Searcharxiv⌕ Search

arXiv subjects

H. Aussel

Publications and source records attributed to H. Aussel.

At least 19 recordsLinked to original sources
arXiv2026

Euclid: Discovery of 31 new quasars at $6.6 < z < 7.8$

We report the discovery of 31 new high-$z$ quasars in the redshift range $6.6 < z < 7.8$. These quasars were selected from approximately 3000 deg$^2$ of sky covered during the first 1.5 years of the Euclid Wide Survey, representing the initial results of the Euclid high-$z$ quasar search. Our candidate selection employed multiple machine-learning and probabilistic techniques applied to the Euclid $I_E$, $Y_E$, $J_E$, and $H_E$ images, supplemented by ancillary $z$-band data when available. Spectroscopic follow-up observations were carried out with Keck, Magellan, and the Large Binocular Telescope (LBT). Among the new discoveries, there are 12 quasars at $z \geq 7$, more than doubling the number of previously known quasars at $z \geq 7$. The newly discovered quasars exhibit $21.2 < J_E < 23.2$ ($-25.5 < M_{1450} < -23.6$), extending quasar studies to the faint end of the quasar luminosity function (QLF) at $z \gtrsim 7$. The quasar with the highest-$z$, EUCL J172902.75+641018.1 at $z \approx 7.77$, sets the new redshift record for the most distant quasar ever reported. These discoveries demonstrate Euclid's transformative role in high-$z$ quasar discovery and set the stage for future follow-up studies of the early galaxies hosting quasars, supermassive black hole growth, and the intergalactic medium in the epoch of reionisation.

astro-ph.GA↗
arXiv2026

Euclid: The convective-transition gap of 47 Tuc

We report the first detection of the `convective-transition gap' (also known as `M-dwarf gap') in the globular cluster 47 Tuc (NGC 104) thanks to Euclid data. This feature, linked to a change in the physical properties of late-type dwarfs, has remained elusive, with only two detections so far. Leveraging the large number of stars, high resolution, and photometric precision enabled by Euclid, we detect a statistically significant, sharp discontinuity in the main-sequence luminosity function of 47 Tuc at $I_{\rm E} \approx 22.9$, which we identify as the convective-transition gap. We compare the observed properties of the gap in 47 Tuc with theoretical models, showing how the gap can be a powerful diagnostic to probe the internal chemical structure of globular clusters, and their multiple stellar populations. Following its initial discovery in the metal-poor cluster NGC 6397, the identification of a convective gap in the metal-rich 47 Tuc suggests that this feature might be more general than previously thought. These results demonstrate that Euclid can be transformative well beyond cosmology, with impact across multiple areas of astrophysics, including resolved stellar populations.

astro-ph.SR↗
arXiv2026

Euclid Quick Data Release (Q2) -- The Euclid Galactic Bulge Survey

The Euclid Quick Data Release Q2 provides an unprecedented deep, wide-field, high-angular-resolution view of the inner Galactic bulge through the Euclid Galactic Bulge Survey (EGBS). Nine contiguous fields covering 4.8 deg$^2$ were observed with the VIS instrument over 24 hours in March 2025. Unlike the nominal Euclid survey strategy, the EGBS employed 16 dithered exposures of 400 s each, corresponding to a total integration time of 1.8 hours per field. Dedicated calibration observations were obtained to derive point spread functions (PSFs). The primary objective of the EGBS is gravitational microlensing, with high-angular-resolution imaging enabling lens-mass measurements to better than 10%. The survey provides an optical reference dataset for previously discovered microlensing events and future observations of the Galactic bulge. The Q2 data were processed with the VIS-PF pipeline. The non-standard observing strategy required dedicated calibration products, while the extreme stellar density necessitated modifications to the astrometric calibration and cosmic-ray detection procedures. These improvements have since been incorporated into later pipeline versions. We describe the motivation, observing strategy, data processing, products, and first results of the EGBS. Astrometric residuals with respect to the Gaia DR3 catalogue are 5.5 mas in right ascension and 4.4 mas in declination across the survey area, while the photometric zero points are calibrated to 1.5%. The Q2 release includes calibrated single-dither images, dedicated PSF models, and photometric catalogues containing approximately 45 million detected sources per dither down to AB magnitude 26. Although incomplete because of extreme crowding, these products provide a robust astrometric and photometric foundation for future exploitation of the dataset.

