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arXiv:2506.22257v1 Announce Type: new Abstract: We investigate the accuracy and range of validity of the perturbative model for the 2-point (2PCF) and 3-point (3PCF) correlation functions in real space in view of the forthcoming analysis of the Euclid mission spectroscopic sample. We take advantage of clustering measurements from four snapshots of the Flagship I N-body simulations at z = {0.9, 1.2, 1.5, 1.8}, which mimic the expected galaxy population in the ideal case of absence of observational effects such as purity and completeness. For the 3PCF we consider all available triangle configurations given a minimal separation. First, we assess the model performance by fixing the cosmological parameters and evaluating the goodness-of-fit provided by the perturbative bias expansion in the joint analysis of the two statistics, finding overall agreement with the data down to separations of 20 Mpc/h. Subsequently, we build on the state-of-the-art and extend the analysis to include the dependence on three cosmological parameters: the amplitude of scalar perturbations As, the matter density {\omega}cdm and the Hubble parameter h. To achieve this goal, we develop an emulator capable of generating fast and robust modelling predictions for the two summary statistics, allowing efficient sampling of the joint likelihood function. We therefore present the first joint full-shape analysis of the real-space 2PCF and 3PCF, testing the consistency and constraining power of the perturbative model across both probes, and assessing its performance in a combined likelihood framework. We explore possible systematic uncertainties induced by the perturbative model at small scales finding an optimal scale cut of rmin = 30 Mpc/h for the 3PCF, when imposing an additional limitation on nearly isosceles triangular configurations included in the data vector. This work is part of a Euclid Preparation series validating theoretical models for galaxy clustering.

arXiv:2506.22257v1 Announce Type: new Abstract: We investigate the accuracy and range of validity of the perturbative model for the 2-point (2PCF) and 3-point (3PCF) correlation functions in real space in view of the forthcoming analysis of the Euclid mission spectroscopic sample. We take advantage of clustering measurements from four snapshots of the Flagship I N-body simulations at z = {0.9, 1.2, 1.5, 1.8}, which mimic the expected galaxy population in the ideal case of absence of observational effects such as purity and completeness. For the 3PCF we consider all available triangle configurations given a minimal separation. First, we assess the model performance by fixing the cosmological parameters and evaluating the goodness-of-fit provided by the perturbative bias expansion in the joint analysis of the two statistics, finding overall agreement with the data down to separations of 20 Mpc/h. Subsequently, we build on the state-of-the-art and extend the analysis to include the dependence on three cosmological parameters: the amplitude of scalar perturbations As, the matter density {\omega}cdm and the Hubble parameter h. To achieve this goal, we develop an emulator capable of generating fast and robust modelling predictions for the two summary statistics, allowing efficient sampling of the joint likelihood function. We therefore present the first joint full-shape analysis of the real-space 2PCF and 3PCF, testing the consistency and constraining power of the perturbative model across both probes, and assessing its performance in a combined likelihood framework. We explore possible systematic uncertainties induced by the perturbative model at small scales finding an optimal scale cut of rmin = 30 Mpc/h for the 3PCF, when imposing an additional limitation on nearly isosceles triangular configurations included in the data vector. This work is part of a Euclid Preparation series validating theoretical models for galaxy clustering.

arXiv:2506.22287v1 Announce Type: new Abstract: Observing the interplay between galaxies and their gaseous surroundings is crucial for understanding how galaxies form and evolve, including the roles of long-lived cool gas reservoirs, starburst and AGN driven outflows. We use stacked Mg II absorption lines in the spectra of background quasars to study the cool gas out to 9Mpc from massive quiescent, star-forming and post-starburst galaxies with stellar masses $\log_{10}(M_{\mathrm{gal}}/M_\odot) \gtrsim 11.4$ and $0.4 \lesssim z \lesssim 0.8$ selected from the Baryon Oscillation Spectroscopic Survey (BOSS) CMASS galaxies. Consistent with previous studies, we observe a decline in absorption strength indicating a decrease in cool gas content with increasing distance from the galaxies, as well as decreasing star formation rate of the galaxies. Beyond 1Mpc, this decline levels off to the same absorption strength in all galaxy types, suggesting a transition from the circumgalactic medium (CGM) to the intergalactic medium (IGM) at approximately the virial radius of the host dark matter haloes. We find that post-starburst galaxies, that have experienced a recent burst of star formation that has rapidly quenched, exhibit significantly stronger Mg II absorption within 1Mpc than star-forming or quiescent galaxies of the same stellar mass. Because post-starburst galaxies are a potentially significant pathway for the formation of quiescent elliptical galaxies, our results have wide reaching implications for understanding the mechanisms involved in quenching star formation in galaxies. We speculate that the excess cool gas absorption out to 1Mpc around post-starburst galaxies is related to their observed high velocity ($\sim$1000\,km/s) cool gas outflows. Thus, strong, short-lived bursts of star formation impact the CGM around galaxies on Mpc distances and Gyr timescales.

