Volume 554, June 2013
|Number of page(s)||13|
|Published online||17 June 2013|
WSRT observations and surface photometry of two unusual spiral galaxies⋆
Moscow M.V. Lomonosov State University, Sternberg Astronomical Institute,
Universitetskii pr. 13,
2 Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA Dwingeloo, The Netherlands
3 Argelander – Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany
4 New Mexico State University and Apache Point Observatory, Sunspot, NM 88349, USA
Received: 13 December 2012
Accepted: 30 April 2013
We discuss the results of a mass decomposition of two spiral galaxies, NGC 6824 and UGC 11919. In a previous analysis of the Hyperleda catalog, the galaxies were identified as having a peculiar dynamical mass-to-light ratio. The aim of this study is to confirm or disprove the preliminary findings, indicating a non-standard stellar initial mass function (IMF) for the galaxies. The surface photometry in B,V, and R bands was carried out with the Apache Point 0.5-m telescope and the H I data cubes were obtained with the Westerbork Synthesis Radio Telescope (WSRT). Photometric profiles were decomposed into bulge and exponential disk components. Using the obtained H I data cubes, rotation curves of both galaxies were constructed. Employing the photometric profiles, the mass distribution of the galaxies was decomposed into mass components: bulge, stellar disk, gas, and pseudo-isothermal dark halo. We conclude that NGC 6824 possesses a stellar disk with mass-to-light ratio (M/LB)disk = 2.5, in agreement with its color (B − V)0. On the contrary, UGC 11919 appears to have a very lightweight disk. Its dynamically estimated mass corresponds to a low stellar disk mass-to-light ratio (M/LB)disk ≈ 0.5. Under standard assumptions, this ratio does not agree with the relatively red color of the disk, while a bottom light stellar initial mass function is needed to explain the observations.
Key words: galaxies: kinematics and dynamics / galaxies: individual: NGC 6824 / galaxies: structure / galaxies: photometry / galaxies: spiral / galaxies: individual: UGC 11919
FITS files of H I data cubes are available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (18.104.22.168) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/554/A128
© ESO, 2013
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