Browsing by Subject "KINEMATICS"

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  • de Blok, W. J. G.; Walter, Fabian; Ferguson, Annette M. N.; Bernard, Edouard J.; van der Hulst, J. M.; Neeleman, Marcel; Leroy, Adam K.; Ott, Jürgen; Zschaechner, Laura K.; Zwaan, Martin A.; Yun, Min S.; Langston, Glen; Keating, Katie M. (2018)
    We present a 3 degrees x 3 degrees, 105-pointing, high-resolution neutral hydrogen (H I) mosaic of the M81 galaxy triplet, (including the main galaxies M81, M82, and NGC 3077, as well as dwarf galaxy NGC 2976) obtained with the Very Large Array C and D arrays. This H I synthesis mosaic uniformly covers the entire area and velocity range of the triplet. The observations have a resolution of similar to 20 '' or similar to 420 pc. The data reveal many small-scale anomalous velocity features highlighting the complexity of the interacting M81 triplet. We compare our data with Green Bank Telescope observations of the same area. This comparison provides evidence for the presence of a substantial reservoir of low-column density gas in the northern part of the triplet, probably associated with M82. Such a reservoir is not found in the southern part. We report a number of newly discovered kpc-sized low-mass H I clouds with H I masses of a few times 10(6) M-circle dot. A detailed analysis of their velocity widths show that their dynamical masses are much larger than their baryonic masses, which could indicate the presence of dark matter if the clouds are rotationally supported. However, due to their spatial and kinematical association with H I tidal features, it is more likely that the velocity widths indicate tidal effects or streaming motions. We do not find any clouds that are not associated with tidal features down to an H I mass limit of a few times 10(4) M-circle dot. We compare the H I column densities with resolved stellar density maps and find a star formation threshold around 3-6 x 10(20) cm(-2). We investigate the widths of the H I velocity profiles in the triplet and find that extreme velocity dispersions can be explained by a superposition of multiple components along the line of sight near M81 as well as winds or outflows around M82. The velocity dispersions found are high enough that these processes could explain the linewidths of damped-Ly alpha absorbers observed at high redshift.
  • Tatematsu, Ken'ichi; Liu, Tie; Kim, Gwanjeong; Yi, Hee-Weon; Lee, Jeong-Eun; Hirano, Naomi; Liu, Sheng-Yuan; Ohashi, Satoshi; Sanhueza, Patricio; Di Francesco, James; Evans, Neal J.; Fuller, Gary A.; Kandori, Ryo; Choi, Minho; Kang, Miju; Feng, Siyi; Hirota, Tomoya; Sakai, Takeshi; Lu, Xing; Lu'o'ng, Quang Nguyen; Thompson, Mark A.; Wu, Yuefang; Li, Di; Kim, Kee-Tae; Wang, Ke; Ristorcelli, Isabelle; Juvela, Mika; Toth, L. Viktor (2020)
    We mapped two molecular cloud cores in the Orion A cloud with the 7 m Array of the Atacama Compact Array (ACA) of the Atacama Large Millimeter/submillimeterArray (ALMA) and with the Nobeyama 45 m radio telescope. These cores have bright N2D+ emission in single-pointing observations with the Nobeyama 45 m radio telescope, have a relatively high deuterium fraction, and are thought to be close to the onset of star formation. One is a star-forming core, and the other is starless. These cores are located along filaments observed in N2H+ and show narrow line widths of 0.41 km s(-1) and 0.45 km s(-1) in N2D+, respectively, with the Nobeyama 45 m telescope. Both cores were detected with the ALMA ACA 7 m Array in the continuum and molecular lines at Band 6. The starless core G211 shows a clumpy structure with several sub-cores, which in turn show chemical differences. Also, the sub-cores in G211 have internal motions that are almost purely thermal. The starless sub-core G211D, in particular, shows a hint of the inverse P Cygni profile, suggesting infall motion. The star-forming core G210 shows an interesting spatial feature of two N2D+ peaks of similar intensity and radial velocity located symmetrically with respect to the single dust continuum peak. One interpretation is that the two N2D+ peaks represent an edge-on pseudo-disk. The CO outflow lobes, however, are not directed perpendicular to the line connecting both N2D+ peaks.
