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One of the challenges in understanding the quenching processes for galaxies is connecting progenitor star-forming populations to their descendant quiescent populations over cosmic time. Here we attempt a novel approach to this challenge by assuming that the underlying stellar mass distribution of galaxies is not significantly altered during environmental-quenching processes that solely affect the gas content of cluster galaxies, such as strangulation and ram pressure stripping. Using the deep, high-resolution photometry of the Hubble Frontier Fields, we create resolved stellar mass maps for both cluster and field galaxies, from which we determine 2D Sérsic profiles, and obtain Sérsic indices and half-mass radii. We classify the quiescent cluster galaxies into disk-like and bulge-like populations based on their Sérsic indices, and find that bulge-like quiescent galaxies dominate the quiescent population at higher masses (M ⋆ > 109.5 M ⊙), whereas disk-like quiescent galaxies dominate at lower masses (108.5 M ⊙ < M ⋆ < 109.5 M ⊙). Using both the Sérsic indices and half-mass radii, we identify a population of quiescent galaxies in clusters that are morphological analogs of field star-forming galaxies. These analogs are interpreted to be star-forming galaxies that had been environmentally quenched. We use these morphological analogs to compute the environmental-quenching efficiency, and we find that the efficiency decreases with increasing stellar mass. This demonstrates that environmental quenching is more effective on less massive galaxies and that the effect of environment on quenching galaxies is not completely separable from the effect of mass on quenching galaxies.

The most distant galaxies detected were seen when the Universe was a scant 5% of its current age. At these times, progenitors of galaxies such as the Milky Way were about 10,000 times less massive. Using the James Webb Space Telescope (JWST) combined with magnification from gravitational lensing, these low-mass galaxies can not only be detected but also be studied in detail. Here we present JWST observations of a strongly lensed galaxy at z spec  = 8.296 ± 0.001, showing massive star clusters (the Firefly Sparkle) cocooned in a diffuse arc in the Canadian Unbiased Cluster Survey (CANUCS) 1 . The Firefly Sparkle exhibits traits of a young, gas-rich galaxy in its early formation stage. The mass of the galaxy is concentrated in 10 star clusters (49–57% of total mass), with individual masses ranging from 10 5 M ⊙ to 10 6 M ⊙ . These unresolved clusters have high surface densities (>10 3 M ⊙  pc − 2 ), exceeding those of Milky Way globular clusters and young star clusters in nearby galaxies. The central cluster shows a nebular-dominated spectrum, low metallicity, high gas density and high electron temperature, hinting at a top-heavy initial mass function. These observations provide our first spectrophotometric view of a typical galaxy in its early stages, in a 600-million-year-old Universe. JWST observations of a strongly lensed low-mass galaxy in a 600-million-year-old Universe show massive star clusters (the Firefly Sparkle) cocooned in a diffuse arc in the Canadian Unbiased Cluster Survey.

The resolved mass assembly of Milky Way–mass galaxies has been previously studied in simulations, the local Universe, and at higher redshifts using infrared (IR) light profiles. To better characterize the mass assembly of Milky Way analogs (MWAs), as well as their changes in star formation rate (SFR) and color gradients, we construct resolved stellar mass and SFR maps of MWA progenitors selected with abundance matching techniques up to z ∼2 using deep, multiwavelength imaging data from the Hubble Frontier Fields. Our results using stellar mass profiles agree well with previous studies that utilize IR light profiles, showing that the inner 2 kpc of the galaxies and the regions beyond 2 kpc exhibit similar rates of stellar mass growth. This indicates the progenitors of MWAs from z ∼ 2 to the present do not preferentially grow their bulges or their disks. The evolution of the SFR profiles indicates a greater decrease in SFR density in the inner regions versus the outer regions. Sérsic parameters indicate modest growth in the central regions at lower redshifts, perhaps indicating slight bulge growth. However, the Sérsic index does not rise above n ∼ 2 until z < 0.5, meaning these galaxies are still disk-dominated systems. We find that the half-mass radii of the MWA progenitors increase between 1.5 < z < 2, but remain constant at later epochs (z < 1.5). This implies mild bulge growth since z ∼ 2 in MWA progenitors, in line with previous MWA mass assembly studies.

