Publication Date:
2020-11-13
Description:
We present ALMA observations of a small but statistically complete sample of twelve 250μm selected galaxies at z = 0.35 designed to measure their dust submillimeter continuum emission as well as their $
m {^{12}CO(1-0)}$ and atomic carbon [Ci](3P1-3P0) spectral lines. This is the first sample of galaxies with global measures of all three H2-mass tracers and which show star formation rates (4–26 $
m M_{odot }$ yr−1) and infra-red luminosities ($1-6imes 10^{11}, {,
m L_{odot },}$) typical of star forming galaxies in their era. We find a surprising diversity of morphology and kinematic structure; one-third of the sample have evidence for interaction with nearby smaller galaxies, several sources have disjoint dust and gas morphology. Moreover two galaxies have very high $L^{prime }_{
m CI}$ / $L^{prime }_{
m {CO}}$ ratios for their global molecular gas reservoirs; if confirmed, such extreme intensity ratios in a sample of dust selected, massive star forming galaxies presents a challenge to our understanding of ISM. Finally, we use the emission of the three molecular gas tracers, to determine the carbon abundance, $
m {X_{CI}}$ , and CO–$
m {H_2}$ conversion αCO in our sample, using a weak prior that the gas-to-dust ratio is similar to that of the Milky Way for these massive and metal rich galaxies. Using a likelihood method which simultaneously uses all three gas tracer measurements, we find mean values and errors on the mean of $langle {,alpha _{
m {CO}},}
angle =3.0pm 0.5,
m {{,
m M_{odot },}, (K, kms^{-1}, pc^2)^{-1}}$ and $langle {,
m {X_{CI}},}
angle =1.6pm 0.1imes 10^{-5}$ (or ${,alpha _{
m {CI}},}=18.8, {,
m {M_{odot }, (K, kms^{-1}, pc^2)^{-1}},}$) and ${,delta _{
m {GDR}},}=128pm 16$ (or ${,alpha _{
m {850}},}=5.9imes 10^{12},
m {W, Hz^{-1}, {,
m M_{odot },}^{-1}}$), where our starting assumption is that these metal rich galaxies have an average gas-to-dust ratio similar to that of the Milky Way centered on ${,delta _{
m {GDR}},}=135$.
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
Permalink