New Insights into the Diffuse Gas Around Galaxies
Astronomers from IIST have uncovered a remarkable example of gas swirling around a galaxy more than 8 billion years ago. In their new paper,
titled “Kinematic analysis of an Ultra-Strong Mg II absorber at z ≈ 1.13 linking to Circumgalactic Gas Structures,” the team studied spectral signatures in the light from a distant quasar .
Their observations revealed a massive reservoir of cold gas dating back to a time when the Universe was less than half its current age. This gas lies just about 18 kiloparsecs from a large, actively star-forming galaxy. The gas exhibits a very broad velocity spread of nearly 450 km/s, suggesting a highly complex motion — not just simple rotation in the galaxy’s disk. Some of the gas seems to be co-rotating with the galaxy, while other parts move faster or in different directions, painting a picture of dynamic and turbulent surroundings.
The study lead by Purvi Udhwani, a former Junior Project Fellow at IIST now pursuing a PhD at the Australian National University, along with Sameer, a former IIST undergraduate now at the University of Oklahoma, and Dr. Anand Narayanan will be published in one of the forthcoming issues of the Astrophysical Journal. This study provides an important glimpse into the circumgalactic medium — the vast halo of gas that surrounds galaxies and fuels their star formation. Chemical analysis revealed that parts of this gas are already enriched to solar or even higher metallicities, indicating that it has been processed by earlier generations of stars. In essence, it shows that galaxies are not isolated islands of stars and dust, but live within a constantly evolving ecosystem of gas flows that recycle material across cosmic time — shaping how galaxies grow and sustain star formation through the ages.
More can be found here: https://arxiv.org/abs/2510.00729