1710.09839
Detecting black hole binaries by Gaia
Yamaguchi, et al
The prospect of detecting black hole binaries from the orbital motion of the companion stars: ~300-6000 BH binaries during its 5 years of operation, taking into account the IMF, mass transfer, common envelope phase, interstellar absorption and identifiability of BHs. The shape of distribution function of the BH mass is affected most severely by the relation between the zero-age main sequence (ZAMS) stellar mass and the BH mass in parameters adopted in this paper, which implies that BHs detected with Gaia enables constraints on the mass relation.
1710.09818
Following the cosmic evolution of pristine gas II: the search for Pop III-bright galaxies
Sarmento, et al
Direct observational searches for Pop III stars at high-z are faced with the question of how to select the most promising targets for spectroscopic followup. To help answer this, use a large-scale cosmological simulation, augmented with a new sub grid model that tracks the fraction of pristine gas, to follow the evolution of high-z galaxies and the Pop III stars they contain. Generate rest-frame UV luminosity functions for the galaxies and find that they are consistent with current z>=7 observations. Throughout the range 7<=z<=16 identify "Pop III-bright" galaxies as those with at least 75% of their flux coming from Pop III stars. While less than 5% of galaxies brighter than m_UV,AB=31.4 mag are Pop III-bright between 7<=z<=8, roughly a 1/3 of such galaxies are Pop III-bright at z=9, right before reionization occurs in the simulation. Moving to z=10, m_UV,B=31.4 mag corresponds to more luminous galaxies and the Pop III-bright fraction falls off to 15%. Finally at the highest redshifts, a large fraction of all galaxies are Pop III-bright regardless of magnitude. While m_UV,AB=31.4 mag galaxies are likely not detectable during this epoch, find 90% of galaxies at z=16 are Pop III-bright with m_UV,AB <=33 mag, a lensed magnitude limit within reach of the JWST. Thus predict that the best z to search for luminous Pop III-bright galaxies is just before reionization, while lensing surveys for fainter galaxies should push to the highest z possible.
1710.09881
The median density of the Universe
Stücker, Busch, White
Despite the fact that the mean matter density of the universe has been measured to an accuracy of a few percent within the standard LCDM paradigm, its median density is not known even to order of magnitude. Typical points lie in low-density regions and are not part of a collapsed structure of any scale. Locally, the dark matter distribution is then simply a stretched version of that in the universe. In this single-stream regime, the distribution of unsmoothed density is sensitive to the initial power spectrum on all scales, in particular on very small scales, and hence to the nature of dark matter. It cannot be estimated reliably using conventional cosmological simulations because of the enormous dynamic range involved, but a suitable excursion set procedure can be used instead. For the Planck cosmological parameters, a 100 GeV WIMP, corresponding to a free-streaming mass ~1e-6 Msun, results in a median density of ~4e-3 in units of the mean density, whereas a 10 ueV axion with free-streaming mass ~1e-12 Msun gives ~3e-3, and WDM with a (thermal relic) mass of 1 keV gives ~8e-2. In CDM (but not in WDM) universes, single-stream regions are predicted to be topologically isolated by the excursion set formalism. A test by direct N-body simulations seems to confirm this prediction, although it is still subject to finite size and resolution effects. Unfortunately, it is unlikely that any of these properties is observable and so suitable for constraining the properties of DM.
