So far, the LIGO and VIRGO gravitational wave telescopes in place have seen ten black hole mergers and one black hole neutron star merger, since they started operating in 2015, after a review of old data revealed four more events missed the first time around.
The black hole merger data is revealing a lot of intermediate sized black holes never before detected. The black hole-neutron star merger gave rise to a great many important empirical tests of fundamental physics and neutron star structure.
The black hole merger data is revealing a lot of intermediate sized black holes never before detected. The black hole-neutron star merger gave rise to a great many important empirical tests of fundamental physics and neutron star structure.
More gravitational wave telescope resources are under construction and will come on line soon.
More analysis is found in a new preprint. It's abstract notes that:
More analysis is found in a new preprint. It's abstract notes that:
We present results on the mass, spin, and redshift distributions of the ten binary black hole mergers detected in Advanced LIGO's and Advanced Virgo's first and second observing runs. We constrain properties of the binary black hole (BBH) mass spectrum using models with a range of parameterizations of the BBH mass and spin distributions. We find that the mass distribution of the more massive black hole in each binary is well approximated by models with almost no black holes larger than45M⊙ , and a power law index ofα=1.6+1.5−1.7 (90% credibility). We also show that BBHs are unlikely to be composed of black holes with large spins aligned to the orbital angular momentum. Modelling the evolution of the BBH merger rate with redshift, we show that it is increasing with redshift with credibility0.88 . Marginalizing over uncertainties in the BBH population, we find robust estimates of the BBH merger rate density ofR=52.9+55.6−27.0 Gpc−3 yr−1 (90% credibility). As the BBH catalog grows in future observing runs, we expect that uncertainties in the population model parameters will shrink, potentially providing insights into the formation of black holes via supernovae, binary interactions of massive stars, stellar cluster dynamics, and the formation history of black holes across cosmic time.
"The black hole merger data is revealing a lot of intermediate sized black holes never before detected."
ReplyDeletemakes me wonder whether the exclusions for primordial black holes as dark matter based on gravitational lensing is falsified.
LIGO is detecting many more black holes than is suggested by gravitational lensing
"makes me wonder whether the exclusions for primordial black holes as dark matter based on gravitational lensing is falsified."
ReplyDeleteProbably not. If we use LIGO data to estimate the average size of an intermediate black hole, an average intermediate black hole is ca. 13 times the mass of the smallest stellar black hole, and more like 130 times the expected mass of the primordial black holes it is seeking to observe.
Lensing requires a luminous object that is bright enough to be able to discern the lensing effect to be behind the black hole to be detected, almost in a line of sight, and there are only so many of them (a large number, but very finite) within our visual range from Earth. If you can observe quite small lensing effects (because the precision of all optical and EM phenomena is astounding), and the probability of a PBH or intermediate sized BH of being in any given point in the celestial sphere around Earth, then the probability of any given BH (PBH or otherwise) being in a location where you can observe it is roughly the same. So the number of targets (PBHs or intermediate black holes) in the fixed volume of space where it is possible to see if aligned properly with a suitable star is directly proportional to the number density of targets in a given volume. Since PBHs should on the order of 100 times as numerous (or more) than intermediate sized BHs, it is much easier to see PBHs via lensing than it is to see intermediate sized black holes with them.
Also, lensing isn't merely looking for PBHs, it is looking for PHBs numerous enough to make up a significant share of DM. This means that you are looking for a number of PHBs on the order of 8-9 times the total amount of baryonic matter in the universe. In contrast, the total mass of stellar and larger BHs in the universe (including supermassive black holes which are easily detected because they are at the center of galaxies) is on the order of 1% of the baryonic matter in the universe, and naively, intermediate sized BHs shouldn't be more than about 1/3rd of that (and probably less). So, there should be on the order of 2500 times as much mass in PBHs as intermediate sized BHs in the universe if it is a significant component of DM, which implies a N per volume of space for PBHs that are a significant share of DM roughly 250,000 times as great as intermediate sized black holes. So, detecting PBHs with lensing is much, much easier than finding intermediate sized black holes that way.
