An H i study of the collisional ring galaxy NGC 922

Elagali, Ahmed; Wong, O. I.; Oh, Se Heon; Koribalski, B. S.; Bekki, Kenji

doi:10.1093/mnras/sty741

Cited by 10 publications

(20 citation statements)

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“…This will advance our understanding of the collisional ring galaxies' number density, their evolution and whether the drop-through interaction proposed in non-cosmological isolated interaction simulations is frequent enough to explain the observed number density of ring galaxies (Lavery et al 2004;Elmegreen & Elmegreen 2006). Further, observations of collisional ring galaxies suggests that these systems contain on average high amounts of HI gas in comparison with galaxies that have the same stellar mass (Elagali et al 2018), yet are H2 deficient (Higdon et al 2015;Wong et al 2017) especially at the outer rings where the atomic hydrogen surface density is the highest (e.g., in the Cartwheel galaxy ΣHI = 19 − 65 M pc −2 ; Higdon et al 2015). The reason behind this deficiency is not yet well understood, however Wong et al (2017) and Higdon et al (2015) hypothesise that the ISM in ring galaxies behaves differently as a result of the extreme conditions in, e.g., pressure, temperature and metallicity, induced by the drop-through collision.…”

Section: Introductionmentioning

confidence: 80%

“…This agrees with the current theoretical and observational understanding of ring galaxies in the local Universe. For instance, in most of the observed ring galaxies the intruder lies within a physical distance of less than 100 kpc (Elagali et al 2018;Conn et al 2016;Fogarty et al 2011). Figure 9(a) shows a scatter plot of EAGLE galaxies in the ( u − r ) colour-stellar mass plane at z = 0 (left) and z = 0.5 (right).…”

Section: The Host Halos Of Eagle Ring Galaxiesmentioning

confidence: 99%

“…In the local Universe, galaxies are categorised into three main morphological types, i.e., spirals, spheroids, and irregular dwarf systems (Hubble 1926, the Hubble sequence). Observations of galaxies reveal that a considerable fraction (∼ 10 per cent) of galaxies in the local Universe have irregular morphological structures and do not fit within the conventional Hubble classification (Nair & Mayya et al 2005;Wong et al 2006;Romano et al 2008;Fogarty et al 2011;Parker et al 2015;Conn et al 2016;Elagali et al 2018). Depending on the collision's geometry, the target's nucleus can be displaced off its dynamical centre, the whole system (ring and nucleus) can be slightly dislocated from the previous plane of the disk (Mapelli & Mayer 2012) and in some extreme cases the nucleus can completely be disrupted by the collision, producing a centrally smoothed ring with no apparent nucleus (Madore et al 2009).…”

Section: Introductionmentioning

confidence: 99%

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Ring galaxies in the EAGLE hydrodynamical simulations

Elagali

Lagos

Wong

et al. 2018

Monthly Notices of the Royal Astronomical Society

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We study the formation and evolution of ring galaxies in the Evolution and Assembly of GaLaxies and their Environments (EAGLE) simulations. We use the largest reference model Ref-L100N1504, a cubic cosmological volume of 100 comoving megaparsecs on a side, to identify and characterise these systems through cosmic time. The number density of ring galaxies in EAGLE is in broad agreement with the observations. The vast majority of ring galaxies identified in EAGLE (83 per cent) have an interaction origin, i.e., form when one or more companion galaxies drop-through a disk galaxy. The remainder (17 per cent) have very long-lived ring morphologies (> 2 Gyr) and host strong bars. Ring galaxies are HI rich galaxies, yet display inefficient star formation activity and tend to reside in the green valley particularly at z 0.5. This inefficiency is mainly due to the low pressure and metallicity of their interstellar medium (ISM) compared with the ISM of similar star-forming galaxies. We find that the interaction(s) is responsible for decreasing the ISM pressure by causing the ISM gas to flow from the inner regions to the outer disk, where the ring feature forms. At a fixed radius, the star formation efficiency of ring galaxies is indistinguishable from their star-forming counterparts, and thus the main reason for their integrated lower efficiency is the different gas surface density profiles. Since galaxy morphologies are not used to tune the parameters in hydrodynamical simulations, the experiment performed here demonstrates the success of the current numerical models in EAGLE.