arXiv:2506.22287v1 Announce Type: new Abstract: Observing the interplay between galaxies and their gaseous surroundings is crucial for understanding how galaxies form and evolve, including the roles of long-lived cool gas reservoirs, starburst and AGN driven outflows. We use stacked Mg II absorption lines in the spectra of background quasars to study the cool gas out to 9Mpc from massive quiescent, star-forming and post-starburst galaxies with stellar masses $\log_{10}(M_{\mathrm{gal}}/M_\odot) \gtrsim 11.4$ and $0.4 \lesssim z \lesssim 0.8$ selected from the Baryon Oscillation Spectroscopic Survey (BOSS) CMASS galaxies. Consistent with previous studies, we observe a decline in absorption strength indicating a decrease in cool gas content with increasing distance from the galaxies, as well as decreasing star formation rate of the galaxies. Beyond 1Mpc, this decline levels off to the same absorption strength in all galaxy types, suggesting a transition from the circumgalactic medium (CGM) to the intergalactic medium (IGM) at approximately the virial radius of the host dark matter haloes. We find that post-starburst galaxies, that have experienced a recent burst of star formation that has rapidly quenched, exhibit significantly stronger Mg II absorption within 1Mpc than star-forming or quiescent galaxies of the same stellar mass. Because post-starburst galaxies are a potentially significant pathway for the formation of quiescent elliptical galaxies, our results have wide reaching implications for understanding the mechanisms involved in quenching star formation in galaxies. We speculate that the excess cool gas absorption out to 1Mpc around post-starburst galaxies is related to their observed high velocity ($\sim$1000\,km/s) cool gas outflows. Thus, strong, short-lived bursts of star formation impact the CGM around galaxies on Mpc distances and Gyr timescales.

arXiv:2506.15022v2 Announce Type: replace Abstract: WASP-4 b is a hot Jupiter exhibiting a decreasing orbital period, prompting investigations into potential mechanisms driving its evolution. We analyzed 173 transit light curves, including 37 new observations, and derived mid-transit timings with EXOFAST, forming the most extensive TTV dataset for this system. Adding 58 literature timings and removing unreliable data, we constructed a TTV diagram with 216 points. Our analysis considered linear, quadratic, and apsidal motion models, with the quadratic model proving to be significantly superior in all model comparison statistics. We found no significant periodic signals in the data. The quadratic model allows us to infer a tidal quality factor of Q' ~ 80,000 from the orbital decay rate if this is due to stellar tides. Theoretical considerations indicate that such efficient dissipation is possible due to internal gravity waves in the radiative core of WASP-4, but only in our models with a more evolved host star, possibly near the end of its main-sequence lifetime, and with a larger radius than the observed one. Our main-sequence models produce only about a third of the required dissipation (Q' ~ 200,000 - 500,000). Therefore, the observed orbital decay can only be explained by a slightly larger or more evolved host, resembling the case for WASP-12. Our findings highlight the need for further stellar modeling and improvement in our current understanding of tidal dissipation mechanisms driving orbital decay in close-in exoplanetary systems.

