Radio continuum size evolution of star-forming galaxies over 0.35 < z < 2.25

Abstract

To better constrain the physical mechanisms driving star formation, we present the first systematic study of the radio continuum size evolution of star-forming galaxies (SFGs) over the redshift range 0.35 < z < 2.25. We use the VLA COSMOS 3GHz map (noise rms = 2.3 µJy beam −1 , θ beam = 0.75 arcsec) to construct a mass-complete sample of 3184 radio-selected SFGs that reside on and above the main-sequence (MS) of SFGs. We constrain the overall extent of star formation activity in galaxies by applying a 2D-Gaussian model to their radio continuum emission. Extensive Monte Carlo simulations are used to validate the robustness of our measurements and characterize the selection function. We find no clear dependence between the radio size and stellar mass, M , of SFGs with 10.5 log(M /M ) 11.5. Our analysis suggests that MS galaxies are preferentially extended, while SFGs above the MS are always compact. The median effective radius of SFGs on (above) the MS of R eff = 1.5 ± 0.2 (1.0 ± 0.2) kpc remains nearly constant with cosmic time; a parametrization of the form R eff ∝ (1 + z) α yields a shallow slope of only α = −0.26 ± 0.08 (0.12 ± 0.14) for SFGs on (above) the MS. The size of the stellar component of galaxies is larger than the extent of the radio continuum emission by a factor ∼2 (1.3) at z = 0.5 (2), indicating star formation is enhanced at small radii. The galactic-averaged star formation rate surface density (Σ SFR ) scales with the distance to the MS, except for a fraction of MS galaxies ( 10%) that harbor starburst-like Σ SFR . These "hidden" starbursts might have experienced a compaction phase due to disk instability and/or merger-driven burst of star formation, which may or may not significantly offset a galaxy from the MS. We thus propose to jointly use Σ SFR and distance to the MS to better identify the galaxy population undergoing a starbursting phase.

An ALMA Survey of the SCUBA-2 Cosmology Legacy Survey UKIDSS/UDS Field: The Far-infrared/Radio Correlation for High-redshift Dusty Star-forming Galaxies

“…For ease of comparison to the literature, we will therefore adopt a fixed α=−0.80 for all AS2UDS SMGs detected only in the 1.4 GHz map. We note that, while the beam size of our GMRT observations is significantly larger than that of the VLA data, the typical low-frequency radio sizes of SMGs are ∼0 5-1 5 (Miettinen et al 2017;Jiménez-Andrade et al 2019;Thomson et al 2019), similar to the synthesized beam at 1.4 GHz. As such, this is much smaller than the largest angular scale to which we are sensitive with our data of ∼120″ based on the ∼50 hr of data taken in the VLA B-array configuration.…”

Automated Mining of the ALMA Archive in the COSMOS Field (A3COSMOS). I. Robust ALMA Continuum Photometry Catalogs and Stellar Mass and Star Formation Properties for ∼700 Galaxies at z = 0.5–6

“…C.4. Such a diagram is also used in similar works (e.g., Jiménez-Andrade et al 2019;Franco et al 2018). The left panel shows the dependency on S peak and the right panel on S total .…”

CO emission in distant galaxies on and above the main sequence

“…The same definition of starbursts as galaxies deviating from the main sequence has been recently questioned with the advent of high spatial resolution measurements of their dust and gas emission. Compact galaxies with short depletion timescales typical of SBs are now routinely found on the MS, being possibly on their way to leave the sequence (Barro et al 2017a;Popping et al 2017;Elbaz et al 2018;Gómez-Guijarro et al 2019;Puglisi et al 2019;Jiménez-Andrade et al 2019); or galaxies moving within the MS scatter, due to mergers unable to efficiently boost the star formation (Fensch et al 2017) or owing to gravitational instabilities and gas radial redistribution (Tacchella et al 2016).…”