Black holes, gravitational waves and fundamental physics: a roadmap

The grand challenges of contemporary fundamental physics—dark matter, dark energy, vacuum energy, inflation and early universe cosmology, singularities and the hierarchy problem—all involve gravity as a key component. And of all gravitational phenomena, black holes stand out in their elegant simplicity, while harbouring some of the most remarkable predictions of General Relativity: event horizons, singularities and ergoregions. The hitherto invisible landscape of the gravitational Universe is being unveiled before our eyes: the historical direct detection of gravitational waves by the LIGO-Virgo collaboration marks the dawn of a new era of scientific exploration. Gravitational-wave astronomy will allow us to test models of black hole formation, growth and evolution, as well as models of gravitational-wave generation and propagation. It will provide evidence for event horizons and ergoregions, test the theory of General Relativity itself, and may reveal the existence of new fundamental fields. The synthesis of these results has the potential to radically reshape our understanding of the cosmos and of the laws of Nature. The purpose of this work is to present a concise, yet comprehensive overview of the state of the art in the relevant fields of research, summarize important open problems, and lay out a roadmap for future progress. This write-up is an initiative taken within the framework of the European Action on 'Black holes, Gravitational waves and Fundamental Physics'

Simulacije opazovanj plimskega raztrganja zvezd z Velikim sinoptičnim pregledovalnim teleskopom

The Large Synoptic Survey Telescope (LSST) will produce a multi-colour survey of 25000 square deg of the Southern sky during its 10 years of operations. It will observe over 20 billion galaxies and a similar number of stars, map the Solar System and the Milky Way, and probe dark matter and dark energy. In addition, it will discover thousands of transients every night, including new classes of objects, which have not yet been observed. Due to its large coverage of the sky it will be a perfect tool for the search of rare Tidal Disruption Events (TDEs), which occur when a star passes close by a supermassive black hole and gets disrupted by its tidal force. Afterwards the stellar debris fall back to the black hole, initially at a rate exceeding the Eddington rate, producing an outflow, which releases a flare of energy. When the fallback rate subsides below the Eddington rate, the gas accretes onto the black hole via accretion disk. The LSST simulation framework enables us to simulate observations of different types of objects with the LSST. In this work, we include TDEs in the LSST simulation framework, estimate the number of detected TDEs, and simulate their light curves using a theoretical model, which predicts a t^(-2.6) light curve decline with time in the outflow phase and a t^{-0.4} decline in the disk phase. We also take a closer look at the distribution of the detected TDEs over cosmological redshift and black hole mass.Veliki sinoptični pregledovalni teleskop (LSST) bo predvidoma 10 let opazoval 25000 kvadratnih ločnih stopinj veliko območje južnega neba in s tem ustvaril večbarvni pregled neba. V času delovanja bo opazoval 20 milijard galaksij in podobno število zvezd, kartiral Sončev sistem in Galaksijo, ter raziskoval temno snov in temno energijo. Poleg tega bo vsako noč odkril na tisoče tranzientnih dogodkov, med njimi pa bo odkrival tudi takšne objekte, ki do zdaj še niso bili opaženi in so nam še neznani. Ker bo LSST s svojimi opazovanji pokril zelo velik del neba, bo teleskop odlično orodje za iskanje redkih pojavov plimskega raztrganja zvezd. Do plimskega raztrganja zvezde pride, ko se zvezda znajde dovolj blizu supermasivni črni luknji, da lahko njena plimska sila raztrga zvezdo. Po raztrganju ostanki zvezde padajo proti črni luknji. V začetni fazi je količina padanja snovi večja od Eddingtonove limite, zaradi česar snov odpihne iz sistema, nastali veter pa odda blišč svetlobe. Ko količina materiala, ki se vrača proti črni luknji, pade pod Eddingtonovo limito, zvezdni plin pada v črno luknjo prek akrecijskega diska. Simulacijsko orodje teleskopa LSST omogoča simulacije opazovanj različnih vrst objektov s tem teleskopom. V delu smo v simulacijsko orodje teleskopa LSST vključili dogodke plimskih raztrganj zvezd, ocenili število odkritih dogodkov in simulirali njihove svetlobne krivulje. Pri tem smo uporabili teoretični model svetlobne krivulje, ki napoveduje časovno odvisnost svetlobne krivulje plimskih raztrganj zvezd t^(−2.6) v fazi vetra in t^(-0.4) v fazi akrecijskega diska. Podrobneje smo predstavili tudi porazdelitev opazovanih plimskih raztrganj po oddaljenosti oziroma kozmološkem rdečem premiku in masi supermasivne črne luknje