astro-ph.GA↗
arXiv2026

Euclid preparation. First investigation of the impact of cross-contamination on spectroscopic redshift measurements with pixel-level simulations

We present a study on simulated data focused on understanding the performance of the spectroscopic redshift measurements with the Near-Infrared Spectrometer and Photometer (NISP) instrument on Euclid. Simulations include scenarios with different levels of cross-contamination arising from overlapping spectra of nearby sources, which represents one of the main drawbacks of slitless spectroscopy. We present a new analysis based on pixel-level simulations of the NISP images, with the data processed using the Euclid spectroscopic pipeline. We first consider an idealised case with non-overlapping spectra to assess the accuracy and reliability of the redshift measurement as a function of the flux of the H-alpha emission line and galaxy size. We then introduce more realistic contamination scenarios, distinguishing between two contributions: contamination from H-alpha emitters, which are the Euclid targets for cosmological analyses, and contamination from all other galaxies. In the second case, we analyse the impact of cross-contamination with an increasing number of contaminants, from the brighter to the fainter galaxies. Given that our results show no clear evidence that sources fainter than magnitude 20 degrade redshift measurements, we conservatively restrict our analysis to galaxies with magnitudes up to 24. In particular, we provide a preliminary estimate that contamination from galaxies within the same redshift range as the target sample contributes to about 4% of the total degradation due to cross-contamination from all galaxies.

astro-ph.CO↗
arXiv2026

The NIKA2 Cosmological Legacy Survey in COSMOS: Final 1.2mm and 2mm source catalogs and redshift distribution of dusty star-forming galaxies

We present the final 1.2mm and 2mm source catalogs and the redshift distribution of the mm-selected population from the NIKA2 Cosmological Legacy Survey (N2CLS) in the COSMOS field. Our aim is to provide a comprehensive dataset for studying the physical properties and evolution of high-redshift DSFGs. N2CLS covers ~1070 arcmin2 with median noise levels of 315$\mu$Jy and 91$\mu$Jy at 1.2 and 2mm, respectively. Sources are extracted with a S/N threshold of 3.9, ensuring >80% purity. Multi-wavelength counterparts are identified using high-resolution interferometric (sub-)mm data (NOEMA, ALMA) and radio observations (VLA, MeerKAT). Redshifts are compiled from spectroscopic and photometric catalogs (e.g., COSMOSWeb). The N2CLS master catalog includes 323 sources detected at >80% purity, with 104 sources detected in both bands, 197 only at 1.2mm, and 22 only at 2mm. Multi-wavelength identifications are secured for ~89% of the sample. The redshift distribution of 1.2mm sources peaks at 2.8$\pm$0.1, consistent with the epoch of peak cosmic star formation. In the total sample, we lack redshift for ~2% of the identified galaxies, plus 34 sources for which no accurate positional proxy is available, preventing the identification of a multi-wavelength counterpart. We identify 66 galaxies at z>4. The observed redshift distribution agrees well with the SIDES simulations, while four other galaxy evolution models are statistically inconsistent with the data. N2CLS is the largest contiguous deep survey to date with this depth and homogeneous coverage. This homogeneous coverage is important, as 25% of N2CLS sources lack a SCUBA2 850 mic counterpart, likely because the strongly non-uniform noise distribution of the SCUBA2 map results in lower sensitivity in parts of the field.The released data products provide a legacy dataset for studying dust-obscured galaxy evolution.

astro-ph.GA↗
arXiv2026

GASTON-GP: Source catalogue and millimetre variability of massive protostellar objects

