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context. new-generation cosmological simulations are providing huge amounts of data, whose analysis becomes itself a pressing computational problem. in particular, the identification of gravitationally bound structures, known as halo finding, is one of the main analyses. several codes that were developed for this task ... | the halo-finding problem revisited: a deep revision of the asohf code |
motivated by the idea that a subset of high-velocity clouds (hvcs) trace dark matter substructure in the local group, we search for signs of star formation in the smith cloud, a nearby ∼2 × 106 m⊙ hvc currently falling into the milky way. using galex nuv and wise/2mass nir photometry, we apply a series of colour and ap... | a search for star formation in the smith cloud |
context. local group (lg) analogs (lgas) are galaxy associations dominated by a few bright spirals reminiscent of the lg. the ngc 3447/ngc 3447a system is a member of the lgg 225 group, a nearby lga. this system is considered a physical pair composed of an intermediate-luminosity late-type spiral, ngc 3447 itself, and ... | galaxy evolution in groups. ngc 3447/ngc 3447a: the odd couple in lgg 225 |
the first paper in this series showed that quantum chromodynamic axion dark matter, as a highly correlated bose fluid, contains extra-classical physics on cosmological scales. the source of the derived extra-classical physics is exchange-correlation interactions induced by the constraints of symmetric particle exchange... | axion structure formation - ii. the wrath of collapse |
cosmological n-body simulations represent an excellent tool to study the formation and evolution of dark matter (dm) haloes and the mechanisms that have originated the universal profile at the largest mass scales in the universe. in particular, the combination of the velocity dispersion σv with the density ρ can be use... | on the phase-space structure of galaxy clusters from cosmological simulations |
aims: we investigate the core-cusp problem of the λ cold dark matter (λcdm) scenario in the context of the modified newtonian dynamics (mond) paradigm while exploiting the concept of an equivalent newtonian system (ens).methods: by means of particle-mesh n-body simulations in mond, we explored the processes of galaxy f... | structure of the equivalent newtonian systems in mond n-body simulations. density profiles and the core-cusp problem |
the star formation history and the internal dynamics of milky way satellite galaxies are often complicated. in the last years, a substantial fraction of the known faint dwarf satellites have been studied. some of them show embedded stellar substructures, such as star clusters and even globular star clusters. in this wo... | star cluster survival in dark matter haloes: an old cluster in eridanus ii? |
with this paper, we complete a comprehensive study of substructure in dark matter haloes. in paper i, we derived the radial distribution and mass function (mf) of accreted subhaloes (scaled to the radius and mass of the host halo) and showed that they are essentially universal. this is not the case, however, for those ... | an accurate comprehensive approach to substructure: iii. masses and formation times of the host haloes |
we study how gravitational focusing (gf) of dark matter by the sun affects the annual and biannual modulation of the expected signal in non-directional direct dark matter searches, in the presence of dark matter substructure in the local dark halo. we consider the sagittarius stream and a possible dark disk, and show t... | gravitational focusing and substructure effects on the rate modulation in direct dark matter searches |
we study the monojet and dijet channels at the lhc as a tool for searching for squarks and gluinos. we consider two separate r-parity conserving supersymmetric scenarios. in the first scenario we postulate a large mass hierarchy between squarks (q ~) and winos (w ~), and wino-like neutralino is assumed to be the lighte... | monojet signatures from gluino and squark decays |
we show that the $zww$ production process may give complementary informations about scale dependent heavy particle masses and possible final state interactions as compared to previously studied top quark production processes. we illustrate the $p_z$ distribution of the rate of longitudinal $z_l$ component showing its s... | z polarization in $e^+e^-\\to zww $ for testing special interactions of massive particles |
non-resonant production of higgs-pair via heavy intermediate states may be a distinctive signature for extended discrete symmetries when accompaied by large missing transvers energy. we discuss $t$-parity as an example of such symmetry within the littlest higgs model, where a new heavy gauge boson $z'$, the $t$-odd par... | boosted higgs-pair production associated with large $e_t^{miss}$: a signal of $z^\\prime$ |
