A deep near-infrared view of the Ophiuchus galaxy cluster

Galdeano, D.; Coldwell, Georgina; Duplancic, Fernanda; Alonso, Santiago; Pereyra, Luis; Minniti, D.; Bacigalupo, R. Zelada; Valotto, C.; Baravalle, L. D.; Alonso, M. V.; Castellón, J. L. Nilo

doi:10.1051/0004-6361/202243370

Cited by 6 publications

(1 citation statement)

References 37 publications

(40 reference statements)

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“…Using this procedure, Baravalle et al (2021) generated the VVV near-IR galaxy catalogue (VVV NIRGC) that covers the regions of the Sourthern Galactic disc. Also, Coldwell et al (2014); Baravalle et al (2019) and Galdeano et al (2021Galdeano et al ( , 2022Galdeano et al ( , 2023 used similar procedure to study the near-infrared properties of galaxies in galaxy clusters. These works were particularly focused on the galaxy detections.…”

Section: Introductionmentioning

confidence: 99%

AGN candidates in the VVV near-IR galaxy catalogue

Baravalle¹,

Schmidt²,

Alonso³

et al. 2023

Preprint

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The 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 galaxy catalogue that have also WISE counterparts and present variability in the VIrac VAriable Classification Ensemble (VIVACE) catalogue. In the near-infrared colour-colour diagrams, these objects have in general redder colours compared to the rest of the sources in the field. In the mid-infrared 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 𝜎 𝑟 𝑚𝑠 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/day, 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.

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Section: Introductionmentioning

confidence: 99%

AGN candidates in the VVV near-IR galaxy catalogue

Baravalle¹,

Schmidt²,

Alonso³

et al. 2023

Preprint

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Unveiling a new extragalactic structure hidden by the Milky Way

Galdeano

Ferrero

Coldwell

et al. 2022

A&A

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Context. The zone of avoidance (ZoA) does not allow for clear optical observations of extragalactic sources behind the Milky Way due to the meaningful extinction of the optical emission of these objects. Observations in near-infrared (NIR) wavelengths represent a potential source of astronomical discoveries that support the detection of new galaxies and potentially complete the picture of the large-scale structures in this as-yet poorly explored area of the sky. Aims. Our aim is to decipher the nature of the overdensity located behind the Milky Way in tile b204 of the VISTA Variables in Vía Láctea (VVV) survey. Methods. We studied an area of six arcmin around a galaxy concentration located at l = 354.82 • and b = −9.81 • . We selected five galaxies, taking into account the source distribution on the sky to optimise the requested time for the observations, and we obtained the spectra with Flamingos 2 long-slit spectrograph at Gemini South 8.1-meter telescope. To identify and characterise the absorption features, we fit the galaxies underlying spectrum using the starlight code together with the IRTF stellar library. In addition, the spectroscopic findings are reinforced using complementary photometric techniques such as red-sequence and photometric redshift estimation.Results. The mean spectroscopic redshift estimated from the NIR spectra is z = 0.225 ± 0.014. This value presents a good agreement with that obtained from photometric analysis, photoz = 0.21 ± 0.08, and the probability distribution function of the galaxies in the studied region. Also, the red-sequence slope is consistent with the one expected for NIR observations of galaxy clusters. Conclusions. The redshifts obtained from both, photometric and spectroscopic techniques are in good agreement, allowing for the confirmation of the nature of this structure at z = 0.225 ± 0.014, thereby unveiling a new galaxy cluster, VVVGCl-B J181435-381432, behind the Milky Way bulge.

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Enlightening the Universe behind the Milky Way bulge

Duplancic,

Alonso,

Coldwell

et al. 2024

A&A

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The location of the Solar System complicates the detection extragalactic sources beyond the Milky Way 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 in order to discover new background galaxies and complete the census in the ZOA. The goal of this work is to identify galaxies behind the Milky Way bulge using near-infrared (NIR) data from the VISTA Variables in Vía Láctea (VVV) survey. 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 the VSA vvvSource table combined with restrictions on star--galaxy separation parameters obtained from Source Extractor is a successful strategy for achieving acceptable levels of contamination (60<!PCT!>) and high completeness (75<!PCT!>) in the construction of a galaxy target sample. To remove contaminating Galactic sources from the initial target sample, our methodology also incorporates a visual inspection of false-colour RGB images, a crucial quality control carried out following a specifically defined procedure. 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 fresh picture of the Universe hidden behind the curtain of stars, dust, and gas in the unexplored Milky Way bulge region. 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 Milky Way, expanding our knowledge of the Universe in this challenging and impressive region of the sky.

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A deep near-infrared view of the Ophiuchus galaxy cluster

Cited by 6 publications

References 37 publications

AGN candidates in the VVV near-IR galaxy catalogue

AGN candidates in the VVV near-IR galaxy catalogue

Unveiling a new extragalactic structure hidden by the Milky Way

Enlightening the Universe behind the Milky Way bulge

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