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Evidence for Initial Mass Function Variation in Massive Early-Type Galaxies
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DOI：10.1146/annurev-astro-032620-020217.png)
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The initial mass function (IMF), describing the distribution of birth masses of stars, plays a pivotal role in establishing the observable properties of galaxies. This article reviews the evidence for variation in the IMF of massive early-type galaxies (ETGs), especially from spectroscopic studies and from dynamical and gravitational lensingmeasurements over the past decade. The principal conclusions are as follows: The spectra of massive ETGs depart from the predictions of models with MilkyWay-like IMFs in a way that is best reproduced by assuming a steeper (bottom-heavy) IMF below similar to 1 M-circle dot. Lensing and dynamical models, assuming a constantmass-to-light ratio for the stellar component, infer heavy IMFs, superficially supporting the result from spectra. The spectroscopic signal exhibits a steep gradient, however, and may be confined to the innermost region with scales similar to 2 kpc; such internal variation in the stellar mass-to-light ratio would invalidate a key assumption of most dynamics and lensing studies. For masses above the main sequence turnoff in ancient populations (similar to 1 M-circle dot), there is little evidence for a steeper IMF in massive ETGs or their high-redshift progenitors; rather, a slightly shallower slope is preferred in this regime from several different arguments. Steep internal gradients may be responsible for some of the apparent discrepancies between different methods and also point to the cause of the IMF variation being restricted to conditions specific to the in situ formation phase of ETG cores.
Keyword:
galaxies: elliptical, lenticular, cD
galaxies: stellar content
stars: luminosity function
mass function
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期刊
A
IF:
32.5
论文数:
0
被引数:
4
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RETRACTED: IMF shape constraints from stellar populations and dynamics from CALIFA (Retracted Article)撤回: 来自CALIFA的恒星种群和动力学的IMF形状约束 (撤回的文章)
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OAAI分享收藏The stellar initial mass function of early-type galaxies from low to high stellar velocity dispersion: homogeneous analysis of ATLAS3D and Sloan Lens ACS galaxies早期类型星系的恒星初始质量函数从低到高恒星速度色散: ATLAS3D和Sloan Lens ACS星系的均匀分析OAAI
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