether the radiative signature in the MODIS solar bands is primarily that of a water cloud with ice cloud contamination, or visa-versa. Examples in polar and mid-latitude regions will be shown.

Hubble Looks at Light and Dark in the Universe

NASA Image and Video Library

2014-08-29

This new NASA/ESA Hubble Space Telescope image shows a variety of intriguing cosmic phenomena. Surrounded by bright stars, towards the upper middle of the frame we see a small young stellar object (YSO) known as SSTC2D J033038.2+303212. Located in the constellation of Perseus, this star is in the early stages of its life and is still forming into a fully-grown star. In this view from Hubble’s Advanced Camera for Surveys(ACS) it appears to have a murky chimney of material emanating outwards and downwards, framed by bright bursts of gas flowing from the star itself. This fledgling star is actually surrounded by a bright disk of material swirling around it as it forms — a disc that we see edge-on from our perspective. However, this small bright speck is dwarfed by its cosmic neighbor towards the bottom of the frame, a clump of bright, wispy gas swirling around as it appears to spew dark material out into space. The bright cloud is a reflection nebula known as [B77] 63, a cloud of interstellar gas that is reflecting light from the stars embedded within it. There are actually a number of bright stars within [B77] 63, most notably the emission-line star LkHA 326, and it nearby neighbor LZK 18. These stars are lighting up the surrounding gas and sculpting it into the wispy shape seen in this image. However, the most dramatic part of the image seems to be a dark stream of smoke piling outwards from [B77] 63 and its stars — a dark nebula called Dobashi 4173. Dark nebulae are incredibly dense clouds of pitch-dark material that obscure the patches of sky behind them, seemingly creating great rips and eerily empty chunks of sky. The stars speckled on top of this extreme blackness actually lie between us and Dobashi 4173. Credit: ESA/NASA NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA�

Baryonic Dark Matter: The Results from Microlensing Surveys

NASA Astrophysics Data System (ADS)

Alcock, Charles; Allsman, Robyn A.; Alves, David; Axelrod, Tim S.; Becker, Andrew C.; Bennett, David; Cook, Kem H.; Drake, Andrew J.; Freeman, Ken C.; Griest, Kim; Lehner, Matt; Marshall, Stuart; Minniti, Dante; Peterson, Bruce; Pratt, Mark; Quinn, Peter; Rodgers, Alex; Stubbs, Chris; Sutherland, Will; Tomaney, Austin; Vandehei, Thor; Welch, Doug L.

Baryonic material can exist in several dark forms: ``planets," brown dwarfs, very old degenerate dwarf stars, and neutron stars. (Black holes are frequently added to this list, even though a black hole has no baryon number.) These objects, most of which emit some light but at levels below present day detection thresholds, are collectively known as Machos. Several groups have exploited the gravitational microlens signature to search for Machos in the dark halo of the Milky Way. Over 200 microlensing events have been reported (most by the MACHO Project, which uses the Great Melbourne Telescope near this conference site), of which about 20 are toward the Magellanic Clouds. The most straightforward interpretation of the results is that Machos make up between 20% and 100% of the dark matter in the halo, and that these objects weigh about 0.5 msun. Objects of substellar mass do not comprise much of the dark matter. Many alternative interpretations of these results have been proposed. We will discuss strategies for resolving the differences among these competing explanations.

Infrared Image of Low Clouds on Venus

NASA Technical Reports Server (NTRS)

1993-01-01

This false-color image is a near-infrared map of lower-level clouds on the night side of Venus, obtained by the Near Infrared Mapping Spectrometer aboard the Galileo spacecraft as it approached the planet's night side on February 10, 1990. Bright slivers of sunlit high clouds are visible above and below the dark, glowing hemisphere. The spacecraft is about 100,000 kilometers (60,000 miles) above the planet. An infrared wavelength of 2.3 microns (about three times the longest wavelength visible to the human eye) was used. The map shows the turbulent, cloudy middle atmosphere some 50-55 kilometers (30- 33 miles) above the surface, 10-16 kilometers or 6-10 miles below the visible cloudtops. The red color represents the radiant heat from the lower atmosphere (about 400 degrees Fahrenheit) shining through the sulfuric acid clouds, which appear as much as 10 times darker than the bright gaps between clouds. This cloud layer is at about -30 degrees Fahrenheit, at a pressure about 1/2 Earth's surface atmospheric pressure. Near the equator, the clouds appear fluffy and blocky; farther north, they are stretched out into East-West filaments by winds estimated at more than 150 mph, while the poles are capped by thick clouds at this altitude.

Properties of Cold HI Emission Clouds in the Inner-Galaxy ALFA Survey

NASA Astrophysics Data System (ADS)

Hughes, James Marcus; Gibson, Steven J.; Noriega-Crespo, Alberto; Newton, Jonathan; Koo, Bon-Chul; Douglas, Kevin A.; Peek, Joshua Eli Goldston; Park, Geumsook; Kang, Ji-hyun; Korpela, Eric J.; Heiles, Carl E.; Dame, Thomas M.

2017-01-01

Star formation, a critical process within galaxies, occurs in the coldest, densest interstellar clouds, whose gas and dust content are observed primarily at radio and infrared wavelengths. The formation of molecular hydrogen (H2) from neutral atomic hydrogen (HI) is an essential early step in the condensation of these clouds from the ambient interstellar medium, but it is not yet completely understood, e.g., what is the predominant trigger? Even more troubling, the abundance of H2 may be severely underestimated by standard tracers like CO, implying significant "dark" H2, and the quantity of HI may also be in error if opacity effects are neglected. We have developed an automated method to account for both HI and H2 in cold, diffuse clouds traced by narrow-line HI 21-cm emission in the Arecibo Inner-Galaxy ALFA (I-GALFA) survey. Our algorithm fits narrow (2-5 km/s), isolated HI line profiles to determine their spin temperature, optical depth, and true column density. We then estimate the "visible" H2 column in the same clouds with CfA and Planck CO data and the total gas column from dust emission measured by Planck, IRAS, and other surveys. Together, these provide constraints on the dark H2 abundance, which we examine in relation to other cloud properties and stages of development. Our aim is to build a database of H2-forming regions with significant dark gas to aid future analyses of coalescing interstellar clouds. We acknowledge support from NSF, NASA, Western Kentucky University, and Williams College. I-GALFA is a GALFA-HI survey observed with the 7-beam ALFA receiver on the 305-meter William E. Gordon Telescope. The Arecibo Observatory is a U.S. National Science Foundation facility operated under sequential cooperative agreements with Cornell University and SRI International, the latter in alliance with the Ana G. Mendez-Universidad Metropolitana and the Universities Space Research Association.

Cosmic rays, gas and dust in nearby anticentre clouds. I. CO-to-H2 conversion factors and dust opacities

NASA Astrophysics Data System (ADS)

Remy, Q.; Grenier, I. A.; Marshall, D. J.; Casandjian, J. M.

2017-05-01

Aims: We aim to explore the capabilities of dust emission and γ rays for probing the properties of the interstellar medium in the nearby anti-centre region, using γ-ray observations with the Fermi Large Area Telescope (LAT), and the thermal dust optical depth inferred from Planck and IRAS observations. We also aim to study massive star-forming clouds including the well known Taurus, Auriga, Perseus, and California molecular clouds, as well as a more diffuse structure which we refer to as Cetus. In particular, we aim at quantifying potential variations in cosmic-ray density and dust properties per gas nucleon across the different gas phases and different clouds, and at measuring the CO-to-H2 conversion factor, XCO, in different environments. Methods: We have separated six nearby anti-centre clouds that are coherent in velocities and distances, from the Galactic-disc background in H I 21-cm and 12CO 2.6-mm line emission. We have jointly modelled the γ-ray intensity recorded between 0.4 and 100 GeV, and the dust optical depth τ353 at 353 GHz as a combination of H I-bright, CO-bright, and ionised gas components. The complementary information from dust emission and γ rays was used to reveal the gas not seen, or poorly traced, by H I, free-free, and 12CO emissions, namely (I) the opaque H iand diffuse H2 present in the Dark Neutral Medium at the atomic-molecular transition, and (II) the dense H2 to be added where 12CO lines saturate. Results: The measured interstellar γ-ray spectra support a uniform penetration of the cosmic rays with energies above a few GeV through the clouds, from the atomic envelopes to the 12CO-bright cores, and with a small ± 9% cloud-to-cloud dispersion in particle flux. We detect the ionised gas from the H iiregion NGC 1499 in the dust and γ-ray emissions and measure its mean electron density and temperature. We find a gradual increase in grain opacity as the gas (atomic or molecular) becomes more dense. The increase reaches a factor of

The phylogenomic position of the grey nurse shark Carcharias taurus Rafinesque, 1810 (Lamniformes, Odontaspididae) inferred from the mitochondrial genome.

PubMed

Bowden, Deborah L; Vargas-Caro, Carolina; Ovenden, Jennifer R; Bennett, Michael B; Bustamante, Carlos

2016-11-01

The complete mitochondrial genome of the grey nurse shark Carcharias taurus is described from 25 963 828 sequences obtained using Illumina NGS technology. Total length of the mitogenome is 16 715 bp, consisting of 2 rRNAs, 13 protein-coding regions, 22 tRNA and 2 non-coding regions thus updating the previously published mitogenome for this species. The phylogenomic reconstruction inferred from the mitogenome of 15 species of Lamniform and Carcharhiniform sharks supports the inclusion of C. taurus in a clade with the Lamnidae and Cetorhinidae. This complete mitogenome contributes to ongoing investigation into the monophyly of the Family Odontaspididae.

A Search for Companions to Brown Dwarfs in the Taurus and Chamaeleon Star-Forming Regions

NASA Astrophysics Data System (ADS)

Todorov, K. O.; Luhman, K. L.; Konopacky, Q. M.; McLeod, K. K.; Apai, D.; Ghez, A. M.; Pascucci, I.; Robberto, M.

2014-06-01

We have used WFPC2 on board the Hubble Space Telescope to obtain images of 47 members of the Taurus and Chamaeleon I star-forming regions that have spectral types of M6-L0 (M ~ 0.01-0.1 M ⊙). An additional late-type member of Taurus, FU Tau (M7.25+M9.25), was also observed with adaptive optics at Keck Observatory. In these images, we have identified promising candidate companions to 2MASS J04414489+2301513 (ρ = 0.''105/15 AU), 2MASS J04221332+1934392 (ρ = 0.''05/7 AU), and ISO 217 (ρ = 0.''03/5 AU). We reported the first candidate in a previous study, showing that it has a similar proper motion as the primary in images from WFPC2 and Gemini adaptive optics. We have collected an additional epoch of data with Gemini that further supports that result. By combining our survey with previous high-resolution imaging in Taurus, Chamaeleon I, and Upper Sco (τ ~ 10 Myr), we measure binary fractions of 14/93 = 0.15^{+0.05}_{-0.03} for M4-M6 (M ~ 0.1-0.3 M ⊙) and 4/108 = 0.04^{+0.03}_{-0.01} for >M6 (M <~ 0.1 M ⊙) at separations of >10 AU. Given the youth and low density of these regions, the lower binary fraction at later types is probably primordial rather than due to dynamical interactions among association members. The widest low-mass binaries (>100 AU) also appear to be more common in Taurus and Chamaeleon I than in the field, which suggests that the widest low-mass binaries are disrupted by dynamical interactions at >10 Myr, or that field brown dwarfs have been born predominantly in denser clusters where wide systems are disrupted or inhibited from forming. Based on observations performed with the NASA/ESA Hubble Space Telescope, Gemini Observatory, and the W. M. Keck Observatory. The Hubble observations are associated with proposal IDs 11203, 11204, and 11983 and were obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

The Clouds of Isidore

NASA Technical Reports Server (NTRS)

2002-01-01

These views of Hurricane Isidore were acquired by the Multi-angle Imaging SpectroRadiometer (MISR) on September 20, 2002. After bringing large-scale flooding to western Cuba, Isidore was upgraded (on September 21) from a tropical storm to a category 3hurricane. Sweeping westward to Mexico's Yucatan Peninsula, the hurricane caused major destruction and left hundreds of thousands of people homeless. Although weakened after passing over the Yucatan landmass, Isidore regained strength as it moved northward over the Gulf of Mexico.

At left is a colorful visualization of cloud extent that superimposes MISR's radiometric camera-by-camera cloud mask (RCCM) over natural-color radiance imagery, both derived from data acquired with the instrument's vertical-viewing (nadir) camera. Using brightness and statistical metrics, the RCCM is one of several techniques MISR uses to determine whether an area is clear or cloudy. In this rendition, the RCCM has been color-coded, and purple = cloudy with high confidence, blue = cloudy with low confidence, green = clear with low confidence, and red = clear with high confidence.

In addition to providing information on meteorological events, MISR's data products are designed to help improve our understanding of the influences of clouds on climate. Cloud heights and albedos are among the variables that govern these influences. (Albedo is the amount of sunlight reflected back to space divided by the amount of incident sunlight.) The center panel is the cloud-top height field retrieved using automated stereoscopic processing of data from multiple MISR cameras. Areas where heights could not be retrieved are shown in dark gray. In some areas, such as the southern portion of the image, the stereo retrieval was able to detect thin, high clouds that were not picked up by the RCCM's nadir view. Retrieved local albedo values for Isidore are shown at right. Generation of the albedo product is dependent upon observed cloud radiances as a function

The Physical Environment around IRAS 17599-2148: Infrared Dark Cloud and Bipolar Nebula

NASA Astrophysics Data System (ADS)

Dewangan, L. K.; Ojha, D. K.; Zinchenko, I.; Janardhan, P.; Ghosh, S. K.; Luna, A.

2016-12-01

We present a multiscale and multiwavelength study to investigate the star formation process around IRAS 17599-2148, which is part of an elongated filamentary structure (EFS) (extension ˜21 pc) seen in the Herschel maps. Using the Herschel data analysis, at least six massive clumps (M clump ˜ 777-7024 M ⊙) are found in the EFS with a range of temperature and column density of ˜16-39 K and ˜(0.6-11) × 1022 cm-2 (A V ˜ 7-117 mag), respectively. The EFS hosts cold gas regions (I.e., infrared dark cloud) without any radio detection and a bipolar nebula (BN) linked with the H II region IRAS 17599-2148, tracing two distinct environments inferred through the temperature distribution and ionized emission. Based on virial analysis and higher values of self-gravitating pressure, the clumps are found unstable against gravitational collapse. We find 474 young stellar objects (YSOs) in the selected region, and ˜72% of these YSOs are found in the clusters distributed mainly toward the clumps in the EFS. These YSOs might have spontaneously formed due to processes not related to the expanding H II region. At the edges of BN, four additional clumps are also associated with YSO clusters, which appear to be influenced by the expanding H II region. The most massive clump in the EFS contains two compact radio sources traced in the Giant Metre-wave Radio Telescope 1.28 GHz map and a massive protostar candidate, IRS 1, prior to an ultracompact H II phase. Using the Very Large Telescope/NACO near-infrared images, IRS 1 is resolved with a jet-like feature within a 4200 au scale.

Cloud Retrieval Information Content Studies with the Pre-Aerosol, Cloud and ocean Ecosystem (PACE) Ocean Color Imager (OCI)

NASA Astrophysics Data System (ADS)

Coddington, Odele; Platnick, Steven; Pilewskie, Peter; Schmidt, Sebastian

2016-04-01

The NASA Pre-Aerosol, Cloud and ocean Ecosystem (PACE) Science Definition Team (SDT) report released in 2012 defined imager stability requirements for the Ocean Color Instrument (OCI) at the sub-percent level. While the instrument suite and measurement requirements are currently being determined, the PACE SDT report provided details on imager options and spectral specifications. The options for a threshold instrument included a hyperspectral imager from 350-800 nm, two near-infrared (NIR) channels, and three short wave infrared (SWIR) channels at 1240, 1640, and 2130 nm. Other instrument options include a variation of the threshold instrument with 3 additional spectral channels at 940, 1378, and 2250 nm and the inclusion of a spectral polarimeter. In this work, we present cloud retrieval information content studies of optical thickness, droplet effective radius, and thermodynamic phase to quantify the potential for continuing the low cloud climate data record established by the MOderate Resolution and Imaging Spectroradiometer (MODIS) and Visible Infrared Imaging Radiometer Suite (VIIRS) missions with the PACE OCI instrument (i.e., non-polarized cloud reflectances and in the absence of midwave and longwave infrared channels). The information content analysis is performed using the GEneralized Nonlinear Retrieval Analysis (GENRA) methodology and the Collection 6 simulated cloud reflectance data for the common MODIS/VIIRS algorithm (MODAWG) for Cloud Mask, Cloud-Top, and Optical Properties. We show that using both channels near 2 microns improves the probability of cloud phase discrimination with shortwave-only cloud reflectance retrievals. Ongoing work will extend the information content analysis, currently performed for dark ocean surfaces, to different land surface types.

The Brain of the Domestic Bos taurus: Weight, Encephalization and Cerebellar Quotients, and Comparison with Other Domestic and Wild Cetartiodactyla.

PubMed

Ballarin, Cristina; Povinelli, Michele; Granato, Alberto; Panin, Mattia; Corain, Livio; Peruffo, Antonella; Cozzi, Bruno

2016-01-01

The domestic bovine Bos taurus is raised worldwide for meat and milk production, or even for field work. However the functional anatomy of its central nervous system has received limited attention and most of the reported data in textbooks and reviews are derived from single specimens or relatively old literature. Here we report information on the brain of Bos taurus obtained by sampling 158 individuals, 150 of which at local abattoirs and 8 in the dissecting room, these latter subsequently formalin-fixed. Using body weight and fresh brain weight we calculated the Encephalization Quotient (EQ), and Cerebellar Quotient (CQ). Formalin-fixed brains sampled in the necropsy room were used to calculate the absolute and relative weight of the major components of the brain. The data that we obtained indicate that the domestic bovine Bos taurus possesses a large, convoluted brain, with a slightly lower weight than expected for an animal of its mass. Comparisons with other terrestrial and marine members of the order Cetartiodactyla suggested close similarity with other species with the same feeding adaptations, and with representative baleen whales. On the other hand differences with fish-hunting toothed whales suggest separate evolutionary pathways in brain evolution. Comparison with the other large domestic herbivore Equus caballus (belonging to the order Perissodactyla) indicates that Bos taurus underwent heavier selection of bodily traits, which is also possibly reflected in a comparatively lower EQ than in the horse. The data analyzed suggest that the brain of domestic bovine is potentially interesting for comparative neuroscience studies and may represents an alternative model to investigate neurodegeneration processes.

Understating Polarization in the Interstellar Medium Through the Theory of Radiative Torque Alignment

NASA Astrophysics Data System (ADS)

Caputo, Miranda; Andersson, B.-G.; Kulas, Kristin Rose

2018-06-01

Although it is known that the dust grains in the ISM align with magnetic fields, the alignment physics of these particles is still somewhat unclear. Utilizing direct observational data and Radiative Alignment Torque (RAT) theory, further constraints can be put onto this alignment. Due to the physics of this alignment, there is a linear relationship between the extinction of the light seen through a dust cloud (AV) and the wavelength of maximum polarization. A previous study, focusing on the Taurus cloud, found that there is a second, steeper relationship seen beyond an extinction of about four magnitudes, likely due to grain growth, in addition to the original linear relationship. We present early results from observations of low-to-medium extinction lines of sight in the starless cloud L183 (aka L134N), aimed at testing the Taurus results. We are currently extending the survey of stars behind L183 to higher extinctions to better probe the origins of the bifurcation seen in the Taurus results.

On the Surface Formation of NH3 and HNCO in Dark Molecular Clouds - Searching for Wöhler Synthesis in the Interstellar Medium

NASA Astrophysics Data System (ADS)

Fedoseev, Gleb; Lamberts, Thanja; Linnartz, Harold; Ioppolo, Sergio; Zhao, Dongfeng

Despite its potential to reveal the link between the formation of simple species and more complex molecules (e.g., amino acids), the nitrogen chemistry of the interstellar medium (ISM) is still poorly understood. Ammonia (NH _{3}) is one of the few nitrogen-bearing species that have been observed in interstellar ices toward young stellar objects (YSOs) and quiescent molecular clouds. The aim of the present work is to experimentally investigate surface formation routes of NH _{3} and HNCO through non-energetic surface reactions in interstellar ice analogues under fully controlled laboratory conditions and at astrochemically relevant cryogenic temperatures. This study focuses on the formation of NH _{3} and HNCO in CO-rich (non-polar) interstellar ices that simulate the CO freeze-out stage in interstellar dark cloud regions, well before thermal and energetic processing start to become predominant. Our work confirms the surface formation of ammonia through the sequential addition of three hydrogen/deuterium atoms to a single nitrogen atom at low temperature. The H/D fractionation of the formed ammonia is also shown. Furthermore, we show the surface formation of solid HNCO through the interaction of CO molecules with NH radicals - one of the intermediates in the formation of solid NH _{3}. Finally, we discuss the implications of HNCO in astrobiology, as a possible starting point for the formation of more complex prebiotic species.

Impact of Parental Bos taurus and Bos indicus Origins on Copy Number Variation in Traditional Chinese Cattle Breeds

PubMed Central

Zhang, Liangzhi; Jia, Shangang; Plath, Martin; Huang, Yongzhen; Li, Congjun; Lei, Chuzhao; Zhao, Xin; Chen, Hong

2015-01-01

Copy number variation (CNV) is an important component of genomic structural variation and plays a role not only in evolutionary diversification but also in domestication. Chinese cattle were derived from Bos taurus and Bos indicus, and several breeds presumably are of hybrid origin, but the evolution of CNV regions (CNVRs) has not yet been examined in this context. Here, we of CNVRs, mtDNA D-loop sequence variation, and Y-chromosomal single nucleotide polymorphisms to assess the impact of maternal and paternal B. taurus and B. indicus origins on the distribution of CNVRs in 24 Chinese domesticated bulls. We discovered 470 genome-wide CNVRs, only 72 of which were shared by all three Y-lineages (B. taurus: Y1, Y2; B. indicus: Y3), whereas 265 were shared by inferred taurine or indicine paternal lineages, and 228 when considering their maternal taurine or indicine origins. Phylogenetic analysis uncovered eight taurine/indicine hybrids, and principal component analysis on CNVs corroborated genomic exchange during hybridization. The distribution patterns of CNVRs tended to be lineage-specific, and correlation analysis revealed significant positive or negative co-occurrences of CNVRs across lineages. Our study suggests that CNVs in Chinese cattle partly result from selective breeding during domestication, but also from hybridization and introgression. PMID:26260653

Dark Galaxies and Lost Baryons (IAU S244)

NASA Astrophysics Data System (ADS)

Davies, Jonathan I.; Disney, Michael J.

2008-05-01

Preface; Conference prelims; The HI that barked in the night M. J. Disney; The detection of dark galaxies in blind HI surveys J. I. Davies; Red haloes of galaxies - reservoirs of baryonic dark matter? E. Zackrisson, N. Bergvall, C. Flynn, G. Ostlin, G. Micheva and B. Baldwell; Constraints on dark and visible mass in galaxies from strong gravitational lensing S. Dye and S. Warren; Lost baryons at low redshift S. Mathur, F. Nicastro and R. Williams; Observed properties of dark matter on small spatial scales R. Wyse and G. Gilmore; The mass distribution in spiral galaxies P. Salucci; Connecting lost baryons and dark galaxies via QSO absorption lines T. Tripp; ALFALFA: HI cosmology in the local universe R. Giovanelli; The ALFALFA search for (almost) dark galaxies across the HI mass function M. Haynes; HI clouds detected towards Virgo with the Arecibo Legacy Fast ALFA Survey B. Kent; Cosmic variance in the HI mass function S. Schneider; The Arecibo Galaxy Environments Survey - potential for finding dark galaxies and results so far R. Minchin et al.; Free-floating HI clouds in the M81 group E. Brinks, F. Walter and E. Skillman; Where are the stars in dark galaxies J. Rosenberg, J. Salzer and J. Cannon; The halo by halo missing baryon problem S. McGaugh; The local void is really empty R. Tully; Voids in the local volume: a limit on appearance of a galaxy in a dark matter halo A. Tikhonov and A. Klypin; Dim baryons in the cosmic web C. Impey; A census of baryons in galaxy clusters and groups A. Gonzalez, D. Zaritsky and A. Zabludo; Statistical properties of the intercluster light from SDSS image stacking S. Zibetti; QSO strong gravitational lensing and the detection of dark halos A. Maccio; Strong gravitational lensing: bright galaxies and lost dark-matter L. Koopmans; Mapping the distribution of luminous and dark matter in strong lensing galaxies I. Ferreras, P. Saha, L. Williams and S. Burles; Tidal debris posing as dark galaxies P. Duc, F. Bournaud and E. Brinks

Possible maternal offloading of metals in the plasma, uterine and capsule fluid of pregnant ragged-tooth sharks (Carcharias taurus) on the east coast of South Africa.

PubMed

Naidoo, Kristina; Chuturgoon, Anil; Cliff, Geremy; Singh, Sanil; Ellis, Megan; Otway, Nicholas; Vosloo, Andre; Gregory, Michael

2017-07-01

We studied the possible metal offloading onto the progeny of three pregnant female ragged-tooth sharks (Carcharias taurus) (C. taurus). The presences of five metals, i.e. aluminium (Al), arsenic (As), cadmium (Cd), lead (Pb) and selenium (Se) were validated by mass spectrometry in the maternal plasma as well as the intracapsular and uterine fluids (UF) in which embryos develop. Metals were ranked in a decreasing concentration as follows: Plasma: As > Al > Se > Pb > Cd; ICF: As > Se > Al > Cd > Pb and UF: As > Se > Al > Cd > Pb. As was present in the highest concentration in all three sharks. Al, Pb and Cd were found to be the highest within the plasma, while concentrations of Se were similar in all three fluids. These results indicate that C. taurus embryos are exposed to metals during early development, but the impact of this exposure remains unknown. To the best of our knowledge, this is the first investigation to confirm the presence of metals in the fluids that surround the developing C. taurus embryos, a species that is already listed as vulnerable.

Equilibrium Slab Models of Lyman-Alpha Clouds

NASA Technical Reports Server (NTRS)

Charlton, Jane C.; Salpeter, Edwin E.; Hogan, Craig J.

1993-01-01

We model the L(sub y(alpha)) clouds as slabs of hydrogen with an ionizing extragalactic radiation field incident from both sides. In general, the equilibrium configuration of a slab at redshift z approx. less than 5 is determined by a balance of the gas pressure, gravity (including the effects of a dark matter halo), and the pressure exerted by the inter-galactic medium, P(sub ext). These models have been used to make predictions of the number of slabs as a function of the neutral hydrogen column density, N(sub H). A break in the curve is predicted at the transition between regimes where gravity and pressure are the dominant confining forces, with a less rapid decrease at larger N(sub H). The transition from optically thin to optically thick slabs leads to a gap in the distribution, whose location is governed largely by the spectrum of ionizing radiation. There are certain parallels between lines of sight through the outer HI disk of spiral galaxy with increasing radius, and the progression from damped, to Lyman limit, to forest clouds. We discuss briefly the possibility that at least some of the observed low z forest clouds may be a separate population, associated with galaxies, as suggested by the observations of Bahcall et al. This population could dominate the forest at present if the dark matter attached to galaxies should lead to gravity confinement for this disk population, while the isolated clouds remain pressure confined. The formalism developed in this paper will allow a more detailed study. We also discuss a more general parameter study of the equilibrium configuration of slabs, including mock gravity and L(sub y(alpha)) photon trapping.

A Submillimetre Study of Massive Star Formation Within the W51 Complex and Infrared Dark Clouds

NASA Astrophysics Data System (ADS)

Parsons, Harriet Alice Louise

Despite its importance the fundamental question of how massive stars form remains unanswered, with improvements to both models and observations having crucial roles to play. To quote Bate et al. (2003) computational models of star formation are limited because "conditions in molecular clouds are not sufficiently well understood to be able to select a representative sample of cloud cores for the initial conditions". It is this notion that motivates the study of the environments within Giant Molecular Clouds (GMCs) and Infrared Dark Clouds (IRDCs), known sites of massive star formation, at the clump and core level. By studying large populations of these objects, it is possible to make conclusions based on global properties. With this in mind I study the dense molecular clumps within one of the most massive GMCs in the Galaxy: the W51 GMC. New observations of the W51 GMC in the 12CO, 13CO and C18O (3-2) transitions using the HARP instrument on the JCMT are presented. With the help of the clump finding algorithm CLUMPFIND a total of 1575 dense clumps are identified of which 1130 are associated with the W51 GMC, yielding a dense mass reservoir of 1.5 × 10^5 M contained within these clumps. Of these clumps only 1% by number are found to be super-critical, yielding a super-critical clump formation efficiency of 0.5%, below current SFE estimates of the region. This indicates star formation within the W51 GMC will diminish over time although evidence from the first search for molecular outflows presents the W51 GMC in an active light with a lower limit of 14 outflows. The distribution of the outflows within the region searched found them concentrated towards the W51A region. Having much smaller sizes and masses, obtaining global properties of clumps and cores within IRDCs required studying a large sample of these objects. To do this pre-existing data from the SCUBA Legacy Catalogue was utilised to study IRDCs within a catalogues based on 8 μm data. This data identified

Star-Forming Clouds Feed, Churn, and Fall

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-12-01

Molecular clouds, the birthplaces of stars in galaxies throughout the universe, are complicated and dynamic environments. A new series of simulations has explored how these clouds form, grow, and collapse over their lifetimes.This composite image shows part of the Taurus Molecular Cloud. [ESO/APEX (MPIfR/ESO/OSO)/A. Hacar et al./Digitized Sky Survey]Stellar BirthplacesMolecular clouds form out of the matter in between stars, evolving through constant interactions with their turbulent environments. These interactions taking the form of accretion flows and surface forces, while gravity, turbulence, and magnetic fields interplay are thought to drive the properties and evolution of the clouds.Our understanding of the details of this process, however, remains fuzzy. How does mass accretion affect these clouds as they evolve? What happens when nearby supernova explosions blast the outsides of the clouds? What makes the clouds churn, producing the motion within them that prevents them from collapsing? The answers to these questions can tellus about the gas distributed throughout galaxies, revealing information about the environments in which stars form.A still from the simulation results showing the broader population of molecular clouds that formed in the authors simulations, as well as zoom-in panels of three low-mass clouds tracked in high resolution. [Ibez-Meja et al. 2017]Models of TurbulenceIn a new study led by Juan Ibez-Meja (MPI Garching and Universities of Heidelberg and Cologne in Germany, and American Museum of Natural History), scientists have now explored these questions using a series of three-dimensional simulations of a population of molecular clouds forming and evolving in the turbulent interstellar medium.The simulations take into account a whole host of physics, including the effects of nearby supernova explosions, self-gravitation, magnetic fields, diffuse heating, and radiative cooling. After looking at the behavior of the broader population of

Chemistry in Infrared Dark Cloud Clumps: A Molecular Line Survey at 3 mm

NASA Astrophysics Data System (ADS)

Sanhueza, Patricio; Jackson, James M.; Foster, Jonathan B.; Garay, Guido; Silva, Andrea; Finn, Susanna C.

2012-09-01

We have observed 37 Infrared Dark Clouds (IRDCs), containing a total of 159 clumps, in high-density molecular tracers at 3 mm using the 22 m ATNF Mopra Telescope located in Australia. After determining kinematic distances, we eliminated clumps that are not located in IRDCs and clumps with a separation between them of less than one Mopra beam. Our final sample consists of 92 IRDC clumps. The most commonly detected molecular lines are (detection rates higher than 8%) N2H+, HNC, HN13C, HCO+, H13CO+, HCN, C2H, HC3N, HNCO, and SiO. We investigate the behavior of the different molecular tracers and look for chemical variations as a function of an evolutionary sequence based on Spitzer IRAC and MIPS emission. We find that the molecular tracers behave differently through the evolutionary sequence and some of them can be used to yield useful relative age information. The presence of HNC and N2H+ lines does not depend on the star formation activity. On the other hand, HC3N, HNCO, and SiO are predominantly detected in later stages of evolution. Optical depth calculations show that in IRDC clumps the N2H+ line is optically thin, the C2H line is moderately optically thick, and HNC and HCO+ are optically thick. The HCN hyperfine transitions are blended, and, in addition, show self-absorbed line profiles and extended wing emission. These factors combined prevent the use of HCN hyperfine transitions for the calculation of physical parameters. Total column densities of the different molecules, except C2H, increase with the evolutionary stage of the clumps. Molecular abundances increase with the evolutionary stage for N2H+ and HCO+. The N2H+/HCO+ and N2H+/HNC abundance ratios act as chemical clocks, increasing with the evolution of the clumps.

The Brain of the Domestic Bos taurus: Weight, Encephalization and Cerebellar Quotients, and Comparison with Other Domestic and Wild Cetartiodactyla

PubMed Central

Ballarin, Cristina; Povinelli, Michele; Granato, Alberto; Panin, Mattia; Corain, Livio; Peruffo, Antonella; Cozzi, Bruno

2016-01-01

The domestic bovine Bos taurus is raised worldwide for meat and milk production, or even for field work. However the functional anatomy of its central nervous system has received limited attention and most of the reported data in textbooks and reviews are derived from single specimens or relatively old literature. Here we report information on the brain of Bos taurus obtained by sampling 158 individuals, 150 of which at local abattoirs and 8 in the dissecting room, these latter subsequently formalin-fixed. Using body weight and fresh brain weight we calculated the Encephalization Quotient (EQ), and Cerebellar Quotient (CQ). Formalin-fixed brains sampled in the necropsy room were used to calculate the absolute and relative weight of the major components of the brain. The data that we obtained indicate that the domestic bovine Bos taurus possesses a large, convoluted brain, with a slightly lower weight than expected for an animal of its mass. Comparisons with other terrestrial and marine members of the order Cetartiodactyla suggested close similarity with other species with the same feeding adaptations, and with representative baleen whales. On the other hand differences with fish-hunting toothed whales suggest separate evolutionary pathways in brain evolution. Comparison with the other large domestic herbivore Equus caballus (belonging to the order Perissodactyla) indicates that Bos taurus underwent heavier selection of bodily traits, which is also possibly reflected in a comparatively lower EQ than in the horse. The data analyzed suggest that the brain of domestic bovine is potentially interesting for comparative neuroscience studies and may represents an alternative model to investigate neurodegeneration processes. PMID:27128674

Artist's concept of topographical layout of Taurus-Littrow landing site

NASA Image and Video Library

1972-10-01

S72-49761 (October 1972) --- An artist's concept illustrating the topographical layout of the Taurus-Littrow landing site of the Apollo 17 lunar landing mission. The Lunar Module touchdown point is in the center of the smooth area in the middle of the picture. The imposing mountain in the center is South Massif. A portion of North Massif is in the lower right corner of the photograph. Note the ridge-like feature extending from South Massif to North Massif. The southern portion of the ridge is called Lee Scarp and the northerly portion Lincoln Scarp. (This concept is by JSC artist Jerry Elmore).

