INAF1 – Project 1 “Exploringgalaxyevolutionwithdistributionfunctionsacrossthecosmic

time”

Supervisor: Micol Bolzonella (micol.bolzonella@inaf.it)

INAF - Osservatorio di Astrofisica e Scienze dello Spazio di Bologna Via Piero Gobetti 93/3, 40129 Bologna

PhD Project: Exploring galaxy evolution with distribution functions across the cosmic time 20/03/2019

Supervisor: Micol Bolzonella (micol.bolzonella@inaf.it) Collaborators: Elena Zucca (elena.zucca@inaf.it), Sandro Bardelli, Lucia Pozzetti, Olga Cucciati + Euclid team (local and international)

Research description

Distribution functions as a function of redshift, i.e. the evolution of the density of galaxies with a given property (e.g. luminosity, stellar mass, star formation rate), are widely used to derive constraints on galaxy evolution: the luminosity function is a proxy for the evolution of the stellar populations, while the stellar mass function is connected to the mass assembly history of the Universe via star formation or merging events.

These functions can be studied separately for different galaxy classes (e.g. types based on spectrophotometry, morphology, star formation activity, spectroscopic indices) and in different environments (from voids to groups and clusters), providing constraints on the physical processes shaping galaxies observed across the cosmic time.

Various studies are available in the literature, however a homogeneous derivation of distribution functions from low to high redshift is missing, heavily affecting the interpretation of the evolutionary trends.

This thesis project aims at deriving distribution functions from the available and well known spectroscopic and photometric surveys (VVDS, CFHTLS, ELAIS, HSC-SSP, SXDF, COSMOS, VIPERS, VUDS and others, all of them already exploited by our group) with different methodologies and taking into account the different depths of the considered datasets and characteristic observational uncertainties affecting the estimates of physical parameters (e.g. deconvolving the estimates from the Eddington bias). Such a work has never been carried out and will be considered a reference in every statistical study of galaxies. The outcome of this work will be compared to reference theoretical models of galaxy evolution to identify the critical physical processes that are not yet fully understood.

These distribution functions are not only interesting per se, but also as a fundamental ingredient of the emerging technique of empirical models adopted to simulate large samples of galaxies, currently not accessible by standard semi-analytic models on dark matter simulation. This technique is becoming more and more widespread (see e.g. Carretero et al. 2015, Moster et al. 2018 and Beehrozi et al. 2019) and is adopted also in the Euclid collaboration. A reliable derivation of distribution functions is of paramount importance to obtain reliable forecast of galaxy properties in all future surveys. Euclid (ESA Cosmic Vision mission, with launch planned for 2022) is designed to survey 15,000 deg2 with visible (RIZ) and near-infrared (Y, J, H) imaging to HAB=24 with near-infrared slitless spectroscopy (1.25<λ<1.85µm), plus a deeper survey of 40 deg2, two magnitudes fainter. The candidate will be involved in this large international collaboration, being the proposed project a preparatory work both for forecast simulations and to exploit the real data of the survey.

INAF1 – Project 2

“StellarclustersandstellarpopulationsintheeraofGaiaandspectroscopicsurveys”

Supervisor: Angela Bragaglia (angela.bragaglia@inaf.it)

Title of the Project: Stellar clusters and stellar populations in the era of Gaia andspectroscopicsurveysTutor:AngelaBragagliaResearchgroup:A.Mucciarelli(DIFABologna);E.Carretta,E.Dalessandro,L.Origlia,D.Romano,M. Tosi (INAF-OAS Bologna); V. D'Orazi, S. Lucatello, A. Vallenari (INAF-OAPadova)+Gaia-ESOConsortium+WEAVEConsortiumScientific Case: Stellar clusters are important constituents and tracers of the galacticstructure. They reside in the halo (the globular clusters), in the bulge and in the disk(whereweseepredominantlyopenclusters).Theymusthave contributed to the fieldstarspopulation,sincemoststarsforminassociationsandclusterswhichlaterdissolve,dispersingtheirconstituents.Understandingtheconnectionbetweenfieldstarsandtheirparent cluster is fundamental to figure out the cluster formation and dissolutionmechanismandthecontributiontothegeneralchemicalanddynamicalevolutionoftheGalaxy. Stellar clusters are also the ideal site where to test the stellar evolutionarymodels, by studying e.g. the presence and relevance of element diffusion,mixing, etc.Stellar evolutionary models are the best way to derive ages, on whose accuracyultimately rests most of our understanding of galaxy evolution. We are now in aprivileged era, with large surveys from the ground and space missions providing awealth of information. Gaia, the ESA astrometric, photometric, and spectroscopicmission, is revolutionizing our understanding of the Milky Way and of galaxies ingeneral,withitsexquisiteprecisionandaccuracyformorethan1.3billionobjects.The5-dmap (coordinates, propermotions, and parallaxes) of theMilkyWay provided byGaiaiscomplementedbyphotometricandspectroscopiclargesurveysfromtheground,whichaddradialvelocity,metallicity,anddetailedchemicalcompositionforasignificantfractionofGaiastarsofallGalacticcomponentsandinparticularforclustersofallages.WementioninparticulartheGaia-ESOSurvey(withFLAMESontheESOVLT),thejust-to-startWEAVE (at theWHT on Canary Islands) andMOONS (at ESO VLT) and, on asmaller scale but with much higher spectral resolution and with a coverage both inopticalandinfrared,theon-goingLargeProgramSPA(StellarPopulationAstrophysics,PI Origlia) at the Italian telescope Galileo. The full exploitation of Gaia and ground-based spectroscopic data to describe our Galaxy requires a precise and homogenousanalysisofthestellarclusters,incombinationwithstellarmodels.OutlineoftheProject:TheBolognaDIFA,INAF-OASBolognaandINAF-OAPadovaareinvolved inGaia,Gaia-ESO, MOONS,WEAVE, and theLargeProgramSPAat theTNG.ThePhDprojectmainstepsare:1)familiarizationwiththesubjectofstellarclustersandstellarpopulations;2)analysisofdataalreadyinhand,bothfromproprietaryprogramssuchasSPAandfromlargesurveysandspacemissions;3)acquisitionofnewdataandtheiranalysis, ifrequired;4)interpretationandpublicationofresults.ThePhDprojectwill center on (at least) one of the following topics: a) Globular clusters and the linkbetween their chemistryandstructuralproperties;b)Findingdispersedclustersstarsusing chemical anddynamical tagging; c)Using stellar clusters as test of evolutionarymodels.FurtherdevelopmentsorprojectscanbedevisedincollaborationwiththePhDstudent.Contacts:angela.bragaglia@inaf.it;alessio.mucciarelli2@unibo.it