the multicomponent dark matter model with self-scattering and inter-conversions of species into one another is an alternative dark matter paradigm that is capable of resolving the long-standing problems of lambda cold dark matter (λcdm) cosmology at small scales. in this paper, we have studied in detail the properties ... | dark matter haloes in the multicomponent model - ii. density profiles of galactic haloes |
we use a geometric method to derive (two-dimensional) separation functions among pairs of objects within populations of specified position function ${dn}/d{\boldsymbol{r}}$ . we present analytic solutions for separation functions corresponding to a uniform surface density within a circular field, a plummer sphere (view... | two-point separation functions for modeling wide binary systems in nearby dwarf galaxies |
accurately predicting the abundance and structural evolution of dark matter subhaloes is crucial for understanding galaxy formation, large-scale structure, and constraining the nature of dark matter. due to the nonlinear nature of subhalo evolution, cosmological n-body simulations remain its primary method of investiga... | three-wave mixing in superconducting circuits: stabilizing cats with snails |
we present a comprehensive study on how perturbations due to a distribution of lambda cold dark matter (λcdm) dark matter subhalos can lead to star clusters deviating from their orbits. through a large suite of massless test particle simulations, we find that (i) subhalos with masses less than 108 m⊙ negligibly affect ... | the effects of λcdm dark matter substructure on the orbital evolution of star clusters |
the positions of images produced by the gravitational lensing of background sources provide unique insight into galaxy-lens mass distribution. however, even quad images of extended sources are not able to fully characterize the central regions of the host galaxy. most previous work has focused either on the radial dens... | testing the uniqueness of gravitational lens mass models |
as no evidence for classic wimp-based signatures of dark matter have been found at the lhc, several phenomenological studies have raised the possibility of accessing a strongly-interacting dark sector through new collider-event topologies. if dark mesons exist, their evolution and hadronization procedure are currently ... | towards better discrimination and improved modelling of dark-sector showers |
we report near simultaneous imaging using lmircam on the lbti of the quadruply imaged lensed quasar hs 0810+2554 at wavelengths of 2.16, 3.7, and 4.78 μm with a full width at half maximum spatial resolution of 0.″13, 0.″12, and 0.″15 respectively, comparable to hubble space telescope optical imaging. in the z = 1.5 res... | image flux ratios of gravitationally lensed hs 0810+2554 with high-resolution infrared imaging |
in this paper, we investigate the strong lensing statistics in galaxyclusters. we extract dark matter haloes from the millennium-xxl simulation, compute their einstein radius distribution, and find a very good agreement with monte carlo predictions produced with the moka code. the distribution of the einstein radii is ... | characterizing strong lensing galaxy clusters using the millennium-xxl and moka simulations |
the formation of galaxies can be understood in terms of the assembly patterns of each type of galactic component. to perform this kind of analysis, it is necessary to define some criteria to separate those components. decomposition methods based on dynamical properties are more physically motivated than photometry-base... | milky way-like galaxies: stellar population properties of dynamically defined discs, bulges and stellar haloes |
we investigate scalar-tensor theories where matter couples to the scalar field via a kinetically dependent conformal coupling. these models can be seen as the low-energy description of invariant field theories under a global abelian symmetry. the scalar field is then identified with the goldstone mode of the broken sym... | goldstone models of modified gravity |
multiple image gravitational lens systems, and especially quads, are invaluable in determining the amount and distribution of mass in galaxies. this is usually done by mass modelling using parametric or free-form methods. an alternative way of extracting information about lens mass distribution is to use lensing degene... | model-free analysis of quadruply imaged gravitationally lensed systems and substructured galaxies |
we test the darkexp model for relaxed, self-gravitating, collisionless systems against equilibrium dark matter halos from the millennium-ii simulation. while limited tests of darkexp against simulations and observations have been carried out elsewhere, this is the first time the testing is done with a large sample of s... | testing darkexp against energy and density distributions of millennium-ii halos |
