The redshift and star formation mode of AzTEC2: a pair of massive galaxies at $z=4.63$
| Autor: | David H. Hughes, Caitlin M. Casey, E. F. Jiménez-Andrade, Daizhong Liu, Frank Bertoldi, Alexander Karim, E. Romano Díaz, Benjamin Magnelli, Eva Schinnerer, Itziar Aretxaga, K. Harrington, Vernesa Smolčić, M. S. Yun, Anne D. Burnham, Johannes Staguhn, Alfredo Montaña, Jorge A. Zavala |
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| Rok vydání: | 2020 |
| Předmět: |
Active galactic nucleus
AzTEC2 010504 meteorology & atmospheric sciences PRIRODNE ZNANOSTI. Fizika. Astronomija i astrofizika Population FOS: Physical sciences Astrophysics star formation mode 01 natural sciences Submillimeter Array 0103 physical sciences NATURAL SCIENCES. Physics. Astronomy and Astrophysics redshift massive galaxies education 010303 astronomy & astrophysics 0105 earth and related environmental sciences Line (formation) Physics education.field_of_study Star formation Velocity dispersion Astronomy and Astrophysics Astrophysics - Astrophysics of Galaxies Galaxy Redshift Space and Planetary Science Astrophysics of Galaxies (astro-ph.GA) |
| Zdroj: | Astrophysical Journal Volume 890 Issue 2 |
| ISSN: | 0004-637X 1538-4357 |
| DOI: | 10.48550/arxiv.2001.06997 |
| Popis: | We combine observations from the Atacama Large Millimeter/submillimeter Array (ALMA) and the NOrthern Extended Millimeter Array (NOEMA) to assess the redshift and to study the star formation conditions in AzTEC2: one of the brightest sub-millimeter galaxies (SMGs) in the COSMOS field ($S_{\rm 1.1mm}=10.5\pm1.4$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 $^{12}$CO(5$\to$4) line emission, implying a redshift of $4.626\pm0.001$ ($4.633\pm0.001$) for AzTEC2-A (AzTEC2-B) and ruling out previous associations with a galaxy at $z\sim1$. We use the $^{12}$CO(5$\to$4) line emission and adopt typical SMG-like gas excitation conditions to estimate the molecular gas mass, which is $M_{\rm gas}(\alpha_{\rm CO}/2.5)=2.1\pm0.4 \times10^{11}{\rm M}_\odot$ for AzTEC2-A, and a factor four lower for AzTEC2-B. With the infrared-derived star formation rate of AzTEC2-A ($1920\pm100 \,M_\odot{\rm \, yr}^{-1}$) and AzTEC2-B ($710\pm 35\,M_\odot{\rm \,yr}^{-1}$), 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 de-projected rotational velocity of $v_{\rm rot}(i=39^\circ)=660\pm130{\rm \,km\,s}^{-1}$, velocity dispersion $\lesssim100{\rm \,km\,s}^{-1}$, and dynamical mass of $M_{\rm dyn}(i=39^\circ)=2.6^{+1.2}_{-0.9}\times10^{11}\,M_\odot$. 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. Comment: 19 pages, 6 figures, accepted for publication in ApJ |
| Databáze: | OpenAIRE |
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