The processes governing protostellar mass growth remain debated, although episodic accretion is now understood as a key feature of protostellar evolution across all masses. Luminosity bursts have been observed in both low- and high-mass protostars, but the overall statistics remain limited, especially for high-mass objects. Over the past decade, numerical simulations of high-mass core collapse have provided a theoretical framework for interpreting protostellar variability, yet additional observational constraints are required to determine the characteristics and importance of bursts. In this work, we analyse data from GASTON-GP programme, which mapped a 2.4 square degrees region of the Galactic plane (centred at l = 24 deg) at 1.15 and 2.00 mm using NIKA2 on the IRAM 30 m telescope. The survey obtained 11 epochs over four years, offering the first opportunity to study millimetre variability in a large sample of massive protostellar sources. From the combined dataset, we constructed catalogues of 2925 compact sources at 1.15 mm and 1713 at 2.00 mm. Using a dedicated relative calibration scheme, we generated millimetre light curves for around 200 high-signal-to-noise sources and identified one variable candidate. However, it is not protostellar. Consequently, we report no robust detections of variable protostellar sources in GASTON field. This is the direct consequence of observational limitations (i.e., sensitivity, resolution) combined with the lack of any 100-fold luminosity bursts during the observations, which is consistent with estimates inferred from isolated core collapse simulations. This study highlights the need for future high-resolution, high-cadence surveys to constrain the accretion histories of massive protostars.

astro-ph.GA↗
arXiv2026

Spatially-resolved interstellar dust properties in the face-on spiral galaxy M 99 as observed by NIKA2

Large dust grains in thermal equilibrium dominate the far-infrared and contribute to the millimetre continuum of star-forming galaxies, but constraining their properties is difficult due to free-free and synchrotron contamination. We study spatial variations in the dust spectral index, mass, and grain properties in the nearby face-on spiral galaxy M 99. We use new 1.15 and 2 mm continuum observations from NIKA2 on the IRAM 30 m telescope (IMEGIN Guaranteed Time Large Programme) combined with multiwavelength data from UV to radio. The infrared-to-radio SED is decomposed into dust, free-free, and synchrotron components using the hierarchical Bayesian code HerBIE. Dust is modelled via a modified blackbody (MBB) with variable millimetre spectral index beta and the THEMIS dust model with fixed beta. We perform spatially-resolved analysis at scales ~1.75 kpc (~25''), covering the centre, spiral arms, and inter-arm regions. MBB fits reveal beta variations from ~1.6-1.7 in diffuse regions to ~2.3-2.5 in dense star-forming areas, likely due to grain coagulation and changes in silicate-to-carbonaceous ratios. Dust masses from variable beta are up to ~4x higher than fixed-beta models, which systematically bias dust-to-stellar and dust-to-gas ratios. The small grain fraction rises from ~10% in the centre to ~15% in the diffuse disc, anti-correlated with the interstellar radiation field; gas-phase metallicity plays a minor role within 8 kpc. Synchrotron spectral index ranges from ~0.6-0.7 in star-forming regions to ~1.2 in the diffuse medium, consistent with cosmic-ray electron ageing.

astro-ph.GA↗
arXiv2026

Resolved ISM properties and scaling relations in the barred galaxy NGC 3627: constraints from NIKA2 observations