In contrast to lensing, gravitational wave detectors are basically omnidirectional capturing all signals from every direction at once, instead of a small portion of the sky at a time, and so the main limiting factor for a gravitational wave detector is gravitational wave magnitude which is a function of the size of the original event and its distance from us. We can't detect anything much smaller than an intermediate black hole merger with LIGO and VIRGO, because our instruments are sensitive enough yet. And, we can easily calculate the maximum distance of black hole merger events of various sizes at which we can detect the with out instruments. We also have very good theoretical cause to believe that intermediate black hole size ought to follow a power law distribution with the number density of dwarf galaxies providing a high end calibration point for the power law, and the estimated number of stellar black holes and the number of LIGO/VIRGO events so far, putting some loose plus or minus a couple of orders of magnitude bounds on the low end of the distribution.
ReplyDeleteAlso, while our N=1 sample size for neutron star-BH mergers is the minimum it can be, we can use that number to estimate within a couple of orders of magnitude range, the number of binary intermediate black holes relative to the number of neutron stars, and since neutron stars are visible we can estimate to perhaps 1-5% precision, how many neutron stars there are. So, we can leverage our one event to narrow to a couple of orders of magnitude the estimated number of intermediate black holes per volume of space.
There has also been at least one paper estimating what our LIGO data implies with respect to PBH dark matter parameter space. Essentially it allows us to leverage the utility of existing lensing data in a way that basically rules out PBHs as a major DM component for MPBH≳0.01M⊙. https://dispatchesfromturtleisland.blogspot.com/2017/12/more-data-narrows-parameter-space-of.html
One more point. We have lots of data to tell us approximately where anything that constitutes most of dark matter should be located in what mass densities per volume, even though it doesn't tell us much about the number density of DM. But, we have very little comparable data on where intermediate sized black holes should be located and in what densities.
ReplyDeleteSee also
ReplyDeleteRe DM exclusions many not exactly on point. May 23, 2018. https://dispatchesfromturtleisland.blogspot.com/2018/05/more-dark-matter-and-modified-gravity.html
Re DM exclusions including PBH October 23, 2017. https://dispatchesfromturtleisland.blogspot.com/2017/10/dark-matter-particle-theories-are.html
Re PBH DM. September 17, 2016 https://dispatchesfromturtleisland.blogspot.com/2016/09/machos.html
Re consistency of the early LIGO results with strong field predictions of general relativity and discussing PBH parameter space. February 12, 2016 https://dispatchesfromturtleisland.blogspot.com/2016/02/strong-field-predictions-of-general.html
Re my conjecture that there is a maximum physically possible density of mass-energy (which would rule out PBHs) April 2, 2012. https://dispatchesfromturtleisland.blogspot.com/2012/04/conjecture-regarding-asymptotic-freedom.html
Re lots of stuff about BHs and dark matter although little of it directly on point. September 20, 2011. https://dispatchesfromturtleisland.blogspot.com/2011/09/dark-energy-black-holes-dark-matter.html
what i have in mind is
ReplyDeletegalaxy rotation curves follow some flavor of MOND, Deur for you, lee Smolin for me, no dark matter except black holes
then to explain large scale structures and galaxy clusters,
galaxies clusters follow MOND but with only 1/5 the amount dark matter necessary
black holes of some mass as detected by LIGO makes up that gap, assuming neutrino mass of 0.3 ev
Intermediate sized black holes make up only about 0.3% of baryonic matter in the Universe (assuming that it is fair to call matter in a black hole with baryonic origins baryonic at that point). No amount of tweaking of the data can get you even close to the amount of dark matter you need even in a MOND plus cluster dark matter scenario with neutrinos that are very numerous and heavy in clusters and lots of dim matter in clusters (like interstellar hydrogen gas).
