Binary black hole mergers from Population III stars: uncertainties from star formation and binary star properties

Population III (Pop. III) binary stars likely produced the first stellar-born binary black hole (BBH) mergers in the Universe. Here, we quantify the main sources of uncertainty for the merger rate density evolution and mass spectrum of Pop. III BBHs by considering four different star formation histories of Pop. III stars and 11 different configurations of the initial orbital properties of their binary systems. The uncertainty on the orbital properties affects the BBH merger rate density by up to two orders of magnitude; models with shorter initial orbital periods lead to higher BBH merger rates, because they favour the merger via stable mass transfer episodes. The uncertainty on the star formation history has a substantial impact on both the shape and the normalisation of the BBH merger rate density: the peak of the merger rate density shifts from ∼ 8 up to ∼ 16 depending on the assumed star formation rate, while the maximum BBH merger rate density for our fiducial binary population model spans from ∼ 2 to ∼ 30 Gpc^−3 yr^−1. The typical BBH masses are not affected by the star formation rate model and only mildly affected by the binary population parameters. The primary black holes born from Pop. III stars tend to be rather massive (30 − 40 M⊙) with respect to those born from metal-rich stars (8 − 10 M⊙). On the other hand, we expect that Pop. III BBH mergers with primary mass _1 > 60 M⊙ are rare (< 10^−2 Gpc^−3 yr^−1). Finally, we estimate that the Einstein Telescope will detect 10 − 10^4 Pop. III BBH mergers per year, depending on the star formation history and binary star propertiesFILE DESCRIPTION Thanks for taking the time for considering my work and reading what follows. Here we present the file to reproduce the results shown in the paper Santoliquido et al. 2023: REFERENCE. Please cite this work if you use the data provided in this folder. Data are produced using cosmoRate, see https://gitlab.com/Filippo.santoliquido/cosmo_rate_public This dataset is structured as follows: one zip file is provided for each model presented in Santoliquido et al. 2023, e.g. LOG1.zip contains all the data to reproduce the model LOG1. Each zip folder contains: - the evolution of merger rate density with redshift 'MRD_spread_1Z_100_No_MandF2017_0.2_No_No_False_'+SFRD_model+'_0.dat', where SFRD_model can be ['asloth_smooth_off', 'asloth_smooth_off_high', 'asloth_smooth_off_med', 'asloth_smooth_off_low', 'jaacks', 'LiuBromm', 'SW20_smooth_off'] column 1: redshift bin column 2: merger rate density in Gpc^-3 yr^-1 - the catalogs of merging Pop. III BBHs at fixed redshift 'BBH__'+SFRD_model+'_z'+bin_z+'_50_SFR_pw.dat' where SFRD_model can be ['asloth_smooth_off', 'jaacks', 'LiuBromm', 'SW20_smooth_off'] and bin_z is the redshift bin at which the catalog are extracted from and it can be [0.1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 20, 25, 30]. For higher redshift resolution, contact the authors. column 1: 'ID' unique number that identifies each binary system column 2: primary mass 'M1[Msun]' (defined as the most massive BH) column 3: secondary M2[Msun] (defined as the least massive BH, i.e. the mass ratio of merging BBH is always <= 1) column 4: semi-major axis at the onset of gravitational-wave radiation 'SM_ax[Rsun]' column 5: eccentricity at the onset of gravitational-wave radiation 'ecc' column 6: ZAMS mass of the progenitor of the primary-mass system 'Mzams_0[Msun]' column 7: ZAMS mass of the progenitor of the secondary-mass system 'Mzams_1[Msun]' column 8: initial semi-major axis 'SM_ax_ini[Rsun]' column 9: initial eccentricity 'ecc_ini' column 10: formation channel (it can be 0, 1, 2, 3, 33, 4, 44, 5; see Iorio et al. 2022 for details) column 11: CE - common envelope column 12: SMT - stable mass transfer column 13: 'swapped' == 0 if the progenitor star generating the most massive BH, 'swapped' == 1 if the most massive BH comes from the least massive progenitor star column 14: redshift of merger 'z_merg' column 15: redshift of formation 'z_form' Column 16: delay time 'time_delay[yr]' Column 17: progenitor metallicity 'Z_progenitor' (for Pop. III BBHs this is always Z = 10^-11