CEA/DAp seminar organization

Besides the classic heralds of astronomy, from radio waves to X-rays, the past two decades have seen the emergence of four fantastic messengers: astroparticles. Gravitational waves, GeV-TeV gamma rays, PeV neutrinos, and cosmic rays at EeV energies and above are all now, since 2015, informants on the conditions prevailing in the most extreme accelerators that our universe houses. In this talk, I will illustrate the first steps of multi-messenger astronomy with gamma-ray and cosmic-ray signals that have traveled to our ground-based detectors from cosmic scales, ranging from the innards of our super-cluster, Laniakea, to a time when the universe was only a fifth of its current age, beyond z ~ 2. Astroparticles from the most extreme extragalactic emitters not only enable the probe of particle acceleration at energies beyond the reach of human-made facilities, but can also be exploited as tracers of the electromagnetic content of the universe. Magnetic and photon fields populating the largest voids in the cosmos are starting to reveal their mysteries, setting the grounds for the newborn field of gamma-ray cosmology and long-awaited cosmic-ray astronomy. Major astroparticle observatories are under upgrade or construction and they hold a formidable scientific potential for current and next-generation researchers.

Jet-driven core-collapse supernovae belong to the most energetic transients in the universe and are key targets for time-domain astronomy surveys. I will discuss the unique challenges in both input physics and computational modeling for these systems involving all four fundamental forces and highlight recent breakthroughs in full 3D simulations. I will pay particular attention to how these simulations can be used to reveal the engines driving these events and conclude by discussing what remains to be done in order to maximize what we can learn from current and future time-domain transient surveys.

SPHERE is the new generation exoplanet imagers installed at the Very Large Telescope. Since 2015, we have started the large-scale SHINE survey to look for giant exoplanets around a sample of 400 to 600 young, nearby stars (younger than 300 Myr, closer than 150 pc). The main goal of SHINE is to constrain for the first time the population of giant exoplanets in the 5-100 AU range, where previous direct imaging surveys and other detection methods are not sensitive. After describing the SPHERE instrument and the astrophysical context, I will present the current status of SHINE, some of its recent discoveries and the first statistical constraints drawn after 4 years from a sub-sample of 200 observed targets. Finally, I will conclude with instrumental considerations by presenting some evolutions foreseen for the instrument over the next few years.

After a short introduction on ultra-high-energy cosmic-ray (UHECR) physics, I will discuss the implications of the recent Fermi-LAT data regarding the extragalactic gamma-ray background, as well as IceCube very-high energy neutrino data, for the origin of UHECRs.I will show how calculations of the diffuse flux of cosmogenic γ-rays and neutrinos, produced during the propagation of UHECRs in the extragalactic medium, can provide constraints on the possible cosmological evolutions of UHECR sources. I will present in more details the mixed-composition scenario considered in several papers by Globus et al. (which is in agreement with most UHECR data) and show that this model is compatible with both the Fermi-LAT measurements and the current IceCube limits. I will finally discuss the possibility for future experiments to detect cosmogenic neutrinos and further constrain UHECR models, including possible subdominant UHECR proton sources.

Both in the present-day Universe and earlier on, approximately z~3, we have documented profound structural differences between star-forming and quiescent galaxies. The former host their star formation in rotating disks (thinner and colder today, apparently thicker and hotter at high redshifts), the latter are predominantly dynamically hot systems and have spheroidal morphology, At high redshift (z>1) and up to when quiescent systems can be reliably identified (z~3-4), dynamical information becomes more uncertain, at least in passive systems, but this dichotomy seems to persist at least morphologically. Therecent discovery that disks at high redshift (22) have mostly focused on the growth of the core stellar mass density, e.g. at r<1 kpc. These very central volumes are the sink of all the dissipative processes that take place during star formation and while they inform us, in an integral way, on the accretion history of the galaxy of both the dissipative (gas, via cold and hot accretion) and non-dissipative (stars and dark matter, via adiabatic contractions) components, they are baryon-dominated even in today disks and do not contain information on if and how the large-scale structure of galaxies evolves, dark matter included. Here I show novel evidence that the large-scale spatial distribution of stellar mass (from rest-frame light at ~4000 to 6400 Ang), i.e. of one of the two non-dissipative components, of massive galaxies at 1.5

Local contact: E. Daddi, organization: M. Galametz

Comets are icy bodies remnants of the earliest moments of the solar system formation and that are now studied in details by space missions. The most recent spacecraft, Rosetta, has ended its studies in September 2016 after having landed Philae for the first time on the surface of a cometary nucleus and followed 67P on its orbit for more than two Earth years. The on-board scientific instruments have demonstrated the sporadic behavior of the cometary activity as a function of its orbital properties. Cameras have unveiled an irregular surface prone to erosion and deposition of dust, with few spots of ice detected on its surface. Dust particles detectors have shown that two types of solid particles are ejected by the nucleus, one being dense and compact grains and the other being very fluffy irregular dust particles. No specific structures inside the cometary nucleus were detected by instruments sounding inside the nucleus, and the very low density of the cometary material (0.5 g.cm-3) remains difficult to explain. Gaseous particles ejected by the comet contain a high fraction of O2 and complex carbonaceous molecules like glycine, an amino acid that was first detected in situ by Rosetta. We will review the results from the whole Rosetta/Philae mission and describe in details what we have learned about these objects.

Cosmic dust absorbs the optical/UV photons produced by stars and SMBH and re-emits the energy at longer wavelengths in the IR regime. Infrared observations are, therefore, crucial to achieving a complete picture of the star-formation density (SFRD) , and to understanding the properties of dust across cosmic time. Thanks to the latest IR Herschel satellite (2009-2013), a comprehension of the SFRD was estimated up to z~3-4, but recent observations in the sub-mm regime (SCUBA-2) show discrerpancies with previous Herschel results. I will discuss the possible reasons for this discrepancy and show the critical role that the IR SPICA will play in the future .

Space weather is extremely demanding in term of space data for solar, magnetospheric or ionospheric survey. Small satellites are interesting in the sense they are easier to build, cheaper and then accessible to new entities like countries without space history, SMEs and universities. Due to their lowest costs, they also can be launched in constellation for better spatial or temporal coverage. As a complex science dealing with a chain of phenomenon coming from the sun to the Earth through the magnetosphere, space weather can benefits from the multiplication of satellites. After an introduction based on the potentialities and constraints of cubesats, we will focus on two example, AMICal Sat and ATISE developed at the CSUG in Grenoble. We will then extend these example to explain why space weather is a priority application of the cubesats and give a large overview of the project in development.

