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by Wilson Yu04 Feb 2019 03:47 - Nambu-Goto action (Nambu-Goto action)
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by Dr. Wei Wang28 Dec 2018 02:32 - Electrical conductivity (Electrical conductivity)
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by Prof. Hasan Keleş01 Aug 2018 11:58 - RKKY interaction (RKKY interaction)
by Dr. Vadim Cheianov31 Aug 2009 09:28 - Fermi surface (Fermi surface)
by Dr. Vadim Cheianov05 Dec 2010 22:11 - Fingers of God (Fingers of God)
by Dr. Ganna Ivashchenko18 May 2011 22:42 - Leptogenesis (Leptogenesis)
by Dr. Sacha Davidson08 Dec 2010 13:32 - Dzyaloshinskii-Moriya interaction (Dzyaloshinskii-Moriya interaction)
by Dr. George Jackeli28 Aug 2009 09:41
Recently bookmarked papers
with concepts:
- The mass evolution of a coronal mass ejection (CME) is an important parameter characterizing the drag force acting on a CME as it propagates through interplanetary space. Spacecraft measure in-situ plasma densities of CMEs during crossing events, but for investigating the mass evolution, we also need to know the CME geometry, more specific, its volume. Having derived the CME volume and mass from remote sensing data using 3D reconstructed CME geometry, we can calculate the CME density and compare it with in-situ proton density measurements near Earth. From that we may draw important conclusions on a possible mass increase as the CME interacts with the ambient solar wind in the heliosphere. In this paper we will describe in detail the method for deriving the CME volume using the graduated cylindrical shell (GCS) model (Thernisien et al., 2006,2009, see Figure 1). We show that, assuming self-similar expansion, one can derive the volume of the CME from two GCS parameters and that it furthermore can be expressed as a function of distance.Generalized Chern-SimonsRemote sensingEarthSolar windSunCoronal mass ejectionHeliosphereAstronomical UnitSolar Terrestrial Relations ObservatoryShell model...
- The magnetic network extending from the photosphere (solar radius \simeq R_\odot) to lower corona (R_\odot + 10 Mm) plays an important role in the heating mechanisms of the solar atmosphere. Here we further develop the models with realistic open magnetic flux tubes of Gent et al. (2013, 2014) in order to model more complicated configurations. Closed magnetic loops, and combinations of closed and open magnetic flux tubes are modelled. These are embedded within a realistic stratified atmosphere, subject to solar gravity and including the Interface Region. Constructing a magnetic field comprising self-similar magnetic flux tubes, an analytic solution for the kinetic pressure and plasma density is derived following Gent et al. (2014). Combining flux tubes of opposite polarity it is possible to create a steady background magnetic field configuration modelling realistic solar atmosphere. The result can be applied to SOHO/MDI and SDO/HMI and other magnetograms from the solar surface, upon which realistic photospheric motions can be simulated to explore the mechanism of energy transport. We demonstrate this powerful and versatile method with an application to Helioseismic and Magnetic Imager data.CoronaSolar atmospherePhotosphereChromosphereSolar radiusSolar surfaceMagnetic pressureSolar Dynamics ObservatorySolar coronaSuperposition...
- Based on observations of HII regions and the new computations of the recombination coefficients of the He I lines by Porter et al. (2013) we obtain a primordial helium abundance by mass of $Y_P = 0.2446\pm0.0029$. We consider thirteen sources of error for the $Y_P$ determination, some of them are mainly due to systematic effects, while the rest are mainly due to statistical effects. We compare our results with other determinations of $Y_P$ present in the literature. Combining our $Y_P$ value with computations of primordial nucleosynthesis we find a number of neutrino species $N_{eff} = 2.90\pm0.22$, and a neutron mean life $\tau_{\nu} = 872\pm14(s)$.NeutrinoPrimordial helium abundanceBig bang nucleosynthesisSystematic errorRecombination coefficientStatistical errorPlanck missionGalactic chemical evolutionReddeningMultipole moments...
- We study the sensitivity of displaced vertex searches for heavy neutrinos produced in W~boson decays in the LHC detectors ATLAS, CMS and LHCb. We also propose a new search that uses the muon chambers to detect muons from heavy neutrino decays outside the tracker. The sensitivity estimates are based on benchmark models in which the heavy neutrinos mix exclusively with one of the three Standard Model generations. The displaced vertex searches can cover a significant part of the parameter region where heavy neutrinos can explain the baryon asymmetry of the universe via low scale leptogenesis.Sterile neutrinoDisplaced verticesLarge Hadron ColliderMuonCMS experimentStandard ModelATLAS Experiment at CERNLHCb experimentHigh-luminosity LHCFlavour...
- Today, many of the aid systems deployed for visually impaired people are mostly made for a single purpose. Be it navigation, object detection, or distance perceiving. Also, most of the deployed aid systems use indoor navigation which requires a pre-knowledge of the environment. These aid systems often fail to help visually impaired people in the unfamiliar scenario. In this paper, we propose an aid system developed using object detection and depth perceivement to navigate a person without dashing into an object. The prototype developed detects 90 different types of objects and compute their distances from the user. We also, implemented a navigation feature to get input from the user about the target destination and hence, navigate the impaired person to his/her destination using Google Directions API. With this system, we built a multi-feature, high accuracy navigational aid system which can be deployed in the wild and help the visually impaired people in their daily life by navigating them effortlessly to their desired destination.Object detectionApplication programming interfaceGoogle.comObject...
- Today, many of the home automation systems deployed are mostly controlled by humans. This control by humans restricts the automation of home appliances to an extent. Also, most of the deployed home automation systems use the Internet of Things technology to control the appliances. In this paper, we propose a system developed using action recognition to fully automate the home appliances. We recognize the three actions of a person (sitting, standing and lying) along with the recognition of an empty room. The accuracy of the system was 90% in the real-life test experiments. With this system, we remove the human intervention in home automation systems for controlling the home appliances and at the same time we ensure the data privacy and reduce the energy consumption by efficiently and optimally using home appliances.PrivacyInternet of ThingsActionEnergy...
