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Talk Abstract
1- School Inauguration- Dr. Mukesh Kumar Director, CEFIPRA, Indo-French Centre for the Promotion of Advanced Research (IFCPAR/CEFIPRA) , New Delhi, India --------------------------------------------------------------------------------------------------------------------------------------------------------------- 2- Cosmic Reionization- Dr. Tirthankar Roy Choudhury National Centre for Radio Astrophysics, Tata Institute of Fundamental Research (NCRA-TIFR), Pune, India --------------------------------------------------------------------------------------------------------------------------------------------------------------- Abstract : In these lectures, we will discuss (i) the physics of reionization, (ii) methods of probing the reionization epoch observationally, (iii) future probes of reionization using the 21cm line.
3- Galaxy Formation Basics - Prof. Bruno Guiderdoni Centre de Recherche Astrophysique de Lyon (CRAL) --------------------------------------------------------------------------------------------------------------------------------------------------------------- Abstract:In this introductory lecture I will present the theoretical framework of galaxy formation in an expanding universe. After a brief historical foreword, I will review: 1) The power spectrum of density fluctuations; 2) the theory of linear collapse; 3) the Top Hat model as a "toy model" of non-linear collapse and halo formation ; 4) The cooling of bayons within the potential wells of dark matter haloes. This will set the ground for the subsequent presentations of the Semi-Analytical approach and the numerical simulations of galaxy formation.
4-Galaxy evolution and dynamics -
Inter University Centre for Astronomy and Astrophysics (IUCAA), Pune - India
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5- Cosmological simulations of galaxy evolution - Dr. Jokim Rosdahl Centre de Recherche Astrophysique de Lyon (CRAL) --------------------------------------------------------------------------------------------------------------------------------------------------------------- Abstract :Cosmological simulations are an indispensable tool to interpret observations and understand the complex and non-linear physics of galaxy formation. I will describe how we model the typical components of cosmology, dark matter, gas, and stars in cosmological simulations, and how we add to that the emission, propagation, and absorption of radiation — an important component for self-consistent reionisation simulations — in our RAMSES-RT code. I will review results from recent cosmological simulation works, with a focus on reionisation. In a following hands-on session, we will try out RAMSES-RT, with two-dimensional numerical experiments of Stromgren spheres and externally illuminated clouds, playing with the hydrodynamical reaction of gas as it is photo-ionised.
6- Galaxy formation in a ΛCDM Universe: the semi-analytic approach - Dr. Thibault Garel Centre de Recherche Astrophysique de Lyon (CRAL) --------------------------------------------------------------------------------------------------------------------------------------------------------------- Abstract :In the framework of ΛCDM, the mass content of the Universe is dominated by an invisible component, known as dark matter. The formation of structures arises from primordial density fluctuations that can grow and collapse into gravitationally bound objects. Galaxies, which are made of baryons, form through the condensation of the gas within these haloes of dark matter. In this context, the birth and fate of galaxies is directly linked to the hierarchical assembly of dark matter structures across cosmic time. In parallel, the formation of galaxies inside haloes is the result of the complex interaction of many different processes (gas accretion, star formation, mergers, feedback from supernovae, etc) that are responsible for the wide diversity of galaxy properties observed in extra-galactic surveys (e.g. morphologies, colours, rates of star formation). The so-called semi-analytic approach provides an efficient way to combine these different aspects into a coherent picture of galaxy formation in a cosmological context. In this lecture, I will present the methodology used in state-of-the-art semi-analytic models (SAM), the main physical ingredients included, the pros and cons of SAMs, and how their predictions can be compared to observations.
