-
Raul Angulo
DIPC, San Sebastian, Spain
Challenges in large-scale numerical simulations
In this talk, I will discuss several challenges faced by large-scale cosmological simulations: e.g. numerical uncertainties, underlying algorithms, and physical realism. I will then describe how, when the previous challenges are solved, N-body simulations could be a central part of future cosmological analyses.
-
J Richard Bond
CITA, University of Toronto, Canada
Instabilities and Entropies During and After Inflation
We have a good story, even with evidence, that all structure in the universe evolved from the diffusion of quantum-fluctuations that broke the adiabaticity of coarse-grained kinematic field trajectories during inflation. I will describe the use of dynamical systems theory to understand the subsequent complex linear preheating epoch, using Kolmogorov-Sinai entropy to measure the various instabilities that can arise, followed by the highly nonlinear classical-fluctuation generation during heating, as measured by coarse-grained Shannon entropy (the entropy we observe here and now). I will extend the kinematical entropic picture to short-lived instabilities while inflation is ongoing and their impact. A possible observable manifestation is non-standard non-Gaussianities of a form that are not strongly constrained so far with CMB, and that may be better constrained by Large Scale Structure Surveys.
-
François R. Bouchet
IAP, Paris, France
The Cosmic Microwave Background and Cosmology at the end of the Planck satellitte mission
I will describe the observational status of Cosmology after the final delivery of the Planck satelitte, with a short overview of the main achievements and open questions and describe the ambitious plans to move forward.
-
Sebastian Bocquet
LMU, Munich, Germany
Galaxy Cluster Cosmology with the South Pole Telescope
In this talk, I will review the use of galaxy clusters as an accurate cosmological probe. The discussion will follow the most recent analysis of the cluster sample selected through the Sunyaev-Zel’dovich effect in the 2500 square-degree SPT-SZ survey. The sample is supplemented with optical weak gravitational lensing data from Magellan and the Hubble Space Telescope, and X-ray data from Chandra. We will discuss the modelling of the mass-observable relation, the use of weak-lensing data for mass-calibration purposes, and the cosmological and astrophysical implications of our results. I will conclude with an overview over opportunities for SZ cluster cosmology in the next decade.
-
Jens Chluba
University of Manchester, UK
Can relativistic temperature corrections be neglected in the Planck SZ analysis?
I will briefly discuss how relativistic temperature corrections affect the tSZ power spectrum and number count analyses of Planck. Neglecting these effects biases the value of sigma_8 low at the >1sigma level, shifting the derived value closer to the CMB only constraint. We should thus include rSZ in the processing of SZ data.
-
Jacques Delabrouille
APC, Paris, France
The CORE space mission concept
The CORE space mission was proposed to ESA as a Medium-sized next-generation CMB space mission. In this talk, I will review the scientific objectives, mission requirements, and design choices of CORE.
-
Jose Diego
IFCA, Santander, Spain
Constraining Compact Dark Matter with Extreme Magnification Events
I will discuss examples of extreme magnification that have been recently observed and that will be in the near future. These include distant stars at cosmological distances lensed by galaxy clusters or galaxies and lensing of gravitational waves. At large magnifications, the role of microlenes (for instance stars and remnants from the intracluster medium or from the galaxies acting as lenses) become relevant. Observations of this kind can be used to set the strongest limits on exotic forms of dark compact matter, including primordial black holes.
Refs:- http://adsabs.harvard.edu/abs/2018arXiv180604668D
- http://adsabs.harvard.edu/abs/2018ApJ...857...25D
- http://adsabs.harvard.edu/abs/2018NatAs...2..334K Diego et al. In preaparation
-
Marat Gilfanov
Max Planck Institute for Astrophysics, Garching, Germany
Cosmological studies with wide-field X-ray surveys
TBA
-
Shaul Hanany
University of Minnesota, Minneapolis, USA
The Probe of Inflation and Cosmic Origins
The Probe of Inflation and Cosmic Origins (PICO) is a concept for a probe-scale mission that we studied over the last 18 months as part of NASA's preparations for the US 2020 decadal panel. PICO is an imaging polarimeter with a 1.4 m aperture telescope, and 21 frequency bands between 20 and 800 GHz. If flown, PICO will be the most sensitive cosmic microwave background instrument implemented in the next decade. I will describe PICO's science goals and its design.
