arXiv subjects

Paolo Salucci

Publications and source records attributed to Paolo Salucci.

At least 19 recordsLinked to original sources

arXiv2026

Extended Universal Rotational Curve of Spiral Galaxies

In this work, we aim to advance the Universal Rotation Curve (URC) paradigm by leveraging new data and extending its observational domain. Building on previous studies that established the URC using optical rotation curves reaching the galaxy optical radius $R_{opt}$, we exploit the SPARC sample's extended HI rotation curves to construct the URC out to $2R_{opt}$. This crucial extension enables us to investigate the mass distribution of spiral galaxies in a region dominated by dark matter an important step to better constrain galaxy mass models and to explore the nature of the dark matter particle. We find that the URC constructed from the SPARC sample's extended HI rotation curves maintains its universal character out to $2R_{opt}$, with the double-normalized rotation curves collapsing onto a single profile. This extended URC provides new insights into the interplay between baryonic matter and dark matter in shaping galaxy rotation curves, particularly in the outer regions where dark matter dominates. Our results not only reinforce the URC paradigm but also refine our understanding of the mass distribution in spiral galaxies, offering new constraints on galaxy mass models and implications for the nature of dark matter.

astro-ph.GA↗

arXiv2026

Unveiling the Coma Cluster Structure: From the Core to the Hubble Flow

The Coma cluster, embedded in a cosmic filament, is a complex and dynamically active structure in the local Universe. Applying a density-based member selection dbscan to data from the Sloan Digital Sky Survey (SDSS), we identify cluster member galaxies from its virialised core out to the zero-velocity boundary in the least model-dependent way. From dbscan, we infer a projected virial radius of $r_{\rm vir} = \left(1.95 \pm 0.12\right)\,h^{-1}~\text{Mpc}$ and projected zero-velocity radius of $r_{\rm ta} \geq 4.87~{h}^{-1}~\mbox{Mpc}$. Assuming that the barycentre of Coma has zero peculiar velocity, its distance from us is $r_\mathrm{c}=(69.959 \pm 0.012_\mathrm{stat}) \, h^{-1}~\text{Mpc}$ determined from the redshifts of 1092 member galaxies. Cross-correlating with the Cosmicflows-4 (CF4) catalogue enables a velocity-distance analysis. This reveals, for the first time, the Hubble flow surrounding Coma, a first step to investigate the entanglement between Coma's dark matter halo and the dark energy driving the expansion of the surroundings. If $v_\mathrm{c}$ is moving with the cosmic expansion, the CF4 distances yield a Hubble constant $H_0 = (73 \pm {1_\mathrm{stat} \pm 7_\mathrm{sys}})~\mbox{km}/\mbox{s}/\mbox{Mpc}$ with a dominating systematic error from different calibrations for the distance moduli. Mass estimates via caustics, the virial theorem, and the Hubble-flow method yield $M = [0.77, 2.0] \times 10^{15}\,h^{-1}\,M_{\odot}$ consistent with prior mass estimates. Our mass estimates are based on fewer model assumptions in the member selection and require $\sim20\%$ members to attain the same precision. Our approach maps the structure of Coma into its Hubble flow and shows degeneracies between the Hubble constant, the virial radius, and the total mass only using data and models from the single line-of-sight towards Coma.

astro-ph.CO↗

arXiv2025

Unlocking the physics of dwarf galaxies in the 2040s: The case for a next-generation wide-field spectroscopic facility with fibres and IFUs

Dwarf galaxies ($M_{\star} \lesssim 10^{9} M_{\odot}$) are the most numerous galaxies in the Universe and critical probes of dark matter, baryonic feedback, and galaxy formation. Despite significant progress from wide-field imaging surveys, the majority of dwarf candidates beyond the Local Group will lack spectroscopic follow-up, leaving fundamental questions about their internal kinematics, stellar populations, chemical enrichment, and dark matter content unresolved. Existing and planned facilities cannot efficiently provide the necessary spectroscopy for low-surface-brightness dwarfs over wide areas. We advocate for a dedicated large-aperture ($\geq 20$ m), wide-field, highly multiplexed spectroscopic facility with deployable or monolithic IFUs, capable of high signal-to-noise observations down to $I_{\rm E} \gtrsim 22-23$ mag. Such a facility would enable transformative studies of dark matter cores, baryonic feedback, tidal interactions, environmental effects, and stellar populations, extending the spectroscopic exploration of low-mass galaxies to $z \sim 1.5$, and providing decisive tests of $Λ$CDM and alternative dark matter models. Beyond dwarfs, this capability would impact galaxy evolution, strong and weak lensing studies, and cosmology, ensuring that imaging data from the 2030s and 2040s can be fully exploited.

