X ray archeology in the Coma cluster

NASA Technical Reports Server (NTRS)

White, Simon D. M.; Briel, Ulrich G.; Henry, J. Patrick

1993-01-01

Images of X-ray emission from hot gas within the Coma cluster of galaxies are presented. These maps, made with the Rosat satellite, have high signal to noise ratio and allow cluster structure to be analyzed in unprecedented detail. They show greater structural irregularity than could be anticipated from earlier observations of Coma. Emission is detected from a number of bright cluster galaxies in addition to the two known previously. In four cases there is evidence that these galaxies lie at the center of an extended subconcentration within the cluster, possibly the remnant of their associated groups. For at least two galaxies the images show direct evidence for ongoing disruption of their gaseous atmosphere. The luminosity associated with these galaxies is comparable to that detected around similar ellipticals in much poorer environments. Emission is easily detected and appears to become more regular at large radii. The data show that this archetype of a rich and regular galaxy cluster was formed by the merging of several distinct subunits which are not yet fully destroyed.

Isothermality of the gas in the Coma cluster

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

Hughes, J.P.; Yamashita, K.; Okumura, Y.

1988-04-01

The high-quality X-ray spectrum of the Coma cluster observed by the Japanese satelite Tenma in conjunction with imaging data from the Einstein Observatory was used to explore the temperature distribution of the cluster gas. It is found that pure polytropic models are inadequate to describe this temperature distribution. Instead, a hybrid model is proposed consisting of a central isothermal region surrounded by a polytropic distribution. It is shown that as much as 75 percent of the global emission may come from the isothermal component. 30 references.

DEEP ULTRAVIOLET LUMINOSITY FUNCTIONS AT THE INFALL REGION OF THE COMA CLUSTER

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

Hammer, D. M.; Hornschemeier, A. E.; Jenkins, L.

2012-02-01

We have used deep GALEX observations at the infall region of the Coma cluster to measure the faintest ultraviolet (UV) luminosity functions (LFs) presented for a rich galaxy cluster thus far. The Coma UV LFs are measured to M{sub UV} = -10.5 in the GALEX FUV and NUV bands, or 3.5 mag fainter than previous studies, and reach the dwarf early-type galaxy population in Coma for the first time. The Schechter faint-end slopes ({alpha} Almost-Equal-To -1.39 in both GALEX bands) are shallower than reported in previous Coma UV LF studies owing to a flatter LF at faint magnitudes. A Gaussian-plus-Schechtermore » model provides a slightly better parameterization of the UV LFs resulting in a faint-end slope of {alpha} Almost-Equal-To -1.15 in both GALEX bands. The two-component model gives faint-end slopes shallower than {alpha} = -1 (a turnover) for the LFs constructed separately for passive and star-forming galaxies. The UV LFs for star-forming galaxies show a turnover at M{sub UV} Almost-Equal-To -14 owing to a deficit of dwarf star-forming galaxies in Coma with stellar masses below M{sub *} = 10{sup 8} M{sub Sun }. A similar turnover is identified in recent UV LFs measured for the Virgo cluster suggesting this may be a common feature of local galaxy clusters, whereas the field UV LFs continue to rise at faint magnitudes. We did not identify an excess of passive galaxies as would be expected if the missing dwarf star-forming galaxies were quenched inside the cluster. In fact, the LFs for both dwarf passive and star-forming galaxies show the same turnover at faint magnitudes. We discuss the possible origin of the missing dwarf star-forming galaxies in Coma and their expected properties based on comparisons to local field galaxies.« less

Deep UV Luminosity Functions at the Infall Region of the Coma Cluster

NASA Technical Reports Server (NTRS)

Hammer, D. M.; Hornschemeier, A. E.; Salim, S.; Smith, R.; Jenkins, L.; Mobasher, B.; Miller, N.; Ferguson, H.

2011-01-01

We have used deep GALEX observations at the infall region of the Coma cluster to measure the faintest UV luminosity functions (LFs) presented for a rich galaxy cluster thus far. The Coma UV LFs are measured to M(sub uv) = -10.5 in the GALEX FUV and NUV bands, or 3.5 mag fainter than previous studies, and reach the dwarf early-type galaxy population in Coma for the first time. The Schechter faint-end slopes (alpha approximately equal to -1.39 in both GALEX bands) are shallower than reported in previous Coma UV LF studies owing to a flatter LF at faint magnitudes. A Gaussian-plus-Schechter model provides a slightly better parametrization of the UV LFs resulting in a faint-end slope of alpha approximately equal to -1.15 in both GALEX bands. The two-component model gives faint-end slopes shallower than alpha = -1 (a turnover) for the LFs constructed separately for passive and star forming galaxies. The UV LFs for star forming galaxies show a turnover at M(sub UV) approximately equal to -14 owing to a deficit of dwarf star forming galaxies in Coma with stellar masses below M(sub *) = 10(sup 8) solar mass. A similar turnover is identified in recent UV LFs measured for the Virgo cluster suggesting this may be a common feature of local galaxy clusters, whereas the field UV LFs continue to rise at faint magnitudes. We did not identify an excess of passive galaxies as would be expected if the missing dwarf star forming galaxies were quenched inside the cluster. In fact, the LFs for both dwarf passive and star forming galaxies show the same turnover at faint magnitudes. We discuss the possible origin of the missing dwarf star forming galaxies in Coma and their expected properties based on comparisons to local field galaxies.

Origins of ultra-diffuse galaxies in the Coma cluster - I. Constraints from velocity phase-space

NASA Astrophysics Data System (ADS)

Alabi, Adebusola; Ferré-Mateu, Anna; Romanowsky, Aaron J.; Brodie, Jean; Forbes, Duncan A.; Wasserman, Asher; Bellstedt, Sabine; Martín-Navarro, Ignacio; Pandya, Viraj; Stone, Maria B.; Okabe, Nobuhiro

2018-06-01

We use Keck/DEIMOS spectroscopy to confirm the cluster membership of 16 ultra-diffuse galaxies (UDGs) in the Coma cluster, bringing the total number of spectroscopically confirmed UDGs from the Yagi et al. (Y16) catalog to 25. We also identify a new cluster background UDG, confirming that most (˜95 per cent) of the UDGs in the Y16 catalog belong to the Coma cluster. In this pilot study of Coma UDGs in velocity phase-space, we find evidence of a diverse origin for Coma cluster UDGs, similar to normal dwarf galaxies. Some UDGs in our sample are consistent with being late infalls into the cluster environment while some may have been in the cluster for ≥8 Gyr. The late infallen UDGs have higher absolute relative line-of-sight velocities, bluer optical colors, and within the projected cluster core, are smaller in size, compared to the early infalls. The early infall UDGs, which may also have formed in-situ, have been in the cluster environment for as long as the most luminous galaxies in the Coma cluster and they may be failed galaxies which experienced star formation quenching at earlier epochs.

Dwarfs in Coma Cluster

NASA Technical Reports Server (NTRS)

2007-01-01

[figure removed for brevity, see original site] Click on image for larger poster version

This false-color mosaic of the central region of the Coma cluster combines infrared and visible-light images to reveal thousands of faint objects (green). Follow-up observations showed that many of these objects, which appear here as faint green smudges, are dwarf galaxies belonging to the cluster. Two large elliptical galaxies, NGC 4889 and NGC 4874, dominate the cluster's center. The mosaic combines visible-light data from the Sloan Digital Sky Survey (color coded blue) with long- and short-wavelength infrared views (red and green, respectively) from NASA's Spitzer Space Telescope.

X-ray archaeology in the Coma cluster

NASA Technical Reports Server (NTRS)

White, Simon D. M.; Briel, Ulrich G.; Henry, J. P.

1993-01-01

We present images of X-ray emission from hot gas within the Coma cluster of galaxies. These maps, made with the ROSAT satellite, have much higher SNR than any previous X-ray image of a galaxy cluster, and allow cluster structure to be analyzed in unprecedented detail. They show greater structural irregularity than might have been anticipated from earlier observations of Coma. Emission is detected from a number of bright cluster galaxies in addition to the two known previously. In four cases, there is evidence that these galaxies lie at the center of an extended subconcentration within the cluster, possibly the remnant of their associated groups. For at least two galaxies, the images show direct evidence for ongoing disruption of their gaseous atmosphere. The luminosity associated with these galaxies is comparable to that detected around similar ellipticals in much poorer environments. Emission is easily detected to the limit of our field, about 1 deg from the cluster center, and appears to become more regular at large radii. The data show clearly that this archetype of a rich and regular galaxy cluster was, in fact, formed by the merging of several distinct subunits which are not yet fully destroyed.

The role of Dark Matter sub-halos in the non-thermal emission of galaxy clusters

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

Marchegiani, Paolo; Colafrancesco, Sergio, E-mail: Paolo.Marchegiani@wits.ac.za, E-mail: Sergio.Colafrancesco@wits.ac.za

2016-11-01

Annihilation of Dark Matter (DM) particles has been recognized as one of the possible mechanisms for the production of non-thermal particles and radiation in galaxy clusters. Previous studies have shown that, while DM models can reproduce the spectral properties of the radio halo in the Coma cluster, they fail in reproducing the shape of the radio halo surface brightness because they produce a shape that is too concentrated towards the center of the cluster with respect to the observed one. However, in previous studies the DM distribution was modeled as a single spherically symmetric halo, while the DM distribution inmore » Coma is found to have a complex and elongated shape. In this work we calculate a range of non-thermal emissions in the Coma cluster by using the observed distribution of DM sub-halos. We find that, by including the observed sub-halos in the DM model, we obtain a radio surface brightness with a shape similar to the observed one, and that the sub-halos boost the radio emission by a factor between 5 and 20%, thus allowing to reduce the gap between the annihilation cross section required to reproduce the radio halo flux and the upper limits derived from other observations, and that this gap can be explained by realistic values of the boosting factor due to smaller substructures. Models with neutralino mass of 9 GeV and composition τ{sup +} τ{sup −}, and mass of 43 GeV and composition b b-bar can fit the radio halo spectrum using the observed properties of the magnetic field in Coma, and do not predict a gamma-ray emission in excess compared to the recent Fermi-LAT upper limits. These findings make these DM models viable candidate to explain the origin of radio halos in galaxy clusters, avoiding the problems connected to the excessive gamma-ray emission expected from proton acceleration in most of the currently proposed models, where the acceleration of particles is directly or indirectly connected to events related to clusters merging. Therefore, DM models deserve to be better studied both from the theoretical and observational sides; the best spectral bands where it is possible to obtain better information are the radio and the gamma-ray bands, while we do not expect a strong emission in the X-ray band.« less

Thermodynamics of the Coma Cluster Outskirts

NASA Astrophysics Data System (ADS)

Simionescu, A.; Werner, N.; Urban, O.; Allen, S. W.; Fabian, A. C.; Mantz, A.; Matsushita, K.; Nulsen, P. E. J.; Sanders, J. S.; Sasaki, T.; Sato, T.; Takei, Y.; Walker, S. A.

2013-09-01

We present results from a large mosaic of Suzaku observations of the Coma Cluster, the nearest and X-ray brightest hot (~8 keV), dynamically active, non-cool core system, focusing on the thermodynamic properties of the intracluster medium on large scales. For azimuths not aligned with an infalling subcluster toward the southwest, our measured temperature and X-ray brightness profiles exhibit broadly consistent radial trends, with the temperature decreasing from about 8.5 keV at the cluster center to about 2 keV at a radius of 2 Mpc, which is the edge of our detection limit. The southwest merger significantly boosts the surface brightness, allowing us to detect X-ray emission out to ~2.2 Mpc along this direction. Apart from the southwestern infalling subcluster, the surface brightness profiles show multiple edges around radii of 30-40 arcmin. The azimuthally averaged temperature profile, as well as the deprojected density and pressure profiles, all show a sharp drop consistent with an outwardly-propagating shock front located at 40 arcmin, corresponding to the outermost edge of the giant radio halo observed at 352 MHz with the Westerbork Synthesis Radio Telescope. The shock front may be powering this radio emission. A clear entropy excess inside of r 500 reflects the violent merging events linked with these morphological features. Beyond r 500, the entropy profiles of the Coma Cluster along the relatively relaxed directions are consistent with the power-law behavior expected from simple models of gravitational large-scale structure formation. The pressure is also in agreement at these radii with the expected values measured from Sunyaev-Zel'dovich data from the Planck satellite. However, due to the large uncertainties associated with the Coma Cluster measurements, we cannot yet exclude an entropy flattening in this system consistent with that seen in more relaxed cool core clusters.

The origin of low mass particles within and beyond the dust coma envelopes of Comet Halley

NASA Technical Reports Server (NTRS)

Simpson, J. A.; Rabinowitz, D.; Tuzzolino, A. J.; Ksanfomality, L. V.; Sagdeev, R. Z.

1987-01-01

Measurements from the Dust Counter and Mass Analyzer (DUCMA) instruments on VEGA-1 and -2 revealed unexpected fluxes of low mass (up to 10 to the minus 13th power g) dust particles at very great distances from the nucleus (300,000 to 600,000 km). These particles are detected in clusters (10 sec duration), preceded and followed by relatively long time intervals during which no dust is detected. This cluster phenomenon also occurs inside the envelope boundaries. Clusters of low mass particles are intermixed with the overall dust distribution throughout the coma. The clusters account for many of the short-term small-scale intensity enhancements previously ascribed to microjets in the coma. The origin of these clusters appears to be emission from the nucleus of large conglomerates which disintegrate in the coma to yield clusters of discrete, small particles continuing outward to the distant coma.

PCA/HEXTE Observations of Coma and A2319

NASA Technical Reports Server (NTRS)

Rephaeli, Yoel

1998-01-01

The Coma cluster was observed in 1996 for 90 ks by the PCA and HEXTE instruments aboard the RXTE satellite, the first simultaneous, pointing measurement of Coma in the broad, 2-250 keV, energy band. The high sensitivity achieved during this long observation allows precise determination of the spectrum. Our analysis of the measurements clearly indicates that in addition to the main thermal emission from hot intracluster gas at kT=7.5 keV, a second spectral component is required to best-fit the data. If thermal, it can be described with a temperature of 4.7 keV contributing about 20% of the total flux. The additional spectral component can also be described by a power-law, possibly due to Compton scattering of relativistic electrons by the CMB. This interpretation is based on the diffuse radio synchrotron emission, which has a spectral index of 2.34, within the range allowed by fits to the RXTE spectral data. A Compton origin of the measured nonthermal component would imply that the volume-averaged magnetic field in the central region of Coma is B =0.2 micro-Gauss, a value deduced directly from the radio and X-ray measurements (and thus free of the usual assumption of energy equipartition). Barring the presence of unknown systematic errors in the RXTE source or background measurements, our spectral analysis yields considerable evidence for Compton X-ray emission in the Coma cluster.

The distribution of early- and late-type galaxies in the Coma cluster

NASA Technical Reports Server (NTRS)

Doi, M.; Fukugita, M.; Okamura, S.; Turner, E. L.

1995-01-01

The spatial distribution and the morohology-density relation of Coma cluster galaxies are studied using a new homogeneous photmetric sample of 450 galaxies down to B = 16.0 mag with quantitative morphology classification. The sample covers a wide area (10 deg X 10 deg), extending well beyond the Coma cluster. Morphological classifications into early- (E+SO) and late-(S) type galaxies are made by an automated algorithm using simple photometric parameters, with which the misclassification rate is expected to be approximately 10% with respect to early and late types given in the Third Reference Catalogue of Bright Galaxies. The flattened distribution of Coma cluster galaxies, as noted in previous studies, is most conspicuously seen if the early-type galaxies are selected. Early-type galaxies are distributed in a thick filament extended from the NE to the WSW direction that delineates a part of large-scale structure. Spiral galaxies show a distribution with a modest density gradient toward the cluster center; at least bright spiral galaxies are present close to the center of the Coma cluster. We also examine the morphology-density relation for the Coma cluster including its surrounding regions.

Deep Galex Observations of the Coma Cluster: Source Catalog and Galaxy Counts

NASA Technical Reports Server (NTRS)

Hammer, D.; Hornschemeier, A. E.; Mobasher, B.; Miller, N.; Smith, R.; Arnouts, S.; Milliard, B.; Jenkins, L.

2010-01-01

We present a source catalog from deep 26 ks GALEX observations of the Coma cluster in the far-UV (FUV; 1530 Angstroms) and near-UV (NUV; 2310 Angstroms) wavebands. The observed field is centered 0.9 deg. (1.6 Mpc) south-west of the Coma core, and has full optical photometric coverage by SDSS and spectroscopic coverage to r-21. The catalog consists of 9700 galaxies with GALEX and SDSS photometry, including 242 spectroscopically-confirmed Coma member galaxies that range from giant spirals and elliptical galaxies to dwarf irregular and early-type galaxies. The full multi-wavelength catalog (cluster plus background galaxies) is 80% complete to NUV=23 and FUV=23.5, and has a limiting depth at NUV=24.5 and FUV=25.0 which corresponds to a star formation rate of 10(exp -3) solar mass yr(sup -1) at the distance of Coma. The GALEX images presented here are very deep and include detections of many resolved cluster members superposed on a dense field of unresolved background galaxies. This required a two-fold approach to generating a source catalog: we used a Bayesian deblending algorithm to measure faint and compact sources (using SDSS coordinates as a position prior), and used the GALEX pipeline catalog for bright and/or extended objects. We performed simulations to assess the importance of systematic effects (e.g. object blends, source confusion, Eddington Bias) that influence source detection and photometry when using both methods. The Bayesian deblending method roughly doubles the number of source detections and provides reliable photometry to a few magnitudes deeper than the GALEX pipeline catalog. This method is also free from source confusion over the UV magnitude range studied here: conversely, we estimate that the GALEX pipeline catalogs are confusion limited at NUV approximately 23 and FUV approximately 24. We have measured the total UV galaxy counts using our catalog and report a 50% excess of counts across FUV=22-23.5 and NUV=21.5-23 relative to previous GALEX measurements, which is not attributed to cluster member galaxies. Our galaxy counts are a better match to deeper UV counts measured with HST.

Semiempirical limits on the thermal conductivity of intracluster gas

NASA Technical Reports Server (NTRS)

David, Laurence P.; Hughes, John P.; Tucker, Wallace H.

1992-01-01

A semiempirical method for establishing lower limits on the thermal conductivity of hot gas in clusters of galaxies is described. The method is based on the observation that the X-ray imaging data (e.g., Einstein IPC) for clusters are well described by the hydrostatic-isothermal beta model, even for cooling flow clusters beyond about one core radius. In addition, there are strong indications that noncooling flow clusters (like the Coma Cluster) have a large central region (up to several core radii) of nearly constant gas temperature. This suggests that thermal conduction is an effective means of transporting and redistributing the thermal energy of the gas. This in turn has implications for the extent to which magnetic fields in the cluster are effective in reducing the thermal conductivity of the gas. Time-dependent hydrodynamic simulations for the gas in the Coma Cluster under two separate evolutionary scenarios are presented. One scenario assumes that the cluster potential is static and that the gas has an initial adiabatic distribution. The second scenario uses an evolving cluster potential. These models along with analytic results show that the thermal conductivity of the gas in the Coma Cluster cannot be less than 0.1 of full Spitzer conductivity. These models also show that high gas conductivity assists rather than hinders the development of radiative cooling in the central regions of clusters.

Search for Gamma-Ray Emission from the Coma Cluster with Six Years of Fermi-LAT Data

NASA Technical Reports Server (NTRS)

Ackermann, M.; Ajello, M.; Albert, A.; Atwood, W. B.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.;

Search for gamma-ray emission from the Coma Cluster with six years of Fermi-LAT data

DOE PAGES

Ackermann, M.

2016-03-08

We present results from γ-ray observations of the Coma cluster incorporating 6 years of Fermi-LAT data and the newly released “Pass 8” event-level analysis. Our analysis of the region reveals low-significance residual structures within the virial radius of the cluster that are too faint for a detailed investigation with the current data. Using a likelihood approach that is free of assumptions on the spectral shape we derive upper limits on the γ-ray flux that is expected from energetic particle interactions in the cluster. We also consider a benchmark spatial and spectral template motivated by models in which the observed radiomore » halo is mostly emission by secondary electrons. In this case, the median expected and observed upper limits for the flux above 100MeV are 1.7 x 10 -9 ph cm -2 s -1 and 5.2 x 10 -9 ph cm -2 s -1 respectively (the latter corresponds to residual emission at the level of 1:8σ). These bounds are comparable to or higher than predicted levels of hadronic gamma-ray emission in cosmic-ray models with or without reacceleration of secondary electrons, although direct comparisons are sensitive to assumptions regarding the origin and propagation mode of cosmic rays and magnetic field properties. The minimal expected γ-ray flux from radio and star-forming galaxies within the Coma cluster is roughly an order of magnitude below the median sensitivity of our analysis.« less

SUZAKU OBSERVATIONS OF SUBHALOS IN THE COMA CLUSTER

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

Sasaki, Toru; Matsushita, Kyoko; Sato, Kosuke

2015-06-10

We observed three massive subhalos in the Coma cluster with Suzaku. These subhalos, labeled “ID 1,” “ID 2,” and “ID 32,” were detected with a weak-lensing survey using Subaru/Suprime-Cam, and are located at the projected distances of 1.4 r{sub 500}, 1.2 r{sub 500}, and 1.6 r{sub 500} from the center of the Coma cluster, respectively. The subhalo “ID 1” has a compact X-ray excess emission close to the center of the weak-lensing mass contour, and the gas mass to weak-lensing mass ratio is about 0.001. The temperature of the emission is about 3 keV, which is slightly lower than thatmore » of the surrounding intracluster medium (ICM) and that expected for the temperature versus mass relation of clusters of galaxies. The subhalo “ID 32” shows an excess emission whose peak is shifted toward the opposite direction from the center of the Coma cluster. The gas mass to weak-lensing mass ratio is also about 0.001, which is significantly smaller than regular galaxy groups. The temperature of the excess is about 0.5 keV and significantly lower than that of the surrounding ICM and far from the temperature versus mass relation of clusters. However, there is no significant excess X-ray emission in the “ID 2” subhalo. Assuming an infall velocity of about 2000 km s{sup −1}, at the border of the excess X-ray emission, the ram pressures for “ID 1” and “ID 32” are comparable to the gravitational restoring force per area. We also studied the effect of the Kelvin–Helmholtz instability to strip the gas. Although we found X-ray clumps associated with the weak-lensing subhalos, their X-ray luminosities are much lower than the total ICM luminosity in the cluster outskirts.« less

Observing RAM Pressure Stripping and Morphological Transformation in the Coma Cluster

NASA Astrophysics Data System (ADS)

Gregg, Michael; West, Michael

2017-07-01

The two largest spirals in the Coma cluster, NGC4911 and NGC4921, are being vigorously ram-pressure stripped by the hot intracluster medium. Our HST ACS and WFC3 images have revealed galactic scale shock fronts, giant "Pillars of Creation", rivulets of dust, and spatially coherent star formation in these grand design spirals. We have now obtained HST WFC3 imaging of five additional large Coma spirals to search for and investigate the effects of ram pressure stripping across the wider cluster environment. The results are equally spectacular as the first two examples. The geometry of the interactions in some cases allows an estimation of the various time scales involved, including gas flows out of the disk leading to creation of the ICM, and the attendant triggered star formation in the galaxy disks. The global star formation patterns yield insights into the spatial and temporal ISM-ICM interactions driving cluster galaxy evolution and ultimately transforming morphologies from spiral to S0. These processes were much more common in the early Universe when the intergalactic and intracluster components were initially created from stripping and destruction of member galaxies.

Ultraviolet and optical view of galaxies in the Coma Supercluster

NASA Astrophysics Data System (ADS)

Mahajan, Smriti; Singh, Ankit; Shobhana, Devika

2018-05-01

The Coma supercluster (100h-1Mpc) offers an unprecedented contiguous range of environments in the nearby Universe. In this paper we present a catalogue of spectroscopically confirmed galaxies in the Coma supercluster detected in the ultraviolet (UV) wavebands. We use the arsenal of UV and optical data for galaxies in the Coma supercluster covering ˜500 square degrees on the sky to study their photometric and spectroscopic properties as a function of environment at various scales. We identify the different components of the cosmic-web: large-scale filaments and voids using Discrete Persistent Structures Extractor, and groups and clusters using Hierarchical Density-based spatial clustering of applications with noise, respectively. We find that in the Coma supercluster the median emission in Hα inclines, while the g - r and FUV - NUV colours of galaxies become bluer moving further away from the spine of the filaments out to a radius of ˜1 Mpc. On the other hand, an opposite trend is observed as the distance between the galaxy and centre of the nearest cluster or group decreases. Our analysis supports the hypothesis that properties of galaxies are not just defined by its stellar mass and large-scale density, but also by the environmental processes resulting due to the intrafilament medium whose role in accelerating galaxy transformations needs to be investigated thoroughly using multi-wavelength data.

FORTY-SEVEN MILKY WAY-SIZED, EXTREMELY DIFFUSE GALAXIES IN THE COMA CLUSTER

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

Van Dokkum, Pieter G.; Merritt, Allison; Geha, Marla

2015-01-10

We report the discovery of 47 low surface brightness objects in deep images of a 3° × 3° field centered on the Coma cluster, obtained with the Dragonfly Telephoto Array. The objects have central surface brightness μ(g, 0) ranging from 24-26 mag arcsec{sup –2} and effective radii r {sub eff} = 3''-10'', as measured from archival Canada-France-Hawaii Telescope images. From their spatial distribution we infer that most or all of the objects are galaxies in the Coma cluster. This relatively large distance is surprising as it implies that the galaxies are very large: with r {sub eff} = 1.5-4.6 kpcmore » their sizes are similar to those of L {sub *} galaxies even though their median stellar mass is only ∼6 × 10{sup 7} M {sub ☉}. The galaxies are relatively red and round, with (g – i) = 0.8 and (b/a) = 0.74. One of the 47 galaxies is fortuitously covered by a deep Hubble Space Telescope Advanced Camera for Surveys (ACS) observation. The ACS imaging shows a large spheroidal object with a central surface brightness μ{sub 475} = 25.8 mag arcsec{sup –2}, a Sérsic index n = 0.6, and an effective radius of 7'', corresponding to 3.4 kpc at the distance of Coma. The galaxy is not resolved into stars, consistent with expectations for a Coma cluster object. We speculate that these ''ultra-diffuse galaxies'' may have lost their gas supply at early times, possibly resulting in very high dark matter fractions.« less

Studies of cluster X-ray sources, energy spectra for the Perseus, Virgo, and Coma clusters

NASA Technical Reports Server (NTRS)

Kellogg, E.; Baldwin, J. R.; Koch, D.

1975-01-01

Final Uhuru X-ray differential-energy spectra are presented for the Perseus, Virgo, and Coma clusters. Power-law and isothermal bremsstrahlung model spectra with low-energy cutoffs are given, and the energy-dependent Gaunt factor is calculated for the bremsstrahlung. The spectra, which are best fits to the Uhuru data between 2 and 10 keV, are compared with previous observations of these sources in the energy range from 0.1 to 100 keV. The problem of parameter estimation is discussed, error bars with 68% confidence are given for the independently determined slope and cutoff parameters, and the 68% confidence limits are plotted for the fitted spectral functions. The data for Perseus above 20 keV marginally favor the bremsstrahlung fit, those for Virgo between 0.25 and 1.0 keV clearly favor that curve, and those for Coma indicate a low-energy turnover or cutoff. Implications of such a cutoff are briefly discussed.

A NuSTAR OBSERVATION OF THE CENTER OF THE COMA CLUSTER

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

Gastaldello, Fabio; Molendi, S.; Wik, Daniel R.

2015-02-20

We present the results of a 55 ks NuSTAR observation of the core of the Coma Cluster. The global spectrum can be explained by thermal gas emission, with a conservative 90% upper limit to non-thermal inverse Compton (IC) emission of 5.1 × 10{sup –12} erg cm{sup –2} s{sup –1} in a 12' × 12' field of view. The brightness of the thermal component in this central region does not allow more stringent upper limits on the IC component when compared with non-imaging instruments with much larger fields of view where claims of detections have been made. Future mosaic NuSTAR observations ofmore » Coma will further address this issue. The temperature map shows a relatively uniform temperature distribution with a gradient from the hot northwest side to the cooler southeast, in agreement with previous measurements. The temperature determination is robust given the flat effective area and low background in the 3-20 keV band, making NuSTAR an ideal instrument to measure high temperatures in the intracluster medium.« less

THERMODYNAMICS OF THE COMA CLUSTER OUTSKIRTS

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

Simionescu, A.; Werner, N.; Urban, O.

2013-09-20

We present results from a large mosaic of Suzaku observations of the Coma Cluster, the nearest and X-ray brightest hot ({approx}8 keV), dynamically active, non-cool core system, focusing on the thermodynamic properties of the intracluster medium on large scales. For azimuths not aligned with an infalling subcluster toward the southwest, our measured temperature and X-ray brightness profiles exhibit broadly consistent radial trends, with the temperature decreasing from about 8.5 keV at the cluster center to about 2 keV at a radius of 2 Mpc, which is the edge of our detection limit. The southwest merger significantly boosts the surface brightness,more » allowing us to detect X-ray emission out to {approx}2.2 Mpc along this direction. Apart from the southwestern infalling subcluster, the surface brightness profiles show multiple edges around radii of 30-40 arcmin. The azimuthally averaged temperature profile, as well as the deprojected density and pressure profiles, all show a sharp drop consistent with an outwardly-propagating shock front located at 40 arcmin, corresponding to the outermost edge of the giant radio halo observed at 352 MHz with the Westerbork Synthesis Radio Telescope. The shock front may be powering this radio emission. A clear entropy excess inside of r{sub 500} reflects the violent merging events linked with these morphological features. Beyond r{sub 500}, the entropy profiles of the Coma Cluster along the relatively relaxed directions are consistent with the power-law behavior expected from simple models of gravitational large-scale structure formation. The pressure is also in agreement at these radii with the expected values measured from Sunyaev-Zel'dovich data from the Planck satellite. However, due to the large uncertainties associated with the Coma Cluster measurements, we cannot yet exclude an entropy flattening in this system consistent with that seen in more relaxed cool core clusters.« less

New red jewels in Coma Berenices

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

Terrien, Ryan C.; Mahadevan, Suvrath; Deshpande, Rohit

2014-02-20

We have used Sloan Digital Sky Survey-III (SDSS-III) Apache Point Observatory Galactic Evolution Experiment (APOGEE) radial velocity observations in the near-infrared H-band to explore the membership of the nearby (86.7 ± 0.9 pc) open cluster Coma Berenices (Melotte 111), concentrating on the poorly populated low-mass end of the main sequence. Using SDSS-III APOGEE radial velocity measurements, we confirm the membership of eight K/M dwarf members, providing the first confirmed low-mass members of the Coma Berenices cluster. Using R ∼ 2000 spectra from IRTF-SpeX, we confirm the independently luminosity classes of these targets, and find their metallicities to be consistent withmore » the known solar mean metallicity of Coma Berenices and of M dwarfs in the solar neighborhood. In addition, the APOGEE spectra have enabled measurement of vsin i for each target and detection for the first time of the low-mass secondary components of the known binary systems Melotte 111 102 and Melotte 111 120, as well as identification of the previously unknown binary system 2MASS J12214070+2707510. Finally, we use Kilodegree Extremely Little Telescope photometry to measure photometric variability and rotation periods for a subset of the Coma Berenices members.« less

ROSAT observations of Coma Cluster galaxies

NASA Technical Reports Server (NTRS)

Dow, K. L.; White, S. D. M.

1995-01-01

The approximately 86 ks ROSAT Position Sensitive Proportional Counter (PSPC) image of the Coma Cluster is deeper than any previous X-ray observation of a galaxy cluster. We search for X-ray emission from 35 individual galaxies in a magnitude-limited sample, all of which lie within 20 arcmins of the optical axis in at least one of the four Coma pointings. We detect seven galaxies in the 0.4-2.4 keV band at a significance level exceeding 3 sigma, and a further four at above 2 sigma. Although we can set only upper limits on the individual flux from each of the other galaxies, we are able to measure their mean flux by stacking the observations. The X-ray luminosities of the seven detections range from 6.2 x 10(exp 40) to 1.5 x 10(exp 42) ergs/s (0.4-2.4 keV for H(sub 0) = 50 km/s/Mpc). For galaxies with a blue absolute magnitude of about -21 we find a mean X-ray luminosity of 1.3 x 10(exp 40) ergs/s. The ratio of X-ray to optical luminosity is substantially smaller for such subjects than for the brightest galaxies in the cluster. The X-ray luminosities of the four brightest galaxies are ill-defined, however, because of ambiguity in distinguishing galaxy emission from cluster emission. Each object appears to be related to significant structure in the diffuse intracluster medium. We also investigate emission in the softer 0.2-0.4 keV band where detections are less significant because of the higher background, and we discuss the properties of a number of interesting individual sources. The X-ray luminosities of the Coma galaxies are similar to those of galaxies in the Virgo Cluster and in other regions with relatively low galaxy density. We conclude that large-scale environmental effects do not significantly enhance or suppress the average X-ray emission from galaxies, but that individual objects vary in luminosity substantially in a way which may depend on the detailed history of their environment.

Coma cluster of galaxies

NASA Image and Video Library

1999-12-02

Atlas Image mosaic, covering 34 x 34 on the sky, of the Coma cluster, aka Abell 1656. This is a particularly rich cluster of individual galaxies over 1000 members, most prominently the two giant ellipticals, NGC 4874 right and NGC 4889 left.

Testing a generalized cubic Galileon gravity model with the Coma Cluster

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

Terukina, Ayumu; Yamamoto, Kazuhiro; Okabe, Nobuhiro

2015-10-01

We obtain a constraint on the parameters of a generalized cubic Galileon gravity model exhibiting the Vainshtein mechanism by using multi-wavelength observations of the Coma Cluster. The generalized cubic Galileon model is characterized by three parameters of the turning scale associated with the Vainshtein mechanism, and the amplitude of modifying a gravitational potential and a lensing potential. X-ray and Sunyaev-Zel'dovich (SZ) observations of the intra-cluster medium are sensitive to the gravitational potential, while the weak-lensing (WL) measurement is specified by the lensing potential. A joint fit of a complementary multi-wavelength dataset of X-ray, SZ and WL measurements enables us tomore » simultaneously constrain these three parameters of the generalized cubic Galileon model for the first time. We also find a degeneracy between the cluster mass parameters and the gravitational modification parameters, which is influential in the limit of the weak screening of the fifth force.« less

Another collision for the Coma cluster

NASA Technical Reports Server (NTRS)

Vikhlinin, A.; Forman, W.; Jones, C.

1996-01-01

The wavelet transform analysis of the Rosat position sensitive proportional counter (PSPC) images of the Coma cluster are presented. The analysis shows, on small scales, a substructure dominated by two extended sources surrounding the two bright clusters NGC 4874 and NGC 4889. On scales of about 2 arcmin to 3 arcmin, the analysis reveals a tail of X-ray emission originating near the cluster center, curving to the south and east for approximately 25 arcmin and ending near the galaxy NGC 4911. The results are interpreted in terms of a merger of a group, having a core mass of approximately 10(exp 13) solar mass, with the main body of the Coma cluster.

The Nature and Origin of UCDs in the Coma Cluster

NASA Astrophysics Data System (ADS)

Chiboucas, Kristin; Tully, R. Brent; Madrid, Juan; Phillipps, Steven; Carter, David; Peng, Eric

2018-01-01

UCDs are super massive star clusters found largely in dense regions but have also been found around individual galaxies and in smaller groups. Their origin is still under debate but currently favored scenarios include formation as giant star clusters, either as the brightest globular clusters or through mergers of super star clusters, themselves formed during major galaxy mergers, or as remnant nuclei from tidal stripping of nucleated dwarf ellipticals. Establishing the nature of these enigmatic objects has important implications for our understanding of star formation, star cluster formation, the missing satellite problem, and galaxy evolution. We are attempting to disentangle these competing formation scenarios with a large survey of UCDs in the Coma cluster. Using ACS two-passband imaging from the HST/ACS Coma Cluster Treasury Survey, we are using colors and sizes to identify the UCD cluster members. With a large size limited sample of the UCD population within the core region of the Coma cluster, we are investigating the population size, properties, and spatial distribution, and comparing that with the Coma globular cluster and nuclear star cluster populations to discriminate between the threshing and globular cluster scenarios. In previous work, we had found a possible correlation of UCD colors with host galaxy and a possible excess of UCDs around a non-central giant galaxy with an unusually large globular cluster population, both suggestive of a globular cluster origin. With a larger sample size and additional imaging fields that encompass the regions around these giant galaxies, we have found that the color correlation with host persists and the giant galaxy with unusually large globular cluster population does appear to host a large UCD population as well. We present the current status of the survey.

The HST/ACS Coma Cluster Survey. II. Data Description and Source Catalogs

NASA Technical Reports Server (NTRS)

Hammer, Derek; Kleijn, Gijs Verdoes; Hoyos, Carlos; Den Brok, Mark; Balcells, Marc; Ferguson, Henry C.; Goudfrooij, Paul; Carter, David; Guzman, Rafael; Peletier, Reynier F.;

DARK MATTER SUBHALOS AND THE X-RAY MORPHOLOGY OF THE COMA CLUSTER

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

Andrade-Santos, Felipe; Nulsen, Paul E. J.; Kraft, Ralph P.

2013-04-01

Structure formation models predict that clusters of galaxies contain numerous massive subhalos. The gravity of a subhalo in a cluster compresses the surrounding intracluster gas and enhances its X-ray emission. We present a simple model, which treats subhalos as slow moving and gasless, for computing this effect. Recent weak lensing measurements by Okabe et al. have determined masses of {approx}10{sup 13} M{sub Sun} for three mass concentrations projected within 300 kpc of the center of the Coma Cluster, two of which are centered on the giant elliptical galaxies NGC 4889 and NGC 4874. Adopting a smooth spheroidal {beta}-model for themore » gas distribution in the unperturbed cluster, we model the effect of these subhalos on the X-ray morphology of the Coma Cluster, comparing our results to Chandra and XMM-Newton X-ray data. The agreement between the models and the X-ray morphology of the central Coma Cluster is striking. With subhalo parameters from the lensing measurements, the distances of the three subhalos from the Coma Cluster midplane along our line of sight are all tightly constrained. Using the model to fit the subhalo masses for NGC 4889 and NGC 4874 gives 9.1 Multiplication-Sign 10{sup 12} M{sub Sun} and 7.6 Multiplication-Sign 10{sup 12} M{sub Sun }, respectively, in good agreement with the lensing masses. These results lend strong support to the argument that NGC 4889 and NGC 4874 are each associated with a subhalo that resides near the center of the Coma Cluster. In addition to constraining the masses and 3-d location of subhalos, the X-ray data show promise as a means of probing the structure of central subhalos.« less

A Giant Warm Baryonic Halo for the Coma Cluster

NASA Technical Reports Server (NTRS)

Bonamente, Max; Lieu, Richard; Joy, Marshall K.; Six, N. Frank (Technical Monitor)

2002-01-01

Several deep PSPC observations of the Coma cluster unveil a very large-scale halo of soft X-ray emission, substantially in excess of the well know radiation from the hot intra-cluster medium. The excess emission, previously reported in the central cluster regions through lower-sensitivity EUVE and ROSAT data, is now evident out to a radius of 2.5 Mpc, demonstrating that the soft excess radiation from clusters is a phenomenon of cosmological significance. The spectrum at these large radii cannot be modeled non-thermally, but is consistent with the original scenario of thermal emission at warm temperatures. The mass of this plasma is at least on par with that of the hot X-ray emitting plasma, and significantly more massive if the plasma resides in low-density filamentary structures. Thus the data lend vital support to current theories of cosmic evolution, which predict greater than 50 percent by mass of today's baryons reside in warm-hot filaments converging at clusters of galaxies.

Spectral constraints on models of gas in clusters of galaxies

NASA Technical Reports Server (NTRS)

Henriksen, M. J.; Mushotzky, R.

1985-01-01

The HEAO 1A2 spectra of clusters of galaxies are used to determine the temperature profile which characterizes the X-ray emitting gas. Strong evidence of nonisothermality is found for the Coma, A85, and A1795 clusters. Properties of the cluster potential which binds the gas are calculated for a range of model parameters. The typical binding mass, if the gas is adiabatic, is 2-4E14 solar masses and is quite centrally concentrated. In addition, the Fe abundance in Coma is .26 + or - .06 solar, less than the typical value (.5) found for rich clusters. The results for the gas in Coma may imply a physical description of the cluster which is quite different from what was previously believed.

A NuSTAR observation of the center of the Coma Cluster

DOE PAGES

Gastaldello, Fabio; Wik, Daniel R.; Molendi, S.; ...

2015-02-20

We present the results of a 55 ks NuSTAR observation of the core of the Coma Cluster. The global spectrum can be explained by thermal gas emission, with a conservative 90% upper limit to non-thermal inverse Compton (IC) emission of 5.1 × 10 –12 erg cm –2 s –1 in a 12' × 12' field of view. The brightness of the thermal component in this central region does not allow more stringent upper limits on the IC component when compared with non-imaging instruments with much larger fields of view where claims of detections have been made. Future mosaic NuSTAR observationsmore » of Coma will further address this issue. In addition, the temperature map shows a relatively uniform temperature distribution with a gradient from the hot northwest side to the cooler southeast, in agreement with previous measurements. The temperature determination is robust given the flat effective area and low background in the 3-20 keV band, making NuSTAR an ideal instrument to measure high temperatures in the intracluster medium.« less

The NGC 4839 group falling into the Coma cluster observed by XMM-Newton

NASA Astrophysics Data System (ADS)

Neumann, D. M.; Arnaud, M.; Gastaud, R.; Aghanim, N.; Lumb, D.; Briel, U. G.; Vestrand, W. T.; Stewart, G. C.; Molendi, S.; Mittaz, J. P. D.

2001-01-01

We present here the first analysis of the XMM-Newton EPIC-MOS data of the galaxy group around NGC 4839, which lies at a projected distance to the Coma cluster center of 1.6h50-1 Mpc. In our analysis, which includes imaging, spectro-imaging and spectroscopy we find compelling evidence for the sub group being on its first infall onto the Coma cluster. The complex temperature structure around NGC 4839 is consistent with simulations of galaxies falling into a cluster environment. We see indications of a bow shock and of ram pressure stripping around NGC 4839. Furthermore our data reveal a displacement between NGC 4839 and the center of the hot gas in the group of about 300h50-1 kpc. With a simple approximation we can explain this displacement by the pressure force originating from the infall, which acts much stronger on the group gas than on the galaxies. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and the USA (NASA). EPIC was developed by the EPIC Consortium led by the Principal Investigator, Dr. M. J. L. Turner. The consortium comprises the following Institutes: University of Leicester, University of Birmingham, (UK); CEA/Saclay, IAS Orsay, CESR Toulouse, (France); IAAP Tuebingen, MPE Garching, (Germany); IFC Milan, ITESRE Bologna, IAUP Palermo, Italy. EPIC is funded by: PPARC, CEA, CNES, DLR and ASI.

The X-ray structure of a galaxy cluster at z = 0.54 - Implications for cluster evolution and cosmology

NASA Technical Reports Server (NTRS)

White, S. D. M.; Silk, J.; Henry, J. P.

1981-01-01

High-resolution X-ray observations of the rich cluster 0016+16 at a redshift of 0.541 are presented. The emitting gas in this cluster is hot and extremely luminous, and its structure resembles that seen in the brightest nearby cluster sources. In most of its properties, 0016+16 resembles a richer version of the Coma cluster, and it offers little support to the hypothesis that clusters at z greater than 0.5 differ fundamentally from nearer objects.

Resolved magnetic dynamo action in the simulated intracluster medium

NASA Astrophysics Data System (ADS)

Vazza, F.; Brunetti, G.; Brüggen, M.; Bonafede, A.

2018-02-01

Faraday rotation and synchrotron emission from extragalactic radio sources give evidence for the presence of magnetic fields extending over ˜ Mpc scales. However, the origin of these fields remains elusive. With new high-resolution grid simulations, we studied the growth of magnetic fields in a massive galaxy cluster that in several aspects is similar to the Coma cluster. We investigated models in which magnetic fields originate from primordial seed fields with comoving strengths of 0.1 nG at redshift z = 30. The simulations show evidence of significant magnetic field amplification. At the best spatial resolution (3.95 kpc), we are able to resolve the scale where magnetic tension balances the bending of magnetic lines by turbulence. This allows us to observe the final growth stage of the small-scale dynamo. To our knowledge, this is the first time that this is seen in cosmological simulations of the intracluster medium. Our mock observations of Faraday rotation provide a good match to observations of the Coma cluster. However, the distribution of magnetic fields shows strong departures from a simple Maxwellian distribution, suggesting that the three-dimensional structure of magnetic fields in real clusters may be significantly different than what is usually assumed when inferring magnetic field values from rotation measure observations.

Ultra-diffuse cluster galaxies as key to the MOND cluster conundrum

NASA Astrophysics Data System (ADS)

Milgrom, Mordehai

2015-12-01

Modified Newtonian Dynamics (MOND) reduces greatly the mass discrepancy in clusters of galaxies,but does leave a global discrepancy of about a factor of 2 (epitomized by the structure of the Bullet Cluster). It has been proposed, within the minimalist and purist MOND, that clusters harbour some indigenous, yet undetected, cluster baryonic (dark) matter (CBDM), whose total amount is comparable with that of the observed hot gas. Koda et al. have recently identified more than a thousand ultra-diffuse, galaxy-like objects (UDGs) in the Coma cluster. These, they argue, require, within Newtonian dynamics, that they are much more massive than their observed stellar component. Here, I propound that some of the CBDM is internal to UDGs, which endows them with robustness. The rest of the CBDM objects formed in now-disrupted kin of the UDGs, and is dispersed in the intracluster medium. The discovery of cluster UDGs is not in itself a resolution of the MOND cluster conundrum, but it lends greater plausibility to CBDM as its resolution. Alternatively, if the UDGs are only now falling into Coma, their large size and very low surface brightness could result from the inflation due to the MOND, variable external-field effect (EFE). I also consider briefly solutions to the conundrum that invoke more elaborate extensions of purist MOND, e.g. that in clusters, the MOND constant takes up larger than canonical values of the MOND constant. Whatever solves the cluster conundrum within MOND might also naturally account for UDGs.

Soft X-ray excess in the Coma cluster from a Cosmic Axion Background

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

Angus, Stephen; Conlon, Joseph P.; Marsh, M.C. David

2014-09-01

We show that the soft X-ray excess in the Coma cluster can be explained by a cosmic background of relativistic axion-like particles (ALPs) converting into photons in the cluster magnetic field. We provide a detailed self-contained review of the cluster soft X-ray excess, the proposed astrophysical explanations and the problems they face, and explain how a 0.1- 1 keV axion background naturally arises at reheating in many string theory models of the early universe. We study the morphology of the soft excess by numerically propagating axions through stochastic, multi-scale magnetic field models that are consistent with observations of Faraday rotation measuresmore » from Coma. By comparing to ROSAT observations of the 0.2- 0.4 keV soft excess, we find that the overall excess luminosity is easily reproduced for g{sub aγγ} ∼ 2 × 10{sup -13} Ge {sup -1}. The resulting morphology is highly sensitive to the magnetic field power spectrum. For Gaussian magnetic field models, the observed soft excess morphology prefers magnetic field spectra with most power in coherence lengths on O(3 kpc) scales over those with most power on O(12 kpc) scales. Within this scenario, we bound the mean energy of the axion background to 50 eV∼< ( E{sub a} ) ∼< 250 eV, the axion mass to m{sub a} ∼< 10{sup -12} eV, and derive a lower bound on the axion-photon coupling g{sub aγγ} ∼> √(0.5/Δ N{sub eff}) 1.4 × 10{sup -13} Ge {sup -1}.« less

Coma cluster of galaxies

NASA Technical Reports Server (NTRS)

1999-01-01

Atlas Image mosaic, covering 34' x 34' on the sky, of the Coma cluster, aka Abell 1656. This is a particularly rich cluster of individual galaxies (over 1000 members), most prominently the two giant ellipticals, NGC 4874 (right) and NGC 4889 (left). The remaining members are mostly smaller ellipticals, but spiral galaxies are also evident in the 2MASS image. The cluster is seen toward the constellation Coma Berenices, but is actually at a distance of about 100 Mpc (330 million light years, or a redshift of 0.023) from us. At this distance, the cluster is in what is known as the 'Hubble flow,' or the overall expansion of the Universe. As such, astronomers can measure the Hubble Constant, or the universal expansion rate, based on the distance to this cluster. Large, rich clusters, such as Coma, allow astronomers to measure the 'missing mass,' i.e., the matter in the cluster that we cannot see, since it gravitationally influences the motions of the member galaxies within the cluster. The near-infrared maps the overall luminous mass content of the member galaxies, since the light at these wavelengths is dominated by the more numerous older stellar populations. Galaxies, as seen by 2MASS, look fairly smooth and homogeneous, as can be seen from the Hubble 'tuning fork' diagram of near-infrared galaxy morphology. Image mosaic by S. Van Dyk (IPAC).

ALP conversion and the soft X-ray excess in the outskirts of the Coma cluster

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

Kraljic, David; Rummel, Markus; Conlon, Joseph P., E-mail: David.Kraljic@physics.ox.ac.uk, E-mail: Markus.Rummel@physics.ox.ac.uk, E-mail: j.conlon1@physics.ox.ac.uk

2015-01-01

It was recently found that the soft X-ray excess in the center of the Coma cluster can be fitted by conversion of axion-like-particles (ALPs) of a cosmic axion background (CAB) to photons. We extend this analysis to the outskirts of Coma, including regions up to 5 Mpc from the center of the cluster. We extract the excess soft X-ray flux from ROSAT All-Sky Survey data and compare it to the expected flux from ALP to photon conversion of a CAB. The soft X-ray excess both in the center and the outskirts of Coma can be simultaneously fitted by ALP tomore » photon conversion of a CAB. Given the uncertainties of the cluster magnetic field in the outskirts we constrain the parameter space of the CAB. In particular, an upper limit on the CAB mean energy and a range of allowed ALP-photon couplings are derived.« less

Deep X-ray and UV Surveys of Galaxies with Chandra, XMM-Newton, and GALEX

NASA Technical Reports Server (NTRS)

Hornschemeier, Ann

2006-01-01

Only with the deepest Chandra surveys has X-ray emission from normal and star forming galaxies (as opposed to AGN, which dominate the X-ray sky) been accessible at cosmologically interesting distances. The X-ray emission from accreting binaries provide a critical glimpse into the binary phase of stellar evolution and studies of the hot gas reservoir constrain past star formation. UV studies provide important, sensitive diagnostics of the young star forming populations and provide the most mature means for studying galaxies at 2 < zeta < 4. This talk will review current progress on studying X-ray emission in concert with UV emission from normal/star-forming galaxies at higher redshift. We will also report on our new, deep surveys with GALEX and XMM-Newton in the nearby Coma cluster. These studies are relevant to DEEP06 as Coma is the nearest rich cluster of galaxies and provides an important benchmark for high-redshift studies in the X-ray and UV wavebands. The 30 ks GALEX (note: similar depth to the GALEX Deep Imaging Survey) and the 110 ks XMM observations provide extremely deep coverage of a Coma outskirts field, allowing the construction of the UV and X-ray luminosity function of galaxies and important constraints on star formation scaling relations such as the X-ray-Star Formation Rate correlation and the X-ray/Stellar Mass correlation. We will discuss what we learn from these deep observations of Coma, including the recently established suppression of the X-ray emission from galaxies in the Coma outskirts that is likely associated with lower levels of past star formation and/or the results of tidal gas stripping.

THE HST/ACS COMA CLUSTER SURVEY. VIII. BARRED DISK GALAXIES IN THE CORE OF THE COMA CLUSTER

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

Marinova, Irina; Jogee, Shardha; Weinzirl, Tim

2012-02-20

We use high-resolution ({approx}0.''1) F814W Advanced Camera for Surveys (ACS) images from the Hubble Space Telescope ACS Treasury survey of the Coma cluster at z {approx} 0.02 to study bars in massive disk galaxies (S0s), as well as low-mass dwarf galaxies in the core of the Coma cluster, the densest environment in the nearby universe. Our study helps to constrain the evolution of bars and disks in dense environments and provides a comparison point for studies in lower density environments and at higher redshifts. Our results are: (1) we characterize the fraction and properties of bars in a sample ofmore » 32 bright (M{sub V} {approx}< -18, M{sub *} > 10{sup 9.5} M{sub Sun }) S0 galaxies, which dominate the population of massive disk galaxies in the Coma core. We find that the measurement of a bar fraction among S0 galaxies must be handled with special care due to the difficulty in separating unbarred S0s from ellipticals, and the potential dilution of the bar signature by light from a relatively large, bright bulge. The results depend sensitively on the method used: the bar fraction for bright S0s in the Coma core is 50% {+-} 11%, 65% {+-} 11%, and 60% {+-} 11% based on three methods of bar detection, namely, strict ellipse fit criteria, relaxed ellipse fit criteria, and visual classification. (2) We compare the S0 bar fraction across different environments (the Coma core, A901/902, and Virgo) adopting the critical step of using matched samples and matched methods in order to ensure robust comparisons. We find that the bar fraction among bright S0 galaxies does not show a statistically significant variation (within the error bars of {+-}11%) across environments which span two orders of magnitude in galaxy number density (n {approx} 300-10,000 galaxies Mpc{sup -3}) and include rich and poor clusters, such as the core of Coma, the A901/902 cluster, and Virgo. We speculate that the bar fraction among S0s is not significantly enhanced in rich clusters compared to low-density environments for two reasons. First, S0s in rich clusters are less prone to bar instabilities as they are dynamically heated by harassment and are gas poor as a result of ram pressure stripping and accelerated star formation. Second, high-speed encounters in rich clusters may be less effective than slow, strong encounters in inducing bars. (3) We also take advantage of the high resolution of the ACS ({approx}50 pc) to analyze a sample of 333 faint (M{sub V} > -18) dwarf galaxies in the Coma core. Using visual inspection of unsharp-masked images, we find only 13 galaxies with bar and/or spiral structure. An additional eight galaxies show evidence for an inclined disk. The paucity of disk structures in Coma dwarfs suggests that either disks are not common in these galaxies or that any disks present are too hot to develop instabilities.« less

A Massive Warm Baryonic Halo in the Coma Cluster

NASA Technical Reports Server (NTRS)

Bonamente, Massimiliano; Joy, Marshall K.; Lieu, Richard

2003-01-01

Several deep PSPC observations of the Coma Cluster reveal a very large scale halo of soft X-ray emission, substantially in excess of the well-known radiation from the hot intracluster medium. The excess emission, previously reported in the central region of the cluster using lower sensitivity Extreme Ultraviolet Explorer (EUVE) and ROSAT data, is now evident out to a radius of 2.6 Mpc, demonstrating that the soft excess radiation from clusters is a phenomenon of cosmological significance. The X-ray spectrum at these large radii cannot be modeled nonthermally but is consistent with the original scenario of thermal emission from warm gas at approx. 10(exp 6) K. The mass of the warm gas is on par with that of the hot X-ray-emitting plasma and significantly more massive if the warm gas resides in low-density filamentary structures. Thus, the data lend vital support to current theories of cosmic evolution, which predict that at low redshift approx. 30%-40% of the baryons reside in warm filaments converging at clusters of galaxies.

VizieR Online Data Catalog: Subaru-UDGs in the Coma cluster (Yagi+, 2016)

NASA Astrophysics Data System (ADS)

Yagi, M.; Koda, J.; Komiyama, Y.; Yamanoi, H.

2016-10-01

We retrieved a wide W-C-RC band (R-band) survey of the Coma cluster of Suprime-Cam from the Subaru public archive (SMOKA; Baba et al. 2002ASPC..281..298B) between 2011 Mar 02 and 2011 Apr 01. (1 data file).

Globular Clusters for Faint Galaxies

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-07-01

The origin of ultra-diffuse galaxies (UDGs) has posed a long-standing mystery for astronomers. New observations of several of these faint giants with the Hubble Space Telescope are now lending support to one theory.Faint-Galaxy MysteryHubble images of Dragonfly 44 (top) and DFX1 (bottom). The right panels show the data with greater contrast and extended objects masked. [van Dokkum et al. 2017]UDGs large, extremely faint spheroidal objects were first discovered in the Virgo galaxy cluster roughly three decades ago. Modern telescope capabilities have resulted in many more discoveries of similar faint galaxies in recent years, suggesting that they are a much more common phenomenon than we originally thought.Despite the many observations, UDGs still pose a number of unanswered questions. Chief among them: what are UDGs? Why are these objects the size of normal galaxies, yet so dim? There are two primary models that explain UDGs:UDGs were originally small galaxies, hence their low luminosity. Tidal interactions then puffed them up to the large size we observe today.UDGs are effectively failed galaxies. They formed the same way as normal galaxies of their large size, but something truncated their star formation early, preventing them from gaining the brightness that we would expect for galaxies of their size.Now a team of scientists led by Pieter van Dokkum (Yale University) has made some intriguing observations with Hubble that lend weight to one of these models.Globulars observed in 16 Coma-cluster UDGs by Hubble. The top right panel shows the galaxy identifications. The top left panel shows the derived number of globular clusters in each galaxy. [van Dokkum et al. 2017]Globulars GaloreVan Dokkum and collaborators imaged two UDGs with Hubble: Dragonfly 44 and DFX1, both located in the Coma galaxy cluster. These faint galaxies are both smooth and elongated, with no obvious irregular features, spiral arms, star-forming regions, or other indications of tidal interactions.The most striking feature of these galaxies, however, is that they are surrounded by a large number of compact objects that appear to be globular clusters. From the observations, Van Dokkum and collaborators estimate that Dragonfly 44 and DFX1 have approximately 74 and 62 globulars, respectively significantly more than the low numbers expected for galaxies of this luminosity.Armed with this knowledge, the authors went back and looked at archival observations of 14 other UDGs also located in the Coma cluster. They found that these smaller and fainter galaxies dont host quite as many globular clusters as Dragonfly 44 and DFX1, but more than half also show significant overdensities of globulars.Main panel: relation between the number of globular clusters and total absolute magnitude for Coma UDGs (solid symbols) compared to normal galaxies (open symbols). Top panel: relation between effective radius and absolute magnitude. The UDGs are significantly larger and have more globular clusters than normal galaxies of the same luminosity. [van Dokkum et al. 2017]Evidence of FailureIn general, UDGs appear to have more globular clusters than other galaxies of the same total luminosity, by a factor of nearly 7. These results are consistent with the scenario in which UDGs are failed galaxies: they likely have the halo mass to have formed a large number of globular clusters, but they were quenched before they formed a disk and bulge. Because star formation never got going in UDGs, they are now much dimmer than other galaxies of the same size.The authors suggest that the next step is to obtain dynamical measurements of the UDGs to determine whether these faint galaxies really do have the halo mass suggested by their large numbers of globulars. Future observations will continue to help us pin down the origin of these dim giants.CitationPieter van Dokkum et al 2017 ApJL 844 L11. doi:10.3847/2041-8213/aa7ca2

Nonpolytropic model for the Coma Cluster

NASA Technical Reports Server (NTRS)

Fusco-Femiano, R.; Hughes, John P.

1994-01-01

In this article we demonstrate, for the first time, how a physically motivated static model for both the gas and galaxies in the Coma Cluster of galaxies can jointly fit all available X-ray and optical imaging and spectroscopic data. The principal assumption of this nonpolytropic model (Cavaliere & Fusco-Femiano 1981, hereafter CFF), is that the intracluster gas temperature is proportional to the square of the galaxy velocity dispersion everywhere throughout the cluster; no other assumption about the gas temperature distribution is required. After demonstrating that the CFF nonpolytropic model is an adequate representation of the gas and galaxy distributions, the radial velocity dispersion profile, and the gas temperature distribution, we derive the following information about the Coma Cluster: 1. The central temperature is about 9 keV and the central density is 2.8 x 10(exp -3)/cm(exp 3) for the X-ray emitting plasma; 2. The binding mass of the cluster is approximately 2 x 10(exp 15) solar mass within 5 Mpc for (H(sub 0) = 50 km/sec/Mpc), with a mass-to-light ratio of approximately 160 solar mass/solar luminosity; 3. The contribution of the gas to the total virial mass increases with distance from the cluster center, and we estimate that this ratio is no greater than approximately 50% within 5 Mpc. The ability of the CFF nonpolytropic model to describe the current X-ray and optical data for the Coma Cluster suggests that a significant fraction of the thermal energy contained in the hot gas in this as well as other rich galaxy clusters may have come from the interaction between the galaxies and the ambient cluster medium. interaction between the galaxies and the ambient cluster medium.

Hubble Sees 'Island Universe' in the Coma Cluster

NASA Image and Video Library

2017-12-08

NASA image release August 10, 2010 A long-exposure Hubble Space Telescope image shows a majestic face-on spiral galaxy located deep within the Coma Cluster of galaxies, which lies 320 million light-years away in the northern constellation Coma Berenices. The galaxy, known as NGC 4911, contains rich lanes of dust and gas near its center. These are silhouetted against glowing newborn star clusters and iridescent pink clouds of hydrogen, the existence of which indicates ongoing star formation. Hubble has also captured the outer spiral arms of NGC 4911, along with thousands of other galaxies of varying sizes. The high resolution of Hubble's cameras, paired with considerably long exposures, made it possible to observe these faint details. NGC 4911 and other spirals near the center of the cluster are being transformed by the gravitational tug of their neighbors. In the case of NGC 4911, wispy arcs of the galaxy's outer spiral arms are being pulled and distorted by forces from a companion galaxy (NGC 4911A), to the upper right. The resultant stripped material will eventually be dispersed throughout the core of the Coma Cluster, where it will fuel the intergalactic populations of stars and star clusters. The Coma Cluster is home to almost 1,000 galaxies, making it one of the densest collections of galaxies in the nearby universe. It continues to transform galaxies at the present epoch, due to the interactions of close-proximity galaxy systems within the dense cluster. Vigorous star formation is triggered in such collisions. Galaxies in this cluster are so densely packed that they undergo frequent interactions and collisions. When galaxies of nearly equal masses merge, they form elliptical galaxies. Merging is more likely to occur in the center of the cluster where the density of galaxies is higher, giving rise to more elliptical galaxies. This natural-color Hubble image, which combines data obtained in 2006, 2007, and 2009 from the Wide Field Planetary Camera 2 and the Advanced Camera for Surveys, required 28 hours of exposure time. The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI) conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc. in Washington, D.C. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA) Acknowledgment: K. Cook (Lawrence Livermore National Laboratory) To learn more about Hubble go to: www.nasa.gov/mission_pages/hubble/main/index.html NASA Goddard Space Flight Center is home to the nation's largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe. Follow us on Twitter Join us on Facebook

Evidence of Absence of Tidal Features in the Outskirts of Ultra Diffuse Galaxies in the Coma Cluster

NASA Astrophysics Data System (ADS)

Mowla, Lamiya; van Dokkum, Pieter; Merritt, Allison; Abraham, Roberto; Yagi, Masafumi; Koda, Jin

2017-12-01

We study the presence of tidal features associated with ultra diffuse galaxies (UDGs) in galaxy clusters. Specifically, we stack deep Subaru images of UDGs in the Coma cluster to determine whether they show position angle twists at large radii. Selecting galaxies with central surface brightness μ (g,0)> 24 magarcsec-2 and projected half-light radius {r}e> 1.5 {kpc}, we identify 287 UDGs in the Yagi et al. catalog of low surface brightness Coma objects. The UDGs have apparent spheroidal shapes with median Sérsic index < n> =0.8 and median axis ratio < b/a> =0.7. The images are processed by masking all background objects and rotating to align the major axis before stacking them in bins of properties such as axis ratio, angle of major axis with respect to the cluster center, and separation from cluster center. Our image stacks reach further than 7 kpc (≳4r e). Analysis of the isophotes of the stacks reveals that the ellipticity remains constant up to the last measured point, which means that the individual galaxies have a non-varying position angle and axis ratio and show no evidence for tidal disruption out to ˜ 4{r}e. We demonstrate this explicitly by comparing our stacks with stacks of model UDGs with and without tidal features in their outskirts. We infer that the average tidal radius of the Coma UDGs is >7 kpc and estimate that the average dark matter fraction within the tidal radius of the UDGs inhabiting the innermost 0.5 Mpc of Coma is >99%.

A Comparison of the Near-Infrared Spectral Features of Early-Type Galaxies in the Virgo and Coma Clusters

NASA Astrophysics Data System (ADS)

Houdashelt, M. L.

1992-05-01

Initial results are presented from an examination of near-infrared spectra (6800 - 9200 Angstroms) of 34 early-type galaxies - 17 in the Virgo cluster, 10 in the Coma cluster and seven field members. It has previously been speculated that E/S0 galaxies of similar luminosity in the Virgo and Coma clusters have different red stellar populations. To explore this possibility, pseudo-equivalent widths of a number of near-IR spectral features have been measured. The important features studied include the TiO bands near 7100, 7890, 8197, 8500 and 8950 Angstroms, which are mainly produced by the late-type stars whose flux contributes only about 10-20\\ the near-IR. The strengths of the Ca triplet (8498, 8542, 8662 Angstroms) and Na I doublet (8183, 8195 Angstroms) are also measured, since these features are affected by the relative contribution of dwarf stars to the red light. Although the main focus of this work is the search for spectral differences among the Coma, Virgo and field E/S0 populations, each subgroup of galaxies (and the sample as a whole) are also examined for correlations among the feature strengths, galaxy color and luminosity.

The Distance to the Coma Cluster from the Tully--Fisher Relation

NASA Astrophysics Data System (ADS)

Herter, T.; Vogt, N. P.; Haynes, M. P.; Giovanelli, R.

1993-12-01

As part of a survey to determine the distances to nearby (z < .04) Abell clusters via application of the Tully--Fisher (TF) relation, we have obtained 21 cm HI line widths, optical rotation curves and photometric I--band CCD images of galaxies within and near the Coma cluster. Because spiral galaxies within the cluster itself are HI deficient and thus are detected marginally or not at all in HI, distance determinations using only the radio TF relation exclude true cluster members. Our sample includes eight HI deficient galaxies within 1.5 degrees of the cluster center, for which optical velocity widths are derived from their Hα and [NII] rotation curves. The 21 cm line widths have been extracted using a new algorithm designed to optimize the measurement for TF applications, taking into account the effects of spectral resolution and smoothing. The optical width is constructed from the velocity histogram, and is therefore a global value akin to the HI width. A correction for turbulent broadening of the HI is derived from comparison of the optical and HI widths. Using a combined sample of 260 galaxies in 11 clusters and an additional 30 field objects at comparable distances, we have performed a calibration of the radio and optical analogs of the TF relation. Preliminary results show a clear linear relationship with a small offset between optical and radio widths, and good agreement in deriving Tully--Fisher distances to clusters. Our Coma sample consists of 28 galaxies with optical widths and 42 with HI line widths, with an overlapping set of 20 galaxies. We will present the data on the Coma cluster, and discuss the results of our analysis.

The Radio Luminosity Function and Galaxy Evolution in the Coma Cluster

NASA Technical Reports Server (NTRS)

Miller, Neal A.; Hornschemeier, Ann E.; Mabasher, Bahram; Brudgesm Terrry J.; Hudson, Michael J.; Marzke, Ronald O.; Smith, Russell J.

2008-01-01

We investigate the radio luminosity function and radio source population for two fields within the Coma cluster of galaxies, with the fields centered on the cluster core and southwest infall region and each covering about half a square degree. Using VLA data with a typical rms sensitivity of 28 (mu)Jy per 4.4" beam, we identify 249 radio sources with optical counterparts brighter than r = 22 (equivalent to M(sub r) = -13 for cluster member galaxies). Comprehensive optical spectroscopy identifies 38 of these as members of the Coma cluster, evenly split between sources powered by an active nucleus and sources powered by active star formation. The radio-detected star-forming galaxies are restricted to radio luminosities between about 10(exp 21) and 10(exp 22) W/Hz, an interesting result given that star formation dominates field radio luminosity functions below about 10(exp 23) W/Hz. The majority of the radio-detected star-forming galaxies have characteristics of starbursts, including high specific star formation rates and optical spectra with strong emission lines. In conjunction with prior studies on post-starburst galaxies within the Coma cluster, this is consistent with a picture in which late-type galaxies entering Coma undergo a starburst prior to a rapid cessation of star formation. Optically bright elliptical galaxies (Mr less than or equals -20.5) make the largest contribution to the radio luminosity function at both the high (> approx. 3x10(exp 22) W/Hz) and low (< approx. 10(exp 21) W/Hz) ends. Through a stacking analysis of these optically-bright ellipticals we find that they continue to harbor radio sources down to luminosities as faint as 3x10(exp 19) W/Hz. However, contrary to published results for the Virgo cluster we find no evidence for the existence of a population of optically faint (M(sub r) approx. equals -14) dwarf ellipticals hosting strong radio AGN.

The optical properties of galaxies in the Ophiuchus cluster

NASA Astrophysics Data System (ADS)

Durret, F.; Wakamatsu, K.; Adami, C.; Nagayama, T.; Omega Muleka Mwewa Mwaba, J. M.

2018-05-01

Context. Ophiuchus is one of the most massive clusters known, but due to its low Galactic latitude its optical properties remain poorly known. Aims: We investigate the optical properties of Ophiuchus to obtain clues on the formation epoch of this cluster, and compare them to those of the Coma cluster, which is comparable in mass to Ophiuchus but much more dynamically disturbed. Methods: Based on a deep image of the Ophiuchus cluster in the r' band obtained at the Canada France Hawaii Telescope with the MegaCam camera, we have applied an iterative process to subtract the contribution of the numerous stars that, due to the low Galactic latitude of the cluster, pollute the image, and have obtained a photometric catalogue of 2818 galaxies fully complete at r' = 20.5 mag and still 91% complete at r' = 21.5 mag. We use this catalogue to derive the cluster Galaxy Luminosity Function (GLF) for the overall image and for a region (hereafter the "rectangle" region) covering exactly the same physical size as the region in which the GLF of the Coma cluster was previously studied. We then compute density maps based on an adaptive kernel technique, for different magnitude limits, and define three circular regions covering 0.08, 0.08, and 0.06 deg2, respectively, centred on the cluster (C), on northwest (NW) of the cluster, and southeast (SE) of the cluster, in which we compute the GLFs. Results: The GLF fits are much better when a Gaussian is added to the usual Schechter function, to account for the excess of very bright galaxies. Compared to Coma, Ophiuchus shows a strong excess of bright galaxies. Conclusions: The properties of the two nearby very massive clusters Ophiuchus and Coma are quite comparable, though they seem embedded in different large-scale environments. Our interpretation is that Ophiuchus was built up long ago, as confirmed by its relaxed state (see paper I) while Coma is still in the process of forming. The photometric catalogue of Ophiuchus (full Table B.1) is 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/613/A20

Spectroscopic characterisation of the stellar content of ultra diffuse galaxies

NASA Astrophysics Data System (ADS)

Ruiz-Lara, T.; Beasley, M. A.; Falcón-Barroso, J.; Román, J.; Pinna, F.; Brook, C.; Di Cintio, A.; Martín-Navarro, I.; Trujillo, I.; Vazdekis, A.

2018-05-01

Understanding the peculiar properties of Ultra Diffuse Galaxies (UDGs) via spectroscopic analysis is a challenging task requiring very deep observations and exquisite data reduction. In this work we perform one of the most complete characterisations of the stellar component of UDGs to date using deep optical spectroscopic data from OSIRIS at GTC. We measure radial and rotation velocities, star formation histories (SFH) and mean population parameters, such as ages and metallicities, for a sample of five UDG candidates in the Coma cluster. From the radial velocities, we confirm the Coma membership of these galaxies. We find that their rotation properties, if detected at all, are compatible with dwarf-like galaxies. The SFHs of the UDG are dominated by old (˜ 7 Gyr), metal-poor ([M/H] ˜ -1.1) and α-enhanced ([Mg/Fe] ˜ 0.4) populations followed by a smooth or episodic decline which halted ˜ 2 Gyr ago, possibly a sign of cluster-induced quenching. We find no obvious correlation between individual SFH shapes and any UDG morphological properties. The recovered stellar properties for UDGs are similar to those found for DDO 44, a local UDG analogue resolved into stars. We conclude that the UDGs in our sample are extended dwarfs whose properties are likely the outcome of both internal processes, such as bursty SFHs and/or high-spin haloes, as well as environmental effects within the Coma cluster.

The near-infrared Tully-Fisher relation - A preliminary study of the Coma and Abell 400 clusters

NASA Technical Reports Server (NTRS)

Guhathakurta, Puragra; Bernstein, Gary; Raychaudhury, Somak; Haynes, Martha; Giovanelli, Riccardo; Herter, Terry; Vogt, Nicole

1993-01-01

We have started a large project to study the NIR Tully-Fisher (TF) relation using H- and I-band surface photometry of spiral galaxies. A preliminary study of 20 spirals in the Coma and Abell 400 clusters is presented. The NIR images have been used to derive accurate inclinations and total magnitudes, and rotational linewidths are measured from high-quality 21-cm Arecibo data. The scatter in the Coma TF plot is found to be 0.19 mag in the H band and 0.20 mag in the I band for a set of 13 galaxies, if we assume that they are all at the same distance. The deviation of the Coma galaxies from the best-fit Tully-Fisher relation is correlated with their redshift, indicating that some of the galaxies are not bound to the cluster. Indeed, if we treat all the galaxies in the Coma sample as undergoing free Hubble expansion, the TF scatter drops to 0.12 and 0.13 mag for the H- and I-band datasets, respectively. The Abell 400 sample is best fit by a common distance model, yielding a scatter of 0.12 mag for seven galaxies in H using a fixed TF slope. We are in the process of studying cluster and field spirals out to about 10,000 km/s in order to calibrate the NIR TF relation and will apply it to more nearby galaxies to measure the peculiar velocity field in the local universe.

X-radiation from clusters of galaxies: Spectral evidence for a hot evolved gas

NASA Technical Reports Server (NTRS)

Serlemitsos, P. J.; Smith, B. W.; Boldt, E. A.; Holt, S. S.; Swank, J. H.

1976-01-01

OSO-8 observations of the X-ray flux in the range 2-60 keV from the Virgo, Perseus, and Coma Clusters provide strong evidence for the thermal origin of the radiation, including iron line emission. The data are adequately described by emission from an isothermal plasma with an iron abundance in near agreement with cosmic levels. A power law description is generally less acceptable and is ruled out in the case of Perseus. Implications on the origin of the cluster gas are discussed.

Preliminary Evidence for a Virial Shock around the Coma Galaxy Cluster

NASA Astrophysics Data System (ADS)

Keshet, Uri; Kushnir, Doron; Loeb, Abraham; Waxman, Eli

2017-08-01

Galaxy clusters, the largest gravitationally bound objects in the universe, are thought to grow by accreting mass from their surroundings through large-scale virial shocks. Due to electron acceleration in such a shock, it should appear as a γ-ray, hard X-ray, and radio ring, elongated toward the large-scale filaments feeding the cluster, coincident with a cutoff in the thermal Sunyaev-Zel’dovich (SZ) signal. However, no such signature was found until now, and the very existence of cluster virial shocks has remained a theory. We find preliminary evidence for a large γ-ray ring of ˜ 5 {Mpc} minor axis around the Coma cluster, elongated toward the large-scale filament connecting Coma and Abell 1367, detected at the nominal 2.7σ confidence level (5.1σ using control signal simulations). The γ-ray ring correlates both with a synchrotron signal and with the SZ cutoff, but not with Galactic tracers. The γ-ray and radio signatures agree with analytic and numerical predictions if the shock deposits ˜ 1 % of the thermal energy in relativistic electrons over a Hubble time and ˜ 1 % in magnetic fields. The implied inverse Compton and synchrotron cumulative emission from similar shocks can contribute significantly to the diffuse extragalactic γ-ray and low-frequency radio backgrounds. Our results, if confirmed, reveal the prolate structure of the hot gas in Coma, the feeding pattern of the cluster, and properties of the surrounding large-scale voids and filaments. The anticipated detection of such shocks around other clusters would provide a powerful new cosmological probe.

The globular cluster systems of 54 Coma ultra-diffuse galaxies: statistical constraints from HST data

NASA Astrophysics Data System (ADS)

Amorisco, N. C.; Monachesi, A.; Agnello, A.; White, S. D. M.

2018-04-01

We use data from the HST Coma Cluster Treasury program to assess the richness of the globular cluster systems (GCSs) of 54 Coma ultra-diffuse galaxies (UDGs), 18 of which have a half-light radius exceeding 1.5 kpc. We use a hierarchical Bayesian method tested on a large number of mock data sets to account consistently for the high and spatially varying background counts in Coma. These include both background galaxies and intra-cluster globular clusters (ICGCs), which are disentangled from the population of member globular clusters (GCs) in a probabilistic fashion. We find no candidate for a GCS as rich as that of the Milky Way, our sample has GCSs typical of dwarf galaxies. For the standard relation between GCS richness and halo mass, 33 galaxies have a virial mass Mvir ≤ 1011 M⊙ at 90 per cent probability. Only three have Mvir > 1011 M⊙ with the same confidence. The mean colour and spread in colour of the UDG GCs are indistinguishable from those of the abundant population of ICGCs. The majority of UDGs in our sample are consistent with the relation between stellar mass and GC richness of `normal' dwarf galaxies. Nine systems, however, display GCSs that are richer by a factor of 3 or more (at 90 per cent probability). Six of these have sizes ≲1.4 kpc. Our results imply that the physical mechanisms responsible for the extended size of the UDGs and for the enhanced GC richness of some cluster dwarfs are at most weakly correlated.

Origins of ultra-diffuse galaxies in the Coma cluster - II. Constraints from their stellar populations

NASA Astrophysics Data System (ADS)

Ferré-Mateu, Anna; Alabi, Adebusola; Forbes, Duncan A.; Romanowsky, Aaron J.; Brodie, Jean; Pandya, Viraj; Martín-Navarro, Ignacio; Bellstedt, Sabine; Wasserman, Asher; Stone, Maria B.; Okabe, Nobuhiro

2018-06-01

In this second paper of the series we study, with new Keck/DEIMOS spectra, the stellar populations of seven spectroscopically confirmed ultra-diffuse galaxies (UDGs) in the Coma cluster. We find intermediate to old ages (˜ 7 Gyr), low metallicities ([Z/H]˜ - 0.7 dex) and mostly super-solar abundance patterns ([Mg/Fe] ˜ 0.13 dex). These properties are similar to those of low-luminosity (dwarf) galaxies inhabiting the same area in the cluster and are mostly consistent with being the continuity of the stellar mass scaling relations of more massive galaxies. These UDGs' star formation histories imply a relatively recent infall into the Coma cluster, consistent with the theoretical predictions for a dwarf-like origin. However, considering the scatter in the resulting properties and including other UDGs in Coma, together with the results from the velocity phase-space study of the Paper I in this series, a mixed-bag of origins is needed to explain the nature of all UDGs. Our results thus reinforce a scenario in which many UDGs are field dwarfs that become quenched through their later infall onto cluster environments, whereas some UDGs could be be genuine primordial galaxies that failed to develop due to an early quenching phase. The unknown proportion of dwarf-like to primordial-like UDGs leaves the enigma of the nature of UDGs still open.

Comparative Study of Broadband Photometry Relations for Ultra-Diffuse and Normal Galaxies in the Coma Cluster

NASA Astrophysics Data System (ADS)

Stone, Maria Babakhanyan

Ultra-diffuse galaxies are a novel type of galaxies discovered first in the Coma cluster. These objects are characterized simultaneously by large sizes and by very low counts of constituent stars. Conflicting theories have been proposed to explain how these large diffuse galaxies could have survived in the harsh environment of clusters. To date, thousands of these new galaxies have been identified in cluster environments. However, further studies are required to understand their relationship to the known giant and dwarf classes of galaxies. The purpose of this study is to compare the trends of inner and outer populations of normal members of the Coma cluster and ultra-diffuse galaxies in color-magnitude space. The present work used several astronomical catalogs to identify the member galaxies based on the coordinates of their positions and to extract available colors and magnitudes. We obtained correlations to convert colors and magnitudes from different systems into the common Sloan Digital Sky Survey system to facilitate the comparative analysis. We showed the quantitative relations describing the color-magnitude trends of galaxies in the core and the outskirts of the cluster. We confirmed that the inner and outer populations of ultra-diffuse galaxies exhibit an offset similar to the normal red sequence galaxies. We presented an initial assessment of stellar population ages and metallicities which correspond to the obtained color offsets. We surveyed the available images of the cluster for outliers, merger candidates, and candidate ultra-diffuse galaxies. We conclude that ultra-diffuse galaxies are an important part of the Coma cluster evolutionary history and future work is needed especially in obtaining spectroscopic data of a larger number of these dim galaxies.

Observations of rich clusters of galaxies at metre wavelengths

NASA Technical Reports Server (NTRS)

Cane, H. V.; Erickson, W. C.; Hanisch, R. J.; Turner, P. J.

1981-01-01

Observations have been made at 10 frequencies between 50 and 120 MHz of 17 rich, X-ray emitting clusters of galaxies with the 78 x 156 m dipole array al Llanherne. The observed flux densities were compared to the flux densities expected on the basis of the known discrete sources in the fields. In no case was a significant flux excess found that might have indicated the presence of a diffuse halo component of radio emission in the cluster. For those clusters in which spectral indices could be determined, the spectra all tend to be much steeper than is normal for extragalactic radio sources, although a strict correlation between the X-ray luminosity and the low-frequency radio luminosity or spectral index is not found. The occurrence of large halo sources such as that which is present in the Coma cluster seems to be quite unusual.

GLOBULAR CLUSTERS AND SPUR CLUSTERS IN NGC 4921, THE BRIGHTEST SPIRAL GALAXY IN THE COMA CLUSTER

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

Lee, Myung Gyoon; Jang, In Sung, E-mail: mglee@astro.snu.ac.kr, E-mail: isjang@astro.snu.ac.kr

2016-03-01

We resolve a significant fraction of globular clusters (GCs) in NGC 4921, the brightest spiral galaxy in the Coma cluster. We also find a number of extended bright star clusters (star complexes) in the spur region of the arms. The latter are much brighter and bluer than those in the normal star-forming region, being as massive as 3 × 10{sup 5} M{sub ⊙}. The color distribution of the GCs in this galaxy is found to be bimodal. The turnover magnitudes of the luminosity functions of the blue (metal-poor) GCs (0.70 < (V − I) ≤ 1.05) in the halo are estimated V(max) = 27.11 ± 0.09 mag and I(max) = 26.21 ± 0.11 mag.more » We obtain similar values for NGC 4923, a companion S0 galaxy, and two Coma cD galaxies (NGC 4874 and NGC 4889). The mean value for the turnover magnitudes of these four galaxies is I(max) = 26.25 ± 0.03 mag. Adopting M{sub I} (max) = −8.56 ± 0.09 mag for the metal-poor GCs, we determine the mean distance to the four Coma galaxies to be 91 ± 4 Mpc. Combining this with the Coma radial velocity, we derive a value of the Hubble constant, H{sub 0} = 77.9 ± 3.6 km s{sup −1} Mpc{sup −1}. We estimate the GC specific frequency of NGC 4921 to be S{sub N} = 1.29 ± 0.25, close to the values for early-type galaxies. This indicates that NGC 4921 is in the transition phase to S0s.« less

Testing chameleon gravity with the Coma cluster

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

Terukina, Ayumu; Yamamoto, Kazuhiro; Lombriser, Lucas

2014-04-01

We propose a novel method to test the gravitational interactions in the outskirts of galaxy clusters. When gravity is modified, this is typically accompanied by the introduction of an additional scalar degree of freedom, which mediates an attractive fifth force. The presence of an extra gravitational coupling, however, is tightly constrained by local measurements. In chameleon modifications of gravity, local tests can be evaded by employing a screening mechanism that suppresses the fifth force in dense environments. While the chameleon field may be screened in the interior of the cluster, its outer region can still be affected by the extramore » force, introducing a deviation between the hydrostatic and lensing mass of the cluster. Thus, the chameleon modification can be tested by combining the gas and lensing measurements of the cluster. We demonstrate the operability of our method with the Coma cluster, for which both a lensing measurement and gas observations from the X-ray surface brightness, the X-ray temperature, and the Sunyaev-Zel'dovich effect are available. Using the joint observational data set, we perform a Markov chain Monte Carlo analysis of the parameter space describing the different profiles in both the Newtonian and chameleon scenarios. We report competitive constraints on the chameleon field amplitude and its coupling strength to matter. In the case of f(R) gravity, corresponding to a specific choice of the coupling, we find an upper bound on the background field amplitude of |f{sub R0}| < 6 × 10{sup −5}, which is currently the tightest constraint on cosmological scales.« less

Cosmic Ray Streaming in Galaxy Clusters

NASA Astrophysics Data System (ADS)

Wiener, Joshua; Gould Zweibel, Ellen; Oh, Siang P.

