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Aims: To unveil the influence of galaxy-galaxy interactions on material transport driven by galactic bars towards the central regions of active galactic nuclei (AGN) galaxies and assess the efficiency of the combined mechanisms of interactions and bars in fueling massive black holes, we examine barred active galaxies in paired systems. Methods: Our study targets barred AGN galaxies in pairs with projected separations $r_{p}< 100 \rm \,kpc \,h^{-1}$ and relative radial velocities of $\Delta V< 500 \rm \,km \,s^{-1}$ within $z<0.1$, using Sloan Digital Sky Survey (SDSS) data. To quantify the impact of interactions, we also created a control sample of barred active galaxies without companions, matched in redshift, absolute r-band magnitude, stellar mass, color, and stellar age. We assessed galactic bar structures through two-dimensional image modeling, considering their wide range of shapes and sizes that may affect material transport ability. Results: We found that nuclear activity, measured by $Lum[OIII]$, increases as projected separations between galaxy pair members decrease. Barred AGN galaxies in close pairs ($r_p<$ 25 kpc $h^{-1}$) show significantly higher nuclear activity compared to the control sample. Barred galaxies with close companions exhibit enhanced nuclear activity across all luminosity, stellar mass, and color ranges. Barred AGN with longer bars show more efficient nuclear activity than those with shorter bars, with a pronounced effect in close pair systems. Nuclear activity increases as pair separations decrease. Barred AGNs in close pairs undergoing major interactions show a substantial excess of high $Lum[OIII]$ values, reflecting increased accretion onto central black holes. These findings suggest that nearby galaxy companions enhance gas flows driven by galactic bars, amplifying central nuclear activity and influencing black hole accretion., Comment: 12 pages, 13 figures, accepted for publication in A&A

Aims. We explore galaxies with ringed structures inhabiting poor and rich groups with the aim of assessing the effects of local density environments on ringed galaxy properties. Methods. We identified galaxies with inner, outer, nuclear, inner+outer (inner and outer rings combined), and partial rings that reside in groups by cross-correlating a sample of ringed galaxies with a group catalog obtained from Sloan Digital Sky Survey (SDSS). The resulting sample was divided based on group richness. To quantify the effects of rings and the role of local density environment on galaxy properties, we constructed a suitable control sample for each catalog of ringed galaxies, consisting of non-ringed galaxies with similar values for the z, magnitude, morphology, group masses, and environmental density distributions as those of ringed ones. We explored the occurrence of ringed galaxies in poor and rich groups and analyzed several galaxy properties, such as SFR, stellar populations, and colors. Results. We obtained a sample of 637 ringed galaxies residing in groups. With 76% of these galaxies inhabiting poor groups and 24% rich groups. In addition, ringed galaxies in groups display a reduction in their star formation activity and aged stellar populations, compared to non-ringed ones in the control samples. However, the SFR is higher for nuclear rings in poor groups than for other types. This disparity may stem from the environmental influence on the internal processes of galaxies, either enhancing or diminishing star formation. Ringed galaxies also show an excess of red colors and tend to populate the green valley and the red sequence of color-magnitude and color-color diagrams, with a surplus of galaxies in the red sequence, while non-ringed galaxies are found in the green valley and the blue region. These trends are more significant in galaxies with ringed structures residing in rich groups., Comment: 13 pages, 11 figures. Accepted for publication in A&A

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 V\'ia L\'actea (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.

