The Ultraviolet Upturn in Elliptical Galaxies and Environmental Effects

Yi, Sukyoung K.; Lee, Jihye; Sheen, Yun Kyeong; Jeong, Hyunjin; Suh, Hyewon; Oh, Kyuseok

doi:10.1088/0067-0049/195/2/22

Cited by 74 publications

(148 citation statements)

References 44 publications

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“…Whatever the physical mechanism that led to such UV-enhanced HB morphology, its better knowledge in the M 31 GC environment could certainly add important clues to a better understanding of the early evolution of the whole cluster system around our nearby galaxy companion, in spite of all the observing problems associated with its large distance. Furthermore, on a larger galactic mass scale, this scenario could also shed light to the well recognized UV-upturn phenomenon, that in most cases seems to constrain the evolution of elliptical galaxies (Yi et al 2011;Buzzoni & Gonzalez-Lopezlira 2008;Buzzoni et al 2012).…”

Section: Summary and Discussionmentioning

confidence: 90%

The horizontal branch morphology of M 31 globular clusters

Bellazzini

Buzzoni

Cacciari

et al. 2012

A&A

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We use deep, high quality color magnitude diagrams obtained with the Hubble Space Telescope to compute a simplified version of the Mironov index (SMI; B B+R ) to parametrize the horizontal branch (HB) morphology for 23 globular clusters in the M 31 galaxy (Sample A), all located in the outer halo at projected distances between 10 kpc and 100 kpc. This allows us to compare them with their Galactic counterparts, for which we estimated the SMI exactly in the same way, in the SMI vs. [Fe/H] plane. We find that the majority of the considered M 31 clusters lie in a significantly different locus, in this plane, with respect to Galactic clusters lying at any distance from the center of the Milky Way. In particular they have redder HB morphologies at a given metallicity, or, in other words, clusters with the same SMI value are ≈0.4 dex more metal rich in the Milky Way than in M 31. We discuss the possible origin of this difference and we conclude that the most likely explanation is that many globular clusters in the outer halo of M 31 formed ≈1-2 Gyr later than their counterparts in the outer halo of the Milky Way, while differences in the cluster-to-cluster distribution of He abundance of individual stars may also play a role. The analysis of another sample of 25 bright M 31 clusters (eighteen of them with M V ≤ −9.0, Sample B), whose SMI estimates are much more uncertain as they are computed on shallow color magnitude diagrams, suggests that extended blue HB tails can be relatively frequent among the most massive M 31 globular clusters, possibly hinting at the presence of multiple populations.

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Section: Summary and Discussionmentioning

confidence: 90%

The horizontal branch morphology of M 31 globular clusters

Bellazzini

Buzzoni

Cacciari

et al. 2012

A&A

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“…Figure A.2, left panel, highlights that its galaxy population is dominated by star-forming galaxies and its ETGs are not passively evolving. Yi et al (2011) established a colour criterion to classify ETGs according to their UV spectral morphology based on three color conditions. Passively evolving ETGs would have NUV−r > 5.4, and FUV−r > 6.6.…”

Section: Discussionmentioning

confidence: 99%

“…Solid lines (left) correspond to the conditions FUV−NUV <0.9, i.e UV rising slope, and NUV−r > 5.4 shows the region of young massive star-free galaxies. These conditions, following the UV classification scheme by Yi et al (2011), separate passive evolving ETGs (region c) from star forming galaxies (region a), see text. In both panels magnitudes were corrected by galactic extinction following Burstein & Heiles (1982).…”