2017-08-01

The origin of diffuse radio emission in galaxy clusters remains an open question in astrophysics. This emission indicates the presence of cluster-wide magnetic fields and high energy cosmic ray (CR) electrons. I will discuss how the properties of the observed radio emission in clusters are shaped by different CR transport processes, namely CR streaming. Recent work has shown that fast streaming may turn off radio emission on relatively short time scales - a full treatment of magnetohydrodynamic (MHD) wave damping shows that streaming may be even faster than previously thought in high β environments. I will briefly introduce the physics behind CR transport, and present simple numerical simulations of the Coma cluster that predict radio emission, as well as other observable signatures such as gamma radiation that can differentiate between models for the source of the CR electrons.

Neutralinos and the Origin of Radio Halos in Clusters of Galaxies

NASA Astrophysics Data System (ADS)

Colafrancesco, S.; Mele, B.

2001-11-01

We assume that the supersymmetric lightest neutralino is a good candidate for the cold dark matter in the galaxy halo and explore the possibility to produce extended diffuse radio emission from high-energy electrons arising from the neutralino annihilation in galaxy clusters whose intracluster medium is filled with a large-scale magnetic field. We show that these electrons fit the population of seed relativistic electrons that is postulated in many models for the origin of cluster radio halos. For a uniform magnetic field of ~1-3 μG the population of seed relativistic electrons from neutralino annihilation can fit the radio halo spectra of two well-studied clusters: Coma and 1E 0657-56. In the case of a magnetic field that is radially decreasing from the cluster center, central values ~8 μG (for Coma) and ~50 μG (for 1E 0657-56) are required to fit the data. The radio halo data strongly favor a centrally peaked dark matter density profile (like a Navarro, Frenk, & White [NFW97] density profile). The shape and the frequency extension of the radio halo spectra are connected with the mass and physical composition of the neutralino. A pure gaugino neutralino with mass Mχ>=80 GeV can reasonably fit the radio halo spectra of both Coma and 1E 0657-56. The model we present here provides a number of extra predictions that make it definitely testable. On the one hand, it agrees quite well with the observations that (1) the radio halo is centered on the cluster dynamical center, usually coincident with the center of its X-ray emission; (2) the radio halo surface brightness is similar to the X-ray one; and (3) the monochromatic radio luminosity at 1.4 GHz correlates strongly with the intracluster (IC) gas temperature. On the other hand, the same model predicts that radio halos should be present in every cluster, which is not presently observed, although the predicted radio halo luminosities can change (decrease) by factors of up to ~102-106, depending on the amplitude and the structure of the IC magnetic field. In addition, neutral pions arising from neutralino annihilation should give rise to substantial amounts of diffuse gamma-ray emission, up to energies of order Mχ, that could be tested by the next-generation gamma-ray experiments.

XMM-Newton observation of the Coma Galaxy cluster. The temperature structure in the central region

NASA Astrophysics Data System (ADS)

Arnaud, M.; Aghanim, N.; Gastaud, R.; Neumann, D. M.; Lumb, D.; Briel, U.; Altieri, B.; Ghizzardi, S.; Mittaz, J.; Sasseen, T. P.; Vestrand, W. T.

2001-01-01

We present a temperature map and a temperature profile of the central part (r < 20' or 1/4 virial radius) of the Coma cluster. We combined 5 overlapping pointings made with XMM/EPIC/MOS and extracted spectra in boxes of 3.5'x3.5'. The temperature distribution around the two central galaxies is remarkably homogeneous (r<10'), contrary to previous ASCA results, suggesting that the core is actually in a relaxed state. At larger distance from the cluster center we do see evidence for recent matter accretion. We confirm the cool area in the direction of NGC 4921, probably due to gas stripped from an infalling group. We find indications of a hot front in the South West, in the direction of NGC 4839, probably due to an adiabatic compression. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and the USA (NASA). EPIC was developed by the EPIC Consortium led by the Principal Investigator, Dr. M. J. L. Turner. The consortium comprises the following Institutes: University of Leicester, University of Birmingham, (UK); CEA/Saclay, IAS Orsay, CESR Toulouse, (France); IAAP Tuebingen, MPE Garching, (Germany); IFC Milan, ITESRE Bologna, IAUP Palermo, Italy. EPIC is funded by: PPARC, CEA, CNES, DLR and ASI.

The Hunt for Missing Dwarf Galaxies

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2015-11-01

Theories of galaxy formation and evolution predict that there should be significantly more dwarf galaxies than have been observed. Are our theories wrong? Or are dwarf galaxies just difficult to detect? Recent results from a survey of a galaxy cluster 62 million light-years away suggest there may be lots of undiscovered dwarf galaxies hiding throughout the universe!Hiding in FaintnessThe missing dwarf problem has had hints of a resolution with the recent discovery of Ultra-Diffuse Galaxies (UDGs) in the Coma and Virgo galaxy clusters. UDGs have low masses and large radii, resulting in a very low surface brightness that makes them extremely difficult to detect. If many dwarfs are UDGs, this could well explain why weve been missing them!But the Coma and Virgo galaxy clusters are similar in that theyre both very massive. Are there UDGs in other galaxy clusters as well? To answer this question, an international team of scientists is running the Next Generation Fornax Survey (NGFS), a survey searching for faint dwarf galaxies in the central 30 square degrees of the Fornax galaxy cluster.The NGFS uses near-UV and optical observations from the Dark Energy Camera mounted on the 4m Blanco Telescope in Chile. The survey is still underway, but in a recent publication led by Roberto P. Muoz (Institute of Astrophysics at the Pontifical Catholic University of Chile), the team has released an overview of the first results from only the central 3 square degrees of the NGFS field.Surprising DetectionGalaxy radii vs. their absolute i-band magnitudes, for the dwarfs found in NGFS as well as other stellar systems in the nearby universe. The NGFS dwarfs are similar to the ultra-diffuse dwarfs found in the Virgo and Coma clusters, but are several orders of magnitude fainter. [Muoz et al. 2015]In just this small central field, the team has found an astounding 284 low-surface-brightness dwarf galaxy candidates 158 of them previously undetected. At the bright end of this sample are dwarf galaxies that resemble the UDGs found in Virgo and Coma clusters, verifying that such objects exist in environments beyond only massive clusters.And at the faint end of the sample, the authors find additional extremely low-surface-brightness dwarfs that are several orders of magnitude fainter even than classical UDGs.The authors describe the properties of these galaxies and compare them to systems like classical UDGs and dwarf spheroidal galaxies in our own Local Cluster. The next step is to determine which of the differences between the sample of NGFS dwarfs and previously known systems are explained by the environmental factors of their host cluster, and which are simply due to sample biases.With much more data from the NGFS still to come, it seems likely that we will soon be able to examine an even larger sample of no-longer-missing dwarfs!CitationRoberto P. Muoz et al 2015 ApJ 813 L15. doi:10.1088/2041-8205/813/1/L15

A Cluster Of Activities On Coma From The Hubble Space Telescope, StarDate, And McDonald Observatory

NASA Astrophysics Data System (ADS)

Hemenway, Mary Kay; Jogee, S.; Fricke, K.; Preston, S.

2011-01-01

With a goal of providing a vast audience of students, teachers, the general public, and Spanish-speakers with activities to learn about research on the Coma cluster of galaxies based on the HST ACS Treasury survey of Coma, McDonald Observatory used a many-faceted approach. Since this research offered an unprecedented legacy dataset, part of the challenge was to convey the importance of this project to a diverse audience. The methodology was to create different products for different (overlapping) audiences. Five radio programs were produced in English and Spanish for distribution on over 500 radio stations in the US and Mexico with a listening audience of over 2 million; in addition to the radio listeners, there were over 13,000 downloads of the English scripts and almost 6000 of the Spanish. Images were prepared for use in the StarDate Online Astronomy Picture of the Week, for ViewSpace (used in museums), and for the StarDate/Universo Teacher Guide. A high-school level activity on the Coma Cluster was prepared and distributed both on-line and in an upgraded printed version of the StarDate/Universo Teacher Guide. This guide has been distributed to over 1700 teachers nationally. A YouTube video about careers and research in astronomy using the Coma cluster as an example was produced. Just as the activities were varied, so were the evaluation methods. This material is based upon work supported by the National Aeronautics and Space Administration under Grant/Contract/Agreement No. HST-EO-10861.35-A issued through the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

Membership determination of open clusters based on a spectral clustering method

NASA Astrophysics Data System (ADS)

Gao, Xin-Hua

2018-06-01

We present a spectral clustering (SC) method aimed at segregating reliable members of open clusters in multi-dimensional space. The SC method is a non-parametric clustering technique that performs cluster division using eigenvectors of the similarity matrix; no prior knowledge of the clusters is required. This method is more flexible in dealing with multi-dimensional data compared to other methods of membership determination. We use this method to segregate the cluster members of five open clusters (Hyades, Coma Ber, Pleiades, Praesepe, and NGC 188) in five-dimensional space; fairly clean cluster members are obtained. We find that the SC method can capture a small number of cluster members (weak signal) from a large number of field stars (heavy noise). Based on these cluster members, we compute the mean proper motions and distances for the Hyades, Coma Ber, Pleiades, and Praesepe clusters, and our results are in general quite consistent with the results derived by other authors. The test results indicate that the SC method is highly suitable for segregating cluster members of open clusters based on high-precision multi-dimensional astrometric data such as Gaia data.

Automated surface photometry for the Coma Cluster galaxies: The catalog

NASA Technical Reports Server (NTRS)

Doi, M.; Fukugita, M.; Okamura, S.; Tarusawa, K.

1995-01-01

A homogeneous photometry catalog is presented for 450 galaxies with B(sub 25.5) less than or equal to 16 mag located in the 9.8 deg x 9.8 deg region centered on the Coma Cluster. The catalog is based on photographic photometry using an automated surface photometry software for data reduction applied to B-band Schmidt plates. The catalog provides accurate positions, isophotal and total magnitudes, major and minor axes, and a few other photometric parameters including rudimentary morphology (early of late type).

Investigating Open Clusters Melotte 111 and NGC 6811

NASA Astrophysics Data System (ADS)

Gunshefski, Linda; Paust, Nathaniel E. Q.; van Belle, Gerard

2018-01-01

We present photometry and color-magnitude diagrams for the open clusters Melotte 111 (Coma Bernices) and NGC 6811. These clusters were observed with Lowell Observatory’s Discovery Channel Telescope Large Monolithic Imager in the V and I bands. The images were reduced with IRAF and photometry was performed with DAOPHOT/ALLSTAR. The resulting photometry extends many magnitudes below the main sequence turnoff. Both clusters are located nearby, (Melotte 111 d=86 pc and NGC 6811 d=1,107) and are evolutionarily young (Melotte 111, age=450 Myr and NGC 6811, age=1,000 Myr). This work marks the first step of a project to determine the cluster main sequence mass functions and examine how the mass functions evolve in young stellar populations.

Fluorine Abundances of AGB Stars in Stellar Clusters

NASA Astrophysics Data System (ADS)

Hren, A.; Lebzelter, T.; Aringer, B.; Hinkle, K. H.; Nowotny, W.

2015-08-01

We have measured the abundance of fluorine, [F/Fe], in a number of AGB stars in stellar clusters have correlated the results with their C/O ratios. This allows us to investigate the change in the fluorine abundance along the evolution on the giant branch. The target list includes primarily O-rich stars in three LMC globular clusters - NGC 1806, NGC 1846 and NGC 1978 - as well as Rup 106 and 47 Tuc in our Galaxy. The observational data were obtained with the PHOENIX spectrograph, and the COMA code was used for modelling the synthetic spectra. Within individual clusters, we find consistent [F/Fe] values at similar C/O for most of our target stars.

IRAS galaxies and the large-scale structure in the CfA slice

NASA Technical Reports Server (NTRS)

Babul, Arif; Postman, Marc

1990-01-01

The spatial distributions of the IRAS and the optical galaxies in the first CfA slice are compared. The IRAS galaxies are generally less clustered than optical ones, but their distribution is essentially identical to that of late-type optical galaxies. The discrepancy between the clustering properties of the IRAS and optical samples in the CfA slice region is found to be entirely due to the paucity of IRAS galaxies in the core of the Coma cluster. The spatial distributions of the IRAS and the optical galaxies, both late and early types, outside the dense core of the Coma cluster are entirely consistent with each other. This conflicts with the prediction of the linear biasing scenario.

Ram Pressure Stripping and Morphological Transformation in the Coma Cluster

NASA Astrophysics Data System (ADS)

Gregg, Michael; West, Michael

2017-01-01

The two largest spiral galaxies in the Coma cluster, NGC4911 and NGC4921, exhibit signs of being vigorously ram-pressure stripped by the hot intracluster medium. HST ACS and WFC3 images have revealed galactic scale shock fronts, giant "Pillars of Creation", rivulets of dust, and spatially coherent star formation in these grand design spirals. All evidence points to these galaxies being stressed by a global external source which can only be the hot intracluster medium (ICM). Inspired by these examples, we have obtained HST WFC3 imaging of five additional large spirals to search for and investigate the effects of ram pressure stripping across the wider Coma cluster. The results are equally spectacular as the first two examples. The geometry of the interactions in some cases allows us to estimate the various time scales involved, including gas flows out of the disk leading to creation of the ICM, and the attendant triggered star formation in the galaxy disks. The global star formation patterns and wholesale tidal stripping of matter yield insights into the spatial and temporal ISM-ICM interactions driving the evolution of galaxies in clusters and ultimately transforming their morphologies from spiral to S0. These processes, much more common in the early Universe, led to the wholesale morphological transformation of Hubble types during the assembly of rich clusters, when the intergalactic populations and hot ICM were first being created and laid down from such stripping and destruction of their member galaxies.We also report on two instrumental aspects of WFC3: 1) using the filter pair F350LP and F600LP to create an extremely broad pseudo Blue-Red color to achieve the greatest observing efficiency with HST, and 2) a WFC3 CCD effect which leads to apparent quantization of background counts, making automatic sky determination challenging when using drizzlepac routines.

Nature of multiple-nucleus cluster galaxies

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

Merritt, D.

1984-05-01

In models for the evolution of galaxy clusters which include dynamical friction with the dark binding matter, the distribution of galaxies becomes more concentrated to the cluster center with time. In a cluster like Coma, this evolution could increase by a factor of approximately 3 the probability of finding a galaxy very close to the cluster center, without decreasing the typical velocity of such a galaxy significantly below the cluster mean. Such an enhancement is roughly what is needed to explain the large number of first-ranked cluster galaxies which are observed to have extra ''nuclei''; it is also consistent withmore » the high velocities typically measured for these ''nuclei.'' Unlike the cannibalism model, this model predicts that the majority of multiple-nucleus systems are transient phenomena, and not galaxies in the process of merging.« less

Some Observations on the Use of the Woodcock-Johnson Tests of Cognitive Ability in Adults with Head Injury.

ERIC Educational Resources Information Center

Tupper, David E.

1990-01-01

The study provides descriptive data on use of the Woodcock-Johnson Tests of Cognitive Ability with 39 adults with closed head injury. Correlational analyses indicated significant relationships between coma duration and performance on the Perceptual Speed and Memory clusters of the test. Time since injury did not correlate with test results.…

DRY MERGER RATE AND POST-MERGER FRACTION IN THE COMA CLUSTER CORE

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

Cordero, Juan P.; Campusano, Luis E.; Haines, Christopher P.

2016-01-20

We evaluate the dry merger activity in the Coma cluster, using a spectroscopically complete sample of 70 red-sequence (RS) galaxies, most of which (∼75%) are located within 0.2R{sub 200} (∼0.5 Mpc) from the cluster center, with data from the Coma Treasury Survey obtained with the Hubble Space Telescope. The fraction of close galaxy pairs in the sample is the proxy employed for the estimation of the merger activity. We identify 5 pairs and 1 triplet, enclosing a total of 13 galaxies, based on limits on projected separation and line-of-sight velocity difference. Of these systems, none show signs of ongoing interaction,more » and therefore we do not find any true mergers in our sample. This negative result sets a 1σ upper limit of 1.5% per Gyr for the major dry merger rate, consistent with the low rates expected in present-day clusters. Detailed examination of the images of all the RS galaxies in the sample reveals only one with low surface brightness features identifiable as the remnant of a past merger or interaction, implying a post-merger fraction below 2%.« less

Analysis and Interpretation of Hard X-ray Emission fromthe Bullet Cluster (1E0657-56), the Most Distant Cluster of Galaxies Observed by the RXTE

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

Petrosian, Vahe; /Stanford U., Phys. Dept. /SLAC /Stanford U., Appl. Phys. Dept.; Madejski, Greg

2006-08-16

Evidence for non-thermal activity in clusters of galaxies is well established from radio observations of synchrotron emission by relativistic electrons. New windows in the Extreme Ultraviolet and Hard X-ray ranges have provided for more powerful tools for the investigation of this phenomenon. Detection of hard X-rays in the 20 to 100 keV range have been reported from several clusters of galaxies, notably from Coma and others. Based on these earlier observations we identified the relatively high redshift cluster 1E0657-56 (also known as RX J0658-5557) as a good candidate for hard X-ray observations. This cluster, also known as the bullet cluster,more » has many other interesting and unusual features, most notably that it is undergoing a merger, clearly visible in the X-ray images. Here we present results from a successful RXTE observations of this cluster. We summarize past observations and their theoretical interpretation which guided us in the selection process. We describe the new observations and present the constraints we can set on the flux and spectrum of the hard X-rays. Finally we discuss the constraints one can set on the characteristics of accelerated electrons which produce the hard X-rays and the radio radiation.« less

KECK/LRIS SPECTROSCOPIC CONFIRMATION OF COMA CLUSTER DWARF GALAXY MEMBERSHIP ASSIGNMENTS

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

Chiboucas, Kristin; Tully, R. Brent; Marzke, Ronald O.

2010-11-01

Keck/LRIS multi-object spectroscopy has been carried out on 140 of some of the lowest and highest surface brightness faint (19 < R < 22) dwarf galaxy candidates in the core region of the Coma Cluster. These spectra are used to measure redshifts and establish membership for these faint dwarf populations. The primary goal of the low surface brightness sample is to test our ability to use morphological and surface brightness criteria to distinguish between Coma Cluster members and background galaxies using high resolution Hubble Space Telescope/Advanced Camera for Surveys images. Candidates were rated as expected members, uncertain, or expected background.more » From 93 spectra, 51 dwarf galaxy members and 20 background galaxies are identified. Our morphological membership estimation success rate is {approx}100% for objects expected to be members and better than {approx}90% for galaxies expected to be in the background. We confirm that low surface brightness is a very good indicator of cluster membership. High surface brightness galaxies are almost always background with confusion arising only from the cases of the rare compact elliptical (cE) galaxies. The more problematic cases occur at intermediate surface brightness. Many of these galaxies are given uncertain membership ratings, and these were found to be members about half of the time. Including color information will improve membership determination but will fail for some of the same objects that are already misidentified when using only surface brightness and morphology criteria. cE galaxies with B-V colors {approx}0.2 mag redward of the red sequence in particular require spectroscopic follow up. In a sample of 47 high surface brightness, ultracompact dwarf candidates, 19 objects have redshifts which place them in the Coma Cluster, while another 6 have questionable redshift measurements but may also prove to be members. Redshift measurements are presented and the use of indirect means for establishing cluster membership is discussed.« less

A Novel Approach to Constrain the Mass Ratio of Minor Mergers in Elliptical Galaxies: Application to NGC 4889, the Brightest Cluster Galaxy in Coma

NASA Astrophysics Data System (ADS)

Gu, Meng; Ho, Luis C.; Peng, Chien Y.; Huang, Song

2013-08-01

Minor mergers are thought to be important for the buildup and structural evolution of massive elliptical galaxies. In this work, we report the discovery of a system of four shell features in NGC 4889, one of the brightest members of the Coma cluster, using optical images taken with the Hubble Space Telescope and the Sloan Digital Sky Survey. The shells are well aligned with the major axis of the host and are likely to have been formed by the accretion of a small satellite galaxy. We have performed a detailed two-dimensional photometric decomposition of NGC 4889 and of the many overlapping nearby galaxies in its vicinity. This comprehensive model allows us not only to firmly detect the low-surface brightness shells, but, crucially, also to accurately measure their luminosities and colors. The shells are bluer than the underlying stars at the same radius in the main galaxy. We make use of the colors of the shells and the color-magnitude relation of the Coma cluster to infer the luminosity (or mass) of the progenitor galaxy. The shells in NGC 4889 appear to have been produced by the minor merger of a moderate-luminosity (MI ≈ -18.7 mag) disk (S0 or spiral) galaxy with a luminosity (mass) ratio of ~90:1 with respect to the primary galaxy. The novel methodology presented in this work can be exploited to decode the fossil record imprinted in the photometric substructure of other nearby early-type galaxies. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under NASA contract NAS5-26555.

Effect of a chameleon scalar field on the cosmic microwave background

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

Davis, Anne-Christine; Schelpe, Camilla A. O.; Shaw, Douglas J.

2009-09-15

We show that a direct coupling between a chameleonlike scalar field and photons can give rise to a modified Sunyaev-Zel'dovich (SZ) effect in the cosmic microwave background (CMB). The coupling induces a mixing between chameleon particles and the CMB photons when they pass through the magnetic field of a galaxy cluster. Both the intensity and the polarization of the radiation are modified. The degree of modification depends strongly on the properties of the galaxy cluster such as magnetic field strength and electron number density. Existing SZ measurements of the Coma cluster enable us to place constraints on the photon-chameleon coupling.more » The constrained conversion probability in the cluster is P{sub Coma}(204 GHz)<6.2x10{sup -5} at 95% confidence, corresponding to an upper bound on the coupling strength of g{sub eff}{sup (cell)}<2.2x10{sup -8} GeV{sup -1} or g{sub eff}{sup (Kolmo)}<(7.2-32.5)x10{sup -10} GeV{sup -1}, depending on the model that is assumed for the cluster magnetic field structure. We predict the radial profile of the chameleonic CMB intensity decrement. We find that the chameleon effect extends farther toward the edges of the cluster than the thermal SZ effect. Thus we might see a discrepancy between the x-ray emission data and the observed SZ intensity decrement. We further predict the expected change to the CMB polarization arising from the existence of a chameleonlike scalar field. These predictions could be verified or constrained by future CMB experiments.« less

Deep CCD Photometry of the Rich Galaxy Cluster Abel 1656 Characteristics of the Dwarf Elliptical Galaxy Population in the Cluster Core

NASA Astrophysics Data System (ADS)

Secker, Jeffrey Alan

1995-01-01

We have developed a statistically rigorous and automated method to implement the detection, photometry and classification of faint objects on digital images. We use these methods to analyze deep R- and B-band CCD images of the central ~ 700 arcmin ^2 of the Coma cluster core, and an associated control field. We have detected and measured total R magnitudes and (B-R) colors for a sample of 3741 objects on the galaxy cluster fields, and 1164 objects on a remote control field, complete to a limiting magnitude of R = 22.5 mag. The typical uncertainties are +/- 0.06 and +/-0.12 mag in total magnitude and color respectively. The dwarf elliptical (dE) galaxies are confined to a well-defined sequence in the color range given by 0.7<= (B-R)<= 1.9 mag: within this interval there are 2535 dE candidates on our fields in the cluster core, and 694 objects on the control field. With an image scale of 0.53 arcsec/pixel and seeing near 1.2 arcsec, a large fraction of the dE galaxy candidates are resolved. We find a significant metallicity gradient in the radial distribution of the dwarf elliptical galaxies, which goes as Z~ R^{-0.32 } outwards from the cluster center at NGC 4874. As well, there is a strong color-luminosity correlation, in the sense that more luminous dE galaxies are redder in the mean. These effects give rise to a radial variation in the cluster luminosity function. The spatial distribution of the faint dE galaxies is well fit by a standard King model with a central surface density of Sigma _0 = 1.44 dEs arcmin^{ -2}, a core radius R_{ rm c} = 18.7 arcmin (~eq 0.44 Mpc), and a tidal radius of 1.44 deg ( ~eq 2.05 Mpc). This core is significantly larger than R_{rm c} = 12.3 arcmin (~eq 0.29 Mpc) found for the bright cluster galaxies. The composite luminosity function for Coma galaxies is modeled as the sum of a log -normal distribution for the giant galaxies and a Schechter function for the dwarf elliptical galaxies, with a faint -end slope of alpha = -1.41, consistent with known faint-end slopes for the Virgo and Fornax clusters. The early-type dwarf-to-giant ratio for the Coma cluster core is consistent with that of the Virgo cluster, and thus with the rich Coma cluster being formed as the merger of multiple less-rich galaxy clusters.

The Fundamental Plane and the Surface Brightness Test for the Expansion of the Universe

NASA Astrophysics Data System (ADS)

Kjaergaard, Per; Jorgensen, Inger; Moles, Mariano

1993-12-01

We have determined the Petrosian radius, rη , and the enclosed mean surface brightness within the Petrosian radius, <μ>η, for 33 elliptical and S0 galaxies in the Coma cluster from new accurate CCD surface photometry. For the Petrosian parameter η = 1.39, rη and <μ>η are compared with the effective radius, re, and the effective mean surface brightness, <μ>e derived from fitting a de Vaucouleurs law. The fundamental plane (FP) expressed using rη and <μ>η is the same as the FP found by Jørgensen, Franx, & Kjaergaard (1993) using re and <μ>e. The FP can be used to predict the mean surface brightness within the effective radius or the corresponding Petrosian radius (η = 1.39) with an uncertainty of ±0.14 mag for Coma cluster ellipticals. Thus the FP, applied to clusters, appears to be a suitable tool for performing the surface brightness test (SBT) for the expansion of the universe. We suggest that instead of correcting individual galaxies to some standard conditions, e.g., the same metric radius, the fundamental plane itself should be considered the standard. It is argued that the metric size enclosing around 75% of the total light represents a reasonable compromise between resolution and faint level detection when performing the SBT. This radius could be derived as the Petrosian radius corresponding to η = 2.0 or from a global fit to that part of the observed profile which encompasses 75% of the total light. In case both small and large galaxies are well described by a de Vaucouleurs law the global fit can be performed on a smaller central part of the brightness profile. The use of the FP involves the time consuming determinations of velocity dispersions. We find that <μ>η (η = 1.39) can be predicted from the log rη alone with an accuracy of 0.3 mag for the Coma cluster ellipticals. Our discussion of the various error contributions to the predicted mean surface brightness for faint cluster ellipticals at redshifts z < 0.5 shows that the final error is probably dominated by extra scatter due to, e.g., environmental and evolutionary effects. Thus it might be possible that the use of velocity dispersions are not necessary. To get significant results for the SBT, clusters out to a redshift of approximately z = 0.3 have to be observed. For the most distant galaxies light levels down to about 25-26 mag arcsec-2 in the red and sizes as small as approximately 2" have to be accurately measured. We outline an observational program which will allow the control of the different sources of scatter, including cosmic evolution, producing conclusive results about the expansion of the universe.

THE GALAXY LUMINOSITY FUNCTIONS DOWN TO M{sub R} = -10 IN THE COMA CLUSTER

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

Yamanoi, Hitomi; Komiyama, Yutaka; Yagi, Masafumi

2012-08-15

We derived the luminosity function (LF) of dwarf galaxies in the Coma Cluster down to M{sub R} = -10 at three fields located at the center, intermediate, and outskirt of the cluster. The LF (-19 < M{sub R} < -10) shows no significant differences among the three fields. It shows a clear dip at M{sub R} {approx} -13 and is composed of two distinct components of different slopes; the bright component with -19 < M{sub R} < -13 has a flatter slope than the faint component with -13 < M{sub R} < -10 which has a steep slope. The brightmore » component (-19 < M{sub R} < -13) consists mostly of red extended galaxies including few blue galaxies whose colors are typical of late-type galaxies. On the other hand, the faint component (-13 < M{sub R} < -10) consists largely of point-spread-function-like compact galaxies. We found that both these compact galaxies and some extended galaxies are present in the center while only compact galaxies are seen in the outskirt. In the faint component, the fraction of blue galaxies is larger in the outskirt than in the center. We suggest that the dwarf galaxies in the Coma Cluster, which make up the two components in the LF, are heterogeneous with some different origins.« less

Relativistic protons in the Coma galaxy cluster: first gamma-ray constraints ever on turbulent reacceleration

NASA Astrophysics Data System (ADS)

Brunetti, G.; Zimmer, S.; Zandanel, F.

2017-12-01

The Fermi-LAT (Large Area Telescope) collaboration recently published deep upper limits to the gamma-ray emission of the Coma cluster, a cluster hosting the prototype of giant radio haloes. In this paper, we extend previous studies and use a formalism that combines particle reacceleration by turbulence and the generation of secondary particles in the intracluster medium to constrain relativistic protons and their role for the origin of the radio halo. We conclude that a pure hadronic origin of the halo is clearly disfavoured as it would require excessively large magnetic fields. However, secondary particles can still generate the observed radio emission if they are reaccelerated. For the first time the deep gamma-ray limits allow us to derive meaningful constraints if the halo is generated during phases of reacceleration of relativistic protons and their secondaries by cluster-scale turbulence. In this paper, we explore a relevant range of parameter space of reacceleration models of secondaries. Within this parameter space, a fraction of model configurations is already ruled out by current gamma-ray limits, including the cases that assume weak magnetic fields in the cluster core, B ≤ 2-3 μG. Interestingly, we also find that the flux predicted by a large fraction of model configurations assuming magnetic fields consistent with Faraday rotation measures (RMs) is not far from the limits. This suggests that a detection of gamma-rays from the cluster might be possible in the near future, provided that the electrons generating the radio halo are secondaries reaccelerated and the magnetic field in the cluster is consistent with that inferred from RM.

Zeldovich pancakes in observational data are cold

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

Brinckmann, Thejs; Lindholmer, Mikkel; Hansen, Steen

The present day universe consists of galaxies, galaxy clusters, one-dimensional filaments and two-dimensional sheets or pancakes, all of which combine to form the cosmic web. The so called ''Zeldovich pancakes' are very difficult to observe, because their overdensity is only slightly greater than the average density of the universe. Falco et al. [1] presented a method to identify Zeldovich pancakes in observational data, and these were used as a tool for estimating the mass of galaxy clusters. Here we expand and refine that observational detection method. We study two pancakes on scales of 10 Mpc, identified from spectroscopically observed galaxiesmore » near the Coma cluster, and compare with twenty numerical pancakes.We find that the observed structures have velocity dispersions of about 100 km/sec, which is relatively low compared to typical groups and filaments. These velocity dispersions are consistent with those found for the numerical pancakes. We also confirm that the identified structures are in fact two-dimensional structures. Finally, we estimate the stellar to total mass of the observational pancakes to be 2 · 10{sup −4}, within one order of magnitude, which is smaller than that of clusters of galaxies.« less

A multi-frequency analysis of possible dark matter contributions to M31 gamma-ray emissions

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

Beck, G.; Colafrancesco, S., E-mail: geoffrey.beck@wits.ac.za, E-mail: sergio.colafrancesco@wits.ac.za

We examine the possibility of a dark matter (DM) contribution to the recently observed gamma-ray spectrum seen in the M31 galaxy. In particular, we apply limits on Weakly Interacting Massive Particle DM annihilation cross-sections derived from the Coma galaxy cluster and the Reticulum II dwarf galaxy to determine the maximal flux contribution by DM annihilation to both the M31 gamma-ray spectrum and that of the Milky-Way Galactic Centre. We limit the energy range between 1 and 12 GeV in M31 and Galactic Centre spectra due to the limited range of former's data, as well as to encompass the high-energy gamma-raymore » excess observed in the latter target. In so doing, we will make use of Fermi-LAT data for all mentioned targets, as well as diffuse radio data for the Coma cluster. The multi-target strategy using both Coma and Reticulum II to derive cross-section limits, as well as multi-frequency data, ensures that our results are robust against the various uncertainties inherent in modelling of indirect DM emissions. Our results indicate that, when a Navarro-Frenk-White (or shallower) radial density profile is assumed, severe constraints can be imposed upon the fraction of the M31 and Galactic Centre spectra that can be accounted for by DM, with the best limits arising from cross-section constraints from Coma radio data and Reticulum II gamma-ray limits. These particular limits force all the studied annihilation channels to contribute 1% or less to the total integrated gamma-ray flux within both M31 and Galactic Centre targets. In contrast, considerably more, 10−100%, of the flux can be attributed to DM when a contracted Navarro-Frenk-White profile is assumed. This demonstrates how sensitive DM contributions to gamma-ray emissions are to the possibility of cored profiles in galaxies. The only channel consistently excluded for all targets and profiles (except for ∼ 10 GeV WIMPs) is the direct annihilation into photons. Finally, we discuss the ramifications of evidence in favour of cored halo density profiles for DM explanations of galactic gamma-ray emission.« less

GalWeight: A New and Effective Weighting Technique for Determining Galaxy Cluster and Group Membership

NASA Astrophysics Data System (ADS)

Abdullah, Mohamed H.; Wilson, Gillian; Klypin, Anatoly

2018-07-01

We introduce GalWeight, a new technique for assigning galaxy cluster membership. This technique is specifically designed to simultaneously maximize the number of bona fide cluster members while minimizing the number of contaminating interlopers. The GalWeight technique can be applied to both massive galaxy clusters and poor galaxy groups. Moreover, it is effective in identifying members in both the virial and infall regions with high efficiency. We apply the GalWeight technique to MDPL2 and Bolshoi N-body simulations, and find that it is >98% accurate in correctly assigning cluster membership. We show that GalWeight compares very favorably against four well-known existing cluster membership techniques (shifting gapper, den Hartog, caustic, SIM). We also apply the GalWeight technique to a sample of 12 Abell clusters (including the Coma cluster) using observations from the Sloan Digital Sky Survey. We conclude by discussing GalWeight’s potential for other astrophysical applications.

A Suzaku Search for Nonthermal Emission at Hard X-Ray Energies in the Coma Cluster

DTIC Science & Technology

2008-09-01

monochromatic fluxes FR(νR), FX (νX) at frequencies νR , νX, for a power-law distribution of electrons, from which we can derive an expression for the magnetic...field as B = C(p)(1 + z)(p+5)/(p+1) ( FR FX )2/(p+1) ( νR νX )(p−1)/(p+1) , (14) where p is the index of the electron distribution N (E) ∝ E−p and is...IN THE COMA CLUSTER 1711 like NuStar,10 Astro -H (previously NeXT),11 and Simbol-X.12 If the IC emission is localized, then our joint fitting

Star formation and galaxy evolution in different environments, from the field to massive clusters

NASA Astrophysics Data System (ADS)

Tyler, Krystal

This thesis focuses on how a galaxy's environment affects its star formation, from the galactic environment of the most luminous IR galaxies in the universe to groups and massive clusters of galaxies. Initially, we studied a class of high-redshift galaxies with extremely red optical-to-mid-IR colors. We used Spitzer spectra and photometry to identify whether the IR outputs of these objects are dominated by AGNs or star formation. In accordance with the expectation that the AGN contribution should increase with IR luminosity, we find most of our very red IR-luminous galaxies to be dominated by an AGN, though a few appear to be star-formation dominated. We then observed how the density of the extraglactic environment plays a role in galaxy evolution. We begin with Spitzer and HST observations of intermediate-redshift groups. Although the environment has clearly changed some properties of its members, group galaxies at a given mass and morphology have comparable amounts of star formation as field galaxies. We conclude the main difference between the two environments is the higher fraction of massive early-type galaxies in groups. Clusters show even more distinct trends. Using three different star-formation indicators, we found the mass-SFR relation for cluster galaxies can look similar to the field (A2029) or have a population of low-star-forming galaxies in addition to the field-like galaxies (Coma). We contribute this to differing merger histories: recently-accreted galaxies would not have time for their star formation to be quenched by the cluster environment (A2029), while an accretion event in the past few Gyr would give galaxies enough time to have their star formation suppressed by the cluster environment. Since these two main quenching mechanisms depend on the density of the intracluster gas, we turn to a group of X-ray underluminous clusters to study how star-forming galaxies have been affected in clusters with lower than expected X-ray emission. We find the distribution of star-forming galaxies with respect to stellar mass varies from cluster to cluster, echoing what we found for Coma and A2029. In other words, while some preprocessing occurs in groups, the cluster environment still contributes to the quenching of star formation.

Coma cluster ultradiffuse galaxies are not standard radio galaxies

NASA Astrophysics Data System (ADS)

Struble, Mitchell F.

2018-02-01

Matching members in the Coma cluster catalogue of ultradiffuse galaxies (UDGs) from SUBARU imaging with a very deep radio continuum survey source catalogue of the cluster using the Karl G. Jansky Very Large Array (VLA) within a rectangular region of ∼1.19 deg2 centred on the cluster core reveals matches consistent with random. An overlapping set of 470 UDGs and 696 VLA radio sources in this rectangular area finds 33 matches within a separation of 25 arcsec; dividing the sample into bins with separations bounded by 5, 10, 20 and 25 arcsec finds 1, 4, 17 and 11 matches. An analytical model estimate, based on the Poisson probability distribution, of the number of randomly expected matches within these same separation bounds is 1.7, 4.9, 19.4 and 14.2, each, respectively, consistent with the 95 per cent Poisson confidence intervals of the observed values. Dividing the data into five clustercentric annuli of 0.1° and into the four separation bins, finds the same result. This random match of UDGs with VLA sources implies that UDGs are not radio galaxies by the standard definition. Those VLA sources having integrated flux >1 mJy at 1.4 GHz in Miller, Hornschemeier and Mobasher without SDSS galaxy matches are consistent with the known surface density of background radio sources. We briefly explore the possibility that some unresolved VLA sources near UDGs could be young, compact, bright, supernova remnants of Type Ia events, possibly in the intracluster volume.

Galaxy clusters in simulations of the local Universe: a matter of constraints

NASA Astrophysics Data System (ADS)

Sorce, Jenny G.; Tempel, Elmo

2018-06-01

To study the full formation and evolution history of galaxy clusters and their population, high-resolution simulations of the latter are flourishing. However, comparing observed clusters to the simulated ones on a one-to-one basis to refine the models and theories down to the details is non-trivial. The large variety of clusters limits the comparisons between observed and numerical clusters. Simulations resembling the local Universe down to the cluster scales permit pushing the limit. Simulated and observed clusters can be matched on a one-to-one basis for direct comparisons provided that clusters are well reproduced besides being in the proper large-scale environment. Comparing random and local Universe-like simulations obtained with differently grouped observational catalogues of peculiar velocities, this paper shows that the grouping scheme used to remove non-linear motions in the catalogues that constrain the simulations affects the quality of the numerical clusters. With a less aggressive grouping scheme - galaxies still falling on to clusters are preserved - combined with a bias minimization scheme, the mass of the dark matter haloes, simulacra for five local clusters - Virgo, Centaurus, Coma, Hydra, and Perseus - is increased by 39 per cent closing the gap with observational mass estimates. Simulacra are found on average in 89 per cent of the simulations, an increase of 5 per cent with respect to the previous grouping scheme. The only exception is Perseus. Since the Perseus-Pisces region is not well covered by the used peculiar velocity catalogue, the latest release lets us foresee a better simulacrum for Perseus in a near future.

A CCD survey of galaxies. IV. Observations with the 2.1 M telescope at San Pedro Martir.

NASA Astrophysics Data System (ADS)

Gavazzi, G.; Boselli, A.; Carrasco, L.

1995-09-01

Continuing a CCD survey of galaxies belonging or projected onto the Coma and Hercules Superclusters, to the A262 and Cancer clusters, we present isophote maps and photometric profiles in the Johnson system of 111 galaxies (67 in the V and B bands, 42 only in V, 2 only in B) obtained with the 2.1 m telescope at San Pedro Martir (Baja California, Mexico).

Chemical composition of A and F dwarfs members of the Hyades open cluster

NASA Astrophysics Data System (ADS)

Gebran, M.; Vick, M.; Monier, R.; Fossati, L.

2010-11-01

Aims: Abundances of 15 chemical elements have been derived for 28 F and 16 A stars members of the Hyades open cluster in order to set constraints on self-consistent evolutionary models that include radiative and turbulent diffusion. Methods: A spectral synthesis, iterative procedure was applied to derive the abundances from selected high-quality lines in high-resolution, high-signal-to-noise spectra obtained with SOPHIE and AURELIE at the Observatoire de Haute Provence. Results: The abundance patterns found for A and F stars in the Hyades resemble those observed in Coma Berenices and Pleiades clusters. In graphs representing the abundances versus the effective temperature, A stars often display much more scattered abundances around their mean values than the coolest F stars do. Large star-to-star variations are detected in the Hyades A dwarfs in their abundances of C, Na, Sc, Fe, Ni, Sr, Y, and Zr, which we interpret as evidence of transport processes competing with radiative diffusion. In A and Am stars, the abundances of Cr, Ni, Sr, Y, and Zr are found to be correlated with that of Fe as in the Pleiades and in Coma Berenices. The ratios C/Fe and O/Fe are found to be anticorrelated with Fe/H as in Coma Berenices. All Am stars in the Hyades are deficient in C and O and overabundant in elements heavier than Fe but not all are deficient in Ca and/or Sc. The F stars have solar abundances for almost all elements except for Si. The overall shape of the abundance pattern of the slow rotator HD 30210 cannot be entirely reproduced by models including radiative diffusion and different amounts of turbulent diffusion. Conclusions: While part of the discrepancies between derived and predicted abundances could come from non-LTE effects, including competing processes such as rotational mixing and/or mass loss seems necessary in order to improve the agreement between the observed and predicted abundance patterns. Tables 5 to 8 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/523/A71Based on observations at the Observatoire de Haute-Provence, France.

Dwarf Galaxies in the Coma Cluster. II. Photometry and Analysis

NASA Astrophysics Data System (ADS)

Secker, J.; Harris, W. E.; Plummer, J. D.

1997-12-01

We use the data set derived in our previous paper (Secker & Harris 1997) to study the dwarf galaxy population in the central =~ 700 arcmin(2) of the Coma cluster, the majority of which are early-type dwarf elliptical (dE) galaxies. Analysis of the statistically-decontaminated dE galaxy sequence in the color-magnitude diagram reveals that the mean dE color at R = 18.0 mag is (B-R) =~ 1.4 mag, but that a highly significant trend of color with magnitude exists (Delta (B-R)/Delta R = -0.056+/-0.002 mag) in the sense that fainter dEs are bluer and thus presumably more metal-poor. The mean color of the faintest dEs in our sample is (B-R) =~ 1.15 mag, consistent with a color measurement of the diffuse intracluster light in the Coma core. This intracluster light could then have originated from the tidal disruption of faint dEs in the cluster core. The total galaxy luminosity function (LF) is well modeled as the sum of a log-normal distribution for the giant galaxies, and a Schechter function for the dE galaxies with a faint-end slope alpha = -1.41+/-0.05. This value of alpha is consistent with those measured for the Virgo and Fornax clusters. The spatial distribution of the faint dE galaxies (19.0 < R <= 22.5 mag) is well fit by a standard King model with a central surface density of Sigma_0 = 1.17 dEs arcmin(-2) and a core radius R_c = 22.15 arcmin ( =~ 0.46h(-1) Mpc). This core is significantly larger than the R_c = 13.71 arcmin ( =~ 0.29h(-1) Mpc) found for the cluster giants and the brighter dEs (R <= 19.0 mag), again consistent with the idea that faint dEs in the dense core have been disrupted. Finally, we find that most dEs belong to the general Coma cluster potential rather than as satellites of individual giant galaxies: An analysis of the number counts around 10 cluster giants reveals that they each have on average 4+/- 1 dE companions within a projected radius of 13.9h(-1) kpc. (SECTION: Galaxies)

Observational data needs useful for modeling the coma

NASA Technical Reports Server (NTRS)

Huebner, W. F.; Giguere, P. T.

1981-01-01

A computer model of comet comae is described; results from assumed composition of frozen gases are summarized and compared to coma observations. Restrictions on relative abundance of some frozen constituents are illustrated. Modeling, when tightly coupled to observational data, can be important for comprehensive analysis of observations, for predicting undetected molecular species and for improved understanding of coma and nucleus. To accomplish this, total gas production rates and relative elemental abundances of H:C:N:O:S are needed as a function of heliocentric distance of the comet. Also needed are relative column densitites and column density profiles with well defined diaphragm range and pointing position on the coma. Production rates are less desirable since they are model dependent. Total number (or upper limits) of molecules in the coma and analysis of unidentified spectral lines are needed also.

High β effects on cosmic ray streaming in galaxy clusters

NASA Astrophysics Data System (ADS)

Wiener, Joshua; Zweibel, Ellen G.; Oh, S. Peng

2018-01-01

Diffuse, extended radio emission in galaxy clusters, commonly referred to as radio haloes, indicate the presence of high energy cosmic ray (CR) electrons and cluster-wide magnetic fields. We can predict from theory the expected surface brightness of a radio halo, given magnetic field and CR density profiles. Previous studies have shown that the nature of CR transport can radically effect the expected radio halo emission from clusters (Wiener, Oh & Guo 2013). Reasonable levels of magnetohydrodynamic (MHD) wave damping can lead to significant CR streaming speeds. But a careful treatment of MHD waves in a high β plasma, as expected in cluster environments, reveals damping rates may be enhanced by a factor of β1/2. This leads to faster CR streaming and lower surface brightnesses than without this effect. In this work, we re-examine the simplified, 1D Coma cluster simulations (with radial magnetic fields) of Wiener et al. (2013) and discuss observable consequences of this high β damping. Future work is required to study this effect in more realistic simulations.

Nonthermal Particles and Radiation Produced by Cluster Merger Shocks

DTIC Science & Technology

2003-09-10

NONTHERMAL PARTICLES AND RADIATION PRODUCED BY CLUSTER MERGER SHOCKS Robert C. Berrington and Charles D. Dermer Naval Research Laboratory, Code 7653...of the merging cluster and is assumed to be constant as the shock propagates outward from the cluster center. In this paper , we model the cluster ...emission in the60–250 eV band for a number of clus- ters. These clusters include Virgo , Coma, Fornax, A2199, A1795, and A4059 (Lieu et al. 1996a, 1996b

Particle Sizes in the Coma of Comet 45P/Honda-Mrkos-Pajdušáková from Arecibo Radar Observations

NASA Astrophysics Data System (ADS)

Springmann, Alessondra; Howell, Ellen S.; Harmon, John K.; Lejoly, Cassandra; Rivera-Valentin, Edgard G.; Virkki, Anne; Zambrano-Marin, Luisa F.; Taylor, Patrick A.; Harris, Walter M.; Mueller, Beatrice E. A.; Samarasinha, Nalin H.; Rodriguez Sanchez-Vahamonde, Carolina

2017-10-01

Radar observations of cometary comae can provide information about not only the cross-section of the coma, but also constraints on the particle sizes comprising the coma. Harmon et al. (2011) described analysis of radar observations of comet 103P/Hartley 2 to constrain the sizes of its coma particles, as well as modeling to analyze the particle velocity distribution in the coma and orientation with respect to the sun. Arecibo Observatory planetary radar system observations of comet 45P/Honda-Mrkos-Pajdušáková were obtained 9-16 February 2017 by transmitting a continuous wave of polarized radio waves at the comet. By examining the polarization ratios of the returned signal (whether it has the same sense or opposite sense of the transmitted signal), we can look for non-zero same sense polarization signal. Detectable same sense signal indicates the presence of particles with sizes larger than the Rayleigh transition size criteria, a = λ/2π ≈ 2 cm (for the Arecibo wavelength of 12.6 cm).The observations show strong opposite sense signal return from the comet nucleus, as well as a larger ‘skirt’ of surrounding grains in the coma. Preliminary analysis of this data indicates at least a weak same sense polarized signal, implying a population of grains larger than 2 cm in the coma. The sizes of particles in the coma, compared with the area of the coma, can help us constrain the minimum mass for particles at the Rayleigh size limit in the 45P coma. Further, a detectable grain halo of large particles around 45P would imply significant lofting of grains from the comet nucleus.ReferencesHarmon, John K., et al. "Radar observations of comet 103P/Hartley 2." The Astrophysical Journal Letters 734.1 (2011): L2.

Comment on “Modeling of opposition effects with ensembles of clusters: Interplay of various scattering mechanisms” by Elena V. Petrova, Victor P. Tishkovets, Klaus Jockers, 2007 [Icarus 188, 233 245

NASA Astrophysics Data System (ADS)

Shkuratov, Yuriy G.; Zubko, Evgenij S.

2008-04-01

We show that the mechanism called "near-field effect" [e.g., Petrova, E.V., Tishkovets, V.P., Jockers, K., 2007. Icarus 188, 233-245], which is used to explain wide-phase-angle negative polarization branch observed for planetary regoliths and cometary comas, is not realistic as it contradicts laboratory experiments and results of modeling with discrete dipole approximation calculations.

Energy spectra of X-ray clusters of galaxies

NASA Technical Reports Server (NTRS)

Avni, Y.

1976-01-01

A procedure for estimating the ranges of parameters that describe the spectra of X-rays from clusters of galaxies is presented. The applicability of the method is proved by statistical simulations of cluster spectra; such a proof is necessary because of the nonlinearity of the spectral functions. Implications for the spectra of the Perseus, Coma, and Virgo clusters are discussed. The procedure can be applied in more general problems of parameter estimation.

Bright end of the color-magnitude relation for cD, E and S0 galaxies

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

Lugger, P.M.

1979-11-01

Schild and Davis's (Astron. J. 84, 311 (1979)) galaxy photometry for cD's in poor clusters is compared with Sandage's (Astrophys. J. 176, 21(1979)) color-magnitude relation defined by elliptical and S0 galaxies in the Virgo and Coma clusters. The cD galaxies are found to be somewhat bluer on average than galaxies of similar magnitude in the Virgo and Coma sample, consistent with the predictions of the galactic cannibalism model proposed by Hausman and Ostriker (Astrophys. J. 224, 320 (1978)). However, a more uniform selection of galaxy photometry is required before any definitive conclusions regarding the bright end of the color-magnitude relationmore » can be made.« less

Galaxy collisions as a mechanism of ultra diffuse galaxy (UDG) formation

NASA Astrophysics Data System (ADS)

Baushev, A. N.

2018-04-01

We suggest a possible mechanism of ultra diffuse galaxy formation: the UDGs may occur as a result of a central collision of galaxies. If the galaxies are young and contain a lot of gas, the collision may kick all the gas off the systems and thus strongly suppress any further star formation. As a result, the galaxies now have a very low surface brightness and other properties typical of the ultra diffuse galaxies. We use the Coma cluster (where numerous UDGs were recently discovered) to test the efficiency of the process. The mechanism works very well and can transform a significant fraction of the cluster population into ultra diffuse galaxies. The UDGs formed by the process concentrate towards the center of the cluster, and their globular cluster systems remain undamaged, in accordance with observational results. The projected surface density of UDGs in the cluster may help us to recognize the mechanism of UDG formation, or clarify relative contributions of several possible competitive mechanisms at work.

The Expansion of Clusters of Galaxies

DTIC Science & Technology

1961-01-01

investigators, currently we have usable data for a number of other clusters and groups. It is true that, with the exception of the Virgo Cluster , in each case...progress. Throughout this paper , the term "system of galaxies" is used as a synonym of the term " cluster " appearing in the theory of the spatial...mentioned at the beginning of the paper . Whether these outliers should be treated as members of the Coma Cluster or not is a subjective matter and

Gas Dynamics and Kinetics in the Cometary Coma: Theory and Observations

NASA Technical Reports Server (NTRS)

Combi, Michael R.; Harris, Walter M.; Smyth, William H.

2005-01-01

Our ability to describe the physical state of the expanding coma affects fundamental areas of cometary study both directly and indirectly. In order to convert measured abundances of gas species in the coma to gas production rates, models for the distribution and kinematics of gas species in the coma are required. Conversely, many different types of observations, together with laboratory data and theory, are still required to determine coma model attributes and parameters. Accurate relative and absolute gas production rates and their variations with time and from comet to comet are crucial to our basic understanding of the composition and structure of cometary nuclei and their place in the solar system. We review the gas dynamics and kinetics of cometary comae from both theoretical and observational perspectives, which are important for understanding the wide variety of physical conditions that are encountered.

The Globular Cluster System of the Coma cD Galaxy NGC 4874 from Hubble Space Telescope ACS and WFC3/IR Imaging

NASA Astrophysics Data System (ADS)

Cho, Hyejeon; Blakeslee, John P.; Chies-Santos, Ana L.; Jee, M. James; Jensen, Joseph B.; Peng, Eric W.; Lee, Young-Wook

2016-05-01

We present new Hubble Space Telescope (HST) optical and near-infrared (NIR) photometry of the rich globular cluster (GC) system NGC 4874, the cD galaxy in the core of the Coma cluster (Abell 1656). NGC 4874 was observed with the HST Advanced Camera for Surveys in the F475W (g 475) and F814W (I 814) passbands and with the Wide Field Camera 3 IR Channel in F160W (H 160). The GCs in this field exhibit a bimodal optical color distribution with more than half of the GCs falling on the red side at g 475-I 814 > 1. Bimodality is also present, though less conspicuously, in the optical-NIR I 814-H 160 color. Consistent with past work, we find evidence for nonlinearity in the g 475-I 814 versus I 814-H 160 color-color relation. Our results thus underscore the need for understanding the detailed form of the color-metallicity relations in interpreting observational data on GC bimodality. We also find a very strong color-magnitude trend, or “blue tilt,” for the blue component of the optical color distribution of the NGC 4874 GC system. A similarly strong trend is present for the overall mean I 814-H 160 color as a function of magnitude; for M 814 < -10 mag, these trends imply a steep mass-metallicity scaling with Z\\propto {M}{{GC}}1.4+/- 0.4, but the scaling is not a simple power law and becomes much weaker at lower masses. As in other similar systems, the spatial distribution of the blue GCs is more extended than that of the red GCs, partly because of blue GCs associated with surrounding cluster galaxies. In addition, the center of the GC system is displaced by 4 ± 1 kpc toward the southwest from the luminosity center of NGC 4874, in the direction of NGC 4872. Finally, we remark on a dwarf elliptical galaxy with a noticeably asymmetrical GC distribution. Interestingly, this dwarf has a velocity of nearly -3000 km s-1 with respect to NGC 4874; we suggest it is on its first infall into the cluster core and is undergoing stripping of its GC system by the cluster potential. Based on observations with the NASA/ESA Hubble Space Telescope, obtained from the Space Telescope Science Institute (STScI), which is operated by AURA, Inc., under NASA contract NAS 5-26555. These observations are associated with program #11712.

The Problem of Hipparcos Distances to Open Clusters. Report 1; Constraints from Multicolor a Main-Sequence Fitting

NASA Technical Reports Server (NTRS)

Pinsonneault, Marc H.; Stauffer, John; Soderblom, David R.; King, Jeremy R.; Hanson, Robert B.

1998-01-01

Parallax data from the Hipparcos mission allow the direct distance to open clusters to be compared with the distance inferred from main-sequence (MS) fitting. There are surprising differences between the two distance measurements. indicating either the need for changes in the cluster compositions or reddening, underlying problems with the technique of MS fitting, or systematic errors in the Hipparcos parallaxes at the 1 mas level. We examine the different possibilities, focusing on MS fitting in both metallicity-sensitive B-V and metallicity-insensitive V-I for five well-studied systems (the Hyades, Pleiades, alpha Per, Praesepe, and Coma Ber). The Hipparcos distances to the Hyades and alpha Per are within 1 sigma of the MS-fitting distance in B-V and V-I, while the Hipparcos distances to Coma Ber and the Pleiades are in disagreement with the MS-fitting distance at more than the 3 sigma level. There are two Hipparcos measurements of the distance to Praesepe; one is in good agreement with the MS-fitting distance and the other disagrees at the 2 sigma level. The distance estimates from the different colors are in conflict with one another for Coma but in agreement for the Pleiades. Changes in the relative cluster metal abundances, age related effects, helium, and reddening are shown to be unlikely to explain the puzzling behavior of the Pleiades. We present evidence for spatially dependent systematic errors at the 1 mas level in the parallaxes of Pleiades stars. The implications of this result are discussed.

MAPPING THE GAS TURBULENCE IN THE COMA CLUSTER: PREDICTIONS FOR ASTRO-H

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

ZuHone, J. A.; Markevitch, M.; Zhuravleva, I.

2016-02-01

Astro-H will be able for the first time to map gas velocities and detect turbulence in galaxy clusters. One of the best targets for turbulence studies is the Coma cluster, due to its proximity, absence of a cool core, and lack of a central active galactic nucleus. To determine what constraints Astro-H will be able to place on the Coma velocity field, we construct simulated maps of the projected gas velocity and compute the second-order structure function, an analog of the velocity power spectrum. We vary the injection scale, dissipation scale, slope, and normalization of the turbulent power spectrum, andmore » apply measurement errors and finite sampling to the velocity field. We find that even with sparse coverage of the cluster, Astro-H will be able to measure the Mach number and the injection scale of the turbulent power spectrum—the quantities determining the energy flux down the turbulent cascade and the diffusion rate for everything that is advected by the gas (metals, cosmic rays, etc.). Astro-H will not be sensitive to the dissipation scale or the slope of the power spectrum in its inertial range, unless they are outside physically motivated intervals. We give the expected confidence intervals for the injection scale and the normalization of the power spectrum for a number of possible pointing configurations, combining the structure function and velocity dispersion data. Importantly, we also determine that measurement errors on the line shift will bias the velocity structure function upward, and show how to correct this bias.« less

Mapping the Gas Turbulence in the Coma Cluster: Predictions for Astro-H

NASA Technical Reports Server (NTRS)

ZuHone, J. A.; Markevitch, M.; Zhuravleva, I.

2016-01-01

Astro-H will be able for the first time to map gas velocities and detect turbulence in galaxy clusters. One of the best targets for turbulence studies is the Coma cluster, due to its proximity, absence of a cool core, and lack of a central active galactic nucleus. To determine what constraints Astro-H will be able to place on the Coma velocity field, we construct simulated maps of the projected gas velocity and compute the second-order structure function, an analog of the velocity power spectrum. We vary the injection scale, dissipation scale, slope, and normalization of the turbulent power spectrum, and apply measurement errors and finite sampling to the velocity field. We find that even with sparse coverage of the cluster, Astro-H will be able to measure the Mach number and the injection scale of the turbulent power spectrum-the quantities determining the energy flux down the turbulent cascade and the diffusion rate for everything that is advected by the gas (metals, cosmic rays, etc.). Astro-H will not be sensitive to the dissipation scale or the slope of the power spectrum in its inertial range, unless they are outside physically motivated intervals. We give the expected confidence intervals for the injection scale and the normalization of the power spectrum for a number of possible pointing configurations, combining the structure function and velocity dispersion data. Importantly, we also determine that measurement errors on the line shift will bias the velocity structure function upward, and show how to correct this bias.

Mass concentrations associated with extended X-ray sources in the core of the Coma cluster

NASA Technical Reports Server (NTRS)

Vikhlinin, A.; Forman, W.; Jones, C.

1994-01-01

Using a deep (approx. 20,200 s) ROSAT Position Sensitive Proportional Counter (PSPC) image we have examined the central region of the Coma cluster. Two extended regions of enhanced X-ray emission are found, centered at the positions of the brightest elliptical galaxies in the cluster: NGC 4874 and NGC 4889. Spectral analysis of the sources reveals no evidence of any difference between the spectra of these sources and that of the surrounding cluster emission. We assume that the enhancement in the X-ray surface brightness results from gas density enhancements and also that the underlying mass concentrations lie either at the cluster center or 1 core radius out of the center (420 kpc). With these assumptions, we derive total masses of 1.2 x 10(exp 13) - 1.6 x 10(exp 13), and 0.9 x 10(exp 13) - 1.8 x 10(exp 13) Solar mass within 2 min (80 kpc) of NGC 4874 and NGC 4889, respectively, assuming a Hubble constant H(sub 0) = 50 km/s/Mpc. Corresponding mass-to-light ratios for the galaxies are 30-40 and 25-50 in solar units, increasing at larger radii and approaching the values derived for the entire cluster at distances of more than approximately 150 kpc from the galaxies.

Gravitational anti-screening as an alternative to dark matter

NASA Astrophysics Data System (ADS)

Penner, A. Raymond

2016-04-01

A semiclassical model of the screening of electric charge by virtual electric dipoles, as found in electrodynamic theory, will be presented. This model is then applied to the hypothetical case of an electric force where like charges attract. The resulting anti-screening of the electric charge is found to have the same functional dependence on the field source and observation distance that is found with the Baryonic Tully-Fisher Relationship. This leads to an anti-screening model for the gravitational force which is then used to determine the theoretical rotational curve of the Galaxy and the theoretical velocity dispersions and shear values for the Coma cluster. These theoretical results are found to be in good agreement with the corresponding astronomical observations. The screening of electric charge as found in QED and the larger apparent masses of galaxies and galactic clusters therefore appears to be two sides of the same coin.

Spectroscopic Profiles of Comets Garradd and McNaught

NASA Astrophysics Data System (ADS)

Harris, Ien; Pierce, Donna M.; Cochran, Anita L.

2017-10-01

We have used the integral-field unit spectrograph (the George and Cynthia Mitchell Spectrograph) on the 2.7m Harlan J. Smith telescope at McDonald Observatory to obtain spectroscopic images of the comae of several comets. The images were obtained for various radical species (C2, C3, CN, NH2). Radial and azimuthal average profiles of the radical species were created to enhance any observed cometary coma morphological features. We compare the observed coma features across the observed species and over the different observation periods in order to constrain possible rotational states of the observed comets, as well as determine possible source differences in the coma between the observed radical species. We will present results for several comets, including C/2009 P1 (Garradd) and 260P (McNaught).

Keck/LRIS Spectroscopy of the Distant Cluster Cl0016+16

NASA Astrophysics Data System (ADS)

Wirth, Gregory D.; Koo, David C.

1994-12-01

The rich galaxy cluster Cl0016+16 at z=0.55 initially achieved visibility (Koo 1981) for being the original ``anti Butcher-Oemler effect'' cluster: its galaxy population was found to be almost entirely red, indistinguishable in rest-frame color from local E/S0 galaxies, despite the expectation that higher redshift clusters should have a greater proportion of blue galaxies (Butcher & Oemler 1978, 1984). Interest in this cluster has heightened over the last decade as: X-ray observations found it to be among the most luminous clusters known (Henry et al. 1992); radio observations showed it to be among only a handful of clusters exhibiting a Sunyaev-Zel'dovich microwave decrement, useful for measuring the Hubble Constant (Lasenby 1992); optical spectroscopy revealed a significant population of ``E+A'' galaxies, enigmatic objects with spectra suggesting a recently-concluded episode of star formation (Dressler & Gunn 1992). Further observations by ROSAT, ASCA, and HST have established Cl0016+16 as among the best-studied clusters beyond Coma. The red nature of its galaxy population makes Cl0016+16 a prime candidate for the study of cluster galaxy evolution. As part of an ongoing effort to study the early-type galaxies in this cluster, we recently used the Keck Telescope and Low-Resolution Imaging Spectrograph to obtain high quality spectra of 19 cluster members at 6 Angstroms (FWHM) resolution. This poster describes the preliminary results from these data, which will allow us to investigate galaxy age and metallicity at lookback times nearly halfway to the Big Bang, probe the internal kinematics of galaxies at z=0.55, and thus perhaps trace the evolution of the ``fundamental plane'' for E/S0 galaxies.

The Three Sources of Gas in the Comae of Comets

NASA Technical Reports Server (NTRS)

Huebner, W. F.

1995-01-01

Surface water ice on a comet nucleus is the major source of coma gas. Dust, entrained by coma gas, fragments and vaporizes, forming a second, distributed source of coma gas constituents. Ice species more volatile than water ice below the surface of the nucleus are a third source of coma gas. Vapors from these ices, produced by heat penetrating into the nucleus, diffuse through pores outward into the coma. The second and third sources provide minor, but sometimes easily detectible, gaseous species in the coma. We present mixing ratios of observed minor coma constituents relative to water vapor as a function of heliocentric and cometocentric distances and compare these ratios with model predictions, assuming the sources of the minor species are either coma dust or volatile ices in the nucleus.

An X-ray method for detecting substructure in galaxy clusters - Application to Perseus, A2256, Centaurus, Coma, and Sersic 40/6

NASA Technical Reports Server (NTRS)

Mohr, Joseph J.; Fabricant, Daniel G.; Geller, Margaret J.

1993-01-01

We use the moments of the X-ray surface brightness distribution to constrain the dynamical state of a galaxy cluster. Using X-ray observations from the Einstein Observatory IPC, we measure the first moment FM, the ellipsoidal orientation angle, and the axial ratio at a sequence of radii in the cluster. We argue that a significant variation in the image centroid FM as a function of radius is evidence for a nonequilibrium feature in the intracluster medium (ICM) density distribution. In simple terms, centroid shifts indicate that the center of mass of the ICM varies with radius. This variation is a tracer of continuing dynamical evolution. For each cluster, we evaluate the significance of variations in the centroid of the IPC image by computing the same statistics on an ensemble of simulated cluster images. In producing these simulated images we include X-ray point source emission, telescope vignetting, Poisson noise, and characteristics of the IPC. Application of this new method to five Abell clusters reveals that the core of each one has significant substructure. In addition, we find significant variations in the orientation angle and the axial ratio for several of the clusters.

Photometric redshifts as a tool for studying the Coma cluster galaxy populations

NASA Astrophysics Data System (ADS)

Adami, C.; Ilbert, O.; Pelló, R.; Cuillandre, J. C.; Durret, F.; Mazure, A.; Picat, J. P.; Ulmer, M. P.

2008-12-01

Aims: We apply photometric redshift techniques to an investigation of the Coma cluster galaxy luminosity function (GLF) at faint magnitudes, in particular in the u* band where basically no studies are presently available at these magnitudes. Methods: Cluster members were selected based on probability distribution function from photometric redshift calculations applied to deep u^*, B, V, R, I images covering a region of almost 1 deg2 (completeness limit R ~ 24). In the area covered only by the u* image, the GLF was also derived after a statistical background subtraction. Results: Global and local GLFs in the B, V, R, and I bands obtained with photometric redshift selection are consistent with our previous results based on a statistical background subtraction. The GLF in the u* band shows an increase in the faint end slope towards the outer regions of the cluster. The analysis of the multicolor type spatial distribution reveals that late type galaxies are distributed in clumps in the cluster outskirts, where X-ray substructures are also detected and where the GLF in the u* band is steeper. Conclusions: We can reproduce the GLFs computed with classical statistical subtraction methods by applying a photometric redshift technique. The u* GLF slope is steeper in the cluster outskirts, varying from α ~ -1 in the cluster center to α ~ -2 in the cluster periphery. The concentrations of faint late type galaxies in the cluster outskirts could explain these very steep slopes, assuming a short burst of star formation in these galaxies when entering the cluster. Based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. This work is also partly based on data products produced at TERAPIX and the Canadian Astronomy Data Centre as part of the Canada-France-Hawaii Telescope Legacy Survey, a collaborative project of NRC and CNRS. Also based on data from W. M. Keck Observatory which is operated as a scientific partnership between the California Institute of Technology, the University of California, and NASA. It was made possible by the generous financial support of the W. M. Keck Foundation.

Incidence, predictors and outcomes of postoperative coma: an observational study of 858,606 patients.

PubMed

Newman, Jessica; Blake, Kathryn; Fennema, Jordan; Harris, David; Shanks, Amy; Avidan, Michael S; Kelz, Max B; Mashour, George A

2013-08-01

Coma is a state of profound unresponsiveness that can occur as a serious perioperative complication. The study of risk factors for, and sequelae of, postoperative coma has been limited due to the rarity of the event. To determine the incidence, risk factors and impact of postoperative coma in a large patient population. Observational study using a prospectively gathered national dataset. Data from 858 606 patients were analysed. The incidence of postoperative coma of more than 24-h duration was identified. Logistic regression was used to identify independent predictors and develop a risk model of postoperative coma in derivation and validation cohorts; 30-day mortality was also analysed. The incidence of postoperative coma was 0.06%. Multivariate analysis revealed the following independent predictors: liver disease, systemic sepsis, age at least 63 years, renal disease, emergency operation, cardiac disease, hypertension, prior neurological disease, diabetes mellitus and BMI 25 to 29.99 kg m (protective). These predictors were incorporated into a risk index classification; odds ratios for postoperative coma increased from 2.5 with one risk factor to 18.4 with three. Coma was associated with 74.2% all-cause mortality; coma associated with cardiac arrest had a 1.9-fold higher mortality. This is the largest study of postoperative coma ever reported and will be useful for determining risk of coma of more than 24 h duration when evaluating an unresponsive patient following surgery. Data on prognosis will aid medical and ethical decision-making for the comatose surgical patient.

Survey for Ortho-to-Para Abundance Ratios (OPRs) of NH2 in Comets: Revisit to the Meaning of OPRs of Cometary Volatiles

NASA Astrophysics Data System (ADS)

Kawakita, Hideyo; Shinnaka, Yoshiharu; Jehin, Emmanuel; Decock, Alice; Hutsemekers, Damien; Manfroid, Jean

2016-10-01

Since molecules having identical protons can be classified into nuclear-spin isomers (e.g., ortho-H2O and para-H2O for water) and their inter-conversions by radiative and non-destructive collisional processes are believed to be very slow, the ortho-to-para abundance ratios (OPRs) of cometary volatiles such as H2O, NH3 and CH4 in coma have been considered as primordial characters of cometary molecules [1]. Those ratios are usually interpreted as nuclear-spin temperatures although the real meaning of OPRs is in strong debate. Recent progress in laboratory studies about nuclear-spin conversion in gas- and solid-phases [2,3] revealed short-time nuclear-spin conversions for water, and we have to reconsider the interpretation for observed OPRs of cometary volatiles. We have already performed the survey for OPRs of NH2 in more than 20 comets by large aperture telescopes with high-resolution spectrographs (UVES/VLT, HDS/Subaru, etc.) in the optical wavelength region [4]. The observed OPRs of ammonia estimated from OPRs of NH2, cluster around ~1.1 (cf. 1.0 as a high-temperature limit), indicative of ~30 K as nuclear-spin temperatures. We present our latest results for OPRs of cometary NH2 and discuss about the real meaning of OPRs of cometary ammonia, in relation to OPRs of water in cometary coma. Chemical processes in the inner coma may play an important role to achieve un-equilibrated OPRs of cometary volatiles in coma.This work was financially supported by MEXT Supported Program for the Strategic Research Foundation at Private Universities, 2014-2018 (No. S1411028) (HK) and by Graint-in-Aid for JSPS Fellows, 15J10864 (YS).References:[1] Mumma & Charnley, 2011, Annu. Rev. Astro. Astrophys. 49, 471.[2] Hama & Watanabe, 2013, Chem. Rev. 113, 8783.[3] Hama et al., 2008, Science 351, 6268.[4] Shinnaka et al., 2011, ApJ 729, 81.

Galaxy clusters in local Universe simulations without density constraints: a long uphill struggle

NASA Astrophysics Data System (ADS)

Sorce, Jenny G.

2018-06-01

Galaxy clusters are excellent cosmological probes provided that their formation and evolution within the large scale environment are precisely understood. Therefore studies with simulated galaxy clusters have flourished. However detailed comparisons between simulated and observed clusters and their population - the galaxies - are complicated by the diversity of clusters and their surrounding environment. An original way initiated by Bertschinger as early as 1987, to legitimize the one-to-one comparison exercise down to the details, is to produce simulations constrained to resemble the cluster under study within its large scale environment. Subsequently several methods have emerged to produce simulations that look like the local Universe. This paper highlights one of these methods and its essential steps to get simulations that not only resemble the local Large Scale Structure but also that host the local clusters. It includes a new modeling of the radial peculiar velocity uncertainties to remove the observed correlation between the decreases of the simulated cluster masses and of the amount of data used as constraints with the distance from us. This method has the particularity to use solely radial peculiar velocities as constraints: no additional density constraints are required to get local cluster simulacra. The new resulting simulations host dark matter halos that match the most prominent local clusters such as Coma. Zoom-in simulations of the latter and of a volume larger than the 30h-1 Mpc radius inner sphere become now possible to study local clusters and their effects. Mapping the local Sunyaev-Zel'dovich and Sachs-Wolfe effects can follow.

VizieR Online Data Catalog: Gaia DR1 open cluster members (Gaia Collaboration+, 2017)

NASA Astrophysics Data System (ADS)

Gaia Collaboration; van Leeuwen F.; Vallenari, A.; Jordi, C.; Lindegren, L.; Bastian, U.; Prusti, T.; de Bruijne, J. H. J.; Brown, A. G. A.; Babusiaux, C.; Bailer-Jones, C. A. L.; Biermann, M.; Evans, D. W.; Eyer, L.; Jansen, F.; Klioner, S. A.; Lammers, U.; Luri, X.; Mignard, F.; Panem, C.; Pourbaix, D.; Randich, S.; Sartoretti, P.; Siddiqui, H. I.; Soubiran, C.; Valette, V.; Walton, N. A.; Aerts, C.; Arenou, F.; Cropper, M.; Drimmel, R.; Hog, E.; Katz, D.; Lattanzi, M. G.; O'Mullane, W.; Grebel, E. K.; Holland, A. D.; Huc, C.; Passot, X.; Perryman, M.; Bramante, L.; Cacciari, C.; Castaneda, J.; Chaoul, L.; Cheek, N.; de Angeli, F.; Fabricius, C.; Guerra, R.; Hernandez, J.; Jean-Antoine-Piccolo, A.; Masana, E.; Messineo, R.; Mowlavi, N.; Nienartowicz, K.; Ordonez-Blanco, D.; Panuzzo, P.; Portell, J.; Richards, P. J.; Riello, M.; Seabroke, G. M.; Tanga, P.; Thevenin, F.; Torra, J.; Els, S. G.; Gracia-Abril, G.; Comoretto, G.; Garcia-Reinaldos, M.; Lock, T.; Mercier, E.; Altmann, M.; Andrae, R.; Astraatmadja, T. L.; Bellas-Velidis, I.; Benson, K.; Berthier, J.; Blomme, R.; Busso, G.; Carry, B.; Cellino, A.; Clementini, G.; Cowell, S.; Creevey, O.; Cuypers, J.; Davidson, M.; De Ridder, J.; de Torres, A.; Delchambre, L.; Dell'Oro, A.; Ducourant, C.; Fremat, Y.; Garcia-Torres, M.; Gosset, E.; Halbwachs, J.-L.; Hambly, N. C.; Harrison, D. L.; Hauser, M.; Hestroffer, D.; Hodgkin, S. T.; Huckle, H. E.; Hutton, A.; Jasniewicz, G.; Jordan, S.; Kontizas, M.; Korn, A. J.; Lanzafame, A. C.; Manteiga, M.; Moitinho, A.; Muinonen, K.; Osinde, J.; Pancino, E.; Pauwels, T.; Petit, J.-M.; Recio-Blanco, A.; Robin, A. C.; Sarro, L. M.; Siopis, C.; Smith, M.; Smith, K. W.; Sozzetti, A.; Thuillot, W.; van Reeven, W.; Viala, Y.; Abbas, U.; Abreu Aramburu, A.; Accart, S.; Aguado, J. J.; Allan, P. M.; Allasia, W.; Altavilla, G.; Alvarez, M. A.; Alves, J.; Anderson, R. I.; Andrei, A. H.; Anglada Varela, E.; Antiche, E.; Antoja, T.; Anton, S.; Arcay, B.; Bach, N.; Baker, S. G.; Balaguer-Nunez, L.; Barache, C.; Barata, C.; Barbier, A.; Barblan, F.; Barrado, Y. Navascues D.; Barros, M.; Barstow, M. A.; Becciani, U.; Bellazzini, M.; Bello Garcia, A.; Belokuro, V. V.; Ben Djoya, P.; Berihuete, A.; Bianchi, L.; Bienayme, O.; Billebaud, F.; Blagorodnova, N.; Blanco-Cuaresma, S.; Boch, T.; Bombrun, A.; Borrachero, R.; Bouquillon, S.; Bourda, G.; Bouy, H.; Bragaglia, A.; Breddels, M. A.; Brouillet, N.; Bruesemeister, T.; Bucciarelli, B.; Burgess, P.; Burgon, R.; Burlacu, A.; Busonero, D.; Buzzi, R.; Caffau, E.; Cambras, J.; Campbell, H.; Cancelliere, R.; Cantat-Gaudin, T.; Carlucci, T.; Carrasco, J. M.; Castellani, M.; Charlot, P.; Charnas, J.; Chiavassa, A.; Clotet, M.; Cocozza, G.; Collins, R. S.; Costigan, G.; Crifo, F.; Cross, N. J. G.; Crosta, M.; Crowley, C.; Dafonte, C.; Damerdji, Y.; Dapergolas, A.; David, P.; David, M.; De Cat, P.; de Felice, F.; de Laverny, P.; de Luise, F.; de March, R.; de Martino, D.; de Souza, R.; Debosscher, J.; Del Pozo, E.; Delbo, M.; Delgado, A.; Delgado, H. E.; Di Matteo, P.; Diakite, S.; Distefano, E.; Dolding, C.; Dos Anjos, S.; Drazinos, P.; Duran, J.; Dzigan, Y.; Edvardsson, B.; Enke, H.; Evans, N. W.; Eynard Bontemps, G.; Fabre, C.; Fabrizio, M.; Faigler, S.; Falcao, A. J.; Farras Casas, M.; Federici, L.; Fedorets, G.; Fernandez-Hernandez, J.; Fernique, P.; Fienga, A.; Figueras, F.; Filippi, F.; Findeisen, K.; Fonti, A.; Fouesneau, M.; Fraile, E.; Fraser, M.; Fuchs, J.; Gai, M.; Galleti, S.; Galluccio, L.; Garabato, D.; Garcia-Sedano, F.; Garofalo, A.; Garralda, N.; Gavras, P.; Gerssen, J.; Geyer, R.; Gilmore, G.; Girona, S.; Giuffrida, G.; Gomes, M.; Gonzalez-Marcos, A.; Gonzalez-Nunez, J.; Gonzalez-Vidal, J. J.; Granvik, M.; Guerrier, A.; Guillout, P.; Guiraud, J.; Gurpide, A.; Gutierrez-Sanchez, R.; Guy, L. P.; Haigron, R.; Hatzidimitriou, D.; Haywood, M.; Heiter, U.; Helmi, A.; Hobbs, D.; Hofmann, W.; Holl, B.; Holland, G.; Hunt, J. A. S.; Hypki, A.; Icardi, V.; Irwin, M.; Jevardat de Fombelle, G.; Jofre, P.; Jonker, P. G.; Jorissen, A.; Julbe, F.; Karampelas, A.; Kochoska, A.; Kohley, R.; Kolenberg, K.; Kontizas, E.; Koposov, S. E.; Kordopatis, G.; Koubsky, P.; Krone-Martins, A.; Kudryashova, M.; Kull, I.; Bachchan, R. K.; Lacoste-Seris, F.; Lanza, A. F.; Lavigne, J.-B.; Le Poncin-Lafitte, C.; Lebreton, Y.; Lebzelter, T.; Leccia, S.; Lecler, C. N.; Lecoeur-Taibi, I.; Lemaitre, V.; Lenhardt, H.; Leroux, F.; Liao, S.; Licata, E.; Lindstrom, H. E. P.; Lister, T. A.; Livanou, E.; Lobel, A.; Loeffler, W.; Lopez, M.; Lorenz, D.; MacDonald, I.; Magalhaes Fernandes, T.; Managau, S.; Mann, R. G.; Mantelet, G.; Marchal, O.; Marchant, J. M.; Marconi, M.; Marinoni, S.; Marrese, P. M.; Marschalko, G.; Marshall, D. J.; Martin-Fleitas, J. M.; Martino, M.; Mary, N.; Matijevic, G.; Mazeh, T.; McMillan, P. J.; Messina, S.; Michalik, D.; Millar, N. R.; Miranda, B. M. H.; Molina, D.; Molinaro, R.; Molinaro, M.; Molnar, L.; Moniez, M.; Montegriffo, P.; Mor, R.; Mora, A.; Morbidelli, R.; Morel, T.; Morgenthaler, S.; Morris, D.; Mulone, A. F.; Muraveva, T.; Musella, I.; Narbonne, J.; Nelemans, G.; Nicastro, L.; Noval, L.; Ordenovic, C.; Ordieres-Mere, J.; Osborne, P.; Pagani, C.; Pagano, I.; Pailler, F.; Palacin, H.; Palaversa, L.; Parsons, P.; Pecoraro, M.; Pedrosa, R.; Pentikaeinen, H.; Pichon, B.; Piersimoni, A. M.; Pineau, F.-X.; Plachy, E.; Plum, G.; Poujoulet, E.; Prsa, A.; Pulone, L.; Ragaini, S.; Rago, S.; Rambaux, N.; Ramos-Lerate, M.; Ranalli, P.; Rauw, G.; Read, A.; Regibo, S.; Reyle, C.; Ribeiro, R. A.; Rimoldini, L.; Ripepi, V.; Riva, A.; Rixon, G.; Roelens, M.; Romero-Gomez, M.; Rowell, N.; Royer, F.; Ruiz-Dern, L.; Sadowski, G.; Sagrista Selles, T.; Sahlmann, J.; Salgado, J.; Salguero, E.; Sarasso, M.; Savietto, H.; Schultheis, M.; Sciacca, E.; Segol, M.; Segovia, J. C.; Segransan, D.; Shih, I.-C.; Smareglia, R.; Smart, R. L.; Solano, E.; Solitro, F.; Sordo, R.; Soria Nieto, S.; Souchay, J.; Spagna, A.; Spoto, F.; Stampa, U.; Steele, I. A.; Steidelmueller, H.; Stephenson, C. A.; Stoev, H.; Suess, F. F.; Sueveges, M.; Surdej, J.; Szabados, L.; Szegedi-Elek, E.; Tapiador, D.; Taris, F.; Tauran, G.; Taylor, M. B.; Teixeira, R.; Terrett, D.; Tingley, B.; Trager, S. C.; Turon, C.; Ulla, A.; Utrilla, E.; Valentini, G.; van Elteren, A.; van Hemelryck, E.; Vanleeuwen, M.; Varadi, M.; Vecchiato, A.; Veljanoski, J.; Via, T.; Vicente, D.; Vogt, S.; Voss, H.; Votruba, V.; Voutsinas, S.; Walmsley, G.; Weiler, M.; Weingrill, K.; Wevers, T.; Wyrzykowski, L.; Yoldas, A.; Zerjal, M.; Zucker, S.; Zurbach, C.; Zwitter, T.; Alecu, A.; Allen, M.; Allende Prieto, C.; Amorim, A.; Anglada-Escude, G.; Arsenijevic, V.; Azaz, S.; Balm, P.; Beck, M.; Bernstein, H.-H.; Bigot, L.; Bijaoui, A.; Blasco, C.; Bonfigli, M.; Bono, G.; Boudreault, S.; Bressan, A.; Brown, S.; Brunet, P.-M.; Bunclark, P.; Buonanno, R.; Butkevich, A. G.; Carret, C.; Carrion, C.; Chemin, L.; Chereau, F.; Corcione, L.; Darmigny, E.; de Boer, K. S.; de Teodoro, P.; de Zeeuw, P. T.; Delle Luche, C.; Domingues, C. D.; Dubath, P.; Fodor, F.; Frezouls, B.; Fries, A.; Fustes, D.; Fyfe, D.; Gallardo, E.; Gallegos, J.; Gardiol, D.; Gebran, M.; Gomboc, A.; Gomez, A.; Grux, E.; Gueguen, A.; Heyrovsky, A.; Hoar, J.; Iannicola, G.; Isasi Parache, Y.; Janotto, A.-M.; Joliet, E.; Jonckheere, A.; Keil, R.; Kim, D.-W.; Klagyivik, P.; Klar, J.; Knude, J.; Kochukhov, O.; Kolka, I.; Kos, J.; Kutka, A.; Lainey, V.; Lebouquin, D.; Liu, C.; Loreggia, D.; Makarov, V. V.; Marseille, M. G.; Martayan, C.; Martinez-Rubi, O.; Massart, B.; Meynadier, F.; Mignot, S.; Munari, U.; Nguyen, A.-T.; Nordlander, T.; O'Flaherty, K. S.; Ocvirk, P.; Olias Sanz, A.; Ortiz, P.; Osorio, J.; Oszkiewicz, D.; Ouzounis, A.; Palmer, M.; Park, P.; Pasquato, E.; Peltzer, C.; Peralta, J.; Peturaud, F.; Pieniluoma, T.; Pigozzi, E.; Poels, J.; Prat, G.; Prod'homme, T.; Raison, F.; Rebordao, J. M.; Risquez, D.; Rocca-Volmerange, B.; Rosen, S.; Ruiz-Fuertes, M. I.; Russo, F.; Sembay, S.; Serraller Vizcaino, I.; Short, A.; Siebert, A.; Silva, H.; Sinachopoulos, D.; Slezak, E.; Soffel, M.; Sosnowska, D.; Straizys, V.; Ter Linden, M.; Terrell, D.; Theil, S.; Tiede, C.; Troisi, L.; Tsalmantza, P.; Tur, D.; Vaccari, M.; Vachier, F.; Valles, P.; van Hamme, W.; Veltz, L.; Virtanen, J.; Wallut, J.-M.; Wichmann, R.; Wilkinson, M. I.; Ziaeepour, H.; Zschocke, S.

