S0 galaxies are faded spirals: clues from their angular momentum content

The distribution of galaxies in the stellar specific angular momentum versus stellar mass plane ($j_{\star}$-$M_{\star}$) provides key insights into their formation mechanisms. In this paper, we determine the location in this plane of a sample of ten field/group unbarred lenticular (S0) galaxies from the CALIFA survey. We performed a bulge-disc decomposition both photometrically and kinematically to study the stellar specific angular momentum of the disc components alone and understand the evolutionary links between S0s and other Hubble types. We found that eight of our S0 discs have a distribution in the $j_{\star}$-$M_{\star}$ plane that is fully compatible with that of spiral discs, while only two have values of $j_{\star}$ lower than the spirals. These two outliers show signs of recent merging. Our results suggest that merger and interaction processes are not the dominant mechanisms in S0 formation in low-density environments. Instead, S0s appear to be the result of secular processes and the fading of spiral galaxies after the shutdown of star formation.Comment: 35 pages, 22 figures. Accepted for publication in MNRA

LITTLE THINGS in 3D: robust determination of the circular velocity of dwarf irregular galaxies

Dwarf Irregular galaxies (dIrrs) are the smallest stellar systems with extended HI discs. The study of the kinematics of such discs is a powerful tool to estimate the total matter distribution at these very small scales. In this work, we study the HI kinematics of 17 galaxies extracted from the `Local Irregulars That Trace Luminosity Extremes, The HI Nearby Galaxy Survey' (LITTLE THINGS). Our approach differs significantly from previous studies in that we directly fit 3D models (two spatial dimensions plus one spectral dimension) using the software $^\text{3D}$BAROLO, fully exploiting the information in the HI datacubes. For each galaxy we derive the geometric parameters of the HI disc (inclination and position angle), the radial distribution of the surface density, the velocity-dispersion ($\sigma_v$) profile and the rotation curve. The circular velocity (V$_{\text{c}}$), which traces directly the galactic potential, is then obtained by correcting the rotation curve for the asymmetric drift. As an initial application, we show that these dIrrs lie on a baryonic Tully-Fisher relation in excellent agreement with that seen on larger scales. The final products of this work are high-quality, ready-to-use kinematic data ($\textrm{V}_\textrm{c}$ and $\sigma_v$) that we make publicly available. These can be used to perform dynamical studies and improve our understanding of these low-mass galaxies.Comment: 36 pages, 28 figures, 2 tables. Submitted to MNRAS (revised version after the referee report). The final rotation curves can be downloaded from http://www.filippofraternali.com/styled-9/index.htm

"Off piste" beyond the disc of the Milky Way: Structure of the stellar halo and dynamics of nearby dwarf galaxies

In this thesis we have exploited state-of-the-art datasets and techniques and/or proposed new methods to study the matter distribution in the stellar halo of our Galaxy and to study the kinematics and dynamics properties of a sample of nearby dwarf irregular galaxies (dIrrs). In the first part of the thesis, we focused on the study on the stellar halo of the Milky Way. In particular, we exploited the first data release of Gaia obtaining the first all-sky view of the RR Lyrae distribution in the inner part of the stellar halo. In the second part of this thesis, we studied the HI kinematics of 17 nearby dIrrs extracted from the LITTLE THINGS survey. Concerning the analysis of HI datacubes, our approach differs significantly from previous studies in that we exploit the 3D dimensions (two spatial dimensions and one spectral dimension) of the data using a state-of-the-art 3D fitting tool. In the last part of the thesis, we exploited the results obtained in the analysis of the dIrrs focusing on two important scaling relations: the “baryonic Tully-Fisher relation” and the “radial acceleration relation”. We compared our results with the ones obtained in previous works focusing on more massive galaxies. Finally, we made use of the velocity dispersions and of the star formation rates of the dIrrs in our sample to investigate whether the observed turbulence in the HI can be sustained by the energy injected in the ISM by the star formation activity

Confronting fuzzy dark matter with the rotation curves of nearby dwarf irregular galaxies