INAF1 – Project 3

“Thevariableandmulti-messengerskywithCTA”

Supervisor: Andrea Bulgarelli (andrea.bulgarelli@inaf.it)

ProposalforanINAFPhDFellowship

Thevariableandmulti-messengerskywithCTA

Supervisors: Andrea Bulgarelli (INAF, OAS Bologna) Co-Advisors: Cristian Vignali (UNIBO), Eliana Palazzi, Paola Grandi, Bia Boccardi, Eleonora Torresi, Vito Sguera, Mauro Dadina, Giovanni De Cesare, Massimo Cappi, Luciano Nicastro (INAF, OAS Bologna) Context. The Cherenkov Telescope Array (CTA), will be the major observatory for very high energy gamma-ray astronomy over the next decade and beyond. The scientific potential of CTA is extremely broad, exploring the extreme universe, from the origin and role or relativistic cosmic particles to the frontier of physics (dark matter, quantum gravity), to the study of extreme environments and, connected with them, the transients phenomena. Wider field of view, improved sensitivity, a one to two order-of-magnitude collection area improvement makes CTA a powerful instrument for time-domain astrophysics. The CTA Observatory will be capable of issuing alerts on variable and transient phenomena and will closely interact with complementary astrophysical facilities, accepting triggers from them, enabling multi-wavelength and multi-messenger approaches that will lead to a deeper understanding of the broad-band non-thermal properties of target sources. To capture these phenomena during their evolution and for effective communication to the astrophysical community, the speed is crucial and can be achieved using the real-time analysis system for the fast identification of flaring events, from targeted observation to serendipitous discoveries during surveys. INAF is deeply involved in the development of CTA, in particular of the ASTRI Small Size Telescopes. The advisors of this proposal are participating in different scientific CTA working groups from extra-Galactic surveys to transients, have substantial experience on gamma-ray real-time domain astronomy (AGILE, Fermi, Integral), in the definition of strategies and systems for fast reaction to transients in the multi-messenger and multi-wavelength context. Proposed activities. In the following we depict three possible activities:

1) The ability to rapidly respond to external alerts is built into the CTA design. The candidate contributes to set strategies for CTA and ASTRI reaction to external transients (i.e. Radio-Loud AGN, gravitational waves, neutrinos, GRB, gamma-ray binaries, etc.); in particular, the purpose is to consider the potential variable sources that CTA may detect, how to identify them with the CTA real-time analysis and their likelihood, and how to select science alerts for the follow-up strategies based on scientific ranking and observatory constraints. The PhD candidate will focus the study on a specific class of transients.

2) The ability to rapidly issue science alerts is another key aspect of the CTA design. CTA will conduct a census of particle acceleration in the universe by performing surveys of the sky at unprecedented sensitivity at very high energies. An extragalactic survey will cover 25% of the total sky, with the primary objective to construct an unbiased very high-energy extragalactic source catalog. In addition to the detection of sources in a quiescent state, a potential discovery field could be a serendipitous detection of fast flaring sources. The candidate could contribute to consider the potential variable sources that CTA may discover during surveys, and define key strategies for their identification with the CTA real-time analysis. The focus is the serendipitous discovery of blazars in the transient state.

3) Among Radio-Loud AGN, radio galaxies are essential to address important issues related to the structure of the jets, the processes accelerating particles and their energy budget. They are also invoked as good extra-galactic cosmic-ray accelerators, thus possible sources of high-energy neutrinos (> 100 TeV). Unlike blazars, they offer a unique perspective to explore the jet at different scales, even regions where the relativistic plasma is still accelerating (as recently suggested by high-resolution radio studies). As a first step, the candidate will examine all the radio galaxies detected in the Fourth Fermi-LAT Catalog of AGN (4FGL). The gamma-ray spectral and temporal properties, combined with high-resolution radio observations, will be used to constrain the physical processes at work in the jet, and in particular, those leading to the emission of the high-energy particles. Once the PhD candidate has consolidated her/his understanding of the physical context, she/he will evaluate the best observational strategies for CTA to detect radio galaxies both in pointing and survey mode.

