Anand Narayanan

RESEARCH

My research is in studying the properties of diffuse gas in the intergalactic medium and in regions surrounding galxies. For this, I rely on spectroscopic observations. I have made use of optical and ultraviolet spectra of quasars obtained from ground-based facilities like the VLT and Keck telescopes and space based observatories like the Hubble Space Telescope and FUSE satellite. For the last several years, my students and I have been looking at absorption from hydrogen and heavier elements in the low redshift universe to detect gas over a range of temperatures, especially in the 100,000 to a million kelvin. Such gas phase harbors, in the current universe, as much as 40% of the cosmic budget of baryons. We have also been looking at mutliphase properties of gas associated with galaxy clusters and filaments. In addition, we have also used HST far-UV spectra to study outflows from active galactic nuclei.

BARYON CENSUS AT LOW REDSHIFT

Over the nearly 13 billion year history of our universe, only 10% of the total number of baryons (ordinary matter) have collapsed to form structures such as galaxies and galaxy clusters. In other words, galaxy formation has been a relatively inefficient process. Computer simulations of structure formation in a dark energy, dark matter dominated universe suggests that the vast majority of baryons in the nearby universe rests as shock-heated plasma outside of galaxies with temperatures of a million kelvin and densities as low as 1 particle per 100,000 cubic centimeter. Observationally this highly ionized phase of the baryons is just beginning to be discovered. For the last few years, I have been using the Cosmic Origins Spectrograph data to probe environments where these warm-hot baryons might be lurking. On a broader scale, the work adds a level of detail to the ongoing efforts to understand baryonic reservoirs outside of galaxies, and complete the baryon census at low redshift. This work was started, and is being continued, in collaboration with Blair Savage, and Bart Wakker.

HIGH METALLICITY GAS CLOUDS OUTSIDE OF GALAXIES

I also work on spectroscopic detections and analysis of high metallicity compact gas clouds outside of the star forming environments of galaxies. The exact origin of such gas clouds were a mystery for a while. Through systematic surveys, using ultraviolet and optical spectra of more than 100 quasars, my collaborators and I produced a large census of such gas clouds over the past 6 billion year history of the universe. Based on the observed number statistics and constraints derived for the ionization modeling we have proposed that a significant population of these gas clouds are supernova enriched or tidally stripped high velocity gas in the extended halos of external galaxies. This work was started, and is being continued, in collaboration with Jane Charlton and Toru Misawa.

OUTFLOWS FROM ACTIVE GALACTIC NUCLEI

More recently, in collaboration with Srianand Raghunathan, Sowgat Muzahid and Vikram Khaire , I have started looking into highly ionized outflows from active galactic nuclei. Accretion of gas by supermassive black holes at the centers of galaxies trigger such outflows. These are thought to considerably influence the evolution of galaxies, particularly their star formation history. Outflows from AGNs are complex in nature, multi-scaled (10 pc - 10 kpc sizes) and multi-phased (10 K - 10 million K). Not all of these have been sufficiently observed or adequately understood. We are interested in finding such outflows in the ultraviolet spectra of AGNs, model them and understand the overall energetics of outflows, and their chemical enrichment.

PUBLICATIONS

GO TO:  GOOGLE SCHOLAR LINK

• Pradeep, Jayadev; Narayanan, Anand; Muzahid, Sowgat; Nagai, Daisuke; Charlton, Jane C.; Srianand, Raghunathan. Detection of metal-rich, cool-warm gas in the outskirts of galaxy clusters, 2019, Monthly Notices of the Royal Astronomical Society, 488, 5327   MORE INFO


• Manuwal, A., Narayanan, A., Muzahid, S., Charlton, J. C., Khaire, V., Chand, H. C IV absorbers tracing cool gas in dense galaxy group/cluster environments, 2019, Monthly Notices of the Royal Astronomical Society, 485, 30,   MORE INFO


• Muzahid, S., Fonseca, G., Roberts, A., Rosenwasser, B., Richter, P., Narayanan, A., Churchill, C W., Charlton, J C. COS-Weak: Probing the CGM using analogs of weak Mg II absorbers at z < 0.3, 2018, Monthly Notices of the Royal Astronomical Society, 476, 4965.   MORE INFO


• Narayanan, A., Savage, B. D., Mishra, P. K., Wakker, B. P., Khaire, V., Wadadekar, Y. Detection of Low Metallicity Warm Plasma in a Galaxy Overdensity Environment at z = 0.2, 2018, Monthly Notices of the Royal Astronomical Society, 475, 3529.   MORE INFO


• Pachat, S., Narayanan, A., Khaire, V., Savage, B. D., Muzahid, S., Wakker, B. P. Detection of two intervening Ne VIII absorbers probing warm gas at z = 0.6, 2017, Monthly Notices of the Royal Astronomical Society, Volume 471, Issue 1, 792.   MORE INFO