We investigate phenomenologically the viability of fuzzy dark matter (FDM). We do this by confronting the predictions of the model, in particular, the formation of a solitonic core at the center of dark matter halos, with a homogeneous and robust sample of high-resolution rotation curves from the ''LITTLE THINGS in 3D'' catalog. This comprises a collection of isolated, dark matter dominated dwarf-irregular galaxies that provides an optimal benchmark for cosmological studies. We use a statistical framework based on Markov chain Monte Carlo techniques that allows us to extract relevant parameters such as the axion mass, the mass of the solitonic core, the mass of the dark matter halo and its concentration parameter with a rather loose set of priors except for the implementation of a core-halo relation that is predicted by simulations. The results of the fits are used to perform various diagnostics on the predictions of the model. FDM provides an excellent fit to the rotation curves of the ''LITTLE THINGS in 3D'' catalog, with axion masses determined from different galaxies clustering around $m_a\approx2\times10^{-23}$ eV. However, we find two major problems in our analysis. First, the data follow scaling relations of the properties of the core which are not consistent with the predictions of the soliton. This problem is particularly acute in the core radius - mass relation with a tension that, at face value, has a significance $\gtrsim5\sigma$. The second problem is related to the strong suppression of the linear power spectrum that is predicted by FDM for the axion mass preferred by the data. This can be constrained very conservatively by the galaxy counts in our sample, which leads to a tension exceeding again $5\sigma$. We estimate the effects of baryons in our analysis and discuss whether they could alleviate the tensions of the model with observations.Comment: 22 pages, 9 figures, 3 table

ER access by foreign citizens between 1999 and 2014 in five large hospital of Rome, Italy

...Lack of information about the health services and the status of illegal immigrant can make difficult for foreign population to access primary care, leading to misuse of emergency rooms (ER). This study investigated the accesses between January 1999 and December 2014 to the ERs of five large hospital of Rome, Italy

Avaliação de opções de troca e opções de spread européias e americanas

This present paper aims at evaluating european and american exchange options and spread options. When the European options are considered, the model developed is based on Monte Carlo Simulations, taking into consideration the joint simulation of the underwriter’s price. The results of this model are compared with the premiums estimated by Margrabe (1978) and Kirk (1995) formulas. Additionally, the sensibility of the premiums relative to changes in some inputs parameters was analyzed, contributing for the correct understanding of these derivatives. When the american options are considered, the model developed consists in an adaption of the Least Square Monte Carlo (LSMC) method developed by Longstaff e Schwartz (2001), so as to contemplate the multidimensional case. The results presented by this model were then compared with that presented by two other models, based on pyramidal lattices, developed by Rubinstein (1994) and Brandimarte (2006). Besides comparing the results presented by these three models, the sensibility of the premiums relative to changes in some inputs parameters was analyzed, confirming the consistence of the results presented. It’s important to note that, different from the pyramidal lattices, the adaption of the LSMC model has the advantage to allow the extension for three or more underwriters.

Kinematics of the Palomar 5 stellar stream from RR Lyrae stars

Thin stellar streams, formed from the tidal disruption of globular clusters, are important gravitational tools, sensitive to both global and small-scale properties of dark matter. The Palomar 5 stellar stream (Pal 5) is an exemplar stream within the Milky Way: Its $\sim 20^\circ$ tidal tails connect back to the progenitor cluster, and the stream has been used to study the shape, total mass, and substructure fraction of the dark matter distribution of the Galaxy. However, most details of the phase-space distribution of the stream are not fully explained, and dynamical models that use the stream for other inferences are therefore incomplete. Here we aim to measure distance and kinematic properties along the Pal 5 stream in order to motivate improved models of the system. We use a large catalog of RR Lyrae-type stars (RRLs) with astrometric data from the Gaia mission to probabilistically identify RRLs in the Pal 5 stream. RRLs are useful because they are intrinsically-luminous standard candles and their distances can be inferred with small relative precision ($\sim3\%$). By building a probabilistic model of the Pal 5 cluster and stream in proper motion and distance, we find 27 RRLs consistent with being members of the cluster (10) and stream (17). Using these RRLs, we detect gradients in distance and proper motion along the stream, and provide an updated measurement of the distance to the Pal 5 cluster using the RRLs, $d = 20.6 \pm 0.2~\textrm{kpc}$. We provide a catalog of Pal 5 RRLs with inferred membership probabilities for future modeling work.Comment: 13 pages, 4 figures. Published in A

