Broad Mass Distribution Research Articles

Fractionation of Glycans from Hot‐Water Extracts with Ceramic Ultrafiltration Membranes

AbstractExtraction of hemicelluloses from biomass with pressurized hot‐water employs the mechanism of autohydrolysis for molecular weight reduction. In a pilot‐scale extraction of depectinized apple pomace, molecular weight was 30 kDa with a broad mass distribution including monomers and their degradation products. Ultrafiltration with sequential use of ceramic membranes with decreasing cut‐off yielded a suitable fraction with molecular weight of 9 kDa representing 10 % of the extracted hemicelluloses. Further autohydrolytic treatment of the extracted hemicellulose decreases molecular weight while increasing the mass of degradation products. For a series of hydrolysates sequential filtration through ceramic membranes was further tested for fractionation and purification. The efficiency of this fractionation was analyzed by size exclusion chromatography and a total mass balance of the ultrafiltration process is given as an evaluation for suitability of purifying and fraction glycans.

Confronting solutions of the Gallium Anomaly with reactor rate data

Recently, several models have been suggested to reduce the tension between Gallium and reactor antineutrino spectral ratio data which is found in the framework of 3+1 active-sterile neutrino mixing. Among these models, we consider the extensions of 3+1 mixing with a finite wavepacket size, or the decay of the heaviest neutrino ν4, or the possibility to have a broad ν4 mass distribution. We consider the reactor antineutrino rate data and we show that these models cannot eliminate the tension between Gallium and reactor rate data that is found in the 3+1 neutrino mixing framework. Indeed, we show that the parameter goodness of fit remains small. We consider also a model which explains the Gallium Anomaly with non-standard decoherence in the framework of three-neutrino mixing. We find that it is compatible with the reactor rate data.

Search for subsolar-mass black hole binaries in the second part of Advanced LIGO’s and Advanced Virgo’s third observing run

ABSTRACT We describe a search for gravitational waves from compact binaries with at least one component with mass $0.2$–$1.0 \, \mathrm{M}_\odot$ and mass ratio q ≥ 0.1 in Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) and Advanced Virgo data collected between 2019 November 1, 15:00 utc and 2020 March 27, 17:00 utc. No signals were detected. The most significant candidate has a false alarm rate of $0.2 \, \rm {yr}^{-1}$. We estimate the sensitivity of our search over the entirety of Advanced LIGO’s and Advanced Virgo’s third observing run, and present the most stringent limits to date on the merger rate of binary black holes with at least one subsolar-mass component. We use the upper limits to constrain two fiducial scenarios that could produce subsolar-mass black holes: primordial black holes (PBH) and a model of dissipative dark matter. The PBH model uses recent prescriptions for the merger rate of PBH binaries that include a rate suppression factor to effectively account for PBH early binary disruptions. If the PBHs are monochromatically distributed, we can exclude a dark matter fraction in PBHs $f_\mathrm{PBH} \gtrsim \, 0.6$ (at 90 per cent confidence) in the probed subsolar-mass range. However, if we allow for broad PBH mass distributions, we are unable to rule out fPBH = 1. For the dissipative model, where the dark matter has chemistry that allows a small fraction to cool and collapse into black holes, we find an upper bound fDBH < 10−5 on the fraction of atomic dark matter collapsed into black holes.

A boosted gravitational wave background for primordial black holes with broad mass distributions and thermal features

Primordial black holes (PBHs) with a wide mass distribution imprinted by the thermal history of the Universe, which naturally produces a high peak at the solar mass scale, could explain the gravitational-wave events seen by LIGO/Virgo and up to the totality of the dark matter. We show that compared to monochromatic or log-normal mass functions, the gravitational wave backgrounds (GWBs) from early PBH binaries and from late binaries in clusters are strongly enhanced at low frequency and could even explain the NANOGrav observations. This enhancement comes from binaries with very low mass ratios, involving solar-mass and intermediate-mass PBHs at low frequency, solar-mass and subsolar-mass at high frequency. LISA could distinguish the various models, while in the frequency band of ground-based detectors, we find that the GWB from early binaries is just below the current LIGO/Virgo limits and above the astrophysical background, if they also explain black hole mergers. The GWB from binaries in clusters is less boosted but has a different spectral index than for neutron stars, astrophysical black holes or early PBH binaries. It is detectable with Einstein Telescope or even with the LIGO/Virgo design sensitivity.