• Pachat, S., Narayanan, A., Muzahid, S., Khaire, V., Srianand, R., Wakker, B. P., Savage, B. D. A pair of O VI and broad Ly-alpha absorbers probing warm gas in a galaxy group environment at z ~ 0.4, 2016, Monthly Notices of the Royal Astronomical Society, Volume 458, Issue 1, 733.   MORE INFO


• Hussain, T., Muzahid, S.,Narayanan, A., Srianand, R., Wakker, B. P., Charlton, J. C.; Pathak, A. HST/COS detection of a Ne VIII absorber towards PG 1407+265: An unambiguous tracer of collisionally ionized hot gas?, 2015, Monthly Notices of the Royal Astronomical Society, Volume 446, Issue 3, 2444.  MORE INFO


• Muzahid, S., Srianand, R., Arav, N., Savage, B. D.,Narayanan, A.HST/COS Observations of a New Population of Associated QSO Absorbers, 2013, Monthly Notices of Royal Astronomical Society, Volume 431, Issue 3, 2885.  MORE INFO


• Rodriguez Hidalgo, P., Wessels, K., Charlton, J. C.,Narayanan, A., Mshar, A., Cucchiara, A., Jones, T. Evolution of the Population of Very Strong Mg II Absorbers, 2012, Monthly Notices of Royal Astronomical Society, Volume 427, Issue 3, 1801.  MORE INFO


• Muzahid, S., Srianand, R., Savage, B. D.,Narayanan, A., Mohan, V., Dewangan, G. C. Highly Ionized Collimated Outflow from HE0238-1904, 2012, Monthly Notices of Royal Astronomical Society Letters, Volume 424, Issue 1, L59.  MORE INFO


• Savage, B.; Kim, T.-S.; Keeney, B.;Narayanan, A.; Stocke, J.; Wakker, B. P. The Properties of Two Low Redshift O VI Absorbers and Their Associated Galaxies Toward 3C 263, 2012, Astrophysical Journal, Volume 753, Issue 1, 80.  MORE INFO


• Narayanan, A.,Savage, B. D., Wakker, B. P. Cosmic Origins Spectrograph Observations of Warm Intervening Gas at z = 0.325 towards 3C263, 2012, Astrophysical Journal, Volume 752, Issue 1, 65.  MORE INFO


• Savage, B. D., Lehner, N.,Narayanan, A., COS Observations of Metal Line and Broad Lyman-alpha Absorption in the Multi-phase O VI and Ne VIII System at z = 0.20701 toward HE 0226-4110, 2011, Astrophysical Journal, Volume 743, Issue 2, 180.  MORE INFO


• Savage, B. D.,Narayanan, A., Lehner, N., Wakker, B. P., A Multiphase Absorber Containing O VI and Broad H I Directly Tracing Million Kelvin Plasma at Low Redshift Toward HE 0153-4520, 2011, Astrophysical Journal, Volume 731, Issue 1, 14.  MORE INFO


• Narayanan, A., Savage, B. D., Wakker, B. P., Danforth, C. W., Yao, Y., Keeney, B. A., Shull, J. M., Sembach, K. R., Froning, C. S., Green, J. C., 2011, Astrophysical Journal, Volume 730, Issue 1, 15.  MORE INFO


• Narayanan, A., Wakker, B. P., Savage, B. D., Keeney, B. A., Shull, J. M., Stocke, J. T., & Sembach, K. R., Cosmic Origins Spectrograph and FUSE Observations of T ~ 100,000 K Gas In A Nearby Galaxy Filament, 2010, Astrophysical Journal, Volume 721, Issue 2, pp. 960 - 974.  MORE INFO


• Savage, B. D.,Narayanan, A., Wakker, B. P., Stocke, J. T., Keeney, B. A., Shull, J. M., Sembach, K. R., Yao, Y., & Green, J. C., O VI Absorbers Tracing Hot Gas Associated with a Pair of Galaxies at z = 0.167, 2010, Astrophysical Journal, Volume 719, Issue 2, pp. 1526-1545.  MORE INFO


• Narayanan, A., Savage, B. D., Wakker, B. P., Highly Ionized Plasma in the Halo of a Luminous Spiral Galaxy Near z = 0.225, 2010, Astrophysical Journal, Volume 712, Issue 2, pp. 1443 - 1460.  MORE INFO


• Narayanan, A., Wakker, B. P., & Savage, B. D., Detection of Ne VIII in a Multi-phase Intergalactic System Towards 3c 263, 2009, Astrophysical Journal, Volume 703, Issue 1, pp. 74-80.  MORE INFO


