arXiv subjects

Nataša Pavlov

Publications and source records attributed to Nataša Pavlov.

4 recordsLinked to original sources

arXiv2026

Puzzling Ultra-Diffuse Galaxy Evolution (PUDGE). II. A transformation pathway from ultra-diffuse galaxies to compact dwarfs in galaxy clusters

Ultra-diffuse galaxies (UDGs) and compact dwarfs (CDs) occupy opposite extremes of the structural parameter space of dwarf galaxies, yet their spatial distributions in clusters suggest a possible evolutionary connection. Observational studies have reported a pronounced anticorrelation between the two populations interpreted as evidence that CDs represent tidally stripped remnants of diffuse progenitors, a scenario that implicitly assumes a compact stellar nucleus must be present at infall to survive environmental processing. We tested this hypothesis using the IllustrisTNG cosmological simulation (TNG100) by examining the UDG and CD populations in seven galaxy clusters and tracing the evolutionary histories of 112 present-day CDs. We confirm that TNG100 reproduces the observed spatial anticorrelation, with CDs concentrated within $d/R_{200} \lesssim 0.2$ and UDGs preferentially inhabiting the cluster outskirts. Tracing CDs back in time, we identified eight systems whose progenitors undergo a transient UDG phase, with extremely high gas fractions ($f_{\rm gas} \gtrsim 0.8$), immediately before cluster infall. In all eight systems, a vast majority of the present-day stellar mass was assembled after the epoch of maximum spatial extent, and the peak star formation rate during the transformation is the highest each galaxy achieves across its entire lifetime. The UDG progenitors show no prominent stellar cores before infall, demonstrating that the compact component of the resulting CD is not an exposed preexisting nucleus but is instead freshly built through starburst-driven star formation during the stripping process itself. Our results reveal a physically motivated UDG-to-CD transformation pathway driven entirely by cluster environment that is fundamentally distinct from classical tidal stripping scenarios and highlight the critical role of gas richness as a prerequisite for this channel.

astro-ph.GA↗

arXiv2026

The habitability trade-off: Chemical decoupling and quenching in massive galaxies

Massive galaxies experience complex evolutionary processes, including mergers and gas accretion, which can disrupt the chemical equilibrium between their stellar and gaseous components. Using the IllustrisTNG (TNG100) simulation at $z=0$, we investigated the prevalence and physical properties of such chemically decoupled systems within the massive star-forming galaxy population. We identify a substantial subpopulation ($\sim 31.5\%$ of the sample) that exhibits systematic stellar-gas decoupling, characterised by a metal-rich stellar component coexisting with a diluted gas reservoir. These non-equilibrium galaxies are closely linked to recent merger activity and partial quenching, and display systematically suppressed star-formation rates and reduced gas fractions, consistent with a transitional evolutionary phase. We then examined the implications of this phase for galaxy-scale habitability prescriptions by applying a terrestrial planet abundance proxy that combines stellar mass, gas-phase metallicity, and the rate of sterilising events. Despite their diluted gas reservoirs, non-equilibrium galaxies dominate the high end of the inferred present-day habitability proxy distribution, exceeding equilibrium systems by more than an order of magnitude. We interpret this as a habitability trade-off: the same gas dilution and quenching processes that reduce the efficiency of future terrestrial planet formation simultaneously create a transient phase of suppressed radiation hazards for existing planets. The Andromeda galaxy (M31) shows qualitative similarities to this chemically decoupled population, suggesting that galaxies exiting their peak star-forming phase represent a distinct and highly relevant demographic for galaxy-scale habitability. Galactic habitability is therefore intrinsically time-dependent.

astro-ph.GA↗

arXiv2025

Discovery of a galaxy associated with the HI cloud FAST J0139+4328

The search for ``dark galaxies,'' a key prediction of the lambda cold dark matter, has yielded few viable candidates. Recently, FAST J0139+4328 was reported as the first isolated dark galaxy in the nearby universe, based on a neutral hydrogen (HI) detection and a non-detection in the Pan-STARRS1 survey. To verify the nature of this candidate, we obtained deep optical imaging, using the $1.4\,\mathrm{m}$ \textit{Milanković} and $0.6\,\mathrm{m}$ \textit{Nedeljković} telescopes, and spectroscopic follow-up of the field. We report the unambiguous discovery of a low-surface-brightness (LSB) optical counterpart at the location of the HI cloud. Furthermore, the detection of H$α$ emission via the $6\,\mathrm{m}$ Big Telescope Alt-Azimuthal (BTA) confirms that the stellar system lies at a redshift consistent with the HI source, establishing their physical association. Through detailed photometry and employing color-dependent mass-to-light scaling relations, we derive a total stellar mass of $M_\star = (7.2 \pm 3.7) \times 10^6\, M_{\odot}$, about an order of magnitude higher than the previously estimated upper limit. Using the literature HI mass, this implies a gas-to-stellar mass ratio of $M_{\mathrm{HI}} / M_{\star} = 11.5 \pm 6.4$. Our findings demonstrate that FAST J0139+4328 is not a dark galaxy but an extremely gas-rich LSB dwarf galaxy, whose stellar component was simply below the detection limit of the Pan-STARRS1 survey. This reclassification resolves the status of this prominent dark galaxy candidate and underscores the necessity of deep optical follow-up to classify faint HI-selected systems.

astro-ph.GA↗

arXiv2025

Puzzling Ultra-Diffuse Galaxy Evolution (PUDGE). I. The existence of a Nube-like galaxy in IllustrisTNG

The recent discovery of the most extended ultra-diffuse galaxy (UDG), Nube, has raised yet another question about the validity of the cold dark matter (CDM) model. The studies using cosmological and zoom-in simulations, which assume CDM, failed to replicate galaxies with the structural properties of Nube. However, the simulation box or the examined population of UDGs may be too narrow to fully capture the range of effects that can lead to the formation of such extraordinary galaxies. In this work we present a case study of a Nube-like galaxy from TNG100, the most extended simulated UDG examined to date that closely mirrors the structural properties of the observed Nube galaxy. Since its formation, the simulated Nube-like galaxy has already been ultra-diffuse and evolved mainly in isolated regions with occasional interactions. Its last major merger was finalized about 1.336 Gyr ago and left no trace of interaction apart from further extending the stellar size. This evolutionary pathway, featuring a recent merger that expanded an already ultra-diffuse stellar system, is unique and innovative compared to previous studies. We argue that multiple proposed formation mechanisms can operate simultaneously, further expanding the UDGs and making them extreme outliers of the mass-size relation under favorable conditions. Therefore, it is essential to study these simulated extreme outliers, their formation, and, more importantly, their evolution. We also highlight the necessity of carefully analyzing and interpreting the simulated data and better understanding the limitations of a chosen simulation. Thus, if Nube is considered an extreme outlier, its properties are not in tension with the standard cosmological model.

astro-ph.GA↗