Aims: We present a statistical analysis of different characteristics of ringed spiral galaxies with the aim of assessing the effects of rings on disk galaxy properties. Methods: We built a catalog of ringed galaxies from the Sloan Digital Sky Survey Data Release 14 (SDSS-DR14). Via visual inspection of SDSS images, we classified the face-on spiral galaxies brighter than $g < 16.0$ mag into galaxies with: an inner ring, an outer ring, a nuclear ring, both an inner and an outer ring, and a pseudo-ring. In addition to rings, we recorded morphological types and the existence of bars, lenses, and galaxy pair companions with or without interaction. With the goal of providing an appropriate quantification of the influence of rings on galaxy properties, we also constructed a suitable control sample of non-ringed galaxies with similar redshift, magnitude, morphology, and local density environment distributions to those of ringed ones. Results: We found 1868 ringed galaxies, accounting for 22% of the full sample of spiral galaxies. In addition, within galaxies with ringed structures, 46% have an inner ring, 10% an outer ring, 20% both an inner and an outer ring, 6% a nuclear ring, and 18% a partial ring. Moreover, 64% of the ringed galaxies present bars. We also found that ringed galaxies have both a lower efficiency of star formation activity and older stellar populations (as derived with the $D_n(4000)$ spectral index) with respect to non-ringed disk objects from the control sample. Galaxies with ringed structures present an excess of high metallicity values compared to non-ringed ones, which show a $12 + \rm Log (\rm O /\rm H)$ distribution toward lower values. These findings seem to indicate that rings are peculiar structures that produce an accelerating galactic evolution, strongly altering the physical properties of their host galaxies., Comment: 12 pages, 15 figures, 3 tables, accepted for publication in A&A

We use SDSS-DR14 to construct a sample of galaxy systems consisting of a central object and two satellites. We adopt projected distance and radial velocity difference criteria and impose an isolation criterion to avoid membership in larger structures. We also classify the interaction between the members of each system through a visual inspection of galaxy images, finding $\sim80\%$ of the systems lack evidence of interactions whilst the remaining $\sim20\%$ involve some kind of interaction, as inferred from their observed distorted morphology. We have considered separately, samples of satellites and central galaxies, and each of these samples were tested against suitable control sets to analyse the results. We find that central galaxies showing signs of interactions present evidence of enhanced star formation activity and younger stellar populations. As a counterpart, satellite samples show these galaxies presenting older stellar populations with a lower star formation rate than the control sample. The observed trends correlate with the stellar mass content of the galaxies and with the projected distance between the members involved in the interaction. The most massive systems are less affected since they show no star formation excess, possibly due to their more evolved stage and less gas available to form new stars. Our results suggest that it is arguable a transfer of material during interactions, with satellites acting as donors to the central galaxy. As a consequence of the interactions, satellite stellar population ages rapidly and new bursts of star formation may frequently occur in the central galaxy., Comment: 14 pages, 12 figures, accepted for publication in MNRAS

In this work we analyze a sample of close galaxy pairs (relative projected separation $<25 h^{-1}$kpc and relative radial velocities $< 350$ km s$^{-1}$) using a weak lensing analysis based on the CFHT Stripe 82 Survey. We determine halo masses for the Total sample of pairs as well as for Interacting, Red and Higher luminosity pair subsamples with $\sim 3\sigma$ confidence. The derived lensing signal for the total sample can be fitted either by a singular isothermal sphere with $\sigma_V = 223 \pm 24$ km s$^{-1}$ or a NFW profile with $R_{200} = 0.30 \pm 0.03\,h^{-1}$ Mpc. The pair total masses and total $r$ band luminosities imply an average mass-to-light ratio of $\sim 200\,h\,M_\odot/L_\odot$. On the other hand, Red pairs which include a larger fraction of elliptical galaxies, show a larger mass-to-light ratio of $\sim 345\,h\,M_\odot/L_\odot$. Derived lensing masses were compared to a proxy of the dynamical mass, obtaining a good correlation. However, there is a large discrepancy between lensing masses and the dynamical mass estimates, which could be accounted by astrophysical processes such as dynamical friction, by the inclusion of unbound pairs, and by significant deviations of the density distribution from a SIS and NFW profiles in the inner regions. We also compared lensing masses with group mass estimates obtained from the Yang et al. galaxy group catalog, finding a very good agreement with the sample of groups with 2 members. Red and Blue pairs show large differences between group and lensing masses, which is likely due to the single mass-to-light ratio adopted to compute the group masses., Comment: 10 pages, 7 figures, 2 tables, accepted for publication in A&A