2017-04-01

We have determined and examined the astrometric data for 19 open clusters, ranging from the Hyades at just under 47pc to NGC 2422 at nearly 440pc. The clusters are : the Hyades, Coma Berenices, the Pleiades, Praesepe, alpha Per, IC 2391, IC 2602, Blanco 1, NGC 2451, NGC 6475, NGC 7092, NGC 2516, NGC 2232, IC 4665, NGC 6633, Collinder 140, NGC 2422, NGC 3532 and NGC 2547. (2 data files).

Observation of CO2 in Comet C/2012 K5 LINEAR

NASA Astrophysics Data System (ADS)

McKay, Adam; Kelley, Michael; DiSanti, Michael; Chanover, Nancy

2012-12-01

The study of cometary composition is important to understanding the formation and evolution of our solar system. Comets have undergone very little thermal evolution in their lifetimes, which results in their near pristine composition. The nucleus of a comet is very rarely detected directly. Instead, we observe the coma that surrounds the nucleus. Physical and chemical processes in the coma affect its composition, and therefore coma composition is not a direct representation of nuclear composition. An important trend is the observed variation of coma composition with heliocentric distance, most likely influenced by the volatility of the main surface ices, H2O, CO2, and CO. Infrared studies of these molecules are complicated by telluric features, so often daughter molecules of these species such as OH are observed instead. A potentially effective tracer for these primary ices is atomic oxygen in the coma. However, the relationship between these ices and atomic oxygen is only understood at a qualitative level. We propose to use Spitzer observations in IRAC's 4.5 micron band pass to observe the CO2 v3 band at 4.26 microns in comet C/2012 K5 LINEAR. These observations will be coordinated with observations of atomic oxygen obtained at Apache Point Observatory and observations of H2O at Keck. These near simultaneous observations of H2O, CO2, and atomic oxygen in a cometary coma will increase our understanding of the link between these primary ices and atomic oxygen. With a complete understanding of the relationship between atomic oxygen and the primary ices on the nucleus, observations of atomic oxygen can serve as a powerful proxy for the production of these primary volatiles and aid our understanding of the variation in coma composition as a function of heliocentric distance, and therefore the composition of the nucleus and how our solar system was formed.

Non-Random Spatial Distribution of Impacts in the Stardust Cometary Collector

NASA Technical Reports Server (NTRS)

Westphal, Andrew J.; Bastien, Ronald K.; Borg, Janet; Bridges, John; Brownlee, Donald E.; Burchell, Mark J.; Cheng, Andrew F.; Clark, Benton C.; Djouadi, Zahia; Floss, Christine

2007-01-01

In January 2004, the Stardust spacecraft flew through the coma of comet P81/Wild2 at a relative speed of 6.1 km/sec. Cometary dust was collected at in a 0.1 sq m collector consisting of aerogel tiles and aluminum foils. Two years later, the samples successfully returned to earth and were recovered. We report the discovery that impacts in the Stardust cometary collector are not distributed randomly in the collecting media, but appear to be clustered on scales smaller than approx.10 cm. We also report the discovery of at least two populations of oblique tracks. We evaluated several hypotheses that could explain the observations. No hypothesis was consistent with all the observations, but the preponderance of evidence points toward at least one impact on the central Whipple shield of the spacecraft as the origin of both clustering and low-angle oblique tracks. High-angle oblique tracks unambiguously originate from a noncometary impact on the spacecraft bus just forward of the collector. Here we summarize the observations, and review the evidence for and against three scenarios that we have considered for explaining the impact clustering found on the Stardust aerogel and foil collectors.

Globular clusters and environmental effects in galaxy clusters

NASA Astrophysics Data System (ADS)

Sales, Laura

2016-10-01

Globular clusters are old compact stellar systems orbiting around galaxies of all types. Tens of thousands of them can also be found populating the intra-cluster regions of nearby galaxy clusters like Virgo and Coma. Thanks to the HST Frontier Fields program, GCs are starting now to be detected also in intermediate redshift clusters. Yet, despite their ubiquity, a theoretical model for the formation and evolution of GCs is still missing, especially within the cosmological context.Here we propose to use cosmological hydrodynamical simulations of 18 galaxy clusters coupled to a post-processing GC formation model to explore the assembly of galaxies in clusters together with their expected GC population. The method, which has already been implemented and tested, will allow us to characterize for the first time the number, radial distribution and kinematics of GCs in clusters, with products directly comparable to observational maps. We will explore cluster-to-cluster variations and also characterize the build up of the intra-cluster component of GCs with time.As the method relies on a detailed study of the star-formation history of galaxies, we will jointly constrain the predicted quenching time-scales for satellites and the occurrence of starburst events associated to infall and orbital pericenters of galaxies in massive clusters. This will inform further studies on the distribution, velocity and properties of post-starburst galaxies in past, ongoing and future HST programs.

Structure of Cometary Dust Particles

NASA Astrophysics Data System (ADS)

Levasseur-Regourd, A. C.; Hadamcik, E.; Lasue, J.

2004-11-01

The recent encounter of Stardust with comet 81P/Wild 2 has provided highly spatially resolved data about dust particles in the coma. They show intense swarms and bursts of particles, suggest the existence of fragmenting low-density particles formed of higher density sub-micrometer components [1], and definitely confirm previous results (inferred from Giotto encounter with comet Grigg-Skjellerup [2] and remote light scattering observations [3]). The light scattering properties (mostly polarization, which does not depend upon disputable normalizations) of dust in cometary comae will be summarized, with emphasis on the spatial changes and on the wavelength and phase angle dependence. Experimental and numerical simulations are needed to translate these observed light scattering properties in terms of physical properties of the dust particles (e.g. size, morphology, albedo, porosity). New experimental simulations (with fluffy mixtures of sub-micron sized silica and carbon grains) and new numerical simulations (with fractal aggregates of homogeneous or core-mantled silicate and organic grains) will be presented. The results are in favor of highly porous particles built up (by ballistic-cluster-cluster agglomeration) from grains of interstellar origin. The perspectives offered by laboratory simulations with aggregates built under conditions representative of the early solar system on board the International Space Station will be presented, together with the perspectives offered by future experiments on board the Rosetta cometary probe. Supports from CNES and ESA are acknowledged [1] Tuzzolino et al., Science, 304, 1776, 2004, [2] N. McBride et al., Mon. Not. R. Astron. Soc., 289, p. 535-553, 1997, [3] Levasseur-Regourd and Hadamcik, J. Quant. Spectros. Radiat. Transfer, 79-80, 903-910, 2003.

The effects of hypoglycemic and alcoholic coma on the blood-brain barrier permeability

PubMed Central

Yorulmaz, Hatice; Seker, Fatma Burcu; Oztas, Baria

2011-01-01

In this investigation, the effects of hypoglycemic coma and alcoholic coma on the blood-brain barrier (BBB) permeability have been compared. Female adult Wistar albino rats weighing 180-230 g were divided into three groups: Control group (n=8), Alcoholic Coma Group (n=18), and Hypoglycemic Coma group (n=12). The animals went into coma approximately 3-4 hours after insulin administration and 3-5 minutes after alcohol administration. Evans blue (4mL/kg) was injected intravenously as BBB tracer. It was observed that the alcoholic coma did not significantly increase the BBB permeability in any of the brain regions when compared to control group. Changes in BBB permeability were significantly increased by the hypoglycemic coma in comparison to the control group values (p<0.01). Our findings suggest that hypoglycemic and alcoholic coma have different effects on the BBB permeability depending on the energy metabolism. PMID:21619558

Taking the Measure of the Universe: Precision Astrometry with SIM Planetquest (Preprint)

DTIC Science & Technology

2006-10-09

the orbits of nearby galaxies and groups going out to the distance of the Virgo Cluster . The orbits are in comoving coordinates. This is just a...single solution of a set of several solutions using present 3-d positions as inputs. The four massive objects ( Virgo Cluster , Coma Group, CenA Group, and... Virgo Cluster from a Numerical Action Method calculation with parameters M/L = 90 for spirals and 155 for ellipticals, Ωm = 0.24, ΩΛ = 0.76. The axes are

A Dusty Coma Model of Comet Hyakutake

NASA Astrophysics Data System (ADS)

Boice, D. C.; Benkhoff, J.

1996-09-01

We present a multifluid, hydrodynamic model for the gas, dust, and plasma flow in a cometary coma appropriate for Comet Hyakutake. The model accounts for three sources of gas release: sublimation from surface ices, transport of gas from subsurface regions through the surface, and release of gas from dust in the coma. The simulations are based on a spherically symmetric neutral coma model with detailed photo and gas-phase chemistry and dust entrainment by the gas. The model includes a separate energy balance for the electrons, separate flow of the neutral gas, fast neutral atomic and molecular hydrogen, and dust entrainment with fragmentation. The simulations allow a study of how certain features of a cometary coma, e.g., spatial distributions of gas-phase species and dust of various sizes, change with heliocentric distance. Special attention is given to observations of hydrocarbon and sulphur species. In comparison with observations, the model can be used to characterize the environment surrounding Hyakutake and aid in assimilating a variety of diverse observations of this bright comet. A complete description of the model and more extensive results with comparisons to observations where possible will be presented.

Analysis of IUE Observations of Hydrogen in Comets

NASA Technical Reports Server (NTRS)

Combi, Michael R.; Feldman, Paul D.

1998-01-01

The 15-years worth of hydrogen Lyman-alpha observations of cometary comae obtained with the International Ultraviolet Explorer (IUE) satellite had gone generally unanalyzed because of two main modeling complications. First, the inner comae of many bright (gas productive) comets are often optically thick to solar Lyman-alpha radiation. Second, even in the case of a small comet (low gas production) the large IUE aperture is quite small as compared with the immense size of the hydrogen coma, so an accurate model which properly accounts for the spatial distribution of the coma is required to invert the infrared brightnesses to column densities and finally to H atom production rates. Our Monte Carlo particle trajectory model (MCPTM), which for the first time provides the realistic full phase space distribution of H atoms throughout the coma has been used as the basis for the analysis of IUE observations of the inner coma. The MCPTM includes the effects of the vectorial ejection of the H atoms upon dissociation of their parent species (H2O and OH) and of their partial collisional thermalization. Both of these effects are crucial to characterize the velocity distribution of the H atoms. This combination of the MCPTM and spherical radiative transfer code had already been shown to be successful in understanding the moderately optically thick coma of comet P/Giacobini-Zinner and the coma of comet Halley that varied from being slightly to very optically thick. Both of these comets were observed during solar minimum conditions. Solar activity affects both the photochemistry of water and the solar Lyman-alpha radiation flux. The overall plan of this program here was to concentrate on comets observed by IUE at other time during the solar cycle, most importantly during the two solar maxima of 1980 and 1990. Described herein are the work performed and the results obtained.

Jet Morphology and Coma Analysis of Comet 103P/Hartley 2

NASA Astrophysics Data System (ADS)

Vaughan, Charles M.; Pierce, Donna M.; Cochran, Anita L.

2017-12-01

Spectral data for the coma of Hartley 2 were acquired across four nights in late 2010 using an integral field spectrometer at McDonald Observatory. For the 30 observations during these four nights, we detected five radical species in the coma: C2, C3, CH, CN, and NH2. Using division by azimuthal mean and division by radial profile, we enhanced 150 images of the coma to reveal subtle coma structure. These images revealed noticeable temporal evolution and spatial variations between species. To quantify the observed variation between species, we partitioned the coma and used analysis of variance (ANOVA) techniques to provide a statistical basis for heterogeneity. Nearly every ANOVA test indicated a spatially diverse distribution in the coma when considering all species collectively. To examine the temporal behavior, we used the works by Belton et al., Thomas et al., and Bruck Syal et al. to predict nucleus orientation and active jet directions at our observation times. Several of these reported jet sites correlated to high radical concentrations, and the sites on the smaller lobe are more closely associated with high radical concentrations. Lastly, we provide constraints for the suspect parent molecules of the detected radicals, and we propose that photolysis reactions occurring at or near extended icy grains are a source for the more enigmatic radicals, such as C3.

Analysis of hydrogen H-alpha observations of the coma of Comet P/Halley

NASA Technical Reports Server (NTRS)

Smyth, William H.; Marconi, M. L.; Scherb, Frank; Roesler, Fred L.

1993-01-01

The Monte Carlo Particle Trajectory Model of Combi and Smyth (1988) is used here to analyze observations of the H-alpha coma of Comet Halley. The solar excitation mechanism for the H-alpha emissions line is described. The H2O production rates derived for the H-alpha brightness measurements are shown to be very consistent with the H2O production rates determined from other Comet Halley observations of the H, O, and OH comae. Revised H2O production rates determined from 6300 A brightness measurements are presented.

Diagnostic Simulations of the Lunar Exosphere using Coma and Tail

NASA Astrophysics Data System (ADS)

Lee, Dong Wook; Kim, Sang J.

2017-10-01

The characteristics of the lunar exosphere can be constrained by comparing simulated models with observational data of the coma and tail (Lee et al., JGR, 2011); and thus far a few independent approaches on this issue have been performed and presented in the literature. Since there are two-different observational constraints for the lunar exosphere, it is interesting to find the best exospheric model that can account for the observed characteristics of the coma and tail. Considering various initial conditions of different sources and space weather, we present preliminary time-dependent simulations between the initial and final stages of the development of the lunar tail. Based on an updated 3-D model, we are planning to conduct numerous simulations to constrain the best model parameters from the coma images obtained from coronagraph observations supported by a NASA monitoring program (Morgan, Killen, and Potter, AGU, 2015) and future tail data.

Understanding Supermassive Black Hole Growth Mechanisms in the SSA22 Protocluster

NASA Astrophysics Data System (ADS)

Bonine, Brett; Lehmer, Bret

2018-01-01

The SSA22 protocluster is a collection of galaxies at redshift z = 3.09, corresponding to a look back time of 11.6 billion years. Observations of the protocluster allow for the investigation of galaxy properties of such protocluster environments in the early universe, potentially giving insight into the formation and evolution of galaxy clusters visible in the local universe (e.g., the Coma Cluster). Compared to other field galaxies at a similar redshift, a larger fraction of galaxies in SSA22 have been found to possess active galactic nuclei (AGN). This enhanced AGN activity suggests a relationship between the environment within the cluster and the growth of supermassive black holes (SMBHs). I will clarify the role that the protocluster environment at z = 3.09 plays in enhancing the growth of SMBHs in the cluster. To accomplish this, we are analyzing recently obtained WFC3 F160W data from the Hubble Space Telescope (HST) in SSA22, and equivalent archival CANDELS data in the Hubble Deep Field-North, to compare the merger rates and stellar mass distributions of galaxies in the SSA22 protocluster and in the field. Our goal is to assess the relative role that mergers play in enhancing the SMBH growth observed in over-dense regions in the z = 3 Universe.

Chemical Recycling of HCN in Cometary Comae

NASA Astrophysics Data System (ADS)

Boice, Daniel C.; Kawakita, Hideyo; Shinnaka, Yoshiharu; Mumma, Michael J.; Kobayashi, Hitomi; Ogawa, Sayuri

2014-11-01

Modeling is essential to understand the important physical and chemical processes that occur in cometary comae, especially the relationship between putative parent and daughter molecules, such as, HCN and CN. Photochemistry is a major source of ions and electrons that further initiate key gas-phase reactions, contributing to the plethora of molecules and atoms observed in comets. The effects of photoelectrons that interact via impacts are important to the overall excitation and dissociation processes in the inner coma. We consider the relevant processes in the collision-dominated, inner coma of a comet within a global modeling framework to understand observations of HCN and CN. The CN source(s) must be able to produce highly collimated jets, be consistent with the observed CN parent scale length, and have a production rate consistent with the observed CN production. HCN fulfills these conditions in some comets (e.g., 1P/Halley, Hale-Bopp) while it does not in others (e.g., 8P/Tuttle, 6P/d’Arrest, 73P/S-W3, 2P/Encke, 9P/Temple 1 and C/2007 W1).We investigate the chemistry of HCN with our chemical kinetics coma model including a network with other possible CN parents, as well as a dust component that may be a potential source of CN. It is seen that the major destruction pathways of HCN are via photo dissociation (into H and CN) and protonation with water group ions - primarily H3O+. We point out the intriguing “recycling” of HCN via protonation reactions with H3O+, H2O+, OH+, and subsequent dissociative recombination. It seems that HCN molecules observed in the coma can consist of those initially released from the nucleus and those that are freshly formed at different locations in the coma via these protonation/dissociation reactions. We will investigate implications for reconciling discrepancies between observations of HCN and CN in cometary comae.Acknowledgements: We appreciate support from the NSF Planetary Astronomy Program. This program is partially supported by the MEXT Supported Program for the Strategic Research Foundation at Private Universities, 2014-2018.

A CO2-rich coma model applied to the neutral coma of Comet West

NASA Technical Reports Server (NTRS)

Mitchell, G. F.; Swift, M. B.; Huntress, W. T.

1982-01-01

Models of the cometary coma in which the dominant volatile is CO2 have been constructed for a range of heliocentric distances. Model coma abundances of C2, C3, and CN are compared with the abundances observed in Comet West and are found to be in good agreement. Furthermore, the variation with heliocentric distance of C2, C3, and CN model abundances agree well with the observed variation in Comet West. The present work lends detailed support to a previous suggestion that a substance more volatile than water, such as CO2, controls the evaporation of the nucleus of Comet West. The implications for cometary formation are briefly discussed.

Streaming Clumps Ejection Model and the Heterogeneous Inner Coma of Comet Wild 2

NASA Technical Reports Server (NTRS)

Clark, B. C.; Economou, T. E.; Green, S. F.; Sandford, S. A.; Zolensky, M. E.

2004-01-01

The conventional concept of cometary comae is that they are dominated by fine particulates released individually by sublimation of surface volatiles and subsequent entrainment in the near-surface gas. It has long been recognized that such particulates could be relatively large, with early estimates that objects perhaps up to one meter in size may be levitated from the surface of the typical cometary nucleus. However, the general uniformity and small average particulate size of observed comae and the relatively smooth, monotonic increases and decreases in particle density during the Giotto flythrough of comet Halley s coma in 1986 reinforced the view that the bulk of the particles are released at the surface, are fine-sized and inert. Jets have been interpreted as geometrically constrained release of these particulates. With major heterogeneities observed during the recent flythrough of the inner coma of comet Wild 2, these views deserve reconsideration.

Discovery of Main-belt Comet P/2006 VW139 by Pan-STARRS1

NASA Astrophysics Data System (ADS)

Hsieh, Henry H.; Yang, Bin; Haghighipour, Nader; Kaluna, Heather M.; Fitzsimmons, Alan; Denneau, Larry; Novaković, Bojan; Jedicke, Robert; Wainscoat, Richard J.; Armstrong, James D.; Duddy, Samuel R.; Lowry, Stephen C.; Trujillo, Chadwick A.; Micheli, Marco; Keane, Jacqueline V.; Urban, Laurie; Riesen, Timm; Meech, Karen J.; Abe, Shinsuke; Cheng, Yu-Chi; Chen, Wen-Ping; Granvik, Mikael; Grav, Tommy; Ip, Wing-Huen; Kinoshita, Daisuke; Kleyna, Jan; Lacerda, Pedro; Lister, Tim; Milani, Andrea; Tholen, David J.; Vereš, Peter; Lisse, Carey M.; Kelley, Michael S.; Fernández, Yanga R.; Bhatt, Bhuwan C.; Sahu, Devendra K.; Kaiser, Nick; Chambers, K. C.; Hodapp, Klaus W.; Magnier, Eugene A.; Price, Paul A.; Tonry, John L.

2012-03-01

The main-belt asteroid (300163) 2006 VW139 (later designated P/2006 VW139) was discovered to exhibit comet-like activity by the Pan-STARRS1 (PS1) survey telescope using automated point-spread-function analyses performed by PS1's Moving Object Processing System. Deep follow-up observations show both a short (~10'') antisolar dust tail and a longer (~60'') dust trail aligned with the object's orbit plane, similar to the morphology observed for another main-belt comet (MBC), P/2010 R2 (La Sagra), and other well-established comets, implying the action of a long-lived, sublimation-driven emission event. Photometry showing the brightness of the near-nucleus coma remaining constant over ~30 days provides further evidence for this object's cometary nature, suggesting it is in fact an MBC, and not a disrupted asteroid. A spectroscopic search for CN emission was unsuccessful, though we find an upper limit CN production rate of Q CN < 1.3 × 1024 mol s-1, from which we infer a water production rate of Q_H_2O<10^{26} mol s-1. We also find an approximately linear optical spectral slope of 7.2%/1000 Å, similar to other cometary dust comae. Numerical simulations indicate that P/2006 VW139 is dynamically stable for >100 Myr, while a search for a potential asteroid family around the object reveals a cluster of 24 asteroids within a cutoff distance of 68 m s-1. At 70 m s-1, this cluster merges with the Themis family, suggesting that it could be similar to the Beagle family to which another MBC, 133P/Elst-Pizarro, belongs.

DISCOVERY OF MAIN-BELT COMET P/2006 VW{sub 139} BY Pan-STARRS1

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

Hsieh, Henry H.; Yang Bin; Haghighipour, Nader

2012-03-20

The main-belt asteroid (300163) 2006 VW{sub 139} (later designated P/2006 VW{sub 139}) was discovered to exhibit comet-like activity by the Pan-STARRS1 (PS1) survey telescope using automated point-spread-function analyses performed by PS1's Moving Object Processing System. Deep follow-up observations show both a short ({approx}10'') antisolar dust tail and a longer ({approx}60'') dust trail aligned with the object's orbit plane, similar to the morphology observed for another main-belt comet (MBC), P/2010 R2 (La Sagra), and other well-established comets, implying the action of a long-lived, sublimation-driven emission event. Photometry showing the brightness of the near-nucleus coma remaining constant over {approx}30 days provides furthermore » evidence for this object's cometary nature, suggesting it is in fact an MBC, and not a disrupted asteroid. A spectroscopic search for CN emission was unsuccessful, though we find an upper limit CN production rate of Q{sub CN} < 1.3 Multiplication-Sign 10{sup 24} mol s{sup -1}, from which we infer a water production rate of Q{sub H{sub 2O}}<10{sup 26} mol s{sup -1}. We also find an approximately linear optical spectral slope of 7.2%/1000 A, similar to other cometary dust comae. Numerical simulations indicate that P/2006 VW{sub 139} is dynamically stable for >100 Myr, while a search for a potential asteroid family around the object reveals a cluster of 24 asteroids within a cutoff distance of 68 m s{sup -1}. At 70 m s{sup -1}, this cluster merges with the Themis family, suggesting that it could be similar to the Beagle family to which another MBC, 133P/Elst-Pizarro, belongs.« less

Coma morphology of comet 67P controlled by insolation over irregular nucleus

NASA Astrophysics Data System (ADS)

Shi, X.; Hu, X.; Mottola, S.; Sierks, H.; Keller, H. U.; Rose, M.; Güttler, C.; Fulle, M.; Fornasier, S.; Agarwal, J.; Pajola, M.; Tubiana, C.; Bodewits, D.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Barucci, M. A.; Bertaux, J.-L.; Bertini, I.; Boudreault, S.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Deller, J.; Groussin, O.; Gutiérrez, P. J.; Hviid, S. F.; Ip, W.-H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J.-R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Lopez-Moreno, J. J.; Marzari, F.; Naletto, G.; Oklay, N.; Toth, I.; Vincent, J.-B.

2018-05-01

While the structural complexity of cometary comae is already recognizable from telescopic observations1, the innermost region, within a few radii of the nucleus, was not resolved until spacecraft exploration became a reality2,3. The dust coma displays jet-like features of enhanced brightness superposed on a diffuse background1,4,5. Some features can be traced to specific areas on the nucleus, and result conceivably from locally enhanced outgassing and/or dust emission6-8. However, diffuse or even uniform activity over topographic concavity can converge to produce jet-like features9,10. Therefore, linking observed coma morphology to the distribution of activity on the nucleus is difficult11,12. Here, we study the emergence of dust activity at sunrise on comet 67P/Churyumov-Gerasimenko using high-resolution, stereo images from the OSIRIS camera onboard the Rosetta spacecraft, where the sources and formation of the jet-like features are resolved. We perform numerical simulations to show that the ambient dust coma is driven by pervasive but non-uniform water outgassing from the homogeneous surface layer. Physical collimations of gas and dust flows occur at local maxima of insolation and also via topographic focusing. Coma structures are projected to exhibit jet-like features that vary with the perspective of the observer. For an irregular comet such as 67P/Churyumov-Gerasimenko, near-nucleus coma structures can be concealed in the shadow of the nucleus, which further complicates the picture.

The specific entropy of elliptical galaxies: an explanation for profile-shape distance indicators?

NASA Astrophysics Data System (ADS)

Lima Neto, G. B.; Gerbal, D.; Márquez, I.

1999-10-01

Dynamical systems in equilibrium have a stationary entropy; we suggest that elliptical galaxies, as stellar systems in a stage of quasi-equilibrium, may have in principle a unique specific entropy. This uniqueness, a priori unknown, should be reflected in correlations between the fundamental parameters describing the mass (light) distribution in galaxies. Following recent photometrical work on elliptical galaxies by Caon et al., Graham & Colless and Prugniel & Simien, we use the Sérsic law to describe the light profile and an analytical approximation to its three-dimensional deprojection. The specific entropy is then calculated, supposing that the galaxy behaves as a spherical, isotropic, one-component system in hydrostatic equilibrium, obeying the ideal-gas equations of state. We predict a relation between the three parameters of the Sérsic law linked to the specific entropy, defining a surface in the parameter space, an `Entropic Plane', by analogy with the well-known Fundamental Plane. We have analysed elliptical galaxies in two rich clusters of galaxies (Coma and ABCG 85) and a group of galaxies (associated with NGC 4839, near Coma). We show that, for a given cluster, the galaxies follow closely a relation predicted by the constant specific entropy hypothesis with a typical dispersion (one standard deviation) of 9.5per cent around the mean value of the specific entropy. Moreover, assuming that the specific entropy is also the same for galaxies of different clusters, we are able to derive relative distances between Coma, ABGC 85, and the group of NGC 4839. If the errors are due only to the determination of the specific entropy (about 10per cent), then the error in the relative distance determination should be less than 20per cent for rich clusters. We suggest that the unique specific entropy may provide a physical explanation for the distance indicators based on the Sérsic profile put forward by Young & Currie and recently discussed by Binggeli & Jerjen.

Dust in Cometary Comae: Present Understanding of the Structure and Composition of Dust Particles

NASA Technical Reports Server (NTRS)

Levasseur-Regourd, A. C.; Zolensky, M.; Lasue, J.

2007-01-01

In situ probing of a very few cometary comae has shown that dust particles present a low albedo and a low density, and that they consist of both rocky material and refractory organics. Remote observations of solar light scattered by cometary dust provide information on the properties of dust particles in the coma of a larger set of comets. The observations of the linear polarization in the coma indicate that the dust particles are irregular, with a size greater (on the average) than about one micron. Besides, they suggest, through numerical and experimental simulations, that both compact grains and fluffy aggregates (with a power law of the size distribution in the -2.6 to -3 range), and both rather transparent silicates and absorbing organics are present in the coma. Recent analysis of the cometary dust samples collected by the Stardust mission provide a unique ground truth and confirm, for comet 81P/Wild 2, the results from remote sensing observations. Future space missions to comets should, in the next decade, lead to a more precise characterization of the structure and composition of cometary dust particles.

Solar-insolation-induced changes in the coma morphology of comet 67P/Churyumov-Gerasimenko. Optical monitoring with the Nordic Optical Telescope

NASA Astrophysics Data System (ADS)

Zaprudin, B.; Lehto, H. J.; Nilsson, K.; Somero, A.; Pursimo, T.; Snodgrass, C.; Schulz, R.

2017-07-01

Context. 67P/Churyumov-Gerasimenko (67P/C-G) is a short-period Jupiter family comet with an orbital period of 6.55 yr. Being the target comet of ESA's Rosetta mission, 67P/C-G has become one of the most intensively studied minor bodies of the solar system. The Rosetta Orbiter and the Philae Lander have brought us unique information about the structure and activity of the comet nucleus, as well as its activity along the orbit, composition of gas, and dust particles emitted into the coma. However, as Rosetta stayed in very close proximity to the cometary nucleus (less than 500 km with a few short excursions reaching up to 1500 km), it could not see the global picture of a coma at the scales reachable by telescopic observations (103 - 105 km). Aims: In this work we aim to connect in-situ observations made by Rosetta with the morphological evolution of the coma structures monitored by the ground-based observations. In particular, we concentrate on causal relationships between the coma morphology and evolution observed with the Nordic Optical Telescope (NOT) in the Canary Islands, and the seasonal changes of the insolation and the activity of the comet observed by the Rosetta instruments. Methods: Comet 67P/C-G was monitored with the NOT in imaging mode in two colors. Imaging optical observations were performed roughly on a weekly basis, which provides good coverage of short- and long-term variability. With the three dimensional modeling of the coma produced by active regions on the southern hemisphere, we aim to qualify the observed morphology by connecting it to the activity observed by Rosetta. Results: During our monitoring program, we detected major changes in the coma morphology of comet 67P/C-G. These were long-term and long-lasting changes. They do not represent any sudden outburst or short transient event, but are connected to seasonal changes of the surface insolation and the emergence of new active regions on the irregular shaped comet nucleus. We have also found significant deviations in morphological changes from the prediction models based on previous apparitions of 67P/C-G, like the time delay of the morphology changes and the reduced activity in the northern hemisphere. According to our modeling of coma structures and geometry of observations, the changes are clearly connected with the activity in the southern hemisphere observed by the Rosetta spacecraft.

Dust emission from comets at large heliocentric distances. I - The case of comet Bowell /1980b/

NASA Technical Reports Server (NTRS)

Houpis, H. L. F.; Mendis, D. A.

1981-01-01

Alternative processes of dust emission from comets at large heliocentric distances are considered, in order to explain the dust coma observed in comet Bowell (1980b) at a heliocentric distance as large as 7.17 AU. It is shown that the electrostatic blow-off of dust from a charged, H2O-dominated nucleus having a layer of loose, fine dust may be the formation process of the dust coma, with the coma size expected from the process being comparable to the observed value and the dust grain size being equal to or less than 0.4 microns in size. The upper limit for the total mass in the coma is 3.9 x 10 to the 8th g, and the spatial extension less than 10,000 km. The observed activity may alternatively be due to dust entrainment by the sublimating gas from a CO2-dominated nucleus.

Using Spectroscopic Profiles to Study the Morphology of Comets

NASA Astrophysics Data System (ADS)

Harris, Ien; Pierce, Donna M.; Cochran, Anita L.

2016-10-01

We have used the integral-field unit spectrograph (the George and Cynthia Mitchell Spectrograph) on the 2.7m Harlan J. Smith telescope at McDonald Observatory to obtain spectroscopic images of the comae of several comets. The images were obtained for various radical species (C2, C3. CH, CN, NH2). Radial and azimuthal average profiles of the radical species were created to enhance any observed cometary coma morphological features. We compare the observed coma features across the observed species and over the different observation periods in order to constrain possible rotational states of the observed comets. We will present results for several comets, including 2009P1 (Garradd). This work was funded by NASA's Planetary Atmospheres program (Award No. NNX14AH186).

VizieR Online Data Catalog: Galaxies morphology and IR photometry III. (Gavazzi+, 2000)

NASA Astrophysics Data System (ADS)

Gavazzi, G.; Franzetti, P.; Scodeggio, M.; Boselli, A.; Pierini, D.; Baffa, C.; Lisi, F.; Hunt, L. K.

1999-11-01

We present near-infrared H-band (1.65μm) surface photometry of 558 galaxies in the Coma Supercluster and in the Virgo cluster. This data set, obtained with the Arcetri NICMOS3 camera ARNICA mounted on the Gornergrat Infrared Telescope, is aimed at complementing, with observations of mostly early-type objects, our NIR survey of spiral galaxies in these regions, presented in previous papers of this series. Magnitudes at the optical radius, total magnitudes, isophotal radii and light concentration indices are derived. We confirm the existence of a positive correlation between the near-infrared concentration index and the galaxy H-band luminosity (2 data files).

The Inner Coma Physical Environments of Ecliptic Comets 45P/Honda-Mrkos-Pajdusakova, 2P/Encke, and 41P/Tuttle-Giacobini-Kresak Revealed Through Long-Slit Spectroscopy at NASA IRTF

NASA Astrophysics Data System (ADS)

Bonev, Boncho P.; DiSanti, Michael A.; Roth, Nathan; Dello Russo, Neil; Vervack, Ronald J.; Gibb, Erika L.; Villanueva, Geronimo Luis; Combi, Michael R.; Fougere, Nicolas; Kawakita, Hideyo; McKay, Adam J.; Saki, Mohammad; Cordiner, Martin; Protopapa, Silvia; de Val-Borro, Miguel

2017-10-01

Understanding the physical processes in the inner regions of cometary atmospheres is vital for interpretation of molecular cometary emission at all wavelengths. Furthermore, because ecliptic comets are continuously evaluated as space mission targets, understanding their coma environments is a central theme in both enhancing the science return of past missions (EPOXI, Rosetta) and in selecting future mission targets. With this motivation, we report long-slit high-resolution observations of H2O emission in the comae of three ecliptic comets observed in early 2017: 45P/Honda-Mrkos-Pajdusakova, 2P/Encke, and 41P/Tuttle-Giacobini-Kresak. Using the new crossed-dispersed spectrograph iSHELL at NASA IRTF, we detected a suite of water rovibrational emission lines from these comets and measured the spatial distributions of H2O rotational temperatures and molecular column densities. Both parameters are highly diagnostic of the physical environment in cometary comae, the competition between cooling and heating processes in these environments, and the presence (or lack thereof) of extended coma sources of gas-phase H2O. Comets 2P and 45P allowed a rare glimpse into coma physics at small (< 0.6 AU) heliocentric distances, where photochemical heating is particularly important, but direct H2O observations have been sparse. Our results add to the small sample of spatial-spectral measurements of this type. They will be discussed in the context of coma physics models along with prospects for investigations during the upcoming favorable apparitions of ecliptic comets 21P/Giacobini-Zinner and 46P/Wirtanen. We gratefully acknowledge support from the NASA Solar System Workings, Planetary Atmospheres, Earth and Space Science Fellowship, Solar System Observations, Emerging Worlds, and Astrobiology Programs, and NSF Solar and Planetary Research Grants. We are grateful to the entire IRTF staff for their help with these challenging observations, most of which were done during daytime.

Are the virial masses of clusters smaller than we think?

NASA Technical Reports Server (NTRS)

Cowie, L. L.; Henriksen, M.; Mushotzky, R.

1987-01-01

The constraints that the available X-ray spectral and imaging data place on the mass distribution and mass to light ratio of rich clusters are considered. It was found for the best determined cases that the mass to light ratio is less than 125 h sub 50 at radii exceeding 1 h sub 50 Mpc. The mass to light ratio is approximately constant at radii exceeding 1 h sub 50 Mpc but may rise to values of roughly 200 h sub 50 in the central regions. The fraction of the total mass that is in baryons, primarily the hot X-ray emitting gas, is roughly 30 percent thus setting the mass to light ratio of the dark material to roughly 70. The model that fits the X-ray data for Coma is in good agreement with the observed optical velocity dispersion vs. radius data.

Are the virial masses of clusters smaller than we think?

NASA Technical Reports Server (NTRS)

Cowie, L. L.; Henriksen, M.; Mushotzky, R.

1986-01-01

The constraints that the available X-ray spectral and imaging data place on the mass distribution and mass to light ratio of rich clusters are considered. It was found for the best determined cases that the mass to light ratio is less than 125 h sub 50 at radii exceeding 1 h sub 50 Mpc. The mass to light ratio is approximately constant at radii exceeding 1 h sub 50 Mpc but may rise to values of roughly 200 h sub 50 in the central regions. The fraction of the total mass that is in baryons, primarily the hot X-ray emitting gas, is roughly 30% thus setting the mass to light ratio of the dark material to roughly 70. The model that fits the X-ray data for Coma is in good agreement with the observed optical velocity dispersion vs. radius data.

Jet Morphology and Coma Analysis of 103P/Hartley 2: Temporal Evolution and Interspecies Comparisons

NASA Astrophysics Data System (ADS)

Vaughan, Charles M.; Pierce, Donna M.; Cochran, Anita L.

2014-11-01

We present our results on an expanded study of the jet and coma behavior of comet 103P/Hartley 2 (a continuation of original results presented in Vaughan et al. 2012). We observed Hartley 2 pre- and post-perihelion in 2010 using the George and Cynthia Mitchell Spectrograph on the 2.7 m telescope at McDonald Observatory. Data for CN, C2, C3, CH, and NH2 were collected over six nights from 15 July to 10 November. The spectral data were used to create coma maps for each of the observed species, and the maps were processed using radial and azimuthal division techniques to create enhanced images of the coma to examine coma morphological features. To compliment the ongoing investigation of Hartley 2 as studied by the EPOXI flyby mission, we use findings from other researchers (Belton et al. 2012; Syal et al. 2012; Thomas et al. 2012) to identify dust jet locations on the nucleus and compare the computed jet directions to the radical densities in the coma at our observation times. We also calculate production rates and mixing ratios with water for suspected parent species. This work was funded by the National Science Foundation Graduate K-12 (GK-12) STEM Fellows program (Award No. DGE-0947419) and NASA’s Planetary Atmospheres program (Award No. NNX14AH18G).

Dwarf galaxy populations in present-day galaxy clusters - II. The history of early-type and late-type dwarfs

NASA Astrophysics Data System (ADS)

Lisker, Thorsten; Weinmann, Simone M.; Janz, Joachim; Meyer, Hagen T.

2013-06-01

How did the dwarf galaxy population of present-day galaxy clusters form and grow over time? We address this question by analysing the history of dark matter subhaloes in the Millennium II cosmological simulation. A semi-analytic model serves as the link to observations. We argue that a reasonable analogue to early morphological types or red-sequence dwarf galaxies are those subhaloes that experienced strong mass-loss, or alternatively those that have spent a long time in massive haloes. This approach reproduces well the observed morphology-distance relation of dwarf galaxies in the Virgo and Coma clusters, and thus provides insight into their history. Over their lifetime, present-day late types have experienced an amount of environmental influence similar to what the progenitors of dwarf ellipticals had already experienced at redshifts above 2. Therefore, dwarf ellipticals are more likely to be a result of early and continuous environmental influence in group- and cluster-size haloes, rather than a recent transformation product. The observed morphological sequences of late-type and early-type galaxies have developed in parallel, not consecutively. Consequently, the characteristics of today's late-type galaxies are not necessarily representative for the progenitors of today's dwarf ellipticals. Studies aiming to reproduce the present-day dwarf population thus need to start at early epochs, model the influence of various environments, and also take into account the evolution of the environments themselves.

The evolution of early-type galaxies in nearby clusters: breaking the age-metallicity degeneracy with Spitzer IRS Blue Peak-Up Imaging

NASA Astrophysics Data System (ADS)

Bressan, Alessandro; Buson, Lucio; Clemens, Marcel; Danese, Luigi; Granato, Gian Luigi; Panuzzo, Pasquale; Rampazzo, Roberto; Silva, Laura; Valdes, Jose Ramon

2005-06-01

We have shown with Cycle 1 observations that Spitzer has the capability of disentangling age and metallicity in old stellar populations. By looking to the broad emission feature left by dust enshrouded asymptotic giant branch stars above 9.7 microns, Spitzer IRS can provide direct evidence that the colour- magnitude relation of Virgo ellipticals is mainly driven by metallicity. However, with the IRS spectrograph we can only probe the bright tail of the colour-magnitude relation, and only in the nearest cluster. We propose to use IRS Blue Peak-Up, the only Spitzer band that looks directly in the core of that spectral feature, to reach fainter galaxies. We will perform a thorough investigation of early type galaxies along the colour-magnitude relation in Virgo and in Coma clusters. These observations, when coupled with already existing IRAC and Optical-NIR observations, will allow a) an unbiased census of the stellar populations in cluster early type galaxies; b) an estimate of the AGB material recycled into the ISM in these systems; c) a direct check of the universality of the colour- magnitude relation on a wide range of magnitudes; d) a spatial study of the stellar populations within the galaxies, e.g. investigating differences between bulge and disk populations within S0; e) the most secure reference frame with which to compare the evolution of early type galaxies in other environments (groups and field).

Coma Morphology Due to an Extended Active Region and Implications for the Spin State of Comet Hale-Bopp

NASA Technical Reports Server (NTRS)

Samarasinha, Nalin H.

2000-01-01

We show that the circular character of continuum structures observed in the coma of comet Hale-Bopp around the perihelion passage is most likely due to a dust jet from a large extended active region on the surface. Coma morphology due to a wide jet is different from that due to a narrow jet. The latter shows foreshortening effects due to observing geometry, wider jet produces more circular features. This circularization effect provides a self-consistent explanation for the evolution of near-perihelion coma morphology. No changes in the direction of the rotational angular momentum vector are required during this period in contrast to the models of Schleicher et al. This circularization effect also enables us to produce near-circular coma features in the S-E quadrant during 1997 late February and therefore questions the basic premise on which Sekanina bases his morphological arguments for a gravitationally bound satellite nucleus.

Abundant molecular oxygen in the coma of comet 67P/Churyumov-Gerasimenko.

PubMed

Bieler, A; Altwegg, K; Balsiger, H; Bar-Nun, A; Berthelier, J-J; Bochsler, P; Briois, C; Calmonte, U; Combi, M; De Keyser, J; van Dishoeck, E F; Fiethe, B; Fuselier, S A; Gasc, S; Gombosi, T I; Hansen, K C; Hässig, M; Jäckel, A; Kopp, E; Korth, A; Le Roy, L; Mall, U; Maggiolo, R; Marty, B; Mousis, O; Owen, T; Rème, H; Rubin, M; Sémon, T; Tzou, C-Y; Waite, J H; Walsh, C; Wurz, P

2015-10-29

The composition of the neutral gas comas of most comets is dominated by H2O, CO and CO2, typically comprising as much as 95 per cent of the total gas density. In addition, cometary comas have been found to contain a rich array of other molecules, including sulfuric compounds and complex hydrocarbons. Molecular oxygen (O2), however, despite its detection on other icy bodies such as the moons of Jupiter and Saturn, has remained undetected in cometary comas. Here we report in situ measurement of O2 in the coma of comet 67P/Churyumov-Gerasimenko, with local abundances ranging from one per cent to ten per cent relative to H2O and with a mean value of 3.80 ± 0.85 per cent. Our observations indicate that the O2/H2O ratio is isotropic in the coma and does not change systematically with heliocentric distance. This suggests that primordial O2 was incorporated into the nucleus during the comet's formation, which is unexpected given the low upper limits from remote sensing observations. Current Solar System formation models do not predict conditions that would allow this to occur.

The topology of large-scale structure. VI - Slices of the universe

NASA Astrophysics Data System (ADS)

Park, Changbom; Gott, J. R., III; Melott, Adrian L.; Karachentsev, I. D.

1992-03-01

Results of an investigation of the topology of large-scale structure in two observed slices of the universe are presented. Both slices pass through the Coma cluster and their depths are 100 and 230/h Mpc. The present topology study shows that the largest void in the CfA slice is divided into two smaller voids by a statistically significant line of galaxies. The topology of toy models like the white noise and bubble models is shown to be inconsistent with that of the observed slices. A large N-body simulation was made of the biased cloud dark matter model and the slices are simulated by matching them in selection functions and boundary conditions. The genus curves for these simulated slices are spongelike and have a small shift in the direction of a meatball topology like those of observed slices.

The topology of large-scale structure. VI - Slices of the universe

NASA Technical Reports Server (NTRS)

Park, Changbom; Gott, J. R., III; Melott, Adrian L.; Karachentsev, I. D.

1992-01-01

Results of an investigation of the topology of large-scale structure in two observed slices of the universe are presented. Both slices pass through the Coma cluster and their depths are 100 and 230/h Mpc. The present topology study shows that the largest void in the CfA slice is divided into two smaller voids by a statistically significant line of galaxies. The topology of toy models like the white noise and bubble models is shown to be inconsistent with that of the observed slices. A large N-body simulation was made of the biased cloud dark matter model and the slices are simulated by matching them in selection functions and boundary conditions. The genus curves for these simulated slices are spongelike and have a small shift in the direction of a meatball topology like those of observed slices.

Monte Carlo Particle Trajectory Models for Neutral Cometary Gases. II. The Spatial Morphology of the Lyman-Alpha Coma

NASA Astrophysics Data System (ADS)

Combi, Michael R.; Smyth, William H.

1988-04-01

The Monte Carlo particle-trajectory model (MCPTM) developed in Paper 1 is applied to explain the observed morphology of the spatially extended Lyα comae of comets. The physical processes and assumptions used in the model as they relate to the photodissociation of H2O and OH and the solar radiation pressure acceleration are presented herein. For this first application, the rocket and Skylab images of the Lyα coma of comet Kohoutek were chosen for study. The self-consistent modeling analysis of these data consisted of two parts. The first part entailed using a steady state spherically symmetric inner coma MCPTM coupled with a simple gas-dynamic model to calculate the physical development of the coma, i.e., the dependence of coma temperature and outflow speed on radial distance to the center of the nucleus, as a function of the (time) heliocentric distance of the comet. The inner coma MCPTM was used to calculate correctly the photo-chemical heating of the coma due to the partial collisional thermalization of the hot hydrogen atoms produced in the photodissociation of water molecules. In the second part of the analysis the results from the first part were used in a fully time-dependent and three-dimensional extended coma MCPTM which includes the explicit calculation of partial thermalization of the H atoms by multiple collisions with coma molecules. The same physical model yielded very good matches between the modeled Lycα isophotes and those observed in both of the two very different images of comet Kohoutek. The production rate was varied in time as implied by the shape of the visual light curve. All other physical parameters were varied only according to their naturally expected heliocentric distance and velocity dependencies. The complete physical description of the inner coma provided by the coupled gas-dynamic/MCPTM calculation was needed to obtain a good fit to the data. The correct inner coma description is important since it provides not only the initial conditions for the photodissociated H atoms but also (and most importantly) the collisional targets for the H atoms produced in the innermost regions of the coma. Simplistic descriptions for the coma (single speed and perfectly radial molecular motion) do not yield realistic isophote contours. The implications of the model results as they apply to other comets, species, and a variety of conditions are also discussed.

Prognosis of patients in coma after acute subdural hematoma due to ruptured intracranial aneurysm.

PubMed

Torné, Ramon; Rodríguez-Hernández, Ana; Romero-Chala, Fabián; Arikan, Fuat; Vilalta, Jordi; Sahuquillo, Juan

2016-04-01

Acute subdural hematomas (aSDH) secondary to intracranial aneurysm rupture are rare. Most patients present with coma and their functional prognosis has been classically considered to be very poor. Previous studies mixed good-grade and poor-grade patients and reported variable outcomes. We reviewed our experience by focusing on patients in coma only and hypothesized that aSDH might worsen initial mortality but not long-term functional outcome. Between 2005 and 2013, 440 subarachnoid hemorrhage (SAH) patients were admitted to our center. Nineteen (4.3%) were found to have an associated aSDH and 13 (2.9%) of these presented with coma. Their prospectively collected clinical and outcome data were reviewed and compared with that of 104 SAH patients without aSDH who presented with coma during the same period. Median aSDH thickness was 10mm. Four patients presented with an associated aneurysmal cortical laceration and only one had good recovery. Overall, we observed good long-term outcomes in both SAH patients in coma with aSDH and those without aSDH (38.5% versus 26.4%). Associated aSDH does not appear to indicate a poorer long-term functional prognosis in SAH patients presenting with coma. Anisocoria and brain herniation are observed in patients with aSDH thicknesses that are smaller than those observed in trauma patients. Despite a high initial mortality, early surgery to remove the aSDH results in a good outcome in over 60% of survivors. Aneurysmal cortical laceration appears to be an independent entity which shows a poorer prognosis than other types of aneurysmal aSDH. Copyright © 2015 Elsevier Ltd. All rights reserved.

A Survey of Variable Extragalactic Sources with XTE's All Sky Monitor (ASM)

NASA Technical Reports Server (NTRS)

Jernigan, Garrett

1998-01-01

The original goal of the project was the near real-time detection of AGN utilizing the SSC 3 of the ASM on XTE which does a deep integration on one 100 square degree region of the sky. While the SSC never performed sufficiently well to allow the success of this goal, the work on the project has led to the development of a new analysis method for coded aperture systems which has now been applied to ASM data for mapping regions near clusters of galaxies such as the Perseus Cluster and the Coma Cluster. Publications are in preparation that describe both the new method and the results from mapping clusters of galaxies.

Spectroscopic Investigations of Fragment Species in the Coma

NASA Technical Reports Server (NTRS)

Feldman, Paul D.; Cochran, Anita L.; Combi, Michael R.

2004-01-01

The content of the gaseous coma of a comet is dominated by fragment species produced by photolysis of the parent molecules issuing directly from the icy nucleus of the comet. Spectroscopy of these species provides complementary information on the physical state of the coma to that obtained from observations of the parent species. Extraction of physical parameters requires detailed molecular and atomic data together with reliable high-resolution spectra and absolute fluxes of the primary source of excitation, the Sun. The large database of observations, dating back more than a century, provides a means to assess the chemical and evolutionary diversity of comets.

Radical formation in the coma from photodissociation of ice grains

NASA Technical Reports Server (NTRS)

Jackson, William M.; Gerth, Christopher

1990-01-01

Long ago visual observations of comets suggested that there are jets in comets but it has only been recently that A'Hearn et al. have proven that some of these jets are due to emission from the CN radical. Recent studies in the lab have shown that CN radicals can be ejected directly into the gas phase from the photolysis of frozen vapors if the parent molecular has been excited to repulsive excited state. This later observation suggests that the jets that have been observed may be due to photodissociation of icy grains in the coma. A theory of radical formation from icy grains is presented. It is shown that direct formation of free radicals in the coma is an effective way to produce radicals from icy grains in the coma. The model predicts that icy grains could produce from 6 to 800,000 OH radicals/s per grain depending upon whether the radius of the grain is 0.3 to 100 micron.

Is the Size Evolution of Massive Galaxies Accelerated in Cluster Environments?

NASA Astrophysics Data System (ADS)

Wilson, Gillian

2013-10-01

At z 1.6 the main progenitors of present-day massive clusters are undergoing rapid collapse, and have the highest rates of galaxy merging and assembly. Recent observational studies have hinted at accelerated galaxy evolution in dense environments at this epoch, including increased merger rates and rapid growth in galaxy size relative to the field. We propose WFC3 G102 spectroscopy and F125W {Broad J} imaging of a sample of four massive spectroscopically-confirmed clusters at z = 1.6. Our primary scientific goal is to leverage the CANDELS Wide Legacy dataset to carry out a head-to-head comparison of the sizes of cluster members relative to the field {as a function of stellar mass and Sersic index}, and quantify the role of environment in the observed rapid evolution in galaxy sizes since z = 2. These clusters are four of the highest significance overdensities in the 50 square degree SWIRE fields, and will evolve over time to have present-day masses similar to Coma. They were detected using IRAC [3.6]-[4.5] color, which identifies galaxy overdensities regardless of optically red or blue color. A heroic ground-based spectroscopic campaign has resulted in 44 spectroscopically-confirmed members. However this sample is heavily biased toward star-forming {SF} galaxies, and WFC3 spectroscopy is essential to definitively determine cluster membership for 200 members, without bias with respect to quiescent or SF type. The F125W {rest-frame V-band} imaging is necessary to measure the sizes and morphologies of cluster members. 17-passband broadband imaging spanning UV, optical, near-IR, Spitzer IR and Herschel far-IR is already in hand.

Polarization imaging of comets at geocentric distances smaller than 0.5 au: Comet 73P/Schwassmann-Wachmann 3

NASA Astrophysics Data System (ADS)

Hadamcik, E.; Levasseur-Regourd, A.-C.

2014-07-01

Remote observations of sunlight scattered by solid particles provide information on the particle properties for a large variety of comets. When comets approach the Sun, solid particles and gases are released from the surface or from the inner layers [1,2]. If the comet is close enough to the Earth, the inner coma may be studied. Different coma regions are observed corresponding to different dust properties, e.g., in jets or fresh ejected dust around the coma. Narrow-band continuum filters or broader-band filters in less contaminated spectral domains (red or near infrared) are currently used to avoid or reduce the contributions from gaseous emission. Comet 73P/Schwassmann-Wachmann 3 is a fascinating fragmenting comet. Different observations in 1995 revealed an increase of activity and at least four fragments of the nucleus. In its 2011 apparition, the fragments were well separated and appeared like small individual comets. In 2006, its apparition was very favorable and allowed high- spatial resolution imaging by different complementary techniques. We observed three fragments of comet 73P/Schwassmann-Wachmann 3 from April 27 to May 3, 2006, by imaging polarimetry with the 80-cm telescope at Observatoire de Haute-Provence. The distance to the Earth was smaller than 0.2 au. Fragment C resembles a classical active comet. Regions of high and lower polarization were observed in the inner coma, appearing to change almost periodically. The variation of polarization in the inner coma was important from one night to the next one, the whole coma polarization being about constant for nucleus distances greater than 2000 km and increasing with the phase angle. Fragment B continued its (sequential) fragmentation, with a region of secondary fragments progressively moving away from the main nucleus in the antisolar direction. The chemical composition has been reported as being similar in all the fragments [3], but differences were observed between them in polarization underlining differences in, e.g., structure or size distribution of the particles during their ejection and fragmentation. The variation of polarization in the coma and around the fragments will be presented. Finally, a comparison to other comets, including split comets observed at small geocentric distances, will be provided.

A Multi-frequency analysis of dark matter annihilation interpretations of recent anti-particle and γ-ray excesses in cosmic structures

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

Beck, G.; Colafrancesco, S., E-mail: geoff.m.beck@gmail.com, E-mail: sergio.colafrancesco@wits.ac.za

2016-05-01

The Fermi-LAT observation of a γ-ray excess from the galactic-centre, as well as the PAMELA, AMS, and AMS-2 anti-particle excesses, and the recent indications of a Fermi-LAT γ-ray excess in the Reticulum II dwarf galaxy have all been variously put forward as possible indirect signatures of supersymmetric neutralino dark matter. These are of particular interest as the neutralino annihilation models which fit these observations must have observable consequences across the frequency spectrum, from radio to γ-ray emission. Moreover, since dark matter is expected to be a major constituent of cosmic structure, these multi-frequency consequences should be common to such structuresmore » across the mass spectrum, from dwarf galaxies to galaxy clusters. Thus, in this work we make predictions for the multi-frequency spectra of three well-known sources dominated by dark matter on cluster, galaxy and dwarf galaxy scales, e.g. the Coma cluster, the galaxy M81, and the Draco dwarf galaxy, using models favoured by dark matter interpretations of the aforementioned observations. We pay special attention to the consequences for these models when their cross-sections are renormalised to reproduce the recent γ-ray excess observed in the Reticulum II dwarf galaxy, as well as using cross-sections from the Fermi-LAT dwarf galaxy limits, which throw a dark matter interpretation of this excess into doubt. We find that the multi-frequency data of Coma and Draco are in conflict with the dark matter interpretation of the AMS, PAMELA and Fermi positron excess. Additionally, models derived from Fermi-LAT galactic centre observations, and AMS-2 re-analysis, present similar but less extensive conflicts. Using the sensitivity projections for the Square Kilometre Array, the Cherenkov Telescope Array, as well as the ASTROGAM and ASTRO-H satellites, we determine the detection prospects for a subset of neutralino models that remain consistent with Planck cosmological constraints. Although the SKA has the greatest sensitivity to dark matter models, we demonstrate that ASTRO-H is well positioned to probe the inverse-Compton scattering emissions from neutralino annihilation and identify characteristics of the spectra which contain information about the neutralino mass and annihilation channel. This means that, given environments with favourable X-ray backgrounds, multi-frequency observation with the next generation of experiments will allow for unprecedented sensitivity to the neutralino parameter space as well as offsetting the individual weaknesses of each observation mode. Finally we show that all of the studied models can be better tested with the SKA phase 1.« less

Development and Preliminary Validation of the Coma Arousal Communication Scale.

PubMed

Garin, Julie; Reina, Margot; DeiCas, Paula; Rousseaux, Marc

To develop a Coma Arousal Communication Scale and perform preliminary validation. A group of experts developed a questionnaire to assess communication between patients emerging from coma and caregiver (participation, communication modes, and themes) and the strategies used to facilitate communication. To assess the scale's psychometric characteristics, it was presented to the caregivers of 40 inpatients admitted to 5 coma units and (to obtain reference data) to 29 control participants. The Coma Arousal Communication Scale displayed good intra- and interrater reliability as judged by intraclass correlation coefficients (between 0.76 and 0.98) and Bland and Altman plots. Cohen κ coefficient revealed moderate to almost perfect levels of agreement for most individual items and slight levels for a few items dealing with compensatory strategies. We observed good internal consistency, relations with the Wessex Head Injury Matrix, and sensitivity to change for patients who had sustained brain injury in the previous 6 months. The Coma Arousal Communication Scale provides accurate information about communication skills of individuals emerging from coma. However, some compensatory strategies adopted by caregivers are difficult to characterize.

Revealing the Formation Mechanism of Ultra-Diffuse Galaxies

NASA Astrophysics Data System (ADS)

Garmire, Gordon

2017-09-01

Recently a population of large, very low optical surface brightness galaxies, so called ultra-diffuse galaxies (UDGs), were discovered in the outskirts of Coma clusters. Stellar line-of-sight velocity dispersions suggest large dark matter halo masses of 10^12 M_sun with very low baryon fractions ( 1%). The outstanding question waiting to be answered is: How do UDGs form and evolve? One theory is that UDGs are related to bright galaxies, however they are prevented from building a normal stellar population through various violent processes, such as gas stripping. We propose to observe Dragonfly 44, the most massive UDG known, for 100 ks with ACIS-I to test some of the formation theories.

Subaru Weak-lensing Survey of Dark Matter Subhalos in the Coma Cluster: Subhalo Mass Function and Statistical Properties

NASA Astrophysics Data System (ADS)

Okabe, Nobuhiro; Futamase, Toshifumi; Kajisawa, Masaru; Kuroshima, Risa

2014-04-01

We present a 4 deg2 weak gravitational lensing survey of subhalos in the very nearby Coma cluster using the Subaru/Suprime-Cam. The large apparent size of cluster subhalos allows us to measure the mass of 32 subhalos detected in a model-independent manner, down to the order of 10-3 of the virial mass of the cluster. Weak-lensing mass measurements of these shear-selected subhalos enable us to investigate subhalo properties and the correlation between subhalo masses and galaxy luminosities for the first time. The mean distortion profiles stacked over subhalos show a sharply truncated feature which is well-fitted by a Navarro-Frenk-White (NFW) mass model with the truncation radius, as expected due to tidal destruction by the main cluster. We also found that subhalo masses, truncation radii, and mass-to-light ratios decrease toward the cluster center. The subhalo mass function, dn/dln M sub, in the range of 2 orders of magnitude in mass, is well described by a single power law or a Schechter function. Best-fit power indices of 1.09^{+0.42}_{-0.32} for the former model and 0.99_{-0.23}^{+0.34} for the latter, are in remarkable agreement with slopes of ~0.9-1.0 predicted by the cold dark matter paradigm. The tangential distortion signals in the radial range of 0.02-2 h -1 Mpc from the cluster center show a complex structure which is well described by a composition of three mass components of subhalos, the NFW mass distribution as a smooth component of the main cluster, and a lensing model from a large scale structure behind the cluster. Although the lensing signals are 1 order of magnitude lower than those for clusters at z ~ 0.2, the total signal-to-noise ratio, S/N = 13.3, is comparable, or higher, because the enormous number of background source galaxies compensates for the low lensing efficiency of the nearby cluster. Based on data collected from the Subaru Telescope and obtained from SMOKA, operated by the Astronomy Data Center, National Astronomical Observatory of Japan.

Far-Infrared Emission of Intracluster Dust (ICD)

NASA Astrophysics Data System (ADS)

Arimoto, N.; Takagi, T.; Hanami, H.

2000-12-01

In the young universe, clusters of galaxies could be bright FIR-Submm sources due to the dust emissions from young ellipticals. The intracluster dust (ICD) could also contribute to the FIR-Submm emissions considerably, but the ICD is fragile in the ambient hot ICM. Therefore, a chance to detect the ICD emission would be much smaller than the dust emissions from galaxies. Dust emissions from elliptical galaxies (EROs) in the young Coma cluster at a distance of z=2-3 would be easily detected by a future mission of H2L2 satellite, thus the FIR-Submm survey would become a powerful tool for searching high-z clusters.

Radio-continuum survey of the Coma/A1367 supercluster. IV - 1.4 GHz observations of CGCG galaxies

NASA Astrophysics Data System (ADS)

del Castillo, E.; Gavazzi, G.; Jaffe, W.

1988-05-01

1.4 GHz radio-continuum observations of 148 CGCG galaxies in the Coma supercluster region were obtained with the VLA in C array configuration. Comparison with previous measurements at 0.6 GHz leads to an average spectral index >α< = 0.8. The structures of 29 galaxies in this region determined with high-resolution VLA (A array) observations are presented.

Modeling the coma of 2060 Chiron

NASA Technical Reports Server (NTRS)

Boice, D. C.; Konno, I.; Stern, S. Alan; Huebner, W. F.

1991-01-01

Observations of comet-like activity and a resolved coma have established that 2060 Chiron is a comet. Determinations of its radius range from 65 to 200 km. This unusually large size for a comet suggests that the atmosphere of Chiron is intermediate to the tightly bound, thin atmospheres typical of planets and satellite and the greatly extended atmospheres in free expansion typical of cometary comae. Under certain conditions it may gravitationally bind an atmosphere that is thick compared to its size, while a significant amount of gas escapes to an extensive exosphere. These attributes coupled with reports of sporadic outbursts at large heliocentric distances and the identification of CN in the coma make Chiron a challenging object to model. Simple models of gas production and the dusty coma were recently presented but a general concensus on many basic features has not emerged. Development was begun on a more complete coma model of Chiron. The objectives are to report progress on this model and give the preliminary results for understanding Chiron.

The Large-Grained Dust Coma of 174P/Echeclus

NASA Technical Reports Server (NTRS)

Bauer, James M.; Choi, Young-Jun; Weissman, Paul R.; Stansberry, John A.; Fernandez, Yanga R.; Roe, Henry G.; Buratti, Bonnie J.; Sung, Hyun-Il

2008-01-01

On 2005 December 30, Y.-J. Choi and P. R. Weissman discovered that the formerly dormant Centaur 2000 EC98 was in strong outburst. Previous observations by P. Rousselot et al. spanning a 3-year period indicated a lack of coma down to the 27 mag arcsec 2 level.We present Spitzer Space Telescope MIPS observations of this newly active Centaur--now known as 174P/Echeclus (2000 EC98)--or 60558 Echeclus--taken in 2006 late February. The images show strong signal at both the 24 and 70 micron bands and reveal an extended coma about 2' in diameter. Analyses yield estimates of the coma signal contribution that are in excess of 90% of the total signal in the 24 micron band. Dust production estimates ranging from 1.7-4 x 10(exp 2) kg/s are on the order of 30 times that seen in other Centaurs. Simultaneous visible-wavelength observations were also obtained with Palomar Observatory's 200-inch telescope, the 1.8-m Vatican Advanced Technology Telescope, the Bohyunsan Optical Astronomy Observatory (BOAO) 1.8-m telescope, and Table Mountain Observatory's 0.6-m telescope, revealing a coma morphology nearly identical to the mid-IR observations. The grain size distribution derived from the data yields a log particle mass power-law with slope parameter (alpha) = -0.87 +/- 0.07, and is consistent with steady cometary-activity, such as that observed during the Stardust spacecraft's encounter at 81P/Wild 2, and not with an impact driven event, such as that caused by the Deep Impact experiment.

Repeatability of the Dust and Gas Morphological Structures in the Coma of Comet

NASA Astrophysics Data System (ADS)

Lejoly, Cassandra; Samarasinha, N. H.; Ojha, L.; Schleicher, D. G.

2013-10-01

Comet 1P/Halley is the most famous comet in history and has been observed for over two millennia, making it one of the most extensively studied comets. The morphology in the coma of comet 1P/Halley originates due to the activity at the nucleus and could be used as a probe of the nuclear rotation and the activity. We will present the results from a study summarizing the evolution of coma morphology of comet 1P/Halley observed from ground between October 1985 and June 1986. The results to be presented include analysis of dust features as well as gas (CN) features in the coma and comparisons will be made between their spatial and temporal evolution. About 80 CN images and 300 continuum images from the Small Bodies Node of the NASA Planetary Data System were analyzed using image enhancement techniques that were not available n the 1980s. This enables us to see coma structure never observed before in comet 1P/Halley. Because of the comet's proximity to Earth, most of our best signal-to-noise images were taken in the March-April interval of 1986. Despite the limited coverage of preceding and following months, there is a sufficient number of images to monitor morphological evolution over many months. The initial synodic periods as a function of time used to phase the images together were extrapolated from the lightcurves of the active coma (Schleicher et al. 1990, AJ, 100, 896-912). We will present the periods of repeatability of individual coma features measured using the position angle at different spatial distances from the nucleus in adjacent cycles. Separate features appear to have slightly different periods of repeatability, perhaps depending on the corresponding source regions on the nucleus and/or projection effects. The periods of repeatability of coma morphologies will be presented as a function of time from the perihelion. These results will ultimately be used in detailed modeling of the coma morphologies of comet 1P/Halley over the 1985-1986 apparition in order to characterize the activity of the comet. This work is supported by NASA Planetary Atmospheres grant NNX11AD85G and C.L.'s participation at the meeting is supported by a gift to the Lunar and Planetary Laboratory at the University of Arizona.

End-of-mission ROSINA/COPS measurements as a probe of the innermost coma of comet 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Tenishev, V.; Fougere, N.; Rubin, M.; Tzou, C. Y.; Combi, M. R.; Altwegg, K.; Gombosi, T. I.; Shou, Y.; Huang, Z.; Hansen, K. C.; Toth, G.

2017-12-01

A cometary coma is a unique phenomenon in the Solar system that represents an example of a planetary atmosphere influenced by little or no gravity. Due to the negligible gravity of a comet's nucleus, a coma has a characteristic size that exceeds that of the nucleus itself by many orders of magnitude. An extended dusty gas cloud that forms a coma is affected mainly by molecular collisions, radiative cooling, and photolytic, charge-exchange, and impact-ionization reactions. Such an environment has been extensively observed during the recent Rosetta mission, which was the first mission that escorts a comet along its way through the Solar system for an extended amount of time with the main scientific objectives of characterizing comet's nucleus, determining the surface composition, and studying the comet's activity development. The ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) Comet Pressure Sensor (COPS) onboard the Rosetta spacecraft has performed one of the most exciting observations of the innermost coma during the spacecraft descend maneuver during the last ten hours of the mission when the random and outflow directed pressures in the coma have been measured all the way down to the comet's surface. Performed at such close proximity to the nucleus, these observations can help to characterize effects due to topological features and/or the gas local conditions at the surface of the nucleus. The major focus of the presented study is analyzing of the end-of-mission pressure measurements by the ROSINA/COPS instrument. Because the coma at a heliocentric distance of 3.8 AU was in a collisionless regime, it can be described by solving the Liouville equation, as we have done in our analysis. We have used the SHAP5 nucleus model to account for the topology of the volatile source. Spacecraft trajectory and the instrument pointing with respect to the comet's nucleus have been obtained with the SPICE library. Here, we present results of our analysis and discuss the effects of the surface topology and that of the local surface volatile injection on the distribution of gas in the innermost coma of comet 67P/Churyumov-Gerasimenko.

Analysis of the ROSINA/COPS end-of-mission measurements of the coma of comet 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Tenishev, Valeriy; Combi, Michael R.; Fougere, Nicolas; Rubin, Martin; Tzou, Chia-Yu; Shou, Yinsi; Gombosi, T. I.; Altwegg, Kathrin; Huang, Zhenguang; Toth, Gabor; Hansen, Kenneth C.

2017-10-01

A cometary coma is a unique phenomenon in the Solar system that represents an example of a planetary atmosphere influenced by little or no gravity. Due to the negligible gravity of a comet’s nucleus, a coma has a characteristic size that exceeds that of the nucleus itself by many orders of magnitude. An extended dusty gas cloud that forms a coma is affected mainly by molecular collisions, radiative cooling, and photolytic, charge-exchange, and impact-ionization reactions.Such an environment has been extensively observed during the recent Rosetta mission, which was the first mission that escorts a comet along its way through the Solar system for an extended amount of time with the main scientific objectives of characterizing comet’s nucleus, determining the surface composition, and studying the comet’s activity development.The ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) Comet Pressure Sensor (COPS) onboard the Rosetta spacecraft has performed one of the most exciting observations of the innermost coma during the spacecraft descend maneuver during the last ten hours of the mission when the random and outflow directed pressures in the coma have been measured all the way down to the comet’s surface. Performed at such close proximity to the nucleus, these observations can help to characterize effects due to topological features and/or the gas local conditions at the surface of the nucleus.The major focus of the presented study is analyzing of the end-of-mission pressure measurements by the ROSINA/COPS instrument. Because the coma at a heliocentric distance of 3.8 AU was in a collisionless regime, it can be described by solving the Liouville equation, as we have done in our analysis. We have used the SHAP5 nucleus model to account for the topology of the volatile source. Spacecraft trajectory and the instrument pointing with respect to the comet’s nucleus have been obtained with the SPICE library. Here, we present results of our analysis and discuss the effects of the surface topology and that of the local surface volatile injection on the distribution of gas in the innermost coma of comet 67P/Churyumov-Gerasimenko.

Chemistry in the Dusty Coma of Comet Hale-Bopp

NASA Astrophysics Data System (ADS)

Boice, D. C.; Cochran, A. L.; Disanti, M. A.; Huebner, W. F.

1998-09-01

Recent progress on a multifluid, hydrodynamic model is presented for the dusty gas flow in the inner coma of comet Hale-Bopp at several heliocentric distances. The simulations are based on a 1-D neutral coma model with detailed photo and gas-phase chemistry and dust entrainment by the gas, a separate energy balance for the electrons, separate flow of the neutral gas, fast neutral atomic and molecular hydrogen, and dust entrainment with fragmentation. The model accounts for three sources of gas release: sublimation from surface ices, transport of gas from subsurface regions through the surface, and release of gas from dust in the coma. This permits a consistent study of the importance and strength of each possible source for a variety of gas-phase species. The simulations allow a study of the changes with heliocentric distance of features within a cometary coma, e.g., spatial distributions of gas-phase species and dust of various sizes and the velocity and temperature profiles. In particular, the model is used to probe spatial distributions of gas-phase species (e.g., CN, CH, C_3, C_2, HCN, HNC, CO) and dust, and the velocity and temperature structure to understand the complex gas-phase chemistry that occurs in the inner coma. Comparisons with observations are made where available to characterize the environment surrounding comet Hale-Bopp and to aid in assimilating a variety of diverse observations of this unique comet.

Hall effect in the coma of 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Huang, Z.; Tóth, G.; Gombosi, T. I.; Jia, X.; Combi, M. R.; Hansen, K. C.; Fougere, N.; Shou, Y.; Tenishev, V.; Altwegg, K.; Rubin, M.

2018-04-01

Magnetohydrodynamics simulations have been carried out in studying the solar wind and cometary plasma interactions for decades. Various plasma boundaries have been simulated and compared well with observations for comet 1P/Halley. The Rosetta mission, which studies comet 67P/Churyumov-Gerasimenko, challenges our understanding of the solar wind and comet interactions. The Rosetta Plasma Consortium observed regions of very weak magnetic field outside the predicted diamagnetic cavity. In this paper, we simulate the inner coma with the Hall magnetohydrodynamics equations and show that the Hall effect is important in the inner coma environment. The magnetic field topology becomes complex and magnetic reconnection occurs on the dayside when the Hall effect is taken into account. The magnetic reconnection on the dayside can generate weak magnetic field regions outside the global diamagnetic cavity, which may explain the Rosetta Plasma Consortium observations. We conclude that the substantial change in the inner coma environment is due to the fact that the ion inertial length (or gyro radius) is not much smaller than the size of the diamagnetic cavity.

Discovery of a young asteroid cluster associated with P/2012 F5 (Gibbs)

NASA Astrophysics Data System (ADS)

Novaković, Bojan; Hsieh, Henry H.; Cellino, Alberto; Micheli, Marco; Pedani, Marco

2014-03-01

We present the results of our search for a dynamical family around the active Asteroid P/2012 F5 (Gibbs). By applying the hierarchical clustering method, we discover an extremely compact 9-body cluster associated with P/2012 F5. The statistical significance of this newly discovered Gibbs cluster is estimated to be >99.9%, strongly suggesting that its members share a common origin. The cluster is located in a dynamically cold region of the outer main-belt at a proper semi-major axis of ∼3.005 AU, and all members are found to be dynamically stable over very long timescales. Backward numerical orbital integrations show that the age of the cluster is only 1.5 ± 0.1 Myr. Taxonomic classifications are unavailable for most of the cluster members, but SDSS spectrophotometry available for two cluster members indicate that both appear to be Q-type objects. We also estimate a lower limit of the size of the parent body to be about 10 km, and find that the impact event which produced the Gibbs cluster is intermediate between a cratering and a catastrophic collision. In addition, we search for new main-belt comets in the region of the Gibbs cluster by observing seven asteroids either belonging to the cluster, or being very close in the space of orbital proper elements. However, we do not detect any convincing evidence of the presence of a tail or coma in any our targets. Finally, we obtain optical images of P/2012 F5, and find absolute R-band and V-band magnitudes of HR = 17.0 ± 0.1 mag and HV = 17.4 ± 0.1 mag, respectively, corresponding to an upper limit on the diameter of the P/2012 F5 nucleus of ∼2 km.

STANDARD STARS AND EMPIRICAL CALIBRATIONS FOR Hα AND Hβ PHOTOMETRY

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

Joner, Michael D.; Hintz, Eric G., E-mail: joner@byu.edu, E-mail: hintz@byu.edu

2015-12-15

We define an Hα photometric system that is designed as a companion to the well established Hβ index. The new system is built on spectrophotometric observations of field stars as well as stars in benchmark open clusters. We present data for 75 field stars, 12 stars from the Coma star cluster, 24 stars from the Hyades, 17 stars from the Pleiades, and 8 stars from NGC 752 to be used as primary standard stars in the new systems. We show that the system transformations are relatively insensitive to the shape of the filter functions. We make comparisons of the Hαmore » index to the Hβ index and illustrate the relationship between the two systems. In addition, we present relations that relate both hydrogen indices to equivalent width and effective temperature. We derive equations to calibrate both systems for Main Sequence stars with spectral types in the range O9 to K2 for equivalent width and A2 to K2 for effective temperature.« less

The dust distribution within the inner coma of comet P/Halley 1982i - Encounter by Giotto's impact detectors

NASA Technical Reports Server (NTRS)

Mcdonnell, J. A. M.; Evans, G. C.; Evans, S. T.; Alexander, W. M.; Burton, W. M.; Firth, J. G.; Bussoletti, E.; Grard, R. J. L.; Hanner, M. S.; Sekanina, Z.

1987-01-01

Analyses are presented of Giotto's Dust Impact Detection System experiment measurements of dust grains incident on the Giotto dust shield along its trajectory through the coma of comet P/Halley on March 13 and 14, 1986. Ground-based CCD imagery of the inner coma dust continuum at the time of the encounter are used to derive the area of grains intercepted by Giotto. Data obtained at large masses show clear evidence of a decrease in the mass distribution index at these masses within the coma; it is shown that such a value of the mass index can furnish sufficient mass for consistency with an observed deceleration.

A New 3D Multi-fluid Model: A Study of Kinetic Effects and Variations of Physical Conditions in the Cometary Coma

NASA Astrophysics Data System (ADS)

Shou, Y.; Combi, M.; Toth, G.; Tenishev, V.; Fougere, N.; Jia, X.; Rubin, M.; Huang, Z.; Hansen, K.; Gombosi, T.; Bieler, A.

2016-12-01

Physics-based numerical coma models are desirable whether to interpret the spacecraft observations of the inner coma or to compare with the ground-based observations of the outer coma. In this work, we develop a multi-neutral-fluid model based on the BATS-R-US code of the University of Michigan, which is capable of computing both the inner and outer coma and simulating time-variable phenomena. It treats H2O, OH, H2, O, and H as separate fluids and each fluid has its own velocity and temperature, with collisions coupling all fluids together. The self-consistent collisional interactions decrease the velocity differences, re-distribute the excess energy deposited by chemical reactions among all species, and account for the varying heating efficiency under various physical conditions. Recognizing that the fluid approach has limitations in capturing all of the correct physics for certain applications, especially for very low density environment, we applied our multi-fluid coma model to comet 67P/Churyumov-Gerasimenko at various heliocentric distances and demonstrated that it yields comparable results to the Direct Simulation Monte Carlo (DSMC) model, which is based on a kinetic approach that is valid under these conditions. Therefore, our model may be a powerful alternative to the particle-based model, especially for some computationally intensive simulations. In addition, by running the model with several combinations of production rates and heliocentric distances, we characterize the cometary H2O expansion speeds and demonstrate the nonlinear dependencies of production rate and heliocentric distance. Our results are also compared to previous modeling work and remote observations, which serve as further validation of our model.

Asymmetric Spherical Coupled Escape Probability: Model and Results for Optically Thick Cometary Comae

NASA Astrophysics Data System (ADS)

Gersch, Alan; A'Hearn, M. F.

2012-05-01

We have adapted the Coupled Escape Probability method of radiative transfer calculations for use in asymmetrical spherical situations and applied it to modeling molecular emission spectra of potentially optically thick cometary comae. Recent space missions (e.g. Deep Impact & EPOXI) have provided spectra from comets of unprecedented spatial resolution of the regions of the coma near the nucleus, where the coma may be optically thick. Currently active missions (e.g. Rosetta) and hopefully more in the future will continue the trend and demonstrate the need for better modeling of comae with optical depth effects included. Here we present a brief description of our model and results of interest for cometary studies, especially for space based observations. Although primarily motivated by the need for comet modeling, our (asymmetric spherical) radiative transfer model could be used for studying other astrophysical phenomena as well.

Nonthermal emission from clusters of galaxies

NASA Astrophysics Data System (ADS)

Kushnir, Doron; Waxman, Eli

2009-08-01

We show that the spectral and radial distribution of the nonthermal emission of massive, M gtrsim 1014.5Msun, galaxy clusters may be approximately described by simple analytic expressions, which depend on the cluster thermal X-ray properties and on two model parameter, βcore and ηe. βcore is the ratio of the cosmic-ray (CR) energy density (within a logarithmic CR energy interval) and the thermal energy density at the cluster core, and ηe(p) is the fraction of the thermal energy generated in strong collisionless shocks, which is deposited in CR electrons (protons). Using a simple analytic model for the evolution of intra-cluster medium CRs, which are produced by accretion shocks, we find that βcore simeq ηp/200, nearly independent of cluster mass and with a scatter Δln βcore simeq 1 between clusters of given mass. We show that the hard X-ray (HXR) and γ-ray luminosities produced by inverse Compton scattering of CMB photons by electrons accelerated in accretion shocks (primary electrons) exceed the luminosities produced by secondary particles (generated in hadronic interactions within the cluster) by factors simeq 500(ηe/ηp)(T/10 keV)-1/2 and simeq 150(ηe/ηp)(T/10 keV)-1/2 respectively, where T is the cluster temperature. Secondary particle emission may dominate at the radio and very high energy (gtrsim 1 TeV) γ-ray bands. Our model predicts, in contrast with some earlier work, that the HXR and γ-ray emission from clusters of galaxies are extended, since the emission is dominated at these energies by primary (rather than by secondary) electrons. Our predictions are consistent with the observed nonthermal emission of the Coma cluster for ηp ~ ηe ~ 0.1. The implications of our predictions to future HXR observations (e.g. by NuStar, Simbol-X) and to (space/ground based) γ-ray observations (e.g. by Fermi, HESS, MAGIC, VERITAS) are discussed. In particular, we identify the clusters which are the best candidates for detection in γ-rays. Finally, we show that our model's results agree with results of detailed numerical calculations, and that discrepancies between the results of various numerical simulations (and between such results and our model) are due to inaccuracies in the numerical calculations.

Far-infrared properties of cluster galaxies

NASA Technical Reports Server (NTRS)

Bicay, M. D.; Giovanelli, R.

1987-01-01

Far-infrared properties are derived for a sample of over 200 galaxies in seven clusters: A262, Cancer, A1367, A1656 (Coma), A2147, A2151 (Hercules), and Pegasus. The IR-selected sample consists almost entirely of IR normal galaxies, with Log of L(FIR) = 9.79 solar luminosities, Log of L(FIR)/L(B) = 0,79, and Log of S(100 microns)/S(60 microns) = 0.42. None of the sample galaxies has Log of L(FIR) greater than 11.0 solar luminosities, and only one has a FIR-to-blue luminosity ratio greater than 10. No significant differences are found in the FIR properties of HI-deficient and HI-normal cluster galaxies.