arXiv:2506.15022v2 Announce Type: replace Abstract: WASP-4 b is a hot Jupiter exhibiting a decreasing orbital period, prompting investigations into potential mechanisms driving its evolution. We analyzed 173 transit light curves, including 37 new observations, and derived mid-transit timings with EXOFAST, forming the most extensive TTV dataset for this system. Adding 58 literature timings and removing unreliable data, we constructed a TTV diagram with 216 points. Our analysis considered linear, quadratic, and apsidal motion models, with the quadratic model proving to be significantly superior in all model comparison statistics. We found no significant periodic signals in the data. The quadratic model allows us to infer a tidal quality factor of Q' ~ 80,000 from the orbital decay rate if this is due to stellar tides. Theoretical considerations indicate that such efficient dissipation is possible due to internal gravity waves in the radiative core of WASP-4, but only in our models with a more evolved host star, possibly near the end of its main-sequence lifetime, and with a larger radius than the observed one. Our main-sequence models produce only about a third of the required dissipation (Q' ~ 200,000 - 500,000). Therefore, the observed orbital decay can only be explained by a slightly larger or more evolved host, resembling the case for WASP-12. Our findings highlight the need for further stellar modeling and improvement in our current understanding of tidal dissipation mechanisms driving orbital decay in close-in exoplanetary systems.

arXiv:2506.21677v1 Announce Type: new Abstract: We present Galaxy-Galaxy Lensing measurements obtained by cross-correlating spectroscopically observed galaxies from the first data release of the Dark Energy Spectroscopic Instrument (DESI) with source galaxies from the Hyper Suprime-Cam Subaru Strategic Survey, the Kilo-Degree Survey, the Sloan Digital Sky Survey, and the Dark Energy Survey. Specifically, we measure the excess surface mass density $\Delta\Sigma$ and tangential shear $\gamma_\mathrm{t}$ for the Bright Galaxy Sample and Luminous Red Galaxies measured within the first year of observations with DESI. To ensure robustness, we test the measurements for systematic biases, finding no significant trends related to the properties of the \acrshort{desi} lens galaxies. We identify a significant trend with the average redshift of source galaxies, however, this trend vanishes once we apply shifts to the Hyper Suprime-Cam Subaru Strategic Survey redshift distributions that are also favored by their fiducial cosmology analysis. Additionally, we compare the observed scatter in the measurements with the theoretical covariance and find excess scatter, driven primarily by small-scale measurements of $r\leq 1 \, \mathrm{Mpc}/h$; measurements on larger scales are consistent at the $2\,\sigma$ level. We further present the projected clustering measurements $w_p$ of the galaxy samples in the the first data release of DESI. These measurements, which will be made publicly available, serve as a foundation for forthcoming cosmological analyses.

arXiv:2506.21677v1 Announce Type: new Abstract: We present Galaxy-Galaxy Lensing measurements obtained by cross-correlating spectroscopically observed galaxies from the first data release of the Dark Energy Spectroscopic Instrument (DESI) with source galaxies from the Hyper Suprime-Cam Subaru Strategic Survey, the Kilo-Degree Survey, the Sloan Digital Sky Survey, and the Dark Energy Survey. Specifically, we measure the excess surface mass density $\Delta\Sigma$ and tangential shear $\gamma_\mathrm{t}$ for the Bright Galaxy Sample and Luminous Red Galaxies measured within the first year of observations with DESI. To ensure robustness, we test the measurements for systematic biases, finding no significant trends related to the properties of the \acrshort{desi} lens galaxies. We identify a significant trend with the average redshift of source galaxies, however, this trend vanishes once we apply shifts to the Hyper Suprime-Cam Subaru Strategic Survey redshift distributions that are also favored by their fiducial cosmology analysis. Additionally, we compare the observed scatter in the measurements with the theoretical covariance and find excess scatter, driven primarily by small-scale measurements of $r\leq 1 \, \mathrm{Mpc}/h$; measurements on larger scales are consistent at the $2\,\sigma$ level. We further present the projected clustering measurements $w_p$ of the galaxy samples in the the first data release of DESI. These measurements, which will be made publicly available, serve as a foundation for forthcoming cosmological analyses.