we present a novel method for determining the total matter surface density of the galactic disc by analysing the kinematics of a dynamically cold stellar stream that passes through or close to the galactic plane. the method relies on the fact that the vertical component of energy for such stream stars is approximately ... | measuring the matter density of the galactic disc using stellar streams |
dwarf spheroidal galaxies (dsph) orbiting the milky way are complex objects often with complicated star formation histories and internal dynamics. in this work, we search for stellar substructures in four of the classical dsph satellites of the milky way: sextans, carina, leo i, and leo ii. we apply two methods to sear... | cold, old, and metal-poor: new stellar substructures in the milky way’s dwarf spheroidals |
the dynamical and virial mass of the milky way galaxy is estimated using latest high precision stellar halo and dwarf galaxy satellite kinematics. the new data suggest the galaxy is a highly compact, classically thermalized object. kinematics exhibit significant velocity-spatial substructure, distinctive dynamic partit... | a physical interpretation of milky way galaxy dynamics from precision astrometrics |
substructures of dark matter halo, called subhaloes, provide important clues to understand the nature of dark matter. we construct a useful model to describe the properties of subhalo mass functions based on the well-known analytical prescriptions, the extended press-schechter theory. the unevolved subhalo mass functio... | semi-analytical frameworks for subhaloes from the smallest to the largest scale |
tidal debris streams from galaxy satellites can provide insight into the dark matter distribution in halos. this is because we have more information about stars in a debris structure than about a purely random population of stars: we know that in the past they were all bound to the same dwarf galaxy; and we know that t... | tidal debris as a dark matter probe |
we present reconstructions of galaxy-cluster-scale mass distributions from simulated gravitational lensing data sets including strong lensing, weak lensing shear, and measurements of quadratic image distortions - flexion. the lensing data is constructed to make a direct comparison between mass reconstructions with and ... | reconstruction of small-scale galaxy cluster substructure with lensing flexion |
it has recently been proposed that if the galactic dark matter halo were triaxial it would induce lumpiness in the velocity distribution of halo stars in the solar neighbourhood through orbital resonances. these substructures could therefore provide a way of measuring its shape. we explore the robustness of this propos... | on the feasibility of constraining the triaxiality of the galactic dark halo with orbital resonances using nearby stars |
the dynamics of binary stars provides a unique avenue to gather insight into the study of the structure and dynamics of star clusters and galaxies. in this paper, we present the results of a set of n-body simulations aimed at exploring the evolution of binary stars during the early evolutionary phases of ultra-faint dw... | evolution of binary stars in the early evolutionary phases of ultra-faint dwarf galaxies |
in the context of the beyond ultradeep frontier fields and legacy observations (buffalo) survey, we present a new analysis of the merging galaxy cluster macs j0416.1-2403 (z = 0.397) and its parallel field using hubble frontier fields (hff) data. we measure the surface mass density from a weak-lensing analysis and char... | setting the scene for buffalo: a study of the matter distribution in the hff galaxy cluster macs j0416.1-2403 and its parallel field |
we propose and test a method for applying statistical photometric parallax to main-sequence turnoff stars in the sloan digital sky survey (sdss). using simulated data, we show that if our density model is similar to the actual density distribution of our data, we can reliably determine the density model parameters of t... | fitting the density substructure of the stellar halo with milkyway@home |
associations of dwarf galaxies are loose systems composed exclusively of dwarf galaxies. these systems were identified in the local volume for the first time more than 30 yr ago. we study these systems in the cosmological framework of the λ cold dark matter (λcdm) model. we consider the small multidark planck simulatio... | associations of dwarf galaxies in a λcdm universe |
the lambda cold dark matter (lcdm) paradigm makes specific predictions for the abundance, structure, substructure and clustering of dark matter halos, the sites of galaxy formation. these predictions can be directly tested, in the low-mass halo regime, by dark matter-dominated dwarf galaxies. a number of potential chal... | dwarf galaxies as cosmological probes |
the milky way's (mw) satellite population is a powerful probe of warm dark matter (wdm) models as the abundance of small substructures is very sensitive to the properties of the wdm particle. however, only a partial census of the mw's complement of satellite galaxies exists because surveys of the mw's close environs ar... | the milky way's total satellite population and constraining the mass of the warm dark matter particle |