  • Türk, Helen; Lippus, Pärtel; Simko, Juraj (2017)
    The three-way quantity system is a well-known phonological feature of Estonian. In a number of studies it has been shown that quantity is realized in a disyllabic foot by the stressed-to-unstressed syllable rhyme duration ratio and also by pitch movement as the secondary cue. The stressed syllable rhyme duration is achieved by combining the length of the vowel and the coda consonant, which enables minimal septets of CVCV-sequences based on segmental duration. In this study we analyze articulatory (EMA) recordings from four native Estonian speakers producing all possible quantity combinations of intervocalic bilabial stops in two vocalic contexts (/alpha-i/ vs. /i-alpha/). The analysis shows that kinematic characteristics (gesture duration, spatial extent, and peak velocity) are primarily affected by quantity on the segmental level: Phonologically longer segments are produced by longer and larger lip closing gestures and, in reverse, shorter and smaller lip opening movements. Tongue transition gesture is consistently lengthened and slowed down by increasing consonant quantity. In general, both kinematic characteristics and intergestural coordination are influenced by non-linear interactions between segmental quantity levels as well as vocalic context.
  • Kosonen, Jukka; Kulmala, Juha-Pekka; Mueller, Erich; Avela, Janne (2017)
    Anti-pronation orthoses, like medially posted insoles (MPI), have traditionally been used to treat various of lower limb problems. Yet, we know surprisingly little about their effects on overall foot motion and lower limb mechanics across walking and running, which represent highly different loading conditions. To address this issue, multi-segment foot and lower limb mechanics was examined among 11 over-pronating men with normal (NORM) and MPI insoles during walking (self-selected speed 1.70 +/- 0.19 m/s vs 1.72 +/- 0.20 m/s, respectively) and running (4.04 +/- 0.17 m/s vs 4.10 +/- 0.13 m/s, respectively). The kinematic results showed that MPI reduced the peak forefoot eversion movement in respect to both hindfoot and tibia across walking and running when compared to NORM (p <0.05-0.01). No differences were found in hindfoot eversion between conditions. The kinetic results showed no insole effects in walking, but during running MPI shifted center of pressure medially under the foot (p <0.01) leading to an increase in frontal plane moments at the hip (p <0.05) and knee (p <0.05) joints and a reduction at the ankle joint (p <0.05). These findings indicate that MPI primarily controlled the forefoot motion across walking and running. While kinetic response to MPI was more pronounced in running than walking, kinematic effects were essentially similar across both modes. This suggests that despite higher loads placed upon lower limb during running, there is no need to have a stiffer insoles to achieve similar reduction in the forefoot motion than in walking. (C) 2017 Elsevier Ltd. All rights reserved.
  • Rollett, T.; Moestl, C.; Isavnin, A.; Davies, J. A.; Kubicka, M.; Amerstorfer, U. V.; Harrison, R. A. (2016)
    In this study, we present a new method for forecasting arrival times and speeds of coronal mass ejections (CMEs) at any location in the inner heliosphere. This new approach enables the adoption of a highly flexible geometrical shape for the CME front with an adjustable CME angular width and an adjustable radius of curvature of its leading edge, i.e., the assumed geometry is elliptical. Using, as input, Solar TErrestrial RElations Observatory (STEREO) heliospheric imager (HI) observations, a new elliptic conversion (ElCon) method is introduced and combined with the use of drag-based model (DBM) fitting to quantify the deceleration or acceleration experienced by CMEs during propagation. The result is then used as input for the Ellipse Evolution Model (ElEvo). Together, ElCon, DBM fitting, and ElEvo form the novel ElEvoHI forecasting utility. To demonstrate the applicability of ElEvoHI, we forecast the arrival times and speeds of 21 CMEs remotely observed from STEREO/HI and compare them to in situ arrival times and speeds at 1 AU. Compared to the commonly used STEREO/HI fitting techniques (Fixed-phi, Harmonic Mean, and Self-similar Expansion fitting), ElEvoHI improves the arrival time forecast by about 2 to +/- 6.5 hr and the arrival speed forecast by approximate to 250 to +/- 53 km s(-1), depending on the ellipse aspect ratio assumed. In particular, the remarkable improvement of the arrival speed prediction is potentially beneficial for predicting geomagnetic storm strength at Earth.
  • Leroy, Adam K.; Bolatto, Alberto D.; Ostriker, Eve C.; Walter, Fabian; Gorski, Mark; Ginsburg, Adam; Krieger, Nico; Levy, Rebecca C.; Meier, David S.; Mills, Elisabeth; Ott, Juergen; Rosolowsky, Erik; Thompson, Todd A.; Veilleux, Sylvain; Zschaechner, Laura K. (2018)
    NGC 253 hosts the nearest nuclear starburst. Previous observations show a region rich in molecular gas, with dense clouds associated with recent star formation. We used the Atacama Large Submillimeter/Millimeter Array (ALMA) to image the 350 GHz dust continuum and molecular line emission from this region at 2 pc resolution. Our observations reveal similar to 14 bright, compact (similar to 2-3 pc FWHM) knots of dust emission. Most of these sources are likely to be forming super star clusters (SSCs) based on their inferred dynamical and gas masses, association with 36 GHz radio continuum emission, and coincidence with line emission tracing dense, excited gas. One source coincides with a known SSC, but the rest remain invisible in Hubble near-infrared (IR) imaging. Our observations imply that gas still constitutes a large fraction of the overall mass in these sources. Their high brightness temperature at 350 GHz also implies a large optical depth near the peak of the IR spectral energy distribution. As a result, these sources may have large IR photospheres, and the IR radiation force likely exceeds L/c. Still, their moderate observed velocity dispersions suggest that feedback from radiation, winds, and supernovae are not yet disrupting most sources. This mode of star formation appears to produce a large fraction of stars in the burst. We argue for a scenario in which this phase lasts similar to 1 Myr, after which the clusters shed their natal cocoons but continue to produce ionizing photons. The strong feedback that drives the observed cold gas and X-ray outflows likely occurs after the clusters emerge from this early phase.
