Gravitational wave observations of binary black hole mergers Miami 2017 James A. Clark December 15, 2017 The story so far. In two observing runs (\O1", \O2") we have so observed: O1: GW150914, LVT1510121, GW151226 • O2: GW170104, GW170608, GW170814 • 1 \LVT": LIGO-Virgo transient, lower significance 1 / 21 Masses GW150914: spectacular discovery of unknown class of black hole, subsequent measurements probing black hole mass distribution ! 2 / 21 A New Population of Black Holes 3 / 21 Overview This talk: an introduction to gravitational wave (GW) observations of binary black hole (BBH) mergers 1 BBH Observations GW150914 GW151226 GW170104 GW170608 GW170814 2 Astrophysical Implications Progenitor Systems Image: butterfly1 4 / 21 BBH Observations GW150914 On September 14, 2015. first detection at > 5σ (FAR< 10−7 yr−1) SNR=24, (m1; m2) = (36; 29) M , D ∼ 410 Mpc [1] 5 / 21 Inferring Source Properties Binary parameter space: Component masses: m1, m2 • 2 3 = 6 spin components • × Binary orientation: θJN , φc, • Sky-location & distance: (α; δ)& • D 15-dimensional waveform model! Inspiral phase evolution accurately modeled via post-Newtonian theory: Leading-order amplitude and phase evolution: chirp mass [2]: • (m m )3=5 = 1 2 c 1=5 M (m1 + m2) Additional parameters (q = m2=m1 1), effective spin χeff enter at • ≤ higher PN-order Effective spin { most important combination of spins for evolution of • inspiral [3]: 6 / 21 c ~χ1 ~χ1 χeff = + L^ GM m1 m2 · Inferring Source Properties Source properties (generally) determined from Bayesian analysis of a given waveform model: Time series data output from detector, given a signal h(t), noise • n(t): d(t) = h(t) + n(t) Signal h(t) is a linear combination of polarizations, weighted by • antenna beam patterns F+;×: ~ ~ h(t) = F+(α; δ; )h+(t; θ) + F×(α; δ; )h×(t; θ) ~ Source properties θ = c ; q; χeff ; ; θJN ; φc;::: • fM D g Information about source properties θ~ is determined from posterior probability density function: p(θ~ d~) p(θ~) (d~ θ~) j ∼ L j Assumes signal model faithfully models the underlying signal! 7 / 21 GW150914: Masses ) Component mass distributions [4] Final mass & spin [4] • Fitting formula from numerical relativity (NR) for final mass, spin +4:5±0:8 +4:1±0:7 • Initial Mtot = 65:0−4:0±0:7 M , Final Mtot = 62:0−3:7±0:6 M 2 • Erad ∼ 3 M c : peak luminosity >> than entire electromagnetic (EM)-observable Universe! 8 / 21 GW150914: Cross-validation Two approaches to waveform reconstruction: 1. h(t) = h(t; c ; q; χeff ; ; θJN ; φc;::: ) M D 2. h(t) = wavelet decomposition dictated by coherent network signal Excellent agreement validation of BBH waveform models [4, 5] ! 9 / 21 GW151226 SNR=13, (m1; m2) = (14:2; 7:5) M , D ∼ 440 Mpc [6] 10 / 21 GW151226 Source Properties: spin configuration Figure 1: Component spin magnitudes & Mass-weighted spin χ and in-plane eff orientations spin-components χp [6] • Lower mass ! merger at higher frequency, longer inspiral • Longer inspiral ! more informative spin measurement • p(χeff > 0jD) > 99% ! at least 1 BH has non-zero spin 11 / 21 GW150914, LVT151012 & GW151226: durations & spins 12 / 21 GW170104 More distant cousin of GW150914: SNR=13, (m1; m2) = (31:2; 19:4) M , D ∼ 880 Mpc [7] Waveform reconstructions remain consistent p(χeff < 0jD) = 0:82 ! large total spin aligned with orbital angular momentum is disfavored 13 / 21 GW170608 Most recent result, lightest BBH so far! SNR=13, (m1; m2) = (12; 7) M , D ∼ 340 Mpc [8] Potential selection bias ! systems with uninformative precession (χp) Spin inferences for GW170608 [8] measurements 14 / 21 GW170814 First Virgo observation, first triple-detector detection! [9] Hanford Livingston Virgo 14 12 10 8 SNR 6 4 2 0 5.0 4.5 256 4.0 3.5 128 3.0 2.5 64 2.0 1.5 Frequency [Hz] 32 1.0 0.5 Normalized Amplitude 16 0.0 ] 1.0 -21 2 5 5 0.5 0.0 0 0 0 noise σ 0.5 − 5 5 − 2 − − Whitened Strain [10 1.0 − 0.46 0.48 0.50 0.52 0.54 0.56 0.46 0.48 0.50 0.52 0.54 0.56 0.46 0.48 0.50 0.52 0.54 0.56 Time [s] Time [s] Time [s] SNR=18, (m1; m2) = (30:5; 25:3) M , D ∼ 540 Mpc [9] 15 / 21 GW170814: Sky localization Triple-coincident observations sky localization ! • 1 GW detector: omni-directional but non-uniform • 2 GW detectors: time-delay constrains source to annulus + amplitude ratio constraints • 3 GW detectors: intersection of 2 annuli ! sky-patches Geometry of HLV network and signal travel times [10] • Initial HL rapid localization: 1160 deg2 • Rapid localization +Virgo: 100 deg2 2 Localization of GW170814 [9] • Full parameter