भारतीय खगोलभौतिकी संस्थान
Indian Institute of Astrophysics
Exploring the Universe since 1786
An Autonomous Institute under the
Department of Science & Technology
Government of India
Research Highlights
RESEARCH HIGHLIGHTS | IIA
Exploring NGC 2345: A Comprehensive study of a young open cluster through photometric and kinematic analysis
BHATT, B. C | May 01, 2024
We conducted a photometric and kinematic analysis of the young open cluster NGC 2345 using CCD UBV data from 2 m Himalayan Chandra Telescope, Gaia Data Release 3, Two Micron All-Sky Survey, and the Photometric All-Sky Survey data sets. We found 1732 most probable cluster members with membership probability higher than 70%. The fundamental and structural parameters of the cluster are determined based on the cluster members. The mean proper motion of the cluster is estimated to be = −1.34 ± 0.20 and μδ = 1.35 ± 0.21 mas yr−1. Based on the radial density profile, the estimated radius is ∼12 8 (10.37 pc). Using color–color and color–magnitude diagrams, we estimate the reddening, age, and distance to be 0.63 ± 0.04 mag, 63 ± 8 Myr, and 2.78 ± 0.78 kpc, respectively. The mass function slope for main-sequence stars is determined as 1.2 ± 0.1. The mass function slope in the core, halo, and overall region indicates a possible hint of mass segregation. The cluster's dynamical relaxation time is 177.6 Myr, meaning ongoing mass segregation, with complete equilibrium expected in 100–110 Myr. Apex coordinates are determined as −40 89 ± 0.12, − 44 99 ± 0.15. The cluster's orbit in the Galaxy suggests early dissociation into field stars due to its close proximity to the Galactic disk.
RESEARCH HIGHLIGHTS | IIA
Baryonic Ecosystem IN Galaxies (BEINGMgII) II. Unveiling the nature of galaxies harbouring cool gas reservoirs
RAVI JOSHI | Mar 19, 2025
We search for the galaxies associated with the intervening Mg II absorbers over a redshift range of 0.4 ≤ z ≤ 1 using imaging data from DESI Legacy Imaging Surveys and measure the redshift based on the direct detection of nebular emission in the background quasar spectra from the SDSS survey. We find 270 Mg II absorbers associated with strong O [II] or O [III] and Hβ nebular emissions, at a 2.5σ level. Among them, for 213 Mg II absorbers, we detect an absorber host galaxy at impact parameters of 4 ≤ ρ ≤ 16 kpc, including three absorbers associated with a galaxy pair, with a best-fit galaxy spectral energy distribution model based on multi-passband photometric data from DESI Legacy Imaging surveys, supplemented with the infrared VISTA and unWISE imaging surveys. The detection rate of the Mg II absorber host with strong O [II] nebular emission in the finite SDSS fibre of a 2–3 arcsec diameter increases from 0.2% to ∼3% with an increasing equivalent width from 0.3 Å to ∼3.5 Å, which remains near-constant across the probed redshift range. The associated Mg II host galaxies exhibit a wide range of stellar mass from 7.94 ≤ log(M⋆/M⊙)≤11.11, with an average star formation rate (SFR) of 5.81 M⊙ yr−1. The Mg II absorber hosts selected based on O [II] nebular emission mostly exhibit active star-forming systems including 13.4% starburst systems, but 10.2% with a suppressed SFR. The near-constant absorption strength at low-impact parameters suggests a high gas covering fraction. We find that the Mg II equivalent width (W2796) positively correlates with the SFR and specific SFR, likely indicating their wind origin. The average velocity offset between the host and the absorber suggests that the Mg II gas is bound within the dark matter halo.
