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[ABRIDGED] We present the first results from the largest spectroscopic survey
to date of an intermediate redshift galaxy cluster, the z=0.834 cluster RX
J0152.7-1357. We use the colors of galaxies, assembled from a D~12 Mpc region
centered on the cluster, to investigate the properties of the red-sequence as a
function of density and clustercentric...
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... the observed color fractions (solid circles) and the field interloper-corrected fractions (open circles) are shown. The red galaxy fractions are given in Table 1. A clear trend of galaxy colors exists with local density as ex- pected from the correlation between clustercentric radius and local density at R 2 Mpc where a large number of galaxies in our sample lie. ...
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Citations
... A spectrophotometric approach adds low-resolution (R ∼ 30) optical prism spectra-which can be obtained for thousands of galaxies in one observation-to the fluxes in broadband filters. The continuous wavelength coverage in the optical with broadband filters extending into the NIR enables redshift uncertainties σ z 0.01(1 + z), a method developed and implemented successfully in Patel et al. (2009), Coil et al. (2011. We adopt this spectrophotometric approach needed to accurately characterize the ∼17,000 galaxies in our radio-selected sample. ...
We present the initial sample of redshifts for 3839 galaxies in the MeerKAT DEEP2 field—the most sensitive ∼1.4 GHz radio field yet observed with σ n = 0.55 μ Jy beam ⁻¹ , reaching the confusion limit. Using a spectrophotometric technique combining coarse optical spectra with broadband photometry, we obtain redshifts with σ z ≲ 0.01(1 + z ), as determined from repeat observations. The resulting radio luminosity functions between 0.2 < z < 1.3 from our sample of 3839 individual galaxies are in remarkable agreement with those inferred from previous modeling of radio source counts, confirming a ≳50% excess in radio-based star formation rate density (SFRD) ( z ) measurements at 0.2 < z < 1.3 compared to those from the UV–IR. Several sources of systematic error are discussed—totalling ∼0.13 dex when added in quadrature. Even in the event that all systematic errors work to decrease the radio-based SFRD values, they are incapable of reconciling differences between the radio-based measurements with those from the UV–IR at 0.5 < z < 1.3. We conclude that significant work remains to have confidence in a full accounting of the star formation budget of the Universe.
... This trend is seen also at fixed stellar mass, meaning that some external effects specific to a dense environment are required to shape galaxies (e.g., Peng et al. 2010). At higher redshift, the relationships mentioned above seem to persist at least z∼1.5 (e.g., Tanaka et al. 2005;Patel et al. 2009;Nantais et al. 2016;Lemaux et al. 2019;Tomczak et al. 2019). Although several physical processes have been proposed such as ram pressure stripping and galaxy-galaxy interactions or mergers, the relative importance of these processes is yet unknown. ...
Galaxies change their properties as they assemble into clusters. In order to understand the physics behind that, we need to go back in time and observe directly what is occurring in galaxies as they fall into a cluster. We have conducted a narrowband and J -band imaging survey on a cluster CL1604-D at z = 0.923 using a new infrared instrument SWIMS installed at the Subaru Telescope. The narrowband filter, NB1261, matches to H α emission from the cluster at z = 0.923. Combined with a wide range of existing data from various surveys, we have investigated galaxy properties in and around this cluster in great detail. We have identified 27 H α emitters associated with the cluster. They have significant overlap with MIPS sources and are located exclusively in the star-forming regime on the rest-frame UVJ diagram. We have identified two groups of galaxies near the cluster in the 2D spatial distribution and the phase-space diagram, which are likely to be in-falling to the cluster main body. We have compared various physical properties of star-forming galaxies, such as specific star formation rates (burstiness) and morphologies (merger) as a function of environment, cluster center, older group, younger group, and the field. As a result, a global picture has emerged on how the galaxy properties are altered as they assemble into a denser region. This includes the occurrence of mergers, enhancement of star formation activity, excursion to the dusty starburst phase, and eventual quenching to a passive phase.
... Since the work of Kodama & Arimoto (1997), questions about the red sequence have shifted toward how it forms. De Lucia et al. (2007), Andreon (2008), Patel et al. (2009), and others have tried to constrain how the faint end of the red sequence is established. Searches for high-redshift clusters have led to observations of early red sequences (e.g., Kodama et al. 2007;Strazzullo et al. 2019), directly constraining the formation time more robustly than stellar population models of z=0 clusters. ...
