The molecular gas content and fuel efficiency of starbursts at z ~ 1.6 with ALMA

Silverman, J D, Rujopakarn, W, Daddi, E, Renzini, A, Rodighiero, G, Liu, D, Puglisi, A, Sargent, M, Mancini, C, Kartaltepe, J, Kashino, D, Koekemoer, A, Arimoto, N, Béthermin, M, Jin, S, Madgis, G, Nagao, T, Onodera, M, Sanders, D and Valentino, F (2018) The molecular gas content and fuel efficiency of starbursts at z ~ 1.6 with ALMA. Astrophysical Journal, 867 (2). pp. 1-12. ISSN 0004-637X

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We present an analysis of the molecular gas properties, based on CO(2 - 1) emission, of twelve starburst galaxies at z~1.6 selected by having a boost (>~4x) in their star formation rate (SFR) above the average star-forming galaxy at an equivalent stellar mass. ALMA observations are acquired of six additional galaxies than previously reported through our effort. As a result of the larger statistical sample, we significantly detect, for the first time at high-z, a systematically lower L'_CO/L_IR ratio in galaxies lying above the star-forming `main sequence' (MS). Based on an estimate of alpha_CO (i.e., the ratio of molecular gas mass to L'_CO(1-0)), we convert the observational quantities (e.g., L'_CO/L_IR) to physical units (M_gas/SFR) that represent the gas depletion time or its inverse, the star formation efficiency. We interpret the results as indicative of the star formation efficiency increasing in a continuous fashion from the MS to the starburst regime, whereas the gas fractions remain comparable to those of MS galaxies. Although, the balance between an increase in star-formation efficiency or gas fraction depends on the adopted value of alpha_CO as discussed.

Item Type: Article
Schools and Departments: School of Mathematical and Physical Sciences > Physics and Astronomy
Research Centres and Groups: Astronomy Centre
Subjects: Q Science > QB Astronomy
Depositing User: Mark Sargent
Date Deposited: 28 Nov 2018 10:55
Last Modified: 28 Nov 2018 10:55

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