Colour-magnitude relations and spectral line strengths in the Coma cluster

Terlevich, A. I.; Küntschner, H.; Bower, Richard G.; Caldwell, Nelson; Sharples, R. M.

doi:10.1046/j.1365-8711.1999.02941.x

Cited by 61 publications

(76 citation statements)

References 48 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…However, it has been noted by various investigators (e.g. Terlevich et al 1999;Poggianti et al 2001;Kuntschner et al 2002) that Hβ tends to give systematically older ages than Hγ + Hδ.…”

Section: Balmer Lines Hβ Vs Hγ and Hδmentioning

confidence: 95%

The formation of S0 galaxies: evidence from globular clusters

Barr¹,

Bedregal²,

Aragón-Salamanca³

et al. 2007

A&A

View full text Add to dashboard Cite

Aims. We devise a simple experiment to test the theory that lenticular (S0) galaxies form from spirals whose star formation has been shut down. An individual galaxy's fading is measured using the globular cluster specific frequency (S N ), defined as the number of globular clusters normalised by the galaxy luminosity. This is compared with a spectroscopically-derived age estimate. Methods. We make NTT/EMMI long-slit spectroscopic observations of 11 S0 galaxies at z < 0.006. We measure the absorption-line indices, Hδ, Hγ, Mgb, Fe5270 and Fe5335 within the central r e /8. By inverting single-stellar population models, luminosity-weighted mean ages, metallicities and α-element abundance ratios are derived. We estimate the amount of fading a galaxy has undergone by comparing each galaxy's S N with its deviation from the mean spiral S N . Results. Galaxies with higher S N have older stellar populations. Moreover, we find that the zero-point and amount of fading is consistent with a scenario where lenticulars are formed by the quenching of star formation in spiral galaxies. Our data also rule out any formation method for S0s which creates a large number of new globular clusters. We confirm that previous results showing a relationship between S N and color are driven by the S N −Age relation. Five galaxies show detectable Hβ,lines. However, only in the two youngest galaxies is this emission unambiguously from star formation. Conclusions. Our results are consistent with the theory that S0 galaxies are formed when gas in normal spirals is removed, possibly as a result of a change in environment. The on-going star formation in the youngest galaxies hints that the timescale of quenching is 1 Gyr. We speculate, therefore, that the truncation of star formation is a rather gentle process unlikely to involve a rapid burst of star formation.

show abstract

“…However, it has been noted by various investigators (e.g. Terlevich et al 1999;Poggianti et al 2001;Kuntschner et al 2002) that Hβ tends to give systematically older ages than Hγ + Hδ.…”

Section: Balmer Lines Hβ Vs Hγ and Hδmentioning

confidence: 95%

The formation of S0 galaxies: evidence from globular clusters

Barr¹,

Bedregal²,

Aragón-Salamanca³

et al. 2007

A&A

View full text Add to dashboard Cite

show abstract

“…Although, classically, the Mg 2 -σ relation has been interpreted as the interplay between mass and metallicity (Forbes et al 1998;Kobayashi & Arimoto 1999;Terlevich et al 1999), nowadays there is still much debate as to whether this relation reflects trends in stellar ages, in metallicities, or in the relative abundance of different heavy elements (e.g., T98; Jørgensen 1999; Trager et al 2000b;K01;Poggianti et al 2001a;Mehlert et al 2003;Caldwell et al 2003;Thomas et al 2005). The problem is due to the well-known agemetallicity degeneracy, which makes very difficult to separate both effects with the current stellar population models.…”