Analysis of Bos taurus and Sus scrofa X and Y chromosome transcriptome highlights reproductive driver genes

PubMed Central

Khan, Faheem Ahmed; Liu, Hui; Zhou, Hao; Wang, Kai; Qamar, Muhammad Tahir Ul; Pandupuspitasari, Nuruliarizki Shinta; Shujun, Zhang

2017-01-01

The biology of sperm, its capability of fertilizing an egg and its role in sex ratio are the major biological questions in reproductive biology. To answer these question we integrated X and Y chromosome transcriptome across different species: Bos taurus and Sus scrofa and identified reproductive driver genes based on Weighted Gene Co-Expression Network Analysis (WGCNA) algorithm. Our strategy resulted in 11007 and 10445 unique genes consisting of 9 and 11 reproductive modules in Bos taurus and Sus scrofa, respectively. The consensus module calculation yields an overall 167 overlapped genes which were mapped to 846 DEGs in Bos taurus to finally get a list of 67 dual feature genes. We develop gene co-expression network of selected 67 genes that consists of 58 nodes (27 down-regulated and 31 up-regulated genes) enriched to 66 GO biological process (BP) including 6 GO annotations related to reproduction and two KEGG pathways. Moreover, we searched significantly related TF (ISRE, AP1FJ, RP58, CREL) and miRNAs (bta-miR-181a, bta-miR-17-5p, bta-miR-146b, bta-miR-146a) which targeted the genes in co-expression network. In addition we performed genetic analysis including phylogenetic, functional domain identification, epigenetic modifications, mutation analysis of the most important reproductive driver genes PRM1, PPP2R2B and PAFAH1B1 and finally performed a protein docking analysis to visualize their therapeutic and gene expression regulation ability. PMID:28903352

On the Non-Equilibrium Population Distribution of E-Methanol in Dark Clouds

NASA Astrophysics Data System (ADS)

Wollman, Emma

2007-12-01

The goal of this project was to determine the typical distribution of rotational level populations in the k=0 ladder of E-methanol in dark clouds in order to provide another observational test for theoretical models of pumping. We used our own observations of several sources with the 12-m ARO telescope on Kitt Peak as well as the published observational results by Slysh et al. (1999). The relative level populations (excitation temperatures) were determined from the measured intensity ratios of a series of the J(0)-J(-1) transitions of E-methanol under the assumption of spontaneous, optically thin emission. We observed the J(0)-J(-1) lines in six sources: W75N, DR21N, DR21, and three positions at DR21OH. The J=1 to J=5 lines were observed for all sources and the J=7 line was observed for W75N, DR21N, and one position in DR21OH. We also used Slysh et al.'s results for the J=1 through 4 lines in 52 sources, for the J=5 line in 50 sources, for the J=6 line in 15 sources, and for the J=7 and 8 lines in 2 sources. We determined the excitation temperatures of the involved levels in the k=0 ladder relative to the 1(0) level for each source and averaged the results over the sources. The average excitation temperatures demonstrate strong evidence of overcooling in the k=0 ladder - the excitation temperature increases linearly with increasing energy, from 8 K to 35 K. Our observations confirm this tendency of overcooling. We will discuss the agreement of these results with the predictions of the current models of methanol pumping. The author thanks the technical staff of the 12-m ARO telescope for help with the observations. This project was supported by the NSF/REU grant AST-0354056 and the Nantucket Maria Mitchell Association.

Radar Evaluation of Optical Cloud Constraints to Space Launch Operations

NASA Technical Reports Server (NTRS)

Merceret, Francis J.; Short, David A.; Ward, Jennifer G.

2005-01-01

Weather constraints to launching space vehicles are designed to prevent loss of the vehicle or mission due to weather hazards (See, e.g., Ref 1). Constraints include Lightning Launch Commit Criteria (LLCC) designed to avoid natural and triggered lightning. The LLCC currently in use at most American launch sites including the Eastern Range and Kennedy Space Center require the Launch Weather Officer to determine the height of cloud bases and tops, the location of cloud edges, and cloud transparency. The preferred method of making these determinations is visual observation, but when that isn't possible due to darkness or obscured vision, it is permissible to use radar. This note examines the relationship between visual and radar observations in three ways: A theoretical consideration of the relationship between radar reflectivity and optical transparency. An observational study relating radar reflectivity to cloud edge determined from in-situ measurements of cloud particle concentrations that determine the visible cloud edge. An observational study relating standard radar products to anvil cloud transparency. It is shown that these three approaches yield results consistent with each other and with the radar threshold specified in Reference 2 for LLCC evaluation.

Impact of Parental Bos taurus and Bos indicus Origins on Copy Number Variation in Traditional Chinese Cattle Breeds.

PubMed

Zhang, Liangzhi; Jia, Shangang; Plath, Martin; Huang, Yongzhen; Li, Congjun; Lei, Chuzhao; Zhao, Xin; Chen, Hong

2015-08-10

Copy number variation (CNV) is an important component of genomic structural variation and plays a role not only in evolutionary diversification but also in domestication. Chinese cattle were derived from Bos taurus and Bos indicus, and several breeds presumably are of hybrid origin, but the evolution of CNV regions (CNVRs) has not yet been examined in this context. Here, we of CNVRs, mtDNA D-loop sequence variation, and Y-chromosomal single nucleotide polymorphisms to assess the impact of maternal and paternal B. taurus and B. indicus origins on the distribution of CNVRs in 24 Chinese domesticated bulls. We discovered 470 genome-wide CNVRs, only 72 of which were shared by all three Y-lineages (B. taurus: Y1, Y2; B. indicus: Y3), whereas 265 were shared by inferred taurine or indicine paternal lineages, and 228 when considering their maternal taurine or indicine origins. Phylogenetic analysis uncovered eight taurine/indicine hybrids, and principal component analysis on CNVs corroborated genomic exchange during hybridization. The distribution patterns of CNVRs tended to be lineage-specific, and correlation analysis revealed significant positive or negative co-occurrences of CNVRs across lineages. Our study suggests that CNVs in Chinese cattle partly result from selective breeding during domestication, but also from hybridization and introgression. © The Author(s) 2015. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

Fundamental Particle Structure in the Cosmological Dark Matter

NASA Astrophysics Data System (ADS)

Khlopov, Maxim

2013-11-01

The nonbaryonic dark matter of the universe is assumed to consist of new stable forms of matter. Their stability reflects symmetry of micro-world and mechanisms of its symmetry breaking. Particle candidates for cosmological dark matter are lightest particles that bear new conserved quantum numbers. Dark matter particles may represent ideal gas of noninteracting particles. Self-interacting dark matter weakly or superweakly coupled to ordinary matter is also possible, reflecting nontrivial pattern of particle symmetry in the hidden sector of particle theory. In the early universe the structure of particle symmetry breaking gives rise to cosmological phase transitions, from which macroscopic cosmological defects or primordial nonlinear structures can be originated. Primordial black holes (PBHs) can be not only a candidate for dark matter, but also represent a universal probe for superhigh energy physics in the early universe. Evaporating PBHs turn to be a source of even superweakly interacting particles, while clouds of massive PBHs can serve as nonlinear seeds for galaxy formation. The observed broken symmetry of the three known families may provide a simultaneous solution for the problems of the mass of neutrino and strong CP-violation in the unique framework of models of horizontal unification. Dark matter candidates can also appear in the new families of quarks and leptons and the existence of new stable charged leptons and quarks is possible, hidden in elusive "dark atoms." Such possibility, strongly restricted by the constraints on anomalous isotopes of light elements, is not excluded in scenarios that predict stable double charged particles. The excessive -2 charged particles are bound in these scenarios with primordial helium in O-helium "atoms," maintaining specific nuclear-interacting form of the dark matter, which may provide an interesting solution for the puzzles of the direct dark matter searches. In the context of cosmoparticle physics, studying

Sarcocystis heydorni, n. sp. (Apicomplexa: Protozoa) with cattle (Bos taurus) and human (Homo sapiens) cycle

USDA-ARS?s Scientific Manuscript database

Cattle (Bos taurus) are intermediate hosts for four species of Sarcocystis, S. cruzi, S. hirsuta, S. hominis, and S. rommeli. Of these four species, mature sarcocysts of S. cruzi are thin-walled (< 1µm) whereas S. hirsuta, S. hominis, and S. rommeli have thick walls (4 µm or more). Here we describe ...

Aerosol-Forming Reactions of Glyoxal, Methylglyoxal and Amino Acids in Clouds

NASA Astrophysics Data System (ADS)

de Haan, D. O.; Smith, K. W.; Stroik, D. R.; Corrigan, A. L.; Lee, F. E.; Phan, J. T.; Conley, A. C.

2008-12-01

Glyoxal and methylglyoxal are two common aldehydes present in fog and cloud water. Amino acids are present in clouds at similar concentrations. Here we present bulk and aerosol mass spectroscopic data demonstrating that irreversible reactions between glyoxal and amino acids, triggered by droplet evaporation, produce N-derivatized imidazole compounds along with deeply colored Maillard reaction products. These reactions can occur in the dark and in the absence of oxidants. Reactions between methylglyoxal and amino acids produce analogous methylated products plus oligomers with masses up to m/z = 1000. These reactions, which go to completion on the 10-min-timescale of cloud processing, could be significant sources of secondary organic aerosol and humic-like substances (HULIS or brown carbon).

The abundance of CO in diffuse interstellar clouds - An ultraviolet survey

NASA Technical Reports Server (NTRS)

Federman, S. R.; Glassgold, A. E.; Jenkins, E. B.; Shaya, E. J.

1980-01-01

CO was detected in 17 directions and its upper limits were estimated in 21 directions by a UV survey carried out with the Copernicus satellite in the C-X 1088 A and E-X 1076 A lines toward 48 bright stars. The CO column densities range from 10 to the 12th to 10 to the 17th/sq cm and correlate with C I and H2. The tendency of the C I/CO ratio to be about 10 follows the ratio of particular atomic and molecular cross-sections and the physical parameters of interstellar clouds. Finally, the connection between UV observations in diffuse clouds and radio observations of (C-13)O in dark clouds is discussed.

Core Emergence in a Massive Infrared Dark Cloud: A Comparison between Mid-IR Extinction and 1.3 mm Emission

NASA Astrophysics Data System (ADS)

Kong, Shuo; Tan, Jonathan C.; Arce, Héctor G.; Caselli, Paola; Fontani, Francesco; Butler, Michael J.

2018-03-01

Stars are born from dense cores in molecular clouds. Observationally, it is crucial to capture the formation of cores in order to understand the necessary conditions and rate of the star formation process. The Atacama Large Millimeter/submillimeter Array (ALMA) is extremely powerful for identifying dense gas structures, including cores, at millimeter wavelengths via their dust continuum emission. Here, we use ALMA to carry out a survey of dense gas and cores in the central region of the massive (∼105 M ⊙) infrared dark cloud (IRDC) G28.37+0.07. The observation consists of a mosaic of 86 pointings of the 12 m array and produces an unprecedented view of the densest structures of this IRDC. In this first Letter about this data set, we focus on a comparison between the 1.3 mm continuum emission and a mid-infrared (MIR) extinction map of the IRDC. This allows estimation of the “dense gas” detection probability function (DPF), i.e., as a function of the local mass surface density, Σ, for various choices of thresholds of millimeter continuum emission to define “dense gas.” We then estimate the dense gas mass fraction, f dg, in the central region of the IRDC and, via extrapolation with the DPF and the known Σ probability distribution function, to the larger-scale surrounding regions, finding values of about 5% to 15% for the fiducial choice of threshold. We argue that this observed dense gas is a good tracer of the protostellar core population and, in this context, estimate a star formation efficiency per free-fall time in the central IRDC region of ɛ ff ∼ 10%, with approximately a factor of two systematic uncertainties.

Ionisation in turbulent magnetic molecular clouds. I. Effect on density and mass-to-flux ratio structures

NASA Astrophysics Data System (ADS)

Bailey, Nicole D.; Basu, Shantanu; Caselli, Paola

2017-05-01

little structural difference between the SL and CR-only models, while below this threshold the ionisation structure significantly affects the formation of filaments. This holds true for both sets of models. Analysis of the mass within cores and filaments shows that the mass decreases as the degree of turbulence increases. Finally, observed filaments within the Taurus L1495/B213 complex are best reproduced by models with supercritical mass-to-flux ratios and/or at least mildly supersonic turbulence, however, our models show that the sterile fibres observed within Taurus may occur in highly ionised, subcritical environments. Conclusions: From the analysis of the simulations, we conclude that in the presence of low turbulent velocities, the ionisation structure of the medium still plays a role in shaping the structure of the cloud, however, above Mach 2, the differences between the two profiles become indistinguishable. However, differences may be present in the underlying velocity structure. Kinematics studies will be the focus of the next paper in this series. Regions with fertile fibres likely indicate a trans- or supercritical mass-to-flux ratio within the region while sterile fibres are likely subcritical and transient.

The wavelet transform as an analysis tool for structure identification in molecular clouds

NASA Astrophysics Data System (ADS)

Gill, Arnold Gerald

1993-01-01

Of the many methods used to attempt to understand the complex structure of giant molecular clouds, perhaps the most commonly used are the autocorrelation functions (ACF), the structure function, and the power spectrum. However, these do not give unique interpretations of structure, as is shown by explicit examples compared to the Taurus Molecular Complex. Thus, another, independent method of analysis is indicated. Here, the wavelet transform is presented, a relatively new technique less than 10 years old. It can be thought of as a band-pass filter that identifies structures of specific sizes. In addition, its mathematical properties allow it to be used to identify fractal structures and accurately identify the scaling exponent. This is shown by the wavelet transform identifying the fractal dimension of a hierarchical rain cloud model first proposed by Frisch et al. (1978). A wavelet analysis is then carried out for a range of astronomical CO data, including the clouds Orion A and B and NGC 7538 (in (12)CO) and Orion A and B, Mon R2, and L1551 (in (13)CO). The data analyzed consists of the velocities of the fitted Gaussians to the individual spectra, the halfwidths and amplitude of these Gaussians, and the total area of the spectral line. For most of the clouds investigated, each of these data types showed a very high degree of scaling coherence over a wide range of scales, from down at the beam spacing up to the full size of the cloud. The analysis carried out uses both the scaling and structure identification strengths of the wavelet transform The fragmentation parameters used by Scalo (1985) and the parameters of the geometric molecular cloud description introduced by Henriksen (1986) are calculated for each cloud. These results are all consistent with previous observations of these and other molecular clouds, though they are obtained individually for each cloud investigated. It is found that the uncertainties are of a magnitude that the differentiation of

Extinction map of Chamaeleon I molecular cloud with DENIS star counts.

NASA Astrophysics Data System (ADS)

Cambresy, L.; Epchtein, N.; Copet, E.; de Batz, B.; Kimeswenger, S.; Le Bertre, T.; Rouan, D.; Tiphene, D.

1997-08-01

Massive, large scale star counts in the J (1.25μm) band provided by the Deep Near Infrared Survey of the Southern Sky (DENIS) are used for the first time to draw out an extinction map of the Chamaeleon I dark cloud. We derived a 2' resolution map of the cloud from J star counts within an area of 1.5°x3° around the centre of the cloud using an adaptive grid method and applying a wavelet decomposition. Possible contaminating young stellar objects within the cloud are removed, although they are shown to have a negligible effect on the counts. A comparison of our extinction map with the cold contribution of the IRAS 100μm emission shows an almost perfect matching. It is shown that J star counts supersede optical counts on Schmidt plate where A_V_>4.

Cosmic-ray exposure history at Taurus-Littrow

NASA Technical Reports Server (NTRS)

Drozd, R. J.; Hohenberg, C. M.; Morgan, C. J.; Podosek, F. A.; Wroge, M. L.

1977-01-01

Recent surface history at Taurus-Littrow is dominated by emplacement of the Central Cluster and Bright Mantle morphological units, both believed to have resulted from arrival of ejecta from a large primary crater, probably Tycho. This paper reports new noble gas data for eight Apollo 17 rocks. Kr-81 - Kr cosmic ray exposure ages for these rocks affirm the observation of a pronounced grouping of ages, reinforcing the photogeologic evidence for the site-wide nature of the Central Cluster event. The consequences of post-cratering shielding changes are considered and it is concluded that the differences can reasonably be attributed to these changes, particularly because of the greater likelihood of rollover and impact fragmentation of the relatively smaller rocks from which most age data have been obtained. These considerations also lead to a more refined age estimate of 109 plus or minus 4 m.y. for Central Cluster, the Bright Mantle, and Tycho.

Dark and Stormy Jupiter

NASA Image and Video Library

2018-06-14

This image captures the intensity of the jets and vortices in Jupiter's North North Temperate Belt. NASA's Juno spacecraft took this color-enhanced image at 10:31 p.m. PDT on May 23, 2018 (1:31 a.m. EDT on May 24), as Juno performed its 13th close flyby of Jupiter. At the time, the spacecraft was about 4,900 miles (7,900 kilometers) from the tops of the clouds of the gas giant planet at a northern latitude of about 41 degrees. The view is oriented with south on Jupiter toward upper left and north toward lower right. The North North Temperate Belt is the prominent reddish-orange band left of center. It rotates in the same direction as the planet and is predominantly cyclonic, which in the northern hemisphere means its features spin in a counter-clockwise direction. Within the belt are two gray-colored anticyclones. To the left of the belt is a brighter band (the North North Temperate Zone) with high clouds whose vertical relief is accentuated by the low angle of sunlight near the terminator. These clouds are likely made of ammonia-ice crystals, or possibly a combination of ammonia ice and water. Although the region as a whole appears chaotic, there is an alternating pattern of rotating, lighter-colored features on the zone's north and south sides. Scientists think the large-scale dark regions are places where the clouds are deeper, based on infrared observations made at the same time by Juno's JIRAM experiment and Earth-based supporting observations. Those observations show warmer, and thus deeper, thermal emission from these regions. To the right of the bright zone, and farther north on the planet, Jupiter's striking banded structure becomes less evident and a region of individual cyclones can be seen, interspersed with smaller, darker anticyclones. https://photojournal.jpl.nasa.gov/catalog/PIA22423

Chemical compositions, free amino acid contents and antioxidant activities of Hanwoo (Bos taurus coreanae) beef by cut

USDA-ARS?s Scientific Manuscript database

The objective of this study was to evaluate chemical compositions, free amino acid contents, and antioxidant activities of different cuts of Hanwoo (Bos taurus coreanae) beef. Beef preferences and prices in the Korean market depend on cut. Therefore, comparisons were made between high-preference (gr...

Is the gas-phase OH+H2CO reaction a source of HCO in interstellar cold dark clouds? A kinetic, dynamic and modelling study

PubMed Central

Ocaña, A. J.; Jiménez, E.; Ballesteros, B.; Canosa, A.; Antiñolo, M.; Albaladejo, J.; Agúndez, M.; Cernicharo, J.; Zanchet, A.; del Mazo, P.; Roncero, O.; Aguado, A.

2018-01-01

Chemical kinetics of neutral-neutral gas-phase reactions at ultralow temperatures is a fascinating research subject with important implications on the chemistry of complex organic molecules in the interstellar medium (T∼10-100K). Scarce kinetic information is currently available for this kind of reactions at T<200 K. In this work we use the CRESU (Cinétique de Réaction en Ecoulement Supersonique Uniforme, which means Reaction Kinetics in a Uniform Supersonic Flow) technique to measure for the first time the rate coefficients (k) of the gas-phase OH+H2CO reaction between 22 and 107 K. k values greatly increase from 2.1×10-11 cm3 s-1 at 107 K to 1.2×10-10 cm3 s-1 at 22 K. This is also confirmed by quasi-classical trajectories (QCT) at collision energies down to 0.1 meV performed using a new full dimension and ab initio potential energy surface, recently developed which generates highly accurate potential and includes long range dipole-dipole interactions. QCT calculations indicate that at low temperatures HCO is the exclusive product for the OH+H2CO reaction. In order to revisit the chemistry of HCO in cold dense clouds, k is reasonably extrapolated from the experimental results at 10K (2.6×10-10 cm3 s-1). The modeled abundances of HCO are in agreement with the observations in cold dark clouds for an evolving time of 105-106 yrs. The different sources of production of HCO are presented and the uncertainties in the chemical networks discussed. This reaction can be expected to be a competitive process in the chemistry of prestellar cores. The present reaction is shown to account for a few percent of the total HCO production rate. Extensions to photodissociation regions and diffuse clouds environments are also commented. PMID:29880977

Is the Gas-phase OH+H2CO Reaction a Source of HCO in Interstellar Cold Dark Clouds? A Kinetic, Dynamic, and Modeling Study

NASA Astrophysics Data System (ADS)

Ocaña, A. J.; Jiménez, E.; Ballesteros, B.; Canosa, A.; Antiñolo, M.; Albaladejo, J.; Agúndez, M.; Cernicharo, J.; Zanchet, A.; del Mazo, P.; Roncero, O.; Aguado, A.

2017-11-01

The chemical kinetics of neutral-neutral gas-phase reactions at ultralow temperatures is a fascinating research subject with important implications on the chemistry of complex organic molecules in the interstellar medium (T ˜ 10-100 K). Scarce kinetic information is currently available for these kinds of reactions at T < 200 K. In this work, we use the Cinétique de Réaction en Ecoulement Supersonique Uniforme (CRESU; Reaction Kinetics in a Uniform Supersonic Flow) technique to measure for the first time the rate coefficients (k) of the gas-phase OH+H2CO reaction between 22 and 107 K. The k values greatly increase from 2.1 × 10-11 cm3 s-1 at 107 K to 1.2 × 10-10 cm3 s-1 at 22 K. This is also confirmed by quasi-classical trajectories (QCT) at collision energies down to 0.1 meV performed using a new full dimension and ab initio potential energy surface that generates highly accurate potential and includes long-range dipole-dipole interactions. QCT calculations indicate that at low temperatures HCO is the exclusive product for the OH+H2CO reaction. In order to revisit the chemistry of HCO in cold dense clouds, k is reasonably extrapolated from the experimental results at 10 K (2.6 × 10-10 cm3 s-1). The modeled abundances of HCO are in agreement with the observations in cold dark clouds for an evolving time of 105-106 yr. The different sources of production of HCO are presented and the uncertainties in the chemical networks are discussed. The present reaction is shown to account for a few percent of the total HCO production rate. This reaction can be expected to be a competitive process in the chemistry of prestellar cores. Extensions to photodissociation regions and diffuse cloud environments are also addressed.

Is the gas-phase OH+H2CO reaction a source of HCO in interstellar cold dark clouds? A kinetic, dynamic and modelling study.

PubMed

Ocaña, A J; Jiménez, E; Ballesteros, B; Canosa, A; Antiñolo, M; Albaladejo, J; Agúndez, M; Cernicharo, J; Zanchet, A; Del Mazo, P; Roncero, O; Aguado, A

2017-11-20

Chemical kinetics of neutral-neutral gas-phase reactions at ultralow temperatures is a fascinating research subject with important implications on the chemistry of complex organic molecules in the interstellar medium (T∼10-100K). Scarce kinetic information is currently available for this kind of reactions at T<200 K. In this work we use the CRESU ( Cinétique de Réaction en Ecoulement Supersonique Uniforme , which means Reaction Kinetics in a Uniform Supersonic Flow) technique to measure for the first time the rate coefficients ( k ) of the gas-phase OH+H 2 CO reaction between 22 and 107 K. k values greatly increase from 2.1×10 -11 cm 3 s -1 at 107 K to 1.2×10 -10 cm 3 s -1 at 22 K. This is also confirmed by quasi-classical trajectories (QCT) at collision energies down to 0.1 meV performed using a new full dimension and ab initio potential energy surface, recently developed which generates highly accurate potential and includes long range dipole-dipole interactions. QCT calculations indicate that at low temperatures HCO is the exclusive product for the OH+H 2 CO reaction. In order to revisit the chemistry of HCO in cold dense clouds, k is reasonably extrapolated from the experimental results at 10K (2.6×10 -10 cm 3 s -1 ). The modeled abundances of HCO are in agreement with the observations in cold dark clouds for an evolving time of 10 5 -10 6 yrs. The different sources of production of HCO are presented and the uncertainties in the chemical networks discussed. This reaction can be expected to be a competitive process in the chemistry of prestellar cores. The present reaction is shown to account for a few percent of the total HCO production rate. Extensions to photodissociation regions and diffuse clouds environments are also commented.

CO-ices in embedded Young Stellar Objects

NASA Astrophysics Data System (ADS)

Teixeira, Teresa Cláeira V. S.

1998-09-01

significance of the results is discussed. Excellent fits to the nonpolar component of the CO-ices along the observed lines-of-sight are produced with ion irradiated pure CO ices. The possible origin of the ion irradiation is discussed, covering flares on the YSOs, cosmic rays and X-ray and UV processing. Predictions are made for the abundance of CO2 and methanol in the mantles. Furthermore, a comparison is made between the results of observations of CO and H2 O ices towards the Taurus and Ophiuchus dark clouds. The column densities of the ices are compared with the visual extinction, Av, through the clouds, and with the 1.3mm continuum emission from the YSOs. The inclusion of the objects in Taurus observed in this work resulted in the appearance of a discontinuity in the relation between the water-ice column density and Av, at the value of Av for which the optical depth at 3 microns (the wavelength of the water-ice absorption feature) is unity. Finally, all the observations and results discussed throughout the thesis are brought together to address their implications in the current understanding of the conditions in Taurus and Ophiuchus. Thesis and published paper available at http://www.obs.aau.dk/~tct/

THE PHYSICAL ENVIRONMENT AROUND IRAS 17599–2148: INFRARED DARK CLOUD AND BIPOLAR NEBULA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dewangan, L. K.; Janardhan, P.; Ojha, D. K.

We present a multiscale and multiwavelength study to investigate the star formation process around IRAS 17599–2148, which is part of an elongated filamentary structure (EFS) (extension ∼21 pc) seen in the Herschel maps. Using the Herschel data analysis, at least six massive clumps (M {sub clump} ∼ 777–7024 M {sub ⊙}) are found in the EFS with a range of temperature and column density of ∼16–39 K and ∼(0.6–11) × 10{sup 22} cm{sup −2} (A {sub V}  ∼ 7–117 mag), respectively. The EFS hosts cold gas regions (i.e., infrared dark cloud) without any radio detection and a bipolar nebula (BN) linked with the Hmore » ii region IRAS 17599–2148, tracing two distinct environments inferred through the temperature distribution and ionized emission. Based on virial analysis and higher values of self-gravitating pressure, the clumps are found unstable against gravitational collapse. We find 474 young stellar objects (YSOs) in the selected region, and ∼72% of these YSOs are found in the clusters distributed mainly toward the clumps in the EFS. These YSOs might have spontaneously formed due to processes not related to the expanding H ii region. At the edges of BN, four additional clumps are also associated with YSO clusters, which appear to be influenced by the expanding H ii region. The most massive clump in the EFS contains two compact radio sources traced in the Giant Metre-wave Radio Telescope 1.28 GHz map and a massive protostar candidate, IRS 1, prior to an ultracompact H ii phase. Using the Very Large Telescope/NACO near-infrared images, IRS 1 is resolved with a jet-like feature within a 4200 au scale.« less

Comparison View of Mars Cloud Cover

NASA Technical Reports Server (NTRS)

1997-01-01

These color and black and white pictures of Mars were taken by NASA's Hubble Space Telescope just two weeks after Earth made its closest approach to the Red Planet during the 1997 opposition. When the Hubble pictures were taken Mars was at a distance of 62 million miles (100 million kilometers) and the resolution at the center of the disk is 13.5 miles/pixel (22 kilometers/pixel). Both images were made with the Wide Field and Planetary Camera 2. The color composite (left image) is constructed from three images taken in red (673 nanometers), green (502 nm) and blue (410 nm) light. The right image, in blue light only, brings out details in the cloud structure and is remarkably similar to weather satellite pictures taken of Earth. A planetary-scale wave curls around the north pole, similar in behavior to high latitude cold fronts which descend over North America and Europe during springtime.

The picture was taken when Mars was near aphelion, its farthest point from the Sun. The faint sunlight results in cold atmospheric conditions which stimulate the formation of water ice clouds. The clouds themselves further reduce atmospheric temperatures. Atmospheric heating, resulting when sunlight is absorbed by the dust, is reduced when ice forms around the dust particles and causes the dust to gravitationally settle to the ground.

These images of Mars are centered at approximately 94 degrees longitude and 23 degrees N latitude (oriented with north up). The four largest Tharsis Montes (massive extinct volcanoes) are visible as dark spots extending through the clouds. The vast canyon system, Valles Marineris, stretches across the eastern (lower right) half of the image; the Pathfinder landing site is near the eastern edge of the image. It is early summer in the northern hemisphere, and the North polar cap has retreated to about 80 degrees N latitude; the 'residual' summer cap, which is composed of water ice, is about one-third the size of the 'seasonal' winter cap, which

Jets and Water Clouds on Jupiter

NASA Astrophysics Data System (ADS)

Lian, Yuan; Showman, A. P.

2012-10-01

Ground-based and spacecraft observations show that Jupiter exhibits multiple banded zonal jet structures. These banded jets correlate with dark and bright clouds, often called "belts" and "zones". The mechanisms that produce these banded zonal jets and clouds are poorly understood. Our previous studies showed that the latent heat released by condensation of water vapor could produce equatorial superrotation along with multiple zonal jets in the mid-to-high latitudes. However, that previous work assumed complete and instant removal of condensate and therefore could not predict the cloud formation. Here we present an improved 3D Jupiter model to investigate some effects of cloud microphysics on large-scale dynamics using a closed water cycle that includes condensation, three-dimensional advection of cloud material by the large-scale circulation, evaporation and sedimentation. We use a dry convective adjustment scheme to adjust the temperature towards a dry adiabat when atmospheric columns become convectively unstable, and the tracers are mixed within the unstable layers accordingly. Other physics parameterizations included in our model are the bottom drag and internal heat flux as well as the choices of either Newtonian heating scheme or gray radiative transfer. Given the poorly understood cloud microphysics, we perform case studies by treating the particle size and condensation/evaporation time scale as free parameters. We find that, in some cases, the active water cycle can produce multiple banded jets and clouds. However, the equatorial jet is generally very weak in all the cases because of insufficient supply of eastward eddy momentum fluxes. These differences may result from differences in the overall vertical stratification, baroclinicity, and moisture distribution in our new models relative to the older ones; we expect to elucidate the dynamical mechanisms in continuing work.

Lyman-α forest constraints on decaying dark matter

NASA Astrophysics Data System (ADS)

Wang, Mei-Yu; Croft, Rupert A. C.; Peter, Annika H. G.; Zentner, Andrew R.; Purcell, Chris W.

2013-12-01

We present an analysis of high-resolution N-body simulations of decaying dark matter cosmologies focusing on the statistical properties of the transmitted Lyman-α (Lyα) forest flux in the high-redshift intergalactic medium (IGM). In this type of model a dark matter particle decays into a slightly less massive stable dark matter daughter particle and a comparably light particle. The small mass splitting provides a nonrelativistic kick velocity Vk=cΔM/M to the daughter particle resulting in free-streaming and subsequent damping of small-scale density fluctuations. Current Lyα forest power spectrum measurements probe comoving scales up to ˜2-3h-1Mpc at redshifts z˜2-4, providing one of the most robust ways to probe cosmological density fluctuations on relatively small scales. The suppression of structure growth due to the free-streaming of dark matter daughter particles also has a significant impact on the neutral hydrogen cloud distribution, which traces the underlying dark matter distribution well at high redshift. We exploit Lyα forest power spectrum measurements to constrain the amount of free-streaming of dark matter in such models and thereby place limits on decaying dark matter based only on the dynamics of cosmological perturbations without any assumptions about the interactions of the decay products. We use a suite of dark-matter-only simulations together with the fluctuating Gunn-Peterson approximation to derive the Lyα flux distribution. We argue that this approach should be sufficient for our main purpose, which is to demonstrate the power of the Lyα forest to constrain decaying dark matter models. We find that Sloan Digital Sky Survey 1D Lyα forest power spectrum data place a lifetime-dependent upper limit Vk≲30-70km/s for decay lifetimes ≲10Gyr. This is the most stringent model-independent bound on invisible dark matter decays with small mass splittings. For larger mass splittings (large Vk), Lyα forest data restrict the dark matter

Cold Water Vapor in the Barnard 5 Molecular Cloud

NASA Technical Reports Server (NTRS)

Wirstrom, E. S.; Charnley, S. B.; Persson, C. M.; Buckle, J. V.; Cordiner, M. A.; Takakuwa, S.

2014-01-01

After more than 30 yr of investigations, the nature of gas-grain interactions at low temperatures remains an unresolved issue in astrochemistry. Water ice is the dominant ice found in cold molecular clouds; however, there is only one region where cold ((is) approximately 10 K) water vapor has been detected-L1544. This study aims to shed light on ice desorption mechanisms under cold cloud conditions by expanding the sample. The clumpy distribution of methanol in dark clouds testifies to transient desorption processes at work-likely to also disrupt water ice mantles. Therefore, the Herschel HIFI instrument was used to search for cold water in a small sample of prominent methanol emission peaks. We report detections of the ground-state transition of o-H2O (J = 110-101) at 556.9360 GHz toward two positions in the cold molecular cloud, Barnard 5. The relative abundances of methanol and water gas support a desorption mechanism which disrupts the outer ice mantle layers, rather than causing complete mantle removal.

Observations and simulations of three-dimensional radiative interactions between Arctic boundary layer clouds and ice floes

NASA Astrophysics Data System (ADS)

Schäfer, M.; Bierwirth, E.; Ehrlich, A.; Jäkel, E.; Wendisch, M.

2015-01-01

Based on airborne spectral imaging observations three-dimensional (3-D) radiative effects between Arctic boundary layer clouds and ice floes have been identified and quantified. A method is presented to discriminate sea ice and open water in case of clouds from imaging radiance measurements. This separation simultaneously reveals that in case of clouds the transition of radiance between open water and sea ice is not instantaneously but horizontally smoothed. In general, clouds reduce the nadir radiance above bright surfaces in the vicinity of sea ice - open water boundaries, while the nadir radiance above dark surfaces is enhanced compared to situations with clouds located above horizontal homogeneous surfaces. With help of the observations and 3-D radiative transfer simulations, this effect was quantified to range between 0 and 2200 m distance to the sea ice edge. This affected distance Δ L was found to depend on both, cloud and sea ice properties. For a ground overlaying cloud in 0-200 m altitude, increasing the cloud optical thickness from τ = 1 to τ = 10 decreases Δ L from 600 to 250 m, while increasing cloud base altitude or cloud geometrical thickness can increase Δ L; Δ L(τ = 1/10) = 2200 m/1250 m for 500-1000 m cloud altitude. To quantify the effect for different shapes and sizes of the ice floes, various albedo fields (infinite straight ice edge, circles, squares, realistic ice floe field) were modelled. Simulations show that Δ L increases by the radius of the ice floe and for sizes larger than 6 km (500-1000 m cloud altitude) asymptotically reaches maximum values, which corresponds to an infinite straight ice edge. Furthermore, the impact of these 3-D-radiative effects on retrieval of cloud optical properties was investigated. The enhanced brightness of a dark pixel next to an ice edge results in uncertainties of up to 90 and 30% in retrievals of cloud optical thickness and effective radius reff, respectively. With help of Δ L quantified here, an

The effect of moonlight on observation of cloud cover at night, and application to cloud climatology

NASA Technical Reports Server (NTRS)

Hahn, Carole J.; Warren, Stephen G.; London, Julius

1995-01-01

Ten years of nighttime weather observations from the Northern Hemisphere in December were classified according to the illuminance of moonlight or twilight on the cloud tops, and a threshold level of illuminance was determined, above which the clouds are apparently detected adequately. This threshold corresponds to light from a full moon at an elevation angle of 6 deg, light from a partial moon at higher elevation, or twilight from the sun less than 9 deg bvelow the horizon. It permits the use of about 38% of the observations made with the sun below the horizon. The computed diurnal cycles of total cloud cover are altered considerably when this moonlight criterion is imposed. Maximum cloud cover over much of the ocean is now found to be at night or in the morning, whereas computations obtained without benefit of the moonlight criterion, as in our published atlases, showed the time of maximum to be noon or early afternoon in many regions. The diurnal cycles of total cloud cover we obtain are compared with those of the International Satellite Cloud Climatology Project (ISCCP) for a few regions; they are generally in better agreement if the moonlight criterion is imposed on the surface observations. Using the moonlight criterion, we have analyzed 10 years (1982-91) of surface weather observations over land and ocean, worldwide, for total cloud cover and for the frequency of occurrence of clear sky, fog, and precipitation. The global average cloud cover (average of day and night) is about 2% higher if the moonlight criterion is imposed than if all observations are used. The difference is greater in winter than in summer, because of the fewer hours of darkness in summer. The amplitude of the annual cycle of total cloud cover over the Arctic Ocean and at the South Pole is diminished by a few percent when the moonlight criterion is imposed. The average cloud cover for 1982-91 is found to be 55% for Northern Hemisphere land, 53% for Southern Hemisphere land, 66% for

What Goes Up Must Come Down: The Lifecycle of Convective Clouds (492nd Brookhaven Lecture)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jensen, Michael

Some clouds look like cotton balls and others like anvils. Some bring rain, some snow and sleet, and others, just shade. But, whether big and billowy or dark and stormy, clouds affect far more than the weather each day. Armed with measurements of clouds’ updrafts and downdrafts—which resemble airflow in a convection oven—and many other atmospheric interactions, scientists from Brookhaven Lab and other institutions around the world are developing models that are crucial for understanding Earth’s climate and forecasting future climate change. During his lecture, Dr. Jensen provides an overview of the importance of clouds in the Earth’s climate systemmore » before explaining how convective clouds form, grow, and dissipate. His discussion includes findings from the Midlatitude Continental Convective Clouds Experiment (MC3E), a major collaborative experiment between U.S. Department of Energy (DOE) and NASA scientists to document precipitation, clouds, winds, and moisture in 3-D for a holistic view of convective clouds and their environment.« less

The GBT 3mm Survey of Infall and Fragmentation of Dense Cores in Taurus

NASA Astrophysics Data System (ADS)

Seo, Youngmin; Goldsmith, Paul; Shirley, Yancy L.; Church, Sara; Frayer, David

2018-01-01

We present preliminary results of the infall and fragmentation survey toward a complete population of prestellar cores in Taurus that was carried out with the 16-element W-band focal plane array receiver (Argus) on the 100m Green Bank Telescope. The survey is designed take advantage of the 8.5” angular resolution and high sensitivity of Argus on the GBT to trace infall motions in HCN 1-0 & HCO+ 1-0 and find any evidence of fragmentation in N2H+ & NH2D within prestellar cores ranging in size from 0.05 pc to 0.0075 pc (1500 AU), which is a typical size scale of individual planetary systems. The scientific goal is to estimate the fraction of infall candidates from a complete population of prestellar cores and to understand internal velocity structure during the final gravitational collapse before forming stars. The survey started in the winter of 2016 and is to continue to the end of January 2018. So far, we observed 23 prestellar cores out of 65 targets in HCN 1-0 and HCO+ 1-0. We have so far found only two prestellar cores (L1495A-N, L1521D) out of 23 observed that show infall signatures, which is a fraction of infalling cores less than half of that reported by the previous surveys toward the bright, dense cores in various molecular clouds (Lee et al. 2004; Sohn et al. 2007). We also found that L1495A-N has a highly asymmetric infall motion which does not fit to a conventional model of dense core collapse, while L1521D has a slow infall motion similar to L1544.