- WD 1145+017 is a unique white dwarf system that has a heavily polluted atmosphere, an infrared excess from a dust disk, numerous broad absorption lines from circumstellar gas, and changing transit features, likely from fragments of an actively disintegrating asteroid. Here, we present results from a large photometric and spectroscopic campaign with Hubble, Keck , VLT, Spitzer, and many other smaller telescopes from 2015 to 2018. Somewhat surprisingly, but consistent with previous observations in the u' band, the UV transit depths are always shallower than those in the optical. We develop a model that can quantitatively explain the observed "bluing" and the main findings are: I. the transiting objects, circumstellar gas, and white dwarf are all aligned along our line of sight; II. the transiting object is blocking a larger fraction of the circumstellar gas than of the white dwarf itself. Because most circumstellar lines are concentrated in the UV, the UV flux appears to be less blocked compared to the optical during a transit, leading to a shallower UV transit. This scenario is further supported by the strong anti-correlation between optical transit depth and circumstellar line strength. We have yet to detect any wavelength-dependent transits caused by the transiting material around WD 1145+017.White dwarfCircumstellar gasLight curveTelescopesAbsorption lineDust diskCosmic Origins SpectrographHIRES spectrometerAbsorption featureAsteroids...
- Hard and soft classification techniques are the conventional ways of image classification on satellite data. These classifiers have number of drawbacks. Firstly, these approaches are inappropriate for mixed pixels. Secondly, these approaches do not consider spatial variability. Kriging based soft classifier (KBSC) is a non-parametric geostatistical method. It exploits the spatial variability of the classes within the image. This letter compares the performance of KBSC with other conventional hard/soft classification techniques. The satellite data used in this study is the Wide Field Sensor (WiFS) from the Indian Remote Sensing Satellite -1D (IRS-1D). The ground hyperspectral signatures acquired from the agricultural fields by a hand held spectroradiometer are used to detect subpixel targets from the satellite images. Two measures of closeness have been used for accuracy assessment of the KBSC to that of the conventional classifications. The results prove that the KBSC is statistically more accurate than the other conventional techniques.ClassificationInfrared Spectrometer on SpitzerRemote sensingSatellite ImageField...
- As planets grow the exchange of angular momentum with the gaseous component of the protoplanetary disc produces a net torque resulting in a variation of the semi-major axis of the planet. For low-mass planets not able to open a gap in the gaseous disc this regime is known as type I migration. Pioneer works studied this mechanism in isothermal discs finding fast inward type I migration rates that were unable to reproduce the observed properties of extrasolar planets. In the last years, several improvements have been made in order to extend the study of type I migration rates to non-isothermal discs. Moreover, it was recently shown that if the planet's luminosity due to solid accretion is taken into account, inward migration could be slowed down and even reversed. In this work, we study the planet formation process incorporating, and comparing, updated type I migration rates for non-isothermal discs and the role of planet's luminosity over such rates. We find that the latter can have important effects on planetary evolution, producing a significant outward migration for the growing planets.PlanetPlanetesimalPlanet formationAccretionMass accretion rateViscosityHydrodynamical simulationsLuminosityThermal massEntropy...
- In a previous paper I gave a presentation for the Quillen higher algebraic K-groups of an exact category in terms of "acyclic binary multicomplexes". In this paper I take that presentation as a definition of the higher K-groups, generalize it to the relative K-groups of an exact functor between exact categories, and produce the corresponding long exact sequence by elementary means, without homotopy theory.Exact categoryExact sequenceIsomorphismChain complexBinary numberQuasi-isomorphismMapping coneExact functorPermutationAutomorphism...
- In this paper we show how to use elementary methods to prove that the volume of Sl_k R / Sl_k Z is zeta(2) * zeta(3) * ... * zeta(k) / k. Using a version of reduction theory presented in this paper, we can compute the volumes of certain unbounded regions in Euclidean space by counting lattice points and then appeal to the machinery of Dirichlet series to get estimates of the growth rate of the number of lattice points appearing in the region as the lattice spacing decreases. We also present a proof of the closely related result that the Tamagawa number of Sl_k Q is 1 that is somewhat simpler and more arithmetic than Weil's. His proof proceeds by induction on k and appeals to the Poisson summation formula, whereas the proof here brings to the forefront local versions of the formula, one for each prime p, which help to illuminate the appearance of values of zeta functions in formulas for volumes.
- We offer an introduction for mathematicians to the univalent foundations of Vladimir Voevodsky, aiming to explain how he chose to encode mathematics in type theory and how the encoding reveals a potentially viable foundation for all of modern mathematics that can serve as an alternative to set theory.IsomorphismGroupoidInteractive theorem proverFormal languagesFormal systemVector spaceClassical mathematicsMonoidEmpty Lattice ApproximationConjunction...
- For any elliptic curve $E$ over $k\subset \Bbb R$ with $E({\Bbb C})={\Bbb C}^\times/q^{\Bbb Z}$, $q=e^{2\pi iz}, \Im(z)>0$, we study the $q$-average $D_{0,q}$, defined on $E({\Bbb C})$, of the function $D_0(z) = \Im(z/(1-z))$. Let $\Omega^+(E)$ denote the real period of $E$. We show that there is a rational function $R \in {\Bbb Q}(X_1(N))$ such that for any non-cuspidal real point $s\in X_1(N)$ (which defines an elliptic curve $E(s)$ over $\Bbb R$ together with a point $P(s)$ of order $N$), $\pi D_{0,q}(P(s))$ equals $\Omega^+(E(s))R(s)$. In particular, if $s$ is $\Bbb Q$-rational point of $X_1(N)$, a rare occurrence according to Mazur, $R(s)$ is a rational number.Elliptic curveModular formEisenstein seriesRational functionArithmeticWolfram MathematicaAlgebraic theoryAlgebraic K-theoryHomogeneous functionPolylogarithm...
- We describe, by matrix factorizations, the rank one graded maximal Cohen-Macaulay modules over the hypersurface Y_1^3+Y_2^3+Y_3^3+Y_4^3.RankMatrix FactorizationPermutationSyzygyClassificationIsomorphismComputer algebra systemVector bundleElliptic curveRegular local ring...
- We show that any lexsegment ideal with linear resolution has linear quotients with respect to a suitable ordering of its minimal monomial generators. For completely lexsegment ideals with linear resolution we show that the decomposition function is regular. For arbitrary lexsegment ideals we compute the depth and the dimension. As application we characterize the Cohen-Macaulay lexsegment ideals.RegularizationMapping coneIsomorphismPolynomial ringMorphismKeyphraseHomogenizationKoszul complexExact sequenceResolution...
- We study join-meet ideals associated with modular non-distributive lattices. We give a lower bound for the regularity and show that they are not linearly related.Exact sequenceDiamond cubicDiamondGröbner basisPolynomial ringGraded algebraRankIrreducible elementAttentionSoftware...
