Radio Spectra and Sizes of Atacama Large Millimeter/submillimeter Array-identified Submillimeter Galaxies: Evidence of Age-related Spectral Curvature and Cosmic-Ray Diffusion?

Thomson, A. P.; Smail, Ian; Swinbank, A. M.; Simpson, J. M.; Arumugam, V.; Stach, S. M.; Murphy, E. J.; Rujopakarn, W.; Almaini, O.; An, Fangxia; Blain, A. W.; Chen, Chian-Chou; Cooke, Elizabeth A.; Dudzevičiūtė, U.; Edge, A. C.; Farrah, D.; Gullberg, B.; Hartley, W. G.; Ibar, E.; Maltby, David T.; Michałowski, M. J.; Simpson, Chris; Werf, P. P. van der; Wardlow, J. L.

doi:10.3847/1538-4357/ab32e7

Cited by 28 publications

(63 citation statements)

References 107 publications

(175 reference statements)

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“…Motivated by the strength of the stacked emission, we estimate the 3 GHz flux density of each of the radiofaint SMGs by extracting the pixel flux density at the position of each source in the VLA map: the 3 GHz maps are calibrated in units of Jy per beam and the pixel value represents the total flux density for an unresolved source at a given position. At the resolution of the VLA imaging we expect that the radio emission from the AS2COSMOS SMGs will be marginally-resolved (intrinsic FWHM ∼ 0.6 ; e.g., Biggs & Ivison 2008;Miettinen et al 2015;Thomson et al 2019) and, as such, our simple flux estimates will systematically underestimate the total flux of each source. To correct for this effect we compare the pixel and total flux densities the 193 AS2COSMOS with counterparts in the VLA / 3 GHz catalogue.…”

Section: Radiomentioning

confidence: 93%

An ALMA survey of the brightest sub-millimetre sources in the SCUBA-2–COSMOS field

Simpson

Smail

Dudzevičiūtė

et al. 2020

Monthly Notices of the Royal Astronomical Society

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136

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We present an ALMA study of the ∼180 brightest sources in the SCUBA-2 850-μm map of the COSMOS field from the S2COSMOS survey, as a pilot study for AS2COSMOS – a full survey of the ∼1000 sources in this field. In this pilot study, we have obtained 870-μm continuum maps of an essentially complete sample of the brightest 182 sub-millimetre sources ($S_{850\, \mu \rm m}\gt $ 6.2 mJy) in COSMOS. Our ALMA maps detect 260 sub-millimetre galaxies (SMGs) spanning a range in flux density of $S_{870\, \mu \rm m}$ = 0.7–19.2 mJy. We detect more than one SMG counterpart in 34 ± 2 per cent of sub-millimetre sources, increasing to 53 ± 8 per cent for SCUBA-2 sources brighter than $S_{850\, \mu \rm m}\gt $ 12 mJy. We estimate that approximately one-third of these SMG–SMG pairs are physically associated (with a higher rate for the brighter secondary SMGs, $S_{870\, \mu \rm m}\gtrsim$ 3 mJy), and illustrate this with the serendipitous detection of bright [C ii] 157.74-μm line emission in two SMGs, AS2COS 0001.1 and 0001.2 at z = 4.63, associated with the highest significance single-dish source. Using our source catalogue, we construct the interferometric 870-μm number counts at $S_{870\, \mu \rm m}\gt $ 6.2 mJy. We use the extensive archival data of this field to construct the multiwavelength spectral energy distribution of each AS2COSMOS SMG, and subsequently model this emission with magphys to estimate their photometric redshifts. We find a median photometric redshift for the $S_{870\, \mu \rm m}\gt $ 6.2 mJy AS2COSMOS sample of z = 2.87 ± 0.08, and clear evidence for an increase in the median redshift with 870-μm flux density suggesting strong evolution in the bright end of the 870-μm luminosity function.

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Section: Radiomentioning

confidence: 93%

An ALMA survey of the brightest sub-millimetre sources in the SCUBA-2–COSMOS field

Simpson

Smail

Dudzevičiūtė

et al. 2020

Monthly Notices of the Royal Astronomical Society

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136

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“…10). We use these photometric redshifts to k-correct our observed-frame 1.5-GHz flux densities to rest-frame 1.4 GHz, and measure radio luminosity densities L 1.4 GHz via the equation 1of Thomson et al (2019), though with an additional correction A ≡ (1.40/1.51) −α , which accounts for the slight offset in frequency between our observed-frame 1.51-GHz observations and the observed-frame 1.4 GHz, which is the central frequency most commonly associated with L-band radio observations:…”

Section: The Redshift and Luminosity Distributions Of E-merge Dr1 Soumentioning

confidence: 99%

“…Unsurprisingly, we find that lower S/N point sources have a greater tendency to be upscattered in size than higher S/N point sources. Following Bondi et al (2008) and Thomson et al (2019), we parameterize this size 'up-scattering' as a function of S/N by measuring the envelope in size versus S/N below which 99 per cent of the simulated point sources lie. We determine that 1 per cent of point sources scatter above an envelope of log (R P /arcsec) = −1.05log (S/N) − 0.25.…”

