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multicomponent dark matter with inter-conversions of mass eigenstates into one another is known to successfully and simultaneously resolve λcdm problems at galactic and sub-galactic scales. here, we present n-body simulations of the simplest two-component (2cdm) model with large set of velocity-dependent cross-sections, σ(v) va , and compare them with observational data. they show that the 2cdm paradigm with the self-interaction cross-sections 0 . 01 <=σ0 / m <= 1 cm2g-1 and the mass degeneracy δm / m 10-7 -10-8 robustly resolves the substructure and too-big-to-fail problems by suppressing the substructure with vcirc , max < 100 km s-1. furthermore, 2cdm robustly suppresses central cusps in dwarf halos with m 4 - 5 ×1011m⊙ , thus resolving the core-cusp problem as well. the core radii are controlled by σ0 / m and the dm cross-section's velocity-dependent power-law indices (as ,ac) , but are largely insensitive to the species' mass degeneracy. next, there is disagreement between the radial distribution of dwarfs in a host halo observed in the local group and simulated with cdm, which poses one more small-scale problem to cdm, which is alleviated by 2cdm. partially supported by doe grant de-sc0016368. | dark matter halos in the multicomponent model. substructure and density profiles of galactic halos |
strong gravitational microlensing (gm) events provide us a possibility to determine both the parameters of microlensed source and microlens. gm can be an important clue to understand the nature of dark matter on comparably small spatial and mass scales (i.e. substructure), especially when speaking about the combination of astrometrical and photometrical data about high amplification microlensing events (hame). in the same time, fitting of hame lightcurves of microlensed sources is quite time-consuming process. that is why we test here the possibility to apply the statistical machine learning techniques to determine the source and microlens parameters for the set of hame lightcurves, using the simulated set of amplification curves of sources microlensed by point masses and clumps of dm with various density profiles. | determining the parameters of high amplification microlensing events by means of statistical machine learning techniques |
we use 8 gravitational lens systems with quadruply imaged quasars and their observed flux ratio anomalies obtained using data in mid-infrared, radio or spectral narrow lines as a baseline, to estimate the amount of substructure in the dark matter halo of lens galaxies. we assume that the smooth gravitational potential of the galaxies is well modeled by a singular isothermal ellipsoid (sie) plus external shear (γ) and an additional singular isothermal sphere (sis) in some cases, and that the cause of the flux ratio anomalies is dark matter subhalos described by pseudo-jaffe density profiles. our bayesian estimate for the einstein radius of the subhalos is b = 0.0003^{+0.0005}_{-0.0002} arcsec, and their abundance (as a fraction of the total surface density of the lens galaxy at the image positions) is α =ê0.075^{+0.030}_{-0.021}. | estimating the size and abundance of dark matter subhaloes with gravitational millilensing |
the questions on the existence of the three color quark symmetry and three quark-lepton generations could have the origin associated with the new exotic symmetries outside the cartan-killing-lie algebras/groups. our long-term search for these symmetries has been began with our calabi-yau space classification on the basis of the n-ary algebra for the reflexive projective numbers and led us to the expansion of the binary n = 2 complex and hyper complex numbers in the framework of the n-ary complex and hyper-complex numbers with n = 3, 4, … where we constructed new abelian and non-abelian symmetries. we have studied then norm-division properties of the abelian nary complex numbers and have built the infinite chain of the abelian groups u(n-1) = [u(1) × … × u(1)](n-1). we have developed the n-ary holomorphic (polymorphic) analysis on the n-ary complex space ncn, which led us to the generalization of the quadratic laplace equations for the harmonic functions. the generalized laplace equations for the n-ary harmonic functions give us the n-th order homogeneous differential equations which are invariant with respect to the abelian n-ary groups u(n-1) and with some new spatial properties. further consideration of the non-abelian n-ary hyper-complex numbers opens the infinite series of the non-abelian tnsu(n)-lie groups(n=3,4,…) and its corresponding tnsu(n) algebras. one of the exceptional features of these symmetry groups is the appearance of some new n-dimensional spinors that could lead to an extension of the concept of the su(2)-spin, to the appearance of n-dimensional quantum structures -exotic "n-spinor" matter(n = 3, 4, … - maarcrions). it is natural to assume that these new exotic "quantum spinor states" could be candidates for the pra-matter of the quark-charge leptons or/and for the dark matter. we will be also interested in the detection of the exotic quantum 'n-spinor" matter in the neutrino and hadron experiments. | ternary su(3)-group symmetry and its possible applications in hadron-quark substructure. towards a new spinor-fermion structure |
the caterpillar project is a beautiful series of high-resolution cosmological simulations. the goal of this project is to examine the evolution of dark-matter halos like the milky ways, to learn about how galaxies like ours formed. this immense computational project is still in progress, but the caterpillar team is already providing a look at some of its first results.lessons from dark-matter haloswhy simulate the dark-matter halos of galaxies? observationally, the formation history of our galaxy is encoded in galactic fossil record clues, like the tidal debris from disrupted satellite galaxies in the outer reaches of our galaxy, or chemical abundance patterns throughout our galactic disk and stellar halo.but to interpret this information in a way that lets us learn about our galaxys history, we need to first test galaxy formation and evolution scenarios via cosmological simulations. then we can compare the end result of these simulations to what we observe today.this figure illustrates the difference that mass resolution makes. in the left panel, the mass resolution is 1.5*10^7 solar masses per particle. in the right panel, the mass resolution is 3*10^4 solar masses per particle [griffen et al. 2016]a computational challengedue to how computationally expensive such simulations are, previous n-body simulations of the growth of milky-way-like halos have consisted of only one or a few halos each. but in order to establish a statistical understanding of how galaxy halos form and find out whether the milky ways halo is typical or unusual! it is necessary to simulate a larger number of halos.in addition, in order to accurately follow the formation and evolution of substructure within the dark-matter halos, these simulations must be able to resolve the smallest dwarf galaxies, which are around a million solar masses. this requires an extremely high mass resolution, which adds to the computational expense of the simulation.first outcomesthese are the challenges faced by the caterpillar project, detailed in a recently published paper led by brendan griffen (massachusetts institute of technology). the caterpillar project was designed to simulate 70 milky-way-size halos (quadrupling the total number of halos that have been simulated in the past!) at a high mass resolution (10,000 solar masses per particle) and time resolution (5 myr per snapshot). the project is extremely computationally intense, requiring 14 million cpu hours and 700 tb of data storage!mass evolution of the first 24 caterpillar halos (selected to be milky-way-size at z=0). the inset panel shows the mass evolution normalized by the halo mass at z=0, demonstrating the highly varied evolution these different halos undergo. [griffen et al. 2016]in this first study, the griffen and collaboratorsshow the end states for the first 24 halos of the project, evolved from a large redshift to today (z=0). they use these initialresults to demonstrate the integrity of their data and the utility of their methods, which include new halo-finding techniques that recover more substructure within each halo.the first results from the caterpillar project are already enough to show clear general trends, such as the highly variable paths the different halos take as they merge, accrete, and evolve, as well as how different their ends states can be. statistically examining the evolution of these halos is an importantnext step in providinginsight intothe origin and evolution of the milky way, and helping us to understand how our galaxy differs from other galaxies of similar mass. keep an eye out for future results from this project!bonuscheck out this video (make sure to watch in hd!) of how the first 24 milky-way-like halos from the caterpillar simulations form. seeingthese halos evolve simultaneously is an awesome way to identifythe similarities and differences between them.citationbrendan f. griffen et al 2016 apj 818 10. doi:10.3847/0004-637x/818/1/10 | simulating halos with the caterpillar project |
canucs gto program is a jwst spectroscopy and imaging survey of five massive galaxy clusters and ten parallel fields using the niriss low-resolution grisms, nircam imaging and nirspec multi-object spectroscopy. the primary goal is to understand the evolution of low mass galaxies across cosmic time. the resolved emission line maps and line ratios for many galaxies, with some at resolution of 100pc via the magnification by gravitational lensing will enable determining the spatial distribution of star formation, dust and metals. other science goals include the detection and characterization of galaxies within the reionization epoch, using multiply-imaged lensed galaxies to constrain cluster mass distributions and dark matter substructure, and understanding star-formation suppression in the most massive galaxy clusters. in this talk i will describe the science goals of the canucs program. the proposed prime and parallel observations will be presented with details of the implementation of the observation strategy using jwst proposal planning tools. | the canadian niriss unbiased cluster survey (canucs) |
structures within molecules and nuclei have relationships to astronomical patterns. the cobe cosmic scale plots, and large scale surveys of galaxy clusters have patterns also repeating and well known at atomic scales. the induction, strong force, and nuclear binding energy periods within the big bang are revealed to have played roles in the formation of these large scale distributions. equations related to the enormous patterns also model chemical bonds and likely nucleus and nucleon substructures. ratios of the forces that include gravity are accurately calculated from the distributions and shapes. in addition, particle masses and a great many physical constants can be derived with precision and accuracy from astrophysical shapes. a few very basic numbers can do modelling from nucleon internals to molecules to super novae, and up to the visible universe. equations are also provided along with possible structural configurations for some cold dark matter and dark energy. | basic equations interrelate atomic and nuclear properties to patterns at the size scales of the cosmos, extended clusters of galaxies, galaxies, and nebulae |
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 to 150 kpc for each galaxy, and include stunning disrupting satellites, streams and shells. current cold dark matter based simulations provide testable predictions for the physical properties (e.g ages and metallicities) of in-situ/accreted components, but the lack of a robust observational census of outer halos for a wide range of galaxies beyond the local group prevents robust conclusions. our proposed observations of the halo substructures in ngc 253 and ngc 5128 will confirm their distance, group membership, and allow for an accurate derivation of their luminosities, metallicities, and star formation histories: for the first time, substructures around milky way-sized halos beyond the local group will be characterized in great detail. the substructures' properties will be compared to those of the smooth halo, as derived from our wide-field imaging as well as from extant hst halo observations, and to similar substructures in the halos of the milky way and m31. this program will constitute a critical observational test to cosmological predictions of the hierarchical assembly process. | resolved halo substructures beyond the local group: the assembly histories of ngc 253 and ngc 5128 |
the low-mass slope of the galaxy stellar mass function is significantly shallower than that of the theoretical dark matter halo mass function, leading to several possible interpretations including: 1) stellar mass does not fully represent galaxy mass, 2) galaxy formation becomes increasingly inefficient in lower mass halos, and 3) environmental effects, such as stripping and merging, may change the mass function. to investigate these possible scenarios, we present the census of stellar, baryonic (stars + cold gas), and dynamical masses of galaxies and galaxy groups for the resolve and eco surveys. resolve is a highly complete volume-limited survey of ~1500 galaxies, enabling direct measurement of galaxy mass functions without statistical completeness corrections down to baryonic mass mb ~ 10^9 msun. eco provides a larger data set (~10,000 galaxies) complete down to mb ~ 10^9.4 msun. we show that the baryonic mass function has a steeper low-mass slope than the stellar mass function due to the large population of low-mass, gas-rich galaxies. the baryonic mass function’s low-mass slope, however, is still significantly shallower than that of the dark matter halo mass function. a more direct probe of total galaxy mass is its characteristic velocity, and we present resolve’s preliminary galaxy velocity function, which combines ionized-gas rotation curves, stellar velocity dispersions, and estimates from scaling relations. the velocity function also diverges from the dark matter halo velocity function at low masses. to study the effect of environment, we break the mass functions into different group halo mass bins, finding complex substructure, including a depressed and flat low-mass slope for groups with halo masses ~10^11.4-12 msun, which we refer to as the nascent group regime, with typical membership of 2-4 galaxies. this substructure is suggestive of efficient merging or gas stripping in nascent groups, which we find also have large scatter in their cold-baryon fractions, possibly pointing to diversity in hot halo gas content in this regime. this work is supported by nsf grant ast-0955368, the nc space grant graduate research fellowship program, and a unc royster society dissertation completion fellowship. | a mass census of the nearby universe with resolve and eco |
a search for low mass resonances decaying to a jet pair in association with an initial state radiation jet or photon is presented. the isr object acts as the event trigger, and the resonance jet pair is subsequently boosted and reconstructed as a large-radius jet. novel jet substructure techniques allow for signal jets to be selected over the dominant multi-jet and gamma+jet backgrounds. the search uses 36.1 fb-1 of pp collision data at a center-of-mass energy of 13 tev collected in 2015 and 2016 by the atlas detector at the lhc. resonances are searched for in the mass range of 100-220 gev, and no significant deviation from the standard model is found. limits are placed on the production cross section of a benchmark leptophobic z' model in the context of a dark matter mediator, as well as the z'-sm coupling. | search for low mass di-jet resonances produced in association with initial state radiation at atlas |
the lambda cold dark matter (dm) model successfully explains the distribution of large scale structure and the cosmic microwave background but, there are several problems concerning the distribution of dm on sub-galactic scales. robust measurements of the distribution of dm in low mass dwarf galaxies are key to understand the true nature of dm. in this work, we present two new techniques for characterizing the kinematics of dispersion supported systems. the first method identifies localized kinematic substructure in line-of-sight velocity data while the second separates global stellar populations utilizing metallicty, line-of-sight velocity, and spatial information. we apply the first method to the dwarf spheroidal galaxy ursa minor and find two localized kinematic substructures at high significance. we present new keck/deimos spectroscopic observations of ursa minor, motivated by the previous detection, which form the largest spectroscopic data set of ursa minor. with the new data, we identify two chemodynamical stellar population at high significance with distinct kinematic, metallicity, and spatial distributions. by utilizing the dynamics of multiple stellar populations we break halo profile degeneracies and find the dm slope is more consistent with a 'cored' halo than a 'cuspy' halo. we present a complementary study comparing a large sample of literature rotation curves to dark matter halos influenced by baryonic processes. the analysis suggests that baryonic processes are an inconsistent solution to the 'core-cusp' problem. | investigations of the inner dark matter density profiles of dwarf galaxies using multiple chemodynamical populations and rotation curves |
we use high-resolution n-body simulations to study the effect of a galactic disc on the dynamical evolution of dark matter substructures with orbits and structural parameters extracted from the aquarius a-2 merger tree. satellites are modelled as equilibrium n-body realizations of generalized hernquist profiles with 2 × 106 particles and injected in the analytical evolving host potential at zinfall, defined by the peak of their mass evolution. we select all substructures with m200(zinfall) &gt 108 m⊙ and first pericentric distances rp &lt r200. motivated by observations of milky way dwarf spheroidal galaxies, we also explore satellite models with cored dark matter profiles with a fixed core size rc = 0.8 as, where as is the hernquist scale radius. we find that models with cuspy satellites have twice as many surviving substructures at z = 0 than their cored counterparts, and four times as many if we only consider those on orbits with rp &lt 0.1 r200. for a given profile, adding an evolving disc potential reduces the number of surviving substructures further by a factor of &lt2 for satellites on orbits which penetrate the disc (rp &lt 20 kpc). for large rp, where tidal forces and the effect of the disc become negligible, the number of satellites per pericentre bin converges to similar values for all four models. | the effect of a disc on the population of cuspy and cored dark matter substructures in milky way-like galaxies |