we present a new strong-lensing (sl) mass reconstruction of the six hubble frontier fields (hff) clusters with the maximum-entropy reconstruction (mars) algorithm. mars is a new free-form inversion method, which suppresses spurious small-scale fluctuations while achieving excellent convergence in positions of multiple ... | model-independent mass reconstruction of the hubble frontier field clusters with mars based on self-consistent strong-lensing data |
we use mid-infrared 3.6 and 4.5 μm imaging of ngc 3906 from the spitzer survey of stellar structure in galaxies (s4g) to understand the nature of an unusual offset between its stellar bar and the photometric center of an otherwise regular, circular outer stellar disk. we measure an offset of ∼910 pc between the center ... | the odd offset between the galactic disk and its bar in ngc~3906 |
the abundance of galaxy clusters in the low-redshift universe provides an important cosmological test, constraining a product of the initial amplitude of fluctuations and the amount by which they have grown since early times. the degeneracy of the test with respect to these two factors remains a limitation of abundance... | cluster assembly times as a cosmological test |
context. the study of cluster substructures is important for the determination of the cluster dynamical status, assembly history, and the evolution of cluster galaxies, and it allows us to set constraints on the nature of dark matter and cosmological parameters.aims: we present and test ds+, a new method for the identi... | ds+: a method for the identification of cluster substructures |
recent observations have revealed a trove of unexpected morphological features in many of the milky way's stellar streams. explanations for such features include time-dependent deformations of the galactic gravitational potential, local disruptions induced by dark matter substructure, and special configurations of the ... | stream fanning and bifurcations: observable signatures of resonances in stellar stream morphology |
we present new mid-ir observations of the quadruply lensed quasar q2237+0305 taken with canaricam on the gran telescopio canarias. mid-ir emission by hot dust, unlike the optical and near-ir emission from the accretion disk, is unaffected by the interstellar medium (extinction/scattering) or stellar microlensing. we co... | observations of the lensed quasar q2237+0305 with canaricam at gtc |
we propose a novel method to select satellite galaxies in outer regions of galaxy groups or clusters using weak gravitational lensing. the method is based on the theoretical expectation that the tangential shear pattern around satellite galaxies would appear with negative values at an offset distance from the center of... | weak gravitational lensing as a probe of physical properties of substructures in dark matter halos |
in this work, we explore the idea that substructures like stellar clusters could be formed from the tidal stream produced in galactic minor mergers. we use n-body and sph simulations of satellite galaxies interacting with a larger galaxy. we study the distribution of mass in streams to identify overdensity regions in w... | substructure formation in tidal streams of galactic minor mergers |
we report the 4σ detection of a faint object with a flux of ∼ 0.3 {mjy}, in the vicinity of the quadruply lensed qso mg 0414+0534 using the atacama large millimeter/submillimeter array (alma) band 7. the object is most probably a dusty dark dwarf galaxy, which has not been detected in either the optical, near-infrared,... | evidence for a dusty dark dwarf galaxy in the quadruple lens mg 0414+0534 |
nyx is a nearby, prograde, and high-eccentricity stellar stream physically contained in the thick disk, but its origin is unknown. nyx could be the remnant of a disrupted dwarf galaxy, in which case the associated dark matter substructure could affect terrestrial dark matter direct-detection experiments. alternatively,... | high-resolution chemical abundances of the nyx stream |
observations of diffuse starlight in the outskirts of galaxies provide fundamental constraints on the cosmological context of galaxy assembly in the lambda cold dark matter model, which predicts that galaxies grow through a combination of in-situ star formation and accretion of stars from other galaxies. accreted stars... | unveiling the nature of giant ellipticals and their stellar halos with the vst |
we study the impact of thermal inflation on the formation of cosmological structures and present astrophysical observables which can be used to constrain and possibly probe the thermal inflation scenario. these are dark matter halo abundance at high redshifts, satellite galaxy abundance in the milky way, and fluctuatio... | small-scale effects of thermal inflation on halo abundance at high-z, galaxy substructure abundance, and 21-cm power spectrum |