The successful candidate will learn high-energy data analysis techniques. The candidate will also gain experience in transients follow-up using the data of the current gamma-ray space missions. Based on the interests of the candidate, application of machine-learning techniques for the definition of observational strategies could be an additional benefit.

INAF1 – Project 4

“Hydrodynamicalsimulationsofyoungglobularclusters”

Supervisor: Francesco Calura (francesco.calura@inaf.it)

Dottorato di Ricerca in Astronomia (XXXV Ciclo), Università degli studi di Bologna Title of the proposed phd project: Hydrodynamical simulations of young globular clusters Supervisor: Francesco Calura - Osservatorio di Astrofisica e Scienza dello Spazio di Bologna In young globular clusters, the heating generated by first generation (FG) massive stars in the pre-supernova (SN) and supernova phases is sufficient to expel the metal-enriched gas even in the most massive (107 Msun) systems. In this thesis we plan to run hydrodynamical simulations to study the evolution of a young star cluster after all the FG supernovae have exploded, to test in which way such a system can re-accrete gas and form new stars, and which is the role played by the energetic feedback of newly born stellar generations in regulating its star formation history. We plan to use the RAMSES code (Teyssier 2002, A&A, 385, 337), a grid-based hydrodynamic code which includes an Adaptive Mesh Refinement (AMR) technique to reach a high resolution in regions of particular interest. The proposer of this thesis is well experienced with the use of such code. In the last few years, he has run several simulations aimed at describing a variety of physical environments (from a young globular cluster to an active galactic nucleus pumping energy into the intergalactic medium) whose results were included in various peer-reviewed publications (Calura et al., 2015, ApJ, 814, L14 [C15]; Gilli et al. 2017, A&A, 603, 69; Bellazzini et al. 2018, MNRAS, 476, 4565; Calura et al. 2019, MNRAS, submitted). As initial conditions, we plan to start with a gas-free system, when FG SNe have exploded and the most massive FG asymptotic giant stars are starting to return mass and energy into the system. Moreover, the cluster is embedded in a gas distribution (which may represent the disc of a galaxy at high redshift) and can re-accrete gas from it. The proposed setup will include the gravitational effect of first generations stars, the self-gravity of the gas, radiative cooling, mass return from aging stellar populations, an N-body solver to follow the motion of newly born stars, and finally the feedback released from second generation (SG) stars. In a work which is now submitted to MNRAS, we have already created a setup to describe a realistic physical environment for a star forming GC and we run a preliminary, limited set of simulations to test it. Such explorative simulations span a very limited portion of the parameter space, they lack several fundamental ingredients and are basically designed to set the ground for further, more extended studies. A few topics which can be developed with this thesis include: • A study of the effects of the feedback of massive stars on gas accretion. Such ingredient is

completely missing in previous studies and is fundamental in regulating second generation star formation. In the past, the stellar feedback of FG stars has already been investigated (C15) and it will be easy to implement such process in the setup described in this project.

• A survey of simulations aimed at exploring the SG formation in clusters with a broad range of different structural parameters (e. g., initial mass and size) and designed to follow the subsequent, long-term dynamical evolution of the cluster.

• A study of the spectral properties of the stellar populations, in order to compare them with the properties of real stellar clusters. The progenitors of globular clusters have recently been found at high redshift (z > 3) in gravitationally lensed fields, and some of them appear to be composed by two subcomponents, including a dense aggregate surrounded by a more diffuse component (Vanzella, Calura, Meneghetti et al. 2019, MNRAS, 483, 3618). With our suite of simulations and with the use of a spectrophotometric code, such as STARBUST99 (Leitherer et al. 2014), it will be possible not only to estimate the absolute magnitude of the system and compare it to the ones of real clusters, but also to compute light profiles and even to generate mock images, including also the distorsion generated by gravitational lensing (in collaboration with E. Vanzella and M. Meneghetti, INAF-OAS). The properties of the simulated clusters will also be compared with the ones of the youngest star clusters (with ages of ~ 2Gyr) hosting multiple populations and recently discovered in the Magellanic Clouds (e. g., Martocchia et al. 2018, MNRAS, 477, 4696), in collaboration with E. Dalessandro (INAF-OAS).

INAF1 – Project 5 “Massassemblyatz>2:galaxyandstructureformationinproto-clusters”

Supervisor: Olga Cucciati (olga.cucciati@inaf.it)

INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna - INAF PhD project -

Mass assembly at z>2: galaxy and structure formation in proto-clusters Supervisor: Olga Cucciati (INAF – OAS) – olga.cucciati@inaf.it Research group: Roberto Decarli (INAF-OAS), Margherita Talia (UniBo), Christian Vignali (UniBo), Micol Bolzonella (INAF-OAS), Lucia Pozzetti (INAF-OAS) Collaborations: VUDS and VANDELS teams Proto-clusters of galaxies are crucial sites for studying how mass build up in high-density regions of the early universe. Numerical simulations and semi-analytical models show for instance that proto-clusters at z~4 contribute up to 25% of the Cosmic Star Formation Rate Density (CSFRD) of the Universe, and comprise a fraction of the cosmic volume almost three orders of magnitude larger than at z=0. The CSFRD, that tells us the average rate at which stars are formed at all epochs in the universe, rises from the very early universe up to z~2, and then falls at z<2. Intriguingly, the hierarchical structure formation of DM structures plays a role in both the rise and fall of the CSFRD. Indeed, there are physical processes taking place in high-density regions of the universe which are able to enhance or to quench the star formation in galaxies. In particular, we expect to observe signatures of both kinds of processes in the redshift range 2<z<3, given the evolutionary state of DM structures at these epochs and the time scales for these processes to have some effect. The proposed project is focused on the study of proto-clusters identified in the VUDS and VANDELS spectroscopic surveys at 2<z<4. Both these surveys come with high-quality multi-wavelength data (from radio, to IR, optical and X-ray) , used and to be used to derive

galaxy properties. In particular, the interested student will 1) characterise the identified proto-clusters (total mass, shape, 3D distribution…), and infer their evolution with simulations and theoretical models; 2) analyse galaxy properties (SFR, stellar mass, gas content, spectral features, presence of AGN...) as a function of environment. This double approach will allow the student to constrain the evolution of both structures and galaxies. The analysis will include also comparisons with numerical simulations and semi-analytical models of galaxy evolution, to constrain how mass, at all levels, assembles in the universe. The interested student will work on data already available (like eg HST, ALMA, CHANDRA...), and will collaborate to prepare and apply for new observations with state-of-the-art instruments.

Fig.1 - The 3D shape of the Hyperion proto-supercluster at z=2.45 (Cucciati+2018)

INAF1 – Project 6

“Starclustersacrosscosmictime”

Supervisor: Emanuele Dalessandro (emanuele.dalessandro@inaf.it)

Starclustersacrosscosmictime

Supervisor:EmanueleDalessandroCollaborators:M.Bellazzini(INAF-OAS),F.Calura(INAF-OAS),L.Origlia(INAF-OAS),A.Sollima(INAF-OAS),E.Vanzella(INAF-OAS),F.R.Ferraro(Unibo),B.Lanzoni(Unibo),E.Vesperini(IndianaUniversity-USA),A.L.Varri(TokyoUniversity-Japan)

Globularcluster formation isan important, ifnot thedominant,modeof star formation in theearlyuniverse. Infact, the traditional view of star cluster evolution argues that all or most stars are born in star clusters thateventuallydisruptedonshorttimescales.Asaconsequence,understandingthephysicalprocessesatthebasisofglobular cluster formation has important implications in many astrophysical fields, ranging from the ionizationbudgetoftheearlyuniverse,totheglobalstellarmassassemblyofgalaxies,formationofmultiplepopulationsandtothescalesofthestarformationprocessitself. A large variety of models for stellar cluster formation have been put forward in therecentpast,howevertheinitialconditionsandthephysicalprocessesdrivingtheirgrowthandcharacterizingtheirearliestevolutionaryphasesareyettobeunderstood.Asamatteroffact,theformationofglobularclusters inacosmological context and their tangled connection with galactic nuclei and dwarf galaxies remains a majorchallengeinmodernastrophysicsattheinterfacebetweenstarandgalaxyformation.

Theproposedprojectaimsattacklingthisopenquestionbyfollowingtheformationandevolutionofstarclustersindifferent environments in our proximity, where stellar populations can be studied with great detail. In thisframeworktheprojectisfocusedonthreeideallocallaboratoriescharacterizedbysignificantlydifferentformationandenvironmentalproperties, suchas the innerandouterMilkyWaydiskand theMagellanicClouds.Themaintargetsofsuchanapproachare i)thesocalledYoungMassiveClustersandtheirsurroundingfields,whichsharethesamemass,structureandlifetimeofoldglobularspopulatingthebulgesandhalosofmanygalaxies,ii)youngclusters in gravitationally bound multiplets, which are possible ancestors of massive and old systems, and iii)regionsofongoingstarformation,asforexampletheScutumandPerseuscomplexesalongtheMilkyWayspiralarms.

Theprojectwillfollowthreemainlinesofinvestigation: 1)Constraining the initial conditionsof star formingcluster regions in theMilkyWaybyexploiting the6Dphasespace enabled by the ESA Gaia mission and large spectroscopic surveys. Compare observational results withtheoretical models and supply initial conditions for N-body models and ideal benchmarks for hydrodynamicalsimulations,whicharebeingdevelopedinourinstitute. 2)Characterizing thepresent-daypropertiesandconstraining the finalby-productsofbinary/multiple clusters inthecontextofmassiveanddynamicallycomplexsystemformation. 3)Derivingandreverse-engineeringpresent-daystructuralandkinematicpropertiesofmultiplepopulationsinoldclusterstotrackbacktheirinitialconditionsandevolution.

Thecharacterizationofthestellarcontentofthesesystemsintermsoftheirphotometricproperties,structuresandkinematicswillrepresentamilestoneinthefieldofclusteredstarformationandwillallowustotesti)theroleofenvironmentonclusterformation,ii)theinterplaybetweentherelativeimportanceofindividualclustersbecomingunbound due to gas expulsion as opposed to the hypothesis of hierarchical structure formation and iii) thecontributionofclusterformationonlargescalestructuresintheirhostgalaxies.

