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      Volume 34, Issue 2

      June 2013,   pages  75-192

    • Editorial

      Ram Sagar

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    • The Thirty Meter Telescope (TMT): An International Observatory

      Gary H. Sanders

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      The Thirty Meter Telescope (TMT) will be the first truly global ground-based optical/infrared observatory. It will initiate the era of extremely large (30-meter class) telescopes with diffraction limited performance from its vantage point in the northern hemisphere on Mauna Kea, Hawaii, USA. The astronomy communities of India, Canada, China, Japan and the USA are shaping its science goals, suite of instrumentation and the system design of the TMT observatory. With large and open Nasmyth-focus platforms for generations of science instruments, TMT will have the versatility and flexibility for its envisioned 50 years of forefront astronomy. The TMT design employs the filled-aperture finely-segmented primary mirror technology pioneered with the W.M. Keck 10-meter telescopes. With TMT’s 492 segments optically phased, and by employing laser guide star assisted multi-conjugate adaptive optics, TMT will achieve the full diffraction limited performance of its 30-meter aperture, enabling unprecedented wide field imaging and multi-object spectroscopy. The TMT project is a global effort of its partners with all partners contributing to the design, technology development, construction and scientific use of the observatory. TMT will extend astronomy with extremely large telescopes to all of its global communities.

    • India’s Participation in the Thirty-Meter Telescope Project

      B. Eswar Reddy

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      In 2010, the Department of Science and Technology (DST), Govt. of India, approved astronomers’ proposal of India joining the international consortium of the USA, Japan, Canada and China to build and operate the next generation mega ground based optical and infrared telescope known as the Thirty-Meter Telescope (TMT) after its aperture size of 30-meter diameter. Since then, India is engaged in many aspects of the TMT project, both at technical and policy levels. In this article, I confine to the description of India’s efforts leading up to the decision to join the consortium, and the progress made since then with respect to India’s technical contributions to the project.

    • The Thirty-Meter Telescope: Science and Instrumentation for a Next-Generation Observatory

      Luc Simard

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      The Thirty-Meter Telescope international observatory will enable transformational observations over the full cosmic timeline all the way from the first luminous objects in the Universe to the planets and moons of our own solar system. To realize its full scientific potential, TMT will be equipped with a powerful suite of adaptive optics systems and science instruments. Three science instruments will be available at first light: an optical multi-object spectrometer, a nearinfrared multi-slit spectrometer and a diffraction-limited near-infrared imager and integral field spectrometer. In addition to these three instruments, a diverse set of new instruments under study will bring additional workhorse capabilities to serve the science interests of a broad user community. The development of TMT instruments represents a large, long-term program that offers a wide range of opportunities to all TMT partners.

    • A Status Report on the Thirty Meter Telescope Adaptive Optics Program

      B. L. Ellerbroek

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      We provide an update on the recent development of the adaptive optics (AO) systems for the Thirty Meter Telescope (TMT) since mid-2011. The first light AO facility for TMT consists of the Narrow Field Infra-Red AO System (NFIRAOS) and the associated Laser Guide Star Facility (LGSF). This order 60 × 60 laser guide star (LGS) multi-conjugate AO (MCAO) architecture will provide uniform, diffraction-limited performance in the J, H and K bands over 17–30 arcsec diameter fields with 50 per cent sky coverage at the galactic pole, as is required to support TMT science cases. The NFIRAOS and LGSF subsystems completed successful preliminary and conceptual design reviews, respectively, in the latter part of 2011. We also report on progress in AO component prototyping, control algorithm development, and system performance analysis, and conclude with an outline of some possible future AO systems for TMT.

    • Synergy Between Radio and Optical Telescopes: Optical Followup of Extragalactic Radio Sources

      C. H. Ishwara-Chandra

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      Distance measurement is a must to characterize any source in the sky. In the radio band, it is rarely possible to get distance or redshift measurements. The optical band is the most used band to get distance estimate of sources, even for those originally discovered in other bands of the electromagnetic spectrum. However, the spectroscopic redshift measurements even for fairly bright radio sample is grossly incomplete, implying un-explored discovery space. Here we discuss the scope of optical follow up of radio sources, in particular the radio loud AGNs, from the present generation radio telescopes.

    • Spectro-Polarimetry of Self-Luminous Extrasolar Planets

      Sujan Sengupta

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      Planets which are old and close to their parent stars are considered as reflecting planets because their intrinsic temperature is extremely low but they are heated strongly by the impinging stellar radiation and hence radiation of such planets are the reflected star light that is governed by the stellar radiation, orbital distance and albedo of the planet. These planets cannot be resolved from the host stars. The second kind of exoplanets are those which are very young and hence they have high intrinsic temperature. They are far away from their star and so they can be resolved by blocking the star-light. It is now realized that radiation of such planets are linearly polarized due to atmospheric scattering and polarization can determine various physical properties including the mass of such directly detected self-luminous exoplanets. It is suggested that a spectropolarimeter of even low spectral resolution and with a capacity to record linear polarization of 0.5–1% at the thirty-meter telescope would immensely help in understanding the atmosphere, especially the cloud chemistry of the self-luminous and resolvable exoplanets.

    • Core-Collapse Supernovae and Gamma-Ray Bursts in TMT Era

      S. B. Pandey

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      Study of energetic cosmic explosions as a part of time domain astronomy is one of the key areas that could be pursued with upcoming Giant segmented optical-IR telescopes with a very large photon collecting area applying cutting edge technology. Existing 8–10 m class telescopes have been helpful to improve our knowledge about core-collapse supernovae, gamma-ray bursts and nature of their progenitors and explosion mechanisms. However, many aspects about these energetic cosmic explosions are still not well-understood and require much bigger telescopes and back-end instruments with high precision to address the evolution of massive stars and high-redshift Universe in more detail. In this presentation, possible thrust research areas towards core-collapse supernovae and gamma-ray bursts with the Thirty-Meter Telescope and back-end instruments are presented.

    • Generation of a Near Infra-Red Guide Star Catalog for Thirty-Meter Telescope Observations

      Smitha Subramanian Annapurni Subramaniam Luc Simard Kim Gillies A. N. Ramaprakash G. C. Anupama C. S. Stalin Swara Ravindranath B. Eswar Reddy

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      The requirements for the production of a near Infra-Red Guide Star Catalog (IRGSC) for Thirty Meter Telescope (TMT) observations are identified and presented. A methodology to compute the expected J band magnitude of stellar sources from their optical (𝑔, 𝑟 , 𝑖 ) magnitudes is developed. The computed and observed J magnitudes of sources in three test fields are compared and the methodology developed is found to be satisfactory for the magnitude range, JVega = 16–22 mag. From this analysis, we found that for the production of final TMT IRGSC (with a limiting magnitude of JVega = 22 mag), we need 𝑔, 𝑟, 𝑖 bands optical data which go up to 𝑖AB ∼ 23 mag. Fine tuning of the methodology developed, such as using Spectral Energy Distribution (SED) template fitting for optimal classification of stars in the fainter end, incorporating spectral libraries in the model, to reduce the scatter, and modification of the existing colour–temperature relation to increase the source density are planned for the subsequent phase of this work.

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    • Continuous Article Publication

      Posted on January 27, 2016

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