arXiv subjects

M. Korsaga

Publications and source records attributed to M. Korsaga.

6 recordsLinked to original sources

arXiv2026

Angular momentum in isolated disc galaxies: Insights from TNG100

Angular momentum is a fundamental property that shapes the evolution of disc galaxies, strongly influencing the internal mechanisms that regulate star formation. Its content within disc galaxies is predicted to change over time, mainly as a result of external processes that regulate galaxy evolution. While several numerical studies paint a complex picture of angular momentum variation with environmental mechanisms, a recent observational finding suggests that galaxies are subject to angular momentum loss when they undergo interactions. By studying the stellar angular momentum of simulated disc galaxies selected at various degrees of isolation, we aim to investigate whether isolation affects the stellar angular momentum content of disc galaxies and assess whether the environmental trends previously reported for baryonic angular momentum may also be reflected exclusively in the stellar component. We selected star-forming disc galaxies in the IllustrisTNG simulation suite, for which we computed an isolation parameter based on local density. Using a density threshold, we identified isolated discs from non-isolated galaxies and performed a comparative study of their angular momentum content against other evolutionary parameters. We find that isolation alone does not define the angular momentum content of a galaxy. Rather, whether a disc is gas-rich or gas-poor is directly linked to the specific angular momentum content, $j_*$, of its stellar disc.

astro-ph.GA↗

arXiv2026

The size of the HI disk across different environments: isolated, compact groups, clusters, and pairs

The 21 cm line of atomic hydrogen (HI) is a sensitive tracer of the outer disk of galaxies, where environmental signatures are most apparent. The relative extent of HI disks compared to optical disks ($D_{\rm HI}$ vs $D_{25}$) is thought to provide a quantitative measure of such imprint, yet systematic comparisons between extreme environments remain scarce. We quantify the relative extent of HI disks in Hickson Compact Groups (HCGs) and in the Analysis of the interstellar Medium in Isolated GAlaxies (AMIGA) sample, using AMIGA as a control sample that captures secular evolution with minimal external influence. We calculate HI diameters by directly fitting an ellipse to the $1\,M_{\odot}\,{\rm pc}^{-2}$ iso-density contour. Because $D_{\rm HI}$ and $D_{25}$ are nonlinearly related, we avoid the traditional $D_{\rm HI}/D_{25}$ ratio, which carries a size-dependent bias, and instead quantify truncation as the residual from the isolated-galaxy $D_{\rm HI}$-$D_{25}$ baseline, which we establish for AMIGA via Bayesian analysis. The full analysis is provided as a reproducible Python package and Snakemake workflow. HCG galaxies lie systematically below the isolated-galaxy baseline in the $D_{\rm HI}$-$D_{25}$ plane. When members with HI nondetections are included as upper limits, HCGs have HI disks at least ~71% smaller than expected for isolated galaxies of the same optical diameter. The truncation increases monotonically along the HCG evolutionary sequence, from Phase 1 to Phase 3. A comparison with literature samples places HCGs at the most-truncated end, statistically indistinguishable from the Virgo cluster sample (VIVA). Compared to AMIGA, HI disks are typically smaller relative to the optical disk in loose groups, compact groups, and cluster infall/field environments, and are most strongly truncated in HCGs and in the Virgo cluster sample.

astro-ph.GA↗

arXiv2025

MeerKAT view of Hickson Compact Groups: II. HI deficiency in the core and surrounding regions

Hickson compact groups (HCGs) offer an ideal environment for investigating galaxy transformation as a result of interactions. It has been established that the evolutionary sequence of HCGs is marked by an intermediate stage characterised by a substantial amount of HI in their intragroup medium (IGrM) in the form of tidal tails and bridges (Phase 2), rapidly followed by a final stage where no IGrM gas is found and where their member galaxies are highly HI-deficient (Phase 3). Despite numerous single-dish and interferometric HI studies on the HCGs, a clear HI picture of the groups within their large-scale environment still remains to be uncovered. Taking advantage of the MeerKAT's high column density sensitivity and large field-of-view, we aim to investigate the rapid transformation of HCGs from the intermediate to late phases, and establish a picture of their gas content variations in the context of their large-scale environments. We performed MeerKAT observations of six HCGs selected to represent the intermediate and late phases of the proposed evolutionary sequence. Combining the HI observations with data from recent wide-field optical surveys, we evaluated the HI deficiencies of galaxies in a ~30' radius of the HCGs. We find that galaxies surrounding both phases exhibit similar distributions in their gas content. Similarly, galaxies making up the cores of Phase 2 HCGs are comparable to their neighbours in terms of HI deficiencies. However, Phase 3 groups are over an order of magnitude more deficient than their surroundings, supporting previous findings that late-phase HCG galaxies are more evolved than their large-scale environments.

