List of Extra-galactic talks

[37] Topic: Probing The Associated Environment of the BAL Quasar Q0059-2735

Speaker: Pritam J. Borah
Affiliation: Tejput Central University
Date (yyyy-mm-dd): 2014-07-22
Time: 12:30hr
Venue: ARIES Auditorium

Abstract: The outflows up to 30000-40000 km/s velocity offset are generally seen as broad absorption in about 10 percent of QSOs. Study of their physical properties give important insight about the environment of Active Galactic Nuclei. Here we have studied the nature of broad as well as narrow absorption line system at z_abs=1.5811 seen in the spectrum of Q0059-2735 with z_em=1.593. In our analysis we have used its high resolution ($sim 41,000$) data obtained Ultra-Violet Echelle Spectrograph(UVES) mounted on Very Large Telescope (VLT). We adopted Voigt profile decomposition method to compute the column densities of various ions considering the covering factor to be unity. The ratios of various ionic column densities have been used to constrain the photoionization models of the absorbing cloud. Given that Voigt profile decomposition intrinsically assumes unit covering factor, and our result by Inhomogeneous absorption model pretty much fits the observed spectrum,this allows us to approximate that this absorbing cloud responsible for the outflow should have covering factor very close to unity. Later electron density (n_e) has been calculated by using collisionally excited SiII lines and ionization parameter by photoionization modelling of the cloud.


About Speaker: Academy fellow, and INSPIRE fellow at Tejpur University Assam


[36] Topic: Astrophysical Line driven winds

Speaker: Ms Reetika Joshi
Affiliation: Kumaun University
Date (yyyy-mm-dd): 2014-07-02
Time: 15:30hr
Venue: ARIES Auditorium

Abstract: A subset of Active Galactic Nuclei(AGN) show broad absorption lines (BAL), with line width and velocity relative to AGN as large as few thousands km/s. These BAL are commonly interpreted as high velocity winds from accretion disks. Among many scenario, one possible mechanism of these high velocity winds is due to the line driven radiative acceleration. We have first explored theory of line driven radiative acceleration mechanism and with an aim to apply it to the recent BAL QSOs catalogs. We find a strong correlation of maximum relative velocity offset and BALQSOs luminosity as is expected in the model of radiation driven wind acceleration.


About Speaker: INSPIRE fellow at Kumaun University.


[35] Topic: Proposing a Method for Particle Accelerators

Speaker: Mukesh Kumar Vyas
Affiliation: Research Scholar, Aries
Date (yyyy-mm-dd): 2013-12-12
Time: 15:30hr
Venue: ARIES Auditorium

Abstract: The talk is designed to implement the concept of aberration of light into particle acceleration process. It provides an efficient method to accelerate charged particles up to advanced energy level. In another stage the theoretical treatment of the concept also presents some astrophysical process that can trigger protons up to enormous energy amount and results into cosmic rays.


About Speaker: Research Scholar, ARIES


[34] Topic: Spectral variability of X-ray bright Hi-BALQSOs

Speaker: Jhilik Majumdar
Affiliation: Jadavpur University(IAS fellow)
Date (yyyy-mm-dd): 2013-08-22
Time: 12:30hr
Venue: Auditorium

Abstract: Broad Absorption Line Quasars (BALQSOs) enable study of the energetic outflows with velocities up to 0.2-0.3c accompanying the matter accreting to the super-massive black hole. The high absorbing columns in these outflowing winds (10^23 - 10^24 cm-2 ) forces the BALQSOs to be X-ray faint. Due to such reasons, almost all BALQSOs have been discovered by optical surveys, the X-ray properties of BALQSOs remain mostly unknown. However, recently there has been discovery of many X-ray loud BALQSOs, which are found to be very useful to understand their peculiar environments around the central engine, in conjunction to their optical properties such as variability of optical spectral absorption line associated with the quasars itself. Here we have used sample of well selected, 13 X-Ray bright Hi-ionization BALQSOs, having optical to X-ray slope > -1.80, to quantify their variability over 1yr to 10yr time scale. We will present our observation, spectral reductions, along with quantificatin of the percentage variation seen on the CIV and SiIV absorption troughs. Finally possible mechanism, which need further investigation will also be highlighted.


About Speaker: MSc student visiting from Jadavpur University, for her two month summer project under IAS summer fellowship program.


[33] Topic: The ILMT project : optical quality tests and prospective detection of gravitationally lensed QSOs.

Speaker: Dr. Francois Finet
Affiliation: ARIES
Date (yyyy-mm-dd): 2013-08-21
Time: 15:30hr
Venue: Auditorium

Abstract: The International Liquid Mirror Telescope (ILMT) project is a joint collaboration between different universities and research institutes in Belgium, India, Canada and Poland, for the design, construction and operation of a 4 meter telescope at the Devasthal Observatory, that will use the liquid mirror technology. The first part of this talk will introduce the ILMT project, the telescope and its technology particularities, as well as an innovative instrument that has been designed for the measure of its primary mirror optical quality. The ILMT has been designed to perform a photometric variability survey of a narrow strip of sky, making it very suitable for the detection and follow-up of photometrically variable sources such as supernovae and quasars. The second part of the talk will present an estimate of the number of QSOs to be detected within the ILMT survey, and of the expected number of multiply imaged sources among these caused by the presence of a deflector near the lines-of-sight. We will then explain how this statistical sample of multiply imaged QSOs is intended to be used as cosmological probe, and we will therefore introduce a new mathematical approach for the estimate the lensing probabilities, based on the joined probability density of the observed QSOs.


About Speaker: Speaker is Visiting Scientist at ARIES.


