What will it mean to be a gravitational wave astronomer? Alberto Vecchio Imaging the future: Gravitational wave astronomy Penn State 27 th – 30 th October, 2004

Outline Some general remarks Three possible research projects Conclusions Imaging the future: GW astronomy A Vecchio

Gravitational waves provide a new and unique view of the universe “orthogonal” to ordinary astronomy –Astronomy –Cosmology –Fundamental physics Imaging the future: GW astronomy A Vecchio Gravitational wave astronomy

Astronomy in a new frequency band Tests of the behaviour of gravity in the strongly non- linear relativistic regime A new arena for fundamental physics and the exploration of fundamental fields at high energy and early cosmic times Gravitational wave astronomy Imaging the future: GW astronomy A Vecchio

Are GW astronomers “special”? Is there a fundamental difference between a GW astronomer and a radio/x-ray/optical/… astronomer? –No: then we should simple learn from what astronomers have done in the past and act consequently –Yes: then may be our approach ought to be different from “traditional astronomy” We have had a long time to prepare gravitational wave astronomy; this is surely not the case for the other frequency bands –Is it necessary good? –Is there the danger that “the unexpected” does not have a place in our plan, so that we won’t be ready for it? We want to do all in one go: all-sky, all-frequency, all-sources surveys of the GW sky Imaging the future: GW astronomy A Vecchio

Three possible research projects for a (GW) astronomer Black hole demographics and channels of black hole formation EM radiation in GW bursts Mapping the early universe Imaging the future: GW astronomy A Vecchio

Instruments Several ground-based interferometers (>) 3 in US 2 in Europe 1 in Japan And possibly one in China and one in Australia A few very-high frequency resonant detectors 2 in Europe 1 in Brazil LISA The band 0.1 mHz – 10 kHz is essentially completely covered, although between a 0.1 Hz and a few Hz not in an optimal way Imaging the future: GW astronomy A Vecchio

Black hole demographics – 1 Study of the BH formation history and channels (let’s concentrate on the range 100 – 10,000 Msun).The goal: –dN/dMdz –Link between BHs and their environment Start from catalogue of detected sources covering ~ 10 yr, say 100 to 1000 sources –Late stage of coalescence detected with HF interferometers –Some low redshift IMBH+BH/NS detected with LISA (and possibly by both LISA and HF) –High redshift IMBH binaries detected by LISA –MBH+IMBH (EMRI) detected by LISA Imaging the future: GW astronomy A Vecchio

Black hole demographics – 2 Need most accurate determination of the source parameters: download the original time series around the events and re-do the analysis: –Use most accurate waveforms produced by GR community –Use some fancy algorithm to do a multi-detector multi-parameter fit and generate the best estimate of the source parameters –Of course this is likely to be computationally intensive and I’ll run everything on the grid At the end of this stage one can produce dN/dMdz and study some simple properties, such as correlations between e.g. M and spin This will also produce an update version of the catalogue Imaging the future: GW astronomy A Vecchio

Black hole demographics – 3 I have the BH formation history (in the relevant mass range), now I need to find models that explain it I need to know where (i.e. environment) BH are: –Galaxy –Field –Globular cluster –… I need to go on the archives of the major relevant surveys in a number of observational bands and check what’s in the GW error box If there are sure detections of other interesting objects (such as isolated BHs) I should probably include them as well Imaging the future: GW astronomy A Vecchio

Black hole demographics – 4 Now I need to do some modelling, such as: –Initial mass function and stellar evolution –Dynamics of dense star clusters –Dynamics of galaxy cores with different density profiles –N-body simulation of galaxy mergers + gas to study star formation rate –Evolution of structures in the high z universe (hierarchical clustering for different models) – I need model for dark matter, black hole seeds and distribution, … –… Only at the end of this I will be able to argue that we have physical models to explain different paths of BH formation Or we just can’t explain the observations which will require some serious work on the modelling side Imaging the future: GW astronomy A Vecchio

EM/GW – 1 The goal is to establish whether during violent GW bursts there is a “channel” though which part of the available energy can be converted into and radiated as EM waves: –During a supernova explosion there is all sorts of radiation (including neutrinos) –What about NS-NS binaries? Are they the progenitors of (some class of) gamma ray bursts? –And black hole binaries? “In vacuum” With accretion disks This is a: –GW all sky on-line survey –Where I need to provide in real time pointing information (that could even be early warning) for coordinated follow up observations with other telescopes Imaging the future: GW astronomy A Vecchio

EM/GW – 2 The GW survey requires: –Robust and reliable 24x7 on-line network analysis –Method and infrastructure for Accessing the data simultaneously Processing the data Broadcasting the results to other observatories (including other GW instruments) –Coordinated scheduling for data taking (a minimum number of detectors need always to be on-line) There is little to do with LISA But for ground-based experiments this is necessary Agreements at project level: some telescope time needs to be dedicated to this effort Imaging the future: GW astronomy A Vecchio

EM/GW – 3 Whether or not GW-EM associations are found, the results of this survey require a “global” interpretation –Model fitting of observations in different frequency bands will likely be carried out first, and will lead to “consistency checks” –But then one model is required to explain consistently all the observations of the same source in the different frequency bands This requires a non negligible effort by the theoretical community –GR –Magneto-hydrodynamics –… Imaging the future: GW astronomy A Vecchio

Mapping the GW early universe Assume LISA reaches a sensitivity  ~ in some portion of the spectrum: opportunity for quantum- gravity phenomenology –WMAP-like analysis –But to test radically new ideas and theories We need: –Sophisticated data analysis techniques (Markov Chain Monte Carlo + large simulations) – we can gain a lot from CMB experience –Models for GW signals (from “incomplete” theories) –Modelling and “subtraction” of foregrounds and individual sources Imaging the future: GW astronomy A Vecchio

Conclusions What will it mean to be a gravitational wave astronomer? Imaging the future: GW astronomy A Vecchio

Conclusions What will it mean to be a gravitational wave astronomer? –As I said, I don’t really know. –However… Imaging the future: GW astronomy A Vecchio

Conclusions (cont’) Gravitational wave astronomers can not work in “isolation”: they will provide data to, and closely collaborate with a number of communities: –Astronomers – from stars to super-clusters –Cosmologists –Relativists –Nuclear and particle physicists –Theoretical physicists It takes time to learn how to work together The modus operandi of those communities is very different Imaging the future: GW astronomy A Vecchio

Conclusions (cont’) We need to pay attention to technical issues that could prove to be the actual major roadblocks: –Data formats, conversions, access –Software and computational resources Hopefully, presently ongoing efforts in our and other fields will make our life easier: –Grid computing –Virtual Observatory “Bidding for telescope time”: does it have any role in the life of a GW astronomer? Imaging the future: GW astronomy A Vecchio