-
Girish Kulkarni
TIFR, Mumbai
Large Lyman-alpha opacity fluctuations in models of late reionization
High-redshift QSO spectra show large spatial fluctuations in the Lyman-alpha opacity of the intergalactic medium on surprisingly large scales at z>= 5.5. In this talk, I will present a radiative transfer simulation of cosmic reionization driven by galaxies that reproduces this large scatter and the rapid evolution of the Lyman-alpha opacity distribution at 5
-
Yen-Ting Lin
ASIAA, Taipei, Taiwan
Time invariance of the stellar mass--halo mass at high halo mass end: implications on the buildup of cluster galaxy population
The scaling between the total stellar mass of galaxies and cluster mass (Mstar--Mcl) is critical in understanding the buildup of the cluster galaxy population: while its amplitude depends on the star formation efficiency averaged over all progenitor halos, its slope is important in evaluating the strength of tidal stripping in dense environments. In addition, the BCG stellar mass--cluster mass correlation constrains the AGN feedback efficiency in cluster centers. We have measured these correlations with a large cluster sample at z=0.3-1 from the Subaru Hyper Suprime-Cam survey. The Mstar--Mcl relation is found to be independent of redshift, with a slope of 0.7 that indicates a large degree of stripping for member galaxies (implying a huge amount of intracluster light). The invariance in time of the scaling is challenging to reproduce by state-of-the-art simulations. We discuss implications of these scaling relations on the cluster assembly history.
-
Andrea Valerio Macciò
NYU, Abu Dhabi
Dark matter distribution in realistic simulated galaxies
The observed dark matter distribution in galaxies seems to contradict the predictions of the Cold Dark Matter paradigm. These predictions are usually based on pure gravity (Nbody) simulations, raising then the question whether the galaxy formation process my alleviate this tension. Results based on the NIHAO simulation suit show that current data do not disprove nor challenge the CDM model, and that claims in this direction are based on a poor comparison between data and theoretical predictions. I will present some future tests that will help us understanding the dark matter nature.
-
Joseph J. Mohr
LMU & MPE, Munich, Germany
New Galaxy Cluster Science with DES, RASS and SPT: a prelude to eROSITA
Large solid angle multiwavelength surveys are a boon to studies of rare, massive galaxy clusters and their use for tests of cosmology and structure formation. In the 5000 deg2 overlap region of the ROSAT X-ray All Sky Survey (RASS) and Dark Energy Survey (DES), we have applied the new cluster confirmation tool MCMF (Klein+18a) to create a catalog of 2000 (mostly new) X-ray selected galaxy clusters. Crucial for this analysis is the removal of contamination caused by random superpositions of non-cluster X-ray sources with optical clusters. This sample is ~7x larger than published RASS samples over the same area, and it extends to redshift z~1, pushing to lower masses at every redshift (Klein+18b). We validate the contamination and selection function for this sample, finding that the X-ray luminosity functions constructed within redshift bins extending to z=0.9 are in good agreement with expectations from externally calibrated scaling relations and cosmological parameters. We apply this tool also to Sunyaev- Zel’dovich effect (SZE)selected cluster candidatesin the overlap region with DES, going deeper in the SZE maps to construct a much larger cluster sample than that built up previously using cluster by cluster optical followup. The DES dataset also enables improved photometric redshifts and weak lensing mass calibration of the RASS and SPT (and future eROSITA) cluster samples. While the single cluster mass constraints from DES are typically quite weak, the use of large cluster samples to directly constrain the astrophysical observable—mass relations holds promise for an accurate empirical mass calibration that will enable precise and accurate cosmological studies.
-
Pierluigi Monaco
INAF-OATS, Trieste, Italy
Approximate Methods for the Generation of Dark Matter Halo Catalogs in the Age of Precision Cosmology
The next generation of galaxy surveys will allow cosmologists to beat down the statistical uncertainty, so the error on parameter estimation will be dominated by systematics. Proper control of systematics requires the analysis of a large number of simulated catalogs, but the requirements on such simulations make the production of even a single realization a numerical challenge. This has prompted the development of approximated methods, rooted in the cosmological theory developments of the 70's and 80's. I will review this topic, describing the most up-to-date methods and their performance obtained through extensive comparisons carried out in preparation of the Euclid mission.
Reference:>
P. Monaco, 2016, Galaxies, vol. 4, issue 4, p. 53, https://www.mdpi.com/2075-4434/4/4/53 -
Alexandre Refregier
ETH Zurich, Switzerland
Cosmology with the Dark Energy Survey
The Dark Energy Survey is a state of the art imaging survey in the southern hemisphere. We will summarize the status of the experiment and its latest cosmological results.
-
Claudia de Rham
Imperial College UK
Gravitational Rainbows
The recent direct detection of gravitational waves marks the beginning of a new era for physics and astronomy with an opportunity the probe gravity at its most fundamental level and have already been used to successfully constrain or rule out many effective field theories relevant for cosmology. I will discuss the strengths and limitations of these constraints and explore other complementary approaches in segregating between various effective field theories.
