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Brief my Curiculam-Vita as given below:

Academic History

Awards and Distinctions

• Life membership of Astronomical Society of India.

• 2009: Selected as an ** Young Associate of the Indian Academy of Sciences Bangalore, 2009-20 12**

• 2006: Awarded Peter Gruber Foundation fellowship 2006 by International Astronomical Union.

• 2006: Awarded R K Bhalla award 2006 by Indian Physics Association (Pune Chapter).

• 2001: 2 year Junior Research Fellowship and 3 year Senior Research Fellowship awarded by Council of Scientific and Industrial Research (CSIR) Govt. of India.

• 2001: Qualify the all-India Joint Entrance Screening Test (JEST) with a percentile of 98.6, for admission to premier research institutes in India.

• 2000: Qualify the all-India UGC-NET/CSIR Test and awarded CSIR JRF .

Main Research Interests: Quasar astronomy

1. Probing the cosmological variation of fundamental constant, using QSOs absorption lines.

2. On the nature of AGN feedbacks

3. Investigation the environments and central engine of Active galactic Nuclei.

4. Probing the the nature of newly discovered Weak Emission Line QSOs

5. Black-hole mass estimation and AGN multi-wavelength study.

6. Cosmology with Quasar absorption line studies: extra-galactic UV-radiation field, QSOs densidity field

7. QSOs absorption line studies as probe of astrophysical magnetic filed.

Main Scientific Contribution

Does the fundamental constants of nature change with cosmic time?

Search for the variation of the fundamental constants is motivated by various unification theories. Detecting or constraining such possible time variations of fundamental physical constants is an important step toward a complete understanding of basic physics. One of these constants is the so-called "fine structure constant", $\alpha$ = $e^2/\hbar c$, which play crucial role the way light interacts with atoms.

In fact, quite strong constraints are already known to exist for the possible variation of the fine structure constant. One such constraint is of geological nature (from a ancient natural fission reactor which was active roughly 2,000 million years ago), suggesting the change of $\alpha$, if any should be smaller than about 2 parts per 100 millions.

However, what about changes much earlier in the history of the Universe?

To measure this we must find means to probe still further into the past. And this is where astronomy and cosmology play a crucial role, as by observing very remote objects one can look back over a long time span, and hence can test the values of the physical constants when the Universe had even 1/4th of its present age, that is, about 10,000 million years ago.

If the fine-structure constant happens to change over the duration of the light’s journey from remote objects, the energy levels in the atoms would be affected and the wavelengths of the absorption lines would be shifted by different amounts. By comparing the relative shifts with respect to laboratory values, it is possible to calculate $\alpha$ as a function of distance from us, that is, as a function of the age of the Universe.

These measures are however extremely delicate and require a very good modelling of the quasar absorption lines. They also put exceedingly strong requirements on the quality of the astronomical spectra. They must have enough resolution to allow very precise measurement of minuscule shifts in the spectra. And a sufficient number of photons must be captured in order to provide a statistically unambiguous result.

Over past few years our group have been involved extensively in such project viz”to detect the possible variation of the fine-structure constant”. In our experiments we have used 19 high redshift Quasar spectra taken with Ultra-violet and Visible Echelle Spectrograph (UVES) mounted on ESO’s Kueyen 8.2-m telescope. In addition we have also used best high resolution spectrograph (R $\approx 112000$) to chase various systematics involved in this experiment.

The main result of our extensive study is that over the last 10,000 million years, the relative variation of $\alpha$ = $e^2/\hbar c$, must be less than 0.6 part per million. This become the strongest constraint from quasar absorption lines studies to date. In addition this new result also does not support previous claims of a statistically significant change of $\alpha$ with time, which was obtained using another 10m class telescope at Hawaii. As a result, our measurements have been considered very timely especially either to constrain or rule out among many models of fundamental physics.

In adition our group was also involved in constraining the variation of proton-to-electron mass ratios an another similar kind of experiments, apart from other usual astronomy and astrophysical research projects, as summarise below.

Other Key Science contributions summary:

• Up to what extent of velocity offset, AGN outflows pollute its intervening absorption line system? Our group for the first time give evidences that associated absorbers in AGN environment can have offset velocity as high as 30000Km/s, in contrast to the existing upper limits of 5000 km/s. Comparative studies using large sample of different type of QSOs such as blazar, CDQs, FSRQs, LDQs are also carried out.

• Are Radio-quiete(RQ) weak Emission line quasars (WLQ), RQ counter part of Bl Lacs objects (BLOs)? Based on our first systematic investigation of Weak Emission line (using INOV, spectral and polarimetric analysis), it seem that these peculiar class of AGN are the early evolution of of QSOs phase, rather than the possible radio-quite counter part of BL-Lacs; though we revealed two best candidate for the elusive radio-quiet BLOs and both need to be followed up.

• Why the majority of broad absorption line QSOs are X-ray Weak? For this using line variability study is one of the powerful methods, we carried out systematic study of X-ray bright BAL-QSOs, and discovered the cased of highest kinematic shift and strength variability of CIV broad absorption line (BAL) trough in two high-ionization X-ray bright QSOs.

• Quasar probing Quasars: Does QSOs reside in over dense regions? We find evidence that the proximity effect in longitudinal and transverse direction do differ in close QSOs pairs, a possible evidence of over density and probable an-isotropic radiation filed, based on largest SDSS/ESO pair sample till now.

• What are the nature of Narrow-line Seyfert galaxy(NLSY1)? Multi-wavelength systematic study of NLSY1 with main aspects as: (i) new NLSY1 catalog based on SDSS DR-12, INOV characterization on various sub-sample, largest sample in X-ray analyzed to get new spectral slope verses Eddington ratios. About 30hr on target observation using ASTROSAT already done to find the SED difference of variable and non-variable NLSYS1.

• Faraday rotation measure evolution, as probable of high-z magnetic field: The technique developed to deal with large data set, has been implemented to address also another interesting issue, that do the intervening Mg ii absorber (i.e intervening galaxies) contribute in the Faraday residual rotation measured in radio-frequency? A sample as large as 1100 source with optical spectra and rotation measure is used to estimate $\sigma_{rrm}$ excess in sample with Mg ii absorber over sigh-line without such absorbers. This is being extended to infer the cosmic magnetic field, magnetic bridge in interacting galaxies based on the improvement we expect with upcoming SKA higher sensitivity (supported also by SERB grant $\sim$Rs 21 lacs).

• Devising observatory project “Devasthal optical telescope - AGN Reverberation Monitoring (DOT-ARM): Probing AGN black-hole masses and broad line regions". A multi science goals observatory project, being funded by DST-SERB ($\sim$ 41 lacs grant). Road map for automation, to make best use of observing time/data archiving, by suitable combination of ARIES 1.3m and 3.6m telescope.

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