The Maunakea Spectroscopic Explorer (MSE, formerly Next Generation CFHT) is an advanced project to profoundly transform the current CFHT into a survey telescope with a 10-meter mirror and a dedicated, heavily multiplexed, wide-field spectrograph with a wavelength coverage of 0.4-1.8 micron and multiple spectral resolutions. MSE is borne out as the response to the astronomical community's need for a large aperture, dedicated, spectroscopic survey facility in synergy with imaging surveys (LSST, WFIRST, ...) and giant telescopes (GMT, ELT, TMT). The project is now entering preliminary design phase after successfully completing its conceptual design. We will present the current architecture of the observatory as well as the expected performance characteristics of the project and describe the science that is driving this unique facility: unveiling the properties of the faint universe, whether they relate to the origin and diversity of stellar systems, Milky Way archaeology at the earliest time, galaxy evolution across cosmos times, or illuminating the dark universe. Finally, we will conclude with an overview of the project's partnership and organization.

Cold gas plays a central role in feeding and regulating star formation and growth of supermassive black holes (SMBH) in galaxy nuclei. Particularly powerful activity occurs when interactions of gas-rich galaxies funnel large amounts of gas and dust into nuclei of luminous and ultra luminous infrared galaxies (LIRGs/ULIRGs). These dusty objects are of key importance to galaxy mass assembly over cosmic time. It is also increasingly clear that feedback from star formation and AGNs is fundamental to regulating the evolution of galaxies in the nearby Universe as well as at earlier epochs. Mechanical feedback occurs in the form of winds, turbulence, supernova bubbles and superbubbles, AGN jets and backflows. There is mounting evidence that massive amount of cold molecular gas is being expelled from galaxy nuclei and starburst regions by the feedback process. With the advent of ALMA and the NOEMA telescopes we can now study the structure, physical conditions and chemistry of the cold flows and the dusty nuclei at unprecedented sensitivity and resolution. I will focus on recent ALMA and NOEMA studies of AGN and starburst outflows from dusty galaxies. I will, for example, present recent ALMA studies with resolutions of 20 milli arcseconds (2 – 7 pc) of the launch regions of molecular outflows and jets in the nearby LIRGs NGC1377 and IC860. These outflows are different from each-other where NGC1377 shows a 150 pc scale radio-quiet molecular jet (that appears to be precessing) while the IC860 flow is exceedingly compact and dense and appears to be in a young phase. I will also discuss observational methods that reach behind the curtain of dust in the most obscured centers of U/LIRGs , allowing us to undertake new studies of heretofore hidden, rapid evolutionary phases of galaxy nuclei.

Let's assume dark matter is a particle. The DM theories currently tested, either with direct or indirect detection, cover only a tiny range of the allowed DM parameters space. A new, viable, DM candidate, the Axion Quark Nugget (AQN), has been proposed by Zhitnitsky (2003), partly inspired by the quark nuggets (Witten 1984). In the AQN model, DM particles are very massive (gram mass) and interact very rarely, but very strongly, with the baryonic sector. They behave as cold dark matter, and yet are made of regular matter, without contradicting primordial nucleosynthesis. In this talk, I will review the basic properties of this model and some of its astrophysical successes obtained so far. I will then discuss recent work we have done on how this DM interacts with the solar corona and how the model can be more thoroughly tested in the future.

We will review the relevance of historical observations for current astrophysical problems, in particular for the reconstruction of solar activity in the 17th century Maunder Minimium and the pre-telescopic time - as well as the study of historical supernovae in our Galaxy. Among other observations, we will discuss the strong 14-C variation around AD 775 detected in trees around the world and discuss possible causes like a nearby supernova, a Galactic gamma-ray burst, a solar super-flare, etc.

Being complex systems containing vast amounts of gas, dust, and stars, galaxies allow us to study the Universe in great detail. It is inside these systems that stars form, and transform the simplest of elements, hydrogen, into heavy elements essential for life as we know it. In the last few years I have worked dissecting galaxies in an effort to obtain clues to their chemical evolution histories. Star clusters, both Globular and Young Massive Clusters (YMCs), are attractive test laboratories for several astrophysical reasons. Given that these objects can be observed and studied in detail at larger distances than individual stars, one can use them as tracers of stellar populations outside of our own Milky Way. Using spectroscopic observations of star clusters covering a broad range of ages (~2 Myr to ~12 Gyr) we probe the chemical enrichment history of the host galaxy. I will discuss recent work exploiting spectroscopic observations acquired with both the ESO Very Large Telescope and the Hubble Space Telescope where we proved that both detailed abundance and metallicity analyses are possible for star clusters at distances of several Mpc.

For the first time, horizon scale structure around a supermassive black hole was imaged with the EventHorizonTelescope. In this talk, I will discuss the physical interpretation of the ring-like structure emerging in the center of the galaxy M87. To compare the observations with theoretical expectations, a library of ~60000 theoretical images was obtained from 3D GRMHD simulations with different black hole spins, masses and orientations. The data is consistent with most simulations of a radiatively inefficient accretion flow and yields a black hole mass of 6.5x10^9 Msun, in excellent agreement with the stellar dynamical measurement. Further firm parameter constraints are currently thwarted by the stochastic nature of the underlying models as well as the uncertain modeling of electron physics in near collision-less regimes. More constraints are set by including multi-wavelength data and by using limits on the jet power. I will also briefly discuss implications to alternatives to GR and future prospects for physics with the EHT.

The classical picture of protoplanetary discs forming smooth, continuous structures of gas and dust has been challenged by the growing number of spatially resolved observations. These observations indicate that radial discontinuities and large-scale asymmetries may be common features of the emission of protoplanetary discs, which are often interpreted as signatures of the presence of (unseen) planetary companions. During this seminar, I will report our recent and ongoing efforts to predict the dust’s radio emission in protoplanetary discs due to the presence and orbital evolution of giant planets, through gas+dust hydrodynamical simulations post-processed with dust radiative transfer calculations. I will show via these models that recent ALMA observations strongly suggest the presence of several planets in the discs around MWC 758 and HD 169142.

Recently, X-ray observations revealed that some of evolved supernova remnants (SNRs) have plasmas in which the recombination process becomes more dominant than the ionization process. In most of these SNRs having the recombining plasma (RP), association of molecular and atomic clouds are observed. This implies that the evolution of SNRs are considered to be deeply related to the environment of the ambient gas, though they are not fully understood. In order to study physical and astrophysical causes of the formation of the RP in evolved SNRs, we develop a new framework that provides both X-ray spectra and images of evolved SNRs with an age of > 104 yr. Our model calculates the time evolution of temperatures of electron and ions, which are not considered in previous plasma models, based on a one-dimensional Lagrangian hydrodynamics simulation. We include physical processes of shock heating, energy exchange by Coulomb interaction, radiative cooling and evolution of ionization states. The spectra are composed of bremsstrahlung and emissions by atomic transition of major elements calculated from atomic properties of AtomDB. Since effects of the surrounding environment of SNRs is important in their evolution, we investigate the relation between plasma states in SNRs and interstellar medium (ISM) density using our model by changing ISM density (1, 3, 10, and 30 cm-3). In our simulation, the RP is naturally produced in evolved SNRs (~ 104 yr) which exploded in the dense ISM. We characterize spectra by the electron temperature and ionization temperature that is an indicator of describing the ionization state. As a result of comparing these temperatures of our model with the observations, we successfully demonstrate that the time evolution of ionization and recombination are in excellent agreement with the observed values. Our model holds promising application for future X-ray missions with a high resolution spectrometer.

