The influence of binary interactions on infrared passbands of populations

Abstract

In our evolutionary population synthesis models, the samples of binaries are reproduced by the 'patched' Monte Carlo simulation and the stellar masses, integrated J, H, K, L, L2 and M magnitudes, mass-to-light ratios and broad colours involving infrared bands are presented, for an extensive set of instantaneous-burst binary stellar populations. In addition, the fluctuations in the integrated colours, which have been given by Zhang et al. (2005), are reduced. By comparing the results for binary stellar populations with (Model A) and without (Model B) binary interactions we show that the inclusion of binary interactions makes the stellar mass of a binary stellar population smaller (~3.6-4.5% during the past 15Gyr); magnitudes greater (except U, ~0.18mag at the most); colours smaller (~0.15mag for V-K at the most); the mass-to-light ratios greater (~0.06 for K-band) except those in the U and B passbands at higher metallicities. And, Binary interactions make the V magnitude less sensitive to age, R and I magnitudes more sensitive to metallicity. Given an age, the absolute values of the differences in the stellar mass, magnitudes, mass-to-light ratios (except those in the U and B bands) between Models A and B reach the maximum at Z=0.0001, i.e., the effects of binary interactions on these parameters reach the maximum, while the differences in some colours reach the maximum at Z ~0.01-0.0004. On the contrary, the absolute value of the difference in the stellar mass is minimal at Z=0.03, those in the U,B,V magnitudes and the mass-to-light ratios in the U and B bands reach the minimum at Z ~0.01-0.004.