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Stellar dynamics of blue compact galaxies - II. Further indications of a merger in ESO 338-IG04
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Astronomy and Space Physics.
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2008 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, Vol. 479, no 3, 725-733 p.Article in journal (Refereed) Published
Abstract [en]

Context. Luminous blue compact galaxies, common at z similar to 1 but now relatively rare, show disturbed kinematics in emission lines. Aims. As part of a programme to understand their formation and evolution, we have investigated the stellar dynamics of a number of nearby objects in this class. Methods. We obtained long-slit spectra with VLT/FORS2 in the spectral region covering the near-infrared calcium triplet. In this paper we focus on the well-known luminous blue compact galaxy ESO338-IG04 (Tololo 1924 - 416). A previous investigation, using Fabry-Perot interferometry, showed that this galaxy has a chaotic Ha velocity field, indicating that either the galaxy is not in dynamical equilibrium or that Ha does not trace the gravitational potential due to feedback from star formation. Results. Along the apparent major axis, the stellar and ionised gas velocities for the most part follow each other. The chaotic velocity field must therefore be a sign that the young stellar population in ESO338-IG04 is not in dynamical equilibrium. The most likely explanation, which is also supported by its morphology, is that the galaxy has experienced a merger and that this has triggered the current starburst. Summarising the results of our programme so far, we note that emission-line velocity fields are not always reliable tracers of stellar motions, and go on to assess the implications for kinematic studies of similar galaxies at intermediate redshift.

Place, publisher, year, edition, pages
2008. Vol. 479, no 3, 725-733 p.
Keyword [en]
galaxies : evolution, galaxies : kinematics and dynamics, galaxies : individual : ESO338-IG04, galaxies : starburst, galaxies : interactions
National Category
Physical Sciences
URN: urn:nbn:se:uu:diva-112414DOI: 10.1051/0004-6361:20078916ISI: 000253454600011OAI: oai:DiVA.org:uu-112414DiVA: diva2:286174
Available from: 2010-01-14 Created: 2010-01-13 Last updated: 2013-01-23
In thesis
1. Star-forming Dwarf Galaxies: Internal motions and evolution
Open this publication in new window or tab >>Star-forming Dwarf Galaxies: Internal motions and evolution
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The study of dwarf galaxies is important in order to better understand the physics of the young universe and how larger galaxies form and evolve. In this work we focus on Blue Compact Galaxies (BCGs) which havemuch enhanced star formation (starbursts), causing blue colours and strong emission line spectra.

Investigating of the inner motions of BCGs provides a means for determining masses and understanding what triggered the current starburst. We have used the Very Large Telescope to perform challenging observations of the stellar motions in several BCGs, as seen in the near-infrared Ca-triplet absorption lines. By comparing these to the kinematics of the ionized interstellar medium, we were able to look into the role of feeback from stellar winds and supernova explosions, as well as further strengthen the notion that the merging of galaxies plays an important role.

Spatially resolved spectroscopy can yield information about the 3D-structure of galaxies. We have used a Fabry-Perot interferometer to study the kinematics of the interstellar medium in two samples of galaxies, each containing about twenty objects. We find strong indications for ongoing galaxy mergers that correlate well with the strength of the star-formation activity. Furthermore, by estimating dynamical masses, BCGs are shown to be on average not dynamically supported by rotation.

In addition, we have used data from the Sloan Digital Sky Survey to study the frequency of starbursts in the local universe and the connection to their descendants. We selected starbursts by the strength of emission in H-alpha, the first Balmer recombination line, and post-starbursts by the strength of absorption in H-delta. These are indicators of currently ongoing and recent, on the order of 100 Myr, star-formation, respectively. By modelling the stellar populations we derive ages and masses and can establish a link between starbursts and postbursts in a time sequence. We find that starbursts are active on a 100 Myr timescale but are rare objects in the local universe.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. 27 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 977
Galaxy, Galaxies, Dynamics, Kinematics, Starburst, Dwarf Galaxies, Blue Compact Galaxies, Star Formation, Galaxy mergers, 3D-Spectroscopy, Spectroscopy
National Category
Astronomy, Astrophysics and Cosmology
Research subject
urn:nbn:se:uu:diva-181481 (URN)978-91-554-8483-5 (ISBN)
Public defence
2012-11-12, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Available from: 2012-10-19 Created: 2012-09-24 Last updated: 2013-01-23Bibliographically approved

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