Rich Clusters Of Galaxies Research Articles

Feedback and Brightest Cluster Galaxy Formation: ACS Observations of the Radio Galaxy TN J1338−1942 atz= 4.1

We present deep optical imaging of the z = 4.1 radio galaxy TN J1338-1942, obtained using the Advanced Camera for Surveys (ACS) on board the Hubble Space Telescope, as well as ground-based near-infrared imaging data from the European Southern Observatory (ESO) Very Large Telescope (VLT). The radio galaxy is known to reside within a large galaxy overdensity (both in physical extent and density contrast). There is good evidence that this region is the progenitor of a present-day rich galaxy cluster. TN J1338 is the dominant galaxy in the protocluster in terms of size and luminosity (in both the optical and near-infrared) and therefore seems destined to evolve into the brightest cluster galaxy. The high spatial resolution ACS images reveal several kiloparsec-scale features within and around the radio galaxy. The continuum light is aligned with the radio axis and is resolved into two clumps in the i775 and z850 bands. These components have luminosities ~109 L☉ and sizes of a few kpc. The estimated nebular continuum, scattered light, synchrotron- and inverse Compton-scattering contributions to the aligned continuum light are only a few percent of the observed total, indicating that the observed flux is likely dominated by forming stars. The estimated star formation rate for the whole radio galaxy is ~200 M☉ yr-1. A simple model in which the jet has triggered star formation in these continuum knots is consistent with the available data. A striking, but small, linear feature is evident in the z850 aligned light and may be indicative of a large-scale shock associated with the advance of the radio jet. The rest of the aligned light also seems morphologically consistent with star formation induced by shocks associated with the radio source, as seen in other high-z radio galaxies (e.g., 4C 41.17). An unusual feature is seen in Lyα emission. A wedge-shaped extension emanates from the radio galaxy perpendicularly to the radio axis. This naturally connects to the surrounding asymmetric, large-scale (~100 kpc) Lyα halo. We posit that the wedge is a starburst-driven superwind associated with the first major epoch of formation of the brightest cluster galaxy. The shock and wedge are examples of feedback processes due to both active galactic nucleus and star formation in the earliest stages of massive galaxy formation.

The Remnants of Intergalactic Supernovae

Intergalactic Type Ia supernovae (SNe) have been discovered recently in rich galaxy clusters. These SNe are likely the descendants of an intergalactic stellar population, which has been discovered in recent years through a variety of tracers. We estimate the observational signatures of the associated SN remnants (SNRs) in the unusual intracluster medium (ICM) environment. We find that if Type Ia SNe still have a circumstellar medium (CSM) at the time of explosion, then their remnants are visible in the optical for ~102-103 yr, with properties similar to young galactic SNRs. In contrast with galactic SNRs, in which the ejecta from the explosion interacts with the interstellar medium (ISM), intracluster SNRs become undetectable in the optical band once their ejecta passes beyond the CSM and enters the hot and tenuous ICM. If Type Ia SNe have a CSM, there should be ~150 young SNRs in the nearby Virgo Cluster, with an Hα luminosity of ~1035 ergs s-1 and an angular size of ~01. We investigate the possibility that members of this SNR population may have recently been detected but incorrectly identified as intergalactic H II regions. Alternatively, if optical intergalactic SNRs do not exist in Virgo, this will constitute evidence that Type Ia SNe are devoid of a CSM, with implications for progenitor scenarios. Regardless of the presence of a CSM, about 10 older SNRs per square degree should be detectable in Virgo in the radio band, with fluxes of order 0.1 mJy at 1 GHz. Their angular sizes (~1''), morphologies, and lack of optical association with distant galaxies can distinguish them from the much more numerous background population. Their detection would provide an accurate measurement of the intracluster SN rate. Deep pointed observations toward the site of SN 1980I, a possibly intergalactic Type Ia event in Virgo, could test for the existence of a CSM by comparison to our predictions for the early-time development of intergalactic SNRs.

