Strange Hosts of Blue Compact Galaxies

DOI: 10.1007/10995020_58

ABSTRACT Luminous Blue Compact Galaxies (BCGs) have low metallicities, high gas consumption rates and are frequently involved in mergers.
These are properties characteristic of young galaxies in the hierarchical formation scenario. Local BCGs can therefore be
used as a complement to high redshift studies provided that the evolution of BCGs can be understood in more detail and be
applied to early galaxy formation. Although much is known about the central starburst, few studies discuss the relation between
the starburst and the progenitor, or the “host galaxy” of the starburst. Here we report of an effort to derive information
about the host from the colours of the faint halo.

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    ABSTRACT: Aims: We present deep surface photometry of a volume-limited sample of 21 UM emission line galaxies in broadband optical UBVRI and near infrared (NIR) HKs filters. The sample comprises 19 blue compact galaxies (BCGs) and two spirals. Methods: We separated the burst and host populations for each galaxy and compared them to stellar evolutionary models with and without nebular emission contribution. We measured and analyzed the A180 asymmetry in all filters, the concentration index C, the scale length, and the central surface brightness of the host galaxy. Results: A shift in the average A180 asymmetry is detected from optical to NIR. This shift seems correlated with the morphological class of the BCGs. Using the color-asymmetry relation, we identify five BCGs in the sample as 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. Reduced images (FITS files) are only available at the CDS via anonymous ftp to ( or via
    Astronomy and Astrophysics 08/2013; · 5.08 Impact Factor
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    ABSTRACT: Optical and near-IR surface photometry of the halos of edge-on disk galaxies and blue compact galaxies have revealed a very red spectral energy distribution, which cannot easily be reconciled with normal, metal-poor stellar populations like that in the stellar halo of the Milky Way. Using spectral evolutionary models, we demonstrate that a stellar population of low to intermediate metallicity, but with an extremely bottom-heavy initial mass function, can explain the red halos around both types of objects. Other previously suggested explanations, like nebular emission or very metal-rich stars, are shown to fail in this respect. This indicates that, if the reported halo colours are correct, halo populations dominated by low-mass stars may be a phenomenon common to galaxies of very different Hubble types. Potential tests of this hypothesis are discussed, along with its implications for the baryonic dark matter content of galaxies. We also report on the status of searches for red halos around types of galaxies for which this phenomenon has not yet been reported (post-starbursts, ellipticals and low surface brightness galaxies).
    Proceedings of the International Astronomical Union 01/2007; 235:148-148.
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    ABSTRACT: Deep optical/near-IR surface photometry of galaxies outside the Local Group have revealed the existence of faint and very red halos around objects as diverse as spirals and blue compact galaxies. The colors of these structures are much too extreme to be reconciled with resolved stellar populations like those seen in the halos of the Milky Way or M 31, and alternative explanations like dust reddening, high metallicities or nebular emission are also disfavored. A stellar population obeying an extremely bottom-heavy initial mass function, similar to that recently reported for the LMC field population, is on the other hand consistent with all available data. Because of its high mass-to-light ratio, such a population would effectively behave as baryonic dark matter and could account for some of the baryons still missing from local inventories. Here, we report on a number of recent developments in this field.