-
Roman Scoccimarro
New York University, USA
Galaxy Bias Loops
We discuss the importance of one-loop corrections due to non-linear galaxy bias in predicting the galaxy power spectrum and bispectrum. In particular, we study how to use the time evolution of bias to reduce the number of free parameters while at the same time providing an accurate framework for current and upcoming galaxy redshift surveys.
-
Jonathan Sievers
McGill University, Montreal, Canada
HIRAX and Fast Radio Bursts
The Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX) is a planned 1024-element radio array that will be built in the South African Karoo desert. While it's primary focus is on observing baryon acoustic oscillations, HIRAX will also be a premiere instrument for discovering fast radio bursts (FRBs). With the addition of outrigger stations across southern Africa, HIRAX will also be able to localize a large fraction of its non-repeating FRBs to ~30 mas. With the dramatic increase in FRB discovery rate promised by instruments like CHIME and HIRAX, FRBs can also be used to help probe cosmology.
-
Kandaswamy Subramanian
IUCAA, Pune, India
Turbulent origin of Magnetic fields in Galaxies and clusters
The universe is magnetised, from stars like the Sun, to the large-scale coherent magnetic fields detected in galaxies and galaxy clusters. When and how did they originate? The standard picture involves a cosmic battery which generates a seed magnetic field which is then amplified and maintained by turbulent dynamo. In such dynamos the kinetic energy of motions get converted to magnetic energy. We review the basic idea behind such dynamos and the main challenges they encounter. While it is relatively easy for magnetic energy to grow, explaining the observed degree of spatio-temporal coherence of cosmic magnetic fields remains challenging. Understanding the magnetic history of the universe will also be important for the many processes involved in galaxy and galaxy cluster formation and evolution.
-
Kenneth Wong
Kavli IPMU / NAOJ, Tokyo, Japan
Cosmology from Gravitational Lens Time Delays
Strong gravitational lens systems with time delays between the multiple images are a powerful probe of cosmology and astrophysics. In particular, the time-delay distance from such a system is primarily sensitive to the Hubble constant (H0) that is key to probing dark energy, neutrino physics, and the spatial curvature of the Universe, as well as discovering new physics. The H0 Lenses In COSMOGRAIL’s Wellspring (H0LiCOW) project aims to measure H0 from several lensed quasars using deep Hubble Space Telescope imaging, precise time delay measurements from the COSMOGRAIL monitoring project, a measurement of the velocity dispersion of the lens galaxies, and a characterization of the mass distribution along the line of sight. Based on analyses of the first four H0LiCOW lenses, we constrain H0 to ~3% precision for a flat Lambda CDM cosmology. These results are consistent with independent determinations of H0 using type Ia supernovae calibrated by the distance ladder method, and are in moderate tension with the latest Planck results for a similar cosmology, hinting at possible new physics beyond the standard LCDM model and highlighting the importance of this independent probe.
-
Shadab Alam
University of Edinburgh, UK
Solving the nonlinear galaxy clustering
The galaxy clustering at scales below 30 Mpc/h have been measured with very high precision in several galaxy redshift surveys such as GAMA, BOSS, eBOSS, VIPERS etc. But these measurements are very difficult to model due to non-linear structure formation, especially in redshift space. This requires modelling the evolution of both the density and velocity field of the universe in the highly non-linear regime. It is difficult to use an analytical model in such a non-linear regime as it fails to satisfy the assumption of small perturbations. In this talk, I will describe how one can try to model such a regime with N-body simulation and what can we learn from such an analysis with a HOD (halo occupation distribution) approach. I will also show some latest result from GAMA galaxy sample at low redshift.
-
Surhud S More
IUCAA, Pune
Cosmological constraints from the Subaru Hyper Suprime-Cam Survey
How does dark energy affect the growth of cosmic structure? The Hyper Suprime-Cam Survey conducted from the Subaru telescope is a 1400 square degree imaging survey of the sky designed to answer this question. The depth, the wide field of view combined with the excellent imaging quality makes it ideal to study the shapes of millions of galaxies in a large part of the sky. Gravitational lensing, the bending of light due to gravity, induces tiny distortions in the shapes of these galaxies. These tiny distortions together reveal the matter distribution and can be used to measure the growth of cosmic structure. I will report on the cosmology results from the first year of the HSC survey covering 140 square degrees on the sky. We measure and model the cosmic shear power spectrum and constrain the amplitude of density fluctuations in the Universe today. Comparisons to the fluctuations expected from Planck in the CMB data shows hints of small deviations. I will discuss the implications and the future prospects of confirming or ruling out these deviations.
