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The radial gradient of gas-phase metallicity is a powerful probe of the chemical and structural evolution of star-forming galaxies, closely tied to disk formation and gas kinematics in the early universe. We present spatially resolved chemical and dynamical properties for a sample of 26 galaxies at $0.5 \lesssim z \lesssim 1.7$ from the MSA-3D survey. These innovative observations provide 3D spectroscopy of galaxies at a spatial resolution approaching JWST's diffraction limit and a high spectral resolution of $R\simeq2700$. The metallicity gradients measured in our galaxy sample range from $-$0.05 to 0.02 dex~kpc$^{-1}$. Most galaxies exhibit negative or flat radial gradients, indicating lower metallicity in the outskirts or uniform metallicity throughout the entire galaxy. We confirm a tight relationship between stellar mass and metallicity gradient at $z\sim1$ with small intrinsic scatter of 0.02 dex~kpc$^{-1}$. Our results indicate that metallicity gradients become increasingly negative as stellar mass increases, likely because the more massive galaxies tend to be more "disky". This relationship is consistent with the predictions from cosmological hydrodynamic zoom-in simulations with strong stellar feedback. This work presents the effort to harness the multiplexing capability of JWST NIRSpec/MSA in slit-stepping mode to map the chemical and kinematic profiles of high-redshift galaxies in large samples and at high spatial and spectral resolution., Comment: 23 pages, 6 figures, 1 table; submitted to ApJL

Integral field spectroscopy (IFS) is a powerful tool for understanding the formation of galaxies across cosmic history. We present the observing strategy and first results of MSA-3D, a novel JWST program using multi-object spectroscopy in a slit-stepping strategy to produce IFS data cubes. The program observed 43 normal star-forming galaxies at redshifts $0.5 \lesssim z \lesssim 1.5$, corresponding to the epoch when spiral thin-disk galaxies of the modern Hubble sequence are thought to emerge, obtaining kpc-scale maps of rest-frame optical nebular emission lines with spectral resolution $R\simeq2700$. Here we describe the multiplexed slit-stepping method which is $>15$ times more efficient than the NIRSpec IFS mode for our program. As an example of the data quality, we present a case study of an individual galaxy at $z=1.104$ (stellar mass $M_{*} = 10^{10.3}~M_{\odot}$, star formation rate~$=3~M_{\odot}$ yr$^{-1}$) with prominent face-on spiral structure. We show that the galaxy exhibits a rotationally supported disk with moderate velocity dispersion ($\sigma = 36^{+5}_{-4}$~\kms), a negative radial metallicity gradient ($-0.020\pm0.002$~dex\,kpc$^{-1}$), a dust attenuation gradient, and an exponential star formation rate density profile which closely matches the stellar continuum. These properties are characteristic of local spirals, indicating that mature galaxies are in place at $z\sim1$. We also describe the customized data reduction and original cube-building software pipelines which we have developed to exploit the powerful slit-stepping technique. Our results demonstrate the ability of JWST slit-stepping to study galaxy populations at intermediate to high redshifts, with data quality similar to current surveys of the $z\sim0.1$ universe., Comment: 24 pages, 12 figures, 1 table; submitted to ApJ, comments welcome. Our custom designed data reduction pipeline and example processed data-cube will be publicly released before the JWST Cycle 4 deadline

We study the spatially resolved outflow properties of CSWA13, an intermediate mass ($M_*=10^{9}~\mathrm{M}_{\odot}$), gravitationally lensed star-forming galaxy at $z=1.87$. We use Keck/KCWI to map outflows in multiple rest-frame ultraviolet ISM absorption lines, along with fluorescent Si II$^*$ emission, and nebular emission from C III] tracing the local systemic velocity. The spatial structure of outflow velocity mirrors that of the nebular kinematics, which we interpret to be a signature of a young galactic wind that is pressurizing the ISM of the galaxy but is yet to burst out. From the radial extent of Si II$^*$ emission, we estimate that the outflow is largely encapsulated within $3.5$ kpc. We explore the geometry (e.g., patchiness) of the outflow by measuring the covering fraction at different velocities, finding that the maximum covering fraction is at velocities $v\simeq-150$ km$\,$s$^{-1}$. Using the outflow velocity ($v_{out}$), radius ($R$), column density ($N$), and solid angle ($\Omega$) based on the covering fraction, we measure the mass loss rate $\log\dot{m}_{out}/(\mathrm{M}_{\odot}\text{yr}^{-1}) = 1.73\pm0.23$ and mass loading factor $\log\eta = 0.04\pm0.34$ for the low-ionization outflowing gas in this galaxy. These values are relatively large and the bulk of the outflowing gas is moving with speeds less than the escape velocity of the galaxy halo, suggesting that the majority of outflowing mass will remain in the circumgalactic medium and/or recycle back into the galaxy. The results support a picture of high outflow rates transporting mass and metals into the inner circumgalactic medium, providing the gas reservoir for future star formation., Comment: Submitted to ApJ. Comments welcome (17 pages, 10 figures, 1 table)

