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<i>Spitzer Planck Herschel</i> Infrared Cluster (SPHerIC) survey: Candidate galaxy clusters at 1.3 < <i>z</i> < 3 selected by high star-formation rate
摘要： There is a lack of large samples of spectroscopically confirmed clusters and protoclusters at high redshifts, z > 1.5. Discovering and characterizing distant (proto-)clusters is important for yielding insights into the formation of large-scale structure and on the physical processes responsible for regulating star-formation in galaxies in dense environments. The Spitzer Planck Herschel Infrared Cluster (SPHerIC) survey was initiated to identify these characteristically faint and dust-reddened sources during the epoch of their early assembly. We present Spitzer/IRAC observations of 82 galaxy (proto-)cluster candidates at 1.3 < zp < 3.0 that were vetted in a two step process: (1) using Planck to select by color those sources with the highest star-formation rates, and (2) using Herschel at higher resolution to separate out the individual red sources. The addition of the Spitzer data enables efficient detection of the central and massive brightest red cluster galaxies (BRCGs). We find that BRCGs are associated with highly significant, extended and crowded regions of IRAC sources which are more overdense than the field. This result corroborates our hypothesis that BRCGs within the Planck–Herschel sources trace some of the densest and actively star-forming proto-clusters in the early Universe. On the basis of a richness-mass proxy relation, we obtain an estimate of their mean masses which suggests our sample consists of some of the most massive clusters at z ≈ 2 and are the likely progenitors of the most massive clusters observed today.
关键词： galaxies: star formation,submillimeter: galaxies,infrared: galaxies,galaxies: evolution,galaxies: clusters: general,galaxies: high-redshift
更新于2025-09-23 15:23:52
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Do cluster properties affect the quenching rate?
摘要： The quenching rate is known to depend on galaxy stellar mass and environment, however, possible dependences on the hosting halo properties, such as mass, richness, and dynamical status, are still debated. The determination of these dependences is hampered by systematics, induced by noisy estimates of cluster mass or by the lack of control on galaxy stellar mass, which may mask existing trends or introduce fake trends. We studied a sample of local clusters (20 with 0.02 < z < 0.1 and log(M200/M(cid:3)) (cid:2) 14), selected independent of the galaxy properties under study, having homogeneous optical photometry and X-ray estimated properties. Using those top quality measurements of cluster mass, hence of cluster scale, richness, iron abundance, and cooling time/presence of a cool-core, we study the simultaneous dependence of quenching on these cluster properties on galaxy stellar mass M and normalised cluster-centric distance r/r200. We found that the quenching rate can be completely described by two variables only, galaxy stellar mass and normalised cluster-centric distance, and is independent of halo properties (mass, richness, iron abundance, and central cooling time/presence of a cool-core). These halo properties change, in most cases, by less than 3% the probability that a galaxy is quenched, once the mass-size (M200 – r200) scaling relation is accounted for through cluster-centric distance normalisation.
关键词： galaxies: star formation,galaxies: evolution,galaxies: clusters: general
更新于2025-09-23 15:22:29
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The GALEX Ultraviolet Virgo Cluster Survey (GUViCS)
摘要： We study the role of the environment on galaxy evolution using a sample of 868 galaxies in the Virgo cluster and in its surrounding regions that are selected from the GALEX Ultraviolet Virgo Cluster Survey (GUViCS) with the purpose of understanding the origin of the red sequence in dense environments. The sample spans a wide range in morphological types (from dwarf ellipticals to Im and BCD) and stellar masses (107 (cid:2) Mstar (cid:2) 1011.5 M(cid:3)). We collected multifrequency data covering the whole electromagnetic spectrum for most of the galaxies, including UV, optical, mid- and far-infrared imaging data, as well as optical and HI spectroscopic data. We ?rst identify the di?erent dynamical substructures that compose the Virgo cluster, and we calculate the local density of galaxies using di?erent methods. We then study the distribution of galaxies belonging to the red sequence, the green valley, and the blue cloud within the di?erent cluster substructures or as a function of galaxy density. Our analysis indicates that all the most massive galaxies (Mstar (cid:3) 1011 M(cid:3)) are slow rotators and are the dominant galaxies of the di?erent cluster substructures, which are generally associated with a di?use X-ray emission. They are probably the result of major merging events that occurred at early epochs, as also indicated by their very old stellar populations. Slow rotators of lower stellar mass (108.5 (cid:2) Mstar (cid:2) 1011 M(cid:3)) are also preferentially located within the di?erent high-density substructures of the cluster. Their position in the velocity space indicates that they are virialised within the cluster; thus, they are Virgo members since its formation. They have been shaped by gravitational perturbations occurring within the infalling groups that later form the cluster (pre-processing). On the contrary, low-mass star-forming systems are extremely rare in the inner regions of the Virgo cluster A, where the density of the intergalactic medium is at its maximum. Our ram pressure stripping models consistently indicate that these star-forming systems can be rapidly deprived of their interstellar medium during their interaction with the intergalactic medium. The lack of gas quenches their star-formation activity transforming them into quiescent dwarf ellipticals. This mild transformation does not perturb the kinematic properties of these galaxies, which still have rotation curves typical of star-forming systems.