- Matroids are ubiquitous in modern combinatorics. As discovered by Gelfand, Goresky, MacPherson and Serganova there is a beautiful connection between matroid theory and the geometry of Grassmannians: realizable matroids correspond to torus orbits in Grassmannians. Further, as observed by Fink and Speyer general matroids correspond to classes in the $K$-theory of Grassmannians. This yields in particular a geometric description of the Tutte polynomial. In this review we describe all these constructions in detail, and moreover we generalise some of them to polymatroids. More precisely, we study the class of flag matroids and their relations to flag varieties. In this way, we obtain an analogue of the Tutte polynomial for flag matroids.TorusPolytopeTutte polynomialRankGrassmannianVector spaceGraphToric varietyIrreducible representationEmbedding...
- In this paper we characterize the Gorenstein $t$-spread Veronese algebras.PolytopeConvex polytopePolynomial ringSupporting hyperplaneVector spaceComputer algebra systemClassificationCohen-Macaulay ringGraded algebraIsomorphism...
- Astrophysical and cosmological observations currently provide the only robust, empirical measurements of dark matter. Future observations with Large Synoptic Survey Telescope (LSST) will provide necessary guidance for the experimental dark matter program. This white paper represents a community effort to summarize the science case for studying the fundamental physics of dark matter with LSST. We discuss how LSST will inform our understanding of the fundamental properties of dark matter, such as particle mass, self-interaction strength, non-gravitational couplings to the Standard Model, and compact object abundances. Additionally, we discuss the ways that LSST will complement other experiments to strengthen our understanding of the fundamental characteristics of dark matter. More information on the LSST dark matter effort can be found at https://lsstdarkmatter.github.io/ .Dark matterLarge Synoptic Survey TelescopeDark matter subhaloAstrometric microlensingGalaxySelf-interacting dark matterDark matter haloStarPrimordial black holeDwarf galaxy...
- We present our results from training and evaluating a convolutional neural network (CNN) to predict the shapes of galaxies from wide field survey images. As ground truth, we use conventional shape measurements from an overlapping superior, deeper survey with less sky coverage. In particular, we predict galaxy shapes from images of the DR1 data release of Dark Energy Survey (DES) using shape measurements from the Canada-France Hawaii Telescope Lensing Survey (CFHTLenS). We demonstrate that CNN predictions from DES images reproduce the results of CFHTLenS at bright magnitudes and show a significantly higher correlation with CFHTLenS at fainter magnitudes than DES results from conventional image analysis. The more accurate shape measurements with the CNN increase the effective galaxy density of DES by 35% compared to the official DES Y1 METACALIBRATION catalogue and by 150% compared to the IM3SHAPE catalogue. Prediction of shape parameters with a CNN is also extremely fast, it takes only 0.2 milliseconds per galaxy, improving 4 orders of magnitudes over model fitting. Our proposed setup is applicable to current and next generation weak lensing surveys where higher quality ground truth shapes can be measured in dedicated deep fields.GalaxyConvolutional neural networkDark Energy SurveyPoint spread functionCFHTLenS surveyEllipticityGround truthWeak lensingLensing surveyMilky Way...
- The discovery of Fast Radio Bursts (FRBs) at cosmological distances has opened a powerful window on otherwise unseen matter in the Universe. In the 2020s, observations of $>10^{4}$ FRBs will assess the baryon contents and physical conditions in the hot/diffuse circumgalactic, intracluster, and intergalactic medium, and test extant compact-object dark matter models.Fast Radio BurstsDispersion measureCircumgalactic mediumHost galaxyCompact starMilky WayIntra-cluster mediumBaryon contentTime delayGalaxy...
- This document illustrates the feasibility of a few per cent level measurement of the local black hole occupation fraction in low mass galaxies through wide-field, high angular resolution X-ray imaging observations of local volume galaxies. The occupation fraction, particularly at the low end of the galaxy luminosity function, is a key benchmark for any model which aims to reproduce the formation and growth of super-massive black holes and their host galaxies. Our proposed measurement will complement orthogonal efforts that are planned in X-rays at high red-shifts, as well as in the local Universe with ground-based facilities.Black holeGalaxyLow-mass galaxyX-ray binaryHost galaxyMilky WayGalaxy luminosity functionActive Galactic NucleiMassive black holeLocal Volume...
- In the upcoming decade cadenced wide-field imaging surveys will increase the number of identified $z<0.3$ Type~Ia supernovae (SNe~Ia) from the hundreds to the hundreds of thousands. The increase in the number density and solid-angle coverage of SNe~Ia, in parallel with improvements in the standardization of their absolute magnitudes, now make them competitive probes of the growth of structure and hence of gravity. The peculiar velocity power spectrum is sensitive to the growth index $\gamma$, which captures the effect of gravity on the linear growth of structure through the relation $f=\Omega_M^\gamma$. We present the first projections for the precision in $\gamma$ for a range of realistic SN peculiar-velocity survey scenarios. In the next decade the peculiar velocities of SNe~Ia in the local $z<0.3$ Universe will provide a measure of $\gamma$ to $\pm 0.01$ precision that can definitively distinguish between General Relativity and leading models of alternative gravity.SupernovaPeculiar velocitySupernova Type IaAbsolute magnitudeGeneral relativityGravitationSurveysFieldPrecisionUniverse...
- In this white paper we explore the capabilities required to identify and study supermassive black holes formed from heavy seeds ($\mathrm{M_{\bullet}} \sim 10^4 - 10^6 \, \mathrm{M_{\odot}}$) in the early Universe. To obtain an unequivocal detection of heavy seeds we need to probe mass scales of $\sim 10^{5-6} \, \mathrm{M_{\odot}}$ at redshift $z \gtrsim 10$. From this theoretical perspective, we review the observational requirements and how they compare with planned/proposed instruments, in the infrared, X-ray and gravitational waves realms. In conclusion, detecting heavy black hole seeds at $z \gtrsim 10$ in the next decade will be challenging but, according to current theoretical models, feasible with upcoming/proposed facilities. Their detection will be fundamental to understand the early history of the Universe, as well as its evolution until now. Shedding light on the dawn of black holes will certainly be one of the key tasks that the astronomical community will focus on in the next decade.Black holeDirect Collapse Black HoleSupermassive black holeHost galaxyGravitational waveThe early UniverseObservatoriesMetallicityBlack hole massGas clouds...
