arXiv subjects

Luis Pereyra

Publications and source records attributed to Luis Pereyra.

7 recordsLinked to original sources

arXiv2026

The role of filaments in the large-scale conformity signal

We investigate the large-scale conformity signal and its connection with the large-scale structure, focusing on low-mass central galaxies, after excluding galaxies that were satellites in the past. We measure the signal across different environments identified with the DisPerSE algorithm, including group outskirts, cluster outskirts, filaments, filament outskirts, and other environments (voids and walls) in order to assess how each population contributes to the large-scale conformity signal. We use the galaxy catalogs from the IllustrisTNG300 simulation and the semi-analytic model MDPL2-SAG. In SAG, galaxies embedded in filamentary regions emerge as the primary contributors to the large-scale conformity signal, closely reproducing its overall shape and amplitude. In TNG300, galaxies located in filamentary regions also exhibit a coherent, albeit weaker, conformity signal once galaxies that were satellites in the past are excluded. We also examine whether the signal depends on the adopted filament definition. We find no substantial differences when varying the filament thickness or considering galaxies in overlapping regions. Instead, the signal remains strong and largely insensitive to these differences. We then investigate the dependence of the conformity signal on filament linear density, length, and mass. The signal is enhanced in high-linear density, short, and high-mass filaments, but remains present in low-linear density, long, and low-mass filaments, although with a slightly lower amplitude. Finally, we find that low-mass central galaxies located in close proximity to interacting massive systems show an amplified conformity signal extending up to 4 Mpc/h. Overall, our results indicate that filamentary regions, and the tidal forces from neighboring massive systems play a fundamental role in shaping the large-scale conformity signal.

astro-ph.GA↗

arXiv2023

Enlightening the Universe behind the Milky Way Bulge

Context. The location of the Solar System constrains the detection of extragalactic sources beyond the Milky Way(MW) plane. The optical observations are hampered in the so--called Zone of Avoidance (ZOA) where stellar crowding and Galactic absorption are severe. Observations at longer wavelengths are needed to discover new background galaxies and complete the census in the ZOA. Aims. The goal of this work is to identify galaxies behind the MW Bulge using near-infrared (NIR) data from the VISTA Variables in Vía Láctea (VVV) survey. Methods. To this end we made use of different VISTA Science Archive (VSA) tools in order to extract relevant information from more than 32 billion catalogued sources in the VVV Bulge region. We find that initial photometric restriction on sources from VSA \texttt{vvvSource} table combined with restrictions on star--galaxy separation parameters obtained from Source Extractor is a successful strategy to achieve acceptable levels of contamination (60\%) and a high completeness (75\%) in the construction of a galaxy target sample. To decontaminate the initial target sample from Galactic sources our methodology also incorporates the visual inspection of false colour RGB images, a crucial quality control which was carried out following a specifically defined procedure. Results. Under this methodology we find 14480 galaxy candidates in the VVV Bulge region making this sample the largest catalogue to date in the ZOA. Moreover these new sources provide a \textbf{fresh} picture of the Universe hidden behind the curtain of stars, dust and gas in the unexplored MW Bulge region. Conclusions. The results from this work further demonstrate the potential of the VVV/VVVX survey to find and study a large number of galaxies and extragalactic structures obscured by the MW, enlightening our knowledge of the Universe in this challenging and impressive region of the sky.

astro-ph.GA↗

arXiv2022

Anisotropic infall in the outskirst of clusters

We analyse the connection between the star formation quenching of galaxies and their location in theoutskirts of clusters in the redshift range $z=[0,2]$ by estimating the fraction of red galaxies. More specifically, we focus on galaxies that infall isotropically from those that are infalling alongside filaments. We use a sample of galaxies obtained from the semi-analytic model of galaxy formation SAG applied to the MultiDark simulation. {\textsc{mdpl2}}. In agreement with observational results, we find that the infall regions show levels of star formation that are intermediate between those of galaxies in clusters and in the field. Moreover, we show that, in the redshift range [0-0.85], the quenching of the star formation is stronger in the filamentary region than in the isotropic infall region. We also study the fraction of red galaxies as a function of the normalised distance to the cluster centre and find that, for radii $R/R_{200}> 3 $, the fraction of red galaxies in the filamentary region is considerably larger than in the isotropic infall region. From the analysis of properties of the main progenitors of galaxies identified at $z = 0$, we find that they have different evolutionary behaviours depending on the stellar mass and environment. Our results confirm the observational findings that suggest that the infall regions of clusters play an important role in the pre-processing of galaxies along most of the evolutionary history of galaxies.

