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in the lambda cold dark matter hierarchical structure formation paradigm, a spiral galaxy's stellar halo is thought to have formed through the accretion of smaller dwarf galaxies onto the larger galaxy. the remnant stars from each accretion event trace out a different shape or morphology in the stellar halo, and as a w... | studying the accretion history of the milky way using mock observations of galaxy formation simulations |
a critical challenge to the cold dark matter (cdm) paradigm is that there are fewer satellites observed around the milky way than found in simulations of dark matter substructure. we show that there is a match between the observed satellite counts corrected by the detection efficiency of the sloan digital sky survey (f... | there is no missing satellites problem |
we propose wfc3 uvis imaging of a new sample of 21 gravitationally lensed lyman-alpha emitting galaxies (laes) discovered within the million-galaxy spectroscopic database of the baryon oscillation spectroscopic survey (boss) of the third sloan digital sky survey (sdss-iii). these systems consist of massive galaxies at ... | quantifying cold dark matter substructure with a qualitatively new gravitational lens sample |
in this thesis, we harness the power of modern scientic computing to explore the formation and evolution of cosmological structure in a wide variety of astrophysical scenarios. we explore the nonlinear dynamics associated with the interplay between cold dark matter (cdm), baryons, ionizing radiation, and cosmic neutrin... | simulating the universe: nonlinear formation and evolution of cosmic structure |
the abundance of substructure within dark matter halos surrounding galaxies has been an area of intensive study for over a decade. the number of observed low-mass satellites of the milky way is about three orders of magnitude lower than what cold dark matter (cdm) simulations predict, an issue that is referred to as th... | mapping the small-scale structure of dark matter halos with strong gravitational lensing |
rr lyrae stars are powerful tracers of galactic structure, substructure (intact and disrupted dwarf satellite galaxies), accretion history, and dark matter content. the characteristic photometric variability pattern of rr lyrae stars makes it relatively easy to tell them apart from other stars (sample contaminants) and... | discovery of the most distant milky way halo rr lyrae stars |
tidal streams are promising candidates for studying dark matter (dm) subhalos at the smallest scales predicted by cdm. studies have proposed that tidal streams can be perturbed by interactions with dm subhalos, causing over- and underdensities (known as "gaps") in the stellar density along the stream, which is otherwis... | effects of dark matter subhalos on tidal streams |
abell 1240 belongs to a rare class of merging galaxy clusters with symmetric double radio relics. in order to reconstruct the merging scenario of this interesting system, it is important to map out the dark matter distribution and identify substructures. we present the first weak-lensing analysis of abell 1240 with sub... | revealing substructures in abell 1240 with subaru weak gravitational lensing |
ngc1052-df2 and ngc1052-df4 are two puzzling ultra-diffuse galaxies: they have low velocity dispersions indicating little to no dark matter content, as well as overly luminous and large globular clusters compared to the milky way population. our group proposes a new model where these two galaxies formed jointly in the ... | a trail of dark matter-free galaxies from a bullet dwarf collision |
cosmological dark matter simulations predict that the central regions of halos have 1/r density cusps. baryonic processes and dark matter microphysics may resculpt these dark matter cusps, but these process are poorly understood and only weakly constrained by observations of a few low redshift halos. we have discovered... | a unique probe of the dark matter distribution in a halo at z=1: a strong lens with a bright central image |
deap-3600 is a low-background, single-phase liquid argon (lar) direct detection experiment looking for nuclear recoils from wimp dark matter, operating 2 km underground at snolab (sudbury, canada). the detector consists of 3279 kg of lar contained in a spherical acrylic vessel. lar is an excellent scintillator, transpa... | status of deap-3600 at snolab |
detecting hot gas in cluster outskirts is one of the major goals of our next-generation x-ray and sub-mm/sz facilities. it is important to understand how accretion and mergers shape clusters near and beyond the virial radius. even though cosmological simulations have been extensively used for these studies, idealized m... | evolution of shocks and splashback boundaries in cluster outskirts |
