Studies of flux anomalies statistics and perturbations in stellar streams have the potential to constrain models of warm dark matter (WDM), including sterile neutrinos. Producing these constraints requires a parametrization of the WDM mass function relative to that of the cold dark matter (CDM) equivalent. We use five WDM models with half-mode masses, $M_\mathrm{hm}=[1.3,35]\times10^{8}$~$M_{\odot}$, spread across simulations of the Local Group, lensing ellipticals and the $z=2$ universe, to generate such a parametrization: we fit parameters to a functional form for the WDM-to-CDM halo mass function ratio, $n_\mathrm{WDM}(M_{X})/n_\mathrm{CDM}(M_{X})$, of ($1+(αM_\mathrm{hm}/M_{X})^β)^γ$. For $M_{X}\equiv$ virial mass of central halos we obtain $α=2.3$, $β=0.8$, and $γ=-1.0$, and this fit is steeper than the extended Press-Schechter formalism predicts. For $M_{X}\equiv$ mass of subhalos we instead obtain $α=4.2$, $β=2.5$ and $γ=-0.2$; in both mass definitions the scatter is $\sim20$~per~cent. The second fit typically underestimates the relative abundance of $z=2$ WDM subhaloes at the tens of per cent level. We caution that robust constraints will require bespoke simulations and a careful definition of halo mass, particularly for subhalos of mass $<10^{8}M_{\odot}$.
We present a comprehensive analysis of the halo model of cosmological large to small-scale structure statistics in the case of warm dark matter (WDM) structure formation scenarios. We include the effects of WDM on the linear matter power spectrum, halo density profile, halo concentration relation, halo mass function, subhalo density profile, subhalo mass function and biasing of the smooth dark matter component. As expected, we find large differences at the smallest physical scales in the nonlinear matter power spectrum predicted in the halo model between WDM and cold dark matter even for reaso…
Cold dark matter (CDM) is a well established paradigm to describe cosmological structure formation, and works extraordinarily well on large, linear, scales. Progressing further in dark matter physics requires being able to understand structure formation in the non-linear regime, both for CDM and its alternatives. This short note describes a calculation, and accompanying code, WarmAndFuzzy, incorporating the popular models of warm and fuzzy dark matter (WDM and FDM) into the standard halo model to compute the non-linear matter power spectrum. The FDM halo model power spectrum has not been compu…
The apparent presence of large core radii in Low Surface Brightness galaxies has been claimed as evidence in favor of warm dark matter. Here we show that WDM halos do not have cores that are large fractions of the halo size: typically, r_core/r_200 < 0.001. This suggests an astrophysical origin for the large cores observed in these galaxies, as has been argued by other authors.
Warm Dark Matter (WDM) cosmologies are a viable alternative to the Cold Dark Matter (CDM) scenario. Unfortunately, an accurate scrutiny of the WDM predictions with N-body simulations has proven difficult due to numerical artefacts. Here, we report on cosmological simulations that, for the first time, are devoid of those problems, and thus, are able to accurately resolve the WDM halo mass function well below the cut-off. We discover a complex picture, with perturbations at different evolutionary stages populating different ranges in the halo mass function. On the smallest mass scales we can res…
Using the model for (bottom-up) hierarchical halo growth recently developed by Salvador-Solé et al. (2012), we derive the typical spherically averaged density profile for haloes with several relevant masses in the concordant warm dark matter (ΛWDM) cosmology with non-thermal sterile neutrinos of two different masses. The predicted density profiles become flat at small radii, as expected from the effects of the spectrum cutoff. The core cannot be resolved, however, because the non-null particle velocity yields the fragmentation of minimum mass protohaloes in small nodes, which invalidates the m…
We propose a new mechanism for the delivery of gas to the heart of galactic nuclei. We show that warm halo clouds must periodically impact galactic centers and potentially deliver a large (~10^{4-6} M_{solar}) mass of gas to the galactic nucleus in a singular event. The impact of an accreting warm halo cloud originating far in the galactic halo can, depending on mixing, produce a nuclear starburst of low metallicity stars as well as low luminosity accretion onto the central black hole. Based on multiphase cooling around a LambdaCDM distribution of halos we calculate the nuclear impact rate, th…
