Infrared Properties of Galaxies Malhotra and collaborators used
Infrared Space Observatory data to study the far-infrared line emission from galaxies. In particular, she demonstrated that the 158 micron emission line of ionized carbon becomes a relatively less prominent spectral feature in galaxies with higher infrared luminosity and/or warmer interstellar dust.
Lyman Alpha Galaxies and Cosmological Reionization Malhotra initiated the Large Area Lyman Alpha survey in the late 1990s. This was one of the first research projects to successfully identify galaxies in the early universe using their
Lyman alpha emission lines, a method that had been first proposed in 1967 by Bruce Partridge and
Jim Peebles. She has gone on to study
galaxies with strong Lyman alpha lines in detail. In particular, she demonstrated that they tend to be young, with extreme star formation properties and (for galaxies) small sizes. She also pioneered the technique of using Lyman alpha galaxies to study cosmological reionization, leading a 2004 paper that demonstrated that the gas between galaxies was already mostly ionized at redshift 6.5, when the universe was less than a billion years old. Recently, she, her former Ph.D. student V. S. Tilvi, and other collaborators identified the most distant galaxy group so far known (EGS77), and found evidence that these galaxies are ionizing their surroundings. She is the US
principal investigator of the ongoing multinational LAGER project (Lyman Alpha Galaxies in the Epoch of Reionization), which is identifying hundreds of Lyman alpha galaxies in the epoch of cosmic dawn.
Slitless Spectroscopy from Space Malhotra has led three
Hubble Space Telescope treasury programs (GRAPES, PEARS, and FIGS) that have collectively advanced the application of
slitless spectroscopic observations from space. While initially designed to identify galaxies in the distant universe, these projects have also proven invaluable for identifying galaxies at intermediate distances, studying the chemical compositions of those galaxies, and even studying stars in our own Galaxy. Further developments of these techniques form a core part of the planned observing programs for ESA's
Euclid mission and NASA's
Roman mission, and Malhotra is helping develop plans for the
Roman application.
Pea galaxies Malhotra has directed multiple PhD students in studying
Green Pea galaxies. She and her collaborators have demonstrated that these comparatively local objects bear striking similarities to Lyman alpha galaxies in the early universe, which is valuable because the pea galaxies are easier to study in detail than their more distant counterparts. == Students ==