Resolved CO(1-0) emission and gas properties in luminous dusty star forming galaxies at z=2-4

Abstract

We present the results of a survey of CO(1-0) emission in 14 infrared luminous dusty star forming galaxies (DSFGs) at 2 < z < 4 with the NSF's Karl G. Jansky Very Large Array. All sources are detected in CO(1-0), with an ~1arcsec angular resolution. Seven sources show extended and complex structure. We measure CO luminosities of $(\hat{I}¼)L_{CO(1-0)}^{\prime }=0.4-2.9x10^{11}$ K km s${}^{-1}$ pc${}^2$, and molecular gas masses of ($\hat{I}¼$)M${}_{H2}$ = 1.3 - 8.6 x 10${}^{11}$ Mo, where (μ) is the magnification factor. The derived molecular gas depletion times of t${}_{\mathrm{dep}}$ = 40 - 460 Myr, cover the expected range of both normal star forming galaxies and starbursts. Comparing to the higher-J CO transitions previously observed for the same sources, we find CO temperature brightness ratios of r${}_{32/10}$ = 0.4 - 1.4, r${}_{43/10}$ = 0.4 - 1.7, and r${}_{54/10}$ = 0.3 - 1.3. We find a wide range of CO spectral line energy distributions (SLEDs), in agreement with other high-z DSFGs, with the exception of three sources that are most comparable to the Cloverleaf and APM08279+5255. Based on radiative transfer modelling of the CO SLEDs we determine densities of n${}_{H2}$ = 0.3 - 8.5 x 10${}^3$ cm${}^{-3}$ and temperatures of T${}_K$ = 100 - 200 K. Lastly, four sources are detected in the continuum, three have radio emission consistent with their infrared derived star formation rates, while HerBS-70E requires an additional synchrotron radiation component from an active galactic nucleus. Overall, we find that even though the sample is similarly luminous in the infrared, by tracing the CO(1-0) emission a diversity of galaxy and excitation properties are revealed, demonstrating the importance of CO(1-0) observations in combination to higher-J transitions.

25pages , 13 figures, Accepted for publication at ApJ