We study the evolving environment dependence of mass accretion by dark haloes in simulations of cold and warm dark matter (CDM and WDM) cosmologies. The latter allows us to probe the nature of halo growth at scales below the WDM half-mode mass, which form an extreme regime of nonlinear collisionless dynamics and offer an excellent test-bed for ideas relating to hierarchical growth. As environmental proxies, we use the local halo-centric matter density $δ$ and tidal anisotropy $α$, as well as large-scale halo bias $b_1$. Our analysis, while reproducing known trends for environment-dependent acc…
We describe a methodology to accurately compute halo mass functions, progenitor mass functions, merger rates and merger trees in non-cold dark matter universes using a self-consistent treatment of the generalized extended Press-Schechter formalism. Our approach permits rapid exploration of the subhalo population of galactic halos in dark matter models with a variety of different particle properties or universes with rolling, truncated, or more complicated power spectra. We make detailed comparisons of analytically derived mass functions and merger histories with recent warm dark matter cosmolo…
The recent detection of a 3.5 keV X-ray line from the centres of galaxies and clusters by Bulbul et al. (2014a) and Boyarsky et al. (2014a) has been interpreted as emission from the decay of 7 keV sterile neutrinos which could make up the (warm) dark matter (WDM). As part of the COpernicus COmplexio (COCO) programme, we investigate the properties of dark matter haloes formed in a high-resolution cosmological $N$-body simulation from initial conditions similar to those expected in a universe in which the dark matter consists of 7 keV sterile neutrinos. This simulation and its cold dark matter (…
High resolution N-body simulations of galactic cold dark matter haloes indicate that we should expect to find a few satellite galaxies around the Milky Way whose haloes have a maximum circular velocity in excess of 40 kms. Yet, with the exception of the Magellanic Clouds and the Sagittarius dwarf, which likely reside in subhaloes with significantly larger velocities than this, the bright satellites of the Milky Way all appear to reside in subhaloes with maximum circular velocities below 40 kms. As recently highlighted by Boylan-Kolchin et al., this discrepancy implies that the majority of the …
The free streaming of warm dark matter particles dampens the fluctuation spectrum, flattens the mass function of haloes and imprints a fine grained phase density limit for dark matter structures. The phase space density limit is expected to imprint a constant density core at the halo center on the contrary to what happens for cold dark matter. We explore these effects using high resolution simulations of structure formation in different warm dark matter scenarios. We find that the size of the core we obtain in simulated haloes is in good agreement with theoretical expectations based on Liouvil…
The nature of the dark matter can affect the collapse time of dark matter haloes, and can therefore be imprinted in observables such as the stellar population ages and star formation histories of dwarf galaxies. In this paper we use high resolution hydrodynamical simulations of Local Group-analogue (LG) volumes in cold dark matter (CDM), sterile neutrino warm dark matter (WDM) and self-interacting dark matter (SIDM) models with the EAGLE galaxy formation code to study how galaxy formation times change with dark matter model. We are able to identify the same haloes in different simulations, sin…
Well-motivated elementary particle candidates for the dark matter, such as the sterile neutrino, behave as warm dark matter (WDM).For particle masses of order a keV, free streaming produces a cutoff in the linear fluctuation power spectrum at a scale corresponding to dwarf galaxies. We investigate the abundance and structure of WDM haloes and subhaloes on these scales using high resolution cosmological N-body simulations of galactic haloes of mass similar to the Milky Way's. On scales larger than the free-streaming cutoff, the initial conditions have the same power spectrum and phases as one o…
We study the components of cool and warm/hot gas in the circumgalactic medium (CGM) of simulated galaxies and address the relative production of OVI by photoionization versus collisional ionization, as a function of halo mass, redshift, and distance from the galaxy halo center. This is done utilizing two different suites of zoom-in hydro-cosmological simulations, VELA (6 halos; $z>1$) and NIHAO (18 halos; to $z=0$), which provide a broad theoretical basis because they use different codes and physical recipes for star formation and feedback. In all halos studied in this work, we find that colli…
