The population of galaxies in the distant clusters Cl 1613+ 3104 and Cl 1600+ 4109 (original) (raw)
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The colour-magnitude relations of ClJ1226.9+3332, a massive cluster of galaxies at z= 0.89
Monthly Notices of the Royal Astronomical Society, 2006
The colour-magnitude relations of one of the most massive (≈ 10 15 M ⊙ ), high redshift (z = 0.89) clusters of galaxies known have been studied. Photometry has been measured in the V, R, I, z, F606W, F814W, J and K bands to a depth of K ≈ 20.5 = K * + 2.5 and spectroscopy confirms 27 K band selected galaxies as members of the cluster. The V − K colours are equivalent to a rest-frame colour of ≈ 2700Å − J, and provide a very sensitive measure of star-formation activity. Hubble Space Telescope imaging with the Advanced Camera for Surveys has been used to morphologically classify the galaxies.
Photometric and Morphological Properties of Nearby Cluster Galaxies
The Astrophysical Journal Supplement Series, 2004
Photometric observations are presented for 8747 galaxies in the fields of 28 clusters with redshifts in the range 0:05 < z < 0:11 and spanning a wide range in Abell richness class. The primary motivation for this study is to provide a nearby sample of clusters whose galaxy populations can be used to provide an anchor point for evolutionary studies of cluster galaxy populations. The present analysis focuses on the sequence of luminous red galaxies that form a tight correlation in the colormagnitude plane. An ensemble cluster constructed from the full sample shows the red sequence clearly and the observed dispersion-not corrected for observational errors-is (V À I) ¼ 0:071 AE 0:006 down to M I(AB) ¼ À19:5. Selecting only early-type galaxies on the basis of their fractional bulge luminosity (B=T) reduces the observed dispersion to (V À I) ¼ 0:050 AE 0:006 mag, a significantly smaller dispersion than the full sample at more than the 95% confidence level. The slope of the color-magnitude relation in (V À I)=I is À0:023 AE 0:006. This set of clusters shows a red sequence that has the same mean color in all clusters (V À I) AB ¼ 0:91 AE 0:03 (measured at M I(AB) ¼ À23) and has the same intrinsic dispersion, (V À I) ¼ 0:04 AE 0:01, in all clusters within the observational errors. Thus, these clusters form a remarkably homogeneous family as represented by their luminous red galaxy populations.
Monthly Notices of the Royal Astronomical Society, 2002
We present a photometric investigation of the variation in galaxy colour with environment in 11 X-ray-luminous clusters at 0:07 # z # 0:16 taken from the Las Campanas/AAT Rich Cluster Survey. We study the properties of the galaxy populations in individual clusters, and take advantage of the homogeneity of the sample to combine the clusters together to investigate weaker trends in the composite sample. We find that modal colours of galaxies lying on the colour-magnitude relation in the clusters become bluer by dðB 2 RÞ=dr p ¼ 20:022^0:004 from the cluster core out to a projected radius of r p ¼ 6 Mpc, further out in radius than any previous study. We also examine the variation in modal galaxy colour with local galaxy density, S, for galaxies lying close to the colour-magnitude relation, and find that the median colour shifts bluewards by dðB 2 RÞ=d log 10 ðSÞ ¼ 20:076^0:009 with decreasing local density across three orders of magnitude. We show that the position of the red envelope of galaxies in the colour-magnitude relation does not vary as a function of projected radius or density within the clusters, suggesting that the change in the modal colour results from an increasing fraction of bluer galaxies within the colour-magnitude relation, rather than a change in the colours of the whole population. We show that this shift in the colour-magnitude relations with projected radius and local density is greater than that expected from the changing morphological mix based on the local morphology-density relation. We therefore conclude that we are seeing a real change in the properties of galaxies on the colour-magnitude relation in the outskirts of clusters. The simplest interpretation of this result (and similar constraints in local clusters) is that an increasing fraction of galaxies in the lower density regions at large radii within clusters exhibit signatures of star formation in the recent past, signatures which are not seen in the evolved galaxies in the highest density regions.
Photometric properties of clusters of galaxies
We report the first results of a long term program aimed at investigating the photometric properties of the cores of Abell and X-ray selected (EMSS, Gioia et al. 1990) clusters of galaxies. We observed 77 clusters of galaxies in the redshift range 0.05 ≤ z ≤ 0.25 in the Gunn g, r and i filters: in this paper we present the data on 59 clusters with good absolute photometry and on another group of 8 clusters with acceptable relative photometry. For all these clusters we show color-magnitude diagrams in the two colors: when, as in most cases, the early type galaxy sequence is identifiable, we compare it with the expectation from the Virgo c-m relation and find that the Virgo relation holds to z ∼ 0.2. We do not find any sign of active evolution in cluster galaxies since that epoch, nor in the percentage of blue galaxies or in the early type galaxy colors, if we accept that the scatter is of the order of 0.2-0.3 mag with respect to the expectations on the basis of standard k-corrections. We point out the presence of a certain number of anomalously red galaxies in the r − i color, which are too red with respect to their g − r color to be normal field galaxies at a redshift higher than the cluster one. Finally we briefly compare a few properties of the two subsamples of optically selected and X-ray selected clusters.