arXiv:2506.21677v1 Announce Type: new Abstract: We present Galaxy-Galaxy Lensing measurements obtained by cross-correlating spectroscopically observed galaxies from the first data release of the Dark Energy Spectroscopic Instrument (DESI) with source galaxies from the Hyper Suprime-Cam Subaru Strategic Survey, the Kilo-Degree Survey, the Sloan Digital Sky Survey, and the Dark Energy Survey. Specifically, we measure the excess surface mass density $\Delta\Sigma$ and tangential shear $\gamma_\mathrm{t}$ for the Bright Galaxy Sample and Luminous Red Galaxies measured within the first year of observations with DESI. To ensure robustness, we test the measurements for systematic biases, finding no significant trends related to the properties of the \acrshort{desi} lens galaxies. We identify a significant trend with the average redshift of source galaxies, however, this trend vanishes once we apply shifts to the Hyper Suprime-Cam Subaru Strategic Survey redshift distributions that are also favored by their fiducial cosmology analysis. Additionally, we compare the observed scatter in the measurements with the theoretical covariance and find excess scatter, driven primarily by small-scale measurements of $r\leq 1 \, \mathrm{Mpc}/h$; measurements on larger scales are consistent at the $2\,\sigma$ level. We further present the projected clustering measurements $w_p$ of the galaxy samples in the the first data release of DESI. These measurements, which will be made publicly available, serve as a foundation for forthcoming cosmological analyses.

arXiv:2506.22416v1 Announce Type: new Abstract: We present a measurement of the amplitude of matter fluctuations over the redshift range 0.8 <= z <= 3.5 from the cross correlation of over 1.2 million spectroscopic quasars selected by the Dark Energy Spectroscopic Instrument (DESI) across 7,200 deg$^2$ (approx 170 quasars/deg$^2$) and Planck PR4 (NPIPE) cosmic microwave background (CMB) lensing maps. We perform a tomographic measurement in three bins centered at effective redshifts z=1.44, 2.27 and 2.75, which have ample overlap with the CMB lensing kernel. From a joint fit using the angular clustering of all three redshift bins (auto and cross-spectra), and including an $\Omega_m$ prior from DESI DR1 baryon acoustic oscillations to break the $\Omega_m-\sigma_8$ degeneracy, we constrain the amplitude of matter fluctuations in the matter-dominated regime to be $\sigma_8=0.929^{+0.059}_{-0.074}$ and $S_8\equiv \sigma_8(\Omega_m/0.3)^{0.5} = 0.922^{+0.059}_{-0.073}$. We provide a growth of structure measurement with the largest spectroscopic quasar sample to date at high redshift, which is 1.5$\sigma$ higher than predictions from $\Lambda$CDM fits to measurements of the primary CMB from Planck PR4. The cross-correlation between PR4 lensing maps and DESI DR1 quasars is detected with a signal-to-noise ratio of 21.7 and the quasar auto-correlation at 27.2 for the joint analysis of all redshift bins. We combine our measurement with the CMB lensing auto-spectrum from the ground-based Atacama Cosmology Telescope (ACT DR6) and Planck PR4 to perform a sound-horizon-free measurement of the Hubble constant, yielding $H_0=69.1^{+2.2}_{-2.6}\,\mathrm{km}\,\mathrm{s}^{-1}\mathrm{Mpc}^{-1}$ through its sensitivity to the matter-radiation equality scale.

arXiv:2506.22416v1 Announce Type: new Abstract: We present a measurement of the amplitude of matter fluctuations over the redshift range 0.8 <= z <= 3.5 from the cross correlation of over 1.2 million spectroscopic quasars selected by the Dark Energy Spectroscopic Instrument (DESI) across 7,200 deg$^2$ (approx 170 quasars/deg$^2$) and Planck PR4 (NPIPE) cosmic microwave background (CMB) lensing maps. We perform a tomographic measurement in three bins centered at effective redshifts z=1.44, 2.27 and 2.75, which have ample overlap with the CMB lensing kernel. From a joint fit using the angular clustering of all three redshift bins (auto and cross-spectra), and including an $\Omega_m$ prior from DESI DR1 baryon acoustic oscillations to break the $\Omega_m-\sigma_8$ degeneracy, we constrain the amplitude of matter fluctuations in the matter-dominated regime to be $\sigma_8=0.929^{+0.059}_{-0.074}$ and $S_8\equiv \sigma_8(\Omega_m/0.3)^{0.5} = 0.922^{+0.059}_{-0.073}$. We provide a growth of structure measurement with the largest spectroscopic quasar sample to date at high redshift, which is 1.5$\sigma$ higher than predictions from $\Lambda$CDM fits to measurements of the primary CMB from Planck PR4. The cross-correlation between PR4 lensing maps and DESI DR1 quasars is detected with a signal-to-noise ratio of 21.7 and the quasar auto-correlation at 27.2 for the joint analysis of all redshift bins. We combine our measurement with the CMB lensing auto-spectrum from the ground-based Atacama Cosmology Telescope (ACT DR6) and Planck PR4 to perform a sound-horizon-free measurement of the Hubble constant, yielding $H_0=69.1^{+2.2}_{-2.6}\,\mathrm{km}\,\mathrm{s}^{-1}\mathrm{Mpc}^{-1}$ through its sensitivity to the matter-radiation equality scale.

