arXiv subjects

M. Gatto

Publications and source records attributed to M. Gatto.

22 records · Page 2Linked to original sources

arXiv2021

STEP Survey II: Structural Analysis of 170 star clusters in the SMC

We derived surface brightness profiles in the \emph{g} band for 170 Small Magellanic Cloud (SMC) star clusters (SCs) mainly located in the central region of the galaxy. We provide a set of homogeneous structural parameters obtained by fitting Elson, Fall \& Freeman (EFF) and King models. Through a careful analysis of their colour-magnitude diagrams (CMDs) we also supply the ages for a subsample of 134 SCs. For the first time, such a large sample of SCs in the SMC is homogeneously characterized in terms of their sizes, luminosities and masses, widening the probed region of the parameter space, down to hundreds of solar masses. We used these data to explore the evolution of the SC's structural parameters with time. In particular, we confirm the existence of a physical mechanism that induces an increase of the core radius after 0.3-1.0 Gyr. We suggest that cluster mass could be the main parameter driving the inner expansion, as none of the SCs having $\log (M/M_{\odot}) \leq 3.5$~dex analysed in this work undergoes to such an expansion. We also detected a mass-size relationship almost over the entire range of SCs masses investigated here. Finally, our data suggest that globally the SMC SC system is dynamically evolved.

astro-ph.GA↗

arXiv2021

YMCA-1: a new remote star cluster of the Milky Way?

We report the possible discovery of a new stellar system (YMCA-1), identified during a search for small scale overdensities in the photometric data of the YMCA survey. The object's projected position lies on the periphery of the Large Magellanic Cloud about $13^\circ$ apart from its center. The most likely interpretation of its color-magnitude diagram, as well as of its integrated properties, is that YMCA-1 may be an old and remote star cluster of the Milky Way at a distance of 100 kpc from the Galactic center. If this scenario could be confirmed, then the cluster would be significantly fainter and more compact than most of the known star clusters residing in the extreme outskirts of the Galactic halo, but quite similar to Laevens~3. However, much deeper photometry is needed to firmly establish the actual nature of the cluster and the distance to the system.

astro-ph.GA↗

arXiv2020

A search for star clusters in the outskirts of the Large Magellanic Cloud: indication of clusters in the age gap

The YMCA (Yes, Magellanic Clouds Again) and STEP ({The SMC in Time: Evolution of a Prototype interacting late-type dwarf galaxy) projects are deep g,i photometric surveys carried out with the VLT Survey Telescope (VST) and devoted to study the outskirts of the Magellanic System. A main goal of YMCA and STEP is to identify candidate stellar clusters and complete their census out to the outermost regions of the Magellanic Clouds. We adopted a specific over-density search technique coupled with a visual inspection of the color magnitude diagrams (CMDs) to select the best candidates and estimate their ages. To date, we analysed a region of 23 sq. deg. in the outskirts of the Large Magellanic Cloud, detecting 85 candidate cluster candidates, 16 of which have estimated ages falling in the so called "age gap". We use these objects together with literature data to gain insight into the formation and interaction history of the Magellanic Clouds.

astro-ph.GA↗

arXiv2020

COSTA: the COld STream finder Algorithm. Searching for kinematical substructures in the phase space of discrete tracers

Context: We present COSTA (COld STream finder Algorithm), a novel algorithm to search for cold kinematical substructures in the phase space of planetary nebulae (PNe) and globular clusters (GCs) in the halo of massive galaxies and intracluster regions. Aims: COSTA aims at detecting small sized, low velocity dispersion streams, as the ones produced in recent interactions of dwarf galaxies with the halo of more massive galaxies, including the ones sitting in the central region of rich galaxy clusters. Methods: COSTA is based on a deep friend-of-friend procedure that isolates groups of N particles with small velocity dispersion (between 10 kms and $\sim$ 100 kms), using an iterative (n) sigma-clipping over a defined number of (k) neighbor particles. The algorithm has three parameters (k-n-N), plus a velocity dispersion cut-off, which defines the "coldness" of the stream, that are set using Montecarlo realizations of the sample under exam. Results: In this paper, we show the ability of COSTA to recover simulated streams on mock data-sets of discrete kinematical tracers with different sizes and measurement errors, from publicly available hydrodynamical simulations. We also show the best algorithm set-up for a realistic case of stream finding in the core of the Fornax cluster, for future applications of COSTA to real populations of PNe and GCs. Conclusions: COSTA can be generalized to all problems of finding small substructures in the phase space of a limited sample of discrete tracers, provided that the algorithm is trained on realistic mock observations reproducing the specific dataset under exam.

astro-ph.GA↗