- We analyze the optical morphologies of galaxies in the IllustrisTNG simulation at $z\sim0$ with a Convolutional Neural Network trained on visual morphologies in the Sloan Digital Sky Survey. We generate mock SDSS images of a mass complete sample of $\sim12,000$ galaxies in the simulation using the radiative transfer code SKIRT and include PSF and noise to match the SDSS r-band properties. The images are then processed through the exact same neural network used to estimate SDSS morphologies to classify simulated galaxies in four morphological classes (E, S0/a, Sab, Scd). The CNN model finds that $\sim95\%$ of the simulated galaxies fall in one the four main classes with high confidence. The mass-size relations of the simulated galaxies divided by morphological type also reproduce well the slope and the normalization of observed relations which confirms the realism of optical morphologies in the TNG suite. However, the Stellar Mass Functions decomposed into different morphologies still show significant discrepancies with observations both at the low and high mass end. We find that the high mass end of the SMF is dominated in TNG by massive disk galaxies while early-type galaxies dominate in the observations according to the CNN classifications. The present work highlights the importance of detailed comparisons between observations and simulations in comparable conditions.GalaxySloan Digital Sky SurveyStellar massConvolutional neural networkMilky WayHigh massClassificationIllustrisTNG simulationLate-type galaxyMessier 15...
- ClusterPyXT is a new software pipeline to generate spectral temperature, X-ray surface brightness, pressure, and density maps from X-ray observations of galaxy clusters. These data products help elucidate the physics of processes occurring within clusters of galaxies, including turbulence, shock fronts, nonthermal phenomena, and the overall dynamics of cluster mergers. ClusterPyXT automates the creation of these data products with minimal user interaction, and allows for rapid analyses of archival data with user defined parameters and the ability to straightforwardly incorporate additional observations. In this paper, we describe in detail the use of this code and release it as an open source Python project on GitHub.Cluster of galaxiesSurface brightnessIntra-cluster mediumChandra X-ray ObservatorySoftwareX-ray temperaturePythonMilky WayTurbulenceHI column density...
- Massive 10^6-10^10 Msun black holes (BHs) are ubiquitous in local galactic nuclei. They were common by the time the Universe is several Gyr old, and many of them were in place within the first 1~Gyr after the Big Bang. Their quick assembly has been attributed to mechanisms such as the rapid collapse of gas into the nuclei of early protogalaxies, accretion and mergers of stellar-mass BHs accompanying structure formation at early times, and the runaway collapse of early, ultra-dense stellar clusters. The origin of the early massive BHs remains an intriguing and long-standing unsolved puzzle in astrophysics. Here we discuss strategies for discerning between BH seeding models using electromagnetic observations. We argue that the most direct answers will be obtained through detection of BHs with masses M<10^5 Msun at redshifts z>10, where we expect them to first form. Reaching out to these redshifts and down to these masses is crucial, because BHs are expected to lose the memory of their initial assembly by the time they grow well above 10^5 Msun and are incorporated into higher-mass galaxies. The best way to detect 10^4-10^5 Msun BHs at high redshifts is by a sensitive X-ray survey. Critical constraining power is augmented by establishing the properties and the environments of their host galaxies in deep optical/IR imaging surveys. Required OIR data can be obtained with the JWST and WFIRST missions. The required X-ray flux limits (down to 10^{-19} erg/s/cm^2) are accessible only with a next-generation X-ray observatory which has both high (sub-1") angular resolution and high throughput. A combination of deep X-ray and OIR surveys will be capable of probing several generic markers of the BH seed scenarios, and resolving the long-stanging puzzle of their origin. These electromagnetic observations are also highly synergistic with the information from LISA on high-z BH mergers.Black holeGalactic nucleiX-ray surveysAccretionJames Webb Space TelescopeProtogalaxyHost galaxyWide Field Infrared Survey TelescopeX-ray observatoryStellar mass black holes...
- Two groundbreaking new facilities will commence operations early in the 2020s and thereafter define much of the broad landscape of US optical-infrared astronomy in the remaining decade. The Large Synoptic Survey Telescope (LSST), perched atop Cerro Pachon in the Chilean Andes, will revolutionize the young field of Time Domain Astronomy through its wide-field, multi-band optical imaging survey. At the same time, the James Webb Space Telescope (JWST), orbiting at the Sun-Earth L2 Lagrange point, will provide stunningly high-resolution views of selected targets from the red end of the optical spectrum to the mid-infrared. However, the spatial resolution of the LSST observations will be limited by atmospheric seeing, while JWST will be limited in its time-domain capabilities. This paper highlights the scientific opportunities lying between these two landmark missions, i.e., science enabled by systems capable of astronomical observations with both high cadence in the time domain and high resolution in the spatial domain. The opportunities range from constraining the late phases of stellar evolution in nearby resolved populations to constraining dark matter distributions and cosmology using lensed transient sources. We describe a system that can deliver the required capabilities.James Webb Space TelescopeLarge Synoptic Survey TelescopeInfrared astronomyDark Matter Density ProfileStellar evolutionCosmologyEarthSunLagrangian pointResolution...
- I analyze the postdoctoral career tracks of a nearly-complete sample of astronomers from 28 United States graduate astronomy and astrophysics programs spanning 13 graduating years (N=1063). A majority of both men and women (65% and 66%, respectively) find long-term employment in astronomy or closely-related academic disciplines. No significant difference is observed in the rates at which men and women are hired into these jobs following their PhDs, or in the rates at which they leave the field. Applying a two-outcome survival analysis model to the entire data set, the relative academic hiring probability ratio for women vs. men at a common year post-PhD is H_(F/M) = 1.08 (+0.20, -0.17; 95% CI); the relative leaving probability ratio is L_(F/M) = 1.03 (+0.31, -0.24). These are both consistent with equal outcomes for both genders (H_(F/M) = L_(F/M) = 1) and rule out more than minor gender differences in hiring or in the decision to abandon an academic career. They suggest that despite discrimination and adversity, women scientists are successful at managing the transition between PhD, postdoctoral, and faculty/staff positions.Survival analysisLongitudinal studyStatisticsHazard ratioMarketAttentionNew MexicoMultidimensional ArraySecurityAerospace...