Constraints on the merging binary neutron star mass distribution and equation of state based on the incidence of jets in the population

A relativistic jet has been produced in the single well-localised binary neutron star (BNS) merger detected to date in gravitational waves (GWs), and the local rates of BNS mergers and short gamma-ray bursts are of the same order of magnitude. This suggests that jet formation is not a rare outcome for BNS mergers, and we show that this intuition can be turned into a quantitative constraint: at least about one-third of GW-detected BNS mergers and at least about one-fifth of all BNS mergers should produce a successful jet (90% credible level). Whether a jet is launched depends on the properties of the merger remnant and of the surrounding accretion disc, which in turn are a function of the progenitor binary masses and equation of state (EoS). The incidence of jets in the population therefore carries information about the binary component mass distribution and EoS. Under the assumption that a jet can only be produced by a black hole remnant surrounded by a non-negligible accretion disc, we show how the jet incidence can be used to place a joint constraint on the space of BNS component mass distributions and EoS. The result points to a broad mass distribution, with particularly strong support for masses in the 1.3 − 1.6 M⊙ range. The constraints on the EoS are shallow, but we show how they will tighten as the knowledge on the jet incidence improves. We also discuss how to extend the method to include future BNS mergers, with possibly uncertain jet associations.

Reaction dynamics of the C12+Ta181 system near the Coulomb barrier: Evidence of fusion-fission events

Background: Interaction of a heavy projectile with a heavy target produces a massive compound nucleus (CN), which deexcites through two possible modes: evaporation of light particles and fission. In order to develop a clear understanding of fusion-fission (FF) dynamics, it is important to explore the preactinide region at energies around and above the Coulomb barrier.Purpose: The objective is to study the dynamics involved in the fusion of $^{12}\mathrm{C}$, a cluster structured projectile, with $^{181}\mathrm{Ta}$ target, at energies within 4.3--6.0 MeV/nucleon, by measuring the production cross sections of the radionuclides formed through complete/incomplete fusion (CF/ICF) and fission processes. In addition, the mass distribution of fission fragments, which is an important fission observable, is probed for a better understanding of dynamics.Method: Tantalum foil, backed by the aluminum catcher, arranged in a stack, was bombarded by $^{12}\mathrm{C}$ ions of 52--73 MeV energy. The off-beam $\ensuremath{\gamma}$-ray spectrometry method was adopted to measure the activity of the residues produced in each Ta target after the end of bombardment (EOB), and cross sections were calculated. To analyze the experimental cross sections, PACE4 and EMPIRE3.2.2 reaction model codes were employed. Further, the mass distribution of fission fragments was explored to obtain mass variance information.Results: In general, measured excitation functions of the residues produced through the evaporation of particles in $^{12}\mathrm{C}+^{181}\mathrm{Ta}$ reaction showed good agreement with the predictions of PACE4. ICF of $^{12}\mathrm{C}$ in $^{181}\mathrm{Ta}$ target with strength up to $7.7%$ has been observed and compared with the strength deduced from previously reported data for the same system. However, no signature of precompound processes has been observed in this study. A total of 12 fission fragments within $71\ensuremath{\le}A\ensuremath{\le}135$ mass range have been identified. Further, mass variance is rising with increasing mass asymmetry, which hints at the importance of entrance-channel parameters' role in deciding the spread of the mass distribution.Conclusions: Good agreement of PACE4 with the excitation functions of $xn$ channel evaporation residues confirms their production through the CF mechanism. Enhancement of cross sections in the $\ensuremath{\alpha}xn$ channel is attributed to the ICF process. Further, evidence of the production of fission fragments through a compound nuclear mechanism is indicated as a broad and symmetric mass distribution, observed through the Gaussian fitting. The trend of mass variance with rising excitation energy and mass asymmetry is found to be growing.

Stimuli-responsive electrospun nanofibers based on PNVCL-PVAc copolymer in biomedical applications.