a one-electron quantum cyclotron, quantum mon-demolition (qnd) detection, inhibited spontaneous emission, a split dilution refrigerator, and a self-shielded superconducting solenoid have been used to measure the electron's magnetic moment. this most precise determination of a property of an elementary particle, to 1.3 ... | new measurement of the electron magnetic moment and a new dark photon limit |
stellar halo of a galaxy preserves most of the information and assembly history and it could play a crucial role to understand the hierarchical structure formation. the nonlinear nature of the hierarchical structure formation and the wide range of physical processes involved, demand full physics computational models bu... | cosmological stellar halo simulations with cosang |
strong gravitational lensing is a promising method for probing the nature and distribution of dark matter on sub-galactic scales. in addition to the subhalos of the main lens, dark matter halos along the line-of-sight between the observer and the source contribute significantly to the subtle perturbations to lensed ima... | investigating dark matter microphysics with strong gravitational lensing anisotropies |
we develop two new methods to measure the structure of matter around the milky way using stellar tidal streams from disrupting dwarf galaxies and globular clusters. the dark matter halo of the milky way is expected to be triaxial and filled with substructure, but measurements of the shape and profile of dark matter aro... | inferring the 3d gravitational field of the milky way with stellar streams |
in this paper, we investigated the influence of dark matter in galactic halos on the dynamics of galaxies in merger events, using n-body simulations. in the standard cosmological picture, large massive galaxies are formed by mergers of smaller ones. these mergers are very important for galactic dynamics and evolution. ... | dark matter halos in galaxy mergers |
one outstanding question in cosmology is, what are the smallest galaxies that can form? the answer to this question can tell us much about galaxy formation, and even of the properties of dark matter itself. a candidate for the smallest galaxies that can form are the ultrafaint galaxies. the star formation of ultrafaint... | the smallest galaxies in the universe: investigating the origins of ultra-faint galaxies |
relating observations of cluster galaxies or the gas content to the total mass of the underlying dark matter halos is a key challenge in the current cluster cosmology community. on the other hand, accurate measurement of hot and cold phase baryon covariance in clusters will offer important constraints on hydrodynamic m... | closed box nature of galaxy clusters through multi-wavelength analysis |
like strings of lights wrapped around a tree, stellar streams trace out the gravitational potential of the milky way, as well as providing a snapshot of the process of accretion by which galaxies grow. in recent years, wide-area photometric surveys like sdss and des have revealed an abundance of stellar substructure in... | disentangling the holiday lights: tracing the milky way's accretion history and gravitational potential with stellar streams |
stars escaping globular clusters form thin, long and kinematically-cold tidal streams. in pristine conditions, these streams have nearly uniform density, however, new gaia observations of one such structure in the milky way halo have revealed a likely site of perturbation. the on-sky morphology suggests a recent, close... | dynamical evidence for a dark substructure in the milky way halo |
among the most fundamental predictions of lcdm cosmology is the existence of a large number of dark subhalos in and around galaxies, most of which should be entirely devoid of stars. confirming the existence of this substructure stands among the most important empirical challenges in modern cosmology. the goal of this ... | accurate predictions for dark matter substructure |
we introduce coupled semi-analytic n-body galaxies (cosang), a hybrid cosmological algorithm for stellar halo simulations. it combines a fast n-body model (gadget3) with a semi-analytic model (sage) to add baryonic potentials. this live interaction at each time-step can produce more accurate dynamics than pure n-body s... | connecting dark matter halos to stellar halos with coupling semi-analytic and n-body galaxies (cosang) |
one of the goals of theoretical galaxy formation is to use simulations combined with observations in order to constrain the fundamental physics that govern the formation of galaxies. of particular interest are physical processes that can impact the formation of small-scale structures. among the things we can potentiall... | exploring fundamental physics with small-scale structures |
the structure of dark matter halo is hierarchical. among them, small-scale structures in dark matter halo (so-called subhalos) can enhance dark matter annihilation signals. it is necessary to quantify boost factors by those subhalos to derive the property of dark matter with current/future gamma-ray observations. in or... | modeling evolution of dark matter substructure and annihilation boost |