- We introduce a galaxy cluster mass observable, $\mu_\star$, based on the stellar masses of cluster members, and we present results for the Dark Energy Survey (DES) Year 1 observations. Stellar masses are computed using a Bayesian Model Averaging method, and are validated for DES data using simulations and COSMOS data. We show that $\mu_\star$ works as a promising mass proxy by comparing our predictions to X-ray measurements. We measure the X-ray temperature-$\mu_\star$ relation for a total of 150 clusters matched between the wide-field DES Year 1 redMaPPer catalogue, and Chandra and XMM archival observations, spanning the redshift range $0.1<z<0.7$. For a scaling relation which is linear in logarithmic space, we find a slope of $\alpha = 0.488\pm0.043$ and a scatter in the X-ray temperature at fixed $\mu_\star$ of $\sigma_{{\rm ln} T_X|\mu_\star}=0.266^{+0.019}_{-0.020}$ for the joint sample. By using the halo mass scaling relations of the X-ray temperature from the Weighing the Giants program, we further derive the $\mu_\star$-conditioned scatter in mass, finding $\sigma_{{\rm ln} M|\mu_\star}=0.26^{+ 0.15}_{- 0.10}$. These results are competitive with well-established cluster mass proxies used for cosmological analyses, showing that $\mu_\star$ can be used as a reliable and physically motivated mass proxy to derive cosmological constraints.Dark Energy SurveyStellar massGalaxyCluster mass proxyX-ray temperatureScaling lawStarMilky WayBayesian Model AveragingCluster of galaxies...
- With the advent of large scale surveys the manual analysis and classification of individual radio source morphologies is rendered impossible as existing approaches do not scale. The analysis of complex morphological features in the spatial domain is a particularly important task. Here we discuss the challenges of transferring crowdsourced labels obtained from the Radio Galaxy Zoo project and introduce a proper transfer mechanism via quantile random forest regression. By using parallelized rotation and flipping invariant Kohonen-maps, image cubes of Radio Galaxy Zoo selected galaxies formed from the FIRST radio continuum and WISE infrared all sky surveys are first projected down to a two-dimensional embedding in an unsupervised way. This embedding can be seen as a discretised space of shapes with the coordinates reflecting morphological features as expressed by the automatically derived prototypes. We find that these prototypes have reconstructed physically meaningful processes across two channel images at radio and infrared wavelengths in an unsupervised manner. In the second step, images are compared with those prototypes to create a heat-map, which is the morphological fingerprint of each object and the basis for transferring the user generated labels. These heat-maps have reduced the feature space by a factor of 248 and are able to be used as the basis for subsequent ML methods. Using an ensemble of decision trees we achieve upwards of 85.7% and 80.7% accuracy when predicting the number of components and peaks in an image, respectively, using these heat-maps. We also question the currently used discrete classification schema and introduce a continuous scale that better reflects the uncertainty in transition between two classes, caused by sensitivity and resolution limits.ClassificationFIRST surveyWide-field Infrared Survey ExplorerEuclidean distanceRadio galaxyGalaxy ZooRadio sourcesRegressionRandom forestFeature space...
- The blossoming field of joint gravitational wave and electromagnetic (GW-EM) astronomy is one of the most promising in astronomy. The first, and only, joint GW-EM event GW170817 provided remarkable science returns that still continue to this day. Continued growth in this field requires increasing the sample size of joint GW-EM detections. In this white paper, we outline the case for using some percentage of LSST survey time for dedicated target-of-opportunity follow up of GW triggers in order to efficiently and rapidly identify optical counterparts. We show that the timeline for the LSST science survey is well matched to the planned improvements to ground based GW detectors in the next decade. LSST will become particularly crucial in the later half of the 2020s as more and more distant GW sources are detected. Lastly, we highlight some of the key science goals that can be addressed by a large sample of joint GW-EM detections.Gravitational waveNeutron starLarge Synoptic Survey TelescopeBlack holeLaser Interferometer Gravitational-Wave ObservatoryGW170817Optical identificationLuminosity distanceMilky WayBinary black hole system...
- We analyse 850um continuum observations of eight massive X-ray detected galaxy clusters at z~0.8-1.6 taken with SCUBA-2 on the James Clerk Maxwell Telescope. We find an average overdensity of 850um-selected sources of a factor of 4+/-2 per cluster within the central 1Mpc compared to the field. We investigate the multiwavelength properties of these sources and identify 34 infrared counterparts to 26 SCUBA-2 sources. Their colours suggest that the majority of these counterparts are probable cluster members. We use the multi-wavelength far-infrared photometry to measure the total luminosities and total cluster star-formation rates demonstrating that they are roughly three orders of magnitude higher than local clusters. We predict the H-band luminosities of the descendants of our cluster submillimetre galaxies and find that their stellar luminosity distribution is consistent with that of passive elliptical galaxies in z~0 clusters. Together, the faded descendants of the passive cluster population already in place at z~1 and the cluster submillimetre galaxies are able to account for the total luminosity function of early-type cluster galaxies at z~0. This suggests that the majority of the luminous passive population in z~0 clusters are likely to have formed at z>>1 through an extreme, dust-obscured starburst event.Star formation rateGalaxyLuminosityStar formationMassive clusterVirial cluster massCluster samplingCluster coreInfrared sourcesFull width at half maximum...
- We present a catalog of 47 wide-angle tailed radio galaxies (WATs), the WATCAT; these galaxies were selected by combining observations from the National Radio Astronomy Observatory/Very Large Array Sky Survey (NVSS), the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST), and the Sloan Digital Sky Survey (SDSS), and mainly built including a radio morphological classification. We included in the catalog only radio sources showing two-sided jets with two clear "warmspots" (i.e., jet knots as bright as 20% of the nucleus) lying on the opposite side of the radio core, and having classical extended emission resembling a plume beyond them. The catalog is limited to redshifts z $\leq$ 0.15, and lists only sources with radio emission extended beyond 30 kpc from the host galaxy. We found that host galaxies of WATCAT sources are all luminous (-20.5 $\gtrsim$ Mr $\gtrsim$ -23.7), red early-type galaxies with black hole masses in the range $10^8\lesssim $ M$_{\rm BH} \lesssim 10^9$ M$_\odot$. The spectroscopic classification indicates that they are all low-excitation galaxies (LEGs). Comparing WAT multifrequency properties with those of FRI and FRII radio galaxies at the same redshifts, we conclude that WATs show multifrequency properties remarkably similar to FRI radio galaxies, having radio power of typical FRIIs.Sloan Digital Sky SurveyRadio galaxyHost galaxyLuminosityNational Radio Astronomy Observatory VLA Sky SurveyEarly-type galaxyRadio sourcesPlumeGalaxyClassification...