Poly(N-vinylcaprolactam) (PNVCL) is a suitable alternative for biomedical applications due to its biocompatibility, biodegradability, non-toxicity, and showing phase transition at the human body temperature range. The purpose of this study was to synthesize a high molecular weight PNVCL-PVAc thermo-responsive copolymer with broad mass distribution suitable for electrospun nanofiber fabrication. The chemical structure of the synthesized materials was detected by FTIR and 1HNMR spectroscopies. N-Vinyl caprolactam/vinyl acetate copolymers (159,680 molecular weight (g/mol) and 2.51 PDI) were synthesized by radical polymerization. The phase transition temperature of N-vinyl caprolactam/vinyl acetate copolymer was determined by conducting a contact angle test at various temperatures (25, 26, 28, and 30 [Formula: see text]). The biocompatibility of the nanofibers was also evaluated, and both qualitative and quantitative results showed that the growth and proliferation of 929L mouse fibroblast cells increased to 80% within 48h. These results revealed that the synthesized nanofibers were biocompatible and not cytotoxic. The results confirmed that the synthesized copolymers have good characteristics for biomedical applications.

Characterization of Classical Vaccines by Charge Detection Mass Spectrometry.

Vaccines induce immunity by presenting disease antigens through several platforms ranging from individual protein subunits to whole viruses. Due to the large difference in antigen size, the analytical techniques employed for vaccine characterization are often platform-specific. A single, robust analytical technique capable of widespread, cross-platform use would be of great benefit and allow for comparisons across manufacturing processes. One method that spans the antigen mass range is charge detection mass spectrometry (CDMS). CDMS is a single-ion approach where the mass-to-charge ratio (m/z) and charge are measured simultaneously, allowing accurate mass distributions to be measured for heterogeneous analytes over a broad size range. In this work, CDMS was used to characterize the antigens from three classical multivalent vaccines, inactivated poliomyelitis vaccine (IPOL), RotaTeq, and Gardasil-9, directly from commercial samples. For each vaccine, the antigen purity was inspected, and in the whole virus vaccines, empty virus particles were detected. For IPOL, information on the extent of formaldehyde cross-linking was obtained. RotaTeq shows a narrow peak at 61.06 MDa. This is at a slightly lower mass than expected for the double-layer particle, suggesting that around 10 pentonal trimers are missing. For Gardasil-9, buffer exchange of the vaccine resulted in very broad mass distributions. However, removal of the virus-like particles from the aluminum adjuvant using a displacement reaction generated a spectrum with narrow peaks.

Results of Search for Magnetized Quark-Nugget Dark Matter from Radial Impacts on Earth

Magnetized quark nuggets (MQNs) are a recently proposed dark-matter candidate consistent with the Standard Model and with Tatsumi’s theory of quark-nugget cores in magnetars. Previous publications have covered their formation in the early universe, aggregation into a broad mass distribution before they can decay by the weak force, interaction with normal matter through their magnetopause, and a first observation consistent MQNs: a nearly tangential impact limiting their surface-magnetic-field parameter Bo from Tatsumi’s ~1012+/−1 T to 1.65 × 1012 T +/− 21%. The MQN mass distribution and interaction cross section strongly depend on Bo. Their magnetopause is much larger than their geometric dimensions and can cause sufficient energy deposition to form non-meteorite craters, which are reported approximately annually. We report computer simulations of the MQN energy deposition in water-saturated peat, soft sediments, and granite, and report the results from excavating such a crater. Five points of agreement between observations and hydrodynamic simulations of an MQN impact support this second observation being consistent with MQN dark matter and suggest a method for qualifying additional MQN events. The results also redundantly constrain Bo to ≥ 4 × 1011 T.

Charge Manipulation Using Solution and Gas-Phase Chemistry to Facilitate Analysis of Highly Heterogeneous Protein Complexes in Native Mass Spectrometry.

Structural heterogeneity is a significant challenge complicating (and in some cases making impossible) electrospray ionization mass spectrometry (ESI MS) analysis of noncovalent complexes comprising structurally heterogeneous biopolymers. The broad mass distribution exhibited by such species inevitably gives rise to overlapping ionic signals representing different charge states, resulting in a continuum spectrum with no discernible features that can be used to assign ionic charges and calculate their masses. This problem can be circumvented by using limited charge reduction, which utilizes gas-phase chemistry to induce charge-transfer reactions within ionic populations selected within narrow m/z windows, thereby producing well-defined and readily interpretable charge ladders. However, the ionic signal in native MS typically populates high m/z regions of mass spectra, which frequently extend beyond the precursor ion isolation limits of most commercial mass spectrometers. While the ionic signal of single-chain proteins can be shifted to lower m/z regions simply by switching to a denaturing solvent, this approach cannot be applied to noncovalent assemblies due to their inherent instability under denaturing conditions. An alternative approach explored in this work relies on adding supercharging reagents to protein solutions as a means of increasing the extent of multiple charging of noncovalent complexes in ESI MS without compromising their integrity. This shifts the ionic signal down the m/z scale to the region where ion selection and isolation can be readily accomplished with a front-end quadrupole, followed by limited charge reduction of the isolated ionic population. The feasibility of the new approach is demonstrated using noncovalent complexes formed by hemoglobin with structurally heterogeneous haptoglobin.

