arXiv subjects

Carlo Cannarozzo

Publications and source records attributed to Carlo Cannarozzo.

11 recordsLinked to original sources

arXiv2026

Feedback driven interactions between dark and luminous matter to explain tight galaxy scaling relations

The tight empirical correlation linking the stellar disk scale length $R_d$ to the dark matter scale radius $r_0$ has been proposed as possible evidence for a fundamental coupling between baryons and dark matter beyond gravity. We re-examine the physical origin of this relation using a sample of 31 galaxies from the NIHAO cosmological hydrodynamical simulations, which include no dark matter-baryon interactions beyond gravity and baryonic feedback processes. NIHAO naturally reproduces both the normalization and the small scatter of the observed $R_d-r_0$ relation at $z=0$, while yielding a slightly shallower slope. By tracking galaxies from $z=2$ to $z=0$, we identify three distinct evolutionary classes: systems undergoing disk expansion, contraction, and quasi-static evolution. Using a Bayesian hierarchical framework, we provide the first characterization of the cosmic evolution of the $R_d-r_0$ relation, tracing the evolution of its normalization, slope, and intrinsic scatter from $z=2$ to the present day. We find a mild decrease in normalization ($\sim0.07$ dex), a flattening of the slope from $α\simeq 1.05$ to $α\simeq 0.95$, and a weak decline in the intrinsic scatter toward lower redshift, suggesting that galaxies evolve preferentially along the relation while jointly re-balancing their stellar and dark matter scales. By comparing hydrodynamical simulations with their dark-matter-only counterparts, we isolate the impact of baryons and baryonic feedback on halo structure. Our results show that stellar feedback alone can reshape the central potential and naturally establish the observed coupling between luminous and dark matter, without requiring modifications to the dark sector.

astro-ph.GA↗

arXiv2026

Empirical estimates of how massive galaxies can be in ΛCDM

Using Extreme Value Statistics applied to the observed galaxy stellar mass and the UV luminosity functions, we empirically estimate masses and luminosities of the most extreme galaxies in cosmological surveys, including the full sky. We incorporate uncertainties in stellar mass measurements (Eddington bias) and the scatter in the stellar-halo mass relation to derive empirical limits for galaxies residing in the most massive halos. The maximum observed $M_\ast$ strongly depends on survey area and redshift, ranging from $M_\ast \sim 7 \times 10^{12} M_\odot$ for full-sky surveys at $z\sim0$ to $M_\ast \sim 10^{10}M_\odot$ at $z\sim16$. Massive galaxies, particularly at high redshift, approach the theoretical maximum baryonic mass available in halos $M_\ast \sim 0.16 \times M_{\mathrm{vir}}$, consistent with previous claims. Accounting for measurement uncertainties significantly reduces the inferred maximum $M_\ast$ by up to $\sim1$ dex at $z\gtrsim10$, yielding stellar masses consistent with $M_\ast < 0.16$ at all redshifts. Assuming a perfect rank-order correspondence between the most massive halos and galaxies would guarantee this inequality at all redshifts. At 2 $\lesssim$ z $\lesssim$ 6, the most massive galaxies have stellar masses comparable to the total cold gas reservoir from cold and cooling flows, suggesting near-maximal star formation efficiencies, SFEs. At higher redshifts, halos are predicted to host galaxies undergoing starburst phases. When accounting for dust attenuation and adopting empirically inferred SFEs, we find good agreement between the model and the brightest observed UV galaxies at high redshifts. At lower redshifts, however, observed UV galaxies are too bright. Overall, our results indicate that current observations remain broadly consistent with $Λ$CDM once statistical and observational effects are properly accounted for.

astro-ph.GA↗

arXiv2025

The Outskirt Stellar Mass of Low-Redshift Massive Galaxies is an Excellent Halo Mass Proxy in Illustris/IllustrisTNG Simulations

Recent observations suggest that the extended stellar halos of low-redshift massive galaxies are tightly connected to the assembly of their dark matter halos. In this paper, we use the Illustris, IllustrisTNG100, and IllustrisTNG300 simulations to compare how different stellar aperture masses trace halo mass. For massive central galaxies ($M_\star\geq 10^{11.2}M_\odot$), we find that a 2D outskirt stellar mass measured between 50 to 100 kpc ($M_{\star,[50,100]}$) consistently outperforms other aperture-based stellar masses. We further show that $M_{\star,[50,100]}$ correlates better with halo mass than the total amount of accreted stars (the ex situ mass), which suggests that not all accreted stars connect to halo assembly equally. While the galaxy formation recipes are different between Illustris and IllustrisTNG100, the two simulations yield consistent ex situ outskirt fractions for massive galaxies (about 70% in $M_{\star,[50,100]}$). These results demonstrate the potential of using the outskirt stellar mass to deepen our understanding of galaxy-halo connection in massive dark matter halos and trace dark matter halos better.