7- Indirect diagnostics to detect the escape of ionising radiation for galaxies at the epoch of reionization - Dr. Anne Verhamme University of Geneva, Switzerland --------------------------------------------------------------------------------------------------------------------------------------------------------------- Abstract : Cosmic reionization corresponds to the period in the history of the Universe during which the predominantly neutral intergalactic medium was ionised by the emergence of the first luminous sources. Young stars in primeval galaxies may be the sources of reionization, if the ionising radiation, called Lyman continuum (LyC), that they produce can escape their interstellar medium: the escape fraction of LyC photons from galaxies is one of the main unknowns of reionization studies. In this lecture, I will review three indirect diagnostics of LyC leakage that were recently reported in the literature, and present recent observations and simulations of these diagnostics. The first diagnostic for LyC leakage relates the escape of the strongly resonant Lyman-alpha radiation from galaxies to the LyC escape. The second diagnostic proposes that the strength of Oxygen lines ratios can trace density-bounded interstellar regions. The third diagnostic relates the metallic absorption line strengths to the porosity of the absorbing interstellar gas in front of the stars. The increasing opacity of the intergalactic medium with redshift renders direct LyC detections impossible during reionisation. Indirect methods are the only probes of LyC leakage in the distant Universe, and these indirect diagnostics will soon become observables at the redshifts of interest with JWST, revealing the role of galaxies as the sources of cosmic reionization.
8-Analytical modelling of H II bubbles during reionisation-
Inter University Centre for Astronomy and Astrophysics (IUCAA), Pune - India
--------------------------------------------------------------------------------------------------------------------------------------------------------------- Abstract : The excursion set approach is a very successful tool in building simple and intuitive analytical models of the formation of cosmological large scale structure. I will discuss an application of the excursion set approach to modelling the evolution of ionised bubbles during the epoch of reionisation, highlighting the insights gained as well as pitfalls. Such analyses are potentially useful for predicting the observability of signals targeted by upcoming experiments such as the SKA.9-Large Scale structures -
Inter University Centre for Astronomy and Astrophysics (IUCAA), Pune - India
--------------------------------------------------------------------------------------------------------------------------------------------------------------- 10- Gravitational Lensing and MUSE- Dr. Centre de Recherche Astrophysique de Lyon (CRAL) --------------------------------------------------------------------------------------------------------------------------------------------------------------- Abstract : The MUSE integral-field unit (IFU) spectrograph is a powerful instrument, capable of providing radial velocity and kinematic information for hundreds of galaxies over a large (1 square arcmin) field of view in a single exposure. One area that has benefited tremendously from MUSE as a redshift engine is gravitational lensing, as knowing the distances of both the foreground and background galaxies makes it possible to derive physical parameters from the lensing data, such as the mass distribution of the deflector or the intrinsic brightness of the background sources. In this talk I will highlight some of the recent efforts combining lensing and MUSE data, especially the work being done by the MUSE Lensing Clusters GTO team. In particular, I will present new mass models of the Frontier Field clusters, highlight the resolved spectroscopic properties of lensed Giant Arcs, and discuss endeavors in detecting and classifying new, distant Lyman-alpha emitters.
11- Galaxy Formation and Evolution from Deep Spectroscopic Surveys- Prof. Laurence Tresse Centre de Recherche Astrophysique de Lyon (CRAL) --------------------------------------------------------------------------------------------------------------------------------------------------------------- Abstract : Cosmic Star Formation History and deep spectroscopic surveys.