Modeling of the illumination driven coma of 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Bieler, André

2015-04-01

In this paper we present results modeling 67P/Churyumov-Gerasimenko's (C-G) neutral coma properties observed by the Rosetta ROSINA experiment with 3 different model approaches. The basic assumption for all models is the idea that the out-gassing properties of C-G are mainly illumination driven. With this assumption all models are capable of reproducing most features in the neutral coma signature as detected by the ROSINA-COPS instrument over several months. The models include the realistic shape model of the nucleus to calculate the illumination conditions over time which are used to define the boundary conditions for the hydrodynamic (BATS-R-US code) and the Direct Simulation Monte Carlo (AMPS code) simulations. The third model finally computes the projection of the total illumination on the comet surface towards the spacecraft. Our results indicate that at large heliocentric distances (3.5 to 2.8 AU) most gas coma structures observed by the in-situ instruments can be explained by uniformly distributed activity regions spread over the whole nucleus surface.

Composition/Structure/Dynamics of comet and planetary satellite atmospheres

NASA Technical Reports Server (NTRS)

Combi, Michael R. (Principal Investigator)

1995-01-01

This research program addresses two cases of tenuous planetary atmospheres: comets and Io. The comet atmospheric research seeks to analyze a set of spatial profiles of CN in comet Halley taken in a 7.4-day period in April 1986; to apply a new dust coma model to various observations; and to analyze observations of the inner hydrogen coma, which can be optically thick to the resonance scattering of Lyman-alpha radiation, with the newly developed approach that combines a spherical radiative transfer model with our Monte Carlo H coma model. The Io research seeks to understand the atmospheric escape from Io with a hybrid-kinetic model for neutral gases and plasma given methods and algorithms developed for the study of neutral gas cometary atmospheres and the earth's polar wind and plasmasphere. Progress is reported on cometary Hydrogen Lyman-alpha studies; time-series analysis of cometary spatial profiles; model analysis of the dust comae of comets; and a global kinetic atmospheric model of Io.

Optical and Near-Infrared Structural Properties of Cluster Galaxies at z ~ 0.3

NASA Astrophysics Data System (ADS)

La Barbera, F.; Busarello, G.; Merluzzi, P.; Massarotti, M.; Capaccioli, M.

2002-06-01

Structural parameters (half-light radius re, mean effective surface brightness <μ>e, and Sersic index n, parameterizing the light profile shape) are derived for a sample of galaxies in the rich cluster AC 118 at z=0.31, so far the largest (N=93) sample of galaxies at intermediate redshift with structural parameters measured in the near-infrared. The parameters are obtained in two optical wavebands (V and R) and in the K band, corresponding approximately to the B, V, and H rest frame. The distributions of re at z=0.31 match those for the Coma Cluster (i.e., for the local universe) both in the optical and in the NIR. The K-band distribution is of particular interest, since the NIR light mimics the mass distribution of galaxies. The similarity of the distributions for the two clusters (AC 118 and Coma) proves that the galaxies at the bright end of the luminosity function did not significantly change their sizes since z~0.3 to the present epoch. The ratio of the optical to the NIR half-light radius shows a marked trend with the shape of the light profile (Sersic index n). In galaxies with n>~4 (typical bright ellipticals) re,NIR~0.6re,opt, while the average ratio is 0.8 for galaxies with lower n (typical disk systems). Moreover, the NIR Sersic index is systematically larger than in the optical for n<~4. These results, translated into optical and optical-NIR color gradients, imply that the optical color gradients at z~0.3 are similar to those of nearby galaxies. The optical-NIR color gradients are in the average larger, ranging from -0.73 mag dex-1 for n<~4 to -0.35 mag dex-1 for n>~4. Models with ``pure age'' or ``pure metallicity'' gradients are unable to reconcile our color gradients estimates with observations at z~0, but we argue that the combined effects of age and metallicity might explain consistently the observed data: passive evolution (plus the possible effect of dust absorption) may account for the differences between the optical and NIR structural properties. The lack of any major change in re,NIR since z~0.3 suggests that merging involving bright galaxies did not play a significant role in the last ~4.4 Gyr (ΩM=0.3, ΩΛ=0, H0=50 km s-1 Mpc-1). The results of the present paper will be applied to the study of the scaling laws in subsequent works. Based on observations collected at European Southern Observatory (ESO 62.O-0369, 63.O-0257, 64.O-0236) and on data from the STScI Science Archive.

Vibrational and rotational excitation of CO in comets. Part 1: Non-equilibrium calculations. Part 2: Results of the calculation for standard bright comet, comet Iras-Araki-Alcock and comet Halley

NASA Technical Reports Server (NTRS)

Chin, G.; Weaver, H. A.

1984-01-01

The vibrational and rotational excitation of the CO molecule in cometary comae were investigated using a model which includes IR vibrational pumping by the solar flux, vibrational and rotational radiative decay, and collisional coupling among rotational states. Steady state was not assumed in solving the rate equations. The evolution of a shell of CO gas was monitored as it expanded from the nucleus into the outer coma. Collisional effects were treated using a kinetic temperature profile derived from theoretical work on the coma energy balance. The kinetic temperature was assumed to be extremely cold in the inner coma; this has significant consequences for the CO excitation. If optical depth effects are ignored, only low J transitions will be significantly excited in comets observed at high spatial resolution. Ground-based observations of CO co-vibrational and rotational transitions will be extremely difficult due to lack of sensitivity and/or terrestrial absorption. However, CO should be detectable from a large comet with favorable observing geometry if the CO is a parent molecule present at the 10% level (or greater) relative to H2O. Observations using cooled, spaceborne instruments should be capable of detecting CO emission from even moderately bright comets.

Vibrational and rotational excitation of CO in comets. Part 1: Non-equilibrium calculations. Part 2: Results of the calculation for standard bright comet, comet Iras-Araki-Alcock and comet Halley

NASA Astrophysics Data System (ADS)

Chin, G.; Weaver, H. A.

1984-05-01

The vibrational and rotational excitation of the CO molecule in cometary comae were investigated using a model which includes IR vibrational pumping by the solar flux, vibrational and rotational radiative decay, and collisional coupling among rotational states. Steady state was not assumed in solving the rate equations. The evolution of a shell of CO gas was monitored as it expanded from the nucleus into the outer coma. Collisional effects were treated using a kinetic temperature profile derived from theoretical work on the coma energy balance. The kinetic temperature was assumed to be extremely cold in the inner coma; this has significant consequences for the CO excitation. If optical depth effects are ignored, only low J transitions will be significantly excited in comets observed at high spatial resolution. Ground-based observations of CO co-vibrational and rotational transitions will be extremely difficult due to lack of sensitivity and/or terrestrial absorption. However, CO should be detectable from a large comet with favorable observing geometry if the CO is a parent molecule present at the 10% level (or greater) relative to H2O. Observations using cooled, spaceborne instruments should be capable of detecting CO emission from even moderately bright comets.

Production, Outflow Velocity, and Radial Distribution of H2O and OH in the Coma of Comet C/1995 O1 [Hale-Bopp] from Wide Field Imaging of OH

NASA Technical Reports Server (NTRS)

Harris, Walter M.; Scherb, Frank; Mierkiewicz, Edwin; Oliverson, Ronald; Morgenthaler, Jeffrey

2003-01-01

Observations of OH are a useful proxy of the water production rate (Q(sub H2O)) and outflow velocity (V(sub out)) in comets. From wide field images taken on 03/28/1997 and 04/08/1997 that capture the entire scale length of the OH coma of comet C/1995 O1 (Hale-Bopp), we obtain Q(sub H2O) from the model-independent method of aperture summation. With an adaptive ring summation algorithm, we extract the radial brightness distribution of OH 0-0 band emission out to cometocentric distances of up to 10(exp 6) km, both as azimuthal averages and in quadrants covering different position angles relative to the comet-Sun line. These profiles are fit using both fixed and variable velocity 2-component spherical expansion models to estimate V(sub OH) with increasing distance from the nucleus. The OH coma of Hale-Bopp was more spatially extended than previous comets, and this extension is best matched by a variable acceleration of H2O and OH that acted across the entire coma, but was strongest within 1-2 x 10(exp 4) km from the nucleus. Our models indicate that V(sub OH) at the edge of our detectable field of view (10(exp 6) km) was approx. 2-3 times greater in Hale-Bopp than for a 1P/Halley-class comet at 1 AU, which is consistent with the results of more sophisticated gas-kinetic models, extrapolation from previous observations of OH in comets with Q(sub H2O) greater than 10(exp 29)/s , and direct radio measurements of the outer coma Hale-Bopp OH velocity. The most probable source of this acceleration is thermalization of the excess energy of dissociation of H2O and OH over an extended collisional coma. When the coma is broken down by quadrants in position angle, we find an azimuthal asymmetry in the radial distribution that is characterized by an increase in the spatial extent of OH in the region between the orbit-trailing and anti-sunward directions. Model fits specific to this area and comparison with radio OH measurements suggest greater acceleration here, with V(sub OH) approx. 1.5 times greater at a 10(exp 6) km cometocentric distance than elsewhere in the coma. We discuss several mechanisms that may have acted within the coma to produce the observed effect.

Spectroscopy of the Perseus Cluster

NASA Technical Reports Server (NTRS)

Jones, Christine; Mushotzky, Richard F. (Technical Monitor)

2004-01-01

We present preliminary results of a XMM-Newton 50 ks observation of the Perseus Cluster that provides an unprecedented view of the central 0.5 Mpc region. The projected gas temperature declines smoothly by a factor of 2 from a maximum value of approx. 7 keV in the outer regions to just above 3 keV at the cluster center. Over this same range, the heavy-element abundance rises slowly from 0.4 to 0.5 solar as the radius decreases from 14 ft. to 5 ft., and then it rises to a peak of almost 0.7 solar at 1&farcm;25 before declining to 0.4 at the center. Th global east-west asymmetry of the gas temperature and surface brightness distributions, approximately aligned with the chain of bright galaxies, suggests an ongoing merger, although the modest degree of the observed asymmetry certainly excludes a major merger interpretation. The chain of galaxies probably traces the filament along which accretion started some time ago and is continuing at the present time. A cold and dense (low-entropy) cluster core like Perseus is probably well "protected" against the penetration of the gas of infalling groups and poor clusters, whereas in non-cooling core clusters such as Coma and A1367, infalling subclusters can penetrate deeply into the core region. In Perseus, gas associated with infalling groups may be stripped completely at the outskirts of the main cluster and only compression waves (shocks) may reach the central regions. We argue, and show supporting simulations, that the passage of such a wave(s) can qualitatively explain the overall horseshoe shaped appearance of the gas temperature map (the hot horseshoe surrounds the colder, low-entropy core) as well as other features of the Perseus Cluster core. These simulations also show that as compression waves traverse the cluster core, they can induce oscillatory motion of the cluster gas that can generate multiple sharp "edges" on opposite sides of the central galaxy. Gas motions induced by mergers may be a natural way to explain the high frequency of "edges" seen in clusters with cooling cores.

The distribution of gas and ions in the inner coma of 67P/Churyumov-Gerasimenko between 3 AU before and after its perihelion

NASA Astrophysics Data System (ADS)

Bodewits, Dennis; Lara, Luisa; La Forgia, Fiorangela; A'Hearn, Michael F.; Knollenberg, Jörg; Lazzarin, Monica; Li, Zhong-Yi; Osiris Team

2016-10-01

Rosetta explored a regime not accessible before: the inner coma of a low-activity comet at a large range of heliocentric distances. The Wide Angle Camera (WAC) of the OSIRIS instrument on board the Rosetta spacecraft is equipped with several narrowband filters that are centered on the emission lines and bands of various molecules and ions. These filters center on fragment species that are relatively bright and that have been used for numerous comet studies from the ground (e.g. A'Hearn et al. 1995). Surprisingly, we found that outside 2 AU pre-perihelion, the emission in the filters was dominated by emission from dissociative electron impact excitation (Bodewits et al. 2016). Closer to perihelion, higher gas densities reduced electron temperatures in the inner coma and photo-processes drove much if not most of the emission from the comet. Our observations allowed us to study changes in the physical environment of the inner coma, and Rosetta's excursions as far as 1000 km from the surface allowed us to study different regions of the coma.In this contribution, we will summarize the results of our OSIRIS observations from approximately 3 AU before to 3 AU after perihelion.

Period change of a contact binary system RW Comae Berenices

NASA Astrophysics Data System (ADS)

Maithong, Wiraporn; Phao-ai, Parinda

2017-08-01

In this work, we studied about the period change of a contact binary system RW Comae Berenices. The binary system was observed on March 9th, 2016 by the 105 mm diameter of a refraction telescope with the DSLR digital camera at the Regional Observatory for the Public Nakhon Ratchasima, Thailand. The photometry used the IRIS program. The period change was analyzed by used the O-C diagram. The result shows that the period of the RW Comae Berenices is increasing with 1.89×10-3 seconds/year.

Modeling Coma Gas Jets in Comet Hale-Bopp

NASA Technical Reports Server (NTRS)

Lederer, S. M.; Campins, H.

2001-01-01

We present an analysis of OH, CN, and C2 jets observed in Comet Hale-Bopp. The relative contributions from and composition of the coma gas sources, and the parameters describing the active areas responsible for the gas jets will be discussed. Additional information is contained in the original extended abstract.

Physical observations of comets: Their composition, origin and evolution

NASA Technical Reports Server (NTRS)

Cochran, Anita L.; Barker, Edwin S.; Cochran, William D.

1991-01-01

The composition, origins, and evolution of comets were studied. The composition was studied using spectroscopic observations of primarily brighter comets at moderate and high resolution for the distribution of certain gases in the coma. The origins was addressed through an imaging search for the Kuiper belt of comets. The evolution was addressed by searching for a link between comets and asteroids using an imaging approach to search for an OH coma.

Spectroscopic studies of the molecular parentage of radical species in cometary comae

NASA Astrophysics Data System (ADS)

Lewis, Benjamin; Pierce, Donna; Cochran, Anita

2015-11-01

We have observed several comets using an integral-field unit spectrograph (the George and Cynthia Mitchell Spectrograph) on the 2.7m Harlan J. Smith telescope at McDonald Observatory. Full-coma spectroscopic images were obtained for various radical species (C2, C3, CH, CN, NH2). By constructing azimuthal average profiles from the full-coma spectroscopic images we can test Haser model parameters with our observations. The Haser model was used to determine production rates and possible parent lifetimes that would be consistent with the model. By iterating through a large range of possible parents lifetimes, we can see what range of values in which the Haser model is consistent with observations. Also, this type of analysis gives us perspective on how sensitive the model's fit quality is to changes in parent lifetimes. Here, we present the work completed to date, and we compare our results to other comet taxonomic surveys.

Physical process in the coma of comet 67P derived from narrowband imaging of fragment species

NASA Astrophysics Data System (ADS)

Perez Lopez, F.; Küppers, M.; Marín-Yaseli de la Parra, J.; Besse, S.; Moissl, R.

2017-09-01

During the rendezvous of the Rosetta spacecraft with comet 67P/Churyumov-Gerasimenko, the OSIRIS scientific cameras monitored the near-nucleus gas environment in various narrow-band filters, observing various fragment species. It turned out that the excitation processes in the innermost coma are significantly different from the overall coma, as observed from the ground [1]. In particular, some of the observed emissions of fragments (daughter molecules) are created by direct dissociation of parent molecules, and in those cases the spatial distribution of the emission directly maps the distribution of parent molecules. We investigate the evolution of the brightness and distribution of the emissions over time to improve our understanding of the underlying emission mechanisms and to derive the spatial distribution of H2O and CO2. The outcome will provide constraints on the homogeneity of the cometary nucleus.

Jet morphology and coma analysis of comet 103P/Hartley 2

NASA Astrophysics Data System (ADS)

Vaughan, Charles M.

In 2010, comet 103P/Hartley 2 was observed pre- and post-perihelion using the George and Cynthia Mitchell Integral Field Spectrometer on the 2.7-m telescope at McDonald Observatory in Texas. Data for gaseous radicals C2, C3, CH, CN, and NH2 were collected over six nights from 15 July to 10 November. The spectral data were used to create coma maps for each of the observed species, and the maps were processed using radial and azimuthal mean division techniques to create enhanced images of the coma, revealing subtle morphological features. 340 enhanced coma images were created for each observation and species. Visual inspection reveals that the coma is heterogeneous between the five detected radicals, and statistical analyses verify this result. To compliment the ongoing investigation of Hartley 2 as studied by the EPOXI flyby mission, findings from other researchers (Belton et al., 2012; Syal et al., 2012; and Thomas et al., 2012) are used to characterize the nucleus spin state and identify dust jet locations on the nucleus. With rotational period measurements from EPOXI, dust jet vectors on the nucleus surface are rotated to relevant observation times in November to compare the computed jet directions with the radical densities in the coma. Dust jet sites on the smaller nucleus lobe show a stronger correlation with high radical concentrations than the dust sites on the larger nucleus lobe. Production rates for potential parentage of radical species are calculated using the radial outflow Haser model (Haser, 1957), which are compared to mixing ratios relative to water from separate campaigns to constrain parentage. NH3 is likely the sole producer of NH2, whereas CN may be produced from a combination of HCN, C2N2, and CH3CN. Traditional parentage of C2, C3, and CH do not yield acceptable fits or suitable mixing ratios with the Haser model, and it is possible that extended coma ices having relatively short scale lengths greatly contribute to production of these radicals. These results provide further evidence that the Hartley 2 nucleus is heterogeneous in composition, and the rotational analysis indicates that specific jet sites are correlated with certain radical species.

Modeling the Thermodynamic Properties of the Inner Comae of Comets

NASA Astrophysics Data System (ADS)

Boice, Daniel C.

2017-10-01

Introduction: Modeling is central to understand the important properties of the cometary environment. We have developed a comet model, SUISEI, that self-consistently includes the relevant physicochemical processes within a global modeling framework, from the porous subsurface layers of the nucleus to the interaction with the solar wind. Our goal is to gain valuable insights into the intrinsic properties of cometary nuclei so we can better understand observations and in situ measurements. SUISEI includes a multifluid, reactive gas dynamics simulation of the dusty coma (ComChem) and a suite of other coupled numerical simulations. This model has been successfully applied to a variety of comets in previous studies over the past three decades. We present results from a quantitative study of the thermodynamic properties and chemistry of cometary comae as a function of cometocentric and heliocentric distance to aid in interpretation of observations and in situ measurements of comets.Results and Discussion: ComChem solves the fluid dynamic equations for the mass, momentum, and energy of three neutral fluids (H, H2, and the heavier bulk fluid), ions, and electrons. In the inner coma, the gas expands, cools, accelerates, and undergoes many photolytic and gas-phase chemical reactions tracking hundreds of sibling species. The code handles the transition to free molecular flow and describes the spatial distribution of species in the coma of a comet. Variations of neutral gas temperature and velocity with cometocentric distance and heliocentric distance for a comet approaching the Sun from 2.5 to 0.3 AU are presented. Large increases in the gas temperatures (>400 K) due to photolytic heating in the coma within ~0.5 AU are noted, with dramatic effects on the chemistry, optical depth, and other coma properties. Results are compared to observations when available.Conclusions: SUISEI has proven to be a unique and valuable model to understand the relevant physical processes and properties of small Solar System bodies, including near-Sun comets and asteroids.Acknowledgments: This work was supported by FAPESP under Grant No. 2015/03176-8 and the National Science Foundation Planetary Astronomy Program Grant No. 0908529.

THE INNER COMA OF COMET C/2012 S1 (ISON) AT 0.53 AU AND 0.35 AU FROM THE SUN

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

Bonev, Boncho P.; Villanueva, Geronimo L.; Paganini, Lucas

2014-11-20

Using long-slit spectroscopy at the NASA Infrared Telescope Facility, we extracted H{sub 2}O production rates and spatial profiles of gas rotational temperature and molecular column abundance in comet C/2012 S1 ISON, observed at heliocentric distances of 0.53 and 0.35 AU. These measurements uniquely probed the physical environment in the inner collisional coma of this comet during its first (and last) approach to the Sun since being emplaced in the Oort Cloud some 4.5 billion years ago. Our observations revealed a comet evolving on various timescales, both over hours and days. At 0.35 AU, ISON showed a considerable decrease in water production ratemore » in less than 2 hr, likely declining from a major outburst. Our measured temperature spatial distributions reflect the competition between the processes that cause heating and cooling in the coma, and also provide insight about the prevalent mechanism(s) of releasing gas-phase H{sub 2}O. The observed temperatures suggest that the comet was likely ejecting icy material continuously, which sublimated in the coma and heated the ambient gas, augmenting fast H-atoms produced by H{sub 2}O photolysis. ISON adds to the very limited sample of comets for which spatial-spectral studies of water temperatures have been conducted. These studies are now feasible and can be extended to comets having a variety of gas production rates. Continued synergy of such observations with both space missions like Rosetta and with physical models is strongly encouraged in order to gain a deeper understanding of the processes in the inner collisional zone of the cometary coma.« less

Observations of faint comets at McDonald Observatory: 1978-1980

NASA Technical Reports Server (NTRS)

Barker, E. S.; Cochran, A. L.; Rybski, P. M.

1981-01-01

Modern observational techniques, developed for spectroscopy and photometry of faint galaxies and quasars, successfully applied to faint comets on the 2.7 m telescope. The periodic comets Van Biesbrock, Ashbrook-Jackson, Schwassmann-Wachmann 1, Tempel 2, Encke, Forbes, Brooks 2, Stephan-Oterma and the new comets Bradfield (19791), Bowell (1980b), Chernis-Petrauskas (1980k) were observed. The comets ranged in magnitude from 10th to 20th magnitude. For comets fainter than 19th magnitude, reflectance spectra at 100A resolution and area photometry were obtained. On comets of 17th or 18th magnitude, spectrometric scans (6A resolution) of the nucleus or inner coma region. On those comets which are brighter than 16th magnitude spatial spectrophotometric (6A resolution) studies of the inner and extended comae were done. An extensive spatial study of the comae of P/Encke and P/Stephen-Oterma, correlated with heliocentric distance is taking place. The observing process used is described and examples of the results obtained to date are discussed.

Dark matter searches with Cherenkov telescopes: nearby dwarf galaxies or local galaxy clusters?

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

Sánchez-Conde, Miguel A.; Cannoni, Mirco; Gómez, Mario E.

2011-12-01

In this paper, we compare dwarf galaxies and galaxy clusters in order to elucidate which object class is the best target for gamma-ray DM searches with imaging atmospheric Cherenkov telescopes (IACTs). We have built a mixed dwarfs+clusters sample containing some of the most promising nearby dwarf galaxies (Draco, Ursa Minor, Wilman 1 and Segue 1) and local galaxy clusters (Perseus, Coma, Ophiuchus, Virgo, Fornax, NGC 5813 and NGC 5846), and then compute their DM annihilation flux profiles by making use of the latest modeling of their DM density profiles. We also include in our calculations the effect of DM substructure.more » Willman 1 appears as the best candidate in the sample. However, its mass modeling is still rather uncertain, so probably other candidates with less uncertainties and quite similar fluxes, namely Ursa Minor and Segue 1, might be better options. As for galaxy clusters, Virgo represents the one with the highest flux. However, its large spatial extension can be a serious handicap for IACT observations and posterior data analysis. Yet, other local galaxy cluster candidates with more moderate emission regions, such as Perseus, may represent good alternatives. After comparing dwarfs and clusters, we found that the former exhibit annihilation flux profiles that, at the center, are roughly one order of magnitude higher than those of clusters, although galaxy clusters can yield similar, or even higher, integrated fluxes for the whole object once substructure is taken into account. Even when any of these objects are strictly point-like according to the properties of their annihilation signals, we conclude that dwarf galaxies are best suited for observational strategies based on the search of point-like sources, while galaxy clusters represent best targets for analyses that can deal with rather extended emissions. Finally, we study the detection prospects for present and future IACTs in the framework of the constrained minimal supersymmetric standard model. We find that the level of the annihilation flux from these targets is below the sensitivities of current IACTs and the future CTA.« less

Dark Matter Searches with Cherenkov Telescopes: Nearby Dwarf Galaxies or Local Galaxy Clusters?

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

Sanchez-Conde, Miguel A.; /KIPAC, Menlo Park /SLAC /IAC, La Laguna /Laguna U., Tenerife; Cannoni, Mirco

2012-06-06

In this paper, we compare dwarf galaxies and galaxy clusters in order to elucidate which object class is the best target for gamma-ray DM searches with imaging atmospheric Cherenkov telescopes (IACTs). We have built a mixed dwarfs+clusters sample containing some of the most promising nearby dwarf galaxies (Draco, Ursa Minor, Wilman 1 and Segue 1) and local galaxy clusters (Perseus, Coma, Ophiuchus, Virgo, Fornax, NGC 5813 and NGC 5846), and then compute their DM annihilation flux profiles by making use of the latest modeling of their DM density profiles. We also include in our calculations the effect of DM substructure.more » Willman 1 appears as the best candidate in the sample. However, its mass modeling is still rather uncertain, so probably other candidates with less uncertainties and quite similar fluxes, namely Ursa Minor and Segue 1, might be better options. As for galaxy clusters, Virgo represents the one with the highest flux. However, its large spatial extension can be a serious handicap for IACT observations and posterior data analysis. Yet, other local galaxy cluster candidates with more moderate emission regions, such as Perseus, may represent good alternatives. After comparing dwarfs and clusters, we found that the former exhibit annihilation flux profiles that, at the center, are roughly one order of magnitude higher than those of clusters, although galaxy clusters can yield similar, or even higher, integrated fluxes for the whole object once substructure is taken into account. Even when any of these objects are strictly point-like according to the properties of their annihilation signals, we conclude that dwarf galaxies are best suited for observational strategies based on the search of point-like sources, while galaxy clusters represent best targets for analyses that can deal with rather extended emissions. Finally, we study the detection prospects for present and future IACTs in the framework of the constrained minimal supersymmetric standard model. We find that the level of the annihilation flux from these targets is below the sensitivities of current IACTs and the future CTA.« less

Dark matter searches with Cherenkov telescopes: nearby dwarf galaxies or local galaxy clusters?

NASA Astrophysics Data System (ADS)

Sánchez-Conde, Miguel A.; Cannoni, Mirco; Zandanel, Fabio; Gómez, Mario E.; Prada, Francisco

2011-12-01

In this paper, we compare dwarf galaxies and galaxy clusters in order to elucidate which object class is the best target for gamma-ray DM searches with imaging atmospheric Cherenkov telescopes (IACTs). We have built a mixed dwarfs+clusters sample containing some of the most promising nearby dwarf galaxies (Draco, Ursa Minor, Wilman 1 and Segue 1) and local galaxy clusters (Perseus, Coma, Ophiuchus, Virgo, Fornax, NGC 5813 and NGC 5846), and then compute their DM annihilation flux profiles by making use of the latest modeling of their DM density profiles. We also include in our calculations the effect of DM substructure. Willman 1 appears as the best candidate in the sample. However, its mass modeling is still rather uncertain, so probably other candidates with less uncertainties and quite similar fluxes, namely Ursa Minor and Segue 1, might be better options. As for galaxy clusters, Virgo represents the one with the highest flux. However, its large spatial extension can be a serious handicap for IACT observations and posterior data analysis. Yet, other local galaxy cluster candidates with more moderate emission regions, such as Perseus, may represent good alternatives. After comparing dwarfs and clusters, we found that the former exhibit annihilation flux profiles that, at the center, are roughly one order of magnitude higher than those of clusters, although galaxy clusters can yield similar, or even higher, integrated fluxes for the whole object once substructure is taken into account. Even when any of these objects are strictly point-like according to the properties of their annihilation signals, we conclude that dwarf galaxies are best suited for observational strategies based on the search of point-like sources, while galaxy clusters represent best targets for analyses that can deal with rather extended emissions. Finally, we study the detection prospects for present and future IACTs in the framework of the constrained minimal supersymmetric standard model. We find that the level of the annihilation flux from these targets is below the sensitivities of current IACTs and the future CTA.

Neuroanatomical Predictors of Awakening in Acutely Comatose Patients

PubMed Central

Kowalski, Robert G.; Buitrago, Manuel M.; Duckworth, Josh; Chonka, Zachary D.; Puttgen, H. Adrian; Stevens, Robert D.; Geocadin, Romergryko G.

2016-01-01

Objective Lateral brain displacement has been associated with loss of consciousness and poor outcome in a range of acute neurologic disorders. We studied the association between lateral brain displacement and awakening from acute coma. Methods This prospective observational study included all new onset coma patients admitted to the Neurosciences Critical Care Unit (NCCU) over 12 consecutive months. Head computed tomography (CT) scans were analyzed independently at coma onset, after awakening, and at follow-up. Primary outcome measure was awakening, defined as the ability to follow commands before hospital discharge. Secondary outcome measures were discharge Glasgow Coma Scale (GCS), modified Rankin Scale, Glasgow Outcome Scale, and hospital and NCCU lengths of stay. Results Of the 85 patients studied, the mean age was 58 ± 16 years, 51% were female, and 78% had cerebrovascular etiology of coma. Fifty-one percent of patients had midline shift on head CT at coma onset and 43 (51%) patients awakened. In a multivariate analysis, independent predictors of awakening were younger age (odds ratio [OR] = 1.039, 95% confidence interval [CI] = 1.002–1.079, p = 0.040), higher GCS score at coma onset (OR = 1.455, 95% CI = 1.157–1.831, p = 0.001), nontraumatic coma etiology (OR = 4.464, 95% CI = 1.011–19.608, p = 0.048), lesser pineal shift on follow-up CT (OR = 1.316, 95% CI = 1.073–1.615, p = 0.009), and reduction or no increase in pineal shift on follow-up CT (OR = 11.628, 95% CI = 2.207–62.500, p = 0.004). Interpretation Reversal and/or limitation of lateral brain displacement are associated with acute awakening in comatose patients. These findings suggest objective parameters to guide prognosis and treatment in patients with acute onset of coma. PMID:25628166

Spatial and Temporal Variations of Atomic Species in the Coma of Comet 67P/Churyumov-Gerasimenko as Observed by Rosetta’s ALICE UV Spectrograph during Great Circle Scans

NASA Astrophysics Data System (ADS)

Knight, Matthew M.; Weaver, Harold A.; Vervack, Ronald J.; A'Hearn, Michael; Bertaux, Jean-Loup; Feaga, Lori M.; Feldman, Paul D.; Parker, Joel Wm.; Schindhelm, Eric; Steffl, Andrew J.; Stern, S. Alan; Bieler, Andre; Combi, Michael R.; Fougere, Nicolas; Keeney, Brian A.; Medina, Richard; Noonan, John; Pineau, Jon; Versteeg, Maarten H.

2017-10-01

The Alice far-ultraviolet (FUV) imaging spectrograph on the Rosetta orbiter obtained spatially resolved spectra of 67P/Churyumov-Gerasimenko (67P) from 700-2050 Å with a spectral resolution of 8-12 Å. Observations of 67P were obtained by Alice continually from arrival at the comet in August 2014 through the end of the mission in September 2016. “Great Circle” observations were performed every few weeks from January 2015 through May 2016 to survey the coma away from the nucleus. These sequences consisted of a series of slews along a celestial great circle passing through the nucleus, e.g., covering off-nadir angles from approximately 0-180°, with pauses for observations by Alice and other instruments. Alice’s line of sight during these scans included signal to the edge of the coma, thus sampling very different parts of the coma than most other instruments.We report here on observations acquired during these Great Circle scans that allow us to investigate the spatial distributions of various emissions, as well as seasonal variations in the coma composition. Bright lines consistently included H Ly-b, the OI triplet near 1304 Å, CI near 1657 Å, and the SI triplet near 1820 Å. Spatial distributions of the OI, CI, and SI brightnesses have been determined and are being fitted with Haser models. The process is more complicated than for traditional remote sensing FUV observations due to Rosetta’s location in the coma and because resonant scattering does not always dominate the excitation. Preliminary modeling yields H2O and CO2 production rates consistent with contemporaneous measurements obtained by other instruments on Rosetta and production rates that generally peak a few weeks after perihelion. A surprising phenomenon is a slight increase in OI brightness at large off-nadir angles for some Great Circles while the other measured emissions continue to decrease. We are investigating possible explanations.Rosetta is an ESA mission with contributions from its member states and NASA. The Alice team acknowledges continuing support from NASA’s Jet Propulsion Laboratory through contract 1336850 to the Southwest Research Institute.

Jet Morphology and Coma Analysis of 103P/Hartley 2

NASA Astrophysics Data System (ADS)

Vaughan, Charles; Pierce, D.; Dorman, G.; Cochran, A.

2012-10-01

We have observed comet 103P/Hartley 2 using the George and Cynthia Mitchell Spectrograph (formerly VIRUS-P) on the 2.7 m telescope at McDonald Observatory (Hill et al. 2008). Data for CN, C2, C3, and NH2 were collected over six nights from 2010 July 15 to November 10. The data were processed to form images of the coma for each of the observed species. We have performed azimuthal average division on each of the coma images to examine jet morphology and have investigated the nature of the production of the radical species using our modified vectorial model (Ihalawela et al. 2011). This work enhances the ongoing investigation of the chemistry and outgassing behavior of Hartley 2 as studied by the EPOXI flyby mission.

1.65 μm (H-band) surface photometry of galaxies. III. observations of 558 galaxies with the TIRGO 1.5 m telescope

NASA Astrophysics Data System (ADS)

Gavazzi, G.; Franzetti, P.; Scodeggio, M.; Boselli, A.; Pierini, D.; Baffa, C.; Lisi, F.; Hunt, L. K.

2000-02-01

We present near-infrared H-band (1.65 μm ) surface photometry of 558 galaxies in the Coma Supercluster and in the Virgo cluster. This data set, obtained with the Arcetri NICMOS3 camera ARNICA mounted on the Gornergrat Infrared Telescope, is aimed at complementing, with observations of mostly early-type objects, our NIR survey of spiral galaxies in these regions, presented in previous papers of this series. Magnitudes at the optical radius, total magnitudes, isophotal radii and light concentration indices are derived. We confirm the existence of a positive correlation between the near-infrared concentration index and the galaxy H-band luminosity Based on observations taken at TIRGO (Gornergrat, Switzerland). TIRGO is operated by CAISMI-CNR, Arcetri, Firenze, Italy. 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

Chemical and Hydrodynamical Models of Cometary Comae

NASA Technical Reports Server (NTRS)

Charnley, Steven

2012-01-01

Multi-fluid modelling of the outflowing gases which sublimate from cometary nuclei as they approach the Sun is necessary for understanding the important physical and chemical processes occurring in this complex plasma. Coma chemistry models can be employed to interpret observational data and to ultimately determine chemical composition and structure of the nuclear ices and dust. We describe a combined chemical and hydrodynamical model [1] in which differential equations for the chemical abundances and the energy balance are solved as a function of distance from the cometary nucleus. The presence of negative ions (anions) in cometary comae is known from Giotto mass spectrometry of 1P/Halley. The anions O(-), OH(-), C(-), CH(-) and CN(-) have been detected, as well as unidentified anions with masses 22-65 and 85-110 amu [2]. Organic molecular anions such as C4H(-) and C6H(-) are known to have a significant impact on the charge balance of interstellar clouds and circumstellar envelopes and have been shown to act as catalysts for the gas-phase synthesis of larger hydrocarbon molecules in the ISM, but their importance in cometary comae has not yet been fully explored. We present details of new models for the chemistry of cometary comae that include atomic and molecular anions and calculate the impact of these anions on the coma physics and chemistry af the coma.

Coma dust scattering concepts applied to the Rosetta mission

NASA Astrophysics Data System (ADS)

Fink, Uwe; Rinaldi, Giovanna

2015-09-01

This paper describes basic concepts, as well as providing a framework, for the interpretation of the light scattered by the dust in a cometary coma as observed by instruments on a spacecraft such as Rosetta. It is shown that the expected optical depths are small enough that single scattering can be applied. Each of the quantities that contribute to the scattered intensity is discussed in detail. Using optical constants of the likely coma dust constituents, olivine, pyroxene and carbon, the scattering properties of the dust are calculated. For the resulting observable scattering intensities several particle size distributions are considered, a simple power law, power laws with a small particle cut off and a log-normal distributions with various parameters. Within the context of a simple outflow model, the standard definition of Afρ for a circular observing aperture is expanded to an equivalent Afρ for an annulus and specific line-of-sight observation. The resulting equivalence between the observed intensity and Afρ is used to predict observable intensities for 67P/Churyumov-Gerasimenko at the spacecraft encounter near 3.3 AU and near perihelion at 1.3 AU. This is done by normalizing particle production rates of various size distributions to agree with observed ground based Afρ values. Various geometries for the column densities in a cometary coma are considered. The calculations for a simple outflow model are compared with more elaborate Direct Simulation Monte Carlo Calculation (DSMC) models to define the limits of applicability of the simpler analytical approach. Thus our analytical approach can be applied to the majority of the Rosetta coma observations, particularly beyond several nuclear radii where the dust is no longer in a collisional environment, without recourse to computer intensive DSMC calculations for specific cases. In addition to a spherically symmetric 1-dimensional approach we investigate column densities for the 2-dimensional DSMC model on the day and night side of the comet. Our calculations are also applied to estimates of the dust particle densities and flux which are useful for the in-situ experiments on Rosetta.

A new 3D multi-fluid model: a study of kinetic effects and variations of physical conditions in the cometary coma

NASA Astrophysics Data System (ADS)

Shou, Yinsi; Combi, Michael R.; Toth, Gabor; Huang, Zhenguang; Jia, Xianzhe; Fougere, Nicolas; Tenishev, Valeriy; Gombosi, T. I.; Hansen, Kenneth C.; Bieler, Andre

2016-10-01

Physics-based numerical coma models are desirable whether to interpret the spacecraft observations of the inner coma or to compare with the ground-based observations of the outer coma. In this work, we develop a multi-neutral-fluid model based on BATS-R-US in the University of Michigan's SWMF (Space Weather Modeling Framework), which is capable of computing both the inner and the outer coma and simulating time-variable phenomena. It treats H2O, OH, H2, O, and H as separate fluids and each fluid has its own velocity and temperature, with collisions coupling all fluids together. The self-consistent collisional interactions decrease the velocity differences, re-distribute the excess energy deposited by chemical reactions among all species, and account for the varying heating efficiency under various physical conditions. Recognizing that the fluid approach has limitations in capturing all of the correct physics for certain applications, especially for very low density environment, we applied our multi-fluid coma model to comet 67P/Churyumov-Gerasimenko (CG) at various heliocentric distances and demonstrated that it is able to yield comparable results as the Direct Simulation Monte Carlo (DSMC) model, which is based on a kinetic approach that is valid under these conditions. Therefore, our model may be a powerful alternative to the particle-based model, especially for some computationally intensive simulations. In addition, by running the model with several combinations of production rates and heliocentric distances, we can characterize the cometary H2O expansion speeds and demonstrate the nonlinear effect of production rates or photochemical heating. Our results are also compared to previous modeling work (e.g., Bockelee-Morvan & Crovisier 1987) and remote observations (e.g., Tseng et al. 2007), which serve as further validation of our model. This work has been partially supported by grant NNX14AG84G from the NASA Planetary Atmospheres Program, and US Rosetta contracts JPL #1266313, JPL #1266314 and JPL #1286489.

Low Metallicities and Old Ages for Three Ultra-diffuse Galaxies in the Coma Cluster

NASA Astrophysics Data System (ADS)

Gu, Meng; Conroy, Charlie; Law, David; van Dokkum, Pieter; Yan, Renbin; Wake, David; Bundy, Kevin; Merritt, Allison; Abraham, Roberto; Zhang, Jielai; Bershady, Matthew; Bizyaev, Dmitry; Brinkmann, Jonathan; Drory, Niv; Grabowski, Kathleen; Masters, Karen; Pan, Kaike; Parejko, John; Weijmans, Anne-Marie; Zhang, Kai

2018-05-01

A large population of ultra-diffuse galaxies (UDGs) was recently discovered in the Coma cluster. Here we present optical spectra of three such UDGs, DF 7, DF 44, and DF 17, which have central surface brightnesses of μ g ≈ 24.4–25.1 mag arcsec‑2. The spectra were acquired as part of an ancillary program within the SDSS-IV MaNGA Survey. We stacked 19 fibers in the central regions from larger integral field units (IFUs) per source. With over 13.5 hr of on-source integration, we achieved a mean signal-to-noise ratio in the optical of 9.5 Å‑1, 7.9 Å‑1, and 5.0 Å‑1, respectively, for DF 7, DF 44, and DF 17. Stellar population models applied to these spectra enable measurements of recession velocities, ages, and metallicities. The recession velocities of DF 7, DF 44, and DF 17 are {6599}-25+40 km s‑1, {6402}-39+41 km s‑1, and {8315}-43+43 km s‑1, spectroscopically confirming that all of them reside in the Coma cluster. The stellar populations of these three galaxies are old and metal-poor, with ages of {7.9}-2.5+3.6 Gyr, {8.9}-3.3+4.3 Gyr, and {9.1}-5.5+3.9 Gyr, and iron abundances of [Fe/H] -{1.0}-0.4+0.3, -{1.3}-0.4+0.4, and -{0.8}-0.5+0.5, respectively. Their stellar masses are (3–6) × 108 M ⊙. The UDGs in our sample are as old or older than galaxies at similar stellar mass or velocity dispersion (only DF 44 has an independently measured dispersion). They all follow the well-established stellar mass–stellar metallicity relation, while DF 44 lies below the velocity dispersion-metallicity relation. These results, combined with the fact that UDGs are unusually large for their stellar masses, suggest that stellar mass plays a more important role in setting stellar population properties for these galaxies than either size or surface brightness.

Discovery of an Ultra-diffuse Galaxy in the Pisces--Perseus Supercluster

NASA Astrophysics Data System (ADS)

Martínez-Delgado, David; Läsker, Ronald; Sharina, Margarita; Toloba, Elisa; Fliri, Jürgen; Beaton, Rachael; Valls-Gabaud, David; Karachentsev, Igor D.; Chonis, Taylor S.; Grebel, Eva K.; Forbes, Duncan A.; Romanowsky, Aaron J.; Gallego-Laborda, J.; Teuwen, Karel; Gómez-Flechoso, M. A.; Wang, Jie; Guhathakurta, Puragra; Kaisin, Serafim; Ho, Nhung

2016-04-01

We report the discovery of DGSAT I, an ultra-diffuse, quenched galaxy located 10.°4 in projection from the Andromeda galaxy (M31). This low-surface brightness galaxy (μV = 24.8 mag arcsec-2), found with a small amateur telescope, appears unresolved in sub-arcsecond archival Subaru/Suprime-Cam images, and hence has been missed by optical surveys relying on resolved star counts, in spite of its relatively large effective radius (Re(V) = 12″) and proximity (15‧) to the well-known dwarf spheroidal galaxy And II. Its red color (V - I = 1.0), shallow Sérsic index (nV = 0.68), and the absence of detectable Hα emission are typical properties of dwarf spheroidal galaxies and suggest that it is mainly composed of old stars. Initially interpreted as an interesting case of an isolated dwarf spheroidal galaxy in the local universe, our radial velocity measurement obtained with the BTA 6 m telescope (Vh = 5450 ± 40 km s-1) shows that this system is an M31-background galaxy associated with the filament of the Pisces-Perseus supercluster. At the distance of this cluster (˜78 Mpc), DGSAT I would have an Re ˜ 4.7 kpc and MV ˜ -16.3. Its properties resemble those of the ultra-diffuse galaxies (UDGs) recently discovered in the Coma cluster. DGSAT I is the first case of these rare UDGs found in this galaxy cluster. Unlike the UDGs associated with the Coma and Virgo clusters, DGSAT I is found in a much lower density environment, which provides a fresh constraint on the formation mechanisms for this intriguing class of galaxy.

On the Origins of Starburst and Poststarburst Galaxies in Nearby Clusters

NASA Astrophysics Data System (ADS)

Caldwell, Nelson; Rose, James A.; Dendy, Kristi

1999-01-01

Hubble Space Telescope (HST) Wide Field Planetary Camera 2 images in B (F450W) and I (F814W) have been obtained for three starburst (SB) and two poststarburst (PSB) galaxies in the Coma Cluster and for three such galaxies in the cluster DC 048-52. V (F555W) and I images for an additional PSB galaxy in Coma have been extracted from the HST archive. Six of these galaxies were previously classified as E/S0 on the basis of ground-based images, two as Sa, and the other as an irregular. The HST images reveal these SB/PSB galaxies to be heterogeneous in morphology. Nevertheless, a common theme is that many of them, especially the SB galaxies, tend to have centralized spiral structure that appears simply as a bright ``bulge'' on ground-based images. In addition, while some PSB galaxies exhibit distinct spiral structure, on the whole they have smoother morphologies than the SB galaxies. The morphologies and luminosity profiles are generally consistent with substantial starbursts, in the form of centralized spiral structure (the SB galaxies), that fade into smoother morphologies (the PSB galaxies), with lingering spectroscopic evidence for past central starbursts. An important point is that the PSB galaxies retain disks; i.e., they have not evolved into spheroidal systems. While the morphologies revealed in the HST images are heterogeneous, and thus may not fit well into a single picture, we see evidence in several cases that the morphologies and centralized star formation have been driven by external tidal perturbations. We discuss several physical mechanisms for inducing star formation in cluster galaxies with a view toward explaining the particular morphologies seen in the HST images.

DISCOVERY OF AN ULTRA-DIFFUSE GALAXY IN THE PISCES-PERSEUS SUPERCLUSTER

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

Martínez-Delgado, David; Grebel, Eva K.; Läsker, Ronald

We report the discovery of DGSAT I, an ultra-diffuse, quenched galaxy located 10.°4 in projection from the Andromeda galaxy (M31). This low-surface brightness galaxy (μ{sub V} = 24.8 mag arcsec{sup −2}), found with a small amateur telescope, appears unresolved in sub-arcsecond archival Subaru/Suprime-Cam images, and hence has been missed by optical surveys relying on resolved star counts, in spite of its relatively large effective radius (R{sub e}(V) = 12″) and proximity (15′) to the well-known dwarf spheroidal galaxy And II. Its red color (V − I = 1.0), shallow Sérsic index (n{sub V} = 0.68), and the absence of detectable Hα emission aremore » typical properties of dwarf spheroidal galaxies and suggest that it is mainly composed of old stars. Initially interpreted as an interesting case of an isolated dwarf spheroidal galaxy in the local universe, our radial velocity measurement obtained with the BTA 6 m telescope (V{sub h} = 5450 ± 40 km s{sup −1}) shows that this system is an M31-background galaxy associated with the filament of the Pisces-Perseus supercluster. At the distance of this cluster (∼78 Mpc), DGSAT I would have an R{sub e} ∼ 4.7 kpc and M{sub V} ∼ −16.3. Its properties resemble those of the ultra-diffuse galaxies (UDGs) recently discovered in the Coma cluster. DGSAT I is the first case of these rare UDGs found in this galaxy cluster. Unlike the UDGs associated with the Coma and Virgo clusters, DGSAT I is found in a much lower density environment, which provides a fresh constraint on the formation mechanisms for this intriguing class of galaxy.« less

Clinical characteristics and outcomes of myxedema coma: Analysis of a national inpatient database in Japan.

PubMed

Ono, Yosuke; Ono, Sachiko; Yasunaga, Hideo; Matsui, Hiroki; Fushimi, Kiyohide; Tanaka, Yuji

2017-03-01

Myxedema coma is a life-threatening and emergency presentation of hypothyroidism. However, the clinical features and outcomes of this condition have been poorly defined because of its rarity. We conducted a retrospective observational study of patients diagnosed with myxedema coma from July 2010 through March 2013 using a national inpatient database in Japan. We investigated characteristics, comorbidities, treatments, and in-hospital mortality of patients with myxedema coma. We identified 149 patients diagnosed with myxedema coma out of approximately 19 million inpatients in the database. The mean (standard deviation) age was 77 (12) years, and two-thirds of the patients were female. The overall proportion of in-hospital mortality among cases was 29.5%. The number of patients was highest in the winter season. Patients treated with steroids, catecholamines, or mechanical ventilation showed higher in-hospital mortality than those without. Variations in type and dosage of thyroid hormone replacement were not associated with in-hospital mortality. The most common comorbidity was cardiovascular diseases (40.3%). The estimated incidence of myxedema coma was 1.08 per million people per year in Japan. Multivariable logistic regression analysis revealed that higher age and use of catecholamines (with or without steroids) were significantly associated with higher in-hospital mortality. The present study identified the clinical characteristics and outcomes of patients with myxedema coma using a large-scale database. Myxedema coma mortality was independently associated with age and severe conditions requiring treatment with catecholamines. Copyright © 2016 The Authors. Production and hosting by Elsevier B.V. All rights reserved.

An Integrated Modeling Study for Coordinated Observations of H, O, OH, and H2O(+) Emissions in the Coma and Ion Tail of the Comet Hale-Bopp

NASA Technical Reports Server (NTRS)

Smyth, William H.

2001-01-01

This project has two overall objectives. One objective is to advance our general understanding of both the comet neutral atmosphere and the cometary plasma in the atmosphere and ion tall. The other objective is to obtain specific key information about comet Hale-Bopp that is generally important for Hale-Bopp studies. The primary emphasis in this project is to analyze, in a self-consistent manner, excellent quality high resolution image and line profile observations obtained by the University of Wisconsin for H, O, OH, and H2O+ emissions from the inner coma, outer coma, and ion tail of Hale-Bopp. The information on the spatial and velocity distributions of H2O neutral and ionized photo-products in the inner coma, outer coma, and in the H2O+ ion tail is of substantial and direct importance in the development of an integrated understanding of the complex structure and dynamics of the neutral and plasma species in the atmosphere of Hale-Bopp in particular and comets in general. The H2O production rate of Hale-Bopp is determined and, together with the other information related to the structure and dynamics of the neutral and plasma atmospheres obtained in this study, provide critical information important for a wide variety of research conducted by other groups.

The Cool Stellar Populations of Early-Type Galaxies and the Galactic Bulge

NASA Astrophysics Data System (ADS)

Houdashelt, Mark Lee

1995-01-01

Red (6800-9200 A) and near-infrared (K-band) spectra have been obtained for 34 early-type galaxies in the Virgo cluster, the Coma cluster and the field. The strengths of the Ca II triplet (lambdalambda 8498, 8542, 8662 A), the Na I doublet ( lambdalambda8183, 8195 A), the Mg I lambda8807 A line, and molecular bands of TiO and VO were measured from the red spectra. Absorption due to the CO band with bandhead at 2.29 mu m was measured from the near-infrared spectra. The behavior of the spectral indices was examined for the Virgo galaxy nuclei as functions of luminosity and color. Overall, the CO, TiO and Na I indices were found to be stronger in redder and brighter galaxies. The Mg I and the Ca II triplet lines did not vary significantly among galaxies of different color or brightness. These trends are consistent with a change in chemical composition producing the well-known color-magnitude relation for early -type galaxies. No significant differences were detected among galaxies of similar luminosity in the Virgo cluster, the Coma cluster and the field. To simulate the stellar population changes implied by the radial color gradients observed in early-type galaxies, models were constructed to represent the integrated light of the Galactic bulge as a function of latitude. A field in Baade's Window (BW) was studied first and the stellar population there was found to be quite inhomogeneous. The BW model indicated that the integrated light of BW is giant -dominated, and the BW spectral energy distribution is very similar to that of the nucleus of a low-luminosity early -type galaxy. From models of BW and a field at b = -8^circ, radial gradients were estimated for the Galactic bulge and compared to the changes which occur along a luminosity sequence of early -type galaxies in the Virgo cluster. This comparison showed that: (1) the Na I and I(8197) indices increase steeply with redder colors in the Virgo galaxies but appear to decrease with color in the Galactic bulge; this effect is not understood but may be caused by some deficiency in the modelling; and (2) differences in the slopes of the TiO-color trends in E/S0 galaxies and in the Galactic bulge may indicate that the (Ti/Fe) ratio is changing differently in these two instances.

Using an integral-field unit spectrograph to study radical species in cometary coma

NASA Astrophysics Data System (ADS)

Lewis, Benjamin; Pierce, Donna M.; Vaughan, Charles M.; Cochran, Anita

2015-01-01

We have observed several comets using an integral-field unit spectrograph (the George and Cynthia Mitchell Spectrograph) on the 2.7m Harlan J. Smith telescope at McDonald Observatory. Full-coma spectroscopic images were obtained for various radical species (C2, C3, CN, NH2). Various coma enhancements were used to identify and characterize coma morphological features. The azimuthal average profiles and the Haser model were used to determine production rates and possible parent molecules. Here, we present the work completed to date, and we compare our results to other comet taxonomic surveys. This work was funded by the National Science Foundation Graduate K-12 (GK-12) STEM Fellows program (Award No. DGE-0947419), NASA's Planetary Atmospheres program (Award No. NNX14AH18G), and the Fund for Astrophysical Research, Inc.

Using an integral-field unit spectrograph to study radical species in cometary coma

NASA Astrophysics Data System (ADS)

Lewis, Benjamin; Pierce, Donna; Cochran, Anita; Vaughan, Charles

2014-11-01

We have observed several comets using an integral-field unit spectrograph (the George and Cynthia Mitchell Spectrograph) on the 2.7m Harlan J. Smith telescope at McDonald Observatory. Full-coma spectroscopic images were obtained for various radical species (C2, C3, CN, NH2). Various coma enhancements were used to identify and characterize coma morphological features. The azimuthal average profiles and the Haser model were used to determine production rates and possible parent molecules. Here, we present the work completed to date, and we compare our results to other comet taxonomic surveys. This work was funded by the National Science Foundation Graduate K-12 (GK-12) STEM Fellows program (Award No. DGE-0947419), NASA’s Planetary Atmospheres program (Award No. NNX14AH18G), and the Fund for Astrophysical Research, Inc.

H2O(+) structures in the inner plasma tail of comet Austin

NASA Technical Reports Server (NTRS)

Jockers, Klaus; Bonev, T.; Geyer, E. H.

1992-01-01

We present images of comet Austin 1989c1 in the light of H2O(+) from which the contribution of the dust continuum and the gas coma was completely removed. We describe the behavior of the H2O(+) plasma in the inner coma where it is reliably observed for the first time.

Formation of C3 and C2 in Cometary Comae

NASA Astrophysics Data System (ADS)

Hölscher, Alexander

2015-03-01

Comets are remnants from the Solar System formation. They reside at large distances from the Sun and are believed to store deep freeze imprints of the chemical and physical conditions at the time the Solar System formed. The main ice component of a comet is H2O followed by CO and CO2 with additional small amounts of molecules with varying complexity. Comets also contain large amounts of dust. If a comet approaches the Sun the ices begin to sublimate giving rise to the cometary coma. The molecules producing the coma can be observed in the infrared, the radio wavelength range and at optical wavelengths. To constrain the formation of the Solar System, models require knowledge of the composition for a statistically significant number of comets. This favors optical observations of e.g. C3 (tricarbon) and C2 (dicarbon) since these species allow observations even of relatively faint comets and do not require space missions (infrared observations). However, one has to link these observed photodissociation product species (daughter species) to the molecules that originally sublimated from the comet nucleus surface, i.e. the so-called parent molecules, as e.g. C2H2 (acetylene) for C2. However, for C3 no parent molecules have been identified so far. This thesis investigates the formation of C3 and C2 radicals in cometary comae due to photodissociation of observed and in the literature proposed hydrocarbon parent molecules. For this purpose a one-dimensional multi-fluid coma chemistry model has been improved and applied. This work added new photo reactions to the model, updated the hydrocarbon photo rate coefficients and quantified their uncertainty. A sensitivity analysis has been carried out to determine the reactions whose uncertainty most affect the model output uncertainty. Special attention should be paid to these so-called key reactions in future laboratory experiments and quantum chemical computations to reduce the model output uncertainty more effectively. This will allow to better constrain which parent molecules are responsible for the observational C3 and C2 column densities. Based on observations of the four sample comets C/2001 Q4 (NEAT), C/2002 T7 (LINEAR), 9P (Tempel 1) and C/1995 O1 (Hale-Bopp), this work investigates which combination of the following proposed parent molecules C4H2 (diacetylene), CH2C2H2 (allene), CH3C2H (propyne), C2H4 (ethene) and observed parent molecules C2H2 and HC3N (cyanoacetylene) can best reproduce the observational C3 and C2 column densities in cometary comae, taking into account the uncertainties in photodissociation rate coefficients. It was found that the investigated photodissociation rate coefficients have large uncertainties and also a significant effect on the C3 and C2 model column densities. The responsible key reactions were determined with the sensitivity analysis. The important result of this thesis is that one can reasonably well reproduce the observations of comets with the improved model at rh = 1.00 AU (NEAT) and rh = 3.78 AU (Hale-Bopp), within the photodissociation uncertainties using realistic parent molecule production rate ratios and by various combinations of the investigated parent molecules. To confirm the agreement (NEAT, Hale-Bopp) and to clearify remaining discrepancies (LINEAR, Tempel 1) between model and observations requires additional observations of parent and daughter molecules in the coma of comets as well as in situ measurements of cometary ices (Rosetta).zeige weniger

The Complex Outgassing of Comets and the Resulting Coma, a Direct Simulation Monte-Carlo Approach

NASA Astrophysics Data System (ADS)

Fougere, Nicolas

During its journey, when a comet gets within a few astronomical units of the Sun, solar heating liberates gases and dust from its icy nucleus forming a rarefied cometary atmosphere, the so-called coma. This tenuous atmosphere can expand to distances up to millions of kilometers representing orders of magnitude larger than the nucleus size. Most of the practical cases of coma studies involve the consideration of rarefied gas flows under non-LTE conditions where the hydrodynamics approach is not valid. Then, the use of kinetic methods is required to properly study the physics of the cometary coma. The Direct Simulation Monte-Carlo (DSMC) method is the method of choice to solve the Boltzmann equation, giving the opportunity to study the cometary atmosphere from the inner coma where collisions dominate and is in thermodynamic equilibrium to the outer coma where densities are lower and free flow conditions are verified. While previous studies of the coma used direct sublimation from the nucleus for spherically symmetric 1D models, or 2D models with a day/night asymmetry, recent observations of comets showed the existence of local small source areas such as jets, and extended sources via sublimating icy grains, that must be included into cometary models for a realistic representation of the physics of the coma. In this work, we present, for the first time, 1D, 2D, and 3D models that can take into account the full effects of conditions with more complex sources of gas with jets and/or icy grains. Moreover, an innovative work in a full 3D description of the cometary coma using a kinetic method with a realistic nucleus and outgassing is demonstrated. While most of the physical models used in this study had already been developed, they are included in one self-consistent coma model for the first time. The inclusion of complex cometary outgassing processes represents the state-of-the-art of cometary coma modeling. This provides invaluable information about the coma by refining the understanding of the material that constitutes comets. This helps us to comprehend the process of the Solar System formation, one of the top priority questions in the 2013-2022 Planetary Science Decadal survey.

A Chemical Model of the Coma of Comet C/2009 P1 (Garradd)

NASA Astrophysics Data System (ADS)

Boice, Daniel C.; Kawakita, H.; Kobayashi, H.; Naka, C.; Phelps, L.

2012-10-01

Modeling is essential to understand the important physical and chemical processes that occur in cometary comae. Photochemistry is a major source of ions and electrons that further initiate key gas-phase reactions, leading to the plethora of molecules and atoms observed in comets. The effects of photoelectrons that react via impacts are important to the overall ionization. We identify the relevant processes within a global modeling framework to understand simultaneous observations in the visible and near-IR of Comet C/2009 (Garradd) and to provide valuable insights into the intrinsic properties of its nucleus. Details of these processes are presented in the collision-dominated, inner coma of the comet to evaluate the relative chemical pathways and the relationship between parent and sibling molecules. Acknowledgements: We appreciate support from the NSF Planetary Astronomy Program.

The Spatial Distribution of C2, C3, and NH in Comet 2P/Encke

NASA Astrophysics Data System (ADS)

Dorman, Garrett; Pierce, Donna M.; Cochran, Anita L.

2013-12-01

We examine the spatial distribution of C2, C3, and NH radicals in the coma of comet Encke in order to understand their abundances and distributions in the coma. The observations were obtained from 2003 October 22-24, using the 2.7 m telescope at McDonald Observatory. Building on our original study of CN and OH, we have used our modified version of the vectorial model, which treats the coma as one large cone, in order to reproduce Encke's highly aspherical and asymmetric coma. Our results suggest that NH can be explained by the photodissociation of NH2, assuming that NH2 is produced rapidly from NH3 in the innermost coma. Our modeling of C2 and C3 suggests a multi-generational photodissociation process may be required for their production. Using the results of our previous study, we also obtain abundance ratios with respect to OH and CN. Overall, we find that Encke exhibits typical carbon-chain abundances, and the results are consistent with other studies of comet Encke.

MMN and novelty P3 in coma and other altered states of consciousness: a review.

PubMed

Morlet, Dominique; Fischer, Catherine

2014-07-01

In recent decades, there has been a growing interest in the assessment of patients in altered states of consciousness. There is a need for accurate and early prediction of awakening and recovery from coma. Neurophysiological assessment of coma was once restricted to brainstem auditory and primary cortex somatosensory evoked potentials elicited in the 30 ms range, which have both shown good predictive value for poor coma outcome only. In this paper, we review how passive auditory oddball paradigms including deviant and novel sounds have proved their efficiency in assessing brain function at a higher level, without requiring the patient's active involvement, thus providing an enhanced tool for the prediction of coma outcome. The presence of an MMN in response to deviant stimuli highlights preserved automatic sensory memory processes. Recorded during coma, MMN has shown high specificity as a predictor of recovery of consciousness. The presence of a novelty P3 in response to the subject's own first name presented as a novel (rare) stimulus has shown a good correlation with coma awakening. There is now a growing interest in the search for markers of consciousness, if there are any, in unresponsive patients (chronic vegetative or minimally conscious states). We discuss the different ERP patterns observed in these patients. The presence of novelty P3, including parietal components and possibly followed by a late parietal positivity, raises the possibility that some awareness processes are at work in these unresponsive patients.

MMN and Novelty P3 in Coma and Other Altered States of Consciousness: A Review

PubMed Central

Morlet, Dominique; Fischer, Catherine

2014-01-01

In recent decades, there has been a growing interest in the assessment of patients in altered states of consciousness. There is a need for accurate and early prediction of awakening and recovery from coma. Neurophysiological assessment of coma was once restricted to brainstem auditory and primary cortex somatosensory evoked potentials elicited in the thirty millisecond range, which have both shown good predictive value for poor coma outcome only. In this paper, we review how passive auditory oddball paradigms including deviant and novel sounds have proved their efficiency in assessing brain function at a higher level, without requiring the patient’s active involvement, thus providing an enhanced tool for the prediction of coma outcome. The presence of an MMN in response to deviant stimuli highlights preserved automatic sensory memory processes. Recorded during coma, MMN has shown high specificity as a predictor of recovery of consciousness. The presence of a novelty P3 in response to the subject’s own first name presented as a novel (rare) stimulus has shown a good correlation with coma awakening. There is now a growing interest in the search for markers of consciousness, if there are any, in unresponsive patients (chronic vegetative or minimally conscious states). We discuss the different ERP patterns observed in these patients. The presence of novelty P3, including parietal components and possibly followed by a late parietal positivity, raises the possibility that some awareness processes are at work in these unresponsive patients. PMID:24281786

An X-ray and optical study of the cluster of galaxies Abell 754

NASA Technical Reports Server (NTRS)

Fabricant, D.; Beers, T. C.; Geller, M. J.; Gorenstein, P.; Huchra, J. P.

1986-01-01

X-ray and optical data for A754 are used to study the relative distribution of the luminous and dark matter in this dense, rich cluster of galaxies with X-ray luminosity comparable to that of the Coma Cluster. A quantitative statistical comparison is made of the galaxy positions with the total mass responsible for maintaining the X-ray emitting gas in hydrostatic equilibrium. A simple bimodal model which fits both the X-ray and optical data suggests that the galaxies are distributed consistently with the projected matter distribution within the region covered by the X-ray map (0.5-1 Mpc). The X-ray and optical estimates of the mass in the central region of the cluster are 2.9 x 10 to the 14th and 3.6 + or - 0.5 x 10 to the 14th solar masses, respectively.

Modeling the Deep Impact Near-nucleus Observations of H2O and CO2 in Comet 9P/Tempel 1 Using Asymmetric Spherical Coupled Escape Probability

NASA Astrophysics Data System (ADS)

Gersch, Alan M.; A’Hearn, Michael F.; Feaga, Lori M.

2018-04-01

We have applied our asymmetric spherical adaptation of Coupled Escape Probability to the modeling of optically thick cometary comae. Expanding on our previously published work, here we present models including asymmetric comae. Near-nucleus observations from the Deep Impact mission have been modeled, including observed coma morphology features. We present results for two primary volatile species of interest, H2O and CO2, for comet 9P/Tempel 1. Production rates calculated using our best-fit models are notably greater than those derived from the Deep Impact data based on the assumption of optically thin conditions, both for H2O and CO2 but more so for CO2, and fall between the Deep Impact values and the global pre-impact production rates measured at other observatories and published by Schleicher et al. (2006), Mumma et al. (2005), and Mäkinen et al. (2007).

Formation of jets in Comet 19P/Borrelly by subsurface geysers

USGS Publications Warehouse

Yelle, R.V.; Soderblom, L.A.; Jokipii, J.R.

2004-01-01

Observations of the inner coma of Comet 19P/Borrelly with the camera on the Deep Space 1 spacecraft revealed several highly collimated dust jets emanating from the nucleus. The observed jets can be produced by acceleration of evolved gas from a subsurface cavity through a narrow orifice to the surface. As long as the cavity is larger than the orifice, the pressure in the cavity will be greater than the ambient pressure in the coma and the flow from the geyser will be supersonic. The gas flow becomes collimated as the sound speed is approached and dust entrainment in the gas flow creates the observed jets. Outside the cavity, the expanding gas loses its collimated character, but the density drops rapidly decoupling the dust and gas, allowing the dust to continue in a collimated beam. The hypothesis proposed here can explain the jets seen in the inner coma of Comet 1P/Halley as well, and may be a primary mechanism for cometary activity. ?? 2003 Published by Elsevier Inc.

Origin of the fundamental plane of elliptical galaxies in the Coma cluster without fine-tuning

NASA Astrophysics Data System (ADS)

Chiu, Mu-Chen; Ko, Chung-Ming; Shu, Chenggang

2017-03-01

Thirty years after the discovery of the fundamental plane, explanations of the tilt of the fundamental plane with respect to the virial plane are still in need of fine-tuning. In this paper, we try to explore the origin of this tilt from the perspective of modified Newtonian dynamics (MOND) by applying the 16 Coma galaxies available in J. Thomas et al. [Mon. Not. R. Astron. Soc. 415, 545 (2011), 10.1111/j.1365-2966.2011.18725.x]. Based on the mass models that can reproduce de Vaucouleurs' law closely, we find that the tilt of the traditional fundamental plane is naturally explained by the simple form of the MONDian interpolating function, if we assume a well motivated choice of anisotropic velocity distribution, and adopt the Kroupa or Salpeter stellar mass-to-light ratio. Our analysis does not necessarily rule out a varying stellar mass-to-light ratio.

Photometry of the comet 2060 Chiron

NASA Technical Reports Server (NTRS)

Buratti, Bonnie J.; Marcialis, Robert L.; Dunbar, R. Scott

1991-01-01

The comet 2060 Chiron has proven to be an interesting and enigmatic object. Situated between the orbits of Saturn and Uranus, it was originally classified as the most distant asteroid. It began to show cometary behavior in 1987 by increasing a full magnitude in brightness and developing a coma; there is evidence also for similar earlier outbursts. A thorough study of Chiron is important for two reasons: (1) it is a transition object defining the relationship between comets, asteroids, and meteorites; and (2) a full description of its changes in brightness - particularly on time scale of hours - will provide an empirical foundation for understanding the physical mechanisms (including outgassing, sublimation of volatiles, and even significant mass ejections) driving the evolution of comets. Short term outbursts were observed in early 1989, and a rapid decrease in brightness of Chiron's coma was observed in 1990 in the V and R filters. Also, a rotational lightcurve was detected of the nucleus with an amplitude only 1/4 that observed in its quiescent state: this fact indicates the increased importance of the optically thin coma to the observed brightness.

Hco+ in the Coma of Comet Hale-Bopp

NASA Astrophysics Data System (ADS)

Lovell, A. J.; Schloerb, F. P.; Bergin, E. A.; Dickens, J. E.; De Vries, C. H.; Senay, M. C.; Irvine, W. M.

1997-05-01

Maps of comet C/1995 O1 (Hale-Bopp) in the millimeter-wave emission of the ion HCO^+ revealed a local minimum near the nucleus position, with a maximum about 100,000 km in the antisolar direction. These observed features of the HCO^+ emission require a low abundance of HCO^+ due to enhanced destruction in the inner coma of the comet, within a region of low electron temperature (T_e). To set constraints on the formation of HCO^+ in the coma, as well as the location and magnitude of the transition to higher T_e, the data are compared with the results of ion-molecule chemistry models.

HCO+ in the coma of comet Hale-Bopp

NASA Technical Reports Server (NTRS)

Lovell, A. J.; Schloerb, F. P.; Bergin, E. A.; Dickens, J. E.; Devries, C. H.; Senay, M. C.; Irvine, W. M.; Ferris, J. P. (Principal Investigator)

1997-01-01

Maps of comet C/1995 O1 (Hale-Bopp) in the millimeter-wave emission of the ion HCO+ revealed a local minimum near the nucleus position, with a maximum about 100,000 km in the antisolar direction. These observed features of the HCO+ emission require a low abundance of HCO+ due to enhanced destruction in the inner coma of the comet, within a region of low electron temperature (Te). To set constraints on the formation of HCO+ in the coma, as well as the location and magnitude of the transition to higher Te, the data are compared with the results of ion-molecule chemistry models.

Numerical simulations of particle orbits around 2060 Chiron

NASA Technical Reports Server (NTRS)

Stern, S. A.; Jackson, A. A.; Boice, D. C.

1994-01-01

Scattered light from orbiting or coorbiting dust is a primary signature by which Earth-based observers study the activity and atmosphere of the unusual outer solar system object 2060 Chiron. Therefore, it is important to understand the lifetime, dynamics, and loss rates of dust in its coma. We report here dynamical simulations of particles in Chiron's collisionless coma. The orbits of 17,920 dust particles were numerically integrated under the gravitational influence of Chiron, the Sun, and solar radiation pressure. These simulations show that particles ejected from Chiron are more likely to follow suborbital trajectories, or to escape altogether, than to enter quasistable orbits. Significant orbital lifetimes can only be achieved for very specific launch conditions. These results call into question models of a long-term, bound coma generated by discrete outbursts, and instead suggest that Chiron's coma state is closely coupled to the nearly instantaneous level of Chiron's surface activity.

Evidence for methane and ammonia in the coma of comet P/Halley

NASA Technical Reports Server (NTRS)

Allen, M.; Delitsky, M.; Huntress, W.; Yung, Y.; Ip, W.-H.

1987-01-01

Methane and ammonia abundances in the coma of Halley are derived from Giotto ion mass spectrometer data using an Eulerian model of chemical and physical processes inside the contact surface to simulate Giotto high-intensity spectrometer ion mass spectral data for mass-to-charge ratios (m/q) from 15 to 19. The ratio m/q = 19/18 as a function of distance from the nucleus is not reproduced by a model for a pure water coma. It is necessary to include the presence of NH3, and uniquely NH3, in coma gases in order to explain the data. A ratio of production rates Q(NH3)/Q(H2O) = 0.01 = 0.02 results in model values approximating the Giotto data. Methane is identified as the most probable source of the distinct peak at m/q = 15. The observations are fit best with Q(CH4)/Q(Q2O) = 0.02. The chemical composition of the comet nucleus implied by these production rate ratios is unlike that of the outer planets. On the other hand, there are also significant differences from observations of gas phase interstellar material.

Comet 209P/LINEAR's Very Close Approach to Earth: Probing the Inner-Coma Physical Environment and Volatile Composition

NASA Astrophysics Data System (ADS)

Bonev, Boncho P.; DiSanti, Michael; Mumma, Michael; Gibb, Erika; Villanueva, Geronimo; Paganini, Lucas; Combi, Michael; Magee-Sauer, Karen

2014-02-01

Using NIRSPEC at Keck 2 we propose spatially-resolved high- resolution spectroscopic observations of H_2O emission in the coma of the Jupiter-family comet 209P/LINEAR. The exceptionally small geocentric distance - 0.06 AU - will afford very high spatial resolution. Using long-slit spectroscopy we will measure the spatial variation of the temperature and column density of water, providing a very rare direct quantitative view of the physical state in the innermost region of a cometary atmosphere, within 50-100 km from the nucleus. To maximize the science return, we will also measure the abundances of CH_3OH and C_2H_6 simultaneously with H_2O. Only one instrument setting is required for our entire investigation, thereby optimizing observing efficiency. Our proposed study targets improved understanding of the near-nucleus coma physics, and of the primary volatile composition of Jupiter-family comets, a dynamical group which remains underrepresented in modern taxonomical studies. In addition, this project will provide a context for interpreting results from the Rosetta mission, and also a test of state-of-the-art physical models of the coma.

Observations and analysis of O(1D) and NH2 line profiles for the coma of comet P/Halley

NASA Technical Reports Server (NTRS)

Smyth, William H.; Combi, Michael R.; Roesler, Fred L.; Scherb, Frank

1995-01-01

A set of high-resolution Fabry-Perot measurements of the coma of comet P/Halley was acquired in the (O I) 6300 A and NH2 6298.62 A emission lines. These high-resolution measurements provide the first optical observations capable of studying directly the photochemical kinetics and dynamic outflow of the coma. The observations were analyzed by a Monte Carlo Particle Trajectory Model. The agreement of the model and observed line profiles was excellent and verified the underlying dynamics, exothermic photodissociative chemistry, and collisional thermalization in the coma. The somewhat wider intrinsic line profile width for the O(1D) emission in 1986 January compared to 1986 May, is, for example, produced by the larger outflow speeds and gas temperatures nearer perihelion in January. The January O(1D) profile, which is wider than the January NH2 profile, is indicative of the photochemical kinetics in the dissociation of the parent molecules H2O and OH in the coma. The absolute calibration of the observations in 1986 January allowed the production rates for H2O and the NH2-parent molecules to be determined. The average daily water production rates derived from the O(1D) emission data for January 16 and 17 are presented. These very large water production rates are consistent with the extrapolated (and 7.6 day time variable) water production rates determined from the analysis of lower spectral resolution observations for O(1D) and H-alpha emissions that covered the time period up to January 13. The large production rates on January 16 and 17 establish that the maximum water production rate for comet Halley accurred pre-perihelion in January. Implications drawn from comparison with 18 cm radio emission data in January suggest that the peak water production rate was even larger. The average production rate for NH3 determined from the NH2 emission data for January 17 was (1.48 +/- 0.10) x 10(exp 28) molecules/s, yielding an NH3/H2O production rate ratio of 0.55%.

Large-scale dust jets in the coma of 67P/Churyumov-Gerasimenko as seen by the OSIRIS instrument onboard Rosetta

NASA Astrophysics Data System (ADS)

Lara, L. M.; Lowry, S.; Vincent, J.-B.; Gutiérrez, P. J.; Rożek, A.; La Forgia, F.; Oklay, N.; Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Agarwal, J.; Auger, A.-T.; A'Hearn, M. F.; Barucci, M. A.; Bertaux, J.-L.; Bertini, I.; Besse, S.; Bodewits, D.; Cremonese, G.; Davidsson, B.; Da Deppo, V.; Debei, S.; De Cecco, M.; El-Maarry, M. R.; Ferri, F.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez-Marques, P.; Güttler, C.; Hviid, S. F.; Ip, W.-H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J.-R.; Kührt, E.; Küppers, M.; Lazzarin, M.; Lin, Z.-Y.; López-Moreno, J. J.; Magrin, S.; Marzari, F.; Michalik, H.; Moissl-Fraund, R.; Moreno, F.; Mottola, S.; Naletto, G.; Pajola, M.; Pommerol, A.; Thomas, N.; Sabau, M. D.; Tubiana, C.

2015-11-01

Context. During the most recent perihelion passage in 2009 of comet 67P/Churyumov-Gerasimenko (67P), ground-based observations showed an anisotropic dust coma where jet-like features were detected at ~ 1.3 AU from the Sun. The current perihelion passage is exceptional as the Rosetta spacecraft is monitoring the nucleus activity since March 2014, when a clear dust coma was already surrounding the nucleus at 4.3 AU from the Sun. Subsequently, the OSIRIS camera also witnessed an outburst in activity between April 27 and 30, and since mid-July, the dust coma at rh ~ 3.7-3.6 AU preperihelion is clearly non-isotropic, pointing to the existence of dust jet-like features. Aims: We aim to ascertain on the nucleus surface the origin of the dust jet-like features detected as early as in mid-July 2014. This will help to establish how the localized comet nucleus activity compares with that seen in previous apparitions and will also help following its evolution as the comet approaches its perihelion, at which phase most of the jets were detected from ground-based observations. Determining these areas also allows locating them in regions on the nucleus with spectroscopic or geomorphological distinct characteristics. Methods: Three series of dust images of comet 67P obtained with the Wide Angle Camera (WAC) of the OSIRIS instrument onboard the Rosetta spacecraft were processed with different enhancement techniques. This was made to clearly show the existence of jet-like features in the dust coma, whose appearance toward the observer changed as a result of the rotation of the comet nucleus and of the changing observing geometry from the spacecraft. The position angles of these features in the coma together with information on the observing geometry, nucleus shape, and rotation, allowed us to determine the most likely locations on the nucleus surface where the jets originate from. Results: Geometrical tracing of jet sources indicates that the activity of the nucleus of 67P gave rise during July and August 2014 to large-scale jet-like features from the Hapi, Hathor, Anuket, and Aten regions, confirming that active regions may be present on the nucleus localized at 60° northern latitude as deduced from previous comet apparitions. There are also hints that large-scale jets observed from the ground are possibly composed, at their place of origin on the nucleus surface, of numerous small-scale features.

Burst Suppression on Processed Electroencephalography as a Predictor of Post-Coma Delirium in Mechanically Ventilated ICU Patients

PubMed Central

Andresen, Jennifer M.; Girard, Timothy D.; Pandharipande, Pratik P.; Davidson, Mario A.; Ely, E. Wesley; Watson, Paula L.

2015-01-01

Objectives Many patients, due to a combination of illness and sedatives, spend a considerable amount of time in a comatose state that can include time in burst suppression. We sought to determine if burst suppression measured by processed electroencephalography (pEEG) during coma in sedative-exposed patients is a predictor of post-coma delirium during critical illness. Design Observational convenience sample cohort Setting Medical and surgical ICUs in a tertiary care medical center Patients Cohort of 124 mechanically ventilated ICU patients Measurements and Main Results Depth of sedation was monitored twice daily using the Richmond Agitation-Sedation Scale and continuously monitored by pEEG. When non-comatose, patients were assessed for delirium twice daily using Confusion Assessment Method for the ICU (CAM-ICU). Multiple logistic regression and Cox proportional hazards regression were used to assess associations between time in burst suppression and both incidence and time to resolution of delirium, respectively, adjusting for time in deep sedation and a principal component score consisting of APACHE II score and cumulative doses of sedatives while comatose. Of the 124 patients enrolled and monitored, 55 patients either never had coma or never emerged from coma yielding 69 patients for whom we performed these analyses; 42 of these 69 (61%) had post-coma delirium. Most patients had burst-suppression during coma, though often short-lived [ median (intraquartile range) time in burst suppression, 6.4 (1-58) minutes]. After adjusting for covariates, even this short time in burst suppression independently predicted a higher incidence of post-coma delirium [odds ratio 4.16; 95% confidence interval (CI) 1.27-13.62; p=0.02] and a lower likelihood (delayed) resolution of delirium (hazard ratio 0.78; 95% CI 0.53-0.98; p=0.04). Conclusions Time in burst suppression during coma, as measured by processed EEG, was an independent predictor of incidence and time to resolution of post-coma/post-deep sedation delirium. These findings of this single center investigation support lighter sedation strategies. PMID:25072756

Physical processes in comets

NASA Technical Reports Server (NTRS)

Whipple, F. L.; Huebner, W. F.

1976-01-01

The paper discusses physical processes in comets which involve solar and nuclear radial forces that affect the motions of gases and icy grains, gas-phase chemistry very close to the nuclei of large comets near the sun, sublimation of icy grains, dissociation of parent molecules into radicals and of radicals into atoms, and ionization by sunlight and collisions. The composition and dimensions of nuclei are examined along with variations in intrinsic brightness, the nature of volatiles, gas production rates in the coma, characteristics of icy grains in the coma, and the structure of streamers, ion tails, and dust tails. The structure of the coma is described in detail on the basis of spectroscopic observations of several comets. The origin of comets is briefly reviewed together with the relation of comets to earth, the interplanetary complex, and the interstellar medium. Desirable future observations are noted, especially by space missions to comets.

Non-Thermal Hard X-Ray Emission in Galaxy Clusters Observed with the BeppoSAX PDS

NASA Technical Reports Server (NTRS)

Nevalainen, Jukka H.; Oosterbroeck, T.; Bonamente, Max; Six, N. Frank (Technical Monitor)

2002-01-01

We studied the X-ray emission in a sample of clusters using the BeppoSAX PDS instrument in the 20 -- 80 keV energy band. We estimated the non-thermal cluster emission (HXR) by modeling the thermal contribution from the cluster gas and the non-thermal contamination from the AGN in the field, and propagating the corresponding uncertainties. We also evaluated and propagated the systematic uncertainties due to the background fluctuations. The resulting non-thermal component is detected at a sigma level in approx. 50 % of the non-significantly AGN-contaminated clusters, i.e. in clusters A2142, A2256, A3376, Coma, Ophiuchus and Virgo. Furthermore, Virgo is detected at a 4 sigma level. All the clusters detected at a 2 sigma level exhibit some degree of merger signatures, i.e. deviations from the azimuthally symmetric brightness and temperature distributions, while the relaxed clusters are detected at a lower confidence. The data are consistent with a scenario whereby relaxed clusters have no non-thermal hard X-ray component, whereas merger clusters do, with a 20 -- 80 keV luminosity of approx. 10(exp 42-44)((h(sub 50))(exp -2))(erg/s). Consistent with merger boosting of cluster temperatures, the non-thermal luminosity increases by 2-3 orders of magnitude between the average cluster temperatures 2 and 10 keV, as L(sub NTE) is proportional to T(sup j) with j = 2.4+/-0.3. These results corroborate the assumption which is the essential element in most non-thermal hard X-ray emission models. The co-added spectrum of all non-significantly AGN-contaminated clusters indicates a power-law spectrum for the non-thermal component with a photon index of 1.5+/-0.25 at 1 sigma confidence level. Unless there is a high energy cut-off in the electron velocity distribution, the total spectrum implies that Inverse Compton scatter of Cosmic Microwave Background photons from electron population dominates over the non-thermal bremsstrahlung in producing hard X-rays in clusters on the merger shock acceleration of electrons in clusters.

Radio continuum survey of the Coma/A1367 supercluster. I - 610 MHz observations of CGCG galaxies in four groups

NASA Astrophysics Data System (ADS)

Jaffe, W.; Gavazzi, G.; Valentijn, E.

1986-02-01

Radio continuum observations obtained with the Westerbork Radio Synthesis Telescope at 0.6 GHz of four groups of galaxies in the Coma/A1367 supercluster area are presented. Ninety-nine CGCG galaxies were surveyed, yielding the detection of 21 objects. A wide-angle-tail radio galaxy, NGC 4061, is found in the NGC 4065 group. Analysis of this source suggests a relatively low value (neT ≡ 1000 cm-3K) for the intracluster gas pressure in this group.

Modeling of the Inner Coma of Comet 67P/Churyumov-Gerasimenko Constrained by VIRTIS and ROSINA Observations

NASA Astrophysics Data System (ADS)

Fougere, N.; Combi, M. R.; Tenishev, V.; Bieler, A. M.; Migliorini, A.; Bockelée-Morvan, D.; Toth, G.; Huang, Z.; Gombosi, T. I.; Hansen, K. C.; Capaccioni, F.; Filacchione, G.; Piccioni, G.; Debout, V.; Erard, S.; Leyrat, C.; Fink, U.; Rubin, M.; Altwegg, K.; Tzou, C. Y.; Le Roy, L.; Calmonte, U.; Berthelier, J. J.; Rème, H.; Hässig, M.; Fuselier, S. A.; Fiethe, B.; De Keyser, J.

