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0000-0001-9089-6151
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Publisher: EDP Sciences
Date: 10-2010
Publisher: SPIE
Date: 12-07-2008
DOI: 10.1117/12.787398
Publisher: EDP Sciences
Date: 09-2010
Publisher: American Astronomical Society
Date: 12-1985
DOI: 10.1086/163682
Publisher: American Astronomical Society
Date: 08-1990
DOI: 10.1086/115523
Publisher: American Astronomical Society
Date: 09-1991
DOI: 10.1086/115922
Publisher: EDP Sciences
Date: 04-2022
DOI: 10.1051/0004-6361/202243307
Abstract: Dwarf galaxies are affected by all the evolutionary processes normally at work in galaxies of any mass. As fainter and less massive galaxies, however, dwarf galaxies are particularly susceptible to environmental mechanisms that can more easily perturb these systems. Importantly, the presence of nearby large galaxies is expected to have a profound effect on dwarf galaxies. Gravitational (especially tidally induced) effects from the large galaxy can cause mass to be lost from the dwarf, and the passage of the dwarf through the gaseous medium surrounding the large galaxy can additionally cause the dwarf to lose its own gas through a process called ram-pressure stripping. Such effects are considered to be the main sources of difference between “satellite” and “field” dwarf galaxy populations. Here, we report on new observations of the gaseous content of Wolf–Lundmark–Melotte (WLM), an archetype of isolated, gas-rich field dwarf galaxies in the Local Universe, which presents a much more complex situation. Previous studies of its gaseous disk suggest it has perturbed kinematics here, we identify four trailing, extended gas clouds lying in the direction opposite to WLM’s spatial motion, as well as a spatial offset between the WLM gas and stars. Overall, the morphology and kinematics of this gas show that WLM is undergoing ram-pressure stripping, despite being 930 and 830 kpc from the Milky Way and M 31, respectively. This finding indicates the presence of an intergalactic, gaseous reservoir far from large galaxies whose evolutionary role in galaxies, both large and small, may not be fully appreciated.
Publisher: American Astronomical Society
Date: 2006
DOI: 10.1086/508859
Publisher: American Astronomical Society
Date: 03-2002
DOI: 10.1086/338899
Publisher: Oxford University Press (OUP)
Date: 31-12-2014
Publisher: IOP Publishing
Date: 09-2002
DOI: 10.1086/342355
Publisher: SPIE
Date: 12-07-2008
DOI: 10.1117/12.788929
Publisher: SPIE
Date: 14-06-2006
DOI: 10.1117/12.669433
Publisher: American Astronomical Society
Date: 06-1995
DOI: 10.1086/175824
Publisher: Oxford University Press (OUP)
Date: 25-10-2011
Publisher: Cambridge University Press (CUP)
Date: 08-2012
DOI: 10.1017/S1743921314012009
Abstract: It is very difficult to start from scratch a new Astrophysics program in a country with very little or no researchers in the field. In 2007, we began to set-up an Astrophysics program by TWINNING the Université de Ouagadougou with the Université de Montréal in Canada, the Université de Provence in France and the University of Cape Town in South Africa. Already, courses are given at the undergraduate and Master levels and a teaching Observatory has been built. A 1m research telescope was also moved from the La Silla Observatory in Chile to Burkina Faso and the infrastructure is being built at the moment on mount Djaogari in the north-eastern part of the country. In the meantime, 6 students are doing their PhD in Astrophysics overseas (Canada, France and South Africa) and will become the core of the research group at the Université de Ouagadougou. An engineer is also doing his PhD in Astronomical Instrumentation to help with the maintenance of the equipment on the Research Telescope.
Publisher: EDP Sciences
Date: 07-2020
DOI: 10.1051/0004-6361/201935802
Abstract: Context. The ellipsoid of random motions of the gaseous medium in galactic disks is often considered isotropic, as appropriate if the gas is highly collisional. However, the collisional or collisionless behavior of the gas is a subject of debate. If the gas is clumpy with a low collision rate, then the often observed asymmetries in the gas velocity dispersion could be hints of anisotropic motions in a gaseous collisionless medium. Aims. We study the properties of anisotropic and axisymmetric velocity ellipsoids from maps of the gas velocity dispersion in nearby galaxies. This data allow us to measure the azimuthal-to-radial axis ratio of gas velocity ellipsoids, which is a useful tool to study the structure of gaseous orbits in the disk. We also present the first estimates of perturbations in gas velocity dispersion maps by applying an alternative model that considers isotropic and asymmetric random motions. Methods. High-quality velocity dispersion maps of the atomic medium at various angular resolutions of the nearby spiral galaxy Messier 33, are used to test the anisotropic and isotropic velocity models. The velocity dispersions of hundreds of in idual molecular clouds are also analyzed. Results. The H I velocity dispersion of M 33 is systematically larger along the minor axis, and lower along the major axis. Isotropy is only possible if asymmetric motions are considered. Fourier transforms of the H I velocity dispersions reveal a bisymmetric mode which is mostly stronger than other asymmetric motions and aligned with the minor axis of the galaxy. Within the anisotropic and axisymmetric velocity model, the stronger bisymmetry is explained by a radial component that is larger than the azimuthal component of the ellipsoid of random motions, thus by gaseous orbits that are dominantly radial. The azimuthal anisotropy parameter is not strongly dependent on the choice of the vertical dispersion. The velocity anisotropy parameter of the molecular clouds is observed highly scattered. Conclusions. Perturbations such as H I spiral-like arms could be at the origin of the gas velocity anisotropy in M 33. Further work is necessary to assess whether anisotropic velocity ellispsoids can also be invoked to explain the asymmetric gas random motions of other galaxies.
Publisher: Cambridge University Press (CUP)
Date: 08-2006
DOI: 10.1017/S1743921307002554
Abstract: Giant HI shells, with diameters of hundreds of parsecs and expansion velocities of 10-20 s −1 are characteristic observed features of local gas rich galaxies. Although a predictable consequence of the impact of OB associations on the ISM doubts have been raised, as OB stars are not present in the centres of the majority of these shells. Here we combine our observations of expanding ionized shells in luminous H II regions with basic dynamical models to give support to the scenario in which OB associations do produce the HI shells.