Simulations of Early Structure Formation: Primordial Gas Clouds

NASA Astrophysics Data System (ADS)

Yoshida, Naoki; Abel, Tom; Hernquist, Lars; Sugiyama, Naoshi

2003-08-01

We use cosmological simulations to study the origin of primordial star-forming clouds in a ΛCDM universe, by following the formation of dark matter halos and the cooling of gas within them. To model the physics of chemically pristine gas, we employ a nonequilibrium treatment of the chemistry of nine species (e-, H, H+, He, He+, He++, H2, H+2, H-) and include cooling by molecular hydrogen. By considering cosmological volumes, we are able to study the statistical properties of primordial halos, and the high resolution of our simulations enables us to examine these objects in detail. In particular, we explore the hierarchical growth of bound structures forming at redshifts z~25-30 with total masses in the range ~105-106Msolar. We find that when the amount of molecular hydrogen in these objects reaches a critical level, cooling by rotational line emission is efficient, and dense clumps of cold gas form. We identify these ``gas clouds'' as sites for primordial star formation. In our simulations, the threshold for gas cloud formation by molecular cooling corresponds to a critical halo mass of ~5×105h-1Msolar, in agreement with earlier estimates, but with a weak dependence on redshift in the range z>16. The complex interplay between the gravitational formation of dark halos and the thermodynamic and chemical evolution of the gas clouds compromises analytic estimates of the critical H2 fraction. Dynamical heating from mass accretion and mergers opposes relatively inefficient cooling by molecular hydrogen, delaying the production of star-forming clouds in rapidly growing halos. We also investigate the effect of photodissociating ultraviolet radiation on the formation of primordial gas clouds. We consider two extreme cases, first by including a uniform radiation field in the optically thin limit and second by accounting for the maximum effect of gas self-shielding in virialized regions. For radiation with Lyman-Werner band flux J>10-23 ergs s-1 cm-2 Hz-1 sr-1, hydrogen

The dynamical properties of dense filaments in the infrared dark cloud G035.39-00.33

NASA Astrophysics Data System (ADS)

Henshaw, J. D.; Caselli, P.; Fontani, F.; Jiménez-Serra, I.; Tan, J. C.

2014-05-01

Infrared dark clouds (IRDCs) are unique laboratories to study the initial conditions of high-mass star and star cluster formation. We present high-sensitivity and high-angular-resolution Institut de Radioastronomie Millimétrique (IRAM) Plateau de Bure Interferometer observations of N2H+ (1-0) towards IRDC G035.39-00.33. It is found that G035.39-00.33 is a highly complex environment, consisting of several mildly supersonic filaments (σ _NT/cs ˜ 1.5), separated in velocity by <1 km s-1. Where multiple spectral components are evident, moment analysis overestimates the non-thermal contribution to the line-width by a factor of ˜2. Large-scale velocity gradients evident in previous single-dish maps may be explained by the presence of substructure now evident in the interferometric maps. Whilst global velocity gradients are small (<0.7 km s-1 pc-1), there is evidence for dynamic processes on local scales (˜1.5-2.5 km s-1 pc-1). Systematic trends in velocity gradient are observed towards several continuum peaks. This suggests that the kinematics are influenced by dense (and in some cases, starless) cores. These trends are interpreted as either infalling material, with accretion rates ˜(7 ± 4) × 10-5 M⊙ yr-1, or expanding shells with momentum ˜24 ± 12 M⊙ km s-1. These observations highlight the importance of high-sensitivity and high-spectral-resolution data in disentangling the complex kinematic and physical structure of massive star-forming regions.

The simulation of molecular clouds formation in the Milky Way

NASA Astrophysics Data System (ADS)

Khoperskov, S. A.; Vasiliev, E. O.; Sobolev, A. M.; Khoperskov, A. V.

2013-01-01

Using 3D hydrodynamic calculations we simulate formation of molecular clouds in the Galaxy. The simulations take into account molecular hydrogen chemical kinetics, cooling and heating processes. Comprehensive gravitational potential accounts for contributions from the stellar bulge, two- and four-armed spiral structure, stellar disc, dark halo and takes into account self-gravitation of the gaseous component. Gas clouds in our model form in the spiral arms due to shear and wiggle instabilities and turn into molecular clouds after t ≳ 100 Myr. At the times t ˜ 100-300 Myr the clouds form hierarchical structures and agglomerations with the sizes of 100 pc and greater. We analyse physical properties of the simulated clouds and find that synthetic statistical distributions like mass spectrum, `mass-size' relation and velocity dispersion are close to those observed in the Galaxy. The synthetic l-v (galactic longitude-radial velocity) diagram of the simulated molecular gas distribution resembles observed one and displays a structure with appearance similar to molecular ring of the Galaxy. Existence of this structure in our modelling can be explained by superposition of emission from the galactic bar and the spiral arms at ˜3-4 kpc.

Impact of parental Bos taurus and Bos indicus origins on copy number variation in traditional Chinese cattle breeds

USDA-ARS?s Scientific Manuscript database

Copy number variation (CNV) is an important component of genomic structural variation and plays a role not only in evolutionary diversification but also domestication. Chinese cattle were derived from Bos taurus and Bos indicus, and several breeds presumably are of hybrid origin, but the evolution o...

APEX/SABOCA observations of small-scale structure of infrared-dark clouds . I. Early evolutionary stages of star-forming cores

NASA Astrophysics Data System (ADS)

Ragan, Sarah E.; Henning, Thomas; Beuther, Henrik

2013-11-01

Infrared-dark clouds (IRDCs) harbor the early phases of cluster and high-mass star formation and are comprised of cold (~20 K), dense (n > 104 cm-3) gas. The spectral energy distribution (SED) of IRDCs is dominated by the far-infrared and millimeter wavelength regime, and our initial Herschel study examined IRDCs at the peak of the SED with high angular resolution. Here we present a follow-up study using the SABOCA instrument on APEX which delivers 7.8″ angular resolution at 350 μm, matching the resolution we achieved with Herschel/PACS, and allowing us to characterize substructure on ~0.1 pc scales. Our sample of 11 nearby IRDCs are a mix of filamentary and clumpy morphologies, and the filamentary clouds show significant hierarchical structure, while the clumpy IRDCs exhibit little hierarchical structure. All IRDCs, regardless of morphology, have about 14% of their total mass in small scale core-like structures which roughly follow a trend of constant volume density over all size scales. Out of the 89 protostellar cores we identified in this sample with Herschel, we recover 40 of the brightest and re-fit their SEDs and find their properties agree fairly well with our previous estimates (⟨ T ⟩ ~ 19 K). We detect a new population of "cold cores" which have no 70 μm counterpart, but are 100 and 160 μm-bright, with colder temperatures (⟨ T ⟩ ~ 16 K). This latter population, along with SABOCA-only detections, are predominantly low-mass objects, but their evolutionary diagnostics are consistent with the earliest starless or prestellar phase of cores in IRDCs. Based on observations carried out with the Atacama Pathfinder Experiment (APEX). APEX is a collaboration between Max Planck Institut für Radioastronomie (MPIfR), Onsala Space Observatory (OSO), and the European Southern Observatory (ESO).Appendices are available in electronic form at http://www.aanda.org

Quantum field theory of interacting dark matter and dark energy: Dark monodromies

DOE PAGES

D’Amico, Guido; Hamill, Teresa; Kaloper, Nemanja

2016-11-28

We discuss how to formulate a quantum field theory of dark energy interacting with dark matter. We show that the proposals based on the assumption that dark matter is made up of heavy particles with masses which are very sensitive to the value of dark energy are strongly constrained. Quintessence-generated long-range forces and radiative stability of the quintessence potential require that such dark matter and dark energy are completely decoupled. However, if dark energy and a fraction of dark matter are very light axions, they can have significant mixings which are radiatively stable and perfectly consistent with quantum field theory.more » Such models can naturally occur in multi-axion realizations of monodromies. The mixings yield interesting signatures which are observable and are within current cosmological limits but could be constrained further by future observations« less

Quantum field theory of interacting dark matter and dark energy: Dark monodromies

DOE Office of Scientific and Technical Information (OSTI.GOV)

D’Amico, Guido; Hamill, Teresa; Kaloper, Nemanja

We discuss how to formulate a quantum field theory of dark energy interacting with dark matter. We show that the proposals based on the assumption that dark matter is made up of heavy particles with masses which are very sensitive to the value of dark energy are strongly constrained. Quintessence-generated long-range forces and radiative stability of the quintessence potential require that such dark matter and dark energy are completely decoupled. However, if dark energy and a fraction of dark matter are very light axions, they can have significant mixings which are radiatively stable and perfectly consistent with quantum field theory.more » Such models can naturally occur in multi-axion realizations of monodromies. The mixings yield interesting signatures which are observable and are within current cosmological limits but could be constrained further by future observations« less

Dark Skies and Clouds Move in at Phoenix site

NASA Technical Reports Server (NTRS)

2008-01-01

Clouds of dust and ice swirl past the Surface Stereo Imager (SSI) camera on NASA's Phoenix Mars Lander in a series of images taken on the 132nd Martian day of the mission (Oct. 7, 2008). The images show the increase in storm activity and potential for snowfall.

The solar powered spacecraft was disabled by decreased light from heavy dust storms in the area a few weeks later. The last communication heard from the lander occurred on Nov. 2, 2008.

The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

Gas-grain chemical models of star-forming molecular clouds as constrained by ISO and SWAS observations

NASA Astrophysics Data System (ADS)

Charnley, S. B.; Rodgers, S. D.; Ehrenfreund, P.

2001-11-01

We have investigated the gaseous and solid state molecular composition of dense interstellar material that periodically experiences processing in the shock waves associated with ongoing star formation. Our motivation is to confront these models with the stringent abundance constraints on CO2, H2O and O2, in both gas and solid phases, that have been set by ISO and SWAS. We also compare our results with the chemical composition of dark molecular clouds as determined by ground-based telescopes. Beginning with the simplest possible model needed to study molecular cloud gas-grain chemistry, we only include additional processes where they are clearly required to satisfy one or more of the ISO-SWAS constraints. When CO, N2 and atoms of N, C and S are efficiently desorbed from grains, a chemical quasi-steady-state develops after about one million years. We find that accretion of CO2 and H2O cannot explain the [CO2/H2O]ice ISO observations; as with previous models, accretion and reaction of oxygen atoms are necessary although a high O atom abundance can still be derived from the CO that remains in the gas. The observational constraints on solid and gaseous molecular oxygen are both met in this model. However, we find that we cannot explain the lowest H2O abundances seen by SWAS or the highest atomic carbon abundances found in molecular clouds; additional chemical processes are required and possible candidates are given. One prediction of models of this type is that there should be some regions of molecular clouds which contain high gas phase abundances of H2O, O2 and NO. A further consequence, we find, is that interstellar grain mantles could be rich in NH2OH and NO2. The search for these regions, as well as NH2OH and NO2 in ices and in hot cores, is an important further test of this scenario. The model can give good agreement with observations of simple molecules in dark molecular clouds such as TMC-1 and L134N. Despite the fact that S atoms are assumed to be continously

Probing dark matter physics with galaxy clusters

NASA Astrophysics Data System (ADS)

Dalal, Neal

2016-10-01

We propose a theoretical investigation of the effects of a class of dark matter (DM) self-interactions on the properties of galaxy clusters and their host dark matter halos. Recent work using HST has claimed the detection of a particular form of DM self-interaction, which can lead to observable displacements between satellite galaxies within clusters and the DM subhalos hosting them. This form of self-interaction is highly anisotropic, favoring forward scattering with low momentum transfer, unlike isotropically scattering self-interacting dark matter (SIDM) models. This class of models has not been simulated numerically, clouding the interpretation of the claimed offsets between galaxies and lensing peaks observed by HST. We propose to perform high resolution simulations of cosmological structure formation for this class of SIDM model, focusing on three observables accessible to existing HST observations of clusters. First, we will quantify the extent to which offsets between baryons and DM can arise in these models, as a function of the cross section. Secondly, we will also quantify the effects of this type of DM self-interaction on halo concentrations, to determine the range of cross-sections allowed by existing stringent constraints from HST. Finally we will compute the so-called splashback feature in clusters, specifically focusing on whether SIDM can resolve the current discrepancy between observed values of splashback radii in clusters compared to theoretical predictions for CDM. The proposed investigations will add value to all existing deep HST observations of galaxy clusters by allowing them to probe dark matter physics in three independent ways.

Static structure of chameleon dark matter as an explanation of dwarf spheroidal galaxy cores

NASA Astrophysics Data System (ADS)

Chanda, Prolay Krishna; Das, Subinoy

2017-04-01

We propose a novel mechanism that explains the cored dark matter density profile in recently observed dark matter rich dwarf spheroidal galaxies. In our scenario, dark matter particle mass decreases gradually as a function of distance towards the center of a dwarf galaxy due to its interaction with a chameleon scalar. At closer distance towards the Galactic center the strength of attractive scalar fifth force becomes much stronger than gravity and is balanced by the Fermi pressure of the dark matter cloud; thus, an equilibrium static configuration of the dark matter halo is obtained. Like the case of soliton star or fermion Q-star, the stability of the dark matter halo is obtained as the scalar achieves a static profile and reaches an asymptotic value away from the Galactic center. For simple scalar-dark matter interaction and quadratic scalar self-interaction potential, we show that dark matter behaves exactly like cold dark matter (CDM) beyond a few kpc away from the Galactic center but at closer distance it becomes lighter and Fermi pressure cannot be ignored anymore. Using Thomas-Fermi approximation, we numerically solve the radial static profile of the scalar field, fermion mass and dark matter energy density as a function of distance. We find that for fifth force mediated by an ultralight scalar, it is possible to obtain a flattened dark matter density profile towards the Galactic center. In our scenario, the fifth force can be neglected at distance r ≥1 kpc from the Galactic center and dark matter can be simply treated as heavy nonrelativistic particles beyond this distance, thus reproducing the success of CDM at large scales.

The mass distribution of clumps within infrared dark clouds. A Large APEX Bolometer Camera study

NASA Astrophysics Data System (ADS)

Gómez, L.; Wyrowski, F.; Schuller, F.; Menten, K. M.; Ballesteros-Paredes, J.

2014-01-01

Aims: We present an analysis of the dust continuum emission at 870 μm in order to investigate the mass distribution of clumps within infrared dark clouds (IRDCs). Methods: We map six IRDCs with the Large APEX BOlometer CAmera (LABOCA) at APEX, reaching an rms noise level of σrms = 28-44 mJy beam-1. The dust continuum emission coming from these IRDCs was decomposed by using two automated algorithms, Gaussclumps and Clumpfind. Moreover, we carried out single-pointing observations of the N2H+ (3-2) line toward selected positions to obtain kinematic information. Results: The mapped IRDCs are located in the range of kinematic distances of 2.7-3.2 kpc. We identify 510 and 352 sources with Gaussclumps and Clumpfind, respectively, and estimate masses and other physical properties assuming a uniform dust temperature. The mass ranges are 6-2692 M⊙ (Gaussclumps) and 7-4254 M⊙ (Clumpfind), and the ranges in effective radius are ~0.10-0.74 pc (Gaussclumps) and 0.16-0.99 pc (Clumpfind). The mass distribution, independent of the decomposition method used, is fitted by a power law, dN/dM ∝ Mα, with an index (α) of -1.60 ± 0.06, consistent with the CO mass distribution and other high-mass star-forming regions. Based on data acquired with the Atacama Pathfinder Experiment (APEX). APEX is a collaboration between the Max-Planck-Institut für Radioastronomie, the European Southern Observatory, and the Onsala Space Observatory.Full Tables 3 and 4 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/561/A148

Dark matter as a trigger for periodic comet impacts.

PubMed

Randall, Lisa; Reece, Matthew

2014-04-25

Although statistical evidence is not overwhelming, possible support for an approximately 35×106  yr periodicity in the crater record on Earth could indicate a nonrandom underlying enhancement of meteorite impacts at regular intervals. A proposed explanation in terms of tidal effects on Oort cloud comet perturbations as the Solar System passes through the galactic midplane is hampered by lack of an underlying cause for sufficiently enhanced gravitational effects over a sufficiently short time interval and by the time frame between such possible enhancements. We show that a smooth dark disk in the galactic midplane would address both these issues and create a periodic enhancement of the sort that has potentially been observed. Such a disk is motivated by a novel dark matter component with dissipative cooling that we considered in earlier work. We show how to evaluate the statistical evidence for periodicity by input of appropriate measured priors from the galactic model, justifying or ruling out periodic cratering with more confidence than by evaluating the data without an underlying model. We find that, marginalizing over astrophysical uncertainties, the likelihood ratio for such a model relative to one with a constant cratering rate is 3.0, which moderately favors the dark disk model. Our analysis furthermore yields a posterior distribution that, based on current crater data, singles out a dark matter disk surface density of approximately 10M⊙/pc2. The geological record thereby motivates a particular model of dark matter that will be probed in the near future.

COMPARISON VIEW OF MARS CLOUD COVER

NASA Technical Reports Server (NTRS)

2002-01-01

These color and black and white pictures of Mars were taken by NASA's Hubble Space Telescope just two weeks after Earth made its closest approach to the Red Planet during the 1997 opposition. When the Hubble pictures were taken Mars was at a distance of 62 million miles (100 million kilometers) and the resolution at the center of the disk is 13.5 miles/pixel (22 kilometers/pixel). Both images were made with the Wide Field and Planetary Camera 2. The color composite (left image) is constructed from three images taken in red (673 nanometers), green (502 nm) and blue (410 nm) light. The right image, in blue light only, brings out details in the cloud structure and is remarkably similar to weather satellite pictures taken of Earth. A planetary-scale wave curls around the north pole, similar in behavior to high latitude cold fronts which descend over North America and Europe during springtime. The picture was taken when Mars was near aphelion, its farthest point from the Sun. The faint sunlight results in cold atmospheric conditions which stimulate the formation of water ice clouds. The clouds themselves further reduce atmospheric temperatures. Atmospheric heating, resulting when sunlight is absorbed by the dust, is reduced when ice forms around the dust particles and causes the dust to gravitationally settle to the ground. These images of Mars are centered at approximately 94 degrees longitude and 23 degrees N latitude (oriented with north up). The four largest Tharsis Montes (massive extinct volcanoes) are visible as dark spots extending through the clouds. The vast canyon system, Valles Marineris, stretches across the eastern (lower right) half of the image; the Pathfinder landing site is near the eastern edge of the image. It is early summer in the northern hemisphere, and the North polar cap has retreated to about 80 degrees N latitude; the 'residual' summer cap, which is composed of water ice, is about one-third the size of the 'seasonal' winter cap, which

First stars of the ρ Ophiuchi dark cloud. XMM-Newton view of ρ Oph and its neighbors

NASA Astrophysics Data System (ADS)

Pillitteri, I.; Wolk, S. J.; Chen, H. H.; Goodman, A.

2016-08-01

Star formation in molecular clouds can be triggered by the dynamical action of winds from massive stars. Furthermore, X-ray and UV fluxes from massive stars can influence the life time of surrounding circumstellar disks. We present the results of a 53 ks XMM-Newton observation centered on the ρ Ophiuchi A+B binary system. ρ Ophiuchi lies in the center of a ring of dust, likely formed by the action of its winds. This region is different from the dense core of the cloud (L1688 Core F) where star formation is at work. X-rays are detected from ρ Ophiuchi as well as a group of surrounding X-ray sources. We detected 89 X-ray sources, 47 of them have at least one counterpart in 2MASS+All-WISE catalogs. Based on IR and X-ray properties, we can distinguish between young stellar objects (YSOs) belonging to the cloud and background objects. Among the cloud members, we detect three debris-disk objects and 22 disk-less - Class III young stars.We show that these stars have ages in 5-10 Myr, and are significantly older than the YSOs in L1688. We speculate that they are the result of an early burst of star formation in the cloud. An X-ray energy of ≥5 × 1044 erg has been injected into the surrounding mediumover the past 5 Myr, we discuss the effects of such energy budget in relation to the cloud properties and dynamics.

The Feedback of Star Formation Based on Large-scale Spectroscopic Mapping Technology

NASA Astrophysics Data System (ADS)

Li, H. X.

2017-05-01

Star Formation is a fundamental topic in astrophysics. Although there is a popular model of low-mass star formation, every step of the process is full of physical and chemical complexity. One of the key questions is the dynamical feedback during the process of star formation. The answer of this question will help us to understand the star formation and the evolution of molecular clouds. We have identified outflows and bubbles in the Taurus molecular cloud based on the ˜ 100 deg2 Five College Radio Astronomy Observatory 12CO(1-0) and 13CO(1-0) maps and the Spitzer young stellar object (YSO) catalog. In the main 44 deg2 area of Taurus, we found 55 outflows, of which 31 were previously unknown. We also found 37 bubbles in the entire 100 deg2 area of Taurus, all of which had not been identified before. After visual inspection, we developed an interactive IDL pipeline to confirm the outflows and bubbles. This sample covers a contiguous region with a linear spatial dynamic range of ˜ 1000. Among the 55 outflows, we found that bipolar, monopolar redshifted, and monopolar blueshifted outflows account for 45%, 44%, and 11%, respectively. There are more red lobes than blue ones. The occurrence of more red lobes may result from the fact that Taurus is thin. Red lobes tend to be smaller and younger. The total mass and energy of red lobes are similar to blue lobes on average. There are 3 expanding bubbles and 34 broken bubbles among all the bubbles in Taurus. There are more outflow-driving YSOs in Class I, Flat, and Class II while few outflow-driving YSOs in Class III, which indicates that outflows more likely appear in the earlier stage (Class I) than in the later phase (Class III) of star formation. There are more bubble-driving YSOs of Class II and Class III while there are few bubble-driving YSOs of Class I and Flat, implying that the bubble structures are more likely to occur in the later stage of star formation. The total kinetic energy of the identified outflows is

Into the Darkness: Interstellar Extinction Near the Cepheus OB3 Molecular Cloud

NASA Astrophysics Data System (ADS)

Fitzpatrick, Edward L.; Jacklin, S.; Massa, D.

2014-01-01

We present the results of a followup investigation to a study performed by Massa and Savage (1984, ApJ, 279, 310) of the properties of UV interstellar extinction in the region of the Cepheus OB3 molecular cloud. That study was performed using UV photometry and spectro-photometry from the ANS and IUE satellites. We have extended this study into the IR, utilizing the uniform database of IR photometry available from the 2MASS project. This is a part of a larger program whose goal is to study the properties of extinction in localized regions, where we hope to find clues to dust grain growth and destruction processes through spatial correlations of extinction with distinct environmental properties. Similarly to Massa and Savage’s UV results, we find that the IR extinction properties on the Cepheus OB3 region vary systematically with the apparent proximity of the target stars to the molecular cloud. We also find that the UV extinction and the IR extinction are crudely correlated. The methodology leading to these results and their implications are discussed.

Theoretical studies in interstellar cloud chemistry

NASA Technical Reports Server (NTRS)

Chiu, Y. T.; Prasad, S. S.

1993-01-01

This final report represents the completion of the three tasks under the purchase order no. SCPDE5620,1,2F. Chemical composition of gravitationally contracting, but otherwise quiescent, interstellar clouds and of interstellar clouds traversed by high velocity shocks, were modeled in a comprehensive manner that represents a significant progress in modeling these objects. The evolutionary chemical modeling, done under this NASA contract, represents a notable advance over the 'classical' fixed condition equilibrium models because the evolutionary models consider not only the chemical processes but also the dynamical processes by which the dark interstellar clouds may have assumed their present state. The shock calculations, being reported here, are important because they extend the limited chemical composition derivable from dynamical calculations for the total density and temperature structures behind the shock front. In order to be tractable, the dynamical calculations must severely simplify the chemistry. The present shock calculations take the shock profiles from the dynamical calculations and derive chemical composition in a comprehensive manner. The results of the present modeling study are still to be analyzed with reference to astronomical observational data and other contemporary model predictions. As far as humanly possible, this analysis will be continued with CRE's (Creative Research Enterprises's) IR&D resources, until a sponsor is found.

[CII] observations of H2 molecular layers in transition clouds

NASA Astrophysics Data System (ADS)

Velusamy, T.; Langer, W. D.; Pineda, J. L.; Goldsmith, P. F.; Li, D.; Yorke, H. W.

2010-10-01

We present the first results on the diffuse transition clouds observed in [CII] line emission at 158 μm (1.9 THz) towards Galactic longitudes near 340° (5 LOSs) & 20° (11 LOSs) as part of the HIFI tests and GOT C+ survey. Out of the total 146 [CII] velocity components detected by profile fitting we identify 53 as diffuse molecular clouds with associated 12CO emission but without 13CO emission and characterized by AV < 5 mag. We estimate the fraction of the [CII] emission in the diffuse HI layer in each cloud and then determine the [CII] emitted from the molecular layers in the cloud. We show that the excess [CII] intensities detected in a few clouds is indicative of a thick H2 layer around the CO core. The wide range of clouds in our sample with thin to thick H2 layers suggests that these are at various evolutionary states characterized by the formation of H2 and CO layers from HI and C+, respectively. In about 30% of the clouds the H2 column densities (“dark gas”) traced by the [CII] is 50% or more than that traced by 12CO emission. On the average ~25% of the total H2 in these clouds is in an H2 layer which is not traced by CO. We use the HI, [CII], and 12CO intensities in each cloud along with simple chemical models to obtain constraints on the FUV fields and cosmic ray ionization rates. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

A global cloud map of the nearest known brown dwarf.

PubMed

Crossfield, I J M; Biller, B; Schlieder, J E; Deacon, N R; Bonnefoy, M; Homeier, D; Allard, F; Buenzli, E; Henning, Th; Brandner, W; Goldman, B; Kopytova, T

2014-01-30

Brown dwarfs--substellar bodies more massive than planets but not massive enough to initiate the sustained hydrogen fusion that powers self-luminous stars--are born hot and slowly cool as they age. As they cool below about 2,300 kelvin, liquid or crystalline particles composed of calcium aluminates, silicates and iron condense into atmospheric 'dust', which disappears at still cooler temperatures (around 1,300 kelvin). Models to explain this dust dispersal include both an abrupt sinking of the entire cloud deck into the deep, unobservable atmosphere and breakup of the cloud into scattered patches (as seen on Jupiter and Saturn). However, hitherto observations of brown dwarfs have been limited to globally integrated measurements, which can reveal surface inhomogeneities but cannot unambiguously resolve surface features. Here we report a two-dimensional map of a brown dwarf's surface that allows identification of large-scale bright and dark features, indicative of patchy clouds. Monitoring suggests that the characteristic timescale for the evolution of global weather patterns is approximately one day.

Hazard mitigation with cloud model based rainfall and convective data

NASA Astrophysics Data System (ADS)

Gernowo, R.; Adi, K.; Yulianto, T.; Seniyatis, S.; Yatunnisa, A. A.

2018-05-01

Heavy rain in Semarang 15 January 2013 causes flood. It is related to dynamic of weather’s parameter, especially with convection process, clouds and rainfall data. In this case, weather condition analysis uses Weather Research and Forecasting (WRF) model used to analyze. Some weather’s parameters show significant result. Their fluctuations prove there is a strong convection that produces convective cloud (Cumulonimbus). Nesting and 2 domains on WRF model show good output to represent weather’s condition commonly. The results of this study different between output cloud cover rate of observation result and output of model around 6-12 hours is because spinning-up of processing. Satellite Images of MTSAT (Multifunctional Transport Satellite) are used as a verification data to prove the result of WRF. White color of satellite image is Coldest Dark Grey (CDG) that indicates there is cloud’s top. This image consolidates that the output of WRF is good enough to analyze Semarang’s condition when the case happened.

The velocity characteristics of dusty filaments in the JCMT GBS clouds

NASA Astrophysics Data System (ADS)

Buckle, J. V.; Salji, C.; Richer, J. S.

2013-07-01

Large scale, high resolution spectral and continuum imaging maps have revealed, to an unprecedented extent, the characteristics of filamentary structure in star-forming molecular clouds, and their close association with star-forming cores. The filaments are associated with the formation of dense molecular cores where star formation occurs, and recent models highlight the important relationship between filaments and star-forming clusters. Velocity-coherent filaments have been proposed as the parent structures of star forming cores in Taurus. In Serpens, accretion flows along filaments have been proposed as the continuous source of mass for the star forming cluster. An evolutionary scenario for filaments based on velocity dispersion and column density measurements has recently been proposed, which we test with large scale molecular line and dust continuum maps. The JCMT Gould Belt Survey with SCUBA-2 and HARP provides dust continuum observations at 850 and 450 micron, and 12CO/13CO/C18O J=3-2 spectral line mapping of several nearby molecular clouds, covering large angular scales at high resolution. Velocities and linewidths of optically thin species, such as C18O which traces the warm, dense gas associated with star formation, are critical for an estimate of the virial stability of filamentary structures. The data and analyses that we present provide robust statistics over a large range of starless and protostellar evolutionary states. We present the velocity characteristics of dusty filaments in Orion, probing the physics at the boundary of filamentary structure and star formation. Using C18O, we investigate the internal structure of filaments, based on fragmentation and velocity coherence in the molecular line data. Through velocity dispersion measurements, we determine whether the filamentary structures are bound, and compare results between clouds of different star formation characteristics.

Sensitive survey for 13CO, CN, H2CO, and SO in the disks of T Tauri and Herbig Ae stars. II. Stars in ρ Ophiuchi and upper Scorpius

NASA Astrophysics Data System (ADS)

Reboussin, L.; Guilloteau, S.; Simon, M.; Grosso, N.; Wakelam, V.; Di Folco, E.; Dutrey, A.; Piétu, V.

2015-06-01

Aims: We attempt to determine the molecular composition of disks around young low-mass stars in the ρ Oph region and to compare our results with a similar study performed in the Taurus-Auriga region. Methods: We used the IRAM 30 m telescope to perform a sensitive search for CN N = 2-1 in 29 T Tauri stars located in the ρ Oph and upper Scorpius regions. 13CO J = 2-1 is observed simultaneously to provide an indication of the level of confusion with the surrounding molecular cloud. The bandpass also contains two transitions of ortho-H2CO, one of SO, and the C17O J = 2-1 line, which provides complementary information on the nature of the emission. Results: Contamination by molecular cloud in 13CO and even C17O is ubiquitous. The CN detection rate appears to be lower than for the Taurus region, with only four sources being detected (three are attributable to disks). H2CO emission is found more frequently, but appears in general to be due to the surrounding cloud. The weaker emission than in Taurus may suggest that the average disk size in the ρ Oph region is smaller than in the Taurus cloud. Chemical modeling shows that the somewhat higher expected disk temperatures in ρ Oph play a direct role in decreasing the CN abundance. Warmer dust temperatures contribute to convert CN into less volatile forms. Conclusions: In such a young region, CN is no longer a simple, sensitive tracer of disks, and observations with other tracers and at high enough resolution with ALMA are required to probe the gas disk population. Based on observations carried out with the IRAM 30-m telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).Appendix A is available in electronic form at http://www.aanda.org

Hierarchical fragmentation and differential star formation in the Galactic `Snake': infrared dark cloud G11.11-0.12

NASA Astrophysics Data System (ADS)

Wang, Ke; Zhang, Qizhou; Testi, Leonardo; van der Tak, Floris; Wu, Yuefang; Zhang, Huawei; Pillai, Thushara; Wyrowski, Friedrich; Carey, Sean; Ragan, Sarah E.; Henning, Thomas

2014-04-01

We present Submillimeter Array (SMA) λ = 0.88 and 1.3 mm broad-band observations, and Very Large Array (VLA) observations in NH3 (J, K) = (1,1) up to (5,5), H2O and CH3OH maser lines towards the two most massive molecular clumps in infrared dark cloud (IRDC) G11.11-0.12. Sensitive high-resolution images reveal hierarchical fragmentation in dense molecular gas from the ˜1 pc clump scale down to ˜0.01 pc condensation scale. At each scale, the mass of the fragments is orders of magnitude larger than the Jeans mass. This is common to all four IRDC clumps we studied, suggesting that turbulence plays an important role in the early stages of clustered star formation. Masers, shock heated NH3 gas, and outflows indicate intense ongoing star formation in some cores while no such signatures are found in others. Furthermore, chemical differentiation may reflect the difference in evolutionary stages among these star formation seeds. We find NH3 ortho/para ratios of 1.1 ± 0.4, 2.0 ± 0.4, and 3.0 ± 0.7 associated with three outflows, and the ratio tends to increase along the outflows downstream. Our combined SMA and VLA observations of several IRDC clumps present the most in-depth view so far of the early stages prior to the hot core phase, revealing snapshots of physical and chemical properties at various stages along an apparent evolutionary sequence.

MEST-Tyche will take its dark comets to impact our solar system in 20 years

NASA Astrophysics Data System (ADS)

Cao, Dayong

2012-03-01

Tyche has many dark comets like Oort cloud. It went near our solar system every 25-27 million years. It could take its dark comets to impact our earth. Tyche and its dark comet absorb light like a dark light which is a negative black-body radiation. (1) Eddν=-c1dνd^3dνe^c2dνd/Td-1. Among it, Ed: the dark energy, νd: the dark frequence, Td: the dark temperature, c1d,c2d: the constant. So when they go near us, their wave has a against Doppler redshift as 0.000165. And they will inbreak solar system at the rate of 99AU/y, from the distance of 1,500AU and in 20 years. It can cause the broken ozonosphere, the lithosphere to crack, many big activity volcanic and the continental drift. And it can darked the light and colded the climate to the Great Ice Age. Not only it will break our environment by a special ``nuclear explosion'' under low temperature, but also the dark life will change the Genetic code of our life. So it will kill many lives and will produce new life. So it could trigger the Mass Extinction. We can bulid up a new pair of nuclear reactor (include dark nuclear energy) to drive a universal craft and can change the orbit of our earth for evading the impaction. We need a new life-information technology to develop our life and consciousness.

Modified dark matter: Relating dark energy, dark matter and baryonic matter

NASA Astrophysics Data System (ADS)

Edmonds, Douglas; Farrah, Duncan; Minic, Djordje; Ng, Y. Jack; Takeuchi, Tatsu

Modified dark matter (MDM) is a phenomenological model of dark matter, inspired by gravitational thermodynamics. For an accelerating universe with positive cosmological constant (Λ), such phenomenological considerations lead to the emergence of a critical acceleration parameter related to Λ. Such a critical acceleration is an effective phenomenological manifestation of MDM, and it is found in correlations between dark matter and baryonic matter in galaxy rotation curves. The resulting MDM mass profiles, which are sensitive to Λ, are consistent with observational data at both the galactic and cluster scales. In particular, the same critical acceleration appears both in the galactic and cluster data fits based on MDM. Furthermore, using some robust qualitative arguments, MDM appears to work well on cosmological scales, even though quantitative studies are still lacking. Finally, we comment on certain nonlocal aspects of the quanta of modified dark matter, which may lead to novel nonparticle phenomenology and which may explain why, so far, dark matter detection experiments have failed to detect dark matter particles.

Dark energy in the dark ages

NASA Astrophysics Data System (ADS)

Linder, Eric V.