astro-ph.IM↗

arXiv2025

Issues in the Investigations of the Dark Matter Phenomenon in Galaxies: Parcere Personis, Dicere de Vitiis

It is always more evident that the kinematics of galaxies provide us with unique information on the Nature of the dark particles and on the properties of the galaxy Dark Matter (DM) halos. However, in investigating this topic, we have to be very careful about certain issues related to the assumptions that we take or to the practices that we follow. Here, we critically discuss such issues, that, today, result of fundamental importance, in that we have realized that the Nature of the DM will be not provided by The Theory but, has to be inferred by reverse engineering the observational scenario.

astro-ph.CO↗

arXiv2024

Tully-Fisher Relation of Late-type Galaxies at $0.6 \leq z \leq 2.5$

We present a study of the stellar and baryonic Tully-Fisher relation within the redshift range of $0.6 \leq z \leq 2.5$ utilizing observations of \sfgs. This dataset, as explored in \citet{GS23}, comprises of disk-like galaxies spanning a stellar mass range of $8.89 \leq \log(M_{star} \ [\mathrm{M_\odot}]) \leq 11.5$, baryonic mass range of $9.0 \leq \log(M_{bar} [\mathrm{M_\odot}]) \leq 11.5$, and circular velocity range of $1.65 \leq \log(V_c \ [{\rm km/s}]) \leq 2.85$. Stellar masses of these objects are estimated using spectral energy distribution fitting techniques, while gas masses are determined via scaling relations. Circular velocities are directly derived from the Rotation Curves (RCs), after meticulously correcting for beam smearing and pressure support. Our analysis confirms that our sample adheres to the fundamental mass-size relations of galaxies and reflects the evolution of velocity dispersion in galaxies, in line with previous findings. This reaffirms the reliability of our photometric and kinematic parameters (i.e., $M_{star}$ and $V_c$), thereby enabling a comprehensive examination of the Tully-Fisher relation. To attain robust results, we employed a novel orthogonal likelihood fitting technique designed to minimize intrinsic scatter around the best-fit line, as required at \hz. For the STFR, we obtained a slope of $α=3.03\pm 0.25$, an offset of $β= 3.34\pm 0.53$, and an intrinsic scatter of $ζ_{int}=0.08$ dex. Correspondingly, the BTFR yielded $α=3.21\pm 0.28$, $β=3.16\pm 0.61$, and $ζ_{int}=0.09$ dex. Our findings suggest a subtle deviation in the stellar and baryonic Tully-Fisher relation with respect to local studies, which is most-likely due to the evolutionary processes governing disk formation.