estimation: 60 deg 16 / 21 Observation Summary: Sky localization 90% credible sky-areas GW150914: 230 deg2 [11] LVT151012: 1600 deg2 [11] GW151226: 850 deg2 [11] GW170104: 1200 deg2 [7] GW170814: 50 deg2 [9] 17 / 21 Astrophysical Implications Massive BH Progenitor Systems GW150914: m1; m2 > all • known BH masses BH formation: • 1. Supernova + fall-back 2. Failed SN + prompt collapse Key factor: stellar wind • metallicity Z: Figure 2: Dependence of maximum BH mass on Low Z ! lower opacity, metallicity [12] (Bands: GW150914 m1, m2) weaker winds & less mass-loss Conclusion: GW150914 BBH formed in a low-metallicity environment 18 / 21 Constraining Binary Evolution Scenarios BBH formation channels (see e.g., [11]): 1. dense stellar environment dynamical formation 3 ! 2. isolated binary evolution with a common envelope phase 3 3. chemically homogeneous evolution, tidally-locked binaries 7 Expect large, aligned spins: implausible in light of GW170104 Dynamical BBH formation [13] BBH through isolated evolution [14] 19 / 21 Summary GW BBH observations • becoming \routine" (!) GWs encode source parameters • Some parameters measured well (e.g., chirp mass) Others much harder (e.g., mass ratio, spin orientations) GW observations starting to • probe black hole formation & evolution Expected BBH detection rates from O1 [11] Just scraping the surface: • Whole suites of tests of general relativity! • Higher-order multipoles + precession in waveform models • Direct comparisons with numerical relativity • Searches for \intermediate" mass BBH (> 100 M ) 20 / 21 Observation Summary: Spins & Masses Watch this space! 21 / 21 O1 Source Parameters Figure 3: Trigger characteristics and source parameters for the O1 BBH triplet [11] GW170104 Figure 4: Trigger characteristics and source parameters for GW170104 [7] GW170608, GW170814 Figure 6: Trigger characteristics and source Figure 5: Trigger characteristics and source parameters for GW170814 [9] parameters for GW170608 [8] References [1] B. P. Abbott et al. [Virgo and LIGO Scientific Collaborations], , \Observation of Gravitational Waves from a Binary Black Hole Merger", Phys. Rev. Lett. 116, 061102 (2016), arXiv:1602.03837 [2] B. S. Sathyaprakash & B. F. Schutz, \Physics, Astrophysics and Cosmology with Gravitational Waves", Living Rev. Relativ. (2009) [3] P. Ajith et al, \Inspiral-Merger-Ringdown Waveforms for Black-Hole Binaries with Nonprecessing Spins" Phys. Rev. Lett. 106, 241101 (2011) [4] B. P. Abbott et al. [Virgo and LIGO Scientific Collaborations], , \Properties of the binary black hole merger GW150914", Phys. Rev. Lett. 116, 241102 (2016), arXiv:1602.03840 References [5] B. P. Abbott et al. [Virgo and LIGO Scientific Collaborations], \Tests of general relativity with GW150914", Phys. Rev. Lett. 116, 221101 (2016), arXiv:1602.03841 [6] B. P. Abbott et al. [Virgo and LIGO Scientific Collaborations], , \GW151226: Observation of Gravitational Waves from a 22-Solar-Mass Binary Black Hole Coalescence", Phys. Rev. Lett. 16 241103 (2016) arXiv:1606.04855 [7] B. P. Abbott et al. [Virgo and LIGO Scientific Collaborations], \GW170104: Observation of a 50-Solar-Mass Binary Black Hole Coalescence at Redshift 0.2", Phys. Rev. Lett. 118, 221101 (2017) [8] B. P. Abbott et al. [Virgo and LIGO Scientific Collaborations], \GW170608: Observation of a 19-solar-mass Binary Black Hole Coalescence", Submitted to Astrophys. J. Lett (2017), arxiv:1711.05578 References [9] B. P. Abbott et al. [Virgo and LIGO Scientific Collaborations], \GW170814: A Three-Detector Observation of Gravitational Waves from a Binary Black Hole Coalescence", Phys. Rev. Lett. 119, 141101 (2017), arxiv:1709.09660 [10] S. Chatterji et al., \Coherent network analysis technique for discriminating gravitational-wave bursts from instrumental noise", Phys. Rev. D 74, 082005 (2006) [11] B. P. Abbott et al. [Virgo and LIGO Scientific Collaborations], , \Binary Black Hole Mergers in the first Advanced LIGO Observing Run", Phys. Rev. X 6, 041015 (2016), arXiv:1606.04856 [12] B. P. Abbott et al. [Virgo and LIGO Scientific Collaborations], , \Astrophysical Implications of the Binary Black-Hole Merger GW150914", Astrophys. J. Lett., 818, L22, (2016), arXiv:1602.03846 References [13] C. Rodriguez, et al., \Dynamical Formattion of the GW150914 Binary Black Hole", Astrophys. J. Lett. 824 1 (2016) [14] K. Belczynski et al., \The first gravitational-wave source from the isolated evolution of two stars in the 40100 solar mass range", Nature 534, 512{515 (2016).