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Disk galaxies at intermediate redshift (z ~ 0.7) have been found in previous work to display more optically thick behaviour than their local counterparts in the rest-frame B-band surface brightness, suggesting an evolution in dust properties over the past ~6 Gyr. We compare the measured luminosities of face-on and edge-on star-forming galaxies at different wavelengths (Ultraviolet (UV), mid-infrared (MIR), far-infrared (FIR), and radio) for two well-matched samples of disk-dominated galaxies: a local Sloan Digital Sky Survey (SDSS)-selected sample at z ~ 0.07 and a sample of disks at z ~ 0.7 drawn from Cosmic Evolution Survey (COSMOS). We have derived correction factors to account for the inclination dependence of the parameters used for sample selection. We find that typical galaxies are transparent at MIR wavelengths at both redshifts, and that the FIR and radio emission is also transparent as expected. However, reduced sensitivity at these wavelengths limits our analysis; we cannot rule out opacity in the FIR or radio. Ultra-violet attenuation has increased between z ~ 0 and z ~ 0.7, with the z ~ 0.7 sample being a factor of ~3.4 more attenuated. The larger UV attenuation at z ~ 0.7 can be explained by more clumpy dust around nascent star-forming regions. There is good agreement between the fitted evolution of the normalisation of the SFRUV versus 1 − cos(i) trend (interpreted as the clumpiness fraction) and the molecular gas fraction/dust fraction evolution of galaxies found out to z < 1. [ABSTRACT FROM AUTHOR]

By combining high-sensitivity LOFAR 150 MHz, uGMRT 400 MHz and 1250 MHz, GMRT 610 MHz, and VLA 5 GHz data in the ELAIS-N1 field, we study the radio spectral properties of radio-detected star-forming galaxies (SFGs) at observer-frame frequencies of 150–5000 MHz. We select ∼3500 SFGs that have both LOFAR 150 MHz and GMRT 610 MHz detections, and obtain a median two-point spectral index of |$\alpha _{150}^{610}=-0.51\pm 0.01$|⁠. The photometric redshift of these SFGs spans z  = 0.01−6.21. We also measure the two-point radio spectral indices at 150–400–610–1250 MHz and 150–610–5000 MHz, respectively, for the GMRT 610-MHz-detected SFGs, and find that, on average, the radio spectrum of SFGs is flatter at low frequency than at high frequency. At observer-frame 150–5000 MHz, we find that the radio spectrum slightly steepens with increasing stellar mass. However, we only find that the radio spectrum flattens with increasing optical depth at V band at |$\nu \lesssim 1$|  GHz. We suggest that spectral ageing due to the energy loss of CR electrons and thermal free–free absorption could be among the possible main physical mechanisms that drive the above two correlations, respectively. In addition, both of these mechanisms could physically explain why the radio spectrum is flatter at low frequency than at high frequency. [ABSTRACT FROM AUTHOR]

