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497 results on '"Hensler, G."'

168. Continuous star formation in BCD galaxies.

Author

Recchi, S. and Hensler, G.

Subjects
*DWARF galaxies, *STAR formation, *ASTRONOMY, *MOLECULAR evolution, *SPECTRUM analysis, *ASTROPHYSICS
Abstract

Blue Compact Dwarf galaxies are generally believed to be unevolved objects, due to their blue colors, compact appearance and large gas fractions. Owing to the short gas consumption time-scales, they have been thought to be very young and characterized by bursting star formation. By means of 2-D hydrodynamical simulations, coupled with detailed chemical yields originating from SNeII, SNeIa and intermediate-mass stars, we study the dynamical and chemical evolution of galaxies with structural parameters similar to the Blue Compact Galaxies IZw18 and NGC1569. Bursts of star formation with negligible durations are not able to account for the chemical and morphological properties of these galaxies. The best way to reproduce the chemical composition of these objects is by assuming a long-lasting episode of star formation (270 Myr for IZw18 and 1.4 Gyr for NGC1569) and a more recent episode, separated from the previous one by a short quiescent period. In most of the explored cases, the derived chemical composition of the galaxy is dominated by the products of the old stars, since the enriched gas produced by young stars is in a too hot phase to be detectable with the optical spectroscopy. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Published
2005
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180. Gravitational fragmentation in expanding shells.

Author

Araki, H., Beig, R., Ehlers, J., Frisch, U., Hepp, K., Jaffe, R. L., Kippenhahn, R., Weidenmüller, H. A., Wess, J., Zittartz, J., Beiglböck, W., Lehr, Sabine, Breitschwerdt, Dieter, Freyberg, Michael, Trümper, Joachim, Theis, Ch., Ehlerová, S., Palouš, J., and Hensler, G.

Abstract

We investigate the gravitational fragmentation in expanding shells by applying an instability ‘thermometer' similar to the Toomre parameter for instabilities in self-gravitating disks. For Sedov-like evolving systems the onset of instability is mainly depending on the density of the ambient medium and the sound speed of the shell matter, whereas the energy injection rate is less important. Shells evolve towards gravitational instability, if the density gradient of the ambient medium is shallower than an isothermal profile, otherwise they become more stable. For density gradients flatter than ∝ r−1, the fragmentation becomes non-linear on the same time scale as the gravitational instability needs to start. In a homogeneous ambient medium the typical size of gravitationally unstable shells is 1 kpc for a gas density of n=1 cm−3 and decreases to 10 pc for n=104 cm−3. [ABSTRACT FROM AUTHOR]

Published
1998
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181. Star formation in expanding shells: When and where.

Author

Araki, H., Beig, R., Ehlers, J., Frisch, U., Hepp, K., Jaffe, R. L., Kippenhahn, R., Weidenmüller, H. A., Wess, J., Zittartz, J., Beiglböck, W., Lehr, Sabine, Breitschwerdt, Dieter, Freyberg, Michael, Trümper, Joachim, Ehlerová, S., Palouš, J., Theis, Ch., and Hensler, G.

Abstract

The fragmentation of expanding shells and subsequent star formation are analyzed using an analytical model and computer simulations. We discuss the role of the sound speed in the ambient interstellar medium and the influence of the finite thickness of the gaseous disk. [ABSTRACT FROM AUTHOR]

Published
1998
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183. A Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE): XVI. The ubiquity of truncated star-forming discs across the Virgo cluster environment.

Author

Morgan, C. R., Balogh, M. L., Boselli, A., Fossati, M., Lawlor-Forsyth, C., Sazonova, E., Amram, P., Boquien, M., Braine, J., Cortese, L., Côté, P., Cuillandre, J. C., Ferrarese, L., Gwyn, S., Hensler, G., Junais, and Roediger, J.