in the prevailing lambda cold dark matter cosmology, galaxies grow continuously in mass through hierarchical assembly of smaller systems, and dark matter halos host substructures down to the resolution limit of the simulations. hierarchical evolution should occur at all scales, implying that the satellites of the milky... | satellites of satellites: the power of combining hst photometry and gaia |
we present the results of alma observations of dust continuum emission and molecular rotational lines, including the alma compact array, toward a dense core mc27 (a.k.a. l1521f) in taurus, which is considered to be at very early stage of star formation. detailed column density distribution with a size scale from a few ... | stars are formed by mergers of dark matter planets |
simulations based on λcdm cosmology predict thousands of substructures under galactic scale have not been detected in the local universe. one hypothesis proposes that most of these substructures are dark for various astrophysical reasons. gravitational lensing provides a powerful alternative way to probe dark substruct... | exploring a potential bias in dark matter investigations using strongly lensed quasars |
ever since the discovery of the first gravitational lens system by walsh, carswell and weymann in 1979, there has been tremendous excitement in the astronomy community about exploiting the power of gravitational lenses. lenses act as cosmic telescopes, magnifying the emission from sources in the background. this helps ... | observations and modelling of gravitational lenses |
high-resolution studies of nearby stellar populations have served as a foundation for our quest to understand the nature of galaxies. today, studies of resolved stellar populations constrain fundamental relations -- such as the initial mass function of stars, the time scales of stellar evolution, the timing of mass los... | resolving the milky way and nearby galaxies with wfirst |
recent efforts to understand the dynamical history of the milky way by exploring the observational signatures of accreted substructure have yielded a number of interesting results. however, it is difficult to interpret the significance of the results in a cosmological context because the unique formation history of the... | understanding the impact of formation history on the dynamical distribution of substructure using the "milky way"-est simulation suite |
i present a brief overview of how stellar halos may be used to constrain the process of galaxy formation. in particular, streams and substructure in stellar halos trace merger events but can also be used to determine the mass distribution of the host galaxy and hence put constraints on the nature of dark matter. much o... | stellar halos and the link to galaxy formation |
we present results from follow-up spectroscopic observations of clustered cepheid candidates identified from k-band light curves towards the norma constellation (chakrabarti et al. 2015), as well as others that we have found more recently. the average radial velocity of these stars is ~ 200 km/s, which is large and dis... | a receding halo sub-structure towards norma |
tidal streams of globular clusters are ideal tracers of the galactic gravitational potential. compared to the few known, complex and diffuse dwarf-galaxy streams, they are kinematically cold, have thin morphologies and are abundant in the halo of the milky way. their coldness and thinness in combination with potential ... | globular cluster streams as galactic high-precision scales |
the molecular clouds (mcs), which are observed as giant molecular clouds, isolated bok globules and/or infrared dark clouds, are the nurseries for forming stars and planets. observations show that the mcs are influenced by diverse forms of magnetic field lines. the magnetic field gradients can produce the ambipolar dif... | non-isothermal effects on the static equilibria of magnetized layers of molecular clouds |
collisions between galaxy clusters are a frequent scenario in the hierarchical model of structures. dissociative collisions provide an extreme environment of interaction between clusters of galaxies, where the properties of dark matter (dm) in relation to baryonic matter become evident. investigating dissociative scena... | the role of gas and dark matter in the dissociative collision of galaxy cluster abell 2034 |
we use a catalogue of stellar binaries with wide separations (up to 1 pc) identified by the gaia satellite to constrain the presence of extended substructure within the milky way galaxy. heating of the binaries through repeated encounters with substructure results in a characteristic distribution of binary separations,... | constraining dark matter substructure with gaia wide binaries |
in this work, we present updated results on an ongoing dark matter search using astrometric weak gravitational lensing. following the analysis in mondino et al. (2020), results are reported on a dark matter search using proper motions on stars in the magellanic clouds from gaia's most recent data release. additionally,... | astrometric weak lensing constraints on dark matter substructure with gaia edr3 |