ReplyDeleteAlso, your assumed neutrino mass of 0.3 eV (I presume that this is an average of the three SM neutrino mass eigenstates) is more than 10 times to high for an average, and more at least 4-5 times the heaviest of the SM neutrino masses. And, astronomy measurements of Neff (the effective number of neutrino types of about 10 eV or less in mass) quite definitively rules out the possibility of one or more than one sterile neutrino or similar particle other than the three SM neutrinos in a mass range that would include a 0.3 eV neutrino or sterile neutrino mass. So, again, even in a MOND-DM hybrid with only cluster DM, neutrinos can't come close to providing enough mass to account for even 20% of cluster mass in addition to the problem that any thermal relic DM candidate would be way to hot (i.e. have far to high of an average velocity) to produce observed levels of large scale structure in clusters.
Thirdly, it is worth noting that tools like lensing are more powerful in clusters than they are in many other places, because there are lots of fairly bright stars in the near background from almost every angle in a cluster. If we were to break out exclusion ranges for PBHs in clusters v. non-clusters (not that I've ever seen a paper that does this), the exclusion range for PBHs due to lensing data ought to take up significantly more of the available PBH parameter space in clusters than it does than elsewhere.
Another problem for a cluster and large scale structure filament DM hypothesis is that while the mass to luminosity scaling relationship in clusters differs from the Tully-Fisher relationship that MOND gives rise to, there is a similar more or less lockstep M to L relationship in clusters to the one seen in galaxies. (I'm sure I've cited a paper on that point sometime although one doesn't immediately come to mind.)
ReplyDeleteSo, a cluster and large scale structure filament DM hypothesis ultimately runs up against the same kind of problem getting the DM in the universe to the right places in the right proportions that WDM and CDM do at the galactic scale.
An ordinary matter only and gravity modification hypothesis with a gravity modification that explains both galaxy DM and cluster DM is a much cleaner and easier to formulate a narrative for hypothesis than a MOND plus much less DM hypothesis, even if it is challenging to come up with just the right formula to capture both relationships. And, BH dark matter of any kind really isn't a good solution to any of the DM problems. (It also doesn't solve the CMB peak problem because the lambdaCDM solution to that problem requires collisionless DM which PBHs most emphatically are not.
re "Intermediate sized black holes make up only about 0.3% of baryonic matter in the Universe (assuming that it is fair to call matter in a black hole with baryonic origins baryonic at that point)."
ReplyDeleteare primordial black holes formed during the planck era after the big bang considered "baryonic"?
re "(It also doesn't solve the CMB peak problem because the lambdaCDM solution to that problem requires collisionless DM which PBHs most emphatically are not.)"
I don't know about the collisionless part, but I had in mind quantum mechanical black holes with masses on order of planck 10^19ev or even lighter depending on the details of QG. there are papers on arvix on this topic.
since you believe in MOND in the form of Deur, obviously that would cause some changes in large scale structure formation and other differences than in the lamda cdm model.
cosmology and large scale stricture would be different under MOND.
i'm thinking MOND + quantum mechanical black holes with masses on order of planck 10^19ev
re: "No amount of tweaking of the data can get you even close to the amount of dark matter you need even in a MOND plus cluster dark matter scenario with neutrinos that are very numerous and heavy in clusters and lots of dim matter in clusters (like interstellar hydrogen gas). "
ReplyDeleteMilgrom had a paper where he theorizes 2ev neutrinos could account for the dark matter, if u want i can try to find it. granted that planck mission suggests best fit of the sum of the 3 neutrinos is 0.3 ev, that is something of a gap, Milgrom also theorizes that black holes and unseen baryonic matter could make up the gap.
there's also extended MOND, modifying gravity yet again for the galaxy cluster scale.
"planck mission suggests best fit of the sum of the 3 neutrinos is 0.3 ev,"
ReplyDeleteThe latest round of data has gotten the sum of the three neutrino masses down to something not much over 0.1 eV, and the minimum sum of three neutrino masses from mass eigenstate mass differences is about 0.06 eV.
what would happen if you had a near infinite number of these neutrinos orbiting the space around a supermassive black hole?
ReplyDeletei've mused that black holes plus neutrino fluid could explain the third peak CMB and even dark matter.