7 research outputs found
High energy gamma-ray sources in the VVV survey - II. The AGN counterparts
© 2024 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY), https://creativecommons.org/licenses/by/4.0/We identified Active Galactic Nuclei (AGN) candidates as counterparts to unidentified gamma-ray sources (UGS) from the Fermi-LAT Fourth Source Catalogue at lower Galactic latitudes. Our methodology is based on the use of near- and mid-infrared photometric data from the VISTA Variables in the Vía Láctea (VVV) and Wide-field Infrared Survey Explorer (WISE) surveys. The AGN candidates associated with the UGS occupy very different regions from the stars and extragalactic sources in the colour space defined by the VVV and WISE infrared colours. We found 27 near-infrared AGN candidates possibly associated with 14 Fermi-LAT sources using the VVV survey. We also found 2 blazar candidates in the regions of 2 Fermi-LAT sources using WISE data. There is no match between VVV and WISE candidates. We have also examined the Ks light curves of the VVV candidates and applied the fractional variability amplitude (σrms) and the slope of variation in the Ks passband to characterise the near-infrared variability. This analysis shows that more than 85 per cent of the candidates have slopes in the Ks passband \gt;10−4 mag/day and present σrms values consistent with a moderate variability. This is in good agreement with typical results seen from type-1 AGN. The combination of YJHKs colours and Ks variability criteria was useful for AGN selection, including its use in identifying counterparts to Fermi γ-ray sources.Peer reviewe
High energy gamma-ray sources in the VVV survey -- II. The AGN counterparts
We identified Active Galactic Nuclei (AGN) candidates as counterparts to
unidentified gamma-ray sources (UGS) from the Fermi-LAT Fourth Source Catalogue
at lower Galactic latitudes. Our methodology is based on the use of near- and
mid-infrared photometric data from the VISTA Variables in the V\'ia L\'actea
(VVV) and Wide-field Infrared Survey Explorer (WISE) surveys. The AGN
candidates associated with the UGS occupy very different regions from the stars
and extragalactic sources in the colour space defined by the VVV and WISE
infrared colours. We found 27 near-infrared AGN candidates possibly associated
with 14 Fermi-LAT sources using the VVV survey. We also found 2 blazar
candidates in the regions of 2 Fermi-LAT sources using WISE data. There is no
match between VVV and WISE candidates. We have also examined the K
light curves of the VVV candidates and applied the fractional variability
amplitude () and the slope of variation in the
K passband to characterise the near-infrared variability. This
analysis shows that more than 85% of the candidates have slopes in the
K passband mag/day and present
values consistent with a moderate variability. This is
in good agreement with typical results seen from type-1 AGN. The combination of
YJHK colours and K variability criteria was useful
for AGN selection, including its use in identifying counterparts to Fermi
-ray sources.Comment: 16 pages, 19 figures, 4 tables. Accepted for publication in Monthly
Notices of the Royal Astronomical Society (MNRAS
The VVV Near-IR Galaxy Catalogue beyond the Galactic disk
Knowledge about the large-scale distribution of galaxies is far from complete
in the Zone of Avoidance, which is mostly due to high interstellar extinction
and to source confusion at lower Galactic latitudes. Past near-infrared (NIR)
surveys, such as the Two Micron All Sky Survey (2MASS), have shown the power of
probing large-scale structure at these latitudes. Our aim is to map the galaxy
distribution across the Southern Galactic plane using the VISTA Variables in
the V\'ia L\'actea Survey (VVV), which reach 2 to 4 magnitudes deeper than
2MASS. We used SExtractor + PSFEx to identify extended objects and to measure
their sizes, the light concentration index, magnitudes, and colours.
