About Me

Hi! I'm Robin Eappen, a PhD researcher in astronomy and astrophysics at the University of Bonn, working under the supervision of Prof. Pavel Kroupa. My research focuses on galaxy formation and evolution within the framework of Modified Newtonian Dynamics (MOND). I explore how massive galaxies in the early universe formed and evolved without invoking cold or warm dark matter, providing new perspectives on long-standing cosmological questions.

Let there be light and there was light, they tried the same with darkness (dark matter) but then came Milgrom 😜

Somewhere someone once said...

"I began with fresh hopes and ambitions, seeking to explore and elucidate the surrounding mysteries. Yet, my fervent journey was abruptly halted by the so-called 'experts' in power. They scrutinized and demanded revisions that aligned with their narrative. I resisted succumbing entirely, making only a few changes. But unbeknownst to me, the essence of my work vanished. Ambitions and explorations were torn away, and now I find myself a cog driven by these 'experts'."
"In a world where the currency of value is often measured in coins and clout, the depth of artistry and scientific marvels sometimes evades the grasp of those solely chasing monetary and authoritative eminence. The richness of these disciplines, like elusive constellations, often remains veiled to the eyes fixated on material worth and dominance. Yet I, a mere mortal, am but a whisper in the symphony of voices, unable to echo a resounding opinion amidst the clamor."
Galaxy simulation image
Top panel: Surface projection plot of merged model galaxy from Eappen & Kroupa (2025)
Bottom panel: Surface projection plot of model galaxy from Eappen & Kroupa (2025)

My Work

In my first major study, I investigated the monolithic collapse of post-Big-Bang gas clouds in Milgromian gravity. This work showed that early-type galaxies (ETGs) can form rapidly, with star formation timescales (SFTs) that align with observations. These results challenge the hierarchical merger paradigm by demonstrating that short SFTs are a natural consequence of MOND-based cosmology, consistent with the observed downsizing effect in galaxy formation (Eappen et al. 2022, MNRAS).

Galaxy simulation image
SFT - mass relation

Building on this, I studied the formation of compact massive relic galaxies—ancient systems that have remained largely unchanged since their formation. By simulating the collapse of isolated gas clouds, I found that MOND can naturally reproduce these relics with structural and kinematic properties similar to observed systems like NGC 1277 (Eappen 2024, MNRAS).

Rotational velocity Velocity dispersion
Rotational velocity and Velocity dispersion profiles

In my most recent work, I extended these models to analyze the morphological and structural evolution of ETGs within MOND, including galaxy mergers. The simulations reveal that mergers of relic galaxies yield systems with realistic ellipticity, rotation, and scaling relations—such as the Fundamental Plane and Kormendy relation—closely matching those of observed elliptical galaxies (Eappen & Kroupa 2025, Galaxies).

Galaxy simulation image
Classical Vrot - ellipticity plot

Together, these studies support Milgromian dynamics as a compelling alternative to dark matter-based cosmology, particularly at the galaxy scale.

Publications

📄 The formation of early-type galaxies in Milgromian Dynamics
Eappen et al. (2022), MNRAS
📄 The formation of compact massive relic galaxies in MOND
Eappen & Kroupa (2024), MNRAS
📄 Scaling relations of early-type galaxies in MOND
Eappen & Kroupa (2025), Galaxies
🖼 Poster presented at Epoch of Galaxy Quenching 2022
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🖼 Poster presented at Wide-Field Spectroscopy vs Galaxy Formation (Tucson, Arizona) & LEM workshop (CfA Boston, 2023)
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Contact Me

Please feel free to contact me if you have any queries or are interested in discussions.