The non-linear infrared-radio correlation of low-<i>z</i> galaxies: implications for redshift evolution, a new radio SFR recipe, and how to minimize selection bias

Molnár, D. Cs.; Sargent, M.; Leslie, S. K.; Magnelli, B.; Schinnerer, E.; Zamorani, G.; Delhaize, J.; Smolčić, Vernesa; Tisanić, Krešimir; Vardoulaki, E.

doi:10.1093/mnras/stab746

Cited by 44 publications

(44 citation statements)

References 88 publications

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“…However, as described in Section §4.2.1, the cut of SNR > 3 at GMRT 325 MHz biases our sample towards the SFGs with a relatively steeper radio spectrum at observer-frame 0.33-3 GHz. This might be the reason that our median IR is slightly lower than the measurements of some previous works (e.g., Bell 2003;Ivison et al 2010;Thomson et al 2014;Molnár et al 2021).…”

Section: Fir-radio Correlation For Bright 3 Ghz Sfgscontrasting

confidence: 81%

Radio spectral properties of star-forming galaxies in the MIGHTEE-COSMOS field and their impact on the far-infrared-radio correlation

Vaccari

Smail

et al. 2021

Monthly Notices of the Royal Astronomical Society

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We study the radio spectral properties of 2,094 star-forming galaxies (SFGs) by combining our early science data from the MeerKAT International GHz Tiered Extragalactic Exploration (MIGHTEE) survey with VLA, GMRT radio data, and rich ancillary data in the COSMOS field. These SFGs are selected at VLA 3 GHz, and their flux densities from MeerKAT 1.3 GHz and GMRT 325 MHz imaging data are extracted using the ‘super-deblending’ technique. The median radio spectral index is $\alpha _{\rm 1.3\, GHz}^{\rm 3\, GHz}=-0.80\pm 0.01$ without significant variation across the rest-frame frequencies ∼1.3–10 GHz, indicating radio spectra dominated by synchrotron radiation. On average, the radio spectrum at observer-frame 1.3–3 GHz slightly steepens with increasing stellar mass with a linear fitted slope of β = −0.08 ± 0.01, which could be explained by age-related synchrotron losses. Due to the sensitivity of GMRT 325 MHz data, we apply a further flux density cut at 3 GHz (S3 GHz ≥ 50 μJy) and obtain a sample of 166 SFGs with measured flux densities at 325 MHz, 1.3 GHz, and 3 GHz. On average, the radio spectrum of SFGs flattens at low frequency with the median spectral indices of $\alpha ^{\rm 1.3\, GHz}_{\rm 325\, MHz}=-0.59^{+0.02}_{-0.03}$ and $\alpha ^{\rm 3.0\, GHz}_{\rm 1.3\, GHz}=-0.74^{+0.01}_{-0.02}$. At low frequency, our stacking analyses show that the radio spectrum also slightly steepens with increasing stellar mass. By comparing the far-infrared-radio correlations of SFGs based on different radio spectral indices, we find that adopting $\alpha _{\rm 1.3\, GHz}^{\rm 3\, GHz}$ for k-corrections will significantly underestimate the infrared-to-radio luminosity ratio (qIR) for >17 per cent of the SFGs with measured flux density at the three radio frequencies in our sample, because their radio spectra are significantly flatter at low frequency (0.33–1.3 GHz).

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Section: Fir-radio Correlation For Bright 3 Ghz Sfgscontrasting

confidence: 81%

Radio spectral properties of star-forming galaxies in the MIGHTEE-COSMOS field and their impact on the far-infrared-radio correlation

Vaccari

Smail

et al. 2021

Monthly Notices of the Royal Astronomical Society

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“…Condon 1992;Tabatabaei et al 2017;Davies et al 2017), and the broad correlation is well documented, (e.g. Condon et al 2002;Murphy 2009;Murphy et al 2011;Molnár et al 2021). However, the detailed correlations and the underlying mechanisms are still the subject of much debate (e.g.…”

Section: Nearby Galaxiesmentioning

confidence: 91%

The Evolutionary Map of the Universe pilot survey

Norris

Marvil

Collier

et al. 2021

Publ. Astron. Soc. Aust.