The PTOLEMY project aims to develop a scalable design for a Cosmic Neutrino Background (CNB) detector, the first of its kind and the only one conceived that can look directly at the image of the Universe encoded in neutrino background produced in the first second after the Big Bang. The scope of the work for the next three years is to complete the conceptual design of this detector and to validate with direct measurements that the non-neutrino backgrounds are below the expected signal from the Big Bang. In this talk I discuss in details the theoretical aspects of the experiment and its physics goals. In particular, I mainly address three issues. First the sensitivity of PTOLEMY to the standard neutrino mass scale. I then consider the perspectives of the experiment to detect the CNB via neutrino capture on tritium as a function of the neutrino mass scale and the energy resolution of the apparatus. Finally, I consider an extra sterile neutrino with mass in the eV range, coupled to the active states via oscillations, which has been advocated in view of neutrino oscillation anomalies. This extra state would contribute to the tritium decay spectrum, and its properties, mass and mixing angle, could be studied by analyzing the features in the beta decay electron spectrum.

From the cosmic-ray spectrum, we know that there must be objects in our galaxy that can accelerate particles to above PeV energies, but it's not clear what they are. Very-High-Energy gamma-rays (E>100 GeV to >100 TeV) provide a useful tool for searching for these accelerators, since they provide a view of non-thermal photon emission from the sites where particles are accelerated. I will present an overview of the problem, how we are using telescopes like HESS (and later CTA) to search for these "PeVatrons" and what difficulties have been encountered. Finally, I will show the latest results, including evidence for an acceleration event in the Galactic Center.

In this talk, I shall review the most peculiar aspects of cosmology in the radio band, with a special focus on the Square Kilometre Array (SKA) radio-telescope and its pathfinders. I shall present the main radio probes that can be exploited for late-time cosmology: continuum and 21-cm line galaxy surveys, neutral hydrogen intensity mapping, and even weak lensing cosmic shear at radio frequencies. Moreover, I shall also discuss the added value of multi- wavelength synergies, presenting some show-case example of the power of radio-optical cross-correlations to test the fundaments of the concordance cosmological model, such as the nature of dark matter and dark energy, or tests of inflation and gravity.

Strong gravitational lenses with measured time delays between the multiple images can be used to determine the Hubble constant that sets the expansion rate of the Universe. Measuring the Hubble constant is crucial for inferring properties of dark energy, spatial curvature of the Universe and neutrino physics. I will describe techniques for measuring the Hubble constant from lensing with a realistic account of systematic uncertainties. A program initiated to measure the Hubble constant to <3.5% in precision from strong lenses is in progress, and I will present the latest results and their implications. Search is underway to find new lenses in imaging surveys. An exciting discovery of the first strongly lensed supernova offered a rare opportunity to perform a true blind test of our modeling techniques. I will show the bright prospects of gravitational lens time delays as an independent and competitive cosmological probe.

The study of the filamentary structures in massive star-forming regions is undergoing a revolution, thanks in large part to the unprecedented high angular resolution and sensitivity that ALMA provides. We have used ALMA to conduct an observational study of two massive filaments and a hub-filament system with the main goal of building a picture of their global dynamical properties and fragmentation. We present the results for the Monoceros R2 (hereafter MonR2) molecular cloud, one of the nearest and clearest examples of a hub-filament system. The central hub hosts a cluster of massive protostars associated with an expanding HII region, where a number of filaments are converging. We have estimated total the mass accretion rate along the filaments on the order of 10^(- 3) Msun/yr. Inside the central hub, the filaments appear twisted forming a spiral-like structure, with signs of rotation and infall motions. Overall, the hub-filament system in MonR2 suggests a scenario of non- isotropic global collapse, forming a massive stellar cluster. We also present our results for G357, which is a massive filament similar to the integral shaped filament (ISF) in Orion A, but shows remarkably low star formation activity. The comparison of the fragmentation and dynamics of G357 and the ISF enables us to address the early evolution of massive filaments.

The cosmic microwave background (CMB) research told us a remarkable story: the structure we see in our Universe such as galaxies, stars, planets, and eventually ourselves originated from tiny quantum fluctuations generated in the early Universe. With the WMAP we have confirmed many of the key predictions of inflation including flatness and statistical homogeneity of our Universe, Gaussianity and adiabaticity of primordial density fluctuations, and a small but non-zero deviation from the scale-invariant spectrum of density fluctuations. Yet, the extraordinary claim requires extraordinary evidence. The last prediction of inflation that is yet to be confirmed is the existence of primordial gravitational waves whose wavelength can be as big as billions of light years. To this end we have proposed to JAXA a new satellite mission called LiteBIRD, whose primary scientific goal is to find signatures of gravitational waves in the polarisation of the CMB. In this presentation we describe the current state of affairs regarding our understanding of the early Universe, physics of polarisation of CMB, and the LiteBIRD mission.

Formulating a Predictive Theory of Galaxy Evolution requires understanding star formation and its dependence on the local environment, spanning the scales from individual stars to kpc–size structures. The physical conditions within galaxies determine the formation of stars, star clusters, and larger structures, and their subsequent evolution. In turn, these structures, through feedback, affect the evolution of the host galaxy. HST observations of external galaxies have enabled the characterization of the young stellar populations with unprecedented accuracy and detail, thus aiding the census and description of those populations. These observations are being used to quantify the spatial distribution and clustering of young stars, and investigate the impact and imprint of the physical conditions of both the local and global environment on the formation and evolution of the multi-scale structures. I will concentrate mainly on the results of the Legacy ExtraGalactic UV Survey (LEGUS), an HST Treasury programs that is investigating these issues using multi-color imaging, from the near-UV to the I, of a sample of nearby galaxies. I will also briefly introduce successor programs that promise to expand our understanding of star formation and feedback on galactic scales.

The discovery and characterization of extrasolar planets has been data-driven:  clearly there are more things in heaven and earth than are dreamt of in our philosophies.  As the demographics of the myriad diverse systems becomes known, we begin to piece together the larger story of their formation and evolution. Ultimately, we seek to understand the prospects for life elsewhere in the Universe. In addition to this scientific quest, ‘exploration’ also plays a role. In particular, the nearest star systems provide an opportunity to explore in detail strange new worlds. The announcement of a planet < 10 Mearth in the liquid-water zone of Proxima Centari sent shock waves through the community. What is the nature of this planetary system found in our own galactic backyard? Could it be habitable? Here we will review plans to try to image small planets from the ground in thermal emission around the nearest stars, including development of a new generation of mid-infrared detectors with high quantum efficiency, low noise, and suitable for ground-based use, as well as instruments planned for the next generation extremely large telescopes such as METIS on the E-ELT. We will also discuss the power of imaging planets both in reflected light and thermal emission, and the possibility of detecting the greenhouse effect in a world outside the Solar System.