Context. Given the unprecedented depth achieved in current large radio surveys, we are starting to probe populations of radio sources that have not been studied in the past. However, identifying and categorising these objects, differing in size, shape and physical properties, is becoming a more difficult task. Aims. In this data paper we present and characterise the multi-component radio sources identified in the VLA-COSMOS Large Project at 3 GHz (0.75 arcsec resolution, 2.3 μJy beam−1 rms), i.e. the radio sources which are composed of two or more radio blobs. Methods. The classification of objects into multi-components was done by visual inspection of 351 of the brightest and most extended blobs from a sample of 10,899 blobs identified by the automatic code BLOBCAT. For that purpose we used multi-wavelength information of the field, such as the 1.4 GHz VLA-COSMOS data and the Ultra Deep Survey with the VISTA telescope (UltraVISTA) stacked mosaic available for COSMOS. Results. We have identified 67 multi-component radio sources at 3 GHz: 58 sources with active galactic nucleus (AGN) powered radio emission and nine star-forming galaxies. We report eight new detections that were not observed by the VLA-COSMOS Large Project at 1.4 GHz, due to the slightly larger area coverage at 3 GHz. The increased spatial resolution of 0.75 arcsec has allowed us to resolve (and isolate) multiple emission peaks of 28 extended radio sources not identified in the 1.4 GHz VLA-COSMOS map. We report the multi-frequency flux densities (324 MHz, 325 MHz, 1.4 GHz & 3 GHz), star formation rates, and stellar masses of these objects. We find that multi-component objects at 3 GHz VLA-COSMOS inhabit mainly massive galaxies (> 1010.5 M⊙). The majority of the multi-component AGN lie below the main sequence of star-forming galaxies (SFGs), in the green valley and the quiescent region. Furthermore, we provide detailed descriptions of the objects and find that amongst the AGN there are two head-tail, ten core-lobe, nine wide-angle-tail (WAT), eight double-double or Z-/X-shaped, three bent-tail radio sources, and 26 symmetric sources, while amongst the SFGs we find the only star-forming ring seen in radio emission in COSMOS. Additionally, we report a large number (32 out of 58) of disturbed/bent multi-component AGN, 18 of which do not lie within X-ray groups in COSMOS (redshift range 0.08 ≤ z <  1.53). Conclusion. The high angular resolution and sensitivity of the 3 GHz VLA-COSMOS data set give us the opportunity to identify peculiar radio structures and sub-structures of multi-component objects, and relate them to physical phenomena such as AGN or star-forming galaxies. This study illustrates the complexity of the μJy radio-source population; at the sensitivity and resolution of 3 GHz VLA-COSMOS, the radio structures of AGN and SFG both emitting radio continuum emission, become comparable in the absence of clear, symmetrical jets. Thus, disentangling the AGN and SFG contributions using solely radio observations can be misleading in a number of cases. This has implications for future surveys, such as those done by square kilometre array (SKA) and precursors, which will identify hundreds of thousands of multi-component objects. [ABSTRACT FROM AUTHOR]

Local galaxies from the Sloan Digital Sky Survey (SDSS) are used to provide additional support for an evolutionary pathway in which active galactic nucleus activity is associated with star formation quenching. Composite, Seyfert 2, and LINER galaxies account for ∼60 per cent of all star formation in massive galaxies (M ⋆ > 1010.5 M⊙). Inclusion of these galaxies results in a 'turnover' in the star formation rate and stellar mass (SFR− M ⋆) relation for massive galaxies. Our analysis shows that bulge growth has already occurred in the most massive galaxies (M ⋆ > 1010.5 M⊙), and bulges continue to grow as galaxies quench and redden, (g − r)  = 0.5 → 0.75. Significant bulge growth is also occurring in low mass starburst galaxies (M ⋆ < 1010.5 M⊙) at 0.5 dex above the 'main sequence' (MS), where we find an increase in B/T from 0.1 → 0.3 and bluer colours, (g − r) < 0.25 compared to low-mass galaxies on the MS. [ABSTRACT FROM AUTHOR]

This work presents a study of galactic outflows driven by stellar feedback. We extract mainsequence disc galaxies with stellar mass 109 ≤ M*/ M ≤ 5.7 × 1010 at redshift z = 0 from the highest resolution cosmological simulation of the Evolution and Assembly of GaLaxies and their Environments (EAGLE) set. Synthetic gas rotation velocity and velocity dispersion (σ) maps are created and compared to observations of disc galaxies obtained with the Sydney-AAO (Australian Astronomical Observatory) Multi-object Integral field spectrograph (SAMI), where σ- values greater than 150 km s−1 are most naturally explained by bipolar outflows powered by starburst activity. We find that the extension of the simulated edge-on (pixelated) velocity dispersion probability distribution depends on stellar mass and star formation rate surface density (ΣSFR), with low-MM*/low- ΣSFR galaxies showing a narrow peak at low σ (~30 km s−1) and more active, high-MM*/high-ΣSFR galaxies reachingσ >150 km s−1. Although supernova-driven galactic winds in the EAGLE simulations may not entrain enough gas with T <105 K compared to observed galaxies, we find that gas temperature is a good proxy for the presence of outflows. There is a direct correlation between the thermal state of the gas and its state of motion as described by the σ-distribution. The following equivalence relations hold in EAGLE: (i) low- σ peak ⇔disc of the galaxy ⇔gas with T <105 K; (ii) high- σ tail ⇔galactic winds ⇔gas with T ≥105 K. [ABSTRACT FROM AUTHOR]