ORCID Profile
0000-0002-4984-9641
Current Organisations
University of Western Australia
,
Raman Research Institute Trust
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Publisher: Cambridge University Press (CUP)
Date: 10-2021
DOI: 10.1017/S1743921320003452
Abstract: We report results from a multi-frequency investigation of very nearby accreting supermassive black holes. We seek to test the hypothesis that imprints of AGN feedback are present at z ˜ 0. Our s le contains about 130 AGN which were chosen to have redshifts less than 0.02, so our optical imaging typically has several spatial resolution elements across the host galaxy. In addition to optical IFU measurements for all the 130 objects, we have GMRT and archival VLA imaging for subsets of the s le, and also ATCA, ASTROSAT and Chandra observations for select objects. We present our most recent results based on the multi-frequency data, for the systematics of the s le as a whole and on in idual objects, that includes a binary black hole precursor.
Publisher: AIP Publishing
Date: 2019
DOI: 10.1063/1.5110134
Publisher: Springer Science and Business Media LLC
Date: 03-2017
Publisher: Springer Science and Business Media LLC
Date: 19-11-2022
Publisher: American Astronomical Society
Date: 25-03-2009
Publisher: American Astronomical Society
Date: 02-03-2015
Publisher: EDP Sciences
Date: 10-2001
Publisher: Unpublished
Date: 2017
Publisher: Oxford University Press (OUP)
Date: 08-1990
Abstract: To investigate the nature of extragalactic radio sources with extended emission on only one side of the active nucleus, we have observed a s le of suspected candidates with both the VLA and MERLIN. In this paper, we present observations of 13 sources which were either suspected of being ‘one-sided’ or were known to have lobes of very different surface brightnesses. Many of the candidates were found to have emission on both sides of the nucleus. Using our observations as well as those available in the literature, we have compiled a s le of 4C quasars having one-sided radio structure. We have then compared some of their properties with a s le of 4C quasars which are two-sided, in order to determine whether their apparently onesided structure is due to relativistic beaming in sources inclined at small angles to the line-of-sight. We find that the median values of fc, the fraction of emission from the core used as a statistical measure of source orientation, and l, their projected linear sizes are consistent with the hypothesis that the one-sided quasars are seen at smaller angles to the line-of-sight than the two-sided ones. We also suggest that the ϕ-fc relation for quasars, where ϕ is the angle between the core polarization vector and the overall radio axis, is consistent with this model, and discuss how the lobe depolarization properties may be useful for further investigations of this interpretation. The velocities required to explain the apparently one-sided quasars in the relativistic beaming framework are in the range of ˜ 0.2-0.8 c. The scarcity of highluminosity, Fanaroff-Riley class II radio galaxies with one-sided structure is consistent with the suggestion that they are at larger angles to the line-of-sight than quasars. In this case, the core-dominated radio galaxies are possibly the lowluminosity, Fanaroff-Riley class I radio galaxies seen at small angles to the line-ofsight, manifesting themselves as BL Lac objects in the more extreme cases.
Publisher: Cambridge University Press (CUP)
Date: 03-2004
Publisher: Elsevier BV
Date: 10-2003
Publisher: Springer Science and Business Media LLC
Date: 06-1986
DOI: 10.1007/BF02715035
Publisher: EDP Sciences
Date: 27-07-2011
Publisher: Informa UK Limited
Date: 08-2001
Publisher: Springer Science and Business Media LLC
Date: 2003
Publisher: Informa UK Limited
Date: 08-2001
Publisher: Springer Science and Business Media LLC
Date: 06-1989
DOI: 10.1007/BF02719317
Publisher: AIP Publishing
Date: 2019
DOI: 10.1063/1.5110093
Publisher: Springer Science and Business Media LLC
Date: 27-10-2010
Publisher: AIP Publishing LLC
Date: 2015
DOI: 10.1063/1.4937705
Publisher: EDP Sciences
Date: 09-2011
Publisher: American Astronomical Society
Date: 24-03-2015
Publisher: Oxford University Press (OUP)
Date: 15-04-1991
Publisher: Oxford University Press (OUP)
Date: 08-06-2017
Publisher: World Scientific Pub Co Pte Lt
Date: 09-2008
DOI: 10.1142/S0218271808013133
Abstract: We re-examine the differences observed in the pc-scale magnetic field geometry of high and low optical polarization quasars (HPQs, LPRQs) using the MOJAVE s le. We find that, as previously reported, HPQ jets exhibit predominantly transverse B fields while LPRQ jets tend to display longitudinal B fields. We attempt to understand these results along with the different B field geometry observed in the low and high energy peaked BL Lacs (LBLs, HBLs) using a simple picture wherein the spinning central black holes in these AGNs influence the speed and strength of the jet components (spine, sheath). Higher spin rates in HPQs compared to LPRQs and in LBLs compared to HBLs could explain the different total radio powers, VLBI jet speeds, and the observed B field geometry in these AGN classes.