The birth of a neutron star with an extremely strong magnetic field, called a magnetar, has emerged as a promising scenario to power a variety of outstanding explosive events. This includes gamma-ray bursts, supernovae with extreme kinetic energies called hypernovae and super-luminous supernovae. The origin of these extreme magnetic fields (of the order of 10^15 Gauss) is not fully understood yet and requires an amplification over several orders of magnitude during the formation of the neutron star. I will describe our current understanding of the physical processes that may lead to this magnetic field amplification and the consequences for the explosion properties.

Recent observations have emphasized the importance of the formation and evolution of magnetized filamentary molecular clouds in the process of star formation. Theoretical and observational investigations have provided convincing evidence for the formation of molecular cloud cores by the gravitational fragmentation of filamentary molecular clouds. Thus, the mass function and rotations of molecular cloud cores should be directly related to the properties of the filamentary molecular cloud, which determines the initial size and mass distribution of a protoplanetary disk around a protostar created in a core. In this talk I explain our current understanding of the star formation processes in the Galactic disk, and summarize various processes that are required in describing the filamentary molecular clouds to understand the star formation rate/efficiency, the stellar initial mass function, and the angular momentum distribution of protoplanetary disks in their early evolutionary phase.

Star formation is one of the main drivers of galaxy evolution, but an understanding of this process remains elusive. This is caused by a lack of systematic observational constraints on cloud scales. Star formation in galaxies is expected to be highly dependent on the galactic structure and environment, as it results from a competition between mechanisms such as gravitational collapse, shear, spiral arm passages, cloud-cloud collisions, and feedback. A statistically representative sample of galaxies is therefore needed to probe the wide range of conditions under which stars form. I will present the first systematic characterisation of the evolutionary timeline of molecular clouds and star-forming regions, derived by applying the statistical method of Kruijssen & Longmore (2014) and Kruijssen et al. (2018) to homogeneous ALMA + optical observations at 50 pc resolution of a large sample of star- forming disc galaxies out to 17 Mpc (obtained in the context of the PHANGS collaboration). This method uses the multi-scale nature of the star formation relation to constrain the timeline and efficiencies for star formation and feedback on the cloud scale, across a wide variety of galactic environments. I will show that star formation is regulated by efficient stellar feedback, driving GMC dispersal on short timescales (1-5 Myr) due to radiation and stellar winds, prior to supernova explosions. This feedback limits GMC lifetimes to about one dynamical timescale (10-30 Myr), with integrated star formation efficiencies of only a few percent. Our findings reveal that galaxies consist of building blocks undergoing vigorous, feedback-driven lifecycles, that vary with the galactic environment and collectively define how galaxies form stars. These observations settle a long-standing question on the multi-scale lifecycle of gas and stars in galaxies, and open up the exciting prospect of studying cloud-scale star formation and feedback in galaxies across cosmic time.

MAXI (Monitor of All-sky X-ray Imager) was launched in 2009 and installed on the International Space Station.It consists of the Gas Slit Camera (GSC) and the Solid-State Camera. The GSC, gas proportional counter array, covers the energy range from 2.0kev to 30keV while the SSC, CCD cameras, covers the energy range from 0.7keV to 7keV. In the seminar, I will focus on the SSC. The SSC consists of 32 CCDs in total with a mechanical slit. The CCD performance is gradually degrading in orbit due to its harsh radiation environment. I will report on the diffuse X-ray background maps obtained in energies of 0.7--1.0, 1.0--2.0, and 2.0--4.0 keV, respectively. They are the first ones that were derived with a solid-state instrument. The diffuse soft X-ray background was discovered in the past by using sounding rocket experiments and studied in detail by ROSAT All Sky Survey (RASS). After that, we learnt that the solar wind charge exchange (SWCX) was a nuisance in X-ray astronomy, particularly below 1.0keV. The SWCX is believed to depend on the solar activity and seriously affects the diffuse X-ray background. RASS was done in high solar activity while SSC was done in low solar activity separating about 20 years. Our result shows a good correlation with that by RASS.

Star formation is a complex process that involves dusty gaseous structures covering orders of magnitude in spatial scales and gas densities. How the physical properties and dynamical evolution of these structures relate to a particular star formation event is yet to be fully uncovered. In the past decade, some progress has been made on linking the properties of low-mass star-forming cores to those of the interstellar filaments in which they most often form. On the other hand, there is also a growing body of evidence suggesting that the reservoirs from which massive (proto)stars accrete gas from are typically much larger than those for low-mass protostars. Trying to determine what physical process fixes the properties of these mass reservoirs, and finding out how they evolve towards the formation of individual stars and stellar clusters is at the heart of current star formation research. In this context, I will present recent observational studies aiming at understanding how gas flows from the scale of a giant molecular cloud to individual massive-star forming cores, and how feedback from recently formed OB stars affect their parent molecular cloud. I will discuss how the corresponding findings impact our current knowledge on molecular cloud structure and dynamical evolution of dense star-forming clumps.

The Universe is infinitely large and dramatically dark, apparently dominated by unknown components which make up most of the matter/energy budget. Fortunately, that tiny 4.6% of baryons act under the robust laws of nuclear physics and stellar evolution, theories which we can use to understand the bright side of the Universe. In this talk I shall discuss interpretative models for distant galaxies and illustrate the historical path that paved the way to modern calculations. I shall then use those models to infer conclusions on the formation and evolution of the most massive galaxies.

Distant galaxy clusters are powerful laboratories for observing the hierarchical growth of large-scale structure, constraining cosmological parameters, and for studying the formation of galaxies. However, distant (z>1.5) clusters are extremely rare and faint, so locating and studying them poses a significant observational challenge. In this seminar, I will review the theory of cluster formation and present recent advances we have made in detecting and studying distant galaxy clusters.

The top recommendation for a large space mission in the US 2010 Decadal Survey was the Wide Field Infrared Survey Telescope (WFIRST). Similarities in hardware requirements between proposed dark energy, exoplanet microlensing, and near infrared surveyor missions allowed for a single mission that would accomplish all three goals. The gift of an existing 2.4 meter telescope to NASA by another US government agency allowed for the addition of a coronagraph that will take images and spectra of nearby exoplanets; this instrument will be a technological stepping stone to imaging other Earths in the 2030s. I will give an overview of WFIRST's proposed instrumentation, science goals, and implementation plan.

