Understanding the origin and evolution of the Milky Way Nuclear Star Cluster
The center of the Milky Way contains the densest star cluster our galaxy. It has a mass of over 10 million suns. It also contains a supermassive black hole of 4 million solar-masses. Because this is the closest supermassive black hole, we can study it in more detail than any other. This combination of a crowded stellar environment around a massive black hole makes for an ideal location to study the interaction between stars and black holes. Because our nuclear star cluster is similar to those of other galaxies, studying its origin and evolution will help us understand the formation of the nuclei of galaxies.
Properties of the supermassive black hole Sgr A*
The supermassive black hole at the Galactic center can be studied in multiple ways. Some of the methods I use are: (1) through its gravitational effect on stars orbiting it, and (2) through near-infrared light arising from gas falling onto the black hole.
Stellar Population
The composition of stars making up the Milky Way nuclear star cluster is complex, as it hosts multiple generations of stars that may have arrived from other parts of the Milky Way. In order to reconstruct the formation history of the nuclear star cluster, I utilize spectroscopy and synthetic spectral grids to differentiate between the different population of stars. The goal is to determine fundamental physical parameters of individual stars such as their effective temperature, surface gravity and elemental abundances.
Related Publications
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The HST-Gaia Near-infrared Astrometric Reference Frame Near the Milky Way Galactic Center
Hosek M. W., Do T., Martinez G. D., Lewis-Merrill R., Ghez A. M., Lu J. R., Sakai S., Anderson J. (2025)
The Astrophysical Journal, 989, 79 -
First Mid-infrared Detection and Modeling of a Flare from Sgr A*
von Fellenberg S. D., Roychowdhury T., Michail J. M., Sumners Z., Sanger-Johnson G., Fazio G. G., Haggard D., Hora J. L., Philippov A., Ripperda B., Smith H. A., Willner S. P., Witzel G., Zhang S., Becklin E. E., Bower G. C., Chandra S., Do T., Garcia Marin M., Gurwell M. A., Ford N. M., Hada K., Markoff S., Morris M. R., Neilsen J., Sabha N. B., Seefeldt-Gail B. (2025)
The Astrophysical Journal, 979, L20 -
New Evidence for a Flux-independent Spectral Index of Sgr A* in the Near-infrared
Paugnat H., Do T., Gautam A. K., Martinez G. D., Ghez A. M., Sakai S., Weldon G. C., Hosek M. W., Haggard Z., O'Neil K. K., Becklin E. E., Witzel G., Lu J. R., Matthews K. (2024)
The Astrophysical Journal, 977, 228 -
Photometric classification of stars around the Milky Way's central black hole: I. Central parsec
Gallego-Cano E., Fritz T., Schödel R., Feldmeier-Krause A., Do T., Nishiyama S. (2024)
Astronomy and Astrophysics, 689, A190 -
General relativistic effects and the near-infrared variability of Sgr A*. II. A systematic approach to temporal asymmetry
von Fellenberg S. D., Witzel G., Bauboeck M., Chung H.-H., Marchili N., Martinez G., Sadun-Bordoni M., Bourdarot G., Do T., Drescher A., Fazio G., Eisenhauer F., Genzel R., Gillessen S., Hora J. L., Mang F., Ott T., Smith H. A., Ros E., Ribeiro D. C., Widmann F., Willner S. P., Anton Zensus J. (2024)
Astronomy and Astrophysics, 688, L12 -
An Estimate of the Binary Star Fraction among Young Stars at the Galactic Center: Possible Evidence of a Radial Dependence