Publisher: American Astronomical Society
Date: 04-1996
DOI: 10.1086/117895
Publisher: Springer Netherlands
Date: 2002
Publisher: Oxford University Press (OUP)
Date: 26-10-2019
Abstract: H i observations of the nearby blue compact dwarf galaxy IC 10 obtained with the Dominion Radio Astrophysical Observatory synthesis telescope, for a total integration of ∼1000 h, are presented. We confirm the NW faint 21 cm H i emission feature discovered in Green Bank Telescope (GBT) observations. The H i feature has an H i mass of 4.7 × 105 M⊙, which is only ∼0.6 ${{\\ \\rm per\\ cent}}$ of the total H i mass of the galaxy (7.8 × 107 M⊙). In the inner disc, the rotation curve of IC 10 rises steeply, then flattens until the last point where it rises again, with a maximum velocity of 30 km s−1. Based on our mass models, the kinematics of the inner disc of IC 10 can be described without the need of a dark matter halo. However, this does not exclude the possible presence of dark matter on a larger scale. It is unlikely that the disturbed features seen in the outer H i disc of IC 10 are caused by an interaction with M 31. Features seen from our simulations are larger and at lower surface density than can be reached by current observations. The higher velocity dispersions seen in regions where several distinct H i features meet with the main core of IC 10 suggest that there is ongoing accretion.
Publisher: Oxford University Press (OUP)
Date: 14-07-2016
Publisher: American Astronomical Society
Date: 03-2021
Abstract: We present the analysis of the diffuse, low column density H i environment of 18 MHONGOOSE galaxies. We obtained deep observations with the Robert C. Byrd Green Bank Telescope and reached down to a 3 σ column density detection limit of N HI = 6.3 × 10 17 cm −2 over a 20 km s −1 line width. We analyze the environment around these galaxies, with a focus on H i gas that reaches column densities below N HI = 10 19 cm −2 . We calculate the total amount of H i gas in and around the galaxies, revealing that nearly all of these galaxies contained excess H i outside of their disks. We quantify the amount of diffuse gas in the maps of each galaxy, defined by H i gas with column densities below 10 19 cm −2 , and find a large spread in percentages of diffuse gas. However, by binning the percentage of diffuse H i into quarters, we find that the bin with the largest number of galaxies is the lowest quartile (0%–25% diffuse H i ). We identified several galaxies that may be undergoing gas accretion onto the galaxy disk using multiple methods of analysis, including azimuthally averaging column densities beyond the disk, and identifying structure within our integrated intensity (moment 0) maps. We measured H i mass outside the disks of most of our galaxies, with rising cumulative flux even at large radii. We also find a strong correlation between the fraction of diffuse gas in a galaxy and its baryonic mass, and we test this correlation using both Spearman and Pearson correlation coefficients. We see evidence of a dark matter halo mass threshold of M halo ∼ 10 11.1 M ☉ in which galaxies with high fractions of diffuse H i all reside below. It is in this regime that cold-mode accretion should dominate. Finally, we suggest a rotation velocity of v rot ∼ 80 km s −1 as an upper threshold to find diffuse-gas-dominated galaxies.
Publisher: Cambridge University Press (CUP)
Date: 2004
DOI: 10.1017/S0074180900183561
Abstract: We present H α emission line velocity fields of two Low Surface Brightness galaxies (LSBs) - UGC 628 and UGC 5005 - obtained using Fabry-Perot (FP) interferometry observations at the Canada-France-Hawaii telescope. Our goal is to study the dynamics of LSBs.
Publisher: Oxford University Press (OUP)
Date: 15-07-2010
Publisher: American Astronomical Society
Date: 07-1985
DOI: 10.1086/163316
Publisher: American Astronomical Society
Date: 12-1989
DOI: 10.1086/168167
Publisher: Springer Netherlands
Date: 1996
Publisher: American Astronomical Society
Date: 12-2000
DOI: 10.1086/316883
Publisher: Oxford University Press (OUP)
Date: 26-04-2018
Publisher: American Astronomical Society
Date: 10-1996
DOI: 10.1086/118110
Publisher: The Company of Biologists
Date: 2019
DOI: 10.1242/JEB.191353
Abstract: Exposure to anoxia leads to rapid ATP depletion, alters metabolic pathways and exacerbates succinate accumulation. Upon re-oxygenation, the preferential oxidation of accumulated succinate most often impairs mitochondrial function. Few species can survive prolonged periods of hypoxia and anoxia at tropical temperatures and those that do may rely on mitochondria plasticity in response to disruptions to oxygen availability. Two carpet sharks, the epaulette shark (Hemiscyllium ocellatum ES) and the grey carpet shark (Chiloscyllium punctatum GCS) display different adaptive responses to prolonged anoxia: while the ES enters energy conserving metabolic depression, the GCS temporarily elevates its haematocrit prolonging oxygen delivery. High-resolution respirometry was used to investigate mitochondrial function in the cerebellum, a highly metabolically active organ that is oxygen sensitive and vulnerable to injury after anoxia/re-oxygenation (AR). Succinate was titrated into cerebellar preparations in vitro, with or without pre-exposure to AR, then the activity of mitochondrial complexes was examined. Like most vertebrates, GCS mitochondria significantly increased succinate oxidation rates, with impaired complex I function post-AR. In contrast, ES mitochondria inhibited succinate oxidation rates and both complex I and II capacities were conserved, resulting in preservation of oxidative phosphorylation capacity post-AR. Divergent mitochondrial plasticity elicited by elevated succinate post A/R parallels the inherently ergent physiological adaptations of these animals to prolonged anoxia, namely the absence (GCS) and presence of metabolic depression (ES). Since anoxia tolerance in these species also occurs at temperatures close to that of humans, examining their mitochondrial responses to AR could provide insights for novel interventions in clinical settings.