Section: Discussionmentioning

confidence: 99%

Galaxy evolution in groups

Mazzei

Marino

Rampazzo

et al. 2018

A&A

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Context. Local Group Analogs are galaxy associations dominated by few bright Spirals reminiscent of the Local Group. The NGC 3447/NGC 3447A system is a member of the LGG 225 group, a nearby Local Group Analog. This system is considered a physical pair composed of an intermediate luminosity late type spiral, NGC 3447 itself, and an irregular companion, NGC 3447A, linked by a faint, short filament of matter. A ring-like structure in the NGC 3447 outskirts has been emphasised by GALEX observations. Aims. This work aims to contribute to the study of galaxy evolution in low density environments, favourable habitat to highly effective encounters, shedding light on the evolution of this system. Methods. We performed a multi-λ analysis of the surface photometry of this system to derive its spectral energy distribution and structural properties using UV, Swift-UVOT, and optical, SDSS images complemented with available far-IR observations. We also characterised the velocity field of the pair using 2D Hα kinematical observations of the system obtained with PUMA@2.2mSPM. All these data are used to constrain smooth particle hydrodynamic simulations with chemo-photometric implementation to shed light on the evolution of this system. Results. The luminosity profiles, from UV to optical wavelengths, are all consistent with the presence of a disc extending and including NGC 3447A. The overall velocity field does not emphasise any significant rotation pattern, rather a small velocity gradient between NGC 3447 and NGC 3447A. Our simulation, detached from a large grid explored to best-fit the global properties of the system, suggests that this arises from an encounter between two halos of equal mass. Conclusions. NGC 3447 and NGC 3447A belong to the same halo, NGC 3447A being a substructure of the same disk including NGC 3447. The halo gravitational instability, enhanced by the encounter, fuels a long lived instability in this dark matter dominated disk, driving the observed morphology. The NGC 3447/NGC 3447A system may warn about a new class of "false pairs" and the potential danger of a misunderstanding of such objects in pair surveys that could produce a severe underestimate of the total mass of the system.

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“…a galaxy devoid of young massive stars. These conditions, following the UV classification scheme by Yi et al (2011), separate passive evolving ETGs (region b) from star forming galaxies (region a), see text). Filled symbols are for galaxies with FUV−r 6.6 mag dwarf galaxies, respectively, have NUV−i > 5.…”

Section: The Uv -Optical Cmdmentioning

confidence: 99%

“…The value FUV−NUV = 0.9 indicates a flat UV spectrum in the λ− versus F λ domain, whereas a negative FUV−NUV corresponds to a bluer population. Yi et al (2011) Figure 9 shows the cumulative distribution of the FUV−NUV colours of NGC5846, and of three groups already analised in the Leo cloud (Paper I and II). This figure points out that the fraction of red UV colours, i.e.…”

Section: The Colour−colour Fuv−nuv Versus Nuv−r Diagrammentioning

confidence: 99%

Galaxy evolution in nearby galaxy groups – III. AGALEXview of NGC 5846, the largest group in the local universe

Marino

Mazzei

Rampazzo

et al. 2016

Mon. Not. R. Astron. Soc.

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We explore the co-evolution of galaxies in nearby groups (V hel 3000 km s −1 ) with a multi-wavelength approach. We analyze GALEX far-UV (FUV) and near-UV (NUV) imaging, and SDSS u,g,r,i,z data of groups spanning a large range of dynamical phases. We characterize the photometric properties of spectroscopically-confirmed galaxy members and investigate the global properties of the groups through a dynamical analysis.Here we focus on NGC 5846, the third most massive association of Early-Type Galaxies (ETG) after the Virgo and Fornax clusters. The group, composed of 90 members, is dominated by ETGs (about 80 per cent), and among ETGs about 40 per cent are dwarfs. Results are compared with those obtained for three groups in the LeoII cloud, which are radically different both in member-galaxy population and dynamical properties. The FUV-NUV cumulative colour distribution and the normalized UV luminosity function (LF) significantly differ due to the different fraction of late-type galaxy population. The UV LF of NGC 5846 resembles that of the Virgo cluster, however our analysis suggests that star-formation episodes are still occurring in most of the group galaxies, including ETGs. The NUV-i colour distribution, the optical-UV colour-colour diagram, and NUV-r vs. M r colour-magnitude relation suggest that the gas contribution cannot be neglected in the evolution of ETG-type group members. Our analysis highlights that NGC 5846 is still in an active phase of its evolution, notwithstanding the dominance of dwarf and bright ETGs and its virialized configuration.

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The Ultraviolet Upturn in Elliptical Galaxies and Environmental Effects

Cited by 74 publications

References 44 publications

The horizontal branch morphology of M 31 globular clusters

The horizontal branch morphology of M 31 globular clusters

Galaxy evolution in groups

Galaxy evolution in nearby galaxy groups – III. AGALEXview of NGC 5846, the largest group in the local universe

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