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Black Hole

Lensing of space time around a black hole. At Oxford we study black holes observationally and theoretically on all size and time scales - it is some of our core work.

Credit: ALAIN RIAZUELO, IAP/UPMC/CNRS. CLICK HERE TO VIEW MORE IMAGES.

Prof. Niranjan Thatte

Professor of Astrophysics

Research theme

  • Astronomy and astrophysics
  • Instrumentation
  • Exoplanets and planetary physics

Sub department

  • Astrophysics

Research groups

  • Astronomical instrumentation
  • Exoplanets and Stellar Physics
  • Galaxy formation and evolution
  • Extremely Large Telescope
Niranjan.Thatte@physics.ox.ac.uk
Telephone: 01865 (2)73412
Denys Wilkinson Building, room 709
  • About
  • Teaching
  • Publications

On the viability of determining galaxy properties from observations I: Star formation rates and kinematics

Monthly Notices of the Royal Astronomical Society Oxford University Press 513:3 (2022) 3906-3924

Authors:

Kearn Grisdale, Laurence Hogan, Dimitra Rigopoulou, Niranjan Thatte, Miguel Pereira-Santaella, Julien Devriendt, Adrianne Slyz, Ismael García-Bernete, Yohan Dubois, Sukyoung K Yi, Katarina Kraljic

Abstract:

We explore how observations relate to the physical properties of the emitting galaxies by post-processing a pair of merging z ∼ 2 galaxies from the cosmological, hydrodynamical simulation NEWHORIZON, using LCARS (Light from Cloudy Added to RAMSES) to encode the physical properties of the simulated galaxy into H α emission line. By carrying out mock observations and analysis on these data cubes, we ascertain which physical properties of the galaxy will be recoverable with the HARMONI spectrograph on the European Extremely Large Telescope (ELT). We are able to estimate the galaxy’s star formation rate and dynamical mass to a reasonable degree of accuracy, with values within a factor of 1.81 and 1.38 of the true value. The kinematic structure of the galaxy is also recovered in mock observations. Furthermore, we are able to recover radial profiles of the velocity dispersion and are therefore able to calculate how the dynamical ratio varies as a function of distance from the galaxy centre. Finally, we show that when calculated on galaxy scales the dynamical ratio does not always provide a reliable measure of a galaxy’s stability against gravity or act as an indicator of a minor merger.
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Unveiling the main sequence to starburst transition region with a sample of intermediate redshift luminous infrared galaxies

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) 512:2 (2022) 2371-2388

Authors:

L Hogan, D Rigopoulou, S García-Burillo, A Alonso-Herrero, L Barrufet, F Combes, I García-Bernete, GE Magdis, M Pereira-Santaella, N Thatte, A Weiß
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HARMONI view of the host galaxies of active galactic nuclei around cosmic noon

Astronomy & Astrophysics EDP Sciences 659 (2022) a79

Authors:

B García-Lorenzo, A Monreal-Ibero, M Pereira-Santaella, N Thatte, C Ramos Almeida, L Galbany, E Mediavilla
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Integral field spectroscopy of luminous infrared main-sequence galaxies at cosmic noon

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) 503:4 (2021) 5329-5350

Authors:

L Hogan, D Rigopoulou, GE Magdis, M Pereira-Santaella, I García-Bernete, N Thatte, K Grisdale, J-S Huang
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Predicting the observability of population III stars with ELT-HARMONI via the helium 1640 Å emission line

Monthly Notices of the Royal Astronomical Society Oxford University Press 501:4 (2021) 5517-5537

Authors:

Kearn Grisdale, Niranjan Thatte, Julien Devriendt, Miguel Pereira Santaella, Adrianne Slyz, Taysun Kimm, Yohan Dubois, Sukyoung Yi

Abstract:

Population III (Pop. III) stars, as of yet, have not been detected, however as we move into the era of extremely large telescopes this is likely to change. One likely tracer for Pop. III stars is the He IIλ1640 emission line, which will be detectable by the HARMONI spectrograph on the European Extremely Large Telescope (ELT) over a broad range of redshifts (2 ≤ z ≤ 14). By post-processing galaxies from the cosmological, AMR-hydrodynamical simulation NEWHORIZON with theoretical spectral energy distributions (SED) for Pop. III stars and radiative transfer (i.e. the Yggdrasil Models and CLOUDY look-up tables, respectively) we are able to compute the flux of He IIλ1640 for individual galaxies. From mock 10 h observations of these galaxies we show that HARMONI will be able to detect Pop. III stars in galaxies up to z ∼ 10 provided Pop. III stars have a top heavy initial mass function (IMF). Furthermore, we find that should Pop. III stars instead have an IMF similar to those of the Pop. I stars, the He IIλ1640 line would only be observable for galaxies with Pop. III stellar masses in excess of 107M⊙⁠, average stellar age <1Myr at z = 4. Finally, we are able to determine the minimal intrinsic flux required for HARMONI to detect Pop. III stars in a galaxy up to z = 10.
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