CAIRNS: The Cluster and Infall Region Nearby Survey. III. Environmental Dependence of Hα Properties of Galaxies

We investigate the environmental dependence of star formation in cluster virial regions and infall regions as part of the Cluster and Infall Region Nearby Survey (CAIRNS), a large spectroscopic survey of the infall regions surrounding nine nearby rich clusters of galaxies. We use complete, homogeneous spectroscopic surveys of Ks-limited samples in eight of the CAIRNS clusters. Our long-slit spectroscopy yields estimates of star formation rates in environments from cluster cores to the general large-scale structure. Galaxies in infall regions probe whether processes affecting star formation are effective over scales larger than cluster virial regions. The fraction of galaxies with current star formation in their inner disks as traced by Hα emission increases with distance from the cluster and converges to the "field" value only at 2–3 virial radii, in agreement with other investigations. However, among galaxies with significant current star formation (EW[Hα] ≥ 2 Å), there is no difference in the distribution of EW[Hα] inside and outside the virial radius. This surprising result, first seen by Carter and coworkers, suggests that (1) star formation is truncated either on very short timescales or only at moderate and high redshifts or (2) that projection effects contaminate the measurement. We quantify the possible impact of mechanisms that only affect the outer parts of galaxies and thus might not be detected in this survey or any fiber-based survey. The number density profiles of star-forming and non-star-forming galaxies indicate that, among galaxies projected inside the virial radius, at least half the former and 20% of the latter are "infall interlopers," galaxies in the infall region but outside the virial region. We show that the kinematics of star-forming galaxies in the infall region closely match those of absorption-dominated galaxies. This result shows that the star-forming galaxies in the infall regions are not interlopers from the field and excludes one model of the backsplash scenario of galaxy transformation. Finally, we quantify systematic uncertainties in estimating the global star formation in galaxies from their inner disks.

Near-infrared imaging of 222 nearby H -strong galaxies from the Sloan Digital Sky Survey

We present UFTI K-band imaging observations of 222 galaxies that are selected from the Sloan Digital Sky Survey to have unusually strong Hδ absorption equivalent widths, W○(Hδ) > 4 A. Using GIM2D, the images are fit with two-dimensional surface brightness models consisting of a simple disk and bulge component to derive B/T, the fraction of luminosity in the bulge. We find that the galaxies with weak or absent Hα or [Oii]λ3727 emission (known as k+a galaxies) are predominantly bulge-dominated (with a mode of B/T~0.6), while galaxies with nebular emission (known as e[a] galaxies) are mostly disk-dominated (B/T~0.1). The morphologies and (r-k) colours of most k+a galaxies are inconsistent with the hypothesis that they result from the truncation of star formation in normal, spiral galaxies. However, their (u-g) and (r-k) colours, as well as their Hdelta line strengths, form a sequence that is well matched by a model in which >5 per cent of the stellar mass has been produced in a recent starburst. The lack of scatter in the dust-sensitive (r-k) colours suggests that the unusual spectra of k+a galaxies are not due to the effects of dust. The e(a) galaxies, on the other hand, have a colour distribution that is distinct from the k+a population, and typical of normal or dusty (τV∼ 2) spiral galaxies. We conclude that many e(a) galaxies are not progenitors of k+a galaxies, but are a separate phenomenon. Both k+a and e(a) galaxies reside in environments (characterized by the local density of galaxies brighter than Mr=-20) that are typical of normal galaxies and that are inconsistent with overdense regions like rich galaxy clusters

Spatially resolved spectroscopy of the E+A galaxies in thez= 0.32cluster AC 114

We present spatially resolved intermediate resolution spectroscopy of a sample of twelve E+A galaxies in the z=0.32 rich galaxy cluster AC 114, obtained with the FLAMES multi-integral field unit system on the European Southern Observatory's VLT. Previous integrated spectroscopy of all these galaxies by Couch & Sharples (1987) had shown them to have strong Balmer line absorption and an absence of [OII 3727] emission -- the defining characteristics of the``E+A'' spectral signature, indicative of an abrupt halt to a recent episode of quite vigorous star formation. We have used our spectral data to determine the radial variation in the strength of Hdelta absorption in these galaxies and hence map out the distribution of this recently formed stellar population. Such information provides important clues as to what physical event might have been responsible for this quite dramatic change in star formation activity in these galaxies' recent past. We find a diversity of behaviour amongst these galaxies in terms of the radial variation in Hdelta absorption: Four galaxies show little Hdelta absorption across their entire extent; it would appear they were misidentified as E+A galaxies in the earlier integrated spectroscopic studies. The remainder show strong Hdelta absorption, with a gradient that is either negative (Hdelta equivalent width decreasing with radius), flat, or positive. By comparing with numerical simulations we suggest that the first of these different types of radial behaviour provides evidence for a merger/interaction origin, whereas the latter two types of behaviour are more consistent with the truncation of star formation in normal disk galaxies. It would seem therefore that more than one physical mechanism is responsible for E+A formation in the same environment.