关键词： galaxies: interactions,galaxies: star formation,galaxies: clusters: general,galaxies: clusters: individual: Virgo,galaxies: ISM,galaxies: evolution
更新于2025-09-23 15:21:21
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Weak lensing magnification of SpARCS galaxy clusters
摘要： Context. Measuring and calibrating relations between cluster observables is critical for resource-limited studies. The mass–richness relation of clusters offers an observationally inexpensive way of estimating masses. Its calibration is essential for cluster and cosmological studies, especially for high-redshift clusters. Weak gravitational lensing magnification is a promising and complementary method to shear studies, that can be applied at higher redshifts. Aims. We aim to employ the weak lensing magnification method to calibrate the mass–richness relation up to a redshift of 1.4. We used the Spitzer Adaptation of the Red-Sequence Cluster Survey (SpARCS) galaxy cluster candidates (0.2 < z < 1.4) and optical data from the Canada France Hawaii Telescope (CFHT) to test whether magnification can be effectively used to constrain the mass of high-redshift clusters. Methods. Lyman-break galaxies (LBGs) selected using the u-band dropout technique and their colours were used as a background sample of sources. LBG positions were cross-correlated with the centres of the sample of SpARCS clusters to estimate the magnification signal, which was optimally-weighted using an externally-calibrated LBG luminosity function. The signal was measured for cluster sub-samples, binned in both redshift and richness. Results. We measured the cross-correlation between the positions of galaxy cluster candidates and LBGs and detected a weak lensing magnification signal for all bins at a detection significance of 2.6–5.5σ. In particular, the significance of the measurement for clusters with z > 1.0 is 4.1σ; for the entire cluster sample we obtained an average M200 of 1.28 +0.23 ?0.21 × 1014 M⊙. Conclusions. Our measurements demonstrated the feasibility of using weak lensing magnification as a viable tool for determining the average halo masses for samples of high redshift galaxy clusters. The results also established the success of using galaxy over-densities to select massive clusters at z > 1. Additional studies are necessary for further modelling of the various systematic effects we discussed.
关键词： galaxies: clusters: general,galaxies: clusters: individual: SpARCS,gravitational lensing: weak
更新于2025-09-23 15:21:21
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OmegaWINGS: OmegaCAM-VST observations of WINGS galaxy clusters
摘要： Context. Wide-field observations targeting galaxy clusters at low redshift are complementary to field surveys and provide the local benchmark for detailed studies of the most massive haloes in the local Universe. The Wide-field Nearby Galaxy-cluster Survey (WINGS) is a wide-field multi-wavelength survey of X-ray selected clusters at z = 0.04–0.07. The original 34' × 34' WINGS field of view has now been extended to cover a 1 deg2 field with both photometry and spectroscopy. Aims. We present the Johnson B- and V-band OmegaCAM at the VST observations of 46 WINGS clusters together with the data reduction, data quality, and Sextractor photometric catalogues. Methods. The data reduction was carried out with a modified version of the ESO-MVM (also known as ALAMBIC) reduction package, adding a cross-talk correction, the gain harmonisation, and a control procedure for problematic CCDs. The stray-light component was corrected for by employing our own observations of populated stellar fields. Results. With a median seeing of 1'' in both bands, our 25-min exposures in each band typically reach the 50% completeness level at V = 23.1 mag. The quality of the astrometric and photometric accuracy has been verified by comparison with the 2MASS and SDSS astrometry, and SDSS and previous WINGS imaging. Star-to-galaxy separation and sky-subtraction procedure were tested comparing them with previous WINGS data. Conclusions. The Sextractor photometric catalogues are publicly available at the CDS and will be included in the next release of the WINGS database on the Virtual Observatory together with the OmegaCAM reduced images. These data form the basis for a large ongoing spectroscopic campaign with AAOmega at the AAT and are being employed for a variety of studies.
