Low surface brightness (LSB) astronomy, and in particular the study of intracluster light (ICL) has been historically held back by instrumental and observational challenges. Thanks to the Elixir-LSB pipeline developed by JC Cuillandre at CEA, the LSB component of the Canada France Imaging Survey (CFIS) is providing an unprecedented amount of premium quality images in the r band with reduced LSB contamination over more than 5000 square degrees in the sky. This is a great occasion to develop novel analysis methods to support and exploit this large survey.  The Detection Algorithm with Wavelets for Intracluster light Studies (DAWIS), developed at IAP to detect and model LSB sources, and parallelized for efficiency, is in the vein of such advances. DAWIS follows a multiresolution vision based on wavelet representation to detect sources, embedded in an iterative synthesis-by-analysis procedure to restore the complete unmasked light distribution of these sources with very good quality. The algorithm is built so sources can be classified based on criteria depending on the analysis goals (see Ellien et al., 2021 for more details). DAWIS is currently being applied to the case of ICL detection in CFIS-LSB. A first test sample of 17 galaxy clusters are being processed to adapt and calibrate the algorithm to the data, including the development of additional features to correctly model foreground unsaturated Milky Way stars, and the automated classification of the ICL

In the Galactic anticentre direction, the rotational velocity (V φ ) is similar to the tangential velocity in the galactic longitude direction (Vl). This allows us to estimate V φ from Gaia early data-release 3 (Gaia EDR3) proper motions for stars without radial velocity measurements, substantially increasing the sample of stars in the outer disk with estimated rotation velocities. The combination of the accurate Gaia EDR3 proper motions with the metallicity estimates inferred from the Pristine survey photometry towards the anticentre allowed us to explore the stellar kinematical distribution of the outer disk over a broad range of metallicities. Our stellar sample towards the anticentre is dominated by a kinematical thin disc with a mean rotation of ∼ −220 km s −1 . However, our analysis reveals the presence of more stellar substructures. The most intriguing is a well populated extension of the kinematical thin disc to down to [Fe/H] ∼ −2 dex, with a scarser extension reaching the extremely metal-poor regime, down to [Fe/H] ∼ −3.5 dex. In addition, a more slowly rotating kinematical thick disc component is also required to explain the observed Vl distribution at [Fe/H] > −1.4 dex. Furthermore, we detect signatures of a “heated disc”, the so-called Splash, at metallicities higher than ∼ −1.4. Finally, at [Fe/H] < −1.4 dex our anticentre sample is dominated by a kinematical halo with a net prograde motion.

Globular clusters (GCs) form an integral part of all types of galaxies. At larger distances where the stellar components are impossible to resolve, these GC systems are one of the possible ways to study the formation history of a galaxy and its surroundings. With the help of wide-field surveys, it has become possible to study these systems for entire galaxy clusters. Such broad coverage allows us to study not only the properties of the galaxy individually but also the surroundings and the system as a whole.

In this work, we use the multi-band photometric data observed as a part of the Next Generation Virgo Cluster Survey (NGVS) and NGVS in infrared (NGVS-IR) that spans the spectral range from near-UV to near-IR. We exploit the exceptional diagnosis power of a combination of UV, optical and near-IR data to identify the GCs in the field around the massive early-type galaxy, M49, and the intra-cluster region between the M49 and M87. We use the wide range of available colors of the GCs in the study and highlight the dependence of their colors on their environment.

Future space-based sky surveys such as those now being prepared within the Euclid consortium can implement GC detection strategies similar to those employed here; they will allow us to detect GCs and measure their properties over large fractions of the sky, opening the door to a variety of new science cases.

This project was funded in part by Project POPSYCLE, ANR-19-CE31-0022, Agence Nationale. de la Recherche, France

Thanks to Euclid's excellent optical resolution and its high sensitivity in the near-IR,  a Legacy product of its Wide survey will be an unprecedented census of globular clusters in the local universe, over a large fraction of the sky and with uniform photometric measurements. On behalf of the working group that is preparing their identification and study, I will present a summary of science cases that can be addressed with such a sample, in various distance intervals. This work is financed in part by Project ANR-19-CE31-0022, Agence Nationale de la Recherche, France.

I will kickstart the conference!

Status of the Euclid Mission in June 2021.

The Diffuse Galactic Light (DGL) is observed in the UV-optical-NIR, even in the darkest regions of the sky. It results from starlight that scatters on dust grains, lighting up interstellar clouds. This is a well known effect close to bright stars (c.f. reflection nebula) but it is also observed far away from bright sources, even in the diffuse interstellar medium that is shined-on by the global interstellar radiation field. Diffuse Galactic light is now observed routinely, with telescope dedicated to low-surface brightness observations (e.g. DRAGONFLY), with specific camera on large telescope (e.g. Megacam on CFHT), and even by amateur astronomers.