Observing TDEs in the era of LSST

The upcoming Large Synoptic Survey Telescope (LSST) will observe ~18000 square degrees of the Southern sky and is expected to discover thousands of transients every night due to its large coverage of the sky and its observing strategy. Being an exceptional transient hunter, we expect the LSST to increase the current observed sample of Tidal Disruption Events (TDEs) by a factor of ~1000 in 10 years of survey duration. TDEs are one of the only probes of dormant supermassive black holes in the Universe, and if their observed optical light curves are sampled frequently enough, TDEs can serve as indicators of SMBH mass. In this talk I will present our simulations of TDE observations with LSST, the resulting SMBH mass distributions of observed TDEs, and the efficiency of different proposed observing strategies of LSST in finding these rare transients

TDEs with LSST

The Large Synoptic Survey Telescope (LSST) is an upcoming ground-based survey telescope in Chile, which will produce a multi-color survey of 18000 square degrees of the Southern Sky during its 10 years of observations. Due to its large coverage of the sky and its observing strategy it will be a perfect tool in search for transient astrophysical events, including rare Tidal Disruption Events (TDEs). TDEs occur when a star passes close by a supermassive black hole (SMBH) in a center of a galaxy and gets disrupted by its tidal forces. These events emit a bright flare of light, which can be observed to cosmological distances. In the seminar I will provide an overview of the LSST and TDEs, and present the preliminary results on the estimated absolute rates of TDE detection in 10 years of LSST operations, which were obtained by simulations of TDE light curves with an end-to-end LSST simulations framework