2006-08-01

Non-negligible dark energy density at high redshifts would indicate dark energy physics distinct from a cosmological constant or "reasonable" canonical scalar fields. Such dark energy can be constrained tightly through investigation of the growth of structure, with limits of ≲2% of total energy density at z ≫ 1 for many models. Intermediate dark energy can have effects distinct from its energy density; the dark ages acceleration can be constrained to last less than 5% of a Hubble e-fold time, exacerbating the coincidence problem. Both the total linear growth, or equivalently σ8, and the shape and evolution of the nonlinear mass power spectrum for z < 2 (using the Linder-White nonlinear mapping prescription) provide important windows. Probes of growth, such as weak gravitational lensing, can interact with supernovae and CMB distance measurements to scan dark energy behavior over the entire range z = 0-1100.

Deflection of jets induced by jet-cloud and jet-galaxy interactions

NASA Astrophysics Data System (ADS)

Mendoza, S.; Longair, M. S.

2001-06-01

The model first introduced by Raga & Cantó in which astrophysical jets are deflected on passing through an isothermal high-density region is generalized by taking into account gravitational effects on the motion of the jet as it crosses the high-density cloud. The problem is also generalized for relativistic jets in which gravitational effects induced by the cloud are neglected. Two further cases, classical and relativistic, are discussed for the cases in which the jet is deflected on passing through the interstellar gas of a galaxy in which a dark matter halo dominates the gravitational potential. The criteria for the stability of jets due to the formation of internal shocks are also discussed.

Alcelaphine gammaherpesvirus 1-induced malignant catarrhal fever in a Watusi (bos taurus africanus) steer in a North American game park

USDA-ARS?s Scientific Manuscript database

A 10 year-old Watusi (Bos taurus africanus) steer housed at a drive-through game park in Winston, Oregon developed severe clinical illness including: fever, marked nasal discharge, injected scleral and conjunctival membranes, plus oral hemorrhages and erosions. The animal responded poorly to support...

Search for the CO-dark Mass in the Central Molecular Zone by using the ASTE 10-m Telescope

NASA Astrophysics Data System (ADS)

Tanaka, Kunihiko

2017-01-01

Atomic carbon (C0) is one of the most abundant carbon-bearing species in the interstellar molecular gas, and its submillimeter lines are good tracers of low-density molecular clouds which are often dark in CO rotational lines. We present a new map of the central 150 pc region of the Milky Way in the 500 GHz [CI] line, which has been recently obtained with the ASTE 10-m telescope. The [CI] emission is brightest toward the central 5-pc region, where massive GMCs are absent. This [CI]-bright region is approximately centered toward Sgr A*, covering the entire circum-nuclear ring (CND) and the western part of the 50-km/s cloud. The C0/CO abundance ratio is 0.5-2 there, and the highest ratio is observed toward the CND but just outside of the 2-pc ring of dense gas. This discovery may suggest that the CO-dark component occupies a significant fraction of the molecular gas in the circumnuclear region.

VizieR Online Data Catalog: Late-type targets in Taurus, Cha I, and Upper Sco (Todorov+, 2014)

NASA Astrophysics Data System (ADS)

Todorov, K. O.; Luhman, K. L.; Konopacky, Q. M.; McLeod, K. K.; Apai, D.; Ghez, A. M.; Pascucci, I.; Robberto, M.

2017-07-01

To characterize the multiplicity of low-mass stars and brown dwarfs in Taurus and Chamaeleon I, we combine the results from our survey with those from previous high-resolution images in these regions. The latter were collected with WFPC2 (Kraus et al. 2006ApJ...649..306K), Keck speckle imaging (Konopacky et al. 2007ApJ...663..394K), and Keck AO imaging (Kraus & Hillenbrand 2012, J/ApJ/757/141) in Taurus and with WFPC2 (Neuhauser et al. 2002A&A...384..999N), the Advanced Camera for Surveys on Hubble (Luhman 2007, J/ApJS/173/104), and AO at the Very Large Telescope (Ahmic et al. 2007ApJ...671.2074A; Lafreniere et al. 2008ApJ...683..844L) in Chamaeleon I. For comparison to these two regions, we also have compiled binary data measured for late-type members of the Upper Sco association ({tau}~11 Myr; Pecaut et al. 2012, J/ApJ/746/154) with WFPC2 and Keck AO (Kraus et al. 2005ApJ...633..452K; Biller et al. 2011ApJ...730...39B; Kraus & Hillenbrand 2012, J/ApJ/757/141). (1 data file).

Dark matter as a weakly coupled dark baryon

NASA Astrophysics Data System (ADS)

Mitridate, Andrea; Redi, Michele; Smirnov, Juri; Strumia, Alessandro

2017-10-01

Dark Matter might be an accidentally stable baryon of a new confining gauge interaction. We extend previous studies exploring the possibility that the DM is made of dark quarks heavier than the dark confinement scale. The resulting phenomenology contains new unusual elements: a two-stage DM cosmology (freeze-out followed by dark condensation), a large DM annihilation cross section through recombination of dark quarks (allowing to fit the positron excess). Light dark glue-balls are relatively long lived and give extra cosmological effects; DM itself can remain radioactive.

Stability of Stellar Periods in the Hyades and Taurus

NASA Astrophysics Data System (ADS)

Rebull, Luisa M.; Stauffer, John R.; K2 Clusters Team

2018-06-01

K2 has opened to us the study of high-precision light curves from which we can derive stellar rotation periods. We have presented period distributions for the Pleiades, Praesepe, Upper Sco and Rho Oph. But, how stable are the periods we are deriving from them? Early ground-based work in Orion (Rebull 2001) suggested that, for the youngest stars, about half the stars had sufficiently different spot distributions in two consecutive years such that periods could not be recovered in the second year. However, now that we have K2, precision and diurnal windowing functions are no longer really much of a concern. For a handful of stars in Hyades and Taurus, the K2 spacecraft monitored them for two non-consecutive 70d windows (campaigns 4, 2015 Feb and 13, 2017 Mar). In this poster, we examine whether or not the light curves are similar in the two epochs, and how accurately the same period can be recovered.

Variability at the edge: highly accreting objects in Taurus

NASA Astrophysics Data System (ADS)

Abraham, Peter; Kospal, Agnes; Szabo, Robert

2017-04-01

In Kepler K2, Campaign 13, we will obtain 80-days-long optical light curves of seven highly accreting T Tauri stars in the benchmark Taurus star forming region. Here we propose to monitor our sample simultaneously with Kepler and Spitzer, to be able to separate variability patterns related to different physical processes. Monitoring our targets with Spitzer during the final 11 days of the K2 campaign, we will clean the light curves from non-accretion effects (rotating stellar spots, dips due to passing dust structures), and construct, for the first time, a variability curve which reflects the time-dependent accretion only. We will then study and understand how time-dependent mass accretion affects the density and temperature structure of the protoplanetary disk, which sets the initial conditions for planet formation. The proposed work cannot be done without the unparalleled precision of Kepler and Spitzer. This unique and one-time opportunity motivated our DDT proposal.

The Apollo 17 mare basalts: Serenely sampling Taurus-Littrow

NASA Technical Reports Server (NTRS)

Neal, Clive R.; Taylor, Lawrence A.

1992-01-01

As we are all aware, the Apollo 17 mission marked the final manned lunar landing of the Apollo program. The lunar module (LM) landed approximately 0.7 km due east of Camelot Crater in the Taurus-Littrow region on the southwestern edge of Mare Serenitatis. Three extravehicular activities (EVA's) were performed, the first concentrating around the LM and including station 1 approximately 1.1 km south-southeast of the LM at the northwestern edge of Steno Crater. The second traversed approximately 8 km west of the LM to include stations 2, 3, 4, and 5, and the third EVA traversed approximately 4.5 km to the northwest of the LM to include stations 6, 7, 8, and 9. This final manned mission returned the largest quantity of lunar rock samples, 110.5 kg/243.7 lb, and included soils, breccias, highland samples, and mare basalts. This abstract concentrates upon the Apollo 17 mare basalt samples.

The Apollo 17 mare basalts: Serenely sampling Taurus-Littrow

NASA Astrophysics Data System (ADS)

Neal, Clive R.; Taylor, Lawrence A.

1992-12-01

As we are all aware, the Apollo 17 mission marked the final manned lunar landing of the Apollo program. The lunar module (LM) landed approximately 0.7 km due east of Camelot Crater in the Taurus-Littrow region on the southwestern edge of Mare Serenitatis. Three extravehicular activities (EVA's) were performed, the first concentrating around the LM and including station 1 approximately 1.1 km south-southeast of the LM at the northwestern edge of Steno Crater. The second traversed approximately 8 km west of the LM to include stations 2, 3, 4, and 5, and the third EVA traversed approximately 4.5 km to the northwest of the LM to include stations 6, 7, 8, and 9. This final manned mission returned the largest quantity of lunar rock samples, 110.5 kg/243.7 lb, and included soils, breccias, highland samples, and mare basalts. This abstract concentrates upon the Apollo 17 mare basalt samples.

Revisiting the Field Geology of Taurus-Littrow

NASA Technical Reports Server (NTRS)

Schmitt, H. H.; Petro, N. E.; Wells, R. A.; Robinson, M. S.; Weiss, B. P.; Mercer, C. M.

2016-01-01

Integration of Apollo 17 field observations and photographs, sample investigations, Lunar Reconnaissance Orbiter Camera images, Chandrayaan-1 Moon Mineralogy Mapper (M(sup 3)) spectra, and Miniature Radio Frequency (Mini-RF) S-band radar images provides new insights into the geology of the valley of Taurus-Littrow on the Moon. Connecting the various remote observations to sample data enables a set of new conclusions to be drawn regarding the geological evolution of the valley. Structural considerations and published and recalculated Ar-40/Ar-39 analyses of samples from the North Massif and the Sculptured Hills indicate that the Crisium basin formed about 3.93 Ga; the Serenitatis basin about 3.82 Ga; and the Imbrium basin no earlier than 3.82 Ga and no later than the average of 3.72 Ga for 33 age dates from samples of the valley's mare basalts. Strong evidence continues to support the conclusion of others (Lucchitta, 1972; Spudis et al., 2011; Fassett et al., 2012) that the Sculptured Hills physiographic unit consists of Imbrium ejecta. Interpretation of M(sup 3) spectral data and Apollo 17 samples indicate that rock units of the Sculptured Hills consist of a largely coherent, Mg-suite pluton. LROC NAC stereo images and Mini-RF data indicate the presence of several exposed pyroclastic fissures across the Sculptured Hills. Rim boulders at Camelot Crater constitute nearly in situ wall rocks of that crater rather than ejecta and provide an opportunity for investigations of remanent magnetic field orientation at the time of the eruption of late mare basalt lavas in the valley. Paleomagnetic field orientation information also may be obtained relative to melt-breccia contacts in North Massif boulders that suggest original horizontal orientations. LROC images indicate the existence of two temporally separate light mantle avalanche deposits. The origin, potential flow mechanisms, and geology of the youngest avalanche from the South Massif have been clarified. The existence

Revisiting the field geology of Taurus-Littrow

NASA Astrophysics Data System (ADS)

Schmitt, H. H.; Petro, N. E.; Wells, R. A.; Robinson, M. S.; Weiss, B. P.; Mercer, C. M.

2017-12-01

Integration of Apollo 17 field observations and photographs, sample investigations, Lunar Reconnaissance Orbiter Camera images, Chandrayaan-1 Moon Mineralogy Mapper (M3) spectra, and Miniature Radio Frequency (Mini-RF) S-band radar images provides new insights into the geology of the valley of Taurus-Littrow on the Moon. Connecting the various remote observations to sample data enables a set of new conclusions to be drawn regarding the geological evolution of the valley. Structural considerations and published and recalculated 40Ar/39Ar analyses of samples from the North Massif and the Sculptured Hills indicate that the Crisium basin formed about 3.93 Ga; the Serenitatis basin about 3.82 Ga; and the Imbrium basin no earlier than 3.82 Ga and no later than the average of 3.72 Ga for 33 age dates from samples of the valley's mare basalts. Strong evidence continues to support the conclusion of others (Lucchitta, 1972; Spudis et al., 2011; Fassett et al., 2012) that the Sculptured Hills physiographic unit consists of Imbrium ejecta. Interpretation of M3 spectral data and Apollo 17 samples indicate that rock units of the Sculptured Hills consist of a largely coherent, Mg-suite pluton. LROC NAC stereo images and Mini-RF data indicate the presence of several exposed pyroclastic fissures across the Sculptured Hills. Rim boulders at Camelot Crater constitute nearly in situ wall rocks of that crater rather than ejecta and provide an opportunity for investigations of remanent magnetic field orientation at the time of the eruption of late mare basalt lavas in the valley. Paleomagnetic field orientation information also may be obtained relative to melt-breccia contacts in North Massif boulders that suggest original horizontal orientations. LROC images indicate the existence of two temporally separate light mantle avalanche deposits. The origin, potential flow mechanisms, and geology of the youngest avalanche from the South Massif have been clarified. The existence of two

OH 18 cm TRANSITION AS A THERMOMETER FOR MOLECULAR CLOUDS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ebisawa, Yuji; Inokuma, Hiroshi; Yamamoto, Satoshi

We have observed the four hyperfine components of the 18 cm OH transition toward the translucent cloud eastward of Heiles Cloud 2 (HCL2E), the cold dark cloud L134N, and the photodissociation region of the ρ-Ophiuchi molecular cloud with the Effelsberg 100 m telescope. We have found intensity anomalies among the hyperfine components in all three regions. In particular, an absorption feature of the 1612 MHz satellite line against the cosmic microwave background has been detected toward HCL2E and two positions of the ρ-Ophiuchi molecular cloud. On the basis of statistical equilibrium calculations, we find that the hyperfine anomalies originate frommore » the non-LTE population of the hyperfine levels, and can be used to determine the kinetic temperature of the gas over a wide range of H{sub 2} densities (10{sup 2}–10{sup 7} cm{sup −3}). Toward the center of HCL2E, the gas kinetic temperature is determined to be 53 ± 1 K, and it increases toward the cloud peripheries (∼60 K). The ortho-to-para ratio of H{sub 2} is determined to be 3.5 ± 0.9 from the averaged spectrum for the eight positions. In L134N, a similar increase of the temperature is also seen toward the periphery. In the ρ-Ophiuchi molecular cloud, the gas kinetic temperature decreases as a function of the distance from the exciting star HD 147889. These results demonstrate a new aspect of the OH 18 cm line that can be used as a good thermometer of molecular cloud envelopes. The OH 18 cm line can be used to trace a new class of warm molecular gas surrounding a molecular cloud, which is not well traced by the emission of CO and its isotopologues.« less

DarkSide search for dark matter

NASA Astrophysics Data System (ADS)

Alexander, T.; Alton, D.; Arisaka, K.; Back, H. O.; Beltrame, P.; Benziger, J.; Bonfini, G.; Brigatti, A.; Brodsky, J.; Bussino, S.; Cadonati, L.; Calaprice, F.; Candela, A.; Cao, H.; Cavalcante, P.; Chepurnov, A.; Chidzik, S.; Cocco, A. G.; Condon, C.; D'Angelo, D.; Davini, S.; De Vincenzi, M.; De Haas, E.; Derbin, A.; Di Pietro, G.; Dratchnev, I.; Durben, D.; Empl, A.; Etenko, A.; Fan, A.; Fiorillo, G.; Franco, D.; Fomenko, K.; Forster, G.; Gabriele, F.; Galbiati, C.; Gazzana, S.; Ghiano, C.; Goretti, A.; Grandi, L.; Gromov, M.; Guan, M.; Guo, C.; Guray, G.; Hungerford, E. V.; Ianni, Al; Ianni, An; Joliet, C.; Kayunov, A.; Keeter, K.; Kendziora, C.; Kidner, S.; Klemmer, R.; Kobychev, V.; Koh, G.; Komor, M.; Korablev, D.; Korga, G.; Li, P.; Loer, B.; Lombardi, P.; Love, C.; Ludhova, L.; Luitz, S.; Lukyanchenko, L.; Lund, A.; Lung, K.; Ma, Y.; Machulin, I.; Mari, S.; Maricic, J.; Martoff, C. J.; Meregaglia, A.; Meroni, E.; Meyers, P.; Mohayai, T.; Montanari, D.; Montuschi, M.; Monzani, M. E.; Mosteiro, P.; Mount, B.; Muratova, V.; Nelson, A.; Nemtzow, A.; Nurakhov, N.; Orsini, M.; Ortica, F.; Pallavicini, M.; Pantic, E.; Parmeggiano, S.; Parsells, R.; Pelliccia, N.; Perasso, L.; Perasso, S.; Perfetto, F.; Pinsky, L.; Pocar, A.; Pordes, S.; Randle, K.; Ranucci, G.; Razeto, A.; Romani, A.; Rossi, B.; Rossi, N.; Rountree, S. D.; Saggese, P.; Saldanha, R.; Salvo, C.; Sands, W.; Seigar, M.; Semenov, D.; Shields, E.; Skorokhvatov, M.; Smirnov, O.; Sotnikov, A.; Sukhotin, S.; Suvarov, Y.; Tartaglia, R.; Tatarowicz, J.; Testera, G.; Thompson, J.; Tonazzo, A.; Unzhakov, E.; Vogelaar, R. B.; Wang, H.; Westerdale, S.; Wojcik, M.; Wright, A.; Xu, J.; Yang, C.; Zavatarelli, S.; Zehfus, M.; Zhong, W.; Zuzel, G.

2013-11-01

The DarkSide staged program utilizes a two-phase time projection chamber (TPC) with liquid argon as the target material for the scattering of dark matter particles. Efficient background reduction is achieved using low radioactivity underground argon as well as several experimental handles such as pulse shape, ratio of ionization over scintillation signal, 3D event reconstruction, and active neutron and muon vetos. The DarkSide-10 prototype detector has proven high scintillation light yield, which is a particularly important parameter as it sets the energy threshold for the pulse shape discrimination technique. The DarkSide-50 detector system, currently in commissioning phase at the Gran Sasso Underground Laboratory, will reach a sensitivity to dark matter spin-independent scattering cross section of 10-45 cm2 within 3 years of operation.

Herbig-Haro objects in the Chamaeleon II dark cloud

DOE Office of Scientific and Technical Information (OSTI.GOV)

Graham, J.A.; Hartigan, P.

1988-04-01

A new photograph and some spectra have been obtained for the group of HH objects HH 52, 53, 54. A long, gaseous streamer extends from HH 54 and produces an appearance very similar to that of HH 12. The spectra provide some additional radial velocities and line-intensity measurements for the group. It is confirmed that HH 54D is a star with no unusual photometric or spectroscopic characteristics. Attention is drawn to the distance of 400 pc derived by FitzGerald (1974, 1976) for a globule in the Cha II cloud, and it is suggested that the whole complex of gas, dust,more » and stars may well be further away than the 140 pc generally assumed. The spatial and velocity characteristics of this group of HH objects are discussed. The data do not support the identifications proposed by Sandell et al. (1987) as sources for the observed flows. 32 references.« less

Differences in Beef Quality between Angus (Bos taurus taurus) and Nellore (Bos taurus indicus) Cattle through a Proteomic and Phosphoproteomic Approach.

PubMed

Rodrigues, Rafael Torres de Souza; Chizzotti, Mario Luiz; Vital, Camilo Elber; Baracat-Pereira, Maria Cristina; Barros, Edvaldo; Busato, Karina Costa; Gomes, Rafael Aparecido; Ladeira, Márcio Machado; Martins, Taiane da Silva

2017-01-01

Proteins are the major constituents of muscle and are key molecules regulating the metabolic changes during conversion of muscle to meat. Brazil is one of the largest exporters of beef and most Brazilian cattle are composed by zebu (Nellore) genotype. Bos indicus beef is generally leaner and tougher than Bos taurus such as Angus. The aim of this study was to compare the muscle proteomic and phosphoproteomic profile of Angus and Nellore. Seven animals of each breed previously subjected the same growth management were confined for 84 days. Proteins were extracted from Longissimus lumborum samples collected immediately after slaughter and separated by two-dimensional electrophoresis. Pro-Q Diamond stain was used in phosphoproteomics. Proteins identification was performed using matrix assisted laser desorption/ionization time-of-flight mass spectrometry. Tropomyosin alpha-1 chain, troponin-T, myosin light chain-1 fragment, cytoplasmic malate dehydrogenase, alpha-enolase and 78 kDa glucose-regulated protein were more abundant in Nellore, while myosin light chain 3, prohibitin, mitochondrial stress-70 protein and heat shock 70 kDa protein 6 were more abundant in Angus (P<0.05). Nellore had higher phosphorylation of myosin regulatory light chain-2, alpha actin-1, triosephosphate isomerase and 14-3-3 protein epsilon. However, Angus had greater phosphorylation of phosphoglucomutase-1 and troponin-T (P<0.05). Therefore, proteins involved in contraction and muscle organization, myofilaments expressed in fast or slow-twitch fibers and heat shock proteins localized in mitochondria or sarcoplasmic reticulum and involved in cell flux of calcium and apoptosis might be associated with differences in beef quality between Angus and Nellore. Furthermore, prohibitin appears to be a potential biomarker of intramuscular fat in cattle. Additionally, differences in phosphorylation of myofilaments and glycolytic enzymes could be involved with differences in muscle contraction force

Differences in Beef Quality between Angus (Bos taurus taurus) and Nellore (Bos taurus indicus) Cattle through a Proteomic and Phosphoproteomic Approach

PubMed Central

Chizzotti, Mario Luiz; Vital, Camilo Elber; Baracat-Pereira, Maria Cristina; Barros, Edvaldo; Busato, Karina Costa; Gomes, Rafael Aparecido; Ladeira, Márcio Machado; Martins, Taiane da Silva

2017-01-01

Proteins are the major constituents of muscle and are key molecules regulating the metabolic changes during conversion of muscle to meat. Brazil is one of the largest exporters of beef and most Brazilian cattle are composed by zebu (Nellore) genotype. Bos indicus beef is generally leaner and tougher than Bos taurus such as Angus. The aim of this study was to compare the muscle proteomic and phosphoproteomic profile of Angus and Nellore. Seven animals of each breed previously subjected the same growth management were confined for 84 days. Proteins were extracted from Longissimus lumborum samples collected immediately after slaughter and separated by two-dimensional electrophoresis. Pro-Q Diamond stain was used in phosphoproteomics. Proteins identification was performed using matrix assisted laser desorption/ionization time-of-flight mass spectrometry. Tropomyosin alpha-1 chain, troponin-T, myosin light chain-1 fragment, cytoplasmic malate dehydrogenase, alpha-enolase and 78 kDa glucose-regulated protein were more abundant in Nellore, while myosin light chain 3, prohibitin, mitochondrial stress-70 protein and heat shock 70 kDa protein 6 were more abundant in Angus (P<0.05). Nellore had higher phosphorylation of myosin regulatory light chain-2, alpha actin-1, triosephosphate isomerase and 14-3-3 protein epsilon. However, Angus had greater phosphorylation of phosphoglucomutase-1 and troponin-T (P<0.05). Therefore, proteins involved in contraction and muscle organization, myofilaments expressed in fast or slow-twitch fibers and heat shock proteins localized in mitochondria or sarcoplasmic reticulum and involved in cell flux of calcium and apoptosis might be associated with differences in beef quality between Angus and Nellore. Furthermore, prohibitin appears to be a potential biomarker of intramuscular fat in cattle. Additionally, differences in phosphorylation of myofilaments and glycolytic enzymes could be involved with differences in muscle contraction force

Direct detection constraints on dark photon dark matter

NASA Astrophysics Data System (ADS)

An, Haipeng; Pospelov, Maxim; Pradler, Josef; Ritz, Adam

2015-07-01

Dark matter detectors built primarily to probe elastic scattering of WIMPs on nuclei are also precise probes of light, weakly coupled, particles that may be absorbed by the detector material. In this paper, we derive constraints on the minimal model of dark matter comprised of long-lived vector states V (dark photons) in the 0.01- 100 keV mass range. The absence of an ionization signal in direct detection experiments such as XENON10 and XENON100 places a very strong constraint on the dark photon mixing angle, down to O (10-15), assuming that dark photons comprise the dominant fraction of dark matter. This sensitivity to dark photon dark matter exceeds the indirect bounds derived from stellar energy loss considerations over a significant fraction of the available mass range. We also revisit indirect constraints from V → 3 γ decay and show that limits from modifications to the cosmological ionization history are comparable to the updated limits from the diffuse γ-ray flux.

Is Self-Interacting Dark Matter Undergoing Dark Fusion?

DOE Office of Scientific and Technical Information (OSTI.GOV)

McDermott, Samuel D.

2017-11-02

We suggest that two-to-two dark matter fusion may be the relaxation process that resolves the small-scale structure problems of the cold collisionless dark matter paradigm. In order for the fusion cross section to scale correctly across many decades of astrophysical masses from dwarf galaxies to galaxy clusters, we require the fractional binding energy released to be greater than v^n ~ [10^{-(2-3)}]^n, where n=1,2 depends on local dark sector chemistry. The size of the dark-sector interaction cross sections must be sigma ~ 0.1-1 barn, moderately larger than for Standard Model deuteron fusion, indicating a dark nuclear scale Lambda ~ O(100 MeV).more » Dark fusion firmly predicts constant sigma v below the characteristic velocities of galaxy clusters. Observations of the inner structure of galaxy groups with velocity dispersion of several hundred kilometer per second, of which a handful have been identified, could differentiate dark fusion from a dark photon model.« less

Is Self-Interacting Dark Matter Undergoing Dark Fusion?

NASA Astrophysics Data System (ADS)

McDermott, Samuel D.

2018-06-01

We suggest that two-to-two dark matter fusion may be the relaxation process that resolves the small-scale structure problems of the cold collisionless dark matter paradigm. In order for the fusion cross section to scale correctly across many decades of astrophysical masses from dwarf galaxies to galaxy clusters, we require the fractional binding energy released to be greater than vn˜(10-(2 -3 ))n , where n =1 , 2 depends on local dark sector chemistry. The size of the dark-sector interaction cross sections must be σ˜0.1 - 1 barn, moderately larger than for standard model deuteron fusion, indicating a dark nuclear scale Λ ˜O (100 MeV ) . Dark fusion firmly predicts constant σ v below the characteristic velocities of galaxy clusters. Observations of the inner structure of galaxy groups with velocity dispersion of several hundred kilometers per second, of which a handful have been identified, could differentiate dark fusion from a dark photon model.

Retrieving Neptune's aerosol properties from Keck OSIRIS observations. I. Dark regions

NASA Astrophysics Data System (ADS)

Luszcz-Cook, S. H.; de Kleer, K.; de Pater, I.; Adamkovics, M.; Hammel, H. B.

2016-09-01

We present and analyze three-dimensional data cubes of Neptune from the OSIRIS integral-field spectrograph on the 10-m W.M. Keck II telescope, from 26 July 2009. These data have a spatial resolution of 0.035/pixel and spectral resolution of R ∼3800 in the H (1.47-1.80 μm) and K (1.97-2.38 μm) broad bands. We focus our analysis on regions of Neptune's atmosphere that are near-infrared dark - that is, free of discrete bright cloud features. We use a forward model coupled to a Markov chain Monte Carlo algorithm to retrieve properties of Neptune's aerosol structure and methane profile above ∼4 bar in these near-infrared dark regions. We construct a set of high signal-to-noise spectra spanning a range of viewing geometries to constrain the vertical structure of Neptune's aerosols in a cloud-free latitude band from 2-12°N. We find that Neptune's cloud opacity at these wavelengths is dominated by a compact, optically thick cloud layer with a base near 3 bar. Using the pyDISORT algorithm for the radiative transfer and assuming a Henyey-Greenstein phase function, we observe this cloud to be composed of low albedo (single scattering albedo = 0.45-0.01+0.01), forward scattering (asymmetry parameter g = 0.50-0.02+0.02) particles, with an assumed characteristic size of ∼1μm. Above this cloud, we require an aerosol layer of smaller (∼0.1μm) particles forming a vertically extended haze, which reaches from the upper troposphere (0.59-0.03+0.04 bar) into the stratosphere. The particles in this haze are brighter (single scattering albedo = 0.91-0.05+0.06) and more isotropically scattering (asymmetry parameter g = 0.24-0.03+0.02) than those in the deep cloud. When we extend our analysis to 18 cloud-free locations from 20°N to 87°S, we observe that the optical depth in aerosols above 0.5 bar decreases by a factor of 2-3 or more at mid- and high-southern latitudes relative to low latitudes. We also consider Neptune's methane (CH4) profile, and find that our retrievals

Cloud Infrastructure & Applications - CloudIA

NASA Astrophysics Data System (ADS)

Sulistio, Anthony; Reich, Christoph; Doelitzscher, Frank

The idea behind Cloud Computing is to deliver Infrastructure-as-a-Services and Software-as-a-Service over the Internet on an easy pay-per-use business model. To harness the potentials of Cloud Computing for e-Learning and research purposes, and to small- and medium-sized enterprises, the Hochschule Furtwangen University establishes a new project, called Cloud Infrastructure & Applications (CloudIA). The CloudIA project is a market-oriented cloud infrastructure that leverages different virtualization technologies, by supporting Service-Level Agreements for various service offerings. This paper describes the CloudIA project in details and mentions our early experiences in building a private cloud using an existing infrastructure.

First Image and Spectrum of a Dark Matter Object

NASA Astrophysics Data System (ADS)

2001-12-01

galaxy, such as the Large Magellanic Cloud (LMC), then the gravitational field of the MACHO will bend the light from the distant star and focus it into our telescopes. The MACHO is acting as a gravitational lens, increasing the brightness of the background star for the short time it takes for the MACHO to pass by. Depending on the mass of the MACHO and its distance from Earth, this period of brightening can last days, weeks or months. The form and duration of the brightening caused by the MACHO - the microlensing "light curve" - can be predicted by theory and searched for as a clear signal of the presence of MACHO Dark Matter. MACHOs are described as "microlenses" since they are much smaller than other known cases of gravitational lensing, such as those observed around clusters of galaxies, cf. ESO PR 19/98. Observations of microlensing events have been done on many occasions with ESO telescope with intersting results, e.g., the recent detection of a corona of a distant star in the Milky Way ( ESO PR 17/01 ). The MACHO Project Astronomers from the Lawrence Livermore National Laboratory , the Center for Particle Astrophysics in the United States and the Australian National University joined forces to form the "MACHO Project" in 1991. This team [2] used a dedicated telescope at the Mount Stromlo Observatory in Australia to monitor the brightness of more than 10 million stars in the Large Magellanic Cloud (LMC) over a period of eight years. The team discovered their first gravitational lensing event in 1993 and have now published approximately twenty instances of microlenses in the direction of the Magellanic Clouds. These results demonstrate that there is a population of MACHO objects in and around the Milky Way galaxy that could comprise as much as 50% of the Milky Way total (baryonic/normal-matter) Dark Matter content. Hubble obtains the first direct image of a MACHO ESO PR Photo 35a/01 ESO PR Photo 35a/01 [Preview - JPEG: 400 x 387 pix - 36k] [Normal - JPEG: 800 x 774

Effect of biological type of cattle on the incidence of the dark, firm, and dry condition in the longissimus muscle.

PubMed

Shackelford, S D; Koohmaraie, M; Wheeler, T L; Cundiff, L V; Dikeman, M E

1994-02-01

The objectives of this experiment were to characterize longissimus muscle color, texture, and firmness for beef carcasses of diverse biological types and to determine the genetic parameters of lean color, texture, and firmness. The carcasses (n = 3,641) used in this experiment were from steers produced by mating Angus, Brahman, Braunvieh, Charolais, Chianina, Galloway, Gelbvieh, Hereford, Jersey, Limousin, Longhorn, Maine Anjou, Nellore, Piedmontese, Pinzgauer, Red Poll, Sahiwal, Salers, Shorthorn, Simmental, South Devon, and Tarentaise sires to Hereford and Angus dams. Steers were fed a corn-corn silage diet from weaning until slaughter at 356 to 575 d of age. Steers were slaughtered at commercial packing plants and longissimus muscle color, texture, and firmness were scored by trained carcass evaluators. Sire line least squares means for lean color, texture, and firmness ranged approximately one unit on a 7-point scale. Chianina crosses had darker-colored lean than all breed groups except Tarentaise and Simmental crosses (P < .05). Moreover, a higher percentage (P < .05) of Chianina crosses than of all other breed groups had unacceptably dark-colored ("dark red" or darker) lean. Bos indicus sire lines were not different from Bos taurus sire lines in frequency of carcasses with unacceptably dark-colored lean. However, Bos indicus crosses were more likely to be scored "very light cherry-red." Lean color and texture were lowly heritable, whereas lean firmness was moderately heritable. Thus, this experiment demonstrated that there is genetic variation in the incidence of the DFD condition; however, genetic variation was small relative to environmental variation.

Optical polarimetry and molecular line studies of L1157 dark molecular cloud

NASA Astrophysics Data System (ADS)

Sharma, Ekta; Soam, Archana; Gopinathan, Maheswar

2018-04-01

Filaments are omnipresent in molecular clouds which are believed to fragment into cores. The detailed process of the evolution from filaments to cores depends critically on the physical conditions in the star forming region. This study aims at characterising gas motions using velocity structure and finding the dynamical importance of magnetic fields in the filament morphology. The plane-of-the-sky component of the magnetic field has been measured using optical polarization of the background stars. The orientation is found to be almost perpendicular to the filament implying its dynamical importance in the evolution of the cloud. Optical polarimetric results match very well with the sub millimetre polarization angles obtained in the inner core regions. The magnetic fields are found to have an orientation of 130° east with respect to north. The angular offset between the outflow axis and the magnetic field direction is found to be 25°. Values for parameters like the excitation temperature, optical depth and column densities have been derived using molecular lines. Optically thick lines show non-gaussian features. The non-thermal widths tell about the presence of turbulent motions whereas the C180 lines follow Gaussian features almost at all the locations observed in the filament.

Hubble Provides Infrared View of Jupiter's Moon, Ring, and Clouds

NASA Technical Reports Server (NTRS)

1997-01-01

Probing Jupiter's atmosphere for the first time, the Hubble Space Telescope's new Near Infrared Camera and Multi-Object Spectrometer (NICMOS) provides a sharp glimpse of the planet's ring, moon, and high-altitude clouds.

The presence of methane in Jupiter's hydrogen- and helium-rich atmosphere has allowed NICMOS to plumb Jupiter's atmosphere, revealing bands of high-altitude clouds. Visible light observations cannot provide a clear view of these high clouds because the underlying clouds reflect so much visible light that the higher level clouds are indistinguishable from the lower layer. The methane gas between the main cloud deck and the high clouds absorbs the reflected infrared light, allowing those clouds that are above most of the atmosphere to appear bright. Scientists will use NICMOS to study the high altitude portion of Jupiter's atmosphere to study clouds at lower levels. They will then analyze those images along with visible light information to compile a clearer picture of the planet's weather. Clouds at different levels tell unique stories. On Earth, for example, ice crystal (cirrus) clouds are found at high altitudes while water (cumulus) clouds are at lower levels.

Besides showing details of the planet's high-altitude clouds, NICMOS also provides a clear view of the ring and the moon, Metis. Jupiter's ring plane, seen nearly edge-on, is visible as a faint line on the upper right portion of the NICMOS image. Metis can be seen in the ring plane (the bright circle on the ring's outer edge). The moon is 25 miles wide and about 80,000 miles from Jupiter.

Because of the near-infrared camera's narrow field of view, this image is a mosaic constructed from three individual images taken Sept. 17, 1997. The color intensity was adjusted to accentuate the high-altitude clouds. The dark circle on the disk of Jupiter (center of image) is an artifact of the imaging system.

This image and other images and data received from the Hubble Space Telescope are

VizieR Online Data Catalog: Infrared photometry of all known members in Taurus (Esplin+, 2014)

NASA Astrophysics Data System (ADS)

Esplin, T. L.; Luhman, K. L.; Mamajek, E. E.