1710.09893
Supernova and prompt gravitational-wave precursors to LIGO gravitational-wave sources and short-GRBs
Michael, Perets
BHs and binary NS mergers had been recently detected through GW emission, with the latter followed by post-merger EM counterparts, appearing seconds up to weeks after the mergers. While post-merger EM counterparts had been anticipated theoretical, very little EM precursor to GW-sources had been proposed, and non observed yet. Here show that a fraction of a few times 1e-4 to 1e-1 of LIGO GW-sources and sGRBs could be predicted by SNe-explosions years to decades before the merger. Each of the BH/NS-progenitors in GW-sources are through to form following a SN, likely accompanied by a natal velocity-kick to the newly born compact object. The evolution and natal-kicks determine the orbits of surviving binaries, and hence the delay-time between the birth of the compact-binary and its final merger through GW_emission. Use data from binary evolution population-synthesis models to show that the delay-time distribution has a non-negligible tail of ultra-short delay-times between 1- 100 yrs, thereby giving rise to potentially observable SNe precursors to GW-sources. Moreover, future LISA/DECIGO GW space-detectors will enable the detection of GW-inspirals in the pre-mergers stage weeks to decades before the final merger. These ultra-short delay-time sources could therefore produce a unique type of promptly appearing LOSA/DECIGO-GW-sources accompanies by coincident SNe. The archival (and/or direct) detection of precursor (coincident) SNe with GW and/or sGRBs will provide unprecedented characterization of the merging-binaries, and their prior evolution through SNe and natal kicks, otherwise inaccessible through other means.
1710.09900
A spectroscopic survey of the fields of 28 strong gravitational lenses: implications for $H_0$
Wilson, Zabludoff, Keeton, et al
SL provides an independent measurement of H0. One remaining systematic is a bias from the additional mass due to a galaxy group at the lens redshift or along the sightline. Quantify this bias for more than 20 SL that have well-sampled sightline mass distributions, focusing on the convergence kappa and shear gamma. In 23% of these fields, a lens group contributes a >=1% convergence bias; in 57%, there is a similarly significant LoS group. For the 9 time delay lens systems, H0 is overestimated by 11+3-2% on average when groups are ignored. In 67% of fields with total kappa >= 0.01, LoS groups contribute >~2x more convergence than do lens groups, indicating that the lens group is not the only important mass. Lens environment affects the ratio of 4 (quad) to two (double) image systems; all seven quads have lens groups while only 3 of 10 doubles do, and the highest convergences due to lens groups are in quads. Calibrate the gamma-kappa relation: log(kappa_tot) =(1.94±0.34) log(gamma_tot) + (1.31±0.49) with a rms scatter of 0.34 dex. Shear, which, unlike convergence, can be measured directly from lensed images, can be a poor predictor of kappa; for 19% of the fields, kappa is >~2 gamma. Thus, accurate cosmology using strong gravitational lenses requires precise measurement and correction for all significant structures in each lens field.
1710.09902
A comparison of the excess mass around CFHTLenS galaxy-pairs to predictions from a semi-analytic model using galaxy-galaxy-galaxy lensing
Simon, Saghiha, Hilbert, Schneider, Boever
G3L lensing is a probe of the matter environment of average galaxy pairs, which is a strong test for galaxy models. Using G3L, map out the distribution of correlated excess-mass around galaxy pairs in the CFHTLenS in a reanalysis of the data. Compare the maps to predictions by a recent SAM which is implanted on the Millennium Simulation. The target galaxies span a range of stellar masses between 1e9-11 Msun, and have z <~0.6 in two z bins; the projected separation between galaxies pairs is chosen between ~170-300 kpc/h in two separation bins. Compared to an earlier G3L study with CFHTLenS galaxies, make more efficient use of the data. In addition, verify the accuracy of the refined stacking technique for the map construction with simulated data and provide a detailed description of the methodology. For a better interpretation of the maps, discuss the impact of chance pairs, i.e., galaxy pairs that appear close to each other in projection only, and introduce an alternative correlation map that is less affected by projection effects but has a lower S/N. For all maps, obtain significant measurements of the excess-mass distribution for all galaxy samples and an overall good agreement with the SAM predictions. There is, however, tentative evidence for a bulge-like feature in the distribution of excess mass that is not predicted by the SAM and similar models. Although there is no strong indications for systematic errors in the maps, this feature may be related to a residual B-mode pattern visible in the average of all maps. Alternatively, misaligned galaxy pairs inside matter haloes or lensing by a misaligned distribution of the intra-cluster gas might also cause a bulge.
1710.09908
A spectroscopic survey of the fields of 28 strong gravitational lenses: the Group Catalog
Wilson, et al
Observational companion paper to 1710.09900. Find 210 groups with at least 5 member galaxies; the median number of members is 8.
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