astro-ph.GA↗

arXiv2024

Radial Tully-Fisher relation and the local variance of Hubble parameter

Utilizing the well-established Radial Tully-Fisher (RTF) relation observed in a `large' (843) sample of local galaxies, we report the maximum allowed variance in the Hubble parameter, $H_0$. We estimate the total intrinsic scatter in the magnitude of the RTF relation(s) implementing a cosmological model-independent cosmographic expansion. We find that the maximum allowed local variation in our baseline analysis, using 4 RTF relations in the galaxy sample is $ΔH_0/H_0 \lesssim 3 \%$ at a $95\%$ C.L. significance. Which is implied form a constraint of $ΔH_0/H_0 = 0.54^{+1.32}_{-1.37} \%$ estimated at $D_{\rm{L}}\sim 10\, [\rm{Mpc}]$. Using only one `best-constrained' radial bin we report a conservative $95\%$ C.L. limit of $ΔH_0/H_0 \lesssim 4 \%$. Through our estimate of maximum variation, we propose a novel method to validate several late-time/local modifications put forth to alleviate the $H_0$ tension. We find that within the range of the current galaxy sample redshift distribution $10 \, [\rm{Mpc}] \le D_{\rm{L}} \le 140\, [\rm{Mpc}]$, it is highly unlikely to obtain a variation of $ΔH_0/H_0 \sim 9\%$, necessary to alleviate the $H_0$-tension. However, we also elaborate on the possible alternative inferences when the innermost radial bin is included in the analysis. Alongside the primary analysis of fitting the individual RTF relations independently, we propose and perform a joint analysis of the RTF relations useful to create a pseudo-standardizable sample of galaxies. We also test for the spatial variation of $H_0$, finding that the current samples' galaxies distributed only in the southern hemisphere support the null hypothesis of isotropy, within the allowed noise levels.

astro-ph.CO↗

arXiv2023

The Quest for the Nature of the Dark Matter: The Need of a New Paradigm

The phenomenon of the Dark matter baffles the researchers: the underlying dark particle has escaped so far the detection and its astrophysical role appears complex and entangled with that of the standard luminous particles. We propose that, in order to act efficiently, alongside with abandoning the current $ΛCDM$ scenario, we need also to shift the Paradigm from which it emerged.

hep-ph↗

arXiv2023

Dark Matter in Fractional Gravity I: Astrophysical Tests on Galactic Scales

[abridged] We explore the possibility that the dark matter (DM) component in galaxies may originate fractional gravity. In such a framework, the standard law of inertia continues to hold, but the gravitational potential associated to a given DM density distribution is determined by a modified Poisson equation including fractional derivatives (i.e., derivatives of non-integer type), that are meant to describe non-local effects. We derive analytically the expression of the potential that in fractional gravity corresponds to various spherically symmetric density profiles, including the Navarro-Frenk-White (NFW) distribution that is usually exploited to describe virialized halos of collisionless DM as extracted from $N-$body cosmological simulations. We show that in fractional gravity the dynamics of a test particle moving in a cuspy NFW density distribution is substantially altered with respect to the Newtonian case (i.e., basing on the standard Poisson equation), mirroring what in Newtonian gravity would instead be sourced by a density profile with an inner core. We test the fractional gravity framework on galactic scales, showing that: (i) it can provide accurate fits to the stacked rotation curves of galaxies with different properties; (ii) it can reproduce to reasonable accuracy the observed shape and scatter of the radial acceleration relation (RAR); (iii) it can properly account for the universal surface density and the core radius vs. disk scale-length scaling relations. Finally, we discuss the possible origin of the fractional gravity behavior as a fundamental or emerging property of the elusive DM component.

astro-ph.GA↗

arXiv2022

Report of the Topical Group on Cosmic Probes of Fundamental Physics for for Snowmass 2021

Cosmic Probes of Fundamental Physics take two primary forms: Very high energy particles (cosmic rays, neutrinos, and gamma rays) and gravitational waves. Already today, these probes give access to fundamental physics not available by any other means, helping elucidate the underlying theory that completes the Standard Model. The last decade has witnessed a revolution of exciting discoveries such as the detection of high-energy neutrinos and gravitational waves. The scope for major developments in the next decades is dramatic, as we detail in this report.

hep-ph↗

arXiv2022

The accurate mass distribution of M87, the Giant Galaxy with imaged shadow of its supermassive black hole, as a portal to new Physics

The very careful Event Horizon Telescope estimate of the mass of the supermassive black hole at the center of the Giant CD galaxy M87, allied with recent high quality photometric and spectroscopic measurements, yields a proper dark/luminous mass decomposition from the galaxy center to its virial radius. That provides us with decisive information on crucial cosmological and astrophysical issues. The dark and the standard matter distributions in a wide first time detected galaxy region under the supermassive black hole gravitational control. The well known supermassive black hole mass vs stellar dispersion velocity relationship at the highest galaxy masses implies an exotic growth of the former. This may be the first case in which one can argue that the supermassive black hole mass growth was also contributed by the Dark Matter component. A huge dark matter halo core in a galaxy with inefficient baryonic feedback is present and consequently constrains the nature of the dark halo particles. The unexplained entanglement between dark/luminous structural properties, already emerged in disk systems, also appears.