2015-12-01

As it orbits around comet 67P/Churyumov-Gerasimenko (CG), the Rosetta spacecraft acquires more information about its main target. The numerous observations made at various geometries and at different times enable a good spatial and temporal coverage of the evolution of CG's cometary coma. However, the question regarding the link between the coma measurements and the nucleus activity remains relatively open notably due to gas expansion and strong kinetic effects in the comet's rarefied atmosphere. In this work, we use coma observations made by the ROSINA-DFMS instrument to constrain the activity at the surface of the nucleus. The distribution of the H2O and CO2 outgassing is described with the use of spherical harmonics. The coordinates in the orthogonal system represented by the spherical harmonics are computed using a least squared method, minimizing the sum of the square residuals between an analytical coma model and the DFMS data. Then, the previously deduced activity distributions are used in a Direct Simulation Monte Carlo (DSMC) model to compute a full description of the H2O and CO2 coma of comet CG from the nucleus' surface up to several hundreds of kilometers. The DSMC outputs are used to create synthetic images, which can be directly compared with VIRTIS measurements. The good agreement between the VIRTIS observations and the DSMC model, itself constrained with ROSINA data, provides a compelling juxtaposition of the measurements from these two instruments. Acknowledgements Work at UofM was supported by contracts JPL#1266313, JPL#1266314 and NASA grant NNX09AB59G. Work at UoB was funded by the State of Bern, the Swiss National Science Foundation and by the ESA PRODEX Program. Work at Southwest Research institute was supported by subcontract #1496541 from the JPL. Work at BIRA-IASB was supported by the Belgian Science Policy Office via PRODEX/ROSINA PEA 90020. The authors would like to thank ASI, CNES, DLR, NASA for supporting this research. VIRTIS was built by a consortium formed by Italy, France and Germany, under the scientific responsibility of the IAPS of INAF, which guides also the scientific operations. The consortium includes also the LESIA of the Observatoire de Paris, and the Institut für Planetenforschung of DLR. The authors wish to thank the RSGS and the RMOC for their continuous support.

Production, Outflow Velocity, and Radial Distribution of H2O and OH in the Coma of Comet C/1995 O1 [Hale-Bopp] from Wide Field Imaging of OH

NASA Technical Reports Server (NTRS)

Harris, Walter M.; Scherb, Frank; Mierkiewicz, Edwin; Oliversen, Ronald; Morgenthaler, Jeffrey

2001-01-01

Observations of OH are a useful proxy of the water production rate (Q(sub H2O)) and outflow velocity (V(sub out)) in comets. We use wide field images taken on 03/28/1997 and 04/08/1997 that capture the entire scale length of the OH coma of comet C/1995O1 (Hale-Bopp) to obtain Q(sub H2O) from the model-independent method of aperture summation. We also extract the radial brightness profile of OH 3080 angstroms out to cometocentric distances of up to 10(exp 6) km using an adaptive ring summation algorithm. Radial profiles are obtained as azimuthal averages and in quadrants covering different position angles relative to the comet-Sun line. These profiles are fit using both fixed and variable velocity two-component spherical expansion models to determine VOH with increasing distance from the nucleus. The OH coma of Hale-Bopp was more spatially extended than in previous comets, and this extension is best matched by a variable acceleration of H2O and OH that acted across the entire coma, but was strongest within 1-2 x 10(exp 4) km from the nucleus. This acceleration led to VOH at 10(exp 6) km that was 2-3 times greater than that obtained from a 1P/Halleytype comet at 1 AU, a result that is consistent with gas-kinetic models, extrapolation from previous observations of OH in comets with Q(sub H2O) > 10(exp 29)/s, and radio measurements of the outer coma Hale-Bopp OH velocity profile. When the coma is broken down by quadrant, we find an azimuthal asymmetry in the radial distribution that is characterized by an increase in the spatial extent of OH in the region between the orbit-trailing and anti-sunward directions. Model fits to this area and comparison with radio OH measurements suggest greater acceleration in this region, with VOH UP to 1.5 times greater at 10(exp 6) km radial distance than elsewhere in the coma.

VizieR Online Data Catalog: CCD Survey of Galaxies IV (Gavazzi+, 1995)

NASA Astrophysics Data System (ADS)

Gavazzi, G.; Boselli, A.; Carrasco, L.

1995-03-01

Continuing a CCD survey of galaxies belonging or projected onto the Coma and Hercules Superclusters, to the A262 and Cancer clusters, we present isophote maps and photometric profiles in the Johnson system of 111 galaxies (67 in the V and B bands, 42 only in V, 2 only in B) obtained with the 2.1m telescope at San Pedro Martir (Baja California, Mexico). (2 data files).

The Meteoroid Fluence at Mars Due to Comet Siding Spring

NASA Technical Reports Server (NTRS)

Moorhead, Althea V.

2014-01-01

Long-period comet C/2013 A1 (Siding Spring) is headed for a close encounter with Mars on 2014 Oct 19. A collision between the comet and the planet has been ruled out, but the comets coma may envelop Mars and its man-made satellites. We present an analytic model of the dust component of cometary comae that describes the spatial distribution of cometary dust and meteoroids and their size distribution. If the coma reaches Mars, we estimate a total incident particle fluence on the planet and its satellites of 0.01 particles per square meter. We compare our model with numerical simulations, data from past comet missions, and recent Siding Spring observations.

[The myxoedema coma exists, we met it].

PubMed

Fritsch, N; Tran-Van, D; Dardare, E; Gentile, A; Deroudilhe, G; Fontaine, B

2007-09-01

The myxoedema coma corresponds to the ultimate evolution of a hypothyroidism and is characterized by a major deficit in thyroid hormones responsible for a collapse of the metabolism. The preventive and curative treatment is based on the administration of thyroid hormones, whose benefits are opposed to the cardiovascular risks related to an iatrogenic hyperthyroidism for patients often old with cardiopathy. We report the case of a 92-year-old patient with unbalanced hypothyroidism and chronic cardiac deficiency, who presented a myxoedema coma in the postoperative period of an urgent digestive surgery. This observation illustrates the difficulties in treating patients with unbalanced hypothyroidism following emergency surgery, in the absence of consensus on the type and the amounts of thyroid hormones substitution.

Modern Observational Techniques for Comets

NASA Technical Reports Server (NTRS)

Brandt, J. C. (Editor); Greenberg, J. M. (Editor); Donn, B. (Editor); Rahe, J. (Editor)

1981-01-01

Techniques are discussed in the following areas: astrometry, photometry, infrared observations, radio observations, spectroscopy, imaging of coma and tail, image processing of observation. The determination of the chemical composition and physical structure of comets is highlighted.

Disruption of posteromedial large-scale neural communication predicts recovery from coma

PubMed Central

de Pasquale, Francesco; Vuillaume, Corine; Riu, Beatrice; Loubinoux, Isabelle; Geeraerts, Thomas; Seguin, Thierry; Bounes, Vincent; Fourcade, Olivier; Demonet, Jean-Francois; Péran, Patrice

2015-01-01

Objective: We hypothesize that the major consciousness deficit observed in coma is due to the breakdown of long-range neuronal communication supported by precuneus and posterior cingulate cortex (PCC), and that prognosis depends on a specific connectivity pattern in these networks. Methods: We compared 27 prospectively recruited comatose patients who had severe brain injury (Glasgow Coma Scale score <8; 14 traumatic and 13 anoxic cases) with 14 age-matched healthy participants. Standardized clinical assessment and fMRI were performed on average 4 ± 2 days after withdrawal of sedation. Analysis of resting-state fMRI connectivity involved a hypothesis-driven, region of interest–based strategy. We assessed patient outcome after 3 months using the Coma Recovery Scale–Revised (CRS-R). Results: Patients who were comatose showed a significant disruption of functional connectivity of brain areas spontaneously synchronized with PCC, globally notwithstanding etiology. The functional connectivity strength between PCC and medial prefrontal cortex (mPFC) was significantly different between comatose patients who went on to recover and those who eventually scored an unfavorable outcome 3 months after brain injury (Kruskal-Wallis test, p < 0.001; linear regression between CRS-R and PCC-mPFC activity coupling at rest, Spearman ρ = 0.93, p < 0.003). Conclusion: In both etiology groups (traumatic and anoxic), changes in the connectivity of PCC-centered, spontaneously synchronized, large-scale networks account for the loss of external and internal self-centered awareness observed during coma. Sparing of functional connectivity between PCC and mPFC may predict patient outcome, and further studies are needed to substantiate this potential prognosis biomarker. PMID:26561296

Disruption of posteromedial large-scale neural communication predicts recovery from coma.

PubMed

Silva, Stein; de Pasquale, Francesco; Vuillaume, Corine; Riu, Beatrice; Loubinoux, Isabelle; Geeraerts, Thomas; Seguin, Thierry; Bounes, Vincent; Fourcade, Olivier; Demonet, Jean-Francois; Péran, Patrice

2015-12-08

We hypothesize that the major consciousness deficit observed in coma is due to the breakdown of long-range neuronal communication supported by precuneus and posterior cingulate cortex (PCC), and that prognosis depends on a specific connectivity pattern in these networks. We compared 27 prospectively recruited comatose patients who had severe brain injury (Glasgow Coma Scale score <8; 14 traumatic and 13 anoxic cases) with 14 age-matched healthy participants. Standardized clinical assessment and fMRI were performed on average 4 ± 2 days after withdrawal of sedation. Analysis of resting-state fMRI connectivity involved a hypothesis-driven, region of interest-based strategy. We assessed patient outcome after 3 months using the Coma Recovery Scale-Revised (CRS-R). Patients who were comatose showed a significant disruption of functional connectivity of brain areas spontaneously synchronized with PCC, globally notwithstanding etiology. The functional connectivity strength between PCC and medial prefrontal cortex (mPFC) was significantly different between comatose patients who went on to recover and those who eventually scored an unfavorable outcome 3 months after brain injury (Kruskal-Wallis test, p < 0.001; linear regression between CRS-R and PCC-mPFC activity coupling at rest, Spearman ρ = 0.93, p < 0.003). In both etiology groups (traumatic and anoxic), changes in the connectivity of PCC-centered, spontaneously synchronized, large-scale networks account for the loss of external and internal self-centered awareness observed during coma. Sparing of functional connectivity between PCC and mPFC may predict patient outcome, and further studies are needed to substantiate this potential prognosis biomarker. © 2015 American Academy of Neurology.

Human Brain Activity Patterns beyond the Isoelectric Line of Extreme Deep Coma

PubMed Central

Kroeger, Daniel; Florea, Bogdan; Amzica, Florin

2013-01-01

The electroencephalogram (EEG) reflects brain electrical activity. A flat (isoelectric) EEG, which is usually recorded during very deep coma, is considered to be a turning point between a living brain and a deceased brain. Therefore the isoelectric EEG constitutes, together with evidence of irreversible structural brain damage, one of the criteria for the assessment of brain death. In this study we use EEG recordings for humans on the one hand, and on the other hand double simultaneous intracellular recordings in the cortex and hippocampus, combined with EEG, in cats. They serve to demonstrate that a novel brain phenomenon is observable in both humans and animals during coma that is deeper than the one reflected by the isoelectric EEG, and that this state is characterized by brain activity generated within the hippocampal formation. This new state was induced either by medication applied to postanoxic coma (in human) or by application of high doses of anesthesia (isoflurane in animals) leading to an EEG activity of quasi-rhythmic sharp waves which henceforth we propose to call ν-complexes (Nu-complexes). Using simultaneous intracellular recordings in vivo in the cortex and hippocampus (especially in the CA3 region) we demonstrate that ν-complexes arise in the hippocampus and are subsequently transmitted to the cortex. The genesis of a hippocampal ν-complex depends upon another hippocampal activity, known as ripple activity, which is not overtly detectable at the cortical level. Based on our observations, we propose a scenario of how self-oscillations in hippocampal neurons can lead to a whole brain phenomenon during coma. PMID:24058669

Chandra Observations of Comet 2P/Encke 2003: First Detection of a Collisionally Thin, Fast Solar Wind Charge Exchange System

NASA Technical Reports Server (NTRS)

Lisse, C. M.; Christian, D. J.; Deneri, K.; Wolk, S. J.; Bodewits, D.; Hoekstra, R.; Combi, M. R.; Makinen, T.; Dryer, M.; Fry, C. D.;

HUT observations of carbon monoxide in the coma of Comet Levy (1990c)

NASA Technical Reports Server (NTRS)

Feldman, P. D.; Davidsen, A. F.; Blair, W. P.; Bowers, C. W.; Dixon, W. V.; Durrance, S. T.; Henry, R. C.; Kriss, G. A.; Kruk, J.; Moos, H. W.

1991-01-01

Observations of comet Levy (1990c) were made with the Hopkins Ultraviolet Telescope during the Astro-1 Space Shuttle mission on 10 Dec. 1990. The spectrum, covering the wavelength range 415 to 1850 A at a spectral emission of 3 A (in first order), shows the presence of carbon monoxide and atomic hydrogen, carbon, and sulfur in the coma. Aside from H I Lyman-beta, no cometary features are detected below 1200 A, although cometary O I and O II would be masked by the same emissions present in the day airglow spectrum. The 9.4 x 116 arcsec aperture corresponds to 12,000 x 148,000 km at the comet. The derived production rate of CO relative to water, 0.13 + or - 0.02, compared with the same ratio derived from IUE observations (made in Sep. 1990) which sample a much smaller region of the coma, 0.04 + or - 0.01, suggests the presence of an extended source of CO, as was found in comet Halley. Upper limits on Ne and Ar abundance are within an order of magnitude or solar abundances.

The Activity of Comet 67P/Churyumov-Gerasimenko as Seen by Rosetta/OSIRIS

NASA Astrophysics Data System (ADS)

Sierks, H.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Rickman, H.; Koschny, D.

2015-12-01

The Rosetta mission of the European Space Agency arrived on August 6, 2014, at the target comet 67P/Churyumov-Gerasimenko. OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) is the scientific imaging system onboard Rosetta. OSIRIS consists of a Narrow Angle Camera (NAC) for the nucleus surface and dust studies and a Wide Angle Camera (WAC) for the wide field gas and dust coma investigations. OSIRIS observed the coma and the nucleus of comet 67P/C-G during approach, arrival, and landing of PHILAE. OSIRIS continued comet monitoring and mapping of surface and activity in 2015 with close fly-bys with high resolution and remote, wide angle observations. The scientific results reveal a nucleus with two lobes and varied morphology. Active regions are located at steep cliffs and collapsed pits which form collimated gas jets. Dust is accelerated by the gas, forming bright jet filaments and the large scale, diffuse coma of the comet. We will present activity and surface changes observed in the Northern and Southern hemisphere and around perihelion passage.

Chemical Recycling of Molecules in Cometary Comae

NASA Astrophysics Data System (ADS)

Boice, Daniel C.; Kawakita, Hideyo; Shinnaka, Yoshiharu; Kobayashi, Hitomi

2015-08-01

Modeling is essential to understand the important physical and chemical processes that occur in cometary comae, especially the relationship between native and sibling molecules, such as, HCN and CN. Photochemistry is a major source of ions and electrons that further initiate key gas-phase reactions, leading to the plethora of molecules and atoms observed in comets. The effects of photoelectrons that react via impacts are important to the overall ionization in the inner coma. We have found that many molecules undergo protonation reactions with primarily water, followed by electron recombination resulting in the original molecules in a vibrationally excited state. These excited molecules spontaneously emit photons back to the ground state. We identify this series of reactions as chemical “recycling.” We discuss the importance of this mechanism for HCN, NH3, and water in comets. We also identify other relevant processes in the collision-dominated, inner coma of a comet within a global modeling framework to better understand observations and in situ measurements of cometary species, especially relationships between native and sibling molecules for the Rosetta Mission to Comet 67P/Churyumov-Gerasimenko.Acknowledgements: We appreciate support from the NSF Planetary Astronomy Program under Grant No. 0908529. This program is partially supported by the MEXT Supported Program for the Strategic Research Foundation at Private Universities, 2014-2018.

Wake-promoting actions of median nerve stimulation in TBI-induced coma: An investigation of orexin-A and orexin receptor 1 in the hypothalamic region.

PubMed

Zhong, Ying-Jun; Feng, Zhen; Wang, Liang; Wei, Tian-Qi

2015-09-01

A coma is a serious complication, which can occur following traumatic brain injury (TBI), for which no effective treatment has been established. Previous studies have suggested that neural electrical stimulation, including median nerve stimulation (MNS), may be an effective method for treating patients in a coma, and orexin‑A, an excitatory hypothalamic neuropeptide, may be involved in wakefulness. However, the exact mechanisms underlying this involvement remain to be elucidated. The present study aimed to examine the arousal‑promoting role of MNS in rats in a TBI‑induced coma and to investigate the potential mechanisms involved. A total of 90 rats were divided into three groups, comprising a control group, sham‑stimulated (TBI) group and a stimulated (TBI + MNS) group. MNS was performed on the animals, which were in a TBI‑induced comatose state. Changes in the behavior of the rats were observed following MNS. Subsequently, hypothalamic tissues were extracted from the rats 6, 12 and 24 h following TBI or MNS, respectively. The expression levels of orexin‑A and orexin receptor‑1 (OX1R) in the hypothalamus were examined using immunohistochemistry, western blotting and an enzyme‑linked immunosorbent assay. The results demonstrated that 21 rats subjected to TBI‑induced coma exhibited a restored righting reflex and response to pain stimuli following MNS. In addition, ignificant differences in the expression levels of orexin‑A and OXIR were observed among the three groups and among the time‑points. Orexin‑A and OX1R were upregulated following MNS. The rats in the stimulated group reacted to the MNS and exhibited a re‑awakening response. The results of the present study indicated that MNS may be a therapeutic option for TBI‑induced coma. The mechanism may be associated with increasing expression levels of the excitatory hypothalamic neuropeptide, orexin-A, and its receptor, OX1R, in the hypothalamic region.

Cometary ion dynamics observed in the close vicinity of comet 67P/Churyumov-Gerasimenko during the intermediate activity period

NASA Astrophysics Data System (ADS)

Berčič, L.; Behar, E.; Nilsson, H.; Nicolaou, G.; Wieser, G. Stenberg; Wieser, M.; Goetz, C.

2018-06-01

Aims: Cometary ions are constantly produced in the coma, and once produced they are accelerated and eventually escape the coma. We describe and interpret the dynamics of the cometary ion flow, of an intermediate active comet, very close to the nucleus and in the terminator plane. Methods: We analysed in situ ion and magnetic field measurements, and characterise the velocity distribution functions (mostly using plasma moments). We propose a statistical approach over a period of one month. Results: On average, two populations were observed, separated in phase space. The motion of the first is governed by its interaction with the solar wind farther upstream, while the second one is accelerated in the inner coma and displays characteristics compatible with an ambipolar electric field. Both populations display a consistent anti-sunward velocity component. Conclusions: Cometary ions born in different regions of the coma are seen close to the nucleus of comet 67P/Churyumov-Gerasimenko with distinct motions governed in one case by the solar wind electric field and in the other case by the position relative to the nucleus. A consistent anti-sunward component is observed for all cometary ions. An asymmetry is found in the average cometary ion density in a solar wind electric field reference frame, with higher density in the negative (south) electric field hemisphere. There is no corresponding signature in the average magnetic field strength.

Compressed spectral arrays of patients with fulminant hepatic failure in hepatic coma undergoing liver transplantation.

PubMed

Takeichi, Takayuki; Asonuma, Katsuhiro; Kim, Ildeok; Inomata, Yukihiro; Kasahara, Mureo; Ohwada, Susumu; Morishita, Yasuo; Tanaka, Koichi

2002-08-01

Assessing the coma status of patients with fulminant hepatic failure (FHF) is important for determining the reversibility of brain damage and for properly timing liver transplantation. The compressed spectral array (CSA) method is a frequency analysis technique that processes electroencephalogram signals by computer to facilitate on-line interpretation. This method has been used to monitor the consciousness levels of neurointensive care unit patients. In this study, we determined whether CSA could be used to assess the coma status of patients with FHF, and whether CSA provided information that was useful in deciding when to proceed with liver transplantation. CSA recording was carried out in 17 FHF patients with encephalopathy (coma grade III-IV) who underwent living-related liver transplantation between August 1997 and May 1999. Recording was performed with a Neuromonitor OEE-72044 (NIHON KOHDEN, Osaka, Japan) every 24 h before and after transplantation, until the patients regained consciousness. The CSAs of healthy controls were distributed almost equally between 0 and 16 Hz. The CSAs of FHF patients in hepatic coma were classified into three patterns. Eight of the 17 patients showed very prominent slow waves of about 2 Hz (group A), and seven patients showed strongly suppressed rapid waves between 8 and 16 Hz (group B). The remaining two patients showed CSA patterns that were similar to those of healthy controls, even though these patients were comatose (group C). Abnormal CSA patterns were observed in 15 of the 17 patients (88%). Group B patients seemed to have higher coma grades than did group A patients. Sixteen patients underwent liver transplantation, completely recovered from hepatic encephalopathy, and subsequently showed CSA patterns similar to those of healthy controls. One patient died without regaining consciousness. These results suggest that CSA is useful in assessing the coma status of FHF patients and in evaluating electrophysiological recovery from hepatic coma after liver transplantation.

Delirium and coma evaluated in mechanically ventilated patients in the intensive care unit in Japan: a multi-institutional prospective observational study.

PubMed

Tsuruta, Ryosuke; Oda, Yasutaka; Shintani, Ayumi; Nunomiya, Shin; Hashimoto, Satoru; Nakagawa, Takashi; Oida, Yasuhisa; Miyazaki, Dai; Yabe, Shigemi

2014-06-01

The object of this study is to evaluate the prevalence and effects of delirium on 28-day mortality in critically ill patients on mechanical ventilation in Japan. Prospective cohort study was conducted in medical and surgical intensive care units (ICUs) of 24 medical centers. Patients were followed up daily for delirium during ICU stay after enrollment. Coma was defined with the Richmond Agitation Sedation Scale score of -4 or -5. Delirium was diagnosed using the Confusion Assessment Method for the ICU. The Cox proportional hazards regression model was used to assess the effects of delirium and coma on 28-day mortality, time to extubation, and time to ICU discharge; delirium and coma were included as time-varying covariates after controlling for age, Acute Physiology and Chronic Health Evaluation II score, ventilator-associated pneumonia, and the reason for intubation with infection. Of 180 patients, 115 patients (64%) developed delirium. Moreover, 15 patients (8%) died within 28 days after ICU admission, including 7 patients who experienced coma and 8 patients who experienced both coma and delirium. There were no deaths among patients who did not experience coma. Delirium was associated with a shorter time to extubation (hazard ratio [HR], 2.52; 95% confidence interval [CI], 1.65-3.85; P<.001) and a shorter ICU length of stay in comatose patients (HR, 1.59; 95% CI, 1.04-2.44; P=.034), whereas delirium appeared with prolonged time to ICU discharge among patients without coma, although statistical significance was not detected due to limited analytical power (HR, 0.62; 95% CI, 0.34-1.12; P=.114). Delirium during ICU stay was not associated with higher mortality. Further study is needed to investigate the discrepancy between these and previous data. Copyright © 2014 Elsevier Inc. All rights reserved.

Coma and vegetative states: state of the art and proposal of a novel approach combining existing coma scales.

PubMed

Bonsignore, Luca Tommaso; Macrì, Simone; Orsi, Paolo; Chiarotti, Flavia; Alleva, Enrico

2014-01-01

Brain damage of various aetiologies can lead to different disorders of consciousness (DOC), varying from coma to vegetative, to minimally conscious states. Each state is characterised by a different degree of wakefulness, awareness, pain sensitivity and is differentially handled with respect to treatment, ethical considerations and end-oflife decisions. Thus, its correct identification is crucial while devising or modulating appropriate treatment strategies. Actually, the main coma scales cannot always accurately determine the state of consciousness of an individual, while other tools (e.g. imaging techniques) present a certain degree of uncertainty. A complementary approach may be constituted by a 24-hour observation of patients, for a sufficient period of days, using an ad hoc behavioural scale, further correlated with physiological and pharmacological parameters measured on patients. The method herein described might help recognising the presence of consciousness of the different DOC patients, and thus discerning a vegetative from a minimally conscious state.

MIRO Observation of Comet C/2002 T7 (LINEAR) Water Line Spectrum

NASA Technical Reports Server (NTRS)

Lee, Seungwon; Frerking, Margaret; Hofstadter, Mark; Gulkis, Samuel; von Allmen, Paul; Crovisier, Jaques; Biver, Nicholas; Bockelee-Morvan, Dominique

2011-01-01

Comet C/2002 T7 (LINEAR) was observed with the Microwave Instrument for Rosetta Orbiter (MIRO) on April 30, 2004, between 5 hr and 16 hr UT. The comet was 0.63AU distance from the Sun and 0.68AU distance from the MIRO telescope at the time of the observations. The water line involving the two lowest rotational levels at 556.936 GHz is observed at 557.070 GHz due to a large Doppler frequency shift. The detected water line spectrum is interpreted using a non local thermal equilibrium (Non-LTE) molecular excitation and radiative transfer model. Several synthetic spectra are calculated with various coma profiles that are plausible for the comet at the time of observations. The coma profile is modeled with three characteristic parameters: outgassing rate, a constant expansion velocity, and a constant gas temperature. The model calculation result shows that for the distant line observation where contributions from a large coma space is averaged, the combination of the outgassing rate and the gas expansion velocity determines the line shape while the gas temperature has a negligible effect. The comparison between the calculated spectra and the MIRO measured spectrum suggests that the outgassing rate of the comet is about 2.0x1029 molecules/second and its gas expansion velocity about 1.2 km/s at the time of the observations.

The Dependence of the Circumnuclear Coma Structure on the Properties of the Nucleus. IV. Structure of the Night-Side Gas Coma of a Strongly Sublimating Nucleus

NASA Astrophysics Data System (ADS)

Crifo, J. F.; Rodionov, A. V.

2000-12-01

The structure of the nightside coma in the vicinity of a strongly active comet nucleus of pure ice is investigated by solving gasdynamic equations for the flow of water vapour sublimated from—or condensed onto—the nucleus surface. To guarantee the physical validity of the solution, both Euler and Navier-Stokes Equations are solved, and the solutions are compared. A spherical nucleus is considered first and then a triaxial ellipsoidal nucleus. The results show that (1) a fluid coma of significant extent and very complicated physical structure is formed; (2) for low heat conduction transfer across the nucleus from the dayside to the nightside surface, a narrow conical weak shock appears near to the antisolar axis; the whole nightside surface acts as a cold trap for the vapor, part of which recondenses onto it; (3) for intermediate heat conduction, part of the nightside surface becomes weakly sublimating, and a different weak shock pattern is formed; and (4) at high heat conduction, the whole nightside surface is weakly sublimating, and the resulting flow pattern becomes similar to that existing in a coma formed by diffusion from the nucleus interior (see Crifo, Rodionov and Bockelée-Morvan, 1999, Icarus138, 83-106). The results are compared to related model results by other authors, and a discussion is made of their relevance to the 1996 observation of the near-nucleus nightside coma of Comet C/1996 B2 Hyakutake.

The Dragonfly Nearby Galaxies Survey. II. Ultra-Diffuse Galaxies near the Elliptical Galaxy NGC 5485

NASA Astrophysics Data System (ADS)

Merritt, Allison; van Dokkum, Pieter; Danieli, Shany; Abraham, Roberto; Zhang, Jielai; Karachentsev, I. D.; Makarova, L. N.

2016-12-01

We present the unexpected discovery of four ultra-diffuse galaxies (UDGs) in a group environment. We recently identified seven extremely low surface brightness galaxies in the vicinity of the spiral galaxy M101, using data from the Dragonfly Telephoto Array. The galaxies have effective radii of 10″-38″ and central surface brightnesses of 25.6-27.7 mag arcsec-2 in the g-band. We subsequently obtained follow-up observations with HST to constrain the distances to these galaxies. Four remain persistently unresolved even with the spatial resolution of HST/ACS, which implies distances of D\\gt 17.5 Mpc. We show that the galaxies are most likely associated with a background group at ˜27 Mpc containing the massive ellipticals NGC 5485 and NGC 5473. At this distance, the galaxies have sizes of 2.6-4.9 kpc, and are classified as UDGs, similar to the populations that have been revealed in clusters such as Coma, Virgo, and Fornax, yet even more diffuse. The discovery of four UDGs in a galaxy group demonstrates that the UDG phenomenon is not exclusive to cluster environments. Furthermore, their morphologies seem less regular than those of the cluster populations, which may suggest a different formation mechanism or be indicative of a threshold in surface density below which UDGs are unable to maintain stability.

A search for frosts in Comet Bowell /1980b/

NASA Technical Reports Server (NTRS)

Campins, H.; Lebofsky, L. A.; Rieke, G. H.; Lebofsky, M. J.

1982-01-01

Infrared observations of Comet Bowell represent the first search for frost signatures in a comet beyond 2 AU from the sun. Broad- and narrowband photometry has been obtained as well as CVF spectrophotometry of this comet and there is no evidence for absorption features in the spectral area between 1.25 and 2.3 microns. Models of the coma have been generated which constrain the volatile content of the grains an; are in agreement with the observed albedo. The darkness of the coma particles at large heliocentric distances indicates a low albedo nucleus as well. Brightness variations during the observing period seem to indicate an active nucleus at 4.5 AU from the sun.

Modelling observations of the inner gas and dust coma of comet 67P/Churyumov-Gerasimenko using ROSINA/COPS and OSIRIS data: First results

NASA Astrophysics Data System (ADS)

Marschall, R.; Su, C. C.; Liao, Y.; Thomas, N.; Altwegg, K.; Sierks, H.; Ip, W.-H.; Keller, H. U.; Knollenberg, J.; Kührt, E.; Lai, I. L.; Rubin, M.; Skorov, Y.; Wu, J. S.; Jorda, L.; Preusker, F.; Scholten, F.; Gracia-Berná, A.; Gicquel, A.; Naletto, G.; Shi, X.; Vincent, J.-B.

2016-05-01

Context. This paper describes the initial modelling of gas and dust data acquired in August and September 2014 from the European Space Agency's Rosetta spacecraft when it was in close proximity to the nucleus of comet 67P/Churyumov-Gerasimenko. Aims: This work is an attempt to provide a self-consistent model of the innermost gas and dust coma of the comet, as constrained by the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) data set for the gas and by the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) data set for the dust. Methods: The model uses a previously developed shape model for the nucleus, and from this the water sublimation rate and gas temperatures at the surface are computed with a simple thermal model. The gas expansion is modelled with a 3D parallel implementation of a Direct Simulation Monte Carlo algorithm. A dust drag algorithm is then used to produce dust densities in the coma, which are then converted to brightnesses using Mie theory and a line-of-sight integration. Results: We show that a purely insolation-driven model for surface outgassing does not produce a reasonable fit to ROSINA/COPS data. A stronger source in the "neck" region of the nucleus (region Hapi) is needed to match the observed modulation of the gas density in detail. This agrees with OSIRIS data, which shows that the dust emission from the "neck" was dominant in the August-September 2014 time frame. The current model matches this observation reasonably if a power index of 2-3 for the dust size distribution is used. A better match to the OSIRIS data is seen by using a single large particle size for the coma. Conclusions: We have shown possible solutions to the gas and dust distributions in the inner coma, which are consistent with ROSINA and OSIRIS data.

Involuntary movements and coma as the prognostic marker for acute encephalopathy with biphasic seizures and late reduced diffusion.

PubMed

Lee, Sooyoung; Sanefuji, Masafumi; Torio, Michiko; Kaku, Noriyuki; Ichimiya, Yuko; Mizuguchi, Soichi; Baba, Haruhisa; Sakai, Yasunari; Ishizaki, Yoshito; Torisu, Hiroyuki; Kira, Ryutaro; Hara, Toshiro; Ohga, Shouichi

2016-11-15

Acute encephalopathy with biphasic seizures and late reduced diffusion (AESD) occurs in children associated with infection. It is characterized by a prolonged febrile seizure in the first phase, and a cluster of seizures, deterioration of consciousness and the white matter lesions with reduced diffusion in the second phase. The patients often have severe neurological sequelae, but the prognostic indicators remain unknown. The present study aimed to clarify the characteristics of AESD patients who subsequently exhibited severe neurological sequelae. We retrospectively analyzed the clinical and laboratory findings along with the brain imaging in patients who had severe (n=8) and non-severe neurodevelopmental outcomes (n=12). Severe group more frequently showed coma (p=0.014) or involuntary movements including dystonia and oral dyskinesia (p=0.018) before the second phase than non-severe group. Severe group exhibited higher levels of serum alanine aminotransferase than non-severe group (p=0.001). Quantitatively assessed MRI in the second phase revealed that severe group had more extensive lesions than non-severe group, in the anterior (p=0.015) and posterior parts (p=0.011) of the cerebrum and basal ganglia (p=0.020). Early appearing involuntary movements or coma might account for the extension of acute brain lesions and the poor neurological outcomes in AESD patients. Copyright © 2016 Elsevier B.V. All rights reserved.

Millimeter and Submillimeter Observations of comet 67P/C-G with the MIRO Instrument

NASA Astrophysics Data System (ADS)

Hofstadter, Mark D.; Allen, Mark; von Allmen, Paul; Beaudin, Gerard; Biver, Nicolas; Bockelee-Morvan, Dominique; Choukroun, Mathieu; Crovisier, Jacques; Encrenaz, Pierre; Encrenaz, Therese; Frerking, Margaret; Gulkis, Samuel; Hartogh, Paul; Ip, Wing; Janssen, Michael; Jarchow, Christopher; Kamp, Lucas; Keihm, Stephen; Lee, Seungwon; Lellouch, Emmanuel; Leyrat, Cedric; Rezac, Ladislav; Schloerb, Frederick P.; Spilker, Thomas

2014-11-01

The Microwave Instrument for the Rosetta Orbiter (MIRO) makes millimeter and submillimeter observations of the nucleus and coma of Rosetta's target comet. This presentation summarizes the instrument and its observations, with details presented in later talks. MIRO makes continuum measurements at 190 and 563 GHz (1.6 and 0.5 mm) to study the thermal and electrical properties of the nucleus near-surface (depths from ~1 millimeter to 10 centimeters). MIRO also makes spectroscopic measurements of 8 lines near 560 GHz (H2O, H217O, H218O, CO, NH3, and three CH3OH transitions). The abundance, gas velocity, and temperature of those species are measured as functions of time and location. To interpret its data, the MIRO team has developed sophisticated nucleus and coma models. Our goal is to understand the dominant physical processes that create the coupled nucleus-coma system. MIRO has clearly detected water in the coma since 6 June 2014 (heliocentric distance 3.9 AU). Water production varies both with location on the nucleus and time-of-day. We also see an overall increase in production as the comet approaches the Sun. At the time of this writing, only H2O and H218O have been detected by MIRO. Our analysis of spectral data uses a non-LTE coma model, accounting for the boundary layer at the nucleus, regions dominated by gas collisions, electron collisions, and radiative processes. MIRO's continuum channels have detected the nucleus since 19 July 2014, and it has been spatially resolved since early August. Initial results are consistent with a very low thermal inertia surface, as expected for a porous, dusty layer. We expect to provide information on spatial variability of nucleus properties at the meeting. MIRO has developed a 3-D nucleus thermal/radiative model to assist in observation planning and interpretation. In addition to its science objectives, MIRO provides information in support of spacecraft operations. Measurements help predict the gas drag on the spacecraft, and were used in determining the shape of un-illuminated regions of the nucleus and in selecting possible landing sites.

The Geometry and Origin of Ultra-diffuse Ghost Galaxies

NASA Astrophysics Data System (ADS)

Burkert, A.

2017-04-01

The geometry and intrinsic ellipticity distribution of ultra-diffuse galaxies (UDG) is determined from the line-of-sight distribution of axial ratios q of a large sample of UDGs, detected by Koda et al. in the Coma cluster. With high significance, the data rules out an oblate, disk-like geometry, characterized by major axes a = b > c. The data is, however, in good agreement with prolate shapes, corresponding to a = b < c. This indicates that UDGs are not thickened, rotating, axisymmetric disks, puffed up by violent processes. Instead, they are anisotropic elongated cigar- or bar-like structures, similar to the prolate dwarf spheroidal galaxy population of the Local Group. The intrinsic distribution of axial ratios of the Coma UDGs is flat in the range of 0.4 ≤ a/c ≤ 0.9 with a mean value of < a/c> =0.65+/- 0.14. This might provide important constraints for theoretical models of their origin. Formation scenarios that could explain the extended prolate nature of UDGs are discussed.

A revised catalog of CfA galaxy groups in the Virgo/Great Attractor flow field

NASA Technical Reports Server (NTRS)

Nolthenius, Richard

1993-01-01

A new identification of groups and clusters in the CfAl Catalog of Huchra, et al. (1983) is presented, using a percolation algorithm to identify density enhancements. The procedure differs from that of the original Geller and Huchra (1983; GH) catalog in several important respects; galaxy distances are calculated from the Virgo-Great Attractor flow model of Faber and Burnstein (1988), the adopted distance linkage criteria is only approx. 1/4 as large as in the Geller and Huchra catalog, the sky link relation is taken from Nolthenius and White (1987), correction for interstellar extinction is included, and 'by-hand' adjustments to group memberships are made in the complex regions of Virgo/Coma I/Ursa Major and Coma/A1367 (to allow for varying group velocity dispersions and to trim unphysical 'spider arms'). Since flow model distances are poorly determined in these same regions, available distances from the IR Tully-Fisher planetary nebula luminosity function and surface brightness resolution methods are adopted if possible.

Summer outbursts in the coma of 67P/Churyumov-Gerasimenko as observed by VIRTIS-M

NASA Astrophysics Data System (ADS)

Rinaldi, G.; Bockelee-Morvan, D.; Ciarniello, M.; Tozzi, G. P.; Capaccioni, F.; Filacchione, G.; Fink, U.; Doose, L.; Raponi, A.; Capria, M. T.; Erard, S.; Leyrat, C.; Longobardo, A.; Taylor, F.

2017-09-01

In this work, we present an analysis of the outbursts observed by VIRTIS-M for the dates of August 10, September 13 and 14 2015, when the comet was at heliocentric distances of -1.2 AU (inbound) to 1.3 AU (outbound), 2 day before and one month after the perihelion passage respectively. They are characterized by a sudden and short increase of the dust emission, from localized areas with variable degree of collimation, followed by a sweet decrease of activity. The lifetime is between 5 and 15 minutes and the corresponding radiance at 0.55 μm is typically of the order of 10-2 - 1 Watt/m2/str/μm, i.e. 10-20 times larger than the surrounding coma. VIRTIS-M identified 2 main dust plumes morphologies associated to these events: a narrow jet and a broad plumes. We found clear evidence of different colour values in the ouburst with respect to the surrounding coma. This implies that we observed dust with different physical characteristics both in the structures and in the coma. The comparison between IR (VIRTIS-H) and VIS (VIRTISM) observations allows to derive the projected velocity of the small dust grain obtaining 23 -40 m/s. It is also possible to estimate the total mass loss in the outburst, by converting the radiance over an image to a dust cross section, and then to mass assuming a dust size distribution with a power law index of -3. For September 14 large event we estimated a total ejected dust mass of few tens tons as found by Vincent et al. 2016.

Spatial variations of brightness, colour and polarization of dust in comet 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Rosenbush, Vera K.; Ivanova, Oleksandra V.; Kiselev, Nikolai N.; Kolokolova, Ludmilla O.; Afanasiev, Viktor L.

2017-07-01

We present post-perihelion photometric and polarimetric observations of comet 67P/Churyumov-Gerasimenko performed at the 6-m telescope of the SAO RAS in the g-sdss (465/65 nm), r-sdss (620/60 nm) and R filters. Observations in November and December 2015 and April 2016 covered the range of heliocentric distance 1.62-2.72 au and phase angle 33.2°-10.4°. The comet was very active. Two persistent jets and long dust tail were observed during the whole observing period; one more jet was detected only in December. The radial profiles of surface brightness, colour and polarization significantly differed for the coma, jets and tail, and changed with increasing heliocentric distance. The dust production Afρ decreased from 162 cm at r = 1.62 au to 51 cm at r = 2.72 au. The dust colour (g-r) gradually changed from 0.8 mag in the innermost coma to about 0.4 mag in the outer coma. The spectral slope was 8.2 ± 1.7 per cent/100 nm in the 465 to 620 nm wavelength domain. In November and December, the polarization in the near-nucleus area was about 8 per cent, dropped sharply to 2 per cent at the distance above 5000 km and then gradually increased with distance from the nucleus, reaching ˜8 per cent at 40 000 km. In April, at a phase angle 10.4°, the polarization varied between -0.6 per cent in the near-nucleus area and -4 per cent in the outer coma. Circular polarization was not detected in the comet. The spatial variations of brightness, colour and polarization in different structural features suggest some evolution of particle properties, most likely decreasing the size of dust particles.

Abnormal intra-aural pressure waves associated with death in African children with acute nontraumatic coma.

PubMed

Gwer, Samson; Kazungu, Michael; Chengo, Eddie; Ohuma, Eric O; Idro, Richard; Birch, Tony; Marchbanks, Robert; Kirkham, Fenella J; Newton, Charles R

2015-07-01

We explored the relationship between tympanic membrane displacement (TMD) measurements, a tool to monitor intracranial pressure noninvasively, and clinical features and death in children with acute coma in Kilifi, Kenya. Between November 2007 and September 2009, we made serial TMD measurements and clinical observations on children with acute coma (Blantyre coma score (BCS) ≤ 2) on the pediatric high dependency unit of Kilifi District Hospital, and on well children presenting to the hospital's outpatient department for routine follow-up. We examined middle ear function using tympanometry and measured cardiac pulse (CPA) and respiratory pulse pressure amplitudes (RPA) using the TMD analyzer. We recruited 75 children (32 (43%) females; median age 3.3 (IQR: 2.0, 4.3) years). Twenty-one (28%) children died. Higher TMD measurements predicted death. Adjusting for diagnosis, every 50 nl rise in both semirecumbent and recumbent CPA was associated with increased odds of death associated with intracranial herniation (OR: 1.61, 95% confidence interval (CI): 1.07, 2.41; P = 0.02 and OR: 1.35, 95% CI: 1.10, 1.66; P ≤ 0.01 respectively). Raised TMD pulse pressure measurements are associated with death and may be useful in detecting and monitoring risk of intracranial herniation and intracranial pressure in childhood coma.

Observing Interstellar and Intergalactic Magnetic Fields

NASA Astrophysics Data System (ADS)

Han, J. L.

2017-08-01

Observational results of interstellar and intergalactic magnetic fields are reviewed, including the fields in supernova remnants and loops, interstellar filaments and clouds, Hii regions and bubbles, the Milky Way and nearby galaxies, galaxy clusters, and the cosmic web. A variety of approaches are used to investigate these fields. The orientations of magnetic fields in interstellar filaments and molecular clouds are traced by polarized thermal dust emission and starlight polarization. The field strengths and directions along the line of sight in dense clouds and cores are measured by Zeeman splitting of emission or absorption lines. The large-scale magnetic fields in the Milky Way have been best probed by Faraday rotation measures of a large number of pulsars and extragalactic radio sources. The coherent Galactic magnetic fields are found to follow the spiral arms and have their direction reversals in arms and interarm regions in the disk. The azimuthal fields in the halo reverse their directions below and above the Galactic plane. The orientations of organized magnetic fields in nearby galaxies have been observed through polarized synchrotron emission. Magnetic fields in the intracluster medium have been indicated by diffuse radio halos, polarized radio relics, and Faraday rotations of embedded radio galaxies and background sources. Sparse evidence for very weak magnetic fields in the cosmic web is the detection of the faint radio bridge between the Coma cluster and A1367. Future observations should aim at the 3D tomography of the large-scale coherent magnetic fields in our Galaxy and nearby galaxies, a better description of intracluster field properties, and firm detections of intergalactic magnetic fields in the cosmic web.

Modeling of the VIRTIS-M Observations of the Coma of Comet 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Fougere, Nicolas; Combi, Michael R.; Tenishev, Valeriy; Bieler, Andre; Migliorini, Alessandra; Piccioni, Giuseppe; Capaccioni, Fabrizio; Filacchione, Gianrico; Toth, Gabor; Huang, Zhenguang; Gombosi, Tamas; Hansen, Kenneth; Bockelee-Morvan, Dominique; Debout, Vincent; Erard, Stephane; Leyrat, Cedric; Fink, Uwe; Rubin, Martin; Altwegg, Kathrin; Tzou, Chia-Yu; Le Roy, Lena; Calmonte, Ursina; Berthelier, Jean-Jacques; Reme, Henri; Hassig, Myrtha; Fuselier, Stephen; Fiethe, Bjorn; De Keyser, Johan

2015-11-01

The recent images of the inner coma of 67P/Churyumov-Gerasimenko (CG) made by the infrared channel of the VIRTIS-M instrument on board the Rosetta spacecraft show the gas distribution as it expands in the coma (Migliorini et al. 2015, DPS abstract).Since VIRTIS is a remote sensing instrument, a proper modeling of these observations requires the computation of the full coma of comet CG, which necessitates the use of a kinetic approach due to the rather low gas densities. Hence, we apply a Direct Simulation Monde Carlo (DSMC) method to solve the Boltzmann equation and describe CG’s coma from the nucleus surface up to a few hundreds of kilometers. The model uses the SHAP5 nucleus shape model from the OSIRIS team. The gas flux distribution takes into account solar illumination, including self-shadowing. The local activity at the surface of the nucleus is given by spherical harmonics expansion reproducing best the ROSINA-DFMS data. The densities from the DSMC model outputs are then integrated along the line-of-sight to create synthetic images that are directly comparable with the VIRTIS-M column density measurements.The good agreement between the observations and the model illustrates our continuously improving understanding of the physics of the coma of comet CG.AcknowledgementsWork at UofM was supported by contracts JPL#1266313, JPL#1266314 and NASA grant NNX09AB59G. Work at UoB was funded by the State of Bern, the Swiss National Science Foundation and by the European Space Agency PRODEX Program. Work at Southwest Research institute was supported by subcontract #1496541 from the JPL. Work at BIRA-IASB was supported by the Belgian Science Policy Office via PRODEX/ROSINA PEA 90020. The authors would like to thank ASI, CNES, DLR, NASA for supporting this research. VIRTIS was built by a consortium formed by Italy, France and Germany, under the scientific responsibility of the IAPS of INAF, which guides also the scientific operations. The consortium includes also the LESIA of the Observatoire de Paris, and the Institut für Planetenforschung of DLR. The authors wish to thank the RSGS and the RMOC for their continuous support.

Strategy for infrared photometry of comets with ISO

NASA Astrophysics Data System (ADS)

Solc, M.; Vanysek, V.; Gruen, E.

1994-07-01

The launch of the ISO (Infrared Satellite Observatory) by the European Space Agency is scheduled for autumn 1995. Photometry and spectrophotometry observing programs of comets in the wavelength range 2.5-200 microns for the onboard spectrophotometer ISOPHOT is now under final preparation. Technical details for preparing propasals are given. Phenomena in comets to be studied are surface properties of bare cometary nuclei at large heliocentric distances, onset of coma activity, and coma dust and gas emission (in inner solar system). Dust production, dust/gas mass ratio, dust distribution in coma, and their temporal variability are important for understanding the physical processes on nuclei, and spectrophotometry in the range of 2.5-12 microns could provide us with data of the chemical composition of cometary dust. Several active comets expected for the 18-month lifetime of ISO in 1995-1997 were selected for the ISO Central Program according to their orbital and physical parameters: P/Schwassman-Wachmann 1, P/Encke, P/d'Arrest, P/Honda-Mrkos-Pajdusakova, P/Churyumov-Gerasimenko, P/Kopff, P/IRAS, P/Wirtanen, P/Wild 2, P/Grigg-Skjellerup, P/Schwassman-Wachmann 3, P/Machholz, and (2060) Chiron. Four of them match well various constraints put on the observations by the technical arrangement of the satellite and instrument. A simple four-parameter model (size, albedo, rotation, optical thickness)was developed to estimate the temperatures and thermal fluxes of both solid nuclei and dust coma.

Gas Distributions in Comet ISON’s Coma: Concurrent Integral-Field Spectroscopy and Narrow-band Imaging.

NASA Astrophysics Data System (ADS)

Schmidt, Carl; Johnson, Robert E.; Baumgardner, Jeffrey; Mendillo, Michael

2014-11-01

At a solar distance of 0.44 AU, Oort cloud comet C/2012 S1 (ISON) exhibited an outburst phase that was observed by small telescopes at the McDonald Observatory. In conjunction with narrow-band (14Å) imaging over a wide-field, an image-slicer spectrograph ( 20,000) simultaneously measured the spatial distribution of ISON’s coma over a 1.6 x 2.7 arcminute field made up of 246 individual spectra. More than fifty emission lines from C2, NH2, CO, H2O+ and Na were observed within a single Echelle order spanning 5868Å to 5930Å. Spatial reconstructions of these species reveal that ISON’s coma was quite elongated several thousand km along the axis perpendicular to its motion. The ion tail appeared distinctly broader than the neutral Na tail, providing strong evidence that Na in the coma did not originate by dissociative recombination of a sodium bearing molecular ion. Production rates increased from 1.6 ± 0.3 x 1023 to 5.8 ± 1 x 1023 Na atoms/s within 24 hours, outgassing much less than comparable comets relative to ISON’s water production. The anti-sunward Na tail was imaged >106 km from the nucleus. Its distribution indicates origins both near the nucleus and in the dust tail, with the ratio of these Na sources varying on hourly timescales due to outburst activity.

Two New Calcium-rich Gap Transients in Group and Cluster Environments

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

Lunnan, R.; Kasliwal, M. M.; Cao, Y.

We present the Palomar Transient Factory discoveries and the photometric and spectroscopic observations of PTF11kmb and PTF12bho. We show that both transients have properties consistent with the class of calcium-rich gap transients, specifically lower peak luminosities and rapid evolution compared to ordinary supernovae, and a nebular spectrum dominated by [Ca ii] emission. A striking feature of both transients is their host environments: PTF12bho is an intracluster transient in the Coma Cluster, while PTF11kmb is located in a loose galaxy group, at a physical offset ~150 kpc from the most likely host galaxy. Deep Subaru imaging of PTF12bho rules out anmore » underlying host system to a limit of M R > -8.0 mag, while Hubble Space Telescope imaging of PTF11kmb reveals a marginal counterpart that, if real, could be either a background galaxy or a globular cluster. Here, we show that the offset distribution of Ca-rich gap transients is significantly more extreme than that seen for SNe Ia or even short-hard gamma-ray bursts (sGRBs). Thus, if the offsets are caused by a kick, they require higher kick velocities and/or longer merger times than sGRBs. Finally, we also show that almost all Ca-rich transients found to date are in group and cluster environments with elliptical host galaxies, indicating a very old progenitor population; the remote locations could partially be explained by these environments having the largest fraction of stars in the intragroup/intracluster light following galaxy-galaxy interactions.« less

Two New Calcium-rich Gap Transients in Group and Cluster Environments

DOE PAGES

Lunnan, R.; Kasliwal, M. M.; Cao, Y.; ...

2017-02-08

We present the Palomar Transient Factory discoveries and the photometric and spectroscopic observations of PTF11kmb and PTF12bho. We show that both transients have properties consistent with the class of calcium-rich gap transients, specifically lower peak luminosities and rapid evolution compared to ordinary supernovae, and a nebular spectrum dominated by [Ca ii] emission. A striking feature of both transients is their host environments: PTF12bho is an intracluster transient in the Coma Cluster, while PTF11kmb is located in a loose galaxy group, at a physical offset ~150 kpc from the most likely host galaxy. Deep Subaru imaging of PTF12bho rules out anmore » underlying host system to a limit of M R > -8.0 mag, while Hubble Space Telescope imaging of PTF11kmb reveals a marginal counterpart that, if real, could be either a background galaxy or a globular cluster. Here, we show that the offset distribution of Ca-rich gap transients is significantly more extreme than that seen for SNe Ia or even short-hard gamma-ray bursts (sGRBs). Thus, if the offsets are caused by a kick, they require higher kick velocities and/or longer merger times than sGRBs. Finally, we also show that almost all Ca-rich transients found to date are in group and cluster environments with elliptical host galaxies, indicating a very old progenitor population; the remote locations could partially be explained by these environments having the largest fraction of stars in the intragroup/intracluster light following galaxy-galaxy interactions.« less

Jet-like features near the Nucleus of Chiron

NASA Technical Reports Server (NTRS)

Elliot, J. L.; Olkin, C. B.; Dunham, E. W.; Ford, C. H.; Gilmore, D. K.; Kurtz, D.; Lazzaro, D.; Rank, D. M.; Temi, P.; Bandyopadhyay, R. M.;

Hubble Space Telescope observations of comet P/Shoemaker-Levy 9 (1993e)

USGS Publications Warehouse

Weaver, H.A.; Feldman, P.D.; A'Hearn, M.F.; Arpigny, C.; Brown, R.A.; Helin, E.F.; Levy, D.H.; Marsden, B.G.; Meech, K.J.; Larson, S.M.; Noll, K.S.; Scotti, J.V.; Sekanina, Z.; Shoemaker, C.S.; Shoemaker, E.M.; Smith, T.E.; Storrs, A.D.; Yeomans, D.K.; Zellner, B.

1994-01-01

The Hubble Space Telescope observed the fragmented comet P/Shoemaker-Levy 9 (1993e) (P indicates that it is a periodic comet) on 1 July 1993. Approximately 20 individual nuclei and their comae were observed in images taken with the Planetary Camera. After subtraction of the comae light, the 11 brightest nuclei have magnitudes between ~23.7 and 24.8. Assuming that the geometric albedo is 0.04, these magnitudes imply that the nuclear diameters are in the range ~2.5 to 4.3 kilometers. If the density of each nucleus is 1 gram per cubic centimeter, the total energy deposited by the impact of these 11 nuclei into Jupiter's atmosphere next July will be ~4 x 1030 ergs (~108 megatons of TNT). This latter number should be regarded as an upper limit because the nuclear magnitudes probably contain a small residual coma contribution. The Faint Object Spectrograph was used to search for fluorescence from OH, which is usually an excellent indicator of cometary activity. No OH emission was detected, and this can be translated into an upper limit on the water production rate of ~2 x 1027 molecules per second.

EUV phase-shifting masks and aberration monitors

NASA Astrophysics Data System (ADS)

Deng, Yunfei; Neureuther, Andrew R.

2002-07-01

Rigorous electromagnetic simulation with TEMPEST is used to examine the use of phase-shifting masks in EUV lithography. The effects of oblique incident illumination and mask patterning by ion-mixing of multilayers are analyzed. Oblique incident illumination causes streamers at absorber edges and causes position shifting in aerial images. The diffraction waves between ion-mixed and pristine multilayers are observed. The phase-shifting caused by stepped substrates is simulated and images show that it succeeds in creation of phase-shifting effects. The diffraction process at the phase boundary is also analyzed. As an example of EUV phase-shifting masks, a coma pattern and probe based aberration monitor is simulated and aerial images are formed under different levels of coma aberration. The probe signal rises quickly as coma increases as designed.

Near-UV OH Prompt Emission in the Innermost Coma of 103P/Hartley 2

NASA Astrophysics Data System (ADS)

La Forgia, Fiorangela; Bodewits, Dennis; A'Hearn, Michael F.; Protopapa, Silvia; Kelley, Michael S. P.; Sunshine, Jessica; Feaga, Lori; Farnham, Tony

2017-11-01

The Deep Impact spacecraft flyby of comet 103P/Hartley 2 occurred on 2010 November 4, 1 week after perihelion with a closest approach (CA) distance of about 700 km. We used narrowband images obtained by the Medium Resolution Imager on board the spacecraft to study the gas and dust in the innermost coma. We derived an overall dust reddening of 15%/100 nm between 345 and 749 nm and identified a blue enhancement in the dust coma in the sunward direction within 5 km from the nucleus, which we interpret as a localized enrichment in water ice. OH column density maps show an anti-sunward enhancement throughout the encounter, except for the highest-resolution images, acquired at CA, where a radial jet becomes visible in the innermost coma, extending up to 12 km from the nucleus. The OH distribution in the inner coma is very different from that expected for a fragment species. Instead, it correlates well with the water vapor map derived by the HRI-IR instrument on board Deep Impact. Radial profiles of the OH column density and derived water production rates show an excess of OH emission during CA that cannot be explained with pure fluorescence. We attribute this excess to a prompt emission process where photodissociation of H2O directly produces excited OH*(A 2Σ+) radicals. Our observations provide the first direct imaging of near-UV prompt emission of OH. We therefore suggest the use of a dedicated filter centered at 318.8 nm to directly trace the water in the coma of comets.

Thermal modeling of cometary nuclei

USGS Publications Warehouse

Weissman, P.R.; Kieffer, H.H.

1981-01-01

A new model of the sublimation of volatile ices from a cometary nucleus has been developed which includes the effects of diurnal heating and cooling, rotation period and pole orientation, and thermal properties of the ice and subsurface layers. The model also includes the contribution from coma opacity, scattering, and thermal emission, where the properties of the coma are derived from the integrated rate of volatile production by the nucleus. The model is applied to the specific case of the 1986 apparition of Halley's comet. It is found that the generation of a cometary dust coma actually increases the total energy reaching the Halley nucleus. This results because of the significantly greater geometrical cross section of the coma as compared with the bare nucleus, and because the coma provides an essentially isotropic source of multiply scattered sunlight and thermal emission over the entire nucleus surface. For Halley, the calculated coma opacity is approximately 0.2 at 1 AU from the Sun, and 1.2 at perihelion (0.587 AU). At 1 AU this has little effect on dayside temperatures (maximum ???200??K) but raises nightside temperatures (minimum ???150??K) by about 40??K. At perihelion the higher opacity results in a nearly isothermal nucleus with only small diurnal and latitudinal temperature variations. The general surface temperature is 205??K with a maximum of 209??K at local noon on the equator. Some possible consequences of the results with respect to the generation of nongravitational forces, observed volatile production rates for comets, and cometary lifetimes against sublimation are discussed. ?? 1981.

Observation of a rapid decrease in the brightness of the coma of 2060 Chiron in 1990 January

NASA Technical Reports Server (NTRS)

Buratti, Bonnie J.; Dunbar, R. Scott

1991-01-01

Photometric observations of 2060 Chiron in the V and R filters were obtained with the 1.5-m telescope on Palomar Mountain during a 7-hr period on January 20, 1990 (UT). A general decrease of about 10 percent in integrated brightness occurred in both filters. No color dependence to the decrease was observed. A small (about 0.02 mag) rotational light curve, far smaller than the 0.09 mag (peak-to-peak) one observed by Bus et al. (1989) is superposed on the general decrease. On January 29, 1990, Luu and Jewitt (1990) observed an impulsive brightening of Chiron of approximately the same magnitude and time scale as the presently observed decrease in brightness. The combined results provide evidence that Chiron is currently exhibiting short-term fluctuations in the brightness of its coma, in addition to its well-established general decrease in brightness.

The Meteoroid Fluence at Mars Due to Comet C/2013 A1 (Siding Spring)

NASA Technical Reports Server (NTRS)

Moorhead, A.; Wiegert, P.; Blaauw, R.; McCarty, C.; Kingery, A.; Cooke, W.

2014-01-01

Long-period comet C/2013 A1 (Siding Spring) will experience a close encounter with Mars on 2014 Oct 19. A collision between the comet and the planet has been ruled out, but the comet's coma may envelop Mars and its man-made satellites. By the time of the close encounter, five operational spacecraft will be present near Mars. Characterizing the coma is crucial for assessing the risk posed to these satellites by meteoroid impacts. We present an analytic model of cometary comae that describes the spatial and size distributions of cometary dust and meteoroids. This model correctly reproduces, to within an order of magnitude, the number of impacts recorded by Giotto near 1P/Halley [1] and by Stardust near comet 81P/Wild 2 [2]. Applied to Siding Spring, our model predicts a total particle fluence near Mars of 0.02 particles per square meter. In order to determine the degree to which Siding Spring's coma deviates from a sphere, we perform numerical simulations which take into account both gravitational effects and radiative forces. We take the entire dust component of the coma and tail continuum into account by simulating the ejection and evolution of dust particles from comet Siding Spring. The total number of particles simulated is essentially a free parameter and does not provide a check on the total fluence. Instead, these simulations illustrate the degree to which the coma of Siding Spring deviates from the perfect sphere described by our analytic model (see Figure). We conclude that our analytic model sacrifices less than an order of magnitude in accuracy by neglecting particle dynamics and radiation pressure and is thus adequate for order-of-magnitude fluence estimates. Comet properties may change unpredictably and therefore an analytic coma model that enables quick recalculation of the meteoroid fluence is highly desirable. NASA's Meteoroid Environment Office is monitoring comet Siding Spring and taking measurements of cometary brightness and dust production. We will discuss our coma model and nominal fluence taking the latest observations into account.

Ultraviolet and visible variability of the coma of Comet Levy (1990c)

NASA Technical Reports Server (NTRS)

Feldman, P. D.; Budzien, S. A.; Festou, M. C.; A'Hearn, M. F.; Tozzi, G. P.

1992-01-01

A visible lightcurve of Comet Levy obtained with the IUE Fine Error Sensor has revealed short-term coma variability. A production-rate source function is derivable from these data which implies a nucleus exhibiting hemispherically asymmetric activity. The ratio of gas-to-dust-production rates is also noted to exhibit asymmetry. The low dust-outflow velocity derived from observations, at about 200 m/sec, indicates a distribution that is rich in large, 3-10 micron particles.

The cometary magnetic field and its associated electric currents

NASA Technical Reports Server (NTRS)

Ip, W.-H.; Mendis, D. A.

1975-01-01

Two different observations of Comet Kohoutek (1973f) seem to suggest the existence of substantial magnetic fields (not less than 100 gammas) in its coma and tail. The effects of the currents and hydromagnetic waves associated with these magnetic fields are considered. It is shown that while the currents closing through the inner coma may represent an important source of ionization in that region, the dissipation of hydromagnetic waves may also be a significant, if not dominant, source of heating there.

Rosetta/Alice Measurements of Atomic and Molecular Abundances in the Coma of 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Vervack, R. J., Jr.; Weaver, H. A., Jr.; Knight, M. M.; Feldman, P.; Stern, A.; Parker, J. W.; Feaga, L. M.; Steffl, A.; Bertaux, J. L.; A'Hearn, M. F.; Keeney, B. A.

2017-12-01

During the Rosetta orbital phase from August 2014 through September 2016, the Alice far-ultraviolet (FUV) imaging spectrograph routinely monitored the FUV emission from the coma of 67P/Churyumov-Gerasimenko (67P). These data, spanning 700-2050 Å, provide both spatial and temporal information on the evolution of the coma composition throughout the encounter. Emissions from hydrogen (Lyman beta at 1025 Å), oxygen (1304 Å triplet, 1356 Å), sulfur (1429 Å and 1479 Å multiplets, 1814 Å triplet), and carbon (1561 Å, 1657 Å) were regularly observed, as well as emission from the CO Fourth Positive and Cameron bands. We present a preliminary analysis of these emissions with a focus on the abundances in the coma and a mapping of the temporal and spatial variations. Both short-term (days) and long-term (months) variations will be discussed in the context of rotational and seasonal timeframes. We also present ratios among various species with the goal of identifying the dominant processes at work in the coma as a function of time. Rosetta is an ESA mission with contributions from its member states and NASA. The Alice team acknowledges continuing support from NASA's Jet Propulsion Laboratory through contract 1336850 to the Southwest Research Institute. RJV's work was supported by a subcontract from Southwest Research Institute to the Johns Hopkins University Applied Physics Laboratory.

Comet Kohoutek

NASA Technical Reports Server (NTRS)

Gary, Gilmer A. (Editor)

1975-01-01

A compilation of scientific observations (workshop) is presented. Topics discussed are: (1) tail form, structure, and evolution; (2) hydroxyl related observations; (3) molecules and atoms in the coma and tail; (4) photometry and radiometry; and (5) spacecraft and ground based observation data. Color photographs are shown.

MAPPING THE RELEASE OF VOLATILES IN THE INNER COMAE OF COMETS C/2012 F6 (LEMMON) AND C/2012 S1 (ISON) USING THE ATACAMA LARGE MILLIMETER/SUBMILLIMETER ARRAY

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

Cordiner, M. A.; Milam, S. N.; Mumma, M. J.

2014-09-01

Results are presented from the first cometary observations using the Atacama Large Millimeter/Submillimeter Array (ALMA), including measurements of the spatially resolved distributions of HCN, HNC, H{sub 2}CO, and dust within the comae of two comets: C/2012 F6 (Lemmon) and C/2012 S1 (ISON), observed at heliocentric distances of 1.5 AU and 0.54 AU, respectively. These observations (with angular resolution ≈0.''5), reveal an unprecedented level of detail in the distributions of these fundamental cometary molecules, and demonstrate the power of ALMA for quantitative measurements of the distributions of molecules and dust in the inner comae of typical bright comets. In both comets, HCN ismore » found to originate from (or within a few hundred kilometers of) the nucleus, with a spatial distribution largely consistent with spherically symmetric, uniform outflow. By contrast, the HNC distributions are clumpy and asymmetrical, with peaks at cometocentric radii ∼500-1000 km, consistent with release of HNC in collimated outflow(s). Compared to HCN, the H{sub 2}CO distribution in comet Lemmon is very extended. The interferometric visibility amplitudes are consistent with coma production of H{sub 2}CO and HNC from unidentified precursor material(s) in both comets. Adopting a Haser model, the H{sub 2}CO parent scale length is found to be a few thousand kilometers in Lemmon and only a few hundred kilometers in ISON, consistent with the destruction of the precursor by photolysis or thermal degradation at a rate that scales in proportion to the solar radiation flux.« less

The resolved nucleus of Comet Siding Spring (C/2013 A1) in MRO HiRISE images

NASA Astrophysics Data System (ADS)

Farnham, Tony; Kelley, Michael S.; Bodewits, Dennis; Bauer, James M.

2017-10-01

Comet Siding Spring (C/2013 A1) passed within 140,000 km of Mars on 19 Oct 2014. The MRO spacecraft, in orbit around Mars, used its HiRISE camera to monitor the comet during the encounter, obtaining the first resolved images of the nucleus of a dynamically new comet.MRO observed Siding Spring from 60 hr before, to 15 hr after close approach, obtaining 122 images in three different color filters. Close approach images, with a spatial scale as small as 138 m/pix, reveal an elongated crescent that changes shape over the course of the sequence, indicating that we are seeing a ~1 km non-spherical body from different viewpoints as the comet rapidly sweeps past. To better constrain the characteristics of the nucleus, we are performing detailed analyses, including modeling of the inner coma to separate its flux contribution from that of the nucleus. In conjunction with the coma removal, we will model the nucleus as a prolate/triaxial ellipsoid and, combined with the known illumination and viewing conditions, will use the changing aspect in the images to constrain the size, shape, orientation, albedo and possibly the phase dependence of the nucleus.In addition to the close approach observations, the images before and after close approach capture the coma structure and brightness. The photometric lightcurve from these images shows variability with an 8.1 hr period, which is presumed to be the rotational modulation of the coma activity. The observed morphology changes as well, promising to provide a measure of the nucleus' spin axis orientation.We will report on the results from our analyses, and provide the first direct measurements of the nucleus of a dynamically new comet.

Direct Simulation Monte Carlo modelling of the major species in the coma of comet 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Fougere, Nicolas; Altwegg, K.; Berthelier, J.-J.; Bieler, A.; Bockelée-Morvan, D.; Calmonte, U.; Capaccioni, F.; Combi, M. R.; De Keyser, J.; Debout, V.; Erard, S.; Fiethe, B.; Filacchione, G.; Fink, U.; Fuselier, S. A.; Gombosi, T. I.; Hansen, K. C.; Hässig, M.; Huang, Z.; Le Roy, L.; Leyrat, C.; Migliorini, A.; Piccioni, G.; Rinaldi, G.; Rubin, M.; Shou, Y.; Tenishev, V.; Toth, G.; Tzou, C.-Y.

2016-11-01

We analyse the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) - the Double Focusing Mass Spectrometer data between 2014 August and 2016 February to examine the effect of seasonal variations on the four major species within the coma of 67P/Churyumov-Gerasimenko (H2O, CO2, CO, and O2), resulting from the tilt in the orientation of the comet's spin axis. Using a numerical data inversion, we derive the non-uniform activity distribution at the surface of the nucleus for these species, suggesting that the activity distribution at the surface of the nucleus has not significantly been changed and that the differences observed in the coma are solely due to the variations in illumination conditions. A three-dimensional Direct Simulation Monte Carlo model is applied where the boundary conditions are computed with a coupling of the surface activity distributions and the local illumination. The model is able to reproduce the evolution of the densities observed by ROSINA including the changes happening at equinox. While O2 stays correlated with H2O as it was before equinox, CO2 and CO, which had a poor correlation with respect to H2O pre-equinox, also became well correlated with H2O post-equinox. The integration of the densities from the model along the line of sight results in column densities directly comparable to the VIRTIS-H observations. Also, the evolution of the volatiles' production rates is derived from the coma model showing a steepening in the production rate curves after equinox. The model/data comparison suggests that the seasonal effects result in the Northern hemisphere of 67P's nucleus being more processed with a layered structure while the Southern hemisphere constantly exposes new material.

Near-UV OH Prompt Emission in the Innermost Coma of 103P/Hartley 2

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

La Forgia, Fiorangela; Bodewits, Dennis; A’Hearn, Michael F.

The Deep Impact spacecraft flyby of comet 103P/Hartley 2 occurred on 2010 November 4, 1 week after perihelion with a closest approach (CA) distance of about 700 km. We used narrowband images obtained by the Medium Resolution Imager on board the spacecraft to study the gas and dust in the innermost coma. We derived an overall dust reddening of 15%/100 nm between 345 and 749 nm and identified a blue enhancement in the dust coma in the sunward direction within 5 km from the nucleus, which we interpret as a localized enrichment in water ice. OH column density maps show an anti-sunwardmore » enhancement throughout the encounter, except for the highest-resolution images, acquired at CA, where a radial jet becomes visible in the innermost coma, extending up to 12 km from the nucleus. The OH distribution in the inner coma is very different from that expected for a fragment species. Instead, it correlates well with the water vapor map derived by the HRI-IR instrument on board Deep Impact . Radial profiles of the OH column density and derived water production rates show an excess of OH emission during CA that cannot be explained with pure fluorescence. We attribute this excess to a prompt emission process where photodissociation of H{sub 2}O directly produces excited OH*( A {sup 2}Σ{sup +}) radicals. Our observations provide the first direct imaging of near-UV prompt emission of OH. We therefore suggest the use of a dedicated filter centered at 318.8 nm to directly trace the water in the coma of comets.« less

Food deprivation and prior anoxic coma have opposite effects on the activity of a visual interneuron in the locust.

PubMed

Cross, Kevin P; Britton, Samantha; Mangulins, Rebecca; Money, Tomas G A; Robertson, R Meldrum

2017-04-01

We compared how different metabolic stressors, anoxic coma and food deprivation, affected signaling in neural tissue. We used the locust's Descending Contralateral Movement Detector (DCMD) interneuron because its large axon, high firing frequencies, and rapid conduction velocity make it energetically expensive. We exposed locusts to a 30min anoxic coma or 1day of food deprivation and found contrasting effects on signaling within the axon. After a prior anoxic coma, the DCMD fired fewer high-frequency (>200Hz) action potentials (APs) (Control: 12.4±1.6; Coma: 6.3±0.9) with a reduction in axonal conduction velocity (CV) at all frequencies (∼4-8%) when presented with a standard looming visual stimulus. Prior anoxic coma was also associated with a loss of supernormal conduction by reducing both the number of supernormal APs and the firing frequency with the highest CV. Initially, food deprivation caused a significant increase in the number of low- and high-frequency APs with no differences observed in CV. After controlling for isolation, food deprivation resulted in an increase in high-frequency APs (>200Hz: Control: 17.1±1.7; Food-deprived: 19.9±1.3) and an increase in relative conduction velocity for frequencies >150Hz (∼2%). Action potentials of food-deprived animals had a smaller half-width (Control: 0.45±0.02ms; Food-deprived: 0.40±0.01ms) and decay time (Control: 0.62±0.03ms; Food-deprived: 0.54±0.02ms). Our data indicate that the effects of metabolic stress on neural signaling can be stressor-dependent. Copyright © 2017 Elsevier Ltd. All rights reserved.

Dust grains in the coma of 67P/Churyumov-Gerasimenko - link with surface properties and cometary activity

NASA Astrophysics Data System (ADS)

Capria, M. T.; Ivanovski, S.; Zakharov, W.; Capaccioni, F.; Filacchione, G.; De Sanctis, M. C.; Rotundi, A.; Della Corte, V.; Longobardo, A.; Palomba, E.; Colangeli, L.; Bockelee-Morvan, D.; Erard, S.; Leyrat, C.

2016-11-01

The imaging spectrometer VIRTIS and the dust analyzer GIADA, onboard Rosetta, made an extensive observation of the dust particles in the coma of the comet 67P/Churyumov-Gerasimenko. From the analysis of GIADA data, two different kind of particles have been revealed, compact and fluffy with different compositions and dynamical properties. Compact particles are characterized by densities of about 10E3 kg/m3, while fluffy particles have an almost fractal nature, with densities less than 1 kg/m3. In this work we present the initial results of a model linking the dust flux distribution, as obtained from a theoretical thermal nucleus model, with a model describing the dynamics of aspherical grains in the coma. The results are discussed in the context of the latest observations from VIRTIS and GIADA instruments. The 2D nucleus thermal model, when applied to the real shape of the comet, provides the size distribution and physical properties of the emitted grains at different times and location on the surface. The thermal model can simulate grains of various size distribution, composition and physical properties. This information is used as an input for the dust dynamical model that follows the emitted particles in the coma. The main source of heating is the solar illumination. In the dust dynamical model, the grain trajectory of emitted particles remains in a plane perpendicular to the rotational axis and the direction of illumination is taken to be in the same plane (i.e. does not cause transversal forces). The dust particles are assumed to be isothermal convex bodies and temperature changes only induce modest changes in the aerodynamic force (twice higher temperature changes aerodynamic force less than 30%). This study reviews the theoretical values at which temperature difference starts to play a role on the dynamics. We discuss to what extent the particle's temperature affects the terminal velocities of the dust grains in the 67P coma in dependence on their mass and temperature constrained by the observations.

Dust grains in the coma of 67P/Churyumov-Gerasimenko - link with surface properties and cometary activity

NASA Astrophysics Data System (ADS)

Capria, Maria Teresa; Ivanovski, Stavro; Zakharov, Vladimir; Capaccioni, Fabrizio; Filacchione, Gianrico; De Sanctis, Maria Cristina; rotundi, alessandra; della corte, vincenzo; Longobardo, Andrea; Palomba, Ernesto; colangeli, luigi; Bockelee-Morvan, Dominique; Érard, Stéphane; Leyrat, Cedric; VIRTIS, GIADA

2016-10-01

The imaging spectrometer VIRTIS and the dust analyzer GIADA, onboard Rosetta, made an extensive observation of the dust particles in the coma of the comet 67P/Churyumov-Gerasimenko. From the analysis of GIADA data, two different kind of particles have been revealed, compact and fluffy with different compositions and dynamical properties. Compact particles are characterized by densities of about 103 kg/m3, while fluffy particles have an almost fractal nature, with densities less than 1 kg/m3.In this work we present the initial results of a model linking the dust flux distribution, as obtained from a theoretical thermal nucleus model, with a model describing the dynamics of aspherical grains in the coma. The results are discussed in the context of the latest observations from VIRTIS and GIADA instruments.The 2D nucleus thermal model, when applied to the real shape of the comet, provides the size distribution and physical properties of the emitted grains at different times and location on the surface. The thermal model can simulate grains of various size distribution, composition and physical properties. This information is used as an input for the dust dynamical model that follows the emitted particles in the coma. The main source of heating is the solar illumination. In the dust dynamical model, the grain trajectory of emitted particles remains in a plane perpendicular to the rotational axis and the direction of illumination is taken to be in the same plane (i.e. does not cause transversal forces). The dust particles are assumed to be isothermal convex bodies and temperature changes only induce modest changes in the aerodynamic force (twice higher temperature changes aerodynamic force less than ~30%). This study reviews the theoretical values at which temperature difference starts to play a role on the dynamics. We discuss to what extent the particle's temperature affects the terminal velocities of the dust grains in the 67P coma in dependence on their mass and temperature constrained by the observations.

Spectroscopic Observations of Comet C/2013 A1 (Siding Spring) from Mars using ChemCam, OMEGA and SPICAM.

NASA Astrophysics Data System (ADS)

Lasue, J.; Gondet, B.; Bertaux, J. L.; Barraclough, B. L.; Beck, P.; Bender, S.; Bibring, J. P.; Bridges, N. T.; Chaufray, J. Y.; Gasnault, O.; Herkenhoff, K. E.; Langevin, Y.; Le Mouelic, S.; Lemmon, M. T.; Lewin, E.; McConnochie, T. H.; Martín-Torres, J.; Maurice, S.; Meslin, P. Y.; Ming, D. W.; Montmessin, F.; Owen, T. C.; Rapin, W.; Rocard, F.; Wiens, R. C.; Zorzano, M. P.

2014-12-01

Comet Siding Spring will graze Mars on Oct. 19th 2014. Its closest approach from the centre of the planet will be 135,000 km, and its predicted visual magnitude as low as -5.3 (JPL Horizons web site). The observing conditions will be ideal to attempt spectroscopic measurements of the inner coma from the UV to the IR at an unprecedented spectral resolution from the instruments located on and around Mars. ChemCam is a Laser-Induced Breakdown Spectroscopy instrument operating on-board the Mars Science Laboratory rover to analyse the chemical composition of rocks and can be used for passive spectroscopy. ChemCam is equipped with high resolution spectrometers covering the optical range (240-850 nm) with a pixel resolution of 0.05nm up to 470nm and 0.2nm in the near-IR range. The ChemCam passive spectroscopy field of view is 0.65 mrad wide and covers several 100km projected on the coma. Based on predicted magnitude and inner coma intensity variations, we expect to retrieve spectral signatures around the nucleus. Simultaneously the 7 instruments on board Mars Express will take measurements in nadir and limb modes. We will merge the results obtained with ChemCam with those of the 2 imaging spectrometers SPICAM (110-310 nm resolution of 0.6nm and 1-1.7 μm resolution of 1.5 nm) and OMEGA (457-910 nm resolution of 1.5 nm and 2.5-5.1 μm resolution of 15 nm) to obtain the composition and spatial variation of emitting molecules in the different parts of the coma. The instruments will also monitor the atmosphere before and after the encounter to detect any change. We will report on the preparations for the observations and the spectroscopy results, with emphasis on the detection of complex organic molecules and the spatial distribution of H2O and OH in the inner coma. A decision will be made on the adequacy of risk reduction activities for the spacecraft, and planned science operations may need to be cancelled by ESOC.This work is supported by NASA, ESA and CNES.

The Far-Field Hubble Constant

NASA Astrophysics Data System (ADS)

Lauer, Tod

1995-07-01

We request deep, near-IR (F814W) WFPC2 images of five nearby Brightest Cluster Galaxies (BCG) to calibrate the BCG Hubble diagram by the Surface Brightness Fluctuation (SBF) method. Lauer & Postman (1992) show that the BCG Hubble diagram measured out to 15,000 km s^-1 is highly linear. Calibration of the Hubble diagram zeropoint by SBF will thus yield an accurate far-field measure of H_0 based on the entire volume within 15,000 km s^-1, thus circumventing any strong biases caused by local peculiar velocity fields. This method of reaching the far field is contrasted with those using distance ratios between Virgo and Coma, or any other limited sample of clusters. HST is required as the ground-based SBF method is limited to <3,000 km s^-1. The high spatial resolution of HST allows precise measurement of the SBF signal at large distances, and allows easy recognition of globular clusters, background galaxies, and dust clouds in the BCG images that must be removed prior to SBF detection. The proposing team developed the SBF method, the first BCG Hubble diagram based on a full-sky, volume-limited BCG sample, played major roles in the calibration of WFPC and WFPC2, and are conducting observations of local galaxies that will validate the SBF zeropoint (through GTO programs). This work uses the SBF method to tie both the Cepheid and Local Group giant-branch distances generated by HST to the large scale Hubble flow, which is most accurately traced by BCGs.

Homeopathic treatment for prolonged postoperative coma: a case report.

PubMed

Vithoulkas, G; Văcăraș, V; Kavouras, J; Buzoianu, A D; Mărginean, M; Văcăraș, D; Cozma, S

2017-01-01

Coma is the state of unrousable unconsciousness. There are variations in the degree of coma and the findings and signs found on the patient's clinical examination depend on the underlying cause of the disorder. The Glasgow Coma scale evaluates the best motor, verbal and eye answers of the patient. A patient is considered to be in a coma if his Glasgow Coma Scale is below 8 points. The progress that we have made throughout the years has also led to complications that can culminate in a major catastrophe like death, permanent brain damage, coma. A study performed reached the conclusion that prior comorbidity, older age, intraoperative hypotension, and cardiovascular surgery may predispose patients to postoperative coma. The article presents a case of postoperative coma treated successfully with homeopathy. Although a rare complication, postoperative coma is a severe, death-leading condition, causing immense suffering on both the patient and the patient's family. A multidisciplinary and thorough approach is necessary for these patients, but even after a well-conducted therapy, this condition leads to the death of the patient.

Homeopathic treatment for prolonged postoperative coma: a case report

PubMed Central

Vithoulkas, G; Văcăraș, V; Kavouras, J; Buzoianu, AD; Mărginean, M; Văcăraș, D; Cozma, S

2017-01-01

Coma is the state of unrousable unconsciousness. There are variations in the degree of coma and the findings and signs found on the patient’s clinical examination depend on the underlying cause of the disorder. The Glasgow Coma scale evaluates the best motor, verbal and eye answers of the patient. A patient is considered to be in a coma if his Glasgow Coma Scale is below 8 points. The progress that we have made throughout the years has also led to complications that can culminate in a major catastrophe like death, permanent brain damage, coma. A study performed reached the conclusion that prior comorbidity, older age, intraoperative hypotension, and cardiovascular surgery may predispose patients to postoperative coma. The article presents a case of postoperative coma treated successfully with homeopathy. Although a rare complication, postoperative coma is a severe, death-leading condition, causing immense suffering on both the patient and the patient’s family. A multidisciplinary and thorough approach is necessary for these patients, but even after a well-conducted therapy, this condition leads to the death of the patient. PMID:28616086

Deep, wide-field, multi-band imaging of z approximately equal to 0.4 clusters and their environs

NASA Technical Reports Server (NTRS)

Silva, David R.; Pierce, Michael J.