In clusters of galaxies, the red sequence is believed to be a consequence of a correlation between stellar mass and chemical abundances, with more massive galaxies being more metal-rich and, as a consequence, redder. However, there is a color scatter around the red sequence that holds even with precision photometry, implying that the galaxy population is more complicated than as described by a mass–metallicity relation. We use precision photometry from the Cluster Lensing and Supernova survey with Hubble (CLASH) to investigate what drives this scatter. In four CLASH clusters at z = 0.355 ± 0.007, we find that the optical–IR galaxy colors confirm the previously known trend of metallicity along the red sequence but also show a strong connection between stellar age and red sequence offset, with ages ranging from 3 to 8 Gyr. Starting with fixed-age color–magnitude relations motivated by the mass–metallicity correlations of CLASH cluster galaxies, and by adjusting galaxy colors through stellar population models to put them all at the age of our red sequence, we are able to reduce the, e.g., F625W–F814W scatter from 0.051 to 0.026 mag with median photometric errors of 0.029 mag. While we will extend this analysis to the full CLASH sample, in four clusters our technique already provides a color precision in near-total-light apertures to resolve the spread in stellar population formation ages that drives the scatter in the red sequence.
... how the cluster mass evolve with time by accretion of smaller systems) from Poggianti et al. (2006). Triangles: EDisCS (Halliday et al. 2004;); empty pentagons: MORPHS (Girardi and Mezzetti 2001); filled pentagons: CLASH (Postman et al. 2012); grey: independent programs on individual clusters (Kodama et al. 2001;Ebeling et al. 2007; Moran et al. 2007;Koyama et al. 2008;Patel et al. 2009;Tanaka et al. 2009;Lubin et al. 2009)). We see the EDisCS clusters are likely progenitors of the typical low-z clusters, contrarily to the majority of the other cluster survey. ...
... As they are not focused on clusters, field survey such as SDSS (e.g., Baldry et al. 2006) and zCOSMOS (e.g., Knobel et al. 2012;Kovač et al. 2014) tend to spectroscopically undersample the highest density regions and photometry alone is not sufficient to characterize accurately the clusters candidates. Independent programs on individual clusters (e.g., Kodama et al. 2004;Moran et al. 2007;Patel et al. 2009;Tanaka et al. 2009) are difficult to compare, because of the heterogeneity between the datasets (filters used, redshift range, cosmic variance, depth, completeness, etc.), the different estimation of the galaxy properties (e.g. rest-frame u − g or g − r colors, different assumptions to compute stellar masses, SFR derived from the optical or the infrared, etc.) and the methods used to measure the environments (projected or threedimensional density, galaxy number counts in fixed or adaptive aperture, local or global scales, etc. Lubin et al. 2009;ICBS, Oemler et al. 2013; CLASH-VLT, Rosati et al. 2014). ...
... The EDisCS program selected the highest surface brightness clusters in the LCDCS. (Kodama et al. 2001;Ebeling et al. 2007;Moran et al. 2007;Koyama et al. 2008;Patel et al. 2009;Tanaka et al. 2009;Lubin et al. 2009)). We see the EDisCS clusters are likely progenitors of the typical low-z clusters, contrarily to the majority of the other cluster survey. ...
Theory predicts that galaxies are not randomly distributed in the Universe. They form a complex network of filamentary structures, the Cosmic Web, divided in clusters, groups, filaments and walls. This picture has been confirmed by the large galaxy redshift surveys. Galaxy properties like morphology and star formation rates are strongly influenced by their environment. The most radical transformations are observed in galaxy clusters, located at the intersection of filaments. Nevertheless, the location where the environment starts to play a role and the main physical phenomenon responsible for these changes are still unknown. The aim of this thesis is to determine where and how galaxies are affected by the environment, at local and global scales. We gathered high quality photometry in the 5 optical bands $u$, $g$, $r$, $i$ and $z$ with MegaCam on the Canada-France-Hawaii Telescope for 3 medium mass galaxy clusters at intermediate redshift, with a spatial extent on the sky plane reaching 8 to 13 times the cluster virial radii. These clusters were selected to represent as much as possible progenitors of clusters in the local Universe. The core of these clusters have rich ancillary data from the ESO Distant Cluster Survey. The redshift and mass ranges of these clusters, combined to the wide field of the observations make this study unique. We computed photometric redshifts to map the galaxy distribution around the clusters. We were able to identify overdense regions forming groups and filaments, unveiling for the first time the large scale structures in such details for this type of clusters. We studied the fraction of galaxies in the red sequence in different environments, namely in the field, filaments and groups. We find that significant quenching processes are already at work in filaments, even at large cluster-centric distances. We also show that the local neighborhood of galaxies has a stronger impact on galaxy colors than the global environment. An optical spectroscopic follow-up with the VIsible MultiObject Spectrograph on the Very Large Telescope confirms our photometric results. In particular, the fraction of galaxies with detected \otwo emission line is smaller with increasing density. We also find that the star formation rate, determined from [OII], is in average weaker in groups and clusters than in lower density environments. This thesis opens new perspectives to study the way galaxies populate the Cosmic Web. Combined to weak-lensing analysis and cosmological simulations, it will allow a deeper understanding of the structure formation and their baryonic content. It is a first step before extending the results to much larger samples, with the help of the upcoming all-sky cosmological surveys such as Euclid or the Square Kilometer Array.