Publisher: Oxford University Press (OUP)
Date: 15-02-2014
DOI: 10.1093/MNRAS/STU100
Publisher: Oxford University Press (OUP)
Date: 15-10-2018
Publisher: American Astronomical Society
Date: 10-1998
DOI: 10.1086/300540
Publisher: Springer Berlin Heidelberg
Date: 2007
Publisher: American Astronomical Society
Date: 05-2008
Publisher: American Astronomical Society
Date: 02-1994
DOI: 10.1086/116875
Publisher: SPIE
Date: 29-09-2004
DOI: 10.1117/12.552411
Publisher: Oxford University Press (OUP)
Date: 23-08-2016
Publisher: American Astronomical Society
Date: 1988
DOI: 10.1086/114610
Publisher: American Astronomical Society
Date: 04-1988
DOI: 10.1086/114698
Publisher: American Astronomical Society
Date: 11-1991
DOI: 10.1086/186185
Publisher: American Astronomical Society
Date: 09-1990
DOI: 10.1086/115548
Publisher: American Astronomical Society
Date: 09-1990
DOI: 10.1086/115547
Publisher: Oxford University Press (OUP)
Date: 05-12-2008
Publisher: Cambridge University Press (CUP)
Date: 1999
DOI: 10.1071/AS99018
Abstract: After reviewing the H I content and distribution in extreme dwarf irregular (dIrr) and dwarf elliptical (dE) galaxies, previous searches for H I in dwarf spheroidal (dSph) galaxies will be discussed. I will report on the recent detections of H I probably associated with the Local Group (LG) dSph Sculptor and dIrr/dSph Phoenix, obtained with the ATCA, along with a similar detection in the Centaurus Group dSph CEN_41. Data obtained for Sculptor, using the Parkes Multibeam system, will also be presented and the advantage of the wide field for such nearby objects will be emphasised. Finally, the possible origin of the gas and the general problem of the missing ISM in dSph galaxies will be discussed.
Publisher: Springer Science and Business Media LLC
Date: 2002
Publisher: Oxford University Press (OUP)
Date: 04-2008
Publisher: American Astronomical Society
Date: 10-10-2005
DOI: 10.1086/431964
Publisher: Informa UK Limited
Date: 1994
Publisher: American Astronomical Society
Date: 06-08-2004
DOI: 10.1086/424482
Publisher: IOP Publishing
Date: 04-2013
DOI: 10.1086/670382
Publisher: Oxford University Press (OUP)
Date: 11-03-2019
DOI: 10.1093/MNRAS/STZ696
Abstract: A $25\\, \\rm deg^2$ region, including the M81 complex (M81, M82, and NGC 3077), NGC 2976, and IC2574, was mapped during ∼3000 h with the DRAO synthesis telescope. With a physical resolution of ∼1 kpc, these observations allow us to probe a large region down to column density levels of ${\\sim }1\\times 10^{18}\\, \\rm cm^{-2}$ over 16 km s−1, mapping the extent of the H i arm connecting the system and NGC 2976, and resolving the H i clouds adjacent to the arm. The observations also reveal a few clouds located between the system and IC 2574, probably tidally stripped from a past interaction between the two systems. Given the regular velocity distribution in the H i envelope of the system, we attempt and derive an idealized large-scale rotation curve of the system. We observe a flat trend for the rotation velocity of the overall system from 20 kpc out to 80 kpc, well beyond the outskirts of the M81 disk, although with asymmetries like a wiggle at the vicinity of M82. This supports the assumption that intergalactic gas and galaxies in the system participate to a large-scale ordered rotation motion which is dominated by M81. Also, our H i analysis of the group further supports the hypothesis that the galaxies forming the system moved closer from afar, in agreement with numerical simulations.
Publisher: Cambridge University Press (CUP)
Date: 08-2006
DOI: 10.1017/S1743921306005990
Abstract: Carignan et al . (C06, 2006, ApJ, 641, L109) recently presented an extended H I rotation curve (RC) of M31, using single dish observations from the 100m Effelsberg and Green Bank telescopes. These data were obtained along the semi-major axis of the approaching half of the M31 H I disk and showed a flat RC at large radius, which extends up to ~35 kpc (using D = 780 kpc). The kinematical analysis of M31 is pursued here and new deep 21cm observations obtained at the Dominion Radio Astrophysical Observatory (DRAO) are presented. A tilted-ring model is fitted to a new H I velocity field, allowing the derivation of the position angle P . A . and inclination i as a function of radius. We concentrate on the approaching half of the disk in order to compare our new results with those from C06. It is shown that the disk warping of M31 does not severely contaminate the kinematics of the neutral gas. As a consequence, the RC from C06 is in very good agreement with the new derived RC.
Publisher: Oxford University Press (OUP)
Date: 27-09-2019
Abstract: We present the mass models of 31 spiral and irregular nearby galaxies obtained using hybrid rotation curves (RCs) combining high-resolution GHASP Fabry–Perot H α RCs and extended WHISP H i ones together with 3.4 $\\mu$m WISE photometry. The aim is to compare the dark matter (DM) halo properties within the optical radius using only H α RCs with the effect of including and excluding the mass contribution of the neutral gas component, and when using H i or hybrid RCs. Pseudo-isothermal (ISO) core and Navarro–Frenk–White (NFW) cuspy DM halo profiles are used with various fiducial fitting procedures. Mass models using H α RCs including or excluding the H i gas component provide compatible disc M/L. The correlations between DM halo and baryon parameters do not strongly depend on the RC. Clearly, the differences between the fitting procedures are larger than between the different data sets. Hybrid and H i RCs lead to higher M/L values for both ISO and NFW best-fitting models but lower central densities for ISO haloes and higher concentration for NFW haloes than when using H α RCs only. The agreement with the mass model parameters deduced using hybrid RCs, considered as a reference, is better for H i than for H α RCs. ISO density profiles better fit the RCs than the NFW ones, especially when using H α or hybrid RCs. Halo masses at the optical radius determined using the various data sets are compatible even if they tend to be overestimated with H α RCs. Hybrid RCs are thus ideal to study the mass distribution within the optical radius.
Publisher: Oxford University Press (OUP)
Date: 18-05-2020
Abstract: We examine different measures of asymmetry for galaxy H i velocity profiles. We introduce the channel-by-channel asymmetry and the velocity-of-equality statistics to quantify profile asymmetries. Using a s le of simulated galaxies, we examine how these and the standard lopsidedness morphometric statistic depend on a variety of observational effects, including the viewing angle and inclination. We find that our newly introduced channel-by-channel asymmetry is less sensitive to the effects of viewing angle and inclination than other morphometrics. Applying our statistics to the WHISP (Westerbork H i survey of Irregular and SPiral galaxies) H i galaxy s le, we also find that the channel-by-channel asymmetry is a better indicator of visually classified asymmetric profiles. In addition, we find that the lopsidedness–velocity of equality space can be used to identify profiles with deep central dips without visual inspection.
