R-band imaging of the host galaxies of RGB BL Lacertae objects

Free access article

Issue		A&A Volume 400, Number 1, March II 2003


Page(s)		95 - 118
Section		Galactic structure and dynamics
DOI		http://dx.doi.org/10.1051/0004-6361:20021861

A&A 400, 95-118 (2003)
DOI: 10.1051/0004-6361:20021861

R-band imaging of the host galaxies of RGB BL Lacertae objects

K. Nilsson¹, T. Pursimo¹, J. Heidt², L. O. Takalo¹, A. Sillanpää¹ and W. Brinkmann³

¹ Tuorla Observatory, Väisäläntie 20, 21500 Piikkiö, Finland
² Landessternwarte Heidelberg, Königstuhl, 69117 Heidelberg, Germany
³ Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse, 85740 Garching, Germany

(Received 23 August 2002 / Accepted 16 December 2002 )

Abstract
We present optical R-band images of 100 BL Lacertae objects in the ROSAT-Green Bank (RGB) sample obtained at the Nordic Optical Telescope (NOT). For 62 objects we could not find any previously published images in the literature, of these 35 are new BL Lacs discovered during the RGB BL Lac survey. We were able to resolve the host galaxy in 62% of the objects. We analyze the host galaxies using a two-dimensional fitting procedure and tabulate the best-fit core magnitude and host galaxy parameters (magnitude, effective radius, ellipticity, position angle and shape parameter $\beta$ ) for each object. With two exceptions, all objects are better fit by a model representing an elliptical galaxy ( $\beta = 0.25$ ) than by a disk galaxy model ( $\beta = 1.0$ ). In the two exceptions the disk host fit is only marginally better than the elliptical host fit, however, and we do not find a single clear example of a disk-dominated host galaxy. The host galaxies have an average brightness $M_{R}= -23.9 \pm 0.8$ and average effective radius $r_{\rm eff} = 13.2 \pm 0.8$ kpc. Their bulk properties are indistinguishable from normal elliptical and radio galaxies. The median $\beta$ is 0.18, well below the value 0.25 that is normally used to describe ellipticals. However, the difference may be caused by a selection effect due to the dependence of $\beta$ on host galaxy luminosity.

Key words: BL Lacertae objects: general -- galaxies: nuclei -- galaxies: structure

Offprint request: K. Nilsson, kani@astro.utu.fi

SIMBAD Objects

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.