Publisher: Cambridge University Press (CUP)
Date: 12-2009
DOI: 10.1017/S1743921308025805
Abstract: Division X provides a common theme for astronomers using radio techniques to study a vast range of phenomena in the Universe, from exploring the Earth's ionosphere or making radar measurements in the Solar System, via mapping the distribution of gas and molecules in our own Galaxy and in other galaxies, to study the vast explosive processes in radio galaxies and QSOs and the faint afterglow of the Big Bang itself.
Publisher: Springer Science and Business Media LLC
Date: 12-2011
Publisher: Elsevier BV
Date: 10-2003
Publisher: Oxford University Press (OUP)
Date: 12-1987
Publisher: Springer Science and Business Media LLC
Date: 12-1984
DOI: 10.1007/BF02714470
Publisher: American Astronomical Society
Date: 06-10-2005
DOI: 10.1086/497984
Publisher: AIP Publishing LLC
Date: 2015
DOI: 10.1063/1.4937669
Publisher: EDP Sciences
Date: 06-2013
Publisher: Cambridge University Press (CUP)
Date: 12-2012
Publisher: Springer International Publishing
Date: 2016
Publisher: Informa UK Limited
Date: 02-10-2014
Publisher: Oxford University Press (OUP)
Date: 02-2008
Publisher: Cambridge University Press (CUP)
Date: 14-05-2010
DOI: 10.1017/S1743921310005259
Abstract: The business meeting of Division X in the IAU 2009GA took place in three sessions during the day of August 6, 2009. The meeting, being well attended, started with the approval for the meeting agenda. Then the triennium reports were made in the first session by the president of Division X, Ren-Dong Nan, and by the chairs of three working groups: “Historic Radio Astronomy WG” by Wayne Orchiston, “Astrophysically Important Lines WG” by Masatoshi Ohishi, and “Global VLBI WG” by Tasso Tzioumis (proxy chair appointed by Steven Tingay). Afterwards, a dozen reports from observatories and worldwide significant projects have been presented in the second session. Business meeting of “Interference Mitigation WG” was located in the third session.
Publisher: Springer Science and Business Media LLC
Date: 02-02-2035
Publisher: Cambridge University Press (CUP)
Date: 09-2014
DOI: 10.1017/S1743921315002124
Abstract: We investigate the systematics of the properties of highly relativistic jets at multiple frequencies, including Fermi , and MOJAVE data. We test the hypothesis that the blazar ide constitutes a dichotomy. We also explore possible measures of the Doppler factor for these highly Doppler-beamed active galactic nuclei.
Publisher: Springer Science and Business Media LLC
Date: 11-04-2015
Publisher: Springer Berlin Heidelberg
Date: 2008
Publisher: Cambridge University Press (CUP)
Date: 08-2015
DOI: 10.1017/S1743921316003458
Abstract: A country-wide awareness c aign was conducted in India on the trail of Comet ISON, which built upon the networks created during IYA2009, thus maximising its reach.