we present the results of study the 2d distribution of galaxies in 254 rich open galaxy clusters. the clusters have no concentration to the center, so all kinds of substructures are clearly seen. regular linear substructures in galaxy clusters were described in rood & sastry scheme of morphological types according ... | regular substructures in the rich open galaxy clusters |
we present and test tessellation-based recovery of amorphous halo concentrations (tesseract), a non-parametric technique for recovering the concentration of simulated dark matter halos using voronoi tessellation. tesseract is tested on idealized n-body halos that are axisymmetric, triaxial, or contain substructure and ... | voronoi tessellation and non-parametric halo concentration |
gravitational lensing is a powerful tool for quantifying the mass content and distribution in distant galaxies. by using milliarcsecond angular resolution observations of radio-loud gravitationally lensed sources it is also possible to detect and quantify small deviations from a smooth mass density distribution, which ... | gravitational lensing at milliarcsecond angular resolution with vlbi observations |
as established in previous papers of this series, observables in highly distorted and magnified multiple images caused by the strong gravitational lensing effect can be used to constrain the distorting properties of the gravitational lens at the image positions. if the background source is extended and contains substru... | generalized model-independent characterization of strong gravitational lenses viii. automated multiband feature detection to constrain local lens properties |
we present the first flexion-focused gravitational lensing analysis of the hubble frontier field observations of abell 2744 (z = 0.308). we apply a modified analytic image model technique to measure source galaxy flexion and shear values at a final number density of 82 arcmin-2. by using flexion data alone, we are able... | flexion in abell 2744 |
the outer milky way stellar structure known as "the monoceros ring" was discovered in imaging data in 2002. since then, numerous photometric and spectroscopic explorations of this structure, some 18 kpc from the galactic center and at low galactic latitudes, have led to a rich discussion in the field on its composition... | the monoceros ring, and other substructure near the galactic plane |
experimental results on no2 are explained based on the add-model of large extra compactified dimensions of space. we assume that gravity is sufficiently strong in a compactification space of the size of the molecule to affect the vibrational motion of the nuclei by causing an asymmetric perturbation in the symmetric st... | do extra compactified dimensions of space cause a substructure underlying the expected eigenstates of a molecule? |
we introduce a new halo/subhalo finder, hiker (a halo finder based on kernel-shift algorithm), which takes advantage of a machine learning method - the mean-shift algorithm combined with the plummer kernel function, to effectively locate density peaks corresponding to halos/subhalos in density field. based on these den... | hiker: a halo-finding method based on kernel-shift algorithm |
the morphology of haloes inform about both cosmological and galaxy formation models. we use the minkowski functionals (mfs) to characterize the actual morphology of haloes, only partially captured by smooth density profile, going beyond the spherical or ellipsoidal symmetry. we employ semi-analytical haloes with nfw an... | morphology of dark matter haloes beyond triaxiality |
the predicted size of dark matter substructures in kilo-parsec scales is model-dependent. therefore, if the correlations between dark matter mass densities as a function of the distances between them are measured via observations, we can scrutinize dark matter scenarios. in this paper, we present an assessment procedur... | assessment of dark matter models using dark matter correlations across dwarf spheroidal galaxies |
gadget-4 (galaxies with dark matter and gas interact) is a parallel cosmological n-body and sph code that simulates cosmic structure formation and calculations relevant for galaxy evolution and galactic dynamics. it is massively parallel and flexible, and can be applied to a variety of different types of simulations, o... | gadget-4: parallel cosmological n-body and sph code |
measurements of velocity and density perturbations along stellar streams in the milky way provide a time-integrated measure of dark matter substructure at larger galactic radius than the complementary instantaneous inner-halo strong lensing detection of dark matter sub-halos in distant galaxies. an interesting case to ... | velocity variations in the phoenix-hermus star stream |
a very general cosmological consideration suggests that, along with galactic dark matter halos, much smaller dark matter structures may exist. these structures are usually called `clumps', and their mass extends to 10-6 m ⊙ or even lower. the clumps should give the main contribution into the signal of dark matter annih... | can the dark matter annihilation signal be significantly boosted by substructures? |