Morphological and colour constraints and visual inspection were used to confirm
galaxies. We present the resulting VVV NIR Galaxy Catalogue of 5563 visually
confirmed galaxies, of which only 45 were previously known. This is the largest
catalogue of galaxies towards the Galactic plane, with 99% of these galaxies
being new discoveries. We found that the galaxy density distribution closely
resembled the distribution of low interstellar extinction of the existing NIR
maps. We also present a description of the 185 2MASS extended sources observed
in the region, of which 16% of these objects had no previous description, which
we have now classified. We conclude that interstellar extinction and stellar
density are the main limitations for the detection of background galaxies in
the Zone of Avoidance. The VVV NIR Galaxy Catalogue is a new data set providing
information for extragalactic studies in the Galactic plane.Comment: Accepted for publication in Monthly Notices of the Royal Astronomical
Society Main Journal 21 page
Galaxy clustering in the VVV Near-IR Galaxy Catalogue
Mapping galaxies at low Galactic latitudes and determining their clustering
status are fundamental steps in defining the large-scale structure in the
nearby Universe. The VVV Near-IR Galaxy Catalogue (VVV NIRGC) allows us to
explore this region in great detail. Our goal is to identify galaxy
overdensities and characterize galaxy clustering in the Zone of Avoidance. We
use different clustering algorithms to identify galaxy overdensities: the
Voronoi tessellations, the Minimum Spanning Tree and the Ordering Points To
Identify the Clustering Structure. We studied the membership, isolation,
compactness, and flux limits to identify compact groups of galaxies. Each
method identified a variety of galaxy systems across the Galactic Plane that
are publicly available.We also explore the probability that these systems are
formed by concordant galaxies using mock catalogues. Nineteen galaxy systems
were identified in all of the four methods. They have the highest probability
to be real overdensities. We stress the need for spectroscopic follow-up
observations to confirm and characterize these new structures.Comment: 16 pages, 10 figures, 9 tables. Accepted for publication in Monthly
Notices of the Royal Astronomical Society (MNRAS
AGN candidates in the VVV near-IR galaxy catalogue
© 2023 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This is the accepted manuscript version of an article which has been published in final form at https://doi.org/10.1093/mnras/stad490The goal of this work is to search for Active Galactic Nuclei (AGN) in the Galactic disc at very low latitudes with |b|< 2°. For this, we studied the five sources from the VVV near-infrared (IR) galaxy catalogue that have also WISE counterparts and present variability in the VIrac VAriable Classification Ensemble (VIVACE) catalogue. In the near-IR colour-colour diagrams, these objects have in general redder colours compared to the rest of the sources in the field. In the mid-IR ones, they are located in the AGN region, however, there is a source that presents the highest interstellar extinction and different mid-IR colours to be a young stellar object (YSO). We also studied the source variability using two different statistical methods. The fractional variability amplitude σrms ranges from 12.6 to 33.8, being in concordance with previous results found for type-1 AGNs. The slopes of the light curves are in the range (2.6 - 4.7) × 10-4 mag d-1, also in agreement with results reported on quasars variability. The combination of all these results suggest that four galaxies are type-1 AGN candidates, whereas the fifth source likely a YSO candidate.Peer reviewe
The First Galaxy Cluster Discovered by the VISTA Variables in the Vía Láctea Survey
We report the first confirmed detection of the galaxy cluster VVV-J144321-611754 at very low latitudes (l = 315.°836, b = -1.°650) located in the tile d015 of the VISTA Variables in the Vía Láctea (VVV) survey. We defined the region of 30 ×30 arcmin 2 centered in the brightest galaxy finding 25 galaxies. For these objects, extinction-corrected median colors of (H-K s ) = 0.34 ± 0.05 mag, (J-H) = 0.57 ± 0.08 mag, and (J-K s ) = 0.87 ± 0.06 mag; R 1/2 = 1.59 ± 0.″16; C = 3.01 ± 0.08; and Sérsic index n = 4.63 ± 0.39 were estimated. They were visually confirmed showing characteristics of early-type galaxies in the near-IR images. An automatic clustering analysis performed in the whole tile found that the concentration of galaxies VVV-J144321-611754 is a real, compact concentration of early-type galaxies. Assuming a typical galaxy cluster with low X-ray luminosity, the photometric redshift of the brightest galaxy is z = 0.196 ± 0.025. Follow-up near-IR spectroscopy with FLAMINGOS-2 at the Gemini-South telescope revealed that the two brighter cluster galaxies have typical spectra of early-type galaxies and the estimated redshift for the brightest galaxy VVV-J144321.06-611753.9 is z = 0.234 ± 0.022 and that for VVV-J144319.02-611746.1 is z = 0.232 ± 0.019. Finally, these galaxies clearly follow the cluster red sequence in the rest-frame near-IR color-magnitude diagram with a slope similar to a galaxy cluster at a redshift of 0.2. These results are consistent with the presence of a bona fide galaxy cluster beyond the Milky Way disk.Fil: Baravalle, Laura Daniela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Nilo Castellón, José Luis. Universidad de La Serena; ChileFil: Alonso, Maria Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Díaz Tello, J.. Pontificia Universidad Católica de Chile; Chile. Universidad Nacional Autónoma de México; MéxicoFil: Damke, G.. Universidad de La Serena; ChileFil: Valotto, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Cuevas Larenas, H.. Universidad de La Serena; ChileFil: Sánchez, Bruno Orlando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Ríos, M. de los. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Minniti, D.. Universidad Andrés Bello; ChileFil: Domínguez, M.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Gurovich, Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Astronomía Teórica y Experimental. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba. Instituto de Astronomía Teórica y Experimental; ArgentinaFil: Barbá, R.. Universidad de La Serena; ChileFil: Soto, M.. Universidad de Atacama; ChileFil: Castro, F. Milla. Universidad de La Serena; Chil