arXiv:2503.15326v2 Announce Type: replace Abstract: Strong gravitational lensing has the potential to provide a powerful probe of astrophysics and cosmology, but fewer than 1000 strong lenses have been confirmed so far. With a 0.16'' resolution covering a third of the sky, the Euclid telescope will revolutionise the identification of strong lenses, with 170 000 lenses forecasted to be discovered amongst the 1.5 billion galaxies it will observe. We present an analysis of the performance of five machine-learning models at finding strong gravitational lenses in the quick release of Euclid data (Q1) covering 63 deg2. The models have been validated by citizen scientists and expert visual inspection. We focus on the best-performing network: a fine-tuned version of the Zoobot pretrained model originally trained to classify galaxy morphologies in heterogeneous astronomical imaging surveys. Of the one million Q1 objects that Zoobot was tasked to find strong lenses within, the top 1000 ranked objects contain 122 grade A lenses (almost-certain lenses) and 41 grade B lenses (probable lenses). A deeper search with the five networks combined with visual inspection yielded 250 (247) grade A (B) lenses, of which 224 (182) are ranked in the top 20 000 by Zoobot. When extrapolated to the full Euclid survey, the highest ranked one million images will contain 75 000 grade A or B strong gravitational lenses.

arXiv:2503.15326v2 Announce Type: replace Abstract: Strong gravitational lensing has the potential to provide a powerful probe of astrophysics and cosmology, but fewer than 1000 strong lenses have been confirmed so far. With a 0.16'' resolution covering a third of the sky, the Euclid telescope will revolutionise the identification of strong lenses, with 170 000 lenses forecasted to be discovered amongst the 1.5 billion galaxies it will observe. We present an analysis of the performance of five machine-learning models at finding strong gravitational lenses in the quick release of Euclid data (Q1) covering 63 deg2. The models have been validated by citizen scientists and expert visual inspection. We focus on the best-performing network: a fine-tuned version of the Zoobot pretrained model originally trained to classify galaxy morphologies in heterogeneous astronomical imaging surveys. Of the one million Q1 objects that Zoobot was tasked to find strong lenses within, the top 1000 ranked objects contain 122 grade A lenses (almost-certain lenses) and 41 grade B lenses (probable lenses). A deeper search with the five networks combined with visual inspection yielded 250 (247) grade A (B) lenses, of which 224 (182) are ranked in the top 20 000 by Zoobot. When extrapolated to the full Euclid survey, the highest ranked one million images will contain 75 000 grade A or B strong gravitational lenses.

arXiv:2506.21410v1 Announce Type: new Abstract: Stellar streams are sensitive laboratories for understanding the small-scale structure in our Galaxy's gravitational field. Here, we analyze the morphology of the $300S$ stellar stream, which has an eccentric, retrograde orbit and thus could be an especially powerful probe of both baryonic and dark substructures within the Milky Way. Due to extensive background contamination from the Sagittarius stream (Sgr), we perform an analysis combining Dark Energy Camera Legacy Survey photometry, $\textit{Gaia}$ DR3 proper motions, and spectroscopy from the Southern Stellar Stream Spectroscopic Survey ($\textit{S}^5$). We redetermine the stream coordinate system and distance gradient, then apply two approaches to describe $300S$'s morphology. In the first, we analyze stars from $\textit{Gaia}$ using proper motions to remove Sgr. In the second, we generate a simultaneous model of $300S$ and Sgr based purely on photometric information. Both approaches agree within their respective domains and describe the stream over a region spanning $33^\circ$. Overall, $300S$ has three well-defined density peaks and smooth variations in stream width. Furthermore, $300S$ has a possible gap of $\sim 4.7^\circ$ and a kink. Dynamical modeling of the kink implies that $300S$ was dramatically influenced by the Large Magellanic Cloud. This is the first model of $300S$'s morphology across its entire known footprint, opening the door for deeper analysis to constrain the structures of the Milky Way.

