1. |
- Guglielmo, V., et al.
(author)
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The XXL Survey: XXII. the XXL-North spectrophotometric sample and galaxy stellar mass function in X-ray detected groups and clusters
- 2018
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 620
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Journal article (peer-reviewed)abstract
- Context. The fraction of galaxies bound in groups in the nearby Universe is high (50% at z ∼ 0). Systematic studies of galaxy properties in groups are important in order to improve our understanding of the evolution of galaxies and of the physical phenomena occurring within this environment. Aims. We have built a complete spectrophotometric sample of galaxies within X-ray detected, optically spectroscopically confirmed groups and clusters (G&C), covering a wide range of halo masses at z ≤ 0.6. Methods. In the context of the XXL survey, we analyse a sample of 164 G&C in the XXL-North region (XXL-N), at z ≤ 0.6, with a wide range of virial masses (1.24 × 1013 ≤ M500,scal(Mo) ≤ 6.63 × 1014) and X-ray luminosities ((2.27 × 1041 ≤ L500,scalXXL(erg-s-1) ≤ 2.15 × 1044)). The G&C are X-ray selected and spectroscopically confirmed. We describe the membership assignment and the spectroscopic completeness analysis, and compute stellar masses. As a first scientific exploitation of the sample, we study the dependence of the galaxy stellar mass function (GSMF) on global environment. Results. We present a spectrophotometric characterisation of the G&C and their galaxies. The final sample contains 132 G&C, 22 111 field galaxies and 2225 G&C galaxies with r-band magnitude <20. Of the G&C, 95% have at least three spectroscopic members, and 70% at least ten. The shape of the GSMF seems not to depend on environment (field versus G&C) or X-ray luminosity (used as a proxy for the virial mass of the system). These results are confirmed by the study of the correlation between mean stellar mass of G&C members and L500,scalXXL. We release the spectrophotometric catalogue of galaxies with all the quantities computed in this work. Conclusions. As a first homogeneous census of galaxies within X-ray spectroscopically confirmed G&C at these redshifts, this sample will allow environmental studies of the evolution of galaxy properties.
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2. |
- Guglielmo, V., et al.
(author)
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The XXL Survey: XXX. Characterisation of the XLSSsC N01 supercluster and analysis of the galaxy stellar populations
- 2018
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In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 620
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Journal article (peer-reviewed)abstract
- Context. Superclusters form from the largest enhancements in the primordial density perturbation field and extend for tens of Mpc, tracing the large-scale structure of the Universe. X-ray detections and systematic characterisations of superclusters and the properties of their galaxies have only been possible in the last few years. Aims. We characterise XLSSsC N01, a rich supercluster at z ∼ 0.3 detected in the XXL Survey, composed of X-ray clusters of different virial masses and X-ray luminosities. As one of the first studies on this topic, we investigate the stellar populations of galaxies in different environments in the supercluster region. Methods. We study a magnitude-limited (r ≤ 20) and a mass-limited sample (log(M ∗ Mo) ≥ 10.8) of galaxies in the virialised region and in the outskirts of 11 XLSSsC N01 clusters, in high-density field regions, and in the low-density field. We compute the stellar population properties of galaxies using spectral energy distribution (SED) and spectral fitting techniques, and study the dependence of star formation rates (SFR), colours, and stellar ages on environment. Results. For r ≤ 20, the fraction of star-forming/blue galaxies, computed either from the specific-SFR (sSFR) or rest-frame colour, shows depletion within the cluster virial radii, where the number of galaxies with log (sSFR/ yr-1) > -12 and with (g - r) restframe < 0.6 is lower than in the field. For log(M ∗ Mo) ≥ 10.8, no trends with environment emerge, as massive galaxies are mostly already passive in all environments. No differences among low- and high-density field members and cluster members emerge in the sSFR-mass relation in the mass-complete regime. Finally, the luminosity-weighted age-mass relation of the passive populations within cluster virial radii show signatures of recent environmental quenching. Conclusions. The study of luminous and massive galaxies in this supercluster shows that while environment has a prominent role in determining the fractions of star-forming/blue galaxies, its effects on the star formation activity in star-forming galaxies are negligible.
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3. |
- Salinas Froemel, Vicente Horacio, 1996, et al.
(author)
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Constraining the duration of ram pressure stripping features in the optical from the direction of jellyfish galaxy tails
- 2024
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In: Monthly Notices of the Royal Astronomical Society. - 0035-8711 .- 1365-2966. ; 533:1, s. 341-359
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Journal article (peer-reviewed)abstract
- Ram pressure stripping is perhaps the most efficient mechanism for removing gas and quenching galaxies in dense environments, as they move through the intergalactic medium. Extreme examples of on-going ram pressure stripping are known as jellyfish galaxies, characterized by a tail of stripped material that can be directly observed in multiple wavelengths. Using the largest homogeneous broad-band optical jellyfish candidate sample in local clusters known to date, we measure the angle between the direction of the tails visible in the galaxies, and the direction towards the host cluster centre. We find that 33 per cent of the galaxy tails point away from the cluster centre, 18 per cent point towards the cluster centre, and 49 per cent point elsewhere. Moreover, we find stronger signatures of ram pressure stripping happening on galaxies with a tail pointing away and towards the cluster centre, and larger velocity dispersion profiles for galaxies with tails pointing away. These results are consistent with a scenario where ram pressure stripping has a stronger effect for galaxies following radial orbits on first infall. The results also suggest that in many cases, radially infalling galaxies are able to retain their tails after pericenter and continue to experience significant on-going ram pressure stripping. We further constrain the lifespan of the optical tails from the moment they first appear to the moment they disappear, by comparing the observed tail directions with matched N-body simulations through Bayesian parameter estimation. We obtain that galaxy tails appear for the first time at ∼ 1.16R200 and disappear ∼ 660 Myr after pericenter.
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