arXiv subjects

Nicolas Flagey

Publications and source records attributed to Nicolas Flagey.

At least 19 recordsLinked to original sources

arXiv2024

Hydroxyl Lines and Moonlight: a High Spectral Resolution Investigation of NIR skylines from Maunakea to guide NIR spectroscopic surveys

Subtracting the changing sky contribution from the near-infrared (NIR) spectra of faint astronomical objects is challenging and crucial to a wide range of science cases such as estimating the velocity dispersions of dwarf galaxies, studying the gas dynamics in faint galaxies, measuring accurate redshifts, and any spectroscopic studies of faint targets. Since the sky background varies with time and location, NIR spectral observations, especially those employing fiber spectrometers and targeting extended sources, require frequent sky-only observations for calibration. However, sky subtraction can be optimized with sufficient a priori knowledge of the sky's variability. In this work, we explore how to optimize sky subtraction by analyzing 1075 high-resolution NIR spectra from the CFHT's SPIRou on Maunakea, and we estimate the variability of 481 hydroxyl (OH) lines. These spectra were collected during two sets of three nights dedicated to obtaining sky observations every five and a half minutes. During the first set, we observed how the Moon affects the NIR, which has not been accurately measured at these wavelengths. We suggest accounting for the Moon contribution at separation distances less than 10 degrees when 1) reconstructing the sky using principal component analysis 2) observing targets at Y JHK mags fainter than ~15 and 3) attempting a sky subtraction better than 1%. We also identified 126 spectral doublets, or OH lines that split into at least two components, at SPIRou's resolution. In addition, we used Lomb-Scargle Periodograms and Gaussian process regression to estimate that most OH lines vary on similar timescales, which provides a valuable input for IR spectroscopic survey strategies. The data and code developed for this study are publicly available.

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arXiv2024

JWST MIRI Flight Performance: Imaging

The Mid-Infrared Instrument (MIRI) aboard the James Webb Space Telescope (JWST) provides the observatory with a huge advance in mid-infrared imaging and spectroscopy covering the wavelength range of 5 to 28 microns. This paper describes the performance and characteristics of the MIRI imager as understood during observatory commissioning activities, and through its first year of science operations. We discuss the measurements and results of the imager's point spread function, flux calibration, background, distortion and flat fields as well as results pertaining to best observing practices for MIRI imaging, and discuss known imaging artefacts that may be seen during or after data processing. Overall, we show that the MIRI imager has met or exceeded all its pre-flight requirements, and we expect it to make a significant contribution to mid-infrared science for the astronomy community for years to come.

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arXiv2023

A Year of Wavefront Sensing with JWST in Flight: Cycle 1 Telescope Monitoring and Maintenance Summary

We summarize JWST's measured telescope performance across science Cycle 1. The stability of segments alignments is typically better than 10 nanometers RMS between measurements every two days, leading to highly stable point spread functions. The frequency of segment "tilt events" decreased significantly, and larger tilt events ceased entirely, as structures gradually equilibrated after cooldown. Mirror corrections every 1-2 months now maintain the telescope below 70 nm RMS wavefront error. Observed micrometeoroid impacts during cycle 1 had negligible effect on science performance, consistent with preflight predictions. As JWST begins Cycle 2, its optical performance and stability are equal to, and in some ways better than, the performance reported at the end of commissioning.

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arXiv2023

The James Webb Space Telescope Mission: Optical Telescope Element Design, Development, and Performance

The James Webb Space Telescope (JWST) is a large, infrared space telescope that has recently started its science program which will enable breakthroughs in astrophysics and planetary science. Notably, JWST will provide the very first observations of the earliest luminous objects in the Universe and start a new era of exoplanet atmospheric characterization. This transformative science is enabled by a 6.6 m telescope that is passively cooled with a 5-layer sunshield. The primary mirror is comprised of 18 controllable, low areal density hexagonal segments, that were aligned and phased relative to each other in orbit using innovative image-based wavefront sensing and control algorithms. This revolutionary telescope took more than two decades to develop with a widely distributed team across engineering disciplines. We present an overview of the telescope requirements, architecture, development, superb on-orbit performance, and lessons learned. JWST successfully demonstrates a segmented aperture space telescope and establishes a path to building even larger space telescopes.