Plimski blišči skozi oči observatorija Vere C. Rubin

Tidal Disruption Events (TDEs) are rare transients, which are considered to be promising tools in probing supermassive black holes (SMBHs) and their environments in quiescent galaxies, accretion physics, and jet formation mechanisms. The majority of $approx$ 60 detected TDEs has been discovered with large field of view time-domain surveys in the last two decades. Currently, about 10 TDEs are discovered per year, and we expect this number will increase largely once the Legacy Survey of Space and Time (LSST) at Vera C. Rubin Observatory begins its observations. In this work we demonstrate and explore the capabilities of the LSST to study TDEs. To begin with, we simulate LSST observations of TDEs over $10$ years of survey duration by including realistic SED models from MOSFiT into the simulation framework of the LSST. SEDs are then converted into observed fluxes and light curves are simulated with the LSST observing strategy minion_1016. Simulated observations are used to estimate the number of TDEs the LSST is expected to observe and to assess the possibility of probing the SMBH mass distribution in the Universe with the observed TDE sample. We find that the LSST has a potential of observing ~1000 TDEs per year, the exact number depending on the SMBH mass distribution and the adopted observing strategy. In spite of this large number, we find that probing the SMBH mass distribution with LSST observed TDEs will not be straightforward, especially at the low-mass end. This is largely attributed to the fact that TDEs caused by low-mass black holes ($le 10^6 M_odot$) are less luminous and shorter than TDEs by heavier SMBHs ($> 10^6 M_odot$), and the probability of observationally missing them with LSST is higher. Second, we built a MAF TDE metric for photometric identification of TDEs based on LSST data. We use the metric to evaluate the performance of different proposed survey strategies in identifying TDEs with pre-defined identification requirements. Since TDEs are blue in color for months after peak light, which separates them well from SNe and AGN, we include u-band observations as one of the criteria for a positive identification. We find that the number of identified TDEs strongly depends of the observing strategy and the number of u-band visits to a given field in the sky. Observing strategies with a larger number of u-band observations perform significantly better. For these strategies up to 10% of LSST observed TDEs satisfy the identification requirements.Plimski blišči so redki tranzientni izvori svetlobe v vesolju, ki nastanejo ob plimskem raztrganju zvezde v bližini črne luknje. Z njimi lahko preučujemo supermasivne črne luknje v neaktivnih galaksijah in fizikalne pogoje v njihovih okolicah, fiziko akrecije ter mehanizme nastanka relativističnih curkov. Večina od približno 60 znanih plimskih raztrganj zvezd je bila odkrita v zadnjih dveh desetletjih s širokokotnimi pregledi neba, trenutno pa je odkritih okoli 10 novih dogodkov na leto. Pričakujemo, da bo prihodnji pregled neba ``Legacy Survey of Space and Time\u27\u27 (LSST) na observatoriju Vere C. Rubin omogočil opazovanja velikega števila plimskih bliščev. V tem delu predstavimo zmogljivosti pregleda neba LSST za preučevanje plimskih raztrganj zvezd. Najprej simuliramo opazovanja plimskih raztrganj zvezd med desetimi leti trajanja pregleda neba LSST. V simulacijsko orodje teleskopa LSST vključimo realistična plimska raztrganja zvezd in njihove spektralne porazdelitve energije. Slednje izračunamo z modelom MOSFiT. Svetlobne krivulje različnih dogodkov simuliramo z opazovalno strategijo minion_1016, jakost svetlobe ob določenem času pa izračunamo iz spektralne porazdelitve energije. Na podlagi simuliranih opazovanj ocenimo število plimskih raztrganj zvezd, ki bi jih LSST lahko odkril ter preučimo, kako uporaben je opazovan vzorec za določanje porazdelitve črnih lukenj v središčih galaksij po njihovih masah. Ugotovimo, da lahko LSST odkrije ~1000 novih plimskih raztrganj zvezd na leto, natančno število je odvisno od privzete porazdelitve črnih lukenj po masah ter od opazovalne strategije. Kljub velikemu številu zaznanih plimskih raztrganj zvezd ugotovimo, da določanje porazdelitve črnih lukenj po njihovih masah ne bo enostavno. Plimska raztrganja zvezd, ki vključujejo manj masivne črne luknje ($le 10^6 M_odot$), so manj svetla in krajša od tistih, ki jih povzročijo bolj masivne črne luknje ($> 10^6 M_odot$). Verjetnost, da bo LSST takšne dogodke zgrešil, je velika, posledično pa je težko določiti porazdelitev črnih lukenj po masah za manj masivne črne luknje. V drugem delu disertacije predstavimo metriko MAF za fotometrično identifikacijo plimskih raztrganj zvezd na podlagi podatkov pregleda neba LSST. Metriko uporabimo za oceno zmogljivosti različnih predlaganih opazovalnih strategij teleskopa pri prepoznavanju plimskih raztrganj zvezd s predhodno določenimi merili za identifikacijo. Za razliko od supernov in aktivnih galaktičnih jeder so plimski blišči modre barve in ostanejo modri še nekaj mesecev po vrhu svetlosti. Kot enega od meril za identifikacijo zato vključimo opazovanja v filtru u. Ugotovimo, da je število identificiranih plimskih raztrganj zvezd močno odvisno od privzete opazovalne strategije in od števila opazovanj določenega polja na nebu v filtru u. Opazovalne strategije z večjim številom opazovanj v filtru u so bistveno boljše za fotometrično prepoznavanje plimskih raztrganj zvezd. Pri njih do 10% opazovanih dogodkov izpolnjuje kriterije za identifikacijo, opredeljene v metriki