astro-ph.GA↗

arXiv2025

On matching galaxy number densities to reconstruct galaxy evolutionary tracks

The cumulative number density matching approach equates number densities between adjacent redshifts to derive empirical galaxy evolution tracks from the observed galaxy stellar mass function. However, it is well known that this approach overlooks scatter in mass assembly histories and merger effects, with previous studies relying on model-based corrections, either from hydrodynamical cosmological simulations or adjustments to the evolution of cumulative number density with redshift. Here, we revisit this approach, showing that dark matter halo assembly histories imply evolving number densities that are far from constant. These exhibit an average slope of $d \log n_\text{vir} /dz \sim 0.2$ dex for progenitors at $z=0$, leading to evolutionary tracks where galaxies are $\sim2-3$ times smaller in mass at $z\sim2$ and an order of magnitude smaller by $z\sim7$ compared to the number density matching approach. We show that evolving halo number densities provide realistic evolutionary tracks without relying on model-based corrections. Accounting for random errors in stellar mass measurements is also crucial for robust track derivation. We also discuss a generalization that incorporates a galaxy's star formation activity. When additionally considering the scatter around the $M_\ast-M_\text{vir}$ relation ($\sim0.15$ dex), our evolving halo cumulative number density approach shows that some observed stellar masses, $M_{\text{obs},\ast}$, can exceed the universal baryon fraction $f_\text{bar}\sim0.16$. For instance, at $z=5$, around $2\%$ of progenitor galaxies of haloes with $M_\text{vir} \sim 3\times 10^{12}\,M_\odot$ have $M_{\text{obs},\ast}>f_\text{bar} \; M_\text{vir}$, suggesting a potential ``early galaxy formation problem''. However, when deconvolving mass from random errors this tension is reduced with significant confidence at the $\sim5-6σ$ level.

astro-ph.GA↗

arXiv2025

Relationship between 2D and 3D Galaxy Stellar Mass and Correlations with Halo Mass

Recent studies suggest that the stars in the outer regions of massive galaxies trace halo mass better than the inner regions and that an annular stellar mass provides a low scatter method of selecting galaxy clusters. However, we can only observe galaxies as projected two-dimensional objects on the sky. In this paper, we use a sample of simulated galaxies to study how well galaxy stellar mass profiles in three dimensions correlate with halo mass, and what effects arise when observationally projecting stellar profiles into two dimensions. We compare 2D and 3D outer stellar mass selections and find that they have similar performance as halo mass proxies and that, surprisingly, a 2D selection sometimes has marginally better performance. We also investigate whether the weak lensing profiles around galaxies selected by 2D outer stellar mass suffer from projection effects. We find that the lensing profiles of samples selected by 2D and 3D definitions are nearly identical, suggesting that the 2D selection does not create a bias. These findings underscore the promise of using outer stellar mass as a tool for identifying galaxy clusters.

astro-ph.CO↗

arXiv2025

Gas accretion at high redshift: cold flows all the way

We study in detail how massive galaxies accrete gas through cosmic time using cosmological hydrodynamical simulations from the High-z Evolution of Large and Luminous Objects (HELLO) and the Numerical Investigation of a Hundred Astrophysical Objects (NIHAO) projects. We find that accretion through cold filaments at high redshift (z ~ 2-4) is a key factor in maintaining the high star formation rates (> 100 Msun/yr) observed in these galaxies, and that more than 75% of the total gas participating in the star formation process is accreted via this channel at high z even in haloes well above 10^12 Msun. The low volume occupancy of the filaments allows plenty of space for massive gas outflows generated by the vigorous star formation and AGN activity, with the cold incoming gas and the hot outflowing gas barely interacting. We present a model based on a Bayesian hierarchical formalism that accurately describes the evolution of the cold fraction accretion with redshift and halo mass. Our model predicts a relatively constant critical mass (Mc) for the cold-to-hot transition up to z ~ 1.3 and an evolving critical mass log(Mc) proportional to log(1+z)^1.7 at higher redshift. Overall, our findings provide deeper insight into the cosmic evolution of gas accretion modes and offer a robust framework for understanding how cold accretion contributes to galaxy growth across different epochs.

