Two interacting galaxies hiding as one, revealed by MaNGA

Ciraulo, Barbara Mazzilli; Melchior, A. L.; Maschmann, Daniel; Katkov, Ivan; Halle, Anaelle; Combes, F.; Gelfand, Joseph D.; Yazeedi, Aisha Al

doi:10.1051/0004-6361/202141319

Cited by 8 publications

(5 citation statements)

References 66 publications

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“…Considering the excess of S0 and Sa galaxies and the central star formation enhancement found in star-forming DP galaxies (M20), a minor merger can explain the observed characteristics of DP emission-line galaxies. During a close encounter in a minor merger, one can observe a DP signature which is similar to the case discussed in Mazzilli Ciraulo et al (2021). However, this is not necessarily the final stage of the merger but a superposition of two galaxies aligned with the line of sight.…”

Section: Strong Double-peak Features In Disc Galaxies: Bars or Minor ...mentioning

confidence: 54%

“…In order to distinguish between the different mechanisms, discussed here, additional A46, page 18 of 22 information about a spatial distribution of the kinematic signatures is needed. As shown in Mazzilli Ciraulo et al (2021), relying on integrated field spectroscopy with the Mapping Nearby Galaxies at APO (MaNGA, Bundy et al 2015) survey, one can spatially disentangle two different gas components. In this very case, the central DP signature found in the central 3 SDSS spectrum, originates from two superposed discs.…”

Section: Resolving Double-peak Emission Lines and The Importance Of F...mentioning

confidence: 99%

“…On the other hand, a merger scenario becomes increasingly likely if one finds different characteristics in the two emission-line components (Maschmann & Melchior 2019). Using integrated field spectroscopy, Mazzilli Ciraulo et al (2021) detected two galaxies aligned inside the line of sight, creating a DP emission line. In a recent study, the molecular gas content of DP galaxies selected from above the main star-forming sequence was studied in Maschmann et al (2022).…”

Section: Introductionmentioning

confidence: 99%

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The origin of double-peak emission-line galaxies: Rotating discs, bars, or galaxy mergers?

Maschmann

Halle

Melchior

et al. 2023

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Emission lines with a double-peak (DP) shape, detected in the centre of galaxies, have been extensively used in the past to identify peculiar kinematics such as dual active galactic nuclei (AGNs), outflows, or mergers. With a more general approach considering a large DP galaxy sample selected from the Sloan Digital Sky Survey (SDSS), a connection to minor merger galaxies with ongoing star formation was suggested. To gain a better understanding of different mechanisms creating a DP signature, in this paper, we explore synthetic SDSS spectroscopic observations computed from disc models and simulations. We show how a DP signature is connected to the central part of the rotation curve of galaxies, which is mostly shaped by the stellar bulge. We, furthermore, find that bars can create strong DP emission-line signatures when viewed along their major axis. Major mergers can form a central rotating disc in late post-coalescence merger stages (1 Gyr after the final coalescence), which creates a DP signature. Minor mergers tend to show a DP feature with no correlation to the galaxy inclination within 350 Myr after the final coalescence. Comparisons of these scenarii with observations disfavour major mergers, since they show predominantly elliptical and only a few S0 morphologies. Furthermore, at such a late merger stage, the enhanced star formation is most likely faded. Bars and minor mergers, on the other hand, can be compared quite well with the observations. Both observations coincide with increased star formation found in observations, and minor mergers in particular do not show any dependency with the observation direction. However, observations resolving the galaxy kinematics spatially are needed to distinguish between the discussed possibilities. More insight into the origin of DP will be gained by a broader comparison with cosmological simulations. The understanding of the DP origin can provide important tools to study the mass growth of galaxies in future high redshift surveys.

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Section: Strong Double-peak Features In Disc Galaxies: Bars or Minor ...mentioning

confidence: 54%

Section: Resolving Double-peak Emission Lines and The Importance Of F...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The origin of double-peak emission-line galaxies: Rotating discs, bars, or galaxy mergers?

Maschmann

Halle

Melchior

et al. 2023

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“…DP signatures were found to be related to merging processes in Comerford et al (2018) and Maschmann & Melchior (2019). In a recent study, Mazzilli Ciraulo et al (2021) succeeded in resolving two independent kinematic components using integrated field spectroscopy of a DP emission-line galaxy and identified two galaxies in the process of merging, superimposed in a projection along the line of sight.…”

Section: Introductionmentioning

confidence: 99%

“…While this configuration could result from repetitive minor mergers, as discussed by Bournaud et al (2007), it could also correspond to a rotating inner structure. However, as discussed in detail in Mazzilli Ciraulo et al (2021), integrated field spectroscopy is needed to identify two individual gas components and conclusively identify galaxy mergers. In this work, we studied statistical properties of a sub-sample of 52 galaxies with SDSS spectra.…”

Section: Introductionmentioning

confidence: 99%

Central star formation in double-peak, gas-rich radio galaxies

Maschmann

Melchior

Combes

et al. 2022

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The respective contributions of gas accretion, galaxy interactions, and mergers to the mass assembly of galaxies, as well as the evolution of their molecular gas and star-formation activity are still not fully understood. In a recent work, a large sample of double-peak (DP) emission-line galaxies have been identified from the SDSS. While the two peaks could represent two kinematic components, they may be linked to the large bulges that their host galaxies tend to have. Star-forming DP galaxies display a central star-formation enhancement and have been discussed as compatible with a sequence of recent minor mergers. In order to probe merger-induced star-formation mechanisms, we conducted observations of the molecular-gas content of 35 star-forming DP galaxies in the upper part of the main sequence (MS) of star formation (SF) with the IRAM 30 m telescope. Including similar galaxies 0.3 dex above the MS and with existing molecular-gas observations from the literature, we finally obtained a sample of 52 such galaxies. We succeeded in fitting the same kinematic parameters to the optical ionised- and molecular-gas emission lines for ten (19%) galaxies. We find a central star-formation enhancement resulting most likely from a galaxy merger or galaxy interaction, which is indicated by an excess of gas extinction found in the centre. This SF is traced by radio continuum emissions at 150 MHz, 1.4 GHz, and 3 GHz, all three of which are linearly correlated in log with the CO luminosity with the same slope. The 52 DP galaxies are found to have a significantly larger amount of molecular gas and longer depletion times, and hence a lower star-formation efficiency, than the expected values at their distance of the MS. The large bulges in these galaxies might be stabilising the gas, hence reducing the SF efficiency. This is consistent with a scenario of minor mergers increasing the mass of bulges and driving gas to the centre. We also excluded the inwards-directed gas migration and central star-formation enhancement as the origin of a bar morphology. Hence, these 52 DP galaxies could be the result of recent minor mergers that funnelled molecular gas towards their centre, triggering SF, but with moderate efficiency.

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