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Deep multiband surface photometry on a sample of 24 blue compact galaxies - I
Stockholm University, Faculty of Science, Department of Astronomy.
Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
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2013 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 431, no 1, 102-144 p.Article in journal (Refereed) Published
Abstract [en]

We present deep optical and near-infrared (NIR) UBVRIHKs imaging data for 24 blue compact galaxies (BCGs). The individual exposure times are on average similar to 40 min in the optical (B) and similar to 90 min in the NIR, but on occasion up to similar to 5 h for a single target and filter, observed with 2.5, 3.5, 8.2-m telescopes. The sample contains luminous dwarf and intermediate-mass BCGs which are predominantly metal poor, although a few have near-solar metallicities. We have analysed isophotal and elliptical integration surface brightness and colour profiles, extremely deep (mu(B) less than or similar to 29 mag arcsec(-2)) contour maps and RGB images for each galaxy in the sample, and provide a morphological classification where such is missing. 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 M-B greater than or similar to -18. For a number of galaxies we discover a distinct LSB component dominant around and beyond the Holmberg radius. For the specific case of ESO 400-43A&B we detect an optical bridge between the two companion galaxies at the mu(V) similar to 28th mag arcsec(-2) isophotal level. Synthetic disc tests are performed to verify that we can trace such faint components with negligible errors down to mu(B) = 28 and mu(K) = 23 mag arcsec(-2). By examining the structural parameters (central surface brightness mu(0) and scalelength h(r)) 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 mu(0) and h(r) of the BCGs host deviate from those of dwarf ellipticals (dEs) 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, mu(B) = 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.

Place, publisher, year, edition, pages
2013. Vol. 431, no 1, 102-144 p.
Keyword [en]
galaxies: fundamental parameters, galaxies: irregular, galaxies: photometry, galaxies: starburst
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:su:diva-90774DOI: 10.1093/mnras/stt146ISI: 000318343600034OAI: oai:DiVA.org:su-90774DiVA: diva2:628713
Funder
Swedish Research Council, 2011-5349Knut and Alice Wallenberg Foundation
Note

AuthorCount:8;

Available from: 2013-06-14 Created: 2013-06-11 Last updated: 2017-12-06Bibliographically approved
In thesis
1. Unveiling the nature of blue compact galaxies
Open this publication in new window or tab >>Unveiling the nature of blue compact galaxies
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Blue compact galaxies (BCGs) are gas-rich star-forming low redshift galaxies with low metallicities. In some cases the relative strength of the starburst can be so high that it completely dominates the light output of the galaxy, an obstacle which has been countered by deeper optical imaging data and observations in the near infra-red (NIR) regime. This has revealed an older population referred to as the "host". In an effort to study the hosts of BCGs we have analyzed new and extremely deep UBVRIHKs imaging data for 46 high and low luminosity BCGs. For several BCGs the data reveal previously undetected extended low surface brightness components beyond the μB~26 mag arcsec-2 isophote. These are predominantly the luminous BCGs in the sample, and they show tails, plumes, optical bridges between companion galaxies, and other signs of merging or strong tidal interactions. The low luminosity BCGs, on the other hand, are well represented by an exponential disk profile down to the reliability limit of the data at a surface brightness level of μB~28 mag arcsec-2.

The burst and host populations are examined separately. The integrated colors of both are compared to predictions from spectral evolutionary models, giving an indication of their respective ages and metallicities. Our analysis suggests that for the luminous BCGs a strong contribution by nebular emission is present almost down to the Holmberg radius, invalidating the host structural parameters obtained from brighter isophotes. Possible evolutionary links to quiescent galaxies like dEs, dIs, and LSBGs are explored by examining the structural parameters derived from two radial ranges typically assumed to be dominated by the underlying host galaxy. In this parameter space the luminous BCGs in our sample deviate from their low luminosity counterparts and from BCG data in the literature. They are instead consistent with the structural properties of giant low surface brightness galaxies with central surface brightnesses μB≥23 mag arcsec-2. We further examine the asymmetry and concentration parameters for the sample and study the correlation between the minimum asymmetry distribution in the optical and NIR vs morphological class, concentration and integrated colors to identify mergers/tidally interacting galaxies. A shift in the asymmetry distribution occurs for low luminosity BCGs from the optical to the NIR. In contrast, we find that the flocculent asymmetry component (due to star formation) completely dominates the composite asymmetry of high luminosity BCGs. We introduce an alternative asymmetry measure which successfully traces the dynamical asymmetry component (due to merging/tidal interaction) of the host.  

Place, publisher, year, edition, pages
Stockholm: Department of Astronomy, Stockholm University, 2012. 45 p.
Keyword
blue compact galaxies, starbursts, host galaxy, stellar populations, surface photometry, optical and NIR broadband
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Astronomy
Identifiers
urn:nbn:se:su:diva-75765 (URN)978-91-7447-525-8 (ISBN)
Public defence
2012-06-01, sal FB 55, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Manuscript. Paper 5: Manuscript.

Available from: 2012-05-11 Created: 2012-04-26 Last updated: 2013-11-19Bibliographically approved

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Micheva, GenovevaÖstlin, GöranZackrisson, ErikMarquart, Thomas
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