We present the results of a systematic search for candidate quiescent galaxies in the distant universe in 11 JWST fields with publicly available observations collected during the first 3 months of operations and covering an effective sky area of ∼145 arcmin 2 . We homogeneously reduce the new JWST data and combine them with existing observations from the Hubble Space Telescope. We select a robust sample of ∼80 candidate quiescent and quenching galaxies at 3 < z < 5 using two methods: (1) based on their rest-frame UVJ colors, and (2) a novel quantitative approach based on Gaussian mixture modeling of the near-UV − U , U − V , and V − J rest-frame color space, which is more sensitive to recently quenched objects. We measure comoving number densities of massive ( M⋆ ≥ 10 10.6M⊙ ) quiescent galaxies consistent with previous estimates relying on ground-based observations, after homogenizing the results in the literature with our mass and redshift intervals. However, we find significant field-to-field variations of the number densities up to a factor of 2–3, highlighting the effect of cosmic variance and suggesting the presence of overdensities of red quiescent galaxies at z > 3, as could be expected for highly clustered massive systems. Importantly, JWST enables the robust identification of quenching/quiescent galaxy candidates at lower masses and higher redshifts than before, challenging standard formation scenarios. All data products, including the literature compilation, are made publicly available.
There is a large consensus that gas in high-z galaxies is highly turbulent, because of a combination of stellar feedback processes and gravitational instabilities driven by mergers and gas accretion. In this paper, we present the analysis of a sample of five Dusty Star Forming Galaxies (DSFGs) at 4 ≲ z ≲ 5. Taking advantage of the magnifying power of strong gravitational lensing, we quantified their kinematic and dynamical properties from ALMA observations of their [C ii] emission line. We combined the dynamical measurements obtained for these galaxies with those obtained from previous studies to build the largest sample of z ∼ 4.5 galaxies with high-quality data and sub-kpc spatial resolutions, so far. We found that all galaxies in the sample are dynamically cold, with rotation-to-random motion ratios, V/σ, between 7 and 15. The relation between their velocity dispersions and their star formation rates indicates that stellar feedback is sufficient to sustain the turbulence within these galaxies and no further mechanisms are needed. In addition, we performed a rotation curve decomposition to infer the relative contribution of the baryonic (gas, stars) and dark matter components to the total gravitational potentials. This analysis allowed us to compare the structural properties of the studied DSFGs with those of their descendants, the local early type galaxies. In particular, we found that five out of six galaxies of the sample show the dynamical signature of a bulge, indicating that the spheroidal component is already in place at z ∼ 4.5.
This paper examines the need for large-scale, sustainable changes, and the effects of citizens' active participation and design co-operating to realise such changes. Section 1, starting from Pelle Ehn's last contribution, deals with participatory design and how it can be extended from the traditional idea of participation as the integration of users in projects, to the concept of participation as the interaction of active groups of citizens with open and articulated processes in the direction of socio-technical changes. Section 2 introduces the idea of planning by projects strategy and presents five design projects. Section 3 discusses how participatory design can be extended to give a rationale for these large-scale projects and what designers did in practice: triggered citizens’ interest, aligned their motivations and empowered their capabilities. The idea emerging from this discussion is that when participatory design is intended as an approach aiming at broad and complex transformation processes its traditional notion must integrate the concept of social innovation (first step) and evolve towards the idea of an open process where a multiplicity of small, diverse, participated initiatives (or local projects) interact (second step) to achieve a larger vision.
9 August 2021 in Monthly Notices of the Royal Astronomical Society
While the kinematics of galaxies up to z ∼ 3 have been characterized in detail, only a handful of galaxies at high redshift (z > 4) have been examined in such a way. The Atacama Large Millimeter/submillimeter Array (ALMA) Large Program to INvestigate [C ii] at Early times (ALPINE) survey observed a statistically significant sample of 118 star-forming main-sequence galaxies at z = 4.4–5.9 in [C ii]158 |$\mu$|m emission, increasing the number of such observations by nearly 10×. A preliminary qualitative classification of these sources revealed a diversity of kinematic types (i.e. rotators, mergers, and dispersion-dominated systems). In this work, we supplement the initial classification by applying quantitative analyses to the ALPINE data: a tilted ring model (TRM) fitting code (3Dbarolo), a morphological classification (Gini-M20), and a set of disc identification criteria. Of the 75 [C ii]-detected ALPINE galaxies, 29 are detected at sufficient significance and spatial resolution to allow for TRM fitting and the derivation of morphological and kinematic parameters. These 29 sources constitute a high-mass subset of the ALPINE sample (|$M_*\gt 10^{9.5}\, \mathrm{M}_{\odot }$|). We robustly classify 14 of these sources (six rotators, five mergers, and three dispersion-dominated systems); the remaining sources showing complex behaviour. By exploring the G-M20 of z > 4 rest-frame far-infrared and [C ii] data for the first time, we find that our 1 arcsec ∼ 6 kpc resolution data alone are insufficient to separate galaxy types. We compare the rotation curves and dynamical mass profiles of the six ALPINE rotators to the two previously detected z ∼ 4–6 unlensed main-sequence rotators, finding high rotational velocities (∼50–250 km s−1) and a diversity of rotation curve shapes.
16 February 2023 in Monthly Notices of the Royal Astronomical Society
The discovery of galaxies with regularly rotating discs at redshifts ≥ 4 has been a puzzling challenge to galaxy formation models that tend to predict chaotic gas kinematics in the early Universe as a consequence of gas accretion, mergers and efficient feedback. In this work, we investigated the kinematics of five highly resolved galaxies at z ∼ 4.5 observed with ALMA in the [CII] 158 μm emission line. The sample is diverse: AzTEC1 (starburst galaxy), BRI1335-0417 (starburst and quasar host galaxy), J081740 (normal star-forming galaxy) and SGP38326 (two starburst galaxies in a group). The five galaxies show velocity gradients, but four were found to be rotating discs while the remaining, AzTEC1, is likely a merger. We studied the gas kinematics of the discs using 3DBAROLO and found that they rotate with maximum rotation velocities between 198 and 562 km s−1 while the gas velocity dispersions, averaged across the discs, are between 49 and 75 km s−1. The rotation curves are generally flat and the galaxies have ratios of ordered-to-random motion (V/σ) between 2.7 and 9.8. We present CANNUBI, an algorithm for fitting the disc geometry of rotating discs in 3D emission-line observations prior to modelling the kinematics, with which we find indications that these discs may have thicknesses of the order of 1 kpc. This study shows that early disc formation with a clear dominance of rotation with respect to turbulent motions is present across a variety of galaxy types.