Optical and radio observations of a sample of 52 powerful ultra-steep spectrum radio sources

We present the results of radio (VLA) and optical (ESO/La Silla) imaging of a sample of 52 radio sources having an ultra-steep radio spectrum with α mostly steeper than −1.1 at decimetre wavelengths (median α = −1.22). Radio-optical overlays are presented to an astrometric accuracy of ∼1 �� . For 41 of the sources, radio spectral indices are newly determined using unpublished observations made with the 100-m Effelsberg radio telescope. For 14 of the sources identified with relatively brighter optical counterparts, spectroscopic observations were also carried out at La Silla and their redshifts are found to lie in the range 0.4 to 2.6. These observations have revealed three distant clusters of galaxies with redshifts of 0.55, 0.75 and 0.79, and we suggest that, together with an ultra-steep radio spectrum and relaxed radio morphology, the presence of a LINER spectrum in the optical can be used as a powerful indicator of rich clusters of galaxies. Additional candidates of this type in our sample are pointed out. Also, sources exhibiting particularly interesting radio-optical morphological relationships are highlighted. We further note the presence of six sources in our sample for which the optical counterpart (either detected or undetected) is fainter than R ∼ 24 and the radio extent is small (<10 �� ). These ultra-steep spectrum radio sources are good signposts for discovering massive galaxies out to very large redshifts.

Thermal Evolution of Supernova Iron in Elliptical Galaxies

Interpretations of the spatial distribution, abundance ratios, and global masses of metals in the hot gas of galaxy clusters in terms of supernova enrichment have been problematical. For example, the abundance of iron and other elements occasionally declines toward the center just where the stellar and supernova densities are highest. Also, the mass of gas-phase iron per unit stellar mass or light is lower in elliptical galaxies and groups than in rich galaxy clusters. We discuss hypothetical scenarios in which these abundance anomalies can result from the preferential buoyant separation of metals. However, in this and all previous attempts to explain these metallicity observations it has been assumed that all metals created by supernovae are present in either visible stars or the hot gas. We discuss here the possibility that some of the iron expelled into the hot gas by Type Ia supernovae may have radiatively cooled, avoiding detection by X-ray and optical observers. Hydrodynamic models of Type Ia explosions in the hot gas inside elliptical galaxies create a gas of nearly pure iron that is several times hotter than the local interstellar gas. We describe the subsequent thermal evolution of the iron-rich gas as it radiates and thermally mixes with the surrounding gas. There is a critical time by which the iron ions must mix into the ambient gas to avoid rapid radiative cooling. We find that successful mixing is possible if the iron ions diffuse with large mean free paths, as in an unmagnetized plasma. However, the Larmor radii of the iron ions are exceptionally small in microgauss fields, so the field geometry must be highly tangled or radial to allow the iron to mix by diffusion faster than it cools by radiative losses. The possibility that some of the supernova iron cools cannot be easily discounted.

Constraining galaxy formation models with dwarf ellipticals in clusters

Recent observations demonstrate that dwarf galaxies in clusters, despite their faintness, may be a critical galaxy type for understanding the physical processes behind galaxy formation. Dwarfs are the most common type of galaxy and are particularly abundant in rich galaxy clusters. The dominate model for explaining the formation of these systems thorough Cold Dark Matter models is that the bulk of their stellar mass formed early, and within their present environments. Recent results however suggest that some dwarfs appear in clusters after the bulk of its members form, a scenario not predicted in standard hierarchical structure formation models. Many of these systems appear to be younger and more metal rich than dwarfs in lower density areas, suggesting they are possibly created by a tidal process induced by the cluster. Several general galaxy cluster observations, including steep luminosity functions and the origin of intracluster light, are natural outcomes of these processes.

UCDs in Fornax and Abell 1689

We review some properties of ultra compact dwarf galaxies (UCDs) in Fornax and of their brighter counterparts in Abell 1689, among which are two M32 twins, and discuss various possible UCD formation scenarios. We note that it is indispensable to carefully take into account the bright end of the globular cluster luminosity function when estimating the number density of UCDs. It is suggested that the search for more luminous UCDs in dense and rich galaxy clusters is the best way towards establishing UCDs as a new class of galaxies.