astro-ph.CO↗

arXiv2022

Observational Evidence of Evolving Dark Matter Profiles at $z\leq 1$

We investigate the dark matter halos of 256 star-forming disc-like galaxies at $z\sim 1$ using the KMOS redshift one spectroscopic survey (KROSS). This sample covers the redshifts $0.6 \leq z \leq 1.04$, effective radii $0.69 \leq R_e [\mathrm{kpc}] \leq 7.76$, and total stellar masses $8.7 \leq log(M_{\mathrm{star}} \ [\mathrm{M_\odot}]) \leq 11.32$. We present a mass modelling approach to study the rotation curves of these galaxies, which allow us to dynamically calculate the physical properties associated with the baryons and the dark matter halo. For the former we assume a Freeman disc, while for the latter we employ the NFW and the Burkert halo profiles, separately. At the end, we compare the results of both cases with state-of-the-art cosmological galaxy simulations (EAGLE, TNG100 and TNG50). We find that the {\em cored} dark matter halo emerged as the dominant quantity from a radius 1-3 times the effective radius. Its fraction to the total mass is in good agreement with the outcome of hydrodynamical galaxy simulations. Remarkably, we found that the dark matter core of $z\sim 1$ star-forming galaxies are smaller and denser than their local counterparts. We conclude that dark matter halos have gradually expanded over the past 6.5 Gyrs. That is, observations are capable of capturing the dark matter response to the baryonic processes (e.g. feedbacks), and thus giving us the first empirical evidence of {\em gravitational potential fluctuations} in the inner region of galaxies, which can be verified with deep surveys and future missions.

astro-ph.GA↗

arXiv2021

Fundamental properties of the dark and the luminous matter from Low Surface Brightness discs

Dark matter (DM) is one of the biggest mystery in the Universe. In this review, after a brief discussion of the DM evidences and the main proposed candidates and scenarios for the DM phenomenon, we focus on recent results on rotating disc galaxies giving a special attention to the Low Surface Brightness (LSB) galaxies. The main observational properties related to the baryonic matter in LSBs, investigated over the last decades, are briefly recalled. Next, the LSBs are analysed by means of the mass modelling of their rotation curves both individually and stacked. The latter analysis, via the Universal Rotation Curve (URC) method, results really powerful in giving a global/universal description of the disc galaxies properties. We show the presence in LSBs of scaling relations between the galactic structural properties and we compare them with those of galaxies of different morphologies. The findings confirm, for all disc systems, a strong entanglement between the luminous matter (LM) and the DM. Moreover, we report how in LSBs the tight relationship between their radial gravitational acceleration $g$ and their baryonic component $g_b$ results to also depend on the galactic radius at which the former have been measured. Finally, LSB galaxies strongly challenge the $Λ$CDM scenario with the relative collisionless dark particle and, alongside with the non-detection of the latter, contribute to guide us towards a new scenario for the DM phenomenon.

astro-ph.GA↗

arXiv2021

Dark Matter Fraction in z~1 Star-Forming Galaxies

We present a observational study of the dark matter fraction in 225 rotation supported star-forming galaxies at $z\approx 0.9$ having stellar mass range: $ 9.0 \leq log(M_* \ \mathrm{M_\odot}) \leq 11.0$ and star formation rate: $0.49 \leq log \left(SFR \ \mathrm{[M_{\odot}\ yr^{-1}]} \right) \leq 1.77$. This is a sub sample of KMOS redshift one spectroscopic survey (KROSS) previously studied by \citet{GS20}. The stellar masses ($M_*$) of these objects were previously estimated using mass-to-light ratios derived from fitting the spectral energy distribution of the galaxies. Star formation rates were derived from the H$_α$ luminosities. The total gas masses ($M_{gas}$) are determined by scaling relations of molecular and atomic gas \citep[][respectively] {Tacconi2018, Lagos2011}. The dynamical masses ($M_{dyn}$) are directly derived from the rotation curves (RCs) at different scale lengths (effective radius: $R_e$, $\sim 2 \ R_e$ and $\sim 3 \ R_e$) and then the dark matter fractions ($f_{ DM }=1-M_{bar}/M_{dyn}$) at these radii are calculated. We report that at $z\sim 1$ only a small fraction ($\sim 5\%$) of our sample has a low ($< 20\%$) DM fraction within $\sim$ 2-3 $R_e$. The majority ($> 72\%$) of SFGs in our sample have dark matter dominated outer disks ($\sim 5-10$ kpc) in agreement with local SFGs. Moreover, we find a large scatter in the fraction of dark matter at a given stellar mass (or circular velocity) with respect to local SFGs, suggesting that galaxies at $z \sim 1$, a) span a wide range of stages in the formation of stellar disks, b) have diverse DM halo properties coupled with baryons.