Section: The Index-velocity Dispersion Relationsmentioning

confidence: 99%

Stellar populations of early-type galaxies in different environments

Sánchez‐Blázquez

Gorgas

Cardiel

et al. 2006

A&A

120

164

View full text Add to dashboard Cite

Aims. This paper commences a series devoted to the study of the stellar content of early-type galaxies. The goal of the series is to set constraints on the evolutionary status of these objects. Methods. In this paper we describe the details of the galaxy sample, the observations, and the data reduction. Line-strength indices and velocity dispersions (σ) are measured in 98 early-type galaxies drawn from different environments, and the relation of the indices with the velocity dispersion analysed in detail.Results. The present sample indicates that some of the index-σ relations depend on galaxy environment. In particular, the slope of the relation between Balmer lines and σ is steeper for galaxies in the Virgo cluster, small groups, and in the field than for galaxies in the Coma cluster. In several indices there is also a significant offset in the zero point between the relations defined by the different subsamples. The slopes of the index-σ relation for the Virgo and low-density environment galaxies are explained by a variation of both age and metallicity, with velocity dispersion, as previously noted in other studies. For the galaxies in the Coma cluster, however, the relation of the indices with σ only requires a variation of the abundance along the σ sequence. In agreement with other studies, we find that the models that better reproduce the slopes are those in which the α elements vary more than the Fe-peak elements along the σ sequence, while, at a given σ, older galaxies show an higher α/Fe ratio. Conclusions. The results can be explained assuming that galaxies in the Coma cluster have experienced a truncated star formation and chemical enrichment history compared to a more continuous time-extended history for their counterparts in lower density environments.

show abstract

“…In particular, important information comes from the spectral types of member galaxies, since star formation could increase or, alternatively, stop during the merging phase; thus the spectral signatures of past activity are useful to determine the relevant timescales (e.g. Bekki 1999;Terlevich et al 1999). We are planning further studies of A520 in this perspective.…”

Section: Conclusion: A520 At the Crossing Of Three Lss Filamentsmentioning

confidence: 99%

Cluster Abell 520: a perspective based on member galaxies

Girardi

Barrena

Boschin

et al. 2008

A&A

View full text Add to dashboard Cite

Context. The connection of cluster mergers with the presence of extended, diffuse radio sources in galaxy clusters is still debated. An interesting case is the rich, merging cluster Abell 520, containing a radio halo. A recent gravitational analysis has shown in this cluster the presence of a massive dark core suggested to be a possible problem for the current cold dark matter paradigm. Aims. We aim to obtain new insights into the internal dynamics of Abell 520 analyzing velocities and positions of member galaxies. Methods. Our analysis is based on redshift data for 293 galaxies in the cluster field obtained combining new redshift data for 8 galaxies acquired at the TNG with data obtained by CNOC team and other few data from the literature. We also use new photometric data obtained at the INT telescope. We combine galaxy velocities and positions to select 167 cluster members around z ∼ 0.201. We analyze the cluster structure using the weighted gap analysis, the KMM method, the Dressler-Shectman statistics and the analysis of the velocity dispersion profiles. We compare our results with those from X-ray, radio and gravitational lensing analyses. Results. We compute a global line-of-sight (LOS) velocity dispersion of galaxies, σ v = 1066 +67 −61 km s −1 . We detect the presence of a high velocity group (HVG) with a rest-frame relative LOS velocity of v rf ∼ 2000 km s −1 with respect to the main system (MS). Using two alternative cluster models we estimate a mass range M(<1 h 70 M . We also find that the MS shows evidence of subclumps along two preferred directions. The main, complex structure NE1 + NE2 (with a velocity comparable to that of the MS) and the SW structure (at v rf ∼ +1100 km s −1 ) define the NE-SW direction, the same of the merger suggested by X-ray and radio data. The E and W structures (at v rf ∼ −1150 and v rf ∼ −300 km s −1 ) define the E-W direction. Moreover, we find no dynamical trace of an important structure around the lensing dark core. Rather, the HVG and a minor MS group, having different velocities, are roughly centered in the same position of the lensing dark core, i.e. are somewhat aligned with the LOS. Conclusions. We find that Abell 520 is definitely a very complex system. Our results suggest that we are looking at a cluster forming at the crossing of three filaments of the large scale structure. The filament aligned with the LOS and projected onto the center of the forming cluster might explain the apparent massive dark core shown by gravitational lensing analysis.

show abstract

Colour-magnitude relations and spectral line strengths in the Coma cluster

Cited by 61 publications

References 48 publications

The formation of S0 galaxies: evidence from globular clusters

The formation of S0 galaxies: evidence from globular clusters

Stellar populations of early-type galaxies in different environments

Cluster Abell 520: a perspective based on member galaxies

Contact Info

Product

Resources

About