Publisher: American Astronomical Society
Date: 18-03-2016
Publisher: American Astronomical Society
Date: 11-1999
DOI: 10.1086/301066
Publisher: American Astronomical Society
Date: 09-2003
DOI: 10.1086/377312
Publisher: American Astronomical Society
Date: 09-1988
DOI: 10.1086/185260
Publisher: American Astronomical Society
Date: 29-07-2013
Publisher: Oxford University Press (OUP)
Date: 07-2004
Publisher: American Astronomical Society
Date: 06-07-2017
Publisher: Cambridge University Press (CUP)
Date: 12-2011
DOI: 10.1017/S1743921311022599
Abstract: We performed a deep H i and Hα mapping of M31 and M33 in order to get accurate kinematical data of those two galaxies and also to make a comparison between the H i and Hα kinematics. The H i data were obtained with the DRAO interferometer and the Hα data with the Fabry-Perot system of the Observatoire du mont Mégantic using an EMCCD as a detector. These data will give us the best possible datasets to derive accurate rotation curves and mass models for those two Local Group spirals and provide some new data for the H ii regions studies of these galaxies. While the H i observations are of low resolution (~1 arcmin), the high resolution of the Hα data (~1 arcsec) should allow us to get much more details in the central regions, allowing at the same time a much better determination of the kinematical parameters. Hence, the inner part of the rotation curve, so inportant to constraint properly the mass models, will be determined more accurately.
Publisher: American Astronomical Society
Date: 2005
DOI: 10.1086/425853
Publisher: American Astronomical Society
Date: 2006
DOI: 10.1086/498340
Publisher: Oxford University Press (OUP)
Date: 15-07-2015
Publisher: American Astronomical Society
Date: 06-10-2009
Publisher: Academy of Science of South Africa
Date: 31-07-2013
Publisher: Oxford University Press (OUP)
Date: 23-03-2023
Abstract: The transformation and evolution of a galaxy is strongly influenced by interactions with its environment. Neutral hydrogen (H i) is an excellent way to trace these interactions. Here, we present H i observations of the spiral galaxy NGC 895, which was previously thought to be isolated. High-sensitivity H i observations from the MeerKAT large survey project MIGHTEE reveal possible interaction features, such as extended spiral arms and the two newly discovered H i companions, that drive us to change the narrative that it is an isolated galaxy. We combine these observations with deep optical images from the Hyper Suprime Camera to show an absence of tidal debris between NGC 895 and its companions. We do find an excess of light in the outer parts of the companion galaxy MGTH$\\_$J022138.1-052631, which could be an indication of external perturbation and thus possible sign of interactions. Our analysis shows that NGC 895 is an actively star-forming galaxy with a SFR of 1.75 ± 0.09[M⊙/yr], a value typical for high-stellar mass galaxies on the star-forming main sequence. It is reasonable to state that different mechanisms may have contributed to the observed features in NGC 895, and this emphasizes the need to revisit the target with more detailed observations. Our work shows the high potential and synergy of using state-of-the-art data in both H i and optical to reveal a more complete picture of galaxy environments.
Publisher: EDP Sciences
Date: 11-2020
DOI: 10.1051/0004-6361/202038894
Abstract: Aims. We present the results of three commissioning H I observations obtained with the MeerKAT radio telescope. These observations make up part of the preparation for the forthcoming MHONGOOSE nearby galaxy survey, which is a MeerKAT large survey project that will study the accretion of gas in galaxies and the link between gas and star formation. Methods. We used the available H I data sets, along with ancillary data at other wavelengths, to study the morphology of the MHONGOOSE s le galaxy, ESO 302-G014, which is a nearby gas-rich dwarf galaxy. Results. We find that ESO 302-G014 has a lopsided, asymmetric outer disc with a low column density. In addition, we find a tail or filament of H I clouds extending away from the galaxy, as well as an isolated H I cloud some 20 kpc to the south of the galaxy. We suggest that these features indicate a minor interaction with a low-mass galaxy. Optical imaging shows a possible dwarf galaxy near the tail, but based on the current data, we cannot confirm any association with ESO 302-G014. Nonetheless, an interaction scenario with some kind of low-mass companion is still supported by the presence of a significant amount of molecular gas, which is almost equal to the stellar mass, and a number of prominent stellar clusters, which suggest recently triggered star formation. Conclusions. These data show that MeerKAT produces exquisite imaging data. The forthcoming full-depth survey observations of ESO 302-G014 and other s le galaxies will, therefore, offer insights into the fate of neutral gas as it moves from the intergalactic medium onto galaxies.
Publisher: Oxford University Press (OUP)
Date: 19-07-2008
DOI: 10.1111/J.1365-2966.2008.13422.X
Abstract: We present the Fabry–Perot observations obtained for a new set of 108 galaxies in the frame of the Gassendi Hα survey of SPirals (GHASP). The GHASP survey consists of 3D Hα data cubes for 203 spiral and irregular galaxies, covering a large range in morphological types and absolute magnitudes, for kinematics analysis. The new set of data presented here completes the survey. The GHASP s le is by now the largest s le of Fabry–Perot data ever published. The analysis of the whole GHASP s le will be done in forthcoming papers. Using adaptive binning techniques based on Voronoi tessellations, we have derived Hα data cubes from which are computed Hα maps, radial velocity fields as well as residual velocity fields, position–velocity diagrams, rotation curves and the kinematical parameters for almost all galaxies. Original improvements in the determination of the kinematical parameters, rotation curves and their uncertainties have been implemented in the reduction procedure. This new method is based on the whole 2D velocity field and on the power spectrum of the residual velocity field rather than the classical method using successive crowns in the velocity field. Among the results, we point out that morphological position angles have systematically higher uncertainties than kinematical ones, especially for galaxies with low inclination. The morphological inclination of galaxies having no robust determination of their morphological position angle cannot be constrained correctly. Galaxies with high inclination show a better agreement between their kinematical inclination and their morphological inclination computed assuming a thin disc. The consistency of the velocity litude of our rotation curves has been checked using the Tully–Fisher relationship. Our data are in good agreement with previous determinations found in the literature. Nevertheless, galaxies with low inclination have statistically higher velocities than expected and fast rotators are less luminous than expected.