We present the first comparison of observed stellar continuum spectra of high-redshift galaxies and mock galaxy spectra generated from hydrodynamical simulations. The mock spectra are produced from the IllustrisTNG TNG100 simulation combined with stellar population models and take into account dust attenuation and realistic observational effects (aperture effects and noise). We compare the simulated $D_n4000$ and EW(H$\delta$) of galaxies with $10.5 \leq \log(M_\ast/M_\odot) \leq 11.5$ at $0.6 \leq z \leq 1.0$ to the observed distributions from the LEGA-C survey. TNG100 globally reproduces the observed distributions of spectral indices, implying that the age distribution of galaxies in TNG100 is generally realistic. Yet there are small but significant differences. For old galaxies, TNG100 shows small $D_n4000$ when compared to LEGA-C, while LEGA-C galaxies have larger EW(H$\delta$) at fixed $D_n4000$. There are several possible explanations: 1) LEGA-C galaxies have overall older ages combined with small contributions (a few percent in mass) from younger ($<1$~Gyr) stars, while TNG100 galaxies may not have such young sub-populations; 2) the spectral mismatch could be due to systematic uncertainties in the stellar population models used to convert stellar ages and metallicities to observables. In conclusion, the latest cosmological galaxy formation simulations broadly reproduce the global age distribution of galaxies at $z\sim1$ and, at the same time, the high quality of the latest observed and simulated datasets help constrain stellar population synthesis models as well as the physical models underlying the simulations., Comment: 17 pages, 12 figures, accepted by AJ

We present spatially resolved stellar kinematics for 797 $z=0.6-1$ galaxies selected from the LEGA-C survey and construct axisymmetric Jeans models to quantify their dynamical mass and degree of rotational support. The survey is $K_s$-band selected, irrespective of color or morphological type, and allows for a first assessment of the stellar dynamical structure of the general $L^*$ galaxy population at large lookback time. Using light profiles from Hubble Space Telescope imaging as a tracer, our approach corrects for observational effects (seeing convolution and slit geometry), and uses well-informed priors on inclination, anisotropy and a non-luminous mass component. Tabulated data include total mass estimates in a series of spherical apertures (1, 5, and 10 kpc; 1$\times$ and 2$\times$\re), as well as rotational velocities, velocity dispersions and anisotropy. We show that almost all star-forming galaxies and $\sim$50\% of quiescent galaxies are rotation-dominated, with deprojected $V/\sigma\sim1-2$. Revealing the complexity in galaxy evolution, we find that the most massive star-forming galaxies are among the most rotation-dominated, and the most massive quiescent galaxies among the least rotation-dominated galaxies. These measurements set a new benchmark for studying galaxy evolution, using stellar dynamical structure for galaxies at large lookback time. Together with the additional information on stellar population properties from the LEGA-C spectra, the dynamical mass and $V/\sigma$ measurements presented here create new avenues for studying galaxy evolution at large lookback time., Comment: Accepted for publication in ApJ. Data table will be published with journal article and is now available upon request