Star forming dwarf galaxies are by far the most abundant type of galaxies in the local Universe. They also lie at the base of the hierarchical structure formation ladder - as they later merge into larger halos. Understanding the baryon cycle in these galaxies is critical towards solving the major mismatches between observations and simulations of structure formation. Empirically constraining the relationship between gas and star formation in these galaxies remains challenging though, given their faintness across all observed wavelengths. I will describe our efforts to empirically quantify the relation between gas and star formation using the 21 cm emission line from atomic hydrogen (HI) as a tracer of gas, not only in dwarfs but also in the HI-dominated outskirts of spirals.

eROSITA (extended ROentgen Survey with an Imaging Telescope Array) is the core instrument on the Russian/German Spektrum-Roentgen-Gamma (SRG) mission which is current scheduled for launch in 2018. In the soft band (0.5-2 keV), the deep All-sky survey will be 30 times more sensitive than the previous ROSAT All-sky survey, while the first ever true all-sky survey will be mapped in the hard band (2-8 keV). The design driving science is the detection of large samples of galaxy clusters to redshifts z > 1, in order to study the large scale structure in the Universe and test cosmological models including Dark Energy. In addition, eROSITA is expected to yield a sample of around 3 million active galactic nuclei, which is bound to revolutionize our view of the evolution of supermassive black holes and their impact on the process of structure formation in the Universe. Finally, the survey will also provide new insights into a wide range of astrophysical phenomena, including neutron stars and pulsars, X-ray binaries, active stars and diffuse emission from supernova remnants. The talk reports on the status of eROSITA and its scientific prospects. In the end, I will also briefly discuss how the German eROSITA consortium is activated for ensuring an adequate follow-up of the sources to be discovered.

The ability to obtain high quality data in a short amount of time or indeed to recover high resolution images from from incomplete blurred and noisy data can significantly improve the results of experiments potentially leading to new and exciting scientific discoveries. Mathematical techniques such as compressed sensing and sparse regularisation provide these benefits for many sources of data in a variety of different fields. Compressed Sensing for Magnetic Resonance Imaging and Cosmology (COSMIC) is a CEA DRF funded project that brings together MRI experts at NeuroSpin with astronomical image analysis experts at CosmoStat in order to develop an open source software package called PySAP (Python Sparse data Analysis Package) that implements these signal processing tools. This talk will provide a brief introduction to the types of problems encountered in acquiring/processing MRI and astrophysical images and demonstrate how the tools provided in PySAP can be beneficial.

The formation of stars is a fundamental aspect of how matter evolves in the Universe. It dictates timescales, chemical and structure evolution of baryons. It is the respiration of galaxies; star formation makes galaxies “boil”, bubble and fragment. Without it the Universe would have ended up in a sterile collection of gravitational singularities. Star formation creates structures as a result of specific non-linear physical processes. In that respect, a galaxy is a complex, self-organized system. This complexity is revealed by the multi-scale and multi-phase nature of the interstellar medium. This talk will be about the use of multi-wavelength, and especially hyper-spectral data, to uncover aspects of the energy and matter cascade of the interstellar medium of the Milky Way. I will present how such data (dust, CO, 21 cm) and their comparison to numerical simulations, can be used to get a clearer view of the evolution of diffuse matter in a galaxy like the Milky Way. In particular I will present recent results on the use of dust scattering to trace the cascade of the ISM cascade down to very small scales, as well as our current work on the analysis of large 21 cm datasets to uncover the first steps of the formation of cold and dense structures in the diffuse ISM.

Over the past 45 years, investigations of ultraviolet absorption features in stellar spectra have revealed that most of the heavy elements in the interstellar medium are depleted from the gas phase to values well below solar or B star reference abundances. The strengths of such depletions reveal the composition of dust grains in space, and they can be characterized by a limited set of parameters that are closely linked to the average gas densities and the condensation temperatures of the elements. Two outstanding mysteries remain: one is the fact that the depletion of oxygen exceeds that needed for forming silicates or metallic oxides, and the other is that the chemically inert element krypton shows some depletion. When we observe absorption features to derive the element abundances in distant galaxies, we must understand how to correct for depletions by using the patterns found in our Galaxy or the Small Magellanic Cloud as examples. Comparisons of interstellar abundances to those found in circumstellar disks may help us to understand better the replenishment and dispersal of gaseous matter in such systems.

In this presentation I will talk mainly about Cassini discoveries and results concerning the outer edge of Saturn’s main rings, that is a very peculiar place called the «Roche limit». In this region, accretion processes are balanced by tidal forces producing a variety of time variable structures because of the endless competition of these two processes. Temporary moons, ringlets regularly destroyed by moonless interactions, a complex interplay have been discovered. I will talk about mainly about of strange physics of this region and show that moons and rings are the two sides of a same system. Many discovered processes are similar to still unobserved mechanisms invoked for planetary formation. The discussion will also extend to the formation of short-period planets around white dwarves, that can be explained by exactly the same processes.

The Multi-Unit Spectroscopic Explorer (MUSE) is an integral field spectrograph with unique capabilities on the Very Large Telescope. With its high sensitivity and by providing a complete view of the optical spectrum over 1 arcmin2 it has been a tremendous breakthrough in the way galactic and extragalactic observations are performed. The success of MUSE calls for new ideas for the next generation of IFUs, and I will present the concept of a BlueMUSE. With a field of view increased up to 1.4 x 1.4 arcmin2 and a higher spectral resolution, BlueMUSE is covering wavelengths down to the atmospheric cut-off (350 nm). The current instrumental concept currently being investigated includes the use of curved detectors. BlueMUSE opens up a new range of galactic and extragalactic science cases allowed by its specific capabilities: including for example the study of young stars, the properties of the gas in the circumgalactic medium, and high redshift clusters.

Wojtak, Hansen and Hjorth and others have measured the long-predicted gravitational redshift of light escaping from galaxy clusters. The effect is very small, corresponding to a velocity shift of only about 10 km/s, but the result appears to be fairly robust and seemed to be in good agreement with general relativity predictions and possibly in conflict with some alternative theories. The effect was initially imagined to be a simple astronomical analogue of the famous terrestrial Pound and Rebka experiment that verified Einstein's theoretical prediction. However, it was soon realised that the physics of this effect is considerably more complex. As I shall describe, there are actually three other contributions to the measured signal that need to be taken into account. I shall describe recent attempts to model these effects using N-body experiments, and how this effect may be useful for testing alternative theories of gravity. Understanding this apparently simple effect reveals some subtleties in special relativity and also sheds light on the interpretation of redshifts in cosmology.

The gas mass and star formation rate of damped Lyman-alpha absorbers (DLAs), a population of high-redshift absorption-selected galaxies, have been open questions in the field of galaxy evolution for more than three decades. This talk will describe new results from ALMA searches for CO and CII-158 micron emission from a sample of DLAs over a wide range of redshifts, z~0.5-4.2. These are the first CO and CII-158 micron detections in DLA host galaxies, providing a new window on physical conditions in absorption-selected galaxies, and yielding a new tool to identify DLA host galaxies at high redshifts.

In the local universe, a star has a higher probability of being in a galaxy of the mass of the Milky Way than in any other galaxy, and we have the opportunity to be able to study one such galaxy from the inside. We can, in particular, study its stellar mass growth with time, and understand how each of the known stellar populations is connected to this mass growth history. While much is expected from the analysis of the Gaia data in this regard, it is safe to say that a change of paradigm concerning the stellar populations of our Galaxy is already under way, due in particular to important results coming from the analysis of recent spectroscopic surveys. I will present and discuss some of these results.