12- Formation and Evolution of Galaxies -
Inter University Centre for Astronomy and Astrophysics (IUCAA), Pune - India
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13- From the upgraded GMRT to the SKA : an Indian perspective- Prof. Yashwant Gupta National Centre for Radio Astrophysics, Tata Institute of Fundamental Research (NCRA-TIFR), Pune, India --------------------------------------------------------------------------------------------------------------------------------------------------------------- Abstract : The Giant Metrewave Radio Telescope (GMRT) is today a major international Radio Astronomy facility working in five discrete bands in the frequency range of 150 MHz to 1500 MHz, with a maximum instantaneous bandwidth of 32 MHz. Consisting of 30 fully steerable antennas of 45 metre diameter each, it can be used as an aperture-synthesis array for imaging, as well as a phased array to study compact radio sources such as pulsars. The GMRT has produced several important results in the past 15 years of operations -- a few interesting ones will be highlighted. The GMRT is undergoing a major upgrade that will improve its sensitivity by a factor of upto three and make it a much more versatile instrument. The goal is to have seamless frequency coverage from about 100 to 1500 MHz, with a maximum instantaneous bandwidth of 400 MHz; improved receiver systems with higher G/Tsys; versatile digital back-end correlator and pulsar receiver usig the latest FPGA and GPU technologies; revamped servo system; sophisticated monitor and control system; and matching improvements in infrastructure and computing. This upgrade will keep the GMRT at the forefront as one of the most sensitive facility in the 200 to 1000 MHz range, till the SKA phase I comes along. Most of the sub-systems are nearing completion and the upgrade GMRT has been released to users in a phased manner in the last couple of years, with the final release planned for later this year. Overview of the upgrade activities, some early results from the upgraded GMRT and its future potential will be highlighted. Looking a bit further into the future, the SKA is the major project that involves many countries today. The current status of Indian participation in the SKA project and plans for the future will be presented. 14-Gravitational Lens -
Tata Institute of Fundamental Research (TIFR), Homi Bhabha Road, Mumbai 400 005 - India --------------------------------------------------------------------------------------------------------------------------------------------------------------- Einstein's General Relativity relates the Structure of the Space-Time with its Energy content, which implies that a massive body curves the space around it. Gravitational lens is a direct consequence of the shear on a beam of light propagating along this curved space and it is one of the earliest important tests of Relativity. This manifests as multiple images of a background object or extended linear structures like arcs or rings or a field of slight distortion of background galaxies called the lens shear, from which Astronomers determine the mass of the lensing object en route as well as the large scale geometry of the Universe. 15- X-ray studies of shock and cold-fronts in galaxy clusters- Dr. Department of Physics, Dyanand Science College, Latur 413512, India --------------------------------------------------------------------------------------------------------------------------------------------------------------- Abstract : Gravitational lensing by massive galaxy clusters is one of the main routes being used to probe the very distant Universe. By combining the power of gravitational magnification with the high sensitivity of space-based (HST) or ground-based instruments (e.g. MUSE) it is possible to probe the luminosity function at high redshift down to the lowest luminosities, typically M_AB~ - 15 in the rest-frame UV. With the advent of JWST, the combination of deep imaging / spectroscopy and strong lensing is the only way to characterise some of the most distant galaxies at z>9. 16- Galaxy clusters and SKA-
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17- Galaxy clusters and lensing- Dr. Centre de Recherche Astrophysique de Lyon (CRAL) --------------------------------------------------------------------------------------------------------------------------------------------------------------- Abstract : Gravitational lensing by massive galaxy clusters is one of the main routes being used to probe the very distant Universe. By combining the power of gravitational magnification with the high sensitivity of space-based (HST) or ground-based instruments (e.g. MUSE) it is possible to probe the luminosity function at high redshift down to the lowest luminosities, typically M_AB~ - 15 in the rest-frame UV. With the advent of JWST, the combination of deep imaging / spectroscopy and strong lensing is the only way to characterise some of the most distant galaxies at z>9. 18-ALMA: Molecular gas across cosmic times and environments- Observatoire de Paris - Site de Paris (OP) -
Observatoire de Paris, INSU, CNRS : UMR8112, 61 Av de l'Observatoire 75014 PARIS - France
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Collège de France (CDF)
Collège de France, 11 place Marcelin Berthelot F-75231 Paris Cedex 05 - France
--------------------------------------------------------------------------------------------------------------------------------------------------------------- Abstract: Observations over redshift reveal that star formation is progressively quenched in more massive galaxies and in denser environments. What are the main physical mechanisms able to moderate and stop star formation? It will be shown how the gas fraction decreases with time, while the bulge-to-disk mass ratio increases. Both play a role in the winding down of star formation, and the morphology quenching.
