The issue of preservation and improvement of the Gaia catalogue throughout the next few decades is addressed. The goal of this study is to evaluate the feasibility of astrometric parameter update, for objects already in the catalogue, by inclusion of new observations from other space missions, in particular CSST. The proposed approach consists in modeling the astrometric fit of sources in the extragalactic region of the Gaia sample with new observations, using the stars in the local field as reference for each target. The concept is verified by simulation, in the framework of the expectations on the Gaia astrometric performance and on the data from the forthcoming CSST Optical Survey. This approach can mitigate the natural degradation of the initial precision on coordinates of Gaia sources with time by improving proper motions by a factor > 3 , thus improving the positional precision in future epochs. Moreover, the catalogue is densified by the inclusion of objects below the Gaia limiting magnitude, improving on the galactic population census and on extragalactic population. CSST-OS data will reduce the Gaia precision degradation on positions by a factor of 2.7 over 30 years and increase the number of available reference sources over 40% of the sky. Future observations from other missions may further improve on the Gaia catalogue by extending the sky coverage and temporal baseline.

/pdf/consolidation-of-the-gaia-catalogue-with-chinese-space-1x6dbo62.pdf

Consolidation of the Gaia catalogue with Chinese Space Station Telescope astrometry

Euclid is a European Space Agency (ESA) mission designed to constrain the properties of dark energy and gravity via weak gravitational lensing and galaxy clustering. It will carry out a wide area imaging and spectroscopy survey in visible and near-infrared bands, covering approximately 15 000 deg 2 of the extragalactic sky in six years. Euclid will be equipped with a 1.2 m diameter Silicon Carbide (SiC) mirror telescope feeding two instruments built by the Euclid Consortium: a high-quality panoramic visible imager and a near-infrared photometer and spectrograph. These proceedings brieﬂy describe the satellite and its instruments, which are optimised for pristine point spread function and reduced stray light, producing very crisp images. Furthermore, we summarise the survey strategy, the global scheduling, and the preparations for the satellite commissioning and the Science

Euclid in a nutshell

Abstract In the past, high- z active galactic nuclei (AGNs) were given a minor role as possible drivers of reionization, despite initial evidence in favor of their large space densities at low luminosities by Chandra and the Hubble Space Telescope. Recent observations from JWST are finding relatively large numbers of faint AGNs at z &gt; 4, convincingly confirming these early results. We present a sample of z ∼ 5 AGNs, both from wide, shallow ground-based surveys and from deep, pencil-beam observations from JWST, allowing us to estimate their space densities with unprecedented accuracy. The bright end ( M 1450 &lt; −26) of the z ∼ 5 AGN luminosity function is well constrained, with a rather steep slope. The faint end ( M 1450 ≥ −22) indicates a high space density, the scatter is significant, and the knee ( M 1450 ∼ −24) is mostly undetermined. Comparisons with state-of-the-art models find reasonable agreement with the observed AGN luminosity function at z = 5, while the predicted space density evolution at higher redshifts appears to be too fast with respect to observational constraints. Given the large variance at the faint end, we consider different options in fitting the luminosity functions and deriving the ionizing emissivity. Even in the most conservative scenario, the photoionization rate produced by z ∼ 5 AGNs is consistent with the ultraviolet background measurements. A slow evolution of the space density of faint AGNs is observed, indicating that active SMBHs are probably producing large amounts of ionizing photons at z &gt; 6, well into the Epoch of Reionization. This is an important indication that high- z AGNs could be major contributors to the reionization of the Universe. 

What Are the Pillars of Reionization? Revising the AGN Luminosity Function at z ∼ 5

While the cosmic microwave background (CMB) dipole is largely assumed entirely kinematic, there appears evidence that a part of it is primordial. Such possibility arises in models implying a tilt, interpreted as a dark ﬂow, across the observable Universe. The kinematic nature of the entire CMB dipole can be probed using the dipole of cosmic backgrounds from galaxies after the last scattering. The near-IR cosmic infrared background (CIB) spectral energy distribution leads to an ampliﬁed dipole compared to the CMB. The CIB dipole is aﬀected by galaxy clustering, decreasing with fainter, more distant galaxies, and by Solar System emissions and Galactic dust, which dominate the net CIB cosmological dipole in the optical/near-IR. We propose a technique that enables an accurate measurement of the kinematic near-IR CIB dipole. The CIB, eﬀectively the integrated galaxy light (IGL), would be reconstructed from resolved galaxies in the forthcoming space-borne wide surveys covering four bands 0.9 to 2.5 𝜇 m. The galaxies will be sub-selected from the identiﬁed magnitude range where the dipole component from galaxy clustering is below the expected kinematic dipole. Using this technique the dipole can be measured in each of the bands at the statistical signal-to-noise 𝑆 / 𝑁 > ∼ 50–100 with the forthcoming Euclid and Roman surveys, isolating CMB dipole’s kinematic nature.

/pdf/probing-the-rest-frame-of-the-universe-with-near-ir-cosmic-s7wpwwpn.pdf

Probing the rest-frame of the Universe with near-IR cosmic infrared background

Euclid, an ESA mission designed to characterise dark energy and dark matter, passed its Mission Critical Design Review in November 2018. It was demonstrated that the project is ready to start integration and test of the main systems, and that it has the ability to fulfil its top-level mission requirements. In addition, based on the performances at M-CDR, the scientific community has verified that the science requirements can be achieved for the Weak Lensing and Galaxy Clustering dark energy probes, namely a dark energy Figure of Merit of 400 and a 2% accuracy in the growth factor exponent gamma. We present the status of the main elements of the Euclid mission in the light of the demanding high optical performance which is the essential design driver is the to meet the scientific requirements. We include the space segment comprising of a service module and payload module hosting the telescope and its two scientific instruments, and the ground segment, which encompasses the operational and science ground segment. The elements for the scientific success of the mission for a timely release of the data are shortly presented: the processing and calibration of the data, and the design of the sky survey. Euclid is presently on schedule for a launch in September 2022.

/pdf/euclid-mission-status-after-mission-critical-design-3uyw5a5min.pdf

Euclid mission status after mission critical design

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Euclid mission status after mission critical design