We investigate the interplay between star formation, interstellar medium (ISM) components, and dust properties in NGC 3627 using new NIKA2 1.15 and 2 mm observations from the IMEGIN Large Program. Our goal is to analyze dust and radio emission, decompose contributions in the millimeter-centimeter regime, and explore ISM properties within the galaxy. We perform spectral energy distribution fitting, at both global and spatial scales, using the THEMIS dust model within the HerBIE code, applied to data from 3.4 $\mu$m to 6 cm. We decompose emission into dust, free-free, and synchrotron components, and examine correlations with gas surface density and star formation activity. Additionally, we analyze the small dust grain fraction and its variation across the galaxy. We find $\sim$10% radio emission at 2 mm, peaking at 18% in the southern bar-end, which hosts the highest star formation activity. However, an isolated star-forming region beyond this bar-end is the most efficient, as indicated by its elevated dust production efficiency and effective yield, predicted by our simplistic dust evolution model. The 160 $\mu$m emission shows the strongest correlation with molecular gas, while 1.15 mm better traces the dust mass surface density. Small grains, which make up $\sim$13% of dust mass (2 $\times$ 10$^{7}$ M$_{\odot}$), are depleted in intense radiation fields, with a notable deficit in the southern tidal tail. ISM properties and chemical evolution indicate that dynamical processes, such as bar-driven gas flows and tidal interactions, are crucial in shaping the galactic structure, influencing star formation efficiency, and dust distribution.

astro-ph.GA↗
arXiv2026

Euclid: Improving redshift distribution reconstruction using a deep-to-wide transfer function

The Euclid mission seeks to understand the Universe expansion history and the nature of dark energy, which requires a very accurate estimate of redshift distribution. Achieving this accuracy relies on reference samples with spectroscopic redshifts, together with a procedure to match them to survey sources for which only photometric redshifts are available. One important source of systematic uncertainty is the mismatch in photometric properties between galaxies in the Euclid survey and the reference objects. We develop a method to degrade the photometry of objects with deep photometry to match the properties of any shallower survey in the multi-band photometric space, preserving all the correlations between the fluxes and their uncertainties. We compare our transfer method with more demanding image-based methods, such as Balrog from the Dark Energy Survey Collaboration. According to metrics, our method outperforms Balrog. We implement it in the redshift distribution reconstruction, based on the self-organising map approach of arXiv:1509.03318, and test it using a realistic sample from the Euclid Flagship Simulation. We find that the key ingredient is to ensure that the reference objects are distributed in the colour space the same way as the wide-survey objects, which can be efficiently achieved with our transfer method. In our best implementation, the mean redshift biases are consistently reduced across the tomographic bins, bringing a significant fraction of them within the Euclid accuracy requirements in all tomographic bins. Equally importantly, the tests allow us to pinpoint which step in the calibration pipeline has the strongest impact on achieving the required accuracy. Our approach also reproduces the overall redshift distributions, which are crucial for applications such as angular clustering.

astro-ph.CO↗
arXiv2025

NIKA2 Cosmological Legacy Survey. First measurement of the confusion noise at the IRAM 30 m telescope

The NIKA2 Cosmological Legacy Survey (N2CLS) is a large programme using the NIKA2 dual-band camera on the IRAM 30\,m telescope. Its goal is to improve our understanding of the physics of distant Dusty Star Forming Galaxies (DSFGs) by carrying out deep surveys of two fields, GOODS-North and COSMOS. This work is focussed on GOODS-North, which was observed for 78.2 hours, simultaneously at 1.2 and 2\,mm, with a field of view of $\sim$240\,arcmin$^2$. With such a deep integration, we were able to measure, for the first time, the confusion noise limits at the 30\,m telescope using the best sampled $\sim 62$\,arcmin$^2$ and masking sources with a flux greater than 0.54 or 0.17\,mJy at 1.2 or 2\,mm, respectively. We found a confusion noise of $139.1^{+ 15.9}_{- 19.2}\pm11.9$\,$\mu$Jy/beam at 1.2\,mm and $38.6^{+ 9.6}_{- 13.1} \pm3.7$\,$\mu$Jy/beam at 2\,mm (the first uncertainty is statistical, the second is the cosmic variance). In this region, this corresponds to half the instrumental noise. To derive these estimates, we devised a novel estimator, referred to as the cross variance, which also enabled us to estimate the correlated confusion noise between the two bands. Thus, we obtained a result of $49.6^{+ 15.9}_{- 24.8}\pm 6.4$\,$\mu$Jy/beam. These values are consistent with the state of the art Simulated Infrared Dusty Extragalactic Sky (SIDES) model.

