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The Subaru Seminar is usually held in Room 104 of the Hilo Base Facility, adjacent to the main lobby. Everyone is welcome to attend. If you are interested in giving a seminar, please contact Subaru seminar organizers (Tae-Soo Pyo, Sherry Yeh, Nagayoshi Ohashi) by email : (please change"_at" to @).

February 14, Friday, at 11:00 am

" Deep multiband surface photometry on 45 star forming BCGs "

Genoveva Micheva

(Subaru Telescope)

We present deep optical and near--infrared (NIR) UBVRIHKs imaging data for 24 blue compact galaxies (BCGs) and a volume--limited subsample of 21 UM emission line galaxies. The data contain luminous dwarf and intermediate-mass BCGs, as well as low-mass, faint and compact targets. Most galaxies are metal-poor, although a few have near-solar metallicities. We have analyzed isophotal and elliptical integration surface brightness and color profiles, extremely deep (uB<~29 mag arcsec^-2) contour maps and RGB images for each galaxy in the sample, and provide a morphological classification where such is missing. We have measured the total galaxy colors, the colors of the underlying host galaxy, and the colors of the burst, and compare these to the predictions of new state-of-the-art spectral evolutionary models (SEMs) both with and without contribution by nebular emission. Synthetic disk tests are performed to verify that we can trace such faint components with negligible errors down to uB=28 mag arcsec^-2 and uK=23 mag arcsec^-2. Separating the burst from the underlying host, we find that regardless of the total luminosity the host galaxy has the properties of a low surface brightness (LSB) dwarf with MB>~-18. For a number of galaxies we discover a distinct LSB component dominant around and beyond the Holmberg radius. For the specific case of ESO400 43A&B we detect an optical bridge between the two companion galaxies at the uV~28th mag arcsec^-2 isophotal level. By examining the structural parameters (central surface brightness u0 and scale length hr) derived from two radial ranges typically assumed to be dominated by the underlying host galaxy, we demonstrate the importance of sampling the host well away from the effects of the burst. We find that u0 and hr of the BCGs host deviate from those of dwarf ellipticals (dE) and dwarf irregulars (dI) solely due to a strong burst contribution to the surface brightness profile almost down to the Holmberg radius. Structural parameters obtained from a fainter region, uB=26-28 mag arcsec^-2, are consistent with those of true LSB galaxies for the starbursting BCGs in our sample, and with dEs and dIs for the BCGs with less vigorous star formation. We further measure and analyse the A180 asymmetry and the concentration index C in all filters. A shift in the average A180 asymmetry is detected from optical to NIR. This shift appears correlated with the morphological class of the BCGs. Using the color-asymmetry relation, we identify some BCGs as undergoing mergers, which is confirmed by their morphological class. Though clearly separated from normal galaxies in the concentration--asymmetry parameter space, we find that it is not possible to distinguish luminous starbursting BCGs from the merely star forming low luminosity BCGs.

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