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| Paper: |
Diagnosis of the IMF in the Universe using C, N Abundances |
| Volume: |
445, Why Galaxies Care about AGB Stars II: Shining Examples and Common Inhabitants |
| Page: |
549 |
| Authors: |
Tsujimoto, T.; Bekki, K. |
| Abstract: |
Recently-determined C, N, and O abundances in the most metal-poor
damped Lyman-alpha systems (DLAs) are compared with those of
extremely metal-poor stars in the Galactic halo as well as
extragalactic H II regions to unravel nucleosynthesis and
enrichment in the early Universe. These comparisons reveal a puzzling
feature showing a relatively high C/O ratio and a low N/O ratio in
DLAs, which is theoretically hard to interpret. Here we propose that
these elemental features are evidence that in metal-poor DLAs, the
initial mass function (IMF) has a cut-off at the upper-mass end,
around 20 – 25 M☉, and thus lacks massive stars that provide
the nucleosynthesis products, resulting in the low C/O and high N/O
ratios. In contrast, we find that some metal-rich extragalactic
H II regions in local disk galaxies appear to have a
top-heavy IMF. This suggests that the IMFs are likely to be
different even among disk galaxies. Besides, there are earlier
claims that high-z early-type galaxies possess a top-heavy IMF.
Accordingly, we claim a non-universal IMF from the high to low
redshift Universe. |
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