Gautam A. K., Do T., Ghez A. M., Chu D. S., Hosek M. W., Sakai S., Naoz S., Morris M. R., Ciurlo A., Haggard Z., Lu J. R. (2024)
The Astrophysical Journal, , 164 -
High-resolution, Mid-infrared Color Temperature Mapping of the Central 10″ of the Galaxy
Dinh C. K., Ciurlo A., Morris M. R., Schödel R., Ghez A., Do T. (2024)
The Astronomical Journal, , 41 -
Constraining a Companion of the Galactic Center Black Hole Sgr A*
Will C. M., Naoz S., Hees A., Tucker A., Zhang E., Do T., Ghez A. (2023)
The Astrophysical Journal, , 58 -
Near-infrared Flux Distribution of Sgr A* from 2005-2022: Evidence for an Enhanced Accretion Episode in 2019
Weldon G. C., Do T., Witzel G., Ghez A. M., Gautam A. K., Becklin E. E., Morris M. R., Martinez G. D., Sakai S., Lu J. R., Matthews K., Hosek M. W., Haggard Z. (2023)
The Astrophysical Journal, , L33 -
Stellar Populations in the Central 0.5 pc of Our Galaxy. III. The Dynamical Substructures
Jia S., Xu N., Lu J. R., Chu D. S., O'Neil K. K., Drechsler W. B., Hosek M. W., Sakai S., Do T., Ciurlo A., Gautam A. K., Ghez A. M., Becklin E., Morris M. R., Bentley R. O. (2023)
The Astrophysical Journal, , 18 -
Evidence of a Decreased Binary Fraction for Massive Stars within 20 milliparsecs of the Supermassive Black Hole at the Galactic Center
Chu D. S., Do T., Ghez A., Gautam A. K., Ciurlo A., O'neil K. K., Hosek M. W., Hees A., Naoz S., Sakai S., Lu J. R., Chen Z., Bentley R. O., Becklin E. E., Matthews K. (2023)
The Astrophysical Journal, , 94 -
The formation history of our Galaxy's nuclear stellar disc constrained from HST observations of the Quintuplet field
Schödel R., Nogueras-Lara F., Hosek M., Do T., Lu J., Martínez Arranz A., Ghez A., Rich R. M., Gardini A., Gallego-Cano E., Cano González M., Gallego-Calvente A. T. (2023)
Astronomy and Astrophysics, , L8 -
The Star Formation History of the Milky Way's Nuclear Star Cluster
Chen Z., Do T., Ghez A. M., Hosek M. W., Feldmeier-Krause A., Chu D. S., Bentley R. O., Lu J. R., Morris M. R. (2023)
The Astrophysical Journal, , 79 -
The Swansong of the Galactic Center Source X7: An Extreme Example of Tidal Evolution near the Supermassive Black Hole
Ciurlo A., Campbell R. D., Morris M. R., Do T., Ghez A. M., Becklin E. E., Bentley R. O., Chu D. S., Gautam A. K., Gursahani Y. A., Hees A., O'Neil K. K., Lu J. R., Martinez G. D., Naoz S., Sakai S., Schödel R. (2023)
The Astrophysical Journal, , 136 -
AIROPA IV: Validating point spread function reconstruction on various science cases
Terry S. K., Lu J. R., Turri P., Ciurlo A., Gautam A., Do T., Fitzgerald M. P., Ghez A., Hosek M., Witzel G. (2023)
Journal of Astronomical Telescopes, Instruments, and Systems, , 018003 -
Measuring the Orbits of the Arches and Quintuplet Clusters Using HST and Gaia: Exploring Scenarios for Star Formation near the Galactic Center
Hosek M. W., Do T., Lu J. R., Morris M. R., Ghez A. M., Martinez G. D., Anderson J. (2022)
The Astrophysical Journal, , 68 -
Regularized 3D spectroscopy with CubeFit: Method and application to the Galactic Center circumnuclear disk
Paumard T., Ciurlo A., Morris M. R., Do T., Ghez A. M. (2022)
Astronomy and Astrophysics, , A97 -
AIROPA III: testing simulated and on-sky data
Turri P., Lu J. R., Witzel G., Ciurlo A., Do T., Ghez A. M., Fitzgerald M. P., Britton M. C., Ragland S., Terry S. K. (2022)
Journal of Astronomical Telescopes, Instruments, and Systems, , 039002 -
Multiwavelength Variability of Sagittarius A* in 2019 July
