An official website of the United States government
Abstract The rapid advancement of large-scale cosmological simulations has opened new avenues for cosmological and astrophysical research. However, the increasing diversity among cosmological simulation models presents a challenge to therobustness. In this work, we develop the Model-Insensitive ESTimator (Miest), a machine that canrobustlyestimate the cosmological parameters, Ωmandσ8, from neural hydrogen maps of simulation models in the Cosmology and Astrophysics with MachinE Learning Simulations project—IllustrisTNG,SIMBA, Astrid, and SWIFT-Eagle. An estimator is consideredrobustif it possesses a consistent predictive power across all simulations, including those used during the training phase. We train our machine using multiple simulation models and ensure that it only extracts common features between the models while disregarding the model-specific features. This allows us to develop a novel model that is capable of accurately estimating parameters across a range of simulation models, without being biased toward any particular model. Upon the investigation of the latent space—a set of summary statistics, we find that the implementation ofrobustnessleads to the blending of latent variables across different models, demonstrating the removal of model-specific features. In comparison to a standard machine lackingrobustness, the average performance of Mieston the unseen simulations during the training phase has been improved by ∼17% for Ωmand 38% forσ8. By using a machine learning approach that can extractrobust, yet physical features, we hope to improve our understanding of galaxy formation and evolution in a (subgrid) model-insensitive manner, and ultimately, gain insight into the underlying physical processes responsible forrobustness.
more »
« less
A rare isocyanide derived from an unprecedented neutral yttrium( ii ) bis(amide) complex
A room temperature stable Y(ii)bis(amide) has been prepared and fully characterized. The complex reacts withtert-butylisocyanide to make a rare example of a transition metal isocyanide, CN–Y(NHAr*)2.
more »
« less
- Award ID(s):
- 1953254
- PAR ID:
- 10473746
- Publisher / Repository:
- Royal Society of Chemistry
- Date Published:
- Journal Name:
- Chemical Science
- Volume:
- 14
- Issue:
- 16
- ISSN:
- 2041-6520
- Page Range / eLocation ID:
- 4257 to 4264
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract The physics of recombination lines in the Heisinglet system is expected to be relatively simple, supported by accurate atomic models. We examine the intensities of Heisingletsλ3614, λ3965, λ5016, λ6678, and λ7281 and the triplet Heiλ5876 in various types of ionized nebulae and compare them with theoretical predictions to test the validity of the “Case B” recombination scenario and the assumption of thermal homogeneity. Our analysis includes 85 spectra from Galactic and extragalactic Hiiregions, 90 from star-forming galaxies, and 218 from planetary nebulae, all compiled by the Deep Spectra of Ionized Regions Database Extended (DESIRED-E) project. By evaluating the ratios Heiλ7281/λ6678 and Heiλ7281/λ5876, we determineTe(Hei) and compare it with direct measurements ofTe([Oiii]λ4363/λ5007). We find thatTe(Hei) is systematically lower thanTe([Oiii]) across most objects and nebula types. Additionally, we identify a correlation between the abundance discrepancy factor (ADF(O2+)) and the differenceTe([Oiii]) –Te(Hei) for planetary nebulae. We explore two potential explanations: photon loss fromn1P → 11Stransitions and temperature inhomogeneities. Deviations from “Case B” may indicate photon absorption by Hirather than Heiand/or generalized ionizing photon escape, highlighting the need for detailed consideration of radiative transfer effects. If temperature inhomogeneities are widespread, identifying a common physical phenomenon affecting all ionized nebulae is crucial. Our results suggest that both scenarios can contribute to the observed discrepancies.more » « less
-
Abstract As part of the Deciphering the Interplay between the Interstellar medium, Stars, and the Circumgalactic medium (DIISC) survey, we present the UV metal absorption features in the circumgalactic medium (CGM) near the Higas disk (<4.5RHI) of 31 nearby galaxies through quasar absorption-line spectroscopy. Of the ions under study, Siiiiλ1206 was most frequently detected (18 of 31 sight lines), while Ciiλ1334 and Siiiλ1260 were detected in 17 and 15 of 31 sight lines, respectively. Many components were consistent with photoionization equilibrium models; most of the cold and cool gas phase clouds were found to have lengths smaller than 2 kpc. Sight lines with smaller impact parameters (ρ) normalized by the galaxy’s virial radius (Rvir) and Hiradius (RHI) tend to have more components and larger rest-frame equivalent widths (Wr) than those that probe the CGM at larger radii. In particular, we find that the location of metals are better traced byρ/RHIrather than the traditionalρ/Rvir. Larger covering fractions are found closer to galaxies, with a radial decline that depends on theWrlimit used. Our results provide new insights into the spatial distribution of metals around the Hidisks of low-redshift galaxies.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/d3sc00171g