19-Multiwavelength view on AGNs -
Tata Institute of Fundamental Research (TIFR), Homi Bhabha Road, Mumbai 400 005 - India --------------------------------------------------------------------------------------------------------------------------------------------------------------- Nearby AGN, like Seyfert Galaxies, are ideal objects to give a multi-wavelength perspective on a variety of phenomena occurring near supermassive black holes like structure of accretion disks, disk-jet connection, effect of black hole spin and magnetic field for jet acceleration etc. X-ray spectral variability studies using Chandra and XMM and long term multi-wavelength monitoring using RXTE and Swift have firmly established the close similarities between AGN and stellar mass black holes. Wide band X-ray spectral studies using NuSTAR and multi-wavelength observations using AstroSat have provided new insights into this filed. I will review recent results from AstroSat on multi-wavelength studies of nearby AGN.
20-A Radio View on AGN -
National Centre for Radio Astrophysics - Tata Institute of Fundamental Research (NCRA), Pune - India
--------------------------------------------------------------------------------------------------------------------------------------------------------------- Active Galactic Nuclei (AGN) are actively accreting supermassive black holes that sometimes possess parsec-scale or kiloparsec-scale radio jets. The origin of these outflows is an important unsettled question in AGN astrophysics. The different extents, powers and morphology of these outflows suggest complex differences in the central engines of AGN. In order to fully understand these central engines, outflows are being studied at multiple wavelengths ranging from X-rays by space-borne telescopes to low radio frequencies by ground-based telescopes like the GMRT and LOFAR. I will present an overview of Radio AGN with current and upcoming telescopes.
21-HI 21-cm studies of galaxies -
Inter University Centre for Astronomy and Astrophysics (IUCAA), Pune - India
--------------------------------------------------------------------------------------------------------------------------------------------------------------- Deep galaxy surveys have revealed that the global star formation rate (SFR) density in the universe peaks at 1< z <2 and sharply declines towards z = 0. The AGN activity also peaks during the same epoch. A clear picture of underlying processes that drive the evolution of star formation and AGN activity is yet to emerge. In this talk, I will review how HI 21-cm emission and absorption line observations can be used to map the atomic gas in galaxies and understand the evolution of SF and AGN activity. 22-Working towards an SKA HI revolution -
GEPI, l'Observatoire de Paris, France ---------------------------------------------------------------------------------------------------------------------------------------------------------------
23-NenuFAR- SKA pathfinder - LESIA, UMR CNRS 8109, Observatoire de Paris, 92195 MEUDON, France
--------------------------------------------------------------------------------------------------------------------------------------------------------------- Abstract: I will present the project NenuFAR (New extension in Nançay upgrading LOFAR), an official low-frequency SKA pathfinder presently in construction and commissioning in Nançay (France). NenuFAR consists of 102 mini-arrays (MA) of 19 dual polarization antennas each. 96 MA cover densely a disk (core) of 400m in diameter, and 6 MA are located at distances up to ~3 km. NenuFAR will cover the range 10-85 MHz, and be three instruments in one: (i) the core, connected to the receivers of the French LOFAR (FR606) station, will form a giant LOFAR station replacing the LOFAR FR606 LBA field and be used as part of LOFAR; this LOFAR Super Station (LSS) will improve the sensitivity of long baselines and thus the quality of high angular resolution imaging at low frequencies with LOFAR. (ii) the core will simultaneously be a standalone compact beamformer providing high instantaneous sensitivity, that will allows us to search efficiently for weak unresolved sources such as pulsars, exoplanets, stars, … (iii) finally, NenuFAR will also (and simultaneously) be a standalone imager that can be used in two modes: a fast (1 sec) coarse resolution (1°) mode, using the 96 MA of the core only, and a slow (6-8 hours) medium resolution (~8’) mode using all the 102 MA, core + distant; this mode will enable imaging studies in cosmology (search for the dark ages / cosmic dawn signal), planetary and stellar physics (exoplanets, stars and their plasma interactions), and the study of galaxies, clusters and haloes.
