An assessment of the evidence from ATLAS(3D) for a variable initial mass function

作者：Clauwens Bart^*; Schaye Joop; Franx Marijn

来源：Monthly Notices of the Royal Astronomical Society, 2015, 449(4): 4091-4104.

DOI：10.1093/mnras/stv603

• galaxies: elliptical and lenticular, cD
• galaxies: fundamental parameters
• galaxies: ISM
• galaxies: kinematics and dynamics
• galaxies: luminosity function, mass function
• galaxies: stellar content

The ATLAS(3D) Survey has reported evidence for a non-universal stellar initial mass IMF) for early-type galaxies (ETGs). The IMF was constrained by comparing stellar mass measurements from kinematic data with those from spectral energy distribution (SED) fitting. Here, we investigate possible effects of scatter in the reported stellar mass measurements and their potential impact on the IMF determination. We find that a trend of the IMF mismatch parameter with the kinematic mass-to-light ratio, comparable to the trend observed by Cappellari et al., could arise if the Gaussian errors of the kinematic mass determination are typically 30 per cent. Without additional data, it is hard to separate between the option that the IMF has a true large intrinsic variation or the option that the errors in the determination are larger than anticipated. A correlation of the IMF with other properties would help to make this distinction, but no strong correlation has been found yet. The strongest correlation is with velocity dispersion. However, it has a large scatter and the correlation depends on sample selection and distance measurements. The correlation with velocity dispersion could be partly caused by the colour-dependent calibration of the surface brightness fluctuation distances of Tonry et al. We find that the K-band luminosity-limited ATLAS(3D) Survey is incomplete for the highest M/L galaxies below 10(10.3) M-circle dot. There is a significant IMF-velocity dispersion trend for galaxies with SED masses above this limit, but no trend for galaxies with kinematic masses above this limit. We also find an IMF trend with distance, but no correlation between nearest neighbour ETGs, which excludes a large environmental dependence. Our findings do not rule out the reported IMF variations, but they suggest that further study is needed.

• 出版日期2015-6-1