Open AccessKinematical signatures of hidden stellar discs
Author(s) -
Magorrian John
Publication year - 1999
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.1999.02135.x
Subject(s) - physics , surface brightness , galaxy , astrophysics , rotational symmetry , bulge , brightness , line of sight , range (aeronautics) , astronomy , mechanics , materials science , composite material
The deprojection of the surface brightness distribution of an axisymmetric galaxy does not have a unique solution unless the galaxy is viewed precisely edge‐on. I present an algorithm that finds the full range of smooth axisymmetric density distributions consistent with a given surface brightness distribution and inclination angle, and use it to investigate the effects of this non‐uniqueness on the line‐of‐sight velocity profiles (VPs) of two‐integral models of both real and toy discy galaxies viewed at a range of inclination angles. Photometrically invisible face‐on discs leave very clear signatures in the minor‐axis VPs of the models (Gauss‐‐Hermite coefficients h 4 ≥ 0.1), provided the disc‐to‐bulge ratio is greater than about 3 per cent. I discuss the implications of these hitherto neglected discs for dynamical modelling.