Truncated Star Formation in Compact Groups of Galaxies: A Stellar Population Study

Rosa, I. G. de la; Carvalho, R. R. de; Vazdekis, Alexandre; Barbuy, B.

doi:10.1086/509502

Cited by 47 publications

(61 citation statements)

References 63 publications

(126 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Stars from galaxies in compact groups. De la Rosa et al (2007) have found that galaxies with σ 0 160 km s −1 in Hickson Compact Groups have larger [Mg/Fe] and lower [Z/H] compared to field galaxies of similar masses, and proposed that such galaxies may have their otherwise extended star formation quenched by mergers. 3.…”

Section: The Extended Symmetric Halomentioning

confidence: 99%

The Hydra I cluster core

Barbosa

Arnaboldi

Coccato

et al. 2016

A&A

View full text Add to dashboard Cite

Context. The history of the mass assembly of brightest cluster galaxies may be studied by mapping the stellar populations at large radial distances from the galaxy centre, where the dynamical times are long and preserve the chemodynamical signatures of the accretion events. Aims. We provide extended and robust measurements of the stellar population parameters in NGC 3311, the cD galaxy at the centre of the Hydra I cluster, and out to three effective radii. We wish to characterize the processes that drove the build-up of the stellar light at all these radii. Methods. We obtained the spectra from several regions in NGC 3311 covering an area of ∼3 arcmin 2 in the wavelength range 4800 λ(Å) 5800, using the FORS2 spectrograph at the Very Large Telescope in the Mask exchange unit (MXU) mode. We measured the equivalent widths of seven absorption-features defined in the Lick/IDS system, which were modelled by single stellar populations, to provide luminosity-weighted ages, metallicities, and alpha element abundances. Results. The trends in the Lick indices and the distribution of the stellar population parameters indicate that the stars of NGC 3311 may be divided in two radial regimes, one within and the another beyond one effective radius, R e = 8.4 kpc, similar to the distinction between the inner galaxy and the external halo derived from the NGC 3311 velocity dispersion profile. The inner galaxy (R ≤ R e ) is old (age ∼14 Gyr), has negative metallicity gradients and positive alpha element gradients. The external halo is also very old, but has a negative age gradient. The metal and element abundances of the external halo both have a large scatter, indicating that stars from a variety of satellites with different masses have been accreted. The region in the extended halo associated with the off-centred envelope at 0• < PA < 90• has higher metallicity with respect to the symmetric external halo. Conclusions. The different stellar populations in the inner galaxy and extended halo reflect the dominance of in situ stars in the former and the accreted origin for the large majority of the stars in the latter. The low value of the velocity dispersion in the inner galaxy indicates that its stars are bound to the galaxy's gravitational potential, and the abundances and gradients suggest that the inner galaxy is formed in an outside-in scenario of merging gas-rich lumps, reminiscent of the first phase of galaxy formation. The external halo has a higher velocity dispersion, it is dynamically hotter than the galaxy and its stars are gravitationally driven by the cluster's gravitational potential. The stars in the external halo were removed from their parent galaxies, either disks with truncated star formation, or the outer regions of early-type galaxies. Late mass accretion at large radii is now coming from the tidal stripping of stars from dwarfs and S0 galaxies. These results provide supporting evidence for the recent theoretical models of formation of massive ellipticals as a two-phase process.

show abstract

Section: The Extended Symmetric Halomentioning

confidence: 99%

The Hydra I cluster core

Barbosa

Arnaboldi

Coccato

et al. 2016

A&A

View full text Add to dashboard Cite

show abstract

“…In the low metallicity regime, however, our models combine scaled-solar isochrones with stellar spectra that do not show this abundance ratio pattern (e.g., Edvardsson et al 1993;Schiavon 2007). However our (base) models, can be used to obtain a good proxy for the [Mg/Fe] abundance ratio, if appropriate line indices are employed (Yamada et al 2006;de la Rosa et al 2007). …”