fuzzy dark matter (fdm) has recently emerged as an interesting alternative model to the standard cold dark matter (cdm). in this model, dark matter consists of very light bosonic particles with quantum mechanical effects on galactic scales. since the small-scale behaviour of fdm is completely determined by the mass of ... | no catch-22 for fuzzy dark matter: testing substructure counts and core sizes via high resolution cosmological simulations |
we aim to understand the distribution of dark matter within both the milky way (mw) and external galaxies. in the mw, the dark matter distribution can be constrained now through direct acceleration measurements using pulsar timing and through indirect kinematic methods. my work aims to calibrate indirect methods of cha... | studying dark matter with pulsar timing, stellar streams and strong lensing |
understanding the observable astrophysical consequences of the fundamental properties of dark matter isessential for evaluating diverse observations by hst, from within streams and dwarf galaxies in or near themilky way, to effects on the formation and evolution of structure in cosmologically distant galaxies andcluste... | nonlinear evolution predictions for dark matter substructure, and predictions for gravitational lensing probes |
cosmological observables, from the cmb anisotropy to the census of galaxies in the local universe, offer the most direct and broad tests for the nature of dark matter, including a number of scenarios that are challenging or even impossible to test in a laboratory setting. i will review the status of the recent early-un... | dark matter physics from near-field cosmology |
we have recently pointed out that flattening rotation curves v(r) are naturally explained by elongated (prolate) dark matter (dm) distributions, and provided competitive fits to the sparc database. to further probe the geometry of the halo one needs out-of-plane observables. stellar streams in the milky way, poetically... | the torsion of stellar streams due to a nonspherical dark matter halo |
the analysis of optical images of galaxy-galaxy strong gravitational lensing systems can provide important information about the distribution of dark matter at small scales. however, the modeling and statistical analysis of these images is extraordinarily complex, bringing together source image and main lens reconstruc... | targeted likelihood-free inference of dark matter substructure in strongly-lensed galaxies |
we study the dynamical states of the 30 most massive galaxy clusters in the tng100 simulation at redshift z = 0 using three types of tracers: stars, dark matter particles and satellite galaxies. if the massive galaxy cluster is spherically symmetric and relaxed, we can obtain the underlying total mass distribution accu... | the relaxation of galaxy clusters at redshift z = 0 in illustristng simulation |
a key prediction of cold dark matter (cdm) cosmology is a scale-free hierarchy of bound structure, from the largest galaxy clusters down to earth-mass microhalos. when partnered with the weakly interacting massive particle (wimp) high-energy physics description of cdm, this simple cosmological model makes accurate pred... | seeing in the dark: revealing dark matter microphysics with substructure lensing |
taking secondary particles produced from dark matter (dm) annihilation process to the origin of the extended diffuse radio emission observed in galaxy clusters, we studied both their morphology and radio spectral profile using simulated coma like galaxy clusters. we have considered a neutralino annihilation channel dom... | non-thermal radio emission from dark matter annihilation processes in simulated coma like galaxy clusters |
self-interacting dark matter (sidm) predicts that dark matter halos experience core-collapse, a process where the halo's inner region rapidly increases in density and decreases in size. because of the short timescales and high densities involved, n-body simulations of the process are numerically challenging. we perform... | convergence tests and applications of sidm core-collapse simulations |
smaller substructures merged at different times to form the present-day milky way, and evidence for accretion has been discovered by various astronomical surveys. among all, the gaia collaboration released radial velocity measurements of 33 million stars in the milky way in data release 3 (dr3), a factor of 5 larger th... | using machine learning to catalog accreted stars in gaia esa dr3 survey |
the large-scale structure (lss) of the universe provides scientists with one of the best laboratories for studying lambda cold dark matter (lambdacdm) cosmology. especially at high redshift, we see increased rates of galaxy cluster and galaxy merging in lss relative to the field, which is useful for studying the hierar... | cosmological studies with galaxy clusters, active galactic nuclei, and strongly lensed quasars |
