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Published on : 16 July, 2020


Dunlap Institute for Astronomy and Astrophysics

University of Toronto, Canada.

Observational galaxy formation and evolution


I am an observational astronomer studying the structural evolution of massive galaxies in the early Universe. I am a Dunlap Post-doctoral Fellow at Dunlap Institute for Astronomy and Astrophysics, University of Toronto. I received my PhD in 2020 from Yale University under the supervision of my advisor Prof. Pieter van Dokkum. I study how the structural properties of galaxies have evolved in the last 10 billion years, what factors have contributed to this evolution and how this can be used to infer overall galaxy formation and evolution. I am also intrigued by the challenges of disentangling observational biases from the intrinsic physical properties of galaxies.

I am from Dhaka, Bangladesh and moved to the USA for undergraduate study in astrophysics at Wellesley College, MA. I am an advocate for equal opportunities in scientific research/education for students from countries with limited access to resources. I have taught in the Yale Young African Scholars, am an organizing member of the West African International Summer School for Young Astronomers and have founded an after-school program called Bangladesh Science Outreach in Dhaka, Bangladesh.


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COSMOS-Drift And SHift (COSMOS-DASH) is a HST/WFC3 imaging survey of the COSMOS field in the F160W filter, covering an area of 0.49 deg2, giving 0.66 deg2 of total data in the archive, tripling the extragalactic survey area in near-infrared with HST. The unique Drift And SHift (DASH) observing mode forgoes inefficient guide-star acquisition per pointing by guiding with three gyros alone. With DASH we increased imaging efficiency of WFC3 by eight times to observe wide field medium depth survey. Multiple read-outs per pointing with extremely small drifts between 25 second exposures are then shifted and coadded to create final undistorted deep image. For full details, see Momcheva et al. (2017) and Appendix A1 of Mowla et al. (2019b).

I led the data release and the first scientific paper of COSMOS-DASH, showing that with appropriate data reduction methods, the DASH technique preserves the WFC3 spatial resolution, and that galaxy structural parameters are consistent with those measured from guided surveys. We are planning to expand COSMOS-DASH to cover the entire COSMOS field (1.7 deg^2). If your science can benefit from the wider COSMOS-DASH survey please contact me! Cutouts and colored images (with ACS-F814W) are available on request here.

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Mowla et al. 2019b


The most massive galaxies of the early Universe live today in the centers of groups- and cluster-sized halos and host the most extreme black holes, such as that seen in M87. Because they are rare, little is known about the structure of these galaxies during their build-up at early epochs. Armed with the wide area of the high-resolution COSMOS-DASH image, we were finally able to measure the structural parameters of over a thousand massive galaxies at 0.1 I find that for the most massive galaxies, the size difference between star-forming and quiescent galaxies start to disappear. However, a significant difference remain in the compactness of the light profile between the two sample - massive quiescent galaxies have higher central densities than star-forming galaxies (Mowla et al. 2019b). The morphologies of galaxies at the highest mass end show a wide range and they go from highly star-forming galaxies at z=2 to mostly quiescent galaxies at z=1. Catalog of the structural properties of the most massive galaxies can be found here.