Section: Introductionmentioning

confidence: 99%

MILES SSP Models

et al. 2009

View full text Add to dashboard Cite

Abstract. We present SEDs for single-age, single-metallicity stellar populations (SSPs) covering the full optical spectral range at resolution (FWHM = 2.3Å). These SEDs can be regarded as our base models, as we combine scaled-solar isochrones with an empirical stellar spectral library (MILES), which follows the chemical evolution pattern of the solar neighbourhood. The models rely as much as possible on empirical ingredients as also employ extensive photometric libraries. Thanks to the unprecedented parameter coverage of the MILES library we synthesize SSP SEDs from intermediate-to very-old age regimes, and the metallicity from super-solar to [M/H] = −2.3, all for a suite of IMF shapes and slopes. We propose a new Line Index System (LIS), based on flux-calibrated spectra, to avoid the intrinsic uncertainties associated with the Lick/IDS system and provide more appropriate, uniform, spectral resolution.

show abstract

“…Recent studies using Lick indices to determine the stellar population contents of elliptical galaxies in small samples of HCG have shown that the formation process of these galaxies is similar to that of ellipticals in clusters of galaxies (Proctor et al 2004;Mendes de Oliveira et al 2005;de la Rosa et al 2007), and suggested that their formation took place at least 2 Gyr in the past. This is already older than predicted by the fast merger scenario for CG, which has led some authors (e.g., Proctor et al 2004;Mendes de Oliveira et al 2005) to propose that CG are defying the standard cosmological model of structure formation.…”

Section: Introductionmentioning

confidence: 99%

The star formation histories of Hickson compact group galaxies

Plauchu-Frayn

Olmo

Coziol

et al. 2012

A&A

View full text Add to dashboard Cite

Aims. We study the star formation fistory (SFH) of 210 galaxy members of 55 Hickson compact groups (HCG) and 309 galaxies from the Catalog of Isolated Galaxies (CIG). The SFH traces the variation of star formation over the lifetime of a galaxy, and consequently yields a snapshot picture of its formation. Comparing the SFHs in these extremes in galaxy density allows us to determine the main effects of compact groups (CG) on the formation of galaxies. Methods. We fit our spectra using the spectral synthesis code STARLIGHT and obtained the stellar population contents and mean stellar ages of HCG and CIG galaxies in three different morphological classes: early-type galaxies (EtG), early-type spirals (EtS), and late-type spirals (LtS). Results. We find that EtG and EtS galaxies in HCG show higher contents of old and intermediate stellar populations as well as an important deficit of the young stellar population, which clearly implies an older average stellar age in early galaxies in HCG. For LtS galaxies we find similar mean values for the stellar content and age in the two samples. However, we note that LtS can be split into two subclasses, namely old and young LtS. In HCG we find a higher fraction of young LtS than in the CIG sample, in addition, most of these galaxies belong to groups in which most of the galaxies are also young and actively forming stars. The specific star formation rate (SSFR) of spiral galaxies in the two samples differ. The EtS in HCG show lower SSFR values, while LtS peak at higher values compared with their counterparts in isolation. We also measured the shorter star formation time scale (SFTS) in HCG galaxies, which indicates that they have a shorter star formation activity than CIG galaxies. We take these observations as evidence that galaxies in CG have evolved more rapidly than galaxies in isolation, regardless of their morphology. Our observations are consistent with the hierarchical galaxy formation model, which states that CGs are structures that formed recently from primordial small-mass density fluctuations. From the systematic difference in SFTS we deduce that the HCG have most probably formed ∼3 Gyr in the past. The galaxies in the HCG are not in equilibrium state, but merging without gas (i.e., under dissipationless conditions), which may explain their relatively long lifetime.

show abstract

Truncated Star Formation in Compact Groups of Galaxies: A Stellar Population Study

Cited by 47 publications

References 63 publications

The Hydra I cluster core

The Hydra I cluster core

MILES SSP Models

The star formation histories of Hickson compact group galaxies

Contact Info

Product

Resources

About