Aims. With the aim of performing a suitable comparison of the internal process of galactic bars with respect to the external effect of interactions on driving gas toward the inner most region of the galaxies, we explored the efficiency of both mechanisms on central nuclear activity in active galactic nuclei (AGN) in spiral galaxies. Methods. We selected samples of barred AGN and active objects residing in pair systems, derived from the Sloan Digital Sky Survey (SDSS). In order to carry out a reliable comparison of both samples (AGNs in barred hosts in isolation and in galaxy pairs), we selected spiral AGN galaxies with similar distributions of redshift, magnitude, stellar mass, color and stellar age population from both catalogs. With the goal of providing an appropriate quantification of the influence of bars and interactions on nuclear activity, we also constructed a suitable control sample of unbarred spiral AGNs with similar host properties than the other two samples. Results. We found that barred AGNs show an excess of nuclear activity (as derived from the $Lum[OIII]$) and accretion rate ($\cal R$) with respect to AGN in pairs. In addition, both samples show an excess of high values of $Lum[OIII]$ and $\cal R$ with respect to unbarred AGNs in the control sample. We also found that the fractions of AGNs with powerful nuclear activity and high accretion rates increase toward more massive hosts with bluer colors and younger stellar populations. Moreover, AGNs with bars exhibit a higher fraction of galaxies with powerful $Lum[OIII]$ and efficient $\cal R$ with respect to AGNs inhabiting pair systems. Regarding to AGN belonging to pair systems, we found that the central nuclear activity is remarkably dependent on the galaxy pair companion features., Comment: 13 pages, 9 figures. Accepted for publication in A&A

Aims. With the aim of performing an analysis of the orientations of galaxy pair systems with respect to the underlying large-scale structure, we study the alignment between the axis connecting the pair galaxies and the host cosmic filament where the pair resides. In addition, we analyze the dependence of the amplitude of the alignment on the morphology of pair members as well as filament properties. Methods. We build a galaxy pair catalog requiring $r_p < 100\kpc$ and $\Delta V < 500 \kms $ within redshift $z<0.1$ from the Sloan Digital Sky Survey (SDSS). We divided the galaxy pair catalog taking into account the morphological classification by defining three pair categories composed by elliptical-elliptical (E-E), elliptical-spiral (E-S) and spiral-spiral (S-S) galaxies. We use a previously defined catalog of filaments obtained from SDSS and we select pairs located closer than $1\mpc$ from the filament spine, which are considered as members of filaments. For these pairs, we calculate the relative angle between the axis connecting each galaxy, and the direction defined by the spine of the parent filament. Results. We find a statistically significant alignment signal between the pair axes and the spine of the host filaments consistent with a relative excess of $ \sim$ 15\% aligned pairs. We obtain that pairs composed by elliptical galaxies exhibit a stronger alignment, showing a higher alignment signal for pairs closer than 200 $\kpc$ to the filament spine. In addition, we find that the aligned pairs are associated with luminous host filaments populated with a high fraction of elliptical galaxies. The findings of this work show that large scale structures play a fundamental role in driving galactic anisotropic accretion as induced by galaxy pairs exhibiting a preferred alignment along the filament direction., Comment: 8 pages, 6 figures. Accepted for publication in A&A

We analyse the properties of a sample of 5560 LINER galaxies selected from SDSS-DR12 at low redshift, for a complete range of local density environments. The host LINER galaxies were studied and compared with a well-defined control sample of 5553 non-LINER galaxies matched in red shift, luminosity, morphology and local density. By studying the distributions of galaxy colours and the stellar age population, we find that LINERs are redder and older than the control sample over a wide range of densities.In addition, LINERs are older than the control sample, at a given galaxy colour, indicating that some external process could have accelerated the evolution of the stellar population. The analysis of the host properties shows that the control sample exhibits a strong relation between colours, ages and the local density, while more than 90 per cent of the LINERs are redder and older than the mean values, independently of the neighbourhood density. Furthermore, a detailed study in three local density ranges shows that, while control sample galaxies are redder and older as a function of stellar mass and density, LINER galaxies mismatch the known morphology-density relation of galaxies without low-ionization features. The results support the contribution of hot and old stars to the low-ionization emission although the contribution of nuclear activity is not discarded., Comment: 9 pages, 6 figures. Accepted for publication in MNRAS