when a quasar is gravitationally lensed by a galaxy, its multiple images show light-curves that are offset by awell defined time delay, which depends on the mass profile of the lens and on cosmological distances to the lens and the source. by measuring the time-delay and accurately modelling the deflector's mass profil... | strides: galaxy evolution over cosmic time from new samples of gravitationally lensed quasars |
stellar halos give insight to the initial conditions that existed when a host galaxy first formed and provide details on disrupted satellites by looking at the different stellar populations. an algorithm that is computationally inexpensive compared to hydrodynamic simulations is necessary in order to theoretically stud... | coupling semi-analytic models and n-body simulations: a new way of making galaxies and stellar halos |
we apply the jeans equation to identify subhalos in high-resolution numerical simulations that are potentially consistent with observed properties of milky way dwarf spheroidal (dsph) galaxies. we investigate the effects found by several recent studies that show changes to the dynamical properties of galactic substruct... | the kinematics of milky way satellites as a test of dark matter models |
despite the success of the lambdacdm model at describing the universe on large scales, the model's predictions are at odds with observations on sub-galactic scales. in particular, the model predicts that a milky-way-sized dark matter halo should contain substructures in the form of low mass subhalos. however, there has... | dynamical signatures of dark matter substructures on tidal streams |
we study the abundance of substructure in the matter density near galaxies using alma science verification observations of the strong lensing system sdp.81. we present a method to measure the abundance of subhalos around galaxies using interferometric observations of gravitational lenses. using simulated alma observati... | commentary on hezaveh et al. 2016 titled "best to forget lcdmhc" |
in this work, different aspects of the high-energy radiation are looked at considering the lhc scenario. an event-shape variable and several jet substructure observables are studied with the mote carlo event simulators at the 13 tev center of mass energy scale to mimic the current lhc environment. the event-shape and t... | a simulation study of the soft and hard radiations using jets at the lhc |
in the currently favored cold dark matter (cdm) model, dark matter is concentrated into gravitationally bound clumps known as halos and subhalos. dark matter is only known to interact gravitationally, making subhalos difficult to detect unless they contain baryons. stellar streams, extended tails of stars formed from t... | measuring dark matter with stellar streams |
the fornax cluster provides an unparalleled opportunity to investigate the formation and evolution of earlytype galaxies in a dense environment. deep-field photometric surveys of the fornax cluster, conducted using omegacam and vircam/vista, have provided excellent data for studying the fornax environment. a step furth... | utilizing eso wide field imaging surveys to learn the mass-assmebly of fornax cluster |
the standard cdm model is believed to have problems on small - galactic and sub-galactic - scales, namely the substructure problem (ssp), too-big-to-fail (tbtf) problem and core-cusp problem (ccp). recently, we've shown that a two-component (e.g., flavor-mixed) dark matter (2cdm) model can resolve all these problems al... | dark-matter-only simulations of the 2cdm model with σ(v) as a solution to the cdm small-scale problems |
we show how the higgs boson exchange processes may indicate the occurence of special higgs boson structures (substructures or peculiar interactions with dark matter) from a possible modification of the s-dependence of their cross section. we illustrate the simplest example with the $\mu^+\mu^-\to f\bar f$ process. | higgs boson structure from the shape of the cross section in exchange processes |
context: galaxy clusters are the most massive gravitationally bound structures in the universe and are formed through the process of hierarchical clustering, in which smaller systems undergo a series of mergers to form ever larger clusters. because of the masses involved, mergers between these giants provide a unique l... | merging galaxy clusters: a case study of zwcl 2341.1+0000 and the development of a new forward modeled lensing technique |
searches for new resonances whose decays result in top quarks and/or b-quarks cover a wide range of beyond the standard model (bsm) physics. these searches offer great potential as well as significant challenges in reconstructing and identifying the decay products as well as modeling the sm background. this talk presen... | searches for new resonances decaying to heavy-flavour quarks with the atlas detector at √{ s } = 13 tev |