  • Gaia Collaboration; Luri, X.; Muinonen, K.; Fedorets, G.; Granvik, M.; Penttila, A.; Siltala, L. (2021)
    Context. This work is part of the Gaia Data Processing and Analysis Consortium papers published with the Gaia Early Data Release 3 (EDR3). It is one of the demonstration papers aiming to highlight the improvements and quality of the newly published data by applying them to a scientific case. Aims. We use the Gaia EDR3 data to study the structure and kinematics of the Magellanic Clouds. The large distance to the Clouds is a challenge for the Gaia astrometry. The Clouds lie at the very limits of the usability of the Gaia data, which makes the Clouds an excellent case study for evaluating the quality and properties of the Gaia data. Methods. The basis of our work are two samples selected to provide a representation as clean as possible of the stars of the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC). The selection used criteria based on position, parallax, and proper motions to remove foreground contamination from the Milky Way, and allowed the separation of the stars of both Clouds. From these two samples we defined a series of subsamples based on cuts in the colour-magnitude diagram; these subsamples were used to select stars in a common evolutionary phase and can also be used as approximate proxies of a selection by age. Results. We compared the Gaia Data Release 2 and Gaia EDR3 performances in the study of the Magellanic Clouds and show the clear improvements in precision and accuracy in the new release. We also show that the systematics still present in the data make the determination of the 3D geometry of the LMC a difficult endeavour; this is at the very limit of the usefulness of the Gaia EDR3 astrometry, but it may become feasible with the use of additional external data. We derive radial and tangential velocity maps and global profiles for the LMC for the several subsamples we defined. To our knowledge, this is the first time that the two planar components of the ordered and random motions are derived for multiple stellar evolutionary phases in a galactic disc outside the Milky Way, showing the differences between younger and older phases. We also analyse the spatial structure and motions in the central region, the bar, and the disc, providing new insightsinto features and kinematics. Finally, we show that the Gaia EDR3 data allows clearly resolving the Magellanic Bridge, and we trace the density and velocity flow of the stars from the SMC towards the LMC not only globally, but also separately for young and evolved populations. This allows us to confirm an evolved population in the Bridge that is slightly shift from the younger population. Additionally, we were able to study the outskirts of both Magellanic Clouds, in which we detected some well-known features and indications of new ones.
  • Rawlings, Alexander; Foster, Caroline; van de Sande, Jesse; Taranu, Dan S.; Croom, Scott M.; Bland-Hawthorn, Joss; Brough, Sarah; Bryant, Julia J.; Colless, Matthew; Lagos, Claudia del P.; Konstantopoulos, Iraklis S.; Lawrence, Jon S.; Lopez-Sanchez, Angel R.; Lorente, Nuria P. F.; Medling, Anne M.; Oh, Sree; Owers, Matt S.; Richards, Samuel N.; Scott, Nicholas; Sweet, Sarah M.; Yi, Sukyoung K. (2020)
    We study the behaviour of the spin-ellipticity radial tracks for 507 galaxies from the Sydney AAO Multiobject Integral Field (SAMI) Galaxy Survey with stellar kinematics out to >= 1.5R(e). We advocate for a morpho-dynamical classification of galaxies, relying on spatially resolved photometric and kinematic data. We find the use of spin-ellipticity radial tracks is valuable in identifying substructures within a galaxy, including embedded and counter-rotating discs, that are easily missed in unilateral studies of the photometry alone. Conversely, bars are rarely apparent in the stellar kinematics but are readily identified on images. Consequently, we distinguish the spin-ellipticity radial tracks of seven morpho-dynamical types: elliptical, lenticular, early spiral, late spiral, barred spiral, embedded disc, and 2 sigma galaxies. The importance of probing beyond the inner radii of galaxies is highlighted by the characteristics of galactic features in the spin-ellipticity radial tracks present at larger radii. The density of information presented through spin-ellipticity radial tracks emphasizes a clear advantage to representing galaxies as a track, rather than a single point, in spin-ellipticity parameter space.