关键词： galaxies: fundamental parameters,galaxies: clusters: general,galaxies: photometry,methods: observational,catalogs
更新于2025-09-19 17:15:36
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The <i>Swift</i> X-ray Telescope Cluster Survey
摘要： Aims. We present a spectral analysis of a new, ?ux-limited sample of 72 X-ray selected clusters of galaxies identi?ed with the X-ray Telescope (XRT) on board the Swift satellite down to a ?ux limit of ～10?14 erg s?1 cm?2 (SWXCS). We carry out a detailed X-ray spectral analysis with the twofold aim of measuring redshifts and characterizing the properties of the intracluster medium (ICM) for the majority of the SWXCS sources. Methods. Optical counterparts and spectroscopic or photometric redshifts for some of the sources are obtained with a cross-correlation with the NASA/IPAC Extragalactic Database. Additional photometric redshifts are computed with a dedicated follow-up program with the Telescopio Nazionale Galileo and a cross-correlation with the SDSS. In addition, we also blindly search for the Hydrogen-like and He-like iron Kα emission line complex in the X-ray spectrum. We detect the iron emission lines in 35% of the sample, and hence obtain a robust measure of the X-ray redshift zX with typical rms error 1–5%. We use zX whenever the optical redshift is not available. Finally, for all the sources with measured redshift, background-subtracted spectra are ?tted with a single-temperature mekal model to measure global temperature, X-ray luminosity and iron abundance of the ICM. We perform extensive spectral simulations to accounts for ?tting bias, and to assess the robustness of our results. We derive a criterion to select reliable best-?t models and an empirical formula to account for ?tting bias. The bias-corrected values are then used to investigate the scaling properties of the X-ray observables. Results. Overall, we are able to characterize the ICM of 46 sources with redshifts (64% of the sample). The sample is mostly constituted by clusters with temperatures between 3 and 10 keV, plus 14 low-mass clusters and groups with temperatures below 3 keV. The redshift distribution peaks around z ～ 0.25 and extends up to z ～ 1, with 60% of the sample at 0.1 < z < 0.4. We derive the luminosity?temperature relation for these 46 sources, ?nding good agreement with previous studies. Conclusions. Thanks to the good X-ray spectral quality and the low background of Swift/XRT, we are able to measure ICM temperatures and X-ray luminosities for the 46 sources with redshifts. Once redshifts are available for the remaining 26 sources, this sample will constitute a well-characterized, ?ux-limited catalog of clusters distributed over a broad redshift range (0.1 ≤ z ≤ 1.0) providing a statistically complete view of the cluster population with a selection function that allows a proper treatment of any measurement bias. The quality of the SWXCS sample is comparable to other samples available in the literature and obtained with much larger X-ray telescopes. Our results have interesting implications for the design of future X-ray survey telescopes, characterized by good-quality PSF over the entire ?eld of view and low background.