Boyce H., Haggard D., Witzel G., von Fellenberg S., Willner S. P., Becklin E. E., Do T., Eckart A., Fazio G. G., Gurwell M. A., Hora J. L., Markoff S., Morris M. R., Neilsen J., Nowak M., Smith H. A., Zhang S. (2022)
The Astrophysical Journal, , 7 -
Measuring the {\ensuremath{\alpha}}-abundance of Subsolar-metallicity Stars in the Milky Way's Central Half-parsec: Testing Globular Cluster and Dwarf Galaxy Infall Scenarios
Bentley R. O., Do T., Kerzendorf W., Chu D. S., Chen Z., Konopacky Q., Ghez A. (2022)
The Astrophysical Journal, , 77 -
General relativistic MHD simulations of non-thermal flaring in Sagittarius A*
Chatterjee K., Markoff S., Neilsen J., Younsi Z., Witzel G., Tchekhovskoy A., Yoon D., Ingram A., van der Klis M., Boyce H., Do T., Haggard D., Nowak M. A. (2021)
Monthly Notices of the Royal Astronomical Society, , 5281 -
Rapid Variability of Sgr A* across the Electromagnetic Spectrum
Witzel G., Martinez G., Willner S. P., Becklin E. E., Boyce H., Do T., Eckart A., Fazio G. G., Ghez A., Gurwell M. A., Haggard D., Herrero-Illana R., Hora J. L., Li Z., Liu J., Marchili N., Morris M. R., Smith H. A., Subroweit M., Zensus J. A. (2021)
The Astrophysical Journal, , 73 -
The former companion of hyper-velocity star S5-HVS1
Lu W., Fuller J., Raveh Y., Perets H. B., Li T. S., Hosek M. W., Do T. (2021)
Monthly Notices of the Royal Astronomical Society, , 603 -
Upper Limit on Brackett-{\ensuremath{\gamma}} Emission from the Immediate Accretion Flow onto the Galactic Black Hole
Ciurlo A., Morris M. R., Campbell R. D., Ghez A. M., Do T., Chu D. S. (2021)
The Astrophysical Journal, , 143 -
On Socially Distant Neighbors: Using Binaries to Constrain the Density of Objects in the Galactic Center
Rose S. C., Naoz S., Gautam A. K., Ghez A. M., Do T., Chu D., Becklin E. (2020)
The Astrophysical Journal, , 113 -
On the Origin of a Rotating Metal-poor Stellar Population in the Milky Way Nuclear Cluster
Arca Sedda M., Gualandris A., Do T., Feldmeier-Krause A., Neumayer N., Erkal D. (2020)
The Astrophysical Journal, , L29 -
Revealing the Formation of the Milky Way Nuclear Star Cluster via Chemo-dynamical Modeling
Do T., David Martinez G., Kerzendorf W., Feldmeier-Krause A., Arca Sedda M., Neumayer N., Gualandris A. (2020)
The Astrophysical Journal, , L28 -
Galactic Center IRS 13E: Colliding Stellar Winds or an Intermediate-mass Black Hole?
Zhu Z., Li Z., Ciurlo A., Morris M. R., Zhang M., Do T., Ghez A. M. (2020)
The Astrophysical Journal, , 135 -
Asymmetric spatial distribution of subsolar metallicity stars in the Milky Way nuclear star cluster
Feldmeier-Krause A., Kerzendorf W., Do T., Nogueras-Lara F., Neumayer N., Walcher C. J., Seth A., Schödel R., de Zeeuw P. T., Hilker M., Lützgendorf N., Kuntschner H., Kissler-Patig M. (2020)
Monthly Notices of the Royal Astronomical Society, , 396 -
Search for a Variation of the Fine Structure Constant around the Supermassive Black Hole in Our Galactic Center
Hees A., Do T., Roberts B. M., Ghez A. M., Nishiyama S., Bentley R. O., Gautam A. K., Jia S., Kara T., Lu J. R., Saida H., Sakai S., Takahashi M., Takamori Y. (2020)
Physical Review Letters, , 081101 -
A population of dust-enshrouded objects orbiting the Galactic black hole
Ciurlo A., Campbell R. D., Morris M. R., Do T., Ghez A. M., Hees A., Sitarski B. N., Kosmo O'Neil K., Chu D. S., Martinez G. D., Naoz S., Stephan A. P. (2020)
Nature, , 337 -
A Hidden Friend for the Galactic Center Black Hole, Sgr A*