Subjects
*GALACTIC evolution, *STAR formation, *GALAXY formation, *STAR clusters, VIRGO Cluster
Abstract

We examine the prevalence of truncated star-forming discs in the Virgo cluster down to M* ≃ 107 M⊙. This work makes use of deep, high-resolution imaging in the Hα+[N II] narrow-band from the Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE) and optical imaging from the Next Generation Virgo Survey (NGVS). To aid in the understanding of the effects of the cluster environment on star formation in Virgo galaxies, we take a physically motivated approach to define the edge of the star-forming disc via a drop-off in the radial specific star formation rate profile. A comparison with the expected sizes of normal galactic discs provides a measure of how truncated star-forming discs are in the cluster. We find that truncated star-forming discs are nearly ubiquitous across all regions of the Virgo cluster, including beyond the virial radius (0.974 Mpc). The majority of truncated discs at large cluster-centric radii are of galaxies likely on their first infall. As the intra-cluster medium density is low in this region, it is difficult to explain this population with solely ram-pressure stripping. A plausible explanation is that these galaxies are undergoing starvation of their gas supply before ram-pressure stripping becomes the dominant quenching mechanism. A simple model of starvation shows that this mechanism can produce moderate disc truncations within 1−2 Gyr. This model is consistent with 'slow-then-rapid' or 'delayed-then-rapid' quenching, whereby the early starvation mode drives disc truncations without significant change to the integrated star formation rate, and the later ram-pressure stripping mode rapidly quenches the galaxy. The origin of starvation may be in the group structures that exist around the main Virgo cluster, which indicates the importance of understanding pre-processing of galaxies beyond the cluster virial radius. [ABSTRACT FROM AUTHOR]

Published
2024
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186. Physical Processes in Star–Gas Systems

Author

Spurzem, R., Berczik, P., Hensler, G., Theis, Ch., Amaro-Seoane, P., Freitag, M., and Just, A.

Abstract

AbstractWe first present a recently developed three-dimensional chemodynamic code for galaxy evolution from the Kiev–Kiel collaboration. It follows the evolution of all components of a galaxy, such as dark matter, stars, molecular clouds and diffuse interstellar matter. Dark matter and stars are treated as collisionless N-body systems. The interstellar matter is numerically described by a smoothed particle hydrodynamics approach for the diffuse (hot) gas and a sticky particle scheme for the (cool) molecular clouds. Physical processes, such as star formation, stellar death, or condensation and evaporation processes of clouds interacting with the ISM are described locally. An example application of the model to a star forming dwarf galaxy will be shown for comparison with other codes. Secondly, we will discuss new kinds of exotic chemodynamic processes, as they occur in dense gas–star systems in galactic nuclei, such as non-standard ‘drag’-force interactions, destructive and gas-producing stellar collisions. Their implementation in one-dimensional dynamic models of galactic nuclei is presented. Future prospects to generalise these to three dimensions are in progress and will be discussed.

Published
2004
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187. The Gaia-ESO Public Spectroscopic Survey