The project will take full advantage of a synergic use of available and future Gaia Data Releases and publiclyavailablephotometricandspectroscopicsurveys(suchasVISTA,CLASH,andAPOGEE).Inaddition,itwillmakeuse

ofaformidabledatasetofstate-of-theartproprietaryphotometryandspectroscopyobtainedinthelastyearswithHSTandground-basedfacilitiesattheESO-VLTandTNGtelescopes.

INAF1 – Project 7

“WitnessingtheculminationofstructureformationintheUniverse”

Supervisor: Stefano Ettori (stefano.ettori@inaf.it)

Title of the Project: Witnessing the culmination of structure formation in the Universe

Tutor: S. Ettori, M. Sereno, M. Meneghetti (INAF-OAS Bologna) MA di afferenza: 1.2 Scientific Case: Clusters of galaxies are the nodes of the Cosmic Web, constantly growing through accretion of matter along filaments and via occasional mergers. They are thus excellent laboratories for probing the physics of the gravitational collapse of dark matter and baryons, and for studying the non-gravitational physics that affects their baryonic component. As cluster growth and evolution depends on the underlying cosmology (through initial conditions, cosmic expansion rate and dark matter properties), their number density as a function of mass and redshift, spatial distribution and internal structure are powerful cosmological probes. Moreover, their matter content reflects that of the Universe (85% dark matter, ~12% X-ray emitting gas and 3% galaxies). The hot (T~108 K) tenuous intracluster medium (ICM) accounts for the vast majority (~85%) of their baryonic content, and is observable in two main complementary ways: X-ray, through bremsstrahlung emission, and Sunyaev-Zeldovich effect due to the Inverse Compton of CMB photons over ICM electrons. On the clusters’ properties, many questions are still to be answered: What is the exact imprint of the formation process on the equilibrium state of clusters and how does this impact our ability to weigh them through their baryon signature? What is the true cluster mass scale? What are the statistical properties of the `true' cluster population? How does cluster detectability depend on baryon physics? Can we define a fully consistent evolutionary sequence from z=2 to z=0, over the full mass range? Outline of the Project: the student will study the ultimate products of structure formation in mass and cosmic time, investigating to what extent the ICM is in equilibrium in the dark matter potential, as a function of mass and radius. The analysis will be based on one of the only 2 XMM-Newton AO-17 "Multi-Year Heritage” programs assigned (oversubscription factor of 10; PI: Ettori; coI: Sereno, Meneghetti), that will use 3 Msec to follow-up the 80 remaining candidates in the next 3 years (starting with Spring 2018) of a Planck-SZ-selected sample of 118 objects. This large, unbiased, signal-to-noise limited sample (and, thus, very close to be mass-selected) is built to become the de facto reference for clusters in the local volume and in the high mass regime. Archived Chandra and XMM data will be used to extend the results of these dedicated programs. By resolving spatially the thermodynamic properties of these 118 objects out to the virial radius, we will reconstruct how the dominant baryonic component (aka the hot plasma traced through X-ray and SZ effect) distributes, whether it is in equilibrium within the gravitational potential and how its observational properties correlate with the other multi-wavelength proxies. Combined with data in other wavelengths (radio, optical) and dedicated hydrodynamical simulations, the above described datasets will provide results that will significantly impact our knowledge on (i) the dynamical collapse of the gas on different scales; (ii) the relative importance of gravitational and non-gravitational processes in shaping cluster properties. The student will be part of the international collaboration actively involved in the Heritage project and will work in close collaboration with the PI and Co-Is to fully exploit (primarily) the X-ray and lensing data of this unique and extraordinarily rich dataset in the interpretation of the thermodynamic properties of the collapsed ICM.

INAF1 – Project 8

“High-zAGNinthemid-andfar-IRdomain”

Supervisor: Carlotta Gruppioni (carlotta.gruppioni@inaf.it)

INAF - Osservatorio di Astrofisica e Scienza dello Spazio di Bologna (OAS)

Proposal for one PhD fellowship

High-z AGN in the mid- and far-IR domain

Summary: We propose a PhD project aimed at studying the detectability of high-z (>5) QSOs, their dust amount and properties with the future space mission SPICA, that will be operating at mid- and far-IR wavelengths. Based on the spectral properties of the local and high-z QSOs, we will create simulated spectra in the range covered by JWST, SPICA and ALMA (e.g., from the near-infrared to the millimeter), and will exploit the scientific potential of long-wavelength observations in this kind of studies. The dust properties, either in the quasar host or in the torus around the nucleus, will be modeled by means of galaxy chemical evolution models, in order to understand the evolution of dust and heavy elements from the early Universe to nowadays. Finally, our expected high-z QSO number counts and densities will be compared with the predictions from cosmological simulations.

Background:

Observations in the far-IR and sub-mm regime of the high redshift QSOs can trace the rest-frame mid-/far-infrared emission in the quasar host, as well as key diagnostic lines of their interstellar medium. Observation in these wavebands, especially high sensitivity and high resolution spectroscopic ones, will be crucial to understand the ISM properties (gas and dust) in the brightest and remote objects in the Universe (e.g., Decarli et al. 2018, ApJ, 854, 97; Venemans et al. 2018, ApJ, 866, 159).