arXiv:2506.21410v1 Announce Type: new Abstract: Stellar streams are sensitive laboratories for understanding the small-scale structure in our Galaxy's gravitational field. Here, we analyze the morphology of the $300S$ stellar stream, which has an eccentric, retrograde orbit and thus could be an especially powerful probe of both baryonic and dark substructures within the Milky Way. Due to extensive background contamination from the Sagittarius stream (Sgr), we perform an analysis combining Dark Energy Camera Legacy Survey photometry, $\textit{Gaia}$ DR3 proper motions, and spectroscopy from the Southern Stellar Stream Spectroscopic Survey ($\textit{S}^5$). We redetermine the stream coordinate system and distance gradient, then apply two approaches to describe $300S$'s morphology. In the first, we analyze stars from $\textit{Gaia}$ using proper motions to remove Sgr. In the second, we generate a simultaneous model of $300S$ and Sgr based purely on photometric information. Both approaches agree within their respective domains and describe the stream over a region spanning $33^\circ$. Overall, $300S$ has three well-defined density peaks and smooth variations in stream width. Furthermore, $300S$ has a possible gap of $\sim 4.7^\circ$ and a kink. Dynamical modeling of the kink implies that $300S$ was dramatically influenced by the Large Magellanic Cloud. This is the first model of $300S$'s morphology across its entire known footprint, opening the door for deeper analysis to constrain the structures of the Milky Way.

arXiv:2506.21410v1 Announce Type: new Abstract: Stellar streams are sensitive laboratories for understanding the small-scale structure in our Galaxy's gravitational field. Here, we analyze the morphology of the $300S$ stellar stream, which has an eccentric, retrograde orbit and thus could be an especially powerful probe of both baryonic and dark substructures within the Milky Way. Due to extensive background contamination from the Sagittarius stream (Sgr), we perform an analysis combining Dark Energy Camera Legacy Survey photometry, $\textit{Gaia}$ DR3 proper motions, and spectroscopy from the Southern Stellar Stream Spectroscopic Survey ($\textit{S}^5$). We redetermine the stream coordinate system and distance gradient, then apply two approaches to describe $300S$'s morphology. In the first, we analyze stars from $\textit{Gaia}$ using proper motions to remove Sgr. In the second, we generate a simultaneous model of $300S$ and Sgr based purely on photometric information. Both approaches agree within their respective domains and describe the stream over a region spanning $33^\circ$. Overall, $300S$ has three well-defined density peaks and smooth variations in stream width. Furthermore, $300S$ has a possible gap of $\sim 4.7^\circ$ and a kink. Dynamical modeling of the kink implies that $300S$ was dramatically influenced by the Large Magellanic Cloud. This is the first model of $300S$'s morphology across its entire known footprint, opening the door for deeper analysis to constrain the structures of the Milky Way.

arXiv:2506.20919v1 Announce Type: new Abstract: We report the discovery of CO$_2$ gas emission around HD 23514, an F5V star in the $\sim$150 Myr-old Pleiades cluster, hosting one of the rare giant-impact disks with unique mineralogy dominated by silica dust. We show that the dust feature remains stable over several decades, and that the sub-$\mu$m grains, which give rise to the $\sim$9 $\mu$m feature, are co-spatial with the hot CO$_2$ molecules within the sub-au vicinity of the star. Examining the Spitzer spectrum taken 15 years earlier, we show that the CO$_2$ emission was also present at 4.3 $\sigma$ significance. The existence of tiny silica grains and volatile gas requires special conditions to prevent the rapid loss caused by stellar radiation pressure and photodissociation. We explore several pathways explaining the observed properties and suggest that a past giant impact and/or stripping atmospheric event, involving large bodies with volatile content similar to the carbonaceous chondritic material, can simultaneously explain both the silica and volatile emission. Our discovery provides an important context for the amount of volatiles that a newly formed planet or the largest planetesimals could retain during the giant impact phase in the early solar system evolution.