[32] Topic: Probing the environment of BALQSO J0318-0600

Speaker: Pritam J. Borah
Affiliation: Tejpur University, Aasam
Date (yyyy-mm-dd): 2013-07-24
Time: 15:30hr
Venue: Auditorium

Abstract: The outflows up to 30000-40000 km/s velocity offset are generally seen as broad absorption in about 10 percent of QSOs. Study of their physical properties give important insight about the environment of Active Galactic Nuclei. Here we studied the nature of broad absorption line system at z_abs=1.9257 seen in the spectrum of J0318-0600 with z_em=1.967. In our analysis we have used its high resolution (R~ 40000) data obtained Ultra-Violet Echelle Spectrograph(UVES) mounted on Very Large Telescope (VLT). We adopted Voigt profile decomposition method to compute the column densities of various ions, in contrast to the power law method used in the literature. The ratios of various ions column densities have been used to constrain the photoionization models of the absorbing cloud. Further assuming a reasonable piece-wise power law spectral energy distribution we have estimated the distance of the absorbing cloud from the central engine to be around 6.5 kpc which is very close to the distance estimate obtained using pure power law column density distribution. Given that (i) Voigt profile decomposition intrinsically assumes unit covering factor, and (ii) our result matches with that obtained in literature using power law column density distribution, allow us to conclude that this absorbing cloud responsible for the outflow should have covering factor very close to unity.


About Speaker: Mr. Pritam J. Borah, is summer project student sponsored by India Science academies fellowship program. He is at present affiliate for his integrated MSc at Tejpur University Assam


[31] Topic: The unprecedented 2012 outburst of SN 2009ip

Speaker: Kuntal Misra
Affiliation: ARIES, Nainital
Date (yyyy-mm-dd): 2013-07-10
Time: 15:30hr
Venue: Auditorium

Abstract: I will discuss the comprehensive campaigns that were undertaken by several groups to study the remarkable re-brightening(s) in SN 2009ip.


About Speaker: Scientist C


[30] Topic: Various methods for distance measurement of extra-galactic objects

Speaker: Parth Shah
Affiliation: NIT, Surat
Date (yyyy-mm-dd): 2013-07-03
Time: 12:15hr
Venue: Auditorium

Abstract: The study has been made for measuring distances to extra galactic objects using various methods such as Parallax, Cepheid Variables, Type Ia Supernovae, Tully Fisher relation and Faber Jackson relation.


About Speaker: He is doing Integrated M.Sc. from NIT, Surat, Gujarat.


[29] Topic: Discovery of a new class of hydrogen-rich supernovae from Indian optical telescopes

Speaker: Dr. Brijesh Kumar
Affiliation: ARIES, Nainital
Date (yyyy-mm-dd): 2013-06-26
Time: 15:30hr
Venue: Auditorium

Abstract: We use optical photometric and spectroscopic data from 1-2m class telescopes in India to discover a new class of hydrogen-rich supernovae. An overview of this scientific discovery and its physical significance will be described.


About Speaker: Scientist E


[28] Topic: X-Ray study of 3C273 with XMM-Newton

Speaker: Ms. Nibedita Kalita
Affiliation: Research Scholar
Date (yyyy-mm-dd): 2013-06-24
Time: 16:30hr
Venue: Audotorium

Abstract: I will present my work, search for variability and QPO in the quasar 3C273 with the help of XMM-Newton satellite.


About Speaker: Speaker is Ph.D Scholar in Dept. of physics , Gauhati University, Assam.


[27] Topic: Central Engine of AGN

Speaker: Jai Bhagwan
Affiliation: ARIES
Date (yyyy-mm-dd): 2013-06-12
Time: 15:30hr
Venue: Auditorium

Abstract: Very soon after the interpretation of 3C273 as a cosmologically redshifted object astrophysicists faced the dilemma of explaining its remarkable energetic output. The observed variability time scales limited its size to dimension of order light days. Thus, given that its inferred luminosity L~ 10^47 erg/sec is approximately one million times that of our own galaxy, it was immediately clear that some mechanism other than a dense conglomeration of stars had to be involved. The idea of the central massive object and accretion-powered radiation quickly emerged, primarily due to lack of any other tangible explanation. Hoyle and Fowler (1963) put forth the general concept considering scenarios where a hyperstar accreted from its ambient medium. More detailed models soon followed : Salpeter (1964), ZelDovich (1964), Lynden-Bell (1969). Estimates of AGN black hole masses from several independent methods are now available in the published literature and I will be discuss those results and their implication in this talk.


About Speaker: Research scholar at ARIES


[26] Topic: Weak emission lines quasars

Speaker: Dr. H. Chand
Affiliation: ARIES
Date (yyyy-mm-dd): 2013-05-29
Time: 15:30hr
Venue: Auditorium

Abstract: The broad and strong emission line are the benchmark of bona-fied quasars. With the recent large survey such as SDSS many quasars having very weak emission lines has also been discovered. I shell sumarise the main features of such weak emission line quasars, along with the existing open questions about their nature.


About Speaker: Scientist at ARIES


[25] Topic: Radio-Far infrared correlation in dwarf galaxies

Speaker: Dr. Amitesh Omar
Affiliation: ARIES
Date (yyyy-mm-dd): 2013-05-15
Time: 15:30hr
Venue: Auditorium

Abstract: I will present an overview of much discussed very tight radio far infrared correlation in galaxies. The dwarf and low surface brightness galaxies reveal some evidences that radio-FIR correlation and its tightness in galaxies is a conspiracy. The new results and future prospects in the context of Wolf-Rayet galaxies studied by us will be presented.


About Speaker: Scientist at ARIES