arXiv subjects

A. Bonnefoi

Publications and source records attributed to A. Bonnefoi.

5 recordsLinked to original sources

arXiv2025

Euclid: The potential of slitless infrared spectroscopy: A z=5.4 quasar and new ultracool dwarfs

We demonstrate the potential of Euclid's slitless spectroscopy to discover high-redshift (z>5) quasars and their main photometric contaminant, ultracool dwarfs. Sensitive infrared spectroscopy from space is able to efficiently identify both populations, as demonstrated by Euclid Near-Infrared Spectrometer and Photometer Red Grism (NISP RGE) spectra of the newly discovered z=5.404 quasar EUCL J181530.01+652054.0, as well as several ultracool dwarfs in the Euclid Deep Field North and the Euclid Early Release Observation field Abell 2764. The ultracool dwarfs were identified by cross-correlating their spectra with templates. The quasar was identified by its strong and broad CIII] and MgII emission lines in the NISP RGE 1206-1892 nm spectrum, and confirmed through optical spectroscopy from the Large Binocular Telescope. The NISP Blue Grism (NISP BGE) 926-1366 nm spectrum confirms CIV and CIII] emission. NISP RGE can find bright quasars at z~5.5 and z>7, redshift ranges that are challenging for photometric selection due to contamination from ultracool dwarfs. EUCL J181530.01+652054.0 is a high-excitation, broad absorption line quasar detected at 144 MHz by the LOw-Frequency Array (L144=4e25 W/Hz). The quasar has a bolometric luminosity of 3e12 Lsun and is powered by a 3.4e9 Msun black hole. The discovery of this bright quasar is noteworthy as fewer than one such object was expected in the ~20 deg2 surveyed. This finding highlights the potential and effectiveness of NISP spectroscopy in identifying rare, luminous high-redshift quasars, previewing the census of these sources that Euclid's slitless spectroscopy will deliver over about 14,000 deg2 of the sky.

astro-ph.GA↗

arXiv2025

Euclid preparation. Overview of Euclid infrared detector performance from ground tests

The paper describes the objectives, design and findings of the pre-launch ground characterisation campaigns of the Euclid infrared detectors. The pixel properties, including baseline, bad pixels, quantum efficiency, inter pixel capacitance, quantum efficiency, dark current, readout noise, conversion gain, response nonlinearity, and image persistence were measured and characterised for each pixel. We describe in detail the test flow definition that allows us to derive the pixel properties and we present the data acquisition and data quality check software implemented for this purpose. We also outline the measurement protocols of all the pixel properties presented and we provide a comprehensive overview of the performance of the Euclid infrared detectors as derived after tuning the operating parameters of the detectors. The main conclusion of this work is that the performance of the infrared detectors Euclid meets the requirements. Pixels classified as non-functioning accounted for less than 0.2% of all science pixels. IPC coupling is minimal and crosstalk between adjacent pixels is less than 1% between adjacent pixels. 95% of the pixels show a QE greater than 80% across the entire spectral range of the Euclid mission. The conversion gain is approximately 0.52 ADU/e-, with a variation less than 1% between channels of the same detector. The reset noise is approximately equal to 23 ADU after reference pixels correction. The readout noise of a single frame is approximately 13 $e^-$ while the signal estimator noise is measured at 7 $e^-$ in photometric mode and 9 $e^-$ in spectroscopic acquisition mode. The deviation from linear response at signal levels up to 80 k$e^-$ is less than 5% for 95% of the pixels. Median persistence amplitudes are less than 0.3% of the signal, though persistence exhibits significant spatial variation and differences between detectors.

astro-ph.IM↗

arXiv2025

Euclid preparation: The NISP spectroscopy channel, on ground performance and calibration

ESA's Euclid cosmology mission relies on the very sensitive and accurately calibrated spectroscopy channel of the Near-Infrared Spectrometer and Photometer (NISP). With three operational grisms in two wavelength intervals, NISP provides diffraction-limited slitless spectroscopy over a field of $0.57$ deg$^2$. A blue grism $\text{BG}_\text{E}$ covers the wavelength range $926$--$1366$\,nm at a spectral resolution $R=440$--$900$ for a $0.5''$ diameter source with a dispersion of $1.24$ nm px$^{-1}$. Two red grisms $\text{RG}_\text{E}$ span $1206$ to $1892$\,nm at $R=550$--$740$ and a dispersion of $1.37$ nm px$^{-1}$. We describe the construction of the grisms as well as the ground testing of the flight model of the NISP instrument where these properties were established.

astro-ph.IM↗

arXiv2024

Euclid. III. The NISP Instrument

The Near-Infrared Spectrometer and Photometer (NISP) on board the Euclid satellite provides multiband photometry and R>=450 slitless grism spectroscopy in the 950-2020nm wavelength range. In this reference article we illuminate the background of NISP's functional and calibration requirements, describe the instrument's integral components, and provide all its key properties. We also sketch the processes needed to understand how NISP operates and is calibrated, and its technical potentials and limitations. Links to articles providing more details and technical background are included. NISP's 16 HAWAII-2RG (H2RG) detectors with a plate scale of 0.3" pix^-1 deliver a field-of-view of 0.57deg^2. In photo mode, NISP reaches a limiting magnitude of ~24.5AB mag in three photometric exposures of about 100s exposure time, for point sources and with a signal-to-noise ratio (SNR) of 5. For spectroscopy, NISP's point-source sensitivity is a SNR = 3.5 detection of an emission line with flux ~2x10^-16erg/s/cm^2 integrated over two resolution elements of 13.4A, in 3x560s grism exposures at 1.6 mu (redshifted Ha). Our calibration includes on-ground and in-flight characterisation and monitoring of detector baseline, dark current, non-linearity, and sensitivity, to guarantee a relative photometric accuracy of better than 1.5%, and relative spectrophotometry to better than 0.7%. The wavelength calibration must be better than 5A. NISP is the state-of-the-art instrument in the NIR for all science beyond small areas available from HST and JWST - and an enormous advance due to its combination of field size and high throughput of telescope and instrument. During Euclid's 6-year survey covering 14000 deg^2 of extragalactic sky, NISP will be the backbone for determining distances of more than a billion galaxies. Its NIR data will become a rich reference imaging and spectroscopy data set for the coming decades.

astro-ph.IM↗

arXiv2022

Euclid Near Infrared Spectrometer and Photometer instrument flight model presentation, performance and ground calibration results summary

The NISP (Near Infrared Spectrometer and Photometer) is one of the two Euclid instruments. It operates in the near-IR spectral region (950-2020nm) as a photometer and spectrometer. The instrument is composed of: a cold (135 K) optomechanical subsystem consisting of a Silicon carbide structure, an optical assembly, a filter wheel mechanism, a grism wheel mechanism, a calibration unit, and a thermal control system, a detection system based on a mosaic of 16 H2RG with their front-end readout electronic, and a warm electronic system (290 K) composed of a data processing / detector control unit and of an instrument control unit that interfaces with the spacecraft via a 1553 bus for command and control and via Spacewire links for science data. This paper presents: the final architecture of the flight model instrument and subsystems, and the performance and the ground calibration measurement done at NISP level and at Euclid Payload Module level at operational cold temperature.

astro-ph.IM↗