1993-01-01

The existence of an excess population of blue galaxies in the cores of distant, rich clusters of galaxies, commonly referred to as the 'Butcher-Oemler' effect is now well established. Spectroscopy of clusters at z = 0.2-0.4 has confirmed that the luminous blue populations comprise as much as 20 percent of these clusters. This fraction is much higher that the 2 percent blue fraction found for nearby rich clusters, such as Coma, indicating that rapid galaxy evolution has occurred on a relatively short time scale. Spectroscopy has also shown that the 'blue' galaxies can basically be divided into three classes: 'starburst' galaxies with large (O II) equivalent widths, 'post-starburst' E+A galaxies (i.e. galaxies with strong Balmer lines shortward of 4000A but elliptical-like colors, and normal spiral/irregulars. Unfortunately, it is difficult to obtain enough spectra of individual galaxies in these intermediate redshift clusters to say anything statistically meaningful. Thus, limited information is available about the relative numbers of these three classes of 'blue' galaxies and the associated E/SO population in these intermediate redshift clusters. More statistically meaningful results can be derived from deep imaging of these clusters. However, the best published data to date (e.g. MacLaren et al. 1988; Dressler & Gunn 1992) are limited to the cluster cores and do not sample the galaxy luminosity functions very deeply at the bluest wavelengths. Furthermore, only limited spectro-energy distribution data is available below 4000A in the observed cluster rest frame providing limited sensitivity to 'recent' star formation activity. To improve this situation, we are currently obtaining deep, wide-field UBRI images of all known rich clusters at z approx. equals 0.4. Our main objective is to obtain the necessary color information to distinguish between the E+SO, 'E+A', and spiral/irregular galaxy populations throughout the cluster/supercluster complex. At this redshift, UBRI correspond to rest-frame 2500A/UVR bandpasses. The rest-frame UVR system provides a powerful 'blue' galaxy discriminate given the expected color distribution. Moreover, since 'hot' stars peak near 2500A, that bandpass is a powerful probe of recent star formation activity in all classes of galaxies. In particular, it is sensitive to ellipticals with 'UV excess' populations (MacLaren et al. 1988).

Comet 67P/Churyumov-Gerasimenko during the Rosetta mission: numerical simulation of dusty gas coma

NASA Astrophysics Data System (ADS)

Tenishev, Valeriy; Combi, Michael; Rubin, Martin; Hansen, Kenneth; Gombosi, Tamas

The Rosetta spacecraft is en route to comet 67P/Churyumov-Gerasimenko for a rendezvous, landing, and extensive orbital phase beginning in 2014. Having a limited amount of information regarding its coma, interpretation of measurements and safety consideration of the spacecraft will require modeling of the comet's environment. Such models should be able to simulate both the gas and dust phases of the coma as well as the interaction between them in a self-consistent manner. The relevant physical processes in the coma include photolytic reactions and interaction with the nucleus for the gas phase and drag by the gas, gravity of the nucleus, solar gravity and radiation pressure, and charging by the ambient plasma for the dust phase. Developing of such modeling capabilities will be able to link measurements obtained by different instruments onboard of spacecraft. Some examples of cometary comae simulations can be found in [1-3]. In this work we present our kinetic model of a dusty gas coma [4] with results of its application to the case of comet Churyumov-Gerasimenko at conditions corresponding to some stages the during the Rosetta mission. Based on the surface properties and local production rates obtained by MIRO, RSI and VIRTIS the model will be able to propagate the injected gas and dust into the coma linking the measurements to those obtained by ALICE, MIDAS and ROSINA for the gas phase and COSIMA and GIADA for the dust phase of the coma. A simultaneous simulation of the major components of the multi-phase coma will allow us to link observations of the gas and dust phases. In this work we present results of a numerical study of neutral/ionized multispecies gaseous and electrically charged dust environment of the comet Churyumov-Gerasimenko at a helio-centric distance of 1.3 AU. The simulation is performed in fully 3D geometry with a realistic nucleus model that describes its topological features and source distribution. Both, neutral and ionized components of the gas phase of the coma are simulated kinetically. Photolytic reactions are taken into account. Parameters of the ambient plasma as well as the distribution of electric/magnetic fields are obtained from an MHD simulation [5] of the coma connected to the solar wind. Those parameters are used for calculation of the electric charge of dust grains. Trajectories of ions and electrically charged dust grains are simulated by accounting for the gas drag, Lorentz force, nucleus gravity and radiation pressure. REFFERENCES [1] M.R. Combi, Icarus, 123, 207-226 (1996) [2] Y. Skorov, G.N. Markelov, H.U. Keller, Solar Sys. Res. 38, 455-475 (2004) [3] V.V. Zakharov, A.V. Rodionov, G. A. Lukianov, J.F. Crifo, Icarus 201, 358-380 (2009) [4] V. Tenishev, M. R. Combi, B. Davidsson, Astrophysical Journal, 685, 659-677 (2008) [5] M. Rubin, K. C. Hansen, T. Gombosi, M. R. Combi, K. Altwegg, H. Balsiger, Icarus, 199, 505-519 (2009)

Do We Really Have an Age/H_0 Conflict?

NASA Astrophysics Data System (ADS)

Baum, W. A.

1997-12-01

Two independent methods for estimating the age of the universe can both be linked to the absolute magnitudes of the RR Lyrae stars, one based on stellar evolution in globular clusters and the other based on the Hubble Constant derived from globular clusters as distance indicators. The latter has recently been extracted from HST-WFPC2 data for globular clusters in the Coma Cluster galaxy IC 4051 (Baum et al. 1997, AJ, 113, 1483). If RR Lyrae stars are brighter than we have previously thought, the stellar-evolution age estimate is shortened whereas the Hubble age is increased, so we can ask a very simple question: For what RR Lyrae magnitude zero point would the stellar-evolution age coincide with the Hubble age, and is it a reasonable value? Allowing 1 Gyr for globular clusters to have formed, and assuming a classical Einstein-deSitter universe with Lambda = 0, I find the two ages to coincide if M_V(RR) ~ 0.16[Fe/H] + 0.46, which (among other things) puts the Large Magellanic Cloud at (m-M) = 18.78 +/- 0.17 mag. The implied age of the universe is 11.0 +/- 1.4 Gyr, and the corresponding H_0 = 59 +/- 8 km/s per Mpc.

Ultraviolet Observations of Coronal Mass Ejection Impact on Comet 67P/Churyumov–Gerasimenko by Rosetta Alice

NASA Astrophysics Data System (ADS)

Noonan, John W.; Stern, S. Alan; Feldman, Paul D.; Broiles, Thomas; Wedlund, Cyril Simon; Edberg, Niklas J. T.; Schindhelm, Eric; Parker, Joel Wm.; Keeney, Brian A.; Vervack, Ronald J., Jr.; Steffl, Andrew J.; Knight, Matthew M.; Weaver, Harold A.; Feaga, Lori M.; A’Hearn, Michael; Bertaux, Jean-Loup

2018-07-01

The Alice ultraviolet spectrograph on the European Space Agency Rosetta spacecraft observed comet 67P/Churyumov–Gerasimenko in its orbit around the Sun for just over two years. Alice observations taken in 2015 October, two months after perihelion, show large increases in the comet’s Lyβ, O I 1304, O I 1356, and C I 1657 Å atomic emission that initially appeared to indicate gaseous outbursts. However, the Rosetta Plasma Consortium instruments showed a coronal mass ejection (CME) impact at the comet coincident with the emission increases, suggesting that the CME impact may have been the cause of the increased emission. The presence of the semi-forbidden O I 1356 Å emission multiplet is indicative of a substantial increase in dissociative electron impact emission from the coma, suggesting a change in the electron population during the CME impact. The increase in dissociative electron impact could be a result of the interaction between the CME and the coma of 67P or an outburst coincident with the arrival of the CME. The observed dissociative electron impact emission during this period is used to characterize the O2 content of the coma at two peaks during the CME arrival. The mechanism that could cause the relationship between the CME and UV emission brightness is not well constrained, but we present several hypotheses to explain the correlation.

A simulation of the intracluster medium with feedback from cluster galaxies

NASA Technical Reports Server (NTRS)

Metzler, Christopher A.; Evrard, August E.

1994-01-01

We detail method and report first results from a three-dimensional hydrodynamical and N-body simulation of the formation and evolution of a Coma-sized cluster of galaxies, with the intent of studying the history of the hot, X-ray emitting intracluster medium. Cluster gas, galaxies, and dark matter are included in the model. The galaxies and dark matter fell gravitational forces; the cluster gas also undergoes hydrodynamical effects such as shock heating and PdV work. For the first time in three dimensions, we include modeling of ejection of processed gas from the simulated galaxies by winds, including heating and heavy element enrichment. For comparison, we employ a `pure infall' simulation using the same initial conditions but with no galaxies or winds. We employ an extreme ejection history for galactic feedback in order to define the boundary of likely models. As expected, feedback raises the entropy of the intracluster gas, preventing it from collapsing to densities as high as those attained in the infall model. The effect is more pronounced in subclusters formed at high redshift. The cluster with feedback is always less X-ray luminous, but experiences more rapid luminosity evolution, than the pure infall cluster. Even employing an extreme ejection model, the final gas temperature is only approximately 15% larger than in the infall model. The radial temperature profile is very nearly isothermal within 1.5 Mpc. The cluster galaxies in the feedback model have a velocity dispersion approximately 15% lower than the dark matter. This results in the true ratio of specific energies in galaxies to gas being less than one, beta(sub spec) approximately 0.7. The infall model predicts beta(sub spec) approximately 1.2. Large excursions in these values occur over time, following the complex dynamical history of the cluster. The morphology of the X-ray emission is little affected by feedback. The emission profiles of both clusters are well described by the standard beta-model with beta(sub fit) approximately equal to 0.7 - 0.9. X-ray mass estimates based on the assumptions of hydrostatic equilibrium and the applicability of the beta-model are quite accurate in both cases. A strong, radial iron abundance gradient is present, which develops as a consequence of the steepening of the galaxy density profile over time. Spectroscopic observations using nonimaging detectors with wide (approximately 45 min) fields of view dramatically smear the gradient. Observations with arcminute resolution, made available with the ASCA satellite, would readily resolve the gradient.

Rotation-stimulated structures in the CN and C3 comae of comet 103P/Hartley 2 close to the EPOXI encounter

NASA Astrophysics Data System (ADS)

Waniak, W.; Borisov, G.; Drahus, M.; Bonev, T.

2012-07-01

Context. In late 2010, a Jupiter family comet 103P/Hartley 2 was the subject of an intensive world-wide investigation. On UT October 20.7, the comet approached the Earth within only 0.12 AU, and on UT November 4.6 it was visited by the NASA EPOXI spacecraft. Aims: We joined this international effort and organized a ground-based observing campaign with three key goals to: (1) measure the parameters of the nucleus rotation in a time series of CN; (2) investigate the compositional structure of the coma by comparing the CN images with nightly snapshots of C3; and (3) investigate the photochemical relation of CN to HCN, using the HCN data collected nearly simultaneously with our images. Methods: The images were obtained through narrowband filters using the two-meter telescope of the Rozhen National Astronomical Observatory. They were taken over four nights about the moment of the EPOXI encounter. Image processing methods and periodicity analysis techniques were used to identify transient coma structures and investigate their repeatability and kinematics. Results: We observe shells, arc-, jet- and spiral-like patterns that are very similar for the CN and C3 comae. The CN features expanded outwards with the sky-plane projected velocities of between 0.1 to 0.3 km s-1. A corkscrew structure, observed on November 6, evolved with a much higher velocity of 0.66 km s-1. The photometry of the inner coma of CN shows variability with a period of 18.32 ± 0.30 h (valid for the middle moment of our run, UT 2010 Nov 5.0835), which we attribute to the nucleus rotation. This result is fully consistent with independent determinations around the same time by other teams. The pattern of repeatability is, however, imperfect, which is understendable given the suggested excitation of the rotation state, and the variability detected in CN correlates well with the cyclic changes in HCN, but only in the active phases. The identified coma structures, along with the snapshot of the nucleus orientation obtained by EPOXI, enable us to estimate the spin axis orientation. We obtain RA = 122°, Dec = +16° (epoch J2000.0), neglecting at this point the rotational excitation. Based on data collected with two-meter RCC telescope at Rozhen National Astronomical Observatory.Appendix A and movies are available in electronic form at http://www.aanda.org

Prognostic value of EEG in different etiological types of coma.

PubMed

Khaburzania, M; Beridze, M

2013-06-01

Study aimed at evaluation of prognostic value of standard EEG in different etiology of coma and the influence of etiological factor on the EEG patterns and coma outcome. Totally 175 coma patients were investigated. Patients were evaluated by Glasgow Coma Scale (GCS), clinically and by 16 channel electroencephalography. Auditory evoked potentials studied by EEG -regime for evoked potentials in patients with vegetative state (VS). Patients divided in 8 groups according to coma etiology. All patients were studied for photoreaction, brainstem reflexes, localization of sound and pain, length of coma state and outcome. Brain injury visualized by conventional CT. Outcome defined as death, VS, recovery with disability and without disability. Disability was rated by Disability Rating Scale (DRS). Recovered patients assessed by Mini Mental State Examination (MMSE) scale. Statistics performed by SPSS-11.0. From 175 coma patients 55 patients died, 23 patients found in VS, 97 patients recovered with and without disability. In all etiological groups of coma the background EEG patterns were established. Correspondence analysis of all investigated factors revealed that sound localization had the significant association with EEG delta and theta rhythms and with recovery from coma state (Chi-sqr. =31.10493; p= 0.000001). Among 23 VS patients 9 patients had the signs of MCS and showed the long latency waves (p300) after binaural stimulation. The high amplitude theta frequencies in frontal and temporal lobes significantly correlated with prolongation of latency of cognitive evoked potentials (r=+0.47; p<0.01). Etiological factor had the significant effect on EEG patterns' association with coma outcome only in hemorrhagic and traumatic coma (chi-sqr.=12.95; p<0.005; chi-sqr.=7.92; p<0.03 respectively). Significant correlations established between the delta and theta EEG patterns and coma outcome. Low amplitude decreased power delta and theta frequencies correlated with SND in survived coma patients (r=+0.21; p<0.001; r=+0.27; p<0.001 respectively). Standard EEG is the useful tool for elucidation of coma patients with a high probability to recover as well as those patients, who are at high risk of SND in case of recovery from coma state.

ON THE ORIGIN OF INNER COMA STRUCTURES OBSERVED BY ROSETTA DURING A DIURNAL ROTATION OF COMET 67P/CHURYUMOV–GERASIMENKO

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

Kramer, Tobias; Noack, Matthias

2016-05-20

The Rosetta probe around comet 67P/Churyumov–Gerasimenko (67P) reveals an anisotropic dust distribution of the inner coma with jet-like structures. The physical processes leading to jet formation are under debate, with most models for cometary activity focusing on localized emission sources, such as cliffs or terraced regions. Here we suggest, by correlating high-resolution simulations of the dust environment around 67P with observations, that the anisotropy and the background dust density of 67P originate from dust released across the entire sunlit surface of the nucleus rather than from few isolated sources. We trace back trajectories from coma regions with high local dustmore » density in space to the non-spherical nucleus and identify two mechanisms of jet formation: areas with local concavity in either two dimensions or only one. Pits and craters are examples of the first case; the neck region of the bi-lobed nucleus of 67P is an example of the latter case. The conjunction of multiple sources, in addition to dust released from all other sunlit areas, results in a high correlation coefficient (∼0.8) of the predictions with observations during a complete diurnal rotation period of 67P.« less

FUV Spectral Signatures of Molecules and the Evolution of the Gaseous Coma of Comet 67P/Churyumov–Gerasimenko

NASA Astrophysics Data System (ADS)

Feldman, Paul D.; A’Hearn, Michael F.; Bertaux, Jean-Loup; Feaga, Lori M.; Keeney, Brian A.; Knight, Matthew M.; Noonan, John; Parker, Joel Wm.; Schindhelm, Eric; Steffl, Andrew J.; Stern, S. Alan; Vervack, Ronald J.; Weaver, Harold A.

2018-01-01

The Alice far-ultraviolet imaging spectrograph onboard Rosetta observed emissions from atomic and molecular species from within the coma of comet 67P/Churyumov–Gerasimenko during the entire escort phase of the mission from 2014 August to 2016 September. The initial observations showed that emissions of atomic hydrogen and oxygen close to the surface were produced by energetic electron impact dissociation of H2O. Following delivery of the lander, Philae, on 2014 November 12, the trajectory of Rosetta shifted to near-terminator orbits that allowed for these emissions to be observed against the shadowed nucleus that, together with the compositional heterogeneity, enabled us to identify unique spectral signatures of dissociative electron impact excitation of H2O, CO2, and O2. CO emissions were found to be due to both electron and photoexcitation processes. Thus, we are able, from far-ultraviolet spectroscopy, to qualitatively study the evolution of the primary molecular constituents of the gaseous coma from start to finish of the escort phase. Our results show asymmetric outgassing of H2O and CO2 about perihelion, H2O dominant before and CO2 dominant after, consistent with the results from both the in situ and other remote sensing instruments on Rosetta.

Two ten-billion-solar-mass black holes at the centres of giant elliptical galaxies.

PubMed

McConnell, Nicholas J; Ma, Chung-Pei; Gebhardt, Karl; Wright, Shelley A; Murphy, Jeremy D; Lauer, Tod R; Graham, James R; Richstone, Douglas O

2011-12-08

Observational work conducted over the past few decades indicates that all massive galaxies have supermassive black holes at their centres. Although the luminosities and brightness fluctuations of quasars in the early Universe suggest that some were powered by black holes with masses greater than 10 billion solar masses, the remnants of these objects have not been found in the nearby Universe. The giant elliptical galaxy Messier 87 hosts the hitherto most massive known black hole, which has a mass of 6.3 billion solar masses. Here we report that NGC 3842, the brightest galaxy in a cluster at a distance from Earth of 98 megaparsecs, has a central black hole with a mass of 9.7 billion solar masses, and that a black hole of comparable or greater mass is present in NGC 4889, the brightest galaxy in the Coma cluster (at a distance of 103 megaparsecs). These two black holes are significantly more massive than predicted by linearly extrapolating the widely used correlations between black-hole mass and the stellar velocity dispersion or bulge luminosity of the host galaxy. Although these correlations remain useful for predicting black-hole masses in less massive elliptical galaxies, our measurements suggest that different evolutionary processes influence the growth of the largest galaxies and their black holes.

Physical activity of the selected nearly isotropic comets with perihelia at large heliocentric distance

NASA Astrophysics Data System (ADS)

Kulyk, I.; Rousselot, P.; Korsun, P. P.; Afanasiev, V. L.; Sergeev, A. V.; Velichko, S. F.

2018-03-01

Context. The systematic investigation of comets in a wide range of heliocentric distances can contribute to a better understanding of the physical mechanisms that trigger activity at large distances from the Sun and reveals possible differences in the composition of outer solar system bodies belonging to various dynamical groups. Aims: We seek to analyze the dust environment of the selected nearly isotropic comets with a perihelion distance between 4.5 and 9.1 au, where sublimation of water ice is considered to be negligible. Methods: We present results of multicolor broadband photometric observations for 14 distant active objects conducted between 2008 and 2015 with various telescopes. Images obtained with broadband filters were used to investigate optical colors of the cometary comae and to quantify physical activity of the comet nuclei. Results: The activity level was estimated with Afρ parameters ranging between 95 ± 10 cm and 9600 ± 300 cm. Three returning comets were less active than the dynamically new comets. Dust production rates of the comet nuclei were estimated between 1 and 100 kg s-1 based on some assumptions about the physical properties of dust particles populating comae. The measured colors point out reddening of the continuum for all the comets. The mean values of a normalized reflectivity gradient within the group of the comets amount to 14 ± 2% per 1000 Å and 3 ± 2% per 1000 Å in the BV and VR spectral domains, respectively. The comae of the dynamically new comets, which were observed on their inbound legs, may be slightly redder in the blue spectral interval than comae of the comets observed after the perihelion passages. The dynamically new comets observed both pre- and post-perihelion, seem to have higher production rates post-perihelion than pre-perihelion for similar heliocentric distances.

Constraining the Volatile Composition and Coma Photochemistry in Jupiter Family Comet 41P/Tuttle-Giacobini-Kresak with High Resolution IR and Optical Spectroscopy

NASA Astrophysics Data System (ADS)

McKay, Adam; DiSanti, Michael A.; Cochran, Anita L.; Dello Russo, Neil; Bonev, Boncho P.; Vervack, Ronald J.; Gibb, Erika L.; Roth, Nathan X.; Kawakita, Hideyo

2017-10-01

Over the past 20 years optical and IR spectroscopy of cometary comae has expanded our understanding both of cometary volatile composition and coma photochemistry. However, these observations tend to be biased towards Nearly Isotropic Comets (NIC's) from the Oort Cloud, rather than the generally fainter and less active Jupiter Family Comets (JFC's) that are thought to originate from the Scattered Disk. However, early 2017 provided a rare opportunity to study several JFC's. We present preliminary results from IR and optical spectroscopy of JFC 41P/Tuttle-Giacobini-Kresak obtained during its 2017 apparition. IR spectra were obtained with the NIRSPEC instrument on Keck II and the new iSHELL spectrograph on NASA IRTF. High spectral resolution optical spectra were obtained with the Tull Coude spectrograph on the 2.7-meter Harlan J. Smith Telescope at McDonald Observatory. We will discuss mixing ratios of HCN, NH3, C2H6, C2H2, H2CO, and CH3OH compared to H2O and compare these to previous observations of comets. Preliminary results from the NIRSPEC observations indicate that 41P has typical C2H2 and HCN abundances compared to other JFC's, while the C2H6 abundance is similar to that of NIC's, but is enriched compared to other JFC's. H2CO appears to be heavily depleted in 41P. Analysis of the iSHELL spectra is underway and we will include results from these observations, which complement those from NIRSPEC and extend the scope or our compositional study by measuring additional molecules. We will also present abundances for CN, C2, NH2, C3, and CH obtained from the optical spectra and discuss the implications for the coma photochemistry.This work is supported by the NASA Postdoctoral Program, administered by the Universities Space Research Association, with additional funding from the NSF and NASA PAST.

Constraining the Volatile Composition and Coma Photochemistry in Jupiter Family Comet 41P/Tuttle-Giacobini-Kresak with High Resolution IR and Optical Spectroscopy

NASA Astrophysics Data System (ADS)

McKay, Adam; DiSanti, Michael; Cochran, Anita; Dello Russo, Neil; Bonev, Boncho; Vervack, Ronald; Gibb, Erika; Roth, Nathan; Kawakita, Hideyo

2018-01-01

Over the past 20 years optical and IR spectroscopy of cometary comae has expanded our understanding both of cometary volatile composition and coma photochemistry. However, these observations tend to be biased towards Nearly Isotropic Comets (NIC'S) from the Oort Cloud, rather than the generally fainter and less active Jupiter Family Comets (JFC's) that are thought to originate from the Scattered Disk. However, early 2017 provided a rare opportunity to study several JFC's. We present preliminary results from IR and optical spectroscopy of JFC 41P/Tuttle-Giacobini-Kresak obtained during its 2017 apparition. IR spectra were obtained with the NIRSPEC instrument on Keck II and the new iSHELL spectrograph on NASA IRTF. High spectral resolution optical spectra were obtained with the Tull Coude spectrograph on the 2.7-meter Harlan J. Smith Telescope at McDonald Observatory. We will discuss mixing ratios of HCN, NH3, C2H6, C2H2, H2CO, and CH3OH compared to H2O and compare these to previous observations of comets. Preliminary results from the NIRSPEC observations indicate that 41P has typical C2H2 and HCN abundances compared to other JFC's, while the C2H6 abundance is similar to that of NIC's, but is enriched compared to other JFC's. H2CO appears to be heavily depleted in 41P. Analysis of the iSHELL spectra is underway and we will include results from these observations, which complement those from NIRSPEC and extend the scope or our compositional study by measuring additional molecules. We will also present abundances for CN, C2, NH2, C3, and CH obtained from the optical spectra and discuss the implications for the coma photochemistry.This work is supported by the NASA Postdoctoral Program, administered by the Universities Space Research Association, with additional funding from the NSF and NASA PAST.

Application of Early Nutrition Support in Neurosurgical Coma Patients.

PubMed

Ren, Guoqin

2015-12-01

The present study was conducted to investigate the clinical efficacy of early parenteral and enteral nutrition (PN + EN) support in neurosurgical coma patients. Eighty cases of neurosurgical coma patients were randomly divided into intervention group and control group. The intervention group received early PN + EN support, and the control group received only total enteral nutritional (TEN) support. The levels of hemoglobin (HGB), serum albumin (ALB), prealbumin (PA), and retinol-binding protein (RBP) in two groups on days 1, 10, and 20 were observed. The incidences of pneumonia, stress ulcer, abnormal liver function, abdominal distension, and diarrhea between two groups were also compared. Results found that, on day 10, compared with the control group, the levels of HGB, PA, and RBP in the intervention group were significantly increased (P < 0.05). On day 20, ALB in the intervention group significantly increased (P < 0.05), and the incidences of pneumonia, abdominal distension, and diarrhea in the intervention group were significantly lower than those in the control group (P < 0.05). Compared with only TEN support, early PN + EN support can obviously improve the nutritional status of neurosurgical coma patients and reduce the occurrence of complications.

Interpopulational variation in the cold tolerance of a broadly distributed marine copepod

PubMed Central

Wallace, Gemma T.; Kim, Tiffany L.; Neufeld, Christopher J.

2014-01-01

Latitudinal trends in cold tolerance have been observed in many terrestrial ectotherms, but few studies have investigated interpopulational variation in the cold physiology of marine invertebrates. Here, the intertidal copepod Tigriopus californicus was used as a model system to study how local adaptation influences the cold tolerance of a broadly distributed marine crustacean. Among five populations spanning 18° in latitude, the following three metrics were used to compare cold tolerance: the temperature of chill-coma onset, the chill-coma recovery time and post-freezing recovery. In comparison to copepods from warmer southern latitudes, animals from northern populations exhibited lower chill-coma onset temperatures, shorter chill-coma recovery times and faster post-freezing recovery rates. Importantly, all three metrics showed a consistent latitudinal trend, suggesting that any single metric could be used equivalently in future studies investigating latitudinal variation in cold tolerance. Our results agree with previous studies showing that populations within a single species can display strong local adaptation to spatially varying climatic conditions. Thus, accounting for local adaptation in bioclimate models will be useful for understanding how broadly distributed species like T. californicus will respond to anthropogenic climate change. PMID:27293662

Interpopulational variation in the cold tolerance of a broadly distributed marine copepod.

PubMed

Wallace, Gemma T; Kim, Tiffany L; Neufeld, Christopher J

2014-01-01

Latitudinal trends in cold tolerance have been observed in many terrestrial ectotherms, but few studies have investigated interpopulational variation in the cold physiology of marine invertebrates. Here, the intertidal copepod Tigriopus californicus was used as a model system to study how local adaptation influences the cold tolerance of a broadly distributed marine crustacean. Among five populations spanning 18° in latitude, the following three metrics were used to compare cold tolerance: the temperature of chill-coma onset, the chill-coma recovery time and post-freezing recovery. In comparison to copepods from warmer southern latitudes, animals from northern populations exhibited lower chill-coma onset temperatures, shorter chill-coma recovery times and faster post-freezing recovery rates. Importantly, all three metrics showed a consistent latitudinal trend, suggesting that any single metric could be used equivalently in future studies investigating latitudinal variation in cold tolerance. Our results agree with previous studies showing that populations within a single species can display strong local adaptation to spatially varying climatic conditions. Thus, accounting for local adaptation in bioclimate models will be useful for understanding how broadly distributed species like T. californicus will respond to anthropogenic climate change.

Long-Period Planets in Open Clusters and the Evolution of Planetary Systems

NASA Astrophysics Data System (ADS)

Quinn, Samuel N.; White, Russel; Latham, David W.; Stefanik, Robert

2018-01-01

Recent discoveries of giant planets in open clusters confirm that they do form and migrate in relatively dense stellar groups, though overall occurrence rates are not yet well constrained because the small sample of giant planets discovered thus far predominantly have short periods. Moreover, planet formation rates and the architectures of planetary systems in clusters may vary significantly -- e.g., due to intercluster differences in the chemical properties that regulate the growth of planetary embryos or in the stellar space density and binary populations, which can influence the dynamical evolution of planetary systems. Constraints on the population of long-period Jovian planets -- those representing the reservoir from which many hot Jupiters likely form, and which are most vulnerable to intracluster dynamical interactions -- can help quantify how the birth environment affects formation and evolution, particularly through comparison of populations possessing a range of ages and chemical and dynamical properties. From our ongoing RV survey of open clusters, we present the discovery of several long-period planets and candidate substellar companions in the Praesepe, Coma Berenices, and Hyades open clusters. From these discoveries, we improve estimates of giant planet occurrence rates in clusters, and we note that high eccentricities in several of these systems support the prediction that the birth environment helps shape planetary system architectures.

The CfA redshift survey - Data for the NGP + 30 zone

NASA Technical Reports Server (NTRS)

Huchra, John P.; Geller, Margaret J.; De Lapparent, Valerie; Corwin, Harold G., Jr.

1990-01-01

Redshifts and morphological types are presented for a complete sample of 1093 galaxies with m(pg) less than or equal to 15.5 mag in a 6-deg-wide strip crossing the north Galactic pole. Also presented are redshifts for an additional 92 fainter galaxies in the same strip. Outside of the core of the Coma Cluster, both early- and late-type galaxies trace essentially the same structures in redshift space. Thinner slices illustrate the small velocity dispersion perpendicular to the surfaces in the survey.

Infrared Observations of Cometary Dust and Nuclei

NASA Technical Reports Server (NTRS)

Lisse, Carey

2004-01-01

This bibliography lists citations for publications published under the grant. Subjects of the publications include cometary dust, instellar and interplanetary dust, comet nuclei and comae, Comet Hale-Bopp, infrared observations of comets, mass loss, and comet break-up.

These are two images of the inner coma of Comet Hyakutake

NASA Technical Reports Server (NTRS)

2002-01-01

These are two images of the inner coma of Comet Hyakutake made on April 3 and 4, 1996, using the NASA Hubble Space Telescope Wide Field Planetary Camera 2 (WFPC2). The first one, shown in red, was taken through a narrow-band red filter that shows only sunlight scattered by dust particles in the inner coma of the comet. The second one, shown in blue was taken with an ultraviolet 'Woods' filter image that shows the distribution of scattered ultraviolet radiation from hydrogen atoms in the inner coma. The coma is the head or dusty-gas atmosphere of a comet. The square field of view is 14,000 km on a side and the sun is toward the upper right corner of the image. Hydrogen atoms represent the most abundant gas in the whole coma of the comet. They are produced when solar ultraviolet light breaks up molecules of water, the major constitutent of the nucleus of the comet. These images were taken as part of an observing program to study water photochemistry in comets. Measurements of hydrogen (H) and hydroxyl (OH) in the coma (or atmosphere) of Comet Hyakutake were also made using the Goddard High Resolution Spectrograph (GHRS) and the Faint Object Spectrograph (FOS). A self-consistent analysis of all the data shows that the water production rate of the comet was between 7 and 8 tons per second on the April 3 and 4. A theoretical model was used in the analysis which accounts for the detailed physics and chemistry of the photochemical destruction of the water, the production of the H and OH, and their expansion in the coma (or atmosphere) of the comet. The model matched the velocity measurements of hydrogen atoms made using the high spectral resolution capabilities of the GHRS instrument. The importance of such a detailed model is that is permits the accurate calculation of the production rate of water from observations of H and OH. The inner yellow region near the center of the red dust image is dominated by the contribution from the dust which shows sunward directed spiral jets toward the upper right, and the thin straight particle trail pointing toward the lower left. The trail was a permanent feature of the comet around the time of its close approach to the earth in late March and early April. Also barely visible just beyond the lower left end of the trail are two of the many condensations which were seen to travel slowly down the tail are are believed to be clumps of material released from the nucleus. The inner white region of the blue image appears to show that the hydrogen atoms like the dust might be preferentially ejected toward the sunward or day side of the nucleus. However, this is not true. The asymmetric ultraviolet radiation pattern is produced by a roughly spherical distribution of hydrogen atoms because they are so efficient at scattering the incoming solar ultraviolet light. The atoms on the sunward side actually shadow the atoms on the tailward or night side of the coma. The same detailed model analysis of the coma which explains the expansion of the hydrogen atoms in the coma also explains the appearance of the image. The team was lead by Michael Combi, The University of Michigan, and included Michael Brown, California Institute of Technology, Paul Feldman, Johns Hopkins University, H. Uwe Keller of the Max Planck Institute, Lindau, Robert Meier of the Naval Research Laboratory, and William Smyth of Atmospheric and Environmental Research, Inc. Credit: M.R. Combi (The University of Michigan)

The LCO/Gemini-South campaign for Deep Impact target Comet 9P/Tempel 1: Temporally resolved wide-field narrowband imaging results

NASA Astrophysics Data System (ADS)

Lederer, S. M.; Osip, D. J.; Thomas-Osip, J. E.; DeBuizer, J. M.; Mondragon, L. A.; Schweiger, D. L.; Viehweg, J.; SB Collaboration

2005-08-01

An extensive observing campaign to monitor Comet 9P/Tempel 1 will be conducted from 20 June to 19 July, 2005 at Las Campanas Observatory, Chile. These observations will precede and follow the impact of the Deep Impact projectile, which is likely to create a crater on the nucleus that will act as a fresh active area on the surface of the comet. Discreet nucleus active areas, believed to be the source of coma gas and dust jets, will likely result in changing morphology in the coma. We present the initial results of the wide-field narrowband visible imaging of the comet. Data will be taken with the 2.5m DuPont telescope from 27 June - 9 July, following the comet from 4 rotations prior to impact, to 4 rotations after impact using the narrowband Hale-Bopp filters, including CN, C2, and two continuum filters. These data will allow an accurate determination of the rotation state of the embedded nucleus immediately preceding the impact event as well as a measure of any changes to the rotation state due to the impact. In addition, modeling of these data will provide the total dust and gas production rates from the unaltered nucleus compared to the enhanced dust and gas emission from the newly created active region and freely sublimating pieces of mantle material ejected into the coma by the impactor. We will monitor temporal changes (on hours and days time-scales) in the morphology of both the gas and refractory components. We will use coma morphology studies to estimate the dust and gas outflow velocities and infer the presence of discreet nucleus source regions (pre- and post-impact). Of particular interest is the study of the gas-to-dust ratio and the ratio of the minor carbon species emitted from the newly created active region relative to the pre-impact coma environment.

The kinetics and dynamics of the coma of Halley's comet

NASA Technical Reports Server (NTRS)

Combi, Michael R.

1994-01-01

This grant to the University of Michigan supported the efforts of Michael R. Combi to serve as a co-investigator in collaboration with a larger effort by the principal investigator, William Smyth of Atmospheric and Environmental Research, Inc. The overall objective of this project was to analyze in a self-consistent manner unique optical O((sup 1)D) and NH2 ultra-high resolution line profile data of excellent quality and other supporting lower-resolution spectral data for the coma of comet P/Halley by using highly developed and physically-based cometary coma models in order to determine and explain in terms of physical processes the actual dynamics and photochemical kinetics that occur in the coma. The justification for this work is that it provides a valuable and underlying physical base from which to interpret significantly different types of coma observations in a self-consistent manner and hence bring into agreement (or avoid) apparent inconsistencies that arise from non-physically based interpretations. The level of effort for the Michigan component amounted to less than three person-months over a planned period of three years. The period had been extended at no extra cost to four years because the Michigan grant and the AER contract did not have coincident time periods. An effort of somewhat larger scope was undertaken by the PI. The importance of the O((sup 1)D) profiles is that they provide a direct trace of the water distribution in comets. The line profile shape is produced by the convolution of the outflow velocity and thermal dispersion of the parent water molecules with the photokinetic ejection of the oxygen atoms upon photodissociation of the parent water molecules. Our understanding of the NH2 and its precursor ammonia are important for comet-to-comet composition variations as they relate to the cosmo-chemistry of the early solar nebula. Modeling of the distribution of NH2 is necessary in order to infer the ammonia production rates from NH2 observations.

Evolution of near UV Halley's spectrum in the inner coma

NASA Technical Reports Server (NTRS)

Rousselot, Phillippe; Clairemidi, Jacques; Vernotte, F.; Moreels, Guy

1992-01-01

A direct way to observe the photodissociation of water vapor in a cometary coma is to detect the OH prompt emission. This emission is shifted of delta lambda = 4 nm with respect to the OH 309 nm fluorescence band. The extended data set obtained with the three-channel spectrometer on-board Vega 2 reveals at short distance of the nucleus (i.e., less than 600 km) an excess of emission on the right wing of the OH band which may be interpreted as being mainly due to prompt emission.

The Aftermath of the Largest Cometary Outburst in Recorded History - An In-Depth Study of Comet 17P/Holmes

NASA Astrophysics Data System (ADS)

Stevenson, Rachel Ann

On UT 2007 Oct. 23, Jupiter Family comet 17P/Holmes underwent the largest cometary outburst in recorded history when it brightened by a factor of nearly a million in less than 2 days. This unprecedented event prompted a four-month observing campaign to observe the aftermath of the outburst. The wide field imager, MegaCam mounted on the Canada-France-Hawaii telescope was used to obtain r' images of the nucleus and the rapidly expanding dust coma. These images are unequaled in their quality and scope, and form a unique dataset with which to study the outburst aftermath. This original work examines the morphology of the outburst, and constrains the characteristics of the ejected material. Spatial filtering of images obtained in 2007 Nov. revealed numerous fragments moving away from the nucleus. The fragments were too bright to have been inactive, monolithic blocks and must have been acting as mini-comets with their own sources of sublimating volatiles and dust comae. They represented a significant (~ 10%) of the total ejected mass. The fragments had unusually high velocities relative to the nucleus, suggesting that they were accelerated by high gas pressure inside the nucleus prior to ejection. This work presents the first detection of such large, rapidly moving cometary fragments. The scarcity of similar ejecta around other fragmenting comets may be due to observational biases, rather than being unique to 17P/Holmes. Aperture photometry was used to study the evolution of the inner coma, which faded rapidly in the weeks and months following the initial outburst. Despite the observed fading, the nucleus must have remained active, continuing to supply fresh material to the inner coma. A second, much smaller outburst was detected on UT 2007 Nov. 12, which released an estimated 106 kg of dust into the inner coma. The secondary outburst showed that the nucleus remained unstable for several weeks after the initial event. Surface brightness profiles of the inner coma were constructed for each night of observation. The slopes of the profiles between 10000 km and 25000 km are consistent with dust grains fragmenting near the nucleus. Such fragmenting may be caused by thermal stressing or sublimation of cohesive volatiles. As the comet moved away from the Sun, the profiles also showed a persistent bump, interpreted as a halo of freshly released ice grains. The expected sublimation rates of such grains were examined, and it is concluded that the ice grains must have been contaminated with albedo-lowering regolith that significantly shortened their life-times. The possible characteristics of these dirty ice grains are examined within the context of the observations. The mini-comet fragments, dirty ice grains, and continuing but declining activity together suggest that the outburst of 17P/Holmes excavated material from within the nucleus, and left exposed patches of sublimating volatiles on its surface. The long-term fate of 17P/Holmes is uncertain, but micro-outbursts are likely as the nucleus settles over coming apparitions.

MIRO Computational Model

NASA Technical Reports Server (NTRS)

Broderick, Daniel

2010-01-01

A computational model calculates the excitation of water rotational levels and emission-line spectra in a cometary coma with applications for the Micro-wave Instrument for Rosetta Orbiter (MIRO). MIRO is a millimeter-submillimeter spectrometer that will be used to study the nature of cometary nuclei, the physical processes of outgassing, and the formation of the head region of a comet (coma). The computational model is a means to interpret the data measured by MIRO. The model is based on the accelerated Monte Carlo method, which performs a random angular, spatial, and frequency sampling of the radiation field to calculate the local average intensity of the field. With the model, the water rotational level populations in the cometary coma and the line profiles for the emission from the water molecules as a function of cometary parameters (such as outgassing rate, gas temperature, and gas and electron density) and observation parameters (such as distance to the comet and beam width) are calculated.

Observation of a rapid decrease in the brightness of the coma of 2060 Chiron in 1990 January

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

Buratti, B.J.; Dunbar, R.S.

Photometric observations of 2060 Chiron in the V and R filters were obtained with the 1.5-m telescope on Palomar Mountain during a 7-hr period on January 20, 1990 (UT). A general decrease of about 10 percent in integrated brightness occurred in both filters. No color dependence to the decrease was observed. A small (about 0.02 mag) rotational light curve, far smaller than the 0.09 mag (peak-to-peak) one observed by Bus et al. (1989) is superposed on the general decrease. On January 29, 1990, Luu and Jewitt (1990) observed an impulsive brightening of Chiron of approximately the same magnitude and timemore » scale as the presently observed decrease in brightness. The combined results provide evidence that Chiron is currently exhibiting short-term fluctuations in the brightness of its coma, in addition to its well-established general decrease in brightness. 14 refs.« less

EEG in connection with coma.

PubMed

Wilson, John A; Nordal, Helge J

2013-01-08

Coma is a dynamic condition that may have various causes. Important changes may take place rapidly, often with consequences for treatment. The purpose of this article is to provide a brief overview of EEG patterns in comas with various causes, and indicate how EEG contributes in an assessment of the prognosis for coma patients. The article is based on many years of clinical and research-based experience of EEG used for patients in coma. A self-built reference database was supplemented by searches for relevant articles in PubMed. EEG reveals immediate changes in coma, and can provide early information on cause and prognosis. It is the only diagnostic tool for detecting a non-convulsive epileptic status. Locked-in- syndrome may be overseen without EEG. Repeated EEG scans increase diagnostic certainty and make it possible to monitor the development of coma. EEG reflects brain function continuously and therefore holds a key place in the assessment and treatment of coma.

Water ice grains in comet C/2013 US10 (Catalina)

NASA Astrophysics Data System (ADS)

Protopapa, Silvia; Kelley, Michael S. P.; Yang, Bin; Woodward, Charles E.; Sunshine, Jessica M.

2017-10-01

Knowledge of the the physical properties of water ice in cometary nuclei is critical in determining how the Solar System was formed. While it is difficult to directly study the properties of water ice in comet nuclei, we can study comet interiors through their comae. Cometary activity makes the interiors of these objects available for characterization. However, the properties (grain size, abundance, purity, chemical state) of water-ice grains detected in the coma do not necessarily represent the characteristics of the water ice on the surface and/or in the interior of the nucleus. This is due to the potential physical and chemical evolution of the emitted material. Once in the coma, water-ice grains are heated by sunlight, and if temperatures are warm enough, they sublime. In this case, their sizes and potentially their ice-to-dust fractions are reduced.We present IRTF/SpeX measurements of the Oort cloud comet C/2013 US10 (Catalina), which reached perihelion in Nov 2015 at a heliocentric distance Rh=0.822 AU. Observations of US10 were acquired on UT 2014-08-13, 2016-01-12, and 2016-08-13 (Rh=5.9, 1.3, and 3.9 AU). This set of measurements, spanning a broad range in Rh, are rare and fundamental for estimating how ice grains evolve in the coma. The spectrum obtained close to perihelion is featureless and red sloped, which is consistent with a dust-dominated coma. Conversely, the spectra acquired on August 2014 and 2016 display neutral slopes and absorption bands at 1.5 and 2.0 μm, consistent with the presence of water-ice grains. These variations in water ice with heliocentric distance are correlated with sublimation rates. Additionally, the measurements obtained at 5.8 AU and 3.9 AU are nearly identical, suggesting that water-ice grains, once in the coma, do not sublime significantly. Therefore, the properties of these long-lived water-ice grains may represent their state in the nucleus or immediately after insertion into the coma. We will present radiative transfer models of the data and interpret the results in the context of spacecraft data of cometary nuclei, and of our on-going compositional survey of water-ice grain halos in cometary comae.This work was funded by NASA SSO, NASA PAST and NASA SOFIA grants.

Groundbased cometary studies

NASA Technical Reports Server (NTRS)

Schleicher, David G.

1991-01-01

The physical properties of comets were studied by applying a wide variety of observational techniques. Emphasis is on simultaneous or coordinated observations in different spectral regions (e.g., visible and thermal IR or visible and far UV) or with different instrumentation (imaging, spectroscopy, and photometry). The aim was to: (1) measure the basic properties of cometary nuclei by studying comets whose comae are so anemic that the signal from the nucleus can be extracted; (2) investigate the group characteristics of comets by narrowband photometry applied uniformly to a large sample of comets; (3) understand the detailed physics and chemistry occurring in cometary comae through wide-field charge coupled device (CCD) imaging using narrow filters and through long-slit CCD spectroscopy; and (4) investigate the rotational states of comets through time-resolution photometry.

New Mysteries at Chiron

NASA Technical Reports Server (NTRS)

Elliot, James L.

1998-01-01

Considered as a comet, Chiron is unusual in two respects: (1) it exhibits outbursts at great distances from the sun (nearly up to its aphelion distance of 18.9 AU), and (2) its nucleus is much larger than any other known comet. It is similar in size, however, to the recently discovered Kuiper belt objects, leading to the conjecture that Chiron is closely related to these objects, but its chaotic orbit has brought it much closer to the sun. Our work with the Kuiper Airborne Observatory resulted in the first stellar occultation by Chiron observed simultaneously at visible and infrared wavelengths. We detected four features in the coma, with different degrees of certainty. Our conclusions about Chiron from this work and a previous stellar occultation are: (1) the jet-like features observed provide evidence that the coma material originates from just a few, small active areas, rather than uniform sublimation; (2) a bound coma has possibly been detected; (3) the particle radii in at least one of the jet-like features are larger than 0.25 gm; (4) material in Chiron's orbit plane has likely been detected; and (5) the radius of Chiron's nucleus lies between 83 and 156 km.

The portrayal of coma in contemporary motion pictures.

PubMed

Wijdicks, Eelco F M; Wijdicks, Coen A

2006-05-09

Coma has been a theme of screenplays in motion pictures, but there is no information about its accuracy. The authors reviewed 30 movies from 1970 to 2004 with actors depicting prolonged coma. Accurate depiction of comatose patients was defined by appearance, the complexity of care, accurate cause of coma and probability of awakening, and appropriate compassionate discussion between the physician and family members. Twenty-two key scenes from 17 movies were rated for accuracy by a panel of neurointensivists and neuroscience nurses and then were shown to 72 nonmedical viewers. Accuracy of the scenes was assessed using a Likert Scale. Coma was most often caused by motor vehicle accidents or violence (63%). The time in a comatose state varied from days to 10 years. Awakening occurred in 18 of 30 motion pictures (60%). Awakening was sudden with cognition intact, even after prolonged time in a coma. Actors personified "Sleeping Beauty" (eyes closed, beautifully groomed). Physicians appeared as caricatures. Only two movies had a reasonable accurate representation (Dream Life of Angels and Reversal of Fortune). The majority of the surveyed viewers identified inaccuracy of representation of coma, awakenings, and conversations on the experience of being in a coma, except in 8 of the 22 scenes (36%). Twenty-eight of the 72 viewers (39%) could potentially allow these scenes to influence decisions in real life. Misrepresentation of coma and awakening was common in motion pictures and impacted on the public perception of coma. Neurologic advice regarding prolonged coma is needed.

Time-dependent evolution of the near nuclear coma of cometary nuclei during their rotational motion

NASA Astrophysics Data System (ADS)

Szego, K.; Crifo, J.-F.; Fulle, M.; Rodionov, A. V.

2003-04-01

The new physical model of Rodionov et al. (Planetary and Space Sci., 50, 983, 2002) that describes the cometary activity based on a 3-d collisional gas dynamical model has been successfully applied to account for the dust features observed by the cameras flying onboard of the VEGA and Giotto probes during the encounter with comet Halley. This indicates, in particular, that these structures are dominantly controlled by the nucleus topography. An upgraded version of this model has been recently developed and is being applied to the vast body of data gathered in 1986 on comet Halley. This new version is tridimensional as previously, and, in addition, time-dependent. This allows the exact, self-consistent computation of the whole coma structure (primary and daughter molecules, dust), allowing to study its dependence upon nucleus shape, composition, and rotation. The results presented here assume that the coma is formed by solar-driven sublimation of a homogeneous dusty-ice nucleus with shape and rotational state derived for P/Halley. The results are, however, of quite general significance -- in particular they remain valid for different shapes and for inhomogeneous nucleus. This presentation focuses on the time dependence of the dust and gas features obtained around the nucleus. Movies will summarize the results of the calculations exhibiting the time development of the dust and gas coma and its relation to the surface orography for a rotating nucleus. The effect of nucleus activity on its rotational motion, and possible constraints hampering the observation of the activity will be also analyzed.

VizieR Online Data Catalog: Spectroscopy of standard stars (Joner+, 2015)

NASA Astrophysics Data System (ADS)

Joner, M. D.; Hintz, E. G.

2016-06-01

Between 2005 and 2015, spectroscopic data were obtained using the 1.2-m McKellar Telescope of the Dominion Astrophysical Observatory (DAO). In total, data were secured on 153 nights using the telescope in robotic mode. Observations were made using the Coude spectrograph with the 3231 grating, which provided 40.9Å/mm. Using the Site4 CCD with 15μm pixels gives 0.614Å/pixel. With 4096 pixels along the dispersion axis, this provided a total coverage of approximately 2500Å. Aligning the grating to give a central wavelength of 5710Å allowed a spectral coverage from 4450 to 6970Å, which provided coverage of both Hα and Hβ. In total we examined 75 field stars (table2), 12 stars from the Coma star cluster (table3), 24 from the Hyades (table4), 17 from the Pleiades (table5), and 8 from NGC 752 (table6). These stars cover a spectral type range from O9 to K2. (5 data files).

Can sterile neutrinos be ruled out as warm dark matter candidates?

PubMed

Viel, Matteo; Lesgourgues, Julien; Haehnelt, Martin G; Matarrese, Sabino; Riotto, Antonio

2006-08-18

We present constraints on the mass of warm dark matter (WDM) particles from a combined analysis of the matter power spectrum inferred from the Sloan Digital Sky Survey Lyman-alpha flux power spectrum at 2.2

The inter-rater reliability and prognostic value of coma scales in Nepali children with acute encephalitis syndrome.

PubMed

Ray, Stephen; Rayamajhi, Ajit; Bonnett, Laura J; Solomon, Tom; Kneen, Rachel; Griffiths, Michael J

2018-02-01

Background Acute encephalitis syndrome (AES) is a common cause of coma in Nepali children. The Glasgow coma scale (GCS) is used to assess the level of coma in these patients and predict outcome. Alternative coma scales may have better inter-rater reliability and prognostic value in encephalitis in Nepali children, but this has not been studied. The Adelaide coma scale (ACS), Blantyre coma scale (BCS) and the Alert, Verbal, Pain, Unresponsive scale (AVPU) are alternatives to the GCS which can be used. Methods Children aged 1-14 years who presented to Kanti Children's Hospital, Kathmandu with AES between September 2010 and November 2011 were recruited. All four coma scales (GCS, ACS, BCS and AVPU) were applied on admission, 48 h later and on discharge. Inter-rater reliability (unweighted kappa) was measured for each. Correlation and agreement between total coma score and outcome (Liverpool outcome score) was measured by Spearman's rank and Bland-Altman plot. The prognostic value of coma scales alone and in combination with physiological variables was investigated in a subgroup (n = 22). A multivariable logistic regression model was fitted by backward stepwise. Results Fifty children were recruited. Inter-rater reliability using the variables scales was fair to moderate. However, the scales poorly predicted clinical outcome. Combining the scales with physiological parameters such as systolic blood pressure improved outcome prediction. Conclusion This is the first study to compare four coma scales in Nepali children with AES. The scales exhibited fair to moderate inter-rater reliability. However, the study is inadequately powered to answer the question on the relationship between coma scales and outcome. Further larger studies are required.

Spectral mapping of comet 67P/Churyumov-Gerasimenko with VLT/MUSE and SINFONI

NASA Astrophysics Data System (ADS)

Guilbert-Lepoutre, Aurelie; Besse, Sebastien; Snodgrass, Colin; Yang, Bin

2016-10-01

Comets are supposedly the most primitive objects in the solar system, preserving the earliest record of material from the nebula out of which our Sun and planets were formed, and thus holding crucial clues on the early phases of the solar system formation and evolution. For most small bodies in the solar system we can only access the surface properties, whereas active comet nuclei lose material from their subsurface, so that understanding cometary activity represents an unique opportunity to assess their internal composition, and by extension the composition, the temperature and pressure conditions of the protoplanetary disk at their place of formation.The ESA/Rosetta mission is performing the most thorough investigation of a comet ever made. Rosetta is measuring properties of comet 67P/Churyumov-Gerasimenko at distances between 5 and hundreds of km from the nucleus. However, it is unable to make any measurement over the thousands of km of the rest of the coma. Fortunately, the outer coma is accessible from the ground. In addition, we currently lack an understanding of how the very detailed information gathered from space-based observations can be extrapolated to the many ground-based observations that we can potentially perform. Combining parallel in situ observations with observations from the ground therefore gives us a great opportunity, not only to understand the behavior of 67P, but also to other comets observed exclusively from Earth. As part of the many observations taken from the ground, we have performed a spectral mapping of 67's coma using two IFU instruments mounted on the VLT: MUSE in the visible, and SINFONI in the near-infrared. The observations, carried out in March 2016, will be presented and discussed.

103P/Hartley 2: ground-based monitoring of the EPOXI flyby comet

NASA Astrophysics Data System (ADS)

Tubiana, C.; Snodgrass, C.; Vincent, J.-B.; Barrera, L.; Nowajewski, P.; Retamales, G.; Lister, T.; Boehnhardt, H.

2011-10-01

Comet 103P/Hartley 2 was the fly-by target of the NASA EPOXI mission. Observations of this comet during its previous perihelion passage [1] and in 2008 when it was in its aphelion arc [2, 3] revealed a small and very active nucleus. We observed 103P from March 2010 to January 2011 using the 4m SOAR telescope located at Cerro Pachon, Chile. We took images in UBVRI filters using the SOAR Optical Imager (SOI). In addition, we made use of the large collection of (mostly BVR) images taken of the comet by school pupils using the two robotic 2m Faulkes Telescopes, which cover the same period. At the time of the observations, the comet was moving from 2.8 AU pre-perihelion to 1.6 AU post-perihelion heliocentric distance, when the comet was expected to display the most activity. The main purpose of our observations was the characterization of the activity of comet 103P and its evolution along the perihelion arc. We searched for the presence of dust coma structures and their evolution with changing heliocentric distance and determined gas and dust production rates, the dust color and the variation in these quantities as the comet passed perihelion. While no coma structures were detected between March and July 2010, a clear anisotropy in the coma in the anti-tail direction was detected in images obtained in November 2011 (Fig. 1). At the same place, the Laplace filter detects what might be a jet.

Statistical analysis of dust signals observed by ROSINA/COPS onboard of the Rosetta spacecraft at comet 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Tzou, Chia-Yu; altwegg, kathrin; Bieler, Andre; Calmonte, Ursina; Gasc, Sébastien; Le Roy, Léna; Rubin, Martin

2016-10-01

ROSINA is the in situ Rosetta Orbiter Spectrometer for Ion and Neutral Analysis on board of Rosetta, one of the corner stone missions of the European Space Agency (ESA) to land and orbit the Jupiter family comet 67P/Churyumov-Gerasimenko (67P). ROSINA consists of two mass spectrometers and a pressure sensor. The Reflectron Time of Flight Spectrometer (RTOF) and the Double Focusing Mass Spectrometer (DFMS) complement each other in mass and time resolution.The Comet Pressure Sensor (COPS) provides density measurements of the neutral molecules in the cometary coma of 67P. COPS has two gauges, a nude gauge that measures the total neutral density and a ram gauge that measures the dynamic pressure from the comet. Combining the two COPS is also capable of providing gas dynamic information such as gas velocity and gas temperature of the coma.While Rosetta started orbiting around 67P in August 2014, COPS observed diurnal and seasonal variations of the neutral gas density in the coma. Surprisingly, additional to these major density variation patterns, COPS occasionally observed small spikes in the density that are associated with dust. These dust signals can be interpreted as a result of cometary dust releasing volatiles while heated up near COPS. A statistical analysis of dust signals detected by COPS will be presented.

Immediate coma and poor outcome in subarachnoid haemorrhage are independently associated with an aneurysmal origin.

PubMed

Tsermoulas, Georgios; Flett, Lisa; Gregson, Barbara; Mitchell, Patrick

2013-08-01

Subarachnoid haemorrhage (SAH) may present with coma and this is known to be associated with aneurysmal origin and blood load. Aneurysmal origin is associated with increased blood load and existing data do not allow us to determine if the association between coma and aneurysmal SAH is wholly due to blood load or if aneurysmal origin has an additional independent effect. The objective of our study is to find if an aneurysmal origin is a predictor of acute onset of coma independent of blood load. A series of consecutive patients with spontaneous SAH were divided into two groups: aneurysmal (aSAH) and non-aneurysmal--angiographically negative SAH (naSAH). Blood load was quantified so that the effect of aneurysmal origin could be resolved from the effect of the amount of blood spilled. Non-parametric regression was used to relate blood load to coma and poor outcome rates for aneurysmal bleeds. We analysed a total of 421 patients presenting during the period 2009-2011. Ninety aneurysmal cases presented with coma, seventy immediately in the early phase and seven shortly after rebleeding. None of the naSAH cases presented with immediate coma and 1 developed delayed coma. Delayed coma was associated with acute hydrocephalus in both groups. Aneurysmal origin was found to be an independent determinant of immediate coma (p=0.02) and poor outcome (p<0.001). Immediate coma and poor outcome in SAH are associated with an aneurysmal origin and do not characterize naSAH. Copyright © 2013 Elsevier B.V. All rights reserved.

2 years with comet 67P/Churyumov-Gerasimenko: H2O, CO2, CO as seen by ROSINA RTOF

NASA Astrophysics Data System (ADS)

Hoang, M.; Garnier, P.; Lasue, J.; Reme, H.; Altwegg, K.; Balsiger, H. R.; Bieler, A. M.; Calmonte, U.; Capria, M. T.; Combi, M. R.; De Keyser, J. M.; Fiethe, B.; Fougere, N.; Fuselier, S. A.; Galli, A.; Gasc, S.; Gombosi, T. I.; Hansen, K. C.; Jäckel, A.; Korth, A.; Mall, U.; Migliorini, A.; Rubin, M.; Sémon, T.; Tzou, C. Y.; Waite, J. H., Jr.; Wurz, P.

2017-12-01

The Rosetta space mission investigated comet 67P/Churyumov-Gerasimenko (67P) over two years from August 2014 to September 2016. Onboard the spacecraft, the ROSINA experiment included two mass spectrometers to derive the composition of neutrals and ions, and a COmet Pressure Sensor (COPS) to monitor the density and velocity of the neutrals in the coma. We will here analyse and discuss data from the Reflectron-type Time-Of-Flight instrument during the comet escort phase. The RTOF mass spectrometer possessed a wide mass range and a high temporal resolution (Balsiger et al., 2007). The analysis of 67P/C-G's coma major molecules over the mission showed strong variability of the comet coma's main volatiles concentrations (H2O, CO2, CO) and their relative abundances. The 2 years long Rosetta mission allowed us to observe the seasonal evolution in the atmosphere of 67P, in particular the change occurring during the equinoxes and at perihelion. In this work, we analyze the asymmetry in the outgassing rate before and after the perihelion (13/08/2015), the evolution of abundance ratios through the whole mission, and in particular the behavior of the very volatile CO molecules. Density maps projected on the surface of 67P demonstrate the evolution of the three main coma species after the outbound equinox. We will present first results of our comet nucleus thermal modelling used to simulate the internal structure and temperature evolution of 67P at characteristic surface areas. These results will be compared with the coma composition measurements obtained by ROSINA.

The phase-space structure of nearby dark matter as constrained by the SDSS

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

Leclercq, Florent; Percival, Will; Jasche, Jens

Previous studies using numerical simulations have demonstrated that the shape of the cosmic web can be described by studying the Lagrangian displacement field. We extend these analyses, showing that it is now possible to perform a Lagrangian description of cosmic structure in the nearby Universe based on large-scale structure observations. Building upon recent Bayesian large-scale inference of initial conditions, we present a cosmographic analysis of the dark matter distribution and its evolution, referred to as the dark matter phase-space sheet, in the nearby universe as probed by the Sloan Digital Sky Survey main galaxy sample. We consider its stretchings andmore » foldings using a tetrahedral tessellation of the Lagrangian lattice. The method provides extremely accurate estimates of nearby density and velocity fields, even in regions of low galaxy density. It also measures the number of matter streams, and the deformation and parity reversals of fluid elements, which were previously thought inaccessible using observations. We illustrate the approach by showing the phase-space structure of known objects of the nearby Universe such as the Sloan Great Wall, the Coma cluster and the Boötes void. We dissect cosmic structures into four distinct components (voids, sheets, filaments, and clusters), using the Lagrangian classifiers DIVA, ORIGAMI, and a new scheme which we introduce and call LICH. Because these classifiers use information other than the sheer local density, identified structures explicitly carry physical information about their formation history. Accessing the phase-space structure of dark matter in galaxy surveys opens the way for new confrontations of observational data and theoretical models. We have made our data products publicly available.« less

The phase-space structure of nearby dark matter as constrained by the SDSS

NASA Astrophysics Data System (ADS)

Leclercq, Florent; Jasche, Jens; Lavaux, Guilhem; Wandelt, Benjamin; Percival, Will

2017-06-01

Previous studies using numerical simulations have demonstrated that the shape of the cosmic web can be described by studying the Lagrangian displacement field. We extend these analyses, showing that it is now possible to perform a Lagrangian description of cosmic structure in the nearby Universe based on large-scale structure observations. Building upon recent Bayesian large-scale inference of initial conditions, we present a cosmographic analysis of the dark matter distribution and its evolution, referred to as the dark matter phase-space sheet, in the nearby universe as probed by the Sloan Digital Sky Survey main galaxy sample. We consider its stretchings and foldings using a tetrahedral tessellation of the Lagrangian lattice. The method provides extremely accurate estimates of nearby density and velocity fields, even in regions of low galaxy density. It also measures the number of matter streams, and the deformation and parity reversals of fluid elements, which were previously thought inaccessible using observations. We illustrate the approach by showing the phase-space structure of known objects of the nearby Universe such as the Sloan Great Wall, the Coma cluster and the Boötes void. We dissect cosmic structures into four distinct components (voids, sheets, filaments, and clusters), using the Lagrangian classifiers DIVA, ORIGAMI, and a new scheme which we introduce and call LICH. Because these classifiers use information other than the sheer local density, identified structures explicitly carry physical information about their formation history. Accessing the phase-space structure of dark matter in galaxy surveys opens the way for new confrontations of observational data and theoretical models. We have made our data products publicly available.

Velocity-resolved observations of water in Comet Halley

NASA Technical Reports Server (NTRS)

Larson, Harold P.; Davis, D. Scott; Mumma, Michael J.; Weaver, Harold A.

1986-01-01

High resolution (lambda/delta lambda approx. = 3 x 10 to the 5th power) near-infrared observations of H2O emission from Comet Halley were acquired at the time of maximum post-perihelion geocentric Doppler shift. The observed widths and absolute positions of the H2O line profiles reveal characteristics of the molecular velocity field in the coma. These results support H2O outflow from a Sun-lit hemisphere or the entire nucleus, but not from a single, narrow jet emanating from the nucleus. The measured pre- and post-perihelion outflow velocities were 0.9 + or - 0.2 and 1.4 + or - 0.2 km/s, respectively. Temporal variations in the kinematic properties of the outflow were inferred from changes in the spectral line shapes. These results are consistent with the release of H2O into the coma from multiple jets.

Probing 67P/Churyumov-Gerasimenko's Electron Environment Through Ultraviolet Emission by Rosetta Alice Observations

NASA Astrophysics Data System (ADS)

Schindhelm, Eric; Noonan, John; Keeney, Brian A.; Broiles, Thomas; Bieler, Andre; A'Hearn, Michael F.; Bertaux, Jean-Loup; Feaga, Lori M.; Feldman, Paul D.; Parker, Joel Wm.; Steffl, Andrew Joseph; Stern, S. Alan; Weaver, Harold A.

2016-10-01

The Alice Far-Ultraviolet (FUV) Spectrograph onboard ESA's Rosetta spacecraft has observed the coma of comet 67P/Churyumov-Gerasimenko from far approach in summer 2014 until the end of mission in September 2016. We present an overall perspective of the bright FUV emission lines (HI 1026 Å, OI 1302/1305/1306 Å multiplet, OI] 1356 Å, CO 1510 (1-0) Å, and CI 1657 Å) above the sunward hemisphere, detailing their spatial extent and brightness as a function of time and the heliocentric distance of the comet. We compare our observed gas column densities derived using electron temperatures and densities from the Ion Electron Sensor (IES) with those derived using the Inner Coma Environment Simulator (ICES) models in periods when electron-impact excited emission dominates over solar fluorescence emission. The electron population is characterized with 2 three-dimensional kappa functions, one dense and warm, one rarefied and hot.

Carbonaceous Components in the Comet Halley Dust

NASA Technical Reports Server (NTRS)

Fomenkova, M. N.; Chang, S.; Mukhin, L. M.

1994-01-01

Cometary grains containing large amounts of carbon and/or organic matter (CHON) were discovered by in situ measurements of comet Halley dust composition during VEGA and GIOTTO flyby missions. In this paper, we report the classification of these cometary, grains by means of cluster analysis, discuss the resulting compositional groups, and compare them with substances observed or hypothesized in meteorites, interplanetary dust particles, and the interstellar medium. Grains dominated by carbon and/or organic matter (CHON grains) represent approx. 22% of the total population of measured cometary dust particles. They, usually contain a minor abundance of rock-forming elements as well. Grains having organic material are relatively more abundant in the vicinity of the nucleus than in the outer regions of the coma, which suggests decomposition of the organics in the coma environment. The majority of comet Halley organic particles are multicomponent mixtures of carbon phases and organic compounds. Possibly, the cometary CHON grains may be related to kerogen material of an interstellar origin in carbonaceous meteorites. Pure carbon grains, hydrocarbons and polymers of cyanopolyynes, and multi-carbon monoxides are present in cometary dust as compositionally simple and distinctive components among a variety of others. There is no clear evidence of significant presence of pure formaldehyde or HCN polymers in Halley dust particles. The diversity of types of cometary organic compounds is consistent with the inter-stellar dust model of comets and probably reflects differences in composition of precursor dust. Preservation of this heterogeneity among submicron particles suggest the gentle formation of cometary, nucleus by aggregation of interstellar dust in the protosolar nebula without complete mixing or chemical homogenization at the submicron level.

Intracranial Pressure Monitoring in Infants and Young Children With Traumatic Brain Injury.

PubMed

Dixon, Rebecca R; Nocera, Maryalice; Zolotor, Adam J; Keenan, Heather T

2016-11-01

To examine the use of intracranial pressure monitors and treatment for elevated intracranial pressure in children 24 months old or younger with traumatic brain injury in North Carolina between April 2009 and March 2012 and compare this with a similar cohort recruited 2000-2001. Prospective, observational cohort study. Twelve PICUs in North Carolina. All children 24 months old or younger with traumatic brain injury, admitted to an included PICU. None. The use of intracranial pressure monitors and treatments for elevated intracranial pressure were evaluated in 238 children with traumatic brain injury. Intracranial pressure monitoring (risk ratio, 3.7; 95% CI, 1.5-9.3) and intracranial pressure therapies were more common in children with Glasgow Coma Scale less than or equal to 8 compared with Glasgow Coma Scale greater than 8. However, only 17% of children with Glasgow Coma Scale less than or equal to 8 received a monitoring device. Treatments for elevated intracranial pressure were more common in children with monitors; yet, some children without monitors received therapies traditionally used to lower intracranial pressure. Unadjusted predictors of monitoring were Glasgow Coma Scale less than or equal to 8, receipt of cardiopulmonary resuscitation, nonwhite race. Logistic regression showed no strong predictors of intracranial pressure monitor use. Compared with the 2000 cohort, children in the 2010 cohort with Glasgow Coma Scale less than or equal to 8 were less likely to receive monitoring (risk ratio, 0.5; 95% CI, 0.3-1.0), although the estimate was not precise, or intracranial pressure management therapies. Children in the 2010 cohort with a Glasgow Coma Scale less than or equal to 8 were less likely to receive an intracranial pressure monitor or hyperosmolar therapy than children in the 2000 cohort; however, about 10% of children without monitors received therapies to decrease intracranial pressure. This suggests treatment heterogeneity in children 24 months old or younger with traumatic brain injury and a need for better evidence to support treatment recommendations for this group of children.

Immediate and Long-Term Outcome of Acute H2S Intoxication Induced Coma in Unanesthetized Rats: Effects of Methylene Blue

PubMed Central

Sonobe, Takashi; Chenuel, Bruno; Cooper, Timothy K.; Haouzi, Philippe

2015-01-01

Background Acute hydrogen sulfide (H2S) poisoning produces a coma, the outcome of which ranges from full recovery to severe neurological deficits. The aim of our study was to 1- describe the immediate and long-term neurological effects following H2S-induced coma in un-anesthetized rats, and 2- determine the potential benefit of methylene blue (MB), a compound we previously found to counteract acute sulfide cardiac toxicity. Methods NaHS was administered IP in un-sedated rats to produce a coma (n = 34). One minute into coma, the rats received MB (4 mg/kg IV) or saline. The surviving rats were followed clinically and assigned to Morris water maze (MWM) and open field testing then sacrificed at day 7. Results Sixty percent of the non-treated comatose rats died by pulseless electrical activity. Nine percent recovered with neurological deficits requiring euthanasia, their brain examination revealed major neuronal necrosis of the superficial and middle layers of the cerebral cortex and the posterior thalamus, with variable necrosis of the caudate putamen, but no lesions of the hippocampus or the cerebellum, in contrast to the typical distribution of post-ischemic lesions. The remaining animals displayed, on average, a significantly less effective search strategy than the control rats (n = 21) during MWM testing. Meanwhile, 75% of rats that received MB survived and could perform the MWM test (P<0.05 vs non-treated animals). The treated animals displayed a significantly higher occurrence of spatial search than the non-treated animals. However, a similar proportion of cortical necrosis was observed in both groups, with a milder clinical presentation following MB. Conclusion In conclusion, in rats surviving H2S induced coma, spatial search patterns were used less frequently than in control animals. A small percentage of rats presented necrotic neuronal lesions, which distribution differed from post-ischemic lesions. MB dramatically improved the immediate survival and spatial search strategy in the surviving rats. PMID:26115032

Is the tail of 73P-B/Schwassman-Wachman 1 chasing its Remnant Nucleus?

NASA Technical Reports Server (NTRS)

Wooden, D. H.; Harker, D. E.; Woodward, C. E.; Ehrenfreund, P.; Geers, V. C.; Waters, L. B. F. M.; Cox, N.

2006-01-01

We report on imaging observations of comets 73P-B/Schwassmann-Wachmann 1 and 73P-C/Schwassmann-Wachmann 1 at the IRTF with SpeX (J, K) and MRSI (10 micron narrow band filter set) on 2006 Apr 17-19 UT and 2006 Jun 18-19, and at the VLT with VISIR (1 0 micron narrow band filters, 20 micron) on 2006 Apr 17 UT. Compared to when the comet was in the midst of breaking up in mid-April, in June the tail of 73P-B is much fainter and there is a compact coma detected well separated and ahead of its tail, and fainter than the tail. The width of the tail in J, K, and 10 micron images indicates that the pieces that were shed in April must still be outgassing and releasing small particles into the tail-shaped coma; small grains have relatively short lifetimes in the coma due to radiation pressure. The trailing tail is now well separated from the faint "leader of the pack" compact coma that we suppose is a remaining piece of the nucleus. It will be interesting to see post-perihelion if this "leading compact coma" object continues to gain distance on the debris and continues to weakly outgas and shed small grains. One wonders if it expended its volatiles (available to the surface) in breaking up; a short-lived release of volatiles occurred in the Deep Impact event with comet 9P/Tempel 1. 73P-C is extended with a more elongated coma structure closer to perihelion compared to 2006 Apr 18- 19 UT. The SEDs from 2006 Apr and Jun from SpeX-MIRSI (IRTF) are compared with VISIR (VLT) SEDs from 2006 Apr. Information on the heliocentric dependence of the activity and dust release yields insights into the origin of activity and the relationship between activity and grain size distribution/mineralogy.

Immediate and Long-Term Outcome of Acute H2S Intoxication Induced Coma in Unanesthetized Rats: Effects of Methylene Blue.

PubMed

Sonobe, Takashi; Chenuel, Bruno; Cooper, Timothy K; Haouzi, Philippe

2015-01-01

Acute hydrogen sulfide (H2S) poisoning produces a coma, the outcome of which ranges from full recovery to severe neurological deficits. The aim of our study was to 1--describe the immediate and long-term neurological effects following H2S-induced coma in un-anesthetized rats, and 2--determine the potential benefit of methylene blue (MB), a compound we previously found to counteract acute sulfide cardiac toxicity. NaHS was administered IP in un-sedated rats to produce a coma (n = 34). One minute into coma, the rats received MB (4 mg/kg i.v.) or saline. The surviving rats were followed clinically and assigned to Morris water maze (MWM) and open field testing then sacrificed at day 7. Sixty percent of the non-treated comatose rats died by pulseless electrical activity. Nine percent recovered with neurological deficits requiring euthanasia, their brain examination revealed major neuronal necrosis of the superficial and middle layers of the cerebral cortex and the posterior thalamus, with variable necrosis of the caudate putamen, but no lesions of the hippocampus or the cerebellum, in contrast to the typical distribution of post-ischemic lesions. The remaining animals displayed, on average, a significantly less effective search strategy than the control rats (n = 21) during MWM testing. Meanwhile, 75% of rats that received MB survived and could perform the MWM test (P<0.05 vs non-treated animals). The treated animals displayed a significantly higher occurrence of spatial search than the non-treated animals. However, a similar proportion of cortical necrosis was observed in both groups, with a milder clinical presentation following MB. In conclusion, in rats surviving H2S induced coma, spatial search patterns were used less frequently than in control animals. A small percentage of rats presented necrotic neuronal lesions, which distribution differed from post-ischemic lesions. MB dramatically improved the immediate survival and spatial search strategy in the surviving rats.

ON THE ELECTRON-TO-NEUTRAL NUMBER DENSITY RATIO IN THE COMA OF COMET 67P/CHURYUMOV–GERASIMENKO: GUIDING EXPRESSION AND SOURCES FOR DEVIATIONS

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

Vigren, E.; Eriksson, A. I.; Edberg, N. J. T.

2015-10-10

We compute partial photoionization frequencies of H{sub 2}O, CO{sub 2}, and CO, the major molecules in the coma of comet 67P/Churyumov–Gerasimenko, the target comet of the ongoing ESA Rosetta mission. Values are computed from Thermosphere Ionosphere Mesosphere Energy and Dynamics/Solar EUV Experiment solar EUV spectra for 2014 August 1, 2015 March 1, and for perihelion (2015 August, as based on prediction). From the varying total photoionization frequency of H{sub 2}O, as computed from 2014 August 1 to 2015 May 20, we derive a simple analytical expression for the electron-to-neutral number density ratio as a function of cometocentric and heliocentric distance. Themore » underlying model assumes radial movement of the coma constituents and does not account for chemical loss or the presence of electric fields. We discuss various effects/processes that can cause deviations between values from the analytical expression and actual electron-to-neutral number density ratios. The analytical expression is thus not strictly meant as predicting the actual electron-to-neutral number density ratio, but is useful in comparisons with observations as an indicator of processes at play in the cometary coma.« less

EEG and Coma.

PubMed

Ardeshna, Nikesh I

2016-03-01

Coma is defined as a state of extreme unresponsiveness, in which a person exhibits no voluntary movement or behavior even to painful stimuli. The utilization of EEG for patients in coma has increased dramatically over the last few years. In fact, many institutions have set protocols for continuous EEG (cEEG) monitoring for patients in coma due to potential causes such as subarachnoid hemorrhage or cardiac arrest. Consequently, EEG plays an important role in diagnosis, managenent, and in some cases even prognosis of coma patients.

Calibration of the Tip of the Red Giant Branch Distance Method in IR

NASA Astrophysics Data System (ADS)

Sakai, Shoko

1999-02-01

We propose to investigate the feasibility of the tip of the red giant branch (TRGB) as a distance indicator in IR wavelength. The TRGB has been shown both observationally and theoretically to be an excellent distance indicator in I-band, mainly because of its insensitivity to both metallicity and age. Its accuracy is comparable to that of the Cepheid variable stars. The TRGB method in I-band is currently calibrated by Galactic globular clusters whose distances have been measured with RR Lyrae variables. The main objective of this proposal is to calibrate this method in IR by obtaining JHK photometry for a number of Galactic globular clusters. This is motivated by two related scientific goals: (1) It will be possible in the future to obtain direct distances to galaxies even in Coma cluster using the NGST, but only if the TRGB method has been calibrated accurately in IR filters. If the method is proven reliable, then it can be a powerful tool to map out the density and velocity fields of the local Universe in three dimensions. (2) A considerable amount of effort has been spent on obtaining accurate, direct distances to nearby galaxies. However, this has been difficult for a number of galaxies, including IC 342, because they are located at very low Galactic latitude. These galaxies could potentially have a tremendous effect on the dynamics of the Local Group, depending on their distances. Using the calibrated IR TRGB method, we could solve this uncertainty by measuring their distances directly.

A population of faint low surface brightness galaxies in the Perseus cluster core

NASA Astrophysics Data System (ADS)

Wittmann, Carolin; Lisker, Thorsten; Ambachew Tilahun, Liyualem; Grebel, Eva K.; Conselice, Christopher J.; Penny, Samantha; Janz, Joachim; Gallagher, John S.; Kotulla, Ralf; McCormac, James

2017-09-01

We present the detection of 89 low surface brightness (LSB), and thus low stellar density galaxy candidates in the Perseus cluster core, of the kind named 'ultra-diffuse galaxies', with mean effective V-band surface brightnesses 24.8-27.1 mag arcsec-2, total V-band magnitudes -11.8 to -15.5 mag, and half-light radii 0.7-4.1 kpc. The candidates have been identified in a deep mosaic covering 0.3 deg2, based on wide-field imaging data obtained with the William Herschel Telescope. We find that the LSB galaxy population is depleted in the cluster centre and only very few LSB candidates have half-light radii larger than 3 kpc. This appears consistent with an estimate of their tidal radius, which does not reach beyond the stellar extent even if we assume a high dark matter content (M/L = 100). In fact, three of our candidates seem to be associated with tidal streams, which points to their current disruption. Given that published data on faint LSB candidates in the Coma cluster - with its comparable central density to Perseus - show the same dearth of large objects in the core region, we conclude that these cannot survive the strong tides in the centres of massive clusters.

Far-ultraviolet spectral images of comet Halley from sounding rockets

NASA Technical Reports Server (NTRS)

Mccoy, R. P.; Carruthers, G. R.; Opal, C. B.

1986-01-01

Far-ultraviolet images of comet Halley obtained from sounding rockets launched from White Sands Missile Range, New Mexico, on 24 February and 13 March, 1986, are presented. Direct electrographic images of the hydrogen coma of the comet were obtained at the Lyman-alpha wavelength along with objective spectra containing images of the coma at the oxygen, carbon, and sulfur resonance multiplets. Analysis of the Lyman-alpha images yields hydrogen atom production rates of 1.9 x 10 to the 30th/s and 1.4 x 120 to the 30th/s for the two observations. Images of oxygen, carbon, and sulfur emissions obtained with the objective grating spectrograph are presented for the first set of observations and preliminary production rates are derived for these elements.

Comet Hyakutake C/1996 B2

NASA Technical Reports Server (NTRS)

1998-01-01

These are two images of the inner coma of Comet Hyakutake made on April 3 and 4, 1996, using the NASA Hubble Space Telescope Wide Field Planetary Camera 2 (WFPC2). The first one, shown in red, was taken through a narrow-band red filter that shows only sunlight scattered by dust particles in the inner coma of the comet. The second one, shown in blue was taken with an ultraviolet 'Woods' filter image that shows the distribution of scattered ultraviolet radiation from hydrogen atoms in the inner coma. The coma is the head or dusty-gas atmosphere of a comet. The square field of view is 14,000 km on a side and the sun is toward the upper right corner of the image. Hydrogen atoms represent the most abundant gas in the whole coma of the comet. They are produced when solar ultraviolet light breaks up molecules of water, the major constituent of the nucleus of the comet. These images were taken as part of an observing program to study water photochemistry in comets. Measurements of hydrogen (H) and hydroxyl (OH) in the coma (or atmosphere) of Comet Hyakutake were also made using the Goddard High Resolution Spectrograph (GHRS) and the Faint Object Spectrograph (FOS). A self-consistent analysis of all the data shows that the water production rate of the comet was between 7 and 8 tons per second on the April 3 and 4. A theoretical model was used in the analysis which accounts for the detailed physics and chemistry of the photochemical destruction of the water, the production of the H and OH, and their expansion in the coma (or atmosphere) of the comet. The model matched the velocity measurements of hydrogen atoms made using the high spectral resolution capabilities of the GHRS instrument. The importance of such a detailed model is that is permits the accurate calculation of the production rate of water from observations of H and OH.

The inner yellow region near the center of the red dust image is dominated by the contribution from the dust which shows sunward directed spiral jets toward the upper right, and the thin straight particle trail pointing toward the lower left. The trail was a permanent feature of the comet around the time of its close approach to the Earth in late March and early April. Also barely visible just beyond the lower left end of the trail are two of the many condensations which were seen to travel slowly down the tail are believed to be clumps of material released from the nucleus.

The inner white region of the blue image appears to show that the hydrogen atoms like the dust might be preferentially ejected toward the sunward or day side of the nucleus. However, this is not true. The asymmetric ultraviolet radiation pattern is produced by a roughly spherical distribution of hydrogen atoms because they are so efficient at scattering the incoming solar ultraviolet light. The atoms on the sunward side actually shadow the atoms on the tailward or night side of the coma. The same detailed model analysis of the coma which explains the expansion of the hydrogen atoms in the coma also explains the appearance of the image.

The team was lead by Michael Combi, The University of Michigan, and included Michael Brown, California Institute of Technology, Paul Feldman, Johns Hopkins University, H. Uwe Keller of the Max Planck Institute, Lindau, Robert Meier of the Naval Research Laboratory, and William Smyth of Atmospheric and Environmental Research, Inc.

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/

Myxedema coma leading to respiratory depression in a dog.

PubMed

Atkinson, Kathryn; Aubert, Isabelle

2004-04-01

A 10-year-old, intact male, cocker spaniel was presented with hypothermia, without shivering, and progressive stupor leading to coma. Myxedema coma, potentially precipitated by diuretic therapy, was tentatively diagnosed and treatment initiated, but progressive respiratory depression led to the decision to euthanize. Postmortem findings supported the diagnosis of myxedema coma.

Myxedema coma leading to respiratory depression in a dog

PubMed Central

2004-01-01

Abstract A 10-year-old, intact male, cocker spaniel was presented with hypothermia, without shivering, and progressive stupor leading to coma. Myxedema coma, potentially precipitated by diuretic therapy, was tentatively diagnosed and treatment initiated, but progressive respiratory depression led to the decision to euthanize. Postmortem findings supported the diagnosis of myxedema coma. PMID:15144105

Severe angioedema in myxedema coma: a difficult airway in a rare endocrine emergency.

PubMed

Lee, Christopher H; Wira, Charles R

2009-10-01

Myxedema coma is the most lethal manifestation of hypothyroidism. It is a true medical emergency and can result in profound hemodynamic instability and airway compromise. Myxedema coma currently remains a diagnostic challenge due to the rarity of cases seen today, and failure to promptly initiate therapy with replacement thyroid hormone can be fatal. As thyroid hormone therapy can take days or weeks to reverse the manifestations of myxedema coma, interim supportive therapy is critical while awaiting clinical improvement. Some patients will require endotracheal intubation in the emergency department (ED), and physicians should be aware that unanticipated posterior pharyngeal edema in myxedema coma could severely complicate airway management. Although mechanical ventilation is a well-described adjunctive therapy for myxedema coma, reports of the potential difficulty in securing a definitive airway in these patients are rare. We describe a case of an unidentified woman who presented to the ED with myxedema coma requiring urgent endotracheal intubation and was found to have extensive posterior pharyngeal angioedema inconsistent with her relatively benign external examination. This case highlights the typical features of myxedema coma and discusses our necessity for a rescue device in definitive endotracheal tube placement. Emergency physicians should anticipate a potentially difficult airway in all myxedema coma patients regardless of the degree of external facial edema present.