arXiv:2506.20919v1 Announce Type: new Abstract: We report the discovery of CO$_2$ gas emission around HD 23514, an F5V star in the $\sim$150 Myr-old Pleiades cluster, hosting one of the rare giant-impact disks with unique mineralogy dominated by silica dust. We show that the dust feature remains stable over several decades, and that the sub-$\mu$m grains, which give rise to the $\sim$9 $\mu$m feature, are co-spatial with the hot CO$_2$ molecules within the sub-au vicinity of the star. Examining the Spitzer spectrum taken 15 years earlier, we show that the CO$_2$ emission was also present at 4.3 $\sigma$ significance. The existence of tiny silica grains and volatile gas requires special conditions to prevent the rapid loss caused by stellar radiation pressure and photodissociation. We explore several pathways explaining the observed properties and suggest that a past giant impact and/or stripping atmospheric event, involving large bodies with volatile content similar to the carbonaceous chondritic material, can simultaneously explain both the silica and volatile emission. Our discovery provides an important context for the amount of volatiles that a newly formed planet or the largest planetesimals could retain during the giant impact phase in the early solar system evolution.

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5 Min Read NASA’s Webb Digs into Structural Origins of Disk Galaxies Astronomers pulled from NASA’s James Webb Space Telescope’s data to analyze a sample of 111 edge-on galaxies. The team’s analysis suggests that thick disk formation occurs first, and thin disk formation follows. Full image and caption below. Credits:
NASA, ESA, CSA, T. Tsukui (Australian National University).

Present-day disk galaxies often contain a thick, star-filled outer disk and an embedded thin disk of stars. For instance, our own Milky Way galaxy’s thick disk is approximately 3,000 light-years in height, and its thin disk is roughly 1,000 light-years thick.

How and why does this dual disk structure form? By analyzing archival data from multiple observational programs by NASA’s James Webb Space Telescope, a team of astronomers is closer to answers, as well as understanding the origins of disk galaxies in general.

The team carefully identified, visually verified, and analyzed a statistical sample of 111 edge-on disk galaxies at various periods — up to 11 billion years ago (or approximately 2.8 billion years after the big bang). This is the first time scientists have investigated thick- and thin-disk structures spanning such vast distances, bridging the gap between observers probing the early universe and galactic archaeologists seeking to understand our own galaxy’s history.

“This unique measurement of the thickness of the disks at high redshift, or at times in the early universe, is a benchmark for theoretical study that was only possible with Webb,” said Takafumi Tsukui, lead author of the paper and a researcher at the Australian National University in Canberra. “Usually, the older, thick disk stars are faint, and the young, thin disk stars outshine the entire galaxy. But with Webb’s resolution and unique ability to see through dust and highlight faint old stars, we can identify the two-disk structure of galaxies and measure their thickness separately.”

Image: A Sample of Galaxy Disks (NIRCam) Astronomers pulled from NASA’s James Webb Space Telescope’s data to analyze a sample of 111 edge-on galaxies. The team’s analysis suggests that thick disk formation occurs first, and thin disk formation follows. When this process occurs depends on the galaxy’s mass. NASA, ESA, CSA, T. Tsukui (Australian National University). Data Through Thick and Thin

By analyzing these 111 targets over cosmological time, the team was able to study single-disk galaxies and double-disk galaxies. Their results indicate that galaxies form a thick disk first, followed by a thin disk. The timing of when this takes place is dependent on the galaxy’s mass: high-mass, single-disk galaxies transitioned to two-disk structures around 8 billion years ago. In contrast, low-mass, single-disk galaxies formed their embedded thin disks later on, about 4 billion years ago.

“This is the first time it has been possible to resolve thin stellar disks at higher redshift. What’s really novel is uncovering when thin stellar disks start to emerge,” said Emily Wisnioski, a co-author of the paper at the Australian National University in Canberra. “To see thin stellar disks already in place 8 billion years ago, or even earlier, was surprising.”

A Turbulent Time for Galaxies

To explain this transition from a single, thick disk to a thick and thin disk, and the difference in timing for high- and low-mass galaxies, the team looked beyond their initial edge-on galaxy sample and examined data showing gas in motion from the Atacama Large Millimeter/submillimeter Array (ALMA) and ground-based surveys.

By taking into consideration the motion of the galaxies’ gas disks, the team finds their results align with the “turbulent gas disk” scenario, one of three major hypotheses that has been proposed to explain the process of thick- and thin-disk formation. In this scenario, a turbulent gas disk in the early universe sparks intense star formation, forming a thick stellar disk. As stars form, they stabilize the gas disk, which becomes less turbulent and, as a result, thinner.