• Cucchiara, A., Jones, T., Charlton, J. C., Fox, D. B., Einsig, D., &Narayanan, A.Testing the Possible Intrinsic Origin of the Excess Very Strong Mg II Absorbers Along Gamma-Ray Burst Lines-of-Sight, 2009, Astrophysical Journal, Volume 697, Issue 1, pp. 345-360  MORE INFO


• Narayanan, A., Charlton, J. C., Misawa, T., Green, R. E., & Kim, T-S., The Chemical and Ionization Conditions in Weak Mg II Absorbers, 2008, Astrophysical Journal, Volume 689, Issue 2, pp. 782-815.  MORE INFO


• Misawa, T., Charlton, J. C., &Narayanan, A., Supersolar Metallicity in Weak Mg II Absorption Systems at z ~ 1.7, 2008, Astrophysical Journal, Volume 679, Issue 1, pp. 220-238.  MORE INFO


• Narayanan, A., Misawa, T., Charlton, J. C., & Kim, T-S., A Survey of Weak Mg II Absorbers at 0.4 < z < 2.4, 2007, Astrophysical Journal, Volume 660, Issue 2, pp. 1093-1105.  MORE INFO


• Narayanan, A., Misawa, T., Charlton, J. C., & Ganguly, R., The Advantage of Increased Resolution in the Study of Quasar Absorption Systems, 2006, Astrophysical Journal, Volume 132, Issue 5, pp. 2099-2113.  MORE INFO


• Narayanan, A., Charlton, J. C., Masiero, J. R., & Lynch, R., A Survey of Analogs to Weak Mg II Absorbers in the Present, 2005, Astrophysical Journal, Volume 632, Issue 1, pp. 92-109.  MORE INFO

STUDENT MENTORING

List of students who have worked with me on short term and long term projects. Some of these were project based learning (pedagogical in nature), and some worked on segments from my own research work.

• 2014-2017:   Sachin P C, Indian Institute of Space Science & Technology, Ph D work
• 2011:   Savithri Ezhikode, School of Pure & Applied Physics, Mahatma Gandhi University Kottayam
• 2013:   Keerthi Sasidharan, Rahna P T, School of Pure & Applied Physics, Mahatma Gandhi University Kottayam
• 2013:   Rahul Poruri, Indian Institute of Technology, Chennai
• 2013:   Sachin P C, Indian Institute of Space Science & Technology (Ph D student)
• 2014:   Unnikrishnan Potty, Maharaja's College, Ernakulam
• 2015:   Sangeetha Sudheer, Revathi P P, Devamatha College, Kuravilangadu
• 2015:   Anusree K G, Pondicherry University
• 2016:   Joel D'Cruz, Indian Institute of Space Science & Technology
• 2016:   Sreerag S J, University College, Thiruvananthapuram
• 2016:   Jayalekshmi Pradeep, Government College for Women, Thiruvananthapuram
• 2017:   Gayathri Prasad, Sreelakshmi M Nair, Nayantara Rose Jose, Nandana Uthaman, Alphonsa College, Palai
• 2016-2017:   Kshitija Pawar, Indian Institute of Space Science & Technology, MS - Astrophysics
• 2017:   Gayathri Prasad, Sreelakshmi Nair, Nayantara Jose, Nandana Uthaman, Alphonsa College, Pala
• 2017:   Gayathri Prasad, Sreelakshmi Nair, Nayantara Jose, Nandana Uthaman, Alphonsa College, Pala
• 2017:   Betty Jose, Honey Pinto, Mercy College, Palakkad
• 2017-2018:   Aditya Manuwal, Indian Institute of Space Science & Technology, MS - Astrophysics
• 2018:   Arun Seshadri, Sree Vasya NSS College, Thrissur
• 2018:   Vishnu Varma, Sree Kerala Varma College, Thrissur
• 2018:   Sreelakshmi Sudarshan, Sreepriya C, NSS College, Ottapalam
• 2018-2019:   Jayadev Pradeep, Indian Institute of Space Science & Technology, MS - Astrophysics
• 2018-ongoing :   Sriram Sankar, FISAT
• 2019-ongoing :   Pratyush Anshul, Indian Institute of Space Science & Technology, MS - Astrophysics
• 2019-ongoing :   Mathin Yadav, Indian Institute of Space Science & Technology, Dual Degree - Astrophysics
• 2019-ongoing :   Purvi Udhwani, Indian Institute of Space Science & Technology, Junior Research Fellow

TEACHING

A list of courses taught/co-taught by me at IIST :

