AI insight:
The study provides a refined set of feedback mechanisms for simulating galaxy evolution that aligns well with empirical data, potentially enhancing the accuracy of comparisons between numerical and observational models.
📄 Star formation and feedback in smoothed particle hydrodynamic simulat…
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Stinson, Greg et al. (2006) · Monthly Notices of the Royal Astronomical Society
Reads: 176 · Citations: 732
DOI: 10.1111/j.1365-2966.2006.…
🔗 https://ui.adsabs.harvard.edu/abs/2006MNRAS.373.1074S/abstract
#Astronomy #Astrophysics #Galaxies #Supernovae #Hydrodynamics
Star formation and feedback in smoothed particle hydrodynamic simulations - I. Isolated galaxies
We present an analysis of star formation and feedback recipes appropriate for galactic smoothed particle hydrodynamics simulations. Using an isolated Milky Way-like galaxy, we constrain these recipes based on well-established observational results. Our star formation recipe is based on that of Katz with the additional inclusion of physically motivated supernova feedback recipes. We propose a new feedback recipe in which Type II supernovae are modelled using an analytical treatment of blastwaves. With this feedback mechanism and a tuning of other star formation parameters, the star formation in our isolated Milky Way-like galaxy follows the slope and normalization of the observed Schmidt law. In addition, we reproduce the low-density cut-off and filamentary structure of star formation observed in disc galaxies. Our final recipe will enable better comparison of N-body simulations with observations.
AI insight:
The research on sub-Neptune GJ 9827 d, with a unique water-dominated atmosphere and active host star, provides insights into planetary formation theories and atmospheric loss processes in exoplanets.
📄 JWST/NIRISS Reveals the Water-rich "Steam World" Atmosphere of GJ 982…
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Piaulet-Ghorayeb, Caroline et al. (2024) · The Astrophysical Journal
Reads: 417 · Citations: 91
DOI: 10.3847/2041-8213/ad6f00
🔗 https://ui.adsabs.harvard.edu/abs/2024ApJ...974L..10P/abstract
#Astronomy #Astrophysics #Galaxies #SolarPhysics #ExoplanetAtmospheres
JWST/NIRISS Reveals the Water-rich "Steam World" Atmosphere of GJ 9827 d
With sizable volatile envelopes but smaller radii than the solar system ice giants, sub-Neptunes have been revealed as one of the most common types of planet in the galaxy. While the spectroscopic characterization of larger sub-Neptunes (2.5─4 R <SUB>⊕</SUB>) has revealed hydrogen-dominated atmospheres, smaller sub-Neptunes (1.6─2.5 R <SUB>⊕</SUB>) could either host thin, rapidly evaporating, hydrogen-rich atmospheres or be stable, metal-rich "water worlds" with high mean molecular weight atmospheres and a fundamentally different formation and evolutionary history. Here, we present the 0.6─2.8 μm JWST/NIRISS/SOSS transmission spectrum of GJ 9827 d, the smallest (1.98 R <SUB>⊕</SUB>) warm (T <SUB>eq,A=0.3</SUB> ∼ 620 K) sub-Neptune where atmospheric absorbers have been detected to date. Our two transit observations with NIRISS/SOSS, combined with the existing HST/WFC3 spectrum, enable us to break the clouds─metallicity degeneracy. We detect water in a highly metal-enriched "steam world" atmosphere (O/H of ∼4 by mass and H<SUB>2</SUB>O found to be the background gas with a volume mixing ratio of >31%). We further show that these results are robust to stellar contamination through the transit light source effect. We do not detect escaping metastable He, which, combined with previous nondetections of escaping He and H, supports the steam atmosphere scenario. In water-rich atmospheres, hydrogen loss driven by water photolysis happens predominantly in the ionized form, which eludes observational constraints. We also detect several flares in the NIRISS/SOSS light curves with far-UV energies of the order of 10<SUP>30</SUP> erg, highlighting the active nature of the star. Further atmospheric characterization of GJ 9827 d probing carbon or sulfur species could reveal the origin of its high metal enrichment.
AI insight:
The research explores how third-generation gravitational wave detectors could provide insights into early cosmological history by measuring a stochastic background from cosmic strings across various non-standard cosmological scenarios, potentially revealing new physics energy…
📄 Beyond the Standard Models with cosmic strings
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Gouttenoire, Yann et al. (2020) · Journal of Cosmology and Astroparticle Physics
Reads: 375 · Citations: 178
DOI: 10.1088/1475-7516/2020/07/032
🔗 https://ui.adsabs.harvard.edu/abs/2020JCAP...07..032G/abstract
#Astronomy #Astrophysics #Cosmology #BlackHoles #HighEnergyPhysicsPhenomenology
Beyond the Standard Models with cosmic strings
We examine which information on the early cosmological history can be extracted from the potential measurement by third-generation gravitational-wave observatories of a stochastic gravitational wave background (SGWB) produced by cosmic strings. We consider a variety of cosmological scenarios breaking the scale-invariant properties of the spectrum, such as early long matter or kination eras, short intermediate matter and inflation periods inside a radiation era, and their specific signatures on the SGWB . This requires to go beyond the usually-assumed scaling regime, to take into account the transient effects during the change of equation of state of the universe. We compute the time evolution of the string network parameters and thus the loop-production efficiency during the transient regime, and derive the corresponding shift in the turning-point frequency. We consider the impact of particle production on the gravitational-wave emission by loops. We estimate the reach of future interferometers LISA, BBO, DECIGO, ET and CE and radio telescope SKA to probe the new physics energy scale at which the universe has experienced changes in its expansion history. We find that a given interferometer may be sensitive to very different energy scales, depending on the nature and duration of the non-standard era, and the value of the string tension. It is fascinating that by exploiting the data from different GW observatories associated with distinct frequency bands, we may be able to reconstruct the full spectrum and therefore extract the values of fundamental physics parameters.