PILOT is an experiment with a stratospheric balloon designed to measure the thermal dust polarized emission at 240 microns which enables to measure the geometry of the magnetic field in the Interstellar Medium using multiplexed bolometric detectors developed by CEA for the Herschel PACS mission. In this talk, we will describe the instrument and its performances measured during the first two flights that took place in 2015 and 2017 from Canada and form Australia respectively. We will discuss the first scientific results on the geometry of the magnetic field in the central molecular zone of our Galaxy. We will insist on the strict control of systematic instrumental effects crucial for this type of measurements and the associated difficulties in the data treatment and calibrations. Finally, we will talk of the future PILOT project and in particular its evolution to COPILOT designed to measure the integrated emission of the C+ line in the ISM and to become a demonstrator of the detection chain for the SPICA-POL instrument.

With recent advances in numerical techniques and computing power theoretical modeling of a core-collapse supernova (CCSN), a cataclysmic event marking the end of the lifetime of a massive star, has become feasible in three spatial dimensions. In this talk, I will review recent progress which have been made in modeling the long-term evolution of CCSN explosion starting from the collapse and explosion phase until the SN ejecta transform into the early SN remnant phase. I will discuss how simulation results can be compared with observables such as explosion asymmetries, element distributions, SN light curves, and pulsar kick velocities that are obtained from recent observations of SN and SN remnants.

We will present the science goals of the SVOM mission and how the Microchannel X-ray Telescope (MXT) will contribute to reach them. SVOM a a Sino-French mission (to be launched by the end of 2021) dedicated to Gamma-Ray Bursts and transient sky studies, and MXT is part of the payload that will be delivered by France. It is a focussing soft X-ray (0,3-6 keV) telescope, which is based on a new optical concept called "Lobster-Eye", coupled to a low noise pn CCD detector. The Irfu/DAp carries the scientific responsibility of the entire telescope, and is in charge of the development of the camera, including all the functions around the detector to get optimal performance. We will present the design of the camera, the associated challenges and the recent achievements.

The Sloan Digital Sky Survey (SDSS) has been mapping the sky for almost a decade, providing crucial information on the dark universe though measurements of BAO and RSD (redshift space distortions). As one of the SDSS components, the Lyman-alpha forest survey is a rich source of information. Because it gives access to small (tens of Mpc) scales, it allows one to probe the impact on the clustering of matter of neutrino mass and warm dark matter. I will briefly recall the major goals of SDSS, and introduce the quasar survey where the Lyman-alpha forest is measured. I will then present one of the strongest constraints on neutrino mass from a combination of CMB and Lyman-alpha data. Finally, I will show how the study of clustering in the Lyman-alpha forest can also lead to competitive constraints on warm dark matter and on several models of keV sterile neutrinos.

In 2015, at COP21, governments invited the IPCC to prepare this special report. It was approved by delegates from all governments in October 2018, on the basis of the assessment performed by 91 authors from 40 countries, with 133 contributors, of 6000 publications, after 3 rounds of review (1131 reviewers, more than 42 000 review comments). This report provides the current state of global warming, with 1°C due to human activities; the consequences of an additional half a degree or one degree of global warming; the greenhouse gas emission trajectories consistent with stabilisations at 1.5°C or 2°C; the systems transitions, with an assessment of 6 dimensions of feasibility; the multiple intersections with sustainable development goals. This report is so stimulating that governements could not find words to receive it. In December 2018, at COP24, four of them (Saudi Arabia, Kuweit, USA and Russia) refused to welcome it. The COP24 decision expresses its appreciation for the work done, welcomes the timely completion of the report, and invites parties to make use of it...

Over the last few years, enormous progress has been made probing galaxies in the first two billion years thanks to the incredible capabilities of the Hubble and Spitzer Space Telescopes. Already, more than 1500 probable galaxies are known at redshifts above z~6, and now the current frontier is at z~9-10, with 50 plausible galaxy identifications to date, and a credible spectroscopic redshift determination to z=11.1. Deriving physical properties for these distant galaxies is also an important frontier, and progress has been impressive even as early as z~7-8, with probes of nebular emission-line strengths and specific star formation rates to z~8.5 and new constraints on dust-enshrouded star formation at z>~2 from ALMA. One exciting emerging frontier has been probes of ultra-faint galaxies in the early universe with the Hubble Frontier Fields (HFF) program using gravitational lensing and long exposures. To guarantee the best results, accurate determinations of both the size distribution and lensing models are required. In this colloquium, I describe new work on the HFFs, while surveying many current highlights on early galaxy research.

Exoplanet detection surveys over the last twenty years have revealed a surprising diversity of planets orbiting other stars— this revolution is fuelled by fundamental questions about the place of the Earth and the Solar System in the Universe. How do planets form? What range in architectures of planetary systems exist? How does our Solar System fit into this context? And perhaps the most exciting of all: do other life-bearing planets exist? The study of exoplanet atmospheres is the next step in leveraging exoplanetary detections. This is because a planet’s atmosphere provides a fossil record of its primordial origins and controls its fate, size, appearance, and ultimately its habitability. In this context, I present comparative exoplanetology programs that aim at characterising planetary systems transiting nearby stars through the observations of their atmospheres. Our findings on the atmospheric composition and physical properties provide insights into the formation and evolution of planetary systems and enhance our understanding of our own Solar System’s formation. Finally, I also present strategies for probing habitable exoplanet atmospheres in the quest for bio-signatures.

Over a large range of equilibrium temperatures clouds seem to dominate the transmission spectrum of exoplanets atmospheres, but no trends allowing the classification of these objects have yet emerged. Recently, Kepler observations of the light reflected by hot Jupiters show that an inhomogeneous, asymmetric and time-dependent cloud coverage is present in these planets. Interestingly, this asymmetry depends on the equilibrium temperature of the planet. Using state-of-the-art three dimensional models of hot Jupiters atmospheres, I will show that longitudinal and latitudinal asymmetry in the cloud coverage is expected for these hot planets. The presence of such an inhomogeneous cloud coverage can bias the retrieved abundances from transmission and secondary eclipse spectra and even lead to erroneous molecular detections. Thermal phase curves are also affected, and our understanding of heat transport by the atmosphere cannot be complete without taking clouds into account. The longitudinal cloud asymmetry being a strong function of the condensation temperature of the cloud species, it is a telltale of the cloud composition. Observations and models converge towards a similar conclusion: an L/T-like transition is expected for hot Jupiters, with silicate clouds disappearing from the cooler planets and being replaced by manganese sulfide clouds.

Gamma-ray bursts are the most luminous electromagnetic events in the universe. They fall into two, broad categories: long-duration (more than 2 s) bursts, which are powered by the core collapse of rapidly rotating massive stars, and short-duration (less than 2 s) bursts, for which binary neutron star and neutron star-black hole mergers are the leading progenitor candidates. In both scenarios, gravitational waves are expected to accompany the gamma-ray burst, making these transient phenomena promising events for gravitational-wave follow-up. In this talk, I review the status of targeted searches for gravitational waves in association with gamma-ray bursts and discuss the prospects of joint electromagnetic and gravitation-wave observations. I also present the results of these searches obtained during the first Advanced LIGO observing run, which was carried out between September 2015 and January 2016.