The dark energy dominated warm dark matter (WDM) model is a promising alternative cosmological scenario. We explore large-scale structure formation in this paradigm. We do this in two different ways: with the halo model approach and with the help of an ensemble of high resolution N-body simulations. Combining these quasi-independent approaches, leads to a physical understanding of the important processes which shape the formation of structures. We take a detailed look at the halo mass function, the concentrations and the linear halo bias of WDM. In all cases we find interesting deviations with…
In this paper, we formulate a new model of density distribution for halos made of warm dark matter (WDM) particles. The model is described by a single microphysics parameter - the mass (or, equivalently, the maximal value of the initial phase-space density distribution) of dark matter particles. Given the WDM particle mass and the parameters of a dark matter density profile at the halo periphery, this model predicts the inner density profile. In case of initial Fermi-Dirac distribution, we successfully reproduce cored dark matter profiles from N-body simulations. Also, we calculate the core ra…
We use a suite of cosmological simulations to study the mass-concentration-redshift relation, $c({\rm M},z)$, of dark matter halos. Our simulations include standard $Λ$-cold dark matter (CDM) models, and additional runs with truncated power spectra, consistent with a thermal warm dark matter (WDM) scenario. We find that the mass profiles of CDM and WDM halos are self-similar and well approximated by the Einasto profile. The $c({\rm M},z)$ relation of CDM halos is monotonic: concentrations decrease with increasing virial mass at fixed redshift, and decrease with increasing redshift at fixed mas…
We analyze the properties of dark matter halos in the cold-plus-warm dark matter cosmologies (CWDM). We study their dependence on the fraction and velocity dispersion of the warm particle, keeping the free-streaming scale fixed. To this end we consider three models with the same free-streaming: (1) a mixture of 90% of CDM and 10% of WDM with the mass 1 keV; (2) a mixture of 50% of CDM and 50% of WDM with the mass 5 keV; and (3) pure WDM with the mass 10 keV. "Warm" particles have rescaled Fermi-Dirac spectrum of primordial velocities (as non-resonantly produced sterile neutrinos would have). W…
The free-streaming length of dark matter depends on fundamental dark matter physics, and determines the abundance and concentration of dark matter halos on sub-galactic scales. Using the image positions and flux ratios from eight quadruply-imaged quasars, we constrain the free-streaming length of dark matter and the amplitude of the subhalo mass function (SHMF). We model both main deflector subhalos and halos along the line of sight, and account for warm dark matter (WDM) free-streaming effects on the mass function and mass-concentration relation. By calibrating the scaling of the SHMF with ho…
Halo gas in low-z (z<0.5) >0.1L* galaxies in high-resolution, large-scale cosmological hydrodynamic simulations is examined with respect to three components: (cold, warm, hot) with temperatures equal to (<10^5, 10^{5-6}, >10^6)K, respectively. The warm component is compared, utilizing O VI λλ1032, 1038 absorption lines, to observations and agreement is found with respect to the galaxy-O VI line correlation, the ratio of O VI line incidence rate in blue to red galaxies and the amount of O VI mass in star-forming galaxies. A detailed account of the sources of warm halo gas (stellar feedback heat…
We study the formation of non-linear structures in Warm Dark Matter (WDM) models and in a Long-Lived Charged Massive Particle (CHAMP) model. CHAMPs with a decay lifetime of about 1 yr induce characteristic suppression in the matter power spectrum at subgalactic scales through acoustic oscillations in the thermal background. We explore structure formation in such a model. We also study three WDM models, where the dark matter particles are produced through the following mechanisms: i) WDM particles are produced in the thermal background and then kinematically decoupled; ii) WDM particles are fer…
The weakly interacting massive particle (WIMP) often serves as a candidate for the cold dark matter, however when produced non-thermally it could behave like warm dark matter. In this paper we study the properties of the $γ$-ray emission from annihilation of WIMP dark matter in the halo of our own Milky-Way Galaxy with high resolution $N$-body simulations of a Milky-Way like dark matter halo, assuming different nature of WIMPs. Due to the large free-streaming length in the scenario of warm WIMPs, the substructure contend of the dark matter halo is significantly different from that of the cold …
