A robust estimate of the Milky Way mass from rotation curve data

We present a new estimate of the mass of the Milky Way, inferred via a Bayesian approach by making use of tracers of the circular velocity in the disk plane and stars in the stellar halo, as from the publicly available galkin compilation. We use the rotation curve method to determine the dark matter distribution and total mass under different assumptions for the dark matter profile, while the total stellar mass is constrained by surface stellar density and microlensing measurements. We also include uncertainties on the baryonic morphology via Bayesian model averaging, thus converting a potential source of systematic error into a more manageable statistical uncertainty. We evaluate the robustness of our result against various possible systematics, including rotation curve data selection, uncertainty on the Sun's velocity V0, dependence on the dark matter profile assumptions, and choice of priors. We find the Milky Way's dark matter virial mass to be log10M200DM/ Mo\u2d9 = 11.92+0.06-0.05(stat)\ub10.28\ub10.27(syst) (M200DM=8.3+1.2-0.9(stat) 71011 Mo\u2d9). We also apply our framework to Gaia DR2 rotation curve data and find good statistical agreement with the above results

Searching for TeV DM evidence from Dwarf Irregular Galaxies with the HAWC Observatory

The dynamics of dwarf irregular (dIrr) galaxies are observed to be dominated by dark matter (DM). Recently, the DM density distribution has been studied for 31 dIrrs. Their extended DM halo (Burket type profile) makes these objects good candidates for DM searches. Located in Puebla (Mexico), the High Altitude Water Cherenkov (HAWC) Observatory is an optimal instrument to perform such DM searches, because of its large sky coverage (8.4 sr per day). We analyzed a set of two years of HAWC data and we found no significant DM signal from dIrr galaxies. We present the upper limits for DM annihilation cross-section with dIrr galaxies

Constraints on cross-section and lifetime of dark matter with HAWC Observations of dwarf Irregular galaxies

It has been shown that the dynamics of dwarf Irregular (dIrr) galaxies are dominated by dark matter. It is also observed that these galaxies have low star formation rates and metallicities, and no gamma-ray emission at ultra very high energies is expected. Because of their distance, dark matter content and vast number, dIrr galaxies are good targets to perform indirect dark matter searches by ground-based and wide field of view gamma-ray experiments, like HAWC. We analyzed data at the position of 31 dIrr galaxies within the HAWC field-of-view and no significant excess was found. Here, we present the individual and combined limits on the annihilation cross-section and decay lifetime of weakly interacting massive particles with mass between 1 and 100 TeV

Modeling the Mass Distribution in the Spiral Galaxy NGC 3198

We study the HI Rotation Curve of the spiral galaxy NGC 3198 in terms of mass decomposition. We model the Rotation Curve in the framework of different models for the Dark Matter distribution: the Burkert profile and NFW profile. We show that Universal Rotation Curve (Burkert halo+stellar disk+gas disk) fits data accurately. Instead, the NFW (NFW halo+stellar disk+gas disk) model gives non-physical values of NFW halo parameters. \ua9 Published under licence by IOP Publishing Ltd

Galaxy Evolution at High Redshift: Obscured Star Formation, GRB Rates, Cosmic Reionization, and Missing Satellites

We provide an holistic view of galaxy evolution at high redshift z>4, that incorporates the constraints from various astrophysical/cosmological probes, including the estimate of the cosmic SFR density from UV/IR surveys and long GRB rates, the cosmic reionization history after the latest Planck measurements, and the missing satellites issue. We achieve this goal in a model-independent way by exploiting the SFR functions derived by Mancuso et al. (2016) on the basis of an educated extrapolation of the latest UV/far-IR data from HST/Herschel, and already tested against a number of independent observables. Our SFR functions integrated down to an UV magnitude limit M_UV<-13 (or SFR limit around 10^-2 M_sun/yr) produces a cosmic SFR density in excellent agreement with recent determinations from IR surveys and, taking into account a metallicity ceiling Z<Z_sun/2, with the estimates from long GRB rates. They also yield a cosmic reionization history consistent with that implied by the recent measurements of the Planck mission on the electron scattering optical depth tau_es~0.058; remarkably, this result is obtained under a conceivable assumption regarding the average value f_esc~0.1 of the escape fraction for ionizing photons. We demonstrate via the abundance matching technique that the above constraints concurrently imply galaxy formation to become inefficient within dark matter halos of mass below a few 10^8 M_sun; pleasingly, such a limit is also required not to run into the missing satellite issue. Finally, we predict a downturn of the galaxy luminosity function faintward of M_UV<-12, and stress that its detailed shape, as plausibly probed in the next future by the JWST, will be extremely informative on the astrophysics of galaxy formation in small halos, or even on the microscopic nature of the dark matter

