arXiv subjects

A. Newman

Publications and source records attributed to A. Newman.

4 recordsLinked to original sources

arXiv2026

A Comparative Multi-Hazard Risk Assessment of the US High-Voltage Transmission Network

Modern economies depend critically on high-voltage power transmission networks. Yet this infrastructure is routinely disrupted by natural hazards ranging from earthquakes and floods to tornadoes and geomagnetic storms. Risk assessments have historically addressed hazards in isolation, leaving no common basis for comparing economic impacts across the full hazard portfolio. This study addresses this gap by developing an integrated framework linking hazard characterization, fragility modeling, and macroeconomic impact propagation. The framework is applied consistently across nine primary hazards and one compound freezing rain and wind gust hazard. Using national hazard datasets and a US high-voltage transmission network of over 13,000 line segments and 10,000 substations, we derive failure probabilities, expected damage, affected population, and downstream economic output losses. Among individual hazards, tropical cyclone wind produces the largest expected daily damage at $137 M/day, followed by lightning at $87 M/day, earthquake at $47 M/day, flood at $46 M/day, tornado at $42 M/day, and landslide at $34 M/day. Downstream economic output losses are largest for tornado at $4.93 B/day, followed by flood at $3.59 B/day and earthquake at $3.02 B/day. A 250-year geomagnetic storm produces $2.07 B/day, placing space weather within the range of major terrestrial hazards. The compound freezing rain and wind gust scenario produces the largest stress-test disruption, affecting 237.4 M people and yielding a modeled downstream output loss of $85.16 B/day. These results should be interpreted as first-order bounding estimates, with the compound scenario representing an upper-bound stress test. Overall, the framework establishes a consistent baseline for prioritizing investments in transmission network resilience.

econ.EM↗

arXiv2022

Stellar population gradients at cosmic noon as a constraint to the evolution of passive galaxies

Context: The radial variations of the stellar populations properties within passive galaxies at high redshift contain information about their assembly mechanisms, based on which galaxy formation and evolution scenarios may be distinguished. Aims: The aim of this work is to give constraints on massive galaxy formation scenarios through one of the first analyses of age and metallicity gradients of the stellar populations in a sample of passive galaxies at $z > 1.6$ based on spectroscopic data from the Hubble Space Telescope. Methods: We combined G$141$ deep slitless spectroscopic data and F$160$W photometric data of the spectroscopically passive galaxies at $1.6< z < 2.4$ with $H_{160} < 22.0$ in the field of view of the cluster JKCS $041$. We extracted spectra from different zones of the galaxies, and we analysed them by fitting them with a library of synthetic templates of stellar population models to obtain estimates of the age and metallicity gradients. Results: We obtained reliable measurements of age and metallicity parameters in different spatial zones of $\text{four}$ galaxies. We performed spatially resolved measurements in individual high-redshift galaxies without the need of peculiar situations (i.e. gravitational lensing) for the first time. All four galaxies exhibit negative metallicity gradients. Their amplitude, similar to that measured in galaxies in the local Universe, suggests that the stellar populations of passive galaxies from $z \sim 2$ to $z = 0$ are not redistributed. Conclusions: Although the sample we analysed is small, the results we obtained suggest that the main mechanism that determines the spatial distribution of the stellar population properties within passive galaxies is constrained in the first $3$ Gyr of the Universe. This is consistent with the revised monolithic scenario.

astro-ph.GA↗

arXiv2013

Larger sizes of massive quiescent early-type galaxies in clusters than in the field at 0.8 < z < 1.5

[abridged] The mass-size relation of early-type galaxies (ETGs) has been largely studied in the last years to probe the mass assembly of the most massive objects in the Universe. In this paper, we focus on the mass-size relation of quiescent massive ETGs (Mstar/Msol > 3*10^10) living in massive clusters (M200 ~ 10^14 Mstar) at 0.8< z <1.5, as compared to those living in the field at the same epoch. Our sample contains ~ 400 ETGs in clusters and the same number in the field. Therefore, our sample is approximately an order of magnitude larger than previous studies in the same redshift range for galaxy clusters. We find that ETGs living in clusters are between ~30-50% larger than galaxies with the same stellar mass residing in the field. We parametrize the size using the mass-normalized size, gamma=Re/Mstar^0.57. The gamma distributions in both environments peak at the same position but the distributions in clusters are more skewed towards larger sizes. Since this size difference is not observed in the local Universe, the size evolution at fixed stellar mass from z~1.5 of cluster galaxies is less steep ((1+z)-0.53pm0.04) than the evolution of field galaxies ((1+z)-0.92pm0.04). The size difference seems to be essentially driven by the galaxies residing in the clusters cores (R<0.5*R200). If part of the size evolution is due to mergers, the difference we see between cluster and field galaxies could be due to higher merger rates in clusters at higher redshift, probably during the formation phase of the clusters when velocity dispersions are lower. We cannot exclude however that the difference is driven by newly quenched galaxies which are quenched more efficiently in clusters. The implications of these results for the hierarchical growth of ETGs will be discussed in a companion paper.

astro-ph.CO↗

arXiv2008

Spectral Identification of an Ancient Supernova using Light Echoes in the LMC

We report the successful identification of the type of the supernova responsible for the supernova remnant SNR 0509-675 in the Large Magellanic Cloud (LMC) using Gemini spectra of surrounding light echoes. The ability to classify outbursts associated with centuries-old remnants provides a new window into several aspects of supernova research and is likely to be successful in providing new constraints on additional LMC supernovae as well as their historical counterparts in the Milky Way Galaxy (MWG). The combined spectrum of echo light from SNR 0509-675 shows broad emission and absorption lines consistent with a supernova (SN) spectrum. We create a spectral library consisting of 26 SNe Ia and 6 SN Ib/c that are time-integrated, dust-scattered by LMC dust, and reddened by the LMC and MWG. We fit these SN templates to the observed light echo spectrum using $χ^2$ minimization as well as correlation techniques, and we find that overluminous 91T-like SNe Ia with $\dm15<0.9$ match the observed spectrum best.

astro-ph↗