| 1. |
- Micheva, Genoveva, et al.
(författare)
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Deep V and K band photometry of the host galaxy of Haro 11
- 2009
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Konferensbidrag (populärvet., debatt m.m.)abstract
- Previous studies of the host galaxy of Haro 11 have suggested an extreme red color of V-K=4.2+-0.8 which cannot be reconciled with any normal stellar population of reasonable metallicity. We present the deepest V and K band data to date of the blue compact galaxy (BCG) Haro 11 and derive a new V-K color for the host. Our new data suggest a much more modest value of V-K=2.3+-0.2, which is in the same range as V-K colors measured for several other BCGs. The new Haro 11 color is not abnormally red and can be attributed to an old metal-poor stellar population with a Salpeter initial mass function.
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| 2. |
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| 3. |
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| 4. |
- Zackrisson, Erik, et al.
(författare)
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How the extinction of extragalactic background light affects surface photometry of galaxies, groups and clusters
- 2009
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 397:4, s. 2057-2069
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Tidskriftsartikel (refereegranskat)abstract
- The faint regions of galaxies, groups and clusters hold important clues about how these objects formed, and surface photometry at optical and near-infrared wavelengths represents a powerful tool for studying such structures. Here, we identify a hitherto unrecognized problem with this technique, related to how the night sky flux is typically measured and subtracted from astronomical images. While most of the sky flux comes from regions between the observer and the target object, a small fraction - the extragalactic background light (EBL) - comes from behind. We argue that since this part of the sky flux can be subjected to extinction by dust present in the galaxy/group/cluster studied, standard reduction procedures may lead to a systematic oversubtraction of the EBL. Even very small amounts of extinction can lead to spurious features in radial surface brightness profiles and colour maps of extended objects. We assess the likely impact of this effect on a number of topics in extragalactic astronomy where very deep surface photometry is currently attempted, including studies of stellar haloes, starburst host galaxies, disc truncations and diffuse intragroup/intracluster light. We argue that EBL extinction may provide at least a partial explanation for the anomalously red colours reported for the haloes of disc galaxies and for the hosts of local starburst galaxies. EBL extinction effects also mimic truncations in discs with unusually high dust opacities, but are unlikely to be the cause of such features in general. Failure to account for EBL extinction can also give rise to a non-negligible underestimate of intragroup and intracluster light at the faintest surface brightness levels currently probed. Finally, we discuss how EBL extinction effects may be exploited to provide an independent constraint on the surface brightness of the EBL, using a combination of surface photometry and direct star counts.
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| 7. |
- Zackrisson, Erik, et al.
(författare)
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The Red Halo Phenomenon
- 2006
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 650:2, s. 812-817
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Tidskriftsartikel (refereegranskat)abstract
- Optical and near-IR observations of the halos of disk galaxies and blue compact galaxies have revealed a very red spectral energy distribution that cannot easily be reconciled with a normal, metal-poor stellar population such as that in the stellar halo of the Milky Way. Here spectral evolutionary models are used to explore the consequences of these observations. 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, such as nebular emission or very metal-rich stars, are shown to fail in this respect. This indicates that if the reported halo colors 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.
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| 8. |
- Zackrisson, Erik, et al.
(författare)
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The Red Halos of Disk Galaxies
- 2008
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Ingår i: Formation and Evolution of Galaxy Disks. ; , s. 229-230
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 9. |
- Zackrisson, Erik, et al.
(författare)
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The Red Halos of Galaxies
- 2007
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Ingår i: Galaxy Evolution Across the Hubble Time.
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Konferensbidrag (populärvet., debatt m.m.)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 thisphenomenon has not yet been reported (post-starbursts, ellipticals and low surface brightness galaxies).
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