The bright end of the colour-magnitude relation of cluster galaxies
Monthly Notices of The Royal Astronomical Society, 2011
We investigate the physical processes involved in the development of the red sequence (RS) of cluster galaxies by using a combination of cosmological N-body simulations of clusters of galaxies and a semi-analytic model of galaxy formation. Results show good agreement between the general trend of the simulated RS and the observed colour-magnitude relation (CMR) of early-type galaxies in different magnitude planes. However, in many clusters, the most luminous galaxies (?) depart from the linear fit to observed data, as traced by less luminous ones, displaying almost constant colours. With the aim of understanding this particular behaviour of galaxies in the bright end of the RS, we analyse the dependence with redshift of the fraction of stellar mass contributed to each galaxy by different processes, i.e. quiescent star formation, and starbursts triggered by disc instability and merger events. We find that the evolution of galaxies in the bright end since z≈ 2 is mainly driven by minor and major dry mergers, while minor and major wet mergers are relevant in determining the properties of less luminous galaxies. Since the most luminous galaxies have a narrow spread in ages (1.0 × 1010 yr < t < 1.2 × 1010 yr), their metallicities are the main factor that affects their colours. Their mean iron abundances are close to the solar value and have already been reached at z≈ 1. This fact is consistent with several observational evidence that favour a scenario in which both the slope and scatter of the CMR are in place since z≈ 1.2. Galaxies in the bright end reach an upper limit in metallicity as a result of the competition of the mass of stars and metals provided by the star formation occurring in the galaxies themselves and by the accretion of merging satellites. Star formation activity in massive galaxies (stellar mass M★≳ 1010 M⊙) that takes place at low redshifts contributes with stellar components of high metallicity, but the fraction of stellar mass contributed since z≈ 1 is negligible with respect to the total mass of the galaxy at z= 0. On the other hand, mergers contribute with a larger fraction of stellar mass (≈10-20 per cent), but the metallicity of the accreted satellites is lower by ≈0.2 dex than the mean metallicity of galaxies they merge with. The effect of dry mergers is to increase the mass of galaxies in the bright end, without significantly altering their metallicities. Hence, very luminous galaxies present similar colours that are bluer than those expected if recent star formation activity were higher, thus giving rise to a break in the RS. These results are found for simulated clusters with different virial masses (1014- 1015 h-1 M⊙), supporting the idea of the universality of the CMR in agreement with observational results.
Galaxies and Environment of the Clusters of Galaxies CL 0024+1654 and RX J0152.7-1357
2009
We present the analysis and results of photometric and spectroscopic catalog combined with X-ray data of two non-relaxed clusters CL 0024+1654 (z=0.4) and RX J0152.7-1357 (z=0.8). Using the Spearman correlation analysis we quantify the correlation between morphology, color, and star formation rate of each galaxy with its surrounding number density, mass density, and temperature of Intracluster Medium (ICM). Although our
2002
We present a photometric investigation of the variation in galaxy colour with environment in 11 X-ray-luminous clusters at 0:07 # z # 0:16 taken from the Las Campanas/AAT Rich Cluster Survey. We study the properties of the galaxy populations in individual clusters, and take advantage of the homogeneity of the sample to combine the clusters together to investigate weaker trends in the composite sample. We find that modal colours of galaxies lying on the colour-magnitude relation in the clusters become bluer by dðB 2 RÞ=dr p ¼ 20:022^0:004 from the cluster core out to a projected radius of r p ¼ 6 Mpc, further out in radius than any previous study. We also examine the variation in modal galaxy colour with local galaxy density, S, for galaxies lying close to the colour-magnitude relation, and find that the median colour shifts bluewards by dðB 2 RÞ=d log 10 ðSÞ ¼ 20:076^0:009 with decreasing local density across three orders of magnitude. We show that the position of the red envelope of galaxies in the colour-magnitude relation does not vary as a function of projected radius or density within the clusters, suggesting that the change in the modal colour results from an increasing fraction of bluer galaxies within the colour-magnitude relation, rather than a change in the colours of the whole population. We show that this shift in the colour-magnitude relations with projected radius and local density is greater than that expected from the changing morphological mix based on the local morphology-density relation. We therefore conclude that we are seeing a real change in the properties of galaxies on the colour-magnitude relation in the outskirts of clusters. The simplest interpretation of this result (and similar constraints in local clusters) is that an increasing fraction of galaxies in the lower density regions at large radii within clusters exhibit signatures of star formation in the recent past, signatures which are not seen in the evolved galaxies in the highest density regions.