Ph.D project presentation 1-The properties of the galaxies at the end of reionization-
1 : Aix Marseille Univ, CNRS, LAM, Laboratoire d'Astrophysique de Marseille, Marseille, France
2 : Department of Physics, University of California, Davis, USA
We present a large sample of 89 galaxies with ESO-VLT spectroscopy and confirmed redshifts (from 5.0 to 6.8) drawn from the VIMOS UltraDeep Survey (VUDS, see Le Fèvre et al. 2015). The target selection based on photometric redshifts allows us to maximise the completeness of the sample. Thanks to 1 deg2 area sampled by VUDS the effects of cosmic variance are reduced. In addition the sample is cleaned from low redshift interlopers with [OII] emission, which might be confused with Ly-alpha. A variety of properties (SFRs, stellar masses, UV luminosities, Ly-alpha luminosities) are derived from photometry and spectroscopy. 2-Non-Gaussianity of diffuse galactic foregrounds at low frequencies-
1 : Indian Institute of science education and research, Mohali (IISERM)
2 : National institute of science education and research , Bhubaneshwer (NISER)
Diffuse galactic emission at low frequencies is a major contaminant for studies of redshifted 21 cm line studies. Removal of these foregrounds is essential for exploiting the signal from neutral Hydrogen at high redshifts. It is customary to test efficacy of foreground removal techniques using simulated foreground. Most simulations of foreground signal assume that the distribution on the sky is a Gaussian random field. In this work we test this assumption by computing the Binned Bispectrum (Bucher et al. 2010; Bucher et al. 2016) for the all-sky Haslam 408 MHz map (Haslam et al. 1982; Remazeilles et al. 2015). This is done by applying masks for different brightness temperature in order to assess whether the cooler parts of the sky have different characteristics. We find that regions with a lower brightness temperature indeed have smaller departures from a Gaussian distribution.
3-Bounds on Graviton mass using weak lensing and SZ effect in Galaxy clusters-
1 : Department of Physics and Astrophysics, University of Delhi, India
In General Relativity (GR), the graviton is massless. However, in several theoretical alternatives of GR, a common feature is a non-zero mass for the graviton. These theories can be described as massive gravity theories. The recent detection of gravitational waves from LIGO and VIRGO, which gives us an upper limit on the graviton mass, has led to a resurgence for graviton related studies. Giving mass to the graviton implies that the gravitational potential has the Yukawa form. The difference between the Newtonian and the Yukawa potentials becomes significant at large distances. We use this property of massive gravity theories to probe the mass of graviton. In this work, we use the mass estimates of galaxy clusters measured at various cosmologically defined radial distances measured via the weak lensing (WL) and Sunyaev-Zel'dovich (SZ) effect. Within $1\sigma$ confidence region, we obtain the mass of graviton $m_g < 5.9 \times 10^{-30}$ eV with the corresponding Compton length scale $\lambda_g > 6.82$ Mpc from weak lensing and $m_g < 8.31 \times 10^{-30}$ eV with $\lambda_g > 5.012$ Mpc from SZ effect. This analysis improves the upper bound on graviton mass obtained earlier from galaxy clusters.
4-Energy Distribution in Evolving Dynamical States of Galaxy Clusters and Groups-
Reju John 1 , Surajit Paul 2, Luigi Iapichino 3, Karl Mannheim 4Galaxy clusters grow by continuous accretion and mergers, the most energetic events, which fill the intra-structure medium with shocks and turbulence. These shocks and turbulence are significant as it can effectively influence the energy budget of the Inter-Cluster Medium by shock heating and accelerating particles to ultra-high energies (Cosmic Rays). Diffusive Shock Acceleration (DSA) primarily produces these cosmic rays which get accumulated through Gigayears of cluster formation time. So, clusters are expected to be the most prominent reservoir(s) of Cosmic Rays (CR). Still, surprisingly, clusters are not detected yet by any Gamma-ray telescopes. To decipher the reason, we need a better understanding of CR production process in such objects. With this aim, we have performed cosmological hydrodynamic simulations of the large-scale structure formation. We have studied how CR production is related to the dynamical states of the clusters and determined the phase where they emit themost. We report that the CR production is most efficiently done by the internal merger shocks which occupy the most share of the
simulated cluster volume. The most striking result of this study is a time delay of the CR emission peak. Contrary to the popular notion,
the peak of CR luminosity (is) observed to occur after 1.5 Gyr of the merger of the clusters. The peak of X-ray luminosity and CR luminosity
is also found to be separated by half a Giga year. General assumption that the clusters emit most when they are in merging state or at
the peak of X-ray emission is suggested as the possible reason for the simultaneous non-detection of Gamma rays. Our new finding is
expected to help in strategizing the observation better and may lead to the detection of CRs from clusters in future.