the hawc observatory is a ground-based observatory of tev gamma rays located on the sierra negra drop volcano in mexico. hawc is sensitive to emission from extended gamma-ray sources, so it is able to search for emission from annihilation and decay of tev dark matter (dm) particles in galaxies and galaxy clusters. we p... | searching dark matter signatures from the virgo cluster with hawc |
warm dark matter (wdm) models offer an attractive alternative to the current cold dark matter (cdm) cosmological model. we present a novel method to differentiate between wdm and cdm cosmologies, namely, using weak lensing; this provides a unique probe as it is sensitive to all of the “matter in the beam,” not just dar... | matter in the beam: weak lensing, substructures, and the temperature of dark matter |
in recent years, bose-einstein-condensed dark matter (bec-dm) has become a popular alternative to standard, collisionless cold dark matter (cdm). this bec-dm -also called scalar field dark matter (sfdm)- can suppress structure formation and thereby resolve the small-scale crisis of cdm for a range of boson masses. howe... | to observe, or not to observe, quantum-coherent dark matter in the milky way, that is a question |
the implementation of acacia, a new algorithm to generate dark matter halo merger trees with the adaptive mesh refinement code ramses, is presented. the algorithm is fully parallel and based on the message passing interface. as opposed to most available merger tree tools, it works on the fly during the course of the n-... | acacia: a new method to produce on-the-fly merger trees in the ramses code |
in this work we are going to build the halo mass function for a scalar field dark matter model. this will be done with the aim of determine the minimum size of halos that our model predicts, in contrast with the lcdm model, which predicts an overabundance of substructures. we find that, for a scalar field mass m = 10-2... | towards a calculation of the halo mass function of a scalar field dark matter |
recently a theory about the formation of overdensities of stars along tidal tails of globular clusters has been presented. this theory predicts the position and the time of the formation of such overdensities and was successfully tested with n-body simulations of globular clusters in a point-mass galactic potential. in... | formation and evolution of substructures in tidal tails: spherical dark matter haloes |
the degree of dark matter clustering on small scales presents a strong constraint on its physical nature. one of the most promising avenues for determining the clustering of dark matter on the smallest scales employs narrow stellar streams in the halo of the milky way. in this contribution, i review recent progress in ... | constraining the small-scale clustering of dark matter with stellar streams |
wfirst's combination of wide field and high resolution will revolutionize the study of nearby galaxies. we propose to produce and analyze simulated wfirst data of nearby galaxies and their halos to maximize the scientific yield in the limited observing time available, ensuring the legacy value of wfirst's eventual arch... | wings: wfirst infrared nearby galaxy survey |
in order to constrain the limitations of association methods applied to galaxy surveys, we analysed the catalogue of haloes at z = 0 of a cosmological simulation, trying to reproduce the limitations dealt with by an observational survey. we focused on the percolation method, usually called the friends of friends method... | siblings, friends and acquaintances: testing galaxy association methods |
stellar halos give insight into the initial conditions that existed when a host galaxy first formed and provide details on disrupted satellites via their different stellar populations. an algorithm that is computationally inexpensive compared to hydrodynamic simulations is necessary in order to theoretically study the ... | coupling semi-analytic models and n-body simulations: a new way of making galaxies and stellar halos |
lamost is a special reflecting schmidt telescope. lamost breaks through the bottleneck of the large scale spectroscopic survey observation with both large aperture (effective aperture of 3.6 - 4.9m) and wide field of view (5 degrees). it is an innovative active reflecting schmidt configuration achieved by changing mirr... | spectroscopic survey of lamost |
the milkyway (mw) is surrounded by numerous satellite objects: dwarf galaxies, globular clusters and streams of disrupted systems. together, these form a vast polar structure (vpos), a thin plane spreading to galactocentric distances as large as 250 kpc. the orbital directions of satellite galaxies and the preferred al... | the vast polar structure of the milky way and filamentary accretion of sub-halos |
