173 research outputs found
Seyfert-1 galaxies in WINGS and Omega-WINGS
No full textType-1 nuclear activity is rare in low-redshift clusters of galaxies. An analysis of the WIde field Nearby Galaxy Cluster Survey (WINGS) and of its extension Omega-WINGS revealed only three Seyfert 1 galaxies that are cluster members. We present a focused analysis of their emission line properties according to the interpretation scheme known as the Eigenvector 1/main sequence of quasars. Nuclear activity of the cluster members appears to be modest in the context of low -z type-1 AGN; however, one of the three Seyfert galaxies (WINGS J201158.35-570512.1) is a candidate super-Eddington source. Some general implications on non-thermal activity in clusters are suggested by the low prevalence of Seyfert 1s in the survey, and by the prevalence ratio between type-2 and type-1 AGN, apparently much higher in the cluster environment than in the field. (c) 2023 COSPAR. Published by Elsevier B.V. All rights reserved
AMICO galaxy clusters in KiDS-DR3: sample properties and selection function
No full textWe present the first catalogue of galaxy cluster candidates derived from the third data release of the Kilo-Degree Survey. The sample of clusters has been produced using the Adaptive Matched Identifier of Clustered Objects (AMICO) algorithm. In this analysis, AMICO considers the luminosity, spatial distribution, and photo-z of galaxies, without performing any selection based on their colours. In this way, we minimize the dependence of the selection function on the detectability or even absence of the red sequence in the clusters. The catalogue comprises 7988 candidate galaxy clusters in the redshift range 0.1 < z < 0.8 down to signal-to-noise ratio > 3.5 with a purity approaching 95 per cent over the entire redshift range. In addition to the catalogue of galaxy clusters, we also provide a catalogue of galaxies with their probabilistic association to the detected clusters. We quantify the sample purity, completeness, and the uncertainties of the detections properties, such as richness, redshift, and position, by means of mock galaxy catalogues. The simulations are derived directly from the data to fully reproduce their statistical properties including photo-z uncertainties, unknown absorption across the survey, missing data, spatial correlation of galaxies, and galaxy clusters. Being based on real data, such mock catalogues do not have to rely on the assumptions on which numerical simulations and semi-analytic models are based on. This paper is the first of a series of papers in which we discuss the details and physical properties of the sample presented in this work
Gas-phase Metallicity of Local Active Galactic Nuclei in the GASP and MaNGA Surveys: The Role of Ram Pressure Stripping
No full textGrowing evidence in support of a connection between active galactic nuclei (AGN) activity and the ram pressure stripping (RPS) phenomenon has been found both observationally and theoretically in the past decades. In this work, we further explore the impact of RPS on the AGN activity by estimating the gas-phase metallicity of nuclear regions and the mass–metallicity relation of galaxies at z ≤ 0.07 and with stellar masses , either experiencing RPS or not. To measure oxygen abundances, we exploit Integral Field Spectroscopy data from the GASP and MaNGA surveys, photoionization models generated with the code Cloudy and the code Nebulabayes to compare models and observations. In particular, we build Cloudy models to reproduce line ratios induced by photoionization from stars, AGN, or a contribution of both. We find that the distributions of metallicity and [O iii ] λ 5007 luminosity of galaxies undergoing RPS are similar to the ones of undisturbed galaxies. Independently of the RPS, we do not find a correlation between stellar mass and AGN metallicity in the mass range , while for the star-forming galaxies we observe the well-known mass–metallicity relation between with a scatter mainly driven by the star formation rate and a plateau around . The gas-phase metallicity in the nuclei of AGN hosts is enhanced with respect to those of star-forming galaxies by a factor of ∼ 0.05 dex regardless of the RPS
AMICO galaxy clusters in KiDS-DR3: The impact of estimator statistics on the luminosity-mass scaling relation
No full textContext. As modern-day precision cosmology aims for statistical uncertainties of the percent level or lower, it becomes increasingly important to reconsider estimator assumptions at each step of the process, along with their consequences on the statistical variability of the scientific results.
