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arXiv · 1412.1262

COLDz: Karl G. Jansky Very Large Array discovery of a gas-rich galaxy in COSMOS

L. Lentati·J. Wagg·C. L. Carilli·D. Riechers·P. Capak·F. Walter·M. Aravena·E. da Cunha·J. A. Hodge·R. J. Ivison·I. Smail·C. Sharon·E. Daddi·R. Decarli·M. Dickinson·M. Sargent·N. Scoville·V. Smolcic
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Abstract

The broad spectral bandwidth at mm and cm-wavelengths provided by the recent upgrades to the Karl G. Jansky Very Large Array (VLA) has made it possible to conduct unbiased searches for molecular CO line emission at redshifts, z > 1.31. We present the discovery of a gas-rich, star-forming galaxy at z = 2.48, through the detection of CO(1-0) line emission in the COLDz survey, through a sensitive, Ka-band (31 to 39 GHz) VLA survey of a 6.5 square arcminute region of the COSMOS field. We argue that the broad line (FWHM ~570 +/- 80 km/s) is most likely to be CO(1-0) at z=2.48, as the integrated emission is spatially coincident with an infrared-detected galaxy with a photometric redshift estimate of z = 3.2 +/- 0.4. The CO(1-0) line luminosity is L'_CO = (2.2 +/- 0.3) x 10^{10} K km/s pc^2, suggesting a cold molecular gas mass of M_gas ~ (2 - 8)x10^{10}M_solar depending on the assumed value of the molecular gas mass to CO luminosity ratio alpha_CO. The estimated infrared luminosity from the (rest-frame) far-infrared spectral energy distribution (SED) is L_IR = 2.5x10^{12} L_solar and the star-formation rate is ~250 M_solar/yr, with the SED shape indicating substantial dust obscuration of the stellar light. The infrared to CO line luminosity ratio is ~114+/-19 L_solar/(K km/s pc^2), similar to galaxies with similar SFRs selected at UV/optical to radio wavelengths. This discovery confirms the potential for molecular emission line surveys as a route to study populations of gas-rich galaxies in the future.

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L. Lentati, J. Wagg, C. L. Carilli, D. Riechers, P. Capak, F. Walter, M. Aravena, E. da Cunha, J. A. Hodge, R. J. Ivison, I. Smail, C. Sharon, E. Daddi, R. Decarli, M. Dickinson, M. Sargent, N. Scoville, V. Smolcic. 2014-12-03. COLDz: Karl G. Jansky Very Large Array discovery of a gas-rich galaxy in COSMOS. https://doi.org/10.1088/0004-637x%2F800%2F1%2F67

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