while galaxies are ubiquitous in the universe, and galaxy clusters, the most massive structures are rare, intermediate mass scale objects - galaxy groups - are abundant. however, their properties are not as well studied at present, partly due to the difficulty in characterizing them and their dynamics. besides, they are likely transitory objects that eventually merge into assembling clusters. galaxy groups therefore offer an interesting laboratory to study dynamical processes as well as to probe the interplay between baryons and dark matter. we present the first results from a galaxy group finder algorithm that selects candidates from the large high-resolution cosmological illustris simulation with a view to better understand their formation, and to more accurately characterize them as a class of astrophysical objects. fundamental relations between galaxy groups and their dark matter substructure, their member galaxies, and other observables are characterized. we compare the current observational classification of galaxy groups - compact, fossil, and loose - with correlations recovered from simulations, and propose new criteria to describe galaxy groups. preliminary illustris findings are compared with multi-wavelength observational findings. | bridging the gap: characterizing groups of galaxies |
recent facilities such as the south pole telescope (spt), the herschel space observatory, and the atacama large millimeter array (alma) have opened a window to the millimeter (mm) sky and revealed a unique and unprecedented view of the universe. in a 2500 square degree cosmological survey, spt has systematically identified a large number (>100) of high-redshift strongly gravitationally lensed starburst galaxies. we are conducting a unique spectroscopic redshift survey with alma, targeting carbon monoxide line emission in these sources, across the 3mm spectral window. to date, we have obtained spectroscopic redshifts for 39 sources from 1.8 < z < 5.8, with a median of z=3.8. we are systematically measuring low-j co and [cii] for these sources with atca and apex, making this the largest and most well-studied samples of high-redshift starburst galaxies. we are undertaking a comprehensive and systematic followup campaign to use these "cosmic magnifying glasses" to study the infrared background in unprecedented detail, inform the condition of the interstellar medium in starburst galaxies at high redshift, and place limits on dark matter substructure. i will describe our teams latest science results and discuss the scientific potential of these strongly lensed starburst galaxies within the context of future instruments and facilities. | the redshift distribution of submillimeter galaxies |
flexion is the second order weak gravitational lensing effect responsible for the arclike appearance of sources. it is highly sensitive to dark matter substructure and can greatly increase the resolution of mass maps, but it is very hard to measure. we present an automated flexion measurement pipeline for hubble space telescope data and a preliminary application to the frontier fields cluster macsj0416.1-2403. | substructure in the frontier fields from weak lensing flexion |
measurements of the fine structure constant α, using methods from atomic, condensed-matter, and particle physics, are powerful tests of the overall consistency of theory and experiment across physics. we have measured α = 1/137.035999046(27), at 2 . 0 ×10-10 accuracy, via the recoil frequency of cesium-133 atoms in a matter-wave interferometer. we used multiphoton interactions such as bragg diffraction and bloch oscillations to increase the phase difference for the interferometer to over 12 million radians, which reduced the statistical uncertainty and enabled control of systematic effects at the 0.12 part-per-billion level. this is an unprecedented test of the standard model of particle physics, being the first direct measurement of α with an error below the 5th order quantum electrodynamics contribution in the electron's gyromagnetic anomaly. it also has implications for the unexplained anomaly of the muon's magnetic moment, and strongly constrains multiple dark sector candidates as well as substructure of the electron. | measurement the fine structure constant with bragg diffraction and bloch oscillations |
the properties of the dark matter particle or particles lead to different small scale halo populations, distributions, and evolution over cosmic time. we introduce a new method for characterizing the properties of substructure within galaxies through the power spectrum of potential fluctuations, and demonstrate how complete sets of multiwavelength imaging and time domain observations can be processed directly to infer all facets of the strong gravitational lensing components and source properties, including the dark matter substructure power spectrum constraints. we are able to take advantage of analysis parallels with cosmic background radiation techniques, and furthermore demonstrate how this technique, dubbed the aspen framework, reduces to the long-standing approach of working with reduced or derived observable quantities in lensing. | the aspen framework for dark matter substructure inference from strong gravitational lensing observations |
the cold dark matter (cdm) model of the universe predicts that there should be hundreds to thousands of clumps surrounding a massive galaxy. however, observations have shown that we only see dozens of dwarf galaxies and not the hundreds to thousands that are predicted. this means that either the cdm model prediction is wrong, or most of the substructure consists of dark matter that cannot be observed directly. massive galaxies serve as natural gravitational lenses throughout the universe that allow us to indirectly observe these dark matter perturbations. strong gravitational lensing occurs when these massive elliptical galaxies have the critical density required to bend light from a source located behind it and produce multiple images of that same source. dark matter clumps located near these multiple images affect their positions and flux ratios. we used lensing simulations to quantify how dark matter clumps affect image properties and to characterize this zone of influence through color maps of chi-squared values. our results showed regions around each of the image positions that display significant perturbations for low mass clumps. for higher mass clumps, however, these distinct regions bleed together. we found that there is a correlation between the mass of the dark matter clump and the area it perturbs.this research has been supported by nsf grant phy-1263280. | characterizing the zone of influence of dark matter clumps on image positions and flux ratios in gravitational lensing systems |
a wealth of information on the evolution of structure in the universe can be gained by measuring how the properties of dark matter halos in numerical simulations evolve over time. however, the techniques commonly used to measure halo properties often make assumptions about a halo's structure that are not strictly true, resulting in systematically biased results. tesseract, a non-parametric tessellation-based technique for measuring halo concentration in n-body simulations, does not make any assumptions about a halo's structure, allowing halos to be axisymmetric, triaxial, contain substructure, and have ill-defined centers. preliminary results are presented using tesseract to measure the concentration of dark matter halos in cosmological n-body simulations. | the non-parametric concentration of dark matter halos in cosmological n-body simulations |
context: galaxy clusters grow hierarchically with continuous accretion bookended by major merging events that release immense gravitational potential energy (as much as ∼1065 erg). this energy creates an environment for rich astrophysics. precise measurements of the dark matter halo, intracluster medium, and galaxy population have resulted in a number of important results including dark matter constraints and explanations of the generation of cosmic rays. however, since the timescale of major mergers (∼several gyr) relegates observations of individual systems to mere snapshots, these results are difficult to understand under a consistent dynamical framework. while computationally expensive simulations are vital in this regard, the vastness of parameter space has necessitated simulations of idealized mergers that are unlikely to capture the full richness. merger speeds, geometries, and timescales each have a profound consequential effect, but even these simple dynamical properties of the mergers are often poorly understood. a method to identify and constrain the best systems for probing the rich astrophysics of merging clusters is needed. such a method could then be utilized to prioritize observational follow up and best inform proper exploration of dynamical phase space. task: in order to identify and model a large number of systems, in this dissertation, we compile an ensemble of major mergers each containing radio relics. we then complete a pan-chromatic study of these 29 systems including wide field optical photometry, targeted optical spectroscopy of member galaxies, radio, and x-ray observations. we use the optical observations to model the galaxy substructure and estimate line of sight motion. in conjunction with the radio and x-ray data, these substructure models helped elucidate the most likely merger scenario for each system and further constrain the dynamical properties of each system. we demonstrate the power of this technique through detailed analyses of two individual merging clusters. each are largely bimodal mergers occurring in the plane of the sky. we build on the dynamical analyses of dawson (2013b) and ng et al. (2015) in order to constrain the merger speeds, timescales, and geometry for these two systems, which are among a gold sample earmarked for further follow up. findings: macs j1149.5+2223 has a previously unidentified southern subcluster involved in a major merger with the well-studied northern subcluster. we confirm the system to be among the most massive clusters known, and we study the dynamics of the merger. macs j1149.5+2223 appears to be a more evolved system than the bullet cluster observed near apocenter. zwcl 0008.8+5215 is a less massive but a bimodal system with two radio relics and a cool-core "bullet" analogous to the namesake of the bullet cluster. these two systems occupy different regions of merger phase space with the pericentric relative velocities of ∼2800 km s-1 and ∼1800 km s-1 for macs j1149.5+2223 and zwcl 0008.8+5215, respectively. the time since pericenter for the observed states are ∼1.2 gyr and ∼0.8 gyr, respectivel. in the ensemble analysis, we confirm that radio relic selection is an efficient trigger for the identification of major mergers. in particular, 28 of the 29 systems exhibit galaxy substructure aligned with the radio relics and the disturbed intra-cluster medium. radio relics are typically aligned within 20° of the axis connecting the two galaxy subclusters. furthermore, when radio relics are aligned with substructure, the line of sight velocity difference between the two subclusters is small compared with the infall velocity. this strongly implies radio relic selection is an efficient selector of systems merging in the plane of the sky. while many of the systems are complex with several simultaneous merging subclusters, these systems generally only contain one radio relic. systems with double radio relics uniformly suggest major mergers with two dominant substructures well aligned between the radio relics. conclusions: radio relics are efficient triggers for identifying major mergers occurring within the plane of the sky. this is ideal for observing offsets between galaxies and dark matter distributions as well as cluster shocks. double radio relic systems, in particular, have the simplest geometries, which allow for accurate dynamical models and inferred astrophysics. comparing and contrasting the dynamical models of macs j1149.5+2223 and zwcl 0008.8+5215 with similar studies in the literature (dawson, 2013b; ng et al., 2015; van weeren et al., 2017), a wide range of dynamical phase space (∼ 1500 - 3000 km -1 at pericenter and ∼ 500 - 1500 myr after pericenter) may be sampled with radio relic mergers. with sufficient samples of bimodal systems, velocity dependence of underlying astrophysics may be uncovered. (abstract shortened by proquest.). | observations and modeling of merging galaxy clusters |
we present twelve high resolution cosmological simulations of stellar disks. stellar disks are inserted into zoom-in simulations of cosmological halos by first treating the disks as rigid bodies and slowly growing them to their present day masses and sizes. the rigid disks are allowed to respond to their dark matter halos, and their orientations are evolved per a comoving representation of euler's equations of rigid body dynamics. after a rigid disk finishes growing, it is replaced with a live stellar disk and evolved to present day. we explore the impact that a live stellar disk has on halo substructure and adiabatic contraction, the effect that live disk and halo properties have on bar formation, and the evolution of vertical structure in the thin disk. in particular, we focus on the evolution of stars which are stripped from a disk's outer regions to form stream-like structures at a variety of latitudes. we show that global tidal fields can generate these populations, and invoke them as a means to explain observations of low-latitude milky way structures like the monoceros ring, a13, and triand. | nature vs nurture: cosmological implications for bar formation and galactoseismology |
gravitational lensing is an effect of general relativity, where massive objects, such as galaxies, are able to bend the light path of background sources, making the position of the observed image differ from where the source would be seen in the absence of lensing. if the lens is massive enough, it can produce multiple images of the source, each with a different magnification. however, there may be discrepancies in the predicted and observed magnifications of the images. this difference can be resolved by accounting for additional microlensing due to stars in the lensing galaxy. supernova iptf16geu, discovered in 2016 by the intermediate palomar transient factory, is a lensed source that still has a discrepancy between the predicted and observed image magnifications, even after accounting for microlensing due to stars. we present a more detailed gravitational lensing model that attempts to account for the discrepancy observed in the magnifications of iptf16geu. we find that our more realistic model is an improvement from simpler lensing models, with still the possibility of ongoing millilensing caused by additional objects, such as dark matter substructures, in the lensing galaxy. | probing additional gravitational lensing effects of supernova iptf16geu |
cosmological breakthroughs in the 2020s will arise from measuring the redshift evolution of dark energy, resolving the tension in the expansion rate of the universe, and understanding the impact of dark matter on galaxy substructure. joint processing of euclid/lsst/wfirst data provides the most compelling, economical and tractable path forward. | cosmology in the 2020s needs precision and accuracy: the case for euclid/lsst/wfirst joint survey processing |
measuring the fine-structure constant α allows testing the consistency of theory and experiment across physics. using the recoil frequency of cesium-133 atoms in a matter-wave interferometer, we recorded the most accurate measurement of the fine-structure constant to date: α = 1 / 137 . 035999046(27) at 2 . 0 ×10-10 accuracy. comparison with penning trap measurements of the electron gyromagnetic anomaly ge - 2 via the standard model of particle physics is now limited by the uncertainty in ge - 2 . implications for dark-sector candidates and electron substructure may be a sign of physics beyond the standard model that warrants further investigation. | measurement of the fine-structure constant as a test of the standard model |
the particle nature of dark matter is a defining problem of modern particle physics, arguably the most blatant and most elusive sign of physics beyond the standard model. over the past decades, it has also become a proving ground for diverse scientific collaboration, as a vast array of cosmological, astrophysical, tabletop, and underground probes are harnessed in tandem to address this puzzle. in the past several years, cosmology and astrophysics in particular have surged into prominence, and the ensuing influx of data have offered us new and exciting pathways to search for new physics. in this dissertation we will present several fronts of progress, showcasing how observables from the early and late universe can uncover various facets of dark sector interactions: at the largest scales, we derive model-independent limits on the elastic scattering cross-section between baryons and dark matter using cosmic microwave background data from the planck satellite and measurements of the lyman-alpha forest flux power spectrum from the sloan digital sky survey. at lower redshifts, we consider minimal extensions to the sm by new massive light relics, and forecast the significance at which these new particles, with different masses and temperatures, can be detected by upcoming large-scale structure surveys. we then obtain state-of-the-art constraints from presently available cosmological data. zooming in further, we illustrate the potential of local group dwarf galaxy shapes to elucidate dark matter substructure and self-interactions. we consider methods to infer 3d morphological information on local group dwarf spheroidals, and test the fitness of cdm+hydrodynamics simulations to the observed galaxy shapes. we find that the subpopulation of dwarf galaxies with high mass-to-light ratio reflects an oblate morphology, discrepant with simulations of cdm-sourced galaxies which are explicitly prolate. finally, and closest to us, we analyze the implications of the robust galactic center gamma-ray excess and prospects of forthcoming antideuteron experiments for annihilating dark matter, showcasing the phenomenology of two particle models in particular: one where majorana fermion dark matter annihilates through a cp-violating higgs portal, and one where dirac fermion dark matter annihilates to kinetically-mixed dark photons. | searching for dark matter in the early and late universe |