Aims. We compare L1 regression statistics to the weighted mean, the canonical L2 method based on Gaussian assumptions, to infer the weak gravitational shear signal from a catalog of background ellipticity measurements around a sample of clusters, which has been a standard step in the processes of many recent analyses.
Methods. We use the shape measurements of background sources around 6925 AMICO clusters detected in the KiDS third data release. We investigate the robustness of our results and the dependence of uncertainties on the signal-to-noise ratios of the background source detections. Using a halo model approach, we derive lensing masses from the estimated excess surface density profiles.
Results. The highly significant shear signal allows us to study the scaling relation between the r-band cluster luminosity, L200, and the derived lensing mass, M200. We show the results of the scaling relations derived in 13 bins in L200, with a tightly constrained power-law slope of ∼1.24 ± 0.08. We observe a small, but significant, relative bias of a few percent in the recovered excess surface density profiles between the two regression methods, which translates to a 1σ difference in M200. The efficiency of L1 is at least that of the weighted mean and increases with higher signal-to-noise shape measurements.
Concluions. Our results indicate the relevance of optimizing the estimator for inferring the gravitational shear from a distribution of background ellipticities. The interpretation of measured relative biases can be gauged by deeper observations, and the increased computation times remain feasible
Probing Galaxy Cluster through Weak Lensing using Hyper Suprime-Cam Imaging Survey
No full textreservedThis thesis work focuses on the methodology followed to estimate the masses of clusters through the study of the effects of weak gravitational lensing, detected by the Hyper Suprime-Cam survey. We compared the results for four clusters of different redshifts and the observed differences in the radial profile of each, using two different source selection methods: Color-Color cuts and P(z) cuts.
We used data collected from the first year release (DR1) and its correspond- ing shape catalog (released for the wide-layer S16A data) for the purpose of estimating the tangential shear profile of the clusters. The clusters studied in this work are HSCJ021528-044041 at redshift 0.3323, HSCJ021322-060445 at redshift 0.6841, HSCJ021056-061154 at redshift 0.4340 and HSCJ020525-054356 at redshift 0.2896.
We created a comprehensive compilation of the current methods used in lit- erature using data extracted from the data released by the Hyper-Suprime Cam survey, in particular in terms of galaxy selection within clusters, the selection of source galaxies and mass modeling according to Umetsu et al. [2020]
For this work, we use the CLMM library to estimate the shear components of the ellipticity components available in the shape catalog, for both simulated data (generated galaxy clusters altering redshifts and masses) and real data (DR1 HSC) and compare results based on the redshift differences. We find that the higher the redshift the cluster is at, the lower the accuracy in the results for the mass obtained due to the difficulty in observing and scarcity of the source galaxies.
We also conclude with the comparison of the two source selection methods that the Color-Color cut method rigorously rejects cluster and foreground galaxies but may reduce usable background galaxies, and the P(z) cuts method probabilistically selects background galaxies, potentially leading to larger sample sizes but higher contamination levels. Comparisons with literature show that mass estimates closer to reported values are achieved using the Color-Color cut method over the P(z) cut method
AMICO galaxy clusters in KiDS-DR3: weak lensing mass calibration
No full textWe present the mass calibration for galaxy clusters detected with the AMICO code in KiDS DR3 data. The cluster sample comprises 7000 objects and covers the redshift range 0.1 < z < 0.6. We perform a weak lensing stacked analysis by binning the clusters according to redshift and two different mass proxies provided by AMICO, namely the amplitude A (measure of galaxy abundance through an optimal filter) and the richness λ∗ (sum of membership probabilities in a consistent radial and magnitude range across redshift). For each bin, we model the data as a truncated NFW profile plus a two-halo term, taking into account uncertainties related to concentration and miscentring. From the retrieved estimates of the mean halo masses, we construct the A–M200 and the λ∗–M200 relations. The relations extend over more than 1 order of magnitude in mass, down to M200 ∼ 2 (5) × 1013 M⊙ h−1 at z = 0.2 (0.5), with small evolution in redshift. The logarithmic slope is 2.0 for the A–mass relation, and 1.7 for the λ∗–mass relation, consistent with previous estimations on mock catalogues and coherent with the different nature of the two observables