The two-point correlation of galaxy groups: probing the clustering of dark matter haloes

We analyse the two-point correlation function (2PCF) of galaxy groups identified from the 2-degree Field Galaxy Redshift Survey with the halo-based group finder recently developed by Yang et al. With this group catalogue we are able to estimate the 2PCFs for systems ranging from isolated galaxies to rich clusters of galaxies. The real-space correlation length obtained for these systems ranges from ∼4 to ∼15h−1Mpc, respectively. The observed correlation amplitude (and the corresponding bias factor) as a function of group abundance is well reproduced by associating galaxy groups with dark matter haloes in the standard Λ-cold dark matter model. Redshift distortions are clearly detected in the redshift-space correlation function, the degree of which is consistent with the assumption of gravitational clustering and halo bias in the cosmic density field. In agreement with previous studies we find a strong increase of the correlation length with the mean intergroup separation. Although well-determined observationally, we show that current theoretical predictions are not yet accurate enough to allow for stringent constraints on cosmological parameters. Finally, we use our results to explore the power-law nature of the 2PCF of galaxies. We split the 2PCF into one- and two-group terms, equivalent to the one- and two-halo terms in halo occupation models, and show that the power-law form of the 2PCF is broken, when only including galaxies in the more massive systems.

Cosmology with clusters of galaxies

Rich clusters of galaxies, the largest virialized systems known, place some of the most powerful constraints on cosmology. I discuss below the use of clusters of galaxies in determining two fundamental properties of the universe: the mass-density of the universe, and the distribution of dark matter. I show that several independent methods utilizing clusters of galaxies – cluster dynamics and the mass-to-light function, baryon fraction in clusters, and cluster abundance and its evolution – all indicate the same result: a universe with a low mass-density, ∼20% of the critical density needed to halt the universal expansion, and a mass distribution that approximately traces light on large scales.

Completing H I observations of galaxies in the Virgo cluster

High sensitivity (rms noise $\sim 0.5$ mJy) 21-cm HI line observations were made of 33 galaxies in the Virgo cluster, using the refurbished Arecibo telescope, which resulted in the detection of 12 objects. These data, combined with the measurements available from the literature, provide the first set of HI data that is complete for all 355 late-type (Sa-Im-BCD) galaxies in the Virgo cluster with $m_p \leq 18.0$ mag. The Virgo cluster HI mass function (HIMF) that was derived for this optically selected galaxy sample is in agreement with the HIMF derived for the Virgo cluster from the blind HIJASS HI survey and is inconsistent with the Field HIMF. This indicates that both in this rich cluster and in the general field, neutral hydrogen is primarily associated with late-type galaxies, with marginal contributions from early-type galaxies and isolated HI clouds. The inconsistency between the cluster and the field HIMF derives primarily from the difference in the optical luminosity function of late-type galaxies in the two environments, combined with the HI deficiency that is known to occur in galaxies in rich clusters.

Absence of Dwarf Galaxies at High Redshifts: Evidence from a Galaxy Group

The galaxy group NGC 5044 consists of a luminous giant elliptical galaxy surrounded by a cluster of ~160 low-luminosity and dwarf galaxies, mostly of early type. The cumulative projected radial distribution of dwarf galaxies in the NGC 5044 group, unlike distributions of more luminous galaxies in rich clusters, does not follow a projected dark matter (NFW) profile. A deficiency or absence of low-luminosity galaxies is apparent in NGC 5044 within about 350 kpc. Most of the dwarf galaxies in NGC 5044 entered the virial radius at redshifts z 2.5(af/0.25), where af = 1/(1 + zf) is the epoch of group formation, and very few entered during redshifts z 2.5(af/0.25). The peculiar, non-NFW shape of the projected cumulative dwarf galaxy distribution in NGC 5044 within 350 kpc resembles the characteristic cumulative distribution of dark subhalos that are also known to be relatively young. Dynamical friction is unlikely to explain the apparent lack of group member galaxies at small radii in NGC 5044.