astro-ph.GA↗

arXiv2024

Non-Monotonic Relations of Galaxy Star Formation, Radius, and Structure at Fixed Stellar Mass

We investigate the relation between galaxy structure and star formation rate (SFR) in a sample of $\sim2.9\times10^{4}$ central galaxies with $z<0.0674$ and axial ratios $b/a>0.5$. The star-forming main sequence (SFMS) shows a bend around the stellar mass of $M_\ast\leq{}M_c=2\times10^{10}{}M_{\odot}$. At $M_\ast\leq{}M_c$ the SFMS follows a power-law $\text{SFR}\propto{}M_\ast^{0.85}$, while at higher masses it flattens. $M_c$ corresponds to a dark matter halo mass of $M_\text{vir}\sim{}10^{11.8}M_{\odot}$ where virial shocks occurs. Some galaxy structure (e.g., half-light radius, $R_e$) exhibits a non-monotonic dependence across the SFMS at a fixed $M_\ast$. We find $\text{SFR}\propto{R_e^{-0.28}}$ at fixed $M_\ast$, consistent with the global Kennicutt-Schmidt (KS) law. This finding suggests that galaxy sizes contribute to the scatter of the SFMS. However, at $M_\ast>M_c$ the relationship between SFR and $R_e$ diminishes. Low-mass galaxies above the mean of the SFMS have smaller radii, exhibit compact and centrally concentrated profiles resembling green valley (GV) and quiescent galaxies at the same mass, and have higher $M_{\text{H}_2}/M_\text{HI}$. Conversely, those below the SFMS exhibit larger radii, lower densities, have no GV or quiescent counterparts at their mass and have lower $M_{\text{H}_2}/M_\text{HI}$. The above data suggest two pathways for quenching low-mass galaxies, $M_\ast\leq{}M_c$: a fast one that changes the morphology on the SFMS and a slow one that does not. Above $M_c$, galaxies below the SFMS resemble GV and quiescent galaxies structurally, implying that they undergo a structural transformation already within the SFMS. For these massive galaxies, CG are strongly bimodal, with SFMS galaxies exhibiting negative color gradients, suggesting most star formation occurs in their outskirts, maintaining them within the SFMS.

astro-ph.GA↗

arXiv2022

The Contribution of In-situ and Ex-situ Star Formation in Early-Type Galaxies: MaNGA versus IllustrisTNG

We compare stellar mass surface density, metallicity, age, and line-of-sight velocity dispersion profiles in massive ($M_*\geq10^{10.5}\,\mathrm{M_\odot}$) present-day early-type galaxies (ETGs) from the MaNGA survey with simulated galaxies from the TNG100 simulation of the IllustrisTNG suite. We find an excellent agreement between the stellar mass surface density profiles of MaNGA and TNG100 ETGs, both in shape and normalisation. Moreover, TNG100 reproduces the shapes of the profiles of stellar metallicity and age, as well as the normalisation of velocity dispersion distributions of MaNGA ETGs. We generally also find good agreement when comparing the stellar profiles of central and satellite galaxies between MaNGA and TNG100. An exception is the velocity dispersion profiles of very massive ($M_*\gtrsim10^{11.5}\,\mathrm{M_\odot}$) central galaxies, which, on average, are significantly higher in TNG100 than in MaNGA ($\approx50\,\mathrm{km\,s^{-1}}$). We study the radial profiles of $\mathit{in}$-$\mathit{situ}$ and $\mathit{ex}$-$\mathit{situ}$ stars in TNG100 and discuss the extent to which each population contributes to the observed MaNGA profiles. Our analysis lends significant support to the idea that high-mass ($M_*\gtrsim10^{11}\,\mathrm{M_\odot}$) ETGs in the present-day Universe are the result of a merger-driven evolution marked by major mergers that tend to homogenise the stellar populations of the progenitors in the merger remnant.

astro-ph.GA↗

arXiv2020

Stellar velocity dispersion and initial mass function gradients in dissipationless galaxy mergers