Since massive galaxies can more efficiently convert gas into stars, they settle sooner than their low-mass counterparts, resulting in the earlier formation of thin disks. The team notes that thick- and thin-disk formation are not siloed events: The thick disk continues to grow as the galaxy develops, though it’s slower than the thin disk’s rate of growth.

How This Applies to Home

Webb’s sensitivity is enabling astronomers to observe smaller and fainter galaxies, analogous to our own, at early times and with unprecedented clarity for the first time. In this study, the team noted that the transition period from thick disk to a thick and thin disk roughly coincides with the formation of the Milky Way galaxy’s thin disk. With Webb, astronomers will be able to further investigate Milky Way-like progenitors — galaxies that would have preceded the Milky Way — which could help explain our galaxy’s formation history.

In the future, the team intends to incorporate other data points into their edge-on galaxy sample.

“While this study structurally distinguishes thin and thick disks, there is still much more we would like to explore,” said Tsukui. “We want to add the type of information people usually get for nearby galaxies, like stellar motion, age, and metallicity. By doing so, we can bridge the insights from galaxies near and far, and refine our understanding of disk formation.”

These results were published in the Monthly Notices of the Royal Astronomical Society.

The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).

To learn more about Webb, visit:

https://science.nasa.gov/webb

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Media Contacts

Laura Betz – laura.e.betz@nasa.gov
NASA’s Goddard Space Flight Center, Greenbelt, Md.

Abigail Major – amajor@stsci.edu
Space Telescope Science Institute, Baltimore, Md.

Hannah Braun – hbraun@stsci.edu
Space Telescope Science Institute, Baltimore, Md.

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Keep Exploring Related Topics James Webb Space Telescope

Webb is the premier observatory of the next decade, serving thousands of astronomers worldwide. It studies every phase in the…

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Details Last Updated Jun 26, 2025 Editor Marty McCoy Contact Laura Betz laura.e.betz@nasa.gov Related Terms

• James Webb Space Telescope (JWST)
• Astrophysics
• Galaxies
• Goddard Space Flight Center
• Science & Research
• Spiral Galaxies
• The Universe

X-ray: NASA/CXO/UMass/Z. Li & Q.D. Wang, ESA/XMM-Newton; Infrared: NASA/JPL-Caltech/WISE, Spitzer, NASA/JPL-Caltech/K. Gordon (U. Az), ESA/Herschel, ESA/Planck, NASA/IRAS, NASA/COBE; Radio: NSF/GBT/WSRT/IRAM/C. Clark (STScI); Ultraviolet: NASA/JPL-Caltech/GALEX; Optical: Andromeda, Unexpected © Marcel Drechsler, Xavier Strottner, Yann Sainty & J. Sahner, T. Kottary. Composite image processing: L. Frattare, K. Arcand, J.Major

The Andromeda galaxy, also known as Messier 31 (M31), is a glittering beacon in this image released on June 25, 2025, in tribute to the groundbreaking legacy of astronomer Dr. Vera Rubin, whose observations transformed our understanding of the universe. In the 1960s, Rubin and her colleagues studied M31 and determined that there was some unseen matter in the galaxy that was affecting how the galaxy and its spiral arms rotated. This unknown material was named “dark matter.”

M31 is the closest spiral galaxy to the Milky Way at a distance of about 2.5 million light-years. Astronomers use Andromeda to understand the structure and evolution of our own spiral, which is much harder to do since Earth is embedded inside the Milky Way.

Learn more about this image and experience in sound, too.

Image credit: X-ray: NASA/CXO/UMass/Z. Li & Q.D. Wang, ESA/XMM-Newton; Infrared: NASA/JPL-Caltech/WISE, Spitzer, NASA/JPL-Caltech/K. Gordon (U. Az), ESA/Herschel, ESA/Planck, NASA/IRAS, NASA/COBE; Radio: NSF/GBT/WSRT/IRAM/C. Clark (STScI); Ultraviolet: NASA/JPL-Caltech/GALEX; Optical: Andromeda, Unexpected © Marcel Drechsler, Xavier Strottner, Yann Sainty & J. Sahner, T. Kottary. Composite image processing: L. Frattare, K. Arcand, J.Major