Galactic halo gas traces inflowing star formation fuel and feedback from a galaxy's disk and is therefore crucial to our understanding of galaxy evolution. In this review, we summarize the multi-wavelength observational properties and origin models of Galactic and low redshift spiral galaxy halo gas. Galactic halos contain multiphase gas flows that are dominated in mass by the ionized component and extend to large radii. The densest, coldest halo gas observed in neutral hydrogen (HI) is generally closest to the disk (< 20 kpc), and absorption line results indicate warm and warm-hot diffuse hal…
We explore fundamental properties of the distribution of low mass dark matter halos within the cosmic web using warm dark matter (WDM) and cold dark matter (CDM) cosmological simulations. Using self abundance-matched mock galaxy catalogs, we show that the distribution of dwarf galaxies in a WDM universe, wherein low mass halo formation is heavily suppressed, is nearly indistinguishable to that of a CDM universe whose low mass halos are not seen because galaxy formation is suppressed below some threshold halo mass. However, if the scatter between dwarf galaxy luminosity and halo properties is l…
We present two sets of grid-based hydrodynamical simulations of high-velocity clouds (HVCs) traveling through the diffuse, hot Galactic halo. These HI clouds have been suggested to provide fuel for ongoing star formation in the Galactic disk. The first set of models is best described as a wind-tunnel experiment in which the HVC is exposed to a wind of constant density and velocity. In the second set of models we follow the trajectory of the HVC on its way through an isothermal hydrostatic halo towards the disk. Thus, we cover the two extremes of possible HVC trajectories. The resulting cloud m…
We estimate the detectability of X-ray metal-line emission from the circumgalactic medium (CGM) of galaxies over a large halo mass range ($\mathrm{M}_{\mathrm{200c}} = 10^{11.5}$-$10^{14.5}\,\mathrm{M}_{\odot}$) using the EAGLE simulations. With the XRISM Resolve instrument, a few bright (K-$α$ or Fe L-shell) lines from $\mathrm{M}_{\mathrm{200c}} \gtrsim 10^{13}\,\mathrm{M}_{\odot}$ haloes should be detectable. Using the Athena X-IFU or the Lynx Main Array, emission lines (especially from O VIII and O VII) from the inner CGM of $\mathrm{M}_{\mathrm{200c}} \gtrsim10^{12.5}\,\mathrm{M}_{\odot}$…
Warm dark matter (WDM) can potentially explain small-scale observations that currently challenge the cold dark matter (CDM) model, as warm particles suppress structure formation due to free-streaming effects. Observing small-scale matter distribution provides a valuable way to distinguish between CDM and WDM. In this work, we use observations from the Dark Energy Survey and PanSTARRS1, which observe 270 Milky-Way satellites after completeness corrections. We test WDM models by comparing the number of satellites in the Milky Way with predictions derived from the Semi-Analytical SubHalo Inferenc…
We use the EAGLE (Evolution and Assembly of GaLaxies and their Environments) cosmological simulation to study the distribution of baryons, and far-ultraviolet (O VI), extreme-ultraviolet (Ne VIII) and X-ray (O VII, O VIII, Ne IX, and Fe XVII) line absorbers, around galaxies and haloes of mass $\mathrm{M}_{200c}=10^{11}$-$10^{14.5}\,\mathrm{M}_{\odot}$ at redshift 0.1. EAGLE predicts that the circumgalactic medium (CGM) contains more metals than the interstellar medium across halo masses. The ions we study here trace the warm-hot, volume-filling phase of the CGM, but are biased towards temperat…
We compare model results from a semi-analytic (merger-tree based) framework for high-redshift (z ~ 5-20) galaxy formation against reionization indicators, including the Planck electron scattering optical depth and the ionizing photon emissivity, to shed light on the reionization history and sources in Cold (CDM) and Warm Dark Matter (WDM; particle masses of $m_x = 1.5,3$ and 5 keV) cosmologies. This model includes all the key processes of star formation, supernova feedback, the merger/accretion/ejection driven evolution of gas and stellar mass and the effect of the ultra-violet background (UVB…
We explore the impact of a LWDM cosmological scenario on the clustering properties of large-scale structure in the Universe. We do this by extending the halo model. The new development is that we consider two components to the mass density: one arising from mass in collapsed haloes, and the second from a smooth component of uncollapsed mass. Assuming that the nonlinear clustering of dark matter haloes can be understood, then from conservation arguments one can precisely calculate the clustering properties of the smooth component and its cross-correlation with haloes. We then explore how the th…