5-An analytical study of ram pressure stripping of galaxies-
1 : Indian Institute of Science Education and Research, Mohali,India (IISER-M)
2 : Thapar Institute of Engineering & Technology, Bhadson Road, Patiala, Punjab - India
3 : Indian Institute of science education and research, Mohali (IISERM)
The quenching of star formation in a galaxy in a high-density environment is still a puzzle, which is important for understanding galaxy evolution(Quadri et al. 2011). Ram pressure stripping(Gunn and Gott 1972), as quenching mechanism is found to be one of the main
mechanisms in a cluster environment, but its importance in group and galaxy environments has been a subject of debate for several
years.To differentiate between various mechanisms for quenching in action builds the case for a theoretical model to understand the
variation of ram pressure with the environment and the properties of galaxy passing through it (J.A. Hester 2006). In the present work,
we propose an analytical model for the calculation for ram pressure striping of gas acting against the self-gravity of stars in the absence
of any other process as the galaxy moves through the ambient medium.We assume a disc galaxy passing through a medium and study
how is the gas removed as it passes through the medium. Parameters related to the environment and galaxy have been varied to get
the quantitative idea of their effect on the amount of gas that remains in the galaxies.The results act as an upper bound on the amount
of stripping that can happen due to ram pressure in various environments and hence the quenching of star formation.
6-Giant Radio Galaxies-
Pratik Dabhade
1 : Inter University Centre for Astronomy and Astrophysics, (IUCAA), Pune University Campus, Post Bag 4, 411007, India
In this talk, we will present about Giant Radio Galaxies (GRGs) and highlight the importance of their studies and our efforts to solve major standing problems related to growth and evolution of GRGs and their host AGN. The GRGs represent an extreme class of active galaxies which have linear sizes in the range of ~ 0.5 Mpc to 5 Mpc which places them among the largest single astrophysical objects known to us. From the past four decades, only ~ 400 GRGs are known as oppose to thousands of normal sized radio galaxies. It is unsettled if the large sizes of GRGs indicate the high efficiency of radio jets ejected from the central AGN, or they grow to enormous sizes due to their location in sparser cluster environments. In spite of various studies of GRGs, there is still not a single tested unified model which might explain the immense physical scale and other extreme properties of GRGs. Moreover, till now only a small fraction of these GRGs have been studied in sufficient detail in multiple wavebands for achieving a good understanding of their unusual nature. This puts a restriction on carrying out statistical studies of their properties. We under our project SAGAN (Search & Analysis of GRGs with Associated Nuclei) aim to firstly make a complete sample of all known GRGs with uniformity, secondly find more GRGs from existing radio and optical surveys, thirdly study the hosts of GRGs in multiwavelength to understand the nature of accretion, feedback and their excitation types. We have already discovered nearly 200 new GRGs from NVSS. These numerous GRGs were missed before due to their very low surface brightness features: they were just at the sensitivity limits of existing surveys like NVSS. I will describe the methods used and results of their analysis. --------------------------------------------------------------------------------------------------------------------------------------------------------------- 7-GMRT observations and AGN feedback implications of brightest-
Konstantinos Kolokythas
1 : Inter University Centre for Astronomy and Astrophysics, (IUCAA), Pune University Campus, Post Bag 4, 411007, India
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