Astronomy & Astrophysics

Kiyan Tavangar

PhD Student, Department of Astronomy, Columbia University

I study near-field cosmology, Galactic dynamics in the disk and the halo, and the nature of dark matter, with a focus on stellar streams and phase-space spirals in the Milky Way.

If we share similar interests, I'd be happy to talk with you, your group, or your institution about these topics.

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Research Interests

Dark matter, Galactic structure, and the interplay between observation and theory.

I am interested in discovering the nature of dark matter. Most of my research uses near-field cosmology and Galactic structure, which can offer insights into dark matter subhalos. In particular, I study what stellar streams, elongated arcs of stars stretching tens of degrees across the sky, can tell us about the sizes and structure of these subhalos.

That work led me to dynamics and disequilibria in the nearby universe: phase-space spirals in the disk, warps in the outer halo, and the reflex motion of the Milky Way caused by the LMC.

More generally, I want to work at the nexus of observational and theoretical astrophysics, where I believe the most important breakthroughs in the field can be made.

Research Highlights

A selection of current and past projects. See all projects in detail.

Phase-Space Spirals in the Disk

My main current focus: the "snails" in the Galactic disk, one of its clearest signatures of disequilibrium, studied across multiple projections.

The GD-1 Stream

A flexible density model of GD-1 in Gaia DR3 that constrains stream members and the perturber behind the stream's spur.

Tidal Envelopes Around Globular Clusters

Searching globular clusters in the DELVE data for extratidal features, and testing what LSST will be able to detect.

The Phoenix Stream

My first first-author paper: a detailed characterization of the Phoenix stream in Dark Energy Survey data.

Palomar 13 Tidal Tails

The discovery of extended tidal tails around the globular cluster Palomar 13.

Strong Lensing: COOL-LAMPS

Part of the founding class of the COOL-LAMPS collaboration, which discovered the brightest z ~ 5 galaxy known.

Selected Publications

Full list on SciX and ADS.

2026
Phase-Spirals Across Galactic Disks II: Using large-scale "macro-spirals" in phase-spiral amplitude to derive perturbation times Accepted Tavangar, K. et al. The Astrophysical Journal
arXiv
2026
Phase Spirals Across Galactic Disks I: Exploring dynamical influences on winding Tavangar, K. et al. The Astrophysical Journal, 1005(1), 120
arXiv
2026
The Phase Spiral's Origin and Evolution: Indications from Its Varying Properties across the Milky Way Disk Widmark, A.; Tavangar, K.; Kalish, J.; Johnston, K. V.; Hunt, J. The Astrophysical Journal, 999(1), 52
arXiv
2025
DELVE-ing into the Milky Way's Globular Clusters: Assessing Extratidal Features in NGC 5897, NGC 7492, and Testing Detectability with Deeper Photometry Chiti, A.; Tavangar, K.; et al. The Astronomical Journal, 170(5), 294
arXiv
2025
Inferring the Density and Membership of Stellar Streams with Flexible Models: The GD-1 Stream in Gaia Data Release 3 Tavangar, K. and Price-Whelan, A. M. The Astrophysical Journal, 988(1), 45
arXiv
2022
From the Fire: A Deeper Look at the Phoenix Stream Tavangar, K. et al. The Astrophysical Journal, 925(2), 118
arXiv
2020
Discovery of Extended Tidal Tails Around the Globular Cluster Palomar 13 Shipp, N.; Price-Whelan, A.; Tavangar, K.; Mateu, C.; Drlica-Wagner, A. The Astronomical Journal, 160(5), 244
arXiv

Beyond Research

Outreach, access to science, and a few other things about me.

STEM Prison Outreach Program

I founded and co-organize this program at Columbia. Each semester I recruit volunteers from across Columbia's STEM departments to give outreach lectures to incarcerated students at MDC Brooklyn, on topics including astronomy, neuroscience, climate science and artificial intelligence.

Making astronomy accessible

I'm involved with Columbia's astronomy outreach team, and I think a lot about how to ease the transition from classes to research for undergraduates considering a career in astronomy.

Heritage and languages

I am of French and Iranian heritage. I spent most summers growing up in France, where I still have family, and speak French fluently. I used to speak Farsi, and I have not yet been to Iran.

Sports

I like playing and watching many sports. I played soccer throughout my childhood and ran cross country for the University of Chicago track and field team all through college.

CV & Contact

My most recent CV, and the best ways to reach me.

Kiyan Tavangar

Department of Astronomy, Columbia University, New York, NY
k.tavangar@columbia.edu

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