Searching for TeV Dark Matter in Irregular dwarf galaxies with HAWC Observatory

We present the results of dark matter (DM) searches in a sample of 31 dwarf irregular (dIrr) galaxies within the field of view of the HAWC Observatory. dIrr galaxies are DM dominated objects, which astrophysical gamma-ray emission is estimated to be negligible with respect to the secondary gamma-ray flux expected by annihilation or decay of Weakly Interacting Massive Particles (WIMPs). While we do not see any statistically significant DM signal in dIrr galaxies, we present the exclusion limits ($95\%~\text{C.L.}$) for annihilation cross-section and decay lifetime for WIMP candidates with masses between $1$ and $100~\text{TeV}$. Exclusion limits from dIrr galaxies are relevant and complementary to benchmark dwarf Spheroidal (dSph) galaxies. In fact, dIrr galaxies are targets kinematically different from benchmark dSph, preserving the footprints of different evolution histories. We compare the limits from dIrr galaxies to those from ultrafaint and classical dSph galaxies previously observed with HAWC. We find that the contraints are comparable to the limits from classical dSph galaxies and $\thicksim2$ orders of magnitude weaker than the ultrafaint dSph limits.Comment: 22 pages, 11 figures, 3 table

Sensitivity of the Cherenkov Telescope Array to a dark matter signal from the Galactic centre

We provide an updated assessment of the power of the Cherenkov Telescope Array (CTA) to search for thermally produced dark matter at the TeV scale, via the associated gamma-ray signal from pair-annihilating dark matter particles in the region around the Galactic centre. We find that CTA will open a new window of discovery potential, significantly extending the range of robustly testable models given a standard cuspy profile of the dark matter density distribution. Importantly, even for a cored profile, the projected sensitivity of CTA will be sufficient to probe various well-motivated models of thermally produced dark matter at the TeV scale. This is due to CTA's unprecedented sensitivity, angular and energy resolutions, and the planned observational strategy. The survey of the inner Galaxy will cover a much larger region than corresponding previous observational campaigns with imaging atmospheric Cherenkov telescopes. CTA will map with unprecedented precision the large-scale diffuse emission in high-energy gamma rays, constituting a background for dark matter searches for which we adopt state-of-the-art models based on current data. Throughout our analysis, we use up-to-date event reconstruction Monte Carlo tools developed by the CTA consortium, and pay special attention to quantifying the level of instrumental systematic uncertainties, as well as background template systematic errors, required to probe thermally produced dark matter at these energies

Theoretical predictions for dark matter detection in dwarf irregular galaxies with gamma rays