Author

Gilmore, G., Randich, S., Asplund, M., Binney, J., Bonifacio, P., Drew, J., Feltzing, S., Ferguson, A., Jeffries, R., Micela, G., Negueruela, I., Prusti, T., Rix, H. -W, Vallenari, A., Alfaro, E., Allende-Prieto, C., Babusiaux, C., Bensby, T., Blomme, R., Bragaglia, A., Flaccomio, E., François, P., Irwin, M., Koposov, S., Korn, A., Lanzafame, A., Pancino, E., Paunzen, E., Recio-Blanco, A., Sacco, G., Smiljanic, R., Eck, S., Walton, N., Aden, D., Aerts, C., Affer, L., Alcala, J. -M, Altavilla, G., Alves, J., Antoja, T., Arenou, F., Costanza ARGIROFFI, Asensio Ramos, A., Bailer-Jones, C., Balaguer-Nunez, L., Bayo, A., Barbuy, B., Barisevicius, G., Barrado Y Navascues, D., Battistini, C., Bellas Velidis, I., Bellazzini, M., Belokurov, V., Bergemann, M., Bertelli, G., Biazzo, K., Bienayme, O., Bland-Hawthorn, J., Boeche, C., Bonito, S., Boudreault, S., Bouvier, J., Brandao, I., Brown, A., Bruijne, J., Burleigh, M., Caballero, J., Caffau, E., Calura, F., Capuzzo-Dolcetta, R., Caramazza, M., Carraro, G., Casagrande, L., Casewell, S., Chapman, S., Chiappini, C., Chorniy, Y., Christlieb, N., Cignoni, M., Cocozza, G., Colless, M., Collet, R., Collins, M., Correnti, M., Covino, E., Crnojevic, D., Cropper, M., Cunha, M., Damiani, F., David, M., Delgado, A., Duffau, S., Edvardsson, B., Eldridge, J., Enke, H., Eriksson, K., Evans, N. W., Eyer, L., Famaey, B., Fellhauer, M., Ferreras, I., Figueras, F., Fiorentino, G., Flynn, C., Folha, D., Franciosini, E., Frasca, A., Freeman, K., Fremat, Y., Friel, E., Gaensicke, B., Gameiro, J., Garzon, F., Geier, S., Geisler, D., Gerhard, O., Gibson, B., Gomboc, A., Gomez, A., Gonzalez-Fernandez, C., Gonzalez Hernandez, J., Gosset, E., Grebel, E., Greimel, R., Groenewegen, M., Grundahl, F., Guarcello, M., Gustafsson, B., Hadrava, P., Hatzidimitriou, D., Hambly, N., Hammersley, P., Hansen, C., Haywood, M., Heber, U., Heiter, U., Held, E., Helmi, A., Hensler, G., Herrero, A., Hill, V., Hodgkin, S., Huelamo, N., Huxor, A., Ibata, R., Jackson, R., Jong, R., Jonker, P., Jordan, S., Jordi, C., Jorissen, A., Katz, D., Kawata, D., Keller, S., Kharchenko, N., Klement, R., Klutsch, A., Knude, J., Koch, A., Kochukhov, O., Kontizas, M., Koubsky, P., Lallement, R., Laverny, P., Leeuwen, F., Lemasle, B., Lewis, G., Lind, K., Lindstrom, H. P. E., Lobel, A., Lopez Santiago, J., Lucas, P., Ludwig, H., Lueftinger, T., Magrini, L., Maiz Apellaniz, J., Maldonado, J., Marconi, G., Marino, A., Martayan, C., Martinez-Valpuesta, I., Matijevic, G., Mcmahon, R., Messina, S., Meyer, M., Miglio, A., Mikolaitis, S., Minchev, I., Minniti, D., Moitinho, A., Momany, Y., Monaco, L., Montalto, M., Monteiro, M. J., Monier, R., Montes, D., Mora, A., Moraux, E., Morel, T., Mowlavi, N., Mucciarelli, A., Munari, U., Napiwotzki, R., Nardetto, N., Naylor, T., Naze, Y., Nelemans, G., Okamoto, S., Ortolani, S., Pace, G., Palla, F., Palous, J., Parker, R., Penarrubia, J., Pillitteri, I., Piotto, G., Posbic, H., Prisinzano, L., Puzeras, E., Quirrenbach, A., Ragaini, S., Read, J., Read, M., Reyle, C., Ridder, J., Robichon, N., Robin, A., Roeser, S., Romano, D., Royer, F., Ruchti, G., Ruzicka, A., Ryan, S., Ryde, N., Santos, N., Sanz Forcada, J., Sarro Baro, L. M., Sbordone, L., Schilbach, E., Schmeja, S., Schnurr, O., Schoenrich, R., Scholz, R. -D, Seabroke, G., Sharma, S., Silva, G., Smith, M., Solano, E., Sordo, R., Soubiran, C., Sousa, S., Spagna, A., Steffen, M., Steinmetz, M., Stelzer, B., Stempels, E., Tabernero, H., Tautvaisiene, G., Thevenin, F., Torra, J., Tosi, M., Tolstoy, E., Turon, C., Walker, M., Wambsganss, J., Worley, C., Venn, K., Vink, J., Wyse, R., Zaggia, S., Zeilinger, W., Zoccali, M., Zorec, J., Zucker, D., Zwitter, T., Gaia-ESO Survey Team, Gilmore, G., Randich, S., Asplund, M., Binney, J., Bonifacio, P., Drew, J., Feltzing, S., Ferguson, A., Jeffries, R., Micela, G., Negueruela, I., Prusti, T., Rix, H.