astro-ph.GA↗

arXiv2021

Modelling the Sgr A* Black Hole Immersed in a Dark Matter Spike

In this paper, we investigate the effects of a dark matter (DM) spike on the neighborhood of Sgr A*, the black hole (BH) in the center of the Milky Way galaxy. Our main goal is to investigate whether current and future astronomical observations of Sgr A* could detect the presence of such a DM spike. At first, we construct the spacetime metric around a static and spherically symmetric BH with a DM spike, and later this solution is generalized for a rotating BH using the Newman-Janis-Azreg Aïnou algorithm. For the static BH metric, we use the data of the S2 star orbiting the Sgr A* to determine and analyze the constraints on the two free parameters characterizing the density and the innermost boundary of the DM halo surrounding the BH. Furthermore, by making use of the available observational data for the DM spike density $ρ_\text{sp}$ and the DM spike radius $R_\text{sp}$ in the Milky Way galaxy, we consider a geometrically-thick accretion disk model around the Sgr A* BH and demonstrate that the effect of DM distribution on the shadow radius and the image of the BH is considerably weak for realistic DM densities, becoming significant only when the DM density is of the order $ρ_\text{sp} \sim (10^{-19}-10^{-20})$ g/cm$^3$ near the BH. We further analyze the possibility of observing this effect with radio interferometry, simulating observations with an EHT--like array, and find that it is unlikely to be detectable in the near future.

astro-ph.HE↗

arXiv2021

Flat Rotation Curves of $z\sim 1$ Star-Forming Galaxies and Evidence of Disk-Scale Length Evolution

We investigate the shape of the Rotation Curves (RCs) of $z\sim 1$ star-forming galaxies and compare them with the local star-forming galaxies. For this purpose, we have used $409$ galaxies from the K-band Multi-Object Spectrograph (KMOS) for Redshift One Spectroscopic Survey (KROSS). This sample covers the redshift range $0.57\leq z \leq 1.04$, effective radii $0.69 \leq R_e \left[kpc \right] \leq 7.73$, absolute H-band magnitude $-24.46 \leq M_H \leq -18.85$ with median stellar mass $log\left(M_* \ \left[M_\odot \right]\right)=9.95$ and median total star-formation rate $log\left(SFR_{tot} \ \left[M_\odot \ yr^{-1} \right]\right)=1.49$. Using $^{3D}$BAROLO (Barolo), we extract $Hα$ kinematic maps and corresponding Rotation Curves (RCs). The main advantage of Barolo is that it incorporates the beam smearing in the 3D observational space, which provide us with the intrinsic rotation velocity even in the low spatial resolution data. Using Asymmetric Drift Correction (ADC), we have corrected the RCs for the pressure gradient effect, which seems to be a more dominant effect than beam smearing in high-z galaxies. Nearly all objects ($0.1 <v/ σ< 15$) are affected by the pressure gradient, and we noticed that ADC improves the rotation velocity of these systems by $\sim 10-87\%$. Only a combination of the three techniques (3D-kinematic modelling + 3D-Beamsmearing correction + ADC ) yields the intrinsic RC of an individual galaxy. Further, we present the co-added RCs constructed out of 237 high-quality objects to obtain intrinsic RC shapes out to 6.4 $\times$ disk scale length. We do not see any change in the shape of RCs with respect to the local star-forming disk-type galaxies. In contrast, we do find a significant evolution in the stellar-disk length ($R_D$) of the galaxies. Therefore, we conclude stellar disk evolves over cosmic time while total mass distribution stays constant.