being able to accurately predict the abundance and demographics of dark matter substructure is of paramount importance for many fields of astrophysics: gravitational lensing, galaxy evolution, halo occupation modeling, and even constraining the nature of dark matter. dark matter substructure is typically modeled using ... | dark matter substructure: from numerical noise to cosmological treasure trove |
a clear excess in the fermi-lat data is present at energies around a few gev. the spectrum of this so-called 'gev excess' is remarkably similar to the expected annihilation signal of wimp dark matter. however, a large bulge population of millisecond pulsars living below the fermi-lat detection threshold could also expl... | millisecond pulsars in the galactic bulge? an extended discussion on the wavelet analysis of the fermi-lat data |
the work i have done during my thesis has consisted of both observational and theoretical projects involving dwarf galaxies and cold dark matter (cdm) sub-structure both around the milky way and in redshift z∼0.1 galaxies. the dwarf galaxies around the milky way are distributed in a so-called vast polar structure (vpos... | galactic building blocks: dwarf galaxies near and far |
we model the tidal stream of the milky way globular cluster palomar 5 (pal 5), and show that the unique geometry of the problem yields powerful constraints on the model parameters characterizing the local standard of rest (lsr), the milky way and pal 5 itself. using only sdss data and a few radial velocities from the l... | globular cluster streams as galactic high-precision scales - the poster child palomar 5 |
over the past decades the connection between the angular momentum of dark matter halos and their galaxies' has been discussed in several studies. in a hierarchical λcdm universe, structures grow through accretion of smaller substructures, but at the very beginning the gas cools and collapses into the dark matter halos ... | dynamical properties of galaxies with different morphological types at z=0 and z=2 |
the high altitude water cherenkov (hawc) observatory is an extensive air shower array sensitive to gamma rays between 500 gev - 100 tev. tev photons provide unique tests of fundamental physics phenomena, such as dark matter annihilation and decay. hawc is capable of performing indirect dark matter searches in a mass ra... | dark matter searches with hawc |
in recent decades photometric surveys have revealed a wealth of stellar substructure in the galactic halo, evidence of the ongoing process of galaxy assembly in the milky way. however spectroscopic data are essential for determining the kinematics and abundances of the stars in these structures. in the southern hemisph... | spectroscopic surveys and stellar substructure in the galactic halo |
we propose wfc3 ir imaging of a sample of 112 new strong galaxy-galaxy lensing candidates discovered within the dark energy spectroscopic instrument (desi) legacy imaging surveys, data release 7, using a deep neural network. these candidates are highly likely strong lensing systems (with > 90% confidence). many of t... | confirming strong galaxy gravitational lenses in the desi legacy imaging surveys |
a dark substructure of mass ~3×109 msun has previously been detected in the gravitational lens galaxy sdssj0946+1006 through its perturbation of the lensed images. we demonstrate that this substructure is consistent with being a tidally truncated subhalo, rather than a line-of-sight structure, and requires a concentrat... | can the extremely high-concentration subhalo perturbing gravitational lens sdssj0946+1006 be reconciled with cold dark matter? |
the small-scale distribution of dark matter is, at present, poorly understood. cosmological simulations predict a large number of low-mass subhalos within galaxies, but observations in our local group find a lower number of corresponding satellite galaxies. this tension may be addressed by quantifying low-mass subhalos... | quantifying the dark matter subhalo mass function in z≈0.5 galaxies using lensed lyman-α emitter galaxies. |
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 |
the desi milky way survey (mws) will observe over 8 million stars between 16<r<19 mag during bright time, in addition to brighter stars (10<r<16 mag) in a backup program for poor observing conditions. in this talk we highlight early results from desi commissioning and survey validation programs that showcas... | the desi milky way survey (mws) |
a generic prediction of galaxy formation in the standard cosmological model with cold dark matter is the hierarchical assembly of structure on mass scales ranging from ultra-faint galaxies to galaxy clusters. in the local group, dozens of galaxies have been found orbiting the milky way and andromeda. the question of wh... | the magellanic satellites survey: searching for hierarchical structure formation within the local group |