The influence of the large scale structure on host halos may be studied by examining the angular infall pattern of subhalos. In particular, since warm and cold dark matter cosmologies predict different abundances and internal properties for halos at the low mass end of the mass function, it is interesting to examine if there are differences in how these low mass halos are accreted. The accretion events are defined as the moment a halo becomes a substructure, namely when it crosses its host's virial radius. We quantify the cosmic web at each point by the shear tensor and examine where, with res…
In this third paper of the series, we investigate the effects of warm dark matter with a particle mass of $m_\mathrm{WDM}=3\,\mathrm{keV}$ on the smallest galaxies in our Universe. We present a sample of 21 hydrodynamical cosmological simulations of dwarf galaxies and 20 simulations of satellite-host galaxy interaction that we performed both in a Cold Dark Matter (CDM) and Warm Dark Matter (WDM) scenario. In the WDM simulations, we observe a higher critical mass for the onset of star formation. Structure growth is delayed in WDM, as a result WDM haloes have a stellar population on average two …
We present a Fisher matrix forecast for the sensitivity on the mass of a thermal warm dark matter (WDM) particle from current (DES-like) and future (LSST-like) photometric galaxy surveys using the galaxy angular power spectrum. We model the nonlinear clustering using a modified Halo Model proposed to account for WDM effects. We estimate that from this observable alone a lower bound of $m_{\text{wdm}}>647$\,eV ($m_{\text{wdm}}>126$\,eV) for the LSST (DES) case could be obtained.
Using high-resolution simulations within the Cold and Warm Dark Matter models we study the evolution of small scale structure in the Local Volume, a sphere of 8 Mpc radius around the Local Group. We compare the observed spectrum of mini-voids in the Local Volume with the spectrum of mini-voids determined from the simulations. We show that the \LWDM model can easily explain both the observed spectrum of mini-voids and the presence of low-mass galaxies observed in the Local Volume, provided that all haloes with circular velocities greater than 20 km/s host galaxies. On the contrary within the LC…
We study the impact of a warm dark matter (WDM) cosmology on dwarf galaxy formation through a suite of cosmological hydrodynamical zoom-in simulations of $M_{\rm halo} \approx10^{10}\,M_{\odot}$ dark matter halos as part of the Feedback in Realistic Environments (FIRE) project. A main focus of this paper is to evaluate the combined effects of dark matter physics and stellar feedback on the well-known small-scale issues found in cold dark matter (CDM) models. We find that the $z=0$ stellar mass of a galaxy is strongly correlated with the central density of its host dark matter halo at the time …
We present a framework for high-redshift ($z \geq 7$) galaxy formation that traces their dark matter (DM) and baryonic assembly in four cosmologies: Cold Dark Matter (CDM) and Warm Dark Matter (WDM) with particle masses of $m_x =$ 1.5, 3 and 5 ${\rm keV}$. We use the same astrophysical parameters regulating star formation and feedback, chosen to match current observations of the evolving ultra violet luminosity function (UV LF). We find that the assembly of observable (with current and upcoming instruments) galaxies in CDM and $m_x \geq 3 {\rm keV}$ WDM results in similar halo mass to light ra…
Warm dark matter (WDM) and self-interacting dark matter (SIDM) are often motivated by the inferred cores in the dark matter halos of low surface brightness (LSB) galaxies. We test thermal WDM, non-thermal WDM, and SIDM using high-resolution rotation curves of nine LSB galaxies. We fit these dark matter models to the data and determine the halo core radii and central densities. While the minimum core size in WDM models is predicted to decrease with halo mass, we find that the inferred core radii increase with halo mass and also cannot be explained with a single value of the primordial phase spa…
In warm dark matter scenarios structure formation is suppressed on small scales with respect to the cold dark matter case, reducing the number of low-mass halos and the fraction of ionized gas at high redshifts and thus, delaying reionization. This has an impact on the ionization history of the Universe and measurements of the optical depth to reionization, of the evolution of the global fraction of ionized gas and of the thermal history of the intergalactic medium, can be used to set constraints on the mass of the dark matter particle. However, the suppression of the fraction of ionized mediu…
The recent EDGES collaboration detection of an absorption signal at a central frequency of $ν= 78 \pm 1$ MHz points to the presence of a significant Lyman-$α$ background by a redshift of $z=18$. The timing of this signal constrains the dark matter particle mass ($m_χ$) in the warm dark matter (WDM) cosmological model. WDM delays the formation of small-scale structures, and therefore a stringent lower limit can be placed on $m_χ,$ based on the presence of a sufficiently strong Ly-$α$ background due to star formation at $z=18$. Our results show that the coupling the spin temperature to the gas t…
