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The Lyman Alpha Reference Sample: IX. Revelations from deep surface photometry
Univ Michigan, 311 West Hall,1085 S Univ Ave, Ann Arbor, MI 48109 USA.
Stockholm Univ, Dept Astron, Stockholm Observ, S-10691 Stockholm, Sweden.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Observational Astronomy.ORCID iD: 0000-0003-1096-2636
Stockholm Univ, Dept Astron, Stockholm Observ, S-10691 Stockholm, Sweden.
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2018 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 615, article id A46Article in journal (Refereed) Published
Abstract [en]

Context. The Lyman alpha Reference Sample (LARS) of 14 star-forming galaxies offers a wealth of insight into the workings of these local analogs to high-redshift star-forming galaxies. The sample has been well-studied in terms of Ly alpha and other emission line properties, such as H I mass, gas kinematics, and morphology. Aims. We analyze deep surface photometry of the LARS sample in UBIK broadband imaging obtained at the Nordic Optical Telescope and the Canada-France-Hawaii Telescope, and juxtaposition their derived properties with a sample of local high-redshift galaxy analogs, namely, with blue compact galaxies (BCGs). Methods. We construct radial surface brightness and color profiles with both elliptical and isophotal integration, as well as RGB images, deep contours, color maps, a burst fraction estimate, and a radial mass-to-light ratio profile for each LARS galaxy. Standard morphological parameters like asymmetry, clumpiness, the Gini and M20 coefficients are also obtained and analyzed, as well as isophotal asymmetry profiles for each galaxy. In this context, we compare the LARS sample to the properties of the BCG sample and highlight the differences. Results. Several of these diagnostics indicate that the LARS galaxies have highly disturbed morphologies even at the level of the faintest outer isophotes, with no hint at a regular underlying population, as found in many BCG sample galaxies. The ground-based photometry reaches isophotes down to similar to 28 mag arcsec(-2), while the space-based data reach only similar to 26 mag arcsec(-2). The ground-based observations therefore reveal previously unexplored isophotes of the LARS galaxies. The burst fraction estimate suggests a spatially more extended burst region in LARS than in the BCGs. Comparison to stellar evolutionary models in color-color diagrams reveals complex behavior of the radial color profiles, often inconsistent with a single stellar population of any age and metallicity, but instead suggesting a mixture of at least two stellar populations with a typical young mass fraction in the range 0.1-1%. Conclusions. The galaxies in the LARS sample appear to be in earlier stages of a merger event compared to the BCGs. Standard morphological diagnostics like asymmetry, clumpiness, Gini and M20 coefficients cannot separate the two samples, although an isophotal asymmetry profile successfully captures the average difference in morphology. These morphological diagnostics do not show any correlation with the equivalent width or the escape fraction of Lyman Alpha.

Place, publisher, year, edition, pages
EDP SCIENCES S A , 2018. Vol. 615, article id A46
Keywords [en]
galaxies: evolution, galaxies: individual: LARS, galaxies: irregular, galaxies: starburst, galaxies: photometry
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:uu:diva-361271DOI: 10.1051/0004-6361/201832584ISI: 000438137300001OAI: oai:DiVA.org:uu-361271DiVA, id: diva2:1253747
Funder
Swedish Research CouncilSwedish National Space BoardAvailable from: 2018-10-05 Created: 2018-10-05 Last updated: 2018-10-05Bibliographically approved

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Zackrisson, Erik

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