we compute the weak gravitational lensing signal of isolated, central galaxies obtained from the z=0.5 timestep of the λcdm illustris-1 simulation. the galaxies have stellar masses ranging from 9.5 ≤ log10(m*/msun) ≤ 11.0 and are located outside cluster and rich group environments. although there is local substructure present in the form of small, luminous satellite galaxies, the central galaxies are the dominant objects within the virial radii (r200), and each central galaxy is at least 5 times brighter than any other luminous galaxy within the friends-of-friends halo. we compute the weak lensing signal within projected radii 0.05 < rp/r200 < 1.5 and investigate the degree to which the weak lensing signal is anisotropic. since cdm halos are non-spherical, the weak lensing signal is expected to be anisotropic; however, the degree of anisotropy that is observed depends upon the symmetry axes that are used to define the geometry. the anisotropy is expected to be maximized when the major axis of the projected dark matter mass distribution is used to define the geomety. in practice in the observed universe, one must necessarily use the projected distribution of the luminous mass to define the geometry. if mass and light are not well-aligned, this results in a suppression of the weak lensing anistropy. our initial analysis shows that the ellipticity of the projected dark matter halo is uncorrelated with the ellipticity of the projected stellar mass. that is ɛhalo ≠ f × ɛlight, where f is a constant multiplicative factor. in addition, in projection on the sky, the major axis of the dark matter mass is offset from that of the stellar mass by ∼40o on average. on scales rp ≤ 0.15 r200, the weak lensing anisotropy obtained when using the stellar mass to define the geometry is of order 7% and agrees well with the anisotropy obtained when using the dark matter mass to define the geometry. on scales rp ∼ r200, the anisotropy obtained when using the stellar mass to define the geometry is reduced by an order of magnitude compared to the anisotropy obtained when using the dark matter mass to define the geometry. | weak gravitatational lensing by illustris-1 galaxies |
the roman space telescope's galactic bulge time domain survey will constitute the most sensitive microlensing survey of the galactic bulge to date, opening up new opportunities to search for dark matter (dm). many extensions of the standard model predict the formation of extended dm substructures, such as dm subhalos, boson/axion stars, and halo-dressed primordial black holes. we demonstrate that for such targets, roman will be sensitive to a broad parameter space up to four orders of magnitude below existing constraints. our analysis can be readily applied to other extended dm configurations as well. | new light on dark extended lenses with the roman space telescope |
perturbations to stellar systems can reflect the gravitational influence of dark matter substructures. whereas perturbations to cold stellar systems are the most commonly studied, the sources of perturbations to dynamically hot systems are less ambiguous because such systems cannot support persistent inhomogeneity on small scales. we point out a simple algebraic relationship between the two-point statistics of a hot stellar system and those of the perturbing matter. the density and velocity power spectra of the stars are proportional to the density power spectrum of the perturbers, scaled by $k^{-4}$. this relationship allows easy evaluation of the suitability of a stellar system for detecting dark substructure. as examples, we show that the galactic stellar halo is expected to be sensitive to cold dark matter substructure at wave numbers $k\lesssim 0.4$ kpc$^{-1}$, and the galactic disk might be sensitive to substructure at wave numbers $k\sim 4$ kpc$^{-1}$. these systems could provide direct measurements of the nonlinear matter power spectrum at these wave numbers. | an analytic description of substructure-induced gravitational perturbations of hot stellar systems |
cluster number counts will be a key cosmological probe in the next decade thanks to the euclid satellite mission. for this purpose, cluster detection algorithm performance, which are sensitive to the spatial distribution of the cluster galaxy members and their luminosity function, need to be accurately characterized. using the three hundred hydrodynamical and dark matter only simulations we study a complete sample of massive clusters beyond 7 (5) $\times$ 10$^{14}$ m$_{\odot}$ at redshift 0 (1) on a $(1.48 \ \mathrm{gpc})^3$ volume. we find that the mass resolution of the current hydrodynamical simulations (1.5 $\times$ 10$^9$ m$_{\odot}$) is not enough to characterize the luminosity function of the sample in the perspective of euclid data. nevertheless, these simulations are still useful to characterize the spatial distribution of the cluster substructures assuming a common relative mass threshold for the different flavours and resolutions. by comparing with the dark matter only version of these simulations, we demonstrate that baryonic physics preserves significantly low mass subhalos (galaxies) as have also been observed in previous studies with less statistics. furthermore, by comparing the hydro simulations with higher resolution dark matter only simulations of the same objects and taking the same limit in subhalo mass we find significantly more cuspy galaxy density profiles towards the center of the clusters, where the low mass substructures would tend to concentrate. we conclude that using dark matter only simulation may lead to some biases on the spatial distribution and density of galaxy cluster members. based on the preliminary analysis of few high resolution hydro simulations we conclude that a mass resolution of 1.8 $\times$ 10$^8$ h$^{-1}$ m$_{\odot}$ will be needed for the three hundred simulations to approach the expected magnitude limits for the euclid survey. | the three hundred : contrasting clusters galaxy density in hydrodynamical and dark matter simulations |
the south pole telescope (spt) has systematically identified 90 high-redshift strongly gravitationally lensed submillimeter galaxies (smgs) in a 2500 square-degree cosmological survey of the millimeter (mm) sky. these sources are selected by their extreme mm flux, which is largely independent of redshift and lensing configuration. we are undertaking a comprehensive and systematic followup campaign to use these "cosmic magnifying glasses" to study the infrared background in unprecedented detail, inform the condition of the interstellar medium in starburst galaxies at high redshift, and place limits on dark matter substructure. here we ask for 115.4 hours of deep spitzer/irac imaging to complete our survey of 90 systems to a uniform depth of 30min integrations at 3.6um and 60min at 4.5um. in our sample of 90 systems, 16 have already been fully observed, 30 have been partially observed, and 44 have not been observed at all. our immediate goals are to: 1) constrain the specific star formation rates of the background high-redshift submillimeter galaxies by combining these spitzer observations with our apex, herschel, and alma data, 2) robustly determine the stellar masses and mass-to-light ratios of all the foreground lensing galaxies in the sample by combining these observations with our vlt and gemini data, the dark energy survey, and alma; and 3) provide complete, deep, and uniform nir coverage of our entire sample of lensed systems to characterize the environments of high redshift smgs, maximize the discovery potential for additional spectacular and rare sources, and prepare for jwst. this program will provide the cornerstone data set for two phd theses: kedar phadke at illinois will lead the analysis of stellar masses for the background smgs, and kaja rotermund at dalhousie will lead the analysis of stellar masses for the foreground lenses. | the spt+herschel+alma+spitzer legacy survey: the stellar content of high redshift strongly lensed systems |
the generalisation of proper time, as an alternative to models with extra dimensions of space, has been proposed as the source of the elementary structures of matter. direct connections with the standard model of particle physics together with dark sector candidates can be attained in this manner, through the additional components and symmetry breaking pattern identified on extracting the substructure of the local 4-dimensional spacetime form. in this paper we focus more on the extended and global properties of the theory, both in relation to amalgamating gravity with quantum theory and to broader cosmological issues. contrast will be made with both early s-matrix bootstrap models and more recent cosmological bootstrap techniques. with time playing a central role in the new theory we describe how a 'universal bootstrap' can be constructed and elaborate upon the implications. | generalised proper time and the universal bootstrap |
in this work, we study the $su(2)_l$ singlet complex scalar extended ksvz model that, in addition to providing a natural solution to the strong-cp problem by including a global peccei-quinn symmetry, also furnishes two components of dark matter that satisfy observer relic density without fine-tuning of model parameters. furthermore, this model provides a rich phenomenology by introducing a vector-like quark whose presence can be sensed in collider experiments and dark matter production mechanisms. we explore the possibility of democratic yukawa interaction of the vector-like quark with all up-type quarks and scalar dark matter candidate. we also employ next-to-leading order nlo-qcd correction for vlq pair production to study a unique search at the lhc, generating a pair of boosted tops with sizeable missing transverse momentum. multivariate analysis with jet substructure variables has a strong ability to explore a significant parameter space of this model at the 14 tev lhc. | precision prediction at the lhc of a democratic up-family philic ksvz axion model |
flat rotation curves v(r) are naturally explained by elongated (prolate) dark matter (dm) distributions, and we have provided competitive fits to the sparc database. to further probe the geometry of the halo one needs out-of-plane observables. stellar streams, poetically analogous to airplane contrails, but caused by tidal dispersion of massive substructures such as satellite dwarf galaxies, would lie on a plane should the dm-halo gravitational field be spherically symmetric. we aim at establishing stellar stream torsion, a local observable that measures the deviation from planarity in differential curve geometry. we perform small-scale simulations of tidally distorted star clusters to check that indeed a central force center produces negligible torsion. turning to observational data, we identify among the known streams those that are at largest distance from the galactic center and likely not affected by the magellanic clouds, as most promising for the study, and by means of polynomial fits we extract their differential torsion. we find that the torsion of the few known streams that should be sensitive to most of the milky way's dm halo is much larger than expected for a central spherical bulb alone. this is consistent with non-sphericity of the halo. future studies of stellar stream torsion with larger samples and further out of the galactic plane should be able to extract the ellipticity of the halo to see whether it is just a slight distortion of a spherical shape or rather ressembles a more elongated cigar. | the torsion of stellar streams and the overall shape of galactic gravity's source |
dark matter clusters on all scales, and it is therefore expected that even substructure should host its own substructure. using the extragalactic distance database, we searched for dwarf-galaxy satellites of dwarf galaxies, that is, satellite-of-satellite galaxies, corresponding to these substructures of substructure. from investigation of hubble space telescope data for 117 dwarf galaxies, we report the discovery of a previously unknown dwarf galaxy around the ultra-diffuse m96 companion m96-df6 at 10.2 mpc in the leo-i group. we confirm its dwarf-galaxy nature as a stellar overdensity. modeling its structural parameters with a growth-curve analysis, we find that it is an ultrafaint dwarf galaxy with a luminosity of 1.5 × 105 l⊙, which is 135 times fainter than its host. based on its close projection to m96-df6, it is unlikely that their association occurs simply by chance. we compare the luminosity ratio of this and three other known satellite-of-satellite systems with results from two different cosmological sets of λcdm simulations. for the observed stellar mass range of the central dwarf galaxies, the simulated dwarfs have a higher luminosity ratio between the central dwarf and its first satellite (≈10 000) than observed (≈100), excluding the large and small magellanic cloud (lmc/smc) system. no simulated dwarf analog at these observed stellar masses has the observed luminosity ratio. this cannot be due to missing resolution, because it is the brightest subhalos that are missing. this may indicate that there is a satellite-of-satellite (sos) problem for λcdm in the stellar-mass range between 106 and 108 m⊙, the regime of the classical dwarf galaxies. however, simulated dwarf models at both a lower (< 106 m⊙) and higher (> 108 m⊙) stellar mass have comparable luminosity ratios. for the higher-stellar-mass systems, the lmc/smc system is reproduced by simulations; for the lower stellar masses, no observed satellite-of-satellite system has been observed to date. more observations and simulations of satellite-of-satellite systems are needed to assess whether the luminosity ratio is at odds with λcdm. | a possible dwarf galaxy satellite-of-satellite problem in λcdm |
the difficult task of observing dark matter subhaloes is of paramount importance since it would constrain dark matter particle properties (cold or warm relic) and confirm once again the longstanding $\lambda$cdm model. in the near future the new generation of ground and space surveys will observe thousands of strong gravitational lensing systems providing a unique probe of dark matter substructures. here, we describe a new strong lensing analysis pipeline that combines deep convolutional neural networks with physical models and exploits traditional sampling techniques such as hamiltonian monte carlo. using simulated strong gravitational lensing systems, we discuss first results and characterize the accuracy of the reconstruction of the main lensing parameters. | differentiable probabilistic programming for strong gravitational lensing |
tidal debris structures are striking evidence of hierarchical assembly--the premise that the milky way and galaxies like it have been built over cosmic time through the coalescence of many smaller objects. in the prevailing lambda--cold dark matter cosmology, the vast majority of mergers by number are minor; one dark matter halo, hosting a larger galaxy, dominates the interaction and a smaller object, the satellite, is stripped of mass by tidal forces. when the luminous component of the satellite is disrupted the debris may form structures such as stellar tidal streams or shells, depending on the parameters of the interaction. in this thesis we examine the properties of this debris left behind by minor mergers theoretically, computationally, and observationally, making strides towards a more complete understanding of what tidal debris can tell us about the history of galaxy formation in the universe. around the milky way itself we have examined the properties of the orphan stream, a stellar tidal stream so named due to uncertainty about the position and current state of its progenitor. using 3.6 microm observations taken as part of the spitzer merger history and shape of the galactic halo program, the latest period-luminosity-metallicity relations, and archival data, we compute precise distances to rr lyrae stream members with state-of-the-art 2.5% relative uncertainties. fitting an orbit to the data, we measure an enclosed mass for the milky way that is in good agreement with other recent results, once the biases in orbit fitting are taken into account. by applying the same technique to n-body simulations we determined that the orphan progenitor is most likely similar to the classical dwarf spheroidal satellites. we also examined tidal debris more generally, in particular by investigating the source of the morphological dichotomy between shells and streams. we find that the transition from a stream--like to a shell--like morphology occurs when the differential azimuthal precession between the orbits of stars exceeds the position angle subtended by individual petals of the progenitor orbit's rosette. this statement is cast more precisely in terms of scaling relations that control the dispersion of energy and angular momentum in the debris, and we find that the observed morphology can be predicted for a given host, orbit, and mass ratio. this leads us to the idea that the observed occurrence rates of different morphologies can be used to recover, at the population statistics level, the progenitor satellites' orbital infall distribution. this a part of the cosmological accretion history that is otherwise inaccessible. to achieve this in practice requires an unbiased and automated method to detect and classify substructure; we have developed just such a tool and demonstrate its effectiveness. in the upcoming era of lsst and wfirst the methods and insights developed in this thesis will be useful in decoding the information about the current state and assembly of galaxies encoded in tidal debris. | dynamics and detection of tidal debris |
we develop and implement a model to analyze the internal kinematics of galaxy clusters that may contain subpopulations of galaxies that do not independently trace the cluster potential. the model allows for substructures within the cluster environment, disentangles cluster members from contaminating foreground and background galaxies, and includes an overall cluster rotation term as part of the cluster kinematics. we estimate the cluster velocity dispersion and/or mass while marginalizing over uncertainties in all of the above complexities. in a first application to our published data for abell 267 (a267), we find no evidence for cluster rotation but we identify up to five distinct galaxy subpopulations. we use these results to explore the sensitivity of inferred cluster properties to the treatment of substructure. compared to a model that assumes no substructure, our substructure model reduces the dynamical mass of a267 by $\sim 20\%$ and shifts the cluster mean velocity by $\sim 100$ km s$^{-1}$, approximately doubling the offset with respect to the velocity of a267's brightest cluster galaxy. embedding the spherical jeans equation within this framework, we infer for a267 a dark matter halo of mass $m_{200}=6.77\pm1.06\times10^{14}m_\odot/h$, concentration $\log_{10}c_{200}=0.61\pm0.39$, consistent with the mass-concentration relation found in cosmological simulations. | galaxy cluster mass estimates in the presence of substructure |
this proposal seeks support for a uniform analysis of archival x-ray data on the lovoccs clusters, a nearby, volume-limited sample of 143 clusters of galaxies with halo mass 10^14-10^14.5 solar masses. its primary goal is to characterize and interpret the *deviations* of individual galaxy clusters from the usual scaling relations between a cluster's observable properties and its underlying halo mass, which encode information about the cluster's massassembly and star-formation histories. the lovoccs project is currently gathering highquality weak lensing data that will deliver lensing masses and substructure maps for all of these clusters, along with star-formation histories based on optical photometry. this parallel x-ray analysis will establish how deviations of a cluster's baryonic gas properties from the usual scaling relations correlate with deviations in stellar mass, star-formation history, and mass substructure. it will build upon and extend a population statistics model previously applied to locuss, a smaller sample of higher mass clusters. improvements to that model will enable halo-mass measurements of unsurpassed accuracy in this mass range and will provide a unique window into the links between mass assembly, star formation, and feedback processes in massive galaxies. the work will further nasa's efforts to discover the secrets of the universe and reveal the astrophysics of how the universe transformed dark matter and baryons into galaxies. it will support the development of statistical tools for the much richer datasets to emerge from erosita, the nancy roman telescope, xrism, and athena. | baryonic and weak lensing properties of a volume-limited sample of clusters of galaxies |