We analyse interacting galaxy pairs with evidence of tidal features in the Sloan Digital Sky Survey Data Release 7 (SDSS-DR7). The pairs were selected within $z<0.1$ by requiring a projected separation $r_p < 50 \kpc$ and relative radial velocity $\Delta V < 500 \kms$. We complete spectroscopic pairs using galaxies with photometric redshifts considering $\Delta V_{phot} < 6800 \kms$, taking into account the mean photometric redshift uncertainty. We classify by visual inspection pairs of spirals into co-rotating and counter-rotating systems. For a subsample of non-AGN galaxies, counter-rotating pairs have larger star formation rates, and a higher fraction of young, star-forming galaxies. These effects are enhanced by restricting to $r_p < 12 \kpc$. The distributions of $C$, $D_n(4000)$ and $(M_u-M_r)$ for AGN galaxies show that counter-rotating hosts have bluer colours and younger stellar population than the co-rotating galaxies although the relative fractions of Seyfert, Liner, Composite and Ambiguous AGN are similar. Also, counter-rotating hosts have more powerful AGN as revealed by enhanced $Lum[OIII]$ values. The number of co-rotating systems is approximately twice the number of counter-rotating pairs which could be owed to a more rapid evolution of counter-rotating systems, besides possible different initial conditions of these interacting pairs., Comment: 11 pages, 8 figures accepted for publication in Monthly Notices of the Royal Astronomical Society

With the aim to assess the role of dense environments in galaxy interactions, properties we present an analysis of close galaxy pairs in groups and clusters, obtained from the Sloan Digital Sky Survey Data Release 7 (SDSS-DR7). We identified pairs that reside in groups by cross-correlating the total galaxy pair catalogue with the SDSS-DR7 group catalogue from Zapata et al. (2009). We classify pair galaxies according to the intensity of interaction. We analysed the effect of high density environments on different classes of galaxy-galaxy interactions and we have also studied the impact of the group global environment on pair galaxies. We find that galaxy pairs are more concentrated towards the group centres with respect to the other group galaxy members, and disturbed pairs show a preference to contain the brightest galaxy in the groups. The color-magnitude relation exhibits significant differences between pair galaxies and the control sample, consisting in color tails with a clear excess of extremely blue and red galaxies for merging systems. In addition, pair galaxies show a significant excess of young stellar populations with respect to galaxies in the control sample; this finding suggests that, in dense environments, strong interactions produce an important effect in modifying galaxy properties. We find that the fraction of star forming galaxies decreases toward the group centre; however, galaxy pairs show a more efficient star formation activity than galaxies without a close companion. We have also found that pair galaxies prefer groups with low density global environments with respect to galaxies of the corresponding control sample. Blue, young stellar population galaxies prefer groups within low density global environments., Comment: 10 pages, 11 figures, accepted for publication in A&A

We study galaxy pair samples selected from the Sloan Digital Sky Survey (SDSS-DR7) and we perform an analysis of minor and major mergers with the aim of investigating the dependence of galaxy properties on interactions. We build a galaxy pair catalog requiring rp < 25 kpc h-1 and Delta V < 350 km s-1 within redshift z<0.1. By visual inspection of SDSS images we removed false identifications and we classify the interactions into three categories: pairs undergoing merging, M; pairs with evident tidal features, T; and non disturbed, N. We also divide the pair sample into minor and major interactions according to the luminosity ratio of the galaxy members. We study star formation activity through colors and star formation rates. We find that 10% of the pairs are classified as M. These systems show an excess of young stellar populations as inferred from the Dn(4000) spectral index, colors, and star formation rates of the member galaxies, an effect which we argue, is directly related to the ongoing merging process. We find 30% of the pairs exhibiting tidal features (T pairs) with member galaxies showing evidence of old stellar populations. Regardless of the color distribution, we find a prominent blue peak in the strongest mergers, while pairs with tidal signs under a minor merger show a strong red peak. Therefore, our results show that galaxy interactions are important in driving the evolution of galaxy bimodality. By adding stellar masses and star formation rates of the two members of the pairs, we explore the global efficiency of star formation of the pairs as a whole. We find that, at a given total stellar mass, major mergers are significantly more efficient (a factor 2) in forming new stars, with respect to both minor mergers or a control sample of non-interacting galaxies., Comment: 10 pages, 14 figures, submitted to A&A