Name: Abraham C.-L. Chian

Institution: INPE/MCT

e-mail: achian(no-spam )dge.inpe.br

Partner Contry: BRA

Science Meeting: Yes

User Meeting: No

NGO Staff Meeting: No

Presentation: Yes

Format: Poster

Title: Galactic winds of high-redshift star forming galaxies

Co-author: Abraham C.-L. Chian (1) and Chenggang Shu (2)

Co-authors' Institutions: (1) National Institute for Space Research (INPE) and World Institute for Space Environment Research (WISER), P. O. Box 515, Sao Jose dos Campos-SP 12227-010, Brazil (2) Joint Center for Astrophysics, Shanghai Normal University, Shanghai 200030, China

Abstract:

Galactic-scale bulk motions of gas such as galactic winds and mass outflows (superwinds) have been observed in high-redshift star forming galaxies. For example, Gemini Near Infrared Spectrograph (GNIS) obtained recently observational evidence of shock-ionization due to galactic winds of a red star forming galaxy (van Dokkum et al. 2005). These superwinds are believed to be powered by kinetic energy from supernova explosions, and may change the thermal and chemical properties of the intergalactic medium that forms galaxies. Hence, the understanding of superwinds is essential for understanding the formation of star forming galaxies. In this work, we discuss some theoretical works of superwinds that can shed light to the Gemini obervations of high-redshift star forming galaxies. First, we discuss an analytic model of galactic winds and mass outflows (Shu et al. 2005) to interpret the observations of superwinds which allows the prediction of how the properties of a superwind, such as wind velocity and mass outflow rate, are related to the properties of its star-forming host galaxy, such as size, gas density and star formation rate. This model predicts a threshold of star forming rate density for the generation of observable galactic winds. Galaxies with more concentrated star formation activities produce superwinds with higher velocities. The predicted mass outflow rates are comparable to the corresponding star formation rates. We apply this model to high-redshift Lyman break galaxies and find its predictions to be in good agreement with current observations. Next, we discuss a chaotic model of MHD turbulence in astrophysical winds based on a recent study of Alfven intermittent turbulence driven by chaos in the solar wind (Chian et al. 2006) in order to understand the observations of turbulence in galactic winds and mass outflows. The chaotic nature of astrophysical winds is studied by a nonlinear model of Alfven waves by solving numerically the derivative nonlinear Schroedinger equation. A bifurcation diagram is constructed to identify two types of Alfven chaos related to type-I intermittency and crisis-induced intermittency. We show that an Alfven chaotic attractor is composed of unstable structures (chaotic saddles and unstable periodic orbits) and explain the links between these unstable structures and Alfven intermittency. The role of Alfven intermittent turbulence in superwinds will be analyzed. A. C.-L. Chian, Y. Kamide, E. L. Rempel, W. M. Santana. On the chaotic nature of solar-terrestrial environment: interplanetary Alfven intermittency. J. Geophys. Res. - Space Phys. 111: A07S03, 10.1029 (2006). C.-G. Shu, H.-J. Mo, S.-D. Mao. An analytic model of galactic winds and mass outflows. Chin. J. Astron. Astrophys. 5, 327 (2005). P. G. van Dokkum, M. Kriek, B. Rodgers, M. Frank. Gemini Near Infrared Spectrograph observations of a red star forming galaxy at z=2.225: evidence for shock-ionization due to a galactic wind. ApJ 622, L13 (2005).

Comments: