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Jeon, Seyoung, Sukyoung K. Yi, Yohan Dubois, Aeree Chung, Julien Devriendt, San Han, Ryan A. Jackson, Taysun Kimm, Christophe Pichon i Jinsu Rhee. "Star Formation History and Transition Epoch of Cluster Galaxies Based on the Horizon-AGN Simulation". Astrophysical Journal 941, nr 1 (1.12.2022): 5. http://dx.doi.org/10.3847/1538-4357/ac9d8c.
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Abstract Cluster galaxies exhibit substantially lower star formation rates than field galaxies today, but it is conceivable that clusters were sites of more active star formation in the early universe. Herein, we present an interpretation of the star formation history (SFH) of group/cluster galaxies based on the large-scale cosmological hydrodynamic simulation, Horizon-AGN. We find that massive galaxies in general have small values of e-folding timescales of star formation decay (i.e., “mass quenching”) regardless of their environment, while low-mass galaxies exhibit prominent environmental dependence. In massive host halos (i.e., clusters), the e-folding timescales of low-mass galaxies are further decreased if they reside in such halos for a longer period of time. This “environmental quenching” trend is consistent with the theoretical expectation from ram pressure stripping. Furthermore, we define a “transition epoch” as where cluster galaxies become less star-forming than field galaxies. The transition epoch of group/cluster galaxies varies according to their stellar and host-cluster halo masses. Low-mass galaxies in massive clusters show the earliest transition epoch of ∼7.6 Gyr ago in lookback time. However, this decreases to ∼5.2 Gyr for massive galaxies in low-mass clusters. Based on our findings, we can describe a cluster galaxy’s SFH with regard to the cluster halo-to-stellar mass ratio.
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Kuchner, Ulrike, Roan Haggar, Alfonso Aragón-Salamanca, Frazer R. Pearce, Meghan E. Gray, Agustín Rost, Weiguang Cui, Alexander Knebe i Gustavo Yepes. "An inventory of galaxies in cosmic filaments feeding galaxy clusters: galaxy groups, backsplash galaxies, and pristine galaxies". Monthly Notices of the Royal Astronomical Society 510, nr 1 (27.11.2021): 581–92. http://dx.doi.org/10.1093/mnras/stab3419.
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ABSTRACT Galaxy clusters grow by accreting galaxies from the field and along filaments of the cosmic web. As galaxies are accreted they are affected by their local environment before they enter (pre-processing), and traverse the cluster potential. Observations that aim to constrain pre-processing are challenging to interpret because filaments comprise a heterogeneous range of environments including groups of galaxies embedded within them and backsplash galaxies that contain a record of their previous passage through the cluster. This motivates using modern cosmological simulations to dissect the population of galaxies found in filaments that are feeding clusters, to better understand their history, and aid the interpretation of observations. We use zoom-in simulations from The ThreeHundred project to track haloes through time and identify their environment. We establish a benchmark for galaxies in cluster infall regions that supports the reconstruction of the different modes of pre-processing. We find that up to 45 per cent of all galaxies fall into clusters via filaments (closer than 1 h−1Mpc from the filament spine). 12 per cent of these filament galaxies are long-established members of groups and between 30 and 60 per cent of filament galaxies at R200 are backsplash galaxies. This number depends on the cluster’s dynamical state and sharply drops with distance. Backsplash galaxies return to clusters after deflecting widely from their entry trajectory, especially in relaxed clusters. They do not have a preferential location with respect to filaments and cannot collapse to form filaments. The remaining pristine galaxies (∼30–60 per cent) are environmentally affected by cosmic filaments alone.
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Aguerri, J. A. L., M. Girardi, I. Agulli, A. Negri, C. Dalla Vecchia i L. Domínguez Palmero. "Deep spectroscopy in nearby galaxy clusters – V. The Perseus cluster". Monthly Notices of the Royal Astronomical Society 494, nr 2 (24.03.2020): 1681–92. http://dx.doi.org/10.1093/mnras/staa800.
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ABSTRACT Dwarfs are the largest population of galaxies in number in the nearby Universe. Deep spectroscopic data are still missing to obtain a better understanding of their formation and evolution processes. This study shows the results obtained from a spectroscopic campaign in the Perseus cluster. We have obtained 963 new galaxy spectra. We have measured the recessional velocity of the galaxies by using a cross-correlation technique. These data have been used to obtain the cluster membership, the dynamics of the galaxies, and the spectroscopic luminosity function (LF) of the cluster. The cluster membership was obtained by using the peak + gap technique, reporting a total of 403 galaxies as cluster members within 1.4r200. The mean velocity and velocity dispersion of the cluster galaxies are Vc = 5258 km s−1 and σc = 1040 km s−1, respectively. We obtained M200 = 1.2 × 1015 M⊙ and r200 = 2.2 Mpc for this cluster. The clusters members were classified blue and red according to their g − r stellar colour. The velocity dispersion of these two families of galaxies is different, indicating that the blue galaxies can be classified as recently accreted into the cluster. We present the spectroscopic galaxy LF of the cluster. This function turned to be flat: α = 0.99 ± 0.06. In addition, blue and red galaxies show similar densities in the faint end of the LF. This indicates that Perseus does not have a population of red dwarf galaxias as large as other nearby clusters. We have compared the LF of the Perseus cluster with other spectroscopic LFs of nearby clusters and those from cosmological simulations. This comparison shows that the spectroscopic LF of nearby galaxy cluster is far from universal.
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Pallero, Diego, Facundo A. Gómez, Nelson D. Padilla, Yannick M. Bahé, Cristian A. Vega-Martínez i S. Torres-Flores. "Too dense to go through: the role of low-mass clusters in the pre-processing of satellite galaxies". Monthly Notices of the Royal Astronomical Society 511, nr 3 (17.11.2021): 3210–27. http://dx.doi.org/10.1093/mnras/stab3318.
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ABSTRACT We study the evolution of satellite galaxies in clusters of the c-eagle simulations, a suite of 30 high-resolution cosmological hydrodynamical zoom-in simulations based on the eagle code. We find that the majority of galaxies that are quenched at z = 0 (≳80${{\ \rm per\ cent}}$) reached this state in a dense environment (log10M200[M⊙] ≥13.5). At low redshift, regardless of the final cluster mass, galaxies appear to reach their quenching state in low-mass clusters. Moreover, galaxies quenched inside the cluster that they reside in at z = 0 are the dominant population in low-mass clusters, while galaxies quenched in a different halo dominate in the most massive clusters. When looking at clusters at z > 0.5, their in situ quenched population dominates at all cluster masses. This suggests that galaxies are quenched inside the first cluster they fall into. After galaxies cross the cluster’s r200 they rapidly become quenched (≲1 Gyr). Just a small fraction of galaxies ($\lesssim 15{{\ \rm per\ cent}}$) is capable of retaining their gas for a longer period of time, but after 4 Gyr, almost all galaxies are quenched. This phenomenon is related to ram pressure stripping and is produced when the density of the intracluster medium reaches a threshold of $\rho _{\rm ICM}\, \sim 3 \times 10 ^{-5}$ nH (cm−3). These results suggest that galaxies start a rapid-quenching phase shortly after their first infall inside r200 and that, by the time they reach r500, most of them are already quenched.
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Teague, P. F., i D. Carter. "Modelling Clusters of Galaxies". Publications of the Astronomical Society of Australia 6, nr 2 (1985): 198–202. http://dx.doi.org/10.1017/s1323358000018087.
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AbstractThorough investigation of clusters of galaxies involves the complete modelling of their dynamics and structure. Presented here is a description of such a substantial project utilizing a sample of several rich southern clusters of galaxies. Incorporating results from radial velocity analyses of cluster galaxies and X-ray images of the clusters into rigorously constructed models of the cluster potential well and atmosphere will enable the dynamics, structure and evolution of clusters to be tied down.
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Bogdán, Ákos, Lorenzo Lovisari, Patrick Ogle, Orsolya E. Kovács, Thomas Jarrett, Christine Jones, William R. Forman i Lauranne Lanz. "Detection of a Superluminous Spiral Galaxy in the Heart of a Massive Galaxy Cluster". Astrophysical Journal 930, nr 2 (1.05.2022): 138. http://dx.doi.org/10.3847/1538-4357/ac62cd.
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Abstract It is well established that brightest cluster galaxies (BCGs), residing in the centers of galaxy clusters, are typically massive and quenched galaxies with cD or elliptical morphology. An optical survey suggested that an exotic galaxy population, superluminous spiral and lenticular galaxies, could be the BCGs of some galaxy clusters. Because the cluster membership and the centroid of a cluster cannot be accurately determined based solely on optical data, we followed up a sample of superluminous disk galaxies and their environments using XMM-Newton X-ray observations. Specifically, we explored seven superluminous spiral and lenticular galaxies that are candidate BCGs. We detected massive galaxy clusters around five superluminous disk galaxies and established that one superluminous spiral, 2MASX J16273931+3002239, is the central BCG of a galaxy cluster. The temperature and total mass of the cluster are kT 500 = 3.55 − 0.20 + 0.18 keV and M 500 = (2.39 ± 0.19) × 1014 M ⊙. We identified the central galaxies of the four clusters that do not host superluminous disk galaxies at their cores, and established that the centrals are massive elliptical galaxies. However, for two of the clusters, the offset superluminous spirals are brighter than the central galaxies, implying that the superluminous disk galaxies are the brightest cluster galaxies. Our results demonstrate that superluminous disk galaxies are rarely the central systems of galaxy clusters. This is likely because galactic disks are destroyed by major mergers, which are more frequent in high-density environments. We speculate that the disks of superluminous disk galaxies in cluster cores may have been reformed due to mergers with gas-rich satellites.
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Godłowski, W., i F. Baier. "Galaxy Orientation in Some Abell Clusters". Symposium - International Astronomical Union 186 (1999): 410. http://dx.doi.org/10.1017/s0074180900113245.
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We analyze a sample of galaxies in a region of three rich Abell Clusters. The data are taken from the Edinburgh Catalogue of the cluster. First, we divide the whole cluster area into different parts according to the assumed subclusters. Now we can find the position angles of the cluster and subclusters. We find strong evidence that the position angles of galaxies within our clusters are aligned to a large extent. For the cluster A754, position angles of galaxies tend to be perpendicular to the direction of the position angle of the cluster. Consequently, the angular momentum of galaxies are preferentially perpendicular to the cluster plane. For the cluster A14, position angles of galaxies tend to be parallel to the direction of the position angle of the cluster. Consequently, the angular momentum of galaxies are preferentially parallel to the cluster plane. For the cluster A3667 we obtain a more complicated picture suggesting that the alignment of galaxies in this cluster may have a different shape. From the distribution of the positions angles of galaxies we also found evidence for possible subclustering inside the whole cluster. This result is confirmed by the investigation of the distribution of the vectors normal to the galactic planes. Moreover we confirm the existence of a “line of sight” effect, originally found by Godłowski &, Ostrowski (1996) for galaxies belonging to the clusters in the Tully Catalogue (1988), for the clusters in our basic catalog.
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Anders, Peter, Uta Fritze –. v. Alvensleben i Richard de Grijs. "Young Star Clusters: Progenitors of Globular Clusters!?" Highlights of Astronomy 13 (2005): 366–68. http://dx.doi.org/10.1017/s1539299600015987.
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AbstractStar cluster formation is a major mode of star formation in the extreme conditions of interacting galaxies and violent starbursts. Young clusters are observed to form in a variety of such galaxies, a substantial number resembling the progenitors of globular clusters in mass and size, but with significantly enhanced metallicity. From studies of the metal-poor and metal-rich star cluster populations of galaxies, we can therefore learn about the violent star formation history of these galaxies, and eventually about galaxy formation and evolution. We present a new set of evolutionary synthesis models of our GALEV code, with special emphasis on the gaseous emission of presently forming star clusters, and a new tool to compare extensive model grids with multi-color broad-band observations to determine individual cluster masses, metallicities, ages and extinction values independently. First results for young star clusters in the dwarf starburst galaxy NGC 1569 are presented. The mass distributions determined for the young clusters give valuable input to dynamical star cluster system evolution models, regarding survival and destruction of clusters. We plan to investigate an age sequence of galaxy mergers to see dynamical destruction effects in process.
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Maier, C., C. P. Haines i B. L. Ziegler. "Star-formation quenching of cluster galaxies as traced by metallicity and presence of active galactic nuclei, and galactic conformity". Astronomy & Astrophysics 658 (luty 2022): A190. http://dx.doi.org/10.1051/0004-6361/202141498.
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Aims. We strive to explore the differences in the properties and quenching processes of satellite galaxies in a sample of massive clusters with passive and star-forming (SF) brightest cluster galaxies (BCGs). One aim is to investigate galactic conformity effects, manifested in a correlation between the fraction of satellite galaxies that halted star formation and the state of star formation in the central galaxy. Methods. We explored 18 clusters from the Local Cluster Substructure Survey at 0.15 < z < 0.26, using spectra from the Arizona Cluster Redshift Survey Hectospec survey of about 1800 cluster members at R < R200 in a mass-complete sample. Nine clusters have a SF BCG and nine have a passive BCG, which enable the exploration of galactic conformity effects. We measured the fluxes of emission lines of cluster members, allowing us to derive O/H gas metallicities and to identify active galactic nuclei (AGN). We compared our cluster galaxy sample with a control field sample of about 1300 galaxies with similar masses and at similar redshifts observed with Hectospec as part of the same survey. We used the location of SF galaxies, recently quenched galaxies (RQGs) and AGN in the projected velocity versus the position phase-space (phase-space diagram) to identify objects in the inner regions of the clusters and to compare their fractions in clusters with SF and passive BCGs. Results. The metallicities of log(M/M⊙)≥10 SF cluster galaxies with R < R200 were found to be enhanced with respect to the mass-metallicity relation obtained for our sample of coeval field SF galaxies. This metallicity enhancement among SF cluster galaxies is limited to lower-mass satellites (10 < log(M/M⊙) < 10.7) of the nine clusters with a passive BCG, with no metallicity enhancement seen for SF galaxies in clusters with active BCGs. Many of the SF galaxies with enhanced metallicities are found in the core regions of the phase-space diagram expected for virialized populations. We find a higher fraction of log(M/M⊙)≥10.7 SF galaxies at R < R500 in clusters with active BCGs as compared to clusters with passive BCGs, which stands as a signal of galactic conformity. In contrast, much higher fractions at R < R500 of AGN and, particularly of RQGs, are found in clusters with passive BCGs in comparison to clusters with active BCGs. Conclusions. We deduce that strangulation is initiated in clusters with passive BCGs when SF satellite galaxies pass R200, by stopping the pristine gas inflow that would otherwise dilute the interstellar medium and would keep their metallicities at the level of values similar to those of field galaxies at similar redshifts. These satellite galaxies continue to form stars by consuming the available gas in the disk. For galaxies with massses above log(M/M⊙)∼10.7 that manage to survive and remain SF when traveling to R < R500 of clusters with passive BCGs, we assume that they suffer a rapid quenching of star formation, likely due to AGN triggered by the increasing ram pressure stripping toward the cluster center, which can compress the gas and fuel AGN. These AGN can rapidly quench and maintain quenched satellite galaxies. On the other hand, we found that surviving SF massive satellite galaxies around active BCGs are less affected by environment when they enter R < R500, since we observe R < R500 SF galaxies with masses up to M ∼ 1011 M⊙ and with metallicities typical of coeval field galaxies. This observed galactic conformity implies that active BCGs must maintain their activity over timescales of at least ∼1 Gyr.
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Larsen, Søren S. "Open, Massive and Globular Clusters — Part of the Same Family?" Symposium - International Astronomical Union 207 (2002): 421–27. http://dx.doi.org/10.1017/s0074180900224133.
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Populations of young star clusters show significant differences even among “normal” disk galaxies. In this contribution I discuss how properties of young cluster systems are related to those of their host galaxies, based on a recent study of clusters in a sample of 22 nearby spiral galaxies. Luminous young clusters similar to the “super” star clusters observed in starbursts and mergers exist in several of these galaxies, and it is found that the luminosity of the brightest star cluster as well as the specific luminosity of the cluster systems both correlate well with the host galaxy star formation rate. When considering star clusters in different environments the traditional distinction between “open”, “massive” and “globular” clusters breaks down, underscoring the need for a universal physical description of cluster formation.
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Zepf, Stephen E. "Formation Scenarios for Globular Clusters and Their Host Galaxies". Symposium - International Astronomical Union 207 (2002): 653–63. http://dx.doi.org/10.1017/s0074180900224492.
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This review focuses on how galaxies and their globular cluster systems form. I first discuss the now fairly convincing evidence that some globular clusters form in galaxy starbursts/mergers. One way these observations are valuable is they place important constraints on the physics of the formation of globular clusters. Moreover, it is natural to associate the typically metal-rich clusters forming in mergers with the substantial metal-rich population of globulars around ellipticals, thereby implying an important role for galaxy mergers in the evolution of elliptical galaxies. I also highlight some new observational efforts aimed at constraining how and when elliptical galaxies and their globular cluster systems formed. These include systematic studies of the number of globular clusters around galaxies as a function of morphological type, studies of the kinematics of globular cluster populations in elliptical galaxies, and a variety of observational programs aimed at constraining the relative ages of globular clusters within galaxies as a function of cluster metallicity. The understanding of the formation of globular cluster systems and their host galaxies has grown dramatically in recent years, and the future looks equally promising.
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Anders, Peter, Uta Fritze –. v. Alvensleben i Richard de Grijs. "Young Star Clusters: Metallicity Tracers in External Galaxies". Highlights of Astronomy 13 (2005): 667–69. http://dx.doi.org/10.1017/s1539299600017354.
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AbstractStar cluster formation is a major mode of star formation in the extreme conditions of interacting galaxies and violent star bursts. These newly-formed clusters are built from recycled gas, pre-enriched to various levels within the interacting galaxies. Hence, star clusters of different ages represent a fossil record of the chemical enrichment history of their host galaxy, as well as of the host galaxy’s violent star formation history. We present a new set of evolutionary synthesis models of our GALEV code, specifically developed to include the gaseous emission of presently forming star clusters, and a new tool to analyze multi-color observations with our models. First results for newly-born clusters in the dwarf star-burst galaxy NGC 1569 are presented.
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Garrow, Turner, Jeremy J. Webb i Jo Bovy. "The effects of dwarf galaxies on the orbital evolution of galactic globular clusters". Monthly Notices of the Royal Astronomical Society 499, nr 1 (11.09.2020): 804–13. http://dx.doi.org/10.1093/mnras/staa2773.
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ABSTRACT We investigate the effect that dwarf galaxies have on the orbits, tidal histories, and assumed formation environment of Milky Way globular clusters. We determine the orbits of the Milky Way’s 150 globular clusters in a gravitational potential both with and without dwarf galaxies. We find that the presence of a small number of satellite galaxies can affect the orbits of many of the globular clusters. Over 12 Gyr, we find that the semimajor axis and orbital eccentricity of individual clusters fluctuate with dispersions of the order of $\sim 10{{\ \rm per\ cent}}$ and $\sim 4{{\ \rm per\ cent}}$, respectively. Outer clusters are more strongly affected by dwarf galaxies than inner clusters, with their semimajor axis and orbital eccentricities fluctuating by more than $\sim 15{{\ \rm per\ cent}}$ and $\sim 5{{\ \rm per\ cent}}$, respectively. Using detailed N-body simulations of select clusters, we find that altering their orbital histories can lead to different mass-loss rates and structural evolution. Furthermore, we caution against using kinematics alone to identify whether a Galactic cluster formed in situ or was accreted during a past merger event as these values are no longer conserved. The presence of dwarf galaxies causes the orbital energies and actions of individual clusters to evolve over time, spanning a wider range than that coming from random uncertainties in a cluster’s proper motions and radial velocity.
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Hashimoto, Yasuhiro, J. Patrick Henry i Hans Böhringer. "Dwarf Galaxies and Cluster Environments". Proceedings of the International Astronomical Union 14, S344 (sierpień 2018): 373–76. http://dx.doi.org/10.1017/s1743921318006890.
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AbstractWe report an investigation of the properties of dwarf galaxies (Mr < -15) inside 26 clusters at z = 0.15 – 0.25, using the X-ray data from the Chandra archive, and optical images taken with Subaru Suprime-Cam. Our results include: 1. Investigation of the dwarf galaxy density distribution is sensitive to the background galaxies and the choice of colour selection of galaxies. 2. Cluster-centric dwarf-to-giant ratio is highly sensitive to the level of subtracted background galaxies. 3. A certain fraction of faint galaxies always remain undetected by the detection algorithm near the center of clusters, even after carefully treating the halo or extra diffuse light created by bright galaxies. The number of ‘undetected’ faint galaxies varies significantly from cluster to cluster, and even from pointing to pointing. 4. Dwarf galaxies extend up to 2 Mpc from the center in most clusters. Meanwhile, the distribution of blue dwarf galaxies extends more to the outside. 5. For a given colour, the spatial distributions of dwarf galaxies and giant galaxies become similar. Namely, the most of the radial distribution comes from the colour, rather than the size, of galaxies. 6. Relative to the NFW profile, all of the galaxy populations are showing a deficit near the cluster core (r < 0.3 Mpc). 7. The dwarf-to-giant ratio shows no variation against cluster measures such as the richness and X-ray luminosity, as well as various cluster X-ray characteristics related to possible dynamical status of clusters.
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Bonjean, V., N. Aghanim, P. Salomé, M. Douspis i A. Beelen. "Gas and galaxies in filaments between clusters of galaxies". Astronomy & Astrophysics 609 (styczeń 2018): A49. http://dx.doi.org/10.1051/0004-6361/201731699.
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We have performed a multi-wavelength analysis of two galaxy cluster systems selected with the thermal Sunyaev-Zel’dovich (tSZ) effect and composed of cluster pairs and an inter-cluster filament. We have focused on one pair of particular interest: A399-A401 at redshiftz~ 0.073 seperated by 3 Mpc. We have also performed the first analysis of one lower-significance newly associated pair: A21-PSZ2 G114.09-34.34 atz~ 0.094, separated by 4.2 Mpc. We have characterised the intra-cluster gas using the tSZ signal fromPlanckand, when possible, the galaxy optical and infrared (IR) properties based on two photometric redshift catalogues: 2MPZ and WISExSCOS. From the tSZ data, we measured the gas pressure in the clusters and in the inter-cluster filaments. In the case of A399-A401, the results are in perfect agreement with previous studies and, using the temperature measured from the X-rays, we further estimate the gas density in the filament and findn0= (4.3 ± 0.7) × 10-4cm-3. The optical and IR colour–colour and colour–magnitude analyses of the galaxies selected in the cluster system, together with their star formation rate, show no segregation between galaxy populations, both in the clusters and in the filament of A399-A401. Galaxies are all passive, early type, and red and dead. The gas and galaxy properties of this system suggest that the whole system formed at the same time and corresponds to a pre-merger, with a cosmic filament gas heated by the collapse. For the other cluster system, the tSZ analysis was performed and the pressure in the clusters and in the inter-cluster filament was constrained. However, the limited or nonexistent optical and IR data prevent us from concluding on the presence of an actual cosmic filament or from proposing a scenario.
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Lee, Jong Chul, Ho Seong Hwang i Hyunmi Song. "Searching for Mg ii absorbers in and around galaxy clusters". Monthly Notices of the Royal Astronomical Society 503, nr 3 (5.03.2021): 4309–19. http://dx.doi.org/10.1093/mnras/stab637.
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ABSTRACT To study environmental effects on the circumgalactic medium (CGM), we use the samples of redMaPPer galaxy clusters, background quasars, and cluster galaxies from the Sloan Digital Sky Survey (SDSS). With ∼82 000 quasar spectra, we detect 197 Mg ii absorbers in and around the clusters. The detection rate per quasar is 2.7 ± 0.7 times higher inside the clusters than outside the clusters, indicating that Mg ii absorbers are relatively abundant in clusters. However, when considering the galaxy number density, the absorber-to-galaxy ratio is rather low inside the clusters. If we assume that Mg ii absorbers are mainly contributed by the CGM of massive star-forming galaxies, a typical halo size of cluster galaxies is smaller than that of field galaxies by 30 ± 10 per cent. This finding supports that galaxy haloes can be truncated by interaction with the host cluster.
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Lotz, Marcel, Rhea-Silvia Remus, Klaus Dolag, Andrea Biviano i Andreas Burkert. "Gone after one orbit: How cluster environments quench galaxies". Monthly Notices of the Royal Astronomical Society 488, nr 4 (30.07.2019): 5370–89. http://dx.doi.org/10.1093/mnras/stz2070.
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ABSTRACT The effect of galactic orbits on a galaxy’s internal evolution within a galaxy cluster environment has been the focus of heated debate in recent years. To understand this connection, we use both the $(0.5 \,$Gpc)3 and the Gpc3 boxes from the cosmological hydrodynamical simulation set Magneticum Pathfinder. We investigate the velocity anisotropy, phase space, and the orbital evolution of up to ∼5 × 105 resolved satellite galaxies within our sample of 6776 clusters with $M_{\mathrm{vir}}\,\, \gt\,\, 10^{14} \, \mathrm{M_{\odot }}$ at low redshift, which we also trace back in time. In agreement with observations, we find that star-forming satellite galaxies inside galaxy clusters are characterized by more radially dominated orbits, independent of cluster mass. Furthermore, the vast majority of star-forming satellite galaxies stop forming stars during their first passage. We find a strong dichotomy both in line-of-sight and radial phase space between star-forming and quiescent galaxies, in line with observations. The tracking of individual orbits shows that the star formation of almost all satellite galaxies drops to zero within $1 \, \mathrm{Gyr}$ after infall. Satellite galaxies that are able to remain star forming longer are characterized by tangential orbits and high stellar mass. All this indicates that in galaxy clusters the dominant quenching mechanism is ram-pressure stripping.
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De Propris, Roberto, Malcolm N. Bremer i Steven Phillipps. "Luminosity functions of cluster galaxies". Astronomy & Astrophysics 618 (październik 2018): A180. http://dx.doi.org/10.1051/0004-6361/201833630.
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We derive NUV luminosity functions for 6471 NUV detected galaxies in 28 0.02 < z < 0.08 clusters and consider their dependence on cluster properties. We consider optically red and blue galaxies and explore how their NUV LFs vary in several cluster subsamples, selected to best show the influence of environment. Our composite LF is well fit by the Schechter form with M*NUV = −18.98 ± 0.07 and α = −1.87 ± 0.03 in good agreement with values for the Coma centre and the Shapley supercluster, but with a steeper slope and brighter L* than in Virgo. The steep slope is due to the contribution of massive quiescent galaxies that are faint in the NUV. There are significant differences in the NUV LFs for clusters having low and high X-ray luminosities and for sparse and dense clusters, though none are particularly well fitted by the Schechter form, making a physical interpretation of the parameters difficult. When splitting clusters into two subsamples by X-ray luminosity, the ratio of low to high NUV luminosity galaxies is higher in the high X-ray luminosity subsample (i.e., the luminosity function is steeper across the sampled luminosity range). In subsamples split by surface density, when characterised by Schechter functions the dense clusters have an M* about a magnitude fainter than that of the sparse clusters and α is steeper (−1.9 vs. −1.6, respectively). The differences in the data appear to be driven by changes in the LF of blue (star-forming) galaxies. This appears to be related to interactions with the cluster gas. For the blue galaxies alone, the luminosity distributions indicate that for high LX and high velocity dispersion cluster subsamples (i.e., the higher mass clusters), there are relatively fewer high UV luminosity galaxies (or correspondingly a relative excess of low UV luminosity galaxies) in comparison the lower mass cluster subsamples.
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Kotecha, Sachin, Charlotte Welker, Zihan Zhou, James Wadsley, Katarina Kraljic, Jenny Sorce, Elena Rasia i in. "Cosmic filaments delay quenching inside clusters". Monthly Notices of the Royal Astronomical Society 512, nr 1 (10.02.2022): 926–44. http://dx.doi.org/10.1093/mnras/stac300.
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ABSTRACT We investigate how large-scale cosmic filaments impact the quenching of galaxies within one virial radius of 324 simulated clusters from The Three Hundred project. We track cosmic filaments with the versatile, observation-friendly program DisPerSE and identify haloes hosting galaxies with VELOCIRaptor. We find that cluster galaxies close to filaments tend to be more star forming, bluer, and contain more cold gas than their counterparts further away from filaments. This effect is recovered at all stellar masses. This is in stark contrast with galaxies residing outside of clusters, where galaxies close to filaments show clear signs of density related pre-processing. We first show that the density contrast of filaments is reduced inside the intra-cluster medium. Moreover, examination of flows around and into cluster galaxies shows that the gas flows in intra-cluster filaments are colder and tend to stream along with galaxies in their midst, partially shielding them from strangulation by the hot, dense intra-cluster medium. This also preserves accretion on to satellites and limit ram pressure.
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Pallero, Diego, Facundo A. Gómez, Nelson D. Padilla, S. Torres-Flores, R. Demarco, P. Cerulo i D. Olave-Rojas. "Tracing the quenching history of cluster galaxies in the EAGLE simulation". Monthly Notices of the Royal Astronomical Society 488, nr 1 (27.06.2019): 847–58. http://dx.doi.org/10.1093/mnras/stz1745.
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ABSTRACT We use the Evolution and Assembly of GaLaxies and their Environments (EAGLE) hydrodynamical simulation to trace the quenching history of galaxies in its 10 most massive clusters. We use two criteria to identify moments when galaxies suffer significant changes in their star formation activity: (i) the instantaneous star formation rate (SFR) strongest drop, $\Gamma _{\rm SFR}^{\rm SD}$, and (ii) a ‘quenching’ criterion based on a minimum threshold for the specific SFR of ≲10$^{-11}\,\rm yr^{-1}$. We find that a large fraction of galaxies (${\gtrsim} 60\,{\rm per\,cent}$) suffer their $\Gamma _{\rm SFR}^{\rm SD}$ outside the cluster’s R200. This ‘pre-processed’ population is dominated by galaxies that are either low mass and centrals or inhabit low-mass hosts (1010.5 ≲ Mhost ≲ 1011.0 M⊙). The host mass distribution is bimodal, and galaxies that suffered their $\Gamma _{\rm SFR}^{\rm SD}$ in massive hosts ($10^{13.5} \lesssim M_{\rm host} \lesssim 10^{14.0}\, \mathrm{M}_{\odot }$) are mainly processed within the clusters. Pre-processing mainly limits the total stellar mass with which galaxies arrive in the clusters. Regarding quenching, galaxies preferentially reach this state in high-mass haloes ($10^{13.5} \lesssim M_{\rm host} \lesssim 10^{14.5}\, \mathrm{M}_{\odot }$). The small fraction of galaxies that reach the cluster already quenched have also been pre-processed, linking both criteria as different stages in the quenching process of those galaxies. For the z = 0 satellite populations, we find a sharp rise in the fraction of quenched satellites at the time of first infall, highlighting the role played by the dense cluster environment. Interestingly, the fraction of pre-quenched galaxies rise with final cluster mass. This is a direct consequence of the hierarchical cosmological model used in these simulations.
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Schaeffer, Richard. "Galaxies, Clusters and Fluctuations". Symposium - International Astronomical Union 130 (1988): 215–20. http://dx.doi.org/10.1017/s007418090013606x.
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The luminosity function of galaxies and clusters as well as their correlations can be calculated assuming the many-body correlation functions are scale invariant. The same hypothesis leads to predictions on the fractal dimension of the galaxy distribution. The latter is found to be bifractal that is characterized by two dimensions D=3−γ in the cluster region, and D = (3−γ)(2+α) in the nearly empty regions, α being the index introduced by Schechter for the galaxy luminosity function. Finally, the same models lead to predictions for the evolution of the cluster and x-ray luminosity functions, as well as for the Sunyaev-Zeldovich effect due to all virialized clusters, which is found to be large and to produce fluctuations of order 10−5 at sub-arc minute scalar in the microwave background.
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Amirkhanian, A. S., A. G. Egikian, H. Tiersch i D. Stoll. "AGNs in Shakhbazian Compact Groups". International Astronomical Union Colloquium 184 (2002): 87–88. http://dx.doi.org/10.1017/s0252921100030505.
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The results of CCD spectroscopic observations of Shakhbazian compact groups of galaxies (SHCGs) with the 1.54-m (La Silla, Chile), 2.2-m (Calar Alto, Spain) and 2.6-m (Byurakan) telescopes are presented. According to these preliminary data, about 10% of member galaxies in SHCGs are emission-line galaxies (ELGs) including the broad-line AGNs (of classical Seyfert 1 type) and the narrow-emission-line galaxies.A research program has been developed in the University of Potsdam, Potsdam Astrophysikalisches Institut in cooperation with other observatories (particularly with Byurakan Astrophysical Observatory) to perform photometric and spectroscopic investigations of galaxies in the SHCGs. Within the framework of this program the redshift (radial velocity) measurements have been carried out for more than 200 galaxies in 36 SHCGs. The MIDAS software package was used for processing and interpreting of the galaxy spectra. Most of these redshifts were measured for the first time. 180 member galaxies (90%) in these groups have absorption spectra typical of E and SO galaxies. Twenty galaxies (10%) turn out to be ELGs. They are in the range 0.02 ≤ z ≤ 0.17, i.e., the SHCGs lie in approximately the same redshift space as Abell clusters. These compact groups contain predominantly elliptical and lenticular galaxies (del Olmo 1988; Amirkhanian 1989) like the cores of rich, regular, centrally condensed clusters of galaxies. The fraction of spirals falls in the densest matter concentrations. On the other hand, it is a well-established fact that in the local universe the active objects tend to avoid the cores of dense clusters of galaxies (e.g. Green and Yee 1984). That is why the discovery of an emission-line population with broad-line AGNs in SHCGs (Tiersch et al. 1999) was unexpected. As shown by Dressier, Thompson and Shectman (1985) in their sample of 1268 galaxies in the feilds of 14 rich clusters the ELGs comprise 31% of the field galaxies but only 7% of the cluster galaxies. Similarly, according to their statistics AGNs make up 5% of the field sample, but only 1% of the cluster sample. They note that the difference in the distribution of morphological types can only partially explain this effect. Obviously, some sort of environmental influence is present.
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Ali, Sadman S., Malcolm N. Bremer, Steven Phillipps i Roberto De Propris. "Environmental effects on the UV upturn in local clusters of galaxies". Monthly Notices of the Royal Astronomical Society 487, nr 3 (3.06.2019): 3021–28. http://dx.doi.org/10.1093/mnras/stz1502.
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ABSTRACT We explore the dependence of ultraviolet (UV) upturn colours in early-type cluster galaxies on the properties of their parent clusters (such as velocity dispersion and X-ray luminosity) and on the positions and kinematics of galaxies within them. We use a sample of 24 nearby clusters with highly complete spectroscopy and optical/infrared data to select a suitable sample of red-sequence galaxies, whose far-ultraviolet and NUV magnitudes we measure from archival GALEX data. Our results show that the UV upturn colour has no dependence on cluster properties and has the same range in all clusters. There is also no dependence on the projected position within clusters or on line-of-sight velocity. Therefore, our conclusion is that the UV upturn phenomenon is an intrinsic feature of cluster early-type galaxies, irrespective of their cluster environment.
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Tonry, John L. "Properties of cD Galaxies". Symposium - International Astronomical Union 127 (1987): 89–98. http://dx.doi.org/10.1017/s0074180900185080.
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cD galaxies are the most luminous galaxies in the universe. They are characterized by a surface brightness profile that falls off more slowly with radius than most elliptical galaxies. In most respects D galaxies are a continuous extrapolation from other ellipticals: their M/L and their colors are comparable to other ellipticals, their inner parts are fitted by an r1/4 law, and they follow the same relation between L and σ. On the other hand, their luminosity is too bright to be consistent with the luminosity function of other ellipticals and they are always found at the center of a cluster of other galaxies. Being at the center of a cluster of galaxies often endows D galaxies with a very faint, very extended halo of luminosity and multiple nuclei, but these are more properly associated with the cluster than the D galaxy itself. The connection between the formation of cD galaxies and the formation of clusters remains a mystery. It is still unresolved whether cDs are a byproduct of cluster evolution, whether they formed in parallel with clusters, or whether primeval D are galaxies the seed around which clusters accreted.
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Tawfeek, Amira A., Bernardo Cervantes Sodi, Jacopo Fritz, Alessia Moretti, David Pérez-Millán, Marco Gullieuszik, Bianca M. Poggianti, Benedetta Vulcani i Daniela Bettoni. "Morphology Driven Evolution of Barred Galaxies in OMEGAWINGS Clusters". Astrophysical Journal 940, nr 1 (1.11.2022): 1. http://dx.doi.org/10.3847/1538-4357/ac9976.
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Abstract We present a study of barred galaxies in the cluster environment, exploiting a sample of galaxies drawn from the extended WIde-field Nearby Galaxy-cluster Survey (OmegaWINGS) that covers up to the outer regions of 32 local X-ray selected clusters. Barred galaxies are identified through a semiautomatic analysis of ellipticity and position angle profiles. We find, in agreement with previous studies, a strong codependence of the bar fraction with the galaxy stellar mass and morphological type, being maximum for massive late-type galaxies. The fraction of barred galaxies decreases with increasing cluster mass and with decreasing clustercentric distance, a dependence that vanishes once we control for morphological type, which indicates that the likelihood of a galaxy hosting a bar in the cluster environment is determined by its morphological transformation. At large clustercentric distances, we detect a dependence on the distance to the nearest neighbor galaxy, suggesting that tidal forces with close companions are able to suppress the formation of bars or even destroy them. Barred galaxies in our sample are either early-type, star-forming galaxies located within the virial radii of the clusters or late-type quenched galaxies found beyond the virial radii of the clusters. We propose a scenario in which already quenched barred galaxies that fall into the clusters are centrally rejuvenated by the interplay of the perturbed gas by ram pressure and the bar, in galaxies that are undergoing a morphological transformation.
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Tomooka, Paxton, Eduardo Rozo, Erika L. Wagoner, Han Aung, Daisuke Nagai i Sasha Safonova. "Clusters have edges: the projected phase-space structure of SDSS redMaPPer clusters". Monthly Notices of the Royal Astronomical Society 499, nr 1 (23.09.2020): 1291–99. http://dx.doi.org/10.1093/mnras/staa2841.
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ABSTRACT We study the distribution of line-of-sight velocities of galaxies in the vicinity of Sloan Digital Sky Survey (SDSS) red-sequence Matched-filter Probabilistic Percolation (redMaPPer) galaxy clusters. Based on their velocities, galaxies can be split into two categories: galaxies that are dynamically associated with the cluster, and random line-of-sight projections. Both the fraction of galaxies associated with the galaxy clusters, and the velocity dispersion of the same, exhibit a sharp feature as a function of radius. The feature occurs at a radial scale Redge ≈ 2.2Rλ, where Rλ is the cluster radius assigned by redMaPPer. We refer to Redge as the ‘edge radius’. These results are naturally explained by a model that further splits the galaxies dynamically associated with a galaxy cluster into a component of galaxies orbiting the halo and an infalling galaxy component. The edge radius Redge constitutes a true ‘cluster edge’, in the sense that no orbiting structures exist past this radius. A companion paper tests whether the ‘halo edge’ hypothesis holds when investigating the full three-dimensional phase-space distribution of dark matter substructures in numerical simulations, and demonstrates that this radius coincides with a suitably defined splashback radius.
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Henriksen, Mark J., i Prajwal Panda. "Exploiting Machine Learning and Disequilibrium in Galaxy Clusters to Obtain a Mass Profile". Astrophysical Journal Letters 961, nr 2 (25.01.2024): L36. http://dx.doi.org/10.3847/2041-8213/ad1ede.