Primordial Radius Gap and Potentially Broad Core Mass Distributions of Super-Earths and Sub-Neptunes

Abstract The observed radii distribution of Kepler exoplanets reveals two distinct populations: those that are more likely to be terrestrials (≲1.7R ⊕) and those that are more likely to be gas-enveloped (≳2R ⊕). There exists a clear gap in the distribution of radii that separates these two kinds of planets. Mass-loss processes like photoevaporation by high-energy photons from the host star have been proposed as natural mechanisms to carve out this radius valley. These models favor underlying core mass function of sub-Neptunes that is sharply peaked at ∼4–8M ⊕, but the radial-velocity follow-up of these small planets hints at a more bottom-heavy mass function. By taking into account the initial gas accretion in gas-poor (but not gas-empty) nebula, we demonstrate that (1) the observed radius valley is a robust feature that is initially carved out at formation during late-time gas accretion; and (2) that it can be reconciled with core mass functions that are broad extending well into the sub-Earth regime. The maximally cooled isothermal limit prohibits cores lighter than ∼1–2M ⊕ from accreting enough mass to appear gas-enveloped. The rocky-to-enveloped transition established at formation produces a gap in the radius distribution that shifts to smaller radii farther from the star, similar to that observed. For the best agreement with the data, our late-time gas accretion model favors dust-free accretion in hotter disks with cores slightly less dense than the Earth (∼0.8ρ ⊕) drawn from a mass function that is as broad as .

Spatial Variations of Low-mass Negative Ions in Titan’s Upper Atmosphere

Abstract Observations with Cassini’s Electron Spectrometer discovered negative ions in Titan’s ionosphere, at altitudes between 1400 and 950 km. Within the broad mass distribution extending up to several thousand amu, two distinct peaks were identified at 25.8–26.0 and 49.0–50.1 amu/q, corresponding to the carbon chain anions CN− and/or for the first peak and C3N− and/or C4H− for the second peak. In this study we present the spatial distribution of these low-mass negative ions from 28 Titan flybys with favorable observations between 2004 October 26 and 2012 May 22. We report a trend of lower densities on the night side and increased densities up to twice as high on the day side at small solar zenith angles. To further understand this trend, we compare the negative ion densities to the total electron density measured by Cassini’s Langmuir Probe. We find the low-mass negative ion density and the electron density to be proportional to each other on the day side but independent of each other on the night side. This indicates photochemical processes and is in agreement with the primary production route for the low-mass negative ions being initiated by dissociative reactions with suprathermal electron populations produced by photoionisation. We also find the ratio of to to be highly constrained on the day side, in agreement with this production channel, but notably displaying large variations on the night side.

Enhanced Multiplexing in Fourier Transform Charge Detection Mass Spectrometry by Decoupling Ion Frequency from Mass to Charge Ratio.

Weighing single ions with charge detection mass spectrometry (CDMS) makes it possible to obtain the masses of molecules of essentially unlimited size even in highly heterogeneous samples, but producing a mass histogram that is representative of all of the components in a mixture requires substantial measurement time. Multiple ions can be trapped to reduce analysis time but ion signals can overlap. To determine the maximum gains in analysis speed possible with current instrumentation with multiple ion trapping, simulations calculating the frequency and overlap rate of ions with different mass, charge, and energy ranges were performed. For an analyte with a broad mass distribution, such as long chain polyethylene glycol (PEG, 8MDa), gains in analysis speed of up to 160 times that of prior CDMS experiments are possible. For signals from homogeneous samples, ions with the same m/z have frequencies that overlap and interfere, reducing the effectiveness of multiplexing in experiments where ions have the same energy per charge. We show that by maximizing the decoupling of ion m/z from frequency using a broad range of ion energies, the rate of signal overlap is significantly reduced making it possible to trap more ions. Under optimum decoupling conditions, a measurement speed nearly 50 times greater than that of prior CDMS experiments is possible for RuBisCO (517kDa). The reduction in overlap due to decoupling also results in more accurate quantitation in samples that contain multiple analytes with different concentrations.