Publisher: Cambridge University Press (CUP)
Date: 12-2010
DOI: 10.1017/S1743921311022745
Abstract: The exact contribution of the stellar disk to the overall kinematics of a galaxy remains in most studies a free parameter of the mass models. With the help of chemospectrophotometric evolution models, it is now possible to have a coherent picture of the stellar population of a galaxy including its mass-to-luminosity ratio at every radius spanning a wide range of observable wavelengths. We will focus on discussing the consistency of the mass thus inferred in photometric bands ranging from the FUV to the NIR for in idual galaxies and compare this to the maximum-disc hypothesis.
Publisher: Oxford University Press (OUP)
Date: 13-04-2006
Publisher: Cambridge University Press (CUP)
Date: 1998
DOI: 10.1071/AS98056
Abstract: The Dominion Radio Astrophysical Observatory (DRAO) is carrying out a survey as part of an international collaboration to image the northe, at a common resolution, in emission from all major constituents of the interstellar medium the neutral atomic gas, the molecular gas, the ionised gas, dust and relativistic plasma. For many of these constituents the angular resolution of the images (1 arcmin) will be more than a factor of 10 better than any previous studies. The aim is to produce a publicly-available database of high resolution, high-dynamic range images of the Galaxy for multi-phase studies of the physical states and processes in the interstellar medium. We will sketch the main scientific motivations as well as describe some preliminary results from the Canadian Galactic Plane Survey/Releve Canadien du Plan Galactique (CGPS/RCPG).
Publisher: Cambridge University Press (CUP)
Date: 1996
DOI: 10.1017/S0074180900232695
Abstract: The total mass and total extent of galaxies (including their dark halos) are fundamental parameters that are completely unknown for all galaxies. The best estimates we have for spiral and dwarf irregular galaxies come from detailed mass models using extended HI rotation curves. But, in every galaxy studied so far, such analysis only succeeded to derive lower limits of the total mass and total extent of their dark halo out to the last measured velocity point of the rotation curves which are still flat or even rising, implying that more dark mass is present at larger radii.
Publisher: Cambridge University Press (CUP)
Date: 2004
DOI: 10.1017/S0074180900197104
Abstract: We present HI detections towards several Local Group dSphs and dIrr/dSphs. The possibility that the detected emission can be due to High Velocity Clouds (HVC) is ruled out although it appears that most of our targets are in HVC rich regions.
Publisher: Frontiers Media SA
Date: 18-01-2019
Publisher: American Astronomical Society
Date: 10-10-1998
DOI: 10.1086/306227
Publisher: IOP Publishing
Date: 06-2008
DOI: 10.1086/589844
Publisher: EDP Sciences
Date: 30-05-2005
Publisher: Oxford University Press (OUP)
Date: 03-05-2016
Publisher: IEEE
Date: 08-2017
Publisher: American Astronomical Society
Date: 05-1997
DOI: 10.1086/118376
Publisher: SPIE
Date: 14-07-2008
DOI: 10.1117/12.789498
Publisher: Springer Netherlands
Date: 1984
Publisher: American Astronomical Society
Date: 18-09-2007
DOI: 10.1086/522204
Publisher: Oxford University Press (OUP)
Date: 11-05-2006
Publisher: CSIRO Publishing
Date: 1981
DOI: 10.1071/PH810407
Abstract: Flux densities and positions have been measured at 5000 MHz for all the radio sources in the Parkes 2700 MHz catalogue with S2700 = 0�25 Jy for which no 5000 MHz data have previously been published. The new positions of the sources, which are of considerably higher accuracy than those measured at 2700 MHz, have been examined on the available sky survey material: 17 previously suggested identifications are rejected, but alternative identifications are proposed for 4 of these identifications are proposed for \\18 other sources.
Publisher: Oxford University Press (OUP)
Date: 03-2006
Publisher: American Astronomical Society
Date: 21-10-2009
Publisher: Oxford University Press (OUP)
Date: 06-2011
Publisher: Oxford University Press (OUP)
Date: 16-09-2016
Publisher: Oxford University Press (OUP)
Date: 05-09-2017
Publisher: Cambridge University Press (CUP)
Date: 12-2011
DOI: 10.1017/S1743921311022782
Abstract: During the next decade the IAU intends to mobilize talented astronomers, engineers and teachers around the world, in the service of developing countries. I shall review the content of the IAU Strategic Plan 2010 - 2020 “Astronomy for the Developing World” and give you an update on its implementation. Astronomy is a unique tool for stimulating capacity building because it combines cutting-edge technology with fundamental science and has deep cultural roots. The plan envisages a substantial increase in IAU education and development activities during the next decade. These activities will be bottom-up, with a strong regional influence. An integrated approach tailored to the conditions and needs of each country will involve a mix of education at primary, secondary and tertiary levels and public outreach. As a crucial component of the strategy, the IAU together with the South African National Research Foundation will set up a small office to coordinate and plan the various global activities at the SAAO in Cape Town.
Publisher: Oxford University Press (OUP)
Date: 07-04-2022
Abstract: Observations of the neutral atomic hydrogen (H i) in the nuclear starburst galaxy NGC 4945 with MeerKAT are presented. We find a large amount of halo gas, previously missed by H i observations, accounting for 6.8 per cent of the total H i mass. This is most likely gas blown into the halo by star formation. Our maps go down to a 3σ column density level of 5 × 1018 cm−2. We model the H i distribution using tilted-ring fitting techniques and find a warp on the galaxy’s approaching and receding sides. The H i in the northern side of the galaxy appears to be suppressed. This may be the result of ionization by the starburst activity in the galaxy, as suggested by a previous study. The origin of the warp is unclear but could be due to past interactions or ram pressure stripping. Broad, asymmetric H i absorption lines extending throughout the H i emission velocity channels are present towards the nuclear region of NGC 4945. Such broad lines suggest the existence of a nuclear ring moving at a high circular velocity. This is supported by the clear rotation patterns in the H i absorption velocity field. The asymmetry of the absorption spectra can be caused by outflows or inflows of gas in the nuclear region of NGC 4945. The continuum map shows small extensions on both sides of the galaxy’s major axis that might be signs of outflows resulting from the starburst activity.
