Statistics of galaxy warps in the HDF North and South

¹ Astronomical Institute of St. Petersburg State University, 198504 St. Petersburg, Russia
² Isaac Newton Institute of Chile, St. Petersburg Branch, Russia
³ Depto. Física Teórica y del Cosmos, Universidad de Granada, Spain
⁴ DEMIRM, Observatoire de Paris, 61 Av. de l'Observatoire, 75014 Paris, France
⁵ Groningen Kapteyn Laboratorium, Groningen, The Netherlands

Corresponding author: V. P. Reshetnikov, resh@astro.spbu.ru

Received: 6 September 2001
Accepted: 12 November 2001

Abstract

We present a statistical study of the presence of galaxy warps in the Hubble deep fields. Among a complete sample of 45 edge-on galaxies above a diameter of 13, we find 5 galaxies to be certainly warped and 6 galaxies as good candidates. In addition, 4 galaxies reveal a characteristic U-warp. Compared to statistical studies of local warps, and taking into account the strong bias against observing the outer parts of galaxies at high redshift, these numbers point towards a very high frequency of warps at : almost all galaxy discs might be warped. Furthermore, the amplitude of warps are stronger than for local warps. This is easily interpreted in terms of higher galaxy interactions and matter accretion in the past. This result supports these two mechanisms as the best candidates for the origin of early warps. The mean observed axis ratio of our sample of edge-on galaxies is significantly larger in the high-z sample than is found for samples of local spiral galaxies. This might be due to disk thickening due to more frequent galaxy interactions.