Two-color photometry of clusters of galaxies. III. A2256
Astrophysics, 1989
The results of two-color photometry of the rich cluster of galaxies A2256 in the B and V color system are presented. About 500 galaxies have been identified on the large scale plates of the 2.6-m telescope of the Byurakan Observatory up to approximately 21~8 in B. The luminosity function is constructed in both B and V colors. It has a usual form with the characteristic break at M~ =-19.0 and M~ =-19.9. The projected radial distribution of the number of galaxies and of surface luminosity have a steep density gradient. The luminosity and color segregation effects as well as the distribution of apparent ellipticities and position angles of the major axes of the galaxies have been investigated.
The Astronomical Journal, 2001
New photometric and spectroscopic observations of galaxies in the directions of three distant clusters are presented as part of our ongoing high-redshift cluster survey. The clusters are CL1324+3011 at z = 0.76, CL1604+4304 at z = 0.90, and CL1604+4321 at z = 0.92. We have spectroscopically confirmed cluster membership for 20 to 40 galaxies in each system and have also obtained spectra for over 280 field galaxies spanning the range 0 < z < 2.5. Kinematic estimates of the mass within the central 770h −1 65 kpc of each cluster are in excess of 8 × 10 14 h −1 65 M. The observed x-ray luminosities in these clusters are at least a factor of 3 smaller than those observed in clusters with similar velocity dispersions at z ≤ 0.4. These clusters contain a significant population of elliptical-like galaxies, although these galaxies are not nearly as dominant as in massive clusters at z ≤ 0.5. We also find a large population of blue cluster members. Defining an active galaxy as one in which the rest equivalent width of [OII] is greater than 15Å, the fraction of active cluster galaxies, within the central 1.0 h −1 65 Mpc, is 45%. In the field population, we find that 65% of the galaxies with redshifts between z = 0.40 and z = 0.85 are active, while the fraction is 79% for field galaxies at z > 0.85. The star formation rate normalized by the rest AB B−band magnitude, SFRN, increases as the redshift increases at a given evolving luminosity. At a given redshift, however, SFRN decreases linearly with increasing luminosity indicating a remarkable insensitivity of the star formation rate to the intrinsic luminosity of the galaxy over the range −18 ≥ ABB ≥ −22. Cluster galaxies in the central 1h −1 65 Mpc regions exhibit depressed star formation rates and contain a larger fraction of galaxies with "k" type spectra. The star formation rates in galaxies lying between 1 − 2.5h −1 65 Subject headings: galaxies: clusters: general-cosmology: observations 65 65 kpc regions of these 3 clusters are all in excess of 8 × 10 14 h −1 65 M (for the M P W estimator) and the projected and ring-wise mass estimators yield central values > ∼ 10 15 h −1 65 M. Each of 65 kpc. The unshaded histograms show the distributions for all available data.
The galaxy population of Cl 1601+42 at z=0.54
2002
Photometric redshifts are used to determine the rest frame luminosity function (LF) of both early-type and late-type galaxies to M B ∼ -17.6 for the cluster Cl1601+42 at z = 0.54. The total LF shows a steep faint-end slope α ∼ -1.4, indicating the existence of a numerous population of dwarf galaxies. Luminous galaxies, with M B < ∼ − 19.5 are mostly red, early-type galaxies, with a LF best described by a Gaussian. Faint galaxies are predominantly blue, late-type galaxies, well fitted by a Schechter function with α ∼ -1.7. Compared to clusters at lower redshift, the steepening of the faint end starts at brighter magnitudes for Cl1601+42, which may indicate a brightening of todays dwarf population relative to the giant population with increasing redshift. Early-type galaxies are centrally concentrated, and dominate the core region, implying that the radial gradient of early-type galaxies seen in local clusters is already established at z ∼ 0.5. Bright, late-type galaxies are rare, consistent with a decrease in star formation in field galaxies as they are accreted on to the cluster, while faint, blue galaxies are evenly distributed across the cluster, except for a depletion in the core region. The blue fraction is f B ∼ 0.15, which is somewhat lower than the Butcher-Oemler average at z ∼ 0.5. The value of f B is found to increase with limiting magnitude and with radius from the centre.