Primordial black holes and the origin of the matter-antimatter asymmetry.

We review here a new scenario of hot spot electroweak baryogenesis where the local energy released in the gravitational collapse to form primordial black holes (PBHs) at the quark-hadron (QCD) epoch drives over-the-barrier sphaleron transitions in a far from equilibrium environment with just the standard model CP violation. Baryons are efficiently produced in relativistic collisions around the black holes and soon redistribute to the rest of the universe, generating the observed matter-antimatter asymmetry well before primordial nucleosynthesis. Therefore, in this scenario there is a common origin of both the dark matter to baryon ratio and the photon to baryon ratio. Moreover, the sudden drop in radiation pressure of relativistic matter at H0/W±/Z0 decoupling, the QCD transition and e+e- annihilation enhances the probability of PBH formation, inducing a multi-modal broad mass distribution with characteristic peaks at 10-6, 1, 30 and 106 M⊙, rapidly falling at smaller and larger masses, which may explain the LIGO-Virgo black hole mergers as well as the OGLE-GAIA microlensing events, while constituting all of the cold dark matter today. We predict the future detection of binary black hole (BBH) mergers in LIGO with masses between 1 and 5 M⊙, as well as above 80 M⊙, with very large mass ratios. Next generation gravitational wave and microlensing experiments will be able to test this scenario thoroughly. This article is part of a discussion meeting issue 'Topological avatars of new physics'.

Constraints from microlensing experiments on clustered primordial black holes

Abstract It has recently been proposed that massive primordial black holes (PBH) could constitute all of the dark matter, providing a novel scenario of structure formation, with early reionization and a rapid growth of the massive black holes at the center of galaxies and dark matter halos. The scenario arises from broad peaks in the primordial power spectrum that give both a spatially clustered and an extended mass distribution of PBH. The constraints from the observed microlensing events on the extended mass function have already been addressed. Here we study the impact of spatial clustering on the microlensing constraints. We find that the bounds can be relaxed significantly for relatively broad mass distributions if the number of primordial black holes within each cluster is typically above one hundred. On the other hand, even if they arise from individual black holes within the cluster, the bounds from CMB anisotropies are less stringent due to the enhanced black hole velocity in such dense clusters. This way, the window between a few and ten solar masses has opened up for PBH to comprise the totality of the dark matter.

Seven hints for primordial black hole dark matter

Seven observations point towards the existence of primordial black holes (PBH), constituting the whole or an important fraction of the dark matter in the Universe: the mass and spin of black holes detected by Advanced LIGO/VIRGO, the detection of micro-lensing events of distant quasars and stars in M31, the non-detection of ultra-faint dwarf satellite galaxies with radius below 15 parsecs, evidences for core galactic dark matter profiles, the correlation between X-ray and infrared cosmic backgrounds, and the existence of super-massive black holes very early in the Universe's history. Some of these hints are newly identified and they are all intriguingly compatible with the re-constructed broad PBH mass distribution from LIGO events, peaking on PBH mass $m_{\rm PBH} \approx 3 M_\odot$ and passing all other constraints on PBH abundances. PBH dark matter also provides a new mechanism to explain the mass-to-light ratios of dwarf galaxies, including the recent detection of a diffuse galaxy not dominated by dark matter. Finally we conjecture that between 0.1% and 1% of the events detected by LIGO will involve a PBH with a mass below the Chandrasekhar mass, which would unambiguously prove the existence of PBH.

Primordial black holes from single field models of inflation

Primordial black holes (PBH) have been shown to arise from high peaks in the matter power spectra of multi-field models of inflation. Here we show, with a simple toy model, that it is also possible to generate a peak in the curvature power spectrum of single-field inflation. We assume that the effective dynamics of the inflaton field presents a near-inflection point which slows down the field right before the end of inflation and gives rise to a prominent spike in the fluctuation power spectrum at scales much smaller than those probed by Cosmic Microwave Background (CMB) and Large Scale Structure (LSS) observations. This peak will give rise, upon reentry during the radiation era, to PBH via gravitational collapse. The mass and abundance of these PBH is such that they could constitute the totality of the Dark Matter today. We satisfy all CMB and LSS constraints and predict a very broad range of PBH masses. Some of these PBH are light enough that they will evaporate before structure formation, leaving behind a large curvature fluctuation on small scales. This broad mass distribution of PBH as Dark Matter will be tested in the future by AdvLIGO and LISA interferometers.