astro-ph.GA↗
arXiv2025

Euclid: The first statistical census of dusty and massive objects in the ERO/Perseus field

Our comprehension of the history of star formation at $z>3$ relies on rest-frame UV observations, yet this selection misses the most dusty and massive sources, yielding an incomplete census at early times. Infrared facilities such as Spitzer and the James Webb Space Telescope have revealed a hidden population at $z=3$-$6$ with extreme red colours, named HIEROs (HST-to-IRAC extremely red objects), identified by the criterion $H_{\mathrm{E}}-\mathrm{ch2}>2.25$. Recently, Euclid Early Release Observations (ERO) have made it possible to further study such objects by comparing Euclid data with ancillary Spitzer/IRAC imaging. We investigate a $232$ arcmin$^2$ area in the Perseus field using VIS and NISP photometry, complemented by the four Spitzer channels and ground-based MegaCam bands ($u$, $g$, $r$, ${\rm H}\alpha$, $i$, $z$). Applying the colour cut yields $121$ HIEROs; after removing globular clusters, brown dwarfs, and unreliable cases through visual inspection of multiband cutouts, we obtain a final sample of $42$ robust HIEROs. Photometric redshifts and physical properties are estimated with the SED-fitting code Bagpipes. From the resulting $z_{\mathrm{phot}}$ and $M_*$ values, we compute the galaxy stellar mass function at $3.5<z<5.5$. Even after excluding possible AGN hosts or systems where the stellar mass may be overestimated, the high-mass end remains comparable to previous determinations, suggesting the true abundance could be higher. These results highlight the importance of further study of this obscured population to assess its role in the cosmic star-formation rate density and its consistency with galaxy-formation models, demonstrating Euclid's capability to advance our understanding of dust-hidden star formation across early epochs.

astro-ph.GA↗
arXiv2025

Cosmology Likelihood for Observables in \Euclid (CLOE). 1. Theoretical recipe

As the statistical precision of cosmological measurements increases, the accuracy of the theoretical description of these measurements needs to increase correspondingly in order to infer the underlying cosmology that governs the Universe. To this end, we have created the Cosmology Likelihood for Observables in Euclid (CLOE), which is a novel cosmological parameter inference pipeline developed within the Euclid Consortium to translate measurements and covariances into cosmological parameter constraints. In this first in a series of six papers, we describe the theoretical recipe of this code for the Euclid primary probes. These probes are composed of the photometric 3x2pt observables of cosmic shear, galaxy-galaxy lensing, and galaxy clustering, along with spectroscopic galaxy clustering. We provide this description in both Fourier and configuration space for standard and extended summary statistics, including the wide range of systematic uncertainties that affect them. This includes systematic uncertainties such as intrinsic galaxy alignments, baryonic feedback, photometric and spectroscopic redshift uncertainties, shear calibration uncertainties, sample impurities, photometric and spectroscopic galaxy biases, as well as magnification bias. The theoretical descriptions are further able to accommodate both Gaussian and non-Gaussian likelihoods and extended cosmologies with non-zero curvature, massive neutrinos, evolving dark energy, and simple forms of modified gravity. These theoretical descriptions that underpin CLOE will form a crucial component in revealing the true nature of the Universe with next-generation cosmological surveys such as Euclid.

astro-ph.CO↗
arXiv2025

Thermal Sunyaev-Zel'dovich effect at the core of CL J1226.9+3332 revealed by NOEMA