关键词： intergalactic medium,galaxies: high-redshift,X-rays: galaxies: clusters,galaxies: clusters: general,cosmology: observations
更新于2025-09-09 09:28:46
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A new method to assign galaxy cluster membership using photometric redshifts
摘要： We introduce a new effective strategy to assign group and cluster membership probabilities Pmem to galaxies using photometric redshift information. Large dynamical ranges both in halo mass and cosmic time are considered. The method takes into account the magnitude distribution of both cluster and field galaxies as well as the radial distribution of galaxies in clusters using a non-parametric formalism, and relies on Bayesian inference to take photometric redshift uncertainties into account. We successfully test the method against 1208 galaxy clusters within redshifts z = 0.05?2.58 and masses 1013.29?14.80 M(cid:12) drawn from wide field simulated galaxy mock catalogs mainly developed for the forthcoming Euclid mission. Median purity and completeness values of (55+17 ?10)% and (95+5 ?15)% are reached for galaxies brighter than 0.25 L? within r200 of each simulated halo and for a statistical photometric redshift accuracy σ((zs ? zp)/(1 + zs)) = 0.03. The mean values p = 56% and c = 93% are consistent with the median and have negligible sub-percent uncertainties. Accurate photometric redshifts (σ((zs ? zp)/(1 + zs)) (cid:46) 0.05) and robust estimates for the cluster redshift and cluster center coordinates are required. The dependence of the assignments on photometric redshift accuracy, galaxy magnitude and distance from the halo center, and halo properties such as mass, richness, and redshift are investigated. Variations in the mean values of both purity and completeness are globally limited to a few percent. The largest departures from the mean values are found for galaxies associated with distant z (cid:38) 1.5 halos, faint (～0.25 L?) galaxies, and those at the outskirts of the halo (at cluster-centric projected distances ～r200) for which the purity is decreased, ?p (cid:39) 20% at most, with respect to the mean value. The proposed method is applied to derive accurate richness estimates. A statistical comparison between the true (Ntrue) vs. estimated richness (λ = (cid:80) Pmem) yields on average to unbiased results, Log(λ/Ntrue) = ?0.0051 ± 0.15. The scatter around the mean of the logarithmic difference between λ and the halo mass is 0.10 dex for massive halos (cid:38)1014.5 M(cid:12). Our estimates could therefore be useful to constrain the cluster mass function and to calibrate independent cluster mass estimates such as those obtained from weak lensing, Sunyaev-Zel’dovich, and X-ray studies. Our method can be applied to any list of galaxy clusters or groups in both present and forthcoming surveys such as SDSS, CFHTLS, Pan-STARRS, DES, LSST, and Euclid.
关键词： galaxies: clusters: general,galaxies: groups: general,galaxies: statistics
更新于2025-09-09 09:28:46
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Surface photometry of WINGS galaxies with GASPHOT
摘要： Aims. We present the B, V, and K band surface photometry catalogs obtained by running the automatic software GASPHOT on galaxies from the WINGS cluster survey with isophotal areas larger than 200 pixels. The catalogs can be downloaded at the Centre de Données Astronomiques de Strasbourg. Methods. The luminosity growth curves of stars and galaxies in a given catalog relative to a given cluster image were obtained simultaneously by slicing the image with a fixed surface brightness step in several SExtractor runs. Then, using a single Sersic law convolved with a space-varying point spread function (PSF), GASPHOT performed a simultaneous χ2 best-fit of the major- and minor-axis luminosity growth curves of galaxies. We outline the GASPHOT performances and compare our surface photometry with that obtained by SExtractor, GALFIT, and GIM2D. This analysis is aimed at providing statistical information about the accuracy that is generally achieved by the softwares for automatic surface photometry of galaxies. Results. The GASPHOT catalogs provide the parameters of the Sersic law that fit the luminosity profiles for each galaxy and for each photometric band. They are the sky coordinates of the galaxy center (RA, Dec), the total magnitude (m), the semi-major axis of the effective isophote (Re), the Sersic index (n), the axis ratio (b/a), and a flag parameter (QFLAG) that generally indicates the fit quality. The WINGS-GASPHOT database includes 41 463 galaxies in the B band, 42 275 in the V band, and 71 687 in the K band. The bright early-type galaxies have higher Sersic indices and larger effective radii, as well as redder colors in their center. In general, the effective radii increase systematically from the K to the V and B band. Conclusions. The GASPHOT photometry agrees well with the surface photometry obtained by GALFIT and GIM2D, and with the aperture photometry provided by SExtractor. In particular, the direct comparison of structural parameters derived by different softwares for common galaxies indicates that the systematic differences are small in general. The only significant deviations are most likely due to the peculiar (and very accurate) image processing adopted by WINGS for large galaxies. The main advantages of GASPHOT with respect to other tools are (i) the automatic finding of the local PSF; (ii) the short CPU execution time; and (iii) the remarkable stability against the choice of the initial-guess parameters. All these characteristics make GASPHOT an ideal tool for blind surface photometry of large galaxy samples in wide-field CCD mosaics.
关键词： surveys,catalogs,galaxies: clusters: general
更新于2025-09-04 15:30:14