- We present dynesty, a public, open-source, Python package to estimate Bayesian posteriors and evidences (marginal likelihoods) using Dynamic Nested Sampling. By adaptively allocating samples based on posterior structure, Dynamic Nested Sampling has the benefits of Markov Chain Monte Carlo algorithms that focus exclusively on posterior estimation while retaining Nested Sampling's ability to estimate evidences and sample from complex, multi-modal distributions. We provide an overview of Nested Sampling, its extension to Dynamic Nested Sampling, the algorithmic challenges involved, and the various approaches taken to solve them. We then examine dynesty's performance on a variety of toy problems along with several astronomical applications. We find in particular problems dynesty can provide substantial improvements in sampling efficiency compared to popular MCMC approaches in the astronomical literature. More detailed statistical results related to Nested Sampling are also included in the Appendix.Nested sampling algorithmMonte Carlo Markov chainCovarianceStatistical estimatorBayesianOrder statisticRandom walkPythonBayesian approachExpectation Value...
- The multi-tracer technique employs a ratio of densities of two differently biased galaxy samples that trace the same underlying matter density field, and was proposed to alleviate the cosmic variance problem. Here we propose a novel application of this approach, applying it to two different tracers one of which is the 21-cm signal of neutral hydrogen from the epochs of reionization and comic dawn. The second tracer is assumed to be a sample of high-redshift galaxies, but the approach can be generalized and applied to other high-redshift tracers. We show that the anisotropy of the ratio of the two density fields can be used to measure the sky-averaged 21-cm signal, probe the spectral energy distribution of radiative sources that drive this signal, and extract large-scale properties of the second tracer, e.g., the galaxy bias. Using simulated 21-cm maps and mock galaxy samples, we find that the method works well for an idealized galaxy survey. However, in the case of a realistic galaxy survey which only probes highly biased luminous galaxies, the inevitable Poisson noise makes the reconstruction far more challenging. This difficulty can be mitigated with the greater sensitivity of future telescopes along with larger survey volumes.Hydrogen 21 cm lineGalaxySpectral energy distributionLarge scale structure surveyMilky WayGalaxy biasEpoch of reionizationSquare Kilometre ArrayAstronomical X-ray sourceStatistical error...
- Current cosmological tensions motivate investigating extensions to the standard $\Lambda$CDM model. Additional model parameters are typically varied one or two at a time, in a series of separate tests. The purpose of this paper is to highlight that information is lost by not also examining the correlations between these additional parameters, which arise when their effects on model predictions are similar, even if the parameters are not varied simultaneously. We show how these correlations can be quantified with simulations and Markov Chain Monte Carlo (MCMC) methods. As an example, we assume that $\Lambda$CDM is the true underlying model, and calculate the correlations expected between the phenomenological lensing amplitude parameter, $A_L$, the running of the spectral index, $n_{\rm run}$, and the primordial helium mass fraction, $Y_P$, when these parameters are varied one at a time along with the $\Lambda$CDM parameters in fits to the $\textit{Planck}$ 2015 temperature power spectrum. These correlations are not small, ranging from 0.31 ($A_L-n_{\rm run}$) to $-0.93$ ($n_{\rm run}-Y_P$). We find that the values of these three parameters from the $\textit{Planck}$ data are consistent with $\Lambda$CDM expectations within $0.9\sigma$ when the correlations are accounted for. This does not explain the 1.8-2.7$\sigma$ $\textit{Planck}$ preference for $A_L>1$, but provides an additional $\Lambda$CDM consistency test. For example, if $A_L>1$ was a symptom of an underlying systematic error or some real but unknown physical effect that also produced spurious correlations with $n_{\rm run}$ or $Y_P$ our test might have revealed this. We recommend that future cosmological analyses examine correlations between additional model parameters in addition to investigating them separately, one a time.Monte Carlo Markov chainCovarianceFisher information matrixCosmological parametersCovariance matrixSystematic errorBayesianPlanck missionMaximum likelihoodGaussian distribution...
- The faintness of satellite systems in galaxy groups has contributed to the widely discussed "missing satellite" and "too big to fail" issues. Using techniques based on Tremaine & Richstone (1977), we show that there is no problem with the luminosity function computed from modern codes per se, but that the gap between first and second brightest systems is too big {\it given} the luminosity function, that the same large gap is found in modern, large scale baryonic $\Lambda$CDM simulations such as EAGLE and IllustrisTNG, is even greater in dark matter only simulations, and finally, that this is most likely due to gravitationally induced merging caused by classical dynamical friction. Quantitatively the gap is larger in the computed simulations than in the randomized ones by $1.79 \pm 1.04$, $1.51 \pm 0.93$, $3.43 \pm 1.44$ and $3.33 \pm 1.35$ magnitudes in the EAGLE, IllustrisTNG, and dark matter only simulations of EAGLE and IllustrisTNG respectively. Furthermore the anomalous gaps in the simulated systems are even larger than in the real data by over half a magnitude and are still larger in the dark matter only simulations. Briefly stated, $\Lambda$CDM does not have a problem with an absence of "too big to fail" galaxies. Statistically significant large gaps between first and second brightest galaxies are to be expected.GalaxyLuminosity functionToo big to fail problemN-body simulationEAGLE simulation projectIllustrisTNG simulationStatisticsMilky WayGroup of galaxiesAGN feedback...
- Sub-Saturns straddle the boundary between gas-rich Jupiters and gas-poor super-Earths/sub-Neptunes. Their large radii (4--8$R_\oplus$) suggest that their gas-to-core mass ratios range $\sim$0.1--1.0. With their envelopes as massive as their cores, sub-Saturns are just on the verge of runaway gas accretion; they are expected to be significantly less populous than gas giants. Yet, the observed occurrence rates of sub-Saturns and Jupiters are comparable within $\sim$100 days. We show that in these inner regions of planetary systems, the growth of sub-Saturns/Jupiters is ultimately limited by local and global hydrodynamic flows---runaway accretion terminates and the formation of gas giants is suppressed. We derive a simple analytic formula for the local hydrodynamic accretion rate---an expression that has been previously reported only as an empirical fit to numerical simulations. Evolving simultaneously the background disk gas and the gas accretion onto planetary cores, we find that both the ubiquity of super-Earths/sub-Neptunes and the rarity of gas-rich planets are best explained if an underlying core mass distribution is peaked at $\sim$4.3$M_\oplus$. Within a finite disk lifetime $\sim$10 Myrs, massive cores ($\gtrsim 10M_\oplus$) can become either gas-poor or gas-rich depending on when they assemble but smaller cores ($\lesssim 10M_\oplus$) can only become gas-poor. This wider range of possible outcomes afforded by more massive cores may explain why metal-rich stars harbor a more diverse set of planets.PlanetAccretionSaturnNeptuneCoolingGas giantJupiterMass accretion rateHydrodynamic flowSuper-earth...
