Astrophys.J.663:164-182,2007 We present results from an extensive spectroscopic survey, carried out with
VLT FORS, and from an extensive multiwavelength imaging data set from the HST
Advanced Camera ...for Surveys and ground based facilities, of the cluster of
galaxies RDCS J1252.9-2927. We have spectroscopically confirmed 38 cluster
members in the redshift range 1.22 < z < 1.25. A cluster median redshift of
z=1.237 and a rest-frame velocity dispersion of 747^{+74}_{-84} km/s are
obtained. Using the 38 confirmed redshifts, we were able to resolve, for the
first time at z > 1, kinematic structure. The velocity distribution, which is
not Gaussian at the 95% confidence level, is consistent with two groups that
are also responsible for the projected east-west elongation of the cluster. The
groups are composed of 26 and 12 galaxies with velocity dispersions of
486^{+47}_{-85} km/s and 426^{+57}_{-105} km/s, respectively. The elongation is
also seen in the intracluster gas and the dark matter distribution. This leads
us to conclude that RDCS J1252.9-2927 has not yet reached a final virial state.
We extend the analysis of the color-magnitude diagram of spectroscopic members
to more than 1 Mpc from the cluster center. The scatter and slope of
non-OII-emitting cluster members in the near-IR red sequence is similar to
that seen in clusters at lower redshift. Furthermore, most of the galaxies with
luminosities greater than ~ K_s*+1.5 do not show any OII, indicating that
these more luminous, redder galaxies have stopped forming stars earlier than
the fainter, bluer galaxies. Our observations provide detailed dynamical and
spectrophotometric information on galaxies in this exceptional high-redshift
cluster, delivering an in-depth view of structure formation at this epoch only
5 Gyr after the Big Bang.
Astrophys.J. 623 (2005) 42-56 We present a weak lensing analysis of one of the most distant massive galaxy
cluster known, RDCS 1252.9-2927 at z=1.24, using deep images from the Advanced
Camera for ...Survey (ACS) on board the Hubble Space Telescope (HST). By taking
advantage of the depth and of the angular resolution of the ACS images, we
detect for the first time at z>1 a clear weak lensing signal in both the i
(F775W) and z (F850LP) filters. We measure a 5-\sigma signal in the i band and
a 3-\sigma signal in the shallower z band image. The two radial mass profiles
are found to be in very good agreement with each other, and provide a
measurement of the total mass of the cluster inside a 1Mpc radius of M(<1Mpc) =
(8.0 +/- 1.3) x 10^14 M_\odot in the current cosmological concordance model h
=0.70, \Omega_m=0.3, \Omega_\Lambda=0.7, assuming a redshift distribution of
background galaxies as inferred from the Hubble Deep Fields surveys. A weak
lensing signal is detected out to the boundary of our field (3' radius,
corresponding to 1.5Mpc at the cluster redshift). We detect a small offset
between the centroid of the weak lensing mass map and the brightest cluster
galaxy, and we discuss the possible origin of this discrepancy. The cumulative
weak lensing radial mass profile is found to be in good agreement with the
X-ray mass estimate based on Chandr and XMM-Newton observations, at least out
to R_500=0.5Mpc.
We derive the Ks-band luminosity function (LF) of the z=1.237 massive X-ray luminous cluster of galaxies RDCS J1252.9-2927. Photometric redshifts, derived from deep multi-wavelength BVRIzJKs data, ...and calibrated using a large subset of galaxies with spectroscopic redshifts, are used to separate the cluster galaxy population from the foreground and background field galaxy population. This allows for a simultaneous determination of the characteristic magnitude Ks* and faint end slope alpha of the LF without having to make an uncertain statistical background subtraction. The shape of the bright end of the derived LF is similar to that measured at similar restframe wavelengths (in the z-band) in local clusters, but the characteristic magnitude is brighter by Delta Mz*=-1.40(+0.49/-0.58) magnitudes, suggesting that the massive cluster ellipticals that dominate the bright end of the LF were already in place at z=1.237. The derived alpha is shallower (at the 2.2 sigma level) than the value measured in the z-band in clusters in the local universe, suggesting that RDCS J1252.9-2927 contains a relatively smaller fraction of low mass galaxies than clusters in the local universe. The results presented in this paper are a challenge for semi analytical hierarchical models of galaxy formation which predict the characteristic magnitude to grow fainter and the faint end slope to steepen with redshift as the massive galaxies break up into their progenitors. The observed evolution is consistent with a scenario in which clusters are composed of a population of massive galaxies which formed at high redshift (z>>1) and subsequently evolved passively, and a population of lower mass galaxies which are gradually accreted from the field, primarily at lower redshift (z<1). (Abridged)
A large fraction of the mammalian genome is organized into inactive chromosomal domains along the nuclear lamina. The mechanism by which these lamina associated domains (LADs) are established remains ...to be elucidated. Using genomic repositioning assays, we show that LADs, spanning the developmentally regulated IgH and Cyp3a loci contain discrete DNA regions that associate chromatin with the nuclear lamina and repress gene activity in fibroblasts. Lamina interaction is established during mitosis and likely involves the localized recruitment of Lamin B during late anaphase. Fine-scale mapping of LADs reveals numerous lamina-associating sequences (LASs), which are enriched for a GAGA motif. This repeated motif directs lamina association and is bound by the transcriptional repressor cKrox, in a complex with HDAC3 and Lap2β. Knockdown of cKrox or HDAC3 results in dissociation of LASs/LADs from the nuclear lamina. These results reveal a mechanism that couples nuclear compartmentalization of chromatin domains with the control of gene activity.