We present the third and final data release of the Large Early Galaxy Astrophysics Census (LEGA-C), an ESO/VLT public spectroscopic survey targeting $0.6 < z < 1.0$, Ks-selected galaxies. The data release contains 3528 spectra with measured stellar velocity dispersions and stellar population properties, a 25-fold increase in sample size compared to previous work. This $K_s$-selected sample probes the galaxy population down to $\sim0.3 L^*$, for all colors and morphological types. Along with the spectra we publish a value-added catalog with stellar and ionized gas velocity dispersions, stellar absorption line indices, emission line fluxes and equivalent widths, complemented with structural parameters measured from HST/ACS imaging. With its combination of high precision and large sample size, LEGA-C provides a new benchmark for galaxy evolution studies., Comment: Accepted for publication in ApJS. Data available at http://archive.eso.org/cms/eso-archive-news/Third-and-final-release-of-the-Large-Early-Galaxy-Census-LEGA-C-Spectroscopic-Public-Survey-published.html or https://users.ugent.be/\string~avdrwel/research.html\#legac

We present a novel approach to measure the attenuation curves of 485 individual star-forming galaxies with M$_*$ $>$ 10$^{10}$ M$_{\odot}$ based on deep optical spectra from the VLT/VIMOS LEGA-C survey and multi-band photometry in the COSMOS field. Most importantly, we find that the attenuation curves in the rest-frame $3000-4500$A range are typically almost twice as steep as the Milky Way, LMC, SMC, and Calzetti attenuation curves, which is in agreement with recent studies of the integrated light of present-day galaxies. The attenuation at $4500$A and the slope strongly correlate with the galaxy inclination: face-on galaxies show less attenuation and steeper curves compared to edge-on galaxies, suggesting that geometric effects dominate observed variations in attenuation. Our new method produces $2175$A UV bump detections for 260 individual galaxies. Even though obvious correlations between UV bump strength and global galaxy properties are absent, strong UV bumps are most often seen in face-on, lower-mass galaxies (10 $<$ log$_{10}$(M$_*$/M$_{\odot}$) $<$ 10.5) with low overall attenuation. Finally, we produce a typical attenuation curve for star-forming galaxies at $z\sim0.8$; this prescription represents the effect of dust on the integrated spectral energy distributions of high-redshift galaxies more accurately than commonly used attenuation laws., Comment: 15 pages, 10 figures, 1 table. Accepted for publication in The Astrophysical Journal

We analyze the colors and sizes of 32 quiescent (UVJ-selected) galaxies with strong Balmer absorption ($\mbox{EW}(H\delta) \geq 4$\AA) at $z\sim0.8$ drawn from DR2 of the LEGA-C survey to test the hypothesis that these galaxies experienced compact, central starbursts before quenching. These recently quenched galaxies, usually referred to as post-starburst galaxies, span a wide range of colors and we find a clear correlation between color and half-light radius, such that bluer galaxies are smaller. We build simple toy models to explain this correlation: a normal star-forming disk plus a central, compact starburst component. Bursts with exponential decay timescale of $\sim$~100 Myr that produce $\sim10\%$ to more than 100\% of the pre-existing masses can reproduce the observed correlation. More significant bursts also produce bluer and smaller descendants. Our findings imply that when galaxies shut down star formation rapidly, they generally had experienced compact, starburst events and that the large, observed spread in sizes and colors mostly reflects a variety of burst strengths. Recently quenched galaxies should have younger stellar ages in the centers; multi-wavelength data with high spatial resolution are required to reveal the age gradient. Highly dissipative processes should be responsible for this type of formation history. While determining the mechanisms for individual galaxies is challenging, some recently quenched galaxies show signs of gravitational interactions, suggesting that mergers are likely an important mechanism in triggering the rapid shut-down of star-formation activities at $z\sim0.8$., Comment: 16 pages, 8 figures, 1 table, accepted by ApJ

We use reconstructed star-formation histories (SFHs) of quiescent galaxies at $z=0.6-1$ in the LEGA-C survey to identify secondary star-formation episodes that, after an initial period of quiescence, moved the galaxies back to the star-forming main sequence (blue cloud). $16\pm3$\% of the $z\sim0.8$ quiescent population has experienced such rejuvenation events in the redshift range $0.7