📄 The Rise of the Galactic Empire: Ultraviolet Luminosity Functions at …
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Pérez-González, Pablo G. et al. (2025) · The Astrophysical Journal
Reads: 559 · Citations: 71
DOI: 10.3847/1538-4357/adf8c9
🔗 https://ui.adsabs.harvard.edu/abs/2025ApJ...991..179P/abstract
#Astronomy #Astrophysics #Galaxies #DarkUniverse #GalaxyFormation
The Rise of the Galactic Empire: Ultraviolet Luminosity Functions at z ∼ 17 and z ∼ 25 Estimated with the MIDIS+NGDEEP Ultra-deep JWST/NIRCam Data Set
We present a sample of six F200W and three F277W dropout sources identified as 16 < z < 25 galaxy candidates using the deepest JWST/NIRCam data to date (5σ depths ∼31.5 mag at ≥2 μm), provided by the MIRI Deep Imaging Survey and the Next Generation Deep Extragalactic Exploratory Public survey. We estimate ultraviolet (UV) luminosity functions and densities at z ∼ 17 and z ∼ 25. The number density of galaxies with absolute magnitudes of −19 < M<SUB>UV</SUB> < −18 at z ∼ 17 (z ∼ 25) is a factor of 4 (25) smaller than at z ∼ 12; the luminosity density presents a similar evolution. Compared to state-of-the-art galaxy simulations, we find the need for an enhanced UV-photon production at z = 17─25 in M<SUB>DM</SUB> = 10<SUP>8.5−9.5</SUP> M<SUB>⊙</SUB> dark matter halos, provided by an increase in the star formation efficiency at early times and/or by intense compact starbursts with enhanced emissivity linked to strong burstiness, low or primordial gas metallicities, and/or a top-heavy initial mass function. There are a few robust theoretical predictions for the evolution of galaxies above z ∼ 20 in the literature; however, the continuing rapid drop in the halo mass function would predict a more rapid evolution than we observe if photon production efficiencies remained constant. Our z > 16 candidates present mass-weighted ages around 30 Myr, and attenuations A(V) < 0.1 mag. Their average stellar mass is M<SUB>⋆</SUB> ∼ 10<SUP>7</SUP> M<SUB>⊙</SUB>, implying a stellar-to-baryon mass fraction around 10% if the emissivity increases with redshift, or significantly higher otherwise. Three candidates present very blue UV spectral slopes (β ∼ −3) compatible with Population III young (≲10 Myr) stars and/or high escape fractions of ionizing photons; the rest have β ∼ −2.5 similar to the z = 10─12 samples.
AI insight:
The research presents an innovative approach using ZTF light curves for classifying quasars (QSOs), achieving high confidence in identifications, which is significant considering objects fainter than previous limits are now detectable with this methodology.
📄 QZO: A Catalog of 5 Million Quasars from the Zwicky Transient Facility
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Nakoneczny, S. J. et al. (2025) · The Astrophysical Journal
Reads: 364 · Citations: 5
DOI: 10.3847/1538-4357/adf4e4
🔗 https://ui.adsabs.harvard.edu/abs/2025ApJ...992..153N/abstract
#Astronomy #Astrophysics #AstroAI #ActiveGalacticNuclei #Quasars
QZO: A Catalog of 5 Million Quasars from the Zwicky Transient Facility
Machine learning methods are well established in the classification of quasars (QSOs). However, the advent of light-curve observations adds a great amount of complexity to the problem. Our goal is to use the Zwicky Transient Facility (ZTF) to create a catalog of QSOs. We process the ZTF DR20 light curves with a transformer artificial neural network and combine different surveys with extreme gradient boosting. Based on ZTF g-band and Wide-field Infrared Survey Explorer (WISE) observations, we find 4,849,574 objects classified as QSOs with confidence higher than 90% (QZO). We robustly classify objects fainter than the 5σ signal-to-noise ratio (SNR) limit at g = 20.8 by requiring g < n<SUB>obs</SUB>/80 + 20.375. For 33% of QZO objects, with available WISE data, we publish redshifts with estimated error ∆z/(1 + z) = 0.14. We find that ZTF classification is superior to the Pan-STARRS static bands, and on par with WISE and Gaia measurements, but the light curves provide the most important features for QSO classification in the ZTF data set. Using ZTF g-band data with at least 100 observational epochs per light curve, we obtain a 97% F1 score for QSOs. We find that with 3 day median cadence, a survey time span of at least 900 days is required to achieve a 90% QSO F1 score. However, one can obtain the same score with a survey time span of 1800 days and the median cadence prolonged to 12 days.
AI insight:
The research provides Bayesian estimates for PSR J0030+0451's parameters, revealing a complex hot region configuration that challenges simple spot models and offers insights into neutron star interiors.
