Sangeeta Malhotra is an astrophysicist who studies galaxies, their contents, and their effects on the universe around them. The objects she studies range from our own Milky Way galaxy to some of the earliest and most distant known galaxies in the epoch of cosmic dawn. Malhotra works at the

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding t ...

Goddard Space Flight Center The Goddard Space Flight Center (GSFC) is a major NASA space research laboratory located approximately northeast of Washington, D.C. in Greenbelt, Maryland, United States. Established on May 1, 1959 as NASA's first space flight center, GSFC empl ...

, where she is part of the

Nancy Grace Roman Space Telescope The Nancy Grace Roman Space Telescope (shortened as Roman or the Roman Space Telescope, and formerly the Wide-Field Infrared Survey Telescope or WFIRST) is a NASA infrared space telescope currently in development and scheduled to launch by Ma ...

project. She was previously a tenured full professor at

Arizona State University Arizona State University (Arizona State or ASU) is a public research university in the Phoenix metropolitan area. Founded in 1885 by the 13th Arizona Territorial Legislature, ASU is one of the largest public universities by enrollment in the ...

Education

Malhotra received her bachelor's degree in Physics from

Delhi University Delhi University (DU), formally the University of Delhi, is a collegiate university, collegiate Central university (India), central university located in New Delhi, India. It was founded in 1922 by an Act of the Central Legislative Assembly and ...

in 1988, and her Master's degree in Physics from the Indian Institute of Technology - Kanpur in 1990. In 1995, she became the first woman of color to receive a PhD in Astrophysics from

Princeton University Princeton University is a private university, private research university in Princeton, New Jersey. Founded in 1746 in Elizabeth, New Jersey, Elizabeth as the College of New Jersey, Princeton is the List of Colonial Colleges, fourth-oldest ins ...

. Her Ph.D. supervisor at Princeton was Professor Gillian Knapp. Malhotra's Ph.D. thesis examined the distribution of atomic and molecular gas in the Milky Way galaxy. Results from her thesis work are reproduced in the textbook "Galactic Structure", by Binney and Merrifield.

Career

After completing her Ph.D., Malhotra first held a postdoctoral fellowship at the California Institute of Technology. She next won a NAS
Hubble Fellowship
which she held at the

National Optical Astronomy Observatory The National Optical Astronomy Observatory (NOAO) was the United States national observatory for ground-based nighttime ultraviolet-optical-infrared (OUVIR) astronomy. The National Science Foundation (NSF) funded NOAO to provide forefront astronom ...

in Tucson and subsequently at the

Johns Hopkins University Johns Hopkins University (Johns Hopkins, Hopkins, or JHU) is a private university, private research university in Baltimore, Maryland. Founded in 1876, Johns Hopkins is the oldest research university in the United States and in the western hem ...

in Baltimore, Maryland. She then joined the science staff at the Space Telescope Science Institute in Baltimore, where she worked from 2001-2005. She moved to a faculty position at

in Tempe, Arizona in 2006, where she helped build up the ne
School of Earth and Space Exploration
She moved to NASA's

in early 2017 to take up a position working on development of the

Research

Infrared Properties of Galaxies

Malhotra and collaborators used

Infrared Space Observatory The Infrared Space Observatory (ISO) was a space telescope for infrared light designed and operated by the European Space Agency (ESA), in cooperation with ISAS (now part of JAXA) and NASA. The ISO was designed to study infrared light at wavelengt ...

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 The Lyman-alpha line, typically denoted by Ly-α, is a spectral line of hydrogen (or, more generally, of any one-electron atom) in the Lyman series. It is emitted when the atomic electron transitions from an ''n'' = 2 orbital to the gro ...

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 multinationa
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 The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versa ...

treasury programs
GRAPESPEARS
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

Malhotra has advised over a half dozen Ph.D. thesis students, includin
Steven FinkelsteinNimish Hathi
Vithal Tilvi, Lifang Xia, Huan Yang, Tianxing Jiang, and John Pharo.

Awards and honors

Malhotra was awarded a NASA Hubble Fellowship in 1998.
She is a Legacy Fellow of the American Astronomical Society.

References

{{DEFAULTSORT:Malhotra, Sangeeta Indian astrophysicists Living people NASA astrophysicists 20th-century Indian astronomers 20th-century Indian women scientists 21st-century Indian astronomers 21st-century Indian women scientists Fellows of the American Astronomical Society Delhi University alumni IIT Kanpur alumni Princeton University alumni Year of birth missing (living people)