the maunakea spectroscopic explorer (mse) will conduct a suite of observations that probe the particle nature of dark matter by providing critical input in determining the halo mass function, phase-space distribution, and internal density profiles of dark matter halos across all mass scales. n-body and hydrodynamical s... | astrophysical tests of dark matter with mse |
stellar tidal streams from disrupting globular clusters are among the most dynamically cold systems known. this makes them sensitive to both the global structure of the milky way's gravitational potential and to substructures within it. in particular, a passing dark matter subhalo can cause a gap to form in the stream ... | stellar streams and milky way substructure in the era of lsst and wfirst |
constraining the distribution of small-scale structure in our universe will allow us to probe alternatives to the cold dark matter (cdm) paradigm. strong gravitational lensing offers a unique window into small dark matter halos (109 msun) because these halos impart a gravitational lensing signal even if they do not hos... | reconstructing the subhalo mass function from strong gravitational lensing |
tesseract computes concentrations of simulated dark matter halos from volume information for particles generated using voronoi tesselation. this technique is advantageous as it is non-parametric, does not assume spherical symmetry, and allows for the presence of substructure. tesseract accepts data in a number of forma... | tesseract: tessellation-based recovery of amorphous halo concentrations |
within lcdm, dwarf galaxies like the large magellanic cloud are expected to host many dark matter subhalos, several of which should be massive enough to host faint dwarf companions. recent gaia proper motions have confirmed new members of the lmc-system including three classical mstar > 10^5 msun dsph as well as sev... | faint and ultra-faint dwarf satellites of the lmc in the fire |
hayashi (halo-level analysis of the absorption signal in hi) computes the number of absorption features of the 21cm forest using a semianalytic formalism. it includes the enhancement of the signal due to the presence of substructures within minihalos and supports non-standard cosmologies with impact in the large scale ... | hayashi: halo-level analysis of the absorption signal in hi |
the cold dark matter model predicts that the milky way is formed by the accretion and merger of many smaller dwarf galaxies. the process of accretion and merger will leave stellar streams and other substructures in the milky way, which are the debris of the dwarf galaxies. to better understand the formation history of ... | the research of the milky way's accretion and merger origin |
in the standard cosmological model, the matter content of the universe is dominated by cold dark matter (cdm), collisionless particles that interact with ordinary matter (baryons) only through gravity. gravitationally bound dark-matter halos form hierarchically, with the most massive systems growing through mergers of ... | tensions on small scales: too many galaxy-galaxy strong lenses in galaxy clusters? |
rr lyrae stars are powerful tracers of galactic structure, substructure, accretion history, and dark matter content. the characteristic photometric variability of rr lyrae stars makes it relatively easy to distinguish them from other objects, and they are excellent standard candles. in this paper, we report on the disc... | distant milky way halo rr lyrae stars in the next generation virgo cluster survey: exploring the outer edge of our galaxy |
we present results for utilizing weak lensing analysis in the identification and classification of the dark matter substructure in galaxy clusters. using a previously developed flexion analysis package (flextool) gravitationally lensed images are analyzed for their flexion signal, the anisotropic inward "bowing" of a l... | gravitational flexion measures toward substructure in the frontier fields |
milkyway@home is a 0.5 petaflops volunteer computing platform that is mapping out the density substructure of the sagittarius dwarf tidal stream, the so-called bifurcated portion of the sagittarius stream, and the virgo overdensity, using turnoff stars from the sloan digital sky survey. it is also using the density of ... | characterizing milky way tidal streams and dark matter with milkyway@home |
the nature of dark matter can be better constrained by observing merging galaxy clusters. however, uncertainty in the viewing angle leads to uncertainty in dynamical quantities such as 3-d velocities, 3-d separations, and time since pericenter. the classic timing argument links these quantities via equations of motion,... | merging galaxy clusters: analysis of simulated analogs |
some strong gravitational lens systems exhibit features that cannot be explained by a smooth mass distribution. a possible explanation for these anomalies is the presence of dark matter substructure of the type predicted by lcdm. much work has been done to use these anomalous lens systems to attempt to detect individua... | testing methods to measure dark matter substructure with gravitational lensing |