Maintenance-mode feedback from low-accretion rate AGN, manifesting itself observationally through radio-loudness, is invoked in all cosmological galaxy formation models as a mechanism that prevents excessive star-formation in massive galaxies (M$_*$ $\gtrsim$ 3$\times$10$^{10}$ M$_{\odot}$). We demonstrate that at a fixed mass the incidence of radio-loud AGN (L $>$ 10$^{23}$ WHz$^{- 1}$) identified in the FIRST and NVSS radio surveys among a large sample of quiescent (non-star forming) galaxies selected from the SDSS is much higher in geometrically round galaxies than in geometrically flat, disk-like galaxies. As found previously, the RL AGN fraction increases steeply with stellar velocity dispersion $\sigma_*$ and stellar mass, but even at a fixed velocity dispersion of 200-250 kms$^{-1}$ this fraction increases from 0.3% for flat galaxies (projected axis ratio of q $<$ 0.4) to 5% for round galaxies (q $>$ 0.8). We rule out that this strong trend is due to projection effects in the measured velocity dispersion. The large fraction of radio-loud AGN in massive, round galaxies is consistent with the hypothesis that such AGN deposit energy into their hot gaseous halos, preventing cooling and star-formation. However, the absence of such AGN in disk-like quiescent galaxies -- most of which are not satellites in massive clusters, raises important questions: is maintenance-mode feedback a generally valid explanation for quiescence; and, if so, how does that feedback avoid manifesting at least occasionally as a radio-loud galaxy?, Comment: 7 pages, 5 figures, accepted for publication in ApJ Letters

We present a comparison of the observed, spatially integrated stellar and ionized gas velocity dispersions of $\sim1000$ massive ($\log M_{\star}/M_{\odot}\gtrsim\,10.3$) galaxies in the Large Early Galaxy Astrophysics Census (LEGA-C) survey at $0.6\lesssim\,z\lesssim1.0$. The high $S/N\sim20{\rm\AA^{-1}}$ afforded by 20 hour VLT/VIMOS spectra allows for joint modeling of the stellar continuum and emission lines in all galaxies, spanning the full range of galaxy colors and morphologies. These observed integrated velocity dispersions (denoted as $\sigma'_{g, int}$ and $\sigma'_{\star, int}$) are related to the intrinsic velocity dispersions of ionized gas or stars, but also include rotational motions through beam smearing and spectral extraction. We find good average agreement between observed velocity dispersions, with $\langle\log(\sigma'_{g, int}/\sigma'_{\star, int})\rangle=-0.003$. This result does not depend strongly on stellar population, structural properties, or alignment with respect to the slit. However, in all regimes we find significant scatter between $\sigma'_{g, int}$ and $\sigma'_{\star, int}$, with an overall scatter of 0.13 dex of which 0.05 dex is due to observational uncertainties. For an individual galaxy, the scatter between $\sigma'_{g, int}$ and $\sigma'_{\star, int}$ translates to an additional uncertainty of $\sim0.24\rm{dex}$ on dynamical mass derived from $\sigma'_{g, int}$, on top of measurement errors and uncertainties from Virial constant or size estimates. We measure the $z\sim0.8$ stellar mass Faber-Jackson relation and demonstrate that emission line widths can be used to measure scaling relations. However, these relations will exhibit increased scatter and slopes that are artificially steepened by selecting on subsets of galaxies with progressively brighter emission lines., Comment: 9 pages, 5 figures, Accepted for publication in ApJ Letters

We present the second data release of the Large Early Galaxy Astrophysics Census (LEGA-C), an ESO 130-night public spectroscopic survey conducted with VIMOS on the Very Large Telescope. We release 1988 spectra with typical continuum S / N ~= 20 /Angstrom of galaxies at 0.6 ~< z ~< 1.0, each observed for ~20 hours and fully reduced with a custom-built pipeline. We also release a catalog with spectroscopic redshifts, emission line fluxes, Lick/IDS indices, and observed stellar and gas velocity dispersions that are spatially integrated quantities including both rotational motions and genuine dispersion. To illustrate the new parameter space in the intermediate redshift regime probed by LEGA-C we explore relationships between dynamical and stellar population properties. The star-forming galaxies typically have observed stellar velocity dispersions of ~150 km/s and strong Hdelta absorption (Hd_A ~ 5 Angstrom), while passive galaxies have higher observed stellar velocity dispersions ~200 km/s and weak Hdelta absortion (Hd_A ~ 0 Angstrom). Strong [O III]5007 / Hbeta ratios tend to occur mostly for galaxies with weak Hd_A or galaxies with higher observed velocity dispersion. Beyond these broad trends, we find a large diversity of possible combinations of rest-frame colors, absorption line strengths and emission line detections, illustrating the utility of spectroscopic measurements to more accurately understand galaxy evolution. By making the spectra and value-added catalogs publicly available we encourage the community to take advantage of this very substantial investment in telescope time provided by ESO., Comment: accepted for publication by ApJ; LEGA-C data-release http://www.mpia.de/home/legac/