we show that the signature of two boosted w-jets plus substantial missing energy is very promising for probing heavy charged resonances ( $x^\pm$ ) through the process of $pp\to x^+x^-\to w^+w^- x^0 x^0$ , where $x^0$ denotes the dark matter candidate. the hadronic decay mode of the w boson is considered to maximize the number of signal events. when the mass split between $x^\pm$ and $x^0$ is large, the jet-substructure technique must be utilized to analyze the boosted w-jet. here, we consider the process of chargino pair production at the lhc, i.e., $pp\to \chi_1^+\chi^-_1 \to w^+w^-\chi_1^0\chi_1^0$ , and demonstrate that the proposed signature is able to cover more parameter space of $m_{\chi_1^\pm}$ and $m_{\chi_1^0}$ than the conventional signature of multiple leptons plus missing energy. more importantly, the signature of interest is not sensitive to the spin of heavy resonances. * supported in part by the national science foundation of china (11725520, 11675002, 11635001, 11805013, 12075257) and the fundamental research funds for the central universities (2018ntst09) | new physics and two boosted w-jets plus missing energy |
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 regions of our galaxy. i will discuss how these measurements allow us to precisely reconstruct the 3d distribution of dark matter throughout the galaxy, and for the first time, open the possibility of identifying individual dark-matter substructures. | astrophysical probes of dark matter |
an important open question today is the understanding of the relevance that dark matter (dm) halo substructure may have for dm searches. in the standard cosmological framework, subhalos are predicted to be largely abundant inside larger halos, i.e., galaxies like ours, and are thought to form first and later merge to form larger structures. dwarf satellite galaxies -- the most massive exponents of halo substructure in our own galaxy -- are already known to be excellent targets and, indeed, they are constantly scrutinized by current gamma-ray experiments in their search for dm annihilation signals. lighter subhalos not massive enough to have a visible baryonic counterpart may be good targets as well given their typical number densities and distances. in addition, the clumpy distribution of subhalos residing in larger halos may boost the dm signals considerably. in an era in which gamma-ray experiments possess, for the first time, the exciting potential of reaching the most relevant regions of the dm parameter space, a profound knowledge of the dm targets and scenarios being tested at present is mandatory if we aim for accurate predictions of dm-induced fluxes, for investing significant telescope observing time to selected targets, and for deriving robust conclusions from our dm search efforts. in this regard, a precise characterization of the statistical and structural properties of subhalos becomes critical. with the special issue "the role of halo substructure in gamma-ray dark matter searches" [https://www.mdpi.com/journal/galaxies/special_issues/gamma-raydms], we aimed to summarize where we stand today on our knowledge of the different aspects of the dm halo substructure; to identify what are the remaining big questions, how we could address these and, by doing so, to find new avenues for research. | overlay of the special issue 'the role of halo substructure in gamma-ray dark matter searches' |
in this work, we present a modelling of the galactic sub-clumps based on statistical estimations of the full milky way satellite population. we introduce 10 substructure modellings (sm i , i ∈ {1, … , 10}) with the following varying parameters: a) subhalos inner profile, b) spatial distribution of subhalos, c) mass distribution of subhalos, d) total number of subhalos and e) concentration parameter. the sensitivity curves of cta for sources in each model are calculated for the τ + τ - and bb̅ decay channels. with both detection of a signal (5σ) with the cta and no signal observation, no model was effective in accessing the thermal values of <σv>. we analyse the systematic effect introduced by the substructures models. | uncertainties in measuring the dark matter signal from milky way satellites using cherenkov telescopes |
in this work, we study some properties of the hickson compact groups (hcgs) using n-body simulations for the generalized dark matter (gdm) model, described by three free functions, the sound speed, the viscosity, and the equation of state. we consider three gdm models associated with different values of the free functions to neglect collisional effects. we constructed the initial seeds of our simulations according to the matter power spectrum of gdm linear perturbations, which hold a cut-off at small scales, and explored their effects on the non-linear structure formation at small and intermediate scales. we generated mock catalogues of galaxies for different models and classified hcgs by implementing an algorithm that adapts the original selection method for mock catalogues. once the hcgs samples were classified, we analysed their properties and compared them between models. we found that a larger amount of hcgs are counted in gdm simulations in comparison to cdm counts. this difference suggests that hcgs can proliferate within gdm despite the suppressed substructure, which indicates a possible modification in the hcg formation process within models where dm is not perfectly like cdm. additionally, we identified different mechanisms of clustering, for models with a large amount of galaxy-haloes self-agglomerate because of their abundance while models with fewer galaxy-haloes need massive haloes acting as a dominant potential well. finally, by comparing distributions of different observables of simulated hcgs against observations, we found a good agreement in the intrinsic properties. however, a discrepancy in the velocity dispersion remains unsolved. | compact groups in gdm cosmological simulations |
the statistics of dark matter (dm) substructure are sensitive to the underlying dm model. in particular, the dm thermal velocity sets the cut-off scale for low-mass halos, and the (potentially non-zero) cross-section for dm self-interaction can core out the otherwise cuspy slopes of subhalo inner density profiles, making them less resilient to the strong tidal forces of the host halo. a variety of techniques are being used to determine the dm substructure abundance, and therewith the nature of dm, including gravitational lensing, gaps in stellar streams, and dark matter annihilation. in order for these methods to be successful, it is prudent that we can make reliable theoretical predictions. however, n-body simulations, which is the main tool used to predict the abundance of dm substructure, are hampered by artificial disruption due to inadequate force softening and discreteness noise. i discuss analytical treatments of tidal stripping and heating that can be used to overcome these shortcomings. in particular, i demonstrate that isotropic subhalos in cdm are resilient to complete disruption, even if the central halo contains a central disk. i explicitly show that, contrary to claims in the literature, tidal shocking due to impulsive encounters with a central disk does not lead to sub-halo disruption, and that simulations drastically under-predict the abundance of subhalos close to the central galaxy. i present new n-body simulations, at unprecedented resolution, that follow the tidal evolution of dark matter subhalos without being affected by numerical artefacts. these are used to study, for the first time, the dependence on the orbital anisotropy of the subhalo. it is shown that, contrary to isotropic subhalos, subhalos with a radially anisotropic center can undergo complete disruption. we also show that tidal stripping leads to a rapid isotropization of the bound remnant, and that the orbital anisotropy of the subhalo has a strong impact on the clumpiness of the resulting tidal stream. we discuss implications for the ability to use the demographics of dark matter substructure to inform the nature of dark matter. | on the tidal evolution of dark matter substructure |
observations of galaxy-scale strong gravitational lenses have been used to put constraints on dark matter physics. it is now widely recognized that line-of-sight structures between the source and the observer play a significant role in perturbing lensed images, hence making multi-plane lensing a necessary part of any lens analysis. we propose here to utilize a freshly proposed approach that simplifies the multiplane nature of the lensing problem to an "effective" single mapping between the source and image planes to constrain dark matter. this mapping is fully characterized by two "effective" lensing potentials encompassing the complete structure of the deflection field. we propose to make detailed predictions for the statistical properties of these two potentials and their corresponding correlation function anisotropies in well-motivated dark matter theories. since line-of-sight structure and main-lens substructure contribute differently to each potential, this method has the potential to distinguish these two contributions from one another, potentially improving the constraint on dark matter from strong lensing significantly. we also propose to further develop a likelihood framework to assess the sensitivity of mock data to anisotropic signatures, hence laying the groundwork for a future archival proposal to perform an in-depth study using past hst data. we will also perform forecasts for how future observations could separately constrain observables and what the resulting constraints on dark matter physics would be. | exploring the dark sector with correlation anisotropies |
a source lying near a hyperbolic umbilic (hu) singularity leads to a ring-like image formation, constituting four images with high magnification factors and lying in a small region of the lens plane. since (based on our earlier work) the observed number of hu image formations in cluster lenses is expected to increase in the future, it is timely to investigate them in more detail. like fold and cusp singularities, hu also satisfies the magnification relation, i.e. the signed magnification sum of the four images equals zero. this work presents a detailed study of the hu magnification relation (rhu) considering the elliptical navarro-frenk-white (enfw) lens profile suitable for cluster scale dark matter haloes. our results show that for an isolated enfw lens, rhu is more sensitive to ellipticity than its mass or concentration parameter. an ellipticity greater than 0.3 results in rhu lying close to zero with a small scatter around it. a substructure near the hu image formation causes the average rhu value to deviate from zero and increases the scatter, with the amount of deviation depending on the image type near which the substructure lies. however, a population of substructures in the lens plane (equivalent to the galaxies inside the cluster) does not significantly shift the average rhu value from zero but increases the scatter around it. we find that rhu ≃ 0 for hu image formation in the abell 1703 cluster. repeating this test in other clusters with hu formations can be a useful indicator of substructure in cluster haloes. | exotic image formation in strong gravitational lensing by clusters of galaxies - iv. elliptical nfw lenses and hyperbolic umbilics |
the splashback radius of a dark matter halo, which corresponds to the first apocenter radius reached by infalling matter and substructures, has been detected around galaxy clusters using a multitude of observational methods, including weak lensing measurements. in this manuscript, we present how the splashback feature in the halo density profile affects galaxy cluster masses derived through weak lensing measurements if it is not accounted for. we find that the splashback radius has an increasingly large effect on group-sized halos towards $m_{200m} \sim 10^{13.5} \mathrm{m_\odot}$. depending on the model and the radial scale used, the cluster/group masses can be biased low by more than 0.1 dex. this bias, in turn, would result in a slightly lower $\omega_m$ value if propagated into a cluster cosmology analysis. the splashback effect with group-sized dark matter halos may become important to consider, given the increasingly stringent cosmological constraints coming from optical wide-field surveys. | the effect of splashback on weak lensing mass estimates of galaxy clusters and groups |
dwarf galaxies are valuable laboratories for dynamical studies related to dark matter and galaxy evolution, yet it is currently unknown just how extended their stellar components are. each satellite orbiting within the milky way's (mw's) gravitational potential may undergo tidal stripping by the host galaxy, or alternatively, may themselves have accreted yet smaller systems whose debris settles into the satellite's own stellar halo. both processes could mean that significant populations of member stars are found far from the center of the dwarf. stars in the outskirts of these systems are especially valuable - and rare - tracers of the dwarf's dynamics in low acceleration regimes, and they give insight into the dwarf's evolutionary history. in this work, we examine the mw's ~60 dwarf satellites to search for these rare, distant member stars. using gaia edr3 and a maximum likelihood approach allowing for multi-component extended substructures, we find 9 dwarfs that exhibit a secondary, lower-density, outer profile, that we argue is indicative of an extended stellar halo and/or tidal disruption. our method shows excellent consistency with spectroscopically confirmed members from the literature and requires no radial velocity information. for each dwarf galaxy, we derive a sample of high-confidence members which will prove useful for studying even the faintest mw dwarfs. we also briefly discuss a current spectroscopic follow-up campaign for the most distant dwarf members with the newly commissioned gemini high-resolution optical spectrograph (ghost). already, initial spectra obtained during ghost commissioning has proven useful for comprehensive chemodynamic analysis of these galactic building blocks. | small-scale stellar haloes: detecting extended substructure in the outskirts of milky way dwarf galaxy satellites |
galaxies grow through hierarchical mergers, with high-mass galaxies cannibalizing the satellite dwarf galaxies that orbit them. these galactic accretion events leave behind signatures in the form of tidal debris structures that encode information about their progenitors and hosts. examining these substructures can open a window into the accretion histories of galaxies in the universe, as well as the dark-matter-dominated mass distribution in galaxy halos. by capturing vast numbers of images of tidal debris substructures, upcoming surveys like lsst will provide us with the data required to gain statistically sound constraints on the orbital distributions of satellites. an automated method for analyzing this data is vital for efficiency and consistency. we present an algorithm that can efficiently and reliably measure the properties of tidal debris substructures, yielding results that can be used to constrain the distributions of accreting satellites. our method is capable of distinguishing shell-like and stream-like tidal debris – the most distinct morphologies – and measuring their luminosities and scales, properties that hint at the shape of the satellite orbit, the duration of accretion, and satellite mass. we demonstrate our algorithm on snapshot images from n-body simulations, and explore how analyzing their observable properties will help us unravel the accretion histories of galaxies in our universe, and allow us to probe theories of hierarchical galaxy formation and their underlying cosmological paradigm. | unlocking the history of galaxy mergers through the automated analysis of tidal debris substructures |
we propose acs imaging of four exciting new merging clusters with \`\`dissociative'' morphology---two galaxy subclusters on either side of a central gas concentration, indicative of a recent head-on collision. the imaging will enable a weak lensing analysis that will (i) determine the dark matter halo locations relative to the galaxy subcluster locations; (ii) measure the subcluster masses; and (iii) place limits on the presence of any additional substructures. in conjunction with existing x-ray data and a scheduled spectroscopic survey, the dark matter halo locations and masses will enable accurate modeling of the merger scenario. upper limits on galaxy-dark matter offsets will be translated to upper limits on the momentum exchanged between the dark matter halos. together with accurate modeling of the merger scenario, this will place upper limits on the dark matter scattering cross section. these four systems are promising in that respect because their modest separations suggest that they are seen not long after first pericenter. | four new dissociative merging clusters |
disk galaxies are highly responsive systems that undergo oscillations triggered by various agents such as external forces and tides from satellite galaxies and dark matter substructure. such gravitational interactions tend to throw disk galaxies out of equilibrium. in due course, stellar oscillations lose coherence and perturbations damp out by collisionless relaxation mechanisms like phase-mixing and landau damping, which manifest as phase-space spirals. these dynamical features have recently been observed by gaia in our milky way galaxy, hinting at the possibility of recent interactions in the galactic disk. in this talk i shall demonstrate a general perturbative formalism to compute the disk response to various perturbers such as spiral arms and satellite galaxies and obtain the resultant phase-space spirals. using this formalism, i shall elucidate the perturber characteristics responsible for triggering bending and breathing oscillation modes corresponding to one- and two-armed phase-space spirals. this can be used to constrain the milky way's dynamical history. i shall also discuss the survivability and observability of phase-space spirals in the galactic disk, and illustrate their usefulness as probes of the galactic potential. | phase-space spirals as probes of perturbed, out-of-equilibrium disk galaxies |