-W., Vallenari, A., Alfaro, E., Allende-Prieto, C., Babusiaux, C., Bensby, T., Blomme, R., Bragaglia, A., Flaccomio, E., François, P., Irwin, M., Koposov, S., Korn, A., Lanzafame, A., Pancino, E., Paunzen, E., Recio-Blanco, A., Sacco, G., Smiljanic, R., Van Eck, S., Walton, N., Aden, D., Aerts, C., Affer, L., Alcala, J.-M., Altavilla, G., Alves, J., Antoja, T., Arenou, F., Argiroffi, C., Asensio Ramos, A., Bailer-Jones, C., Balaguer-Nunez, L., Bayo, A., Barbuy, B., Barisevicius, G., Barrado y Navascues, D., Battistini, C., Bellas Velidis, I., Bellazzini, M., Belokurov, V., Bergemann, M., Bertelli, G., Biazzo, K., Bienayme, O., Bland-Hawthorn, J., Boeche, C., Bonito, S., Boudreault, S., Bouvier, J., Brandao, I., Brown, A., de Bruijne, J., Burleigh, M., Caballero, J., Caffau, E., Calura, F., Capuzzo-Dolcetta, R., Caramazza, M., Carraro, G., Casagrande, L., Casewell, S., Chapman, S., Chiappini, C., Chorniy, Y., Christlieb, N., Cignoni, M., Cocozza, G., Colless, M., Collet, R., Collins, M., Correnti, M., Covino, E., Crnojevic, D., Cropper, M., Cunha, M., Damiani, F., David, M., Delgado, A., Duffau, S., Edvardsson, B., Eldridge, J., Enke, H., Eriksson, K., Evans, N. W., Eyer, L., Famaey, B., Fellhauer, M., Ferreras, I., Figueras, F., Fiorentino, G., Flynn, C., Folha, D., Franciosini, E., Frasca, A., Freeman, K., Fremat, Y., Friel, E., Gaensicke, B., Gameiro, J., Garzon, F., Geier, S., Geisler, D., Gerhard, O., Gibson, B., Gomboc, A., Gomez, A., Gonzalez-Fernandez, C., Gonzalez Hernandez, J., Gosset, E., Grebel, E., Greimel, R., Groenewegen, M., Grundahl, F., Guarcello, M., Gustafsson, B., Hadrava, P., Hatzidimitriou, D., Hambly, N., Hammersley, P., Hansen, C., Haywood, M., Heber, U., Heiter, U., Held, E., Helmi, A., Hensler, G., Herrero, A., Hill, V., Hodgkin, S., Huelamo, N., Huxor, A., Ibata, R., Jackson, R., de Jong, R., Jonker, P., Jordan, S., Jordi, C., Jorissen, A., Katz, D., Kawata, D., Keller, S., Kharchenko, N., Klement, R., Klutsch, A., Knude, J., Koch, A., Kochukhov, O., Kontizas, M., Koubsky, P., Lallement, R., de Laverny, P., van Leeuwen, F., Lemasle, B., Lewis, G., Lind, K., Lindstrom, H. P. E., Lobel, A., Lopez Santiago, J., Lucas, P., Ludwig, H., Lueftinger, T., Magrini, L., Maiz Apellaniz, J., Maldonado, J., Marconi, G., Marino, A., Martayan, C., Martinez-Valpuesta, I., Matijevic, G., McMahon, R., Messina, S., Meyer, M., Miglio, A., Mikolaitis, S., Minchev, I., Minniti, D., Moitinho, A., Momany, Y., Monaco, L., Montalto, M., Monteiro, M. J., Monier, R., Montes, D., Mora, A., Moraux, E., Morel, T., Mowlavi, N., Mucciarelli, A., Munari, U., Napiwotzki, R., Nardetto, N., Naylor, T., Naze, Y., Nelemans, G., Okamoto, S., Ortolani, S., Pace, G., Palla, F., Palous, J., Parker, R., Penarrubia, J., Pillitteri, I., Piotto, G., Posbic, H., Prisinzano, L., Puzeras, E., Quirrenbach, A., Ragaini, S., Read, J., Read, M., Reyle, C., De Ridder, J., Robichon, N., Robin, A., Roeser, S., Romano, D., Royer, F., Ruchti, G., Ruzicka, A., Ryan, S., Ryde, N., Santos, N., Sanz Forcada, J., Sarro Baro, L. M., Sbordone, L., Schilbach, E., Schmeja, S., Schnurr, O., Schoenrich, R., Scholz, R.-D., Seabroke, G., Sharma, S., De Silva, G., Smith, M., Solano, E., Sordo, R., Soubiran, C., Sousa, S., Spagna, A., Steffen, M., Steinmetz, M., Stelzer, B., Stempels, E., Tabernero, H., Tautvaisiene, G., Thevenin, F., Torra, J., Tosi, M., Tolstoy, E., Turon, C., Walker, M., Wambsganss, J., Worley, C., Venn, K., Vink, J., Wyse, R., Zaggia, S., Zeilinger, W., Zoccali, M., Zorec, J., Zucker, D., and Zwitter, T.