We analyze stellar age indicators (D$_n$4000 and EW(H$\delta$)) and sizes of 467 quiescent galaxies with $M_\ast \geq 10^{10} M_\odot$ at $z\sim0.7$ drawn from DR2 of the LEGA-C survey. Interpreting index variations in terms of equivalent single stellar population age, we find that the median stellar population is younger for larger galaxies at fixed stellar mass. The effect is significant, yet small; the ages of the larger and the smaller subsets differ by only $<500$ Myr, much less than the age variation among individual galaxies ($\sim1.5$ Gyr). At the same time, quiescent galaxies with the strongest H$\delta$ absorption --- those experienced recent and rapid quenching events --- tend to be smaller than the average. These co-existing trends unify seemingly contradictory results in the literature; the complex correlations between size and age indicators revealed by our large sample of galaxies with high-quality spectra suggest that there are multiple evolutionary pathways to quiescence. Regardless of the specific physical mechanisms responsible for the cessation of star formation in massive galaxies, the large scatter in D$_n$4000 and EW(H$\delta$) immediately implies that galaxies follow a large variety in evolutionary pathways. On the one hand, we see evidence for a process that slowly shuts off star-formation and transforms star-forming galaxies to quiescent galaxies without necessarily changing their structures. On the other hand, there is likely a mechanism that rapidly quenches galaxies, an event that coincides with dramatic structural changes, producing small post-starburst galaxies., Comment: Main part 16 pages, 13 figures. Appendix: 8 figures. Accepted by ApJ

A decade of study has established that the molecular gas properties of star-forming galaxies follow coherent scaling relations out to z~3, suggesting remarkable regularity of the interplay between molecular gas, star formation, and stellar growth. Passive galaxies, however, are expected to be gas-poor and therefore faint, and thus little is known about molecular gas in passive galaxies beyond the local universe. Here we present deep Atacama Large Millimeter/submillimeter Array (ALMA) observations of CO(2-1) emission in 8 massive (Mstar ~ 10^11 Msol) galaxies at z~0.7 selected to lie a factor of 3-10 below the star-forming sequence at this redshift, drawn from the Large Early Galaxy Astrophysics Census (LEGA-C) survey. We significantly detect half the sample, finding molecular gas fractions <~0.1. We show that the molecular and stellar rotational axes are broadly consistent, arguing that the molecular gas was not accreted after the galaxies became quiescent. We find that scaling relations extrapolated from the star-forming population over-predict both the gas fraction and gas depletion time for passive objects, suggesting the existence of either a break or large increase in scatter in these relations at low specific star formation rate. Finally, we show that the gas fractions of the passive galaxies we have observed at intermediate redshifts are naturally consistent with evolution into local massive early-type galaxies by continued low-level star formation, with no need for further gas accretion or dynamical stabilization of the gas reservoirs in the intervening 6 billion years., Comment: 23 pages, 9 figures, accepted to ApJ. Key results in Figures 7, 8, and 9