The stellar initial mass function (IMF) is believed to be non-universal among early-type galaxies (ETGs). Parameterizing the IMF with the so-called IMF mismatch parameter $α_{\rm IMF}$, which is a measure of the stellar mass-to-light ratio of an ensemble of stars and thus of the 'heaviness' of its IMF, one finds that for ETGs $α_{\rm e}$ (i.e. $α_{\rm IMF}$ integrated within the effective radius $R_{\rm e}$) increases with $σ_{\rm e}$ (the line-of-sight velocity dispersion $σ_{\rm los}$ integrated within $R_{\rm e}$) and that, within the same ETG, $α_{\rm IMF}$ tends to decrease outwards. We study the effect of dissipationless (dry) mergers on the distribution of the IMF mismatch parameter $α_{\rm IMF}$ in ETGs using the results of binary major and minor merging simulations. We find that dry mergers tend to make the $α_{\rm IMF}$ profiles of ETGs shallower, but do not alter significantly the shape of the distributions in the spatially resolved $σ_{\rm los}α_{\rm IMF}$ space. Individual galaxies undergoing dry mergers tend to decrease their $α_{\rm e}$, due to erosion of $α_{\rm IMF}$ gradients and mixing with stellar populations with lighter IMF. Their $σ_{\rm e}$ can either decrease or increase, depending on the merging orbital parameters and mass ratio, but tends to decrease for cosmologically motivated merging histories. The $α_{\rm e}$-$σ_{\rm e}$ relation can vary with redshift as a consequence of the evolution of individual ETGs: based on a simple dry-merging model, ETGs of given $σ_{\rm e}$ are expected to have higher $α_{\rm e}$ at higher redshift, unless the accreted satellites are so diffuse that they contribute negligibly to the inner stellar distribution of the merger remnant.

astro-ph.GA↗

arXiv2020

The cosmic evolution of the stellar mass$-$velocity dispersion relation of early-type galaxies

We study the evolution of the observed correlation between central stellar velocity dispersion $σ_\mathrm{e}$ and stellar mass $M_*$ of massive ($M_*\gtrsim 3\times 10^{10}\,\mathrm{M_\odot}$) early-type galaxies (ETGs) out to redshift $z\approx 2.5$, exploiting a Bayesian hierarchical inference formalism. Collecting ETGs from state-of-the-art literature samples, we build a $fiducial$ sample ($0\lesssim z\lesssim 1$), which is obtained with homogeneous selection criteria, but also a less homogeneous $extended$ sample ($0\lesssim z\lesssim 2.5$). Based on the fiducial sample, we find that the $M_*$-$σ_\mathrm{e}$ relation is well represented by $σ_\mathrm{e}\propto M_*^β(1+z)^ζ$, with $β\simeq 0.18$ independent of redshift and $ζ\simeq 0.4$ (at given $M_*$, $σ_\mathrm{e}$ decreases for decreasing $z$, for instance by a factor of $\approx1.3$ from $z=1$ to $z=0$). When the slope $β$ is allowed to evolve, we find it increasing with redshift: $β(z)\simeq 0.16+0.26\log(1+z)$ describes the data as well as constant $β\simeq 0.18$. The intrinsic scatter of the $M_*$-$σ_\mathrm{e}$ relation is $\simeq0.08$ dex in $σ_\mathrm{e}$ at given $M_*$, independent of redshift. Our results suggest that, on average, the velocity dispersion of $individual$ massive ($M_*\gtrsim 3\times 10^{11}\,M_\odot$) ETGs decreases with time while they evolve from $z\approx 1$ to $z\approx 0$. The analysis of the extended sample leads to results similar to that of the fiducial sample, with slightly stronger redshift dependence of the normalisation ($ζ\simeq 0.5$) and weaker redshift dependence of the slope (${\rm d} β/{\rm d} \log (1+z)\simeq 0.18$) when $β$ varies with time. At $z=2$ ETGs with $M_*\approx 10^{11}\,M_\odot$ have, on average, $\approx1.7$ higher $σ_\mathrm{e}$ than ETGs of similar stellar mass at $z=0$.

astro-ph.GA↗

arXiv2020

The merger-driven evolution of massive early-type galaxies

The evolution of the structural and kinematic properties of early-type galaxies (ETGs), their scaling relations, as well as their stellar metallicity and age contain precious information on the assembly history of these systems. We present results on the evolution of the stellar mass-velocity dispersion relation of ETGs, focusing in particular on the effects of some selection criteria used to define ETGs. We also try to shed light on the role that in-situ and ex-situ stellar populations have in massive ETGs, providing a possible explanation of the observed metallicity distributions.

astro-ph.GA↗