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► Lamina-associating DNA sequences (LASs) direct chromatin to the nuclear lamina ► In mammalian cells, LASs are bound by the transcriptional repressor cKrox ► cKrox recruits DNA to the lamina via HDAC3 and lamina-associated protein Lap2β ► Lamina interaction is established during mitosis, likely through recruitment of Lamin B
Binding of a transcriptional repressor complex to DNA sequences enriched in GAGA motifs directs the association of specific chromosome domains to the nuclear lamina during mitosis. These lamin-associated sequences thus couple nuclear compartmentalization of chromatin domains with gene silencing.
Astrophys.J. 639 (2006) 81-94 The color-magnitude relation has been determined for the RDCS J0910+5422
cluster of galaxies at redshift z = 1.106. Cluster members were selected from
HST ACS images, ...combined with ground--based near--IR imaging and optical
spectroscopy. The observed early--type color--magnitude relation (CMR) in
(i_775 -z_850) versus z_850 shows intrinsic scatters in color of 0.042 +/-
0.010 mag and 0.044 +/- 0.020 mag for ellipticals and S0s, respectively. From
the scatter about the CMR, a mean luminosity--weighted age t > 3.3 Gyr (z > 3)
is derived for the elliptical galaxies.
Strikingly, the S0 galaxies in RDCS J0910+5422 are systematically bluer in
(i_775 - z_850) by 0.07 +/- 0.02 mag, with respect to the ellipticals. The
ellipticity distribution as a function of color indicates that the face-on S0s
in this particular cluster have likely been classified as elliptical. Thus, if
anything, the offset in color between the elliptical and S0 populations may be
even more significant.
The color offset between S0 and E corresponds to an age difference of ~1 Gyr,
for a single-burst solar metallicity model. A solar metallicity model with an
exponential decay in star formation will reproduce the offset for an age of 3.5
Gyr, i.e. the S0s have evolved gradually from star forming progenitors.
The early--type population in this cluster appears to be still forming. The
blue early-type disk galaxies in RDCS J0910+5422 likely represent the direct
progenitors of the more evolved S0s that follow the same red sequence as
ellipticals in other clusters.
Thirteen red galaxy pairs are observed and the galaxies associated in pairs
constitute ~40% of the CMR galaxies in this cluster.
The ‘‘top-six’’ non-O157 Shiga toxin–producing Escherichia coli (STEC) serogroups (O26, O45, O103, O111, O121, and O145) most frequently associated with outbreaks and cases of foodborne illnesses ...have been declared as adulterants in beef by the U.S. Department of Agriculture Food Safety and Inspection Service (FSIS). Regulatory testing in beef began in June 2012. The purpose of this study was to evaluate the DuPont BAX System method for detecting these top six STEC strains and strains of E. coli O157:H7. For STEC, the BAX System real-time STEC suite was evaluated, including a screening assay for the stx and eae virulence genes and two panel assays to identify the target serogroups: panel 1 detects O26, O111, and O121, and panel 2 detects O45, O103, O145. For E. coli O157:H7, the BAX System real-time PCR assay for this specific serotype was used. Sensitivity of each assay for the PCR targets was $1.23 | 103 CFU/ml in pure culture. Each assay was 100% inclusive for the strains tested(20 to 50 per assay), and no cross-reactivity with closely related strains was observed in any of the assays. The performance of the BAX System methods was compared with that of the FSIS Microbiology Laboratory Guidebook (MLG) methods for detection of the top six STEC and E. coli O157:H7 strains in ground beef and beef trim. Generally, results of the BAX System method were similar to those of the MLG methods for detecting non-O157 STEC and E. coli O157:H7. Reducing or eliminating novobiocin in modified tryptic soy broth (mTSB) may improve the detection of STEC O111 strains; one beef trim sample inoculated with STEC O111 produced a negative result when enriched in mTSB with 8 mg/liter novobiocin but was positive when enriched in mTSB without novobiocin. The results of this study indicate the feasibility of deploying a panel of real-time PCR assay configurations for the detection and monitoring of the top six STEC and E. coli O157:H7 strains in beef. The approach could easily be adapted for additional multiplex assays should regulations expand to include other O serogroups or virulence genes.
