Starburst to Quiescent from HST/ALMA: Stars and Dust Unveil Minor Mergers in Submillimeter Galaxies at z ~ 4.5

Gómez-Guijarro, C. and Toft, S. and Karim, A. and Magnelli, B. and Magdis, G. E. and Jiménez-Andrade, E. F. and Capak, P. L. and Fraternali, F. and Fujimoto, S. and Riechers, D. A. and Schinnerer, E. and Smolčić, Vernesa and Aravena, M. and Bertoldi, F. and Cortzen, I. and Hasinger, G. and Hu, E. M. and Jones, G. C. and Koekemoer, A. M. and Lee, N. and McCracken, H. J. and Michalowski, M. J. and Navarrete, F. and Pović, M. and Puglisi, A. and Romano-Díaz, E. and Sheth, K. and Silverman, J. D. and Staguhn, J. and Steinhardt, C. L. and Stockmann, M. and Tanaka, M. and Valentino, F. and van Kampen, E. and Zirm, A. (2018) Starburst to Quiescent from HST/ALMA: Stars and Dust Unveil Minor Mergers in Submillimeter Galaxies at z ~ 4.5. Astrophysical Journal, 856. 121-1-121-18. ISSN 0004-637X

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Dust-enshrouded, starbursting, submillimeter galaxies (SMGs) at z ≥ 3 have been proposed as progenitors of z ≥ 2 compact quiescent galaxies (cQGs). To test this connection, we present a detailed spatially resolved study of the stars, dust, and stellar mass in a sample of six submillimeter-bright starburst galaxies at z ∼ 4.5. The stellar UV emission probed by HST is extended and irregular and shows evidence of multiple components. Informed by HST, we deblend Spitzer/ IRAC data at rest-frame optical, finding that the systems are undergoing minor mergers with a typical stellar mass ratio of 1:6.5. The FIR dust continuum emission traced by ALMA locates the bulk of star formation in extremely compact regions (median r_e = 0.70 ± 0.29 kpc), and it is in all cases associated with the most massive component of the mergers (median log(M*/M⊙) = 10.49 ± 0.32). We compare spatially resolved UV slope (β) maps with the FIR dust continuum to study the infrared excess (IRX = L_IR/L_UV)–β relation. The SMGs display systematically higher IRX values than expected from the nominal trend, demonstrating that the FIR and UV emissions are spatially disconnected. Finally, we show that the SMGs fall on the mass–size plane at smaller stellar masses and sizes than the cQGs at z = 2. Taking into account the expected evolution in stellar mass and size between z = 4.5 and z = 2 due to the ongoing starburst and mergers with minor companions, this is in agreement with a direct evolutionary connection between the two populations.

Item Type: Article
Keywords: galaxies: evolution; galaxies: formation; galaxies: high-redshift; galaxies: interactions; galaxies: ISM; galaxies: starburst
Date: 30 March 2018
Subjects: NATURAL SCIENCES > Physics > Astronomy and Astrophysics
Additional Information: © 2018. The American Astronomical Society. All rights reserved. Received 2017 November 1; revised 2018 January 16; accepted 2018 February 20; published 2018 March 30.
Divisions: Faculty of Science > Department of Physics
Publisher: IOP Publishing
Depositing User: Vernesa Smolčić
Date Deposited: 03 May 2019 12:35
Last Modified: 06 May 2019 12:39

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