Observing TDEs in the era of LSST

The upcoming Large Synoptic Survey Telescope (LSST) will observe ~18000 square degrees of the Southern sky and is expected to discover thousands of transients every night due to its large coverage of the sky and its observing strategy. Being an exceptional transient hunter, we expect the LSST to increase the current observed sample of Tidal Disruption Events (TDEs) by a factor of ~1000 in 10 years of survey duration. TDEs are one of the most promising phenomena in the study of dormant supermassive black holes (SMBHs) in the Universe, and if their observed optical light curves are sampled frequently enough, TDEs can serve as indicators of SMBH mass. We present our simulations of TDE observations with the LSST, the resulting SMBH mass distributions of observed TDEs, and the efficiency of different proposed observing strategies of the LSST in finding these rare transients

Simulacije opazovanj plimskega raztrganja zvezd z Velikim sinoptičnim pregledovalnim teleskopom

The Large Synoptic Survey Telescope (LSST) will produce a multi-colour survey of 25000 square deg of the Southern sky during its 10 years of operations. It will observe over 20 billion galaxies and a similar number of stars, map the Solar System and the Milky Way, and probe dark matter and dark energy. In addition, it will discover thousands of transients every night, including new classes of objects, which have not yet been observed. Due to its large coverage of the sky it will be a perfect tool for the search of rare Tidal Disruption Events (TDEs), which occur when a star passes close by a supermassive black hole and gets disrupted by its tidal force. Afterwards the stellar debris fall back to the black hole, initially at a rate exceeding the Eddington rate, producing an outflow, which releases a flare of energy. When the fallback rate subsides below the Eddington rate, the gas accretes onto the black hole via accretion disk. The LSST simulation framework enables us to simulate observations of different types of objects with the LSST. In this work, we include TDEs in the LSST simulation framework, estimate the number of detected TDEs, and simulate their light curves using a theoretical model, which predicts a t^(-2.6) light curve decline with time in the outflow phase and a t^{-0.4} decline in the disk phase. We also take a closer look at the distribution of the detected TDEs over cosmological redshift and black hole mass.Veliki sinoptični pregledovalni teleskop (LSST) bo predvidoma 10 let opazoval 25000 kvadratnih ločnih stopinj veliko območje južnega neba in s tem ustvaril večbarvni pregled neba. V času delovanja bo opazoval 20 milijard galaksij in podobno število zvezd, kartiral Sončev sistem in Galaksijo, ter raziskoval temno snov in temno energijo. Poleg tega bo vsako noč odkril na tisoče tranzientnih dogodkov, med njimi pa bo odkrival tudi takšne objekte, ki do zdaj še niso bili opaženi in so nam še neznani. Ker bo LSST s svojimi opazovanji pokril zelo velik del neba, bo teleskop odlično orodje za iskanje redkih pojavov plimskega raztrganja zvezd. Do plimskega raztrganja zvezde pride, ko se zvezda znajde dovolj blizu supermasivni črni luknji, da lahko njena plimska sila raztrga zvezdo. Po raztrganju ostanki zvezde padajo proti črni luknji. V začetni fazi je količina padanja snovi večja od Eddingtonove limite, zaradi česar snov odpihne iz sistema, nastali veter pa odda blišč svetlobe. Ko količina materiala, ki se vrača proti črni luknji, pade pod Eddingtonovo limito, zvezdni plin pada v črno luknjo prek akrecijskega diska. Simulacijsko orodje teleskopa LSST omogoča simulacije opazovanj različnih vrst objektov s tem teleskopom. V delu smo v simulacijsko orodje teleskopa LSST vključili dogodke plimskih raztrganj zvezd, ocenili število odkritih dogodkov in simulirali njihove svetlobne krivulje. Pri tem smo uporabili teoretični model svetlobne krivulje, ki napoveduje časovno odvisnost svetlobne krivulje plimskih raztrganj zvezd t^(−2.6) v fazi vetra in t^(-0.4) v fazi akrecijskega diska. Podrobneje smo predstavili tudi porazdelitev opazovanih plimskih raztrganj po oddaljenosti oziroma kozmološkem rdečem premiku in masi supermasivne črne luknje