Tunable-Filter Imaging of Quasar Fields atz ~ 1. II. The Star-forming Galaxy Environments of Radio-loud Quasars

We have scanned the fields of six radio-loud quasars using the Taurus Tunable Filter to detect redshifted [O II] λ3727 line–emitting galaxies at redshifts 0.8 < z < 1.3. Forty-seven new emission-line galaxy (ELG) candidates are found. This number corresponds to an average space density about 100 times of that found locally and, at L([O ]) < 1042 ergs s-1 cm-2, is 2–5 times greater than the field ELG density at similar redshifts, implying that radio-loud quasars inhabit sites of above average star formation activity. The implied star formation rates are consistent with surveys of field galaxies at z ~ 1. However, the variation in candidate density between fields is large and indicative of a range of environments, from the field to rich clusters. The ELG candidates also cluster—both spatially and in terms of velocity—about the radio sources. In fields known to contain rich galaxy clusters, the ELGs lie at the edges and outside the concentrated cores of red, evolved galaxies, consistent with the morphology-density relation seen in low-redshift clusters. This work, combined with other studies, suggests that the ELG environments of powerful active galactic nuclei look very much the same from moderate to high redshifts, i.e., 0.8 < z < 4.

The origin and properties of intracluster stars in a rich cluster

We use a multimillion particle N‐body + smooth particle hydrodynamics (SPH) simulation to follow the formation of a rich galaxy cluster in a Λ‐cold dark matter (ΛCDM) cosmology, with the goal of understanding the origin and properties of intracluster stars. The simulation includes gas cooling, star formation, the effects of a uniform ultraviolet background and feedback from supernovae. Haloes that host galaxies as faint as MR=−19.0 are resolved by this simulation, which includes 85 per cent of the total galaxy luminosity in a rich cluster. We find that the accumulation of intracluster light (ICL) is an ongoing process, linked to infall and stripping events. The unbound star fraction varies with time between 10 and 22 per cent of the total amount of cluster stars, with an overall trend to increase with time. The fraction is 20 per cent at z= 0, consistent with observations of galaxy clusters. The surface brightness profile of the cD galaxy shows an excess compared with a de Vaucouleur profile near 200 kpc, which is also consistent with observations. Both massive and small galaxies contribute to the formation of the ICL, with stars stripped preferentially from the outer, lower‐metallicity parts of their stellar distributions. Simulated observations of planetary nebulae (PNe) show significant substructure in velocity space, tracing separate streams of stripped intracluster stars. Despite an unrelaxed distribution, individual intracluster PNe might be useful mass tracers if more than five fields at a range of radii have measured line‐of‐sight velocities, where an accurate mass calculation depends more on the number of fields than the number of PNe measured per field. However, the orbits of intracluster stars are more anisotropic than those of galaxies or dark matter, which leads to a systematic underestimate of cluster mass relative to that calculated with galaxies, if not accounted for in dynamical models. Overall, the properties of ICL formed in a hierarchical scenario are in good agreement with current observations, supporting a model where ICL originates from the dynamical evolution of galaxies in dense environments. ICL should thus be ubiquitous in galaxy clusters.

Determining cosmological parameters from X-ray measurements of strong lensing clusters

We discuss a new method which is potentially capable of constraining cosmological parameters using observations of giant luminous arcs in rich X-ray clusters of galaxies. The mass profile and the mass normalization of the lenses are determined from X-ray measurements. The method also allows to probe the amount and equation of state of the dark energy in the universe. The analysis of a preliminary sample of 6 luminous, relatively relaxed clusters of galaxies strongly favours an accelerating expansion of the universe. Under the assumption that the dark energy is in the form of a cosmological constant, the data provide an estimate of �0 = 1.1 with a statistical error of ±0.2. Including the constraint of a flat universe and an equation of state for the dark energy wX > 1, we obtain M0 = 0.10±0.10 and wX = 0.84±0.14. Relaxing the prior on wX, we find that the null energy condition is satisfied at the 3-σ confidence level.

ChandraandXMM‐NewtonObservations of the Double Cluster A1758

A1758 was classified by Abell as a single rich cluster of galaxies, but a ROSAT observation showed that this system consists of two distinct clusters (A1758N and A1758S) separated by approximately 8' (a projected separation of 2 Mpc in the rest frame of the clusters). Only a few galaxy redshifts have been published for these two clusters, but the redshift of the Fe lines in the Chandra and XMM-Newton spectra shows that the recessional velocities of A1758N and A1758S are within 2100 km s-1. Thus, these two clusters most likely form a gravitationally bound system, but our imaging and spectroscopic analyses of the X-ray data do not reveal any sign of interaction between the two clusters. The Chandra and XMM-Newton observations show that A1758N and A1758S are both undergoing major mergers. A1758N is in the late stages of a large impact parameter merger between two 7 keV clusters. The two remnant cores have a projected separation of 800 kpc. Based on the measured pressure jumps preceding the two cores, they are receding from one another at less than 1600 km s-1. The two cores are surrounded by hotter gas (kT = 9-12 keV) that was probably shock heated during the early stages of the merger. The gas entropy in the two remnant cores is comparable with the central entropy observed in dynamically relaxed clusters, indicating that the merger-induced shocks stalled as they tried to penetrate the high-pressure cores of the two merging systems. Each core also has a wake of low-entropy gas, indicating that this gas was ram pressure stripped without being strongly shocked. A1758S is undergoing a more symmetric (lower impact parameter) merger between two 5 keV clusters. The two remnant cores are nearly coincident as seen in projection on the sky. The two cores are surrounded by hotter gas (9-11 keV), which was probably shock heated during the merger. Based on the pressure jumps preceding the two cores, they must have a relative velocity of less than 1400 km s-1. Unlike A1758N, there is no evidence of wakes of low-entropy gas.