Despite the ubiquity of clumpy star-forming galaxies at high-redshift, the origin of clumps are still largely unconstrained due to the limited observations that can validate the mechanisms for clump formation. We postulate that if clumps form due to the accretion of metal-poor gas that leads to violent disk instability, clumpy galaxies should have lower gas-phase metallicities compared to nonclumpy galaxies. In this work, we obtain the near-infrared spectrum for 42 clumpy and nonclumpy star-forming galaxies of similar masses, star formation rates, and colors at z ≈ 0.7 using the Gemini Near-Infrared Spectrograph (GNIRS) and infer their gas-phase metallicity from the [N ii]λ6584 and Hα line ratio. We find that clumpy galaxies have lower metallicities compared to nonclumpy galaxies, with an offset in the weighted average metallicity of 0.07 ± 0.02 dex. We also find an offset of 0.06 ± 0.02 dex between clumpy and nonclumpy galaxies in a comparable sample of 23 star-forming galaxies at z ≈ 1.5 using existing data from the FMOS-COSMOS survey. Similarly, lower [N ii]λ6584/Hα ratios are typically found in galaxies that have more of their UVrest luminosity originating from clumps, suggesting that clumpier galaxies are more metal-poor. We also derive the intrinsic velocity dispersion and line-of-sight rotational velocity for galaxies from the GNIRS sample. The majority of galaxies have σ0/vc ≈ 0.2, with no significant difference between clumpy and nonclumpy galaxies. Our result indicates that clump formation may be related to the inflow of metal-poor gas; however, the process that forms them does not necessarily require significant, long-term kinematic instability in the disk.

We present a resolved study of 877 progenitors of Milky Way Analogs (MWAs) at 0.3 < z < 5, selected with abundance matching in the 10 fields of the Canadian NIRISS Unbiased Cluster Survey. Utilizing 18–21 bands of deep NIRCam, NIRISS, and Hubble Space Telescope photometry, we create resolved stellar mass maps and star formation rate (SFR) maps via spectral energy distribution fitting with Dense Basis. We examine their resolved stellar mass and specific SFR (sSFR) profiles as a function of galactocentric radius and find clear evidence for inside-out mass assembly. The total M⋆ of the inner 2 kpc regions of the progenitors remains roughly constant (109.3−9.4M⊙) at 2 < z < 5, while the total M⋆ of the regions beyond 2 kpc increases by 0.8 dex, from 107.5M⊙to 108.3M⊙. Additionally, the sSFRs of the outer regions increase with decreasing redshift, until z ∼ 2. The median Sérsic index of the MWA progenitors stays nearly constant at n ∼ 1 at 2 < z < 5, while the half-mass radii of their stellar mass profiles double. We perform additional morphological measurements on the stellar mass maps via the Gini-M20 plane and asymmetry parameters. They show that the rate of double-peak mergers and disturbances to galaxy structure also increases with redshift, with ∼50% of galaxies at 4 < z < 5 classified as disturbed and ∼20% classified as ongoing mergers. Overall, the early evolution of MWAs is revealed as chaotic, with significant mergers and high SFRs. Mass growth is primarily inside-out and galaxies become more disklike after z = 3.

One of the challenges in understanding the quenching processes for galaxies is connecting progenitor star-forming populations to their descendant quiescent populations over cosmic time. Here we attempt a novel approach to this challenge by assuming that the underlying stellar mass distribution of galaxies is not significantly altered during environmental quenching processes that solely affect the gas content of cluster galaxies, such as strangulation and ram-pressure stripping. Using the deep, high-resolution photometry of the Hubble Frontier Fields, we create resolved stellar mass maps for both cluster and field galaxies, from which we determine 2D Sérsic profiles, and obtain Sérsic indices and half-mass radii. We classify the quiescent cluster galaxies into disk-like and bulge-like populations based on their Sérsic indices, and find that bulge-like quiescent galaxies dominate the quiescent population at higher masses (\\(M_ > 10^9.5M_\\)), whereas disk-like quiescent galaxies dominate at lower masses (\\(10^8.5M_< M_ < 10^9.5M_\\)). Using both the Sérsic indices and half-mass radii, we identify a population of quiescent galaxies in clusters that are \"morphological analogues\" of field star-forming galaxies. These analogues are interpreted to be star-forming galaxies that had been environmentally quenched. We use these morphological analogues to compute the environmental-quenching efficiency, and we find that the efficiency decreases with increasing stellar mass. This demonstrates that environmental quenching is more effective on less massive galaxies and that the effect of environment on quenching galaxies is not completely separable from the effect of mass on quenching galaxies.