astro-ph.GA↗

arXiv2020

Einstein, Planck and Vera Rubin: relevant encounters between the Cosmological and the Quantum Worlds

In Cosmology and in Fundamental Physics there is a crucial question like: where the elusive substance that we call Dark Matter is hidden in the Universe and what is it made of?, that, even after 40 years from the Vera Rubin seminal discovery does not have a proper answer. Actually, the more we have investigated, the more this issue has become strongly entangled with aspects that go beyond the established Quantum Physics, the Standard Model of Elementary particles and the General Relativity and related to processes like the Inflation, the accelerated expansion of the Universe and High Energy Phenomena around compact objects. Even Quantum Gravity and very exotic DM particle candidates may play a role in framing the Dark Matter mystery that seems to be accomplice of new unknown Physics. Observations and experiments have clearly indicated that the above phenomenon cannot be considered as already theoretically framed, as hoped for decades. The Special Topic to which this review belongs wants to penetrate this newly realized mystery from different angles, including that of a contamination of different fields of Physics apparently unrelated. We show with the works of this ST that this contamination is able to guide us into the required new Physics. This review wants to provide a good number of these "paths or contamination" beyond/among the three worlds above; in most of the cases, the results presented here open a direct link with the multi-scale dark matter phenomenon, enlightening some of its important aspects. Also in the remaining cases, possible interesting contacts emerges.

gr-qc↗

arXiv2020

Navarro-Frenk-White dark matter profile and the dark halos around disk systems

The $Λ$ cold dark matter ($Λ$CDM) scenario well describes the Universe at large scales, but shows some serious difficulties at small scales: the inner dark matter (DM) density profiles of spiral galaxies generally appear to be cored, without the $r^{-1}$ predicted by N-body simulations in the above scenario. In a more physical context, the baryons in the galaxy might backreact and erase the original cusp through supernova explosions. Before that this effect be investigated, it is important to determine how wide and frequent the discrepancy between observed and N-body predicted profiles is and what its features are. We used more than 3200 quite extended rotation curves (RCs) of good quality and high resolution of disk systems. The curves cover all magnitude ranges. These RCs were condensed into 26 coadded RCs, each of them built with individual RCs of galaxies of similar luminosity and morphology. We performed mass models of these 26 RCs using the Navarro-Frenk-White (NFW) profile for the contribution of the DM halo to the circular velocity and the exponential Freeman disk for that of the stellar disk. The fits are generally poor in all the 26 cases: in several cases, we find $χ^2_{red}>2$. Moreover, the best-fitting values of three parameters of the model ($c$, $M_D$, and $M_{vir}$) combined with those of their 1$σ$ uncertainty clearly contradict well-known expectations of the $Λ$CDM scenario. We also tested the scaling relations that exist in spirals with the fitting outcome: the modeling does not account for these scaling relations. Therefore, NFW halo density law cannot account for the kinematics of the whole family of disk galaxies. It is therefore mandatory for the $ΛCDM$ scenario in any disk galaxy of any luminosity to transform initial cusps into the observed cores.

astro-ph.CO↗

arXiv2020

Paradigms and Scenarios for the Dark Matter Phenomenon

Well known scaling laws among the structural properties of the dark and the luminous matter in disc systems are too complex to be arisen by two inert components that just share the same gravitational field. This brings us to critically focus on the 30-year-old paradigm, that, resting on a priori knowledge of the nature of Dark Matter (DM), has led us to a restricted number of scenarios, especially favouring the collisionless $Λ$ Cold Dark Matter one. Motivated by such observational evidence, we propose to resolve the dark matter mystery by following a new Paradigm: the nature of DM must be guessed/derived by deeply analyzing the properties of the dark and luminous mass distribution at galactic scales. The immediate application of this paradigm leads us to propose the existence of a direct interaction between Dark and Standard Model particles, which has finely shaped the inner regions of galaxies.

astro-ph.CO↗