Galaxy evolution in the environment of ABCG 209

We examine the environmental effects on the photometric properties of galaxies for the rich galaxy cluster ABCG 209 at z=0.209. We use archive CFHT optical imaging of a 42'x28' field centred on the cluster to produce a galaxy sample complete to B=25.0 and R=24.5. Both the composite and red sequence galaxy luminosity functions are found to be dependent on the local galaxy surface density, their faint-end slopes becoming shallower with increasing density. We explain this as a combination of the morphology-density relation, and dwarf galaxies being cannibalised and/or disrupted by the cD galaxy and the ICM in the cluster core. The B-R colour of the red sequence itself appears 0.02mag redder for the highest-density regions, indicative of their stellar populations being marginally (<5%) older or (<20%) more metal-rich. This may be due to the galaxies themselves forming earliest in the rarest overdensities marked by rich clusters, or their star-formation being suppressed earliest by the ICM.

The baryonic mass-velocity relation: clues to feedback processes during structure formation and the cosmic baryon inventory

We show that a global relation between baryonic mass and virial velocity can be constructed from the scale of dwarf galaxies up to that of rich galaxy clusters. The slope of this relation is close to that expected if dark matter halos form in the standard hierarchical cosmogony and capture a universal baryon fraction, once the details of halo structure and the adiabatic contraction of halos due to cooling gas are taken into account. The scatter and deficiency of baryons within low mass halos ($V_{vir} < 50$ km/s) is consistent with the expected suppression of gas accretion by photo-evaporation due to the cosmic UV background at high redshift. The data are not consistent with significant gas removal from strong supernovae winds unless the velocities of galaxies measured from their gas kinematics are significantly lower than the true halo velocities for objects with $V_{vir} < 100$ km/s. Thus models such as $\Lambda$CDM with a steep mass function of halos may find it difficult to reproduce both the baryonic mass-velocity relation presented here whilst at the same time reproducing the flat luminosity/HI function of galaxies. Galaxies hold about 10% of the baryons in the Universe, which is close to the collapsed mass fraction expected within hierarchical models on these scales, suggesting a high efficiency for galaxy formation. Most of the baryons are expected to be evenly distributed between diffuse intergalactic gas in low density environments and the intra-galactic medium within galaxy groups.

Diffusion of ultra-high energy protons in galaxy clusters and secondary X- and gamma-ray emissions

In this work we simulate the propagation of ultra-high energy (UHE) protons in the magnetised intergalactic medium of galaxy clusters (GCs). Differently from previous works on the subject, we trace proton trajectories in configurations of the intra-cluster magnetic field (ICMF), which have been extracted from a constrained magnetic-SPH simulation of the local universe. Such an approach allows us to take into account the effects of several features of the ICMFs, e.g. irregular geometrical structure and field fluctuations due to merger shocks, which cannot be investigated analytically or with usual numerical simulations. Furthermore, we are able to simulate a set of clusters, which have properties quite similar to those of GCs observed in the nearby universe. We estimate the time that UHE protons take to get out of the clusters and found that in the energy range 5×1018≲E≲3×1019 eV proton propagation takes place in the Bohm scattering diffusion regime passing smoothly to a small pitch angle diffusion regime at larger energies. We apply our results to estimate the secondary gamma- and hard X-ray (HXR) emissions produced by UHE protons in a rich GC. We show that the main emission channel is due to the synchrotron HXR radiation of secondary electrons originated by proton photo-pair production scattering onto the CMB. This process may give rise to a detectable signal if a relatively powerful AGN, or a dead quasar, accelerating protons at UHEs is harboured by a rich GC in the local universe.