Seaborn: V0.7.0 (January 2016)

Multimessenger observations of the neutron star merger GW170817 and its kilonova proved that neutron star mergers can synthesize large quantities of r-process elements. If neutron star mergers in fact dominate all r-process element production, then the distribution of kilonova ejecta compositions should match the distribution of r-process abundance patterns observed in stars. The lanthanide fraction (X La ) is a measurable quantity in both kilonovae and metalpoor stars, but it has not previously been explicitly calculated for stars. Here, we compute the lanthanide fraction distribution of metal-poor stars ([Fe/H] < −2.5) to enable comparison to current and future kilonovae. The full distribution peaks at log X La ∼ −1.8, but r-process-enhanced stars ([Eu/Fe] > 0.7) have distinctly higher lanthanide fractions; log X La −1.5. We review observations of GW170817 and find general consensus that the total log X La = −2.2 ± 0.5, somewhat lower than the typical metal-poor star and inconsistent with the most highly r-enhanced stars. For neutron star mergers to remain viable as the dominant r-process site, future kilonova observations should be preferentially lanthanide-rich (including a population of ∼ 10% with log X La > −1.5). These high-X La kilonovae may be fainter and more rapidly evolving than GW170817, posing a challenge for discovery and follow-up observations. Both optical and (mid-)infrared observations will be required to robustly constrain kilonova lanthanide fractions. If such high-X La kilonovae are not found in the next few years, that likely implies that the stars with the highest r-process enhancements have a different origin for their r-process elements.

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“…Software: Astropy (Astropy Collaboration et al Walt et al 2011), matplotlib (Hunter 2007), seaborn (Waskom et al 2016), pandas (Mckinney 2010)…”

Section: Discussionmentioning

confidence: 99%

The Lanthanide Fraction Distribution in Metal-poor Stars: A Test of Neutron Star Mergers as the Dominant r-process Site

Drout

Hansen

2019

ApJ

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“…In the local Universe this corresponds to the mass at which galaxies are primarily slow-rotators, or core ellipticals (e.g., Cappellari et al 2013a,b). In the top row of Figure 4 we show the Gaussian-kernel smoothed, normalized probability distribution functions (Waskom et al 2016) for λ (left, ATLAS 3D and MASSIVE) and (v 5 /σ 0 ) * (right, LEGA-C) for galaxies with log M /M ≥ 10.75, in bins of 0.25 dex. We note that the different distributions identified in Figure 3 likely correspond to a difference in populations of so-called fast-and slow-rotators in the local Universe.…”

Section: Nearby Quiescent Galaxies From the Massive And Atlas 3d Surveysmentioning

confidence: 99%

Stellar Kinematics and Environment at z ∼ 0.8 in the LEGA-C Survey: Massive Slow Rotators Are Built First in Overdense Environments

Cole

Bezanson

Wel

et al. 2020

ApJL

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In this letter, we investigate the impact of environment on integrated and spatially-resolved stellar kinematics of a sample of massive, quiescent galaxies at intermediate redshift (0.6 < z < 1.0). For this analysis, we combine photometric and spectroscopic parameters from the UltraVISTA and Large Early Galaxy Astrophysics Census (LEGA-C) surveys in the COSMOS field and environmental measurements. We analyze the trends with overdensity (1+δ) on the rotational support of quiescent galaxies and find no universal trends at either fixed mass or fixed stellar velocity dispersion. This is consistent with previous studies of the local Universe; rotational support of massive galaxies depends primarily on stellar mass. We highlight two populations of massive galaxies (log M /M ≥ 11) that deviate from the average mass relation. First, the most massive galaxies in the most under-dense regions ((1+δ) ≤ 1) exhibit elevated rotational support. Similarly, at the highest masses (log M /M ≥ 11.25) the range in rotational support is significant in all but the densest regions. This corresponds to an increasing slow-rotator fraction such that only galaxies in the densest environments ((1 + δ) ≥ 3.5) are primarily (90±10%) slow-rotators.This effect is not seen at fixed velocity dispersion, suggesting minor merging as the driving mechanism: only in the densest regions have the most massive galaxies experienced significant minor merging, building stellar mass and diminishing rotation without significantly affecting the central stellar velocity dispersion. In the local Universe, most massive galaxies are slow-rotators, regardless of environment, suggesting minor merging occurs at later cosmic times (z 0.6) in all but the most dense environments.

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“…Software: astroML (VanderPlas et al 2012), IPython/Jupyter (Pérez & Granger 2007), matplotlib (Hunter 2007), NumPy/scipy (van der Walt et al 2011), seaborn (Waskom et al 2016)…”

Section: Discussionmentioning

confidence: 99%

Inference of Heating Properties from "Hot" Non-flaring Plasmas in Active Region Cores. II. Nanoflare Trains

Barnes,

Cargill,

Bradshaw

2016

Preprint

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Despite its prediction over two decades ago, the detection of faint, high-temperature ("hot") emission due to nanoflare heating in non-flaring active region cores has proved challenging. Using an efficient two-fluid hydrodynamic model, this paper investigates the properties of the emission expected from repeating nanoflares (a nanoflare train) of varying frequency as well as the separate heating of electrons and ions. If the emission measure distribution (EM(T )) peaks at T = T m , we find that EM(T m ) is independent of details of the nanoflare train, and EM(T ) above and below T m reflects different aspects of the heating. Below T m the main influence is the relationship of the waiting time between successive nanoflares to the nanoflare energy. Above T m power-law nanoflare distributions lead to an extensive plasma population not present in a monoenergetic train. Furthermore, in some cases characteristic features are present in EM(T ). Such details may be detectable given adequate spectral resolution and a good knowledge of the relevant atomic physics. In the absence of such resolution we propose some metrics that can be used to infer the presence of "hot" plasma.

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Seaborn: V0.7.0 (January 2016)

Cited by 43 publications

References 0 publications

The Lanthanide Fraction Distribution in Metal-poor Stars: A Test of Neutron Star Mergers as the Dominant r-process Site

The Lanthanide Fraction Distribution in Metal-poor Stars: A Test of Neutron Star Mergers as the Dominant r-process Site

Stellar Kinematics and Environment at z ∼ 0.8 in the LEGA-C Survey: Massive Slow Rotators Are Built First in Overdense Environments

Inference of Heating Properties from "Hot" Non-flaring Plasmas in Active Region Cores. II. Nanoflare Trains

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