Publisher: American Astronomical Society
Date: 02-2022
Abstract: There is growing evidence for physical influence between supermassive black holes and their host galaxies. We present a case study of the nearby galaxy NGC 7582, for which we find evidence that galactic substructure plays an important role in affecting the collimation of ionized outflows as well as contributing to the heavy active galactic nucleus (AGN) obscuration. This result contrasts with a simple, small-scale AGN torus model, according to which AGN-wind collimation may take place inside the torus itself, at subparsec scales. Using 3D spectroscopy with the Multi Unit Spectroscopic Explorer instrument, we probe the kinematics of the stellar and ionized gas components as well as the ionization state of the gas from a combination of emission-line ratios. We report for the first time a kinematically distinct core (KDC) in NGC 7582, on a scale of ∼600 pc. This KDC coincides spatially with dust lanes and starbursting complexes previously observed. We interpret it as a circumnuclear ring of stars and dusty, gas-rich material. We obtain a clear view of the outflowing cones over kiloparsec scales and demonstrate that they are predominantly photoionized by the central engine. We detect the back cone (behind the galaxy) and confirm previous results of a large nuclear obscuration of both the stellar continuum and H ii regions. While we tentatively associate the presence of the KDC with a large-scale bar and/or a minor galaxy merger, we stress the importance of gaining a better understanding of the role of galaxy substructure in controlling the fueling, feedback, and obscuration of AGNs.
Publisher: Cambridge University Press (CUP)
Date: 07-2014
DOI: 10.1017/S1743921314009661
Abstract: Here we present the first results from the Siding Spring Southern Seyfert Spectroscopic Snapshot Survey (S7) which aims to investigate the physics of ∼140 radio-detected southern active Galaxies with z .02 through Integral Field Spectroscopy using the Wide Field Spectrograph (WiFeS). This instrument provides data cubes of the central 38×25 arc sec. of the target galaxies in the waveband 340–710nm with the unusually high resolution of R =7000 in the red (530–710nm), and R =3000 in the blue (340–560nm). These data provide the morphology, kinematics and the excitation structure of the extended narrow-line region, probe relationships with the black hole characteristics and the host galaxy, measures host galaxy abundance gradients and the determination of nuclear abundances from the HII regions. From photoionisation modelling, we may determine the shape of the ionising spectrum of the AGN, discover whether AGN metallicities differ from nuclear abundances determined from HII regions, and probe grain destruction in the vicinity of the AGN. Here we present some preliminary results and modelling of both Seyfert galaxies observed as part of the survey.
Publisher: EDP Sciences
Date: 10-09-2004
Publisher: AIP Publishing
Date: 2019
DOI: 10.1063/1.5110070
Publisher: Springer Science and Business Media LLC
Date: 06-1983
DOI: 10.1007/BF02714202
Publisher: Oxford University Press (OUP)
Date: 05-1983
Publisher: Cambridge University Press (CUP)
Date: 2001
DOI: 10.1017/S0074180900220470
Abstract: We present results of our study of the parsec-scale components of radio galaxies as observed at radio, optical and X-ray wavelengths, in the framework of the Unified Scheme.
Publisher: American Astronomical Society
Date: 24-03-2011
Publisher: Oxford University Press (OUP)
Date: 27-06-2017
Publisher: Oxford University Press (OUP)
Date: 28-11-2011
Publisher: American Astronomical Society
Date: 20-07-2006
DOI: 10.1086/504822
Publisher: AIP
Date: 2008
DOI: 10.1063/1.3009522
Publisher: Oxford University Press (OUP)
Date: 20-07-2016
Publisher: American Astronomical Society
Date: 10-06-2016
Publisher: EDP Sciences
Date: 06-2014
Publisher: Springer Science and Business Media LLC
Date: 03-2017
Publisher: Springer Science and Business Media LLC
Date: 03-2017
Publisher: AIP
Date: 2013
DOI: 10.1063/1.4794242
Publisher: Cambridge University Press (CUP)
Date: 08-2015
DOI: 10.1017/S174392131501090X
Abstract: We report on the Siding Spring Southern Seyfert Spectroscopic Snap-shot Survey.
Publisher: Oxford University Press (OUP)
Date: 11-1984
Publisher: American Astronomical Society
Date: 08-1994
DOI: 10.1086/174541
Publisher: AIP Publishing LLC
Date: 2015
DOI: 10.1063/1.4937643
Publisher: American Astronomical Society
Date: 06-1993
DOI: 10.1086/172721
Publisher: Oxford University Press (OUP)
Date: 1987
Publisher: EDP Sciences
Date: 28-09-0027
No related grants have been discovered for Prajval Shastri.