Kavli Affiliate: Luis C. Ho
| First 5 Authors: Jing Wang, Xuchen Lin, Lister Staveley-Smith, Dong Yang, Fabian Walter
| Summary:
We update the HI surface density measurements for a subset of 17 THINGS
galaxies by dealing with the short-spacing problem of the original VLA HI
images. It is the same sample that Bigiel et al. (2010) used to study the
relation between HI surface densities and star formation rate surface densities
in galaxy outer disks, which are beyond the optical radius r25. For ten
galaxies, the update is based on combining original THINGS VLA HI images with
HI images taken by the single-dish FAST in the FEASTS program. The median
increment of HI surface densities in outer disks is 0.15 to 0.4 dex at a given
new HI surface density. Several galaxies change significantly in the shape of
radial profiles HI surface densities, and seven galaxies are now more than
1-$sigma$ below the HI size-mass relation. We update the HI star formation
laws in outer disks. The median relation between HI surface densities and star
formation rate surface densities based on pixelwise measurements shifts
downward by around 0.15 dex because the HI surface density values shift
rightward, and the scatter increases significantly. The scatter of the
relation, indicating the star forming efficiency, exhibits a much stronger
positive correlation with the stellar mass surface density than before. Thus,
detecting the previously missed, diffuse HI due to short-spacing problem of the
VLA observation is important in revealing the true condition and variation of
star formation possibly regulated by stellar feedbacks in localized environment
of outer disks.
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