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arXiv2021

The Transition from Diffuse Molecular Gas to Molecular Cloud Material in Taurus

We study four lines of sight that probe the transition from diffuse molecular gas to molecular cloud material in Taurus. Measurements of atomic and molecular absorption are used to infer the distribution of species and the physical conditions toward stars behind the Taurus Molecular Cloud (TMC). New high-resolution spectra at visible and near infrared wavelengths of interstellar Ca II, Ca I, K I, CH, CH^+, C2, CN, and CO toward HD28975 and HD29647 are combined with data at visible wavelengths and published CO results from ultraviolet measurements for HD27778 and HD30122. Gas densities and temperatures are inferred from C2, CN, and CO excitation and CN chemistry. Our results for HD29647 are noteworthy because the CO column density is 10^{18} cm^{-2} while C2 and CO excitation reveals a temperature of 10 K and density about 1000 cm^{-3}, more like conditions found in dark molecular clouds. Similar results arise from our chemical analysis for CN through reactions involving observations of CH, C2, and NH. Enhanced potassium depletion and a reduced CH/H2 column density ratio also suggest the presence of a dark cloud. The directions toward HD27778 and HD30122 probe molecule-rich diffuse clouds, which can be considered CO-dark gas, while the sight line toward HD28975 represents an intermediate case. Maps of dust temperature help refine the description of the material along the four sight lines and provide an estimate of the distance between HD29647 and a clump in the TMC. An Appendix provides results for the direction toward HD26571; this star also probes diffuse molecular gas.

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arXiv2020

Molecular Gas Heating and Modified Dust Properties in Active Galaxies: Growing Black Holes or Tidal Shocks?

We investigate if and how growing super-massive black holes (SMBH) known as Active Galactic Nuclei (AGN) and gravitational interactions affect the warm molecular gas and dust of galaxies. Our analysis focuses on the morphologies and warm ISM properties of 630 galaxies at z < 0.1. We use grizy images from the Pan-STARRS survey to classify the galaxies into mergers, early mergers, and non-mergers. We use MIR spectroscopic measurements of emission from rotational H2 transitions, dust and PAH features, and silicate emission or absorption lines at 9.7 microns to study how gravitational interactions impact the warm ISM in AGN and non-AGN hosts. We find that in AGN-hosts, the ISM is warmer, the ratios of H2 to PAHs are larger, the PAH emission line ratios and silicate strengths have a wider range of values than in non-AGN hosts. We find some statistical differences between the H2 emission of mergers and non-mergers, but those differences are less statistically significant than those between AGN and non-AGN hosts.

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arXiv2020

Wide field-of-view study of the Eagle Nebula with the Fourier transform imaging spectrograph SITELLE at CFHT

We present the very first wide-field, 11 by 11 arcmin, optical spectral mapping of M16, one of the most famous star-forming regions in the Galaxy. The data were acquired with the new imaging Fourier transform spectrograph SITELLE mounted on the Canada-France-Hawaii Telescope (CFHT). We obtained three spectral cubes with R=10'000 (SN1 filter), 1500 (SN2 filter) and 600 (SN3 filter), centered on the Pillars of Creation and the HH216 flow, covering the main optical nebular emission lines: [O II]3726,29 (SN1), Hb, [O III]4959,5007 (SN2), [N II]6548,84, Ha, and [S II]6717,31 (SN3). We validate the performance, calibration, and data reduction of SITELLE, and analyze the structures in the large field-of-view in terms of their kinematics and nebular emission. We compared the SITELLE data to MUSE integral field observations and other spectroscopic and narrow-band imaging data to validate the performance of SITELLE. We computed gas-phase metallicities via the strong-line method, performed a pixel-by-pixel fit to the main emission lines to derive kinematics of the ionized gas, computed the mass-loss rate of the Eastern pillar (the Spire), and combined the SITELLE data with near-infrared narrow-band imaging to characterize the HH216 flow. The comparison with previously published fluxes demonstrates very good agreement. We disentangle the dependence of the gas-phase metallicities (derived via abundance-tracing line ratios) on the degree of ionization and obtain metallicities that are in excellent agreement with the literature. We confirm the bipolar structure of HH216, find evidence for episodic accretion from the source of the flow, and identify its likely driving source. We compute the mass-loss rate of the Spire pillar on the East side of the H II region and find excellent agreement with the correlation between the mass-loss rate and the ionizing photon flux from the nearby cluster NGC6611.

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arXiv2019

The Maunakea Spectroscopic Explorer

The Maunakea Spectroscopic Explorer is a next-generation massively multiplexed spectroscopic facility currently under development in Hawaii. It is completely dedicated to large-scale spectroscopic surveys and will enable transformative science. In this white paper we summarize the science case and describe the current state of the project.