Publisher: American Astronomical Society
Date: 02-1997
DOI: 10.1086/118280
Publisher: Cambridge University Press (CUP)
Date: 12-2010
DOI: 10.1017/S1743921311022812
Abstract: On the African continent, most of the activities in Astronomy are found in South Africa where full training in Astrophysics is given in a few Universities and where most of the professional astronomers and of the research instruments (from small telescopes to the 11m SALT, in the optical) can be found. In 2007, we started a full program (undergraduate and graduate) in Astrophysics at the Université de Ouagadougou and an Observatory (ODAUO), for teaching purposes, was also built. In October 2009, we put in crates the 1m Marly telescope in La Silla, Chile which will be rebuilt in 2011-12, as a full research telescope, on mount Djaogari in Burkina Faso.
Publisher: American Astronomical Society
Date: 05-1985
DOI: 10.1086/191031
Publisher: American Astronomical Society
Date: 04-10-2018
Publisher: American Astronomical Society
Date: 09-1991
DOI: 10.1086/170450
Publisher: American Astronomical Society
Date: 10-1997
DOI: 10.1086/118565
Publisher: EDP Sciences
Date: 15-02-2016
Publisher: Elsevier BV
Date: 10-2014
Publisher: Oxford University Press (OUP)
Date: 02-05-2019
Publisher: Springer Netherlands
Date: 1989
Publisher: Oxford University Press (OUP)
Date: 18-10-2017
Publisher: American Astronomical Society
Date: 07-2008
DOI: 10.1086/588580
Publisher: SPIE
Date: 07-03-2003
DOI: 10.1117/12.459893
Publisher: American Astronomical Society
Date: 15-09-2011
Publisher: American Astronomical Society
Date: 1990
DOI: 10.1086/115318
Publisher: American Astronomical Society
Date: 04-2001
DOI: 10.1086/319944
Publisher: SPIE
Date: 23-07-2014
DOI: 10.1117/12.2057021
Publisher: Cambridge University Press (CUP)
Date: 12-2010
Publisher: Oxford University Press (OUP)
Date: 04-2015
DOI: 10.1093/MNRAS/STV517
Publisher: American Astronomical Society
Date: 20-01-2005
DOI: 10.1086/426375
Publisher: Cambridge University Press (CUP)
Date: 2004
DOI: 10.1017/S0074180900198171
Abstract: Results are presented from a wide area, high resolution HI synthesis survey of the outer regions of the nearby M81 group, where internal (galactic) and external (group-related) evolution processes can be studied simultaneously in great detail. The survey encompasses the star forming dwarf galaxies M81dwA, UGC4483, and HoII, where evidence of ram pressure stripping was recently discovered. The data do not reveal any intergalactic HI, but the outer parts of HoII are reminiscent of tidal tails. We argue however that those structures are equally consistent with the latest ram pressure models including cooling. The case for a hot intergalactic medium in this poor, spiral-only group is thus still open. The survey also puts tight constraints on possible counterparts to the local high velocity cloud population in an external group, reaching a 3σ column density of 10 19 atom cm −2 and a 6σ limiting mass of 1.5 × 10 5 M ⊙ .
Publisher: European Respiratory Society (ERS)
Date: 27-07-2023
DOI: 10.1183/23120541.00229-2023
Abstract: Pulmonary hypertension due to left heart disease (PH-LHD) is the most frequent form of PH. As differential diagnosis with pulmonary arterial hypertension (PAH) has therapeutic implications, it is important to accurately and non-invasively differentiate PH-LHD from PAH before referral to PH centres. The aim was to develop and validate a machine learning (ML) model to improve prediction of PH-LHD in a population of PAH and PH-LHD patients. Non-invasive PH-LHD predictors from 172 PAH and 172 PH-LHD patients from the PH centre database at the University Hospitals of Leuven were used to develop a ML model. Jacobs score [1] was used as performance benchmark. The dataset was split into a training and test set (70:30) and the best model was selected after 10-fold cross-validation on the training dataset (n=240). The final model was externally validated using 165 patients (91 PAH, 74 PH-LHD) from Erasme Hospital Brussels. In the internal test dataset (n=104), a random forest-based model correctly diagnosed 70% of PH-LHD patients (sensitivity: n=35/50), with 100% PPV, 78% NPV and 100% specificity. The model outperformed the Jacobs score that identified 18% (n=9/50) of the patients with PH-LHD without false positives. In external validation, the model had 64% sensitivity at 100% specificity while Jacobs score had a sensitivity of 3% for no false positives. ML significantly improves the sensitivity of PH-LHD prediction at 100% specificity. Such a model may substantially reduce the number of patients referred for invasive diagnostics without missing PAH diagnoses.
Publisher: Cambridge University Press (CUP)
Date: 2004
DOI: 10.1017/S0074180900183809
Abstract: After looking at the difference in the mass distribution between massive spiral and dwarf irregular (dIrr) and low surface brightness (LSB) galaxies, the central Dark Matter (DM) concentration (flat vs cuspy) in dwarf and LSB galaxies, derived from observations, will be examined. We will then present what kind of observational constraints can be put on the total mass and total extent of DM halos from the studies of in idual galaxies, small groups, satellites' dynamics and tidal tails of interacting systems. Finally, we will discuss how limits on the physical parameters of DM halos could be set by deriving extended rotation curves beyond the HI radius (r r HI ), using either Ly α absorption or H α emission observations.
Publisher: Cambridge University Press (CUP)
Date: 2004
DOI: 10.1017/S0074180900198213
Abstract: We present results from an ongoing survey of the ionized gas kinematics in Virgo cluster spiral galaxies using Fabry-Perot (FP) interferometry. Our goal is to study the environmental effects on galaxy evolution in the Virgo cluster. We report here on the Hα distribution map and velocity field of NGC 4438, an interacting galaxy near the centre of the cluster.