ram-pressure stripped tails have been observed in a handful of individualinteracting galaxies. in an xmm mosaic program targeting the outskirts ofthe hydra a cluster, we discovered a spectacular infalling galaxy groupwith a very long tail (> 400 kpc long) of hot x-ray emitting gas. thissystem shows a striking simila... | a textbook example of ram-pressure stripping in hydra a |
over five observing seasons, which started in august 2013, the dark energy survey (des) will carry out a wide field survey of 5000 square degrees of the southern galactic cap. as much of the wide-field area has not yet been systematically surveyed, we expect to discover many new strongly lensed galaxies and quasars.des... | warped universe: analysis of strong lens candidates from early dark energy survey data |
we use xmm to map the cluster abell 2199 intermediate region (<3/4 virialradius) and search x-ray faint substructures in a wide spacial range froma galaxy to a cluster and larger sizes. we observed this area with suzakuand found a number of structures and a hint of asymmetric large scaleemission. these substructures... | x-ray large scale survey of the nearby galaxy cluster abell2199 |
theory suggests that galactic bars spin down throughout their evolution due to an angular momentum exchange with the inner parts of their dark matter halos. as opposed to a bar with a fixed pattern speed, chiba et al. (2019) proposed that 'resonance sweeping' due to a decelerating galactic bar can explain local kinemat... | resonance sweeping in barred galaxy simulations |
the fundamental properties of dark matter, such as its mass, self-interaction, and coupling to other particles, can have a major impact on the evolution of cosmological density fluctuations on small length scales. strong gravitational lenses have long been recognized as powerful tools to study the dark matter distribut... | small but mighty: dark matter substructures |
the milky way halo contains several thin, dynamically-cold stellar streams that likely formed from the tidal disruption of low-mass stellar systems like globular clusters. these streams are powerful tools for testing dark matter theories: streams will enable mapping the global structure of mass in the galaxy, and are e... | the gd-1 stellar stream suggests the existence of dark substructure in the milky way halo |
we have extended two recently developed theoretical methods, the quantum finite elements (qfe) and the euclidean-signature semi-classical method (esscm). the qfe is a technique for constructing lattice field theories (lfts) on curved riemannian manifolds. we extended the applicability of the qfe to formulating lfts on ... | the tidal evolution of dark matter substructure and the significance of halo-to-halo assembly history variance |
despite being ubiquitous throughout the universe, the fundamental properties of dark matter remain a mystery. while dark matter physics plays little role in the current evolution of large-scale cosmic structures, it does have a major impact on small causal length scales. studying the astrophysical structures that resul... | unlocking dark matter physics out of galactic substructures |
pulsars are precise clocks that can serve as galactic accelerometers. traditionally, the accelerations of stars within the galaxy have been estimated using kinematic analyses that assume the galaxy is in equilibrium. we use pulsar timing measurements to directly measure the galactic acceleration. given the measured gal... | using galactic accelerometers to directly measure dark matter |
msl applies simulation-based inference techniques to the problem of substructure inference in galaxy-galaxy strong lenses. it leverages additional information extracted from the simulator, then trains neural networks to estimate likelihood ratios associated with population-level parameters characterizing dark matter su... | msl: mining for substructure lenses |
the spherical jeans equation is widely used to estimate mass profiles of systems from star clusters to galactic stellar halos to clusters of galaxies. the cumulative mass profile, m(<r), is derived from kinematics of tracers of the potential under the assumptions of spherical symmetry and dynamical equilibrium. we c... | non-parametric spherical jeans mass estimation with b-splines |
we present mid-ir observations taken with canaricam at gran telescopio canarias of the quadruply lensed quasar qso2237+0305. we have obtained flux ratios between the four images that, unlike optical, near-ir and, to a lesser extent, radio emission, are unaffected by the ism (extinction/scattering) or stellar microlensi... | observations of the einstein cross with canaricam |
orbits of individual stars in the milky way trace the underlying gravitational potential, and as such, they provide a unique insight into the distribution of matter in our galaxy. large astronomical projects like gaia, sdss and desi are now measuring precise motions of stars deep into the dark matter-dominated outer re... | reconstruction of the dark matter distribution in the milky way |
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