• Introduction to Astronomy & Astrophysics, Aug - Dec 2010
• Astrophysical Concepts, Aug - Dec 2010
• Astronomical Techniques, Jan -May 2011
• General Physics - II (Astronomy Module), Jan - May 2011
• Galaxies (Structure, Dynamics & Evolution), Aug - Dec 2011
• Cosmology & Astrobiology, Jan - May 2012
• Universe in a Nutshell (Inst. Elective), Aug - Dec 2012
• Astronomy Night Sky Lab, Jan - May 2013
• Universe in a Nutshell (Inst. Elective), Aug - Dec 2013
• Data Analysis Astronomy Lab, Aug - Dec 2013
• Galaxies (Structure, Dynamics & Evolution), Jan - May 2014
• Astronomical Techniques, Jan - May 2014
• Introduction to Astronomy & Astrophysics, Aug - Dec 2014
• Data Analysis Astronomy lab, Aug - Dec 2014
• Galaxies (Structure, Dynamics & Evolution), Jan - May 2015
• Astronomy Night Sky Lab, Jan - May 2015
• Cosmology & Astrobiology, Aug - Dec 2015
• Astronomical Techniques, Aug - Dec 2015
• Cosmology, Jan - May 2016
• Astronomy Lab (Night Sky Observations), Jan - May 2016
• Cosmology & Astrobiology, Aug - Dec 2016
• Introduction to Astronomy & Astrophysics, Aug - Dec 2016
• Galaxies (Structure, Dynamics & Evolution), Jan - May 2017
• Planetary Sciences, Aug - Dec 2017
• Galaxies (Structure, Dynamics & Evolution), Jan - May 2018
• Introduction to Astronomy & Astrophysics, Aug - Dec 2018
• Galaxies (Structure, Dynamics & Evolution), Jan - May 2019

EDUCATION & PUBLIC OUTREACH

Astronomy has a universal appeal. The night sky has always been a portal for stretching human imagination, provoking us to ask some profound questions. In my view, the scientific quest to understand the physical universe, and our place in it, is one of the grandest adventures humans have embarked on. I find great delight in education and public outreach activities where I get to share, and in turn learn, some of the excitement of exploring the cosmos. It is a creative challenge in its own sense, to be able to put across discoveries and ideas in a manner that is simple and accessible to a broad audience. Over the years I have tried to do this through my writings, lectures, and other means. This page lists some of that.

• In 2014 - 15, I scripted and anchored an astronomy documentary series in malayalam for television. This 9 episode series won the 2014 Kerala State Government Award for the best educational program on Television.
  
  
  
  The Hindu newspaper ran a story on this.

• In 2019, a small team of us brought out a 30 minute documentary film on the history of the Travancore Observatory, a facility built in the 1830s.
  
  
  

POPULAR ARTICLES / (Click on the title to download PDF)

• The Big Bang
• Origin of Planetary Systems
• How the Universe Reveals Itself
• India's Mars Orbiter Mission
• Understanding Time Through Stellarium

Since 2013, I have been contributing articles to The Hindu newspaper on science, science heritage and scientists. Below are some of the articles I wrote. Click on the title to access the online version.

• Life on Earth & Beyond - featuring Henry Throop and the search for life elsewhere in the universe
• To Conquer A Formidable Foe - on cancer research
• Bound to Nature - featuring Kerala Biodiversity Board Chairman
• Digging up the Past - on archaeology with Dr. Ajith Kumar
• Interview with Prof. E C G Sudarshan
• The history and heritage of the Travancore Observatory
• Hidden in the mists of time - on the ancient school of mathematics and astronomy of Kerala
• Words from Another Era - on the Oriental Manuscripts Library
• Reclaiming a Hallowed Past - on ayurveda, conversation with Indudharan Menon
• MOM and Children - on India's Mars Orbiter Mission
• What was Cooking in Harappa? - on anthroplogist Brad Chase's work
• The World Within Us - on gut microbes and Jonathan Turney's Book
• Not a Small World Afterall - on ants, and science communication
• Weathering Water Woes - on water conservation
• Fishing For Stories of the Earth - on BBC documentary film maker Ian Stewart

DOCUMENTARY FILM
In 2018, a small team of us brought out a tutorial on ka-ta-pa-ya-adi, an ancient Indian system of encoding numbers into letters of Sanskrit alphabet.

ONLINE COURSE
In 2007, I was part of a team lead by Dr. Jane C. Charlton, that created a web-based introductory astronomy course at the Pennsylvania State Univeristy. Moving away from the usual template of online courses, this course uses a science fiction narrative involving animations and multimedia material to teach the basics of astronomy. One of the team members (Kimberly Herrmann) wrote a short paper about it. The course has had big enrollments over the years, and has since then evolved into a highly interactive and sophisticated online course that resembles a video game.

ABOUT

I was awarded Ph. D from the Department of Astronomy & Astrophysics of the Pennsylvania State University in 2008, where I worked under Jane Charlton. My doctoral dissertation can be found HERE . I also earned my masters in Astronomy & Astrophysics, from Penn State. Prior to that I studied Electrical & Electronics Engineering in the College of Engineering - Thiruvananthapuram.

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