understanding local stellar kinematic substructures in the solar neighbourhood helps build a complete picture of the formation of the milky way, as well as an empirical phase space distribution of dark matter that would inform detection experiments. we apply the clustering algorithm hdbscan on the gaia early third data release to identify a list of the most stable clusters in velocity space and action-angle space, by taking into account the measurement uncertainties and studying the stability of the clustering results. we find 1405 (497) stars in 23 (6) robust clusters in velocity space (action-angle space) that are consistently not associated with noise. we discuss the kinematic properties of these structures and study whether many of the small clusters belong to a similar larger cluster based on their chemical abundances. the clusters found are attributed to the known structures: the gaia sausage-enceladus, the helmi stream, and globular cluster ngc 3201 are found in both spaces, while ngc 104 and the thick disc (sequoia) are identified in velocity space (action-angle space). although we do not identify any new structures, we find that the hdbscan member selection of already known structures is unstable to input kinematics of the stars when resampled within their uncertainties. we therefore present the most stable subset of local kinematic structures, which are consistently identified by the clustering algorithm, and emphasize the need to take into account error propagation during both the manual and automated identification of stellar structures, both for existing ones as well as future discoveries. | robust clustering of the local milky way stellar kinematic substructures with gaia edr3 |
lcdm shows some tension with observations in the non-linear regime of structure formation. this includes abundance, density profiles and substructure amount for dark matter haloes at a range of masses and redshifts. several recipes have been suggested to remedy such tensions including more detailed modelling of baryonic physics, modifications to gravity or variations to the collisionless, cold dark matter paradigm. however, current observational signatures to distinguish such models are elusive due to the vast information compression in the characterisation of observed dark matter structure via e.g. two-point correlation functions or 1d functional forms of density profiles. i will present a full morphological analysis of dark matter structure in the sky based on optimal mass mapping, computer vision and machine learning that alleviates this shortcoming. more specifically, i will focus on two characterisation schemes. the first one derives from classical computer vision and machine learning and extracts up to 3500 characterising elements directly from dark matter mass or shear maps, several of their transformations (fourier, chebyshev, edge, wavelet, ...) and transformation of transformations. the second approach is based on deep learning and applies a multi-layered convolutional neural network, including state-of-the-art methods such as inception layers and region detection, to learn the main characterising features in the dark matter mass and shear maps.we apply these techniques to several sets of numerical simulations, all of which explore different aspects of the underlying model of structure formation. this includes several models of modified gravity, the degeneracy between modified gravity and the presence of massive neutrino, baryonic feedback and models of self-interacting dark matter. i will close with the application of this technique to classify the underlying structure formation model of real data coming from the kids and clash surveys and will give an outlook on the potential of future space and ground-based experiments such as euclid, wfirst and lsst. | learning the shape of and what shapes dark structure |
the objective of this project is to carry out an analysis of planetary systems that orbit orange dwarf stars through computational modeling and build a database with possible candidates for terrestrial exoplanets in the habitability zone of these systems. | formation of superhabitable worlds in the habitable zone of orange dwarf stars |
since the discovery of the first exoplanets in the early 1990s we have seen explosive growth in the field of exoplanetary science, hand-in-hand with technological improvements. we now know of over 4,000 exoplanets, most of which have been detected with two detection techniques: the transit method, and the doppler radial velocity (rv) method. in this thesis, i discuss our efforts to further improve on these techniques to through the development of next-generation astronomical instrumentation. first, i discuss a path to obtain hitherto unachievable differential photometric precisions from the ground using custom-fabricated engineered diffusers. such diffusers mold the focal plane image of a star into a broad and stable top-hat shape, minimizing photometric errors due to non-uniform pixel response, atmospheric seeing effects, imperfect guiding, and telescope-induced variable aberrations seen in defocusing. this reshaping significantly increases the achievable dynamic range of our observations, increasing our observing efficiency and thus better averages over scintillation. in using this technique we have demonstrated 62ppm precision in 30 minute bins on the bright star 16 cyg a using the engineered diffuser we installed on the 3.5m arc telescope at apache point observatory - within a factor of two of kepler's photometric precision on the same star. we discuss our precision diffuser-assisted follow-up observations of nearby transiting exoplanets, allowing us to better characterize their orbital parameters. this technology is inexpensive, scalable, easily adaptable, and is already being used at a number of different observatories for precision ground-based photometric follow-up of transiting planets. second, i discuss the design and development of two next-generation radial velocity spectrographs: the habitable-zone planet finder (hpf), a near-infrared (nir) high-resolution stabilized doppler spectrograph we recently installed at the 10m hobby-eberly telescope at mcdonald observatory in texas, and neid, a precision red-optical high-resolution stabilized doppler spectrograph to be installed on the 3.5m wiyn telescope at kitt peak national observatory in arizona in late 2019. in particular, i discuss the design and performance of the hpf and neid environmental control systems, which have demonstrated sub-milli-kelvin temperature stability and ~1microtorr pressure stability long-term, both of which are essential for precision rvs. further, i discuss the commissioning and early hpf on-sky rv precision demonstrations. in particular, i discuss our rv extractions demonstrating 1.53 m/s rv precision over months on the nearby-bright m4.5-dwarf barnard's star, marking some of the highest rv precisions achieved in the nir to date. additionally, i discuss two recent projects that combine these two technologies to demonstrate their scientific utility on-sky. i discuss the validation of a 2 earth radii sub-neptune-sized planet around the nearby high proper motion m2.5 dwarf g 9-40, using high-precision nir rv observations with hpf, precision diffuser-assisted ground-based photometry with a custom narrow-band photometric filter on the arctic imager at apo, and adaptive optics imaging using the shaneao system at the 3m shane telescope at lick observatory. at a distance of 27.9pc, g 9-40b is currently the second closest transiting planet discovered by the k2 mission to date, and amongst top small m-dwarf planet candidates for transmission spectroscopy with jwst in the future. we also discuss our implementation of an empirical spectral matching algorithm using high-resolution nir hpf spectra, which we use to estimate spectroscopic stellar parameters of the host star, which can easily be used to estimate stellar parameters of other m-dwarf stars observed with hpf. additionally, i discuss the full 3d orbital solution of the neptune-sized m-dwarf planet k2-25b orbiting its m4.5 dwarf star in the 650-800myr old hyades cluster. through jointly fitting the available k2 data, precision ground-based diffuser-assisted transits from arctic at apo and the half-degree imager (hdi) on the 0.9m telescope at kitt peak, and precision nir rvs from hpf, we provide the first mass constraint of k2-25b with a mass of m~50 earth masses. further, in three transits we detect the rossiter-mclaughlin effect of k2-25b, with a sky-projected obliquity of ~3 degrees (consistent with 0 degrees), and true 3d obliquity of ~9 degrees (consistent with 0 at 2 sigma). these observations mark one of the first mass constraint of an exoplanet in a cluster, and the second obliquity measurement of an m-dwarf planetary system, giving us key insights into the formation and subsequent dynamical history of the system. | extreme precision photometry and radial velocimetry from the ground |
we obtained five transits of k2-25b using the astrophysical research consortium telescope imaging camera (arctic) imager on the 3.5m astrophysical research consortium (arc) 3.5m telescope at apache point observatory (apo) on the nights of ut 2017 september 17; 2019 january 4, 18, and 25; and 2019 february 1. all of the transit observations were performed with the engineered diffuser available on arctic, which we designed specifically to enable very high precision photometric observations. we used the sloan digital sky survey (sdss) i' filter, except on the night of 2019 january 18, when we used the sdss z' filter without the diffuser to minimize background moon contamination. we observed four transits of k2-25b using the half-degree imager (hdi) at the wiyn 0.9m telescope at kitt peak national observatory on the nights of ut 2018 february 7 and 21 and 2018 december 14 and 21. we obtained precision near infra red (nir) radial velocities (rvs) of k2-25 with the habitable zone planet finder (hpf) with the twofold goal to constrain the mass of k2-25b and the obliquity of the host star. the hpf is a high-resolution (r~55000) nir fiber-fed spectrograph on the 10m hobby-eberly telescope (het) at mcdonald observatory in texas. (3 data files). | vizier online data catalog: photometry and rvs of k2-25b with hpf (stefansson+, 2020) |
venus currently rotates slowly, with its spin controlled by solid-body and atmospheric thermal tides. however, conditions may have been far different and more amenable to life 4 billion years ago, when the sun was fainter and most of the carbon within venus could have been in solid form, allowing for a low-mass atmosphere. among the best candidates for habitability among known exoplanets are two planets within the optimistic habitable zone of their host star, kepler-62 that are about 1.5 times the radius of earth. we use numerical integrations to investigate how the obliquity would have varied on timescales as large as 1 gyr for a hypothetical rapidly rotating early venus and for these two super-earth size exoplanets. | obliquity variability of a rapidly rotating early venus and of the potentially habitable exoplanets kepler-62e and kepler-62f |
although we have not yet detected life beyond earth, astronomers have made remarkable progress towards the eventual goal of finding an inhabited planet orbiting another star. we now know that small, temperate planets are common and we are actively designing facilities capable of detecting life elsewhere in the galaxy. in celebration of the 50th anniversary of the dps annual meeting, i will review key milestones in the history of our exploration of exoplanet habitability and highlight recent achievements such as the discovery of multiple earth-size planets orbiting within the habitable zones of nearby stars. i will also describe the statistical advances enabled by the nasa kepler mission and the prospects for finding dozens of new potentially habitable planets with nasa's recently launched transiting exoplanet survey satellite. | searching for pale blue dots: the quest for habitable exoplanets |
introduction: rocky exoplanets in the habitable zones (hz) of low mass stars will be prime targets for atmospheric characterization with the james webb space telescope (jwst). such planets are likely tidally locked and the determination of the habitability of those worlds requires the use of 3d global climate models (gcms) to resolve the large-scale atmospheric circulation, heat transport, latitudinal and longitudinal water profiles and cloud coverage. previous studies have determined the inner edge of the hz for various low mass stars considering only a 1 bar background n2 pressure. however, the background pressure can significantly impact the planet's surface temperature, potentially enhance its habitability. results: we show results from our gcm simulations using the community atmosphere model 4 (cam4), assuming a slab ocean configuration, for end member cases of low (0.25 and 0.5 bar) and high (10 bars) n2 atmospheres. we compare our results of the inner edge of the hz with kopparapu et al., (2017), who assumed a 1 bar n2 atmosphere. the assumed background pressure of n2 has a meaningful effect on climate, stratospheric water vapor mixing, and deduced observables. therefore, the inner edge of the habitable zone is sensitive the background gas pressure. | the impact of background n2 pressure on the habitability of tidally locked rocky exoplanets around cool stars |
we report the first detection of co emission lines at high spectral resolution in the thermal spectrum of an exoplanet atmosphere. these emission lines, seen in the spectrum of the ultra hot jupiter wasp-33 b, provide unambiguous evidence of a thermal inversion layer in its atmosphere, and are the first results from the mmt exoplanet atmosphere survey (measure) using aries with the adaptive secondary mirror at the 6.5-m mmt. moreover, by incorporating these r=15,000 spectra into a bayesian framework with 1d phoenix atmospheric models, we show via cross-correlation-to-log-likelihood mapping that the spectra indicate an offset hotspot. this arises as the post-eclipse spectra favour a scaling parameter that creates shallower spectral line models than those for pre-eclipse, indicating variation due to an hotspot rotating in and out of view as the planet orbits its host star. we further modelled the atmosphere with 3d global circulation models using gcmcrt, finding that these phase dependant atmospheric models result in consistent scaling parameters throughout the orbit. this demonstrates that high resolution spectroscopy, even at r=15,000 when it cannot detect the additional doppler shifts from offset hotspots, remains sensitive to the dynamics and 3d nature of exoplanet atmospheres. this bodes well for systems that may require the use of lower resolution spectra to improve photon collection, such as small planets orbiting in the close in habitable zones of small, faint m-dwarfs. | carbon monoxide emission lines indicate an offset hotspot in the inverted atmosphere of the ultra hot jupiter wasp-33 b |
whether m dwarfs are able to host life-bearing planets is an open question owing to high levels of stellar x-ray and uv emission and close-in habitable zones. conversely, the low levels of near-uv emissions at quiescent levels of m dwarfs may make it challenging for abiogenesis (the origin of life) to occur. we considered whether flares from the ~20 myr old m dwarf au mic have the potential to raise the stellar near-uv flux to a level at which prebiotic chemical pathways are triggered over the wavelength range 200-280 nm. we obtained near-uv spectroscopy of au mic using the neil gehrels swift observatory's (swift) ultraviolet and optical telescope's (uvot) grism mode. we analyzed multiple flares, measuring their energy, duration, and amplitude relative to the abiogenesis threshold, over the course of a 52 kilosecond pilot study. our results provide a window into the elevated near-uv flux with which au mic regularly irradiates its planetary system. this work provides constraints on the uv flux that planets orbiting young stars experience, with these results serving as a benchmark for inferring whether young m dwarf stellar activity can help catalyze abiogenic reactions on planetary surfaces. we have shown that swift is able to spectroscopically monitor the flares in the near-uv, observations that are critical for determining if abiogenesis can proceed on exoplanets orbiting low-mass stars. | defining the energy budget for abiogenesis on m-dwarf planets: a pilot study of au mic with swift |
could toi-700 d, an earth-sized planet in the habitable zone of an early-type m-dwarf star, have held on to its atmosphere over long timescales? this question is crucial to understanding whether this recent discovery from the transiting exoplanet survey satellite (tess) is likely to have a habitable surface. in a recent study led by chuanfei dong (princeton university), a team of scientists conducted a series of state-of-the-art simulations to model the atmospheric escape from toi-700 d as the planet is bombarded by its hosts stellar wind. the plots above show the o+ ion density and magnetic field lines in various cases from the authors simulations (see the original image for scales and additional detail). though toi-700 ds atmospheric ion escape rates could be a few orders of magnitude higher than the rates typical of the terrestrial planets in our own solar system, the authors show that toi-700 d could still retain a substantial atmosphere for more than a billion years so it may well be worth exploring this planet further in the future! for more information, check out the full article below.citationatmospheric escape from toi-700 d: venus versus earth analogs, chuanfei dong et al 2020 apjl 896 l24. doi:10.3847/2041-8213/ab982f | featured image: clinging to an atmosphere |
the number of exoplanets in the habitable zone of m dwarfs has increased in the last few years thanks to ground-based observatories and space telescopes. m dwarfs are among the most active stars producing frequent and strong flares, strong stellar wind and high energy radiation. the habitability of these worlds strongly depends on their capability of retaining their atmospheres. planetary magnetospheres play a crucial role in reducing atmospheric loss and thus providing a potentially habitable enviroment. the m dwarf star trappist-1 is of particular interest because it hosts three earth-sized rocky planets in its habitale zone. we calculated the magnetic properties of these planets, such as the suface dipolar field strength and magnetic dipole moment, using a method based on the example of the early earth, which assumes a process involving the exsolution of mgo as the source of the planetary dynamo. in order to follow the evolution of these properties, we applied a thermal evolution model for the trappist-1 planets. the sizes of the magnetospheres, described by the magnetoshperic standoff distance (i.e. the distance from the planet to the point where the stellar wind is balanced by the planetary magnetic field), were derived using previously modeled stellar wind parameters. additionally, we calculated the polar cap area, which indicates the fraction of a planet's surface where magnetic field lines are open and atmosperic escape is possible. based on our results, we will estimate the atmospheric mass loss, which can significantly limit habitability on the planets. | magnetospheres of the trappist-1 planets |