Naoz S., Will C. M., Ramirez-Ruiz E., Hees A., Ghez A. M., Do T. (2020)
The Astrophysical Journal, , L8 -
Consistency of the Infrared Variability of SGR A* over 22 yr
Chen Z., Gallego-Cano E., Do T., Witzel G., Ghez A. M., Schödel R., Sitarski B. N., Becklin E. E., Lu J., Morris M. R., Dehghanfar A., Gautam A. K., Hees A., Hosek M. W., Jia S., Mangian A. C., Matthews K. (2019)
The Astrophysical Journal, , L28 -
Unprecedented Near-infrared Brightness and Variability of Sgr A*
Do T., Witzel G., Gautam A. K., Chen Z., Ghez A. M., Morris M. R., Becklin E. E., Ciurlo A., Hosek M., Martinez G. D., Matthews K., Sakai S., Schödel R. (2019)
The Astrophysical Journal, , L27 -
An Adaptive Scheduling Tool to Optimize Measurements to Reach a Scientific Objective: Methodology and Application to Measurements of Stellar Orbits in the Galactic Center
Hees A., Dehghanfar A., Do T., Ghez A. M., Martinez G. D., Campbell R., Lu J. R. (2019)
The Astrophysical Journal, , 87 -
Relativistic redshift of the star S0-2 orbiting the Galactic Center supermassive black hole
Do T., Hees A., Ghez A., Martinez G. D., Chu D. S., Jia S., Sakai S., Lu J. R., Gautam A. K., O'Neil K. K., Becklin E. E., Morris M. R., Matthews K., Nishiyama S., Campbell R., Chappell S., Chen Z., Ciurlo A., Dehghanfar A., Gallego-Cano E., Kerzendorf W. E., Lyke J. E., Naoz S., Saida H., Schödel R., Takahashi M., Takamori Y., Witzel G., Wizinowich P. (2019)
Science, , 664 -
Improving Orbit Estimates for Incomplete Orbits with a New Approach to Priors: with Applications from Black Holes to Planets
O'Neil K. K., Martinez G. D., Hees A., Ghez A. M., Do T., Witzel G., Konopacky Q., Becklin E. E., Chu D. S., Lu J. R., Matthews K., Sakai S. (2019)
The Astronomical Journal, , 4 -
The Fate of Binaries in the Galactic Center: The Mundane and the Exotic
Stephan A. P., Naoz S., Ghez A. M., Morris M. R., Ciurlo A., Do T., Breivik K., Coughlin S., Rodriguez C. L. (2019)
The Astrophysical Journal, , 58 -
Envisioning the next decade of Galactic Center science: a laboratory for the study of the physics and astrophysics of supermassive black holes
Do T., Ghez A., Becklin E., Genzel R., Psaltis D., Perets H., Armitage P., Gammie C., Quataert E., Hosek M., Gautam A. K., Bentley R. O., Morris M. R., Lu J., O'Neil K. K., Chen Z., Hees A., Ciurlo A., Rich R. M., Kerzendorf W., Dehghanfar A., Naoz S., Beaton R. L., Bellini A., Greene J., Chakrabarti S., Chu D. S., Libralato M., Witzel G., Nishiyama S., Rasio F., Weinberg N. N., Ramirez-Ruiz E., Ozel F., Hora J., Smith H. (2019)
Bulletin of the American Astronomical Society, , 530 -
The Galactic Center: An Improved Astrometric Reference Frame for Stellar Orbits around the Supermassive Black Hole
Sakai S., Lu J. R., Ghez A., Jia S., Do T., Witzel G., Gautam A. K., Hees A., Becklin E., Matthews K., Hosek M. W. (2019)
The Astrophysical Journal, , 65 -
The Galactic Center: Improved Relative Astrometry for Velocities, Accelerations, and Orbits near the Supermassive Black Hole
Jia S., Lu J. R., Sakai S., Gautam A. K., Do T., Hosek M. W., Service M., Ghez A. M., Gallego-Cano E., Schödel R., Hees A., Morris M. R., Becklin E., Matthews K. (2019)
The Astrophysical Journal, , 9 -
Characterizing and Improving the Data Reduction Pipeline for the Keck OSIRIS Integral Field Spectrograph
Lockhart K. E., Do T., Larkin J. E., Boehle A., Campbell R. D., Chappell S., Chu D., Ciurlo A., Cosens M., Fitzgerald M. P., Ghez A., Lu J. R., Lyke J. E., Mieda E., Rudy A. R., Vayner A., Walth G., Wright S. A. (2019)