-
R. Srianand
IUCAA, Pune
Science with Thirty Meter Telescope
In the next decade three extremely large optical-near-IR telescopes will be operational. Indian Astronomy community will be part of one of these telescopes called "Thirty Meter Telescope (TMT)". In this talk I will summarize various Indian contribution to this project and detailed science cases that will be pursued with TMT.
-
Tirthankar Roy Choudhury
NCRA, Pune
Cosmology and high-redshift universe with the Square Kilometre Array
The Square Kilometre Array (SKA) is an international effort to build the largest radio telescope in the world with the aim of studying different problems in astrophysics, cosmology and fundamental physics. India is one of the eleven countries participating in the project. In this talk, we will discuss the specifications and capabilities of the SKA along with the anticipated timeline. Some specific contributions made by Indian community towards the development of the project will also be highlighted. Finally, we will discuss some of the most interesting problems in cosmology and high-redshift universe that can be studied using the SKA.
-
Sandip Trivedi
TIFR, Mumbai
TBA
TBA
-
Biman B. Nath
RRI, Bengaluru
CGM to IGM-- Diffuse gas in the universe
Most of the baryons in the Universe is in a diffuse state. It is either confined to halos around galaxies (circumgalactic medium), or to galaxy clusters (intracluster medium) or it traces the large scale structure of the universe (intergalactic medium). The evolution of structures in the universe has left imprints on this diffuse gas, in the form of its thermal properties, ionisation state and metallicity. We will discuss different physical processes that are important for the diffuse matter in the universe, and what they tell us about the evolution of galaxies and structures.
-
Shiv Sethi
RRI, Bengaluru
Detecting HI signal from the epoch of reionization
I shall discuss the status of ongoing efforts to detect this signal. Currently multiple radio interferometers are involved in this endeavour---GMRT, MWA, LOFAR, and PAPER. In particular, I shall focus on our ongoing work using MWA tracking and drift scan data. Also the possible role uGMRT might play in this effort would be highlighted.
-
Tarun Souradeep
IUCAA, Pune
CMB-Bhārat: A Comprehensive next-gen CMB mission proposal
The observations of the spectrum and anisotropies of the primordial cosmic microwave background (CMB) radiation has spearheaded the transition into an era of precision cosmology, with accurate determination of the cosmological parameters, critical inferences of the early universe and origin of structures. However, over 90% of the polarisation information and an almost untouched spectral information remains to be mapped out with more capable mission with high value returns for Cosmology and ultra-High Energy Physics. I present a case for an next generation CMB space mission as an unique opportunity for India that has presented itself to partake in potentially path breaking discovery, together with a number of guaranteed high science dividends and providing a rich legacy astronomical data.
-
Lyman Page
Princeton University, USA
Measuring the CMB from Chile: a look ahead
Chile is an excellent site from which to measurement the CMB. One benefit is the ability to observe large regions of sky. For sub-degree scale measurements, there is excellent overlap with optical surveys such as LSST and DESI. For measuring primordial B-modes, modulators are likely necessary and have been demonstrated. We describe in broad terms the observing program for Chile for the next few years, in particular the Simons Observatory, and its complementarity to other efforts in space and on the ground.
-
Francesco Piacentini
Sapienza University of Rome, Italy
LSPE and COSMO instrumentos for CMB measurements
The Observational Cosmology group at University of Rome in working on measurements of the CMB since years. The next generation of instruments under development are the Large Scale Polarisation Explorer (LSPE) for CMB polarisation, and COSmic Monopole Observer (COSMO), for absolute spectrum of the CMB. I briefly present the two instruments, their status and prospectives.
-
Ritoban Basu Thakur
Observational Cosmology Group at Caltech
The BICEP-Array Telescope, searching for primordial inflation from the South Pole
Our comprehensive understanding of early universe of physics strongly indicates an epoch of rapid inflation. Detection of a curl-type (B-mode) polarization at degree scales would be a direct proof of inflation. The BICEP/Keck collaboration, with ever improving generations of telescopes operating at the South Pole, has been leading this search for inflation. The new BICEP Array (BA) set of telescopes will begin observing at the South Pole starting in 2020. BA will measure polarized CMB in bands centered at 30, 40, 90, 150, 220 and 270 GHz respectively. The first re ceiver to be deployed will perform the 30/40 GHz measurements, enabling us to understand and therefore model synchrotron contamination to the CMB with high confidence. The following receivers (ranging 90-270 GHz) will focus on the CMB and dust emissions. Therefore with data-driven parametric modeling of all the foregrounds, we will deliver extremely deep and clean CMB polarization maps furthering the search for inflation. This talk will present an overview of the design and expected performance of the BICEP Array instruments, focusing on the 30/40 GHz receiver. I will also outline how BICEP Array will inform the future CMB ‘Stage 4’ experiments, and the “delensing” science case being developed with our neighbor, the South Pole Telescope (SPT-3G).