Using high resolution spectra from the VLT LEGA-C program, we reconstruct the star formation histories (SFHs) of 607 galaxies at redshifts $z = 0.6-1.0$ and stellar masses $\gtrsim10^{10}$M$_{\odot}$ using a custom full spectrum fitting algorithm that incorporates the emcee and FSPS packages. We show that the mass-weighted age of a galaxy correlates strongly with stellar velocity dispersion ($\sigma_*$) and ongoing star-formation (SF) activity, with the stellar content in higher-$\sigma_*$ galaxies having formed earlier and faster. The SFHs of quiescent galaxies are generally consistent with passive evolution since their main SF epoch, but a minority show clear evidence of a rejuvenation event in their recent past. The mean age of stars in galaxies that are star-forming is generally significantly younger, with SF peaking after $z<1.5$ for almost all star-forming galaxies in the sample: many of these still have either constant or rising SFRs on timescales $>100$Myrs. This indicates that $z>2$ progenitors of $z\sim1$ star-forming galaxies are generally far less massive. Finally, despite considerable variance in the individual SFHs, we show that the current SF activity of massive galaxies ($>$L$_*$) at $z\sim1$ correlates with SF levels at least $3$Gyrs prior: SFHs retain `memory' on a large fraction of the Hubble time. Our results illustrate a novel approach to resolve the formation phase of galaxies, and in identifying their individual evolutionary paths, connects progenitors and descendants across cosmic time. This is uniquely enabled by the high-quality continuum spectroscopy provided by the LEGA-C survey., Comment: 18 pages, 9 figures, accepted by ApJ

We present stellar rotation curves and velocity dispersion profiles for 104 quiescent galaxies at $z=0.6-1$ from the Large Early Galaxy Astrophysics Census (LEGA-C) spectroscopic survey. Rotation is typically probed across 10-20kpc, or to an average of 2.7${\rm R_e}$. Combined with central stellar velocity dispersions ($\sigma_0$) this provides the first determination of the dynamical state of a sample selected by a lack of star formation activity at large lookback time. The most massive galaxies ($M_{\star}>2\times10^{11}\,M_{\odot}$) generally show no or little rotation measured at 5kpc ($|V_5|/\sigma_0<0.2$ in 8 of 10 cases), while ${\sim}64\%$ of less massive galaxies show significant rotation. This is reminiscent of local fast- and slow-rotating ellipticals and implies that low- and high-redshift quiescent galaxies have qualitatively similar dynamical structures. We compare $|V_5|/\sigma_0$ distributions at $z\sim0.8$ and the present day by re-binning and smoothing the kinematic maps of 91 low-redshift quiescent galaxies from the CALIFA survey and find evidence for a decrease in rotational support since $z\sim1$. This result is especially strong when galaxies are compared at fixed velocity dispersion; if velocity dispersion does not evolve for individual galaxies then the rotational velocity at 5kpc was an average of ${94\pm22\%}$ higher in $z\sim0.8$ quiescent galaxies than today. Considering that the number of quiescent galaxies grows with time and that new additions to the population descend from rotationally-supported star-forming galaxies, our results imply that quiescent galaxies must lose angular momentum between $z\sim1$ and the present, presumably through dissipationless merging, and/or that the mechanism that transforms star-forming galaxies also reduces their rotational support., Comment: 30 pages, 18 figures, Accepted for Publication in ApJ

Drawing from the LEGA-C dataset, we present the spectroscopic view of the stellar population across a large volume- and mass-selected sample of galaxies at large lookback time. We measure the 4000\AA\ break (D$_n$4000) and Balmer absorption line strengths (probed by H$\delta$) from 1019 high-quality spectra of $z=0.6 - 1.0$ galaxies with $M_\ast = 2 \times 10^{10} M_\odot - 3 \times 10^{11} M_\odot$. Our analysis serves as a first illustration of the power of high-resolution, high-S/N continuum spectroscopy at intermediate redshifts as a qualitatively new tool to constrain galaxy formation models. The observed D$_n$4000-EW(H$\delta$) distribution of our sample overlaps with the distribution traced by present-day galaxies, but $z\sim 0.8$ galaxies populate that locus in a fundamentally different manner. While old galaxies dominate the present-day population at all stellar masses $> 2\times10^{10} M_\odot$, we see a bimodal D$_n$4000-EW(H$\delta$) distribution at $z\sim0.8$, implying a bimodal light-weighted age distribution. The light-weighted age depends strongly on stellar mass, with the most massive galaxies $>1\times10^{11}M_\odot$ being almost all older than 2 Gyr. At the same time we estimate that galaxies in this high mass range are only $\sim3$ Gyr younger than their $z\sim0.1$ counterparts, at odd with pure passive evolution given a difference in lookback time of $>5$ Gyr; younger galaxies must grow to $>10^{11}M_\odot$ in the meantime, and/or small amounts of young stars must keep the light-weighted ages young. Star-forming galaxies at $z\sim0.8$ have stronger H$\delta$ absorption than present-day galaxies with the same D$_n$4000, implying larger short-term variations in star-formation activity., Comment: 17 pages, 9 figures, accepted by ApJ