115

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We present the data and initial results from the first pilot survey of the Evolutionary Map of the Universe (EMU), observed at 944 MHz with the Australian Square Kilometre Array Pathfinder (ASKAP) telescope. The survey covers $270 \,\mathrm{deg}^2$ of an area covered by the Dark Energy Survey, reaching a depth of 25–30 $\mu\mathrm{Jy\ beam}^{-1}$ rms at a spatial resolution of $\sim$ 11–18 arcsec, resulting in a catalogue of $\sim$ 220 000 sources, of which $\sim$ 180 000 are single-component sources. Here we present the catalogue of single-component sources, together with (where available) optical and infrared cross-identifications, classifications, and redshifts. This survey explores a new region of parameter space compared to previous surveys. Specifically, the EMU Pilot Survey has a high density of sources, and also a high sensitivity to low surface brightness emission. These properties result in the detection of types of sources that were rarely seen in or absent from previous surveys. We present some of these new results here.

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“…Our stacking analysis, in turn, provides the typical radio luminosity across a galaxy sample spanning a relatively wide range in star formation rate. While any variations in, for example, the far-infrared/radio correlation as a function of SFR (a non-linear correlation as advocated by e.g., Molnár et al 2021) are averaged across in our analysis, the resulting stacks accurately describe the typical radio luminosities of the underlying sample.…”

Section: Radio Stackingmentioning

confidence: 99%

“…Lowfrequency radio synchrotron emission in star-forming galaxies originates predominantly from the shocks produced by supernovae, and as such forms a delayed tracer of star formation activity (∼ 30 − 100 Myr; Bressan et al 2002). However, both at low and high redshift, the far-infrared/radio correlation remains an area of active investigation, with various studies finding that it may be non-linear, change with cosmic time, or depend on galaxy type or physical parameters such as stellar mass (Ivison et al 2010;Sargent et al 2010;Thomson et al 2014;Basu et al 2015;Magnelli et al 2015;Delhaize et al 2017;Read et al 2018;Algera et al 2020a;Delvecchio et al 2021;Molnár et al 2021). In addition, active galactic nuclei (AGN) may similarly emit at radio wavelengths, and can therefore further bias studies of radio star formation (e.g., Molnár et al 2018;Algera et al 2020a).…”

mentioning

confidence: 99%

COLDz: Probing Cosmic Star Formation With Radio Free-free Emission

Algera,

Hodge,

Riechers

et al. 2021

Preprint

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Radio free-free emission is considered to be one of the most reliable tracers of star formation in galaxies. However, as it constitutes the faintest part of the radio spectrum -being roughly an order of magnitude less luminous than radio synchrotron emission at the GHz frequencies typically targeted in radio surveys -the usage of free-free emission as a star formation rate tracer has mostly remained limited to the local Universe. Here we perform a multi-frequency radio stacking analysis using deep Karl G. Jansky Very Large Array observations at 1.4, 3, 5, 10 and 34 GHz in the COSMOS and GOODS-North fields to probe free-free emission in typical galaxies at the peak of cosmic star formation. We find that z ∼ 0.5 − 3 star-forming galaxies exhibit radio emission at rest-frame frequencies of ∼ 65 − 90 GHz that is ∼ 1.5 − 2× fainter than would be expected from a simple combination of freefree and synchrotron emission, as in the prototypical starburst galaxy M82. We interpret this as a deficit in high-frequency synchrotron emission, while the level of free-free emission is as expected from M82. We additionally provide the first constraints on the cosmic star formation history using free-free emission at 0.5 z 3, which are in good agreement with more established tracers at high redshift. In the future, deep multi-frequency radio surveys will be crucial in order to accurately determine the shape of the radio spectrum of faint star-forming galaxies, and to further establish radio free-free emission as a tracer of high-redshift star formation.

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The non-linear infrared-radio correlation of low-z galaxies: implications for redshift evolution, a new radio SFR recipe, and how to minimize selection bias

Cited by 44 publications

References 88 publications

Radio spectral properties of star-forming galaxies in the MIGHTEE-COSMOS field and their impact on the far-infrared-radio correlation

Radio spectral properties of star-forming galaxies in the MIGHTEE-COSMOS field and their impact on the far-infrared-radio correlation

The Evolutionary Map of the Universe pilot survey

COLDz: Probing Cosmic Star Formation With Radio Free-free Emission

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