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Abstract We use 3D k-means clustering to characterize galaxy substructure in the A2146 cluster of galaxies (z = 0.2343). This method objectively characterizes the cluster’s substructure using projected position and velocity data for 67 galaxies within a 2.305 Mpc circular region centered on the cluster's optical center. The optimal number of substructures is found to be four. Four distinct substructures with rms velocity typical of galaxy groups or low-mass subclusters, when compared to cosmological simulations of galaxy cluster formation, suggest that A2146 is in the early stages of formation. We utilize this disequilibrium, which is so prevalent in galaxy clusters at all redshifts, to construct a radial mass distribution. Substructures are bound but not virialized. This method is in contrast to previous kinematical analyses, which have assumed virialization, and ignored the ubiquitous clumping of galaxies. The best-fitting radial mass profile is much less centrally concentrated than the well-known Navarro–Frenk–White profile, indicating that the dark-matter-dominated mass distribution is flatter pre-equilibrium, becoming more centrally peaked in equilibrium through the merging of the substructure.
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Suran, M. D., i N. A. Popescu. "Colour Gradients in Clusters of Galaxies". Symposium - International Astronomical Union 186 (1999): 405–6. http://dx.doi.org/10.1017/s0074180900113208.
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Wen, Z. L., i J. L. Han. "Photometric redshifts for galaxies in the Subaru Hyper Suprime-Cam and unWISE and a catalogue of identified clusters of galaxies". Monthly Notices of the Royal Astronomical Society 500, nr 1 (27.10.2020): 1003–17. http://dx.doi.org/10.1093/mnras/staa3308.
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ABSTRACT We first present a catalogue of photometric redshifts for 14.68 million galaxies derived from the 7-band photometric data of Hyper Suprime-Cam Subaru Strategic Program and the Wide-field Infrared Survey Explorer using the nearest-neighbour algorithm. The redshift uncertainty is about 0.024 for galaxies of z ≤ 0.7, and steadily increases with redshift to about 0.11 at z ∼ 2. From such a large data set, we identify 21 661 clusters of galaxies, among which 5537 clusters have redshifts z > 1 and 642 clusters have z > 1.5, significantly enlarging the high redshift sample of galaxy clusters. Cluster richness and mass are estimated, and these clusters have an equivalent mass of M500 ≥ 0.7 × 1014 M⊙. We find that the stellar mass of the brightest cluster galaxies (BCGs) in each richness bin does not significantly evolve with redshift. The fraction of star-forming BCGs increases with redshift, but does not depend on cluster mass.
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Côté, Patrick, Laura Ferrarese, Andrés Jordán, John P. Blakeslee, Chin-Wei Chen, Leopoldo Infante, Simona Mei, Eric W. Peng, John L. Tonry i Michael J. West. "An Update on the ACS Virgo and Fornax Cluster Surveys". Proceedings of the International Astronomical Union 3, S246 (wrzesień 2007): 377–86. http://dx.doi.org/10.1017/s1743921308016013.
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AbstractWe present a brief update on the ACS Virgo and Fornax Cluster Surveys —Hubble Space Telescopeprograms to obtainACSimaging for 143 early-type galaxies in the two galaxy clusters nearest to the Milky Way. We summarize a selection of science highlights from the surveys as including new results on the central structure of early-type galaxies, the apparent continuity of photometric and structural parameters between dwarf and giant galaxies, and the properties of globular clusters, diffuse star clusters and ultra-compact dwarf galaxies.
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Harris, William E. "Massive star clusters in galaxies". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 368, nr 1913 (28.02.2010): 889–906. http://dx.doi.org/10.1098/rsta.2009.0256.
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The ensemble of all star clusters in a galaxy constitutes its star cluster system . In this review, the focus of the discussion is on the ability of star clusters, particularly the systems of old massive globular clusters (GCs), to mark the early evolutionary history of galaxies. I review current themes and key findings in GC research, and highlight some of the outstanding questions that are emerging from recent work.
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Olsen, Knut, Bryan Miller, Robert Schommer, Nick Suntzeff i John Bright. "The Globular Cluster Systems of the Sculptor Group". Symposium - International Astronomical Union 207 (2002): 275–80. http://dx.doi.org/10.1017/s0074180900223851.
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We present results from a study to identify the globular cluster systems of six of the brightest galaxies of the Sculptor Group. From Mosaic IICMRimages of the area surrounding the galaxies NGC 45, NGC 55, NGC 247, NGC 253, NGC 300, and NGC 7793, we identify cluster candidates through their morphology, luminosity, and color. We show that many of the Milky Way's globular clusters would appear extended in our images if placed in the Sculptor Group; only in the two most distant galaxies, NGC 45 and NGC 7793, is the discrimination difficult. We find 50–100 candidates per galaxy with integrated properties similar to Milky Way clusters. Published spectroscopic identifications of candidates in NGC 253 lead us to expect that ∼50% of the candidates are true clusters, while the remainder are background galaxies. Study of the Sculptor Group galaxies increases the sample of late-type spiral and Magellanic-type galaxies with known globular cluster systems from 2 to ∼10.
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Roberts, I. D., R. J. van Weeren, S. L. McGee, A. Botteon, A. Ignesti i H. J. A. Rottgering. "LoTSS jellyfish galaxies". Astronomy & Astrophysics 652 (sierpień 2021): A153. http://dx.doi.org/10.1051/0004-6361/202141118.
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Ram pressure stripping is a frequently cited mechanism for quenching galaxy star formation in dense environments. Numerous examples of ram pressure stripping in galaxy clusters are present in literature; however, substantially less work has been focused on ram pressure stripping in lower-mass groups, the most common galaxy environment in the local Universe. In this work we use the LOFAR Two-metre Sky Survey (LoTSS) to search for jellyfish galaxies (i.e., galaxies with ram pressure stripped tails extending beyond the optical disk) in ∼500 SDSS groups (z < 0.05), making this the most comprehensive search for ram pressure stripping in groups to date. We identify 60 jellyfish galaxies in groups with extended, asymmetric radio continuum tails, which are found across the entire range of group mass from 1012.5 < Mgroup < 1014 h−1 M⊙. We compare the group jellyfish galaxies identified in this work with the LoTSS jellyfish galaxies in clusters presented in a recent work, allowing us to compare the effects of ram pressure stripping across three decades in group and cluster mass. We find that jellyfish galaxies are most commonly found in clusters, with the frequency decreasing towards the lowest-mass groups. Both the orientation of observed radio continuum tails and the positions of group jellyfish galaxies in phase space suggest that galaxies are stripped more slowly in groups relative to clusters. Finally, we find that the star formation rates of jellyfish galaxies in groups are consistent with ‘normal’ star-forming group galaxies, which is in contrast to cluster jellyfish galaxies that have clearly enhanced star formation rates. On the whole, there is clear evidence for ongoing ram pressure stripping in galaxy groups (down to very low group masses), though the frequency of jellyfish galaxies and the strength of ram pressure stripping appear lower in groups than in clusters. Differences in the efficiency of ram pressure stripping in groups versus clusters likely contribute to the positive trend between the quenched fraction and host halo mass observed in the local Universe.
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Karick, A. M. "Perhaps They are not Globular Clusters After All". Highlights of Astronomy 13 (2005): 201. http://dx.doi.org/10.1017/s1539299600015677.
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AbstractOur 2dF Fornax Cluster Spectroscopic Survey (FCSS) and follow-up work in the Virgo Cluster have shown that the cores of both galaxy clusters contain a previously-unknown class of object, ultra-compact dwarf (UCD) galaxies. We present high resolution spectroscopy and deep multicolor imaging to show that these enigmatic objects are dynamically distinct from both globular clusters (GCs) and nucleated dwarf galaxies (dE,Ns). Our hypothesis for their origin may explain the observed high “specific frequency” of GCs in central cluster galaxies.
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Kroupa, Pavel. "The influence of star clusters on galactic disks: new insights in star-formation in galaxies". Proceedings of the International Astronomical Union 4, S254 (czerwiec 2008): 209–20. http://dx.doi.org/10.1017/s1743921308027610.
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AbstractStars form in embedded star clusters which play a key role in determining the properties of a galaxy's stellar population. A large fraction of newly born massive stars are shot out from dynamically unstable embedded-cluster cores spreading them to large distances before they explode. Embedded clusters blow out their gas once the feedback energy from the new stellar population overcomes its binding energy, leading to cluster expansion and in many cases dissolution into the galaxy. Galactic disks may be thickened by such processes, and some thick disks may be the result of an early epoch of vigorous star-formation. Binary stellar systems are disrupted in clusters leading to a lower fraction of binaries in the field, while long-lived clusters harden degenerate-stellar binaries such that the SNIa rate may increase by orders of magnitude in those galaxies that were able to form long-lived clusters. The stellar initial mass function of the whole galaxy must be computed by adding the IMFs in the individual clusters. The resulting integrated galactic initial mass function (IGIMF) is top-light for SFRs < 10 M⊙/yr, and its slope and, more importantly, its upper stellar mass limit depend on the star-formation rate (SFR), explaining naturally the mass–metallicity relation of galaxies. Based on the IGIMF theory, the re-calibrated Hα-luminosity–SFR relation implies dwarf irregular galaxies to have the same gas-depletion time-scale as major disk galaxies, implying a major change of our concept of dwarf-galaxy evolution. A galaxy transforms about 0.3 per cent of its neutral gas mass every 10 Myr into stars. The IGIMF-theory also naturally leads to the observed radial Hα cutoff in disk galaxies without a radial star-formation cutoff. It emerges that the thorough understanding of the physics and distribution of star clusters may be leading to a major paradigm shift in our understanding of galaxy evolution.
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Pfeffer, Joel, Kenji Bekki, Warrick J. Couch, Bärbel S. Koribalski i Duncan A. Forbes. "The age gradients of galaxies in EAGLE: outside-in quenching as the origin of young bulges in cluster galaxies". Monthly Notices of the Royal Astronomical Society 511, nr 1 (12.01.2022): 1072–84. http://dx.doi.org/10.1093/mnras/stac074.
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ABSTRACT Many disc galaxies in clusters have been found with bulges of similar age or younger than their surrounding discs, at odds with field galaxies of similar morphology and their expected inside-out formation. We use the Evolution and Assembly of GaLaxies and their Environments (EAGLE) simulations to test potential origins for this difference in field and cluster galaxies. We find, in agreement with observations, that on average disc-dominated field galaxies in the simulations have older inner regions, while similar galaxies in groups and clusters have similarly aged or younger inner regions. This environmental difference is a result of outside-in quenching of the cluster galaxies. Prior to group/cluster infall, galaxies of a given present-day mass and morphology exhibit a similar evolution in their specific star formation rate (sSFR) profiles. Post-infall, the outer sSFRs of group and cluster galaxies significantly decrease due to interstellar medium stripping, while the central sSFR remains similar to field galaxies. Field disc galaxies instead generally retain radially increasing sSFR profiles. Thus, field galaxies continue to develop negative age gradients (younger discs), while cluster galaxies instead develop positive age gradients (younger bulges).
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Werner, S. V., N. A. Hatch, A. Muzzin, R. F. J. van der Burg, M. L. Balogh, G. Rudnick i G. Wilson. "Satellite quenching was not important for z ∼ 1 clusters: most quenching occurred during infall". Monthly Notices of the Royal Astronomical Society 510, nr 1 (3.12.2021): 674–86. http://dx.doi.org/10.1093/mnras/stab3484.
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ABSTRACT We quantify the relative importance of environmental quenching versus pre-processing in z ∼ 1 clusters by analysing the infalling galaxy population in the outskirts of 15 galaxy clusters at 0.8 < z < 1.4 drawn from the GOGREEN and GCLASS surveys. We find significant differences between the infalling galaxies and a control sample; in particular, an excess of massive quiescent galaxies in the infalling region. These massive infalling galaxies likely reside in larger dark matter haloes than similar-mass control galaxies because they have twice as many satellite galaxies. Furthermore, these satellite galaxies are distributed in an NFW profile with a larger scale radius compared to the satellites of the control galaxies. Based on these findings, we conclude that it may not be appropriate to use ‘field’ galaxies as a substitute for infalling pre-cluster galaxies when calculating the efficiency and mass dependence of environmental quenching in high-redshift clusters. By comparing the quiescent fraction of infalling galaxies at 1 < R/R200<3 to the cluster sample (R/R200<1) we find that almost all quiescent galaxies with masses >1011 M⊙ were quenched prior to infall, while up to half of lower mass galaxies were environmentally quenched after passing the virial radius. This means most of the massive quiescent galaxies in z ∼ 1 clusters were self-quenched or pre-processed prior to infall.
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Lee, Seong-Kook, Myungshin Im, Eunhee Ko, Changbom Park, Juhan Kim, Jaehyun Lee i Minhee Hyun. "Star-formation Property of High Redshift Galaxies in Clusters: Perceptive View from Observation and Simulation". Proceedings of the International Astronomical Union 17, S373 (sierpień 2021): 260–63. http://dx.doi.org/10.1017/s1743921322004409.
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AbstractThe evolution of star formation properties of galaxies depends on the environment where galaxies reside, and generally star formation of galaxies in dense environment decreases more quickly. Interestingly, the star formation property of high-redshift galaxies clusters vary largely even though they are at similar redshift. We have found that the large-scale environment surrounding each galaxy cluster can contribute to make this cluster-by-cluster variation. This correlation is found in the results from observational data as well as in the simulations of galaxy formation. We suggest the ‘Web-feeding model’ to explain this trend. Star-forming galaxies falling into the galaxy cluster from surrounding large-scale structure make the quiescent galaxy fraction of the cluster lower than relatively isolated clusters.
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Horta, Danny, Meghan E. Hughes, Joel L. Pfeffer, Nate Bastian, J. M. Diederik Kruijssen, Marta Reina-Campos i Rob A. Crain. "Linking globular cluster formation at low and high redshift through the age–metallicity relation in E-MOSAICS". Monthly Notices of the Royal Astronomical Society 500, nr 4 (12.11.2020): 4768–78. http://dx.doi.org/10.1093/mnras/staa3522.
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ABSTRACT We set out to compare the age–metallicity relation (AMR) of massive clusters from Magellanic Cloud mass galaxies in the E-MOSAICS suite of numerical cosmological simulations with an amalgamation of observational data of massive clusters in the Large and Small Magellanic Clouds (LMC/SMC). We aim to test if: (i) star cluster formation proceeds according to universal physical processes, suggestive of a common formation mechanism for young-massive clusters (YMCs), intermediate-age clusters (IACs), and ancient globular clusters (GCs); (ii) massive clusters of all ages trace a continuous AMR; and (iii) the AMRs of smaller mass galaxies show a shallower relation when compared to more massive galaxies. Our results show that, within the uncertainties, the predicted AMRs of L/SMC-mass galaxies with similar star formation histories to the L/SMC follow the same relation as observations. We also find that the metallicity at which the AMR saturates increases with galaxy mass, which is also found for the field star AMRs. This suggests that relatively low-metallicity clusters can still form in dwarfs galaxies. Given our results, we suggest that ancient GCs share their formation mechanism with IACs and YMCs, in which GCs are the result of a universal process of star cluster formation during the early episodes of star formation in their host galaxies.
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Vikhlinin, Alexei A., Andrei V. Kravtsov, Maxim L. Markevich, Rashid A. Syunyaev i Evgenii M. Churazov. "Clusters of galaxies". Uspekhi Fizicheskih Nauk 184, nr 4 (2014): 339–66. http://dx.doi.org/10.3367/ufnr.0184.201404a.0339.
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Blanchard, Alain. "Clusters of galaxies". New Astronomy Reviews 45, nr 4-5 (marzec 2001): 401–7. http://dx.doi.org/10.1016/s1387-6473(00)00162-7.
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BÖHRINGER, HANS. "Clusters of Galaxies". Annals of the New York Academy of Sciences 759, nr 1 (wrzesień 1995): 67–86. http://dx.doi.org/10.1111/j.1749-6632.1995.tb17517.x.
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Vikhlinin, A. A., A. V. Kravtsov, M. L. Markevich, R. A. Sunyaev i E. M. Churazov. "Clusters of galaxies". Physics-Uspekhi 57, nr 4 (30.04.2014): 317–41. http://dx.doi.org/10.3367/ufne.0184.201404a.0339.