Publisher: Springer Science and Business Media LLC
Date: 2002
Publisher: American Astronomical Society
Date: 25-01-2008
DOI: 10.1086/527473
Publisher: Oxford University Press (OUP)
Date: 20-09-2019
Publisher: Cambridge University Press (CUP)
Date: 1990
DOI: 10.1017/S025292110000498X
Abstract: Results from large-scale mapping of the HI gas in the Sculptor group are presented. From our kinematic analysis, a mean global (M/L B ) ⋍ 9 M ⊙ /L ⊙ (at the last observed velocity point) is found for the in idual galaxies. This is only a factor ~ 10 smaller than the ( M/L B ) dyn ⋍ 90 M ⊙ /L ⊙ derived from a dynamical study of the whole group. The parameters derived from the mass models suggest that most of the unseen matter has to be concentrated around the luminous galaxies. Under the assumption that the Sculptor group is a virialized system and that all the mass is associated with the galaxies, an upper limit of ~ 40 kpc is derived for the size of the dark halos present in the five late-type spirals of the group.
Publisher: Elsevier BV
Date: 11-2014
Publisher: American Astronomical Society
Date: 30-03-2006
DOI: 10.1086/503869
Publisher: EDP Sciences
Date: 2006
DOI: 10.1051/EAS:2006085
Publisher: Oxford University Press (OUP)
Date: 15-11-2018
Publisher: Elsevier BV
Date: 12-2015
Publisher: EDP Sciences
Date: 10-2018
DOI: 10.1051/0004-6361/201833509
Abstract: Context . We present a two-step method to simulate and study non-circular motions in strongly barred galaxies. The first step is to constrain the initial parameters using a Bayesian analysis of each galaxy’s azimuthally averaged rotation curve, the 3.6 μ m surface brightness, and the gas surface density. The second step is to generate equilibrium models using the GalactICS code and evolve them via GADGET-2. Aims . The bar strengths and mock velocity maps of the resulting snapshots are compared to observations in order to determine the best representation of the galaxy. Methods . We apply our method to the unbarred galaxy NGC 3621 and the barred galaxies NGC 1300 and NGC 1530. NGC 3621 provides a validation of our method of generating initial conditions. NGC 1530 has an intermediate bar orientation that allows for a comparison to DiskFit. Finally NGC 1300 has a bar oriented parallel to the galaxy’s major axis, where other algorithms tend to fail. Results . Our models for NGC 3621 and NGC 1530 are comparable to those obtained using commonly available algorithms. Moreover, we produce one of the first mass distribution models for NGC 1300.
Publisher: Oxford University Press (OUP)
Date: 07-2005
Publisher: American Astronomical Society
Date: 06-2006
DOI: 10.1086/503629
Publisher: Elsevier BV
Date: 04-2019
Publisher: Oxford University Press (OUP)
Date: 12-02-2020
Abstract: We analyse the eastern region of a 5° × 5° deep H i survey of the M81 group containing the dwarf galaxy IC 2574 and the H i complex HIJASS J1021+68, located between the dwarf and the M81 system. The data show that IC 2574 has an extended H i envelope that connects to HIJASS J1021+68 in the form of a collection of small clouds, but no evident connection has been found between IC 2574 and the central members of the M81 group. We argue, based on the morphology of the clouds forming HIJASS J1021+68 and its velocity distribution, that the complex is not a dark galaxy as previously suggested, but is instead a complex of clouds either stripped from, or falling on to the primordial H i envelope of IC 2574. We also use the deep H i observations to map the extended H i envelope around IC 2574 and, using a 3D tilted-ring model, we derive the rotation curve of the galaxy to a larger extent than has been done before. Combining the obtained rotation curve to higher resolution curves from the literature, we constrain the galaxy’s dark matter halo parameters.
Publisher: Oxford University Press (OUP)
Date: 20-10-2015
Publisher: SPIE
Date: 12-07-2008
DOI: 10.1117/12.790616
Publisher: Cambridge University Press
Date: 07-12-1989
Publisher: IOP Publishing
Date: 08-2009
DOI: 10.1086/605449
Publisher: American Astronomical Society
Date: 06-1994
DOI: 10.1086/117013
Publisher: Cambridge University Press (CUP)
Date: 08-2019
DOI: 10.1017/S1743921318005793
Abstract: We know that the observed H i (and H 2 ) content cannot explain the SFR observed in galaxies. The only way galaxies can sustain that SFR is by accreting HI-rich dwarf galaxies or Inter-Galactic HI clouds. However, no observation to detect those accretion events has been conclusive so far. Instruments having the necessary sensitivity (e.g. GBT) lack the necessary spatial resolution and those with the proper resolution (e.g. VLA) lack the sensitivity. I will show that both are necessary to detect those illusive H i clouds. The SKA precursor MeerKAT is starting its operation as we speak and will start the Large Survey Programs at the end of 2018. FAST has started its observations in drift scan mode with CRAFTS (Commensal Radio Astronomy Fast Survey). In the near future (2019-20), the best combination to study low column density H i will be to combine the sensitivity of FAST with the spatial resolution of MeerKAT.
Publisher: Wiley
Date: 14-03-2019
Publisher: Springer Science and Business Media LLC
Date: 02-2022
DOI: 10.1007/S12551-022-00937-7
Abstract: In the Carboniferous, insects evolved flight. Intense selection drove for high performance and approximately 100 million years later, Hymenoptera (bees, wasps and ants) emerged. Some species had proportionately small wings, with apparently impossible aerodynamic challenges including a need for high frequency flight muscles (FMs), powered exclusively off aerobic pathways and resulting in extreme aerobic capacities. Modern insect FMs are the most refined and form large dense blocks that occupy 90% of the thorax. These can beat wings at 200 to 230 Hz, more than double that achieved by standard neuromuscular systems. To do so, rapid repolarisation was circumvented through evolution of asynchronous stimulation, stretch activation, elastic recoil and a paradoxically slow Ca 2+ reuptake. While the latter conserves ATP, considerable ATP is demanded at the myofibrils. FMs have diminished sarcoplasmic volumes, and ATP is produced solely by mitochondria, which pack myocytes to maximal limits and have very dense cristae. Gaseous oxygen is supplied directly to mitochondria. While FMs appear to be optimised for function, several unusual paradoxes remain. FMs lack any significant equivalent to the creatine kinase shuttle, and myofibrils are twice as wide as those of within cardiomyocytes. The mitochondrial electron transport systems also release large amounts of reactive oxygen species (ROS) and respiratory complexes do not appear to be present at any exceptional level. Given that the loss of the creatine kinase shuttle and elevated ROS impairs heart function, we question how do FM shuttle adenylates at high rates and tolerate oxidative stress conditions that occur in diseased hearts?