Galaxy morphoto-Z with neural Networks (GaZNets). I. Optimized accuracy and outlier fraction from Imaging and Photometry
No full textIn the era of large sky surveys, photometric redshifts (photo-z) represent
crucial information for galaxy evolution and cosmology studies. In this work,
we propose a new Machine Learning (ML) tool called Galaxy morphoto-Z with
neural Networks (GaZNet-1), which uses both images and multi-band photometry
measurements to predict galaxy redshifts, with accuracy, precision and outlier
fraction superior to standard methods based on photometry only. As a first
application of this tool, we estimate photo-z of a sample of galaxies in the
Kilo-Degree Survey (KiDS). GaZNet-1 is trained and tested on
galaxies collected from KiDS Data Release 4 (DR4), for which spectroscopic
redshifts are available from different surveys. This sample is dominated by
bright (MAGAUTO) and low redshift () systems, however, we
could use 6500 galaxies in the range to effectively extend
the training to higher redshift. The inputs are the r-band galaxy images plus
the 9-band magnitudes and colours, from the combined catalogs of optical
photometry from KiDS and near-infrared photometry from the VISTA Kilo-degree
Infrared survey. By combining the images and catalogs, GaZNet-1 can achieve
extremely high precision in normalized median absolute deviation (NMAD=0.014
for lower redshift and NMAD=0.041 for higher redshift galaxies) and low
fraction of outliers (\% for lower and \% for higher redshift
galaxies). Compared to ML codes using only photometry as input, GaZNet-1 also
shows a % improvement in precision at different redshifts and a
45% reduction in the fraction of outliers. We finally discuss that, by
correctly separating galaxies from stars and active galactic nuclei, the
overall photo-z outlier fraction of galaxies can be cut down to \%.Comment: Accepted for publication in A&
Exploring the AGN-ram pressure stripping connection in local clusters
No full textRam-pressure stripping by the intracluster medium (ICM) is one of the most
advocated mechanisms that affect the properties of cluster galaxies. A recent
study based on a small sample has found that many galaxies showing strong
signatures of ram-pressure stripping also possess an active galactic nucleus
(AGN), suggesting a possible correlation between the two phenomena. This result
has not been confirmed by a subsequent study. Building upon previous findings,
here we combine MUSE observations conducted within the GASP program and a
general survey of the literature to robustly measure the AGN fraction in
cluster's ram pressure stripped galaxies using BPT emission line diagrams.
Considering a sample of 115 ram pressure stripped galaxies with stellar masses
, we find an AGN fraction of . This fraction
strongly depends on stellar mass: it raises to 51% when only ram-pressure
stripped galaxies of masses are considered. We
then investigate whether the AGN incidence is in excess in ram pressure
stripped galaxies compared to non-stripped galaxies, using as comparison a
sample of non-cluster galaxies observed by the survey MaNGA. Considering
mass-matched samples, we find that the incidence of AGN activity is
significantly higher (at a confidence level ) when ram-pressure
stripping is on act, supporting the hypothesis of an AGN-ram pressure
connection
LINGUOCULTURAL ANALYSIS OF TOPONYMS AND DEMONYMS IN BOLIVIAN SPANISH
No full textThe present article analyses the complex system of toponyms and demonyms in Bolivian Spanish. The author describes etymology of toponyms from the department of Potosí by providing the explanation of their morphological structure and connections with local indigenous languages, such as quechua and aymara. Furthermore, special attention is paid to the formation of demonyms via suffixation, as the author offers the table with the analyzed examples and singles out the most expanded suffixes, as well as those that are rarely used. The results have shown that the suffix “-eño” has the leading position, therefore it can be considered the most productive one in Bolivia. The article also analyzes Bolivian toponymic nicknames
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