-
Zeeshan Ahmed
SLAC National Accelerator Laboratory, California
CMB-S4, the ultimate ground-based CMB polarization survey
Ground-based CMB imaging instrumentation is continuing generational leaps in photon-noise-limited sensitivity, while our understanding and mitigation of systematic errors and biases advances for the most difficult CMB measurements such as that of tensor-to-scalar ratio. CMB-S4 is an ambitious multi-frequency, ground-based CMB polarization survey program over 40% of the Southern sky proposed to be built and operated in Chile and Antarctica in the 2020s. It aims to detect or rule out most models of inflation that naturally explain the scalar spectral index (r>0.001); distinguish neutrino mass hierarchy at high significance; search for thermal relics in the early history of the universe before the QCD phase transition; significantly tighten constraints on the epoch of reionization; probe baryonic feedback in galaxy evolution; provide a legacy catalog of clusters and mm-wave sources; and open a new window of discovery in mm-wav e time-domain astrophysics including imaging of gamma-ray bursts and active galaxies. In this talk I will provide a brief introduction to CMB-S4 and a broad overview of its science goals.
-
Benjamin Wandelt
Institut D'Astrophysique de Paris, France
TBA
TBA
-
Shadab Alam
University of Edinburgh, UK
Solving the nonlinear galaxy clustering
The galaxy clustering at scales below 30 Mpc/h have been measured with very high precision in several galaxy redshift surveys such as GAMA, BOSS, eBOSS, VIPERS etc. But these measurements are very difficult to model due to non-linear structure formation, especially in redshift space. This requires modelling the evolution of both the density and velocity field of the universe in the highly non-linear regime. It is difficult to use an analytical model in such a non-linear regime as it fails to satisfy the assumption of small perturbations. In this talk, I will describe how one can try to model such a regime with N-body simulation and what can we learn from such an analysis with a HOD (halo occupation distribution) approach. I will also show some latest result from GAMA galaxy sample at low redshift.
-
Sharvari Nadkarni-Ghosh
IIT, Kanpur
Treating shell crossing in Lagrangian perturbation theory
Lagrangian Perturbation Theory (LPT) has been widely used to model the non-linear growth of large-scale structure analytically. However, this theory suffers from two drawbacks: it does not converge in voids and is not valid beyond shell crossing. The first problem can be overcome by the method of Lagrangian re-expansions [1,2] while the second can be addressed by adding viscous terms. In this talk, I will discuss how to incorporate the viscous terms within the Lagrangian re-expansion framework and as an example of the scheme, demonstrate virialization in a spherical top-hat model. References: 1. S. Nadkarni-Ghosh and D. F. Chernoff, MNRAS 431 (arXiv:1211.5777) 2. S. Nadkarni-Ghosh and D.F. Chernoff, MNRAS 410 (arxXiv: 1005.1217) 3. S. Nadkarni-Ghosh and D.F. Chernoff, in preparation
-
Subinoy Das
IIA, Bangalore
Explaining planck H 0 and \sigma 8 anomally through dark matter decay into radiation
TBA
-
Tuhin Ghosh
NISER, Khurda
Detection of the Thermal Sunyaev-Zel’dovich effect from voids in the large scale structure
Voids have a completely different environment altogether, these being highly under-dense regions can present an scenario for the study of formation and evolution of galaxies, without much hindrance from the complex interactions taking place in other regions like cluster of galaxies. Thermal Sunyaev-Zel’dovich effect has been used in analysis of massive structures such as clusters, or very massive galaxies to find out the presence of hot gas, although it is a tiny fluctuation still is can be observed very effectively when many objects are stacked up together. We use a catalog of void galaxies to show the circumgalactic matter heating up. We are the first to report that contrary to earlier results which show the effects only in massive structures in the stellar mass range of upwards of 10^11.3 M⊙ for a good signal- to-noise (SNR), the best SNR in our case is in the regime of less massive galaxies i.e. < 10^11.3M⊙. We propose that the heating of CGM is due to stellar feedback and not AGN feedback.
