An ALMA survey of submillimetre galaxies in the COSMOS field: The extent of the radio-emitting region revealed by 3 GHz imaging with the Very Large Array

Abstract

We determine the radio size distribution of a large sample of 152 SMGs in COSMOS that were detected with ALMA at 1.3 mm. For this purpose, we used the observations taken by the VLA-COSMOS 3 GHz Large Project. One hundred and fifteen of the 152 target SMGs were found to have a 3 GHz counterpart. The median value of the major axis FWHM at 3 GHz is derived to be $4.6\pm 0.4$ kpc. The radio sizes show no evolutionary trend with redshift, or difference between different galaxy morphologies. We also derived the spectral indices between 1.4 and 3 GHz, and 3 GHz brightness temperatures for the sources, and the median values were found to be $\alpha =-0.67$ and $T_{\mathrm{B}}=12.6\pm 2$ K. Three of the target SMGs, which are also detected with the VLBA, show clearly higher brightness temperatures than the typical values. Although the observed radio emission appears to be predominantly powered by star formation and supernova activity, our results provide a strong indication of the presence of an AGN in the VLBA and X-ray-detected SMG AzTEC/C61. The median radio-emitting size we have derived is 1.5-3 times larger than the typical FIR dust-emitting sizes of SMGs, but similar to that of the SMGs' molecular gas component traced through mid-$J$ line emission of CO. The physical conditions of SMGs probably render the diffusion of cosmic-ray electrons inefficient, and hence an unlikely process to lead to the observed extended radio sizes. Instead, our results point towards a scenario where SMGs are driven by galaxy interactions and mergers. Besides triggering vigorous starbursts, galaxy collisions can also pull out the magnetised fluids from the interacting disks, and give rise to a taffy-like synchrotron-emitting bridge. This provides an explanation for the spatially extended radio emission of SMGs, and can also cause a deviation from the well-known IR-radio correlation.

32 pages (incl. 5 appendices), 17 figures, 7 tables; accepted for publication in A&A; abstract abridged for arXiv

References in corpus (42)

• The Cosmic Evolution Survey (COSMOS) -- Overview
• The James Webb Space Telescope
• Dust Masses, PAH Abundances, and Starlight Intensities in the SINGS Galaxy Sample
• Formation of Massive Galaxies at High Redshift: Cold Streams, Clumpy Disks and Compact Spheroids
• MAMBO Mapping of Spitzer c2d Small Clouds and Cores
• A Dust-Obscured Massive Maximum-Starburst Galaxy at a Redshift of 6.34
• An ALMA survey of Sub-millimeter Galaxies in the Extended Chandra Deep Field South: Physical properties derived from ultraviolet-to-radio modelling
• The Chandra COSMOS Survey, I: Overview and Point Source Catalog
• The VLA-COSMOS 3 GHz Large Project: Continuum data and source catalog release
• The VLA-COSMOS Survey: II. Source Catalog of the Large Project
• Kiloparsec-scale dust disks in high-redshift luminous submillimeter galaxies
• An ALMA survey of submillimetre galaxies in the Extended Chandra Deep Field South: High resolution 870um source counts
• The Formation of Massive, Compact Galaxies at z=2 in the Illustris Simulation
• The SCUBA-2 Cosmology Legacy Survey: ALMA resolves the rest-frame far-infrared emission of sub-millimeter galaxies
• AzTEC Millimetre Survey of the COSMOS Field: I. Data Reduction and Source Catalogue
• ALMA Imaging of Gas and Dust in a Galaxy Protocluster at Redshift 5.3: [CII] Emission in "Typical" Galaxies and Dusty Starbursts ~1 Billion Years after the Big Bang
• VLA-COSMOS 3GHz Large Project: The infrared-radio correlation of star-forming galaxies and AGN to $z\lesssim 6$
• The far-infrared/radio correlation and radio spectral index of galaxies in the SFR-M* plane up to z 2
• An ALMA Survey of Submillimeter Galaxies in the Extended Chandra Deep Field South: Near-infrared morphologies and stellar sizes
• VLA and ALMA Imaging of Intense, Galaxy-Wide Star Formation in z ~ 2 Galaxies
• The VLA-COSMOS Survey: III. Further Catalog Analysis and the Radio Source Counts
• High-resolution radio observations of submillimetre galaxies
• Connecting Far-Infrared and Radio Morphologies of Disk Galaxies: Cosmic-Ray Electron Diffusion After Star Formation Episodes
• Molecular Gas in a Submillimeter Galaxy at z=4.5: Evidence for a Major Merger at 1 Billion Years after the Big Bang
• The statistical properties of stars and their dependence on metallicity: the effects of opacity
• Winds, Clumps, and Interacting Cosmic Rays in M82
• High-Resolution Radio Continuum Measurements of the Nuclear Disks of Arp 220
• The ALMA Frontier Fields survey I: 1.1 mm continuum detections in Abell 2744, MACSJ0416.1-2403 and MACSJ1149.5+2223
• The GOODS-N Jansky VLA 10 GHz Pilot Survey: Sizes of Star-Forming $\mu$Jy Radio Sources
• An ALMA survey of submillimetre galaxies in the Extended Chandra Deep Field South: radio properties and the far-infrared/radio correlation
• Subarcsecond international LOFAR radio images of Arp 220 at 150 MHz: A kpc-scale star forming disk surrounding nuclei with shocked outflows
• Integrated Radio Continuum Spectra of Galaxies
• The SCUBA-2 Cosmology Legacy Survey: the submillimetre properties of Lyman break galaxies at z=3-5
• Clumpy and Extended Starbursts in the Brightest Unlensed Submillimeter Galaxies
• Gas and Dust in the Taffy Galaxies: Ugc12914/15
• Radio--Far infrared correlation in "blue cloud" galaxies with 0<z<1.2
• X-ray Detections of Sub-millimetre Galaxies: Active Galactic Nuclei Versus Starburst Contribution
• Estimating sizes of faint, distant galaxies in the submillimetre regime
• (Sub)millimetre interferometric imaging of a sample of COSMOS/AzTEC submillimetre galaxies IV. Physical properties derived from spectral energy distributions
• Constraining Star Formation and AGN in z~2 Massive Galaxies using High Resolution MERLIN Radio Observations
• Extremely Red Submillimeter Galaxies: New z>~4-6 Candidates Discovered using ALMA and Jansky VLA
• Excitation Conditions in the Multi-component Submillimeter Galaxy SMM J00266+1708

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• The VLA Frontier Field Survey: A Comparison of the Radio and UV/optical size of $0.3\lesssim z\lesssim 3$ star-forming galaxies
• An investigation of the circumgalactic medium around z~2.2 AGN with ACA and ALMA
• Evidence for extended gaseous reservoirs around AGN at cosmic noon from ALMA CO(3-2) observations
• Multi-wavelength properties of 850-$\mu$m selected sources from the North Ecliptic Pole SCUBA-2 survey
• On the Kennicutt-Schmidt scaling law of submillimetre galaxies
• The SCUBA-2 Cosmology Legacy Survey: The EGS deep field -- III. The evolution of faint submillimeter galaxies at $z<4$
• Identification of 4876 Bent-Tail Radio Galaxies in the FIRST Survey Using Deep Learning Combined with Visual Inspection
• Impact of Galactic Interactions on the Evolution of the Far-Infrared-Radio Correlation
• Extended H$\alpha$ over compact far-infrared continuum in dusty submillimeter galaxies -- Insights into dust distributions and star-formation rates at $z\sim 2$