Massive binary black holes from Population II and III stars

Population III stars, born from the primordial gas in the Universe, lose a negligible fraction of their mass via stellar winds and possibly follow a top-heavy mass function. Hence, they have often been regarded as the ideal progenitors of massive black holes (BHs), even above the pair instability mass gap. Here, we evolve a large set of Population III binary stars (metallicity $Z=10^{-11}$) with our population-synthesis code SEVN, and compare them with Population II binary stars ($Z=10^{-4}$). In our models, the lower edge of the pair-instability mass gap corresponds to a BH mass of $\approx{86}$ ($\approx{91}$) M$_\odot$ for single Population III (II) stars. Overall, we find only mild differences between the properties of binary BHs (BBHs) born from Population III and II stars, especially if we adopt the same initial mass function and initial orbital properties. Most BBH mergers born from Population III and II stars have primary BH mass below the pair-instability gap, and the maximum secondary BH mass is $< 50$ M$_\odot$. Only up to $\approx{3.3}$% ($\approx{0.09}$%) BBH mergers from Population III (II) progenitors have primary mass above the gap. Unlike metal-rich binary stars, the main formation channel of BBH mergers from Population III and II stars involves only stable mass transfer episodes in our fiducial model.Comment: 15 pages, 17 figures, comments are welcom

New insights on binary black hole formation channels after GWTC-2: young star clusters versus isolated binaries

With the recent release of the second gravitational-wave transient catalogue (GWTC-2), which introduced dozens of new detections, we are at a turning point of gravitational wave astronomy, as we are now able to directly infer constraints on the astrophysical population of compact objects. Here, we tackle the burning issue of understanding the origin of binary black hole (BBH) mergers. To this effect, we make use of state-of-the-art population synthesis and N-body simulations, to represent two distinct formation channels: BBHs formed in the field (isolated channel) and in young star clusters (dynamical channel). We then use a Bayesian hierarchical approach to infer the distribution of the mixing fraction $f$, with $f=0$ ($f=1$) in the pure dynamical (isolated) channel. %that controls the proportion of isolated and dynamical BBHs. We explore the effects of additional hyper-parameters of the model, such as the spread in metallicity $\sigma_{\text{Z}}$ and the parameter $\sigma_{\text{sp}}$, describing the distribution of spin magnitudes. We find that the dynamical model is slightly favoured with a median value of $f=0.26$, when $\sigma_{\text{sp}}=0.1$ and $\sigma_{\text{Z}}=0.4$. Models with higher spin magnitudes tend to strongly favour dynamically formed BBHs ($f\le{}0.1$ if $\sigma_{\text{sp}}=0.3$). Furthermore, we show that hyper-parameters controlling the rates of the model, such as $\sigma_{\rm Z}$, have a large impact on the inference of the mixing fraction, which rises from $0.18$ to $0.43$ when we increase $\sigma_{\text{Z}}$ from 0.2 to 0.6, for a fixed value of $\sigma_{\text{sp}}=0.1$. Finally, our current set of observations is better described by a combination of both formation channels, as a pure dynamical scenario is excluded at the $99\%$ credible interval, except when the spin magnitude is high.Comment: 13 pages, 10 figures, 2 tables, published in MNRA

Binary black hole mergers from Population III stars: uncertainties from star formation and binary star properties

Population III (Pop. III) binary stars likely produced the first stellar-born binary black hole (BBH) mergers in the Universe. Here, we quantify the main sources of uncertainty for the merger rate density evolution and mass spectrum of Pop. III BBHs by considering four different formation histories of Pop. III stars and 11 models of the initial orbital properties of their binary systems. The uncertainty on the orbital properties affects the BBH merger rate density by up to two orders of magnitude; models with shorter initial orbital periods lead to higher BBH merger rates, because they favour the merger via stable mass transfer episodes. The uncertainty on the star formation history also has a substantial impact on both the shape and the normalisation of the BBH merger rate density: the peak of the merger rate density shifts from $z\sim{8}$ up to $z\sim{16}$ depending on the assumed star formation rate, while the maximum BBH merger rate density for our fiducial binary population model spans from $\sim{2}$ to $\sim{30}$ Gpc$^{-3}$ yr$^{-1}$. The typical BBH masses are not affected by the star formation rate model and only mildly influenced by the binary population parameters. The primary black holes born from Pop. III stars tend to be rather massive ($30-40$ M$_\odot$) with respect to those born from metal-rich stars ($8-10$ M$_\odot$). However, we expect that Pop. III BBH mergers with primary mass $m_1>60$ M$_\odot$ are rare ($<10^{-2}$ Gpc$^{-3}$ yr$^{-1}$). Finally, we estimate that the Einstein Telescope will detect $10-10^4$ Pop. III BBH mergers per year, depending on the star formation history and binary star properties.Comment: 16 pages, 16 figures, 1 table. Comments are welcome. Submitted to MNRA