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Section: Introductionmentioning

confidence: 80%

Section: The Host Halos Of Eagle Ring Galaxiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Ring galaxies in the EAGLE hydrodynamical simulations

Elagali

Lagos

Wong

et al. 2018

Monthly Notices of the Royal Astronomical Society

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“…Enormous effort is aimed towards understanding how such interactions relate to the observed H i content in galaxies and conversely how H i distribution and kinematics uncover the physics of interaction (e.g. Bekki 2008;Pisano et al 2011;Mihos et al 2012;Elagali et al 2018;Bosma 2017, and references therein). Spiral galaxies have a lower H i fraction in high density environments, for instance, near the centers of galaxy clusters (Giovanelli & Haynes 1985;Chung et al 2009) or in HCGs (Verdes-Montenegro et al 2001), than spiral galaxies that reside in the field.…”

Section: Introductionmentioning

confidence: 99%

The neutral hydrogen properties of galaxies in gas-rich groups

Džudžar

Kilborn

Meurer

et al. 2018

Monthly Notices of the Royal Astronomical Society

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We present an analysis of the integrated neutral hydrogen (H i) properties for 27 galaxies within nine low mass, gas-rich, late-type dominated groups which we denote "Choirs". We find that majority of the central Choir galaxies have average H i content: they have a normal gas-mass fraction with respect to isolated galaxies of the same stellar mass. In contrast, we find more satellite galaxies with a lower gas-mass fraction than isolated galaxies of the same stellar mass. A likely reason for the lower gas content in these galaxies is tidal stripping. Both the specific star formation rate and the star formation efficiency of the central group galaxies are similar to galaxies in isolation. The Choir satellite galaxies have similar specific star formation rate as galaxies in isolation, therefore satellites that exhibit a higher star formation efficiency simply owe it to their lower gas-mass fractions. We find that the most H i massive galaxies have the largest H i discs and fall neatly onto the H i size-mass relation, while outliers are galaxies that are experiencing interactions. We find that high specific angular momentum could be a reason for galaxies to retain the large fraction of H i gas in their discs. This shows that for the Choir groups with no evidence of interactions, as well as those with traces of minor mergers, the internal galaxy properties dominate over the effects of residing in a group. The probed galaxy properties strengthen evidence that the Choir groups represent the early stages of group assembly.

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“…It has a recession velocity 𝑣 𝑟 = 3082.46±5.40 km/s corresponding to a distance of 42.46±2.48 Mpc (Koribalski et al 2004). It contains a higher abundance of neutral gas for a galaxy of its size, compared to typical star-forming galaxies (Elagali et al 2018a). The interaction with the dwarf companion has triggered a star-formation episode in the bulge ∼ 300 Myr ago, that continues until now.…”

Section: Introductionmentioning

confidence: 99%

Metallicity and X-ray luminosity variations in NGC 922

Kouroumpatzakis,

Zezas,

Wolter

et al. 2020

Preprint

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We present a systematic study of the metallicity variations within the collisional ring galaxy NGC 922 based on long-slit optical spectroscopic observations. We find a metallicity difference between star-forming regions in the bulge and the ring, with metallicities ranging from almost solar to significantly sub-solar ([12 + log(O/H)] ∼ 8.2). We detect He emission in the bulge and the ring star-forming regions indicating ionization from massive stars associated with recent (< 10 Myr) star-formation, in agreement with the presence of very young star-clusters in all studied regions. We find an anti-correlation between the X-ray luminosity and metallicity of the sub-galactic regions of NGC 922. The different regions have similar stellar population ages leaving metallicity as the main driver of the anti-correlation. The dependence of the X-ray emission of the different regions in NGC 922 on metallicity is in agreement with similar studies of the integrated X-ray output of galaxies and predictions from X-ray binary population models.

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An H i study of the collisional ring galaxy NGC 922

Cited by 10 publications

References 59 publications

Ring galaxies in the EAGLE hydrodynamical simulations

Ring galaxies in the EAGLE hydrodynamical simulations

The neutral hydrogen properties of galaxies in gas-rich groups

Metallicity and X-ray luminosity variations in NGC 922

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