astro-ph.GA↗

arXiv2021

Overdensity of VVV galaxies behind the Galactic bulge

We studied a region of 1.636 square degrees corresponding to the VVV tile $b204$. Using SExtractor, we analysed photometric data generating a catalogue of extended sources in this area. In order to confirm these sources as galaxy candidates we visually inspected RGB images looking for typical galaxy features. Using 2MASX and GCMW catalogued sources we tested completeness and contamination of our catalogue and define suitable colour cuts to select galaxies. We also compared the observational results with those obtained from two semi-analytical models on Dark Matter simulations. One galaxy catalogue was constructed with the SAG semi-analytic model of galaxy formation, and the other one was constructed with the L-Galaxies semi-analytic model.By adopting CLASS-STAR$< 0.5$, $r_{1/2} > 0.7$ arcsec and specific colour cuts (J-Ks$>$0.97, J-H$>$0 and H-Ks$>$0) we generated an automatic catalogue of extended sources. After visual inspection we identified 624 sources with 10$<$Ks$<$17 as galaxy candidates. The contamination of the automatic catalogue is 28% when considering visually confirmed galaxies as reliable objects. The estimated completeness is 87% up to magnitude Ks=13.5. We analysed the spatial distribution of galaxy candidates, finding a high concentration of galaxies in a small region of 15 arcmin radius. This region has three times higher density than similar areas in the tile. We compared the number of galaxies in this small area with the mean density values obtained from a suitable sample of galaxies from semi-analytic models finding that our results are consistent with an overdensity region. Using VVV near-infrared data and mock catalogues we detect new extragalactic sources that have not been identified by other catalogues. We demonstrate the potentiality of the VVV survey studying a large number of galaxy candidates and extragalactic structures obscured by the Milky Way.

astro-ph.GA↗

arXiv2020

GriSPy: A Python package for Fixed-Radius Nearest Neighbors Search

We present a new regular grid search algorithm for quick fixed-radius nearest-neighbor lookup developed in Python. This module indexes a set of k-dimensional points in a regular grid, with optional periodic conditions, providing a fast approach for nearest neighbors queries. In this first installment we provide three types of queries: $bubble$, $shell$ and the $nth-nearest$; as well as three different metrics of interest in astronomy: the $euclidean$ and two distance functions in spherical coordinates of varying precision, $haversine$ and $Vincenty$; and the possibility of providing a custom distance function. This package results particularly useful for large datasets where a brute-force search turns impractical.

astro-ph.IM↗

arXiv2020

A comparison of cosmological filaments catalogues

In this work we compare three catalogues of cosmological filaments identified in the Sloan Digital Sky Survey by means of different algorithms by Tempel et al., Pereyra et al., and Martínez et al. We analyse how different identification techniques determine differences in the filament statistical properties: length, elongation, redshift distribution, and abundance. We find that the statistical properties of the filaments strongly depend on the identification algorithm. We use a volume limited sample of galaxies to characterise other properties of filaments such as: galaxy overdensity, luminosity function of galaxies, mean galaxy luminosity, filament luminosity, and the overdensity profile of galaxies around filaments. In general, we find that these properties primarily depended on filament length. Shorter filaments have larger overdensities, are more populated by red galaxies, and have better defined galaxy overdensity profiles, than longer filaments. Concluding that galaxies belonging to filaments have characteristic signatures depending on the identification algorithm used.

astro-ph.GA↗

arXiv2017

Occurrence of LINER galaxies within the galaxy group environment

We study the properties of a sample of 3967 LINER galaxies selected from SDSS-DR7, respect to their proximity to galaxy groups. The host galaxies of LINER have been analysed and compared with a well defined control sample of 3841 non-LINER galaxies matched in redshift, luminosity, colour, morphology, age and stellar mass content. We find no difference between LINER and control galaxies in terms of colour and age of stellar population as function of the virial mass and distance to the geometric centre of the group. However, we find that LINER are more likely to populate low density environments in spite of their morphology, which is typical of high density regions such as rich galaxy clusters. For rich (poor) galaxy groups, the occurrence of LINER is $\sim$2 times lower (higher) than the occurrence of matched, non-LINER galaxies. Moreover, LINER hosts do not seem to follow the expected morphology-density relation in groups of high virial mass. The high frequency of LINERS in low density regions could be due to the combination of a sufficiently ample gas reservoir to power the low ionization emission and/or enhanced galaxy interaction rates benefiting the gas flow toward their central regions.

astro-ph.GA↗