Section: The Radio Sizes Of Sfgs and Agn From Z = 1-3mentioning

confidence: 99%

“…However, by z ∼ 2 these observations probe rest-frame frequencies ν rest 10-30 GHz, a region of the radio spectrum in which the effects of spectral curvature may become important due to the increasing thermal free-free component at high-frequencies (e.g. Murphy et al 2011), and/or spectral steepening due to cosmic-ray effects (Galvin et al 2018;Thomson et al 2019) and free-free absorption (Tisanić et al 2019). This potential for spectral curvature complicates efforts to measure the rest-frame radio luminosities (conventionally, L 1.4 GHz ) of high-redshift galaxies from these higher-frequency observations.…”

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confidence: 99%

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The e-MERGE Survey (e-MERLIN Galaxy Evolution Survey): overview and survey description

Muxlow

Thomson

Radcliffe

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We present an overview and description of the e-MERGE Survey (e-MERLIN Galaxy Evolution Survey) Data Release 1 (DR1), a large program of high-resolution 1.5-GHz radio observations of the GOODS-N field comprising ∼140 h of observations with enhanced-Multi-Element Remotely Linked Interferometer Network (e-MERLIN) and ∼40 h with the Very Large Array (VLA). We combine the long baselines of e-MERLIN (providing high angular resolution) with the relatively closely packed antennas of the VLA (providing excellent surface brightness sensitivity) to produce a deep 1.5-GHz radio survey with the sensitivity (${\sim}1.5\, \mu$ Jy beam−1), angular resolution (0.2–0.7 arcsec) and field-of-view (∼15 × 15 arcmin2) to detect and spatially resolve star-forming galaxies and active galactic nucleus (AGN) at $z$ ≳ 1. The goal of e-MERGE is to provide new constraints on the deep, sub-arcsecond radio sky which will be surveyed by SKA1-mid. In this initial publication, we discuss our data analysis techniques, including steps taken to model in-beam source variability over an ∼20-yr baseline and the development of new point spread function/primary beam models to seamlessly merge e-MERLIN and VLA data in the uv plane. We present early science results, including measurements of the luminosities and/or linear sizes of ∼500 galaxies selected at 1.5 GHz. In combination with deep Hubble Space Telescope observations, we measure a mean radio-to-optical size ratio of re-MERGE/rHST ∼ 1.02 ± 0.03, suggesting that in most high-redshift galaxies, the ∼GHz continuum emission traces the stellar light seen in optical imaging. This is the first in a series of papers that will explore the ∼kpc-scale radio properties of star-forming galaxies and AGN in the GOODS-N field observed by e-MERGE DR1.

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“…Due to the significant levels of dust obscuration present in these sources, it is not always possible to perform morphological analyses in the optical waveband. Relatively small pilot studies have suggested that such classifications are possible using high resolution radio continuum observations (Biggs & Ivison 2008;Casey et al 2009a,b;Thomson et al 2019). Fortunately, the survey characteristics necessary to find larger samples, in terms of resolution, depth and area covered, are very similar to those required for weak lensing.…”

Section: Introductionmentioning

confidence: 99%

SuperCLASS – I. The super cluster assisted shear survey: Project overview and data release 1

Battye¹,

Brown²,

Casey

et al. 2020

Monthly Notices of the Royal Astronomical Society

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The SuperCLuster Assisted Shear Survey (SuperCLASS) is a legacy programme using the e-MERLIN interferometric array. The aim is to observe the sky at L-band (1.4 GHz) to a r.m.s. of 7 µJy beam −1 over an area of ∼ 1 deg 2 centred on the Abell 981 supercluster. The main scientific objectives of the project are: (i) to detect the effects of weak lensing in the radio in preparation for similar measurements with the Square Kilometre Array (SKA); (ii) an extinction free census of star formation and AGN activity out to z ∼ 1. In this paper we give an overview of the project including the science goals and multi-wavelength coverage before presenting the first data release. We have analysed around 400 hours of e-MERLIN data allowing us to create a Data Release 1 (DR1) mosaic of ∼ 0.26 deg 2 to the full depth. These observations have been supplemented with complementary radio observations from the Karl G. Jansky Very Large Array (VLA) and optical/near infra-red observations taken with the Subaru, Canada-France-Hawaii and Spitzer Telescopes. The main data product is a catalogue of 887 sources detected by the VLA, of which 395 are detected by e-MERLIN and 197 of these are resolved. We have investigated the size, flux and spectral index properties of these sources finding them compatible with previous studies. Preliminary photometric redshifts, and an assessment of galaxy shapes measured in the radio data, combined with a radio-optical cross-correlation technique probing cosmic shear in a supercluster environment, are presented in companion papers.

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Radio Spectra and Sizes of Atacama Large Millimeter/submillimeter Array-identified Submillimeter Galaxies: Evidence of Age-related Spectral Curvature and Cosmic-Ray Diffusion?

Cited by 28 publications

References 107 publications

An ALMA survey of the brightest sub-millimetre sources in the SCUBA-2–COSMOS field

An ALMA survey of the brightest sub-millimetre sources in the SCUBA-2–COSMOS field

The e-MERGE Survey (e-MERLIN Galaxy Evolution Survey): overview and survey description

SuperCLASS – I. The super cluster assisted shear survey: Project overview and data release 1

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