We present deep SofI and ISAAC near-infrared imaging data of the X-ray luminous galaxy cluster RDCS J1252.9-2927. The ISAAC data were taken at the ESO Very Large Telescope under very good seeing ...conditions and reach limiting Vega magnitudes of 25.6 and 24.1 in the J- and Ks-bands respectively. The image quality is 0.45 arc seconds in both passbands. We use these data to construct a colour-magnitude (C-M) diagram of galaxies that are within 20 arc seconds of the cluster center and brighter than Ks=24, which is five magnitudes fainter than the apparent magnitude of a L* galaxy in this cluster. The C-M relation is clearly identified as an over-density of galaxies with colours near J-Ks=1.85. The slope of the relation is -0.05 and the intrinsic scatter is 0.06 magnitudes. Both the slope and the scatter are consistent with the values measured for clusters at lower redshifts. These quantities have not evolved from z=0 to z=1.24. However, significant evolution in the mean J-Ks colour is detected. On average, the galaxies in RDCS J1252.9-2927 are 0.25 magnitudes bluer than early-type galaxies in the Coma cluster. Using instantaneous single-burst solar-metallicity models, the average age of galaxies in the center of RDCS J1252.9-2927 is 2.7 Gyrs.
We present deep HST/ACS observations in g,r,i,z towards the z=4.1 radio
galaxy TN J1338-1942 and its overdensity of >30 spectroscopically confirmed Lya
emitters (LAEs). We select 66 g-band dropouts ...to z=27, 6 of which are also a
LAE. Although our color-color selection results in a relatively broad redshift
range centered on z=4.1, the field of TN J1338-1942 is richer than the average
field at the >5 sigma significance, based on a comparison with GOODS. The
angular distribution is filamentary with about half of the objects clustered
near the radio galaxy, and a small, excess signal (2 sigma) in the projected
pair counts at separations of <10" is interpreted as being due to physical
pairs. The LAEs are young (a few x 10^7 yr), small ( = 0.13") galaxies,
and we derive a mean stellar mass of ~10^8-9 Msun based on a stacked K-band
image. We determine star formation rates, sizes, morphologies, and
color-magnitude relations of the g-dropouts and find no evidence for a
difference between galaxies near TN J1338-1942 and in the field. We conclude
that environmental trends as observed in clusters at much lower redshift are
either not yet present, or are washed out by the relatively broad selection in
redshift. The large galaxy overdensity, its corresponding mass overdensity and
the sub-clustering at the approximate redshift of TN J1338-1942 suggest the
assemblage of a >10^14 Msun structure, confirming that it is possible to find
and study cluster progenitors in the linear regime at z>4.
Astron.Astrophys.432:381-394,2005 We present the results of an extensive spectroscopic survey of RX
J0152.7-1357, one of the most massive distant clusters of galaxies known.
Multi-object ...spectroscopy, carried out with FORS1 and FORS2 on the ESO Very
Large Telescope (VLT), has allowed us to measure more than 200 redshifts in the
cluster field and to confirm 102 galaxies as cluster members. The mean redshift
of the cluster is $z=0.837 \pm 0.001$ and we estimate the velocity dispersion
of the overall cluster galaxy distribution to be $\sim 1600 \mathrm{km \
s^{-1}}$. The distribution of cluster members is clearly irregular, with two
main clumps that follow the X-ray cluster emission mapped by Chandra. A third
clump of galaxies to the east of the central structure and at the cluster
redshift has also been identified. The two main clumps have velocity
dispersions of $\sim919$ and $\sim737 \mathrm{km s^{-1}}$ respectively, and the
peculiar velocity of the two clumps suggests that they will merge into a single
more massive cluster. A segregation in the star formation activity of the
member galaxies is observed. All star forming galaxies are located outside the
high-density peaks, which are populated only by passive galaxies. A population
of red galaxies (belonging to the cluster red sequence) with clear
post-starburst spectral features and OII ($\lambda$3727) emission lines is
observed in the outskirts of the cluster. Two AGNs, which were previously
confused with the diffuse X-ray emission from the intracluster medium in ROSAT
and BeppoSAX observations, are found to be cluster members.
Astrophys.J.637:58-73,2006 We present HST/ACS observations of the most distant radio galaxy known, TN
J0924-2201 at z=5.2. This radio galaxy has 6 spectroscopically confirmed Lya
emitting companion ...galaxies, and appears to lie within an overdense region. The
radio galaxy is marginally resolved in i_775 and z_850 showing continuum
emission aligned with the radio axis, similar to what is observed for lower
redshift radio galaxies. Both the half-light radius and the UV star formation
rate are comparable to the typical values found for Lyman break galaxies at
z~4-5. The Lya emitters are sub-L* galaxies, with deduced star formation rates
of 1-10 Msun/yr. One of the Lya emitters is only detected in Lya. Based on the
star formation rate of ~3 Msun/yr calculated from Lya, the lack of continuum
emission could be explained if the galaxy is younger than ~2 Myr and is
producing its first stars.
Observations in V_606, i_775, and z_850 were used to identify additional
Lyman break galaxies associated with this structure. In addition to the radio
galaxy, there are 22 V-break (z~5) galaxies with z_850<26.5 (5sigma), two of
which are also in the spectroscopic sample. We compare the surface density of
2/arcmin^2 to that of similarly selected V-dropouts extracted from GOODS and
the UDF Parallel fields. We find evidence for an overdensity to very high
confidence (>99%), based on a counts-in-cells analysis applied to the control
field. The excess is suggestive of the V-break objects being associated with a
forming cluster around the radio galaxy.
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