Shutting down or powering up a (U)LIRG? Merger components in distinctly different evolutionary states in IRAS 19115−2124 (the Bird)

Vaïsänen, P.; Reunanen, J.; Kotilainen, Jari; Mattila, S.; Johansson, Peter H.; Ramphul, R.; Romero-Cañizales, C.; Kuncarayakti, H.

doi:10.1093/mnras/stx1685

Cited by 10 publications

(11 citation statements)

References 67 publications

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“…We are not sensitive to any merging populations which are in their final stages, or, as some studies have observed, multi-nucleus systems at sub-arcsecond resolutions (e.g., Smail et al 2003;Alaghband-Zadeh et al 2012;Menéndez-Delmestre et al 2013). Indeed, a recent study of a local Ultra-Luminous Infrared Galaxy (ULIRG 15 ) triple system found that if it were to be found at high redshift, it would likely be misidentified as a clumpy galaxy or a small group (Väisänen et al 2017). However, our results hold for any well resolved components at arcsecond scales, such as those found by Karim et al (2013), where the typical separation is ∼ 6 arcsec.…”

Section: Discussionmentioning

confidence: 99%

Cosmic happenstance: 24-µm selected, multicomponent Herschel sources are line-of-sight projections

Scudder

Oliver

Hurley

et al. 2018

Monthly Notices of the Royal Astronomical Society

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In this paper, we investigate the physical associations between blended far-infrared (FIR)-emitting galaxies, in order to identify the level of line-of-sight projection contamination in the single-dish Herschel data. Building on previous work, and as part of the Herschel Extragalactic Legacy Project (HELP), we identify a sample of galaxies in the COSMOS field which are found to be both FIR-bright (typically ∼ 15 mJy) and blended within the Herschel 250 µm beam. We identify a spectroscopic or photometric redshift for each FIR-bright source. We conduct a joint probability distribution analysis on the redshift probability density functions to determine the fraction of the FIR sources with multiple FIR-bright counterparts which are likely to be found at consistent (∆z< 0.01) redshifts. We find that only 3 (0.4 per cent) of the pair permutations between counterparts are > 50 per cent likely to be at consistent redshifts. A majority of counterparts (72 per cent) have no overlap in their redshift probability distributions whatsoever. This is in good agreement with the results of recent simulations, which indicate that single-dish observations of the FIR sky should be strongly contaminated by line of sight projection effects. We conclude that for our sample of 3.6-and 24-µm selected, FIR-bright objects in the COSMOS field, the overwhelming majority of multi-component FIR systems are line of sight projections within the 18.1 arcsec Herschel beam, rather than physical associations.

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Section: Discussionmentioning

confidence: 99%

Cosmic happenstance: 24-µm selected, multicomponent Herschel sources are line-of-sight projections

Scudder

Oliver

Hurley

et al. 2018

Monthly Notices of the Royal Astronomical Society

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“…1 and Fig. 1, see Väisänen et al 2008Väisänen et al , 2017. The emitting regions in LIRGs are distributed across the galaxies covering regions with sizes between 1 kpc to approximately 10-20 kpc.…”

Section: Hydrogen Recombination Linesmentioning

confidence: 96%

“…1 illustrates the power of such spatially resolved observations. The images show details of the nearby LIRG IRAS 19115-2124 with log(L IR /L ) = 11.91 (for D L = 206 Mpc), a triple merger whose components show signs of multiple stages of galaxy evolution, including the triggering and quenching of SF, and the appearance of AGN activity (Väisänen et al 2008(Väisänen et al , 2017. The authors noted that, if observed at high-z, the lack of the spatial information would have made this system look just like another clumpy starburst, potentially leading to a substantial misinterpretation of the ongoing processes therein.…”

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confidence: 99%

Star formation and nuclear activity in luminous infrared galaxies: An infrared through radio review