Survival rate and expression of Heat-shock protein 70 and Frost genes after temperature stress in Drosophila melanogaster lines that are selected for recovery time from temperature coma.

PubMed

Udaka, Hiroko; Ueda, Chiaki; Goto, Shin G

2010-12-01

In this study, we investigated the physiological mechanisms underlying temperature tolerance using Drosophila melanogaster lines with rapid, intermediate, or slow recovery from heat or chill coma that were established by artificial selection or by free recombination without selection. Specifically, we focused on the relationships among their recovery from heat or chill coma, survival after severe heat or cold, and survival enhanced by rapid cold hardening (RCH) or heat hardening. The recovery time from heat coma was not related to the survival rate after severe heat. The line with rapid recovery from chill coma showed a higher survival rate after severe cold exposure, and therefore the same mechanisms are likely to underlie these phenotypes. The recovery time from chill coma and survival rate after severe cold were unrelated to RCH-enhanced survival. We also examined the expression of two genes, Heat-shock protein 70 (Hsp70) and Frost, in these lines to understand the contribution of these stress-inducible genes to intraspecific variation in recovery from temperature coma. The line showing rapid recovery from heat coma did not exhibit higher expression of Hsp70 and Frost. In addition, Hsp70 and Frost transcription levels were not correlated with the recovery time from chill coma. Thus, Hsp70 and Frost transcriptional regulation was not involved in the intraspecific variation in recovery from temperature coma. Copyright © 2010 Elsevier Ltd. All rights reserved.

Childhood acute non-traumatic coma: aetiology and challenges in management in resource-poor countries of Africa and Asia.

PubMed

Gwer, Samson; Chacha, Clifford; Newton, Charles R; Idro, Richard

2013-08-01

This review examines the best available evidence on the aetiology of childhood acute non-traumatic coma in resource-poor countries (RPCs), discusses the challenges associated with management, and explores strategies to address them. Publications in English and French which reported on studies on the aetiology of childhood non-traumatic coma in RPCs are reviewed. Primarily, the MEDLINE database was searched using the keywords coma, unconsciousness, causality, aetiology, child, malaria cerebral, meningitis, encephalitis, Africa, Asia, and developing countries. 14 records were identified for inclusion in the review. Cerebral malaria (CM) was the commonest cause of childhood coma in most of the studies conducted in Africa. Acute bacterial meningitis (ABM) was the second most common known cause of coma in seven of the African studies. Of the studies in Asia, encephalitides were the commonest cause of coma in two studies in India, and ABM was the commonest cause of coma in Pakistan. Streptococcus pneumoniae was the most commonly isolated organism in ABM. Japanese encephalitis, dengue fever and enteroviruses were the viral agents most commonly isolated. Accurate diagnosis of the aetiology of childhood coma in RPCs is complicated by overlap in clinical presentation, limited diagnostic resources, disease endemicity and co-morbidity. For improved outcomes, studies are needed to further elucidate the aetiology of childhood coma in RPCs, explore simple and practical diagnostic tools, and investigate the most appropriate specific and supportive interventions to manage and prevent infectious encephalopathies.

'Is she alive? Is she dead?' Representations of chronic disorders of consciousness in Douglas Coupland's Girlfriend in a Coma.

PubMed

Colbeck, Matthew

2016-09-01

Depictions of coma have come to dominate literary and filmic texts over the last half century, a phenomenon coinciding with advancements in medical technology that have led to remarkable increases in the survival rates of patients with chronic disorders of consciousness. Authors of coma fiction are preoccupied with the imagined subjective experience of coma, often creating complex, dream-like worlds from which the protagonist must escape if survival is to be achieved. However, such representations appear to conflict with medical case studies and patient narratives that reveal that most often survivors of coma have no recollection of the coma itself. Providing a close reading of Douglas Coupland's Girlfriend in a Coma (1998) against the context of medical literature and diagnoses, this article examines how the coma patient is represented, often depicting the realities of a prolonged vegetative state, in contrast with other popular representations of coma. It explores how the author develops a work of 'fantastic' fiction (a genre defined by the structuralist critic Tzvetan Todorov), using the condition of coma as a metaphor for a postmodern existential crisis, while simultaneously employing mimetic techniques that raise important medical, ethical and philosophical questions surrounding the ontological status of the comatose patient. It is argued that coma fiction, even in its misrepresentation of the condition, can help us to engage with and interrogate how we think about chronic disorders of consciousness, thereby providing a valuable insight into our attitudes towards illness and mortality. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

ERRATUM: 'MAPPING THE GAS TURBULENCE IN THE COMA CLUSTER: PREDICTIONS FOR ASTRO-H'

NASA Technical Reports Server (NTRS)

Zuhone, J. A.; Markevitch, M.; Zhuravleva, I.

2016-01-01

The published version of this paper contained an error in Figure 5. This figure is intended to show the effect on the structure function of subtracting the bias induced by the statistical and systematic errors on the line shift. The filled circles show the bias-subtracted structure function. The positions of these points in the left panel of the original figure were calculated incorrectly. The figure is reproduced below (with the original caption) with the correct values for the bias-subtracted structure function. No other computations or figures in the original manuscript are affected.

IUE observations of Comet Halley: Evolution of the UV spectrum between September 1985 and July 1986

NASA Technical Reports Server (NTRS)

Feldman, P. D.; Festou, Michael C.; Ahearn, M. F.; Arpigny, C.; Butterworth, P. S.; Cosmovici, C. B.; Danks, A. C.; Gilmozzi, R.; Jackson, W. M.; Mcfadden, L. A.

1986-01-01

The ultraviolet spectrum of comet P/Halley was monitored with the IUE between 12 September 1985 and 8 July 1986 (r <2.6 AU pre and post-perihelion) at regular time intervals except for a two-month period around the time of perihelion. A complete characterization of the UV spectrum of the comet was obtained to derive coma abundances and to study the light emission mechanisms of the observed species. The Fine Error Sensor (FES) camera of the IUE was used to photometrically investigate the coma brightness variation on time scales of the order of hours. Spectroscopic observations as well as FES measurements show that the activity of the nucleus is highly variable, particularly at the end of December 1985 and during March and April 1986. The production rates of OH, CS and dust are derived for the entire period of the observations. The total water loss rate for this period is estimated to be 150 million metric tons.

The Comet Halley Handbook: An Observer's Guide. Second Edition.

ERIC Educational Resources Information Center

Yeomans, Donald K.

This handbook contains information on: (1) the orbit of comet Halley; (2) the expected physical behavior of comet Halley in 1985-1986, considering brightness estimates, coma diameters, and tail lengths; (3) observing conditions for comet Halley in 1985-1986; and (4) observing conditions for the dust tail of comet Halley in 1985-1986. Additional…

Infrared spectrophotometry of Comet IRAS-Araki-Alcock (1983d) - A bare nucleus revealed?

NASA Technical Reports Server (NTRS)

Hanner, M. S.; Aitken, D. K.; Knacke, R.; Mccorkle, S.; Roche, P. F.; Tokunaga, A. T.

1985-01-01

Spectra of the central core and surrounding coma of Comet IRAS-Araki-Alcock (1983d) were obtained at 8-13 microns on May 11 and 2-4 microns on May 12, 1983. Spatially resolved measurements at 10 microns with a 4-arcsec beam showed that the central core was more than 100 times brighter than the inner coma only 8 arcsec away; for radially outflowing dust, the brightness ratio would be a factor of 8. The observations of the central core are consistent with direct detection of a nucleus having a radius of approximately 5 km. The temperature of the sunlit hemisphere was greater than 300 K. Spectra of the core are featureless, while spectra of the coma suggest weak silicate emission. The spectra show no evidence for icy grains. The dust production rate on May 11.4 was about 100,000 g/sec, assuming that the gas flux from the dust-producing areas on the nucleus was about 0.00001 g/sq cm per sec.

[Brain function recovery after prolonged posttraumatic coma].

PubMed

Klimash, A V; Zhanaidarov, Z S

2016-01-01

To explore the characteristics of brain function recovery in patients after prolonged posttraumatic coma and with long-unconscious states. Eighty-seven patients after prolonged posttraumatic coma were followed-up for two years. An analysis of a clinical/neurological picture after a prolonged episode of coma was based on the dynamics of vital functions, neurological status and patient's reactions to external stimuli. Based on the dynamics of the clinical/neurological picture that shows the recovery of functions of the certain brain areas, three stages of brain function recovery after a prolonged episode of coma were singled out: brain stem areas, diencephalic areas and telencephalic areas. These functional/anatomic areas of brain function recovery after prolonged coma were compared to the present classifications.

Tests of the Tully-Fisher relation. 1: Scatter in infrared magnitude versus 21 cm width

NASA Technical Reports Server (NTRS)

Bernstein, Gary M.; Guhathakurta, Puragra; Raychaudhury, Somak; Giovanelli, Riccardo; Haynes, Martha P.; Herter, Terry; Vogt, Nicole P.

1994-01-01

We examine the precision of the Tully-Fisher relation (TFR) using a sample of galaxies in the Coma region of the sky, and find that it is good to 5% or better in measuring relative distances. Total magnitudes and disk axis ratios are derived from H and I band surface photometry, and Arecibo 21 cm profiles define the rotation speeds of the galaxies. Using 25 galaxies for which the disk inclination and 21 cm width are well defined, we find an rms deviation of 0.10 mag from a linear TFR with dI/d(log W(sub c)) = -5.6. Each galaxy is assumed to be at a distance proportional to its redshift, and an extinction correction of 1.4(1-b/a) mag is applied to the total I magnitude. The measured scatter is less than 0.15 mag using milder extinction laws from the literature. The I band TFR scatter is consistent with measurement error, and the 95% CL limits on the intrinsic scatter are 0-0.10 mag. The rms scatter using H band magnitudes is 0.20 mag (N = 17). The low width galaxies have scatter in H significantly in excess of known measurement error, but the higher width half of the galaxies have scatter consistent with measurement error. The H band TFR slope may be as steep as the I band slope. As the first applications of this tight correlation, we note the following: (1) the data for the particular spirals commonly used to define the TFR distance to the Coma cluster are inconsistent with being at a common distance and are in fact in free Hubble expansion, with an upper limit of 300 km/s on the rms peculiar line-of-sight velocity of these gas-rich spirals; and (2) the gravitational potential in the disks of these galaxies has typical ellipticity less than 5%. The published data for three nearby spiral galaxies with Cepheid distance determinations are inconsistent with our Coma TFR, suggesting that these local calibrators are either ill-measured or peculiar relative to the Coma Supercluster spirals, or that the TFR has a varying form in different locales.

Tests of the Tully-Fisher relation. 1: Scatter in infrared magnitude versus 21 CM width

NASA Astrophysics Data System (ADS)

Bernstein, Gary M.; Guhathakurta, Puragra; Raychaudhury, Somak; Giovanelli, Riccardo; Haynes, Martha P.; Herter, Terry; Vogt, Nicole P.

1994-06-01

We examine the precision of the Tully-Fisher relation (TFR) using a sample of galaxies in the Coma region of the sky, and find that it is good to 5% or better in measuring relative distances. Total magnitudes and disk axis ratios are derived from H and I band surface photometry, and Arecibo 21 cm profiles define the rotation speeds of the galaxies. Using 25 galaxies for which the disk inclination and 21 cm width are well defined, we find an rms deviation of 0.10 mag from a linear TFR with dI/d(log Wc) = -5.6. Each galaxy is assumed to be at a distance proportional to its redshift, and an extinction correction of 1.4(1-b/a) mag is applied to the total I magnitude. The measured scatter is less than 0.15 mag using milder extinction laws from the literature. The I band TFR scatter is consistent with measurement error, and the 95% CL limits on the intrinsic scatter are 0-0.10 mag. The rms scatter using H band magnitudes is 0.20 mag (N = 17). The low width galaxies have scatter in H significantly in excess of known measurement error, but the higher width half of the galaxies have scatter consistent with measurement error. The H band TFR slope may be as steep as the I band slope. As the first applications of this tight correlation, we note the following: (1) the data for the particular spirals commonly used to define the TFR distance to the Coma cluster are inconsistent with being at a common distance and are in fact in free Hubble expansion, with an upper limit of 300 km/s on the rms peculiar line-of-sight velocity of these gas-rich spirals; and (2) the gravitational potential in the disks of these galaxies has typical ellipticity less than 5%. The published data for three nearby spiral galaxies with Cepheid distance determinations are inconsistent with our Coma TFR, suggesting that these local calibrators are either ill-measured or peculiar relative to the Coma Supercluster spirals, or that the TFR has a varying form in different locales.

Evidence for biasing in the CfA survey

NASA Technical Reports Server (NTRS)

Hamilton, A. J. S.

1988-01-01

Intrinsically bright galaxies appear systematically more correlated than faint galaxies in the Center for Astrophysics redshift survey. The amplification of the two-point correlation function behaves exponentially with luminosity, being essentially flat up to the knee of the luminosity function, then increasing markedly. The amplification reaches a factor of 3.5e + or - 0.4 in the very brightest galaxies. The effect is dominated by spirals rather than ellipticals, so that the correlation function of bright spirals becomes comparable to that of normal ellipticals. Similar results are obtained whether the correlation function is measured in two or three dimensions. The effect persists to separations of a correlation length or more, and is not confined to the cores of the Virgo, Coma, and Abell 1367 clusters, suggesting that the effect is caused by biasing, that is, galaxies kindle preferentially in more clustered regions, rather than by gravitational relaxation.

Quenching of the Star Formation Activity of Galaxies in Dense Environments

NASA Astrophysics Data System (ADS)

Boselli, A.

2017-12-01

The nearby Universe is an ideal laboratory to study the effects of the environments on galaxy evolution. We have analysed the multifrequency properties of galaxies in the nearby clusters Virgo, Coma, and A1367. We have shown that the HI gas content and the activity of star formation of the late-type galaxies start to gradually decrease inwards ˜ one virial radius. We have also shown that late-type galaxies in these clusters have truncated HI, H_2, dust, and star forming discs once the HI gas content is removed by the harsh environment. Some of these galaxies also exibit spectacular tails of atomic neutral, ionised, or hot gas without any counterpart in the stellar component. All this evidence favors ram pressure stripping as the dominant mechanism responsible for the gas removal from the disc, and for the following quenching of the star formation activity.

Accuracy of self-reported length of coma and posttraumatic amnesia in persons with medically verified traumatic brain injury.

PubMed

Sherer, Mark; Sander, Angelle M; Maestas, Kacey Little; Pastorek, Nicholas J; Nick, Todd G; Li, Jingyun

2015-04-01

To determine the accuracy of self-reported length of coma and posttraumatic amnesia (PTA) in persons with medically verified traumatic brain injury (TBI) and to investigate factors that affect self-report of length of coma and PTA duration. Prospective cohort study. Specialized rehabilitation center with inpatient and outpatient programs. Persons (N=242) with medically verified TBI who were identified from a registry of persons who had previously participated in TBI-related research. Not applicable. Self-reported length of coma and self-reported PTA duration. Review of medical records revealed that the mean medically documented length of coma and PTA duration was 6.9±12 and 19.2±22 days, respectively, and the mean self-reported length of coma and PTA duration was 16.7±22 and 106±194 days, respectively. The average discrepancy between self-report and medical record for length of coma and PTA duration was 8.2±21 and 64±176 days, respectively. Multivariable regression models revealed that time since injury, performance on cognitive tests, and medical record values were associated with self-reported values for both length of coma and PTA duration. In this investigation, persons with medically verified TBI showed poor accuracy in their self-report of length of coma and PTA duration. Discrepancies were large enough to affect injury severity classification. Caution should be exercised when considering self-report of length of coma and PTA duration. Copyright © 2015 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

First images of a possible CO(+)-tail of comet P/Schwassmann-Wachmann 1 observed against the dust coma background

NASA Technical Reports Server (NTRS)

Jockers, Klaus; Bonev, T.; Ivanova, Violeta; Rauer, H.

1992-01-01

Comet P/Schwassmann-Wachmann 1 was observed with the 2m-Ritchey-Cretien Telescope of the Bulgarian National Observatory, Rozhen, Bulgaria, using the CCD-camera and focal reducer of the Max-Planck-Institute for Aeronomy. Images were taken in a red continuum window and in the 2-0 A(exp 2)Pi - X(exp 2)Sigma(+) band of CO(+) located in the blue part of the spectrum. The red images reveal an extended dust coma. From a comparison of the red and blue images a dust reddening of 13.2 percent per 1000 A is derived. At 642 nm the magnitude of the comet with a square diaphragm of 4.5 arcsec is 16.6. The blue images, taken in the CO(+) band, show a significantly different brightness distribution which is interpreted as presence of a CO(+) coma and tail superimposed on the continuum. A column density of several 10(exp 10) CO(+) molecules cm(exp -2) is derived. The tail thickness of 10(exp 5) km is unexpectedly small. We estimate the CO(+) production rate to about 6 x 10(exp 26) CO(+) particles s(exp -1). This value does not support the idea that the outbursts of this comet are caused by crystallization of amorphous water ice.

The "Horns" of FK Comae and the Complex Structure of its Outer Atmosphere

NASA Astrophysics Data System (ADS)

Saar, Steven H.; Ayres, T. R.; Kashyap, V.

2014-01-01

As part of a large multiwavelength campaign (COCOA-PUFS*) to explore magnetic activity in the unusual, single, rapidly rotating giant FK Comae, we have taken a time series of moderate resolution FUV spectra of the star with the COS spectrograph on HST. We find that the star has unusual, time-variable emission profiles in the chromosphere and transition region which show horn-like features. We use simple spatially inhomogeneous models to explain the variable line shapes. Modeling the lower chromospheric Cl I 1351 Å line, we find evidence for a very extended, spatial inhomogeneous outer atmosphere, likely composed of many huge "sling-shot" prominences of cooler material with embedded in a rotationally distended corona. We compare these results with hotter hotter transition region lines (Si IV) and optical spectra of the chromospheric He I D3 line. We also employ the model Cl I profiles, and data-derived empirical models, to fit the complex spectral region around the coronal Fe XXI 1354.1 Å line. We place limits on the flux of this line, and show these limits are consistent with expectations from the observed X-ray spectrum. *Campaign for Observation of the Corona and Outer Atmosphere of the Fast-rotating Star, FK Comae This work was supported by HST grant GO-12376.01-A.

The Extremely Low Activity Comet 209P/LINEAR During Its Extraordinary Close Approach in 2014

NASA Astrophysics Data System (ADS)

Schleicher, David G.; knight, Matthew m.

2016-10-01

We present results from our observing campaign of Comet 209P/LINEAR during its exceptionally close approach to Earth during 2014 May, the third smallest perigee of any comet in two centuries. These circumstances permitted us to pursue several studies of this intrinsically faint object, including measurements of gas and dust production rates, searching for coma morphology, and direct detection of the nucleus to measure its properties. Indeed, we successfully measured the lowest water production rates of an intact comet in over 35 years and a corresponding smallest active area, ∼0.007 km2. When combined with the nucleus size found from radar, this also yields the smallest active fraction for any comet, ∼0.024%. In all, this strongly suggests that 209P/LINEAR is on its way to becoming an inert object. The nucleus was detected but could not easily be disentangled from the inner coma due to seeing variations and changing spatial scales. Even so, we were able to measure a double-peaked lightcurve consistent with the shorter of two viable rotational periods found by Hergenrother. Radial profiles of the dust coma are quite steep, similar to that observed for some other very anemic comets, and suggest that vaporizing icy grains are present.

A Rare Case of Myxedema Coma with Neuroleptic Malignant Syndrome (NMS).

PubMed

Dixit, Siddharth; Dutta, Manoj Kumar; Namdeo, Mayank

2015-05-01

Myxedema coma or hypothyroid crisis is an endocrine emergency and needs ICU management. Neuroleptic malignant syndrome (NMS) is another medical emergency which needs high degree of clinical suspicion else mortality can be high. There is a paradox in co existence of myxedema coma and NMS. While one is hypometabolic state another is hypermetabolic state and both can be precipitated by antipsychotics use. Hypothermia and flaccidity commonly expected in myxedema coma may mask fever and rigidity of classical NMS contributing to diagnostic problem and treatment delay. Scientific literature on coexistance of myxedema coma and NMS is sparse. We hereby report first case with coexisting myxedema coma and NMS in a patient of schizophrenia treated with antipsychotic, where classical symptoms of NMS were masked by myxedema coma. Prompt diagnosis and effective management by a team resulted in favourable outcome in our patient. This case is reported to alert intensive care physicians to atypical manifestations of NMS in presence of hypothyroidism.

A Rare Case of Myxedema Coma with Neuroleptic Malignant Syndrome (NMS)

PubMed Central

Dutta, Manoj Kumar; Namdeo, Mayank

2015-01-01

Myxedema coma or hypothyroid crisis is an endocrine emergency and needs ICU management. Neuroleptic malignant syndrome (NMS) is another medical emergency which needs high degree of clinical suspicion else mortality can be high. There is a paradox in co existence of myxedema coma and NMS. While one is hypometabolic state another is hypermetabolic state and both can be precipitated by antipsychotics use. Hypothermia and flaccidity commonly expected in myxedema coma may mask fever and rigidity of classical NMS contributing to diagnostic problem and treatment delay. Scientific literature on coexistance of myxedema coma and NMS is sparse. We hereby report first case with coexisting myxedema coma and NMS in a patient of schizophrenia treated with antipsychotic, where classical symptoms of NMS were masked by myxedema coma. Prompt diagnosis and effective management by a team resulted in favourable outcome in our patient. This case is reported to alert intensive care physicians to atypical manifestations of NMS in presence of hypothyroidism. PMID:26155541

OH Fluorescence and Prompt Emission in comet 103P/Hartley 2 observed by EPOXI mission and expected results for comet 67P/Churyumov-Gerasimenko observed by Rosetta/OSIRIS WAC camera

NASA Astrophysics Data System (ADS)

La Forgia, F.; A'Hearn, M. F.; Lazzarin, M.; Magrin, S.; Bodewits, D.; Bertini, I.; Pajola, M.; Barbier, C.; Sierks, H.

2014-04-01

The OH radical, observed in cometary comae, is the direct dissociation product of water. Given the strong A2∑ - X2II (0, 0) emission band in the near-UV at 308.5 nm due to resonance fluorescence, the OH radical has been used, for years, as a tracer of the water parent molecule. Specifically, the OH fluorescence band provides an immediate tool to monitor the water production rate and its variations with the comet's heliocentric distance, rotational period and possible activity changes. Photolysis of water in cometary comae gives rise, with a non negligible branching ratio, to OH fragments in the first electronically excited state (OH*). This state is very unstable, with a lifetime of about 10-6s (Becker and Haaks, 1973), therefore OH* molecules promptly decay to the ground state. This process, generally referred to as prompt emission (PE), is responsible for an emission band in the near-UV ranging approximatelly from 306 to 325 nm. Original studies and tentative detections of OH PE have been put forth by Bertaux (1986), Budzien and Feldman (1991), Bonev et al. (2004), A'Hearn et al. (2007) using ground and space observations. Both from the above mentioned works together with our analysis, this process is expected to be prominent at short distances from the nucleus, where there is high density of water molecules, requiring the need of spacecraft observations to reach the necessary resolution. The hyperactive Jupiter family comet 103P/Hartley 2 has been visited by EPOXI spacecraft on 4 November 2010 at a minimum distance of 694 km, when it was at 1.064 AU from the Sun (A'Hearn et al. 2011). We present the analysis of photometric observations in OH filter acquired by MRI camera onboard EPOXI used to investigate the spatial distribution of OH in the coma of Hartley 2. The data revealed a radial OH structure within 35 km from the nucleus, appearing to be coming directly from the nucleus, in the region of the central waist. A theoretical computation evidencing a strong possibility that this OH structure could be partially associated with OH PE has been performed. This is strongly supported by the agreement of the OH spatial distribution with the water spatial distribution derived from HRI IR spectrometer observations (A'Hearn et al. 2011). Given the results on comet Hartley 2, we present our expectations and preliminary analysis of OH fluorescence and prompt emission mechanisms in the coma of 67P/Churyumov-Gerasimenko, target of the Rosetta mission. The OSIRIS WAC camera on board Rosetta is equipped with 7 narrowband filters centered on molecular emission bands, including the OH gas filter. This will enable us to investigate OH fluorescence and PE at increasing resolution as Rosetta will approach the comet. This analysis, supported by accompanying observations acquired by OSIRIS WAC camera in the forbidden OI band at 630 nm, will help in further constrain the water photochemistry and the fluorescence and PE processes occurring in the cometary comae.

Water, hydrogen cyanide, and dust production from the distant comet 29P/Scwassmann-Wachmann 1

NASA Astrophysics Data System (ADS)

Bockelee-Morvan, D.; Biver, N.; Opitom, C.; Hutsemekers, D.; Crovisier, J.; Jehin, E.; Hartogh, P.; Szutowizc, S.; Lellouch, E.; Kidger, M.; Vandenbussche, B.; Zakharov, V.; HSSO Team

2014-07-01

Comet 29P/Schwassmann-Wachmann is a periodic comet, also classified as a Centaur, orbiting on a nearly circular orbit at 6 au from the Sun. It is well known for its permanent activity driven by CO outgassing, and its episodic outbursts. Comet 29P was observed in 2010--2011 with the Herschel space observatory. Observations of water and ammonia were performed with the Heterodyne Instrument for the Far-Infrared (HIFI). One set of measurements was obtained two days after a major outburst (16 Apr. 2010). Images of the dust coma at 70 and 160 μ m were obtained using the Photodetector Array Camera and Spectrometer (PACS). To support these observations, observations of CO and HCN were undertaken at the 30-m telescope of the Institut de radioastronomie millimétrique (IRAM). We present an overview of this set of observations. H_2O and CO are detected. We also obtain the first detection of HCN in this distant comet. Relative abundances are similar to those measured in the coma of comet C/1995 O1 (Hale-Bopp) when at r_h = 6 au from the Sun, but strongly differ from coma compositions at r_h = 1 au. The line profiles show evidence that both H_2O, HCN are released from long-lived icy grains. Detailed modeling of water production from icy-grain suggests continuous release of icy grains from the nucleus. The thermal emission from the nucleus is detected in the PACS 70 μ m images. The thermal emission from dust grains is analyzed with a thermal model of dust emission, which takes into account the dust size distribution. Both the size index and the dust production rate are measured.

Intubation is not a marker for coma after in-hospital cardiac arrest: A retrospective study.

PubMed

Berg, Katherine M; Grossestreuer, Anne V; Uber, Amy; Patel, Parth V; Donnino, Michael W

2017-10-01

In-hospital cardiac arrest (IHCA) strikes over 200,000 people in the United States annually. Targeted temperature management (TTM) is considered beneficial in other settings, but there is no prospective data for IHCA. Recent work on TTM and IHCA found an association between TTM and worse outcome. However, the authors used intubation as a marker for coma to determine eligibility for TTM. The validity of this approach is unexplored. Retrospective, single center study of adult patients with IHCA occurring in an intensive care unit, intubated prior to or during the event, or immediately after ROSC. We evaluated the percentage of patients documented as comatose after arrest, defined as Glasgow Comas Score (GCS) <8 for the primary analysis. We also evaluated the difference in hospital survival in patients with GCS <8 versus ≥8. Two sensitivity analyses using different methods for defining coma using post-ROSC GCS were conducted. 29/102 (28%) intubated patients had a post-ROSC GCS≥8, and 22 (22%) were documented as following commands. Survival in patients with GCS≥8 vs.<8 was 62% (18/29) vs. 37% (27/73) in unadjusted analysis (p=0.02). The adjusted odds ratio for survival to hospital discharge was 3.81 (95%CI: 1.37-10.61, p=0.01). Results were similar in both sensitivity analyses. Intubation prior to or during IHCA was not a valid marker of coma after ROSC. Post-ROSC mental status was associated with hospital survival, and thus could be an important confounder when conducting observational studies on the association of TTM with outcomes in this patient population. Copyright © 2017 Elsevier B.V. All rights reserved.

An adaptive and generalizable closed-loop system for control of medically induced coma and other states of anesthesia

NASA Astrophysics Data System (ADS)

Yang, Yuxiao; Shanechi, Maryam M.

2016-12-01

Objective. Design of closed-loop anesthetic delivery (CLAD) systems is an important topic, particularly for medically induced coma, which needs to be maintained for long periods. Current CLADs for medically induced coma require a separate offline experiment for model parameter estimation, which causes interruption in treatment and is difficult to perform. Also, CLADs may exhibit bias due to inherent time-variation and non-stationarity, and may have large infusion rate variations at steady state. Finally, current CLADs lack theoretical performance guarantees. We develop the first adaptive CLAD for medically induced coma, which addresses these limitations. Further, we extend our adaptive system to be generalizable to other states of anesthesia. Approach. We designed general parametric pharmacodynamic, pharmacokinetic and neural observation models with associated guidelines, and derived a novel adaptive controller. We further penalized large steady-state drug infusion rate variations in the controller. We derived theoretical guarantees that the adaptive system has zero steady-state bias. Using simulations that resembled real time-varying and noisy environments, we tested the closed-loop system for control of two different anesthetic states, burst suppression in medically induced coma and unconsciousness in general anesthesia. Main results. In 1200 simulations, the adaptive system achieved precise control of both anesthetic states despite non-stationarity, time-variation, noise, and no initial parameter knowledge. In both cases, the adaptive system performed close to a baseline system that knew the parameters exactly. In contrast, a non-adaptive system resulted in large steady-state bias and error. The adaptive system also resulted in significantly smaller steady-state infusion rate variations compared to prior systems. Significance. These results have significant implications for clinically viable CLAD design for a wide range of anesthetic states, with potential cost-saving and therapeutic benefits.

An adaptive and generalizable closed-loop system for control of medically induced coma and other states of anesthesia.

PubMed

Yang, Yuxiao; Shanechi, Maryam M

2016-12-01

Design of closed-loop anesthetic delivery (CLAD) systems is an important topic, particularly for medically induced coma, which needs to be maintained for long periods. Current CLADs for medically induced coma require a separate offline experiment for model parameter estimation, which causes interruption in treatment and is difficult to perform. Also, CLADs may exhibit bias due to inherent time-variation and non-stationarity, and may have large infusion rate variations at steady state. Finally, current CLADs lack theoretical performance guarantees. We develop the first adaptive CLAD for medically induced coma, which addresses these limitations. Further, we extend our adaptive system to be generalizable to other states of anesthesia. We designed general parametric pharmacodynamic, pharmacokinetic and neural observation models with associated guidelines, and derived a novel adaptive controller. We further penalized large steady-state drug infusion rate variations in the controller. We derived theoretical guarantees that the adaptive system has zero steady-state bias. Using simulations that resembled real time-varying and noisy environments, we tested the closed-loop system for control of two different anesthetic states, burst suppression in medically induced coma and unconsciousness in general anesthesia. In 1200 simulations, the adaptive system achieved precise control of both anesthetic states despite non-stationarity, time-variation, noise, and no initial parameter knowledge. In both cases, the adaptive system performed close to a baseline system that knew the parameters exactly. In contrast, a non-adaptive system resulted in large steady-state bias and error. The adaptive system also resulted in significantly smaller steady-state infusion rate variations compared to prior systems. These results have significant implications for clinically viable CLAD design for a wide range of anesthetic states, with potential cost-saving and therapeutic benefits.

The cometary activity of Centaur P/2004 A1 (LONEOS)

NASA Astrophysics Data System (ADS)

Epifani, E. Mazzotta; Dall'Ora, M.; Perna, D.; Palumbo, P.; Colangeli, L.

2011-08-01

P/2004 A1 (LONEOS) is one of the few active objects in the dynamical class of Centaurs. It has been recently injected into an inner orbit with a perihelion distance q = 5.5 au. The aim of this paper is to characterize the dust coma of this peculiar object, 2.5 yr after its first 'new' perihelion passage inside the Solar system. Broad-band visible images taken at the TNG telescope in 2007 February were analysed in order to characterize the dust coma of the Centaur: it was still quite active at rh = 6.5 au post-perihelion, with a coma and a well-developed wide tail-like structure, with a measured R-Afρ= 162 ± 10 cm in an aperture radius ρ= 104 km. The (V - R) colour and the reddening values depict a scenario of a slightly red dust coma. A dust mass-loss rate of ? = 133 kg s-1 is derived from a photometric model, consistent with a scenario of a quite constant emission rate along the Centaur orbit. An upper limit for the Centaur radius of 3.5 km is derived by some realistic hypotheses on CO molecular production rate and on the mean grain scatterer size in the coma. Dynamical lifetime estimates compared to modelled loss rate result in a radius lower limit of 0.5 km, indicating therefore that the Centaur size is likely of the same order of magnitude of the short-period comets. Based on observations made at the Italian Telescopio Nazionale Galileo (TNG), operated on the island of La Palma by the Fundación Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.

Dynamical Effects of the Scale Invariance of the Empty Space: The Fall of Dark Matter?

NASA Astrophysics Data System (ADS)

Maeder, Andre

2017-11-01

The hypothesis of the scale invariance of the macroscopic empty space, which intervenes through the cosmological constant, has led to new cosmological models. They show an accelerated cosmic expansion after the initial stages and satisfy several major cosmological tests. No unknown particles are needed. Developing the weak-field approximation, we find that the here-derived equation of motion corresponding to Newton’s equation also contains a small outward acceleration term. Its order of magnitude is about \\sqrt{{\\varrho }{{c}}/\\varrho } × Newton’s gravity (ϱ being the mean density of the system and {\\varrho }{{c}} the usual critical density). The new term is thus particularly significant for very low density systems. A modified virial theorem is derived and applied to clusters of galaxies. For the Coma Cluster and Abell 2029, the dynamical masses are about a factor of 5-10 smaller than in the standard case. This tends to leave no room for dark matter in these clusters. Then, the two-body problem is studied and an equation corresponding to the Binet equation is obtained. It implies some secular variations of the orbital parameters. The results are applied to the rotation curve of the outer layers of the Milky Way. Starting backward from the present rotation curve, we calculate the past evolution of the Galactic rotation and find that, in the early stages, it was steep and Keplerian. Thus, the flat rotation curves of galaxies appear as an age effect, a result consistent with recent observations of distant galaxies by Genzel et al. and Lang et al. Finally, in an appendix we also study the long-standing problem of the increase with age of the vertical velocity dispersion in the Galaxy. The observed increase appears to result from the new small acceleration term in the equation of the harmonic oscillator describing stellar motions around the Galactic plane. Thus, we tend to conclude that neither dark energy nor dark matter seems to be needed in the proposed theoretical context.

MID-INFRARED EVIDENCE FOR ACCELERATED EVOLUTION IN COMPACT GROUP GALAXIES

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

Walker, Lisa May; Johnson, Kelsey E.; Gallagher, Sarah C.

2010-11-15

Compact galaxy groups are at the extremes of the group environment, with high number densities and low velocity dispersions that likely affect member galaxy evolution. To explore the impact of this environment in detail, we examine the distribution in the mid-infrared (MIR) 3.6-8.0 {mu}m color space of 42 galaxies from 12 Hickson compact groups (HCGs) in comparison with several control samples, including the LVL+SINGS galaxies, interacting galaxies, and galaxies from the Coma Cluster. We find that the HCG galaxies are strongly bimodal, with statistically significant evidence for a gap in their distribution. In contrast, none of the other samples showmore » such a marked gap, and only galaxies in the Coma infall region have a distribution that is statistically consistent with the HCGs in this parameter space. To further investigate the cause of the HCG gap, we compare the galaxy morphologies of the HCG and LVL+SINGS galaxies, and also probe the specific star formation rate (SSFR) of the HCG galaxies. While galaxy morphology in HCG galaxies is strongly linked to position with MIR color space, the more fundamental property appears to be the SSFR, or star formation rate normalized by stellar mass. We conclude that the unusual MIR color distribution of HCG galaxies is a direct product of their environment, which is most similar to that of the Coma infall region. In both cases, galaxy densities are high, but gas has not been fully processed or stripped. We speculate that the compact group environment fosters accelerated evolution of galaxies from star-forming and neutral gas-rich to quiescent and neutral gas-poor, leaving few members in the MIR gap at any time.« less

Predictors of outcome in myxoedema coma

PubMed Central

Beynon, Jennifer; Akhtar, Simeen; Kearney, Tara

2008-01-01

Myxoedema coma is a rare and life-threatening illness the outcome of which has not been robustly studied in large numbers, partly due to its low incidence. Dutta and colleagues have explored outcome predictors in a developing country where access to thyroid function tests is more limited than in the Western world. Cardiovascular instability, reduced consciousness, persistent hypothermia, and sepsis all contributed to a poorer outcome, as has been demonstrated before, but a generic outcome predictor model was shown to be useful in this group of patients. Unfortunately, this observational study was unable to show differences in outcome based on replacement treatment methods and the mortality remains at 40%. PMID:18254932

Predictors of outcome in myxoedema coma.

PubMed

Beynon, Jennifer; Akhtar, Simeen; Kearney, Tara

2008-01-01

Myxoedema coma is a rare and life-threatening illness the outcome of which has not been robustly studied in large numbers, partly due to its low incidence. Dutta and colleagues have explored outcome predictors in a developing country where access to thyroid function tests is more limited than in the Western world. Cardiovascular instability, reduced consciousness, persistent hypothermia, and sepsis all contributed to a poorer outcome, as has been demonstrated before, but a generic outcome predictor model was shown to be useful in this group of patients. Unfortunately, this observational study was unable to show differences in outcome based on replacement treatment methods and the mortality remains at 40%.

Surface brightness profiles of 10 comets

NASA Astrophysics Data System (ADS)

Jewitt, D. C.; Meech, K. J.

1987-06-01

CCD photometric observations of the comae of 10 comets, obtained at the 4-m and 2.1-m telescopes at KPNO during 1985-1986 using filters centered at 700.5, 650.0, or 546.0 nm, are reported. The data are presented in extensive tables and graphs and characterized in detail. The radial surface brightness profiles are shown to be steeper than predicted by an idealized spherically symmetric steady-state comet model, the steepness increasing with the projected distance from the nucleus. These profiles are attributed, on the basis of Monte Carlo simulations, to imperfect coupling between the sublimated gas and the optically dominant grains of the coma.

Split high-dose oral levothyroxine treatment as a successful therapy option in myxedema coma.

PubMed

Charoensri, Suranut; Sriphrapradang, Chutintorn; Nimitphong, Hataikarn

2017-10-01

High-dose intravenous thyroxine (T4) is the preferable treatment for myxedema coma. We describe the clinical course of a 69-year-old man who presented with myxedema coma and received oral levothyroxine (LT4) therapy (1 mg) in a split dose. This suggests split high-dose oral LT4 as a therapeutic option in myxedema coma.

The 67P/Churyumov-Gerasimenko observation campaign in support of the Rosetta mission.

PubMed

Snodgrass, C; A'Hearn, M F; Aceituno, F; Afanasiev, V; Bagnulo, S; Bauer, J; Bergond, G; Besse, S; Biver, N; Bodewits, D; Boehnhardt, H; Bonev, B P; Borisov, G; Carry, B; Casanova, V; Cochran, A; Conn, B C; Davidsson, B; Davies, J K; de León, J; de Mooij, E; de Val-Borro, M; Delacruz, M; DiSanti, M A; Drew, J E; Duffard, R; Edberg, N J T; Faggi, S; Feaga, L; Fitzsimmons, A; Fujiwara, H; Gibb, E L; Gillon, M; Green, S F; Guijarro, A; Guilbert-Lepoutre, A; Gutiérrez, P J; Hadamcik, E; Hainaut, O; Haque, S; Hedrosa, R; Hines, D; Hopp, U; Hoyo, F; Hutsemékers, D; Hyland, M; Ivanova, O; Jehin, E; Jones, G H; Keane, J V; Kelley, M S P; Kiselev, N; Kleyna, J; Kluge, M; Knight, M M; Kokotanekova, R; Koschny, D; Kramer, E A; López-Moreno, J J; Lacerda, P; Lara, L M; Lasue, J; Lehto, H J; Levasseur-Regourd, A C; Licandro, J; Lin, Z Y; Lister, T; Lowry, S C; Mainzer, A; Manfroid, J; Marchant, J; McKay, A J; McNeill, A; Meech, K J; Micheli, M; Mohammed, I; Monguió, M; Moreno, F; Muñoz, O; Mumma, M J; Nikolov, P; Opitom, C; Ortiz, J L; Paganini, L; Pajuelo, M; Pozuelos, F J; Protopapa, S; Pursimo, T; Rajkumar, B; Ramanjooloo, Y; Ramos, E; Ries, C; Riffeser, A; Rosenbush, V; Rousselot, P; Ryan, E L; Santos-Sanz, P; Schleicher, D G; Schmidt, M; Schulz, R; Sen, A K; Somero, A; Sota, A; Stinson, A; Sunshine, J M; Thompson, A; Tozzi, G P; Tubiana, C; Villanueva, G L; Wang, X; Wooden, D H; Yagi, M; Yang, B; Zaprudin, B; Zegmott, T J

2017-07-13

We present a summary of the campaign of remote observations that supported the European Space Agency's Rosetta mission. Telescopes across the globe (and in space) followed comet 67P/Churyumov-Gerasimenko from before Rosetta's arrival until nearly the end of the mission in September 2016. These provided essential data for mission planning, large-scale context information for the coma and tails beyond the spacecraft and a way to directly compare 67P with other comets. The observations revealed 67P to be a relatively 'well-behaved' comet, typical of Jupiter family comets and with activity patterns that repeat from orbit to orbit. Comparison between this large collection of telescopic observations and the in situ results from Rosetta will allow us to better understand comet coma chemistry and structure. This work is just beginning as the mission ends-in this paper, we present a summary of the ground-based observations and early results, and point to many questions that will be addressed in future studies.This article is part of the themed issue 'Cometary science after Rosetta'. © 2017 The Author(s).

Assessment of refractive astigmatism and simulated therapeutic refractive surgery strategies in coma-like-aberrations-dominant corneal optics.

PubMed

Zhou, Wen; Stojanovic, Aleksandar; Utheim, Tor Paaske

2016-01-01

The aim of the study is to raise the awareness of the influence of coma-like higher-order aberrations (HOAs) on power and orientation of refractive astigmatism (RA) and to explore how to account for that influence in the planning of topography-guided refractive surgery in eyes with coma-like-aberrations-dominant corneal optics. Eleven eyes with coma-like-aberrations-dominant corneal optics and with low lenticular astigmatism (LA) were selected for astigmatism analysis and for treatment simulations with topography-guided custom ablation. Vector analysis was used to evaluate the contribution of coma-like corneal HOAs to RA. Two different strategies were used for simulated treatments aiming to regularize irregular corneal optics: With both strategies correction of anterior corneal surface irregularities (corneal HOAs) were intended. Correction of total corneal astigmatism (TCA) and RA was intended as well with strategies 1 and 2, respectively. Axis of discrepant astigmatism (RA minus TCA minus LA) correlated strongly with axis of coma. Vertical coma influenced RA by canceling the effect of the with-the-rule astigmatism and increasing the effect of the against-the-rule astigmatism. After simulated correction of anterior corneal HOAs along with TCA and RA (strategies 1 and 2), only a small amount of anterior corneal astigmatism (ACA) and no TCA remained after strategy 1, while considerable amount of ACA and TCA remained after strategy 2. Coma-like corneal aberrations seem to contribute a considerable astigmatic component to RA in eyes with coma-like-aberrations dominant corneal optics. If topography-guided ablation is programmed to correct the corneal HOAs and RA, the astigmatic component caused by the coma-like corneal HOAs will be treated twice and will result in induced astigmatism. Disregarding RA and treating TCA along with the corneal HOAs is recommended instead.

Physical properties of dust particles in different comets inferred from observations and experimental simulations

NASA Astrophysics Data System (ADS)

Hadamcik, E.; Levasseur-Regourd, A. C.

2007-08-01

1.Introduction Remote observations of solar light scattered by cometary dust particles provide information on the dust properties for a large variety of comets, in complement to the exceptional in-situ observations (with or without sample returns). The scattered light is partially linearly polarized, with a polarization degree depending on the geometry of observations (phase angle ?) and on the physical properties of the particles. Differences in polarization have been found in cometary comae, pointing to different physical properties of the dust (e.g. sizes of the grains, of the aggregates, structures and porosities, complex refractive indices) [1, 2]. Such differences, as well as an observed polarimetric wavelength effect, tend to show that large aggregates made of submicron-sized grains could be present in some cometary comae regions [3, 4]. On the opposite, more compact particles seem to be present in other comae regions and/or comets [5, 6]. 2. Results We will present observations of different comets. The variations of the dust properties in the coma and their evolution will be discussed. The results will be compared to the results obtained by other observational techniques. On the images of comet 9P/Tempel 1 (at ?=41°) some hours after Deep Impact, two kinds of dust particles are detected: more compact particles with small velocities and fluffy particles ejected by the impact with larger velocities. On the images of comet 73P/Schwassmann-Wachmann 3, in the tail direction of fragment B, a disruption is observed. The dust coma around fragment C is more symmetric. For both A and B, important dust jets are ejected by the nucleus, which are visible on the intensity images in the solar and antisolar directions, and on the polarization maps. 3. Interpretation and conclusion Numerical (7,8,9) and experimental simulations provide an interpretation of the observations in terms of the physical properties of the particles. Experimental simulations have been performed on numerous levitating samples (compact and fluffy) with the PROGRA2 experiment, either in reduced gravity conditions (parabolic flights) [10,11], or lifted by an air-draught (laboratory conditions) [12,13]. The variations of the polarization are correlated to variations in the size of the grains and aggregates and are a function of the complex refractive index and its evolution. The correlation between the variations of the scattered intensity and the linear polarization maps allows us to disentangle different physical properties of the dust. The results are compared to results obtained from previous observations by the same methods. References [1] E. Hadamcik and A.C. Levasseur-Regourd, JQSRT 79-80, 661-678 (2003) [2] A.C. Levasseur-Regourd, E. Hadamcik, JQSRT 79-80, 903-910 (2003) [3] E. Hadamcik, A.C. Levasseur-Regourd, A&A 403, 757- 768 (2003) [4] L. Kolokolova et al., In: Comets II, M.C. Festou et al. (eds), pp 577 (2004) [5] E. Hadamcik, A.C. Levasseur-Regourd, Icarus 166, 188-194 (2003) [6] E. Hadamcik et al., Icarus, accepted. [7] J. Lasue, A.C. Levasseur-Regourd, JQSRT 100, 220-236 (2006) [8] H. Kimura et al., A&A 449, 1243-1254 (2006) [9] A.C. Levasseur-Regourd et al., PSS, in press, available on line (2007) [10] J.-B. Renard et al. Appl. Opt 41, 609-618 (2002) [11] J.-B. Renard et al., Adv. Space Res. 31, 2511-2518 (2003) [12] E. Hadamcik et al., JQSRT 100, 143-156 (2006) [13] E. Hadamcik et al., Icarus, in press, available on line (2007)

Medical problems related to recreational drug use at nocturnal dance parties.

PubMed

Van Sassenbroeck, Diederik K; Calle, Paul A; Rousseau, Filip M; Verstraete, Alain G; Belpaire, Frans M; Monsieurs, Koenraad G; Haentjens, Raoul; Allonsius, Jacques; Van Brantegem, Jean; Haenen, Wim; Buylaert, Walter A

2003-12-01

During 'I love techno' (edition 2001), an indoor rave party attended by 37 000 people, data about medical problems (especially drug-related problems) were collected. To place these data in a wider perspective, a similar registration was done during 'De Nacht', a traditional New Year's Eve dance party held at the same location and attended by 12 000 people. Furthermore, a prospective study on the time course of the level of consciousness (Glasgow Coma Score) and blood concentrations of illicit drugs, especially gamma-hydroxybutyrate was set up. The results revealed that during 'I love techno' the incidence of medical problems was high (66.5/10 000 attendees), but not higher than during 'De Nacht' (70.0/10 000 attendees). At 'I love techno', however, mainly illicit drugs were used, more frequently leading to severe drug-related medical problems. The observations in patients with a drug-related medical problem who had taken gamma-hydroxybutyrate showed that for a given level of consciousness the gamma-hydroxybutyrate concentrations may show important differences, that the transition from coma (Glasgow Coma Score < or =7) to full recovery (Glasgow Coma Score 15) takes only 30-60 min (and only a small decrease in gamma-hydroxybutyrate concentrations), and that the time it takes before a comatose patient reaches the above-mentioned 'transition area' may be a few hours.

[Euthanasia of patients in coma vigil. Results on German medical staff attitudes].

PubMed

Böttger-Kessler, G; Beine, K H

2007-07-01

An examination was made concerning doctors' and nursing staff's attitudes towards active euthanasia of patients suffering from coma vigil (2652 doctors and 5785 nursing staff were interviewed). This investigation made clear that most of the persons asked about this group of patients voted for a change in German laws following the Dutch example. There were noticeable differences observed between the professional groups. A majority (64.79%) were convinced that under certain circumstances it is justified to end intentionally the life of persons in a coma vigil. Of the nursing staff, 70.38% were in favour of this attitude, and 51.53% of the doctors share this opinion. Certain groups supported the question of active euthanasia more clearly than others. These were young participants in the investigation, first-time employees, nondenominational interviewees, those who are dissatisfied with their job situation, who are from the newly-formed German states, and who are divorced. The attitudes expressed by all these people originate in many different motives: thoughts about the patients, aspects concerning jobs, and personal aspects had an influence on results of the investigation. This single investigation which was restricted to patients suffering from coma vigil and to employees of the public health service, does not prove that the total population has generally changed its attitude toward active euthanasia. It is impossible to justify the necessity of new laws about euthanasia based on the above results.

Dopamine agonist therapy in low-response children following traumatic brain injury.

PubMed

Patrick, Peter D; Blackman, James A; Mabry, Jennifer L; Buck, Marcia L; Gurka, Matthew J; Conaway, Mark R

2006-10-01

The objective of this study was to determine whether a dopamine agonist could improve mental status among children in a low-response state following traumatic brain injury. In an 8-week, prospective, double-blind, randomized trial, 10 children and adolescents ages 8 to 21 years (X = 16.7 years) with traumatic brain injury sustained at least 1 month previously and remaining in a low-response state (Rancho Los Amigos Scale level pound 3) received pramipexole or amantadine. Medication dosage was increased over 4 weeks, weaned over 2 weeks, and then discontinued. At baseline and weekly during the study, subjects were evaluated with the Coma Near Coma Scale, Western NeuroSensory Stimulation Profile, and Disability Rating Scale. Scores improved significantly from baseline to the medication phase on the Coma Near Coma Scale, Western NeuroSensory Stimulation Profile, and Disability Rating Scale (P < .005). The weekly rate of change was significantly better for all three measures on medication than off medication (P < .05). Rancho Los Amigos Scale levels improved significantly on medication as well (P < .05). There was no difference in efficacy between amantadine and pramipexole. No unexpected or significant side effects were observed with either drug. This clinical trial supports the benefit of two dopamine agonists in the restoration of functional arousal, awareness, and communication. These drugs can be helpful in accelerating eligibility for acute rehabilitation among children and adolescents who have sustained significant brain injuries.

The Blue Coma: The Role of Methylene Blue in Unexplained Coma After Cardiac Surgery.

PubMed

Martino, Enrico Antonio; Winterton, Dario; Nardelli, Pasquale; Pasin, Laura; Calabrò, Maria Grazia; Bove, Tiziana; Fanelli, Giovanna; Zangrillo, Alberto; Landoni, Giovanni

2016-04-01

Methylene blue commonly is used as a dye or an antidote, but also can be used off label as a vasopressor. Serotonin toxicity is a potentially lethal and often misdiagnosed condition that can result from drug interaction. Mild serotonin toxicity previously was reported in settings in which methylene blue was used as a dye. The authors report 3 cases of life-threatening serotonin toxicity in patients undergoing chronic selective serotonin reuptake inhibitor (SSRI) therapy who also underwent cardiac surgery and received methylene blue to treat vasoplegic syndrome. An observational study. A cardiothoracic intensive care unit (ICU) in a teaching hospital. Three patients who received methylene blue after cardiac surgery, later discovered to be undergoing chronic SSRI therapy. None. All 3 patients received high doses of fentanyl during general anesthesia. They all developed vasoplegic syndrome and consequently were given methylene blue in the ICU. All 3 patients developed serotonin toxicity, including coma, after this administration and diagnostic tests were negative for acute intracranial pathology. Coma lasted between 1 and 5 days. Two patients were discharged from the ICU shortly after awakening, whereas the third patient experienced a complicated postoperative course for concomitant refractory low-cardiac-output syndrome. Patients undergoing chronic SSRI therapy should not be administered methylene blue to treat vasoplegic syndrome. Copyright © 2016 Elsevier Inc. All rights reserved.

Influence of coma aberration on aperture averaged scintillations in oceanic turbulence

NASA Astrophysics Data System (ADS)

Luo, Yujuan; Ji, Xiaoling; Yu, Hong

2018-01-01

The influence of coma aberration on aperture averaged scintillations in oceanic turbulence is studied in detail by using the numerical simulation method. In general, in weak oceanic turbulence, the aperture averaged scintillation can be effectively suppressed by means of the coma aberration, and the aperture averaged scintillation decreases as the coma aberration coefficient increases. However, in moderate and strong oceanic turbulence the influence of coma aberration on aperture averaged scintillations can be ignored. In addition, the aperture averaged scintillation dominated by salinity-induced turbulence is larger than that dominated by temperature-induced turbulence. In particular, it is shown that for coma-aberrated Gaussian beams, the behavior of aperture averaged scintillation index is quite different from the behavior of point scintillation index, and the aperture averaged scintillation index is more suitable for characterizing scintillations in practice.

Analysis of Hubble Space Telescope Observations of an Outburst of Comet 29P/Schwassmann-Wachmann 1

NASA Astrophysics Data System (ADS)

Schambeau, Charles Alfred; Fernandez, Yanga R.; Samarasinha, Nalin H.; Kundu, Arunav

2016-10-01

We present results of a continuing analysis on the spin state of the enigmatic Comet 29P/Schwassmann-Wachmann 1 (SW1). Previous works have reported possible constraints on the spin state including a non-principal axis state [1] or a rotation period of tens of days [2]. This diversity of published answers highlights the complexity of determining the spin state of an active comet nucleus. Previous work by our group using 3D Monte Carlo coma modeling of ground-based outburst observations from 2008 [3] has placed constraints on the spin period for a set of assumed spin-pole orientations. Due to the nature of the 2008 outburst morphology no constraints on the spin-pole orientation could be found.We present here an analysis of Hubble Space Telescope WFPC2 observations of SW1 shortly after a 1996 outburst [4] with which we have further constrained the spin state. The 0.046-arcsec/pixel scale (176 km/pixel at SW1) of the PC detector gives an order-of-magnitude improvement in spatial resolution over our ground-based observations. Two sets of observations from UT 1996 Mar. 11.3 and 12.1 show the ejected dust forming an asymmetric outflow contained on the sunward side of the coma. A projected outflow velocity of 0.15 ± 0.02 km/s was measured, similar to our measured value from the 2008 observations. Enhancements of the images were performed [5] to bring out subtle variations in coma brightness (i.e., jets) and to allow us to search for signatures of the nucleus' rotation during the outburst. Three curved features are seen in both sets of observations and were modeled using the 3D Monte Carlo coma model [6]. We find a spin period on the order of several days, in agreement with our earlier 2008 analysis.[1] Meech, K. J., et al.: 1993, Astron. J., 106, 1222. [2] Miles, R., et al.: 2016, Icarus, 272, 327. [3] Schambeau, C. A., et al.: 2016, Icarus, submitted. [4] Feldman, P. D., et al.: 1996, AAS/DPS Meeting Abstracts, 28, 1084. [5] Samarasinha, N. and Larson, S.: 2014, Icarus, 239, 168. [6] Samarasinha, N. H., 2000, Astron. J. Letters, 529, L107-L110. We thank the Space Telescope Science Institute (AR14294), and the Center for Lunar and Asteroid Surface Science (CLASS, NNA14AB05A) for support of this work.

[The diagnosis and treatment of myxedema coma].

PubMed

Aoki, Chie; Kasai, Kikuo

2012-11-01

Myxedema coma is defined as severe hypothyroidism leading to decreased mental status, hypothermia, and other symptoms related to dysfunction in multiple organs. It is very rare disease with high mortality rate. Early recognition and therapy of myxedema coma are essential, and treatment should be begun on the basis of clinical suspection. However, regimen of myxedema is not well established even now, especially about thyroid hormone supplementation. Japan Thyroid Association is drawing up "The diagnostic criteria of myxedema coma (3rd draft) and preliminary guide to treatment of it". According to this criteria and preliminary guide, the clinical presentation, diagnosis, and treatment of myxedema coma will be reviewed here.

[Clinical efficacy observation of acupuncture at suliao (GV 25) on improving regain of consciousness from coma in severe craniocerebral injury].

PubMed

Xu, Kai-Sheng; Song, Jian-Hua; Huang, Tiao-Hua; Huang, Zhi-Hua; Yu, Lu-Chang; Zheng, Wei-Ping; Chen, Xiao-Shan; Liu, Chuan

2014-06-01

To compare the clinical therapeutic effects differences between acupuncture at Suliao (GV 25) and Shuigou (GV 26) on promoting regain of consciousness from coma in severe craniocerebral injury. Based on regular emergency treatments of neurosurgery, eighty-two cases of craniocerebral injury who were under stable condition were randomly divided into an observation group (42 cases) and a control group (40 cases). Suliao (GV 25) was selected as main aupoint, while Laogong (PC 8) and Yongquan (KI 1), etc. were selected as adjuvant acupoints and Neiguan (PC 6), Sanyinjiao (SP 6), Yifeng (TE 17) and Wangu (GB 12), etc. were selected as matching acupoints in the observation group where a strong needle manipulation was applied to improve the regain of consciousness. The main acupoint of Shuigou (GV 26) along with identical adjuvant acupoints and matching acupoints in the observation group were selected in the control group with identical strong needle manipulation. The treatment was given once a day in both groups, five times per week and ten times were considered as one session. The immediate clinical symptoms after acupuncture at Suliao (GV 25) and Shuigou (GV 26) were observed as well as Glasgow coma scale (GCS) before the treatment, after 45 days and 90 days of treatment to assess the resuscitation time and rate. Also the clinical efficacy was compared between both groups. The occurrence rate of sneezing reflex was 85.7% (36/42) in the observation group, which was higher than 25.0% (10/40) in the control group (P < 0.01). The average resuscitation time was (64.6 +/- 19.4) days in the observation group, which was obviously shorter than (73.8 +/- 14. 6) days in the control group (P < 0.05). The resuscitation rate was 88.1% (37/42) in the observation group, which was similar to 75.0% (30/40) in the control group (P > 0.05). Compared before the treatment, GCS were both improved after the treatment in two groups (both P < 0.01). The 90-day GCS was 9.52 +/- 2.32 in the observation group, which was superior to 8.47 +/-2.14 in the control group (P < 0.05). The curative and markedly effective rate was 45.2% (19/42) in the observation group, which was superior to 22.5% (9/40) in the control group (P < 0.05). The effect of acupuncture at Suliao (GV 25) on improving regain of consciousness from coma in severe craniocerebral injury is positive. It could specifically improve sneezing reflex and stimulate respiratory center, which has more obvious effect than acupuncture at Shuigou (GV 26).

The relation between persistent coma and brain ischemia after severe brain injury.

PubMed

Cheng, Quan; Jiang, Bing; Xi, Jian; Li, Zhen Yan; Liu, Jin Fang; Wang, Jun Yu

2013-12-01

To investigate the relation between brain ischemia and persistent vegetative state after severe traumatic brain injury. The 66 patients with severe brain injury were divided into two groups: The persistent coma group (coma duration ≥10 d) included 51 patients who had an admission Glasgow Coma Scale (GCS) of 5-8 and were unconscious for more than 10 d. There were 15 patients in the control group, their admission GCS was 5-8, and were unconscious for less than 10 d. The brain areas, including frontal, parietal, temporal, occipital lobes and thalamus, were measured by Single Photon Emission Computed Tomography (SPECT). In the first SPECT scan, multiple areas of cerebral ischemia were documented in all patients in both groups, whereas bilateral thalamic ischemia were presented in all patients in the persistent coma group and were absented in the control group. In the second SPECT scan taken during the period of analepsia, with an indication that unilateral thalamic ischemia were persisted in 28 of 41 patients in persistent coma group(28/41,68.29%). Persistent coma after severe brain injury is associated with bilateral thalamic ischemia.

Coma measurement by transmission image sensor with a PSM

NASA Astrophysics Data System (ADS)

Wang, Fan; Wang, Xiangzhao; Ma, Mingying; Zhang, Dongqing; Shi, Weijie; Hu, Jianming

2005-01-01

As feature size decreases, especially with the use of resolution enhancement technique such as off axis illumination and phase shifting mask, fast and accurate in-situ measurement of coma has become very important in improving the performance of modern lithographic tools. The measurement of coma can be achieved by the transmission image sensor, which is an aerial image measurement device. The coma can be determined by measuring the positions of the aerial image at multiple illumination settings. In the present paper, we improve the measurement accuracy of the above technique with an alternating phase shifting mask. Using the scalar diffraction theory, we analyze the effect of coma on the aerial image. To analyze the effect of the alternating phase shifting mask, we compare the pupil filling of the mark used in the above technique with that of the phase-shifted mark used in the new technique. We calculate the coma-induced image displacements of the marks at multiple partial coherence and NA settings, using the PROLITH simulation program. The simulation results show that the accuracy of coma measurement can increase approximately 20 percent using the alternating phase shifting mask.

Distant Jupiter family Comet P/2011 P1 (McNaught)

NASA Astrophysics Data System (ADS)

Korsun, Pavlo P.; Ivanova, Oleksandra V.; Afanasiev, Viktor L.; Kulyk, Irina V.

2016-03-01

The spectra and images obtained through broadband BVRc filters for Jupiter family Comet P/2011 P1 (McNaught) were analyzed. We observed the comet on November 24, 2011, when its heliocentric distance was 5.43 AU. Two dimensional long slit spectra and photometric images were obtained using the focal reducer SCORPIO attached to the prime focus of the 6-m telescope BTA (SAO RAS, Russia). The spectra cover the wavelength range of 4200-7000 Å. No emissions of C2 and CO+, which are expected in this wavelength region, were detected above 3σ level. An upper limit in gas production rate of C2 is expected to be 1.1 × 1024 mol s-1. The continuum shows a reddening effect with the normalized gradient of reflectivity along dispersion of 5.1 ± 1.2% per 1000 Å. The color indices (B-V) = 0.89 ± 0.09 and (V-Rc) = 0.42 ± 0.07 for the nucleus region or (B-V) = 0.68 ± 0.12 and (V-Rc) = 0.39 ± 0.10 for the coma region, which are derived from the photometric data, also evidence that the color of the cometary nucleus and dust are redder with respect to the Sun. The normalized gradients of 5.9 ± 2.9% per 1000 Å and 2.6 ± 1.9% per 1000 Å for VRc filters were obtained for the cometary nucleus and the dust coma, respectively. The estimated dust mass production rate is about 12 kg s-1 for Rc filter. The dust coma like a spiral galaxy edge-on was fitted using a Monte Carlo model. Since it is expected that the particles forming the dust coma consist of ;dirty; ice, Greenberg's model was adopted to track grains with an icy component that evaporates slowly when exposed to solar radiation. The observed coma was fitted assuming two isolated active zones located at the cometocentric latitudes of -8° and -35° with outflow of the dust within the cones having half opening angles of 8° and 70°, respectively. About, 45% and 55% of the observed dust were originated from the high collimated and low collimated active zones, respectively. The spin-axis of the rotating nucleus is positioned in the comet's orbit plane. The sizes of the dust particles were ranged from 5 μm to 1 mm with a power index of -3.0 for the adopted exponential dust size distribution.

VERITAS Discovery of >200 GeV Gamma-Ray Emission from the Intermediate-Frequency-Peaked BL Lacertae Object W Comae

NASA Astrophysics Data System (ADS)

Acciari, V. A.; Aliu, E.; Beilicke, M.; Benbow, W.; Böttcher, M.; Bradbury, S. M.; Buckley, J. H.; Bugaev, V.; Butt, Y.; Celik, O.; Cesarini, A.; Ciupik, L.; Chow, Y. C. K.; Cogan, P.; Colin, P.; Cui, W.; Daniel, M. K.; Ergin, T.; Falcone, A. D.; Fegan, S. J.; Finley, J. P.; Finnegan, G.; Fortin, P.; Fortson, L. F.; Furniss, A.; Gall, D.; Gillanders, G. H.; Grube, J.; Guenette, R.; Gyuk, G.; Hanna, D.; Hays, E.; Holder, J.; Horan, D.; Hui, C. M.; Humensky, T. B.; Imran, A.; Kaaret, P.; Karlsson, N.; Kertzman, M.; Kieda, D. B.; Konopelko, A.; Krawczynski, H.; Krennrich, F.; Lang, M. J.; LeBohec, S.; Lee, K.; Maier, G.; McCann, A.; McCutcheon, M.; Moriarty, P.; Mukherjee, R.; Nagai, T.; Niemiec, J.; Ong, R. A.; Pandel, D.; Perkins, J. S.; Petry, D.; Pohl, M.; Quinn, J.; Ragan, K.; Reyes, L. C.; Reynolds, P. T.; Roache, E.; Rose, H. J.; Schroedter, M.; Sembroski, G. H.; Smith, A. W.; Steele, D.; Swordy, S. P.; Toner, J. A.; Vassiliev, V. V.; Wagner, R.; Wakely, S. P.; Ward, J. E.; Weekes, T. C.; Weinstein, A.; White, R. J.; Williams, D. A.; Wissel, S. A.; Wood, M.; Zitzer, B.

2008-09-01

We report the detection of very high energy γ-ray emission from the intermediate-frequency-peaked BL Lacertae object W Comae (z = 0.102) by VERITAS. The source was observed between 2008 January and April. A strong outburst of γ-ray emission was measured in the middle of March, lasting for only 4 days. The energy spectrum measured during the two highest flare nights is fit by a power law and is found to be very steep, with a differential photon spectral index of Γ = 3.81 +/- 0.35stat+/- 0.34syst. The integral photon flux above 200 GeV during those two nights corresponds to roughly 9% of the flux from the Crab Nebula. Quasi-simultaneous Swift observations at X-ray energies were triggered by the VERITAS observations. The spectral energy distribution of the flare data can be described by synchrotron self-Compton (SSC) or external Compton (EC) leptonic jet models.

Myxoedema coma presenting in status epilepticus.

PubMed Central

Woods, K. L.; Holmes, G. K.

1977-01-01

A 71-year-old woman with myxoedema coma presenting in status epilepticus is reported. Although this complication of myxoedema coma is considered to be fatal the patient described responded dramatically to treatment and remains in good health. PMID:876913

Coma blisters in children: case report and review of the literature.

PubMed

Bosco, Laura; Schena, Donatella; Colato, Chiara; Biban, Paolo; Girolomoni, Giampiero

2013-12-01

Coma-induced blisters is a rare condition associated with prolonged impairment of conscious level, which is relatively well-known in adults following overdose with barbiturates. However, it has been very rarely described in children. A case of coma-bullae occurring in an 11-year-old child with meningoencephalitis is herein reported. The bullous lesions occurred on the limbs and trunks, and evolved into necrotic ulcers in a few days. No correlation with any drug overdosage was found. A skin biopsy revealed epidermal and eccrine sweat gland necrosis with abundant neutrophils, and thrombosis of the vessels in the lower dermis. A comprehensive review of the literature showed that only 5 cases of coma-bullae in children have been published so far. Coma blistering resolves spontaneously within days or weeks. Diagnosis of coma-bullae may require careful clinical-pathologic correlation to exclude other blistering diseases in children.

Anions in Cometary Comae

NASA Technical Reports Server (NTRS)

Charnley, Steven B.

2011-01-01

The presence of negative ions (anions) in cometary comae is known from Giotto mass spectrometry of IP/Halley. The anions 0-, OH-, C-, CH- and CN- have been detected, as well as unidentified anions with masses 22-65 and 85-110 amu (Chaizy et al. 1991). Organic molecular anions are known to have a significant impact on the charge balance of interstellar clouds and circumstellar envelopes and have been shown to act as catalysts for the gas-phase synthesis of larger hydrocarbon molecules in the ISM, but their importance in cometary comae has not yet been explored. We present details of the first attempt to model the chemistry of anions in cometary comae. Based on the combined chemical and hydro dynamical model of Rodgers & Charnley (2002), we investigate the role of large carbon-chain anions in cometary coma chemistry. We calculate the effects of these anions on coma thermodynamics, charge balance and examine their impact on molecule formation.

The Stellar Populations of Two Ultra-diffuse Galaxies from Optical and Near-infrared Photometry

NASA Astrophysics Data System (ADS)

Pandya, Viraj; Romanowsky, Aaron J.; Laine, Seppo; Brodie, Jean P.; Johnson, Benjamin D.; Glaccum, William; Villaume, Alexa; Cuillandre, Jean-Charles; Gwyn, Stephen; Krick, Jessica; Lasker, Ronald; Martín-Navarro, Ignacio; Martinez-Delgado, David; van Dokkum, Pieter

2018-05-01

We present observational constraints on the stellar populations of two ultra-diffuse galaxies (UDGs) using optical through near-infrared (NIR) spectral energy distribution (SED) fitting. Our analysis is enabled by new Spitzer-IRAC 3.6 and 4.5 μm imaging, archival optical imaging, and the prospector fully Bayesian SED fitting framework. Our sample contains one field UDG (DGSAT I), one Virgo cluster UDG (VCC 1287), and one Virgo cluster dwarf elliptical for comparison (VCC 1122). We find that the optical–NIR colors of the three galaxies are significantly different from each other. We infer that VCC 1287 has an old (≳7.7 Gyr) and surprisingly metal-poor ([Z/Z ⊙] ≲ ‑1.0) stellar population, even after marginalizing over uncertainties on diffuse interstellar dust. In contrast, the field UDG DGSAT I shows evidence of being younger than the Virgo UDG, with an extended star formation history and an age posterior extending down to ∼3 Gyr. The stellar metallicity of DGSAT I is sub-solar but higher than that of the Virgo UDG, with [Z/{Z}ȯ ]=-{0.63}-0.62+0.35; in the case of exactly zero diffuse interstellar dust, DGSAT I may even have solar metallicity. With VCC 1287 and several Coma UDGs, a general picture is emerging where cluster UDGs may be “failed” galaxies, but the field UDG DGSAT I seems more consistent with a stellar feedback-induced expansion scenario. In the future, our approach can be applied to a large and diverse sample of UDGs down to faint surface brightness limits, with the goal of constraining their stellar ages, stellar metallicities, and circumstellar and diffuse interstellar dust content.

Analysis of Risk Factors for Hypoglycemic Coma in 194 Patients with Type 2 Diabetes

PubMed Central

Lu, Zefen; Liu, Jianfeng; He, Qing; Chakraborty, Anindita; Zhu, Tiehong

2017-01-01

Background The present study was conducted to analyze possible risk factors in patients with type 2 diabetes who are in hypoglycemic coma. Material/Methods A total of 194 patients with type 2 diabetic hypoglycemic coma who were admitted to our hospital between January 2010 and January 2016 were included. The patients were all in coma on admission, and their blood glucose levels were lower than 2.8 mmol/L. None of the patients had type I diabetes, specific types of diabetes, or gestational diabetes. Multiple linear regression analysis was used to determine possible factors associated with hypoglycemic coma. Results Among the patients, 82 were male and 112 were female (mean age, 66.88±10.62 years). In addition, 72 patients lived in urban areas and 122 lived in rural areas. Occurrence of hypoglycemic coma was correlated with difference between urban and rural residence, glycosylated hemoglobin (HbA1c) level, combined hypertension, and combined neural complications. Self-purchased drugs resulted in significantly lower blood glucose level at the onset of hypoglycemic coma than insulin, secretagogue, or non-secretagogue drugs. Blood glucose level at onset was correlated with season. Patients living in rural areas or with combined macrovascular or microvascular complications had prolonged hospital stay and poor prognosis. Conclusions Our results demonstrate that rural residence, higher HbA1c level, combined hypertension, and combined neural complications increase the incidence of hypoglycemic coma. Use of self-purchased drugs and colder seasons may result in lower blood glucose levels in patients with hypoglycemic coma. PMID:29180613

[Myxedema coma].

PubMed

Rizzo, Leonardo F L; Mana, Daniela L; Bruno, Oscar D; Wartofsky, Leonard

2017-01-01

Hypothyroidism is a frequently diagnosed and simply treated disease. If not recognised, however, in time it may develop into the most severe manifestation of hypothyroidism known as myxedema coma. The term "myxedema coma" is generally seen as misleading since most patients do not initially present in a coma. The typical progression is lethargy evolving into stupor and, eventually, into coma with respiratory failure and hypothermia. It mainly affects elderly women, often occurring in winter and is relatively rare. It can be considered a form of decompensated hypothyroidism often triggered by a variety of non-thyroid conditions or diseases provoking an extremely severe condition of multiple system failure with lethal consequences unless an early diagnosis is made and an aggressive treatment is administered.

Meteor Shower Records: A Reference Table of Observations from Previous Centuries

NASA Astrophysics Data System (ADS)

Koseki, M.

2009-10-01

Meteor history shows the complex nature of meteor showers. The author presents the Comae Berenicids as an example of the difficulties in defining meteor showers for visibility using different observational techniques. It is not useful to give a fixed or coded name to a 'meteor shower' because it may not be real and could lead observers to fictitious results.

JCMT Spectral and Continuum Imaging of Comet 252P/LINEAR

NASA Astrophysics Data System (ADS)

Coulson, Iain M.; Cordiner, Martin A.; Kuan, Yi-Jehng; Tseng, Wei-Ling; Chuang, Yo-Ling; Lin, Zhong-Yi; Milam, Stefanie N.; Charnley, Steven B.; Ip, Wing-Huen

2017-04-01

Comet 252P/LINEAR passed the Earth at a distance of 0.035 au on 2016 March 21, presenting a rare opportunity to study a comet at high spatial resolution. Even with a single dish facility such as JCMT, the chemical structure of the coma could be observed on scales of 500-1000 km, which are smaller than the scale lengths of known distributed cometary molecules. Our week-long observing campaign at JCMT started on March 27 (UT), 12 days after perihelion, and ended on April 3, during which time the comet's distance from Earth increased from 0.045 to 0.078 au. Our observations of the J = 4 - 3 transition of HCN showed generally uniform levels of activity. Expansion velocities were ˜0.6 km s-1 (±10%), and the derived mean HCN production rate during the week was 6.4 × 1024 mol s-1. Comparison with independent estimates of the water production rate during the same period yields a mixing ratio of 0.12% with respect to water. Methanol emissions appear to arise from an extended source—probably in the form of an ice halo—suggesting that all the gases from 252P may originate in large part from the sublimation of icy grains in the coma. Adopting a mean dust particle size of 1 mm, the mass of dust in the coma at the same time is estimated at 4 × 107 kg, implying a total dust production rate of 4 kg s-1. The dust-to-gas mass ratio of ˜0.025 is one of the lowest values ever observed for a comet.

Clinical analysis of penehyclidine hydrochloride combined with hemoperfusion in the treatment of acute severe organophosphorus pesticide poisoning.

PubMed

Liang, M J; Zhang, Y

2015-05-11

This study aimed to observe the clinical curative effect of penehyclidine hydrochloride (PHC) combined with hemoperfusion in treating acute severe organophosphorus pesticide poisoning. We randomly divided 61 patients with severe organophosphorus pesticide poisoning into an experimental group (N = 31) and a control group (N = 30), and we compared the coma-recovery time, mechanical ventilation time, healing time, hospital expenses, and mortality between the two groups. The coma-recovery time, mechanical ventilation time, and healing time were lower in the experimental group than in the control group (P < 0.05), while the hospitalization expenses were higher in the experimental group than in the control group (P < 0.01); moreover, no significant difference was observed in the mortality rate between the two groups. Thus, PHC combined with hemoperfusion exerts a better therapeutic effect in acute severe organophosphorus pesticide poisoning than PHC alone.

The volatile composition of comets

NASA Technical Reports Server (NTRS)

Weaver, H. A.

1988-01-01

Comets may be our best probes of the physical and chemical conditions in the outer regions of the solar nebula during that crucial period when the planets formed. The volatile composition of cometary nuclei can be used to decide whether comets are the product of a condensation sequence similar to that invoked to explain the compositions of the planets and asteroids, or if comets are simply agglomerations of interstellar grains which have been insignificantly modified by the events that shaped the other bodies in the solar system. Although cometary nuclei are not generally accessible to observation, observations of cometary comae can illuminate at least some of the mysteries of the nuclei provided one has a detailed knowledge of the excitation conditions in the coma and also has access to basic atomic and molecular data on the many species present in comets. Examined here is the status of our knowledge of the volatile composition of cometary nuclei and how these data are obtained.

Implications for Nucleus Heterogeneity from the Comparison of Pre- and Post-Equinox Neutral ROSINA Observations Inbound and Outbound Beyond 3 AU

NASA Astrophysics Data System (ADS)

Luspay-Kuti, A.; Altwegg, K.; Berthelier, J. J.; Beth, A.; Dhooghe, F.; Fiethe, B.; Fuselier, S. A.; Gombosi, T. I.; Hansen, K. C.; Hässig, M.; Mall, U.; Mandt, K.; Mousis, O.; Steven, P. M.; Rubin, M.; Trattner, K. J.; Tzou, C. Y.; Wurz, P.

2017-12-01

Pre-equinox ROSINA/DFMS measurements revealed a strongly heterogeneous coma. The concentrations of major and various minor volatile species were found to depend on the latitude and longitude of the nadir point of the spacecraft. The observed time variability of coma species remained consistent for about three months up to equinox. The chemical variability could be generally interpreted in terms of temperature and seasonal effects superposed on some kind of nucleus heterogeneity. We compare here pre-equinox (inbound) ROSINA/DFMS measurements from 2014 to measurements taken after the outbound equinox in 2016, both at heliocentric distances larger than 3 AU. For a direct comparison we limit our observations to the southern, poorly illuminated hemisphere only. We report the similarities and differences in the concentrations and time variability of neutral species under similar insolation conditions (heliocentric distance, season) pre- and post-equinox, and interpret them in light of the pre-equinox observations. Such direct comparison of the neutral behavior is important to better understand the evolution of cometary outgassing.

A redshift survey of IRAS galaxies

NASA Astrophysics Data System (ADS)

Smith, Beverly J.; Kleinmann, S. G.; Huchra, J. P.; Low, F. J.

1987-05-01

Results are presented from a redshift survey of all 72 galaxies detected by IRAS in Band 3 at flux levels equal to or greater then 2 Jy. The luminosity function at the high luminosity end is proportional to L-2, however, a flattening was observed at the low luminosity end indicating that a single power law is not a good description of the entire luminosity function. Only three galaxies in the sample have emission line spectra indicative of AGN's, suggesting that, at least in nearby galaxies, unobscured nuclear activity is not a strong contributor to the far infrared flux. Comparisons between the selected IRAS galaxies and an optically complete sample taken from the CfA redshift survey show that they are more narrowly distributed than those optically selected, in the sence that the IRAS sample includes few galaxies of low absolute blue luminosity. It was also found that the space distributions of the two samples differ: the density enhancement or IRAS galaxies is only approx. 1/3 that of the optically selected galaxies in the core of the Coma cluster.

Rosetta/VIRTIS investigation of the chemistry and activity of comet 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Bockelee-Morvan, Dominique; Drossart, Pierre; Piccioni, Giuseppe; Migliorini, Alessandra; Erard, Stéphane; Capaccioni, Fabrizio; Filacchione, Gianrico; Fougere, Nicolas; Leyrat, Cedric; Crovisier, Jacques; Capaccioni, Fabrizio

2016-07-01

The composition of cometary ices inside cometary nuclei provides clues to the chemistry of the protoplanetary disk where they formed, 4.6 Gyr ago. These ices sublimate when the body approches the Sun, so that the coma molecular species give insights on the nucleus surface and sub-surface composition. So far, most investigations of the coma chemical composition were performed from telescopic observations from the ground or space plateforms. Since August 2014, the ESA/Rosetta spacecraft has been investigating the nucleus and inner coma of 67P/Churyumov-Gerasimenko. This talk will present an overview of the results obtained by the Visual and Infrared Thermal Imaging Spectrometer (VIRTIS) instrument onboard Rosetta, focussing on observations of molecular species. VIRTIS is composed of two channels. The VIRTIS-M channel is a spectro-imager covering the 0.27-5.1 microns range, which allowed us to map the spatial distribution of H2O and CO2 (Migliorini et al. 2016, A&A in press). VIRTIS-H is a high-spectral resolution spectrometer covering the 2-5 microns range. Spectra obtained with VIRTIS-H show signatures of H2O, CO2 (both fundamental and hot bands), 13CO2, CH4 and other C-H bearing species (Bockelee-Morvan et al. A&A, 583, A6,2015). VIRTIS is a key instrument to investigate regional, diurnal and seasonal variations of the comet outgassing.

In Situ Space Gas Dynamic Measurements by the ROSINA Comet Pressure Sensor COPS Onboard Rosetta Spacecraft

NASA Astrophysics Data System (ADS)

Tzou, Chia-Yu; Altwegg, Kathrin; Fiethe, Björn; Gasc, Sébastien; Rubin, Martin

2015-04-01

Rosetta is part of the cornerstone missions executed by the European Space Agency. It is the first space mission to orbit and also land on a comet. The Rosetta Orbiter Spectrometer for Ion and Neutral Analysis (ROSINA) is one of the core payloads on board of the Rosetta spacecraft [Balsiger et al, 2007]. ROSINA's main objective is to determine the major atmospheric and ionospheric composition in the coma and to investigate the gas dynamics around the comet. ROSINA consists of two mass spectrometers and a pressure sensor. The COmet Pressure Sensor (COPS) includes two gauges: the "nude gauge" measures total neutral density in the coma and the "ram gauge" measures the dynamic pressure of the cometary gas flux. The combination of these two gauges makes COPS capable to derive the gas dynamics (velocity and temperature) at the location of the spacecraft. Over several months Rosetta has been carrying out a close study of comet 67P/Churyumov-Gerasimenko. In early August 2014 COPS detected the faint and expanding atmosphere of the comet while it was still outside of 3.5 AU from the Sun. We will present ROSINA COPS observations of the evolution and gas dynamics of the cometary coma following these first observations until spring 2015. Reference: Balsiger, H. et al.: ROSINA-Rosetta Orbiter Spectrometer for Ion and Neutral Analysis, Space Science Reviews, Vol. 128, 745-801, 2007.

Stellar Occultations in the Coma of Comet 67/P Chuyumov-Gerasimenko Observed by the OSIRIS Camera System

NASA Astrophysics Data System (ADS)

Moissl, Richard; Kueppers, Michael

2016-10-01

In this paper we present the results of an analysis on a large part of the existing Image data from the OSIRIS camera system onboard the Rosetta Spacecraft, in which stars of sufficient brightness (down to a limiting magnitude of 6) have been observed through the coma of Comet 67/P Churyumov-Gerasimenko ("C-G"). Over the course of the Rosetta main mission the Coma of the comet underwent large changes in density and structure, owed to the changing insolation along the orbit of C-G. We report on the changes of the stellar signals in the wavelength ranges, covered by the filters of the OSIRIS Narrow-Angle (NAC) and Wide-Angle (WAC) cameras.Acknowledgements: OSIRIS was built by a consortium led by the Max-Planck-Institut für Sonnensystemforschung, Göttingen, Germany, in collaboration with CISAS, University of Padova, Italy, the Laboratoire d'Astrophysique de Marseille, France, the Instituto de Astrofísica de Andalucia, CSIC, Granada, Spain, the Scientific Support Office of the European Space Agency, Noordwijk, The Netherlands, the Instituto Nacional de Técnica Aeroespacial, Madrid, Spain, the Universidad Politéchnica de Madrid, Spain, the Department of Physics and Astronomy of Uppsala University, Sweden, and the Institut für Datentechnik und Kommunikationsnetze der Technischen Universität Braunschweig, Germany.