we report the discovery of toi-700 e, a 0.95 earth radius planet residing in the optimistic habitable zone (hz) of its host star. this discovery was enabled by multiple years of nearly continuous monitoring from nasa's transiting exoplanet survey satellite (tess) mission. the host star, toi-700 (tic 150428135), is a nearby (31.1 pc), quiet, m2 dwarf (v = 13.15). toi-700 is already known to host three planets, including the small, hz planet, toi-700 d. the new planet has an orbital period of 27.8 days and is likely rocky. toi-700 was observed for 21 sectors over years 1 and 3 of the tess mission, including 10 sectors at 20-second cadence in year 3. using this full set of tess data and additional follow-up observations, we identify, validate, and characterize toi-700 e. this discovery adds another world to the very short list of small, hz planets transiting nearby and bright host stars. such systems, where the stars are bright enough that follow-up observations are possible to constrain planet masses and atmospheres using current and future facilities, are incredibly valuable. the presence of multiple small, hz planets makes this system even more enticing for follow-up observations. | a second earth-sized planet in the habitable zone of the m dwarf toi-700 |
planetary-scale magnetic fields provide a unique window into a planet's deep interior. from the magnetic field of the earth to that of jupiter, we have tied the existence of such fields to the presence of an electrically conductive convecting fluid (dynamo source region) in the interior. thus, detections of planetary-scale magnetic field signals offer constraints on the planets' thermal state, interior structure, and dynamics. the discovery of exoplanets and the ubiquitousness of magnetospheric emissions within the solar system motivate theoretical work on exoplanets to predict which ones may host the necessary condition for a dynamo source, i.e. having an electrically conductive convecting fluid with a magnetic reynolds number greater than ~50. previous studies of rocky planets have focused on earth-like ones with an iron-dominated core, silicate mantle and a core mass fraction (cmf) ~ 0.33 in the habitable zone. here, we calculate the thermal evolution of rocky planets with a greater parameter space, with planetary masses from 0.5 to 10 earth-masses, and cmfs from 0.0 to 1.0 and equilibrium temperatures from 255k to 2000k. our aim is to map out the lifetime of the possible dynamo source regions in both the liquid core and magma ocean of these planets. to achieve this, we couple a 1d thermal evolution model with a henyey solver to calculate their thermal evolution. our model solves the energy balance equation in both the core and the mantle. we use the modified mixing length theory appropriate for fluids with high and low reynolds number to model the convective heat flow. in addition, by including the henyey solver, we self-consistently account for adjustments in the interior structure and heating (cooling) due to planet contraction (expansion). for each combination of planetary mass and cmf, we explore 4 scenarios, with and without compositional convection in the liquid outer core due to inner core solidification, as well as mobile and stagnant lid tectonic regimes. the result will be the first-step to aid future surveys searching for magnetic field signals from rocky exoplanets. | a map of the dynamo lifetime of rocky planets |
we present our first light observations with the new ishell spectrograph at the nasa infrared telescope facility. ishell replaces the 25 year old cshell with improvements in spectral grasp (~40x), resolution (70,000 versus 46,000), throughput, optics, and detector characteristics. with cshell, we obtained a radial velocity precision of 3 m/s on a bright red giant and we identified several radial velocity variable m dwarfs for future follow up. our goal with ishell is to characterize the precise radial velocity performance of the methane isotopologue absorption gas cell in the calibration unit. we observe bright nearby radial velocity standards to better understand the instrument and data reduction techniques. we have updated our cshell analysis code to handle multiple orders and the increased number of pixels. it is feasible that we will obtain a radial velocity precision of < 3 m/s, sufficient to detect terrestrial planets in the habitable zone of nearby m dwarfs. we will also follow up radial velocity variables we have discovered, along with transiting exoplanets orbiting m dwarfs identified with the k2 and tess missions. | precise radial velocity first light observations with ishell |
binary stars are ubiquitous; about half of solar-type stars exist in binaries. exoplanet occurrence rate is suppressed in binaries, but some multiples still host planets. multiplicity reduces the size and lifetime of protoplanetary disks, suggesting that binaries not only suppress planet formation but also could fundamentally alter the properties of planets in multiples. binaries also cause observational biases in planet parameters, with undetected multiplicity causing transiting planets to appear smaller than they truly are. to understand the impact of the observational and physical effects of binaries on planet populations, we are performing a spectroscopic survey of kepler binary stars using the hobby-eberly telescope at mcdonald observatory, and we have analyzed two subsamples of planets in binaries. we studied a population of supposed earth-analog planets in binaries and found that more than half of them likely had substantial gaseous atmospheres after correcting for the presence of the secondary star. systems also moved in and out of the habitable zone, indicating that the presence of undetected binary stars can impact occurrence rates for earth-like planets. we also studied a population of small planets to investigate the properties of the radius gap in binaries. the radius gap is a dearth of small planets separating rocky super-earths from gaseous sub-neptunes, and we found that it moves downward in radius from 1.8 earth radii in single stars to 1.5 earth radii in binary stars. this suggests that the planetary core mass function distribution changes between single and binary stars, causing the cores of planets in binaries to be smaller than those in single stars. these results show the challenge and promise of binary stars that host planets: although they present observational challenges for single-star demographics, they are a unique laboratory for exploring the physical impacts of smaller disks and shorter planet-forming timescales on mature exoplanet populations, informing our understanding of planet formation in both single and binary stars. | revealing the demographics and atmospheric evolution of planets in binary stars |
m dwarf stars have emerged as ideal targets for exoplanet observations. their small radii aids planetary discovery, their close-in habitable zones allow short observing campaigns, and their red spectra provide opportunities for transit spectroscopy with jwst. the potential of m dwarfs has been underlined by the discovery of remarkable systems such as the seven earth-sized planets orbiting trappist-1 and the habitable-zone planet around the closest star to the sun. however, to accurately assess the conditions in these systems requires a firm understanding of how m dwarfs differ from the sun, beyond just their smaller size and mass. of particular importance are the time-variable, high-energy ultraviolet and x-ray regions of the m dwarf spectral energy distribution (sed), which can influence the chemistry and lifetime of exoplanet atmospheres, as well as their surface radiation environments. the measurements of the ultraviolet spectral characteristics of low-mass exoplanetary systems (mega-muscles) treasury project, together with the precursor muscles project, aims to produce full seds of a representative sample of m dwarfs, covering a wide range of stellar mass, age, and planetary system architecture. we have obtained x-ray and ultraviolet data for 13 stars using the hubble, chandra and xmm space telescopes, along with ground-based data in the optical and state-of-the-art dem modelling to fill in the unobservable extreme ultraviolet regions. our completed seds will be available as a community resource, with the aim that a close muscles analogue should exist for most m dwarfs of interest. in this presentation i will overview the mega-muscles project, describing our choice of targets, observation strategy and sed production methodology. i will also discuss notable targets such as the trappist-1 host star, comparing our observations with previous data and model predictions. finally, i will present an exciting by-product of the mega-muscles project: time-resolved ultraviolet spectroscopy of stellar flares at multiple targets, spanning a range of stellar types, ages and flare energies. | measurements of the ultraviolet spectral characteristics of low-mass exoplanetary systems (mega-muscles) |
in the age of jwst, temperate terrestrial exoplanets transiting nearby late-type m dwarfs provide unique opportunities for characterizing their atmospheres, as well as searching for biosignature gases. in this context, the benchmark trappist-1 planetary system has garnered the interest of a broad scientific community.the speculoos (search for habitable planets eclipsing ultra-cool stars) project, an exoplanet transit survey targeting a volume-limited (40 pc) sample of about 1700 late-type (m6 and later) dwarfs using a network of 1m-class robotic telescopes, began its scientific operations three years ago. in this talk, i will present an update on the current status of the survey and an overview of recent results.in particular, i will describe how an efficient synergy with the tess mission and other ground-based facilities led to the exciting new discovery of two temperate super-earths transiting a nearby m6 dwarf, with the outer one orbiting in the habitable zone. in terms of potential for atmospheric characterization, we estimate that this planet is the second-most favorable habitable-zone terrestrial planet found so far after the trappist-1 planets. the discovery of this remarkable system offers another rare opportunity to study temperate terrestrial planets around our smallest and coolest neighbours. | an update on the speculoos project and new results |
the james webb space telescope (jwst) will provide an opportunity to investigate the atmospheres of potentially habitable planets. aerosols, significantly mute molecular features in transit spectra because they prevent light from probing the deeper layers of the atmosphere. earth occasionally has stratospheric/high tropospheric clouds at 15-20 km that could substantially limit the observable depth of the underlying atmosphere. we use solar occultations of earth's atmosphere to create synthetic jwst transit spectra of earth analogs orbiting dwarf stars. unlike previous investigations, we consider both clear and cloudy sightlines from the scisat satellite. we find that the maximum difference in effective thickness of the atmosphere between a clear and globally cloudy atmosphere is 8.5 km at 2.28 microns with a resolution of 0.02 microns. after incorporating the effects of refraction and pandexo's noise modeling, we find that jwst would not be able to detect earth like stratospheric clouds if an exo-earth was present in the trappist-1 system, as the cloud spectrum differs from the clear spectrum by a maximum of 10 ppm. these stratospheric clouds are also not robustly detected by taurex when performing spectral retrieval for a cloudy trappist-1 planet. however, if an earth size planet were to orbit in a white dwarf's habitable zone, then, we predict that jwst's nirspec would be able to detect its stratospheric clouds after only 4 transits. we conclude that stratospheric clouds would not impede jwst transit spectroscopy or the detection of biosignatures for earth-like atmospheres. | stratospheric clouds do not impede jwst transit spectroscopy for exoplanets with earth-like atmospheres |
3-d exoplanet climate modeling shows that equilibrium temperature assessments of the habitable zone should account for the higher albedos of slowly rotating planets inside the tidal locking radius and the lower albedos of planets orbiting m stars. | equilibrium temperatures and albedos for habitable m star planets in a coupled atmosphere-ocean general circulation model |
trappist-1 is an extraordinary planetary system with 7 confirmed terrestrial exoplanets, some of which may lie in the habitable zone around the central m dwarf star. m dwarfs are magnetically very active and probably emit a stellar wind that interacts with the planets. stellar winds and their interaction with planetary atmospheres and magnetospheres, if the planets are magnetized, affect the energy budget of their surroundings and ultimately the habitability of those planets. during coronal mass ejections (cmes) intersecting the planets the exposure to increased stellar wind pressure, density and velocity might result in significant heating of the planets surroundings and interior (grayver et al. 2022)[1]. we aim to better understand the space environment around the trappist-1 planets and their interaction with the surrounding stellar wind. we perform magnetohydrodynamic simulations to study the interaction of the planets with the stellar wind. we also study the effect of cmes on the energy budget of planetary atmospheres and magnetospheres, their heating, and possible effects on exoplanet habitability.references a. grayver et al., the astrophysical journal letters 941, l7 (2022) | space environment and poynting fluxes around the trappist-1 exoplanets and effects of coronal mass ejections on their habitability |
jwst will be able to observe the atmospheres of rocky planets transiting nearby m dwarfs. a few such planets are already known (around gj1132, proxima cen, and trappist-1) and tess is predicted to find many more, including 14 habitable zone planets. to interpret observations of these exoplanets' atmospheres, we must understand the high-energy sed of their host stars: x-ray/euv irradiation can erode a planet's gaseous envelope and fuv/nuv-driven photochemistry shapes an atmosphere's molecular abundances, including potential biomarkers like o2, o3, and ch4. our muscles treasury survey (cycles 19+22) used hubble/cos+stis uv observations with contemporaneous x-ray and ground-based data to construct complete seds for 11 low-mass exoplanet hosts. muscles is the most widely used database for early-m and k dwarf (>0.3 m_sun) irradiance spectra and has supported a wide range of atmospheric stability and biomarker modeling work. however, tess will find most of its habitable planets transiting stars less massive than this, and these will be the planets to characterize with jwst. here, we propose to expand the muscles project to: (a) new m dwarf exoplanet hosts with varying properties; (b) reference m dwarfs below 0.3 solar masses that may be used as proxies for m dwarf planet hosts discovered after hst's lifetime; and (c) more rapidly rotating stars of gj1132's mass to probe xuv evolution over gigayear timescales. we propose to gather the first panchromatic seds of rocky planet hosts gj1132 and trappist-1. this proposal extends proven methods to a key new sample of stars, upon which critically depends the long-term goal of studying habitable planet atmospheres with jwst and beyond. | the mega-muscles treasury survey: measurements of the ultraviolet spectral characteristics of low-mass exoplanetary systems |
we present new transit model fitting features and performance of the latest release (9.3, march 2015) of the kepler science operations center (soc) pipeline, which will be used for the final processing of four years of kepler science data later this year. threshold crossing events (tces), which represent transiting planet detections, are generated by the transiting planet search (tps) component of the pipeline and subsequently processed in the data validation (dv) component. the transit model is used in dv to fit tces and derive parameters that are used in various diagnostic tests to validate the planet detections. the standard limb-darkened transit model includes five fit parameters: transit epoch time (i.e. central time of first transit), orbital period, impact parameter, ratio of planet radius to star radius and ratio of semi-major axis to star radius. in the latest kepler soc pipeline codebase, the light curve of the target for which a tce is generated is also fitted by a trapezoidal transit model with four parameters: transit epoch time, depth, duration and ratio of ingress time to duration. the fitted trapezoidal transit model is used in the diagnostic tests when the fit with the standard transit model fails or when the fit is not performed, e.g. for suspected eclipsing binaries. additional parameters, such as the equilibrium temperature and effective stellar flux (i.e. insolation) of the planet candidate, are derived from the transit model fit parameters to characterize pipeline candidates for the search of earth-size planets in the habitable zone. the uncertainties of all derived parameters are updated in the latest codebase to account for the propagated errors of the fit parameters as well as the uncertainties in stellar parameters. the results of the transit model fitting for the tces identified by the kepler soc pipeline are included in the dv reports and one-page report summaries, which are accessible by the science community at nasa exoplanet archive (http://exoplanetarchive.ipac.caltech.edu/</u>). funding for the kepler mission has been provided by the nasa science mission directorate. | transit model fitting in processing four years of kepler science data: new features and performance |
the habitable exoplanet imaging mission, or habex, is one of four flagship mission concepts currently under study for the upcoming 2020 decadal survey of astronomy and astrophysics. the broad goal of habex will be to image and study small, rocky planets in the habitable zones of nearby stars. additionally, habex will pursue a range of other astrophysical investigations, including the characterization of non-habitable exoplanets and detailed observations of stars and galaxies. critical to the capability of habex to understand habitable zone exoplanets will be its ability to search for signs of surface liquid water (i.e., habitability) and an active biosphere. photometry and moderate resolution spectroscopy, spanning the ultraviolet through near-infrared spectral ranges, will enable constraints on key habitability-related atmospheric species and properties (e.g., surface pressure). in this poster, we will discuss approaches to detecting signs of habitability in reflected-light observations of rocky exoplanets. we will also present initial results for modeling experiments aimed at demonstrating the capabilities of habex to study and understand earth-like worlds around other stars. | constraining exoplanet habitability with habex |