2016-08-01

To construct a census of the circumstellar disks in Taurus, we begin by compiling a list of all known members of the region. We adopt the 352 members from Luhman et al. 2010 (cat. J/ApJS/186/111), 4 additional stars that have good evidence of membership from previous studies (Section 5.4), 32 members found in a subsequent survey by K. Luhman (in preparation; 33 if GZ Tau A and B are counted separately), and 25 new members (26 if BS Tau A and B are counted separately) that we have confirmed with spectroscopy (Section 5.3). We also adopt as a member HD 285957, which has a proper motion consistent with that of the Taurus subgroup L1551 (Zacharias et al. 2013, cat. I/322; Luhman et al. 2009ApJ...703..399L) and exhibits evidence of youth in the form of Li absorption (Wichmann et al. 2000A&A...359..181W; Sestito et al. 2008, cat. J/A+A/488/943). We make use of mid-infrared photometry for members of Taurus measured with Spitzer's Infrared Array Camera (IRAC) and the Multiband Imaging Photometer for Spitzer (MIPS). We consider the four bands of IRAC (3.6, 4.5, 5.8, and 8.0μm) and the 24μm band of MIPS, which are denoted as [3.6], [4.5], [5.8], [8.0], and [24], respectively. IRAC produced images with a field of view of 5.2'*5.2' and FWHM of 1.6''-1.9'' for [3.6] to [8.0]. MIPS had a field of view of 5.4'*5.4' and a FWHM of 5.9'' for [24]. Photometry from most Spitzer images for most members of Taurus has been measured by Luhman et al. 2010 (cat. J/ApJS/186/111) (see also Hartmann et al. 2005ApJ...629..881H; Luhman et al. 2006, cat. J/ApJ/647/1180; Guieu et al. 2007, cat. 2007A&A...465..855G; Rebull et al. 2010, cat. J/ApJS/186/259). We have measured photometry of the members that were not considered in Luhman et al. 2010 (cat. J/ApJS/186/111) and all known members appearing in Spitzer images that have become publicly available since that study (Astronomical Observation Requests 26470912, 26471168 26477056, 26475264, 26472704, 26473216, and 23272448). These data were

Dark clouds or silver linings? A stigma threat perspective on the implications of an autism diagnosis for workplace well-being.

PubMed

Johnson, Tiffany D; Joshi, Aparna

2016-03-01

This article unpacks the stigma associated with a developmental disability at work, specifically autism spectrum disorders (ASD), by presenting findings from 2 studies-one interview-based and the other survey-based. Drawing on in-depth interviews with individuals on the autism spectrum, the first study showed that a clinical diagnosis of autism is a milestone event that triggered both positive (silver linings) and negative (dark clouds) responses to work. These positive and negative responses were shaped by the age at which the diagnosis occurred as well as specific work-related contingencies-identity management (disclosing or not disclosing), the importance of the social demands imposed by the job, and organizational support policies for autism. The second study developed and tested propositions derived from the qualitative data by using survey data gathered from working adults with ASD. Results showed that, compared with individuals diagnosed later in life, individuals who were diagnosed at an earlier age experienced greater organization-based self-esteem and lower perceived discrimination when they disclosed their disability, worked in jobs that placed lower social demands on them, or were employed in organizations that offered policies to support workers with ASD. We conclude that, depending on the age of diagnosis, attributes of the employment context can trigger stigma-related threat in different ways and we outline important practical implications of these findings. (c) 2016 APA, all rights reserved).

Direct detection constraints on dark photon dark matter

DOE PAGES

An, Haipeng; Pospelov, Maxim; Pradler, Josef; ...

2015-06-11

Dark matter detectors built primarily to probe elastic scattering of WIMPs on nuclei are also precise probes of light, weakly coupled, particles that may be absorbed by the detector material. In this paper, we derive constraints on the minimal model of dark matter comprised of long-lived vector states V (dark photons) in the 0.01–100KeV mass range. The absence of an ionization signal in direct detection experiments such as XENON10 and XENON100 places a very strong constraint on the dark photon mixing angle, down to Ο(10 –15), assuming that dark photons comprise the dominant fraction of dark matter. This sensitivity tomore » dark photon dark matter exceeds the indirect bounds derived from stellar energy loss considerations over a significant fraction of the available mass range. As a result, we also revisit indirect constraints from V → 3γ decay and show that limits from modifications to the cosmological ionization history are comparable to the updated limits from the diffuse γ-ray flux.« less

Lidar and radar measurements of the melting layer: observations of dark and bright band phenomena

NASA Astrophysics Data System (ADS)

Di Girolamo, P.; Summa, D.; Cacciani, M.; Norton, E. G.; Peters, G.; Dufournet, Y.

2012-05-01

Multi-wavelength lidar measurements in the melting layer revealing the presence of dark and bright bands have been performed by the University of BASILicata Raman lidar system (BASIL) during a stratiform rain event. Simultaneously radar measurements have been also performed from the same site by the University of Hamburg cloud radar MIRA 36 (35.5 GHz), the University of Hamburg dual-polarization micro rain radar (24.15 GHz) and the University of Manchester UHF wind profiler (1.29 GHz). Measurements from BASIL and the radars are illustrated and discussed in this paper for a specific case study on 23 July 2007 during the Convective and Orographically-induced Precipitation Study (COPS). Simulations of the lidar dark and bright band based on the application of concentric/eccentric sphere Lorentz-Mie codes and a melting layer model are also provided. Lidar and radar measurements and model results are also compared with measurements from a disdrometer on ground and a two-dimensional cloud (2DC) probe on-board the ATR42 SAFIRE. Measurements and model results are found to confirm and support the conceptual microphysical/scattering model elaborated by Sassen et al. (2005).

The dark cube: dark and light character profiles.

PubMed

Garcia, Danilo; Rosenberg, Patricia

2016-01-01

Background. Research addressing distinctions and similarities between people's malevolent character traits (i.e., the Dark Triad: Machiavellianism, narcissism, and psychopathy) has detected inconsistent linear associations to temperament traits. Additionally, these dark traits seem to have a common core expressed as uncooperativeness. Hence, some researchers suggest that the dark traits are best represented as one global construct (i.e., the unification argument) rather than as ternary construct (i.e., the uniqueness argument). We put forward the dark cube (cf. Cloninger's character cube) comprising eight dark profiles that can be used to compare individuals who differ in one dark character trait while holding the other two constant. Our aim was to investigate in which circumstances individuals who are high in each one of the dark character traits differ in Cloninger's "light" character traits: self-directedness, cooperativeness, and self-transcendence. We also investigated if people's dark character profiles were associated to their light character profiles. Method. A total of 997 participants recruited from Amazon's Mechanical Turk (MTurk) responded to the Short Dark Triad and the Short Character Inventory. Participants were allocated to eight different dark profiles and eight light profiles based on their scores in each of the traits and any possible combination of high and low scores. We used three-way interaction regression analyses and t-tests to investigate differences in light character traits between individuals with different dark profiles. As a second step, we compared the individuals' dark profile with her/his character profile using an exact cell-wise analysis conducted in the ROPstat software (http://www.ropstat.com). Results. Individuals who expressed high levels of Machiavellianism and those who expressed high levels of psychopathy also expressed low self-directedness and low cooperativeness. Individuals with high levels of narcissism, in contrast

Simultaneous colour visualizations of multiple ALS point cloud attributes for land cover and vegetation analysis

NASA Astrophysics Data System (ADS)

Zlinszky, András; Schroiff, Anke; Otepka, Johannes; Mandlburger, Gottfried; Pfeifer, Norbert

2014-05-01

LIDAR point clouds hold valuable information for land cover and vegetation analysis, not only in the spatial distribution of the points but also in their various attributes. However, LIDAR point clouds are rarely used for visual interpretation, since for most users, the point cloud is difficult to interpret compared to passive optical imagery. Meanwhile, point cloud viewing software is available allowing interactive 3D interpretation, but typically only one attribute at a time. This results in a large number of points with the same colour, crowding the scene and often obscuring detail. We developed a scheme for mapping information from multiple LIDAR point attributes to the Red, Green, and Blue channels of a widely used LIDAR data format, which are otherwise mostly used to add information from imagery to create "photorealistic" point clouds. The possible combinations of parameters are therefore represented in a wide range of colours, but relative differences in individual parameter values of points can be well understood. The visualization was implemented in OPALS software, using a simple and robust batch script, and is viewer independent since the information is stored in the point cloud data file itself. In our case, the following colour channel assignment delivered best results: Echo amplitude in the Red, echo width in the Green and normalized height above a Digital Terrain Model in the Blue channel. With correct parameter scaling (but completely without point classification), points belonging to asphalt and bare soil are dark red, low grassland and crop vegetation are bright red to yellow, shrubs and low trees are green and high trees are blue. Depending on roof material and DTM quality, buildings are shown from red through purple to dark blue. Erroneously high or low points, or points with incorrect amplitude or echo width usually have colours contrasting from terrain or vegetation. This allows efficient visual interpretation of the point cloud in planar

Voyager 1 imaging and IRIS observations of Jovian methane absorption and thermal emission: Implications for cloud structure

NASA Technical Reports Server (NTRS)

West, R. A.; Kupferman, P. N.; Hart, H.

1984-01-01

Images from three filters of the Voyager 1 wide angle camera are used to measure the continuum reflectivity and spectral gradient near 6000 A and the 6190 A band methane/continuum ratio for a variety of cloud features in Jupiter's atmosphere. The dark barge features in the North Equatorial Belt have anomalously strong positive continuum spectral gradients suggesting unique composition. Methane absorption is shown at unprecedented spatial scales for the Great Red Spot and its immediate environment, for a dark barge feature in the North Equatorial Belt, and for two hot spot and plume regions in the North Equatorial Belt. Methane absorption and five micrometer emission are correlated in the vicinity of the Great Red Spot but are anticorrelated in one of the plume hot spot regions. Methane absorption and simultaneous maps of five micrometer brightness temperature is quantitatively compared to realistic cloud structure models which include multiple scattering at five micrometer as well as in the visible. Variability in H2 quadrupole lines are also investigated.

Voyager 1 imaging and IRIS observations of Jovian methane absorption and thermal emission - Implications for cloud structure

NASA Technical Reports Server (NTRS)

West, R. A.; Kupferman, P. N.; Hart, H.

1985-01-01

Images from three filters of the Voyager 1 wide angle camera are used to measure the continuum reflectivity and spectral gradient near 6000 A and the 6190 A band methane/continuum ratio for a variety of cloud features in Jupiter's atmosphere. The dark barge features in the North Equatorial Belt have anomalously strong positive continuum spectral gradients suggesting unique composition. Methane absorption is shown at unprecedented spatial scales for the Great Red Spot and its immediate environment, for a dark barge feature in the North Equatorial Belt, and for two hot spot and plume regions in the North Equatorial Belt. Methane absorption and five micrometer emission are correlated in the vicinity of the Great Red Spot but are anticorrelated in one of the plume hot spot regions. Methane absorption and simultaneous maps of five micrometer brightness temperature are quantitatively compared to realistic cloud structure models which include multiple scattering at five micrometer as well as in the visible. Variability in H2 quadrupole lines are also investigated.

VizieR Online Data Catalog: Mass Distribution of Infrared Dark Clouds (Gomez+, 2014)

NASA Astrophysics Data System (ADS)

Gomez, L.; Wyrowski, F.; Shculler, F.; Menten, K. M.; Ballesteros-Paredes, J.

2014-01-01

Six southern hemisphere clouds with high extinction were observed on 2007-08-25/28 with the LABOCA (Large APEX BOlometer CAmera) instrument on the APEX 12m telescope, at a frequency of 345GHz and a bandwidth of 610GHz (for the instrument, see Siringo et al. 2009A&A...497..945S). (2 data files).

Cold dark matter plus not-so-clumpy dark relics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Diamanti, Roberta; Ando, Shin'ichiro; Weniger, Christoph

Various particle physics models suggest that, besides the (nearly) cold dark matter that accounts for current observations, additional but sub-dominant dark relics might exist. These could be warm, hot, or even contribute as dark radiation. We present here a comprehensive study of two-component dark matter scenarios, where the first component is assumed to be cold, and the second is a non-cold thermal relic. Considering the cases where the non-cold dark matter species could be either a fermion or a boson, we derive consistent upper limits on the non-cold dark relic energy density for a very large range of velocity dispersions,more » covering the entire range from dark radiation to cold dark matter. To this end, we employ the latest Planck Cosmic Microwave Background data, the recent BOSS DR11 and other Baryon Acoustic Oscillation measurements, and also constraints on the number of Milky Way satellites, the latter of which provides a measure of the suppression of the matter power spectrum at the smallest scales due to the free-streaming of the non-cold dark matter component. We present the results on the fraction f {sub ncdm} of non-cold dark matter with respect to the total dark matter for different ranges of the non-cold dark matter masses. We find that the 2σ limits for non-cold dark matter particles with masses in the range 1–10 keV are f {sub ncdm}≤0.29 (0.23) for fermions (bosons), and for masses in the 10–100 keV range they are f {sub ncdm}≤0.43 (0.45), respectively.« less

Conservation of the critically endangered eastern Australian population of the grey nurse shark (Carcharias taurus) through cross-jurisdictional management of a network of marine-protected areas.

PubMed

Lynch, Tim P; Harcourt, Robert; Edgar, Graham; Barrett, Neville

2013-12-01

Between 2001 and 2009, 26 marine-protected areas (MPA) were established on the east Australian seaboard, at least in part, to manage human interactions with a critically endangered population of grey nurse shark, Carcharias taurus. This network is spread across six MPA systems and includes all 19 sites outlined in the National Recovery Plan for C. taurus, though five sites remain open to some forms of fishing. The reserve network has complex cross-jurisdictional management, as the sharks occur in waters controlled by the Australian states of New South Wales (NSW) and Queensland, as well as by the Commonwealth (Federal) government. Jurisdiction is further complicated by fisheries and conservation departments both engaging in management activities within each state. This has resulted in protected area types that include IUCN category II equivalent zones in NSW, Queensland, and Commonwealth marine parks that either overlay or complement another large scaled network of protected sites called critical habitats. Across the network, seven and eight rule permutations for diving and fishing, respectively, are applied to this population of sharks. Besides sites identified by the recovery plan, additional sites have been protected as part of the general development of MPA networks. A case study at one of these sites, which historically was known to be occupied by C. taurus but had been abandoned, appears to shows re-establishment of an aggregation of juvenile and sub-adult sharks. Concurrent with the re-establishment of the aggregation, a local dive operator increased seasonal dive visitation rates at the site fourfold. As a precautionary measure, protection of abandoned sites, which includes nursery and gestating female habitats are options that may assist recovery of the east coast population of C. taurus.

Conservation of the Critically Endangered Eastern Australian Population of the Grey Nurse Shark ( Carcharias taurus) Through Cross-Jurisdictional Management of a Network of Marine-Protected Areas

NASA Astrophysics Data System (ADS)

Lynch, Tim P.; Harcourt, Robert; Edgar, Graham; Barrett, Neville

2013-12-01

Between 2001 and 2009, 26 marine-protected areas (MPA) were established on the east Australian seaboard, at least in part, to manage human interactions with a critically endangered population of grey nurse shark, Carcharias taurus. This network is spread across six MPA systems and includes all 19 sites outlined in the National Recovery Plan for C. taurus, though five sites remain open to some forms of fishing. The reserve network has complex cross-jurisdictional management, as the sharks occur in waters controlled by the Australian states of New South Wales (NSW) and Queensland, as well as by the Commonwealth (Federal) government. Jurisdiction is further complicated by fisheries and conservation departments both engaging in management activities within each state. This has resulted in protected area types that include IUCN category II equivalent zones in NSW, Queensland, and Commonwealth marine parks that either overlay or complement another large scaled network of protected sites called critical habitats. Across the network, seven and eight rule permutations for diving and fishing, respectively, are applied to this population of sharks. Besides sites identified by the recovery plan, additional sites have been protected as part of the general development of MPA networks. A case study at one of these sites, which historically was known to be occupied by C. taurus but had been abandoned, appears to shows re-establishment of an aggregation of juvenile and sub-adult sharks. Concurrent with the re-establishment of the aggregation, a local dive operator increased seasonal dive visitation rates at the site fourfold. As a precautionary measure, protection of abandoned sites, which includes nursery and gestating female habitats are options that may assist recovery of the east coast population of C. taurus.

A Free-Radical Pathway to Hydrogenated Phenanthrene in Molecular Clouds-Low Temperature Growth of Polycyclic Aromatic Hydrocarbons.

PubMed

Thomas, Aaron M; Lucas, Michael; Yang, Tao; Kaiser, Ralf I; Fuentes, Luis; Belisario-Lara, Daniel; Mebel, Alexander M

2017-08-05

The hydrogen-abstraction/acetylene-addition mechanism has been fundamental to unravelling the synthesis of polycyclic aromatic hydrocarbons (PAHs) detected in combustion flames and carbonaceous meteorites like Orgueil and Murchison. However, the fundamental reaction pathways accounting for the synthesis of complex PAHs, such as the tricyclic anthracene and phenanthrene along with their dihydrogenated counterparts, remain elusive to date. By investigating the hitherto unknown chemistry of the 1-naphthyl radical with 1,3-butadiene, we reveal a facile barrierless synthesis of dihydrophenanthrene adaptable to low temperatures. These aryl-type radical additions to conjugated hydrocarbons via resonantly stabilized free-radical intermediates defy conventional wisdom that PAH growth is predominantly a high-temperature phenomenon and thus may represent an overlooked path to PAHs as complex as coronene and corannulene in cold regions of the interstellar medium like in the Taurus Molecular Cloud. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Is Self-Interacting Dark Matter Undergoing Dark Fusion?

DOE PAGES

McDermott, Samuel D.

2018-06-01

Here, we suggest that two-to-two dark matter fusion may be the relaxation process that resolves the small-scale structure problems of the cold collisionless dark matter paradigm. In order for the fusion cross section to scale correctly across many decades of astrophysical masses from dwarf galaxies to galaxy clusters, we require the fractional binding energy released to be greater than v n~(10 –(2–3)) n, where n=1, 2 depends on local dark sector chemistry. The size of the dark-sector interaction cross sections must be σ~0.1–1 barn, moderately larger than for standard model deuteron fusion, indicating a dark nuclear scale Λ~O(100 MeV). Darkmore » fusion firmly predicts constant σv below the characteristic velocities of galaxy clusters. Observations of the inner structure of galaxy groups with velocity dispersion of several hundred kilometers per second, of which a handful have been identified, could differentiate dark fusion from a dark photon model.« less

Is Self-Interacting Dark Matter Undergoing Dark Fusion?

DOE Office of Scientific and Technical Information (OSTI.GOV)

McDermott, Samuel D.

Here, we suggest that two-to-two dark matter fusion may be the relaxation process that resolves the small-scale structure problems of the cold collisionless dark matter paradigm. In order for the fusion cross section to scale correctly across many decades of astrophysical masses from dwarf galaxies to galaxy clusters, we require the fractional binding energy released to be greater than v n~(10 –(2–3)) n, where n=1, 2 depends on local dark sector chemistry. The size of the dark-sector interaction cross sections must be σ~0.1–1 barn, moderately larger than for standard model deuteron fusion, indicating a dark nuclear scale Λ~O(100 MeV). Darkmore » fusion firmly predicts constant σv below the characteristic velocities of galaxy clusters. Observations of the inner structure of galaxy groups with velocity dispersion of several hundred kilometers per second, of which a handful have been identified, could differentiate dark fusion from a dark photon model.« less

Evolutionary process of Bos taurus cattle in favourable versus unfavourable environments and its implications for genetic selection

PubMed Central

O'Neill, Christopher J; Swain, David L; Kadarmideen, Haja N

2010-01-01

The evolutionary processes that have enabled Bos taurus cattle to establish around the globe are at the core to the future success of livestock production. Our study focuses on the history of cattle domestication including the last 60 years of B. taurus breeding programmes in both favourable and unfavourable environments and its consequences on evolution and fitness of cattle. We discuss the emergence of ‘production diseases’ in temperate production systems and consider the evolutionary genetics of tropical adaptation in cattle and conclude that the Senepol, N'Dama, Adaptaur and Criollo breeds, among others with similar evolutionary trajectories, would possess genes capable of improving the productivity of cattle in challenging environments. Using our own experimental evidence from northern Australia, we review the evolution of the Adaptaur cattle breed which has become resistant to cattle tick. We emphasize that the knowledge of interactions between genotype, environment and management in the livestock systems will be required to generate genotypes for efficient livestock production that are both economically and environmentally sustainable. Livestock producers in the 21st century will have less reliance on infrastructure and veterinary products to alleviate environmental stress and more on the animal's ability to achieve fitness in a given production environment. PMID:25567936

Evolutionary process of Bos taurus cattle in favourable versus unfavourable environments and its implications for genetic selection.

PubMed

O'Neill, Christopher J; Swain, David L; Kadarmideen, Haja N

2010-09-01

The evolutionary processes that have enabled Bos taurus cattle to establish around the globe are at the core to the future success of livestock production. Our study focuses on the history of cattle domestication including the last 60 years of B. taurus breeding programmes in both favourable and unfavourable environments and its consequences on evolution and fitness of cattle. We discuss the emergence of 'production diseases' in temperate production systems and consider the evolutionary genetics of tropical adaptation in cattle and conclude that the Senepol, N'Dama, Adaptaur and Criollo breeds, among others with similar evolutionary trajectories, would possess genes capable of improving the productivity of cattle in challenging environments. Using our own experimental evidence from northern Australia, we review the evolution of the Adaptaur cattle breed which has become resistant to cattle tick. We emphasize that the knowledge of interactions between genotype, environment and management in the livestock systems will be required to generate genotypes for efficient livestock production that are both economically and environmentally sustainable. Livestock producers in the 21st century will have less reliance on infrastructure and veterinary products to alleviate environmental stress and more on the animal's ability to achieve fitness in a given production environment.

The dark side of cosmology: dark matter and dark energy.

PubMed

Spergel, David N

2015-03-06

A simple model with only six parameters (the age of the universe, the density of atoms, the density of matter, the amplitude of the initial fluctuations, the scale dependence of this amplitude, and the epoch of first star formation) fits all of our cosmological data . Although simple, this standard model is strange. The model implies that most of the matter in our Galaxy is in the form of "dark matter," a new type of particle not yet detected in the laboratory, and most of the energy in the universe is in the form of "dark energy," energy associated with empty space. Both dark matter and dark energy require extensions to our current understanding of particle physics or point toward a breakdown of general relativity on cosmological scales. Copyright © 2015, American Association for the Advancement of Science.

Duality between a dark state and a quasi-dark state

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hirokawa, Masao, E-mail: hirokawa@amath.hiroshima-u.ac.jp

We study a physical system coupled with two one-mode Bose fields. The physical system is a two-level system or a harmonic oscillator. We prove that each dark and quasi-dark state appears under a proper condition, and then, we derive a duality between the dark state and the quasi-dark state. This duality induces the switch between the dark state and the quasi-dark state.

Chiral Dark Sector

NASA Astrophysics Data System (ADS)

Co, Raymond T.; Harigaya, Keisuke; Nomura, Yasunori

2017-03-01

We present a simple and natural dark sector model in which dark matter particles arise as composite states of hidden strong dynamics and their stability is ensured by accidental symmetries. The model has only a few free parameters. In particular, the gauge symmetry of the model forbids the masses of dark quarks, and the confinement scale of the dynamics provides the unique mass scale of the model. The gauge group contains an Abelian symmetry U (1 )D , which couples the dark and standard model sectors through kinetic mixing. This model, despite its simple structure, has rich and distinctive phenomenology. In the case where the dark pion becomes massive due to U (1 )D quantum corrections, direct and indirect detection experiments can probe thermal relic dark matter which is generically a mixture of the dark pion and the dark baryon, and the Large Hadron Collider can discover the U (1 )D gauge boson. Alternatively, if the dark pion stays light due to a specific U (1 )D charge assignment of the dark quarks, then the dark pion constitutes dark radiation. The signal of this radiation is highly correlated with that of dark baryons in dark matter direct detection.

Chiral Dark Sector.

PubMed

Co, Raymond T; Harigaya, Keisuke; Nomura, Yasunori

2017-03-10

We present a simple and natural dark sector model in which dark matter particles arise as composite states of hidden strong dynamics and their stability is ensured by accidental symmetries. The model has only a few free parameters. In particular, the gauge symmetry of the model forbids the masses of dark quarks, and the confinement scale of the dynamics provides the unique mass scale of the model. The gauge group contains an Abelian symmetry U(1)_{D}, which couples the dark and standard model sectors through kinetic mixing. This model, despite its simple structure, has rich and distinctive phenomenology. In the case where the dark pion becomes massive due to U(1)_{D} quantum corrections, direct and indirect detection experiments can probe thermal relic dark matter which is generically a mixture of the dark pion and the dark baryon, and the Large Hadron Collider can discover the U(1)_{D} gauge boson. Alternatively, if the dark pion stays light due to a specific U(1)_{D} charge assignment of the dark quarks, then the dark pion constitutes dark radiation. The signal of this radiation is highly correlated with that of dark baryons in dark matter direct detection.

Venus - Lower-level Clouds As Seen By NIMS

NASA Technical Reports Server (NTRS)

1990-01-01

These images are two versions of a near-infrared map of lower-level clouds on the night side of Venus, obtained by the Near Infrared Mapping Spectrometer aboard the Galileo spacecraft as it approached the planet February 10, 1990. Taken from an altitude of about 60,000 miles above the planet, at an infrared wavelength of 2.3 microns (about three times the longest wavelength visible to the human eye) the map shows the turbulent, cloudy middle atmosphere some 30-33 miles above the surface, 6-10 miles below the visible cloudtops. The image to the left shows the radiant heat from the lower atmosphere (about 400 degrees Fahrenheit) shining through the sulfuric acid clouds, which appear as much as 10 times darker than the bright gaps between clouds. This cloud layer is at about -30 degrees Fahrenheit, at a pressure about 1/2 Earth's atmospheric pressure. About 2/3 of the dark hemisphere is visible, centered on longitude 350 West, with bright slivers of daylit high clouds visible at top and bottom left. The right image, a modified negative, represents what scientists believe would be the visual appearance of this mid-level cloud deck in daylight, with the clouds reflecting sunlight instead of blocking out infrared from the hot planet and lower atmosphere. Near the equator, the clouds appear fluffy and blocky; farther north, they are stretched out into East-West filaments by winds estimated at more than 150 mph, while the poles are capped by thick clouds at this altitude. The Near Infrared Mapping Spectrometer (NIMS) on the Galileo spacecraft is a combined mapping (imaging) and spectral instrument. It can sense 408 contiguous wavelengths from 0.7 microns (deep red) to 5.2 microns, and can construct a map or image by mechanical scanning. It can spectroscopically analyze atmospheres and surfaces and construct thermal and chemical maps. Designed and operated by scientists and engineers at the Jet Propulsion Laboratory, NIMS involves 15 scientists in the U.S., England, and

The dark cube: dark and light character profiles

PubMed Central

2016-01-01

Background. Research addressing distinctions and similarities between people’s malevolent character traits (i.e., the Dark Triad: Machiavellianism, narcissism, and psychopathy) has detected inconsistent linear associations to temperament traits. Additionally, these dark traits seem to have a common core expressed as uncooperativeness. Hence, some researchers suggest that the dark traits are best represented as one global construct (i.e., the unification argument) rather than as ternary construct (i.e., the uniqueness argument). We put forward the dark cube (cf. Cloninger’s character cube) comprising eight dark profiles that can be used to compare individuals who differ in one dark character trait while holding the other two constant. Our aim was to investigate in which circumstances individuals who are high in each one of the dark character traits differ in Cloninger’s “light” character traits: self-directedness, cooperativeness, and self-transcendence. We also investigated if people’s dark character profiles were associated to their light character profiles. Method. A total of 997 participants recruited from Amazon’s Mechanical Turk (MTurk) responded to the Short Dark Triad and the Short Character Inventory. Participants were allocated to eight different dark profiles and eight light profiles based on their scores in each of the traits and any possible combination of high and low scores. We used three-way interaction regression analyses and t-tests to investigate differences in light character traits between individuals with different dark profiles. As a second step, we compared the individuals’ dark profile with her/his character profile using an exact cell-wise analysis conducted in the ROPstat software (http://www.ropstat.com). Results. Individuals who expressed high levels of Machiavellianism and those who expressed high levels of psychopathy also expressed low self-directedness and low cooperativeness. Individuals with high levels of

Dark Matter and Extragalactic Gas Clouds in the NGC 4532/DDO 137 System

NASA Technical Reports Server (NTRS)

Hoffman, G. L.; Lu, N. Y.; Salpeter, E. E.; Connell, B. M.

1998-01-01

H I synthesis mapping of NGC 4532 and DDO 137, a pair of Sm galaxies on the edge of the Virgo cluster, is used to determine rotation curves for each of the galaxies and to resolve the structure and kinematics of three extragalactic H I clouds embedded in an extended envelope of diffuse HI discovered in earlier Arecibo studies of the system.

Global surface-based cloud observation for ISCCP

NASA Technical Reports Server (NTRS)

1994-01-01

few regions; they are generally in better agreement if the moonlight criterion is imposed on the surface observations. Using the moonlight criterion, we have analyzed ten years (1982-1991) of surface weather observations over land and ocean, worldwide, for total cloud cover and for the frequency of occurrence of clear sky, fog and precipitation The global average cloud cover (average of day and night) is about 2% higher if we impose the moonlight criterion than if we use all observations. The difference is greater in winter than in summer, because of the fewer hours of darkness in the summer. The amplitude of the annual cycle of total cloud cover over the Arctic Ocean and at the South Pole is diminished by a few percent when the moonlight criterion is imposed. The average cloud cover for 1982-1991 is found to be 55% for northern hemisphere land, 53% for southern hemisphere land, 66% for northern hemisphere ocean, and 70% for southern hemisphere ocean, giving a global average of 64%. The global average for daytime is 64.6% for nighttime 63.3%.

Sourcing dark matter and dark energy from α-attractors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mishra, Swagat S.; Sahni, Varun; Shtanov, Yuri, E-mail: swagat@iucaa.in, E-mail: varun@iucaa.in, E-mail: shtanov@bitp.kiev.ua

In [1], Kallosh and Linde drew attention to a new family of superconformal inflationary potentials, subsequently called α-attractors [2]. The α-attractor family can interpolate between a large class of inflationary models. It also has an important theoretical underpinning within the framework of supergravity. We demonstrate that the α-attractors have an even wider appeal since they may describe dark matter and perhaps even dark energy. The dark matter associated with the α-attractors, which we call α-dark matter (αDM), shares many of the attractive features of fuzzy dark matter, with V (φ) = ½ m {sup 2}φ{sup 2}, while having none ofmore » its drawbacks. Like fuzzy dark matter, αDM can have a large Jeans length which could resolve the cusp-core and substructure problems faced by standard cold dark matter. αDM also has an appealing tracker property which enables it to converge to the late-time dark matter asymptote, ( w ) ≅ 0, from a wide range of initial conditions. It thus avoids the enormous fine-tuning problems faced by the m {sup 2}φ{sup 2} potential in describing dark matter.« less

Ultra-compact High Velocity Clouds as Minihalos and Dwarf Galaxies

NASA Astrophysics Data System (ADS)

Faerman, Yakov; Sternberg, Amiel; McKee, Christopher F.

2013-11-01

We present dark matter minihalo models for the Ultra-Compact, High-Velocity H I Clouds (UCHVCs) recently discovered in the 21 cm ALFALFA survey. We assume gravitational confinement of 104 K H I gas by flat-cored dark-matter subhalos within the Local Group. We show that for flat cores, typical (median) tidally stripped cosmological subhalos at redshift z = 0 have dark-matter masses of ~107 M ⊙ within the central 300 pc (independent of total halo mass), consistent with the "Strigari mass scale" observed in low-luminosity dwarf galaxies. Flat-cored subhalos also resolve the mass discrepancy between simulated and observed satellites around the Milky Way. For the UCHVCs, we calculate the photoionization-limited hydrostatic gas profiles for any distance-dependent total observed H I mass and predict the associated (projected) H I half-mass radii, assuming the clouds are embedded in distant (d >~ 300 kpc) and unstripped subhalos. For a typical UCHVC (0.9 Jy km s-1), we predict physical H I half-mass radii of 0.18 to 0.35 kpc (or angular sizes of 0.'6 to 2.'1) for distances ranging from 300 kpc to 2 Mpc. As a consistency check, we model the gas-rich dwarf galaxy Leo T, for which there is a well-resolved H I column density profile and a known distance (420 kpc). For Leo T, we find that a subhalo with M 300 = 8 (± 0.2) × 106 M ⊙ best fits the observed H I profile. We derive an upper limit of P HIM <~ 150 cm-3 K for the pressure of any enveloping hot intergalactic medium gas at the distance of Leo T. Our analysis suggests that some of the UCHVCs may in fact constitute a population of 21 cm-selected but optically faint dwarf galaxies in the Local Group.

Gravitational wave from dark sector with dark pion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsumura, Koji; Yamada, Masatoshi; Yamaguchi, Yuya, E-mail: ko2@gauge.scphys.kyoto-u.ac.jp, E-mail: m.yamada@thphys.uni-heidelberg.de, E-mail: yy@particle.sci.hokudai.ac.jp

In this work, we investigate the spectra of gravitational waves produced by chiral symmetry breaking in dark quantum chromodynamics (dQCD) sector. The dark pion (π) can be a dark matter candidate as weakly interacting massive particle (WIMP) or strongly interacting massive particle (SIMP). For a WIMP scenario, we introduce the dQCD sector coupled to the standard model (SM) sector with classical scale invariance and investigate the annihilation process of the dark pion via the 2π → 2 SM process. For a SIMP scenario, we investigate the 3π → 2π annihilation process of the dark pion as a SIMP using chiralmore » perturbation theory. We find that in the WIMP scenario the gravitational wave background spectra can be observed by future space gravitational wave antennas. On the other hand, when the dark pion is the SIMP dark matter with the constraints for the chiral perturbative limit and pion-pion scattering cross section, the chiral phase transition becomes crossover and then the gravitational waves are not produced.« less

A search for pre-main-sequence stars in high-latitude molecular clouds. 3: A survey of the Einstein database

NASA Technical Reports Server (NTRS)

Caillault, Jean-Pierre; Magnani, Loris; Fryer, Chris

1995-01-01

In order to discern whether the high-latitude molecular clouds are regions of ongoing star formation, we have used X-ray emission as a tracer of youthful stars. The entire Einstein database yields 18 images which overlap 10 of the clouds mapped partially or completely in the CO (1-0) transition, providing a total of approximately 6 deg squared of overlap. Five previously unidentified X-ray sources were detected: one has an optical counterpart which is a pre-main-sequence (PMS) star, and two have normal main-sequence stellar counterparts, while the other two are probably extragalactic sources. The PMS star is located in a high Galactic latitude Lynds dark cloud, so this result is not too suprising. The translucent clouds, though, have yet to reveal any evidence of star formation.

PREDICTED SIZES OF PRESSURE-SUPPORTED HI CLOUDS IN THE OUTSKIRTS OF THE VIRGO CLUSTER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burkhart, Blakesley; Loeb, Abraham

Using data from the ALFALFA AGES Arecibo HI survey of galaxies and the Virgo cluster X-ray pressure profiles from XMM-Newton , we investigate the possibility that starless dark HI clumps, also known as “dark galaxies,” are supported by external pressure in the surrounding intercluster medium. We find that the starless HI clump masses, velocity dispersions, and positions allow these clumps to be in pressure equilibrium with the X-ray gas near the virial radius of the Virgo cluster. We predict the sizes of these clumps to range from 1 to 10 kpc, in agreement with the range of sizes found formore » spatially resolved HI starless clumps outside of Virgo. Based on the predicted HI surface density of the Virgo sources, as well as a sample of other similar resolved ALFALFA HI dark clumps with follow-up optical/radio observations, we predict that most of the HI dark clumps are on the cusp of forming stars. These HI sources therefore mark the transition between starless HI clouds and dwarf galaxies with stars.« less

Lidar and radar measurements of the melting layer in the frame of the Convective and Orographically-induced Precipitation Study: observations of dark and bright band phenomena

NASA Astrophysics Data System (ADS)

di Girolamo, P.; Summa, D.; Bhawar, R.; di Iorio, T.; Norton, E. G.; Peters, G.; Dufournet, Y.

2011-11-01

During the Convective and Orographically-induced Precipitation Study (COPS), lidar dark and bright bands were observed by the University of BASILicata Raman lidar system (BASIL) during several intensive (IOPs) and special (SOPs) observation periods (among others, 23 July, 15 August, and 17 August 2007). Lidar data were supported by measurements from the University of Hamburg cloud radar MIRA 36 (36 GHz), the University of Hamburg dual-polarization micro rain radars (24.1 GHz) and the University of Manchester UHF wind profiler (1.29 GHz). Results from BASIL and the radars for 23 July 2007 are illustrated and discussed to support the comprehension of the microphysical and scattering processes responsible for the appearance of the lidar and radar dark and bright bands. Simulations of the lidar dark and bright band based on the application of concentric/eccentric sphere Lorentz-Mie codes and a melting layer model are also provided. Lidar and radar measurements and model results are also compared with measurements from a disdrometer on ground and a two-dimensional cloud (2DC) probe on-board the ATR42 SAFIRE.