... If we take the radial range 3–4r c v as the " field, " we see that the fraction of red galaxies is in the range of 20%–30% (Figure 19), reaching 65%–90% within 2r c v , in agreement with Mok et al. (2013). In a large galaxy sample study of a z = 0.83 cluster, Patel et al. (2009) find that the red galaxy fraction is 93% ± 3% in the central region of the cluster and declines to a level of 64% ± 3% at a projected cluster-centric radius of ∼3Mpc. In the right column ofFigure 19, for halos in the mass range of 10 13 –10 14 M , we see that within the virial radius the red fractions are in the range of 60%–90%, depending on the satellite to primary galaxy mass ratio, with the overall mean of the red fraction within the virial radius in the range ofFigure 19. ...
... (A color version of this figure is available in the online journal.) 80%–90%. The more central region has a red fraction higher than 80%–90%, consistent with their observation. Patel et al. (2009) also find that the environmental effect extends even beyond 3Mpc, which is about 3 virial radii for their cluster. From the right column inFigure 19, we see that red galaxies dominate up to 3 virial radii, in reasonable accordance with observations. Some of our results are not necessarily straightforward enough to enable one to see the ...
An analysis of more than 3000 galaxies resolved at better than 114 pc/h at
z=0.62 in a LAOZI cosmological adaptive mesh refinement hydrodynamic simulation
is performed and insights gained on star formation quenching and color
migration. The vast majority of red galaxies are found to be within three
virial radii of a larger galaxy, at the onset of quenching when the specific
star formation rate experiences the sharpest decline to fall below
~10^{-2}-10^{-1}/Gyr (depending on the redshift). We shall thus call this
mechanism "environment quenching", which encompasses satellite quenching. Two
physical processes are largely responsible: ram-pressure stripping first
disconnects the galaxy from the cold gas supply on large scales, followed by a
longer period of cold gas starvation taking place in high velocity dispersion
environment, during the early part of which the existing dense cold gas in the
central region (<10kpc) is consumed by in situ star formation. Quenching is
found to be more efficient, but not faster, on average, in denser environment.
Throughout this quenching period and the ensuing one in the red sequence
galaxies follow nearly vertical tracks in the color-stellar-mass diagram. In
contrast, individual galaxies of all masses grow most of their stellar masses
in the blue cloud, prior to the onset of quenching, and progressively more
massive blue galaxies with already relatively older mean stellar ages continue
to enter the red sequence. Consequently, correlations among observables of red
galaxies - such as the age-mass relation - are largely inherited from their
blue progenitors at the onset of quenching. While the color makeup of the
entire galaxy population strongly depends on environment, which is a direct
result of environment quenching, physical properties of blue galaxies as a
sub-population show little dependence on environment.
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 < R 200 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 < R 200 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 < R 500 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 < R 500 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 R 200 , 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 < R 500 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 < R 500 , since we observe R < R 500 SF galaxies with masses up to M ∼ 10 ¹¹ 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.