There is now an increase of interest for the DGL for several reasons. First, it provides a new way to image the structure of the interstellar medium with the greatest details over large areas. Secondly, the DGL brings new informations on the properties of interstellar dust grains, and how they evolve on their journey towards star and planet formation. Finally, the DGL is considered as a potential contamination for cosmological experiments observing in the optical, like Euclid or Vera C. Rubin. For such experiments that aim at measuring the shape of galaxies with high precision, the very anisotropic and filamentary DGL needs to be either avoided or subtracted from the observations. The intervening interstellar medium will not only contaminate the extra-galactic emission, it will also absorb and reddened it. Therefore the wavelength dependence of the extinction (the sum of absorption and scattering), and its variations across the sky, must be known to some degree of precision in order to achieve the cosmological goals of these missions. Currently, the knowledge on interstellar dust is not at par with the task.

In this talk I will present new observations of interstellar dust in the visible / near-infrared range recently obtained with Megacam on the Canada-France-Hawai Telescope. These images reveal the spectacular structure of the interstellar medium with very fine details, over large areas, something that used to be possible only with space telescopes. I will expose how this new way to image the ISM structure provides invaluable informations on the physical processes that shape interstellar matter. I will also present what is known about the albedo curve of in the diffuse interstellar dust, where the extra-galactic studies will be conducted, and the level of variations of this curve that should be expected. This is a fundamental information in order to be able to mitigate the effect of this foreground emission over the largest area. It is also a crucial information for interstellar dust physics in order to evaluate how and where dust grains coagulate and fragment, on their way to larger solid bodies. The LSB observations already available, and the ones to come, will provide the information to study these effects with great details. In that regard, I will advocate for a mutualistic relationship between ISM and LSB experts, like rhinos and oxpeckers.

Cosmic star formation history shows an exponential decline since z~2 i.e. over the last 10 Gyrs (Madau & Dickinson 2014). By combining CFHT deep U band imaging (CLAUDS, U_AB~27) with the HSC-SSP deep survey observed at Subaru (r_AB~27mag), over ~20 deg²  area, the HSC-CLAUDS deep survey aims to better constrain the galaxy evolution during this epoch.

In this talk I will describe the data reduction pipeline and the construction of the multi-band catalog and I will compare its performance with the official HSC pipeline. Of particular interest, I will focus on the 5.5 deg² where UV and Near-IR observations are available. In these regions, we derive reliable photometric redshifts (z/(1+z)~0.016 for i_AB<23.5) and physical parameters with LePhare code up to z~2.

In order to assess the energy balance between the un-obscured and obscured star formation activity, we estimate the infrared excess (IRX=Lir/Luv) as a function of optical rest-frame colors ( (NUV-r) vs (r-K) ) in the COSMOS field where deep Far-IR observations are available (Spitzer+Herschel) and extend the calibration to low mass star-forming galaxies (M_*~10^8.5M_o) with Far-IR stacking techniques.

Then I apply this calibration to ~0.5 Million SF galaxies from the HSC-CLAUDS survey in order to measure the SFR functions and SFR density up to z~2. This result helps constraining the different regulators of star formation activity in the different stellar mass regime over this crucial epoch.

The Gaia astrometric space mission with all sky parallax measurements for about 1.5 billion objects offers the means to complete volume-limited samples with large distance limits. The Gaia Catalogue of Nearby Stars is a clean and well-characterized catalogue of objects within 100 pc of the Sun produced from the Gaia Early Data Release 3 (Gaia EDR3). It has 331 312 entries that is an increase by an order of magnitude with respect to the most complete nearby star census prior to the Gaia mission. Its completeness is at least 92% for stars of stellar type M9. We will show how the catalogue was constructed and why it was not possible before Gaia EDR3. We will present some scientific results drawn from the catalogue, such as the luminosity function with a high signal-to-noise ratio for the main-sequence stars, giants, and white dwarfs, and local manifestations of several streams, superclusters, and halo objects.

Several on-going projects making use of deep optical images obtained with telescopes and cameras of various sizes aim at identifying around nearby massive galaxies the low surface brightness (LSB) collisional debris, predicted by numerical simulations, which are believed to keep the memory of  their past mass assembly. However identifying these diffuse structures and even more characterizing them remain challenging. Carrying  out this last task is all the more important because the various types of tidal features - tails, streams, plumes, shells, bridges, etc. - trace different types of mergers - major, minor, with an early or late type progenitor. Furthermore,  because they have different survival times, they are able to give time constrains on the merger history.  So far most studies, especially those based on the automatic detection of tidal perturbations,  do not disentangle between the different types of  debris. We will present here a tool that allow us to easily make online annotations and classifications of LSB structures including artefacts and foreground light, and  feed a database which is then exploited to precisely characterize their shape, size and surface brightness. We will present the application of this tool to several deep imaging surveys made with the MegaCam camera at CFHT.  Statistics based on the  exploration of the outskirt of about 400 massive early and late galaxies will be discussed.