carmenes (calar alto high-resolution search for m dwarfs with exo-earths with near-infrared and optical echelle spectrographs) is a next-generation instrument currently under construction for the 3.5m telescope at the calar alto observatory by a consortium of eleven spanish and german institutions. commissioning of carmenes will start in april 2015. carmenes will conduct a 600-night exoplanet survey targeting ~300 m dwarfs. an important and unique feature of the carmenes instrument is that it consists of two separate échelle spectrographs, which together cover the wavelength range from 0.55 to 1.7 μm at a spectral resolution of r = 82,000. the spectrographs are fed by fibers from the cassegrain focus of the telescope.the main scientific objective of carmenes is to carry out a survey of late-type main sequence stars with the goal of detecting low-mass planets in their habitable zones (hzs). in the focus of the project are very cool stars later than spectral type m4 and moderately active stars. we aim at being able to detect a 2m⊕ planet in the hz of an m5 star, which requires a long-term radial velocity precision of 1ms-1 per measurement. for stars later than m4 (m < 0.25m⊙), such precision will yield detections of super-earths of 5m⊕ and smaller inside the entire width of the hz. the carmenes survey will thus provide a comprehensive overview of planetary systems around nearby northern m dwarfs. by reaching into the realm of earth-like planets, it will provide a treasure trove for follow-up studies probing their habitability.at the same time, the carmenes survey will generate a unique data set for studies of m star atmospheres, rotation, and activity. the spectra will cover important diagnostic lines for activity (hα, na i d1 and d2, and the ca ii infrared triplet), as well as feh lines around 10,000å, from which the magnetic field can be inferred. correlating the time series of these features with each other, and with wavelength-dependent radial velocities, will provide new insight into the physical properties of m dwarf atmospheres, and will provide excellent discrimination between planetary companions and stellar radial velocity "noise". | carmenes: a spectroscopic survey of m dwarfs and their planets |
we present the science case for a 1.45 meter space telescope to survey the closest, brightest fgkm main sequence stars to search for habitable zone (hz) earth analogs using the precise radial velocity (prv) technique at a precision of 1-10 cm/s. our baseline instrument concept uses three diffraction-limited spectrographs operating in the 0.3-0.4, 0.4-0.9, and 0.9-2.4 microns spectral regions each with a spectral resolution of r=150,000~200,000. because the instrument utilizes a diffraction-limited input beam, each spectrograph arm will be extremely compact, less than 50 cm on a side, and illumination can be stabilized with the coupling of starlight into single mode fibers. with two octaves of wavelength coverage and a cadence unimpeded by any diurnal, atmospheric and most seasonal effects, earthfinder will offer a unique platform for recovering stellar activity signals from starspots, plages, granulation, etc. to detect exoplanets at velocity semi-amplitudes currently not obtainable from the ground. variable telluric absorption and emission lines may potentially preclude achieving prv measurements at or below 10 cm/s in the visible and <50 cm/s in the near-infrared from the ground. placed in an earth-trailing (e.g. spitzer, kepler) or lagrange orbit, the space-based cadence of observations of a star can be year-round at the ecliptic poles, with two 90-day "seasons" every 6 months in the ecliptic plane. this cadence and wavelength coverage will provide a distinct advantage compared to an annual ~3-6 month observing season from the ground for mitigating stellar activity and detecting the orbital periods of hz earth-mass analogs (e.g. ~6-months to ~2 years). finally, we have compiled a list of ancillary science cases for the observatory, ranging from asteroseismology to the direct measurement of the expansion of the universe. | earthfinder: a probe-class mission precise for a radial velocity survey of our nearest stellar neighbors to detect and characterize earth-mass habitable zone analogs using high-resolution uv-vis-nir echelle spectroscopy |
the habitable exoplanet observatory mission (habex) is one of four missions under study for the 2020 astrophysics decadal survey. its goal is to directly image and spectroscopically characterize planetary systems in the habitable zone around nearby sun-like stars. additionally, habex will perform a broad range of general astrophysics science enabled by 100 to 1800 nm spectral range and 3 x 3 arc-minute fov. critical to achieving its the habex science goals is a large, ultra-stable uv/optical/near-ir (uvoir) telescope. the baseline habex telescope is a 4-meter off-axis unobscured three-mirror-anastigmatic, diffraction limited at 400 nm with wavefront stability on the order of a few 10s of picometers. this poster summarizes the opto-mechanical design of the habex baseline optical telescope assembly, including a discussion of how science requirements drive the telescope's specifications, and presents analysis that the baseline telescope structure meets its specified tolerances. | habex baseline telescope design and predicted performance |
the us exoplanet science community urgently requires a radial velocity instrument with the sensitivity to observe rocky planets in the habitable zone, and follow-up the most promising tess candidates. to address this need, we are building neid, the new nn-explore extreme precision doppler spectrometer for the wiyn telescope at kitt peak observatory. the guiding metric for the complete design was the instrument’s performance for its primary science goal, the doppler observation of earth-like exoplanets. it is based on a high optical performance echelle spectrograph built around a classical white pupil relay with large beam size, and is fed by a high-scrambling fiber train. neid covers the wavelength range from 380 - 930nm in a single frame with a resolution of ~100.000. the optics bench is housed in a vacuum chamber for environmental control, reaching sub-millikelvin temperature stability. together with a sophisticated front end to provide excellent atmospheric dispersion correction and guiding stability, this forms a system with predicted doppler precision of <25 cm/s. in this talk, we will present the optical and optomechanical designs, and discuss the interplay of technical design choices and science demands. | the neid doppler spectrometer at wiyn |
the habitable zone (hz) is the region around a star where the stellar radiation is just right to sustain liquid water on the surface of an exoplanet in this zone. the distance between a star and planet is therefore crucial in controlling the habitability and climate of the planet. however, the star-planet distance changes over time because of gravitational interactions in the planetary system. the gravitational pull of a larger planet can make the orbit of another planet more elliptical so the star-planet distance changes across an orbital year which influences the seasonal climate variability. additionally, planet-planet interactions drive changes to the orbital ellipticity on tens-of-thousands to million-year timescales and impacts the long-term climate evolution. in our solar system, for instance, jupiter's gravity has driven earth's ice age cycles. here, we use dynamical simulations of the solar system to show how fast and by how much earth's orbit changes if jupiter's orbit would have been slightly different. we demonstrate that planet-planet interactions contribute greatly to the incoming stellar radiation (and climate). when assessing the potential habitability of an hz exoplanet, it is thus crucial to consider the dynamical evolution of that planet and the climatic implications. | the influence of jupiter on the earth's orbital cycles |
atmospheric mineral dust represents a critical source of variability in planetary climate. dust radiative feedbacks can alter large and local scale dynamics, alternatively warm or cool global temperatures and modify the dust cycle itself. on present-day mars, radiatively active dust may drive storm growth from local to global scales and has been demonstrated to impact both local winds as well as the zonal circulation. on arid, land planets with a large fraction of desiccated soils, the impact of dust may be further heightened. here, we use the nasa ames fv3 model with a fully interactive dust cycle to investigate the impact of radiatively active dust on a mars-like exoplanet when the solar irradiance is altered. at earth insolation, passive dust simulations are recognizably mars-like. however, when radiatively active dust is added, the climate is hugely altered. in particular, we find that radiative heating in the summer polar middle atmosphere strengthens the seasonal hadley circulation, which modifies the spatial distribution and magnitude of surface winds that control dust lifting. we define a new dust lifting regime controlled by radiatively active dust. we consider the impact of dust on potential habitability, including long-term water stability, surface light limits and, if dust is required to shade surfaces, the possibility for periods of low dust and surface sterilization. | the impact of radiatively active dust on land planet climate |
the most effective exoplanet detection method has been transit photometry, wherein we measure the brightness of stars over periods of time. these measurements, or light curves, are later analyzed for dips in brightness caused by objects passing in front of the host star. however, variations in these time series can occur due to numerous factors: including unseen planets, or moons. planetary systems with multiple transiting planets are highly valuable for understanding planet occurrence rates and system architectures; and although we have yet to detect a solar system analog, future surveys might detect the twins of venus and earth transiting a sun-like star. in anticipation of such a discovery, we simulate transit timing observations based on the actual orbital motions of venus and earth — two habitable zone planets which are influenced by the other solar system bodies — with varying noise levels and observation time spans. we then retrieve the system dynamical parameters using ttvfaster, an approximate n-body model for transit time shifts. by considering the presence of an unseen jupiter-, mars-, or saturn-analogue, and the moon, we can gauge the detectability and characterization limits of such objects in exoplanetary systems where two planets are known to transit. we demonstrate that with the retrieval applied to simulated transits of venus and earth that we can, for example: 1). measure the correct masses of both earth and venus (down to 3% error), and constrain their eccentricities; 2). detect jupiter near the correct orbital period and mass; 3). detect the moon; and 4). detect mars (for really high precision). in general, we find that timing precisions of better than 60 seconds and/or survey durations longer than 15 years would be required to meet these goals. unfortunately, jupiter's mass is underestimated in most scenarios, and the moon is degenerate with adding a fourth mars-like planet. the latter of these findings supports dynamical stability tests of multi-planet systems. ultimately, this work will help to guide future missions in detecting and characterizing exoplanet systems analogous to our solar system. | exploring the detectability of solar system analogues by modeling transit timing variations for venus and earth |
the presence of liquid water may be a prerequisite for extraterrestrial habitable environments and in the case of exoplanets the "habitable zone" is defined by conditions allowing liquid water to exist on planetary surfaces. here, the role of pressure is evaluated in context of its impact on the range of potential habitable zones. solutes in aqueous solutions serve as antifreeze agents that extend the fluid range, depending on concentrations, pressures, and which chemical species are present. we have undertaken extensive experimental high-pressure studies of water, of aqueous solutions containing common ions (nacl, na2so4, mgso4, mgcl2), and of high-pressure ices. gibbs energies are determined in a regime extending to 8 gpa for temperatures ranging from 240 k to 800 k. these are the first results that fully and accurately characterize important thermodynamic properties essential for constructing planetary models. our calculations for hypothetical planets ranging from water-rich (ganymede and super-ganymede) to super-earths allow investigation of the impact of thermodynamic differences between properties of pure water and of solutions with variable chemical concentrations and compositions. we find that both concentration and compositional differences have a significant impact on the magnitude of adiabatic temperature gradient in liquid layers, on the presence or absence of high pressure ices, and whether high-pressure ices are buoyant. in addition, assumptions implicit in current thermodynamic databases are found to fail in a pressure regime beyond a few hundred mpa. however, beyond about 1000 mpa our measured chemical potentials (that determine the partitioning of solutes between rock and water) are less complicated than in the low-pressure regime of "traditional" electrolytic chemistry. thus, a new framework for high-pressure thermodynamic calculations is possible that can be readily extended to additional chemical species. | impact of high-pressure chemistry on planetary habitable zones |
many stars of different spectral types with planets in the habitable zone are known to emit flares. until now, studies that investigated the long-term impact of stellar flares and associated coronal mass ejections (cmes) assumed that the planet's interior remains unaffected by interplanetary cmes, only considering the effect of energetic particles interactions on the atmosphere of planets. here, we show that the magnetic flux carried by flare-associated cmes results in planetary interior heating by ohmic dissipation and leads to a family of new interior-exterior interactions. we construct a physical model to study this effect and apply it to the trappist-1 and proxima centauri stars whose flaring activity has been constrained by kepler and tess observations. we pose our model in a stochastic manner to account for uncertainty and variability in major input parameters. our results suggest that the heat dissipated in the silicate mantle is both of sufficient magnitude and longevity to drive geological processes and hence facilitate volcanism and outgassing particularly for the innermost planets. furthermore, our model predicts that joule heating can further be enhanced for planets with an intrinsic magnetic field compared to those without. the associated volcanism and outgassing may continuously replenish the atmosphere and thereby mitigate the erosion of the atmosphere caused by the direct impact of flares and cmes. | interior heating of rocky exoplanets from stellar flares with application to trappist-1 and proxima centauri |
in practice, technologies attempting to recover direct images of extra-solar planets run into noise floors governed by systematics (most notably, quasi-static speckles) before reaching fundamental limits (such as photon noise). to enhance detection reach to higher contrasts, discrimination by exploiting distinctive planetary signatures have been proposed. here we explore a novel possibility: detecting exoplanets around bright variable stars based on the variability-phase difference between the speckles and the reflected light from the planet. hot variable stars (the kind most favorable to this idea) host relatively distant habitable zones, which will allow a considerable phase delay to be displayed by planet in reflection. we have carried out a systematic series of simulations and analysis to explore the potential for this method. we show that this technique could improve contrast reach of an extreme-ao imagery by a factor of 5-10 against speckle noise. | finding exoplanets in the habitable zone with light echoes |
the galactic habitable zone (ghz) is characterized by metallicity, orbital kinematics, star formation rates, supernovae explosions, and time, among other quantities. previously, the outer galaxy (rgc > 16 kpc) was not included in the ghz due to low abundances of the nchops elements – those required for life. recent observations of dense clouds in the outer galaxy, however, have identified various molecules that contain all of the nchops elements, except phosphorus. because this element is essential to prebiotic chemistry, a search was conducted for phosphorus-bearing molecules in these galactic edge clouds using the 12m telescope of the arizona radio observatory (aro) at 2mm in wavelength and the 30m telescope of the institut de radioastronomie millimétrique (iram) at 3mm. from these observations, the j = 2→1 and j = 3→2 rotational transitions of pn, as well as four hyperfine components of the j = 2.5→1.5 transition of po, were detected in edge cloud wb89-621, located 22.6 kpc from the galactic center. the fractional abundances, relative to h2, of pn and po were determined to be f~3.0(±1.6)×10-12 and 2.0(±1.1)×10-11, respectively. this discovery is the furthest identification of phosphorus in any form at such large distances from the galactic center. these results complete the inventory of the nchops elements in the outer galaxy, suggesting that habitable exoplanets may exist out to rgc~23 kpc, redefining the boundaries of the ghz. | phosphorus at the edge of the galaxy: observations of pn and po at rgc 23 kpc |
future large space missions designed to search for biosignatures in the atmospheres of earth-like exoplanets will operate more efficiently and have a higher chance of success if stars with possible earth analogs are known before launch. one way to find these earth-like candidates is with the radial velocity technique, but this method is currently limited by spurious signals introduced by stellar activity (i.e. faculae, starspots). here we show that machine learning techniques such as linear regression and neural networks can effectively remove these activity signals from rv observations. previous efforts have focused on carefully filtering out activity signals in time using gaussian process regression (e.g. haywood et al. 2014). instead, we separate activity signals from true center-of-mass rv shifts using only changes to the average shape of spectral lines, and no information about when the observations were collected. we demonstrate our technique on simulated data, reducing the rv scatter from 82.0 cm s-1 to 3.1 cm s-1 , and on approximately 700 observations taken nearly daily over three years with the harps-n solar telescope, reducing the rv scatter from 1.47 m s-1 to 0.78 m s-1 (a 47% or factor of ~ 1.9 improvement). in the future, these or similar techniques could remove activity signals from observations of stars outside our solar system and eventually help detect habitable-zone earth-mass exoplanets around sun-like stars. in this way, improvements in rv precision could significantly accelerate the characterization of habitable zone earth-sized exoplanets. | removing stellar activity signals from radial velocity measurements using neural networks |
