Kavli Affiliate: Luis C. Ho
| First 5 Authors: Boris S Kalita, Tomoko L Suzuki, Daichi Kashino, John D Silverman, Emanuele Daddi
| Summary:
Star-forming clumps have been found to significantly influence the star
formation of gas-rich $z>1$ galaxies. Using public data from JWST/NIRCam
(COSMOS-Web) and ALMA (FMOS-COSMOS), we study a sample of 32 massive
($>10^{10.5},rm M_{odot}$) main-sequence galaxies at $z_{rm spec}sim1.5$
with $sim0.3,rm kpc$ resolution. We create composite morphological models
consisting of bulge, disk, and clumps to fully ‘deconstruct’ the galaxy images.
With the resulting measurements of the flux and size of these components, we
find the following: (I)The combined contribution of clumps is $1-30%$ towards
the net star formation rate (SFR) of the host while contributing $1-20%$ to
its stellar mass. The clumps show a correlation between their stellar mass and
SFR, but have an increased specific-SFR (sSFR) relative to the star-forming
main sequence, with offsets ranging from $0lesssimDeltalogrm sSFRlesssim
0.4$. They feature star formation surface densities of $10^{-2}-10^{2},rm
M_{odot}/yr/kpc^{2}$, consistent with values observed in local star-forming
and starburst galaxies. (II)The clumps span a large range of characteristic
sizes ($r_{e}sim0.1-1,rm kpc$) and stellar masses ($sim 10^{8.0-9.5},rm
M_{odot}$). We estimate a mass-size relation ($r_{e}proptorm
M_{star}^{,0.52pm0.07}$) along with a stellar mass function (slope,
$alpha=-1.85pm 0.19$), both suggesting a hierarchical nature similar to that
expected in star-forming regions in local galaxies. (III)Our measurements agree
with the properties of stellar clumps in $zgtrsim1$ lensed systems, bridging
the gap between lensed and unlensed studies by detecting structures at sub-kpc
scales.(IV)Clumps are found to be preferentially located along spiral features
visible primarily in the residual rest-frame near-IR images. In conclusion, we
present an observation-based, coherent picture of star-forming clumps at $z>1$.
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