What will it mean to be a gravitational wave astronomer?

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

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

3. Gravitational wave astronomy • 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

4. 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 Imaging the future: GW astronomy A Vecchio

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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

15. Mapping the GW early universe • Assume LISA reaches a sensitivity W~ 10-12 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

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

17. 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

18. 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

19. 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