Perez-Torres,

Mattila,

Alonso-Herrero

et al. 2020

Preprint

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Nearby galaxies offer unique laboratories allowing multi-wavelength spatially resolved studies of the interstellar medium, star formation and nuclear activity across a broad range of physical conditions. In particular, detailed studies of individual local luminous infrared galaxies (LIRGs) are crucial for gaining a better understanding of these processes and for developing and testing models that are used to explain statistical studies of large populations of such galaxies at high redshift for which it is currently impossible to reach a sufficient physical resolution. Here, we provide an overview of the impact of spatially resolved infrared, sub-millimetre and radio observations in the study of the interstellar medium, star formation and active galactic nuclei as well as their interplay in local LIRGs. We also present an overview of the modelling of their spectral energy distributions using state-of-the-art radiative transfer codes. These contribute necessary and powerful 'workhorse' tools for the study of LIRGs (and their more luminous counterparts) at higher redshifts which are unresolved in observations. We describe how spatially-resolved time domain observations have recently opened a new window to study the nuclear activity in LIRGs. We describe in detail the observational characteristics of Arp 299 which is one of the best studied local LIRGs and exemplifies the power of the combination of high-resolution observations at infrared to radio wavelengths together with radiative transfer modelling used to explain the spectral energy distributions of its different components. We summarise the previous achievements obtained using high-spatial

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“…Based on the position on the BPT diagram, the presence of an AGN cannot be confirmed nor ruled out. Larkin et al (1998) suggested the line ratios [Fe II]/Pa β and H 2 /Br γ as a diagnostic of whether galaxies are LINERs or Seyfert type AGNs using the near-IR spectral region, and this idea was further developed in Rodríguez-Ardila et al (2004), Rodríguez-Ardila, Riffel & Pastoriza (2005), Riffel et al (2013), and Väisänen et al (2017). Riffel et al (2013) find 0.6 < [Fe II] / Pa β < 2 and 0.4 < H 2 / Brγ < 6 as determining criteria for an AGN classification based on a large sample of objects, with lower values for these ratios indicating a star-forming galaxy (SFG).…”

Section: Optical and Near-ir Spectral Analysismentioning

confidence: 99%

AT 2017gbl: a dust obscured TDE candidate in a luminous infrared galaxy

Kool

Reynolds

Mattila

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We present the discovery with Keck of the extremely infrared (IR) luminous transient AT 2017gbl, coincident with the Northern nucleus of the luminous infrared galaxy (LIRG) IRAS 23436+5257. Our extensive multi-wavelength follow-up spans ∼900 days, including photometry and spectroscopy in the optical and IR, and (very long baseline interferometry) radio and X-ray observations. Radiative transfer modelling of the host galaxy spectral energy distribution and long-term pre-outburst variability in the mid-IR indicate the presence of a hitherto undetected dust obscured active galactic nucleus (AGN). The optical and near-IR spectra show broad ∼2000 km s−1 hydrogen, He i and O i emission features that decrease in flux over time. Radio imaging shows a fast evolving compact source of synchrotron emission spatially coincident with AT 2017gbl. We infer a lower limit for the radiated energy of 7.3 × 1050 erg from the IR photometry. An extremely energetic supernova would satisfy this budget, but is ruled out by the radio counterpart evolution. Instead, we propose AT 2017gbl is related to an accretion event by the central supermassive black hole, where the spectral signatures originate in the AGN broad line region and the IR photometry is consistent with re-radiation by polar dust. Given the fast evolution of AT 2017gbl, we deem a tidal disruption event (TDE) of a star a more plausible scenario than a dramatic change in the AGN accretion rate. This makes AT 2017gbl the third TDE candidate to be hosted by a LIRG, in contrast to the so far considered TDE population discovered at optical wavelengths and hosted preferably by post-starburst galaxies.

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Shutting down or powering up a (U)LIRG? Merger components in distinctly different evolutionary states in IRAS 19115−2124 (the Bird)

Cited by 10 publications

References 67 publications

Cosmic happenstance: 24-µm selected, multicomponent Herschel sources are line-of-sight projections

Cosmic happenstance: 24-µm selected, multicomponent Herschel sources are line-of-sight projections

Star formation and nuclear activity in luminous infrared galaxies: An infrared through radio review

AT 2017gbl: a dust obscured TDE candidate in a luminous infrared galaxy

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