With the novel world-leading radio telescope LOFAR (the Low Frequency Array), astronomers are expected to detect the cosmological radiation emitted billions of years ago, from the time of the first ‘stars’. However, detection of this weak emission is difficult. Synchrotron emission from our own Galaxy intervenes, like mist on an autumn morning. To clear the view towards the early childhood of the Universe, we need to study the emission from our Galaxy in great detail. During my talk I will give an overview of the LOFAR-EoR key science project, its challenges and present its most recent results. A special focus will be given to the rich morphological features discovered with the LOFAR in several fields at high Galactic latitudes, associated with small column densities of the interstellar medium located somewhere within the Local Bubble. At the end I will discuss their puzzling correlation with the Planck dust polarisation data and HI data.

Polarized emission from cold Galactic dust is the most important and troublesome foreground for searches of an inflation-probing B-mode signal in the polarization of the cosmic microwave background (CMB). To get to the primordial B-modes, we need to subtract polarized emission of magnetized interstellar dust with high accuracy. A critical piece of this puzzle is the 3-d structure of the magnetic field threading dust clouds, which cannot be accessed through microwave observations alone. However, observations of a large number of stars at known distances in optical polarization, tracing the same CMB-obscuring dust, can map the magnetic field between them. The Polar Area Stellar Imaging in Polarization High Accuracy Experiment (PASIPHAE) will deliver such a map combining novel-technology wide-field-optimized optical polarimeters and an extraordinary commitment of observing time by the Skinakas observatory in Crete and the South African Astronomical Observatory. We will cover >9000 square degrees in the areas of the sky targeted by CMB experiments, measuring linear optical polarization at 0.2% accuracy of over 360 stars per square degree, a 1000-fold increase over the state of the art. Such a map would not only boost CMB polarization foreground removal, but it would also have a profound impact in a wide range of astrophysical research, including interstellar medium physics, high-energy astrophysics, and galactic evolution.

The field of gravitational microlensing is booming, in particular due to the success of several space-based missions. I will review recent discoveries and developments in exoplanet search through gravitational microlensing, with a special focus on statistics of exoplanets, brown dwarfs and free-floating planets, and the Spitzer and Kepler/K2 follow-up of microlensing events using space-based parallax. I will outline the prospects of future techniques and instruments, such as the observations of microlensing events through interferometry and the promise of the WFIRST mission for microlensing.

Observations reveal that star formation is progressively quenched in more massive galaxies and in denser environments. What are the main physical mechanisms able to moderate and stop star formation? An obvious one is the energetic feedback from AGN, where recently massive molecular outflows have been observed. Observational evidence will be shown with ALMA and NOEMA results. The mass outflow rate is estimated between 1-5 times the star formation rate. When driven by AGN, these outflows are therefore a clear way to moderate or suppress star formation. However, AGN feedback can be also positive, and evidence will be presented. Group and cluster environment can perturb considerably galaxies, quench their star formation, and transform their morphology in very short time-scales. I will present evidence of gas removal, where not only the external atomic gas is involved, but also inner molecular gas. Star formation still occurs in the tails, however with a much lower efficiency. The survival of dense clouds in harsh environments will be discussed.

In a first part of the seminar I shall discuss how from the observed surface abundances of extremely iron-poor stars, it is possible to deduce interesting properties of the first massive star generations in the Universe. These very iron-poor low mass (and therefore long-lived) stars are made of material made of a mixture of interstellar medium and of ejecta by a few, may be only one star. The very low iron content implies that not many generations of stars could enrich the pocket from which these iron-poor stars formed and thus favor short lifetimes stars as massive ones. The massive star(s) responsible for the main abundance properties of these very iron-poor stars are called the source star(s). First, based on nucleosynthetic arguments, we will deduce that necessarily some mixing processes occurred in the source stars and that only its outer layers have been ejected. Second we shall show how rotation might provide both the driving for the mixing and for the envelope ejection. Third, we shall discuss other consequences of these models for the production of nitrogen, carbon isotopes and s-process elements in the early Universe. In a second part, if time permits, we would like to discuss the origin of some short lived radionuclides that were present, still non-decayed, in the cloud that gave birth to the solar system and were incorporated in some meteorites. We will see that the analysis of tiny amounts of meteoritic material can provide wonderful constraints on the near stellar environment of the solar system 4.56 Gyr ago. In that context we shall discuss the importance of mass loss by stellar winds that seems to be a key ingredient to explain the observed amounts of 26Al and 60Fe.

Structure formation is very sensitive to the primordial conditions and dynamical properties of the Universe. In fact, it is a promising probe of dark energy, dark matter properties, primordial non-gaussianity or neutrino masses. A major difficulty to harvest these results is that a significant fraction of the information lies at non-linear scales. It is thus essential (in particular to extract new physics) to develop efficient tools to study large scale structure beyond linear theory. In this talk I will describe the methods based on perturbation theory of a fluid-like medium, emphasising the new developments. The latter are particularly relevant to understand the evolution of the BAO and to parameterise the influence of small scales on mildly non-linear scales

The interstellar medium (ISM) of galaxies drives galaxy evolution. However, its multi-phase structure is typically unresolved in cosmological galaxy formation simulations. I present recent progress on high-resolution numerical simulations (the SILCC project) investigating the differential impact of major physical processes setting the chemical and thermal multi-phase structure of the ISM including OB stellar winds, radiation and supernova explosions. We find evidence that stellar winds and radiation from massive stars primarily regulate star formation, while supernova explosions set the properties of the outflow driving hot gas. I also discuss the potential impact of non-thermal ISM components - magnetic fields and cosmic rays - on galactic outflows. With these simulations we also make first attempts towards more accurate predictions of important emission lines which are a major observables for galaxy formations studies at all cosmic epochs.

Supernova remnants 101: The large amount of energy released in the supernova explosion leads to the creation of a fast shock wave which is an important source of kinetic and thermal energy in the interstellar medium. This shock wave is also believed to accelerate the bulk of Galactic cosmic rays. As I believe that there has not been a general Supernova remnant (SNR) seminar in a long time, I will take this opportunity to make a short and biased introduction to SNRs, present the current scientific questions, and what we’ve learned from high-energy observations in the recent years. In particular, I will focus on our recent work on the source RX J1713.7−3946, an excellent target to investigate particle acceleration in SNRs since it is one of the brightest sources of the TeV sky and exhibits strong synchrotron emission in X-rays. I will conclude by discussing SNRs from a population point of view in gamma-rays with the Fermi-LAT SNR catalog in the context of time dependent evolution models.