-
Suchetana Chatterjee
Presidency Univ, Kolkata
The Sunyaev Zeldovich Effect from Quasar Feedback
TBA
-
L. Sriramkumar
Indian Institute of Technology Madras, Chennai
Primordial features from ekpyrotic bounces
Certain features in the primordial scalar power spectrum are known to improve the fit to the cosmological data. We examine whether bouncing scenarios can remain viable if future data confirm the presence of such features. In inflation, the fact that the trajectory is an attractor permits the generation of features. However, bouncing scenarios often require fine tuned initial conditions, and it is only the ekpyrotic models that allow attractors. We demonstrate, for the first time, that ekpyrotic scenarios can generate specific features that have been considered in the context of inflation. arXiv:1809.03229 [astro-ph.CO]
-
Debika Chowdhury
TIFR, Mumbai, India
Primordial magnetogenesis and non-â â Gaussianities
Primordial magnetic fields generated in the early universe are expected to have acted as seed fields for the large scale magnetic fields observed today. The origin of primordial magnetic fields has been investigated in inflationary scenarios and it has been possible to generate scale invariant magnetic fields of relevant strengths that are in accordance with observations. In this talk, after a brief review of inflationary magnetogenesis, I shall discuss how one can obtain scale invariant magnetic fields in bouncing scenarios. I shall also describe the characteristics of the cross-correlations between primordial magnetic fields and perturbations in a scalar field in bouncing universes, and how the signatures of these cross-correlations differ from those obtained in de Sitter inflation. Further, I shall discuss the evaluation of the cross-correlations between primordial helical magnetic fields and perturbations in a scalar field in de Sitter inflation. Arxiv references: arXiv:1604.02143 [gr-qc]; arXiv:1807.05530 [astro-ph.CO]; arXiv:1807.07477 [astro-ph.CO]
-
Xun Shi
South-Western Institute For Astronomy Research, Kunming
Turbulence and non-thermal pressure in galaxy clusters
Galaxy clusters are promising probes for cosmology, and yet, their astrophysical complexity leads to significant systematical bias as shown by the Planck CMB-cluster discrepancy. Turbulence in the intracluster medium (ICM) and the corresponding non-thermal pressure are a central piece of the astrophysical complexity that has not been well-explored. I will present a successful phenomelogical model of turbulence-induced non-thermal pressure, as well as some insights into the underlying physics. In particular, the influence of ICM density stratification on turbulence dissipation, an effect so far neglected, can lead to the typical radial distribution of ICM turbulence.
-
Asif Iqbal
RRI, Bengaluru
TBA
TBA
-
Priyanka Singh
INAF, Trieste
Cosmology dependence of galaxy cluster scaling relations
Galaxy clusters are one of the most massive gravitationally bound objects in the Universe. They is also extremely powerful probes of underlying cosmology. Galaxy clusters are generally probed through a variety of observable-mass scaling relations. Therefore, it is important to understand the cosmology dependence of these scaling relations. To do this, we use Magneticum simulations (including radiative cooling, UV background heating, SNe and AGN feedback) exploring twelve different sets of cosmological parameters (varying Hubble constant, matter density, baryon density and sigma8). We construct a universal scaling relation (with log-normal scatter) for gas mass, temperature, luminosity, velocity dispersion, Sunyaev-Zel’dovich effect and the stellar content of galaxy clusters. We discuss the challenges involved in obtaining such universal scaling relation for gas luminosity and stellar mass and the possible solutions.
-
Suvodip Mukherjee
Flatiron Institute, New York
Peering into the Universe with multi-messenger Cosmology
Next generation missions in astrophysics and cosmology are going to explore the Universe over a wide range of redshifts using multi-messenger probes such as electromagnetic waves, gravitational waves, etc. This new provision brings a unique cosmological window to explore the fundamental physics and to unveil cosmic history over a wide range of redshifts. The speaker will introduce a new cosmological multi-messenger probe which will be accessible from the upcoming missions. This new avenue will improve our understanding of the theory of gravity and other aspects of fundamental physics. Co-authors: Benjamin D. Wandelt and Joseph Silk.
-
Susmita Adhikari
Stanford University, Stanford
Galaxy evolution in clusters - Insights from splashback radius and velocity space
I will overview the theoretical and observational developments in splashback radius and talk about how it can be used as a tool to understand galaxy evolution in cluster halos. I will also speak about how combining information about the spatial distribution of galaxies with their distribution in the velocity space can help us distinguish between different models of quenching of star formation around cluster mass halos.