over the last two decades, strong gravitational lensing has emerged as a promising tool for probing the nature and distribution of dark matter on sub-galactic scales. in addition to the main-lens substructure, dark matter halos along the line-of-sight between the observer and the source contribute significantly to the ... | dark matter physics through small-scale lensing anisotropies |
the splashback radius of a dark matter halo, which refers to the radius that infalling matter and substructures approach the apocenter for the first time, has been detected around galaxy clusters using a multitude of observational methods including galaxy cluster weak lensing measurements. in this poster, we present ho... | the effect of splashback on weak lensing mass estimates of galaxy clusters and groups |
we present preliminary results to test the accuracy of association methods applied to galaxy surveys, in order to constraint their limitations and develop possible alternatives to improve them. we focused in the friends-of-friends (fof) method, carrying on the analysis on the dark matter cosmological simulation mdpl2, ... | siblings, friends and acquaintances: testing the galaxy association methods |
this thesis explores wave dark matter and its intriguing phenomenological implications, namely the presence of wave-like signatures on astrophysical length scales. specifically, we assume the dark matter is composed of light bosons with masses below 10 ev, allowing, due to the high phase space occupation number, for a ... | gravitational signatures of wave dark matter |
merger trees track the evolution of halos across multiple snapshots. they assign for halos of a particular snapshot, the set of halos from previous snapshots they possibly originated from. in this work, association rule analysis a well known technique from data mining has been used to build halo merger trees. associati... | application of association rule analysis to study the evolution of halos in cosmological n-body simulations |
the wealth of ongoing and upcoming observations of the milky way (mw) promise an era of "near-field cosmology" that can test the cold dark matter (cdm) paradigm. one of the most exciting and powerful probes of dm is using the mw's stellar streams as "gravitational antennae:" close passages of small dm substructures dyn... | predicting observable signatures for dynamical interactions between dark-matter substructure and stellar streams in the milky way |
the lambda cold dark matter model for structure formation has been very successful at reproducing observations of large scale structures. however, challenges emerge at sub-galactic scales, e.g. the number of dwarfs around the milky way show an order of magnitude difference with simulations (the 'missing satellites prob... | a new dwarf detection algorithm applied to m101 |
weakly interacting massive dark matter (dm) particles are expected to self-annihilate or decay, generating high-energy photons in these processes. this establishes the possibility for indirect detection of dm by \gamma-ray telescopes. for probing the secondary products of dm, accurate knowledge about the dm density dis... | search for galactic dark matter substructures with cherenkov telescopes |
the cosmological model based on cold dark matter (cdm) and dark energy has been hugely successful in describing the observed evolution and large scale structure of our universe. however, at small scales (in the smallest galaxies and at the centers of larger galaxies), a number of observations seem to conflict with the ... | re-examining astrophysical constraints on the dark matter model |
arising from inhomogeneities during inflation, primordial black holes (pbh) have long been proposed as a dark matter candidate. there has been a renewed interest in pbhs after the ligo detections of binary black hole mergers, with claims that these were primordial in nature. gravitational wave observations hold promise... | gravitational wave radiation from primordial black hole clusters |
in most lux data analyses, the collaboration have mostly relied on the lux data processing framework's output known as the ''reduced quantities'' (e.g. event energy, position etc.). however some info embedded in the unprocessed multichannel photomultiplier tube (pmt) time traces were lost in the processing. to extract ... | machine learning applied to background events identification in lux dark matter experiment |
ultralight bosons with de broglie wavelength 1 kpc have been proposed as a model of dark matter (dm) which can potentially evade some problems on small scales (core-cusp, substructure). here we investigate a dwarf dm halo evolution in a tidal field of a host halo taking into account the dm quantum tunneling. this proce... | dwarf halos and ultralight dark matter model |
in this thesis, i study the expected direct and indirect detection signals of dark matter. more precisely, i study three aspects of dark matter; i use hydrodynamic simulations to extract properties of weakly interacting dark matter that are relevant for both direct and indirect detection signals, and construct viable d... | boosting (in)direct detection of dark matter |