- Observations of the Kepler-1625 system with the Kepler and Hubble Space Telescopes have suggested the presence of a candidate exomoon, Kepler-1625b I, a Neptune-radius satellite orbiting a long-period Jovian planet. Here we present a new analysis of the Hubble observations, using an independent data reduction pipeline. We find that the transit light curve is well fit with a planet-only model, with a best-fit $\chi^2_\nu$ equal to 1.01. The addition of a moon does not significantly improve the fit quality. We compare our results directly with the original light curve from Teachey & Kipping (2018), and find that we obtain a better fit to the data using a model with fewer free parameters (no moon). We discuss possible sources for the discrepancy in our results, and conclude that the lunar transit signal found by Teachey & Kipping (2018) was likely an artifact of the data reduction. This finding highlights the need to develop independent pipelines to confirm results that push the limits of measurement precision.PlanetLight curveHubble Space TelescopeStarWide Field Camera 3Monte Carlo Markov chainMultidimensional ArrayNeptuneInclinationGiant planet...
- Nebular emission lines associated with galactic HII regions carry information about both physical properties of the ionised gas and the source of ionising photons as well as providing the opportunity of measuring accurate redshifts and thus distances once a cosmological model is assumed. While nebular line emission has been extensively studied at lower redshift there are currently only few constraints within the epoch of reionisation (EoR, $z>6$), chiefly due to the lack of sensitive near-IR spectrographs. However, this will soon change with the arrival of the Webb Telescope providing sensitive near-IR spectroscopy covering the rest-frame UV and optical emission of galaxies in the EoR. In anticipation of Webb we combine the large cosmological hydrodynamical simulation Bluetides with photoionisation modelling to predict the nebular emission line properties of galaxies at $z=8\to 13$. We find good agreement with the, albeit limited, existing direct and indirect observational constraints on equivalent widths though poorer agreement with luminosity function constraints. We also find that the predicted H$\alpha$ - star formation rate calibration differs significantly from commonly assumed values.LuminosityMetallicityGalaxyLyman recombination continuaEpoch of reionizationEquivalent widthInitial mass functionStellar population synthesisLine emissionStellar mass...
- The acceleration mechanism of EUV/X-ray jets is still unclear. For the most part, there are two candidates for the mechanism. One is magnetic reconnection, and the other is chromospheric evaporation. We observed a relatively compact X-ray jet that occurred between 10:50 - 11:10 UT on February 18, 2011 by using the Solar Dynamics Observatory/Atmospheric Imaging Assembly, and the X-ray Telescope, Solar Optical Telescope, and EUV Imaging Spectrometer aboard Hinode. Our results are as follows: 1) The EUV and X-ray observations show the general characteristics of X-ray jets, such as an arch structure straddling a polarity inversion line, a jet bright point shown at one side of the arch leg, and a spire above the arch. 2) The multi-wavelength observations and Ca II H-band image show the existence of a low-temperature (~10 000K) plasma (i.e., filament) at the center of the jet. 3) In the magnetogram and Ca II H-band image, the filament exists over the polarity inversion line and arch structure is also straddling it. In addition, magnetic cancellation occurs around the jet a few hours before and after the jet is observed. 4) The temperature distribution of the accelerated plasma, which was estimated from Doppler velocity maps, the calculated differential emission measure, and synthetic spectra show that there is no clear dependence between the plasma velocity and its temperature. For the third result above, observational results suggest that magnetic cancellation is probably related to the occurrence of the jet and filament formation. This result suggests that the trigger of the jet is magnetic cancellation rather than an emerging magnetic arch flux. The fourth result indicates that acceleration of the plasma accompanied by an X-ray jet seems to be caused by magnetic reconnection rather than chromospheric evaporation.Magnetic reconnectionHinodeEvaporationSolar Dynamics ObservatoryIntensityBright pointImaging spectrometerIonizationSoft X-raySolar optical telescopes...
- Milky Way (MW) satellites reside within dark matter (DM) subhalos with a broad distribution of circular velocity profiles. This large diversity poses a serious test for the structure formation theory with relevant implications for the DM nature. For the Cold Dark Matter model, the diversity might be a signature of the combined effects of subhalo tidal disruption by the MW disk and strong supernova feedback. For models with a dwarf-scale cutoff in the power spectrum, the diversity is a consequence of the lower abundance of dwarf-scale halos. This diversity is most challenging for Self-Interacting Dark Matter (SIDM) models with cross sections $\sigma/m_\chi\gtrsim1~$cm$^2$g$^{-1}$ where subhalos have too low densities to explain the ultra-faint galaxies. For much larger cross sections, the diversity could be a signature of gravothermal collapse, which would favor velocity-dependent SIDM models with $\sigma/m_\chi>$10 cm$^2$g$^{-1}$ at the scale of MW satellites.Dark matter subhaloSelf-interacting dark matterDark matterMilky Way satelliteFaint galaxiesMilky WayAbundanceETHOSWarm dark matterCircular velocity...
- There is wide consensus that galaxy outflows are one of the most important processes determining the evolution of galaxies through cosmic time, for example playing a key role in shaping the galaxy mass function. Our understanding of outflows and their drivers, however, is in its infancy --- this is particularly true for the cold (neutral atomic and molecular) phases of outflows, which present observational and modeling challenges. Here we outline several key open questions, briefly discussing the requirements of the observations necessary to make progress, and the relevance of several existing and planned facilities. It is clear that galaxy outflows, and particularly cold outflows, will remain a topic of active research for the next decade and beyond.GalaxyGalaxy massGalactic evolutionMass functionMilky WayGas...
- We describe a next major frontier in observational studies of galaxy evolution and star formation: linking the physical conditions in the cold, star-forming interstellar medium to host galaxy and local environment. The integrated gas content of galaxies has been surveyed extensively over the last decades. The link between environment and cold gas density, turbulence, excitation, dynamical state, and chemical makeup remain far less well understood. We know that these properties do vary dramatically and theoretical work posits a strong connection between the state of the gas, its ability to form stars, and the impact of stellar feedback. A next major step in the field will be to use sensitive cm-, mm-, and submm-wave spectroscopy and high resolution spectroscopic imaging to survey the state of cold gas across the whole local galaxy population. Such observations have pushed the capabilities of the current generation of telescopes. We highlight three critical elements for progress in the next decade: (1) robust support and aggressive development of ALMA, (2) the deployment of very large heterodyne receiver arrays on single dish telescopes, and (3) development of a new interferometric array that dramatically improves on current capabilities at cm- and mm-wavelengths (~ 1-115 GHz).GalaxyStar formationMultidimensional ArrayAtacama Large Millimeter ArrayInterstellar mediumStellar feedbackTelescopesTurbulenceOf starsStar...
