Publications by Nicolas Lawrence Etienne Longeard

The Pristine Dwarf-galaxy Survey: Vi. a Vlt/flames Spectroscopic Study of the Dwarf Galaxy Bootes Ii

Pascale Jablonka, Nicolas Lawrence Etienne Longeard

Aims. The Milky Way has a large population of dwarf galaxy satellites. Their properties are sensitive to both cosmology and the physical processes underlying galaxy formation, but these properties are still not properly characterised for the entire satelli ...

EDP SCIENCES S A2025

The Pristine survey: XXV. The very metal-poor Galaxy: Chemodynamics through the follow-up of the Pristine- Gaia synthetic catalogue

Nicolas Lawrence Etienne Longeard

Context. The Pristine-Gaia synthetic catalogue of reliable photometric metallicities makes use of spectrophotometric information from Gaia DR3 XP spectra to calculate metallicity-sensitive CaHK magnitudes, which in turn provides photometric metallicities f ...

2025

Stellar Metallicities and Gradients in the Isolated, Quenched Low-mass Galaxy Tucana

Nicolas Lawrence Etienne Longeard

We measure the metallicities of 374 red giant branch (RGB) stars in the isolated, quenched dwarf galaxy Tucana using Hubble Space Telescope (HST) narrow-band (F395N) Calcium H & K (CaHK) imaging. Our sample is a factor of similar to 7 similar to 7 larger t ...

Iop Publishing Ltd2024

Gaia's brightest very metal-poor (VMP) stars Metallicity catalogue of a thousand VMP stars from Gaia's radial velocity spectrometer spectra

Nicolas Lawrence Etienne Longeard

Context. Gaia DR3 has offered the scientific community a remarkable dataset of approximately one million spectra acquired with the radial velocity spectrometer (RVS) in the calcium II triplet region, which is well suited to identify very metal-poor (VMP) s ...

Edp Sciences S A2024

Stellar Metallicities and Gradients in the Faint M31 Satellites Andromeda XVI and Andromeda XXVIII

Nicolas Lawrence Etienne Longeard

We present ∼300 stellar metallicity measurements in two faint M31 dwarf galaxies, Andromeda XVI (M V = −7.5) and Andromeda XXVIII (M V = -8.8), derived using metallicity-sensitive calcium H and K narrowband Hubble Space Telescope imaging. These are the fir ...

2024

Metallicity Distribution Functions of 13 Ultra-faint Dwarf Galaxy Candidates from Hubble Space Telescope Narrowband Imaging

Nicolas Lawrence Etienne Longeard

We present uniformly measured stellar metallicities of 463 stars in 13 Milky Way (MW) ultra-faint dwarf galaxies (UFDs; M-V = -7.1 to -0.8) using narrowband CaHK (F395N) imaging taken with the Hubble Space Telescope. This represents the largest homogeneous ...

Iop Publishing Ltd2023

The Pristine dwarf galaxy survey-V. The edges of the dwarf galaxy Hercules

Pascale Jablonka, Nicolas Lawrence Etienne Longeard

We present a new spectroscopic study of 175 stars in the vicinity of the dwarf galaxy Hercules (d similar to 132 kpc) with data from the Anglo-Australian Telescope and its AAOmega spectrograph together with the Two Degree Field multi-object system to solve ...

OXFORD UNIV PRESS2023

Metallicity Distribution Function of the Eridanus II Ultra-faint Dwarf Galaxy from Hubble Space Telescope Narrowband Imaging

Nicolas Lawrence Etienne Longeard

We use deep narrowband CaHK (F395N) imaging taken with the Hubble Space Telescope (HST) to construct the metallicity distribution function (MDF) of Local Group ultra-faint dwarf galaxy Eridanus II (Eri II). When combined with archival F475W and F814W data, ...

IOP Publishing Ltd2022

The Pristine dwarf galaxy survey - IV. Probing the outskirts of the dwarf galaxy Bootes I

Pascale Jablonka, Romain Ely Roland Lucchesi, Nicolas Lawrence Etienne Longeard

We present a new spectroscopic study of the dwarf galaxy Bootes I (Boo I) with data from the Anglo-Australian Telescope and its AAOmega spectrograph together with the Two Degree Field multi-object system. We observed 36 high-probability Boo I stars selecte ...

OXFORD UNIV PRESS2022

The Complexity of the Cetus Stream Unveiled from the Fusion of STREAMFINDER and StarGO

Nicolas Lawrence Etienne Longeard

We combine the power of two stream-searching tools, STREAMFINDER and StarGO applied to the Gaia EDR3 data, to detect stellar debris belonging to the Cetus stream system that forms a complex, nearly polar structure around the Milky Way. In this work, we fin ...