Artist's concept of topographical layout of Taurus-Littrow landing site

NASA Technical Reports Server (NTRS)

1972-01-01

An artist's concept illustrating the topographical layout of the Taurus-Littrow landing site, depicting the traverses planned on the Apollo 17 lunar landing mission using the Lunar Roving Vehicle. The Roman numerals indicate the three periods of extravehicular activity (EVA). The Arabic numbers represent the station stops. The mountain in the center of the picture is South Massif. A portion of North Massif is in the lower right corner of the photograph. The names of some of the craters are: Camelot (at Station 5); Emory (nearest Station 1); Sherlock (at station 10); Steno (between Emory and Sherlock); Amundsen (at Station 2); Lara (at Station 3); Henry (nearest Station 6); Shakespeare (nearest Station 9); Cochise (nearest Station 8); and Powell (halfway between Camelot and Emory). Note the ridge-like feature extending from Station 2 to North Massif. The southern portion of the ridge is called Lee Scarp; and the Northerly portion is Lincoln Scarp. This concept is by MSC artist Jerry Elm

ClipCard: Sharable, Searchable Visual Metadata Summaries on the Cloud to Render Big Data Actionable

NASA Astrophysics Data System (ADS)

Saripalli, P.; Davis, D.; Cunningham, R.

2013-12-01

Research firm IDC estimates that approximately 90 percent of the Enterprise Big Data go un-analyzed, as 'dark data' - an enormous corpus of undiscovered, untagged information residing on data warehouses, servers and Storage Area Networks (SAN). In the geosciences, these data range from unpublished model runs to vast survey data assets to raw sensor data. Many of these are now being collected instantaneously, at a greater volume and in new data formats. Not all of these data can be analyzed, nor processed in real time, and their features may not be well described at the time of collection. These dark data are a serious data management problem for science organizations of all types, especially ones with mandated or required data reporting and compliance requirements. Additionally, data curators and scientists are encouraged to quantify the impact of their data holdings as a way to measure research success. Deriving actionable insights is the foremost goal of Big Data Analytics (BDA), which is especially true with geoscience, given its direct impact on most of the pressing global issues. Clearly, there is a pressing need for innovative approaches to making dark data discoverable, measurable, and actionable. We report on ClipCard, a Cloud-based SaaS analytic platform for instant summarization, quick search, visualization and easy sharing of metadata summaries form the Dark Data at hierarchical levels of detail, thus rendering it 'white', i.e., actionable. We present a use case of the ClipCard platform, a cloud-based application which helps generate (abstracted) visual metadata summaries and meta-analytics for environmental data at hierarchical scales within and across big data containers. These summaries and analyses provide important new tools for managing big data and simplifying collaboration through easy to deploy sharing APIs. The ClipCard application solves a growing data management bottleneck by helping enterprises and large organizations to summarize, search

Cloud radiative properties and aerosol - cloud interaction

NASA Astrophysics Data System (ADS)

Viviana Vladutescu, Daniela; Gross, Barry; Li, Clement; Han, Zaw

2015-04-01

The presented research discusses different techniques for improvement of cloud properties measurements and analysis. The need for these measurements and analysis arises from the high errors noticed in existing methods that are currently used in retrieving cloud properties and implicitly cloud radiative forcing. The properties investigated are cloud fraction (cf) and cloud optical thickness (COT) measured with a suite of collocated remote sensing instruments. The novel approach makes use of a ground based "poor man's camera" to detect cloud and sky radiation in red, green, and blue with a high spatial resolution of 30 mm at 1km. The surface-based high resolution photography provides a new and interesting view of clouds. As the cloud fraction cannot be uniquely defined or measured, it depends on threshold and resolution. However as resolution decreases, cloud fraction tends to increase if the threshold is below the mean, and vice versa. Additionally cloud fractal dimension also depends on threshold. Therefore these findings raise concerns over the ability to characterize clouds by cloud fraction or fractal dimension. Our analysis indicate that Principal Component analysis may lead to a robust means of quantifying cloud contribution to radiance. The cloud images are analyzed in conjunction with a collocated CIMEL sky radiometer, Microwave Radiometer and LIDAR to determine homogeneity and heterogeneity. Additionally, MFRSR measurements are used to determine the cloud radiative properties as a validation tool to the results obtained from the other instruments and methods. The cloud properties to be further studied are aerosol- cloud interaction, cloud particle radii, and vertical homogeneity.

Impeded Dark Matter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kopp, Joachim; Liu, Jia; Slatyer, Tracy

Here, we consider dark matter models in which the mass splitting between the dark matter particles and their annihilation products is tiny. Compared to the previously proposed Forbidden Dark Matter scenario, the mass splittings we consider are much smaller, and are allowed to be either positive or negative. To emphasize this modification, we dub our scenario \\Impeded Dark Matter". We also demonstrate that Impeded Dark Matter can be easily realized without requiring tuning of model parameters. For negative mass splitting, we demonstrate that the annihilation cross-section for Impeded Dark Matter depends linearly on the dark matter velocity or may evenmore » be kinematically forbidden, making this scenario almost insensitive to constraints from the cosmic microwave background and from observations of dwarf galaxies. Accordingly, it may be possible for Impeded Dark Matter to yield observable signals in clusters or the Galactic center, with no corresponding signal in dwarfs. Furthermore, for positive mass splitting, we show that the annihilation cross-section is suppressed by the small mass splitting, which helps light dark matter to survive increasingly stringent constraints from indirect searches. As specific realizations for Impeded Dark Matter, we introduce a model of vector dark matter from a hidden SU(2) sector, and a composite dark matter scenario based on a QCD-like dark sector.« less

Impeded Dark Matter

DOE PAGES

Kopp, Joachim; Liu, Jia; Slatyer, Tracy; ...

2016-12-12

Here, we consider dark matter models in which the mass splitting between the dark matter particles and their annihilation products is tiny. Compared to the previously proposed Forbidden Dark Matter scenario, the mass splittings we consider are much smaller, and are allowed to be either positive or negative. To emphasize this modification, we dub our scenario \\Impeded Dark Matter". We also demonstrate that Impeded Dark Matter can be easily realized without requiring tuning of model parameters. For negative mass splitting, we demonstrate that the annihilation cross-section for Impeded Dark Matter depends linearly on the dark matter velocity or may evenmore » be kinematically forbidden, making this scenario almost insensitive to constraints from the cosmic microwave background and from observations of dwarf galaxies. Accordingly, it may be possible for Impeded Dark Matter to yield observable signals in clusters or the Galactic center, with no corresponding signal in dwarfs. Furthermore, for positive mass splitting, we show that the annihilation cross-section is suppressed by the small mass splitting, which helps light dark matter to survive increasingly stringent constraints from indirect searches. As specific realizations for Impeded Dark Matter, we introduce a model of vector dark matter from a hidden SU(2) sector, and a composite dark matter scenario based on a QCD-like dark sector.« less

Adaptive Weibull Multiplicative Model and Multilayer Perceptron Neural Networks for Dark-Spot Detection from SAR Imagery

PubMed Central

Taravat, Alireza; Oppelt, Natascha

2014-01-01

Oil spills represent a major threat to ocean ecosystems and their environmental status. Previous studies have shown that Synthetic Aperture Radar (SAR), as its recording is independent of clouds and weather, can be effectively used for the detection and classification of oil spills. Dark formation detection is the first and critical stage in oil-spill detection procedures. In this paper, a novel approach for automated dark-spot detection in SAR imagery is presented. A new approach from the combination of adaptive Weibull Multiplicative Model (WMM) and MultiLayer Perceptron (MLP) neural networks is proposed to differentiate between dark spots and the background. The results have been compared with the results of a model combining non-adaptive WMM and pulse coupled neural networks. The presented approach overcomes the non-adaptive WMM filter setting parameters by developing an adaptive WMM model which is a step ahead towards a full automatic dark spot detection. The proposed approach was tested on 60 ENVISAT and ERS2 images which contained dark spots. For the overall dataset, an average accuracy of 94.65% was obtained. Our experimental results demonstrate that the proposed approach is very robust and effective where the non-adaptive WMM & pulse coupled neural network (PCNN) model generates poor accuracies. PMID:25474376

Codecaying Dark Matter.

PubMed

Dror, Jeff Asaf; Kuflik, Eric; Ng, Wee Hao

2016-11-18

We propose a new mechanism for thermal dark matter freeze-out, called codecaying dark matter. Multicomponent dark sectors with degenerate particles and out-of-equilibrium decays can codecay to obtain the observed relic density. The dark matter density is exponentially depleted through the decay of nearly degenerate particles rather than from Boltzmann suppression. The relic abundance is set by the dark matter annihilation cross section, which is predicted to be boosted, and the decay rate of the dark sector particles. The mechanism is viable in a broad range of dark matter parameter space, with a robust prediction of an enhanced indirect detection signal. Finally, we present a simple model that realizes codecaying dark matter.

SparkClouds: visualizing trends in tag clouds.

PubMed

Lee, Bongshin; Riche, Nathalie Henry; Karlson, Amy K; Carpendale, Sheelash

2010-01-01

Tag clouds have proliferated over the web over the last decade. They provide a visual summary of a collection of texts by visually depicting the tag frequency by font size. In use, tag clouds can evolve as the associated data source changes over time. Interesting discussions around tag clouds often include a series of tag clouds and consider how they evolve over time. However, since tag clouds do not explicitly represent trends or support comparisons, the cognitive demands placed on the person for perceiving trends in multiple tag clouds are high. In this paper, we introduce SparkClouds, which integrate sparklines into a tag cloud to convey trends between multiple tag clouds. We present results from a controlled study that compares SparkClouds with two traditional trend visualizations—multiple line graphs and stacked bar charts—as well as Parallel Tag Clouds. Results show that SparkClouds ability to show trends compares favourably to the alternative visualizations.

A dark matter scaling relation from mirror dark matter

NASA Astrophysics Data System (ADS)

Foot, R.

2014-12-01

Mirror dark matter, and other similar dissipative dark matter candidates, need an energy source to stabilize dark matter halos around spiral galaxies. It has been suggested previously that ordinary supernovae can potentially supply the required energy. By matching the energy supplied to the halo from supernovae to that lost due to radiative cooling, we here derive a rough scaling relation, RSN ∝ρ0r02 (RSN is the supernova rate and ρ0 ,r0 the dark matter central density and core radius). Such a relation is consistent with dark matter properties inferred from studies of spiral galaxies with halo masses larger than 3 ×1011M⊙. We speculate that other observed galaxy regularities might be explained within the framework of such dissipative dark matter.

A Global, Decadal, Quantitative Record of Absorbing Aerosols above Cloud Using OMI's Near-UV Observations

NASA Astrophysics Data System (ADS)

Torres, O.; Jethva, H. T.; Ahn, C.

2016-12-01

Aerosol-cloud interaction continues to be one of the leading uncertain components of climate models, primarily due to the lack of an adequate knowledge of the complex microphysical and radiative processes of the aerosol-cloud system. The situations when aerosols and clouds are found in the same atmospheric column, for instance, when light-absorbing aerosols such as biomass burning generated carbonaceous particles or wind-blown dust overlay low-level cloud decks, are commonly found over several regions of the world. Contrary to the known cooling effects of these aerosols in cloud-free scenario over dark surface, the overlapping situation of absorbing aerosols over cloud can potentially exert a significant level of atmospheric absorption and produces a positive radiative forcing (warming) at top-of-atmosphere. The magnitude of direct radiative effects of aerosols above cloud directly depends on the aerosol loading, microphysical and optical properties of the aerosol layer and the underlying cloud deck, and geometric cloud fraction. We help in addressing this problem by introducing a novel product of above-cloud aerosol optical depth (ACAOD) of absorbing aerosols retrieved from near-UV observations made by the Ozone Monitoring Instrument (OMI) on board NASA's Aura platform. Physically based on the strong `color ratio' effect in the near-UV caused by the spectral absorption of aerosols above cloud, the algorithm, formally named as OMACA, retrieves the optical depths of aerosols and clouds simultaneously under a prescribed state of atmosphere. Here, we present the algorithm architecture and results from an 11-year global record (2005-2015) including global climatology of frequency of occurrence and ACAOD. The theoretical uncertainty analysis and planned validation activities using measurements from upcoming field campaigns are also discussed.

A Ten-Year Global Record of Absorbing Aerosols Above Clouds from OMI's Near-UV Observations

NASA Technical Reports Server (NTRS)

Jethva, Hiren; Torres, Omar; Ahn, Changwoo

2016-01-01

Aerosol-cloud interaction continues to be one of the leading uncertain components of climate models, primarily due to the lack of an adequate knowledge of the complex microphysical and radiative processes associated with the aerosol-cloud system. The situations when aerosols and clouds are found in the same atmospheric column, for instance, when light-absorbing aerosols such as biomass burning generated carbonaceous particles or wind-blown dust overlay low-level cloud decks, are commonly found over several regional of the world. Contrary to the cloud-free scenario over dark surface, for which aerosols are known to produce a net cooling effect (negative radiative forcing) on climate, the overlapping situation of absorbing aerosols over cloud can potentially exert a significant level of atmospheric absorption and produces a positive radiative forcing at top-of-atmosphere. The magnitude of direct radiative effects of aerosols above cloud depends directly on the aerosol loading, microphysical-optical properties of the aerosol layer and the underlying cloud deck, and geometric cloud fraction. We help in addressing this problem by introducing a novel product of optical depth of absorbing aerosols above clouds retrieved from near-UV observations made by the Ozone Monitoring Instrument (OMI) on board NASA's Aura platform. The presence of absorbing aerosols above cloud reduces the upwelling radiation reflected by cloud and produces a strong 'color ratio' effect in the near-UV region, which can be unambiguously detected in the OMI measurements. Physically based on this effect, the OMACA algorithm retrieves the optical depths of aerosols and clouds simultaneously under a prescribed state of atmosphere. The algorithm architecture and results from a ten-year global record including global climatology of frequency of occurrence and above-cloud aerosol optical depth, and a discussion on related future field campaigns are presented.

Carbon Chemistry in Transitional Clouds from the GOT C+ Survey of CII 158 micron Emission in the Galactic Plane

NASA Astrophysics Data System (ADS)

Langer, W. D.; Velusamy, T.; Pineda, J.; Willacy, K.; Goldsmith, P. F.

2011-05-01

In understanding the lifecycle and chemistry of the interstellar gas, the transition from diffuse atomic to molecular gas clouds is a very important stage. The evolution of carbon from C+ to C0 and CO is a fundamental part of this transition, and C+ along with its carbon chemistry is a key diagnostic. Until now our knowledge of interstellar gas has been limited primarily to the diffuse atomic phase traced by HI and the dense molecular H2 phase traced by CO. However, we have generally been missing an important layer in diffuse and transition clouds, which is denoted by the warm "dark gas'', that is mostly H2 and little HI and CO, and is best traced with C+. Here, we discuss the chemistry in the transition from C+ to C0 and CO in these clouds as understood by a survey of the CII 1.9 THz (158 micron) line from a sparse survey of the inner galaxy over about 40 degrees in longitude as part of the Galactic Observations of Terahertz C+ (GOT C+) program, a Herschel Space Observatory Open Time Key Program to study interstellar clouds by sampling ionized carbon. Using the first results from GOT C+ along 11 LOSs, in a sample of 53 transition clouds, Velusamy, Langer et al. (A&A 521, L18, 2010) detected an excess of CII intensities indicative of a thick H2 layer (a significant warm H2, "dark gas'' component) around the 12CO core. Here we present a much larger, statistically significant sample of a few hundred diffuse and transition clouds traced by CII, along with auxiliary HI and CO data in the inner Galaxy between l=-30° and +30°. Our new and more extensive sample of transition clouds is used to elucidate the time dependent physical and carbon chemical evolution of diffuse to transition clouds, and transition layers. We consider the C+ to CO conversion pathways such as H++ O and C+ + H2 chemistry for CO production to constrain the physical parameters such as the FUV intensity and cosmic ray ionization rate that drive the CO chemistry in the diffuse transition clouds.

Cloud-Top Entrainment in Stratocumulus Clouds

NASA Astrophysics Data System (ADS)

Mellado, Juan Pedro

2017-01-01

Cloud entrainment, the mixing between cloudy and clear air at the boundary of clouds, constitutes one paradigm for the relevance of small scales in the Earth system: By regulating cloud lifetimes, meter- and submeter-scale processes at cloud boundaries can influence planetary-scale properties. Understanding cloud entrainment is difficult given the complexity and diversity of the associated phenomena, which include turbulence entrainment within a stratified medium, convective instabilities driven by radiative and evaporative cooling, shear instabilities, and cloud microphysics. Obtaining accurate data at the required small scales is also challenging, for both simulations and measurements. During the past few decades, however, high-resolution simulations and measurements have greatly advanced our understanding of the main mechanisms controlling cloud entrainment. This article reviews some of these advances, focusing on stratocumulus clouds, and indicates remaining challenges.

Jovian Lightning and Moonlit Clouds

NASA Technical Reports Server (NTRS)

1997-01-01

Jovian lightning and moonlit clouds. These two images, taken 75 minutes apart, show lightning storms on the night side of Jupiter along with clouds dimly lit by moonlight from Io, Jupiter's closest moon. The images were taken in visible light and are displayed in shades of red. The images used an exposure time of about one minute, and were taken when the spacecraft was on the opposite side of Jupiter from the Earth and Sun. Bright storms are present at two latitudes in the left image, and at three latitudes in the right image. Each storm was made visible by multiple lightning strikes during the exposure. Other Galileo images were deliberately scanned from east to west in order to separate individual flashes. The images show that Jovian and terrestrial lightning storms have similar flash rates, but that Jovian lightning strikes are a few orders of magnitude brighter in visible light.

The moonlight from Io allows the lightning storms to be correlated with visible cloud features. The latitude bands where the storms are seen seem to coincide with the 'disturbed regions' in daylight images, where short-lived chaotic motions push clouds to high altitudes, much like thunderstorms on Earth. The storms in these images are roughly one to two thousand kilometers across, while individual flashes appear hundreds of kilometer across. The lightning probably originates from the deep water cloud layer and illuminates a large region of the visible ammonia cloud layer from 100 kilometers below it.

There are several small light and dark patches that are artifacts of data compression. North is at the top of the picture. The images span approximately 50 degrees in latitude and longitude. The lower edges of the images are aligned with the equator. The images were taken on October 5th and 6th, 1997 at a range of 6.6 million kilometers by the Solid State Imaging (SSI) system on NASA's Galileo spacecraft.

The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for

4. DARK CANYON SIPHON VIEW ACROSS DARK CANYON AT ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

4. DARK CANYON SIPHON - VIEW ACROSS DARK CANYON AT LOCATION OF SIPHON. VIEW TO NORTHWEST - Carlsbad Irrigation District, Dark Canyon Siphon, On Main Canal, 1 mile South of Carlsbad, Carlsbad, Eddy County, NM

Homogenizing Surface and Satellite Observations of Cloud. Aspects of Bias in Surface Data.

DTIC Science & Technology

1987-11-10

both ( pannus ), usually below fractus of bad weather, or both ( pannus ), usu- Altostratus or Nimbostratus ally below Altostratus or Nimbostratus 8 Cumulus...Stratocumulus, Stratus of an anvil; either accompanied or not by Cu- or pannus mulonimbus without anvil or fibrous upper part, by Cumulus, Stratocumulus...Stratus or pannus CL clouds invisible owing to darkness, fog, / Stratocumulus, Stratus, Cumulus and Cu- blowing dust or sand, or other similar mulonimbus

A comparison of shock-cloud and wind-cloud interactions: effect of increased cloud density contrast on cloud evolution

NASA Astrophysics Data System (ADS)

Goldsmith, K. J. A.; Pittard, J. M.

2018-05-01

The similarities, or otherwise, of a shock or wind interacting with a cloud of density contrast χ = 10 were explored in a previous paper. Here, we investigate such interactions with clouds of higher density contrast. We compare the adiabatic hydrodynamic interaction of a Mach 10 shock with a spherical cloud of χ = 103 with that of a cloud embedded in a wind with identical parameters to the post-shock flow. We find that initially there are only minor morphological differences between the shock-cloud and wind-cloud interactions, compared to when χ = 10. However, once the transmitted shock exits the cloud, the development of a turbulent wake and fragmentation of the cloud differs between the two simulations. On increasing the wind Mach number, we note the development of a thin, smooth tail of cloud material, which is then disrupted by the fragmentation of the cloud core and subsequent `mass-loading' of the flow. We find that the normalized cloud mixing time (tmix) is shorter at higher χ. However, a strong Mach number dependence on tmix and the normalized cloud drag time, t_{drag}^' }, is not observed. Mach-number-dependent values of tmix and t_{drag}^' } from comparable shock-cloud interactions converge towards the Mach-number-independent time-scales of the wind-cloud simulations. We find that high χ clouds can be accelerated up to 80-90 per cent of the wind velocity and travel large distances before being significantly mixed. However, complete mixing is not achieved in our simulations and at late times the flow remains perturbed.

Physiology and Endocrinology Symposium: influence of cattle genotype (Bos indicus vs. Bos taurus) on oocyte and preimplantation embryo resistance to increased temperature.

PubMed

Paula-Lopes, F F; Lima, R S; Satrapa, R A; Barros, C M

2013-03-01

High environmental temperatures during the hot months of the year reduce reproductive performance in cattle. Summer heat stress depression in fertility is a multifactorial problem; however, there is evidence that the bovine germinal vesicle and maturing oocyte, as well as the early embryo, are major targets of the deleterious effects of heat stress. Such adverse effects are less pronounced in heat-tolerant breeds (Bos indicus) than heat-sensitive breeds (Bos taurus). This genetic variation results from the greater thermoregulatory ability and cellular thermoresistance of heat-tolerant breeds. Heat-induced oocyte cellular damage occurs in both cytoplasmic and nuclear compartments. Heat shock has been shown to reduce oocyte nuclear maturation, induce apoptosis, compromise oocyte cytoskeleton, and impair oocyte mitochondrial function and developmental competence. However, the oocyte cytoplasm is more susceptible to heat shock than the nucleus. This effect is greater for Bos taurus than Bos indicus oocytes. The detrimental effects of heat shock are also critical during the first cleavage divisions when most of the embryonic genome is inactive; however, the bovine embryo becomes more resistant to increased temperature as it proceeds through development. Several studies demonstrated that Bos indicus embryos are more thermotolerant than Bos taurus embryos. Adaptive changes involved in acquisition of thermotolerance are likely derived from changes in gene expression and (or) activity of biochemical molecules that control cellular functions against stress. Recently, molecules such as IGF-I and caspase inhibitor z-DEVD-fmk have been shown to exert a thermoprotective role, rescuing heat-induced oocyte and embryo cellular damage and developmental competence. Therefore, cattle genotype and thermoprotective molecules can be considered as an alternative to modulate the effects of increased temperature in reproductive function.

Properties of Local Group galaxies in hydrodynamical simulations of sterile neutrino dark matter cosmologies

NASA Astrophysics Data System (ADS)

Lovell, Mark R.; Bose, Sownak; Boyarsky, Alexey; Crain, Robert A.; Frenk, Carlos S.; Hellwing, Wojciech A.; Ludlow, Aaron D.; Navarro, Julio F.; Ruchayskiy, Oleg; Sawala, Till; Schaller, Matthieu; Schaye, Joop; Theuns, Tom

2017-07-01

We study galaxy formation in sterile neutrino dark matter models that differ significantly from both cold and from 'warm thermal relic' models. We use the eagle code to carry out hydrodynamic simulations of the evolution of pairs of galaxies chosen to resemble the Local Group, as part of the APOSTLE simulations project. We compare cold dark matter (CDM) with two sterile neutrino models with 7 keV mass: one, the warmest among all models of this mass (LA120) and the other, a relatively cold case (LA10). We show that the lower concentration of sterile neutrino subhaloes compared to their CDM counterparts makes the inferred inner dark matter content of galaxies like Fornax (or Magellanic Clouds) less of an outlier in the sterile neutrino cosmologies. In terms of the galaxy number counts, the LA10 simulations are indistinguishable from CDM when one takes into account halo-to-halo (or 'simulation-to-simulation') scatter. In order for the LA120 model to match the number of Local Group dwarf galaxies, a higher fraction of low-mass haloes is required to form galaxies than is predicted by the eagle simulations. As the census of the Local Group galaxies nears completion, this population may provide a strong discriminant between cold and warm dark matter models.

Dark Matters

ScienceCinema

Joseph Silk

2018-04-17

One of the greatest mysteries in the cosmos is that it is mostly dark.  Astronomers and particle physicists today are seeking to unravel the nature of this mysterious, but pervasive dark matter which has profoundly influenced the formation of structure in the universe.  I will describe the complex interplay between galaxy formation and dark matter detectability and review recent attempts to measure particle dark matter by direct and indirect means.

Airborne observations and simulations of three-dimensional radiative interactions between Arctic boundary layer clouds and ice floes

NASA Astrophysics Data System (ADS)

Schäfer, M.; Bierwirth, E.; Ehrlich, A.; Jäkel, E.; Wendisch, M.

2015-07-01

Based on airborne spectral imaging observations, three-dimensional (3-D) radiative effects between Arctic boundary layer clouds and highly variable Arctic surfaces were identified and quantified. A method is presented to discriminate between sea ice and open water under cloudy conditions based on airborne nadir reflectivity γλ measurements in the visible spectral range. In cloudy cases the transition of γλ from open water to sea ice is not instantaneous but horizontally smoothed. In general, clouds reduce γλ above bright surfaces in the vicinity of open water, while γλ above open sea is enhanced. With the help of observations and 3-D radiative transfer simulations, this effect was quantified to range between 0 and 2200 m distance to the sea ice edge (for a dark-ocean albedo of αwater = 0.042 and a sea-ice albedo of αice = 0.91 at 645 nm wavelength). The affected distance Δ L was found to depend on both cloud and sea ice properties. For a low-level cloud at 0-200 m altitude, as observed during the Arctic field campaign VERtical Distribution of Ice in Arctic clouds (VERDI) in 2012, an increase in the cloud optical thickness τ from 1 to 10 leads to a decrease in Δ L from 600 to 250 m. An increase in the cloud base altitude or cloud geometrical thickness results in an increase in Δ L; for τ = 1/10 Δ L = 2200 m/1250 m in case of a cloud at 500-1000 m altitude. To quantify the effect for different shapes and sizes of ice floes, radiative transfer simulations were performed with various albedo fields (infinitely long straight ice edge, circular ice floes, squares, realistic ice floe field). The simulations show that Δ L increases with increasing radius of the ice floe and reaches maximum values for ice floes with radii larger than 6 km (500-1000 m cloud altitude), which matches the results found for an infinitely long, straight ice edge. Furthermore, the influence of these 3-D radiative effects on the retrieved cloud optical properties was investigated

The Dark Cube: dark character profiles and OCEAN.

PubMed

Garcia, Danilo; González Moraga, Fernando R

2017-01-01

The Big Five traits (i.e., openness, conscientiousness, extraversion, agreeableness, and neuroticism: OCEAN) have been suggested to provide a meaningful taxonomy for studying the Dark Triad: Machiavellianism, narcissism, and psychopathy. Nevertheless, current research consists of mixed and inconsistent associations between the Dark Triad and OCEAN. Here we used the Dark Cube (Garcia & Rosenberg, 2016), a model of malevolent character theoretically based on Cloninger's biopsychosocial model of personality and in the assumption of a ternary structure of malevolent character. We use the dark cube profiles to investigate differences in OCEAN between individuals who differ in one dark character trait while holding the other two constant (i.e., conditional relationships). Participants ( N  = 330) responded to the Short Dark Triad Inventory and the Big Five Inventory and were grouped according to the eight possible combinations using their dark trait scores (M, high Machiavellianism; m, low Machiavellianism; N, high narcissism; n, low narcissism; P, high psychopathy; p, low psychopathy): MNP "maleficent", MNp "manipulative narcissistic", MnP "anti-social", Mnp "Machiavellian", mNP "psychopathic narcissistic", mNp "narcissistic", mnP "psychopathic", and mnp "benevolent". High narcissism-high extraversion and high psychopathy-low agreeableness were consistently associated across comparisons. The rest of the comparisons showed a complex interaction. For example, high Machiavellianism-high neuroticism only when both narcissism and psychopathy were low (Mnp vs. mnp), high narcissism-high conscientiousness only when both Machiavellianism and psychopathy were also high (MNP vs. MnP), and high psychopathy-high neuroticism only when Machiavellianism was low and narcissism was high (mNP vs. mNp). We suggest that the Dark Cube is a useful tool in the investigation of a consistent Dark Triad Theory. This approach suggests that the only clear relationships were narcissism

The Dark Cube: dark character profiles and OCEAN

PubMed Central

González Moraga, Fernando R.

2017-01-01

Background The Big Five traits (i.e., openness, conscientiousness, extraversion, agreeableness, and neuroticism: OCEAN) have been suggested to provide a meaningful taxonomy for studying the Dark Triad: Machiavellianism, narcissism, and psychopathy. Nevertheless, current research consists of mixed and inconsistent associations between the Dark Triad and OCEAN. Here we used the Dark Cube (Garcia & Rosenberg, 2016), a model of malevolent character theoretically based on Cloninger’s biopsychosocial model of personality and in the assumption of a ternary structure of malevolent character. We use the dark cube profiles to investigate differences in OCEAN between individuals who differ in one dark character trait while holding the other two constant (i.e., conditional relationships). Method Participants (N = 330) responded to the Short Dark Triad Inventory and the Big Five Inventory and were grouped according to the eight possible combinations using their dark trait scores (M, high Machiavellianism; m, low Machiavellianism; N, high narcissism; n, low narcissism; P, high psychopathy; p, low psychopathy): MNP “maleficent”, MNp “manipulative narcissistic”, MnP “anti-social”, Mnp “Machiavellian”, mNP “psychopathic narcissistic”, mNp “narcissistic”, mnP “psychopathic”, and mnp “benevolent”. Results High narcissism-high extraversion and high psychopathy-low agreeableness were consistently associated across comparisons. The rest of the comparisons showed a complex interaction. For example, high Machiavellianism-high neuroticism only when both narcissism and psychopathy were low (Mnp vs. mnp), high narcissism-high conscientiousness only when both Machiavellianism and psychopathy were also high (MNP vs. MnP), and high psychopathy-high neuroticism only when Machiavellianism was low and narcissism was high (mNP vs. mNp). Conclusions We suggest that the Dark Cube is a useful tool in the investigation of a consistent Dark Triad Theory. This approach

Comparing different snow products to assess spatio-temporal snow cover patterns in the Central Taurus Mountains, Turkey

NASA Astrophysics Data System (ADS)

Sturm, K.; Helmschrot, J.

2013-12-01

Snow and its spatial and temporal patterns are important for catchment hydrology in the semi-arid eastern Mediterranean. Since most of the annual rainfall is stored as snow during winter and released during drier conditions in spring and summer, downstream regions of the Taurus Mountains relying on snow water temporarily stored in reservoirs for agricultural use are heavily dependent on the timing of snowmelt discharge. Runoff is controlled by the amount of accumulated snow, its distribution, and the climatic conditions controlling spring snowmelt. Thus, knowledge about spatial and temporal snow cover dynamics is essential for sustainable water resources management. The lack of observations in high-altitude regions reinforces the application of different snow products for a better assessment of spatio-temporal snow cover patterns. To better assess the quality of such products, simulated daily snow cover and EO-based snow cover products were compared for the Egribuk subcatchment, in the Central Taurus Mountains, Turkey. Daily information on snow cover, depths, and snow water equivalent was derived from distributed hydrological modeling using the J2000 model. Furthermore, 8-day MODIS snow cover data from Terra (MOD10A2) and Aqua (MYD10A2) satellites at a spatial resolution of 500 m were synchronized to receive cloud-free images. From this effort, 253 images covering the period between 07/04/2002 and 12/27/2007 were used for further analyses. The products were analyzed individually to determine the number of snow-covered days in relation to freezing days, spring snowmelt onsets, and temporal patterns, reflecting the effect of altitude on the percentage snow-covered area (SCA) along a topographic gradient at various time-steps. Monthly and 8-day spatial patterns of a single snow season were also examined. When SCA peaks at all altitudes, in February and March, the results of both products show a good agreement regarding SCA extent. In contrast, the extent of SCA

Heterosis for meat quality and fatty acid profiles in crosses among Bos indicus and Bos taurus finished on pasture or grain.

PubMed

Gama, L T; Bressan, M C; Rodrigues, E C; Rossato, L V; Moreira, O C; Alves, S P; Bessa, R J B

2013-01-01

Physicochemical properties and fatty acid profiles of meat from Bos indicus, Bos taurus and crossbred B. taurus×B. indicus bullocks (n=216), finished on pasture or grain, were used to estimate the effects of heterosis. Meat quality and fatty acid profiles generally benefited with crossbreeding, but the advantages from heterosis differed among finishing systems. The Warner-Bratzler shear-force in fresh and aged meat was reduced due to heterosis in pasture-finishing, but the effect was minor under grain-finishing. With pasture-finishing, heterosis caused an increase of 5% in CLA concentration, but few other changes in fatty acid profiles. In grain-finishing, heterosis caused a reduction in intramuscular fat and cholesterol, increased amounts of PUFA, n-6 fatty acids and PUFA/SFA ratio, and a decline in atherogenic index. The Δ(9) desaturase estimated activity in crossbreds showed a behavior close to B. indicus, suggesting the existence of few loci and a dominance genetic effect on enzymes involved in fatty acid synthesis and metabolism. Copyright © 2012 Elsevier Ltd. All rights reserved.

Dark information of black hole radiation raised by dark energy

NASA Astrophysics Data System (ADS)

Ma, Yu-Han; Chen, Jin-Fu; Sun, Chang-Pu

2018-06-01

The "lost" information of black hole through the Hawking radiation was discovered being stored in the correlation among the non-thermally radiated particles (Parikh and Wilczek, 2000 [31], Zhang et al., 2009 [16]). This correlation information, which has not yet been proved locally observable in principle, is named by dark information. In this paper, we systematically study the influences of dark energy on black hole radiation, especially on the dark information. Calculating the radiation spectrum in the existence of dark energy by the approach of canonical typicality, which is reconfirmed by the quantum tunneling method, we find that the dark energy will effectively lower the Hawking temperature, and thus makes the black hole has longer life time. It is also discovered that the non-thermal effect of the black hole radiation is enhanced by dark energy so that the dark information of the radiation is increased. Our observation shows that, besides the mechanical effect (e.g., gravitational lensing effect), the dark energy rises the stored dark information, which could be probed by a non-local coincidence measurement similar to the coincidence counting of the Hanbury-Brown-Twiss experiment in quantum optics.

The Collection 6 'dark-target' MODIS Aerosol Products

NASA Technical Reports Server (NTRS)

Levy, Robert C.; Mattoo, Shana; Munchak, Leigh A.; Kleidman, Richard G.; Patadia, Falguni; Gupta, Pawan; Remer, Lorraine

2013-01-01

Aerosol retrieval algorithms are applied to Moderate resolution Imaging Spectroradiometer (MODIS) sensors on both Terra and Aqua, creating two streams of decade-plus aerosol information. Products of aerosol optical depth (AOD) and aerosol size are used for many applications, but the primary concern is that these global products are comprehensive and consistent enough for use in climate studies. One of our major customers is the international modeling comparison study known as AEROCOM, which relies on the MODIS data as a benchmark. In order to keep up with the needs of AEROCOM and other MODIS data users, while utilizing new science and tools, we have improved the algorithms and products. The code, and the associated products, will be known as Collection 6 (C6). While not a major overhaul from the previous Collection 5 (C5) version, there are enough changes that there are significant impacts to the products and their interpretation. In its entirety, the C6 algorithm is comprised of three sub-algorithms for retrieving aerosol properties over different surfaces: These include the dark-target DT algorithms to retrieve over (1) ocean and (2) vegetated-dark-soiled land, plus the (3) Deep Blue (DB) algorithm, originally developed to retrieve over desert-arid land. Focusing on the two DT algorithms, we have updated assumptions for central wavelengths, Rayleigh optical depths and gas (H2O, O3, CO2, etc.) absorption corrections, while relaxing the solar zenith angle limit (up to 84) to increase pole-ward coverage. For DT-land, we have updated the cloud mask to allow heavy smoke retrievals, fine-tuned the assignments for aerosol type as function of season location, corrected bugs in the Quality Assurance (QA) logic, and added diagnostic parameters such as topographic altitude. For DT-ocean, improvements include a revised cloud mask for thin-cirrus detection, inclusion of wind speed dependence in the retrieval, updates to logic of QA Confidence flag (QAC) assignment, and

Searching for a dark photon with DarkLight

DOE PAGES

Corliss, R.