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arXiv2019

High Redshift Obscured Quasars and the Need for Optical to NIR, Massively Multiplexed, Spectroscopic Facilities

Most bulge-dominated galaxies host black holes with masses that tightly correlate with the masses of their bulges. This may indicate that the black holes may regulate galaxy growth or vice versa, or that they may grow in lock-step. The quest to understand how, when, and where those black-holes formed motivates much of extragalactic astronomy. Here we focus on a population of galaxies with active black holes in their nuclei (active galactic nuclei or AGN), that are fully or partially hidden by dust and gas: the emission from the broad line region is either completely or partially obscured with a visual extinction of 1 or above. This limit, though not yet precise, appears to be the point at which the populations of AGN may evolve differently. We highlight the importance of finding and studying those dusty AGN at redshifts between 1 and 3, the epoch when the universe may have gone through its most dramatic changes. We emphasize the need for future large multiplexed spectroscopic instruments that can perform dedicated surveys in the optical and NIR to pin down the demographics of such objects and study their reddening properties, star-formation histories, and excitation conditions. These key studies will shed light on the role of black holes in galaxy evolution during the epoch of peak growth activity.

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arXiv2018

The Maunakea Spectroscopic Explorer Book 2018

(Abridged) This is the Maunakea Spectroscopic Explorer 2018 book. It is intended as a concise reference guide to all aspects of the scientific and technical design of MSE, for the international astronomy and engineering communities, and related agencies. The current version is a status report of MSE's science goals and their practical implementation, following the System Conceptual Design Review, held in January 2018. MSE is a planned 10-m class, wide-field, optical and near-infrared facility, designed to enable transformative science, while filling a critical missing gap in the emerging international network of large-scale astronomical facilities. MSE is completely dedicated to multi-object spectroscopy of samples of between thousands and millions of astrophysical objects. It will lead the world in this arena, due to its unique design capabilities: it will boast a large (11.25 m) aperture and wide (1.52 sq. degree) field of view; it will have the capabilities to observe at a wide range of spectral resolutions, from R2500 to R40,000, with massive multiplexing (4332 spectra per exposure, with all spectral resolutions available at all times), and an on-target observing efficiency of more than 80%. MSE will unveil the composition and dynamics of the faint Universe and is designed to excel at precision studies of faint astrophysical phenomena. It will also provide critical follow-up for multi-wavelength imaging surveys, such as those of the Large Synoptic Survey Telescope, Gaia, Euclid, the Wide Field Infrared Survey Telescope, the Square Kilometre Array, and the Next Generation Very Large Array.

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arXiv2018

Maunakea Spectroscopic Explorer Advancing from Conceptual Design

The Maunakea Spectroscopic Explorer (MSE) project has completed its Conceptual Design Phase. This paper is a status report of the MSE project regarding its technical and programmatic progress. The technical status includes its conceptual design and system performance, and highlights findings and recommendations from the System and various subsystems design reviews. The programmatic status includes the project organization and management plan for the Preliminary Design Phase. In addition, this paper provides the latest information related to the permitting process for Maunakea construction.

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arXiv2018

Maunakea Spectroscopic Explorer (MSE) Instrumentation Suite

The Maunakea Spectroscopic Explorer (MSE) is replacement of the existing 3.6-m Canada France Hawaii Telescope into a dedicated wide field highly multiplexed fiber fed spectroscopic facility. MSE is capable of observing over four thousand science targets simultaneously in two resolution modes. The paper describes the unique instrument system capabilities and its components starting from the telescope prime focus and ending at the spectrograph suite. The instrument system components have completed their conceptual designs and they include a Sphinx positioner system, fiber transmission system, low/moderate resolution and high resolution spectrographs and a calibration system. These components will be procured separately and the Project is responsible for their integration and the overall system performance afterward. The paper describes from a system perspective the specific design and interface constraints imposed on the components given the extra interface and integration considerations.

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arXiv2018

Optimal scheduling and science delivery of spectra for millions of targets in thousands of fields: the operational concept of the Maunakea spectroscopic explorer (MSE)

The Maunakea Spectroscopic Explorer (MSE) will each year obtain millions of spectra in the optical to near-infrared, at low (R~3000) to high (R~40000) spectral resolution by observing >3000 spectra per pointing via a highly multiplexed fiber-fed system. Key science programs for MSE include black hole reverberation mapping, stellar population analysis of faint galaxies at high redshift, and sub-km/s velocity accuracy for stellar astrophysics. The architecture of MSE is an assembly of subsystems designed to meet the science requirements and describes what MSE will look like. In this paper we focus on the operations concept of MSE, which describes how to operate a fiber fed, highly multiplexed, dedicated observatory given its architecture and the science requirements. The operations concept details the phases of operations, from selecting proposals within the science community to distributing back millions of spectra to this community. For each phase, the operations concept describes the tools required to support the science community in their analyses and the operations staff in their work. It also highlights the specific needs related to the complexity of MSE with millions of targets to observe, thousands of fibers to position, and different spectral resolution to use. Finally, the operations concept shows how the science requirements on calibration and observing efficiency can be met.