Small distortions in the images of Einstein rings or giant arcs offer the exciting prospect of detecting dark matter haloes or subhaloes of mass below $10^9$M$_{\odot}$, most of which are too small to have made a visible galaxy. A very large number of such haloes are predicted to exist in the cold dark matter model of cosmogony; in contrast other models, such as warm dark matter, predict no haloes below a mass of this order which depends on the properties of the warm dark matter particle. Attempting to detect these small perturbers could therefore discriminate between different kinds of dark m…
We present for the first time the outcomes of a cosmological N-body simulation that simultaneously implements a Warm Dark Matter (WDM) particle candidate and a modified gravitational interaction in the form of $f(R)$ gravity, and compare its results with the individual effects of these two independent extensions of the standard $Λ$CDM scenario, and with the reference cosmology itself. We consider a rather extreme value of the WDM particle mass ($m_{\rm WDM}=0.4$ keV) and a single realisation of $f(R)$ gravity with $|\bar{f}_{R0}|=10^{-5}$, and we investigate the impact of these models and of t…
We propose a novel use of high-redshift galaxies, discovered in deep Hubble Space Telescope (HST) fields around strong lensing clusters. These fields probe small comoving volumes (about 1000 cubic Mpc) at high magnification (μ > 10), and can detect otherwise inaccessible ultra-faint galaxies. Even a few galaxies found in such small volumes require a very high number density of collapsed dark matter (DM) halos. This implies significant primordial power on small scales, allowing these observations to rule out popular alternatives to standard cold dark matter (CDM) models, such as warm dark matte…
Warm dark matter (WDM) has been proposed as an alternative to cold dark matter (CDM), to resolve issues such as the apparent lack of satellites around the Milky Way. Even if WDM is not the answer to observational issues, it is essential to constrain the nature of the dark matter. The effect of WDM on haloes has been extensively studied, but the small-scale initial smoothing in WDM also affects the present-day cosmic web and voids. It suppresses the cosmic "sub-web" inside voids, and the formation of both void haloes and subvoids. In $N$-body simulations run with different assumed WDM masses, w…
We study clusters in Warm Dark Matter (WDM) models of a thermally produced dark matter particle $0.5$ keV in mass. We show that, despite clusters in WDM cosmologies having similar density profiles as their Cold Dark Matter (CDM) counterparts, the internal properties, such as the amount of substructure, shows marked differences. This result is surprising as clusters are at mass scales that are {\em a thousand times greater} than that at which structure formation is suppressed. WDM clusters gain significantly more mass via smooth accretion and contain fewer substructures than their CDM brethren.…
We report the results of extended high--resolution numerical integrations of the Vlasov--Poisson equation for the collapse of spherically symmetric WDM halos. For thermal relics with mass $m=1\,$keV/$c^2$, we find collapsed halos with cores of size from $0.1$ to $0.6\,$kpc. The typical core is hollow, with the mass density decreasing towards the core center by almost three orders of magnitude from its maximum near the core radius $r_{\rm c}$. The core is in equilibrium with the diffused part of the halo but far from virialization. These properties are rooted in the conservation of the squared …
We present results from high--resolution cosmological hydrodynamical simulations of a Milky--Way-sized halo, aimed at studying the effect of feedback on the nature of gas accretion. Simulations include a model of inter-stellar medium and star formation, in which SN explosions provide effective thermal feedback. We distinguish between gas accretion onto the halo, which occurs when gas particles cross the halo virial radius, and gas accretion onto the central galaxy, which takes place when gas particles cross the inner one-tenth of the virial radius. Gas particles can be accreted through three d…
We derive the main physical galaxy properties: mass, halo radius, phase space density and velocity dispersion from a semiclassical gravitational approach in which fermionic WDM is treated quantum mechanically. They turn out to be compatible with observations. Pauli Principle implies for the fermionic DM phase-space density Q(r) = rho(r)/sigma^3(r) the quantum bound Q(r) < K m^4/hbar^3, where m is the DM particle mass, sigma(r) is the DM velocity dispersion and K is a pure number of order one which we estimate. N-body galaxy simulations produce a divergent Q(r) at r = 0 violating this quantum b…