-
Shreya Banerjee
Ben Gurion University of Negev, Beer Sheba
Bounce and cyclic cosmology in weakly broken galileon theories
We investigate the bounce and cyclicity realization in the framework of weakly broken galileon theories. We study bouncing and cyclic solutions at the background level, reconstructing the potential and the galileon functions that can give rise to a given scale factor, and presenting analytical expressions for the bounce requirements. We proceed to a detailed investigation of the perturbations, which after crossing the bouncing point give rise to various observables, such as the scalar and tensor spectral indices and the tensor-to-scalar ratio. We also show that a nonsingular bounce, free of ghosts and gradient instabilities, can be realized in the framework of Horndeski or generalized Galileon cosmology. Finally, in order to make the analysis more transparent we provide an explicit example where a nonsingular bounce can be achieved, without manifest theoretical pathologies. arXiv links: 1604.06932, 808.01170, 1807.00346
-
Subhajit Ghosh
Tata Institute of Fundamental Research, Mumbai
Dark neutrino interactions make gravitational waves blue
TBA
-
Anirban Roy
SISSA, Trieste
Observing Patchy reionization
I'll talk about how detachability of patchy reionization by future CMB experiments. I'll discuss how secondary CMB B mode can be generated due to patchy reionization. reference link: https://arxiv.org/abs/1801.02393
-
Sandeep kumar acharya
TIFR, Mumbai MUMBAI,India
Beyond y, i, and mu: Rich structure of non-thermal relativistic CMB spectral distortions from high energy particle cascades
It is generally assumed that for energy injection before recombination, all of the injected energy is dissipated as heat in the baryon-photon plasma, giving rise to the y-type, i-type, and mu-type distortions in the CMB spectrum. We show that this assumption is incorrect when the energy is injected in the form of energetic (i.e. energy much greater than the background CMB temperature) particles. We evolve the electromagnetic cascades, from the injection of high energy particles, in the expanding Universe and follow the CMB spectral distortion resulting from the interaction of the electromagnetic shower with the background photons, electrons, and ions. The electromagnetic shower loses a substantial fraction of its energy to the CMB spectral distortions before the energy of the particles in the shower has degraded to low enough energies that they can thermalize with the background plasma. This spectral distortion is the result of the interaction of non-thermal energetic electrons in the shower with the CMB and thus has a shape that is substantially different from the y-type or i-type distortions. The shape of the final \emph{non-thermal relativistic} (ntr-type) CMB spectral distortion depends upon the initial energy spectrum of the injected electrons, positrons, and photons and thus has information about the energy injection mechanism e.g. the decay or annihilation channel of the decaying or annihilating dark matter particles. The shape of the spectral distortion is also sensitive to the redshift of energy injection. Our calculations open up a new window into the energy injection at z
-
Matt Hilton
University of KwaZulu-Natal, Durban
The Atacama Cosmology Telescope Sunyaev-Zel'dovich Galaxy Clusters Survey
The Atacama Cosmology Telescope (ACT) is conducting an effectively mass-limited search for galaxy clusters using the redshift-independent Sunyaev-Zel'dovich (SZ) effect. In this talk I will describe our recent work on constructing the two-season ACTPol galaxy cluster catalog (arXiv:1709.05600), and discuss mass calibration of this sample using weak-lensing observations. I will also describe ongoing work with Advanced ACT (AdvACT), which has surveyed approximately 14,000 square degrees of the southern sky, and at the time of writing has detected more than 1500 galaxy clusters out to z = 2. With its clean, well-defined selection function, it is an ideal sample to use to study galaxy evolution in clusters, constrain cosmological parameters, and measure the evolution of both thermal and non-thermal emission by the intracluster medium.
-
Moumita Aich
University of KwaZulu-Natal, Durban, South Africa
Cosmology with HIRAX: combining 21-cm and large-scale structure surveys
The Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX) is a radio telescope array led by University of KwaZulu-Natal, South Africa, that will map nearly all of the southern sky in radio continuum and neutral hydrogen line emission over a frequency range of 400 to 800 MHz. Optical surveys such as Large Synoptic Survey Telescope (LSST), Dark Energy Spectroscopic Instrument (DESI), EUCLID and the Wide Field Infrared Survey Telescope (WFIRST) will also probe the large-scale structure of the universe with much higher precision and depth by mapping the galaxy distribution. Tracing out the visible universe provides a tracer of the underlying matter distribution which in principle correlates with 21-cm cosmology surveys. Both provide us with tracers of dark matter distributions, therefore we expect cross-correlations between the overlapping surveys will provide novel constraints on cosmological parameters, redshift-dependent neutral hydrogen fraction and bias, and probe the relationship between stars and gas in their dark matter halos.