The future Space Infrared telescope for Cosmology and Astrophysics (SPICA) is a proposed ESA M5 mission, whose main scientific goal is to explore the dusty/dust-obscured Universe, both near and far, by conducting sensitive imaging and spectroscopic observations in the mid-/far-infrared (Roelfsema et al. 2018, PASA, 35, 30).

The SPICA Mid-Infrared Instrument (SPICA/SMI) has the ability to conduct low-resolution (LR; R = 50– 120) multi-slit prism spectroscopy covering 17–36µm over a field of view of 12’�10’. It also has a slit-viewer camera (CAM), which can perform 34 µm imaging over the same field of view. These SMI modes will allow wide-field survey programs (Gruppioni et al. 2017, PASA, 34, 55; Kaneda et al. 2017, PASA, 34, 59) particularly effective for detecting AGN-dominated galaxies, which can be substantially brighter than star-forming galaxies in the rest- frame mid-infrared. In fact, at z > 5, SMI will be observing at wavelengths < 6 µm in the rest-frame, where the SEDs of typical star-forming galaxies exhibit a broad trough between a stellar continuum peaking in the near-infrared and a dust continuum peaking in the far-infrared (see, Gruppioni et al. 2017, PASA, 34, 55). In the case of AGN-dominated galaxies, however, a bright power-law AGN continuum could fill this SED trough, and could even overwhelm the light from the host galaxy all together. As a result, the SMI-selected sample of z > 5 ULIRGs is expected to be dominated by galaxies with AGN (Gruppioni et al. 2017, PASA, 34, 55; Kaneda et al. 2017, PASA, 34, 59). Such a sample will be particularly useful for studying the interplay between star formation and black-hole accretion close to the re-ionisation epoch (Spinoglio et al. 2017, PASA, 34, 57; Gruppioni et al. 2017, PASA, 34, 55).

The high-z AGN will then be observed by SPICA’s far-infrared spectrometer SAFARI, which will probe a spectral range (35–230 µm) that will be unexplored by ALMA and JWST. SAFARI will be capable of delivering good-quality spectra for luminous infrared quasars at z = 5 − 10, allowing us to sample spectral features in the rest-frame mid-infrared and to investigate several key scientific issues, such as the relative importance of star formation versus AGN, the hardness of the radiation field, the level of chemical enrichment, and the

properties of the molecular gas (Egami et al. 2018, PASA, 35, 48). For instance, Kaneda et al. (2017) predict that 50 M

¤ of dust will be detectable with SPICA in QSOs at z~10,

thanks to high dust temperature and silicate and carbonaceous features.

However, the SMI mid-infrared surveys providing the primary high-z AGN selection will see a large number of foreground galaxies, among which a small number of high-redshift objects will be hidden. Selecting dusty z > 5 quasars will therefore require a detailed analysis of good-quality multi-wavelength data and accurate simulated spectra. Therefore, accurate simulations of quasar spectra in the mid- and far-IR domain and of their expected number counts (based on evolutionary models and constraints from optical and mm observation) will be crucial to predict what SPICA will be able to detect.

Main Science Goals:

a) Quasars detectability with SPICA (simulated spectra and number densities): based on the data available in the literature, from the optical/near-IR to the mm, for z > 5 quasars (e.g., Decarli et al., 2018, ApJ, 854, 97), and on the local relations derived between the emission line luminosity and the AGN and host galaxy properties (e.g., Gruppioni et al., 2016, MNRAS, 458, 4297), the PhD student will create synthetic spectra of quasars + host galaxy in the infrared regime and perform accurate simulations of quasars surveys in the observed mid-/far-IR wavelength range (i.e., in the range covered by SPICA). This work, combined with evolutionary predictions for quasars, will then provide number counts/density and limiting fluxes (e.g. detectability properties) of quasars to be observed by the SPICA instruments.

b) ISM physical properties and evolution (chemical evolution models): the simulated quasar spectra and number densities will be interpreted in terms of dust and chemical elements properties and evolution by considering galaxy chemical evolution models (e.g., Calura et al. 2017, ), to derive scaling relations and their evolution with redshift.

Thesis Plan:

The candidate will dedicate the first part of the thesis to create simulated spectra of Quasars and their hosts in the mid-IR to mm regime, and to predict the expected high-z (> 5) quasar density in the SPICA range by using multi-wavelength quasar survey data, from the SDSS to Spitzer, Herschel and ALMA, as constraints. The high-z quasar detectability with the SPICA instruments (either imager or spectrograph) will then be studied, together with the physical properties of the quasars and their hosts, obtainable from the SPICA-SAFARI and -SMI spectra. The second part of the thesis will be dedicated to detailed studies of the dust and gas properties and evolution in quasar hosts, by collecting data in the literature and modeling the data with galaxy chemical evolution models (Calura et al., 2014, MNRAS, 438, 2765). The first two/three months will be dedicated to the study of the astrophysical context: quasar physical properties, evolution, optical/mid-/far-IR/sub-mm/mm survey results, mid- and far-IR spectroscopy, the SPICA instruments.

1) About six months will be devoted to the collection of high-z quasar survey data from the literature and to the construction of simulated quasar + host galaxy spectra in the IR/mm domain.

2) About one year will be needed to create a simulated quasar survey detected by SPICA, by combining the simulated spectra with phenomelogical/cosmological evolutionary models. This will be fundamental to optimise the selection/observation of high-z (>5) AGN (first selected in 34-µm images, then followed-up with the SMI and SAFARI spectrometers). The different line detectability will be simulated by using local relations between the IR line luminosity and galaxy and AGN physical properties, like the bolometric AGN luminosity and the star formation rate.

