Kavli Affiliate: Jing Wang
| First 5 Authors: Hugh Roxburgh, Hugh Roxburgh, , ,
| Summary:
We probe the atomic hydrogen (HI) emission from the host galaxies of fast
radio bursts (FRBs) to investigate the emerging trend of disturbance and
asymmetry in the population. Quadrupling the sample size, we detect 13 of 14
new hosts in HI, with the only non-detection arising in a galaxy known to be
transitioning towards quiescence. With respect to typical local Universe
galaxies, FRB hosts are generally massive in HI ($M_HI>10^9 M_odot$), which
aligns with previous studies showing that FRB hosts also tend to have high
stellar masses and are star-forming. However, they span a broad range of other
HI derived properties. In our independent sample of repeater hosts, we observe
a statistically insignificant preference towards lower HI masses compared to
non-repeater hosts, similar to the low-significance trend toward lower stellar
masses previously reported. Using visual inspection alongside various asymmetry
metrics, we identify four unambiguously settled host galaxies, demonstrating
for the first time that a disturbed HI morphology is not a universal feature of
FRB host galaxies. However, we find another six that show clear signs of
disturbance, and three which require deeper, more targeted observations to
reach a conclusion; this brings the confirmed ratio of disturbed-to-settled FRB
hosts to 11:4. Given that roughly a 1:1 ratio is expected for random background
galaxies of similar type, our observed ratio yields a p-value of 0.065. Unlike
earlier indications based on smaller samples, this no longer crosses the
conventional threshold for statistical significance, though is still near
enough to hint at a legitimate excess of disturbance among FRB hosts. Thus, an
even larger sample size of FRB hosts observed in HI is required to fully
clarify whether the trend is genuine or still a consequence of low-number
statistics – a sample that upcoming data releases are well positioned to
provide.
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