-
Pavan Kumar Aluri
Indian Institute of Technology (BHU), VARANASI
TBA
In our recent work, we explored the alignments among even and odd multipoles separately. We found that the common alignment axes form two distinct groups, one in the northern hemisphere and the other in the southern hemisphere contrary to our expectation that they should be randomly oriented over the sky. The even multipoles' common alignment axes are pointing roughly in the same direction as the dipole-quadrupole-octopole alignment and the maximum even mirror parity axis. The odd multipoles' common alignment axis span the region containing the low-l dipole power asymmetry axis and the axis of odd mirror parity maximum. Results of our study are part of the paper : Alignments of parity even/odd-only multipoles in CMB, Pavan K. Aluri, John P. Ralston and Amanda Weltman, Monthly Notices of the Royal Astronomical Society (2017), v472, p2410 https://arxiv.org/abs/1703.07070
-
Sumanta Chakraborty
Indian Association for the Cultivation of Science, Kolkata
TBA
TBA
-
Anjan Ananda Sen
Jamia Millia Islamia Central University, New Delhi
TBA
TBA
-
Pranjal Trivedi
University of Hamburg, Germany
Axion-like Dark Matter Constraints from CMB Birefringence
Axion-like particles (ALPs) are leading dark matter candidates which also arise in effective field theories. We present a sensitive probe for ultra-light dark matter or ALPs - birefringence in the cosmic microwave background (CMB). Birefringence arises from the oscillating ALPs' effective refractive index and is also relevant for laboratory dark matter searches. Constraints derived from the CMB on axion-photon coupling represent three or four orders of magnitude improvement over prior constraints, with further prospects for upcoming cosmological birefringence observations. These constraints on significant regions of coupling vs. ALP mass parameter space and ultra-light dark matter models, are independent of assumed magnetic fields and relatively robust to ALP dark matter fraction limits.
-
Anirban Das
TIFR, Mumbai
Large scale structure with delayed dark matter formation
Various cosmological observations tell us that about 24% of the total energy density of the universe exists in the form of nonrelativistic dark matter. But they fail to provide any information about the epoch or method of formation of the dark matter. There are particle physics models where the cold dark matter is formed late after a phase transition during the history of the universe. A model independent way to probe these models is to study their cosmological aspects. We shall try to compute the matter power spectrum of this delayed dark matter model and discuss the new effects originating due to the late formation of cold dark matter. We shall also try to identify the nature of the dark sector prior to the phase transition from its imprints on the matter power spectrum.
-
Pravabati Chingangbam
IIA, Bengaluru
The shape of quantum fluctuations
Probing the geometry and topology of cosmological fields of the CMB and the large scale structure of matter shed light on the quantum origins of the universe and its subsequent evolution. We will describe how new statistical tools, the Minkowski tensors, can be used for this purpose. The mathematical properties of the Minkowski tensors that are crucial for new morphological information of cosmological fields will be elaborated. We will demonstrate their usefulness with applications to the CMB and LSS. Arxiv references: 1805.08752, 1712.07466, 1707.04386, 1608.07452.
-
Mousumi Das
IIA, Bengaluru
A Radio/X-ray Study of the Hot and Warm Gas around Isolated Galaxies in Voids
We present low frequency radio observations of the extended emission around galaxies lying within voids. Voids contain a sparse but significant population of galaxies that show signatures of ongoing star formation and AGN activity. They are generally late type, gas rich disk galaxies and appear to be similar in nature to normal galaxies in denser environments but are evolving at a much slower rate. The sparse environment of voids allows us to study the evolution of the circum galactic medium (CGM) around AGN or starburst host galaxies in isolated environments. It also allows us to estimate how star forming void galaxies contribute to the hot gas within voids. In this presentation we show that there can be significant radio emission around void galaxies, especially from those lying within larger voids, and in some cases there can be extended X-ray emission as well. The hot/warm gas around these galaxies is due to stellar and AGN feedback processes associated with void galaxies, both of which are triggered by either galaxy interactions or gas accretion from the intergalactic medium. We discuss the implications of our results for understanding the evolution of void galaxies and the hot gas within voids.
-
Niladri Paul
IUCAA, Pune
Calibration of satellite red fraction using colour-dependent clustering measurement from SDSS
Colour of galaxies is a key towards understanding galaxy evolution and star-formation history. In all the statistical models depending on colour, one also needs the red fraction of the central and satellite galaxies separately. One can compute them using a galaxy group catalogue as e.g. Yang catalogue, but these catalogues suffer from issues related to incompleteness and impurity. Another way to model this quantity is from the colour-dependent clustering measurements from SDSS. In this work, the speaker will talk about this second approach within a precision halo model framework which incorporates measurement of halo correlation function directly from N-body simulations.
-
Vikram Rentala
IIT, Bombay
Dark Matter microlensing with GAIA
TBA