Synthesis and characterization of high cis‐polymyrcene using neodymium‐based catalysts

AbstractThe monomer β‐myrcene, a renewable resource, was polymerized in cyclohexane using two different Ziegler‐Natta catalyst systems based on neodymium Nd(Oi‐Pr)3 and NdV3. The Nd(Oi‐Pr)3 was combined with [HNMe2Ph][B(C6F5)4] (or [CPh3][B(C6F5)4]) and Al(i‐Bu)3 (or Al(i‐Bu)2H). Next, the NdV3 was activated using Al(i‐Bu)3 and AlEt2Cl. Both catalyst systems exhibited high polymer yields near 100 % in the established reaction time, high polymer molecular masses, and broad molecular mass distributions. The catalyst systems gave an effective and stereospecific polymerization reaction of β‐myrcene providing high cis selectivity of 1,4‐polymyrcenes (> 92 %) with a glass transition temperature between −66 and −62 °C. The above‐mentioned features of resulting elastomers in conjunction with the polymer's molecular masses and molecular mass distributions proved to be sensitive to borane and alkylaluminum compounds molar ratios, [B]/[Nd] and [Al]/[Nd] using Nd(Oi‐Pr)3 and [Cl]/[Nd] and [Al]/[Nd] with NdV3.

Acquiring Structural Information on Virus Particles with Charge Detection Mass Spectrometry.

Charge detection mass spectrometry (CDMS) is a single-molecule technique particularly well-suited to measuring the mass and charge distributions of heterogeneous, MDa-sized ions. In this work, CDMS has been used to analyze the assembly products of two coat protein variants of bacteriophage P22. The assembly products show broad mass distributions extending from 5 to 15 MDa for A285Y and 5 to 25 MDa for A285T coat protein variants. Because the charge of large ions generated by electrospray ionization depends on their size, the charge can be used to distinguish hollow shells from more compact structures. A285T was found to form T = 4 and T = 7 procapsids, and A285Y makes a small number of T = 3 and T = 4 procapsids. Owing to the decreased stability of the A285Y and A285T particles, chemical cross-linking was required to stabilize them for electrospray CDMS.Graphical Abstract.

The clustering amplitude of X-ray-selected AGN atz∼ 0.8: evidence for a negative dependence on accretion luminosity

The northern tile of the wide-area and shallow XMM-XXL X-ray survey field is used to estimate the average dark matter halo mass of relatively luminous X-ray selected AGN [$\rm log\, L_X (\rm 2-10\,keV)= 43.6^{+0.4}_{-0.4}\,erg/s$] in the redshift interval $z=0.5-1.2$. Spectroscopic follow-up observations of X-ray sources in the XMM-XXL field by the Sloan telescope are combined with the VIPERS spectroscopic galaxy survey to determine the cross-correlation signal between X-ray selected AGN (total of 318) and galaxies (about 20,\,000). We model the large scales (2-25\,Mpc) of the correlation function to infer a mean dark matter halo mass of $\log M / (M_{\odot} \, h^{-1}) = 12.50 ^{+0.22} _{-0.30}$ for the X-ray selected AGN sample. This measurement is about 0.5\,dex lower compared to estimates in the literature of the mean dark matter halo masses of moderate luminosity X-ray AGN [$L_X (\rm 2-10\,keV)\approx 10^{42} - 10^{43}\,erg/s$] at similar redshifts. Our analysis also links the mean clustering properties of moderate luminosity AGN with those of powerful UV/optically selected QSOs, which are typically found in halos with masses few times $10^{12}\,M_{\odot}$. There is therefore evidence for a negative luminosity dependence of the AGN clustering. This is consistent with suggestions that AGN have a broad dark matter halo mass distribution with a high mass tail that becomes sub-dominant at high accretion luminosities. We further show that our results are in qualitative agreement with semi-analytic models of galaxy and AGN evolution, which attribute the wide range of dark matter halo masses among the AGN population to different triggering mechanisms and/or black hole fueling modes.