Publisher: American Astronomical Society
Date: 02-1991
DOI: 10.1086/115696
Publisher: American Astronomical Society
Date: 02-1991
DOI: 10.1086/115695
Publisher: EDP Sciences
Date: 24-04-2007
Publisher: SPIE
Date: 12-07-2008
DOI: 10.1117/12.800300
Publisher: Oxford University Press (OUP)
Date: 07-07-2020
Abstract: We present observations and models of the kinematics and the distribution of the neutral hydrogen (H i) in the isolated dwarf irregular galaxy, Wolf-Lundmark-Melotte (WLM). We observed WLM with the Green Bank Telescope (GBT) and as part of the MeerKAT Early Science Programme, where 16 dishes were available. The H i disc of WLM extends out to a major axis diameter of 30 arcmin (8.5 kpc), and a minor axis diameter of 20 arcmin (5.6 kpc) as measured by the GBT. We use the MeerKAT data to model WLM using the tirific software suite, allowing us to fit different tilted-ring models and select the one that best matches the observation. Our final best-fitting model is a flat disc with a vertical thickness, a constant inclination and dispersion, and a radially varying surface brightness with harmonic distortions. To simulate bar-like motions, we include second-order harmonic distortions in velocity in the tangential and vertical directions. We present a model with only circular motions included and a model with non-circular motions. The latter describes the data better. Overall, the models reproduce the global distribution and the kinematics of the gas, except for some faint emission at the 2σ level. We model the mass distribution of WLM with pseudo-isothermal (ISO) and Navarro–Frenk–White (NFW) dark matter halo models. The NFW and the ISO models fit the derived rotation curves within the formal errors, but with the ISO model giving better reduced chi-square values. The mass distribution in WLM is dominated by dark matter at all radii.
Publisher: Cambridge University Press (CUP)
Date: 12-2006
Publisher: American Astronomical Society
Date: 11-1990
DOI: 10.1086/115612
Publisher: American Astronomical Society
Date: 09-1999
DOI: 10.1086/301021
Publisher: EDP Sciences
Date: 02-1998
DOI: 10.1051/AAS:1998378
Publisher: EDP Sciences
Date: 12-2022
DOI: 10.1051/0004-6361/202243412
Abstract: Cluster substructure and ram pressure stripping in in idual galaxies are among the primary pieces of evidence for the ongoing growth of galaxy clusters as they accrete galaxies and groups from their surroundings. We present a multiwavelength study of the center of the Hydra I galaxy cluster, including exquisite new MeerKAT H I and DECam H α imaging which reveal conclusive evidence for ram pressure stripping in NGC 3312, NGC 3314a, and NGC 3314b through compressed H I contours, well-defined H I tails, and ongoing star formation in the stripped gas. In particular, we quantify the stripped material in NGC 3312, and NGC 3314a, which makes up between 8% and 35% of the gas still in the disk, is forming stars at ∼0.5 M ⊙ yr −1 , and extends ∼30−60 kpc from the main disk. The estimated stellar mass in the tails is an order of magnitude less than the H I mass. A fourth “ring” galaxy at the same velocity does not show signs of ram pressure in H I . In addition, we used the H I and stellar morphologies, combined with a Beta model of the hot intracluster medium, to constrain the real distances of the galaxies to the cluster center, and we used the chance alignment of NGC 3314b behind NGC 3314a to break the degeneracy between whether the galaxies are in front or in back of the cluster. The drag seen in the H I tails supports our preferred scenario that NGC 3312 and NGC 3314a are moving toward us as part of a foreground substructure which has already passed its pericenter and is on “out fall” from the cluster. The high surviving H I content of the galaxies may suggest that the substructure or intragroup medium can protect them from the harshest effects of ram pressure, or that the galaxies are in fact on more tangential orbits.
Publisher: EDP Sciences
Date: 14-05-2004
Publisher: Cambridge University Press (CUP)
Date: 08-2015
DOI: 10.1017/S1743921316003392
Abstract: This presentation describes the web-based Teaching Radio Interferometer being built on the c us of the University of Cape Town, in South Africa, to train the future users of the African VLBI (Very Long Baseline Interferometry) Network (AVN).
Publisher: Cambridge University Press (CUP)
Date: 06-2019
DOI: 10.1017/S1743921319008524
Abstract: We present observations on optical emission lines acquired with the scanning Fabry-Perot interferometer of the observatoire du Mont Mégantic, of the Andromeda galaxy (M31). A 765 order Fabry-Perot were used with a fast readout EM-CCD. From data obtained, kinematic maps and data points for the rotation curve of the innermost part of the galaxy are derived. Several dozen of regions have been scanned with the Fabry-Perot interferometer and narrow band interference filters. The central 10’x10’ were scanned with five different filters. Observations have been made in order to get better Hα data for kinematics purposes.
Publisher: Cambridge University Press (CUP)
Date: 2004
DOI: 10.1017/S0074180900183548
Abstract: We present results obtained from a study of the mass distribution of 24 galaxies observed using Fabry-Pérot techniques, as part of the GHASP survey (see Russeil et al., this meeting). For each galaxy, we combined high resolution H α rotation curves derived from 2-D velocity fields, with low resolution HI data, in order to determine accurately the inner slope of the rotation curve which strongly constrains the distribution of matter. Our work suggests the existence of a constant density core in the center of the dark halos.
Publisher: Elsevier BV
Date: 04-2019
Publisher: Oxford University Press (OUP)
Date: 04-2006
Publisher: EDP Sciences
Date: 19-03-2007
Publisher: CSIRO Publishing
Date: 1981
DOI: 10.1071/PH810445
Abstract: Optical identifications are suggested for 122 weak radio sources from the Parkes 2700 MHz catalogue. Optical positions have been measured for the proposed counterparts and for 81 previously suggested identifications.
Publisher: Oxford University Press (OUP)
Date: 30-05-2018
DOI: 10.1093/MNRAS/STY969
Publisher: EDP Sciences
Date: 10-2016
Publisher: Oxford University Press (OUP)
Date: 19-05-2015
DOI: 10.1093/MNRAS/STV856
Publisher: Oxford University Press (OUP)
Date: 09-2023
Publisher: American Astronomical Society
Date: 06-08-2013
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Claude Carignan.