The Astronomical Journal, , 75 -
An Adaptive Optics Survey of Stellar Variability at the Galactic Center
Gautam A. K., Do T., Ghez A. M., Morris M. R., Martinez G. D., Hosek M. W., Lu J. R., Sakai S., Witzel G., Jia S., Becklin E. E., Matthews K. (2019)
The Astrophysical Journal, , 103 -
Variability Timescale and Spectral Index of Sgr A* in the Near Infrared: Approximate Bayesian Computation Analysis of the Variability of the Closest Supermassive Black Hole
Witzel G., Martinez G., Hora J., Willner S. P., Morris M. R., Gammie C., Becklin E. E., Ashby M. L. N., Baganoff F., Carey S., Do T., Fazio G. G., Ghez A., Glaccum W. J., Haggard D., Herrero-Illana R., Ingalls J., Narayan R., Smith H. A. (2018)
The Astrophysical Journal, , 15 -
The Optical/Near-infrared Extinction Law in Highly Reddened Regions
Hosek M. W., Lu J. R., Anderson J., Do T., Schlafly E. F., Ghez A. M., Clarkson W. I., Morris M. R., Albers S. M. (2018)
The Astrophysical Journal, , 13 -
Super-solar Metallicity Stars in the Galactic Center Nuclear Star Cluster: Unusual Sc, V, and Y Abundances
Do T., Kerzendorf W., Konopacky Q., Marcinik J. M., Ghez A., Lu J. R., Morris M. R. (2018)
The Astrophysical Journal, , L5 -
Confusing Binaries: The Role of Stellar Binaries in Biasing Disk Properties in the Galactic Center
Naoz S., Ghez A. M., Hees A., Do T., Witzel G., Lu J. R. (2018)
The Astrophysical Journal, , L24 -
Investigating the Binarity of S0-2: Implications for Its Origins and Robustness as a Probe of the Laws of Gravity around a Supermassive Black Hole
Chu D. S., Do T., Hees A., Ghez A., Naoz S., Witzel G., Sakai S., Chappell S., Gautam A. K., Lu J. R., Matthews K. (2018)
The Astrophysical Journal, , 12 -
Measuring the effects of General Relativity at the Galactic Center with Future Extremely Large Telescopes
Do T., Hees A., Dehghanfar A., Ghez A., Wright S. (2017)
arXiv:1711.06389 -
Near-infrared variability study of the central 2.3 {\texttimes} 2.3 arcmin$^{2}$ of the Galactic Centre - II. Identification of RR Lyrae stars in the Milky Way nuclear star cluster
Dong H., Schödel R., Williams B. F., Nogueras-Lara F., Gallego-Cano E., Gallego-Calvente T., Wang Q. D., Rich R. M., Morris M. R., Do T., Ghez A. (2017)
Monthly Notices of the Royal Astronomical Society, , 3617 -
Near-infrared variability study of the central 2.3 arcmin {\texttimes} 2.3 arcmin of the Galactic Centre - I. Catalogue of variable sources
Dong H., Schödel R., Williams B. F., Nogueras-Lara F., Gallego-Cano E., Gallego-Calvente T., Wang Q. D., Morris M. R., Do T., Ghez A. (2017)
Monthly Notices of the Royal Astronomical Society, , 3427 -
The Post-periapsis Evolution of Galactic Center Source G1: The Second Case of a Resolved Tidal Interaction with a Supermassive Black Hole
Witzel G., Sitarski B. N., Ghez A. M., Morris M. R., Hees A., Do T., Lu J. R., Naoz S., Boehle A., Martinez G., Chappell S., Schödel R., Meyer L., Yelda S., Becklin E. E., Matthews K. (2017)
The Astrophysical Journal, , 80 -
Testing General Relativity with Stellar Orbits around the Supermassive Black Hole in Our Galactic Center
Hees A., Do T., Ghez A. M., Martinez G. D., Naoz S., Becklin E. E., Boehle A., Chappell S., Chu D., Dehghanfar A., Kosmo K., Lu J. R., Matthews K., Morris M. R., Sakai S., Schödel R., Witzel G. (2017)
Physical Review Letters, , 211101
(See "Updated Publications List" for the full collection)