2016-07-30

Here, we describe the current status of the DarkLight experiment at Jefferson Laboratory. DarkLight is motivated by the possibility that a dark photon in the mass range 10 to 100 MeV/c 2 could couple the dark sector to the Standard Model. DarkLight will precisely measure electron proton scattering using the 100 MeV electron beam of intensity 5 mA at the Jefferson Laboratory energy recovering linac incident on a windowless gas target of molecular hydrogen. We will detect the complete final state including scattered electron, recoil proton, and e +e - pair. A phase-I experiment has been funded and is expectedmore » to take data in the next eighteen months. The complete phase-II experiment is under final design and could run within two years after phase-I is completed. The DarkLight experiment drives development of new technology for beam, target, and detector and provides a new means to carry out electron scattering experiments at low momentum transfers.« less

Spatial and Temporal Distribution of Clouds as Observed by MODIS Onboard the Terra and Aqua Satellites

NASA Technical Reports Server (NTRS)

King, Michael D.; Platnick, Steven; Menzel, Paul; Ackerman, Steven A.

2006-01-01

The Moderate Resolution Imaging Spectroradiometer (MODIS) was developed by NASA and launched onboard the Terra spacecraft on December 18,1999 and Aqua spacecraft on May 4, 2002. It achieved its final orbit and began Earth observations on February 24,2000 for Terra and June 24,2002 for Aqua. A comprehensive set of remote sensing algorithms for cloud masking and the retrieval of cloud physical and optical properties has been developed by members of the MODIS atmosphere science team. The archived products from these algorithms have applications in climate change studies, climate modeling, numerical weather prediction, and fundamental atmospheric research. In addition to an extensive cloud mask, products include cloud-top properties (temperature, pressure, effective emissivity), cloud thermodynamic phase, cloud optical and microphysical parameters (optical thickness, effective particle radius, water path), as well as derived statistics. Over the last year, extensive improvements and enhancements in the global cloud products have been implemented, and reprocessing of all MODIS data on Terra has commenced since first light in February 2000. In the cloud mask algorithm, the most extensive improvements were in distinguishing clouds at nighttime, including the challenging polar darkness regions of the world. Additional improvements have been made to properly distinguish sunglint from clouds in the tropical ocean regions, and to improve the identification of clouds from snow during daytime in Polar Regions. We will show global monthly mean cloud fraction for both Terra and Aqua, and show how similar the global daytime cloud fraction is from these morning and afternoon orbits, respectively. We will also show the zonal distribution of cloud fraction over land and ocean regions for both Terra and Aqua, and show the time series of global cloud fraction from July 2002 through June 2006.

Pregnancy rate and birth rate of calves from a large-scale IVF program using reverse-sorted semen in Bos indicus, Bos indicus-taurus, and Bos taurus cattle.

PubMed

Morotti, F; Sanches, B V; Pontes, J H F; Basso, A C; Siqueira, E R; Lisboa, L A; Seneda, M M

2014-03-15

Obtaining sexed sperm from previously frozen doses (reverse-sorted semen [RSS]) provides an important advantage because of the possibility of using the semen of bulls with desired genetic attributes that have died or have become infertile but from whom frozen semen is available. We report the efficiency of RSS on the pregnancy rate and birth rate of calves in a large-scale program using ovum pick-up and in vitro embryo production (IVEP) from Bos indicus, Bos indicus-taurus, and Bos taurus cattle. From 645 ovum pick-up procedures (Holstein, Gir, and Nelore), 9438 viable oocytes were recovered. A dose of frozen semen (Holstein, Nelore, Brahman, Gir, and Braford) was thawed, and the sperm were sex-sorted and cooled for use in IVF. Additionally, IVF with sperm from three Holstein bulls with freeze-thawed, sex-sorted (RSS) or sex-sorted, freeze-thawed (control) was tested. A total of 2729 embryos were produced, exhibiting a mean blastocyst rate of 29%. Heifers and cows selected for adequate body condition, estrus, and health received 2404 embryos, and 60 days later, a 41% average pregnancy rate was observed. A total of 966 calves were born, and 910 were of a predetermined sex, with an average of 94% accuracy in determining the sex. Despite the lower blastocyst rate with freeze-thawed, sex-sorted semen compared with sex-sorted semen, (P < 0.05), the pregnancy rate (bull I, 45% vs. 40%; II, 35% vs. 50%; and III, 47% vs. 48% for RSS and control, respectively; P > 0.05) and sex-sorted efficiency (bull I, 93% vs. 98%; II, 96% vs. 94%; and III, 96% vs. 97% for RSS and control, respectively; P > 0.05) were similar for each of the three bulls regardless of the sperm type used in the IVF. The sexing of previously frozen semen, associated with IVEP, produces viable embryos with a pregnancy rate of up to 40%, and calves of the desired sex are born even if the paternal bull has acquired some infertility, died, or is located a long distance from the sexing laboratory. Furthermore

Signatures of dark radiation in neutrino and dark matter detectors

NASA Astrophysics Data System (ADS)

Cui, Yanou; Pospelov, Maxim; Pradler, Josef

2018-05-01

We consider the generic possibility that the Universe's energy budget includes some form of relativistic or semi-relativistic dark radiation (DR) with nongravitational interactions with standard model (SM) particles. Such dark radiation may consist of SM singlets or a nonthermal, energetic component of neutrinos. If such DR is created at a relatively recent epoch, it can carry sufficient energy to leave a detectable imprint in experiments designed to search for very weakly interacting particles: dark matter and underground neutrino experiments. We analyze this possibility in some generality, assuming that the interactive dark radiation is sourced by late decays of an unstable particle, potentially a component of dark matter, and considering a variety of possible interactions between the dark radiation and SM particles. Concentrating on the sub-GeV energy region, we derive constraints on different forms of DR using the results of the most sensitive neutrino and dark matter direct detection experiments. In particular, for interacting dark radiation carrying a typical momentum of ˜30 MeV /c , both types of experiments provide competitive constraints. This study also demonstrates that non-standard sources of neutrino emission (e.g., via dark matter decay) are capable of creating a "neutrino floor" for dark matter direct detection that is closer to current bounds than is expected from standard neutrino sources.

Boreal forests, aerosols and the impacts on clouds and climate.

PubMed

Spracklen, Dominick V; Bonn, Boris; Carslaw, Kenneth S

2008-12-28

Previous studies have concluded that boreal forests warm the climate because the cooling from storage of carbon in vegetation and soils is cancelled out by the warming due to the absorption of the Sun's heat by the dark forest canopy. However, these studies ignored the impacts of forests on atmospheric aerosol. We use a global atmospheric model to show that, through emission of organic vapours and the resulting condensational growth of newly formed particles, boreal forests double regional cloud condensation nuclei concentrations (from approx. 100 to approx. 200 cm(-3)). Using a simple radiative model, we estimate that the resulting change in cloud albedo causes a radiative forcing of between -1.8 and -6.7 W m(-2) of forest. This forcing may be sufficiently large to result in boreal forests having an overall cooling impact on climate. We propose that the combination of climate forcings related to boreal forests may result in an important global homeostasis. In cold climatic conditions, the snow-vegetation albedo effect dominates and boreal forests warm the climate, whereas in warmer climates they may emit sufficiently large amounts of organic vapour modifying cloud albedo and acting to cool climate.

Dark energy and extended dark matter halos

NASA Astrophysics Data System (ADS)

Chernin, A. D.; Teerikorpi, P.; Valtonen, M. J.; Dolgachev, V. P.; Domozhilova, L. M.; Byrd, G. G.

2012-03-01

The cosmological mean matter (dark and baryonic) density measured in the units of the critical density is Ωm = 0.27. Independently, the local mean density is estimated to be Ωloc = 0.08-0.23 from recent data on galaxy groups at redshifts up to z = 0.01-0.03 (as published by Crook et al. 2007, ApJ, 655, 790 and Makarov & Karachentsev 2011, MNRAS, 412, 2498). If the lower values of Ωloc are reliable, as Makarov & Karachentsev and some other observers prefer, does this mean that the Local Universe of 100-300 Mpc across is an underdensity in the cosmic matter distribution? Or could it nevertheless be representative of the mean cosmic density or even be an overdensity due to the Local Supercluster therein. We focus on dark matter halos of groups of galaxies and check how much dark mass the invisible outer layers of the halos are able to host. The outer layers are usually devoid of bright galaxies and cannot be seen at large distances. The key factor which bounds the size of an isolated halo is the local antigravity produced by the omnipresent background of dark energy. A gravitationally bound halo does not extend beyond the zero-gravity surface where the gravity of matter and the antigravity of dark energy balance, thus defining a natural upper size of a system. We use our theory of local dynamical effects of dark energy to estimate the maximal sizes and masses of the extended dark halos. Using data from three recent catalogs of galaxy groups, we show that the calculated mass bounds conform with the assumption that a significant amount of dark matter is located in the invisible outer parts of the extended halos, sufficient to fill the gap between the observed and expected local matter density. Nearby groups of galaxies and the Virgo cluster have dark halos which seem to extend up to their zero-gravity surfaces. If the extended halo is a common feature of gravitationally bound systems on scales of galaxy groups and clusters, the Local Universe could be typical or even

Meteorological interpretation of clouds or cloud systems appearing on pictures of the Alpine region received from the Earth Resources Technology Satellite (ERTS-1)

NASA Technical Reports Server (NTRS)

Piaget, A.

1973-01-01

The author has identified the following significant results. Three examples of cloud-interpretation from ERTS-1 pictures are presented. When the wind speed is large enough, the cumuli are found arranged in lines that are in average two kilometers apart from each other. These lines are grouped in lines made of small cumuli and in lines made up of well developed ones. These last lines are fused on the APT picture and appear as single lines. Fog-mapping for a given region is possible if the topography of the region is known. The stratified clouds lying over mountains or in valleys begin to dissolve above the middle of the valleys and not against the slopes. As water shows a weak albedo in the near infrared, wet surfaces will appear darker than their neighborhoods. This feature seems to be confirmed by the dark spot in the north of Bozen (Southern Tyrol) that can be seen on the ERTS-1 picture taken on 31 August 1972.

H2CS abundances and ortho-to-para ratios in interstellar clouds

NASA Technical Reports Server (NTRS)

Minh, Y. C.; Irvine, W. M.; Brewer, M. K.

1991-01-01

Several H2CS ortho and para transitions have been observed toward interstellar molecular clouds, including cold, dark clouds and star-forming regions. H2CS fractional abundances f(H2CS) about 1-2 10 to the -9th relative to molecular hydrogen toward TMC-1, Orion A, and NGC 7538, and about 5 10 to the -10th for L134N are derived. The H2CS ortho-to-para ratios in TMC-1 are about 1.8 toward the cyanopolyyne peak and the ammonia peak, which may indicate the thermalization of H2CS on 10 K grains. A ratio of about 3, the statistical value, for Orion (3N, 1E) and NGC 7538 is derived, while a value of about 2 for Orion (KL) is found.

Identity of Sarcocystis species of the water buffalo (Bubalus bubalis) and cattle (Bos taurus) and the suppression of Sarcocystis sinensis as a nomen nudum

USDA-ARS?s Scientific Manuscript database

There are uncertainties concerning the identity and host species specificity of Sarcocystis species of the water buffalo (Bubalus bubalis) and cattle (Bos taurus). Currently, in cattle three species are recognized with known endogenous stages, viz.: S. cruzi (with canine definitive host), S. hirsuta...

[Detection of hydrodynamically operative tissue in the substantia spongiosa of the femoral head in Bos taurus and Ovis aries].

PubMed

Copf, F; Czarnetzki, A; Lierse, W; Dolenc, A

1990-12-01

The authors show the presence of CC-Tensulae in Bos taurus and Ovis aries. They define CC-Tensulae as tense membranes in openings between the trabeculae of spongy bone. These structures were interpreted in man as a hydrodynamic subsystem which serves the flow and the impulses of mechanical forces. The authors point especially to the similarity that exists between their findings and what has been seen in man.

Close-up of lunar roving vehicle at Apollo 17 Taurus-Littrow landing site

NASA Image and Video Library

1972-12-12

AS17-137-20979 (12 Dec. 1972) --- A close-up view of the lunar roving vehicle (LRV) at the Taurus-Littrow landing site photographed during Apollo 17 lunar surface extravehicular activity. Note the makeshift repair arrangement on the right rear fender of the LRV. During EVA-1 a hammer got underneath the fender and a part of it was knocked off. Astronauts Eugene A. Cernan and Harrison H. Schmitt were reporting a problem with lunar dust because of the damage fender. Following a suggestion from astronaut John W. Young in the Mission Control Center at Houston the crewmen repaired the fender early in EVA-2 using lunar maps and clamps from the optical alignment telescope lamp. Schmitt is seated in the rover. Cernan took this picture.

VizieR Online Data Catalog: Spectroscopy of candidate members in Taurus (Luhman+, 2017)

NASA Astrophysics Data System (ADS)

Luhman, K. L.; Mamajek, E. E.; Shukla, S. J.; Loutrel, N. P.

2017-06-01

We have obtained optical and near-infrared spectra of candidate members of Taurus. The spectra were collected with the Gemini Near-Infrared Imager (NIRI) using the K-band grism and 0.47'' slit (1.9-2.5μm, R=700), the Gemini Multi-Object Spectrograph (GMOS) using the 400line/mm grating and 0.75'' slit (0.56-1μm, R=1500), the Marcario Low-Resolution Spectrograph (LRS) on the Hobby-Eberly Telescope (HET) using the G3 grism and 2'' slit (0.63-0.91μm, R=1100), and SpeX at the NASA Infrared Telescope Facility (IRTF) using either the prism or SXD mode (R=150/750) and 0.8'' slit (0.8-2.5μm). (7 data files).

A new approach to simulating collisionless dark matter fluids

NASA Astrophysics Data System (ADS)

Hahn, Oliver; Abel, Tom; Kaehler, Ralf

2013-09-01

Recently, we have shown how current cosmological N-body codes already follow the fine grained phase-space information of the dark matter fluid. Using a tetrahedral tessellation of the three-dimensional manifold that describes perfectly cold fluids in six-dimensional phase space, the phase-space distribution function can be followed throughout the simulation. This allows one to project the distribution function into configuration space to obtain highly accurate densities, velocities and velocity dispersions. Here, we exploit this technique to show first steps on how to devise an improved particle-mesh technique. At its heart, the new method thus relies on a piecewise linear approximation of the phase-space distribution function rather than the usual particle discretization. We use pseudo-particles that approximate the masses of the tetrahedral cells up to quadrupolar order as the locations for cloud-in-cell (CIC) deposit instead of the particle locations themselves as in standard CIC deposit. We demonstrate that this modification already gives much improved stability and more accurate dynamics of the collisionless dark matter fluid at high force and low mass resolution. We demonstrate the validity and advantages of this method with various test problems as well as hot/warm dark matter simulations which have been known to exhibit artificial fragmentation. This completely unphysical behaviour is much reduced in the new approach. The current limitations of our approach are discussed in detail and future improvements are outlined.

Biogeography, Cloud Base Heights and Cloud Immersion in Tropical Montane Cloud Forests

NASA Astrophysics Data System (ADS)

Welch, R. M.; Asefi, S.; Zeng, J.; Nair, U. S.; Lawton, R. O.; Ray, D. K.; Han, Q.; Manoharan, V. S.

2007-05-01

Tropical Montane Cloud Forests (TMCFs) are ecosystems characterized by frequent and prolonged immersion within orographic clouds. TMCFs often lie at the core of the biological hotspots, areas of high biodiversity, whose conservation is necessary to ensure the preservation of a significant amount of the plant and animal species in the world. TMCFs support islands of endemism dependent on cloud water interception that are extremely susceptible to environmental and climatic changes at regional or global scales. Due to the ecological and hydrological importance of TMCFs it is important to understand the biogeographical distribution of these ecosystems. The best current list of TMCFs is a global atlas compiled by the United Nations Environmental Program (UNEP). However, this list is incomplete, and it does not provide information on cloud immersion, which is the defining characteristic of TMCFs and sorely needed for ecological and hydrological studies. The present study utilizes MODIS satellite data both to determine orographic cloud base heights and then to quantify cloud immersion statistics over TMCFs. Results are validated from surface measurements over Northern Costa Rica for the month of March 2003. Cloud base heights are retrieved with approximately 80m accuracy, as determined at Monteverde, Costa Rica. Cloud immersion derived from MODIS data is also compared to an independent cloud immersion dataset created using a combination of GOES satellite data and RAMS model simulations. Comparison against known locations of cloud forests in Northern Costa Rica shows that the MODIS-derived cloud immersion maps successfully identify these cloud forest locations, including those not included in the UNEP data set. Results also will be shown for cloud immersion in Hawaii. The procedure appears to be ready for global mapping.

Parametric Simulations of the Great Dark Spots of Neptune

NASA Astrophysics Data System (ADS)

Deng, Xiaolong; Le Beau, R.

2006-09-01

Observations by Voyager II and the Hubble Space Telescope of the Great Dark Spots (GDS) of Neptune suggest that large vortices with lifespans of years are not uncommon occurrences in the atmosphere of Neptune. The variability of these features over time, in particular the complex motions of GDS-89, make them challenging candidates to simulate in atmospheric models. Previously, using the Explicit Planetary Isentropic-Coordinate (EPIC) General Circulation Model, LeBeau and Dowling (1998) simulated the GDS-like vortex features. Qualitatively, the drift, oscillation, and tail-like features of GDS-89 were recreated, although precise numerical matches were only achieved for the meridional drift rate. In 2001, Stratman et al. applied EPIC to simulate the formation of bright companion clouds to the Great Dark Spots. In 2006, Dowling et al. presented a new version of EPIC, which includes hybrid vertical coordinate, cloud physics, advanced chemistry, and new turbulence models. With the new version of EPIC, more observation results, and more powerful computers, it is the time to revisit CFD simulations of the Neptune's atmosphere and do more detailed work on GDS-like vortices. In this presentation, we apply the new version of EPIC to simulate GDS-89. We test the influences of different parameters in the EPIC model: potential vorticity gradient, wind profile, initial latitude, vortex shape, and vertical structure. The observed motions, especially the latitudinal drift and oscillations in orientation angle and aspect ratio, are used as diagnostics of these unobserved atmospheric conditions. Increased computing power allows for more refined and longer simulations and greater coverage of the parameter space than previous efforts. Improved quantitative results have been achieved, including voritices with near eight-day oscillations and comparable variations in shape to GDS-89. This research has been supported by Kentucky NASA EPSCoR.

X ray absorption by dark nebulae (HEAO-2 guest investigator program)

NASA Technical Reports Server (NTRS)

Sanders, W. T.

1991-01-01

A study is described of data obtained from the Imaging Proportional Counter (IPC) x ray detector aboard the HEAO-2 satellite (Einstein Observatory). The research project involved a search for absorption of diffuse low energy x ray background emission by galactic dark nebulae. The commonly accepted picture that the bulk of the C band emission originates locally, closer that a few hundred parsec, and the bulk of the M band emission originates farther away than a few hundred parsec, was tested. The idea was to look for evidence of absorption of the diffuse background radiation by nearby interstellar clouds.

Cloud Processed CCN Suppress Stratus Cloud Drizzle

NASA Astrophysics Data System (ADS)

Hudson, J. G.; Noble, S. R., Jr.

2017-12-01

Conversion of sulfur dioxide to sulfate within cloud droplets increases the sizes and decreases the critical supersaturation, Sc, of cloud residual particles that had nucleated the droplets. Since other particles remain at the same sizes and Sc a size and Sc gap is often observed. Hudson et al. (2015) showed higher cloud droplet concentrations (Nc) in stratus clouds associated with bimodal high-resolution CCN spectra from the DRI CCN spectrometer compared to clouds associated with unimodal CCN spectra (not cloud processed). Here we show that CCN spectral shape (bimodal or unimodal) affects all aspects of stratus cloud microphysics and drizzle. Panel A shows mean differential cloud droplet spectra that have been divided according to traditional slopes, k, of the 131 measured CCN spectra in the Marine Stratus/Stratocumulus Experiment (MASE) off the Central California coast. K is generally high within the supersaturation, S, range of stratus clouds (< 0.5%). Because cloud processing decreases Sc of some particles, it reduces k. Panel A shows higher concentrations of small cloud droplets apparently grown on lower k CCN than clouds grown on higher k CCN. At small droplet sizes the concentrations follow the k order of the legend, black, red, green, blue (lowest to highest k). Above 13 µm diameter the lines cross and the hierarchy reverses so that blue (highest k) has the highest concentrations followed by green, red and black (lowest k). This reversed hierarchy continues into the drizzle size range (panel B) where the most drizzle drops, Nd, are in clouds grown on the least cloud-processed CCN (blue), while clouds grown on the most processed CCN (black) have the lowest Nd. Suppression of stratus cloud drizzle by cloud processing is an additional 2nd indirect aerosol effect (IAE) that along with the enhancement of 1st IAE by higher Nc (panel A) are above and beyond original IAE. However, further similar analysis is needed in other cloud regimes to determine if MASE was

Time-varying q-deformed dark energy interacts with dark matter

NASA Astrophysics Data System (ADS)

Dil, Emre; Kolay, Erdinç

We propose a new model for studying the dark constituents of the universe by regarding the dark energy as a q-deformed scalar field interacting with the dark matter, in the framework of standard general relativity. Here we assume that the number of particles in each mode of the q-deformed scalar field varies in time by the particle creation and annihilation. We first describe the q-deformed scalar field dark energy quantum-field theoretically, then construct the action and the dynamical structure of these interacting dark sectors, in order to study the dynamics of the model. We perform the phase space analysis of the model to confirm and interpret our proposal by searching the stable attractor solutions implying the late-time accelerating phase of the universe. We then obtain the result that when interaction and equation-of-state parameter of the dark matter evolve from the present day values into a particular value, the dark energy turns out to be a q-deformed scalar field.

Distinguishing Clouds from Ice over the East Siberian Sea, Russia

NASA Technical Reports Server (NTRS)

2002-01-01

As a consequence of its capability to retrieve cloud-top elevations, stereoscopic observations from the Multi-angle Imaging SpectroRadiometer (MISR) can discriminate clouds from snow and ice. The central portion of Russia's East Siberian Sea, including one of the New Siberian Islands, Novaya Sibir, are portrayed in these views from data acquired on May 28, 2002.

The left-hand image is a natural color view from MISR's nadir camera. On the right is a height field retrieved using automated computer processing of data from multiple MISR cameras. Although both clouds and ice appear white in the natural color view, the stereoscopic retrievals are able to identify elevated clouds based on the geometric parallax which results when they are observed from different angles. Owing to their elevation above sea level, clouds are mapped as green and yellow areas, whereas land, sea ice, and very low clouds appear blue and purple. Purple, in particular, denotes elevations very close to sea level. The island of Novaya Sibir is located in the lower left of the images. It can be identified in the natural color view as the dark area surrounded by an expanse of fast ice. In the stereo map the island appears as a blue region indicating its elevation of less than 100 meters above sea level. Areas where the automated stereo processing failed due to lack of sufficient spatial contrast are shown in dark gray. The northern edge of the Siberian mainland can be found at the very bottom of the panels, and is located a little over 250 kilometers south of Novaya Sibir. Pack ice containing numerous fragmented ice floes surrounds the fast ice, and narrow areas of open ocean are visible.

The East Siberian Sea is part of the Arctic Ocean and is ice-covered most of the year. The New Siberian Islands are almost always covered by snow and ice, and tundra vegetation is very scant. Despite continuous sunlight from the end of April until the middle of August, the ice between the island and the

Water vapor weathering of Taurus-Littrow orange soil - A pore-structure analysis

NASA Technical Reports Server (NTRS)

Cadenhead, D. A.; Mikhail, R. S.

1975-01-01

A pore-volume analysis was performed on water vapor adsorption data previously obtained on a fresh sample of Taurus-Littrow orange soil, and the analysis was repeated on the same sample after its exposure to moist air for a period of approximately six months. The results indicate that exposure of an outgassed sample to high relative pressures of water vapor can result in the formation of substantial micropore structure, the precise amount being dependent on the sample pretreatment, particularly the outgassing temperature. Micropore formation is explained in terms of water penetration into surface defects. In contrast, long-term exposure to moist air at low relative pressures appears to reverse the process with the elimination of micropores and enlargement of mesopores possibly through surface diffusion of metastable adsorbent material. The results are considered with reference to the storage of lunar samples.

Stealth Dark Matter: Dark scalar baryons through the Higgs portal

DOE PAGES

Appelquist, T.; Brower, R. C.; Buchoff, M. I.; ...

2015-10-23

We present a new model of "Stealth Dark Matter": a composite baryonic scalar of an SU(N D) strongly coupled theory with even N D ≥ 4. All mass scales are technically natural, and dark matter stability is automatic without imposing an additional discrete or global symmetry. Constituent fermions transform in vectorlike representations of the electroweak group that permit both electroweak-breaking and electroweak-preserving mass terms. This gives a tunable coupling of stealth dark matter to the Higgs boson independent of the dark matter mass itself. We specialize to SU(4), and investigate the constraints on the model from dark meson decay, electroweakmore » precision measurements, basic collider limits, and spin-independent direct detection scattering through Higgs exchange. We exploit our earlier lattice simulations that determined the composite spectrum as well as the effective Higgs coupling of stealth dark matter in order to place bounds from direct detection, excluding constituent fermions with dominantly electroweak-breaking masses. A lower bound on the dark baryon mass m B ≳ 300 GeV is obtained from the indirect requirement that the lightest dark meson not be observable at LEP II. Furthermore, we briefly survey some intriguing properties of stealth dark matter that are worthy of future study, including collider studies of dark meson production and decay; indirect detection signals from annihilation; relic abundance estimates for both symmetric and asymmetric mechanisms; and direct detection through electromagnetic polarizability, a detailed study of which will appear in a companion paper.« less

Partially acoustic dark matter, interacting dark radiation, and large scale structure

NASA Astrophysics Data System (ADS)

Chacko, Zackaria; Cui, Yanou; Hong, Sungwoo; Okui, Takemichi; Tsai, Yuhsinz

2016-12-01

The standard paradigm of collisionless cold dark matter is in tension with measurements on large scales. In particular, the best fit values of the Hubble rate H 0 and the matter density perturbation σ 8 inferred from the cosmic microwave background seem inconsistent with the results from direct measurements. We show that both problems can be solved in a framework in which dark matter consists of two distinct components, a dominant component and a subdominant component. The primary component is cold and collisionless. The secondary component is also cold, but interacts strongly with dark radiation, which itself forms a tightly coupled fluid. The growth of density perturbations in the subdominant component is inhibited by dark acoustic oscillations due to its coupling to the dark radiation, solving the σ 8 problem, while the presence of tightly coupled dark radiation ameliorates the H 0 problem. The subdominant component of dark matter and dark radiation continue to remain in thermal equilibrium until late times, inhibiting the formation of a dark disk. We present an example of a simple model that naturally realizes this scenario in which both constituents of dark matter are thermal WIMPs. Our scenario can be tested by future stage-IV experiments designed to probe the CMB and large scale structure.

Partially acoustic dark matter, interacting dark radiation, and large scale structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chacko, Zackaria; Cui, Yanou; Hong, Sungwoo

The standard paradigm of collisionless cold dark matter is in tension with measurements on large scales. In particular, the best fit values of the Hubble rate H 0 and the matter density perturbation σ 8 inferred from the cosmic microwave background seem inconsistent with the results from direct measurements. We show that both problems can be solved in a framework in which dark matter consists of two distinct components, a dominant component and a subdominant component. The primary component is cold and collisionless. The secondary component is also cold, but interacts strongly with dark radiation, which itself forms a tightlymore » coupled fluid. The growth of density perturbations in the subdominant component is inhibited by dark acoustic oscillations due to its coupling to the dark radiation, solving the σ 8 problem, while the presence of tightly coupled dark radiation ameliorates the H 0 problem. The subdominant component of dark matter and dark radiation continue to remain in thermal equilibrium until late times, inhibiting the formation of a dark disk. We present an example of a simple model that naturally realizes this scenario in which both constituents of dark matter are thermal WIMPs. Our scenario can be tested by future stage-IV experiments designed to probe the CMB and large scale structure.« less

Partially acoustic dark matter, interacting dark radiation, and large scale structure

DOE PAGES

Chacko, Zackaria; Cui, Yanou; Hong, Sungwoo; ...

2016-12-21

The standard paradigm of collisionless cold dark matter is in tension with measurements on large scales. In particular, the best fit values of the Hubble rate H 0 and the matter density perturbation σ 8 inferred from the cosmic microwave background seem inconsistent with the results from direct measurements. We show that both problems can be solved in a framework in which dark matter consists of two distinct components, a dominant component and a subdominant component. The primary component is cold and collisionless. The secondary component is also cold, but interacts strongly with dark radiation, which itself forms a tightlymore » coupled fluid. The growth of density perturbations in the subdominant component is inhibited by dark acoustic oscillations due to its coupling to the dark radiation, solving the σ 8 problem, while the presence of tightly coupled dark radiation ameliorates the H 0 problem. The subdominant component of dark matter and dark radiation continue to remain in thermal equilibrium until late times, inhibiting the formation of a dark disk. We present an example of a simple model that naturally realizes this scenario in which both constituents of dark matter are thermal WIMPs. Our scenario can be tested by future stage-IV experiments designed to probe the CMB and large scale structure.« less

Chemical evolution of the gas in C-type shocks in dark clouds

NASA Astrophysics Data System (ADS)

Nesterenok, A. V.

2018-07-01

A magnetohydrodynamic model of a steady, transverse C-type shock in a dense molecular cloud is presented. A complete gas-grain chemical network is taken into account: the gas-phase chemistry, the adsorption of gas species on dust grains, various desorption mechanisms, the grain surface chemistry, the ion neutralization on dust grains, the sputtering of grain mantles. The population densities of energy levels of ions CI, CII and OI and molecules H2, CO, H2O are computed in parallel with the dynamical and chemical rate equations. The large velocity gradient approximation is used in the line radiative transfer calculations. The simulations consist of two steps: (i) modelling of the chemical and thermal evolution of a static molecular cloud and (ii) shock simulations. A comparison is made with the results of publicly available models of similar physical systems. The focus of the paper is on the chemical processing of gas material and ice mantles of dust grains by the shock. Sputtering of ice mantles takes place in the shock region close to the temperature peak of the neutral gas. At high shock speeds, molecules ejected from ice mantles are effectively destroyed in hot gas, and their survival time is low—of the order of dozens of years. After a passage of high-speed C-type shock, a zone of high abundance of atomic hydrogen appears in the cooling postshock gas that triggers formation of complex organic species such as methanol. It is shown that abundances of some complex organic molecules (COMs) in the postshock region can be much higher than in the preshock gas. These results are important for interpretation of observations of COMs in protostellar outflows.

MAPPING THE SHORES OF THE BROWN DWARF DESERT. II. MULTIPLE STAR FORMATION IN TAURUS-AURIGA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kraus, Adam L.; Ireland, Michael J.; Martinache, Frantz

2011-04-10

We have conducted a high-resolution imaging study of the Taurus-Auriga star-forming region in order to characterize the primordial outcome of multiple star formation and the extent of the brown dwarf desert. Our survey identified 16 new binary companions to primary stars with masses of 0.25-2.5 M{sub sun}, raising the total number of binary pairs (including components of high-order multiples) with separations of 3-5000 AU to 90. We find that {approx}2/3-3/4 of all Taurus members are multiple systems of two or more stars, while the other {approx}1/4-1/3 appear to have formed as single stars; the distribution of high-order multiplicity suggests thatmore » fragmentation into a wide binary has no impact on the subsequent probability that either component will fragment again. The separation distribution for solar-type stars (0.7-2.5 M{sub sun}) is nearly log-flat over separations of 3-5000 AU, but lower-mass stars (0.25-0.7 M{sub sun}) show a paucity of binary companions with separations of {approx}>200 AU. Across this full mass range, companion masses are well described with a linear-flat function; all system mass ratios (q = M{sub B} /M{sub A} ) are equally probable, apparently including substellar companions. Our results are broadly consistent with the two expected modes of binary formation (free-fall fragmentation on large scales and disk fragmentation on small scales), but the distributions provide some clues as to the epochs at which the companions are likely to form.« less

Cloud vertical profiles derived from CALIPSO and CloudSat and a comparison with MODIS derived clouds

NASA Astrophysics Data System (ADS)

Kato, S.; Sun-Mack, S.; Miller, W. F.; Rose, F. G.; Minnis, P.; Wielicki, B. A.; Winker, D. M.; Stephens, G. L.; Charlock, T. P.; Collins, W. D.; Loeb, N. G.; Stackhouse, P. W.; Xu, K.

2008-05-01

CALIPSO and CloudSat from the a-train provide detailed information of vertical distribution of clouds and aerosols. The vertical distribution of cloud occurrence is derived from one month of CALIPSO and CloudSat data as a part of the effort of merging CALIPSO, CloudSat and MODIS with CERES data. This newly derived cloud profile is compared with the distribution of cloud top height derived from MODIS on Aqua from cloud algorithms used in the CERES project. The cloud base from MODIS is also estimated using an empirical formula based on the cloud top height and optical thickness, which is used in CERES processes. While MODIS detects mid and low level clouds over the Arctic in April fairly well when they are the topmost cloud layer, it underestimates high- level clouds. In addition, because the CERES-MODIS cloud algorithm is not able to detect multi-layer clouds and the empirical formula significantly underestimates the depth of high clouds, the occurrence of mid and low-level clouds is underestimated. This comparison does not consider sensitivity difference to thin clouds but we will impose an optical thickness threshold to CALIPSO derived clouds for a further comparison. The effect of such differences in the cloud profile to flux computations will also be discussed. In addition, the effect of cloud cover to the top-of-atmosphere flux over the Arctic using CERES SSF and FLASHFLUX products will be discussed.

Searching for a dark photon with DarkLight

NASA Astrophysics Data System (ADS)

Corliss, R.; DarkLight Collaboration

2017-09-01

Despite compelling astrophysical evidence for the existence of dark matter in the universe, we have yet to positively identify it in any terrestrial experiment. If such matter is indeed particle in nature, it may have a new interaction as well, carried by a dark counterpart to the photon. The DarkLight experiment proposes to search for such a beyond-the-standard-model dark photon through complete reconstruction of the final states of electron-proton collisions. In order to accomplish this, the experiment requires a moderate-density target and a very high intensity, low energy electron beam. I describe DarkLight's approach and focus on the implications this has for the design of the experiment, which centers on the use of an internal gas target in Jefferson Lab's Low Energy Recirculating Facility. I also discuss upcoming beam tests, where we will place our target and solenoidal magnet in the beam for the first time.

Flight directions of passerine migrants in daylight and darkness: A radar and direct visual study

NASA Technical Reports Server (NTRS)

Gauthreaux, S. A., Jr.

1972-01-01

The application of radar and visual techniques to determine the migratory habits of passerine birds during daylight and darkness is discussed. The effects of wind on the direction of migration are examined. Scatter diagrams of daytime and nocturnal migration track directions correlated with wind direction are presented. It is concluded that migratory birds will fly at altitudes where wind direction and migratory direction are nearly the same. The effects of cloud cover and solar obscuration are considered negligible.

Milliarcsecond resolution infrared observations of young stars in Taurus and Ophiuchus

NASA Astrophysics Data System (ADS)

Simon, M.; Howell, R. R.; Longmore, A. J.; Wilking, B. A.; Peterson, D. M.; Chen, W.-P.

1987-09-01

The paper reports K-band lunar occultation observations of 18 stars in the Taurus and Ophiuchus star-forming regions. Four of the systems, HQ Tau, FF Tau, and SR 12 and ROX 31 in Ophiuchus, are binaries. Their separations, as observed in the projection along the directions of their occultations, range from about 5 to 186 milliarcseconds (mas). SR 12 was also observed by the technique of speckle interferometry in the J, H, and K bands. These observations, taken together with the lunar occultation results, show that SR 12 is an about 0.30 arcsec binary system whose components are late-type stars still approaching the main sequence. The lunar occultation observations reveal extended structure associated with two objects. Elias 29 in Ophiuchus contains a central component about 7 mas in diameter, that radiates most of the flux, and a much larger diffuse component. YLW 16A, also in Ophiuchus, is an extended object about 0.5 arcsec in diameter.