We investigate how the galaxy reservoirs of molecular gas fuelling star formation are transformed while the host galaxies infall onto galaxy cluster cores. As part of the Spatially Extended ESO Distant Cluster Survey (SEEDisCS), we present CO(3-2) observations of 27 star-forming galaxies obtained with the Atacama Large Millimeter Array. These sources are located inside and around CL1411.1−1148 at z = 0.5195, within five times the cluster virial radius. These targets were selected to have stellar masses ( M star ), colours, and magnitudes similar to those of a field comparison sample at similar redshift drawn from the Plateau de Bure high- z Blue Sequence Survey (PHIBSS2). We compare the cold gas fraction ( μ H 2 = M H 2 / M star ), specific star formation rates (SFR/ M star ) and depletion timescales ( t depl = M H 2 /SFR) of our main-sequence galaxies to the PHIBSS2 subsample. While the most of our galaxies (63%) are consistent with PHIBSS2, the remainder fall below the relation between μ H 2 and M star of the PHIBSS2 galaxies at z ∼ 0.5. These low- μ H 2 galaxies are not compatible with the tail of a Gaussian distribution, hence they correspond to a new population of galaxies with normal SFRs but low gas content and low depletion times (≲1 Gyr), absent from previous surveys. We suggest that the star formation activity of these galaxies has not yet been diminished by their low fraction of cold molecular gas.
The commissioning team for the Vera C. Rubin observatory is planning a set of engineering and science verification observations with the Legacy Survey of Space and Time (LSST) commissioning camera and then the Rubin Observatory LSST Camera. The time frame for these observations is not yet fixed, and the commissioning team will have flexibility in selecting fields to observe. In this document, the Dark Energy Science Collaboration (DESC) Commissioning Working Group presents a prioritized list of target fields appropriate for testing various aspects of DESC-relevant science performance, grouped by season for visibility from Rubin Observatory at Cerro Pachon. Our recommended fields include Deep-Drilling fields (DDFs) to full LSST depth for photo-$z$ and shape calibration purposes, HST imaging fields to full depth for deblending studies, and an $\sim$200 square degree area to 1-year depth in several filters for higher-level validation of wide-area science cases for DESC. We also anticipate that commissioning observations will be needed for template building for transient science over a broad RA range. We include detailed descriptions of our recommended fields along with associated references. We are optimistic that this document will continue to be useful during LSST operations, as it provides a comprehensive list of overlapping data-sets and the references describing them.
The study of galaxy protoclusters is beginning to fill in unknown details of the important phase of the assembly of clusters and cluster galaxies. This review describes the current status of this field and highlights promising recent findings related to galaxy formation in the densest regions of the early universe. We discuss the main search techniques and the characteristic properties of protoclusters in observations and simulations, and show that protoclusters will have present-day masses similar to galaxy clusters when fully collapsed. We discuss the physical properties of galaxies in protoclusters, including (proto-)brightest cluster galaxies, and the forming red sequence. We highlight the fact that the most massive halos at high redshift are found in protoclusters, making these objects uniquely suited for testing important recent models of galaxy formation. We show that galaxies in protoclusters should be among the first galaxies at high redshift making the transition from a gas cooling regime dominated by cold streams to a regime dominated by hot intracluster gas, which could be tested observationally. We also discuss the possible connections between protoclusters and radio galaxies, quasars, and \(\hbox {Ly}\alpha \) blobs. Because of their early formation, large spatial sizes and high total star-formation rates, protoclusters have also likely played a crucial role during the epoch of reionization, which can be tested with future experiments that will map the neutral and ionized cosmic web. Lastly, we review a number of promising observational projects that are expected to make significant impact in this growing, exciting field.
We study the environmental dependence of the strength of polycyclic aromatic
hydrocarbon (PAH) emission by AKARI observations of RX J0152.7-1357, a galaxy
cluster at z=0.84. PAH emission reflects the physical conditions of galaxies
and dominates 8 um luminosity (L8), which can directly be measured with the L15
band of AKARI. L8 to infrared luminosity (LIR) ratio is used as a tracer of the
PAH strength. Both photometric and spectroscopic redshifts are applied to
identify the cluster members. The L15-band-detected galaxies tend to reside in
the outskirt of the cluster and have optically green colour, R-z'~ 1.2. We find
no clear difference of the L8/LIR behaviour of galaxies in field and cluster
environment. The L8/LIR of cluster galaxies decreases with
specific-star-formation rate divided by that of main-sequence galaxies, and
with LIR, consistent with the results for field galaxies. The relation between
L8/LIR and LIR is between those at z=0 and z=2 in the literature. Our data also
shows that starburst galaxies, which have lower L8/LIR than main-sequence, are
located only in the outskirt of the cluster. All these findings extend previous
studies, indicating that environment affects only the fraction of galaxy types
and does not affect the L8/LIR behaviour of star-forming galaxies.