Stars originate by the gravitational collapse of a turbulent molecular cloud of a diffuse medium, and are often observed to form clusters. Stellar clusters therefore play an important role in our understanding of star formation and of the dynamical processes at play. However, investigating the star formation is difficult because its physics is complex to be properly modeled, and because star forming regions are obscured by dust, which severely limits observations to infrared and radio bands only. As a consequence hierarchical-step approaches to decompose the problem into different stages are required, as well as reliable assumptions on the initial conditions in the clouds. In this seminar I will report for the first time on the use of asteroseismology, namely the study of stellar oscillations, to put strong constraints on the early formation stages of open clusters, up to more than 8 billion years old. I will introduce you to asteroseismology, and then describe the analysis performed on a sample of 50 red giant stars in the old open clusters NGC 6791 and NGC 6819 observed by NASA Kepler, for which nearly 4000 oscillation modes have been fully characterized. I will therefore present the important discovery made about the rotation history of these clusters and how 3D hydrodynamical simulations for stellar cluster formation can be used to constrain the physical processes of turbulence and rotation that are in action during the proto-cluster formation. The results and implications of this work will be relevant for different fields in astrophysics, including planetary formation and galaxy formation, structure, and evolution.

In this talk I will focus on three aspects of interstellar dust that have a direct bearing on its chemistry and its effects on interstellar chemistry. These are:
- the nano-particle-driven catalytic formation of the key interstellar species H2 and OH,
- the relationship between dust and the diffuse interstellar bands (DIBs) and
- the nature and evolution of core/mantle grains in the interstellar medium.
I will introduce these three topics and discuss what I would consider to be the fundamental links between them within the framework the recent interstellar dust model THEMIS (The Heterogeneous dust Evolution Model for Interstellar Solids; Jones et al. 2013, Köhler et al. 2014, 2015). In essence, it is my view that we can no longer think of dust as only providing a passive surface for the hit-stick-react-unstick formation of radicals and simple molecules such as molecular hydrogen. Instead we should consider the dust itself as a chemically-active source. As proposed within the THEMIS framework, dust is likely undergoing continuous evolution as it responds to its local environment, with the nature of the outer mantle layers playing a key role in that evolution (e.g., Jones et al. 2016, Ysard et al. 2016). This talk takes these ideas further and explores the consequences of an active evolution of dust within the ISM and its effects on the chemistry of the ISM. All of the ideas presented within this talk are published in a series of paper in Royal Society Open Science (Jones 2016a,b,c).

Low-mass galaxies are the most numerous type of extragalactic system at all epochs of the universe. The population of low-mass galaxies in the local volume allows unique astrophysical and cosmological perspectives that are unavailable in more distant or more massive systems. The ALFALFA blind extragalactic HI survey has cataloged tens of thousands of gas-rich galaxies in the local universe and has populated the faint end of the HI mass function with statistical confidence for the first time. In this talk I will present results from comprehensive follow-up observing campaigns designed to study the low-redshift, low-mass, gas-rich population discovered by ALFALFA. The centerpiece of this effort is the Survey of HI in Extremely Low-mass Dwarfs (SHIELD), an ongoing multi-wavelength investigation of the properties of 82 extremely low-mass galaxies selected from the complete ALFALFA catalog. I will also discuss results from parallel ongoing observing programs that explore more exotic low-mass objects, including "ultra compact high velocity clouds" (HI clouds with structural parameters that match those of gas-bearing "mini-halos" if located within ~1 Mpc), candidate "dark galaxies" (systems with extreme hydrogen mass to stellar light ratios), and targeted studies of individual sources of interest (including two of the most metal-poor galaxies known in the universe). Taken as a whole, these observing programs are furthering our understanding of the continuum of galaxy properties in the low-mass regime.

Massive black holes, weighing millions to billions of solar masses, inhabit the centers of today's galaxies. Black hole masses typically scale with properties of their hosts, such as bulge mass and velocity dispersion. The progenitors of these black holes powered luminous quasars within the first billion years of the Universe. The first massive black holes must therefore have formed around the time the first stars and galaxies appeared, and then evolved along with their hosts for the past thirteen billion years. I will discuss some aspects of the cosmic evolution of massive black holes, from their formation to their growth and how different physical processes shape the relation between black holes and galaxies.

I will present cosmology constraints from a combined analysis of galaxy clustering and weak gravitational lensing, using 1321 deg^2 of griz imaging data from the first year of the Dark Energy Survey (DES Y1). The analysis combines (i) the cosmic shear correlation function of 26 million source galaxies in four redshift bins, (ii) the galaxy angular autocorrelation function of 650,000 luminous red galaxies in five redshift bins, and (iii) the galaxy-shear cross-correlation of luminous red galaxy positions and source galaxy shears. These three measurements yield consistent cosmological results, and provide constraints on the amplitude of density fluctuations (S_8 = 0.794+0.029-0.027) and dark energy equation of state (w = -0.80+0.20-0.22) that are competitive and compatible with those from Planck cosmic microwave background measurements. I will also provide an outlook on upcoming weak lensing results from DES on clusters of galaxies and density tomography, a newly developed higher-order statistic.

The evolution of protoplanetary disks is regulated by the interplay of various physical processes related to the interaction between the star and the disk, such as accretion of material onto the star and emission of material through winds. These processes are best studied spectroscopically. Instruments like the VLT/X-Shooter spectrograph allow us to observe simultaneously the signatures of the accretion process, such as the UV-excess and the emission lines, together with lines tracing winds and outflows, such as helium lines and forbidden lines. At the same time, such spectra allow us to robustly derive the physical parameters of the central objects, such as their temperature and their mass.
When this information is combined with observations of disks at sub-mm wavelengths with ALMA it is then possible to quantitatively constrain disk evolution mechanisms.
I will report on the dependence of the mass accretion rate with stellar mass and disk mass for the complete samples of low-mass objects in the Lupus and Chamaeleon star-forming regions, and discuss the theoretical framework we are working on to explain these observations.
I will also present how we are using Gaia data to study young clusters, and how we are preparing to use future Gaia DR2 data to understand the effect of interactions between stars in the cluster on the evolution of disks.

Radio astronomy is entering a new golden age with the emergence of continental-scale ground-based interferometers such as LOFAR, MeerKAT and SKA. They provide a large field of view as well as high angular ("), spectral (Hz) and temporal resolutions (microsecond) at huge sensitivity over a large frequency spectrum (from about 50 MHz to 10s of GHz). At the same time, the recent mathematical framework of "Compressed Sensing" led to new signal processing algorithmic developments that can be used for robust and sparse signal reconstructions. After introducing these two topics, I will present some developments done at their interface that are led by the team Cosmostat and LEPCHE in collaboration with SKA South Africa. Using the general « compressed sensing » framework combined with sparse representations and convex optimization, we developed two important applications for image reconstruction from interferometric data. First, the improved performance of new instruments can be better exploited to study "slow" (more than 1min) and "fast" (less than 1min) radio transients in the image plane. Unlike frame-by-frame detection, we extended the sparse reconstruction to the third dimension by constraining the reconstruction in time, therefore increasing the detection and characterization of the transient sources. Second, LOFAR and SKA are essentially spectrometers which provide measurements in a very large number of frequency channels. Each channel contains a mix of contributions from various astrophysical sources in the field of view. Based on a sparse source separations method, it is possible to disentangle both spatially and spectrally the various contributions for proper spectral imaging. I will then discuss why more developments are required in this field to improve the scientific return of SKA-class instruments with the advanced calibration of the deluge of data generated by these instruments.

Birmingham University