astro-ph.GA↗

arXiv2021

The phantom dark matter halos of the Local Volume in the context of modified Newtonian dynamics

We explore the predictions of Milgromian gravity (MOND) in the Local Universe by considering the distribution of the `phantom' dark matter (PDM) that would source the MOND gravitational field in Newtonian gravity, allowing an easy comparison with the dark matter framework. For this, we specifically deal with the quasi-linear version of MOND (QUMOND). We compute the `stellar-to-(phantom)halo-mass relation' (SHMR), a monotonically increasing power-law resembling the SHMR observationally deduced from spiral galaxy rotation curves in the Newtonian context. We show that the gas-to-(phantom)halo-mass relation is flat. We generate a map of the Local Volume in QUMOND, highlighting the important influence of distant galaxy clusters, in particular Virgo. This allows us to explore the scatter of the SHMR and the average density of PDM around galaxies in the Local Volume, $Ω_{\rm pdm} \approx 0.1$, below the average cold dark matter density in a $Λ$CDM Universe. We provide a model of the Milky Way in its external field in the MOND context, which we compare to an observational estimate of the escape velocity curve. Finally, we highlight the peculiar features related to the external field effect in the form of negative PDM density zones in the outskirts of each galaxy, and test a new analytic formula for computing galaxy rotation curves in the presence of an external field in QUMOND. While we show that the negative PDM density zones would be difficult to detect dynamically, we quantify the weak lensing signal they could produce for lenses at $z \sim 0.3$.

astro-ph.GA↗

arXiv2019

GHASP: an H$α$ kinematical survey of spiral galaxies -- XIII. Distribution of luminous and dark matter in spiral and irregular nearby galaxies using H$α$ and HI rotation curves and WISE photometry

We present the mass models of 31 spiral and irregular nearby galaxies obtained using hybrid rotation curves (RCs) combining high resolution GHASP Fabry-Perot H$α$ RCs and extended WHISP HI ones together with 3.4 $μ$m WISE photometry. The aim is to compare the dark matter (DM) halo properties within the optical radius using only H$α$ RCs with the effect of including and excluding the mass contribution of the neutral gas component, and when using HI or hybrid RCs. Pseudo-isothermal (ISO) core and Navarro-Frenk-White (NFW) cuspy DM halo profiles are used with various fiducial fitting procedures. Mass models using H$α$ RCs including or excluding the HI gas component provide compatible disc M/L. The correlations between DM halo and baryon parameters do not strongly depend on the RC. Clearly, the differences between the fitting procedures are larger than between the different datasets. Hybrid and HI RCs lead to higher M/L values for both ISO and NFW best fit models but lower central densities for ISO halos and higher concentration for NFW halos than when using H$α$ RCs only. The agreement with the mass model parameters deduced using hybrid RCs, considered as a reference, is better for HI than for H$α$ RCs. ISO density profiles better fit the RCs than the NFW ones, especially when using H$α$ or hybrid RCs. Halo masses at the optical radius determined using the various datasets are compatible even if they tend to be overestimated with H$α$ RCs. Hybrid RCs are thus ideal to study the mass distribution within the optical radius.

astro-ph.GA↗

arXiv2018

Early Observations of the MHONGOOSE Galaxies: Getting Ready for MeerKAT

We present early observations of 20 galaxies in the MHONGOOSE survey galaxies using KAT-7, the GBT, and MeerKAT. We present the best calibrators for five of the MHONGOOSE galaxies observed with the KAT-7, and search for signs of gas accretion in the GBT data, down to $3σ$ column density levels of $\rm 2.2\times10^{18}\, cm^{-2}$ over a $\rm 20\, km\, s^{-1}$ linewidth, but identify none. Using the KAT-7 and MeerKAT data, we have derived rotation curves and mass models for NGC 3621 and NGC 7424 out to an unprecedented extent. As a precursor to the SKA, the MeerKAT telescope combines both a high spatial resolution and a large field of view, necessary to map the extended neutral hydrogen in local galaxies. The mass models of the two galaxies were constructed for both the Dark Matter (DM) models (the pseudo-isothermal model and the Navarro-Frenk-White model) and MOND. Overall, we find that the DM models provide a better fit than MOND to the galaxies' rotation curves. Furthermore, the pseudo-isothermal model is found to be the most consistent with the observations.

astro-ph.GA↗