We present first detailed maps of the thermal Sunyaev-Zel'dovich (tSZ) effect on a $z = 0.89$ cluster with the NOrthern Extended Millimeter Array (NOEMA). The high sensitivity of these observations enabled the effective identification and removal of the millimetre-wave sources contaminating the tSZ signal, thus isolating the influence of the hot electron gas of the cluster on the cosmic microwave background radiation from other emissions. The tSZ observed with success by NOEMA was modelled together with previous single-dish observations (IRAM 30-metre, Green Bank Telescope, and Caltech Sub-millimeter Observatory) to obtain the first core-to-outskirts (from $\sim$ 15 to $\sim$ 1500 kpc) pressure profile reconstruction on such a high-redshift galaxy cluster. NOEMA observations with a high angular resolution have shown that the pressure profile is flat in the core of the cluster. These observations confirm the disturbed nature of CL J1226.9+3332 and map for the first time the distribution of its thermal gas at arcsecond scales in the environments of the central cluster galaxy. Our results showcase the excellent capabilities of NOEMA to complement and enhance the data provided by other millimetre-wave instruments in resolving the core of high-redshift clusters via tSZ emission.

astro-ph.CO↗
arXiv2025

The NIKA2 cosmological legacy survey at 2 mm: catalogs, colors, redshift distributions, and implications for deep surveys

Millimeter galaxy surveys are particularly effective in detecting dusty star-forming galaxies at high redshift. While such observations are typically conducted at ~1mm, some studies suggest that 2mm may be better suited for selecting sources at even higher redshifts. We use the unprecedented 2mm data from the N2CLS, together with the SIDES simulation, to study and interpret the statistical properties of 2mm-selected galaxies. We use the N2CLS robust sample at 2mm, which contains 25 sources in the deep GOODS-N field and 90 sources in the wide COSMOS. The sources are matched with the N2CLS 1.2mm sources, the ancillary 850um sources, and redshift catalogs to study the colors and redshift distributions. We also produce end-to-end simulations based on SIDES and the observed N2CLS detector timelines to interpret the data. We find a mean S2/S1.2 color of 0.222$\pm$0.008 with a standard deviation of 0.070$\pm$0.010. We measure a mean redshift of $3.6\pm0.3$ in GOODS-N, which is marginally higher than expectations from SIDES ($2.9\pm0.2$) because of an overdensity at $z\sim5.2$, and $3.2\pm0.2$ in COSMOS, which agrees with the $3.2\pm0.2$ predicted by SIDES. We also show that the observed S2/S1.2 colors exhibit a weak dependence with redshift but a large dispersion, which limits its efficiency to select high-z sources. Finally, we studied the nine 2mm sources not detected at 1.2mm, and found that two of them are radiogalaxies, one is a z~2 galaxy, and the remaining six are compatible with the expected number of spurious detections. The N2CLS survey shows no evidence for any exotic 2mm-only galaxy population. Using SIDES, we show that 2mm samples have a higher mean redshift compared to 1.2mm because they miss z~2 dusty galaxies. Finally, we discuss the efficiency of single-dish and interferometric blind surveys to build samples of high-z dusty galaxies.

astro-ph.GA↗
arXiv2025

NIKA2 Cosmological Legacy Survey: Blind detection of galaxy clusters in the COSMOS field via the Sunyaev-Zel'dovich effect

(Abridged) Clusters of galaxies, formed in the latest stages of structure formation, are unique cosmological probes. With the advent of large CMB surveys like those from the Planck satellite, the ACT and SPT telescopes, we now have access to a large number of galaxy clusters detected at millimeter wavelengths via the thermal Sunyaev-Zel'dovich (tSZ) effect. Nevertheless, it is interesting to complement them with high-angular-resolution (tens of arcseconds) observations to target the lowest-mass and highest-redshift clusters. This is the case of observations with the NIKA2 camera, which is installed on the IRAM 30--m telescope in Pico Veleta, Spain. We used the existing 150 GHz (2 mm) data from the NIKA2 Cosmological Legacy Survey (N2CLS) Large Program to blindly search for galaxy clusters in the well-known COSMOS field, across a 877 arcmin$^2$ region centered on (R.A., Dec.)$_{J2000}$ = (10h00m28.81s, +02d17m30.44s). We first developed a dedicated data reduction pipeline to construct NIKA2 maps at 2 mm. We then used a matched-filter algorithm to extract cluster candidates assuming a universal pressure profile to model the expected cluster tSZ signal. We computed the purity and completeness of the sample by applying the previous algorithm to simulated maps of the sky signal in the COSMOS field. We find a total of 16 cluster candidates at S/N > 4, from which eight have either an optical or X-ray cluster (or group of galaxies) counterpart. This is the first blind detection of clusters of galaxies at mm wavelengths at 18" angular resolution. From this analysis, we confirm that NIKA2 and the IRAM 30--m telescope should be sensitive to low-mass clusters at intermediate and high redshift, complementing current and planned large tSZ-based cluster surveys.