3) About one year will be devoted to the study of the dust and gas properties and evolution, by comparing the simulated results with chemical evolution models.

4) The last three/four months will be dedicated to put the whole project within context, by interpreting the results in light of the previous work from the literature and of the future SPICA observations.

Supervisor: C. Gruppioni (INAF OAS) [Scientific Co-Investigator of the SPICA-SAFARI instrument, leader of the SPICA photometric survey WG and white paper]

Collaborators: R. Decarli (INAF OAS) [World expert of high-z quasars] F. Calura (INAF OAS) [Expert of galaxy chemical evolution models and dust evolution] F. Pozzi (DIFA UniBO referent) [Expert in statistical properties of infrared galaxy and AGN]

PhD Project in the INAF and International Context:

The SPICA project is made up of partners from Europe, Japan and North America. The far-infrared instrument SAFARI is to be provided by a consortium of European, Canadian and US institutes. The SAFARI consortium is lead by SRON for the Netherlands, with as major partners Spain and France, and further significant contributions from Italy, Belgium, Canada, Germany, the UK, Austria, Switzerland, Sweden and the US. The mid-infrared imager/spectrometer, SMI, will be developed by a Japanese university consortium with support by JAXA.

The perspective student will work within the international context of the SPICA collaboration, will attend the international consortium meetings and will be in contact with all the SPICA partners. He/she will participate actively to the preparatory scientific work needed to plan the surveys and to provide the scientific requirements to the mission.

He/she will also be part of the Italian SPICA Team, coordinated by INAF.

The perspective student will also have the opportunity to be involved in a well-established, world-wide network of experts on the studies of high-z quasars, involving researchers at the Max Planck Institute for Astronomy in Heidelberg, Germany, at the Cornell University and the University of Arizona, USA, and the Peking University, China.

Selected Publications on the Subject by the proposers of this project:

• Calura et al.,2014, MNRAS, 438, 2765 • Calura, Pozzi et al., 2017, MNRAS, 465, 54 • Decarli et al., 2017, Nature, 545, 457 • Decarli et al., 2018, ApJ, 854, 97 • Gruppioni et al., 2016, MNRAS, 458, 4297 • Gruppioni et al., 2017, PASA, 34, 55 • Pozzi, Calura, Gruppioni et al., 2015, ApJ, 803, 35 • Venemans, Decarli et al., 2018, ApJ, 866, 59

INAF1 – Project 9 “Stronglensingasaprobeofthenatureofdarkmatter:constraintsonthe

clustersubhalopopulation”

Supervisor: Massimo Meneghetti (massimo.meneghetti@inaf.it)

Title of the project: “Strong lensing as a probe of the nature of dark matter: constraints on the cluster sub-halo population” INAF tutor: Massimo Meneghetti (INAF-OAS), MA di afferenza 1.2 Collaboration: P. Rosati, C. Giocoli (UniFE), L. Moscardini, M. Baldi (UniBO), C. Grillo (UniMI), P. Natarajan (Yale), G. Despali (Max Planck Institut fuer Astrophysik). Scientific case: In the framework of the hierarchical model of structure formation, compatible with the standard cold-dark-matter (CDM) paradigm, galaxy clusters are formed at relatively late epochs through the assembly of smaller structures. These are expected to survive in form of cluster sub-halos for some time after accretion, developing characteristic mass and radial distribution functions. Depending on the nature of dark matter particles, whether they are heavy, collisionless particles or not, the properties of cluster sub-halos would change. For example, the CDM model predicts that the Universe should be clumpy all the way to the smallest sub-solar scales and that a rich population of low-mass structures should exist. Conversely, the high-mass end of the mass function is expected to fall-off exponentially. Models that assume a warm dark matter (WDM) particle predict the existence of much fewer low-mass structures and the presence of a cut-off mass below which the dark matter distribution should be smooth. Scenarios in which the dark-matter particles are collisional, with cross sections which may even depend on the particle velocity, can lead to even more complex modifications of the subhalo mass function. Thus, investigating the small scale structure of galaxy clusters, both observationally and theoretically, is of utmost importance as its probe is a potentially very powerful test of the nature of dark matter. Outline of the project: The candidate will characterize the sub-halo population of the clusters in the CLASH-MUSE sample. These are massive galaxy clusters which have been targeted by the Hubble Space Telescope as part of the CLASH Multi-Cycle-Treasury programme (PI Postman) and of the Frontier Fields Initiative (PI Lotz). Follow-up spectroscopic observations of these systems were carried out with instrumentations at the ESO’s VLT, in particular with the integral field spectrograph MUSE and with VIMOS (PI Rosati). The candidate will use observations of strong gravitational lensing effects occurring both on large scales (cluster-galaxy lensing) and on small scales (galaxy-galaxy lensing) to build robust models of the total cluster mass distribution and to measure the mass in sub-halos. To this goal, she/he will combine strong-lensing and dynamical measurements (internal kinematics of cluster galaxies measured with MUSE). The existing methodologies to perform the mass reconstructions will be extended in order reach higher accuracies by implementing new algorithms to model the effects of substructures as perturbations of the smooth cluster gravitational potential, using their imprint on the lensed images of extended sources (gravitational arcs). In a second step, the candidate will compare the results of the observational analysis to new numerical simulations performed with different assumptions on the properties of the dark-matter particle candidates. She/he will start with a sample of ~30 massive galaxy clusters obtained from N-body hydrodynamical simulations in the framework of the CDM paradigm. The same simulations will be repeated in the context of alternative models of DM (fuzzy dark matter, self interacting dark matter, etc). She/he will also use semi-analytical methods to produce mock cluster mass distributions (using e.g. the code MOKA, Giocoli et al, 2012) for investigating the sensitivity of the lensing signal to changes of several structural properties of the clusters. Finally, she/he will test the accuracy of the lens models by using mock HST and spectroscopic observations of synthetic lenses, obtained with the software SkyLens (Meneghetti et al. 2017).

