The Redshift and Star Formation Mode of AzTEC2: A Pair of Massive Galaxies at z = 4.63

Scientific paper - Original scientific paper

• Author: E. F. Jiménez-Andrade
• Author: J. A. Zavala
• Author: B. Magnelli
• Author: C. M. Casey
• Author: D. Liu
• Author: E. Romano- Díaz
• Author: E. Schinnerer
• Author: K. Harrington
• Author: I. Aretxaga
• Author: A. Karim
• Author: J. Staguhn
• Author: A. D. Burnham
• Author: A. Montaña
• Author: Vernesa Smolčić; MBZ: 336180
• Author: M. Yun
• Author: F. Bertoldi
• Author: D. Hughes
• Author's institution: University of Zagreb; Faculty of Science; (Department of Physics)
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Physics; Astronomy and Astrophysics

Abstract (english)

We combine observations from the Atacama Large Millimeter/submillimeter Array and the NOrthern Extended Millimeter Array to assess the redshift and to study the star formation conditions in AzTEC2, one of the brightest submillimeter galaxies (SMGs) in the COSMOS field (S_1.1mm = 10.5 ± 1.4 mJy). Our high-resolution observations confirm that AzTEC2 splits into two components (namely AzTEC2-A and AzTEC2-B) for which we detect [C II] and ^12CO(5 → 4) line emission, implying a redshift of 4.626 ± 0.001 (4.633 ± 0.001) for AzTEC2-A (AzTEC2-B) and ruling out previous associations with a galaxy at z ~ 1. We use the ^12CO(5 → 4) line emission and adopt typical SMG-like gas excitation conditions to estimate the molecular gas mass, which is M_gas (α_CO/2.5) = 2.1 ± 0.4 x 10^11 M_⊙ for AzTEC2- A, and a factor four lower for AzTEC2-B. With the infrared-derived star formation rate of AzTEC2-A (1920 ± 100 M_⊙ yr^-1 ) and AzTEC2-B (710 ± 35 M_⊙ yr^−1 ), they both will consume their current gas reservoir within (30–200) Myr. We find evidence of a rotation- dominated [C II] disk in AzTEC2-A, with a deprojected rotational velocity of v_rot(i = 39°) = 660 ± 130 km s^−1 , velocity dispersion ≲ 100 km s^−1 , and dynamical mass of M_dyn (i = 39°) = 2.6^+1.2_-0.9 x 10^11 M_⊙. We propose that an elevated gas accretion rate from the cosmic web might be the main driver of the intense levels of star formation in AzTEC2- A, which might be further enhanced by gravitational torques induced by its minor companion (AzTEC2- B). These results strengthen the picture whereby the population of single-dish selected SMGs is rather heterogeneous, including a population of pairs of massive, highly active galaxies in a pre-coalescence phase.

• Keywords (english): redshift; star formation mode; AzTEC2; massive galaxies
• Language: english
• Publication type: Scientific paper - Original scientific paper
• Publication status: Published
• Peer review: Peer review - international
• Publication version: Published version
• Journal title: Astrophysical Journal
• Numbering: vol. 890, no. 2, 171
• p-ISSN: 0004-637X
• e-ISSN: 1538-4357
• DOI: https://doi.org/10.3847/1538-4357/ab6dec
• URN:NBN: urn:nbn:hr:217:915507
• Publication: 2020
• Document URL: https://iopscience.iop.org/article/10.3847/1538-4357/ab6dec
• Type of resource: Text
• Access conditions: Open access
• Public note: © 2020. The American Astronomical Society. All rights reserved. Received 2019 October 28. Accepted 2020 January 16. Published 2020 February 26.
• Created on: 2020-08-27 20:10:57