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arXiv2018

Maximising the sensitivity of next generation multi-object spectroscopy: system budget development and design optimizations for the Maunakea Spectroscopic Explorer

MSE is an 11.25m telescope with a 1.5 sq.deg. field of view. It can simultaneously obtain 3249 spectra at R=3000 from 360-1800nm, and 1083 spectra at R=40000 in the optical. Absolutely critical to the scientific success of MSE is to efficiently access the faint Universe. Here, we describe the adopted systems engineering methodology to ensure MSE meets the challenging sensitivity requirements, and how these requirements are partitioned across three budgets, relating to the throughput, noise and fiber injection efficiency. We then describe how the sensitivity of MSE as a system was estimated at the end of Conceptual Design Phase, and how this information was used to revisit the system design in order to meet the sensitivity requirements while maintaining the overall architectural concept of the Observatory. Finally, we present the anticipated sensitivity performance of MSE and describe the key science that these capabilities will enable.

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arXiv2018

Maunakea Spectroscopic Explorer (MSE): Implementing systems engineering methodology for the development of a new facility

Maunakea Spectroscopic Explorer will be a 10-m class highly multiplexed survey telescope, including a segmented primary mirror and robotic fiber positioners at the prime focus. MSE will replace the Canada France Hawaii Telescope (CFHT) on the summit of Mauna Kea, Hawaii. The multiplexing includes an array of over four thousand fibres feeding banks of spectrographs several tens of meters away. We present an overview of the requirements flow-down for MSE, from Science Requirements Document to Observatory Requirements Document. We have developed the system performance budgets, along with updating the budget architecture of our evolving project. We have also identified the links between subsystems and system budgets (and subsequently science requirements) and included system budget that are unique to MSE as a fiber-fed facility. All of this has led to a set of Observatory Requirements that is fully consistent with the Science Requirements.

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arXiv2018

The science calibration challenges of next generation highly multiplexed optical spectroscopy: the case of the Maunakea Spectroscopic Explorer

MSE is an 11.25m telescope with a 1.5 sq.deg. field of view. It can simultaneously obtain 3249 spectra at R=3000 from 360-1800nm, and 1083 spectra at R=40000 in the optical. The large field of view, large number of targets, as well as the use of more than 4000 optical fibres to transport the light from the focal plane to the spectrographs, means that precise and accurate science calibration is difficult but essential to obtaining the science goals. As a large aperture telescope focusing on the faint Universe, precision sky subtraction and spectrophotometry are especially important. Here, we discuss the science calibration requirements, and the adopted calibration strategy, including operational features and hardware, that will enable the successful scientific exploitation of the vast MSE dataset.

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arXiv2018

Expected observing efficiency of the Maunakea Spectroscopic Explorer (MSE)

The Maunakea Spectroscopic Explorer (MSE) will obtain millions of spectra each year in the optical to near-infrared, at low (R ~ 3,000) to high (R ~ 40,000) spectral resolution by observing >4,000 spectra per pointing via a highly multiplexed fiber-fed system. Key science programs for MSE include black hole reverberation mapping, stellar population analysis of faint galaxies at high redshift, and sub-km/s velocity accuracy for stellar astrophysics. One key metric of the success of MSE will be its survey speed, i.e. how many spectra of good signal-to-noise ratio will MSE be able to obtain every night and every year. This is defined at the higher level by the observing efficiency of the observatory and should be at least 80%, as indicated in the Science Requirements. In this paper we present the observing efficiency budget developed for MSE based on historical data at the Canada-France-Hawaii Telescope and other Maunakea Observatories. We describe the typical sequence of events at night to help us compute the observing efficiency and how we envision to optimize it to meet the science requirements.

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arXiv2018

Modeling and budgeting fiber injection efficiency for the Maunakea spectroscopic explorer (MSE)

The Maunakea Spectroscopic Explorer (MSE) will each year obtain millions of spectra in the optical to near-infrared, at low (R ~ 3,000) to high (R ~ 40,000) spectral resolution by observing >4,000 spectra per pointing via a highly multiplexed fiber-fed system. Key science programs for MSE include black hole reverberation mapping, stellar population analysis of faint galaxies at high redshift, and sub-km/s velocity accuracy for stellar astrophysics. One key metric of the success of MSE will be its survey speed, i.e. how many spectra of good signal-to-noise ratio will MSE be able to obtain every night and every year. The survey speed is directly linked to the allocation efficiency - how many fibers in the focal surface can be allocated to targets - and to the injection efficiency - what fraction of light from a target can enter the fiber at the focal surface. In this paper we focus on the injection efficiency and how to optimize it to increase the signal-to-noise ratio of targets observed in sky dominated conditions. The injection efficiency depends on the size of the fiber and requires highly precise, repeatable and stable positioning of the fiber in the focal surface. We present the allocation budget used for Conceptual Design Review and the modeling that allows to estimate the injection efficiency, which is just one part necessary to meet the science requirements on sensitivities.

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