Dark Sky Protection and Education - Izera Dark Sky Park

NASA Astrophysics Data System (ADS)

Berlicki, Arkadiusz; Kolomanski, Sylwester; Mrozek, Tomasz; Zakowicz, Grzegorz

2015-08-01

Darkness of the night sky is a natural component of our environment and should be protected against negative effects of human activities. The night darkness is necessary for balanced life of plants, animals and people. Unfortunately, development of human civilization and technology has led to the substantial increase of the night-sky brightness and to situation where nights are no more dark in many areas of the World. This phenomenon is called "light pollution" and it can be rank among such problems as chemical pollution of air, water and soil. Besides the environment, the light pollution can also affect e.g. the scientific activities of astronomers - many observatories built in the past began to be located within the glow of city lights making the night observations difficult, or even impossible.In order to protect the natural darkness of nights many so-called "dark sky parks" were established, where the darkness is preserved, similar to typical nature reserves. The role of these parks is not only conservation but also education, supporting to make society aware of how serious the problem of the light pollution is.History of the dark sky areas in Europe began on November 4, 2009 in Jizerka - a small village situated in the Izera Mountains, when Izera Dark Sky Park (IDSP) was established - it was the first transboundary dark sky park in the World. The idea of establishing that dark sky park in the Izera Mountains originated from a need to give to the society in Poland and Czech Republic the knowledge about the light pollution. Izera Dark Sky Park is a part of the astro-tourism project "Astro Izery" that combines tourist attraction of Izera Valley and astronomical education under the wonderful starry Izera sky. Besides the IDSP, the project Astro Izery consists of the set of simple astronomical instruments (gnomon, sundial), natural educational trail "Solar System Model", and astronomical events for the public. In addition, twice a year we organize a 3-4 days

Genome wide scan for quantitative trait loci affecting tick resistance in cattle (Bos taurus × Bos indicus)

PubMed Central

2010-01-01

Background In tropical countries, losses caused by bovine tick Rhipicephalus (Boophilus) microplus infestation have a tremendous economic impact on cattle production systems. Genetic variation between Bos taurus and Bos indicus to tick resistance and molecular biology tools might allow for the identification of molecular markers linked to resistance traits that could be used as an auxiliary tool in selection programs. The objective of this work was to identify QTL associated with tick resistance/susceptibility in a bovine F2 population derived from the Gyr (Bos indicus) × Holstein (Bos taurus) cross. Results Through a whole genome scan with microsatellite markers, we were able to map six genomic regions associated with bovine tick resistance. For most QTL, we have found that depending on the tick evaluation season (dry and rainy) different sets of genes could be involved in the resistance mechanism. We identified dry season specific QTL on BTA 2 and 10, rainy season specific QTL on BTA 5, 11 and 27. We also found a highly significant genome wide QTL for both dry and rainy seasons in the central region of BTA 23. Conclusions The experimental F2 population derived from Gyr × Holstein cross successfully allowed the identification of six highly significant QTL associated with tick resistance in cattle. QTL located on BTA 23 might be related with the bovine histocompatibility complex. Further investigation of these QTL will help to isolate candidate genes involved with tick resistance in cattle. PMID:20433753

HUBBLE SPOTS NORTHERN HEMISPHERIC CLOUDS ON URANUS

NASA Technical Reports Server (NTRS)

2002-01-01

Using visible light, astronomers for the first time this century have detected clouds in the northern hemisphere of Uranus. The newest images, taken July 31 and Aug. 1, 1997 with NASA Hubble Space Telescope's Wide Field and Planetary Camera 2, show banded structure and multiple clouds. Using these images, Dr. Heidi Hammel (Massachusetts Institute of Technology) and colleagues Wes Lockwood (Lowell Observatory) and Kathy Rages (NASA Ames Research Center) plan to measure the wind speeds in the northern hemisphere for the first time. Uranus is sometimes called the 'sideways' planet, because its rotation axis is tipped more than 90 degrees from the planet's orbit around the Sun. The 'year' on Uranus lasts 84 Earth years, which creates extremely long seasons - winter in the northern hemisphere has lasted for nearly 20 years. Uranus has also been called bland and boring, because no clouds have been detectable in ground-based images of the planet. Even to the cameras of the Voyager spacecraft in 1986, Uranus presented a nearly uniform blank disk, and discrete clouds were detectable only in the southern hemisphere. Voyager flew over the planet's cloud tops near the dead of northern winter (when the northern hemisphere was completely shrouded in darkness). Spring has finally come to the northern hemisphere of Uranus. The newest images, both the visible-wavelength ones described here and those taken a few days earlier with the Near Infrared and Multi-Object Spectrometer (NICMOS) by Erich Karkoschka (University of Arizona), show a planet with banded structure and detectable clouds. Two images are shown here. The 'aqua' image (on the left) is taken at 5,470 Angstroms, which is near the human eye's peak response to wavelength. Color has been added to the image to show what a person on a spacecraft near Uranus might see. Little structure is evident at this wavelength, though with image-processing techniques, a small cloud can be seen near the planet's northern limb (rightmost

Physical and Chemical Properties of Protocluster Clumps and Massive Young Stellar Objects Associated to Infrared Dark Clouds

NASA Astrophysics Data System (ADS)

Gomez Gonzalez, Laura

2012-01-01

The study of high-mass stars is important not only because of the effects they produce in their environment through outflows, expanding HII regions, stellar winds, and eventually supernova shock waves, but also because they play a crucial role in estimating star formation rates in other galaxies. Although we have an accepted evolutionary scenario that explains (isolated) low-mass star formation, the processes that produce massive stars (M_star > 8 M_sol) and star clusters, especially their earliest stages, are not well understood. The newly discovered class of interstellar clouds now termed infrared dark clouds (IRDCs) represent excellent laboratories to study the earliest stages of high-mass star formation given that some of the clumps within them are known to have high masses (~100's M_sol), high densities (n > 10^5 cm^-3), and low temperatures (10-20K) as expected for the birthplaces of high-mass stars. Some questions remain unanswered: Do IRDCs harbor the very early stages of high-mass star formation, i.e., the pre-protocluster phase? If so, how do they compare with low-mass star formation sites? Is there chemical differentiation in IRDC clumps? What is the mass distribution of IRDCs? In this dissertation and for the first time, a catalog of 12529 IRDC candidates at 24 um has been created using archival data from the MIPSGAL/Spitzer survey, as a first step in searching for the massive pre-protocluster clumps. From this catalog, a sample of ~60 clumps has been selected in order to perform single-pointing observations with the IRAM 30m, Effelsberg 100m, and APEX 12m telescopes. One IRDC clump seems to be a promising candidate for being in the pre-protocluster phase. In addition, molecular line mapping observations have been performed on three clumps within IRDCs and a detailed chemical study of 10 molecular lines has been carried out. A larger difference in column densities and abundances has been found between these clumps and high-m! ass protostellar objects

Dynamical dark matter: A new framework for dark-matter physics

NASA Astrophysics Data System (ADS)

Dienes, Keith R.; Thomas, Brooks

2013-05-01

Although much remains unknown about the dark matter of the universe, one property is normally considered sacrosanct: dark matter must be stable well beyond cosmological time scales. However, a new framework for dark-matter physics has recently been proposed which challenges this assumption. In the "dynamical dark matter" (DDM) framework, the dark sector consists of a vast ensemble of individual dark-matter components with differing masses, lifetimes, and cosmological abundances. Moreover, the usual requirement of stability is replaced by a delicate balancing between lifetimes and cosmological abundances across the ensemble as a whole. As a result, it is possible for the DDM ensemble to remain consistent with all experimental and observational bounds on dark matter while nevertheless giving rise to collective behaviors which transcend those normally associated with traditional dark-matter candidates. These include a new, non-trivial darkmatter equation of state as well as potentially distinctive signatures in collider and direct-detection experiments. In this review article, we provide a self-contained introduction to the DDM framework and summarize some of the work which has recently been done in this area. We also present an explicit model within the DDM framework, and outline a number of ideas for future investigation.

Dark sector shining through 750 GeV dark Higgs boson at the LHC

NASA Astrophysics Data System (ADS)

Ko, P.; Nomura, Takaaki

2016-07-01

We consider a dark sector with SU(3)C × U(1)Y × U(1)X and three families of dark fermions that are chiral under dark U(1)X gauge symmetry, whereas scalar dark matter X is the SM singlet. U(1)X dark symmetry is spontaneously broken by nonzero VEV of dark Higgs field 〈 Φ 〉, generating the masses of dark fermions and dark photon Z‧. The resulting dark Higgs boson ϕ can be produced at the LHC by dark quark loop (involving 3 generations) and will decay into a pair of photon through charged dark fermion loop. Its decay width can be easily ∼ 45 GeV due to its possible decays into a pair of dark photon, which is not strongly constrained by the current LHC searches pp → ϕ →Z‧Z‧ followed by Z‧ decays into the SM fermion pairs. The scalar DM can achieve thermal relic density without conflict with direct detection bound or the invisible ϕ decay into a pair of DM.

Light chiral dark sector

DOE PAGES

Harigaya, Keisuke; Nomura, Yasunori

2016-08-11

An interesting possibility for dark matter is a scalar particle of mass of order 10 MeV-1 GeV, interacting with a U(1) gauge boson (dark photon) which mixes with the photon. We present a simple and natural model realizing this possibility. The dark matter arises as a composite pseudo-Nambu-Goldstone boson (dark pion) in a non-Abelian gauge sector, which also gives a mass to the dark photon. For a fixed non-Abelian gauge group, SU(N), and a U(1) charge of the constituent dark quarks, the model has only three free parameters: the dynamical scale of the non-Abelian gauge theory, the gauge coupling ofmore » the dark photon, and the mixing parameter between the dark and standard model photons. In particular, the gauge symmetry of the model does not allow any mass term for the dark quarks, and the stability of the dark pion is understood as a result of an accidental global symmetry. The model has a significant parameter space in which thermal relic dark pions comprise all of the dark matter, consistently with all experimental and cosmological constraints. In a corner of the parameter space, the discrepancy of the muon g-2 between experiments and the standard model prediction can also be ameliorated due to a loop contribution of the dark photon. Smoking-gun signatures of the model include a monophoton signal from the e +e - collision into a photon and a "dark rho meson." Observation of two processes in e +e - collision - the mode into the dark photon and that into the dark rho meson - would provide strong evidence for the model.« less

Light chiral dark sector

NASA Astrophysics Data System (ADS)

Harigaya, Keisuke; Nomura, Yasunori

2016-08-01

An interesting possibility for dark matter is a scalar particle of mass of order 10 MeV-1 GeV, interacting with a U (1 ) gauge boson (dark photon) which mixes with the photon. We present a simple and natural model realizing this possibility. The dark matter arises as a composite pseudo-Nambu-Goldstone boson (dark pion) in a non-Abelian gauge sector, which also gives a mass to the dark photon. For a fixed non-Abelian gauge group, S U (N ) , and a U (1 ) charge of the constituent dark quarks, the model has only three free parameters: the dynamical scale of the non-Abelian gauge theory, the gauge coupling of the dark photon, and the mixing parameter between the dark and standard model photons. In particular, the gauge symmetry of the model does not allow any mass term for the dark quarks, and the stability of the dark pion is understood as a result of an accidental global symmetry. The model has a significant parameter space in which thermal relic dark pions comprise all of the dark matter, consistently with all experimental and cosmological constraints. In a corner of the parameter space, the discrepancy of the muon g -2 between experiments and the standard model prediction can also be ameliorated due to a loop contribution of the dark photon. Smoking-gun signatures of the model include a monophoton signal from the e+e- collision into a photon and a "dark rho meson." Observation of two processes in e+e- collision—the mode into the dark photon and that into the dark rho meson—would provide strong evidence for the model.

Light chiral dark sector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harigaya, Keisuke; Nomura, Yasunori

An interesting possibility for dark matter is a scalar particle of mass of order 10 MeV-1 GeV, interacting with a U(1) gauge boson (dark photon) which mixes with the photon. We present a simple and natural model realizing this possibility. The dark matter arises as a composite pseudo-Nambu-Goldstone boson (dark pion) in a non-Abelian gauge sector, which also gives a mass to the dark photon. For a fixed non-Abelian gauge group, SU(N), and a U(1) charge of the constituent dark quarks, the model has only three free parameters: the dynamical scale of the non-Abelian gauge theory, the gauge coupling ofmore » the dark photon, and the mixing parameter between the dark and standard model photons. In particular, the gauge symmetry of the model does not allow any mass term for the dark quarks, and the stability of the dark pion is understood as a result of an accidental global symmetry. The model has a significant parameter space in which thermal relic dark pions comprise all of the dark matter, consistently with all experimental and cosmological constraints. In a corner of the parameter space, the discrepancy of the muon g-2 between experiments and the standard model prediction can also be ameliorated due to a loop contribution of the dark photon. Smoking-gun signatures of the model include a monophoton signal from the e +e - collision into a photon and a "dark rho meson." Observation of two processes in e +e - collision - the mode into the dark photon and that into the dark rho meson - would provide strong evidence for the model.« less

Rock elastic properties and near-surface structure at Taurus-Littrow. [strain measurement of lunar basalt and breccia

NASA Technical Reports Server (NTRS)

Trice, R.; Warren, N.; Anderson, O. L.

1974-01-01

Linear strain measurements are presented for two lunar basalts, 14310,82 and 71055,15 and one breccia, 15498,23 to 5 kb hydrostatic pressure. Compressional and shear acoustic velocities to 5 kb are also presented for the basalts, 14310,82 and 71055,15. These elastic properties, along with geological, seismological and rock mechanics considerations are consistent with a model of the structure of the Taurus-Littrow valley as follows, a thin surface regolith overlying a fractured mixture of basalt flows and ejecta material which in turn overlies a coherent breccia of highland ejecta debris.

Potential impact of microbial activity on the oxidant capacity and organic carbon budget in clouds

NASA Astrophysics Data System (ADS)

Vaïtilingom, Mickael; Deguillaume, Laurent; Vinatier, Virginie; Sancelme, Martine; Amato, Pierre; Chaumerliac, Nadine; Delort, Anne-Marie

2013-01-01

Within cloud water, microorganisms are metabolically active and, thus, are expected to contribute to the atmospheric chemistry. This article investigates the interactions between microorganisms and the reactive oxygenated species that are present in cloud water because these chemical compounds drive the oxidant capacity of the cloud system. Real cloud water samples with contrasting features (marine, continental, and urban) were taken from the puy de Dôme mountain (France). The samples exhibited a high microbial biodiversity and complex chemical composition. The media were incubated in the dark and subjected to UV radiation in specifically designed photo-bioreactors. The concentrations of H2O2, organic compounds, and the ATP/ADP ratio were monitored during the incubation period. The microorganisms remained metabolically active in the presence of ●OH radicals that were photo-produced from H2O2. This oxidant and major carbon compounds (formaldehyde and carboxylic acids) were biodegraded by the endogenous microflora. This work suggests that microorganisms could play a double role in atmospheric chemistry; first, they could directly metabolize organic carbon species, and second, they could reduce the available source of radicals through their oxidative metabolism. Consequently, molecules such as H2O2 would no longer be available for photochemical or other chemical reactions, which would decrease the cloud oxidant capacity.

Dark matter and neutrino mass from the smallest non-Abelian chiral dark sector

NASA Astrophysics Data System (ADS)

Berryman, Jeffrey M.; de Gouvêa, André; Kelly, Kevin J.; Zhang, Yue

2017-10-01

All pieces of concrete evidence for phenomena outside the standard model (SM)—neutrino masses and dark matter—are consistent with the existence of new degrees of freedom that interact very weakly, if at all, with those in the SM. We propose that these new degrees of freedom organize themselves into a simple dark sector, a chiral S U (3 )×S U (2 ) gauge theory with the smallest nontrivial fermion content. Similar to the SM, the dark S U (2 ) is spontaneously broken while the dark S U (3 ) confines at low energies. At the renormalizable level, the dark sector contains massless fermions—dark leptons—and stable massive particles—dark protons. We find that dark protons with masses between 10 and 100 TeV satisfy all current cosmological and astrophysical observations concerning dark matter even if dark protons are a symmetric thermal relic. The dark leptons play the role of right-handed neutrinos and allow simple realizations of the seesaw mechanism or the possibility that neutrinos are Dirac fermions. In the latter case, neutrino masses are also parametrically different from charged-fermion masses and the lightest neutrino is predicted to be massless. Since the new "neutrino" and "dark-matter" degrees of freedom interact with one another, these two new-physics phenomena are intertwined. Dark leptons play a nontrivial role in early Universe cosmology while indirect searches for dark matter involve, decisively, dark-matter annihilations into dark leptons. These, in turn, may lead to observable signatures at high-energy neutrino and gamma-ray observatories, especially once one accounts for the potential Sommerfeld enhancement of the annihilation cross section, derived from the low-energy dark-sector effective theory, a possibility we explore quantitatively in some detail.

Molecular Cloud Evolution VI. Measuring cloud ages

NASA Astrophysics Data System (ADS)

Vázquez-Semadeni, Enrique; Zamora-Avilés, Manuel; Galván-Madrid, Roberto; Forbrich, Jan

2018-06-01

In previous contributions, we have presented an analytical model describing the evolution of molecular clouds (MCs) undergoing hierarchical gravitational contraction. The cloud's evolution is characterized by an initial increase in its mass, density, and star formation rate (SFR) and efficiency (SFE) as it contracts, followed by a decrease of these quantities as newly formed massive stars begin to disrupt the cloud. The main parameter of the model is the maximum mass reached by the cloud during its evolution. Thus, specifying the instantaneous mass and some other variable completely determines the cloud's evolutionary stage. We apply the model to interpret the observed scatter in SFEs of the cloud sample compiled by Lada et al. as an evolutionary effect so that, although clouds such as California and Orion A have similar masses, they are in very different evolutionary stages, causing their very different observed SFRs and SFEs. The model predicts that the California cloud will eventually reach a significantly larger total mass than the Orion A cloud. Next, we apply the model to derive estimated ages of the clouds since the time when approximately 25% of their mass had become molecular. We find ages from ˜1.5 to 27 Myr, with the most inactive clouds being the youngest. Further predictions of the model are that clouds with very low SFEs should have massive atomic envelopes constituting the majority of their gravitational mass, and that low-mass clouds (M ˜ 103-104M⊙) end their lives with a mini-burst of star formation, reaching SFRs ˜300-500 M⊙ Myr-1. By this time, they have contracted to become compact (˜1 pc) massive star-forming clumps, in general embedded within larger GMCs.

Three-wave resonant interactions: Multi-dark-dark-dark solitons, breathers, rogue waves, and their interactions and dynamics

NASA Astrophysics Data System (ADS)

Zhang, Guoqiang; Yan, Zhenya; Wen, Xiao-Yong

2018-03-01

We investigate three-wave resonant interactions through both the generalized Darboux transformation method and numerical simulations. Firstly, we derive a simple multi-dark-dark-dark-soliton formula through the generalized Darboux transformation. Secondly, we use the matrix analysis method to avoid the singularity of transformed potential functions and to find the general nonsingular breather solutions. Moreover, through a limit process, we deduce the general rogue wave solutions and give a classification by their dynamics including bright, dark, four-petals, and two-peaks rogue waves. Ever since the coexistence of dark soliton and rogue wave in non-zero background, their interactions naturally become a quite appealing topic. Based on the N-fold Darboux transformation, we can derive the explicit solutions to depict their interactions. Finally, by performing extensive numerical simulations we can predict whether these dark solitons and rogue waves are stable enough to propagate. These results can be available for several physical subjects such as fluid dynamics, nonlinear optics, solid state physics, and plasma physics.

Low-Cloud Feedbacks from Cloud-Controlling Factors: A Review

DOE PAGES

Klein, Stephen A.; Hall, Alex; Norris, Joel R.; ...

2017-10-24

Here, the response to warming of tropical low-level clouds including both marine stratocumulus and trade cumulus is a major source of uncertainty in projections of future climate. Climate model simulations of the response vary widely, reflecting the difficulty the models have in simulating these clouds. These inadequacies have led to alternative approaches to predict low-cloud feedbacks. Here, we review an observational approach that relies on the assumption that observed relationships between low clouds and the “cloud-controlling factors” of the large-scale environment are invariant across time-scales. With this assumption, and given predictions of how the cloud-controlling factors change with climate warming,more » one can predict low-cloud feedbacks without using any model simulation of low clouds. We discuss both fundamental and implementation issues with this approach and suggest steps that could reduce uncertainty in the predicted low-cloud feedback. Recent studies using this approach predict that the tropical low-cloud feedback is positive mainly due to the observation that reflection of solar radiation by low clouds decreases as temperature increases, holding all other cloud-controlling factors fixed. The positive feedback from temperature is partially offset by a negative feedback from the tendency for the inversion strength to increase in a warming world, with other cloud-controlling factors playing a smaller role. A consensus estimate from these studies for the contribution of tropical low clouds to the global mean cloud feedback is 0.25 ± 0.18 W m –2 K –1 (90% confidence interval), suggesting it is very unlikely that tropical low clouds reduce total global cloud feedback. Because the prediction of positive tropical low-cloud feedback with this approach is consistent with independent evidence from low-cloud feedback studies using high-resolution cloud models, progress is being made in reducing this key climate uncertainty.« less

Low-Cloud Feedbacks from Cloud-Controlling Factors: A Review

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klein, Stephen A.; Hall, Alex; Norris, Joel R.

Here, the response to warming of tropical low-level clouds including both marine stratocumulus and trade cumulus is a major source of uncertainty in projections of future climate. Climate model simulations of the response vary widely, reflecting the difficulty the models have in simulating these clouds. These inadequacies have led to alternative approaches to predict low-cloud feedbacks. Here, we review an observational approach that relies on the assumption that observed relationships between low clouds and the “cloud-controlling factors” of the large-scale environment are invariant across time-scales. With this assumption, and given predictions of how the cloud-controlling factors change with climate warming,more » one can predict low-cloud feedbacks without using any model simulation of low clouds. We discuss both fundamental and implementation issues with this approach and suggest steps that could reduce uncertainty in the predicted low-cloud feedback. Recent studies using this approach predict that the tropical low-cloud feedback is positive mainly due to the observation that reflection of solar radiation by low clouds decreases as temperature increases, holding all other cloud-controlling factors fixed. The positive feedback from temperature is partially offset by a negative feedback from the tendency for the inversion strength to increase in a warming world, with other cloud-controlling factors playing a smaller role. A consensus estimate from these studies for the contribution of tropical low clouds to the global mean cloud feedback is 0.25 ± 0.18 W m –2 K –1 (90% confidence interval), suggesting it is very unlikely that tropical low clouds reduce total global cloud feedback. Because the prediction of positive tropical low-cloud feedback with this approach is consistent with independent evidence from low-cloud feedback studies using high-resolution cloud models, progress is being made in reducing this key climate uncertainty.« less

Baryonic dark clusters in galactic halos and their observable consequences

NASA Technical Reports Server (NTRS)

Wasserman, Ira; Salpeter, Edwin E.

1994-01-01

We consider the possibility that approximately 10% of the mass of a typical galaxy halo is in the form of massive (approximately 10(exp 7) solar masses), compact (escape speeds approximately 100 km/s) baryonic clusters made of neutron stars (approximately 10% by mass), black holes (less than or approximately equal to 1%) and brown dwarfs, asteroids, and other low-mass debris (approximately 90%). These general properties are consistent with several different observational and phenomenological constraints on cluster properties subject to the condition that neutron stars comprise approximately 1% of the total halo mass. Such compact, dark clusters could be the sites of a variety of collisional phenomena involving neutron stars. We find that integrated out to the Hubble distance approximately one neutron star-neutron star or neutron star-black hole collision occurs daily. Of order 0.1-1 asteroid-neutron star collisions may also happen daily in the halo of the Milky Way if there is roughly equal cluster mass per logarithmic particle mass interval between asteroids and brown dwarfs. These event rates are comparable to the frequency of gamma-ray burst detections by the Burst and Transient Source Experiment (BATSE) on the Compton Observatory, implying that if dark halo clusters are the sites of most gamma-ray bursts, perhaps approximately 90% of all bursts are extragalactic, but approximately 10% are galactic. It is possible that dark clusters of the kind discussed here could be detected directly by the Infrared Space Observatory (ISO) or Space Infrared Telescope Facility (SIRTF). If the clusters considered in this paper exist, they should produce spatially correlated gravitational microlensing of stars in the Large Magellanic Cloud (LMC). If 10% of the halo is in the form of dark baryonic clusters, and the remaining 90% is in brown dwarfs and other dark objects which are either unclustered or collected into low-mass clusters, then we expect that two events within

Cloud Spirals and Outflow in Tropical Storm Katrina

NASA Technical Reports Server (NTRS)

2005-01-01

On Tuesday, August 30, 2005, NASA's Multi-angle Imaging SpectroRadiometer retrieved cloud-top heights and cloud-tracked wind velocities for Tropical Storm Katrina, as the center of the storm was situated over the Tennessee valley. At this time Katrina was weakening and no longer classified as a hurricane, and would soon become an extratropical depression. Measurements such as these can help atmospheric scientists compare results of computer-generated hurricane simulations with observed conditions, ultimately allowing them to better represent and understand physical processes occurring in hurricanes.

Because air currents are influenced by the Coriolis force (caused by the rotation of the Earth), Northern Hemisphere hurricanes are characterized by an inward counterclockwise (cyclonic) rotation towards the center. It is less widely known that, at high altitudes, outward-spreading bands of cloud rotate in a clockwise (anticyclonic) direction. The image on the left shows the retrieved cloud-tracked winds as red arrows superimposed across the natural color view from MISR's nadir (vertical-viewing) camera. Both the counter-clockwise motion for the lower-level storm clouds and the clockwise motion for the upper clouds are apparent in these images. The speeds for the clockwise upper level winds have typical values between 40 and 45 m/s (144-162 km/hr). The low level counterclockwise winds have typical values between 7 and 24 m/s (25-86 km/hr), weakening with distance from the storm center. The image on the right displays the cloud-top height retrievals. Areas where cloud heights could not be retrieved are shown in dark gray. Both the wind velocity vectors and the cloud-top height field were produced by automated computer recognition of displacements in spatial features within successive MISR images acquired at different view angles and at slightly different times.

The Multi-angle Imaging SpectroRadiometer observes the daylit Earth continuously, viewing the

Multi-layer Clouds Over the South Indian Ocean

NASA Technical Reports Server (NTRS)

2003-01-01

The complex structure and beauty of polar clouds are highlighted by these images acquired by the Multi-angle Imaging SpectroRadiometer (MISR) on April 23, 2003. These clouds occur at multiple altitudes and exhibit a noticeable cyclonic circulation over the Southern Indian Ocean, to the north of Enderbyland, East Antarctica.

The image at left was created by overlying a natural-color view from MISR's downward-pointing (nadir) camera with a color-coded stereo height field. MISR retrieves heights by a pattern recognition algorithm that utilizes multiple view angles to derive cloud height and motion. The opacity of the height field was then reduced until the field appears as a translucent wash over the natural-color image. The resulting purple, cyan and green hues of this aesthetic display indicate low, medium or high altitudes, respectively, with heights ranging from less than 2 kilometers (purple) to about 8 kilometers (green). In the lower right corner, the edge of the Antarctic coastline and some sea ice can be seen through some thin, high cirrus clouds.

The right-hand panel is a natural-color image from MISR's 70-degree backward viewing camera. This camera looks backwards along the path of Terra's flight, and in the southern hemisphere the Sun is in front of this camera. This perspective causes the cloud-tops to be brightly outlined by the sun behind them, and enhances the shadows cast by clouds with significant vertical structure. An oblique observation angle also enhances the reflection of light by atmospheric particles, and accentuates the appearance of polar clouds. The dark ocean and sea ice that were apparent through the cirrus clouds at the bottom right corner of the nadir image are overwhelmed by the brightness of these clouds at the oblique view.

The Multi-angle Imaging SpectroRadiometer observes the daylit Earth continuously from pole to pole, and every 9 days views the entire globe between 82 degrees north and 82 degrees south latitude

The 2010-2011 Revival of Jupiter's South Equatorial Belt: Perturbations of Temperatures, Clouds and Composition from Infrared Observations

NASA Technical Reports Server (NTRS)

Orton, G.; Fletcher, L.; Yanamandra-Fisher, P.; Sanchez-Lavega, A.; Perez-Hoyos, S.; Baines, K.; de Pater, I.; Wong, M.; Goetz, R.; Valkov, S.;

The Smith Cloud: surviving a high-speed transit of the Galactic disc

NASA Astrophysics Data System (ADS)

Tepper-García, Thor; Bland-Hawthorn, Joss

2018-02-01

The origin and survival of the Smith high-velocity H I cloud has so far defied explanation. This object has several remarkable properties: (i) its prograde orbit is ≈100 km s-1 faster than the underlying Galactic rotation; (ii) its total gas mass (≳ 4 × 106 M⊙) exceeds the mass of all other high-velocity clouds (HVCs) outside of the Magellanic Stream; (iii) its head-tail morphology extends to the Galactic H I disc, indicating some sort of interaction. The Smith Cloud's kinetic energy rules out models based on ejection from the disc. We construct a dynamically self-consistent, multi-phase model of the Galaxy with a view to exploring whether the Smith Cloud can be understood in terms of an infalling, compact HVC that has transited the Galactic disc. We show that while a dark-matter (DM) free HVC of sufficient mass and density can reach the disc, it does not survive the transit. The most important ingredient to survival during a transit is a confining DM subhalo around the cloud; radiative gas cooling and high spatial resolution (≲ 10pc) are also essential. In our model, the cloud develops a head-tail morphology within ∼10 Myr before and after its first disc crossing; after the event, the tail is left behind and accretes on to the disc within ∼400 Myr. In our interpretation, the Smith Cloud corresponds to a gas 'streamer' that detaches, falls back and fades after the DM subhalo, distorted by the disc passage, has moved on. We conclude that subhaloes with MDM ≲ 109 M⊙ have accreted ∼109 M⊙ of gas into the Galaxy over cosmic time - a small fraction of the total baryon budget.

Results from the DarkSide-50 Dark Matter Experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fan, Alden

2016-01-01

While there is tremendous astrophysical and cosmological evidence for dark matter, its precise nature is one of the most significant open questions in modern physics. Weakly interacting massive particles (WIMPs) are a particularly compelling class of dark matter candidates with masses of the order 100 GeV and couplings to ordinary matter at the weak scale. Direct detection experiments are aiming to observe the low energy (<100 keV) scattering of dark matter off normal matter. With the liquid noble technology leading the way in WIMP sensitivity, no conclusive signals have been observed yet. The DarkSide experiment is looking for WIMP darkmore » matter using a liquid argon target in a dual-phase time projection chamber located deep underground at Gran Sasso National Laboratory (LNGS) in Italy. Currently filled with argon obtained from underground sources, which is greatly reduced in radioactive 39Ar, DarkSide-50 recently made the most sensitive measurement of the 39Ar activity in underground argon and used it to set the strongest WIMP dark matter limit using liquid argon to date. This work describes the full chain of analysis used to produce the recent dark matter limit, from reconstruction of raw data to evaluation of the final exclusion curve. The DarkSide- 50 apparatus is described in detail, followed by discussion of the low level reconstruction algorithms. The algorithms are then used to arrive at three broad analysis results: The electroluminescence signals in DarkSide-50 are used to perform a precision measurement of ii longitudinal electron diffusion in liquid argon. A search is performed on the underground argon data to identify the delayed coincidence signature of 85Kr decays to the 85mRb state, a crucial ingredient in the measurement of the 39Ar activity in the underground argon. Finally, a full description of the WIMP search is given, including development of cuts, efficiencies, energy scale, and exclusion curve in the WIMP mass vs. spin

Jupiter's High-Altitude Clouds

NASA Technical Reports Server (NTRS)

2007-01-01

The New Horizons Multispectral Visible Imaging Camera (MVIC) snapped this incredibly detailed picture of Jupiter's high-altitude clouds starting at 06:00 Universal Time on February 28, 2007, when the spacecraft was only 2.3 million kilometers (1.4 million miles) from the solar system's largest planet. Features as small as 50 kilometers (30 miles) are visible. The image was taken through a narrow filter centered on a methane absorption band near 890 nanometers, a considerably redder wavelength than what the eye can see. Images taken through this filter preferentially pick out clouds that are relatively high in the sky of this gas giant planet because sunlight at the wavelengths transmitted by the filter is completely absorbed by the methane gas that permeates Jupiter's atmosphere before it can reach the lower clouds.

The image reveals a range of diverse features. The south pole is capped with a haze of small particles probably created by the precipitation of charged particles into the polar regions during auroral activity. Just north of the cap is a well-formed anticyclonic vortex with rising white thunderheads at its core. Slightly north of the vortex are the tendrils of some rather disorganized storms and more pinpoint-like thunderheads. The dark 'measles' that appear a bit farther north are actually cloud-free regions where light is completely absorbed by the methane gas and essentially disappears from view. The wind action considerably picks up in the equatorial regions where giant plumes are stretched into a long wave pattern. Proceeding north of the equator, cirrus-like clouds are shredded by winds reaching speeds of up to 400 miles per hour, and more pinpoint-like thunderheads are visible. Although some of the famous belt and zone structure of Jupiter's atmosphere is washed out when viewed at this wavelength, the relatively thin North Temperate Belt shows up quite nicely, as does a series of waves just north of the belt. The north polar region of

Stratocumulus Cloud Top Radiative Cooling and Cloud Base Updraft Speeds

NASA Astrophysics Data System (ADS)

Kazil, J.; Feingold, G.; Balsells, J.; Klinger, C.

2017-12-01

Cloud top radiative cooling is a primary driver of turbulence in the stratocumulus-topped marine boundary. A functional relationship between cloud top cooling and cloud base updraft speeds may therefore exist. A correlation of cloud top radiative cooling and cloud base updraft speeds has been recently identified empirically, providing a basis for satellite retrieval of cloud base updraft speeds. Such retrievals may enable analysis of aerosol-cloud interactions using satellite observations: Updraft speeds at cloud base co-determine supersaturation and therefore the activation of cloud condensation nuclei, which in turn co-determine cloud properties and precipitation formation. We use large eddy simulation and an off-line radiative transfer model to explore the relationship between cloud-top radiative cooling and cloud base updraft speeds in a marine stratocumulus cloud over the course of the diurnal cycle. We find that during daytime, at low cloud water path (CWP < 50 g m-2), cloud base updraft speeds and cloud top cooling are well-correlated, in agreement with the reported empirical relationship. During the night, in the absence of short-wave heating, CWP builds up (CWP > 50 g m-2) and long-wave emissions from cloud top saturate, while cloud base heating increases. In combination, cloud top cooling and cloud base updrafts become weakly anti-correlated. A functional relationship between cloud top cooling and cloud base updraft speed can hence be expected for stratocumulus clouds with a sufficiently low CWP and sub-saturated long-wave emissions, in particular during daytime. At higher CWPs, in particular at night, the relationship breaks down due to saturation of long-wave emissions from cloud top.

NASA Finds Direct Proof of Dark Matter

NASA Astrophysics Data System (ADS)

2006-08-01

Dark matter and normal matter have been wrenched apart by the tremendous collision of two large clusters of galaxies. The discovery, using NASA's Chandra X-ray Observatory and other telescopes, gives direct evidence for the existence of dark matter. "This is the most energetic cosmic event, besides the Big Bang, which we know about," said team member Maxim Markevitch of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. Lensing Illustration Gravitational Lensing Explanation These observations provide the strongest evidence yet that most of the matter in the universe is dark. Despite considerable evidence for dark matter, some scientists have proposed alternative theories for gravity where it is stronger on intergalactic scales than predicted by Newton and Einstein, removing the need for dark matter. However, such theories cannot explain the observed effects of this collision. "A universe that's dominated by dark stuff seems preposterous, so we wanted to test whether there were any basic flaws in our thinking," said Doug Clowe of the University of Arizona at Tucson, and leader of the study. "These results are direct proof that dark matter exists." Animation of Cluster Collision Animation of Cluster Collision In galaxy clusters, the normal matter, like the atoms that make up the stars, planets, and everything on Earth, is primarily in the form of hot gas and stars. The mass of the hot gas between the galaxies is far greater than the mass of the stars in all of the galaxies. This normal matter is bound in the cluster by the gravity of an even greater mass of dark matter. Without dark matter, which is invisible and can only be detected through its gravity, the fast-moving galaxies and the hot gas would quickly fly apart. The team was granted more than 100 hours on the Chandra telescope to observe the galaxy cluster 1E0657-56. The cluster is also known as the bullet cluster, because it contains a spectacular bullet-shaped cloud of hundred