RESEARCH HIGHLIGHTS | IIA
Applying the velocity gradient technique in NGC 1333: comparison with dust polarization observations
ARCHANA SOAM | Dec 01, 2024
Magnetic fields (B-fields) are ubiquitous in the interstellar medium (ISM), and they play an essential role in the formation of molecular clouds and subsequent star formation. However, B-fields in interstellar environments remain challenging to measure, and their properties typically need to be inferred from dust polarization observations over multiple physical scales. In this work, we seek to use a recently proposed approach called the velocity gradient technique (VGT) to study B-fields in star-forming regions and compare the results with dust polarization observations in different wavelengths. The VGT is based on the anisotropic properties of eddies in magnetized turbulence to derive B-field properties in the ISM. We investigate that this technique is synergistic with dust polarimetry when applied to a turbulent diffused medium for the purpose of measuring its magnetization. Specifically, we use the VGT on molecular line data toward the NGC 1333 star-forming region (12CO, 13CO, C18O, and N2H+), and we compare the derived B-field properties with those inferred from 214 and 850 μm dust polarization observations of the region using Stratospheric Observatory for Infrared Astronomy/High-Resolution Airborne Wide-band Camera Plus and James Clerk Maxwell Telescope/POL-2, respectively. We estimate both the inclination angle and the 3D Alfvénic Mach number M A from the molecular line gradients. Crucially, testing this technique on gravitationally bound, dynamic, and turbulent regions, and comparing the results with those obtained from polarization observations at different wavelengths, such as the plane-of-sky field orientation, is an important test on the applicability of the VGT in various density regimes of the ISM. We in general do not find a close correlation between the velocity gradient inferred orientations and the dust inferred magnetic field orientations.
Press Releases
PRESS RELEASES | SCOPE
Scientists Chart the Sun's Subsurface Weather Patterns Tied to Its 11-Year Activity Cycle
SCOPE | Apr 29, 2025
An international team of solar physicists has unveiled new insights into the dynamic "inner weather" of the Sun—plasma currents just beneath its surface that pulse in step with its 11-year sunspot cycle. In a study published on the 22nd of April 2025, in the The Astrophysical Journal Letters, researchers from the Indian Institute of Astrophysics (IIA), Stanford University (USA), and the National Solar Observatory (NSO, USA) have traced how these hidden flows shift over time, potentially reshaping our understanding of how the Sun's interior connects to its outer magnetic behavior, which has far-reaching influence on space weather and Earth.
This is based on the paper titled "Solar Cycle Variations in Meridional Flows and Rotational Shear within the Sun's Near-surface Shear Layer", by Anisha Sen, S. P. Rajaguru, Abhinav Govindan Iyer, Ruizhu Chen, Junwei Zhao, and Shukur Kholikov, 2025, Astrophysical Journal Letters, 984, 1.
Press release by PIB published here.
Press release issued by DST here.
Download the paper from here.
PRESS RELEASES | SCOPE
IIA Bengaluru scientists discover a new kind of Stellar Chemistry
SCOPE | Jun 19, 2025
Far away in the Ophiuchus Constellation, a peculiar star named A980, 25800 light years away, is rewriting what we know about stellar chemistry. Researchers have uncovered a cosmic twist -- this mysterious star that belongs to a rare class called Extreme Helium (EHe) stars, carries surprisingly high amount of germanium—a metallic element never before observed in this type of star.
This is based on the paper titled "Detection of Enhanced Germanium in a New Cool Extreme Helium Star A980: Insights and Implications", by Ajay Kumar Saini and Gajendra Pandey, 2025, The Astrophysical Journal, 979, 239.
Press release by PIB published here.
Press release issued by DST here.
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IIA offers a vigorous programme of graduate studies that forms a vital component of research & training. The programme is overseen by the board of graduate studies. The Institute is also a major partner in the Joint Astronomy Programme (JAP), organized by the Indian Institute of Science.
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PhD applications may be submitted through the IIA PhD online applications portal in May. After the initial screening, shortlisted candidates will be interviewed in June. The final list of selected candidates will be announced in July, followed by the commencement of the programme in August. .
Research Fields
Solar Studies
Studies of the Sun and solar system have been the longest pursued discipline at IIA. Members of the group conduct theoretical, numerical modeling, and observational studies in solar physics.
Stars & Galaxies
Research interests of the group members range from exoplanets, star formation, stellar evolution, end states of stars, Interstellar medium, the milky way Galaxy, nearby galaxies, active galaxies and time domain astronomy.
Theory
Members of the theoretical Astrophysics group work on a broad range of topics such as black hole astrophysics, pulsars, exoplanets, astrophysical turbulence & magnetic fields, MHD, cosmology and early universe.
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