IOP Publishing Ltd2022

The pristine dwarf-galaxy survey - III. Revealing the nature of the Milky Way globular cluster Sagittarius II

Pascale Jablonka, Romain Ely Roland Lucchesi, Nicolas Lawrence Etienne Longeard

We present a new spectroscopic study of the faint Milky Way satellite Sagittarius II. Using multiobject spectroscopy from the Fibre Large Array Multi-Element Spectrograph, we supplement the data set of Longeard et al. with 47 newly observed stars, 19 of wh ...

OXFORD UNIV PRESS2021

The Pristine Dwarf-Galaxy survey - II. In-depth observational study of the faint Milky Way satellite Sagittarius II

Pascale Jablonka, Nicolas Lawrence Etienne Longeard

We present an extensive study of the Sagittarius II (Sgr II) stellar system using MegaCam g and i photometry, narrow-band, metallicity-sensitive calcium H&K doublet photometry and Keck II/DEIMOS multiobject spectroscopy. We derive and refine the Sgr II str ...

OXFORD UNIV PRESS2020

The Pristine Inner Galaxy Survey (PIGS) I: tracing the kinematics of metal-poor stars in the Galactic bulge

Carmela Lardo, Nicolas Lawrence Etienne Longeard

Our Galaxy is known to contain a central boxy/peanut-shaped bulge, yet the importance of a classical, pressure-supported component within the central part of the Milky Way is still being debated. It should be most visible at low metallicity, a regime that ...

OXFORD UNIV PRESS2020

The Pristine survey - X. A large population of low-metallicity stars permeates the Galactic disc

Pierre North, Pascale Jablonka, Romain Ely Roland Lucchesi, Nicolas Lawrence Etienne Longeard

The orbits of the least chemically enriched stars open a window on the formation of our Galaxy when it was still in its infancy. The common picture is that these low-metallicity stars are distributed as an isotropic, pressure-supported component since thes ...

OXFORD UNIV PRESS2020

The Hidden Past of M92: Detection and Characterization of a Newly Formed 17 degrees Long Stellar Stream Using the Canada-France Imaging Survey

Nicolas Lawrence Etienne Longeard

We present an analysis of the structure, kinematics, and orbit of a newly found stellar stream emanating from the globular cluster M92 (NGC 6341). This stream was discovered in an improved matched-filter map of the outer Galaxy, based on a "color-color-mag ...

IOP PUBLISHING LTD2020

Tracing the formation of the Milky Way through ultra metal-poor stars

Pascale Jablonka, Nicolas Lawrence Etienne Longeard

We use Gaia DR2 astrometric and photometric data, published radial velocities and MESA models to infer distances, orbits, surface gravities, and effective temperatures for all ultra metal-poor stars ([Fe/H] < -4.0 dex) available in the literature. Assuming ...

OXFORD UNIV PRESS2019

The Pristine survey VI. The first three years of medium-resolution follow-up spectroscopy of Pristine EMP star candidates

Carmela Lardo, Romain Ely Roland Lucchesi, Nicolas Lawrence Etienne Longeard

We present the results of a 3-yr long, medium-resolution spectroscopic campaign aimed at identifying very metal -poor stars from candidates selected with the CaHK, metallicitysensitive Pristine survey. The catalogue consists of a total of 1007 stars, and i ...

OXFORD UNIV PRESS2019

Pristine dwarf galaxy survey - I. A detailed photometric and spectroscopic study of the very metal-poor Draco II satellite

Pascale Jablonka, Silvia Martin de Nicolas Agut, Nicolas Lawrence Etienne Longeard

We present a detailed study of the faint Milky Way satellite Draco II (Dra II) from deep CFHT/MegaCam broad-band g and i photometry and narrow-band metallicity-sensitive CaliK observations, along with follow-up Keck II/DEIMOS multi-object spectroscopy. For ...

OXFORD UNIV PRESS2018

The Pristine survey IV: approaching the Galactic metallicity floor with the discovery of an ultra-metal-poor star

Pascale Jablonka, Marc Gentile, Silvia Martin de Nicolas Agut, Carmela Lardo, Nicolas Lawrence Etienne Longeard

The early Universe presented a star formation environment that was almost devoid of heavy elements. The lowest metallicity stars thus provide a unique window into the earliest Galactic stages, but are exceedingly rare and difficult to find. Here, we presen ...

OXFORD UNIV PRESS2018

The Pristine survey - I. Mining the Galaxy for the most metal-poor stars

Pascale Jablonka, Nicolas Lawrence Etienne Longeard

We present the Pristine survey, a new narrow-band photometric survey focused on the metallicity-sensitive Ca H&K lines and conducted in the Northern hemisphere with the wide-field imager MegaCam on the Canada-France-Hawaii Telescope. This paper reviews our ...

Oxford Univ Press2017