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Hamabata, Akinari, Taira Oogi, Masamune Oguri, Takahiro Nishimichi i Masahiro Nagashima. "New constraints on red-spiral galaxies from their kinematics in clusters of galaxies". Monthly Notices of the Royal Astronomical Society 488, nr 3 (25.07.2019): 4117–25. http://dx.doi.org/10.1093/mnras/stz1991.
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ABSTRACTThe distributions of the pairwise line-of-sight velocity between galaxies and their host clusters are segregated according to the galaxy’s colour and morphology. We investigate the velocity distribution of red-spiral galaxies, which represents a rare population within galaxy clusters. We find that the probability distribution function of the pairwise line-of-sight velocity vlos between red-spiral galaxies and galaxy clusters has a dip at vlos = 0, which is a very odd feature, at 93 per cent confidence level. To understand its origin, we construct a model of the phase-space distribution of galaxies surrounding galaxy clusters in three-dimensional space by using cosmological N-body simulations. We adopt a two component model that consists of the infall component, which corresponds to galaxies that are now falling into galaxy clusters, and the splashback component, which corresponds to galaxies that are on their first (or more) orbit after falling into galaxy clusters. We find that we can reproduce the distribution of the line-of-sight velocity of red-spiral galaxies with the dip with a very simple assumption that red-spiral galaxies reside predominantly in the infall component, regardless of the choice of the functional form of their spatial distribution. Our results constrain the quenching time-scale of red-spiral galaxies to a few Gyr, and the radius where the morphological transformation is effective as $r \sim 0.2 \, h^{-1 } \, \rm {Mpc}$.
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de Grijs, Richard. "From nuclear clusters to halo globulars: Star clusters as basic galactic building blocks". Proceedings of the International Astronomical Union 2, S235 (sierpień 2006): 48–51. http://dx.doi.org/10.1017/s1743921306005035.
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AbstractI assess the similarities and differences between the star-formation modes in quiescent spiral galaxies versus those in violent starburst regions, including galactic nuclei. As opposed to the quiescent star-formation mode, current empirical evidence on the star-formation processes in the extreme, high-pressure environments induced by galaxy encounters strongly suggests that star cluster formation is an important and perhaps even the dominant mode of star formation in such starburst events. This implies that by using star clusters as unique diagnostic probes, we can trace a galaxy's most violent star formation history very well, at least for the past few Gyr. The sizes, luminosities, and mass estimates of the young massive star clusters are entirely consistent with what is expected for young Milky Way-type globular clusters (GCs). Recent evidence lends support to the scenario that GCs, which were once thought to be the oldest building blocks of galaxies, are still forming today.
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Bettoni, Daniela, i Alessandro Omizzolo. "Faint Dwarf galaxies in nearby WINGS clusters: photometric characterization". Proceedings of the International Astronomical Union 14, S344 (sierpień 2018): 363–64. http://dx.doi.org/10.1017/s1743921318005240.
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AbstractIn the cores of galaxy clusters there is a population of lows-mass stellar systems such as dwarf Early-type galaxies, ultra-compact dwarf galaxies (UCDs) and ultra diffuse dwarf galaxies. We present here the photometric and morphological characterization of this population of objects using deep CFHT images of a sample of clusters belonging to the WINGS survey (0.04 < z < 0.06). We study only galaxies that are spectroscopically confirmed members of the cluster. The population of dwarfs ranges from ∽ 30% for the more rich clusters to ∽ 5-6% for the less rich ones.
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Hunt, Qiana, Rupali Chandar, Elena Gallo, Matthew Floyd, Thomas J. Maccarone i David A. Thilker. "The X-Ray Binary-star Cluster Connection in Late-type Galaxies". Astrophysical Journal 953, nr 2 (1.08.2023): 126. http://dx.doi.org/10.3847/1538-4357/ace162.
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Abstract We conduct one of the largest systematic investigations of bright X-ray binaries (XRBs) in both young star clusters and ancient globular clusters (GCs) using a sample of six nearby star-forming galaxies. Combining complete CXO X-ray source catalogs with optical Physics at High Angular Resolution in Nearby Galaxies-Hubble Space Telescope cluster catalogs, we identify a population of 33 XRBs within or near their parent clusters. We find that GCs that host XRBs in spiral galaxies appear to be brighter, more compact, denser, and more massive than the general GC population. However, these XRB hosts do not appear to be preferentially redder or more metal-rich, pointing to a possible absence of the metallicity-boosted formation of low-mass X-ray binaries (LMXBs) that is observed in the GCs of older galaxies. We also find that a smaller fraction of LMXBs is found in spiral GC systems when compared with those in early-type galaxies: between 8% and 50%, or an average of 20% across galaxies in our sample. Although there is a non-negligible probability of a chance superposition between an XRB and an unrelated young cluster, we find that among clusters younger than 10 Myr, which most likely host high-mass XRBs, the fraction of clusters associated with an XRB increases at higher cluster masses and densities. The X-ray luminosity of XRBs appears to increase with the mass of the cluster host for clusters younger than ∼400 Myr, while the inverse relation is found for XRBs in GCs.
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Vedder, C. J. G., i N. E. Chisari. "Galaxy clusters as intrinsic alignment tracers: present and future". Monthly Notices of the Royal Astronomical Society 500, nr 4 (26.11.2020): 5561–69. http://dx.doi.org/10.1093/mnras/staa3633.
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ABSTRACT Galaxies and clusters embedded in the large-scale structure of the Universe are observed to align in preferential directions. Galaxy alignment has been established as a potential probe for cosmological information, but the application of cluster alignments for these purposes remains unexplored. Clusters are observed to have a higher alignment amplitude than galaxies, but because galaxies are much more numerous, the trade-off in detectability between the two signals remains unclear. We present forecasts comparing cluster and galaxy alignments for two extragalactic survey set-ups: a currently available low-redshift survey (Sloan Digital Sky Survey, SDSS) and an upcoming higher redshift survey (Legacy Survey of Space and Time, LSST). For SDSS, we rely on the publicly available redmapper catalogue to describe the cluster sample. For LSST, we perform estimations of the expected number counts while we extrapolate the alignment measurements from SDSS. Clusters in SDSS have typically higher alignment signal-to-noise ratio (S/N) than galaxies. For LSST, the cluster alignment signals quickly wash out with redshift due to a relatively low number count and a decreasing alignment amplitude. Nevertheless, a potential strong suit of clusters is in their interplay with weak lensing: intrinsic alignments can be more easily isolated for clusters than for galaxies. The S/N of cluster alignment can in general be improved by isolating close pairs along the line of sight.
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Hilker, Michael. "Globular Cluster Systems in the Hydra I Galaxy Cluster". Symposium - International Astronomical Union 207 (2002): 281–86. http://dx.doi.org/10.1017/s0074180900223863.
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In this contribution, first results of deep VLT (V,I) photometry in the central region of the Hydra I galaxy cluster are presented. Many star clusters have been identified not only around several early-type galaxies, but also in the intra-cluster field, as far as 250 kpc from the cluster center. Outside the bulges of the central galaxies NGC 3311 and NGC 3309, the intra-cluster globular cluster system is dominated by blue clusters whose spatial distribution is similar to that of the (newly discovered) dwarf galaxies in Hydra I. The color distributions of globular clusters around NGC 3311 and NGC 3309 are multimodal, with a sharp blue peak and a slightly broader distribution of the red cluster population.
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Hattori, M. "A Metal Enriched Dark Cluster of Galaxies at Z = 1". Symposium - International Astronomical Union 187 (2002): 129–38. http://dx.doi.org/10.1017/s0074180900113841.
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Looking for and studying very distant galaxy clusters, clusters at z > 1, are one of the prime subjects of the modern observational cosmology. If the metallicity of the hot intra-cluster medium in very distant galaxy clusters is measured for example, it provides fruitful informations for us to understand the formation and evolution of galaxies. However, difficulty of the study is that there is few confirmed very distant galaxy clusters yet. We first have to search for very distant clusters but it requires very deep observations. A random selection of sky is not practical. We have to select the sky. In this article, it is demonstrated that missing lens problem has close connection with very distant cluster of galaxies and dark lens searches could open a new window for studying very distant cluster of galaxies.