astro-ph.CO↗
arXiv2025

Overdense fireworks in GOODS-N: Unveiling a record number of massive dusty star forming galaxies at z$\sim$5.2 with the N2CLS

As part of the N2CLS Survey, we have identified a remarkable overdensity of eight bright dusty star-forming galaxies at z$\sim$5.2 in the GOODS-N field. Three of these galaxies, N2GN_1_01, 06, and 23 (known as GN10, HDF850.1, and S3, respectively), had previously been spectroscopically confirmed as members of the exceptional large-scale structure at z$\sim$5.1-5.3, which is notably elongated along the line of sight, spanning 30 cMpc. We present the spectroscopic confirmation of N2GN_1_13 at z$_{\rm spec}$=5.182, a massive dusty star-forming galaxy identified through targeted NOEMA observations, and N2GN_1_61 at z$_{\rm spec}$=5.201, revealed using JWST/FRESCO data. In addition to these five spectroscopically confirmed members, we identify three further candidates with photometric redshifts consistent with the overdense structure. These galaxies are massive (with a median stellar mass of 9x 10$^{10}$ M$_{\odot}$) and highly obscured (with a median A$_V$ of 3.3), caught in a short-lived yet extreme starburst phase at z$\sim$5.2. Their high SFRs (with a median of 590 M$_{\odot}$ yr$^{-1}$), efficient baryon to stellar mass conversion ($\epsilon_{\star}>$20%), substantial gas reservoir and dust content, suggest rapid evolution and imminent quenching. Six of these galaxies reside in overdense filaments; the remaining two may trace new distinct structures which will have to be spectroscopically confirmed. These few dusty galaxies dominate the star formation within the overdensity, contributing more than the numerous H$_{\alpha}$ emitters, and surpassing the cosmic average star formation rate density for this epoch. Their properties suggest an accelerated evolution that current models and simulations have difficulty reproducing.

astro-ph.GA↗
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↗
arXiv2025

Continuum, CO and Water vapour maps of the Orion Nebula. First millimetre spectral imaging with Concerto

The millimetre spectrum of Galactic regions and galaxies is rich in continuum and molecular lines. This diversity is mostly explored using either broad-band photometry or high-resolution heterodyne spectroscopy. We aim to map the millimetre continuum emission of Galactic regions with an intermediate spectral resolution between broad-band photometry and heterodyne spectroscopy, enabling us to rapidly cover large sky areas with spectroscopy. We report observations of the Orion Nebula with the CONCERTO instrument, which was installed at the APEX telescope focal plane from 2021 to 2023. We find that the spectrum of Orion is dominated by dust emission with an emissivity index ranging between 1.3 and 2.0, along with strong CO(2-1) and H$_2$O lines, which are naturally separated from the continuum due to the CONCERTO spectral capabilities. Many regions also show strong free-free emission at lower frequencies. We demonstrate the spectral capabilities of CONCERTO at intermediate spectral resolution, with a frequency coverage from 130 to 310 GHz. A sensitivity of 200 mK is achieved in one second, for one beam and a 6 GHz frequency width, over an 18 arcmin diameter field of view, which is within a factor of three of the expectations. We show that we can spectrally disentangle the continuum from the CO line emission, but the line is not resolved at a resolution of $\sim 8000\ \mathrm{km s^{-1}}$. The slope of the millimetre continuum is line-free mapped for the first time in Orion.

astro-ph.GA↗