The structure of galactic disks

Free access article

Issue		A&A Volume 454, Number 3, August II 2006


Page(s)		759 - 772
Section		Extragalactic astronomy
DOI		http://dx.doi.org/10.1051/0004-6361:20064883

A&A 454, 759-772 (2006)
DOI: 10.1051/0004-6361:20064883

Studying late-type spiral galaxies using SDSS

M. Pohlen^{1, 2} and I. Trujillo^{3, 4}

¹ Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700 AV Groningen, The Netherlands
e-mail: pohlen@astro.rug.nl
² Instituto de Astrofísica de Canarias, C/ Via Láctea s/n, 38200 La Laguna, Tenerife, Spain
³ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
⁴ School of Physics and Astronomy, University of Nottingham, University Park, Nottingham NG7 2RD, UK
e-mail: ignacio.trujillo@nottingham.ac.uk

(Received 20 January 2006 / Accepted 26 April 2006)

Abstract
Using imaging data from the SDSS survey, we present the $g^{\prime}$ and $r^{\prime}$ radial stellar light distribution of a complete sample of ~90 face-on to intermediate inclined, nearby, late-type (Sb-Sdm) spiral galaxies. The surface brightness profiles are reliable ( $1 \sigma$ uncertainty less than 0.2 mag) down to $\mu\!\sim\!27\$ mag/ $\Box^{\prime\prime}$ . Only ~10% of all galaxies have a normal/standard purely exponential disk down to our noise limit. The surface brightness distribution of the rest of the galaxies is better described as a broken exponential. About 60% of the galaxies have a break in the exponential profile between $\sim$ 1.5-4.5 times the scalelength followed by a downbending, steeper outer region. Another ~30% shows also a clear break between $\sim$ 4.0-6.0 times the scalelength but followed by an upbending, shallower outer region. A few galaxies have even a more complex surface brightness distribution. The shape of the profiles correlates with Hubble type. Downbending breaks are more frequent in later Hubble types while the fraction of upbending breaks rises towards earlier types. No clear relation is found between the environment, as characterised by the number of neighbours, and the shape of the profiles of the galaxies.

Key words: galaxies: photometry -- galaxies: structure -- galaxies: fundamental parameters -- galaxies: evolution -- galaxies: formation

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