We investigate the stellar kinematics and stellar populations of 58 radio-loud galaxies of intermediate luminosities (L$_{3 GHz}$ $>$ 10$^{23}$ W Hz$^{-1}$ ) at 0.6 < z < 1. This sample is constructed by cross-matching galaxies from the deep VLT/VIMOS LEGA-C spectroscopic survey with the VLA 3 GHz dataset. The LEGA-C continuum spectra reveal for the first time stellar velocity dispersions and age indicators of z $\sim$ 1 radio galaxies. We find that $z\sim 1$ radio-loud AGN occur exclusively in predominantly old galaxies with high velocity dispersions: $\sigma_*>$ 175 km s$^{-1}$, corresponding to black hole masses in excess of $10^8$ M$_{\odot}$. Furthermore, we confirm that at a fixed stellar mass the fraction of radio-loud AGN at z $\sim$ 1 is 5 - 10 times higher than in the local universe, suggesting that quiescent, massive galaxies at z $\sim$ 1 switch on as radio AGN on average once every Gyr. Our results strengthen the existing evidence for a link between high black-hole masses, radio loudness and quiescence at z $\sim$ 1., Comment: 10 pages, 8 figures, 1 table. Accepted for publication in The Astrophysical Journal

Recent studies have found a significant evolution and scatter in the IRX-$\beta$ relation at z > 4, suggesting different dust properties of these galaxies. The total far-infrared (FIR) luminosity is key for this analysis but poorly constrained in normal (main-sequence) star-forming z > 5 galaxies where often only one single FIR point is available. To better inform estimates of the FIR luminosity, we construct a sample of local galaxies and three low-redshift analogs of z > 5 systems. The trends in this sample suggest that normal high-redshift galaxies have a warmer infrared (IR) SED compared to average z < 4 galaxies that are used as prior in these studies. The blue-shifted peak and mid-IR excess emission could be explained by a combination of a larger fraction of the metal-poor inter-stellar medium (ISM) being optically thin to ultra-violet (UV) light and a stronger UV radiation field due to high star formation densities. Assuming a maximally warm IR SED suggests 0.6 dex increased total FIR luminosities, which removes some tension between dust attenuation models and observations of the IRX-$\beta$ relation at z > 5. Despite this, some galaxies still fall below the minimum IRX-$\beta$ relation derived with standard dust cloud models. We propose that radiation pressure in these highly star-forming galaxies causes a spatial offset between dust clouds and young star-forming regions within the lifetime of O/B stars. These offsets change the radiation balance and create viewing-angle effects that can change UV colors at fixed IRX. We provide a modified model that can explain the location of these galaxies on the IRX-$\beta$ diagram., Comment: 34 pages including Appendix, 18 figures (4 in Appendix), 5 tables (1 in Appendix). Accepted for publication in ApJ

We examine the rest-frame ultra-violet (UV) properties of 10 [CII]$\lambda158\,{\rm \mu m}$$-$detected galaxies at $z\sim5.5$ in COSMOS using new HST/WFC3 near-infrared imaging. Together with pre-existing $158\,{\rm \mu m}-$continuum and [CII] line measurements by ALMA, we study their dust attenuation properties on the IRX-$\beta$ diagram, which connects the total dust emission ($\propto$ IRX=log($L_{FIR}/L_{1600}$)) to the line-of-sight dust column ($\propto\beta$). We find systematically bluer UV continuum spectral slopes ($\beta$) compared to previous low-resolution ground-based measurements, which relieves some of the tension between models of dust attenuation and observations at high redshifts. While most of the galaxies are consistent with local starburst or Small Magellanic cloud like dust properties, we find galaxies with low IRX values and a large range in $\beta$ that cannot be explained by models of a uniform dust distribution well mixed with stars. A stacking analysis of Keck/DEIMOS optical spectra indicates that these galaxies are metal-poor with young stellar populations which could significantly alter their spatial dust distribution., Comment: 9 pages, 3 figures, 1 table. Accepted for publication in The Astrophysical Journal