VALES – IV. Exploring the transition of star formation efficiencies between normal and starburst galaxies using APEX/SEPIA Band-5 and ALMA at low redshift
Hughes, T M
Muñoz Arancibia, A
Xu, C K
Willmer, C N A
Xue, Y Q
AffiliationUniv Arizona, Steward Observ
MetadataShow full item record
PublisherOXFORD UNIV PRESS
CitationC Cheng, E Ibar, T M Hughes, V Villanueva, R Leiton, G Orellana, A Muñoz Arancibia, N Lu, C K Xu, C N A Willmer, J Huang, T Cao, C Yang, Y Q Xue, K Torstensson; VALES – IV. Exploring the transition of star formation efficiencies between normal and starburst galaxies using APEX/SEPIA Band-5 and ALMA at low redshift, Monthly Notices of the Royal Astronomical Society, Volume 475, Issue 1, 21 March 2018, Pages 248–256, https://doi.org/10.1093/mnras/stx3183
Rights© 2017 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
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AbstractIn this work, we present new the Swedish-ESO PI receiver for the Atacama Pathfinder Experiment APEX/SEPIA Band-5 observations targeting the CO (J = 2-1) emission line of 24 Herschel-detected galaxies at z = 0.1-0.2. Combining this sample with our recent new Valparafso ALMA Line Emission Survey (VALES), we investigate the star formation efficiencies [SFEs = star formation rate (SFR)/M-H2] of galaxies at low redshift. We find the SFE of our sample bridges the gap between normal star-forming galaxies and Ultra-Luminous Infrared Galaxies (ULIRGs), which are thought to be triggered by different star formation modes. Considering the SFE' as the SFR and the L'(CO) ratio, our data show a continuous and smooth increment as a function of infrared luminosity (or star formation rate) with a scatter about 0.5 dex, instead of a steep jump with a bimodal behaviour. This result is due to the use of a sample with a much larger range of sSFR/sSFR(ms) using LIRGs, with luminosities covering the range between normal and ULIRGs. We conclude that the main parameters controlling the scatter of the SFE in star-forming galaxies are the systematic uncertainty of the alpha(CO) conversion factor, the gas fraction, and physical size.
VersionFinal published version
SponsorsChinese Academy of Sciences (CAS) through the CASSACA Postdoc Grant; CONICYT/ALMA funding Program in Astronomy/PCI Project ; FONDECYT ; Chinese Academy of Sciences (CAS); National Commission for Scientific and Technological Research of Chile (CONICYT) through a CAS-CONICYT Joint Postdoctoral Fellowship; Comite Mixto ESO-GOBIERNO DE CHILE; GEMINI-CONICYT FUND ; CONICYT (Chile) through FONDECYT postdoctoral research grant [3170942, 3160776]; NSFC ; National Key R&D Program of China [2017YFA0402704]; [NSFC-11643003]; [NSFC-11473026]; 
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Planck's dusty GEMS III. A massive lensing galaxy with a bottom-heavy stellar initial mass function at z=1.5Canameras, R.; Nesvadba, N. P. H.; Kneissl, R.; Limousin, M.; Gavazzi, R.; Scott, D.; Dole, H.; Frye, B.; Koenig, S.; Le Floc'h, E.; et al. (EDP SCIENCES S A, 2017-03-24)We study the properties of the foreground galaxy of the Ruby, the brightest gravitationally lensed high-redshift galaxy on the sub-millimeter sky as probed by the Planck satellite, and part of our sample of Planck's dusty GEMS. The Ruby consists of an Einstein ring of 1.4" diameter at z = 3.005 observed with ALMA at 0.1" resolution, centered on a faint, red, massive lensing galaxy seen with HST/WFC3, which itself has an exceptionally high redshift, z = 1.525 +/- 0.001, as confirmed with VLT/X-shooter spectroscopy. Here we focus on the properties of the lens and the lensing model obtained with LENSTOOL. The rest-frame optical morphology of this system is strongly dominated by the lens, while the Ruby itself is highly obscured, and contributes less than 10% to the photometry out to the K band. The foreground galaxy has a lensing mass of (3.70 +/- 0.35) x 10(11) M-Theta Magnification factors are between 7 and 38 for individual clumps forming two image families along the Einstein ring. We present a decomposition of the foreground and background sources in the WFC3 images, and stellar population synthesis modeling with a range of star-formation histories for Chabrier and Salpeter initial mass functions (IMFs). Only the stellar mass range obtained with the latter agrees well with the lensing mass. This is consistent with the bottom-heavy IMFs of massive high-redshift galaxies expected from detailed studies of the stellar masses and mass profiles of their low-redshift descendants, and from models of turbulent gas fragmentation. This may be the first direct constraint on the IMF in a lens at z = 1.5, which is not a cluster central galaxy.
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