Subjects
spectroscopy, stars, kinematics, abundances, Settore FIS/05 - Astronomia E Astrofisica, Astrophysics::Instrumentation and Methods for Astrophysics, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

The Gaia-ESO Public Spectroscopic Survey has begun and will obtain high quality spectroscopy of some 100000 Milky Way stars, in the field and in open clusters, down to magnitude 19, systematically covering all the major components of the Milky Way. This survey will provide the first homogeneous overview of the distributions of kinematics and chemical element abundances in the Galaxy. The motivation, organisation and implementation of the Gaia-ESO Survey are described, emphasising the complementarity with the ESA Gaia mission. Spectra from the very first observing run of the survey are presented.

188. A Goodness of Fit Test for Multivariate Normality

Author

SYRACUSE UNIV N Y, Hensler,G. L., Mehrotra,K. G., Michalek,J. E., SYRACUSE UNIV N Y, Hensler,G. L., Mehrotra,K. G., and Michalek,J. E.

Abstract

A goodness of fit test for multivariate normality is developed. The test procedure reduces the composite null hypothesis to a simple null hypothesis that requires one to test uniformity of a set of observations between 0 and 1.

Published
1976

189. Kinematically Decoupled Cores in Dwarf (Elliptical) Galaxies

Author

Toloba, E., Peletier, R. F., Guhathakurta, P., Ven, G., Samuel Boissier, Boselli, A., Den Brok, M., Falcon-Barroso, J., Hensler, G., Janz, J., Laurikainen, E., Lisker, T., Paudel, S., Rys, A., Salo, H., and Kapteyn Astronomical Institute

Subjects
Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

An overview is given of what we know about the frequency of kinematically decoupled cores in dwarf elliptical galaxies. New observations show that kinematically decoupled cores happen just as often in dwarf elliptical as in ordinary early-type galaxies. This has important consequences for the formation of kinematically decoupled cores. Our currently most popular theory for kinematically decoupled cores in dwarf ellipticals is that they were formed in a poor group environment or in isolation, and subsequent fell into the cluster environment where star formation was quenched.

192. Dust in Cluster Dwarf Elliptical Galaxies

Author

Papaderos, P, Recchi, S, Hensler, G, De Looze, I., Baes, M., Fritz, J., Verstappen, J., Bendo, G. J., Bianchi, S., Bomans, D. J., Boselli, A., Clemens, M., Corbelli, E., Cortese, L., Dariush, A., Davies, J. I., di Serego Alighieri, S., Fadda, D., Garcia-Appadoo, D. A., Gavazzi, G., Giovanardi, C., Grossi, M., Hughes, T. M., Hunt, L. K., Jones, A. P., Madden, S., Magrini, L., Pierini, D., Pohlen, M., Sabatini, S., Smith, Matthew, Vlahakis, C., Xilouris, E. M., Zibetti, S., Papaderos, P, Recchi, S, Hensler, G, De Looze, I., Baes, M., Fritz, J., Verstappen, J., Bendo, G. J., Bianchi, S., Bomans, D. J., Boselli, A., Clemens, M., Corbelli, E., Cortese, L., Dariush, A., Davies, J. I., di Serego Alighieri, S., Fadda, D., Garcia-Appadoo, D. A., Gavazzi, G., Giovanardi, C., Grossi, M., Hughes, T. M., Hunt, L. K., Jones, A. P., Madden, S., Magrini, L., Pierini, D., Pohlen, M., Sabatini, S., Smith, Matthew, Vlahakis, C., Xilouris, E. M., and Zibetti, S.

Abstract

Based on single cross-scan data of the Herschel Virgo Cluster Survey, we report the first detections of dust in cluster early-type dwarf galaxies: VCC 209, VCC 781 and VCC 951. All three galaxies have dust masses Md ≈ 105 − 106 M⊙ and average dust temperatures ≈ 16–20 K. Since these three early-type dwarfs reside in densely crowded regions close to the center of the Virgo cluster, and several Hi-detected dwarfs in the outskirts of Virgo were not detected by Herschel(implying a dust content < 104 M⊙), this might imply that dust in dwarfs is more closely related to the molecular gas, which is more centrally peaked in a galaxy’s potential well and therefore, not easily removed by any stripping mechanism. We conclude that the removal of interstellar dust from these early-type dwarfs appears to be less efficient than the removal of the Hi gas.

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