- We present the results of a survey of the brightest UV-selected galaxies in protoclusters. These proto-brightest cluster galaxy (proto-BCG) candidates are drawn from 179 overdense regions of $g$-dropout galaxies at $z\sim4$ from the Hyper Suprime-Cam Subaru Strategic Program identified previously as good protocluster candidates. This study is the first to extend the systematic study of the progenitors of BCGs from $z\sim2$ to $z\sim4$. We carefully remove possible contaminants from foreground galaxies and, for each structure, we select the brightest galaxy that is at least 1 mag brighter than the fifth brightest galaxy. We select 63 proto-BCG candidates and compare their properties with those of galaxies in the field and those of other galaxies in overdense structures. The proto-BCG candidates and their surrounding galaxies have different rest-UV color $(i - z)$ distributions to field galaxies and other galaxies in protoclusters that do not host proto-BCGs. In addition, galaxies surrounding proto-BCGs are brighter than those in protoclusters without proto-BCGs. The image stacking analysis reveals that the average effective radius of proto-BCGs is $\sim28\%$ larger than that of field galaxies. The $i-z$ color differences suggest that proto-BCGs and their surrounding galaxies are dustier than other galaxies at $z\sim4$. These results suggest that specific environmental effects or assembly biasses have already emerged in some protoclusters as early as $z \sim 4$, and we suggest that proto-BCGs have different star formation histories than other galaxies in the same epoch.GalaxyProtoclustersField galaxyOverdense regionPoint spread functionStellar massLuminosityStar-forming galaxyBrightest cluster galaxyStar formation rate...
- We present the first systematic study of the radio continuum size evolution of star-forming galaxies (SFGs) over the redshift range $0.35<z<2.25$. We use the VLA COSMOS 3GHz map (noise $\rm rms=2.3\,\mu Jy \,beam^{-1}$, $\theta_{\rm beam}=0.75\,\rm arcsec$) to construct a mass-complete sample of 3184 radio-selected SFGs that reside on and above the main-sequence (MS) of SFGs. We find no clear dependence between the radio size and stellar mass, $M_{\star}$, of SFGs with $10.5\lesssim\log(M_\star/\rm M_\odot)\lesssim11.5$. Our analysis suggests that MS galaxies are preferentially extended, while SFGs above the MS are always compact. The median effective radius of SFGs on (above) the MS of $R_{\rm eff}=1.5\pm0.2$ ($1.0\pm0.2$) kpc remains nearly constant with cosmic time; a parametrization of the form $R_{\rm eff}\propto(1+z)^\alpha$ yields a shallow slope of only $\alpha=-0.26\pm0.08\,(0.12\pm0.14)$ for SFGs on (above) the MS. The size of the stellar component of galaxies is larger than the extent of the radio continuum emission by a factor $\sim$2 (1.3) at $z=0.5\,(2)$, indicating star formation is enhanced at small radii. The galactic-averaged star formation rate surface density $(\Sigma_{\rm SFR})$ scales with the distance to the MS, except for a fraction of MS galaxies ($\lesssim10\%$) that harbor starburst-like $\Sigma_{\rm SFR}$. These "hidden" starbursts might have experienced a compaction phase due to disk instability and/or merger-driven burst of star formation, which may or may not significantly offset a galaxy from the MS. We thus propose to jointly use $\Sigma_{\rm SFR}$ and distance to the MS to better identify the galaxy population undergoing a starbursting phase.GalaxyRadio continuum emissionStellar massStar formationCOSMOS surveyVery Large ArrayMonte Carlo methodRadio sourcesOf starsRedshift bins...
- Immensely bright quasars and radio-loud active galactic nuclei (AGNs) provide an enticing opportunity to construct standard candles detectable up to the very early universe. An analytic theory is proposed to measure the distance to powerful \citeauthor{FR+1974} type-II radio sources based on their integrated flux density across a broad range of radio frequencies, and the angular size and axis ratio of their synchrotron-emitting lobes. This technique can be used at low-redshift to construct absolute standard candles in conjunction with X-ray observations of the host cluster, or at high-redshift to measure the relative distances of objects and constrain the curvature of our universe. Distances calculated with this method are consistent for dissimilar objects at the same redshift; the two lobes of Cygnus A have flux densities, linear sizes and spectral break frequencies varying by between 15-35\% yet their fitted distances are the same to within 7\%. These distance estimates together yield a transverse comoving distance to Cygnus A of $261_{-55}^{+70}\rm\, Mpc$ corresponding to a Hubble constant of $H_0 = 64_{-13}^{+17}\rm\, km\, s^{-1}\, Mpc^{-1}$. Large samples of suitable FR-II sources could provide a measure of the Hubble constant independent of existing techniques such as the cosmic microwave background, baryon acoustic oscillations, and type 1a supernovae.Cygnus AStandard candleActive Galactic NucleiMagnetic field strengthRadio sourcesHubble constantCosmologyCosmic microwave backgroundRadio lobesComoving distance...
- In the context of radio galaxy classification, most state-of-the-art neural network algorithms have been focused on single survey data. The question of whether these trained algorithms have cross-survey identification ability or can be adapted to develop classification networks for future surveys is still unclear. One possible solution to address this issue is transfer learning, which re-uses elements of existing machine learning models for different applications. Here we present radio galaxy classification based on a 13-layer Deep Convolutional Neural Network (DCNN) using transfer learning methods between different radio surveys. We find that our machine learning models trained from a random initialization achieve accuracies comparable to those found elsewhere in the literature. When using transfer learning methods, we find that inheriting model weights pre-trained on FIRST images can boost model performance when re-training on lower resolution NVSS data, but that inheriting pre-trained model weights from NVSS and re-training on FIRST data impairs the performance of the classifier. We consider the implication of these results in the context of future radio surveys planned for next-generation radio telescopes such as ASKAP, MeerKAT, and SKA1-MID.FIRST surveyNational Radio Astronomy Observatory VLA Sky SurveyInductive transferClassificationRadio galaxyConvolutional neural networkGalaxy classification systemsMachine learningEntropyArchitecture...
