Radiative Stellar Feedback in Galaxy Formation: Methods and Physics

Radiative feedback (RFB) from stars plays a key role in galaxies, but remains poorly-understood. We explore this using high-resolution, multi-frequency radiation-hydrodynamics (RHD) simulations from the Feedback In Realistic Environments (FIRE) project. We study dwarf through Milky Way masses, and explore RHD effects including H/He photoionization; photoelectric, Lyman Werner, Compton, thermal dust heating; single and multiple-scattering radiation pressure (RP). We also compare fundamentally distinct RHD algorithms: the ray-based LEBRON (exact when optically-thin) and moments-based M1 (exact when optically-thick). In all cases, the dominant RFB channels on galaxy scales are photoionization heating and single-scattering RP. At all masses, most of the ionizing/FUV luminosity from young stars (~half bolometric) is absorbed. In dwarfs, the strongest effect is photoionization heating from the meta-galactic background, suppressing accretion onto galaxies. At MW-mass the meta-galactic background has negligible effects; but local photoionization and single-scattering RP both contribute significantly to regulating the galactic star formation efficiency and lowering central densities. Without some RFB (or other 'rapid' FB), resolved GMCs turn most of their mass into stars, making galaxies dominated by hyper-dense, bound clusters. This makes star formation more violent and 'bursty' when SNe explode in hyper-clustered objects: thus, including RFB tends to 'smooth out' star formation. IR multiple-scattering is rare: the majority of photon absorption occurs in 'normal' GMCs with $A_{V}\sim1$. These conclusions are robust to the RHD method, but M1 produces somewhat stronger RFB effects.Comment: 25 pages, 13 figures, submitted to MNRA

Radiative Stellar Feedback in Galaxy Formation: Methods and Physics

Radiative feedback (RFB) from stars plays a key role in galaxies, but remains poorly-understood. We explore this using high-resolution, multi-frequency radiation-hydrodynamics (RHD) simulations from the Feedback In Realistic Environments (FIRE) project. We study ultra-faint dwarf through Milky Way mass scales, including H+He photo-ionization; photo-electric, Lyman Werner, Compton, and dust heating; and single+multiple scattering radiation pressure (RP). We compare distinct numerical algorithms: ray-based LEBRON (exact when optically-thin) and moments-based M1 (exact when optically-thick). The most important RFB channels on galaxy scales are photo-ionization heating and single-scattering RP: in all galaxies, most ionizing/far-UV luminosity (~1/2 of lifetime-integrated bolometric) is absorbed. In dwarfs, the most important effect is photo-ionization heating from the UV background suppressing accretion. In MW-mass galaxies, meta-galactic backgrounds have negligible effects; but local photo-ionization and single-scattering RP contribute to regulating the galactic star formation efficiency and lowering central densities. Without some RFB (or other 'rapid' FB), resolved GMCs convert too-efficiently into stars, making galaxies dominated by hyper-dense, bound star clusters. This makes star formation more violent and 'bursty' when SNe explode in these hyper-clustered objects: thus, including RFB 'smoothes' SFHs. These conclusions are robust to RHD methods, but M1 produces somewhat stronger effects. Like in previous FIRE simulations, IR multiple-scattering is rare (negligible in dwarfs, ~10% of RP in massive galaxies): absorption occurs primarily in 'normal' GMCs with A_v~1.Comment: 28 pages, 14 figures. Updated to match published MNRAS versio

Hard chrome coating deposited by physical vapour deposition

SIGLEAvailable from CEN Saclay, Service de Documentation, 91191 - Gif-sur-Yvette Cedex (France) / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Magnetic domain configuration of La0.7Sr0.3MnO3 patterned elements

PosterInternational audienceThe magnetization configuration in small La0.7Sr0.3MnO3 elements is investigated as a function of geometry, film thickness, magnetic field, and temperature using x-ray magnetic circular dichroism photoemission electron microscopy (XMCD-PEEM). The patterned elements were defined by focused ion beam (FIB) lithography, and consist of elements varying in shape (from circular, triangular and quadrangular) and size, from 200 nm up to 10 μm. A strong magnetic contrast is observed for all thicknesses (10-50 nm). The magnetic state in the larger elements tends to be multidomain, with complex configurations that are determined by the presence of local pinning sites. These pinning sites are overcome with increasing temperature, and the magnetic configuration evolves into lower energy states. In contrast, the magnetic configuration of the smaller elements are largely determined by the magnetostatic energy contribution, which gives rise to highly symmetric states as found in 3d ferromagnetic structures. Our results show that the magnetism of small LSMO elements is robust nearly up to the critical temperature, with magnetic configurations that can be controlled by suitable geometrical design

Capteurs bio-chimiques Groupe I : capteurs chimiques a fibres optiques

Etude recouvrant les subventions 91-B-0270 a 91-B-0279 inclusesAvailable at INIST (FR), Document Supply Service, under shelf-number : AR 15533 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

Women’s dissatisfaction with inappropriate behavior by health care workers during childbirth care in France: A survey study

Background As part of a decades-long process of restructuring primary care, independent (also known as community) healthcare workers are being encouraged to work in groups to facilitate their coordination and continuity of care in France. French independent midwives perform about half of the early prenatal interviews that identify mothers' needs during pregnancy and then refer them to the appropriate resources. The French government, however, structured the COVID-19 pandemic response around public health institutions and did not directly mobilise these community healthcare workers during the lockdown phase. These responses have raised questions about their role within the healthcare system in crises. This survey’s main objectives were to estimate the proportion of independent midwives who experienced new difficulties in referring women to healthcare facilities or other caregivers and in collaborating with hospitals during the first stage of this pandemic. The secondary objective was to estimate the proportion, according to their mode of practice, of independent midwives who considered that all the women under their care had risked harm due to failed or delayed referral to care. Methods We conducted an online national survey addressed to independent midwives in France from 29 April to 15 May 2020, around the end of the first lockdown (17 March–11 May, 2020). Results Of the 5264 registered independent midwives in France, 1491 (28.3%) responded; 64.7% reported new or greater problems during the pandemic in referring women to health facilities or care-providers, social workers in particular, and 71.0% reported new difficulties collaborating with hospitals. Nearly half (46.2%) the respondents considered that all the women in their care had experienced, to varying degrees, a lack of or delay in care that could have affected their health. This proportion did not differ according to the midwives’ form of practice: solo practice, group practice with other midwives only, or group practice with at least two types of healthcare professionals. Conclusions The pandemic has degraded the quality of pregnant women’s care in France and challenged the French model of care, which is highly compartmentalised between an almost exclusively independent primary care (community) sector and a predominantly salaried secondary care (hospital) sector