this thesis presents a search for dark matter production in association with a higgs boson decaying to a pair of bottom quarks, using data from 20.3 fb-1 of proton-proton collisions at a center-of-mass energy of 8 tev collected by the atlas detector at the lhc. the dark matter particles are assumed to be weakly interac... | search for dark matter produced in association with a higgs boson decaying to two bottom quarks at atlas |
with the completion of 7 tev and 8 tev data taking at the large hadron collider (lhc), the physics community witnessed one of the great triumphs of modern physics: the completion of the standard model (sm) as an effective theory. the final missing particle, the higgs boson, was observed and its mass was measured. howev... | new physics undercover at the lhc |
we request hst/acs imaging to follow up the 10 most prominent newly discovered substructures in the halos of ngc 253 and ngc 5128 (both at d=3.8 mpc, and the dominant galaxies of their respective groups, sculptor and centaurus a). the substructures were found via our ongoing ground-based (magellan/megacam) survey out t... | resolved halo substructures beyond the local group: the assembly histories of ngc 253 and ngc 5128 |
both the milky way (mw) and its massive neighbor, m31, host systems of satellite dwarf galaxies that are relics of their assembly history. nasa observatories, such as hst, wfirst, and jwst, and survey missions, such as gaia and lsst, have/will be used to identify new substructure about the mw and m31 and measure the ki... | the impact of massive satellites on the dark matter halos of the milky way and m31 |
a critical challenge to the cold dark matter (cdm) paradigm is that there are fewer satellites observed around the milky way than found in simulations of dark matter substructure. we show that there is a match between the observed satellite counts corrected by the detection efficiency of the sloan digital sky survey (f... | there is no missing satellites problem |
the high altitude water cherenkov observatory (hawc) is a high energy (500 gev to 100 tev) gamma ray detector located in central mexico. hawc operates via the water cherenkov technique and has both a wide ( 2 sr) field of view and near continuous duty cycle, making it ideal for unbiased sky surveys and analysis of high... | a search for dark matter gamma rays in the galactic halo with hawc |
baryonic feedback at high redshifts has been proposed to explain the inference of dark matter (dm) cores in low-surface brightness and dwarf spheroidal galaxies. however, in the currently favoured cosmological model, structure grows hierarchically and cdm predicts a myriad of small substructures orbiting dwarf galaxies... | dark subhalo accretion onto dwarf galaxies in cdm |
the cold dark matter paradigm predicts that a milky way-like galaxy should be surrounded by thousands of low-mass dark matter halos, many of which are expected to be devoid of stars and gas. the presence of these invisible halos can be inferred using strong gravitational lensing, since dark matter substructure can prod... | detecting and constraining low mass dark matter halos by their perturbations of gravitationally lensed images |
lcdm predicts that the dark matter subhalo mass function is nearly self-similar. we therefore expect massive galaxies as well as smaller, dwarf galaxies to have a substantial amount of dark matter subhalos surrounding them. however, we expect the occurrence and nature of debris structures around dwarfs to be different ... | the frequency of stellar streams around dwarf galaxies |
one outstanding question in cosmology is, what are the smallest galaxies that can form? the answer to this question can tell us much about galaxy formation, and even of the properties of dark matter itself. a candidate for the smallest galaxies that can form are the ultrafaint galaxies. the star formation of ultrafaint... | the smallest galaxies in the universe: investigating the origins of ultra-faint galaxies |
axions, which can solve the strong cp problem, and axion-like particles (alps), which arise naturally in many models of high-scale physics, provide theoretically compelling dark matter candidates. axions and alps which couple to photons have been shown to produce observable radio emission through their conversion to ph... | constraints on axion dark matter from searches for radio signals from neutron stars |
i will present a dynamical analysis of abell 267 (z~0.23) using over 1000 galaxy redshifts from new spectra observed with magellan/m2fs combined with publicly available redshifts from the hectospec cluster survey. for each galaxy, we measure redshift as well as mean age, metallicity, alpha enrichment, and internal velo... | galaxy cluster mass estimates in the presence of substructure |
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