ORIGIN OF MOLECULAR OXYGEN IN COMET 67P/CHURYUMOV–GERASIMENKO

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

Mousis, O.; Ronnet, T.; Brugger, B.

2016-06-01

Molecular oxygen has been detected in the coma of comet 67P/Churyumov–Gerasimenko with abundances in the 1%–10% range by the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis-Double Focusing Mass Spectrometer instrument on board the Rosetta spacecraft. Here we find that the radiolysis of icy grains in low-density environments such as the presolar cloud may induce the production of large amounts of molecular oxygen. We also show that molecular oxygen can be efficiently trapped in clathrates formed in the protosolar nebula (PSN), and that its incorporation as crystalline ice is highly implausible, because this would imply much larger abundances of Armore » and N{sub 2} than those observed in the coma. Assuming that radiolysis has been the only O{sub 2} production mechanism at work, we conclude that the formation of comet 67P/Churyumov–Gerasimenko is possible in a dense and early PSN in the framework of two extreme scenarios: (1) agglomeration from pristine amorphous icy grains/particles formed in ISM and (2) agglomeration from clathrates that formed during the disk’s cooling. The former scenario is found consistent with the strong correlation between O{sub 2} and H{sub 2}O observed in comet 67P/Churyumov-Gerasimenko’s coma while the latter scenario requires that clathrates formed from ISM icy grains that crystallized when entering the PSN.« less

[Clinical course of acute poisoning with olanzapine].

PubMed

Balicka-Slusarczyk, Barbara; Szczeklik, Jerzy; Szpak, Dorota; Groszek, Barbara

2005-01-01

Olanzapine is a new atypical antipsychotic drug acting on different receptors. A variety of pharmacologic effects are responsible for toxicity and the variety of clinical symptoms seen in overdose: tachycardia, agitation or aggression, dysarthria, extrapyramidal dystonic effects, sedation or coma, small pupils, blurred vision, respiratory depression, hypotension. A retrospective analysis of clinical course of eight acute olanzapine intoxication treated at the Department of Clinical Toxicology Jagiellonian University Medical College is presented. CNS symptoms manifested in fluctuations between somnolence/coma and agitation/aggression and miosis were observed in most of the patients. Increased CPK activity was stated in the most of patients. All of the patients recovered, poisoning severity according PSS was moderate and severe.

Coma Associated with Microscopy-Diagnosed Plasmodium vivax: A Prospective Study in Papua, Indonesia

PubMed Central

Hardianto, Setiawan O.; Tjitra, Emiliana; Kenangalem, Enny; Sugiarto, Paulus; Price, Ric N.; Anstey, Nicholas M.

2011-01-01

Background Coma complicates Plasmodium falciparum infection but is uncommonly associated with P. vivax. Most series of vivax coma have been retrospective and have not utilized molecular methods to exclude mixed infections with P. falciparum. Methods We prospectively enrolled patients hospitalized in Timika, Indonesia, with a Glasgow Coma Score (GCS) ≤10 and P. vivax monoinfection on initial microscopy over a four year period. Hematological, biochemical, serological, radiological and cerebrospinal fluid (CSF) examinations were performed to identify other causes of coma. Repeat microscopy, antigen detection and polymerase chain reaction (PCR) were performed to exclude infections with other Plasmodium species. Results Of 24 patients fulfilling enrolment criteria, 5 had clear evidence for other non-malarial etiologies. PCR demonstrated 10 mixed infections and 3 P. falciparum monoinfections. 6 (25%) patients had vivax monoinfection and no apparent alternative cause, with a median GCS of 9 (range 8–10) and a median coma duration of 42 (range 36–48) hours. CSF leukocyte counts were <10/ul (n = 3); 2 of the 3 patients without CSF examination recovered with antimalarial therapy alone. One patient had a tremor on discharge consistent with a post-malarial neurological syndrome. No patient had other organ dysfunction. The only death was associated with pure P. falciparum infection by PCR. Vivax monoinfection-associated risk of coma was estimated at 1 in 29,486 clinical vivax infections with no deaths. In comparison, the risk of falciparum-associated coma was estimated at 1 in 1,276 clinical infections with an 18.5% mortality rate. Conclusions P. vivax-associated coma is rare, occurring 23 times less frequently than that seen with falciparum malaria, and is associated with a high proportion of non-malarial causes and mixed infections using PCR. The pathogenesis of coma associated with vivax malaria, particularly the role of comorbidities, is uncertain and requires further investigation. PMID:21666785

Which EEG patterns in coma are nonconvulsive status epilepticus?

PubMed

Trinka, Eugen; Leitinger, Markus

2015-08-01

Nonconvulsive status epilepticus (NCSE) is common in patients with coma with a prevalence between 5% and 48%. Patients in deep coma may exhibit epileptiform EEG patterns, such as generalized periodic spikes, and there is an ongoing debate about the relationship of these patterns and NCSE. The purposes of this review are (i) to discuss the various EEG patterns found in coma, its fluctuations, and transitions and (ii) to propose modified criteria for NCSE in coma. Classical coma patterns such as diffuse polymorphic delta activity, spindle coma, alpha/theta coma, low output voltage, or burst suppression do not reflect NCSE. Any ictal patterns with a typical spatiotemporal evolution or epileptiform discharges faster than 2.5 Hz in a comatose patient reflect nonconvulsive seizures or NCSE and should be treated. Generalized periodic diacharges or lateralized periodic discharges (GPDs/LPDs) with a frequency of less than 2.5 Hz or rhythmic discharges (RDs) faster than 0.5 Hz are the borderland of NCSE in coma. In these cases, at least one of the additional criteria is needed to diagnose NCSE (a) subtle clinical ictal phenomena, (b) typical spatiotemporal evolution, or (c) response to antiepileptic drug treatment. There is currently no consensus about how long these patterns must be present to qualify for NCSE, and the distinction from nonconvulsive seizures in patients with critical illness or in comatose patients seems arbitrary. The Salzburg Consensus Criteria for NCSE [1] have been modified according to the Standardized Terminology of the American Clinical Neurophysiology Society [2] and validated in three different cohorts, with a sensitivity of 97.2%, a specificity of 95.9%, and a diagnostic accuracy of 96.3% in patients with clinical signs of NCSE. Their diagnostic utility in different cohorts with patients in deep coma has to be studied in the future. This article is part of a Special Issue entitled "Status Epilepticus". Copyright © 2015. Published by Elsevier Inc.

An Atypical Case of Myxedema Coma with Concomitant Nonconvulsive Seizure.

PubMed

Patel, Pratik; Bekkerman, Mikhael; Varallo-Rodriguez, Cristina; Rampersaud, Rajendra

2016-01-01

Hypothyroidism is a prevalent condition in the general population that is treatable with appropriately dosed thyroid hormone replacement medication. Infrequently, patients will present with myxedema coma, characterized by hypothermia, hypotension, bradycardia, and altered mental status in the setting of severe hypothyroidism. Myxedema coma has also been known to manifest in a number of unusual and dangerous forms. Here, we present the case of a woman we diagnosed with an uncharacteristic expression of myxedema coma and nonconvulsive seizure complicated by a right middle cerebral artery infarct.

The child in coma

NASA Technical Reports Server (NTRS)

Lewinn, E. B.

1978-01-01

Children in coma continue to pose medical, social, economic, ethical, moral, and legal problems. Modern life-support technology has aggravated these problems. Coma is viewed as a pathological state of unconsciousness from which the patient has not achieved arousal, and which calls for vigorous action to help him regain consciousness. There are two variables that have an especially important bearing on the ability to achieve arousal. These are: the character of the brain injury that caused the coma, and environmental factors that affect the patient after the injury.

[Evaluation of prognosis in purulent meningitis-myelitis based on the Glasgow Coma Scale].

PubMed

Garlicki, A; Caban, J; Bociaga, M; Krukowiecki, J; Warunek, W; Skwara, P

1996-01-01

We presented data from the investigation of the usefulness of the Glasgow Coma Scale in predicting the outcome of bacterial meningitis. Patients who aggregated high Glasgow Coma Scale scores had a good prognosis, whereas those patients with low scores had a very poor prognosis, inspite of this limitation the Glasgow Coma Scale seems to be a valuable supplement to the physical examination of patients with bacterial meningitis and may help in predicting the outcome of the disease.

Initial Diagnosis and Management of Coma.

PubMed

Traub, Stephen J; Wijdicks, Eelco F

2016-11-01

Coma represents a true medical emergency. Drug intoxications are a leading cause of coma; however, other metabolic disturbances and traumatic brain injury are also common causes. The general emergency department approach begins with stabilization of airway, breathing, and circulation, followed by a thorough physical examination to generate a limited differential diagnosis that is then refined by focused testing. Definitive treatment is ultimately disease-specific. This article presents an overview of the pathophysiology, causes, examination, and treatment of coma. Copyright © 2016 Elsevier Inc. All rights reserved.

Sublimation of icy aggregates in the coma of comet 67P/Churyumov-Gerasimenko detected with the OSIRIS cameras on board Rosetta

NASA Astrophysics Data System (ADS)

Gicquel, A.; Vincent, J.-B.; Agarwal, J.; A'Hearn, M. F.; Bertini, I.; Bodewits, D.; Sierks, H.; Lin, Z.-Y.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Barucci, M. A.; Bertaux, J.-L.; Besse, S.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; Deller, J.; De Cecco, M.; Frattin, E.; El-Maarry, M. R.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Gutiérrez-Marquez, P.; Güttler, C.; Höfner, S.; Hofmann, M.; Hu, X.; Hviid, S. F.; Ip, W.-H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J.-R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Moreno, J. J. Lopez; Lowry, S.; Marzari, F.; Masoumzadeh, N.; Massironi, M.; Moreno, F.; Mottola, S.; Naletto, G.; Oklay, N.; Pajola, M.; Pommerol, A.; Preusker, F.; Scholten, F.; Shi, X.; Thomas, N.; Toth, I.; Tubiana, C.

2016-11-01

Beginning in 2014 March, the OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) cameras began capturing images of the nucleus and coma (gas and dust) of comet 67P/Churyumov-Gerasimenko using both the wide angle camera (WAC) and the narrow angle camera (NAC). The many observations taken since July of 2014 have been used to study the morphology, location, and temporal variation of the comet's dust jets. We analysed the dust monitoring observations shortly after the southern vernal equinox on 2015 May 30 and 31 with the WAC at the heliocentric distance Rh = 1.53 AU, where it is possible to observe that the jet rotates with the nucleus. We found that the decline of brightness as a function of the distance of the jet is much steeper than the background coma, which is a first indication of sublimation. We adapted a model of sublimation of icy aggregates and studied the effect as a function of the physical properties of the aggregates (composition and size). The major finding of this paper was that through the sublimation of the aggregates of dirty grains (radius a between 5 and 50 μm) we were able to completely reproduce the radial brightness profile of a jet beyond 4 km from the nucleus. To reproduce the data, we needed to inject a number of aggregates between 8.5 × 1013 and 8.5 × 1010 for a = 5 and 50 μm, respectively, or an initial mass of H2O ice around 22 kg.

Acute Kidney Injury as a Risk Factor for Delirium and Coma during Critical Illness.

PubMed

Siew, Edward D; Fissell, William H; Tripp, Christina M; Blume, Jeffrey D; Wilson, Matthew D; Clark, Amanda J; Vincz, Andrew J; Ely, E Wesley; Pandharipande, Pratik P; Girard, Timothy D

2017-06-15

Acute kidney injury may contribute to distant organ dysfunction. Few studies have examined kidney injury as a risk factor for delirium and coma. To examine whether acute kidney injury is associated with delirium and coma in critically ill adults. In a prospective cohort study of intensive care unit patients with respiratory failure and/or shock, we examined the association between acute kidney injury and daily mental status using multinomial transition models adjusting for demographics, nonrenal organ failure, sepsis, prior mental status, and sedative exposure. Acute kidney injury was characterized daily using the difference between baseline and peak serum creatinine and staged according to Kidney Disease Improving Global Outcomes criteria. Mental status (normal vs. delirium vs. coma) was assessed daily with the Confusion Assessment Method for the ICU and Richmond Agitation-Sedation Scale. Among 466 patients, stage 2 acute kidney injury was a risk factor for delirium (odds ratio [OR], 1.55; 95% confidence interval [CI], 1.07-2.26) and coma (OR, 2.04; 95% CI, 1.25-3.34) as was stage 3 injury (OR for delirium, 2.56; 95% CI, 1.57-4.16) (OR for coma, 3.34; 95% CI, 1.85-6.03). Daily peak serum creatinine (adjusted for baseline) values were also associated with delirium (OR, 1.35; 95% CI, 1.18-1.55) and coma (OR, 1.44; 95% CI, 1.20-1.74). Renal replacement therapy modified the association between stage 3 acute kidney injury and daily peak serum creatinine and both delirium and coma. Acute kidney injury is a risk factor for delirium and coma during critical illness.

Evolution of Late-type Galaxies in a Cluster Environment: Effects of High-speed Multiple Encounters with Early-type Galaxies

NASA Astrophysics Data System (ADS)

Hwang, Jeong-Sun; Park, Changbom; Banerjee, Arunima; Hwang, Ho Seong

2018-04-01

Late-type galaxies falling into a cluster would evolve being influenced by the interactions with both the cluster and the nearby cluster member galaxies. Most numerical studies, however, tend to focus on the effects of the former with little work done on those of the latter. We thus perform a numerical study on the evolution of a late-type galaxy interacting with neighboring early-type galaxies at high speed using hydrodynamic simulations. Based on the information obtained from the Coma cluster, we set up the simulations for the case where a Milky Way–like late-type galaxy experiences six consecutive collisions with twice as massive early-type galaxies having hot gas in their halos at the closest approach distances of 15–65 h ‑1 kpc at the relative velocities of 1500–1600 km s‑1. Our simulations show that the evolution of the late-type galaxy can be significantly affected by the accumulated effects of the high-speed multiple collisions with the early-type galaxies, such as on cold gas content and star formation activity of the late-type galaxy, particularly through the hydrodynamic interactions between cold disk and hot gas halos. We find that the late-type galaxy can lose most of its cold gas after the six collisions and have more star formation activity during the collisions. By comparing our simulation results with those of galaxy–cluster interactions, we claim that the role of the galaxy–galaxy interactions on the evolution of late-type galaxies in clusters could be comparable with that of the galaxy–cluster interactions, depending on the dynamical history.

Myxedema coma with cardiac tamponade and severe cardiomyopathy.

PubMed

Majid-Moosa, Abdulla; Schussler, Jeffrey M; Mora, Adan

2015-10-01

Myxedema coma is an infrequent but potentially fatal complication of hypothyroidism. We present a rare case of previously undiagnosed hypothyroidism presenting in cardiogenic shock from pericardial tamponade and depressed myocardial contractility in myxedema coma. Here, we focus on cardiovascular complications associated with the condition.

Energy expenditure during barbiturate coma.

PubMed

Ashcraft, Christine M; Frankenfield, David C

2013-10-01

Barbiturate coma may have a significant effect on metabolic rate, but the phenomenon is not extensively studied. The primary purpose of the current study was to compare the metabolic rate of general critical care patients with those requiring barbiturate coma. A secondary purpose was to evaluate the accuracy of the Penn State prediction equation between these 2 groups of patients. Indirect calorimetry was used to measure the resting metabolic rate of mechanically ventilated, critically ill patients in a barbiturate coma and those of similar height, weight, and age but not in a barbiturate coma. Measurements of resting metabolic rate were compared with predictions using the Penn State equation accounting for body size, body temperature, and minute ventilation. The barbiturate coma group had a lower resting metabolic rate than the control group that remained lower even after adjustment for predicted healthy metabolic rate and maximum body temperature (1859 ± 290 vs 2037 ± 289 kcal/d, P = .020). When minute ventilation was also included in the analysis, the resting metabolic rate between the groups became statistically insignificant (1929 ± 229 vs 2023 ± 226 kcal/d, P = .142). The Penn State equation, which uses these variables, was accurate in 73% of the control patients and also the barbiturate coma patients. Resting metabolic rate is moderately reduced in barbiturate coma, but the decrease is out of proportion with changes in body temperature. However, if both body temperature and minute ventilation are considered, then the change is predictable.

Star-Forming Galaxies in the Hercules Cluster: Hα Imaging of A2151

NASA Astrophysics Data System (ADS)

Cedrés, Bernabé; Iglesias-Páramo, Jorge; Vílchez, José Manuel; Reverte, Daniel; Petropoulou, Vasiliki; Hernández-Fernández, Jonathan

2009-09-01

This paper presents the first results of an Hα imaging survey of galaxies in the central regions of the A2151 cluster. A total of 50 sources were detected in Hα, from which 41 were classified as secure members of the cluster and 2 as likely members based on spectroscopic and photometric redshift considerations. The remaining seven galaxies were classified as background contaminants and thus excluded from our study on the Hα properties of the cluster. The morphologies of the 43 Hα selected galaxies range from grand design spirals and interacting galaxies to blue compacts and tidal dwarfs or isolated extragalactic H II regions, spanning a range of magnitudes of -21 <= MB <= -12.5 mag. From these 43 galaxies, 7 have been classified as active galactic nucleus (AGN) candidates. These AGN candidates follow the L(Hα) versus MB relationship of the normal galaxies, implying that the emission associated with the nuclear engine has a rather secondary impact on the total Hα emission of these galaxies. A comparison with the clusters Coma and A1367 and a sample of field galaxies has shown the presence of cluster galaxies with L(Hα) lower than expected for their MB , a consequence of the cluster environment. This fact results in differences in the L(Hα) versus EW(Hα) and L(Hα) distributions of the clusters with respect to the field, and in cluster-to-cluster variations of these quantities, which we propose are driven by a global cluster property as the total mass. In addition, the cluster Hα emitting galaxies tend to avoid the central regions of the clusters, again with different intensity depending on the cluster total mass. For the particular case of A2151, we find that most Hα emitting galaxies are located close to the regions with the higher galaxy density, offset from the main X-ray peak. Overall, we conclude that both the global cluster environment and the cluster merging history play a non-negligible role in the integral star formation properties of clusters of galaxies.

STAR-FORMING GALAXIES IN THE HERCULES CLUSTER: H{alpha} IMAGING OF A2151

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

Cedres, Bernabe; Iglesias-Paramo, Jorge; VIlchez, Jose Manuel

2009-09-15

This paper presents the first results of an H{alpha} imaging survey of galaxies in the central regions of the A2151 cluster. A total of 50 sources were detected in H{alpha}, from which 41 were classified as secure members of the cluster and 2 as likely members based on spectroscopic and photometric redshift considerations. The remaining seven galaxies were classified as background contaminants and thus excluded from our study on the H{alpha} properties of the cluster. The morphologies of the 43 H{alpha} selected galaxies range from grand design spirals and interacting galaxies to blue compacts and tidal dwarfs or isolated extragalacticmore » H II regions, spanning a range of magnitudes of -21 {<=} M{sub B} {<=} -12.5 mag. From these 43 galaxies, 7 have been classified as active galactic nucleus (AGN) candidates. These AGN candidates follow the L(H{alpha}) versus M{sub B} relationship of the normal galaxies, implying that the emission associated with the nuclear engine has a rather secondary impact on the total H{alpha} emission of these galaxies. A comparison with the clusters Coma and A1367 and a sample of field galaxies has shown the presence of cluster galaxies with L(H{alpha}) lower than expected for their M{sub B} , a consequence of the cluster environment. This fact results in differences in the L(H{alpha}) versus EW(H{alpha}) and L(H{alpha}) distributions of the clusters with respect to the field, and in cluster-to-cluster variations of these quantities, which we propose are driven by a global cluster property as the total mass. In addition, the cluster H{alpha} emitting galaxies tend to avoid the central regions of the clusters, again with different intensity depending on the cluster total mass. For the particular case of A2151, we find that most H{alpha} emitting galaxies are located close to the regions with the higher galaxy density, offset from the main X-ray peak. Overall, we conclude that both the global cluster environment and the cluster merging history play a non-negligible role in the integral star formation properties of clusters of galaxies.« less

HUBBLE SPACE TELESCOPE AND HI IMAGING OF STRONG RAM PRESSURE STRIPPING IN THE COMA SPIRAL NGC 4921: DENSE CLOUD DECOUPLING AND EVIDENCE FOR MAGNETIC BINDING IN THE ISM

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

Kenney, Jeffrey D. P.; Abramson, Anne; Bravo-Alfaro, Hector, E-mail: jeff.kenney@yale.edu

Remarkable dust extinction features in the deep Hubble Space Telescope (HST) V and I images of the face-on Coma cluster spiral galaxy NGC 4921 show in unprecedented ways how ram pressure strips the ISM from the disk of a spiral galaxy. New VLA HI maps show a truncated and highly asymmetric HI disk with a compressed HI distribution in the NW, providing evidence for ram pressure acting from the NW. Where the HI distribution is truncated in the NW region, HST images show a well-defined, continuous front of dust that extends over 90° and 20 kpc. This dust front separatesmore » the dusty from dust-free regions of the galaxy, and we interpret it as galaxy ISM swept up near the leading side of the ICM–ISM interaction. We identify and characterize 100 pc–1 kpc scale substructure within this dust front caused by ram pressure, including head–tail filaments, C-shaped filaments, and long smooth dust fronts. The morphology of these features strongly suggests that dense gas clouds partially decouple from surrounding lower density gas during stripping, but decoupling is inhibited, possibly by magnetic fields that link and bind distant parts of the ISM.« less

NASA Hubble Sees Comet ISON Intact

NASA Image and Video Library

2013-10-09

This image from NASA Hubble Space Telescope of the sunward plunging comet ISON suggests that the comet is intact despite some predictions that the fragile icy nucleus might disintegrate as the sun warms it. In this NASA Hubble Space Telescope image taken on October 9, 2013 the comet's solid nucleus is unresolved because it is so small. If the nucleus broke apart then Hubble would have likely seen evidence for multiple fragments. Moreover, the coma or head surrounding the comet's nucleus is symmetric and smooth. This would probably not be the case if clusters of smaller fragments were flying along. What's more, a polar jet of dust first seen in Hubble images taken in April is no longer visible and may have turned off. This color composite image was assembled using two filters. The comet's coma appears cyan, a greenish-blue color due to gas, while the tail is reddish due to dust streaming off the nucleus. The tail forms as dust particles are pushed away from the nucleus by the pressure of sunlight. The comet was inside Mars' orbit and 177 million miles from Earth when photographed. Comet ISON is predicted to make its closest approach to Earth on 26 December, at a distance of 39.9 million miles. http://photojournal.jpl.nasa.gov/catalog/PIA18153

Characterization of dust aggregates in the vicinity of the Rosetta spacecraft

NASA Astrophysics Data System (ADS)

Güttler, C.; Hasselmann, P. H.; Li, Y.; Fulle, M.; Tubiana, C.; Kovacs, G.; Agarwal, J.; Sierks, H.; Fornasier, S.; Hofmann, M.; Gutiérrez Marqués, P.; Ott, T.; Drolshagen, E.; Bertini, I.; Osiris Team

2017-09-01

In a Rosetta/OSIRIS imaging activity in June 2015, we have observed the dynamic motion of particles close to the spacecraft. Due to the focal setting of the OSIRIS Wide Angle Camera (WAC), these particles were blurred, which can be used to measure their distances to the spacecraft. We detected 108 dust aggregates over a 130 minutes long sequence, and find that their sizes are around a millimetre and their distances cluster between 2 m and 40 m from the spacecraft. Their number densities are about a factor 10 higher than expected for the overall coma and highly fluctuating. Their velocities are small compared to the spacecraft orbital motion and directed away from the spacecraft, towards the comet. From this we conclude that they have interacted with the spacecraft and assess three possible scenarios. We prefer a scenario where centimeter-sized aggregates collide with the spacecraft and we would observe the fragments. Ablation of a dust layer on the spacecraft's z panel when rotated towards the sun is a reasonable alternative. We could also measure an acceleration for a subset of 18 aggregates, which is directed away from the sun and can be explain by a rocket effect, which requires a minimum ice fraction in the order of 0.1%

Characterization of dust aggregates in the vicinity of the Rosetta spacecraft

NASA Astrophysics Data System (ADS)

Güttler, C.; Hasselmann, P. H.; Li, Y.; Fulle, M.; Tubiana, C.; Kovacs, G.; Agarwal, J.; Sierks, H.; Fornasier, S.; Hofmann, M.; Gutiérrez Marqués, P.; Ott, T.; Drolshagen, E.; Bertini, I.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; A'Hearn, M. F.; Barucci, M. A.; Bodewits, D.; Bertaux, J.-L.; Boudreault, S.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Deller, J.; Geiger, B.; Groussin, O.; Gutiérrez, P. J.; Hviid, S. F.; Ip, W.-H.; Jorda, L.; Keller, H. U.; Knollenberg, J.; Kramm, J. R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; López-Moreno, J. J.; Marzari, F.; Mottola, S.; Naletto, G.; Oklay, N.; Pajola, M.; Shi, X.; Thomas, N.; Vincent, J.-B.

2017-07-01

In a Rosetta/OSIRIS imaging activity in 2015 June, we have observed the dynamic motion of particles close to the spacecraft. Due to the focal setting of the OSIRIS wide angle camera, these particles were blurred, which can be used to measure their distances to the spacecraft. We detected 109 dust aggregates over a 130 min long sequence, and find that their sizes are around a millimetre and their distances cluster between 2 and 40 m from the spacecraft. Their number densities are about a factor 10 higher than expected for the overall coma and highly fluctuating. Their velocities are small compared to the spacecraft orbital motion and directed away from the spacecraft, towards the comet. From this we conclude that they have interacted with the spacecraft and assess three possible scenarios. In the likeliest of the three scenarios, centimetre-sized aggregates collide with the spacecraft and we would observe the fragments. Ablation of a dust layer on the spacecraft's z panel (remote instrument viewing direction) when rotated towards the Sun is a reasonable alternative. We could also measure an acceleration for a subset of 18 aggregates, which is directed away from the Sun and can be explain by a rocket effect, which requires a minimum ice fraction of the order of 0.1 per cent.

Understanding Phosphorous Chemistry in Comets in Light of Rosetta Results

NASA Astrophysics Data System (ADS)

Boice, Daniel C.; de Almeida, Amaury A.

2016-10-01

Introduction: Phosphorous is a key element in all known forms of life. P-bearing compounds have been observed in the ISM and other regions of space. They are ubiquitous in meteorites, have been detected in the dust component in comets 1P/Halley and 81P/Wild 2, and in the gas phase (atomic P) of 67P/Churyumov-Gerasimenko by the Rosetta Mission. We present results from the first quantitative study of P-bearing molecules in comets to aid in future searches for this important element in comets, shedding light on issues of comet formation and prebiotic to biotic evolution of life. Results and Discussion: Our gas dynamics model of cometary comae with chemical kinetics has been adapted to study this problem. We used phosphine (PH3) as a native molecule with a cosmic abundance mixing ratio. Over 100 photo and gas-phase reactions and 30 P-bearing species were added to the chemical network. The chemistry of PH3 in the inner coma shows the major destruction channels are photo-dissociation and protonation with water-group ions, leading to the recycling of PH3 in this region and the eventual production of atomic P. Conclusion: The model identifies the relevant phosphine chemistry in cometary coma. Protonation reactions of PH3 with water-group ions are important due to its high proton affinity. Abundances are found to be on the order of 10-4 relative to water, about the same as isotopic species. The scale length of PH3 in the coma is about 13,000-16,000 km. We also comment on other Rosetta findings (e.g., O2 and H-). Collaborations with observers using modern telescopic facilities (e.g., Keck 2 and Subaru) are underway to search for phosphorus in comets. Acknowledgments: This work was supported by FAPESP under Grant No. 2015/03176-8 and the National Science Foundation Planetary Astronomy Program Grant No. 0908529.

Millimeter and Submillimeter Observations of Comet 67P's Nucleus, Gas, and Dust with the Rosetta/MIRO Instrument

NASA Astrophysics Data System (ADS)

Hofstadter, Mark

2016-04-01

The Microwave Instrument for the Rosetta Orbiter (MIRO) has been making measurements of comet 67P/C-G since June 2014, when the comet was 3.92 AU from the Sun and Rosetta was approximately 400,000 km from the nucleus. Those first observations were spatially unresolved measurements of the 556 GHz water line, used to infer the abundance and velocity of water vapor in the coma (Gulkis et al. 2015, Science 347). In the almost two years since that time, as the spacecraft has moved closer to the nucleus and the comet has become more active (perihelion at 1.2 AU from the Sun occurred in August 2015), MIRO's submillimeter spectrometer (working at frequencies near 550 GHz, or wavelengths near 0.5 mm) has been used to determine the velocity, abundance, and spatial distribution of H216O, H217O, H218O, CH3OH, NH3, and CO in the coma as a function of time (e.g. water is discussed by Biver et al. 2015 and Lee et al. 2015, Astron. and Astrophys. 583). In addition to its submillimeter spectrometer, MIRO has two broad band continuum channels operating at wavelengths near 0.5 and 1.6 millimeter. These channels are designed to probe the nucleus ˜1 millimeter to 10 cm below the surface. Data have been used to infer properties such as thermal inertia, porosity, and ice content as functions of location, depth, and time (e.g. Schloerb et al. 2015 and Choukroun et al. 2015, Astron. and Astrophys. 583). These channels have also been used to map the distribution of relatively large dust grains (radius > ˜1 mm) in the inner coma of the comet, with the potential to constrain models of dust acceleration, cooling, and fragmentation. This talk will review the latest results from MIRO's measurements of the nucleus, coma, and dust, and discuss some of the processes that couple these components of the comet.

A 17-billion-solar-mass black hole in a group galaxy with a diffuse core.

PubMed

Thomas, Jens; Ma, Chung-Pei; McConnell, Nicholas J; Greene, Jenny E; Blakeslee, John P; Janish, Ryan

2016-04-21

Quasars are associated with and powered by the accretion of material onto massive black holes; the detection of highly luminous quasars with redshifts greater than z = 6 suggests that black holes of up to ten billion solar masses already existed 13 billion years ago. Two possible present-day 'dormant' descendants of this population of 'active' black holes have been found in the galaxies NGC 3842 and NGC 4889 at the centres of the Leo and Coma galaxy clusters, which together form the central region of the Great Wall--the largest local structure of galaxies. The most luminous quasars, however, are not confined to such high-density regions of the early Universe; yet dormant black holes of this high mass have not yet been found outside of modern-day rich clusters. Here we report observations of the stellar velocity distribution in the galaxy NGC 1600--a relatively isolated elliptical galaxy near the centre of a galaxy group at a distance of 64 megaparsecs from Earth. We use orbit superposition models to determine that the black hole at the centre of NGC 1600 has a mass of 17 billion solar masses. The spatial distribution of stars near the centre of NGC 1600 is rather diffuse. We find that the region of depleted stellar density in the cores of massive elliptical galaxies extends over the same radius as the gravitational sphere of influence of the central black holes, and interpret this as the dynamical imprint of the black holes.

Diagnosis of myxedema coma complicated by renal failure: a case report.

PubMed

Takamura, Akiteru; Sangen, Ryusho; Furumura, Yoshiki; Usuda, Daisuke; Kasamaki, Yuji; Kanda, Tsugiyasu

2017-04-01

Myxedema coma, caused by severe lack of thyroid hormone, is characterized by deterioration of mental status, hypothermia, hypotension, hyponatremia, and hypoventilation. We describe an 84-year-old woman who presented with renal failure and new onset severe hypothyroidism leading to challenges in the recognition of myxedema coma.

Myxedema coma in a patient with Down's syndrome.

PubMed

Bansal, Darpan; Nanda, Ashish; Gupta, Ekta; Croker, Mary; Williams, Misty L; Bacchus, Amy; Simmons, Debra; Erbland, Marcia

2006-11-01

hyroid dysfunction is common in Down's syndrome, most common being hypothyroidism. Longstanding, untreated hypothyroidism can lead to myxedema coma. Here we report a patient with Down's syndrome who presented with myxedema coma. The three essential elements for the diagnosis of myxedema coma include altered mental status, defective thermoregulation and a precipitating event or illness; all of these were present in our patient. Also, very high TSH, low T3 and T4, and the rapid response to the treatment with levothyroxine confirmed the diagnosis. Patients with Down's syndrome should have regular screening for thyroid dysfunction.

Thyroid gland disorder emergencies: thyroid storm and myxedema coma.

PubMed

Hampton, Jessica

2013-01-01

Although thyroid dysfunction will develop in more than 12% of the US population during their lifetimes, true thyroid emergencies are rare. Thyroid storm and myxedema coma are endocrine emergencies resulting from thyroid hormone dysregulation, usually coupled with an acute illness as a precipitant. Careful assessment of risk and rapid action, once danger is identified, are essential for limiting morbidity and mortality related to thyroid storm and myxedema coma. This article reviews which patients are at risk, explains thyroid storm and myxedema coma, and describes pharmacological treatment and supportive cares.

An Atypical Case of Myxedema Coma with Concomitant Nonconvulsive Seizure

PubMed Central

Patel, Pratik; Varallo-Rodriguez, Cristina

2016-01-01

Hypothyroidism is a prevalent condition in the general population that is treatable with appropriately dosed thyroid hormone replacement medication. Infrequently, patients will present with myxedema coma, characterized by hypothermia, hypotension, bradycardia, and altered mental status in the setting of severe hypothyroidism. Myxedema coma has also been known to manifest in a number of unusual and dangerous forms. Here, we present the case of a woman we diagnosed with an uncharacteristic expression of myxedema coma and nonconvulsive seizure complicated by a right middle cerebral artery infarct. PMID:27872766

Time variability and heterogeneity in the coma of 67P/Churyumov-Gerasimenko

NASA Astrophysics Data System (ADS)

Hässig, M.; Altwegg, K.; Balsiger, H.; Bar-Nun, A.; Berthelier, J. J.; Bieler, A.; Bochsler, P.; Briois, C.; Calmonte, U.; Combi, M.; De Keyser, J.; Eberhardt, P.; Fiethe, B.; Fuselier, S. A.; Galand, M.; Gasc, S.; Gombosi, T. I.; Hansen, K. C.; Jäckel, A.; Keller, H. U.; Kopp, E.; Korth, A.; Kührt, E.; Le Roy, L.; Mall, U.; Marty, B.; Mousis, O.; Neefs, E.; Owen, T.; Rème, H.; Rubin, M.; Sémon, T.; Tornow, C.; Tzou, C.-Y.; Waite, J. H.; Wurz, P.

2015-01-01

Comets contain the best-preserved material from the beginning of our planetary system. Their nuclei and comae composition reveal clues about physical and chemical conditions during the early solar system when comets formed. ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) onboard the Rosetta spacecraft has measured the coma composition of comet 67P/Churyumov-Gerasimenko with well-sampled time resolution per rotation. Measurements were made over many comet rotation periods and a wide range of latitudes. These measurements show large fluctuations in composition in a heterogeneous coma that has diurnal and possibly seasonal variations in the major outgassing species: water, carbon monoxide, and carbon dioxide. These results indicate a complex coma-nucleus relationship where seasonal variations may be driven by temperature differences just below the comet surface.

Reestablishment of ion homeostasis during chill-coma recovery in the cricket Gryllus pennsylvanicus

PubMed Central

MacMillan, Heath A.; Williams, Caroline M.; Staples, James F.; Sinclair, Brent J.

2012-01-01

The time required to recover from cold-induced paralysis (chill-coma) is a common measure of insect cold tolerance used to test central questions in thermal biology and predict the effects of climate change on insect populations. The onset of chill-coma in the fall field cricket (Gryllus pennsylvanicus, Orthoptera: Gryllidae) is accompanied by a progressive drift of Na+ and water from the hemolymph to the gut, but the physiological mechanisms underlying recovery from chill-coma are not understood for any insect. Using a combination of gravimetric methods and atomic absorption spectroscopy, we demonstrate that recovery from chill-coma involves a reestablishment of hemolymph ion content and volume driven by removal of Na+ and water from the gut. Recovery is associated with a transient elevation of metabolic rate, the time span of which increases with increasing cold exposure duration and closely matches the duration of complete osmotic recovery. Thus, complete recovery from chill-coma is metabolically costly and encompasses a longer period than is required for the recovery of muscle potentials and movement. These findings provide evidence that physiological mechanisms of hemolymph ion content and volume regulation, such as ion-motive ATPase activity, are instrumental in chill-coma recovery and may underlie natural variation in insect cold tolerance. PMID:23184963

Study of the coma of comet 67P/Churyumov-Gerasimenko based on the ROSINA/RTOF instrument onboard Rosetta

NASA Astrophysics Data System (ADS)

Hoang, M.; Garnier, P.; Lasue, J.; Reme, H.; Altwegg, K.; Balsiger, H. R.; Bieler, A. M.; Calmonte, U.; Fiethe, B.; Galli, A.; Gasc, S.; Gombosi, T. I.; Jäckel, A.; Mall, U.; Le Roy, L.; Rubin, M.; Tzou, C. Y.; Waite, J. H., Jr.; Wurz, P.

2015-12-01

The ROSETTA spacecraft of ESA is in the environment of comet 67P/Churyumov-Gerasimenko since August 2014. Among the experiments onboard the spacecraft, the ROSINA experiment (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) includes two mass spectrometers (DFMS and RTOF) to analyze the composition of neutrals and ions, and a pressure sensor (COPS) to monitor the density and velocity of neutrals in the coma [1]. We will here analyze and discuss the data of the ROSINA/RTOF instrument during the comet escort phase. The Reflectron-type Time-Of-Flight (RTOF) mass spectrometer possesses a wide mass range and a high temporal resolution [1,2]. It was designed to measure cometary neutral gas as well as cometary ions. A detailed description of the main volatiles (H2O, CO2, CO) dynamics and of the heterogeneities of the coma will then be provided. The influence of various parameters on the coma measurements is investigated on a statistical basis, with the parameters being distance to the comet, heliocentric distance, longitude and latitude of nadir point. Our analysis of the northern hemisphere summer season shows the presence of water vapor mostly in the illuminated northern hemisphere near the neck region with cyclic diurnal variations whereas CO2 was confined to the cold southern hemisphere with a more spatially homogeneous composition, in agreement with previous observations of 67P [2] or Hartley 2 [3]. A comparison will also be provided with the COPS total density and DFMS abundance measurements. [1] Balsiger et al., "ROSINA - Rosetta Orbiter Spectrometer for Ion and Neutral Analysis", Space Sci. Rev., 2007. [2] Scherer et al., "A novel principle for an ion mirror design in time-of-flight mass spectrometry," Int. Jou. Mass Spectr., 2006. [3] Hässig et al., "Time variability and heterogeneity in the coma of 67P/Churyumov-Gerasimenko", Science, 2015. [4] A'Hearn et al., "EPOXI at comet Hartley 2", Science, 2011.

Coma in fatal adult human malaria is not caused by cerebral oedema

PubMed Central

2011-01-01

Background The role of brain oedema in the pathophysiology of cerebral malaria is controversial. Coma associated with severe Plasmodium falciparum malaria is multifactorial, but associated with histological evidence of parasitized erythrocyte sequestration and resultant microvascular congestion in cerebral vessels. To determine whether these changes cause breakdown of the blood-brain barrier and resultant perivascular or parenchymal cerebral oedema, histology, immunohistochemistry and image analysis were used to define the prevalence of histological patterns of oedema and the expression of specific molecular pathways involved in water balance in the brain in adults with fatal falciparum malaria. Methods The brains of 20 adult Vietnamese patients who died of severe malaria were examined for evidence of disrupted vascular integrity. Immunohistochemistry and image analysis was performed on brainstem sections for activation of the vascular endothelial growth factor (VEGF) receptor 2 and expression of the aquaporin 4 (AQP4) water channel protein. Fibrinogen immunostaining was assessed as evidence of blood-brain barrier leakage and perivascular oedema formation. Correlations were performed with clinical, biochemical and neuropathological parameters of severe malaria infection. Results The presence of oedema, plasma protein leakage and evidence of VEGF signalling were heterogeneous in fatal falciparum malaria and did not correlate with pre-mortem coma. Differences in vascular integrity were observed between brain regions with the greatest prevalence of disruption in the brainstem, compared to the cortex or midbrain. There was a statistically non-significant trend towards higher AQP4 staining in the brainstem of cases that presented with coma (P = .02). Conclusions Histological evidence of cerebral oedema or immunohistochemical evidence of localised loss of vascular integrity did not correlate with the occurrence of pre-mortem coma in adults with fatal falciparum malaria. Enhanced expression of AQP4 water channels in the brainstem may, therefore, reflect a mix of both neuropathological or attempted neuroprotective responses to oedema formation. PMID:21923924

Contemporary Rates of Severe Hypoglycaemia in Youth with Type 1 Diabetes: Variability by Insulin Regimen

PubMed Central

Katz, M. L.; Volkening, L. K.; Anderson, B. J.; Laffel, L. M.

2013-01-01

Aims To determine incidence rates of severe hypoglycaemia and compare incidence rates by insulin regimen in a diverse sample of youth with type 1 diabetes from two sites. Methods In this observational study, 255 youth (51% female) aged 9–15 years receiving varied insulin regimens provided data prospectively for a median of 1.2 years. Reported episodes of severe hypoglycaemia, defined as episodes requiring help from another person for oral treatment or episodes resulting in seizure/coma, and current insulin regimens were collected systematically. Incidence rates were calculated and compared according to insulin regimen in bivariate and multivariate analyses. Results At first encounter, participants had a median age of 12.2 years (range 9.0–15.0), median diabetes duration of 4.4 years (range 1.0–13.0) and mean A1C of 67±12 mmol/mol (8.3±1.1%). The incidence rate was 37.6/100-patient-years for all severe hypoglycaemia and 9.6/100-patient-years for seizure/coma. The incidence rate for severe hypoglycaemia was 31.8/100-patient-years on continuous subcutaneous insulin infusion (CSII), 34.4/100-patient-years on basal-bolus injections (B-B) and 46.1/100-patient-years on NPH (NPH vs. CSII: p=.04). The incidence rate for seizure/coma was 4.5/100-patient-years on CSII, 11.1/100-patient-years on B-B, and 14.4/100-patient-years on NPH (NPH vs. CSII: p=.004). In the multivariate analysis, the rate of seizure/coma was significantly higher for those on NPH vs. CSII (rate ratio 2.9, p=.03). Conclusions Rates of severe hypoglycaemia in youth with type 1 diabetes remain high. CSII was associated with lower rates of all severe hypoglycaemia and seizure/coma in comparison to NPH. PMID:22417321

Coma in fatal adult human malaria is not caused by cerebral oedema.

PubMed

Medana, Isabelle M; Day, Nicholas P J; Sachanonta, Navakanit; Mai, Nguyen T H; Dondorp, Arjen M; Pongponratn, Emsri; Hien, Tran T; White, Nicholas J; Turner, Gareth D H

2011-09-17

The role of brain oedema in the pathophysiology of cerebral malaria is controversial. Coma associated with severe Plasmodium falciparum malaria is multifactorial, but associated with histological evidence of parasitized erythrocyte sequestration and resultant microvascular congestion in cerebral vessels. To determine whether these changes cause breakdown of the blood-brain barrier and resultant perivascular or parenchymal cerebral oedema, histology, immunohistochemistry and image analysis were used to define the prevalence of histological patterns of oedema and the expression of specific molecular pathways involved in water balance in the brain in adults with fatal falciparum malaria. The brains of 20 adult Vietnamese patients who died of severe malaria were examined for evidence of disrupted vascular integrity. Immunohistochemistry and image analysis was performed on brainstem sections for activation of the vascular endothelial growth factor (VEGF) receptor 2 and expression of the aquaporin 4 (AQP4) water channel protein. Fibrinogen immunostaining was assessed as evidence of blood-brain barrier leakage and perivascular oedema formation. Correlations were performed with clinical, biochemical and neuropathological parameters of severe malaria infection. The presence of oedema, plasma protein leakage and evidence of VEGF signalling were heterogeneous in fatal falciparum malaria and did not correlate with pre-mortem coma. Differences in vascular integrity were observed between brain regions with the greatest prevalence of disruption in the brainstem, compared to the cortex or midbrain. There was a statistically non-significant trend towards higher AQP4 staining in the brainstem of cases that presented with coma (P = .02). Histological evidence of cerebral oedema or immunohistochemical evidence of localised loss of vascular integrity did not correlate with the occurrence of pre-mortem coma in adults with fatal falciparum malaria. Enhanced expression of AQP4 water channels in the brainstem may, therefore, reflect a mix of both neuropathological or attempted neuroprotective responses to oedema formation.

The etiology and outcome of non-traumatic coma in critical care: a systematic review.

PubMed

Horsting, Marlene Wb B; Franken, Mira D; Meulenbelt, Jan; van Klei, Wilton A; de Lange, Dylan W

2015-04-29

Non-traumatic coma (NTC) is a serious condition requiring swift medical or surgical decision making upon arrival at the emergency department. Knowledge of the most frequent etiologies of NTC and associated mortality might improve the management of these patients. Here, we present the results of a systematic literature search on the etiologies and prognosis of NTC. Two reviewers independently performed a systematic literature search in the Pubmed, Embase and Cochrane databases with subsequent reference and citation checking. Inclusion criteria were retrospective or prospective observational studies on NTC, which reported on etiologies and prognostic information of patients admitted to the emergency department or intensive care unit. Eventually, 14 studies with enough data on NTC, were selected for this systematic literature review. The most common causes of NTC were stroke (6-54%), post-anoxic coma (3-42%), poisoning (<1-39%) and metabolic causes (1-29%). NTC was also often caused by infections, especially in African studies affecting 10-51% of patients. The NTC mortality rate ranged from 25 to 87% and the mortality rate continued to increase long after the event had occurred. Also, 5-25% of patients remained moderately-severely disabled or in permanent vegetative state. The mortality was highest for stroke (60-95%) and post-anoxic coma (54-89%) and lowest for poisoning (0-39%) and epilepsy (0-10%). NTC represents a challenge to the emergency and the critical care physicians with an important mortality and moderate-severe disability rate. Even though, included studies were very heterogeneous, the most common causes of NTC are stroke, post anoxic, poisoning and various metabolic etiologies. The best outcome is achieved for patients with poisoning and epilepsy, while the worst outcome was seen in patients with stroke and post-anoxic coma. Adequate knowledge of the most common causes of NTC and prioritizing the causes by mortality ensures a swift and adequate work-up in diagnosis of NTC and may improve outcome.

The Split Nucleus of Comet Wilson (C/1986 P1 = 1987 VII).

NASA Astrophysics Data System (ADS)

Meech, Karen J.; Knopp, Graham P.; Farnham, Tony L.; Green, Daniel

1995-07-01

We present CCD observations of Comet Wilson (C/1986 P1 = 1987 VII) from 26 nights during the time period 1986 October to 1991 February, which brackets perihelion, During the observing run of 1988 February, the comet was observed to have split into two fragments. Our broadband CCD photometry, along with photometry from the International Cometary Quarterly, shows a steady decline in brightness of Comet Wilson post-perihelion, with an outburst between heliocentric distances r = 2.8 and 3.3 AU during 1987 October and November. By r ≈ 7 AU, the fragment had faded with respect to the parent and was no longer centrally condensed. A brightness limit of mR ≈ 25, when the comet was at r = 12.65 AU, constrains the primary nucleus to have a maximum radius between 5 and 7 km, assuming an albedo of 0.04. The accuracy of direct orbital solutions for the parent body and fragment to determine the time of splitting was limited by the presence of significant nongravitational forces and the limited fragment orbital coverage. We used the relative position of the fragment with respect to the parent to calculate a time of splitting which was consistent with the time of the observed outburst. We discuss the possible causes of the splitting. The coma of Comet Wilson was observed to have a surface-brightness profile which fell off as p-1 (characteristic of a canonical steady-state coma under the influence of radiation pressure) for all of the data with the exception of the data taken during 1987 November when the gradient was p-1.3 . This steeper slope was probably caused by the injection of new material into the coma during the outburst. During 1986 October, there was a break in the surface-brightness profile slope which may be interpreted as the distance at which grains are swept into the tail. The profiles suggested grain velocities of a few x 10 2 to 10 m sec -1 for grains between 1 and a few hundred micrometers. Finson-Probstein dust modeling showed that ejection of grains began preperihelion at r gt; 6 AU, peaking near perihelion with a very rapid decline thereafter, with an outburst occurring roughly 170 days post-perihelion. We found no evidence for the existence of discrete features in the coma. Both the primary and fragment nuclei grew redder with time, with the fragment being redder than the parent, consistent with the picture of smaller grains leaving the field of view of the aperture more quickly than larger grains.

Chiron stellar occultation candidates: 1993-1996

NASA Technical Reports Server (NTRS)

Bus, S. J.; Wasserman, L. H.; Elliot, J. L.

1994-01-01

A photographic search was conducted for stars that may be occulted by the unusual solar system object (2060) Chiron during the period from fall 1993 through summer 1996. 44 candidates were identified to a limiting V magnitude of 16, and for which the minimum appulse separation with Chiron is predicted to be less than 2.5 arcsec. The successful observation of a stellar occultation by Chiron would give a direct measure of its diameter (currently estimated to be between 60 and 300 km), and would help considerably in constraining Chiron's surface properties and volatile makeup. If at the time of the occultation, Chiron exhibits a significant coma, there is also the potential for measuring the optical-depth profile of the dust in its inner coma.

Development of an objective tool for the diagnosis of myxedema coma.

PubMed

Chiong, Yien V; Bammerlin, Elaine; Mariash, Cary N

2015-09-01

Myxedema coma, a rare entity, with a reported 25%-65% mortality had no objective criteria for making the diagnosis when we began our study. We developed an objective screening tool for myxedema coma to more easily identify patients and examine the best treatment method in future prospective studies to reduce the mortality of this entity. We conducted a retrospective chart review to find all patients aged ≥18 years admitted with myxedema coma from January 1, 2005 through June 13, 2010 at Indiana University Health Methodist Hospital. On the basis of both our retrospective chart review and on literature accounts, we identified 6 criteria to diagnose myxedema coma. We identified 10 patients initially diagnosed with myxedema coma and established a control group consisting of 13 patients identified with altered mental status and increased thyroid-stimulating hormone (TSH) levels. The 6 variables we created for the screening tool were heart rate, temperature, Glasgow coma scale, TSH, free thyroxine, and precipitating factors. The screening tool has a sensitivity and specificity of about 80%. We ran a logistic regression model using the 10 study patients and 13 controls with the 6 variables. No variables alone significantly contributed to the model. However, the overall model was highly significant (P = 0.012), providing strong support for a scoring system that uses these variables simultaneously. This screening tool enables physicians to rapidly diagnose myxedema coma to expedite treatment. A more refined diagnostic tool may be used in future clinical studies designed to determine the optimal treatment. Copyright © 2015 Elsevier Inc. All rights reserved.

A comparative study on assessment procedures and metric properties of two scoring systems of the Coma Recovery Scale-Revised items: standard and modified scores.

PubMed

Sattin, Davide; Lovaglio, Piergiorgio; Brenna, Greta; Covelli, Venusia; Rossi Sebastiano, Davide; Duran, Dunja; Minati, Ludovico; Giovannetti, Ambra Mara; Rosazza, Cristina; Bersano, Anna; Nigri, Anna; Ferraro, Stefania; Leonardi, Matilde

2017-09-01

The study compared the metric characteristics (discriminant capacity and factorial structure) of two different methods for scoring the items of the Coma Recovery Scale-Revised and it analysed scale scores collected using the standard assessment procedure and a new proposed method. Cross sectional design/methodological study. Inpatient, neurological unit. A total of 153 patients with disorders of consciousness were consecutively enrolled between 2011 and 2013. All patients were assessed with the Coma Recovery Scale-Revised using standard (rater 1) and inverted (rater 2) procedures. Coma Recovery Scale-Revised score, number of cognitive and reflex behaviours and diagnosis. Regarding patient assessment, rater 1 using standard and rater 2 using inverted procedures obtained the same best scores for each subscale of the Coma Recovery Scale-Revised for all patients, so no clinical (and statistical) difference was found between the two procedures. In 11 patients (7.7%), rater 2 noted that some Coma Recovery Scale-Revised codified behavioural responses were not found during assessment, although higher response categories were present. A total of 51 (36%) patients presented the same Coma Recovery Scale-Revised scores of 7 or 8 using a standard score, whereas no overlap was found using the modified score. Unidimensionality was confirmed for both score systems. The Coma Recovery Scale Modified Score showed a higher discriminant capacity than the standard score and a monofactorial structure was also supported. The inverted assessment procedure could be a useful evaluation method for the assessment of patients with disorder of consciousness diagnosis.

Galactic Dark Matter Halos and Globular Cluster Populations. III. Extension to Extreme Environments

NASA Astrophysics Data System (ADS)

Harris, William E.; Blakeslee, John P.; Harris, Gretchen L. H.

2017-02-01

The total mass {M}{GCS} in the globular cluster (GC) system of a galaxy is empirically a near-constant fraction of the total mass {M}h\\equiv {M}{bary}+{M}{dark} of the galaxy across a range of 105 in galaxy mass. This trend is radically unlike the strongly nonlinear behavior of total stellar mass M ⋆ versus M h . We discuss extensions of this trend to two more extreme situations: (a) entire clusters of galaxies and (b) the ultra-diffuse galaxies (UDGs) recently discovered in Coma and elsewhere. Our calibration of the ratio {η }M={M}{GCS}/{M}h from normal galaxies, accounting for new revisions in the adopted mass-to-light ratio for GCs, now gives {η }M=2.9× {10}-5 as the mean absolute mass fraction. We find that the same ratio appears valid for galaxy clusters and UDGs. Estimates of {η }M in the four clusters we examine tend to be slightly higher than for individual galaxies, but more data and better constraints on the mean GC mass in such systems are needed to determine if this difference is significant. We use the constancy of {η }M to estimate total masses for several individual cases; for example, the total mass of the Milky Way is calculated to be {M}h=1.1× {10}12 {M}⊙ . Physical explanations for the uniformity of {η }M are still descriptive, but point to a picture in which massive dense star clusters in their formation stages were relatively immune to the feedback that more strongly influenced lower-density regions where most stars form.

Memory disorder related to coma duration after head injury.

PubMed Central

Vilkki, J; Poropudas, K; Servo, A

1988-01-01

The relationship of memory and intelligence test performances to coma duration was studied in 51 head injured patients who had not been operated on for intracranial haematoma. Memory defect was related to coma duration, and was not secondary to impaired perceptual or conceptual analysis of the material to be remembered. PMID:3236022

[Coma in France today].

PubMed

Do, Chung Hi

2015-01-01

Comas result from acute life-threatening neurological failure. To understand coma, it is firstly necessary to define it, to cite the aetiologies and their epidemiology and to describe the chronic disorders of consciousness. It is also important to address the challenges and principles of treatment during the acute phase. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

Between My Body and My "Dead Body": Narratives of Coma.

PubMed

Meoded Danon, Limor

2016-01-01

This article is based on narrative research that focuses on corporeal experience during coma and during the rehabilitation process. Seventeen participants from different areas of Israel who had been in various kinds of coma states reveal what the corporeal experience of coma is. The participants are divided into three types of narrative protagonists--"dead-alive," "rational," and "emissaries." Each of the participants redefined the boundaries of the body, especially in cases when they spoke of experiences they did not understand as corporeal, for example, out-of-body experiences, near-death experiences, or experiences of being between the earthly and unearthly. Their struggle to find suitable words to tell their coma stories emphasizes these boundaries between experiencing and telling, which crossed the normative discursive border of the medical establishment and illustrates the ambiguous nature of human existence. © The Author(s) 2015.

Myxedema coma: diagnosis and treatment.

PubMed

Wall, C R

2000-12-01

Myxedema coma, the extreme manifestation of hypothyroidism, is an uncommon but potentially lethal condition. Patients with hypothyroidism may exhibit a number of physiologic alterations to compensate for the lack of thyroid hormone. If these homeostatic mechanisms are overwhelmed by factors such as infection, the patient may decompensate into myxedema coma. Patients with hypothyroidism typically have a history of fatigue, weight gain, constipation and cold intolerance. Physicians should include hypothyroidism in the differential diagnosis of every patient with hyponatremia. Patients with suspected myxedema coma should be admitted to an intensive care unit for vigorous pulmonary and cardiovascular support. Most authorities recommend treatment with intravenous levothyroxine (T4) as opposed to intravenous liothyronine (T3). Hydrocortisone should be administered until coexisting adrenal insufficiency is ruled out. Family physicians are in an important position to prevent myxedema coma by maintaining a high level of suspicion for hypothyroidism.

Models for Cometary Comae Containing Negative Ions

NASA Technical Reports Server (NTRS)

Cordiner, M. A.; Charnley, S. B.

2012-01-01

The presence of negative ions (anions) in cometary comae is known from Giotto mass spectrometry of IP/Halley. The anions O(-), OH(-), C(-), CH(-) and CN(-) have been detected, as well as unidentified anions with masses 22-65 and 85-110 amu [I]. Organic molecular anions such as C4H(-) and C6H(-) are known to have a significant impact on the charge balance of interstellar clouds and circumstellar envelopes and have been shown to act as catalysts for the gas phase synthesis of larger hydrocarbon molecules in the ISM, but their importance in cometary comae has not yet been fully explored. We present details of our new models for the chemistry of cometary comae that include atomic and molecular anions. We calculate the impact of these anions on the charge balance and examine their importance for cometary coma chemistry.

Observations of Comet Levy (1990c) with the Hopkins Ultraviolet Telescope

NASA Technical Reports Server (NTRS)

Feldman, P. D.; Davidsen, A. F.; Blair, W. P.; Bowers, C. W.; Dixon, W. V.; Durrance, S. T.; Henry, R. C.; Ferguson, H. C.; Kimble, R. A.; Gull, Theodore R.

1991-01-01

Observations of Comet Levy (1990c) were made with the Hopkins Ultraviolet Telescope during the Astro-1 Space Shuttle mission on December 10, 1990. The spectrum, covering the wavelength range 415-1850 A at a spectral resolution of 3 A, shows the presence of carbon monoxide and atomic hydrogen, carbon, and sulfur in the coma. Aside from H I Lyman-beta, no cometary features are detected below 1200 A, although cometary O I and O II would be masked by the same emissions present in the day airglow spectrum. The 9.4 x 116 arcsecond aperture corresponds to 12,000 x 148,000 km at the comet. The derived production rate of CO relative to water is 0.11 + or - 0.02, compared with 0.04 + or - 0.01 derived from IUE observations (made in September 1990) which sample a much smaller region of the coma. This suggests the presence of an extended source of CO, as was found in comet Halley. Upper limits on Ne and Ar abundance are within one order of magnitude of solar abundances.

Water and dust production rates in comet P/Halley derived from ultraviolet and optical observations

NASA Technical Reports Server (NTRS)

Festou, Michel C.

1992-01-01

We evaluate whether the activity of comet P/Halley is due solely to the presence of discrete active areas. We preliminarily conclude that the dark areas of the nucleus contribute to the formation of the coma.

A Study of the Effects of Faint Dust Comae on the Spectra of Asteroids

NASA Astrophysics Data System (ADS)

Rondón, E.; Carvano, J.; Lorenz-Martins, S.

2017-09-01

The presence of dust comae on asteroids and centaurs is a phenomenon that became accepted in the last decades and which challenges the traditional definitions of asteroids and comets. A possible way of improving the chances of discovery of Active Asteroids is to use large multi-colour surveys or catalogs, like SDSS Moving Object Catalog. In this work we analyze the effects of faint dust comae on asteroid spectra and then use it to investigate the effects that a faint dust comae would have over the spectrum, magnitude, and radial profile of asteroids.

Balance of corneal horizontal coma by internal optics in eyes with intraocular artificial lenses: evidence of a passive mechanism.

PubMed

Marcos, Susana; Rosales, Patricia; Llorente, Lourdes; Barbero, Sergio; Jiménez-Alfaro, I

2008-01-01

It is well known that the aberrations of the cornea are partially compensated by the aberrations of the internal optics of the eye (primarily the crystalline lens) in young subjects. This effect has been found not only for the spherical aberration, but also for horizontal coma. It has been debated whether the compensation of horizontal coma is the result of passive mechanism [Artal, P., Benito, A., & Tabernero, J. (2006). The human eye is an example of robust optical design. Journal of Vision, 6 (1), 1-7] or through an active developmental feedback process [Kelly, J. E., Mihashi, T., & Howland, H. C. (2004). Compensation of corneal horizontal/vertical astigmatism, lateral coma, and spherical aberration by internal optics of the eye. Journal of Vision, 4 (4), 262-271]. In this study we investigate the active or passive nature of the horizontal coma compensation using eyes with artificial lenses, where no active developmental process can be present. We measured total and corneal aberrations, and lens tilt and decentration in a group of 38 eyes implanted with two types of intraocular lenses designed to compensate the corneal spherical aberration of the average population. We found that spherical aberration was compensated by 66%, and horizontal coma by 87% on average. The spherical aberration is not compensated at an individual level, but horizontal coma is compensated individually (coefficients of correlation corneal/internal aberration: -0.946, p<0.0001). The fact that corneal (but not total) horizontal coma is highly correlated with angle lamda (computed from the shift of the 1st Purkinje image from the pupil center, for foveal fixation) indicates that the compensation arises primarily from the geometrical configuration of the eye (which generates horizontal coma of opposite signs in the cornea and internal optics). The amount and direction of tilts and misalignments of the lens are comparable to those found in young eyes, and on average tend to compensate (rather than increase) horizontal coma. Computer simulations using customized model eyes and different designs of intraocular lenses show that, while not all designs produce a compensation of horizontal coma, a wide range of aspheric biconvex designs may produce comparable compensation to that found in young eyes with crystalline lenses, over a relatively large field of view. These findings suggest that the lens shape, gradient index or foveal location do not need to be fine-tuned to achieve a compensation of horizontal coma. Our results cannot exclude a fine-tuning for the orientation of the crystalline lens, since cataract surgery seems to preserve the position of the capsule.

Prospects for P-bearing molecules in cometary atmospheres

NASA Astrophysics Data System (ADS)

Boice, Daniel; de Almeida, Amaury

Phosphorus is a key element in all known forms of life and phosphorus-bearing compounds have been observed in space. Phosphorus is ubiquitous in meteorites, albeit in small quantities, with phosphates being found in stoney meteorites and phosphides have been identified in iron meteorites. It has been detected as part of the dust component in comet Halley but searches for P-bearing species in the gas phase in comets have been unsuccessful. Based of its moderate cosmic abundance (eighteenth most abundant element, [P]/[N] = 4 x 10-3 ) and the positive identification of P-bearing species in the interstellar medium (such as, PN, PC, HCP and PO), we would expect simple molecules, diatomics (like PH, PO, PC, PS), triatomics (like HCP and PH2 ), and possibly other polyatomics (like phosphine PH3 and diphosphine P2 H4 ), to exist in cometary ices, hence released into the gas phase upon ice sublimation. Our fluid dynamics model with chemistry of cometary comae (SUISEI) has been adapted to study this problem. SUISEI produces cometocentric abundances of the coma gas species; velocities of the bulk gas, light atomic and molecular hydrogen with escape, and electrons; gas and electron temperatures; column densities to facilitate comparison with observations; coma energy budget quantities; attenuation of the solar irradiance; and other quantities that can be related readily to observations. We present results from the first quantitative study of phosphorus-bearing molecules in comets to identify likely species containing phosphorus to aid in future searches for this important element in comets, possibly shedding light on issues of comet formation (time and place) and matters of the prebiotic to biotic evolution of life. Acknowledgements. This work was supported by the NSF Planetary Astronomy Program.

Development of a real-time wave field reconstruction TEM system (II): correction of coma aberration and 3-fold astigmatism, and real-time correction of 2-fold astigmatism.

PubMed

Tamura, Takahiro; Kimura, Yoshihide; Takai, Yoshizo

2018-02-01

In this study, a function for the correction of coma aberration, 3-fold astigmatism and real-time correction of 2-fold astigmatism was newly incorporated into a recently developed real-time wave field reconstruction TEM system. The aberration correction function was developed by modifying the image-processing software previously designed for auto focus tracking, as described in the first article of this series. Using the newly developed system, the coma aberration and 3-fold astigmatism were corrected using the aberration coefficients obtained experimentally before the processing was carried out. In this study, these aberration coefficients were estimated from an apparent 2-fold astigmatism induced under tilted-illumination conditions. In contrast, 2-fold astigmatism could be measured and corrected in real time from the reconstructed wave field. Here, the measurement precision for 2-fold astigmatism was found to be ±0.4 nm and ±2°. All of these aberration corrections, as well as auto focus tracking, were performed at a video frame rate of 1/30 s. Thus, the proposed novel system is promising for quantitative and reliable in situ observations, particularly in environmental TEM applications.

The relationship between pneumonia and Glasgow coma scale assessment on acute stroke patients

NASA Astrophysics Data System (ADS)

Ritarwan, K.; Batubara, C. A.; Dhanu, R.

2018-03-01

Pneumonia is one of the most frequent medical complications of a stroke. Despite the well-documented association of a stroke associated infections with increased mortality and worse long-term outcome, on the other hand, the limited data available on independent predictors of pneumonia in acute stroke patients in an emergency unit. To determine the independentrelationship between pneumonia and Glasgow Coma Scale assessment on acute stroke patients. The cohort retrospective study observed 55 acute stroke patients who stayed in intensive care unit Adam Malik General Hospital from January until August 2017. Pneumonia was more frequent in patients with Ischemic stroke (OR 5.40; 95% CI: 1.28 – 6.40, p=0.003), higher National Institute of Health Stroke Scale (NIHSS) (p=0.014) and lower Glasgow Coma Scale (p=0.0001). Analysis multivariate logistic regression identified NIHSS as an independent of predictors of pneumonia (95% CI : 1.047 – 1.326, p=0.001). Pneumonia was associated with severity and type of stroke and length of hospital stay. The severity of the deficits evaluated by the NIHSS was shown to be the only independent risk factor for pneumonia in acute stroke patients.

Multispectral study of CO production from C/1995 O1 (Hale-Bopp)

NASA Astrophysics Data System (ADS)

Harris, W. M.; Nordsieck, K. H.; Scherb, F.; Mierkiwicz, E. J.; Morgenthaler, J. P.; Oliversen, R. J.

1998-09-01

A series of unique observartions of CO and its daughter products that were obtained simultaneously as part of the University of Wisconsin/Goddard Space Flight Center Hale-Bopp campaign are presented. CO is the second most abundant volatile species in the coma of comets, one that actually dominates production at large heliocentric distances, however its photchemical evolution is poorly understood due to the lack of good emission line tracers in the visible. On 8 April, 1997, we obtained wide field simultaneous observations of CI (1657 Angstroms) intensity and polarization from a sounding rocket, OI (6300 Angstroms) emission using the Wisconsin Hα Mapper (WHaM) facility, and measurements using the McMath-Pierce Solar telescope of CI (9850 Angstroms) emission at different points in the inner coma. Combined, these data contain information on the radial distribution, source function, equilibrium structure, photochemical lifetime of CO, and the outflow speed of its C and O daughter products. Combined, these results suggest rapid dissociation of CO in the collisionally thick inner coma of Hale-Bopp, followed by a high velocity outflow of the daughter products. Both results suggest some discrepancies with expectations, and we discuss their implications.

In-situ observations of a bi-modal ion distribution in the outer coma of comet P/Halley

NASA Technical Reports Server (NTRS)

Thomsen, M. F.; Feldman, W. C.; Wilken, B.; Jockers, K.; Stuedemann, W.

1987-01-01

Observations obtained by the Johnstone Plasma Analyzer on the Giotto fly-by of comet Halley showed a fairly sudden decrease in the count rate of energetic (about 30 KeV) water-group ions inside about 500,000 km from the nucleus. This decrease was accompanied by the appearance of a new water-group ion population at slightly lower energies (less than 10 KeV). Close inspection reveals that this lower-energy peak was also present somewhat earlier in the postshock flow but only became prominent near the sudden transition just described. It is shown that the observed bimodal ion distribution is well explained in terms of the velocity history of the accreting solar wind flow in the outer coma. The decline in count rate of the energetic pick-up distribution is due to a relatively sudden slowing of the bulk flow there and not to a loss of particles. Hence, charge-exchange cooling of the flow is probably not important at these distances from the nucleus. The observations suggest that pitch-angle scattering is fairly efficient at least after the bow shock, but that energy diffusion is probably not very efficient.

High resolution integral-field spectroscopy of gas and ion distributions in the coma of Comet C/2012 S1 ISON

NASA Astrophysics Data System (ADS)

Schmidt, Carl

2016-02-01

Neutral and ion species in cometary comae exhibit significant differences in their spatial distributions. These distributions reflect the combined effects of sublimation, ion pickup, collisions, solar radiation pressure, photolysis scale lengths of any parent molecules, and photolysis of the species of interest. An image-slicer spectrograph (R ∼ 20,000) is used here to measure C2, NH2, Na, and H2O+ emission lines in Comet C/2012 S1 ISON's coma within a narrow spectral window spanning 5868-5926 Å. These species are mapped over a 1.6 × 2.7 arcmin field made up of 240 individual spectra. While prior cometary observations have found that peak column densities of these species appear either sunward or anti-sunward, ISON's coma was elongated several thousand kilometers along an axis perpendicular to its motion and the sunward vector. The peak brightness of each species was located within 5000 km of the dusty continuum concentration. ISON's water ion tail appeared distinctly broader than the neutral Na tail and no evidence is seen for an extended source of Na by dissociative recombination of a molecular ion. The Na D2/D1 ratio in the head is 1.49 ± 0.06 despite being optically thin, increasing to 1.93 ± 0.07 in the tail. The dust distribution falls off less steeply than the canonical inverse with distance from the nucleus and C2 and NH2 scale lengths indicate an extended source, possibly due to nucleus fragmentation.

Neural signature of coma revealed by posteromedial cortex connection density analysis.

PubMed

Malagurski, Briguita; Péran, Patrice; Sarton, Benjamine; Riu, Beatrice; Gonzalez, Leslie; Vardon-Bounes, Fanny; Seguin, Thierry; Geeraerts, Thomas; Fourcade, Olivier; de Pasquale, Francesco; Silva, Stein

2017-01-01

Posteromedial cortex (PMC) is a highly segregated and dynamic core, which appears to play a critical role in internally/externally directed cognitive processes, including conscious awareness. Nevertheless, neuroimaging studies on acquired disorders of consciousness, have traditionally explored PMC as a homogenous and indivisible structure. We suggest that a fine-grained description of intrinsic PMC topology during coma, could expand our understanding about how this cortical hub contributes to consciousness generation and maintain, and could permit the identification of specific markers related to brain injury mechanism and useful for neurological prognostication. To explore this, we used a recently developed voxel-based unbiased approach, named functional connectivity density (CD). We compared 27 comatose patients (15 traumatic and 12 anoxic), to 14 age-matched healthy controls. The patients' outcome was assessed 3 months later using Coma Recovery Scale-Revised (CRS-R). A complex pattern of decreased and increased connections was observed, suggesting a network imbalance between internal/external processing systems, within PMC during coma. The number of PMC voxels with hypo-CD positive correlation showed a significant negative association with the CRS-R score, notwithstanding aetiology. Traumatic injury specifically appeared to be associated with a greater prevalence of hyper-connected (negative correlation) voxels, which was inversely associated with patient neurological outcome. A logistic regression model using the number of hypo-CD positive and hyper-CD negative correlations, accurately permitted patient's outcome prediction (AUC = 0.906, 95%IC = 0.795-1). These points might reflect adaptive plasticity mechanism and pave the way for innovative prognosis and therapeutics methods.

Marked EEG worsening following Levetiracetam overdose: How a pharmacological issue can confound coma prognosis.

PubMed

Bouchier, Baptiste; Demarquay, Geneviève; Guérin, Claude; André-Obadia, Nathalie; Gobert, Florent

2017-01-01

Levetiracetam is an anti-epileptic drug commonly used in intensive care when seizure is suspected as a possible cause of coma. We propose to question the cofounding effect of Levetiracetam during the prognostication process in a case of anoxic coma. We report the story of a young woman presenting a comatose state following a hypoxic cardiac arrest. After a first EEG presenting an intermediate EEG pattern, a seizure suspicion led to prescribe Levetiracetam. The EEG showed then the appearance of burst suppression, which was compatible with a very severe pattern of post-anoxic coma. This aggravation was in fact related to an overdose of Levetiracetam (the only medication introduced recently) and was reversible after Levetiracetam cessation. The increased plasmatic dosages of Levetiracetam confirming this overdose could have been favoured by a moderate reduction of renal clearance, previously underestimated because of a low body-weight. This EEG dynamic was unexpected under Levetiracetam and could sign a functional instability after anoxia. Burst suppression is classically observed with high doses of anaesthetics, but is not expected after a minor anti-epileptic drug. This report proposes that Levetiracetam tolerance might not be straightforward after brain lesions and engages us to avoid confounding factors during the awakening prognostication, which is mainly based on the severity of the EEG. Hence, prognosis should not be decided on an isolated parameter, especially if the dynamic is atypical after a new prescription, even for well-known drugs. For any suspicion, the drug's dosage and replacement should be managed before any premature care's withdrawal. Copyright © 2016 Elsevier B.V. All rights reserved.

Branched chain amino acids supplemented with L-acetylcarnitine versus BCAA treatment in hepatic coma: a randomized and controlled double blind study.

PubMed

Malaguarnera, Mariano; Risino, Corrado; Cammalleri, Lisa; Malaguarnera, Lucia; Astuto, Marinella; Vecchio, Ignazio; Rampello, Liborio

2009-07-01

Our earlier study has demonstrated that the administration of L-acetylcarnitine (LAC) improves neurological symptoms and serum parameters in hepatic coma. The aim of this work has been to evaluate the efficacy of the LAC and branched chain amino acids (BCAA) versus BCAA, administered in intravenous infusion, in patients with cirrhotic hepatic coma. Forty-eight highly selected patients were enrolled in the study and, after randomization, received blindly LAC+BCAA (n=24) versus BCAA (n=24). The two groups were similar in age, sex, pathogenesis of cirrhosis, and severity of liver disease. The comparison between values before and after LAC planned treatment showed statistical significant differences in neurological findings, evaluated by the Glasgow Scale, ammonia serum levels, blood urea nitrogen, and EEG. After 60 min of the study period, the LAC+BCAA treated patients compared with BCCA treated showed a significant decrease of ammonia serum levels: 41.20 versus 10.40 mumol P<0.05. After 1 day of the study period, the LAC+BCAA treated patients compared with BCCA treated patients showed a significant increase of Glasgow's score: 3.60 versus 1.50 score P<0.05; a significant decrease of ammonia serum levels: 63.30 versus 27.00 mumol P<0.01; a significant improvement of EEG cps/s: 2.70 versus 0.6 P<0.001. No side-effects were observed in our study series. Our study demonstrated that the administration of BCAA supplemented with LAC might improve neurological symptoms and serum ammonium levels in selected cirrhotic patients with hepatic coma.

Cometary science. Time variability and heterogeneity in the coma of 67P/Churyumov-Gerasimenko.

PubMed

Hässig, M; Altwegg, K; Balsiger, H; Bar-Nun, A; Berthelier, J J; Bieler, A; Bochsler, P; Briois, C; Calmonte, U; Combi, M; De Keyser, J; Eberhardt, P; Fiethe, B; Fuselier, S A; Galand, M; Gasc, S; Gombosi, T I; Hansen, K C; Jäckel, A; Keller, H U; Kopp, E; Korth, A; Kührt, E; Le Roy, L; Mall, U; Marty, B; Mousis, O; Neefs, E; Owen, T; Rème, H; Rubin, M; Sémon, T; Tornow, C; Tzou, C-Y; Waite, J H; Wurz, P

2015-01-23

Comets contain the best-preserved material from the beginning of our planetary system. Their nuclei and comae composition reveal clues about physical and chemical conditions during the early solar system when comets formed. ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) onboard the Rosetta spacecraft has measured the coma composition of comet 67P/Churyumov-Gerasimenko with well-sampled time resolution per rotation. Measurements were made over many comet rotation periods and a wide range of latitudes. These measurements show large fluctuations in composition in a heterogeneous coma that has diurnal and possibly seasonal variations in the major outgassing species: water, carbon monoxide, and carbon dioxide. These results indicate a complex coma-nucleus relationship where seasonal variations may be driven by temperature differences just below the comet surface. Copyright © 2015, American Association for the Advancement of Science.

A Case of Myxedema Coma Presenting as a Brain Stem Infarct in a 74-Year-Old Korean Woman

PubMed Central

Ahn, Ji Yun; Kwon, Hyuk-Sool; Ahn, Hee Chol

2010-01-01

Myxedema coma is the extreme form of untreated hypothyroidism. In reality, few patients present comatose with severe myxedema. We describe a patient with myxedema coma which was initially misdiagnosed as a brain stem infarct. She presented to the hospital with alteration of the mental status, generalized edema, hypothermia, hypoventilation, and hypotension. Initially her brain stem reflexes were absent. After respiratory and circulatory support, her neurologic status was not improved soon. The diagnosis of myxedema coma was often missed or delayed due to various clinical findings and concomitant medical condition and precipitating factors. It is more difficult to diagnose when a patient has no medical history of hypothyroidism. A high index of clinical suspicion can make a timely diagnosis and initiate appropriate treatment. We report this case to alert clinicians considering diagnosis of myxedema coma in patients with severe decompensated metabolic state including mental change. PMID:20808690

Severe congestive heart failure patient on amiodarone presenting with myxedemic coma: a case report.

PubMed

Shaheen, Mazen

2009-01-01

This is a case report of myxedema coma secondary to amiodarone-induced hypothyroidism in a patient with severe congestive heart failure (CHF). To our knowledge and after reviewing the literature there is one case report of myxedema coma during long term amiodarone therapy. Myxedema coma is a life threatening condition that carries a mortality reaching as high as 20% with treatment. The condition is treated with intravenous thyroxine (T4) or intravenous tri-iodo-thyronine (T3). Patients with CHF on amiodarone may suffer serious morbidity and mortality from hypothyroidism, and thus may deserve closer follow up for thyroid stimulating hormone (TSH) levels. This case report carries an important clinical application given the frequent usage of amiodarone among CHF patients. The myriad clinical presentation of myxedema coma and its serious morbidity and mortality stresses the need to suspect this clinical syndrome among CHF patients presenting with hypotension, weakness or other unexplained symptoms.

A case of myxedema coma presenting as a brain stem infarct in a 74-year-old Korean woman.

PubMed

Ahn, Ji Yun; Kwon, Hyuk-Sool; Ahn, Hee Chol; Sohn, You Dong

2010-09-01

Myxedema coma is the extreme form of untreated hypothyroidism. In reality, few patients present comatose with severe myxedema. We describe a patient with myxedema coma which was initially misdiagnosed as a brain stem infarct. She presented to the hospital with alteration of the mental status, generalized edema, hypothermia, hypoventilation, and hypotension. Initially her brain stem reflexes were absent. After respiratory and circulatory support, her neurologic status was not improved soon. The diagnosis of myxedema coma was often missed or delayed due to various clinical findings and concomitant medical condition and precipitating factors. It is more difficult to diagnose when a patient has no medical history of hypothyroidism. A high index of clinical suspicion can make a timely diagnosis and initiate appropriate treatment. We report this case to alert clinicians considering diagnosis of myxedema coma in patients with severe decompensated metabolic state including mental change.

[Prognostic value of EEG in acute posttraumatic coma (author's transl)].

PubMed

Walser, H; Friedli, W; Glinz, W

1981-12-01

To evaluate the prognostic power of a single EEG-record, the recordings of 50 patients with posttraumatic coma performed within 48 hours after the injury were compared with the outcome after 6 months. A 5-point scale comprising 2 EEG-patterns being notorious for their dismal prognostic significance (suppression bursts, alpha-coma) and changes of vigilance were used as a mean of visual assessment of the recordings. In 24 out of the 28 patients with a bad outcome, the EEG had shown the patterns of category I, II and III (suppression bursts, alpha coma, no changes of vigilance). Of the 22 patients with a good outcome, the EEG had been classified as IV or V (clearly discernible changes of vigilance, sleep patterns). Further findings of particular dismal prognostic significance were focal epileptic discharges, as 9 out of the 11 patients with this EEG pattern had not survived the posttraumatic coma for more than 6 months.

The radial and azimuthal properties of volatiles and dust in the inner coma of Comet 45P/Honda-Mrkos-Pajdušáková

NASA Astrophysics Data System (ADS)

Harris, Walter M.; Ryan, Erin L.; Springmann, Alessondra; Mueller, Beatrice E. A.; Samarasinha, Nalin H.; Kikwaya Elou, Jean-Baptiste; Howell, Ellen S.; Lejoly, Cassandra; Bodnarik, Julia; Fitzpatrick, Ryleigh; Maciel, Ricardo; Mitchell, Adriana; Watson, Zachary Tyler

2017-10-01

In February 2017 comet 45P/Honda-Mrkos-Pajdušáková (HMP) passed by the Earth at a perigee distance of 0.08 AU. Such encounters provide an important opportunity for study of the inner coma region where gas and dust production occur. We report here on wide-field (30 x 30 arcminute), high-spatial resolution (35 km/pixel) observations of HMP obtained with the 90Prime One imager on the 2.3m Bok telescope at Kitt Peak. The observations were performed on February 16 and 17, when the comet was 0.1 AU from Earth, using a combination of a wide-band Gunn r’ filter and a subset of the HB filter library (OH, CN, C2, Blue Continuum). In this presentation we will discuss the distribution and color of the dust, the relative production rates of volatiles, and the implied parent-daughter photochemical evolution from radial expansion modeling.

Phenytoin intoxication with no symptoms correlated with serum drug level: a case study.

PubMed

Avcil, Mucahit; Duman, Ali; Turkdogan, Kenan Ahmet; Kapci, Mucahit; Akoz, Ayhan; Canakci, Selcuk Eren; Ozluer, Yunus Emre

2015-01-01

In high-dose intake of phenytoin, which is used frequently to treat epilepsy, nystagmus, diplopia, nausea-vomiting, lethargy, confusion, seizure, and coma can be observed. In recent studies on phenytoin intoxication, in which seizure and coma were observed in drug levels greater than 50 ug/mL. The serum phenytoin level of a patient, who consumed approximately 100 pcs of 100 mg phenytoin tablets in an effort to commit suicide, and who had no pathological finding in her neurologic examination, was 124 ug/mL. High drug level and the absence of toxic effect (or the absence of toxic effect correlated with the drug level) indicates that cytochrome P450 is functioning, but there can be a mutation in the MDR1 gene. In our case study, we report on phenytoin intoxication in a patient having a high level of phenytoin but no symptoms correlated with serum drug level, as supported by the findings in the literature.

Analysis of hydrogen Lyman-alpha observations of the coma of Comet P/Halley near the perihelion

NASA Technical Reports Server (NTRS)

Smyth, William H.; Marconi, M. L.; Combi, Michael R.

1995-01-01

The pioneer Venus Orbiter Ultraviolet Spectrometer measurements of the Lyman-alpha intensity of atomic hydrogen excited by solar resonance scattering in the coma of Comet P/Halley acquired from December 28, 1985, to January 6, 1986, and from January 31, 1986, to March 6, 1986, are simulated with the Monte Carlo Particle Trajectory Model corrected for optical depth effects. Spatially detailed comparisons between data and model show excellent agreement and are used to infer that the highest cometary activity may not be at perihelion, but about 2 1/2 weeks before. An improved set of H2O production rates is presented for the period of time that the spectrometer was observing and is found to be consistent with the rates from other types of measurements. The apparent discrepancy between Stewart (1987) in early March and International Ultraviolet Explorer OH derived rates is resolved. The problem with the conversion of 18-cm OH radio brightness to H2O production rates is also discussed.