INAF1 – Project 10 “ThemysteriousFastRadioBurstandtheirpossiblelinkwithGravitational

Waves”

Supervisor: Luciano Nicastro (luciano.nicastro@inaf.it)

ProposalforanINAFPhDFellowship

ThemysteriousFastRadioBurstsandtheirpossiblelinkwithGravitationalWaves

Supervisors: Luciano Nicastro (INAF, OAS Bologna)Co-Advisors: Lorenzo Amati, Andrea Bulgarelli, Eliana Palazzi, Elena Pian, Andrea Rossi, Giulia Stratta (INAF, OAS Bologna)Contact person at DIFA: Marcella Brusa (DIFA and INAF, OAS Bologna) Context. Fast Radio Bursts are bright, ms-long bursts of radio waves likely of extragalactic origin. They were serendipitously identified in surveys from the Parkes telescope since 2007, and have now been detected by several observatories (e.g., Arecibo, Green Bank, Molonglo, ASKAP, CHIME). An increasing number of them is nowadays known to repeat with non-periodic signal. Repetition allows to secure sub-arcsecond location, enabling to identifying the host galaxy characteristics, and in principle to measure the cosmological redshift. While the discovery of the “repeaters” FRBs is a major leap forward which created a wave of excitement in the field, still a large fraction of the FRB population have not been seen to repeat, despite extensive follow-up campaigns. A sensitivity limit is a possibility, but recently it has been suggested that there is strong evidence for more than one population of FRBs. Current estimates on the redshift values of FRBs are z ≈ 0.2–1, corresponding to energies of � 1038–1040 erg and rates of � 10−3 yr−1 per galaxy. The uncertainty in the of FRB location and distance has led to a plethora of progenitor models. It is possible that they are due to a repeating phenomenon such as giant pulses from neutron stars (NSs) or bursts from magnetars, as suggested by the repeating FRB 121102. FRBs that do not repeat could originate from cataclysmic events in compact objects, such as merger of NSs or white dwarfs, or the collapse of a fast spinning, hyper-massive NS into a black hole. FRBs may be connected also with gamma-ray bursts (GRBs), going off shortly after the gamma-ray event. GRBs of the short-duration kind are expected to be produced in binary compact objects merger, which also emit an (isotropic) optical/NIR signal called “kilonova”. Interestingly, almost all the proposed progenitors are expected to emit a simultaneous signal of high frequency (10-1000 Hz) gravitational waves (GWs) that can be detected with the current and future generation of modified Michelson interferometers as the two Advanced LIGO in USA and Advanced Virgo in Italy. The expected diversity in the properties of the GW signals is a potential diagnostic in disentangling different FRB progenitor models. At the same time, FRBs can potentially provide a unique electromagnetic signal to GW events, providing precise source sky localizations and increasing the statistical confidence on the astrophysical origin for sub-threshold GW signals, a precious resource for the GW detectors of the current and future era. INAF is deeply involved in the multi-band follow-up observational campaigns of GRBs afterglows and their host galaxies and of the electromagnetic counterpart of GW sources. Moreover, an increasing activity has been devoted in the last two years to the search of FRBs multi-band counterparts (from optical to gamma ray bands). The advisors of this proposal have long standing experience in the observations of fast transient astrophysical sources that require dedicated and challenging observational strategies in a multi-messenger and multi-wavelength contexts and are part of several international collaborations aimed at the optimizations of these type of follow-up campaigns (e.g. the GRAvitational WAves INAF TeAm, ENGRAVE, CIBO, etc.). Proposed activities. In the already defined context, the work plan and the proposed activities also depend on the scientific and technological interests of the candidate. In the following we depict three possible activities for the candidate:

1) To contribute to set observational strategies for multi-band follow-up campaigns to FRBs, as well as to GW sources and GRBs, focussing on the study of FRBs.

2) To perform multi-band data analysis, both for large and narrow field instruments. 3) To contribute to the development of new methodologies for the management and exploitation of data from a

variety of instruments, in particular optical and infrared. The successful candidate will learn optical and NIR data analysis techniques and is expected to acquire some basic theoretical background on compact objects physics and to contribute to the interpretation of the data in a multi-band and multi-messenger context. Based on the interests of the candidate, additional studies of other interesting classes of astrophysical transient sources serendipitously discovered in the follow-up campaigns could also be performed. The candidate, depending on his/her interest, will also be able to learn how to use and implement database and web tools useful to manage the collected data. Founded through INAF, OAS contribution.