Nabeel Rehemtulla

I'm a third year Astronomy PhD student in CIERA at Northwestern University working with Prof. Adam A. Miller. I focus on augmenting large optical time-domain surveys, like the Zwicky Transient Facility and the Rubin Obesrvatory, with machine learning tools. In terms of astrophysics, I'm interested in the large samples produced by these observatories and observing rare or rapidly evolving transients. On the machine learning side, I am particularly excited by computer vision and multi-modality.

I also work in the DESI Milky Way Survey on modeling the Milky Way's cumulative mass profile with a non-parametric tool I developed called NIMBLE.


Research Projects

Presentations of these projects can be found below.

BTSbot: A ConvNet to automatically identify ZTF transients

Northwestern University, CIERA

The Bright Transient Survey (BTS) relies on visual inspection ("scanning") to select sources for accomplishing its mission of spectroscopically classifying all bright extragalactic transients found by the Zwicky Transient Facility (ZTF). BTSbot provides a bright transient score to individual ZTF alert packets using their image data and 14 extracted features. BTSbot eliminates the need for scanning by automatically identifying new bright transient candidates. BTSbot outperforms BTS scanners in terms of completeness (99% vs. 95%) and identification speed (on average, 7.4 hours quicker).

Codebase publicly available on GitHub

Presentations & Publications

Submitted to ApJ: Publication

Yielded the world's first fully automatic end-to-end discovery and classification of a transient: press release
  Some articles writen about BTSbot: Space.com, Gizmodo, Dropbox blogs

Won 1st prize at the Northwestern CoDEx Visualization Competition

Presented a poster at the Workshop on ML for Astrophysics at the 40th ICML:
Conference proceedings | Poster PDF

Gave an oral talk at the Transients and Variable Universe conference at UIUC:
Slides

Non-Parametric Spherical Jeans Mass Estimation with B-Splines

University of Michigan – Ann Arbor

We consider the application of Jeans modeling to mapping the dark matter distribution in the outer reaches of the Milky Way using field halo stars. To do so, we develop a novel non-parametric routine for solving the spherical Jeans equation by fitting B-splines to the velocity and density profiles of halo stars and an MCMC-based subroutine that deconvolves observational effects from the underlying distributions.

Codebase publicly available under the name NIMBLE (Non-parametrIc jeans Mass with B-spLinEs)

Presentations & Publications

Published as Rehemtulla et al. 2022

Presented an iPoster at 237th AAS meeting and won a Chambliss Astronomy Achievement award.
the iPoster | PDF version

Gave an oral talk at the Michigan Institute for Data Science Poster Symposium 2020 and won the Outstanding Undergraduate Poster award.
the poster | the presentation slides

I wrote a short summary of this project (a bite) for the undergraduate research series on astrobites.org

Star Formation Rate in Merger Galaxies

University of Michigan – Ann Arbor
MDM Observatory, Kitt Peak National Observatory

We observe four target merger galaxies in H-alpha to calcualte their star formation rate densities and compile previously observed data giving us their gas surface density. With these two quantities, we can investigate how various merger galaxies stand in relation to non-mergers with respect to the Kennicutt-Schmidt law.

Presentations & Publications

the observing proposal | write-up of findings


Other Projects

Website Architect for GHOSTS HST Survey

University of Michigan & Leibniz Institute for Astrophysics

I undertook a project rebuilding the Galaxy, Halos, Outer disks, Substructure, Thick disks and Star clusters (GHOSTS) HST survey website. I noted inefficiencies in the source of the current version and designed a rebuild to correct for these and improve expandability. I proposed my rebuild project to GHOSTS P.I. Dr. Roelof de Jong with logistical help from GHOSTS team member and UM professor, Eric Bell. My rebuild employs Jinja, an efficient Python templating engine, to simplify the creation and modification of their webpages.

the GitHub repository

Hobbies

When I'm not staring into a jupyter notebook, I like to keep myself moving and trying new things. During quarantine, I starting baking all kinds of desserts. In order to stay fit after eating the desserts, I've taken up indoor rock climbing.

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