The correlation of weak lensing and Cosmic Microwave Anisotropy (CMB) data traces the pressure distribution of the hot, ionized gas and the underlying matter density field. The measured correlation is dominated by baryons residing in halos. Detecting the contribution from unbound gas by measuring the residual cross-correlation after masking all known halos requires a theoretical understanding of this correlation and its dependence with model parameters. Our model assumes that the gas in filaments is well described by a log-normal probability distribution function, with temperatures $10^{5-7}$K…
Precision analysis of galaxy-galaxy strong gravitational lensing images provides a unique way of characterizing small-scale dark matter halos, and could allow us to uncover the fundamental properties of dark matter's constituents. Recently, gravitational imaging techniques made it possible to detect a few heavy subhalos. However, gravitational lenses contain numerous subhalos and line-of-sight halos, whose subtle imprint is extremely difficult to detect individually. Existing methods for marginalizing over this large population of sub-threshold perturbers to infer population-level parameters a…
Upcoming ground and space-based experiments may have sufficient accuracy to place significant constraints upon high-redshift star formation, Reionization, and dark matter (DM) using the global 21-cm signal of the intergalactic medium. In the early universe, when the relative abundance of low-mass DM halos is important, measuring the global signal would place constraints on the damping of structure formation caused by DM having a higher relic velocity (warm dark matter, or WDM) than in cold dark matter (CDM). Such damping, however, can be mimicked by altering the star formation efficiency (SFE)…
We investigate the possibility to have a constraint on the mass of thermal warm dark matter (WDM) particle from the expected data of the Wide Field Infrared Survey Telescope (WFIRST) survey if all the dark matter is warm. For this purpose we consider the lensing effect of large scale structure based on the warm dark matter scenario on the apparent magnitude of SNe Ia. We use HALOFIT as non-linear matter power spectrum and the variance of PDF. We preform a Fisher matrix analysis and obtain the lower bound of $m_{\rm WDM}>0.167$keV.
We investigate whether the late-time (at $z\leq 100$) velocity dispersion expected in Warm Dark Matter scenarios could have some effect on the cosmic web (i.e., outside of virialized halos). We consider effective hydrodynamical equations, with a pressurelike term that agrees at the linear level with the analysis of the Vlasov equation. Then, using analytical methods, based on perturbative expansions and the spherical dynamics, we investigate the impact of this term for a 1 keV dark matter particle. We find that the late-time velocity dispersion has a negligible effect on the power spectrum on …
Understanding how galaxy properties are linked to the dark matter halos they reside in, and how they co-evolve is a powerful tool to constrain the processes related to galaxy formation. The stellar-to-halo mass relation (SHMR) and its evolution over the history of the Universe provides insights on galaxy formation models and allows to assign galaxy masses to halos in N-body dark matter simulations. We use a statistical approach to link the observed galaxy stellar mass functions on the COSMOS field to dark matter halo mass functions from the DUSTGRAIN simulation and from a theoretical parametri…
The damping on the fluctuation spectrum and the presence of thermal velocities as properties of warm dark matter particles like sterile neutrinos imprint a distinct signature found from the structure formation mechanisms to the internal structures of halos. Using warm dark matter simulations we explore these effects on the structure formation for different particle energies and we find that the formation of structure is more complex than originally assumed, a combination of top-down collapse and hierarchical (bottom-up) clustering on multiple scales. The degree on which one scenario is more pr…
The satellite galaxies of the Milky Way (MW) are effective probes of the underlying dark matter (DM) substructure, which is sensitive to the nature of the DM particle. In particular, a class of DM models have a power spectrum cut-off on the mass scale of dwarf galaxies and thus predict only small numbers of substructures below the cut-off mass. This makes the MW satellite system appealing to constrain the DM properties: feasible models must produce enough substructure to host the number of observed Galactic satellites. Here, we compare theoretical predictions of the abundance of DM substructur…