We investigate rotationally supported dwarf irregular (DIRR) galaxies as a new category of targets for indirect dark matter (DM) searches with gamma-ray telescopes. In the framework of pointlike analysis, pressure-supported dwarf spheroidal (DSPH) galaxies are usually considered as one of the best categories of targets for indirect DM searches, due to their close distance and negligible astrophysical background. Nonetheless, as a result of their uncertain kinematics, the DM content and astrophysical J-factors of DSPHs are usually affected by significant errors. In this paper, we study a sample of 36 DIRRs as prospective targets of interest. In the framework of the universal rotation curve, the kinematics of DIRR galaxies provides a good estimation of their DM halo density distribution and, consequently, of their astrophysical J-factors. We calculate the J-factors for these 36 DIRR galaxies, whose kinematics have been studied in a previous work. We find a range of values comparable with the J-factors of DSPH galaxies. However, differently from DSPHs an extra astrophysical gamma-ray background component is expected in DIRR galaxies, that is due to their star-formation activity. In this paper, we show via a theoretical approach that for galaxies in our sample the extra astrophysical background component is negligible. Therefore, we conclude that DIRR galaxies can be potentially considered as additional pointlike targets for DM searches with gamma rays. As a first application of this study, we show the sensitivity limits of the Fermi-LAT telescope to these objects and we calculate constraints on the DM particle mass and annihilation cross section. We conclude that the results of the individual study of several DIRR galaxies are not yet competitive with respect to the analysis of one of the most promising DSPH galaxies, i.e., SEGUE1. However, taking into account SEGUE1's symmetry-related uncertainties in the J-factor calculation might alter this conclusion. Additionally, we calculate constraints for the combined analysis of the seven most promising DIRR galaxies of our sample

Dark matter search in dwarf irregular galaxies with the Fermi Large Area Telescope

We analyze 11 years of Fermi-Large Area Telescope (LAT) data corresponding to the sky regions of seven dwarf irregular (dIrr) galaxies. DIrrs are dark matter (DM)-dominated systems, proposed as interesting targets for the indirect search of DM with gamma rays. The galaxies represent interesting cases with a strong disagreement between the density profiles (core versus cusp) inferred from observations and numerical simulations. In this work, we addressed the problem by considering two different DM profiles, based on both the fit to the rotation curve (in this case, a Burkert cored profile) and results from N-body cosmological simulations (i.e., Navarro-Frenk-White cuspy profile). We also include halo substructure in our analysis, which is expected to boost the DM signal by a factor of 10 in halos such as those of dIrrs. For each DM model and dIrr, we create a spatial template of the expected DM-induced gamma-ray signal to be used in the analysis of Fermi-LAT data. No significant emission is detected from any of the targets in our sample. Thus, we compute upper limits on the DM annihilation cross section versus mass parameter space. Among the seven dIrrs, we find IC10 and NGC6822 to yield the most stringent individual constraints, independently of the adopted DM profile. We also produce combined DM limits for all objects in the sample, which turn out to be dominated by IC10 for all DM models and annihilation channels, i.e., bb¯, τ+τ-, and W+W-. The strongest constraints are obtained for bb¯ and are at the level of σ 7×10-26 cm3 s-1 at mχ∼6 GeV. Though these limits are a factor of ∼3 higher than the thermal relic cross section at low weakly interacting massive particles masses, they are independent from and complementary to those obtained by means of other targets

The universal rotation curve of dwarf disc galaxies

We use the concept of the spiral rotation curves universality to investigate the luminous and dark matter properties of the dwarf disc galaxies in the local volume (size ~11 Mpc). Our sample includes 36 objects with rotation curves carefully selected from the literature. We find that, despite the large variations of our sample in luminosities (~2 of dex), the rotation curves in specifically normalized units, look all alike and lead to the lower mass version of the universal rotation curve of spiral galaxies found in Persic et al. We mass model the double normalized universal rotation curve V(R/Ropt)/Vopt of dwarf disc galaxies: the results show that these systems are totally dominated by dark matter whose density shows a core size between 2 and 3 stellar disc scalelengths. Similar to galaxies of different Hubble types and luminosities, the core radius r0 and the central density \u3c10 of the dark matter halo of these objects are related by \u3c10r0 ~ 100M 99 pc-2. The structural properties of the dark and luminous matter emerge very well correlated. In addition, to describe these relations, we need to introduce a new parameter, measuring the compactness of light distribution of a (dwarf) disc galaxy. These structural properties also indicate that there is no evidence of abrupt decline at the faint end of the baryonic to halo mass relation. Finally, we find that the distributions of the stellar disc and its dark matter halo are closely related