about a dozen exoplanetary systems have been discovered with three or more planets participating in a chain of mean-motion resonances. the uniquely complex architectures of these so-called "resonant chains" motivate efforts to characterize their planets holistically. in this work, we perform a comprehensive exploration of the spin-axis dynamics of planets in resonant chains. planetary spin states are closely linked with atmospheric dynamics and habitability and are thus especially relevant to resonant chains like trappist-1, which hosts several planets in the habitable zone. considering the full set of observed resonant chains, we calculate the equilibrium states of the planetary axial tilts ("obliquities"). we show that high-obliquity states are stable for the majority of planets in resonant chain systems, even in the presence of strong tidal dissipation. we demonstrate how these high obliquity states could have been attained during the initial epoch of disk-driven orbital migration that established the resonant orbital architectures. our results highlight that both the orbital and spin states of resonant chains are valuable relics of the early stages of planet formation and evolution. | spin dynamics of planets in resonant chains: an abundance of high obliquities |
the most significant challenge to terrestrial planet habitability in the habitable zone of m stars is the maintenance of a planetary atmosphere that is stable against nightside atmospheric collapse. here, we investigate the stabilization potential of atmospheric dust in co2 atmospheres of varying densities. using the exoplanet configuration of the new fv3-based mars global climate model, we find that tenuous atmospheres with surface pressures less than 10mbar can be maintained with reasonable visible global dust opacities between 0.5 and 5. we investigate the primary mechanism by which dust warms the nightside and analyze changes to the planetary dynamics and day to night heat transport. | stabilization of tenuous atmospheres by atmospheric dust in the hz of m-dwarf stars |
direct imaging of earth-like exoplanets in the habitable zone of sun-like stars requires image contrast of ~10^10 at angular separations of around a hundred milliarcseconds. one approach for achieving this performance is to fly a starshade at a long distance in front of the telescope, shading the telescope from the direct starlight, but allowing planets around the star to be seen. the starshade is positioned so that sunlight falls on the surface away from the telescope, so the sun does not directly illuminate it. however, sunlight scattered from the starshade edge can enter the telescope, raising the background light level and potentially preventing the starshade from delivering the required contrast. as a result, starshade edge design has been identified as one of the highest priority technology gaps for external occulter missions in the nasas exoplanet exploration program technology plan 2013. to reduce the sunlight edge scatter to an acceptable level, the edge radius of curvature (roc) should be 1μm or less (commercial razor blades have roc of a few hundred nanometer). this poses a challenging manufacturing requirement and may make the occulter difficult to handle. in this paper we propose an alternative approach to controlling the edge scattering by applying a flexible metamaterial to the occulter edge. metamaterials are artificially structured materials, which have been designed to display properties not found in natural materials. metamaterials can be designed to direct the scatter at planned incident angles away from the space telescope, thereby directly decreasing the contaminating background light. reduction of the background light translates into shorter integration time to characterize a target planet and therefore improves the efficiency of the observations. as an additional benefit, metamaterials also have potential to produce increased tolerance to edge defects. | external occulter edge scattering control using metamaterials for exoplanet detection |
the astro2020 decadal survey recommended a "future large ir/o/uv telescope optimized for observing habitable exoplanets and general astrophysics" to be ready by end of the decade and that mission "to search for biosignatures from a robust number of about ~25 habitable zone [exo]planets." the search for multiple biosignatures requires high quality spectra of broad bandwidth and sufficient signal-to-noise. the combination of spectral resolution, bandwidth, and signal-to-noise-ratio impacts the number of exo-earths that can be spectrally characterized. broader bandwidths and higher signal-to-noise lead to increased integration time and is likely to reduce the number of targets around which an earth-size, habitable zone exoplanet could be sufficiently characterized. an increased integration will also consume a larger share of mission time dedicated to exoplanet direct imaging, possibly resulting in fewer exoplanets with higher quality spectra. previous work (morgan et al. 2022), evaluated the number of earth-size, habitable zone exoplanets that could be spectrally characterized for a range of spectral resolutions, signal-to-noise ratios, and bandwidths for a 6-m diameter exoplanet direct imaging mission for coronagraph-only, starshade-only, and hybrid coronagraph-starshade architectures for three cases: the nominal case of a blind-search survey, the bounding case of perfect-prior knowledge which is useful to determine if target depletion occurs, and the partial-prior knowledge case of a hypothetical extreme precision radial velocity survey. in this paper, we expand the broadband spectra metric from 400 - 1000 nm to include uv (at a low spectral resolution) and the near infrared up to 2 microns. we introduce an approach for expressing the yield for each coronagraph sub-band that contains both the lower bound of the blind search base and the upper bound of the perfect prior case (a depth-of-search indicator), and includes the cumulative exposure time required to reach target depletion for each sub-band. | an approach for calculating exo-earth yield of a 6 m ir/o/uv telescope for various broad bandwidth metrics |
we stand on the edge of an era where we will be able to characterize the atmospheres of terrestrial planets, putting us on the path to answer one of humanity's most compelling questions: are we alone in the universe? although many searches focus on transiting planets around small m dwarfs, the similar sizes of white dwarfs and earth would result in significantly higher transit depths around such stellar remnants, and enable easier characterization of terrestrial planets via transit spectroscopy. additionally the recent discovery of the first transiting planet around a white dwarf has proven that planets can survive on close orbits in these systems. however, an earth-like exoplanet orbiting a white dwarf would be exposed to different uv environments than earth, influencing both its atmospheric photochemistry and uv surface environment. in this talk i will discuss the evolving habitable zones around white dwarfs, how the different uv environment would affect potential biosignatures on orbiting earth-like planets, and present simulations of transit observations with the upcoming james webb space telescope. | life after (stellar) death: habitability around white dwarfs |
during last decade there have been a tremendous increase in detection and characterization of low-mass exoplanets, reaching the earth size and mass domain, in particular those orbiting m dwarf stars, due to their smaller sizes and masses, resulting in planet larger transit amplitude and radial velocity signals. extremely precise instruments such as the espresso spectrograph are designed to detect earth-like planets, requiring in addition a detailed modeling of the stellar activity.espresso is an ultra-stable high-resolution spectrograph, designed and developed involving institutions from switzerland, italy, portugal, spain, and eso, which is located in the combined coudé lab of the vlt at eso, and is able to operate either using one 8.2m-vlt ut or simultaneously with the four vlt uts. espresso started routine operations in october 2018 at eso, and is designed to achieve a radial velocity precision of 10 cm/s, thus opening the possibility to explore new frontiers in science such as the search for rocky planets and the measurement of the variation of physical constants (pepe et al. 2021). espresso is considered a precursor of the ultra-stable high-resolution spectrograph andes (formerly known as hires) for the 39m-elt telescope (marconi et al. 2021).espresso has been very successful so far in detecting and characterizing low-mass planets demonstrating the sub-m/s capabilities of the instrument, providing a unique ground-based facility with great synergy with exoplanet dedicated satellites such as kepler (toledo padrón et al. 2020), tess (demangeon et al. 2021) and cheops (leleu et al. 2021). one of the most relevant recent achievement of espresso is the confirmation of the 11.2d earth mass planet proxima b in the habitable zone of proxima centauri, previously reported in anglada-escudé et al. (2016), and the discovery of the sub-earth mass planet proxima d in a 5.1d orbit with a semiamplitude velocity of 40 cm/s together with a simultaneous, precise characterization of the activity of the star (suárez mascareño et al. 2020; faria et al. 2022). this discovery together with the 5yr period super-earth planet candidate proxima c reported in damasso et al. (2020) composes the currently known planetary system in the nearest stellar neighbour to our sun, encouraging new detail studies of this star with current and future facilities such as andes@elt. in this talk i will briefly summarize the main features of espresso performance focusing on revealing the planetary system around proxima centauri and future prospects. | the planetary system of proxima centauri seen with espresso |
stellar surface inhomogeneities, such as spots, faculae, and magnetic network contaminate and, in some cases, overwhelm the planetary signal in transmission spectra (see, e.g. a detailed review by rackham et al. 2022). in particular the lofty goal of analyzing earth-size planet atmospheres in the habitable zones of m dwarf stars may be prevented until we can disentangle the star surface inhomogeneity from the exoplanet atmosphere signal, e.g., trappist-1. so far, astronomers have tried to remove the magnetic contamination of transmission spectra by using non-magnetic stellar models—a hotter star to model faculae and a cooler star to model star spots. yet this approach dramatically fails to reproduce the complex wavelength dependence of magnetic contamination (witzke et al. 2022). thus, a more comprehensive approach based on realistic magnetohydrodynamics (mhd) simulations of stellar atmospheres and magnetic features within these atmospheres is needed. the magnetohydrodynamics simulations have reached a high degree of maturity and have already revolutionized solar and stellar physics. now they are ready to address the big challenge facing exoplanetary science and allowing us to overcome the barrier imposed by magnetic contamination. we propose to generate a "library" of star spot and star faculae spectra of m and k stars for the community to use in furthering understanding contamination of transmission spectra light curves for atmospheres of exoplanets and, in particular, of rocky exoplanets transiting m dwarf stars. | towards solving the stellar inhomogeneity contamination of exoplanet transmission spectra problem with star spot and faculae spectra |
upcoming large space telescopes such as habex or luvoir will enable the precise measurement of phase curves and secondary eclipses of planets in the habitable zone. in this talk, i will discuss how to accurately and efficiently model these light curves using the starry code package. i will focus in particular on the inverse problem: given an exoplanet light curve, what does the planet's surface actually look like? the linearity of the starry model allows one to infer not only the maximum likelihood solution, but also the full posterior distribution of solutions, allowing one to accurately quantify the uncertainty and the level of degeneracy of the inferred surface map. in particular, i will discuss predictions for the kinds of constraints habex and luvoir will allow us to place on the surface properties of planets in the habitable zone, such as the existence of oceans, continents, ice caps, and clouds. | analytic techniques for mapping the surfaces of habitable worlds |
consisting of two of the brightest stars in the night sky and being the closest sun-like stars, the alpha centauri system is an excellent target for adaptive optics (ao) fed coronagraphic direct imaging searches of its two habitable zones (hzs). the hzs are well resolved, minimizing the requirements on coronagraph inner working angle, and the brightness of the stars provides for excellent ao performance. these traits have motivated several campaigns using current generation 8 m class telescopes, from visible to mid-ir wavelengths. we will review these efforts, placing them in context with limits from radial velocity surveys. we will then discuss the observations of the system with the next generation of 24 to 40 m elts. if equipped with high order "extreme" ao (exao) systems these telescopes can be expected to break new ground in the search for small planets orbiting alpha centauri a & b. we will present performance projections for such systems, and discuss the expected sensitivities of elt exao systems to exoplanets in the alpha centauri system. | prospects for ground-based direct imaging searches of the habitable zones of the alpha centauri system with the elts. |
many exoplanets are located in the 'habitable zone', where the planet-star distance provides habitable surface temperatures that allow liquid surface water. plenty of those planets contain so much water that their entire surface is covered with an ocean or sea-ice (waterworlds). evaluating the surface environment of waterworlds is important to understand the ocean-atmosphere climate interactions and to assess the detectability of potential life-forms. fully ice-covered waterworlds may sustain life in underlying oceans but finding evidence for subsurface life on distant exoplanets will be extremely difficult. surface temperatures, that determine whether water exists as ice, liquid, or gas, are determined by: 1. distance between star and planet, 2. tilt of the planet's rotation axis, 3. atmospheric greenhouse gasses. the star-planet distance controls how much radiation a planet receives. a tilted planetary rotation axis causes an asymmetric distribution of radiation. some regions receive less radiation and are colder than other regions. thirdly, atmospheric greenhouse gasses, such as carbon dioxide (co2), increase surface temperatures across the whole planet. with an earth system model, we investigate temperature distributions and the resulting extent of ice caps for scenarios with different combinations of incoming radiation, the tilt of the rotation axis, and atmospheric co2 concentrations. | areal extent of sea ice on waterworlds: effects of stellar irradiance, greenhouse gas forcing and axial obliquity |
enabling small iwas can dramatically increase a mission yield of earth-like exoplanets in the habitable zones of their stars. several studies showed that yield grows approximately inversely to iwa, meaning a mission with half the iwa doubles the yield of earth-like exoplanets. thus, advancing coronagraph architectures with small iwas has a greater impact on expected yield than parameters such as increasing throughput or improving contrast. the piaacmc (phase-induced amplitude apodization complex mask coronagraph) is a high-performance coronagraph featuring close to 100% throughput, and inner working angles (iwas) that can go as low as 0.5 l/d. its sensitivity to tip/tilt aberrations is close to theoretically best for small inner working angles. this makes the piaacmc a promising option for future exoplanet missions, if its performance can be demonstrated in the lab with realistic jitter and stellar angular sizes. here we describe a new effort funded by nasa tdem (technology development for exoplanet missions) called "laboratory demonstration of high contrast using piaacmc on a segmented aperture". the objective of this effort is to demonstrate and mature starlight suppression technology with the piaacmc for segmented apertures. specifically, we plan to perform a laboratory demonstration in vacuum of 10e-9 contrast with an inner working angle of 2 l/d (or better) in a 10% bandpass centered at 650 nm, using segmented apertures representative of those expected for the luvoir and habex missions (if segmented). this is the basis of the final milestone of our effort. we present our first results, which include a coronagraph design that passed that met our performance requirements in simulation, as well as the design and simulations of the layout on an optical bench. | development of a piaacmc high contrast imaging system for segmented apertures: overview and first results |
habex - the habitable exoplanet imager - is one of four flagship missions that nasa is studying in advance of the next astrophysics decadal survey. the primary goal of habex will be to directly image and characterize rocky planets in the habitable zones of other stars. specifically, habex aims to search for signs of liquid water oceans and biological activity on such worlds. additionally, habex will also be able to pursue a range of other astrophysics investigations, including the study of non-habitable exoplanets, the study of solar system objects, and observations of galaxies. the technical drivers for habex will be determined by the significant challenges associated with the direct imaging and characterization of potentially habitable exoplanets. this requires a large enough collecting area to collect light from these very dim targets, and the ability to block light from the dramatically brighter host star the planet orbits. there are multiple approaches to these challenges, and the goal of the habex study is to demonstrate that at least one can be executed with technologies that can be matured in time for a lunch in the 2030s. in this presentation, we will discuss the top-level exoplanet science goals of habex, and how those goals led to basic and preliminary architectural properties such as aperture size, starlight suppression technique, wavelength range, etc. we will then discuss how these architectural properties could allow for the astronomical study of other targets in and beyond the solar system. | habex: finding and characterizing habitable exoplanets with a potential future flagship astrophysics mission |
m dwarf stars are of a particular interest because of their extremely long lifetimes and close habitable zones which make them great candidates for finding exoplanets and potentially life. however, measuring the ages of m dwarfs is extremely difficult and conventional methods such as magnetic spin down (gyrochronology) requires careful calibration. wide binaries such as hip 43232, comprised of a g type star and an m dwarf, provide unique benchmarks for such a calibration. here we present the age of the solar like oscillator in hip 43232, combining asteroseismology from k2 modeled using diamonds and stellar modeling using mesa. | an asteroseismic age for a solar type star in a wide binary with an m dwarf |
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