The stability of Earth's climate on geological timescales is enabled by the carbon-silicate cycle that acts as a negative feedback mechanism stabilizing surface temperatures via the intake and outgas of atmospheric carbon. On Earth, this thermostat is enabled by plate tectonics that sequesters outgassed CO2 back into the mantle via weathering and subduction at convergent margins. Here we propose a separate tectonic mechanism -- vertical recycling -- that can serve as the vehicle for CO2 outgassing and sequestration over long timescales. The mechanism requires continuous tidal heating, which makes it particularly relevant to planets in the habitable zone of M stars. Dynamical models of this vertical recycling scenario and stability analysis show that temperate climates stable over Gy timescales are realized for a variety of initial conditions, even as the M star dims over time. The magnitude of equilibrium surface temperatures depends on the interplay of sea weathering and outgassing, which in turn depends on planetary carbon content, so that planets with lower carbon budgets are favoured for temperate conditions. Habitability of planets such as found in the Trappist-1 may be rooted in tidally-driven tectonics.

The resolved mass assembly of Milky-Way-mass galaxies has been previously studied in simulations, the local universe, and at higher redshifts using infrared (IR) light profiles. To better characterize the mass assembly of Milky Way Analogues (MWAs), as well as their changes in star-formation rate and color gradients, we construct resolved stellar mass and star-formation rate maps of MWA progenitors selected with abundance matching techniques up to z \\(\\) 2 using deep, multi-wavelength imaging data from the Hubble Frontier Fields. Our results using stellar mass profiles agree well with previous studies that utilize IR light profiles, showing that the inner 2 kpc of the galaxies and the regions beyond 2 kpc exhibit similar rates of stellar mass growth. This indicates the progenitors of MWAs from \\(z 2\\) to the present do not preferentially grow their bulges or their disks. The evolution of the star-formation rate (SFR) profiles indicate greater decrease in SFR density in the inner regions versus the outer regions. Sérsic parameters indicate modest growth in the central regions at lower redshifts, perhaps indicating slight bulge growth. However, the Sérsic index does not rise above \\(n 2\\) until \\(z < 0.5\\), meaning these galaxies are still disk dominated systems. We find that the half-mass radii of the MWA progenitors increase between \\(1.5 < z < 2\\), but remain constant at later epochs (\\(z < 1.5\\)). This implies mild bulge growth since \\(z 2\\) in MWA progenitors, in line with previous MWA mass assembly studies.

Despite the ubiquity of clumpy star-forming galaxies at high-redshift, the origin of clumps are still largely unconstrained due to the limited observations that can validate the mechanisms for clump formation. We postulate that if clumps form due to the accretion of metal-poor gas that leads to violent disk instability, clumpy galaxies should have lower gas-phase metallicities compared to non-clumpy galaxies. In this work, we obtain the near-infrared spectrum for 42 clumpy and non-clumpy star-forming galaxies of similar masses, SFRs, and colors at \\(z0.7\\) using the Gemini Near-Infrared Spectrograph (GNIRS) and infer their gas-phase metallicity from the and line ratio. We find that clumpy galaxies have lower metallicities compared to non-clumpy galaxies, with an offset in the weighted average metallicity of \\(0.070.02\\) dex. We also find an offset of \\(0.060.02\\) dex between clumpy and non-clumpy galaxies in a comparable sample of 23 star-forming galaxies at \\(z1.5\\) using existing data from the FMOS-COSMOS survey. Similarly, lower / ratio are typically found in galaxies that have more of their \\(UV_rest\\) luminosity originating from clumps, suggesting that clumpier galaxies are more metal poor. We also derive the intrinsic velocity dispersion and line-of-sight rotational velocity for galaxies from the GNIRS sample. The majority of galaxies have \\(_0/v_c 0.2\\), with no significant difference between clumpy and non-clumpy galaxies. Our result indicates that clump formation may be related to the inflow of metal-poor gas; however, the process that forms them does not necessarily require significant, long-term kinematic instability in the disk.

We investigate the resolved properties of star-forming clumps and their host galaxies at \\(0.5

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